diff options
| -rw-r--r-- | lib/ssh/doc/standard/draft-ietf-secsh-architecture-15.2.ps | 3315 | ||||
| -rw-r--r-- | lib/ssh/doc/standard/draft-ietf-secsh-architecture-15.txt | 1624 | ||||
| -rw-r--r-- | lib/ssh/doc/standard/draft-ietf-secsh-connect-18.2.ps | 2557 | ||||
| -rw-r--r-- | lib/ssh/doc/standard/draft-ietf-secsh-connect-18.txt | 1232 | ||||
| -rw-r--r-- | lib/ssh/doc/standard/draft-ietf-secsh-filexfer-02.2.ps | 2853 | ||||
| -rw-r--r-- | lib/ssh/doc/standard/draft-ietf-secsh-filexfer-02.txt | 1627 | ||||
| -rw-r--r-- | lib/ssh/doc/standard/draft-ietf-secsh-filexfer-03.2.ps | 3511 | ||||
| -rw-r--r-- | lib/ssh/doc/standard/draft-ietf-secsh-filexfer-03.txt | 1962 | ||||
| -rw-r--r-- | lib/ssh/doc/standard/draft-ietf-secsh-filexfer-04.txt | 2130 | ||||
| -rw-r--r-- | lib/ssh/doc/standard/draft-ietf-secsh-transport-17.2.ps | 3205 | ||||
| -rw-r--r-- | lib/ssh/doc/standard/draft-ietf-secsh-transport-17.txt | 1624 | ||||
| -rw-r--r-- | lib/ssh/doc/standard/draft-ietf-secsh-userauth-18.2.ps | 1881 | ||||
| -rw-r--r-- | lib/ssh/doc/standard/draft-ietf-secsh-userauth-18.txt | 896 |
13 files changed, 0 insertions, 28417 deletions
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matrix invertmatrix matrix concatmatrix - matrix invertmatrix put -%%EndSetup -%%Page: (0,1) 1 -userdict/PStoPSsaved save put -PStoPSmatrix setmatrix -595.000000 0.271378 translate -90 rotate -0.706651 dup scale -userdict/PStoPSmatrix matrix currentmatrix put -userdict/PStoPSclip{0 0 moveto - 595.000000 0 rlineto 0 842.000000 rlineto -595.000000 0 rlineto - closepath}put initclip -/showpage{}def/copypage{}def/erasepage{}def -PStoPSxform concat -%%BeginPageSetup -_S -75 0 translate -/pagenum 1 def -/fname () def -/fdir () def -/ftail () def -/user_header_p false def -%%EndPageSetup -5 701 M -(Network Working Group T. Ylonen) s -5 690 M -(Internet-Draft SSH Communications Security Corp) s -5 679 M -(Expires: March 31, 2004 D. Moffat, Ed.) s -5 668 M -( Sun Microsystems, Inc) s -5 657 M -( Oct 2003) s -5 624 M -( SSH Protocol Architecture) s -5 613 M -( draft-ietf-secsh-architecture-15.txt) s -5 591 M -(Status of this Memo) s -5 569 M -( This document is an Internet-Draft and is in full conformance with) s -5 558 M -( all provisions of Section 10 of RFC2026.) s -5 536 M -( Internet-Drafts are working documents of the Internet Engineering) s -5 525 M -( Task Force \(IETF\), its areas, and its working groups. Note that other) s -5 514 M -( groups may also distribute working documents as Internet-Drafts.) s -5 492 M -( Internet-Drafts are draft documents valid for a maximum of six months) s -5 481 M -( and may be updated, replaced, or obsoleted by other documents at any) s -5 470 M -( time. It is inappropriate to use Internet-Drafts as reference) s -5 459 M -( material or to cite them other than as "work in progress.") s -5 437 M -( The list of current Internet-Drafts can be accessed at http://) s -5 426 M -( www.ietf.org/ietf/1id-abstracts.txt.) s -5 404 M -( The list of Internet-Draft Shadow Directories can be accessed at) s -5 393 M -( http://www.ietf.org/shadow.html.) s -5 371 M -( This Internet-Draft will expire on March 31, 2004.) s -5 349 M -(Copyright Notice) s -5 327 M -( Copyright \(C\) The Internet Society \(2003\). All Rights Reserved.) s -5 305 M -(Abstract) s -5 283 M -( SSH is a protocol for secure remote login and other secure network) s -5 272 M -( services over an insecure network. This document describes the) s -5 261 M -( architecture of the SSH protocol, as well as the notation and) s -5 250 M -( terminology used in SSH protocol documents. It also discusses the SSH) s -5 239 M -( algorithm naming system that allows local extensions. The SSH) s -5 228 M -( protocol consists of three major components: The Transport Layer) s -5 217 M -( Protocol provides server authentication, confidentiality, and) s -5 206 M -( integrity with perfect forward secrecy. The User Authentication) s -5 195 M -( Protocol authenticates the client to the server. The Connection) s -5 184 M -( Protocol multiplexes the encrypted tunnel into several logical) s -5 173 M -( channels. Details of these protocols are described in separate) s -5 129 M -(Ylonen & Moffat Expires March 31, 2004 [Page 1]) s -_R -S -PStoPSsaved restore -userdict/PStoPSsaved save put -PStoPSmatrix setmatrix -595.000000 421.271378 translate -90 rotate -0.706651 dup scale -userdict/PStoPSmatrix matrix currentmatrix put -userdict/PStoPSclip{0 0 moveto - 595.000000 0 rlineto 0 842.000000 rlineto -595.000000 0 rlineto - closepath}put initclip -PStoPSxform concat -%%BeginPageSetup -_S -75 0 translate -/pagenum 2 def -/fname () def -/fdir () def -/ftail () def -/user_header_p false def -%%EndPageSetup -5 723 M -(Internet-Draft SSH Protocol Architecture Oct 2003) s -5 690 M -( documents.) s -5 668 M -(Table of Contents) s -5 646 M -( 1. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 3) s -5 635 M -( 2. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3) s -5 624 M -( 3. Specification of Requirements . . . . . . . . . . . . . . . 3) s -5 613 M -( 4. Architecture . . . . . . . . . . . . . . . . . . . . . . . . 3) s -5 602 M -( 4.1 Host Keys . . . . . . . . . . . . . . . . . . . . . . . . . 4) s -5 591 M -( 4.2 Extensibility . . . . . . . . . . . . . . . . . . . . . . . 5) s -5 580 M -( 4.3 Policy Issues . . . . . . . . . . . . . . . . . . . . . . . 5) s -5 569 M -( 4.4 Security Properties . . . . . . . . . . . . . . . . . . . . 6) s -5 558 M -( 4.5 Packet Size and Overhead . . . . . . . . . . . . . . . . . . 6) s -5 547 M -( 4.6 Localization and Character Set Support . . . . . . . . . . . 7) s -5 536 M -( 5. Data Type Representations Used in the SSH Protocols . . . . 8) s -5 525 M -( 6. Algorithm Naming . . . . . . . . . . . . . . . . . . . . . . 10) s -5 514 M -( 7. Message Numbers . . . . . . . . . . . . . . . . . . . . . . 11) s -5 503 M -( 8. IANA Considerations . . . . . . . . . . . . . . . . . . . . 11) s -5 492 M -( 9. Security Considerations . . . . . . . . . . . . . . . . . . 12) s -5 481 M -( 9.1 Pseudo-Random Number Generation . . . . . . . . . . . . . . 12) s -5 470 M -( 9.2 Transport . . . . . . . . . . . . . . . . . . . . . . . . . 13) s -5 459 M -( 9.2.1 Confidentiality . . . . . . . . . . . . . . . . . . . . . . 13) s -5 448 M -( 9.2.2 Data Integrity . . . . . . . . . . . . . . . . . . . . . . . 16) s -5 437 M -( 9.2.3 Replay . . . . . . . . . . . . . . . . . . . . . . . . . . . 16) s -5 426 M -( 9.2.4 Man-in-the-middle . . . . . . . . . . . . . . . . . . . . . 17) s -5 415 M -( 9.2.5 Denial-of-service . . . . . . . . . . . . . . . . . . . . . 19) s -5 404 M -( 9.2.6 Covert Channels . . . . . . . . . . . . . . . . . . . . . . 19) s -5 393 M -( 9.2.7 Forward Secrecy . . . . . . . . . . . . . . . . . . . . . . 20) s -5 382 M -( 9.3 Authentication Protocol . . . . . . . . . . . . . . . . . . 20) s -5 371 M -( 9.3.1 Weak Transport . . . . . . . . . . . . . . . . . . . . . . . 21) s -5 360 M -( 9.3.2 Debug messages . . . . . . . . . . . . . . . . . . . . . . . 21) s -5 349 M -( 9.3.3 Local security policy . . . . . . . . . . . . . . . . . . . 21) s -5 338 M -( 9.3.4 Public key authentication . . . . . . . . . . . . . . . . . 22) s -5 327 M -( 9.3.5 Password authentication . . . . . . . . . . . . . . . . . . 22) s -5 316 M -( 9.3.6 Host based authentication . . . . . . . . . . . . . . . . . 23) s -5 305 M -( 9.4 Connection protocol . . . . . . . . . . . . . . . . . . . . 23) s -5 294 M -( 9.4.1 End point security . . . . . . . . . . . . . . . . . . . . . 23) s -5 283 M -( 9.4.2 Proxy forwarding . . . . . . . . . . . . . . . . . . . . . . 23) s -5 272 M -( 9.4.3 X11 forwarding . . . . . . . . . . . . . . . . . . . . . . . 24) s -5 261 M -( Normative References . . . . . . . . . . . . . . . . . . . . 24) s -5 250 M -( Informative References . . . . . . . . . . . . . . . . . . . 25) s -5 239 M -( Authors' Addresses . . . . . . . . . . . . . . . . . . . . . 27) s -5 228 M -( Intellectual Property and Copyright Statements . . . . . . . 28) s -5 129 M -(Ylonen & Moffat Expires March 31, 2004 [Page 2]) s -_R -S -PStoPSsaved restore -%%Page: (2,3) 2 -userdict/PStoPSsaved save put -PStoPSmatrix setmatrix -595.000000 0.271378 translate -90 rotate -0.706651 dup scale -userdict/PStoPSmatrix matrix currentmatrix put -userdict/PStoPSclip{0 0 moveto - 595.000000 0 rlineto 0 842.000000 rlineto -595.000000 0 rlineto - closepath}put initclip -/showpage{}def/copypage{}def/erasepage{}def -PStoPSxform concat -%%BeginPageSetup -_S -75 0 translate -/pagenum 3 def -/fname () def -/fdir () def -/ftail () def -/user_header_p false def -%%EndPageSetup -5 723 M -(Internet-Draft SSH Protocol Architecture Oct 2003) s -5 690 M -(1. Contributors) s -5 668 M -( The major original contributors of this document were: Tatu Ylonen,) s -5 657 M -( Tero Kivinen, Timo J. Rinne, Sami Lehtinen \(all of SSH Communications) s -5 646 M -( Security Corp\), and Markku-Juhani O. Saarinen \(University of) s -5 635 M -( Jyvaskyla\)) s -5 613 M -( The document editor is: [email protected]. Comments on this) s -5 602 M -( internet draft should be sent to the IETF SECSH working group,) s -5 591 M -( details at: http://ietf.org/html.charters/secsh-charter.html) s -5 569 M -(2. Introduction) s -5 547 M -( SSH is a protocol for secure remote login and other secure network) s -5 536 M -( services over an insecure network. It consists of three major) s -5 525 M -( components:) s -5 514 M -( o The Transport Layer Protocol [SSH-TRANS] provides server) s -5 503 M -( authentication, confidentiality, and integrity. It may optionally) s -5 492 M -( also provide compression. The transport layer will typically be) s -5 481 M -( run over a TCP/IP connection, but might also be used on top of any) s -5 470 M -( other reliable data stream.) s -5 459 M -( o The User Authentication Protocol [SSH-USERAUTH] authenticates the) s -5 448 M -( client-side user to the server. It runs over the transport layer) s -5 437 M -( protocol.) s -5 426 M -( o The Connection Protocol [SSH-CONNECT] multiplexes the encrypted) s -5 415 M -( tunnel into several logical channels. It runs over the user) s -5 404 M -( authentication protocol.) s -5 382 M -( The client sends a service request once a secure transport layer) s -5 371 M -( connection has been established. A second service request is sent) s -5 360 M -( after user authentication is complete. This allows new protocols to) s -5 349 M -( be defined and coexist with the protocols listed above.) s -5 327 M -( The connection protocol provides channels that can be used for a wide) s -5 316 M -( range of purposes. Standard methods are provided for setting up) s -5 305 M -( secure interactive shell sessions and for forwarding \("tunneling"\)) s -5 294 M -( arbitrary TCP/IP ports and X11 connections.) s -5 272 M -(3. Specification of Requirements) s -5 250 M -( All documents related to the SSH protocols shall use the keywords) s -5 239 M -( "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD",) s -5 228 M -( "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" to describe) s -5 217 M -( requirements. They are to be interpreted as described in [RFC2119].) s -5 195 M -(4. Architecture) s -5 129 M -(Ylonen & Moffat Expires March 31, 2004 [Page 3]) s -_R -S -PStoPSsaved restore -userdict/PStoPSsaved save put -PStoPSmatrix setmatrix -595.000000 421.271378 translate -90 rotate -0.706651 dup scale -userdict/PStoPSmatrix matrix currentmatrix put -userdict/PStoPSclip{0 0 moveto - 595.000000 0 rlineto 0 842.000000 rlineto -595.000000 0 rlineto - closepath}put initclip -PStoPSxform concat -%%BeginPageSetup -_S -75 0 translate -/pagenum 4 def -/fname () def -/fdir () def -/ftail () def -/user_header_p false def -%%EndPageSetup -5 723 M -(Internet-Draft SSH Protocol Architecture Oct 2003) s -5 690 M -(4.1 Host Keys) s -5 668 M -( Each server host SHOULD have a host key. Hosts MAY have multiple) s -5 657 M -( host keys using multiple different algorithms. Multiple hosts MAY) s -5 646 M -( share the same host key. If a host has keys at all, it MUST have at) s -5 635 M -( least one key using each REQUIRED public key algorithm \(DSS) s -5 624 M -( [FIPS-186]\).) s -5 602 M -( The server host key is used during key exchange to verify that the) s -5 591 M -( client is really talking to the correct server. For this to be) s -5 580 M -( possible, the client must have a priori knowledge of the server's) s -5 569 M -( public host key.) s -5 547 M -( Two different trust models can be used:) s -5 536 M -( o The client has a local database that associates each host name \(as) s -5 525 M -( typed by the user\) with the corresponding public host key. This) s -5 514 M -( method requires no centrally administered infrastructure, and no) s -5 503 M -( third-party coordination. The downside is that the database of) s -5 492 M -( name-to-key associations may become burdensome to maintain.) s -5 481 M -( o The host name-to-key association is certified by some trusted) s -5 470 M -( certification authority. The client only knows the CA root key,) s -5 459 M -( and can verify the validity of all host keys certified by accepted) s -5 448 M -( CAs.) s -5 426 M -( The second alternative eases the maintenance problem, since) s -5 415 M -( ideally only a single CA key needs to be securely stored on the) s -5 404 M -( client. On the other hand, each host key must be appropriately) s -5 393 M -( certified by a central authority before authorization is possible.) s -5 382 M -( Also, a lot of trust is placed on the central infrastructure.) s -5 360 M -( The protocol provides the option that the server name - host key) s -5 349 M -( association is not checked when connecting to the host for the first) s -5 338 M -( time. This allows communication without prior communication of host) s -5 327 M -( keys or certification. The connection still provides protection) s -5 316 M -( against passive listening; however, it becomes vulnerable to active) s -5 305 M -( man-in-the-middle attacks. Implementations SHOULD NOT normally allow) s -5 294 M -( such connections by default, as they pose a potential security) s -5 283 M -( problem. However, as there is no widely deployed key infrastructure) s -5 272 M -( available on the Internet yet, this option makes the protocol much) s -5 261 M -( more usable during the transition time until such an infrastructure) s -5 250 M -( emerges, while still providing a much higher level of security than) s -5 239 M -( that offered by older solutions \(e.g. telnet [RFC-854] and rlogin) s -5 228 M -( [RFC-1282]\).) s -5 206 M -( Implementations SHOULD try to make the best effort to check host) s -5 195 M -( keys. An example of a possible strategy is to only accept a host key) s -5 184 M -( without checking the first time a host is connected, save the key in) s -5 173 M -( a local database, and compare against that key on all future) s -5 129 M -(Ylonen & Moffat Expires March 31, 2004 [Page 4]) s -_R -S -PStoPSsaved restore -%%Page: (4,5) 3 -userdict/PStoPSsaved save put -PStoPSmatrix setmatrix -595.000000 0.271378 translate -90 rotate -0.706651 dup scale -userdict/PStoPSmatrix matrix currentmatrix put -userdict/PStoPSclip{0 0 moveto - 595.000000 0 rlineto 0 842.000000 rlineto -595.000000 0 rlineto - closepath}put initclip -/showpage{}def/copypage{}def/erasepage{}def -PStoPSxform concat -%%BeginPageSetup -_S -75 0 translate -/pagenum 5 def -/fname () def -/fdir () def -/ftail () def -/user_header_p false def -%%EndPageSetup -5 723 M -(Internet-Draft SSH Protocol Architecture Oct 2003) s -5 690 M -( connections to that host.) s -5 668 M -( Implementations MAY provide additional methods for verifying the) s -5 657 M -( correctness of host keys, e.g. a hexadecimal fingerprint derived from) s -5 646 M -( the SHA-1 hash of the public key. Such fingerprints can easily be) s -5 635 M -( verified by using telephone or other external communication channels.) s -5 613 M -( All implementations SHOULD provide an option to not accept host keys) s -5 602 M -( that cannot be verified.) s -5 580 M -( We believe that ease of use is critical to end-user acceptance of) s -5 569 M -( security solutions, and no improvement in security is gained if the) s -5 558 M -( new solutions are not used. Thus, providing the option not to check) s -5 547 M -( the server host key is believed to improve the overall security of) s -5 536 M -( the Internet, even though it reduces the security of the protocol in) s -5 525 M -( configurations where it is allowed.) s -5 503 M -(4.2 Extensibility) s -5 481 M -( We believe that the protocol will evolve over time, and some) s -5 470 M -( organizations will want to use their own encryption, authentication) s -5 459 M -( and/or key exchange methods. Central registration of all extensions) s -5 448 M -( is cumbersome, especially for experimental or classified features.) s -5 437 M -( On the other hand, having no central registration leads to conflicts) s -5 426 M -( in method identifiers, making interoperability difficult.) s -5 404 M -( We have chosen to identify algorithms, methods, formats, and) s -5 393 M -( extension protocols with textual names that are of a specific format.) s -5 382 M -( DNS names are used to create local namespaces where experimental or) s -5 371 M -( classified extensions can be defined without fear of conflicts with) s -5 360 M -( other implementations.) s -5 338 M -( One design goal has been to keep the base protocol as simple as) s -5 327 M -( possible, and to require as few algorithms as possible. However, all) s -5 316 M -( implementations MUST support a minimal set of algorithms to ensure) s -5 305 M -( interoperability \(this does not imply that the local policy on all) s -5 294 M -( hosts would necessary allow these algorithms\). The mandatory) s -5 283 M -( algorithms are specified in the relevant protocol documents.) s -5 261 M -( Additional algorithms, methods, formats, and extension protocols can) s -5 250 M -( be defined in separate drafts. See Section Algorithm Naming \(Section) s -5 239 M -( 6\) for more information.) s -5 217 M -(4.3 Policy Issues) s -5 195 M -( The protocol allows full negotiation of encryption, integrity, key) s -5 184 M -( exchange, compression, and public key algorithms and formats.) s -5 173 M -( Encryption, integrity, public key, and compression algorithms can be) s -5 129 M -(Ylonen & Moffat Expires March 31, 2004 [Page 5]) s -_R -S -PStoPSsaved restore -userdict/PStoPSsaved save put -PStoPSmatrix setmatrix -595.000000 421.271378 translate -90 rotate -0.706651 dup scale -userdict/PStoPSmatrix matrix currentmatrix put -userdict/PStoPSclip{0 0 moveto - 595.000000 0 rlineto 0 842.000000 rlineto -595.000000 0 rlineto - closepath}put initclip -PStoPSxform concat -%%BeginPageSetup -_S -75 0 translate -/pagenum 6 def -/fname () def -/fdir () def -/ftail () def -/user_header_p false def -%%EndPageSetup -5 723 M -(Internet-Draft SSH Protocol Architecture Oct 2003) s -5 690 M -( different for each direction.) s -5 668 M -( The following policy issues SHOULD be addressed in the configuration) s -5 657 M -( mechanisms of each implementation:) s -5 646 M -( o Encryption, integrity, and compression algorithms, separately for) s -5 635 M -( each direction. The policy MUST specify which is the preferred) s -5 624 M -( algorithm \(e.g. the first algorithm listed in each category\).) s -5 613 M -( o Public key algorithms and key exchange method to be used for host) s -5 602 M -( authentication. The existence of trusted host keys for different) s -5 591 M -( public key algorithms also affects this choice.) s -5 580 M -( o The authentication methods that are to be required by the server) s -5 569 M -( for each user. The server's policy MAY require multiple) s -5 558 M -( authentication for some or all users. The required algorithms MAY) s -5 547 M -( depend on the location where the user is trying to log in from.) s -5 536 M -( o The operations that the user is allowed to perform using the) s -5 525 M -( connection protocol. Some issues are related to security; for) s -5 514 M -( example, the policy SHOULD NOT allow the server to start sessions) s -5 503 M -( or run commands on the client machine, and MUST NOT allow) s -5 492 M -( connections to the authentication agent unless forwarding such) s -5 481 M -( connections has been requested. Other issues, such as which TCP/) s -5 470 M -( IP ports can be forwarded and by whom, are clearly issues of local) s -5 459 M -( policy. Many of these issues may involve traversing or bypassing) s -5 448 M -( firewalls, and are interrelated with the local security policy.) s -5 426 M -(4.4 Security Properties) s -5 404 M -( The primary goal of the SSH protocol is improved security on the) s -5 393 M -( Internet. It attempts to do this in a way that is easy to deploy,) s -5 382 M -( even at the cost of absolute security.) s -5 371 M -( o All encryption, integrity, and public key algorithms used are) s -5 360 M -( well-known, well-established algorithms.) s -5 349 M -( o All algorithms are used with cryptographically sound key sizes) s -5 338 M -( that are believed to provide protection against even the strongest) s -5 327 M -( cryptanalytic attacks for decades.) s -5 316 M -( o All algorithms are negotiated, and in case some algorithm is) s -5 305 M -( broken, it is easy to switch to some other algorithm without) s -5 294 M -( modifying the base protocol.) s -5 272 M -( Specific concessions were made to make wide-spread fast deployment) s -5 261 M -( easier. The particular case where this comes up is verifying that) s -5 250 M -( the server host key really belongs to the desired host; the protocol) s -5 239 M -( allows the verification to be left out \(but this is NOT RECOMMENDED\).) s -5 228 M -( This is believed to significantly improve usability in the short) s -5 217 M -( term, until widespread Internet public key infrastructures emerge.) s -5 195 M -(4.5 Packet Size and Overhead) s -5 173 M -( Some readers will worry about the increase in packet size due to new) s -5 129 M -(Ylonen & Moffat Expires March 31, 2004 [Page 6]) s -_R -S -PStoPSsaved restore -%%Page: (6,7) 4 -userdict/PStoPSsaved save put -PStoPSmatrix setmatrix -595.000000 0.271378 translate -90 rotate -0.706651 dup scale -userdict/PStoPSmatrix matrix currentmatrix put -userdict/PStoPSclip{0 0 moveto - 595.000000 0 rlineto 0 842.000000 rlineto -595.000000 0 rlineto - closepath}put initclip -/showpage{}def/copypage{}def/erasepage{}def -PStoPSxform concat -%%BeginPageSetup -_S -75 0 translate -/pagenum 7 def -/fname () def -/fdir () def -/ftail () def -/user_header_p false def -%%EndPageSetup -5 723 M -(Internet-Draft SSH Protocol Architecture Oct 2003) s -5 690 M -( headers, padding, and MAC. The minimum packet size is in the order) s -5 679 M -( of 28 bytes \(depending on negotiated algorithms\). The increase is) s -5 668 M -( negligible for large packets, but very significant for one-byte) s -5 657 M -( packets \(telnet-type sessions\). There are, however, several factors) s -5 646 M -( that make this a non-issue in almost all cases:) s -5 635 M -( o The minimum size of a TCP/IP header is 32 bytes. Thus, the) s -5 624 M -( increase is actually from 33 to 51 bytes \(roughly\).) s -5 613 M -( o The minimum size of the data field of an Ethernet packet is 46) s -5 602 M -( bytes [RFC-894]. Thus, the increase is no more than 5 bytes. When) s -5 591 M -( Ethernet headers are considered, the increase is less than 10) s -5 580 M -( percent.) s -5 569 M -( o The total fraction of telnet-type data in the Internet is) s -5 558 M -( negligible, even with increased packet sizes.) s -5 536 M -( The only environment where the packet size increase is likely to have) s -5 525 M -( a significant effect is PPP [RFC-1134] over slow modem lines \(PPP) s -5 514 M -( compresses the TCP/IP headers, emphasizing the increase in packet) s -5 503 M -( size\). However, with modern modems, the time needed to transfer is in) s -5 492 M -( the order of 2 milliseconds, which is a lot faster than people can) s -5 481 M -( type.) s -5 459 M -( There are also issues related to the maximum packet size. To) s -5 448 M -( minimize delays in screen updates, one does not want excessively) s -5 437 M -( large packets for interactive sessions. The maximum packet size is) s -5 426 M -( negotiated separately for each channel.) s -5 404 M -(4.6 Localization and Character Set Support) s -5 382 M -( For the most part, the SSH protocols do not directly pass text that) s -5 371 M -( would be displayed to the user. However, there are some places where) s -5 360 M -( such data might be passed. When applicable, the character set for the) s -5 349 M -( data MUST be explicitly specified. In most places, ISO 10646 with) s -5 338 M -( UTF-8 encoding is used [RFC-2279]. When applicable, a field is also) s -5 327 M -( provided for a language tag [RFC-3066].) s -5 305 M -( One big issue is the character set of the interactive session. There) s -5 294 M -( is no clear solution, as different applications may display data in) s -5 283 M -( different formats. Different types of terminal emulation may also be) s -5 272 M -( employed in the client, and the character set to be used is) s -5 261 M -( effectively determined by the terminal emulation. Thus, no place is) s -5 250 M -( provided for directly specifying the character set or encoding for) s -5 239 M -( terminal session data. However, the terminal emulation type \(e.g.) s -5 228 M -( "vt100"\) is transmitted to the remote site, and it implicitly) s -5 217 M -( specifies the character set and encoding. Applications typically use) s -5 206 M -( the terminal type to determine what character set they use, or the) s -5 195 M -( character set is determined using some external means. The terminal) s -5 184 M -( emulation may also allow configuring the default character set. In) s -5 173 M -( any case, the character set for the terminal session is considered) s -5 129 M -(Ylonen & Moffat Expires March 31, 2004 [Page 7]) s -_R -S -PStoPSsaved restore -userdict/PStoPSsaved save put -PStoPSmatrix setmatrix -595.000000 421.271378 translate -90 rotate -0.706651 dup scale -userdict/PStoPSmatrix matrix currentmatrix put -userdict/PStoPSclip{0 0 moveto - 595.000000 0 rlineto 0 842.000000 rlineto -595.000000 0 rlineto - closepath}put initclip -PStoPSxform concat -%%BeginPageSetup -_S -75 0 translate -/pagenum 8 def -/fname () def -/fdir () def -/ftail () def -/user_header_p false def -%%EndPageSetup -5 723 M -(Internet-Draft SSH Protocol Architecture Oct 2003) s -5 690 M -( primarily a client local issue.) s -5 668 M -( Internal names used to identify algorithms or protocols are normally) s -5 657 M -( never displayed to users, and must be in US-ASCII.) s -5 635 M -( The client and server user names are inherently constrained by what) s -5 624 M -( the server is prepared to accept. They might, however, occasionally) s -5 613 M -( be displayed in logs, reports, etc. They MUST be encoded using ISO) s -5 602 M -( 10646 UTF-8, but other encodings may be required in some cases. It) s -5 591 M -( is up to the server to decide how to map user names to accepted user) s -5 580 M -( names. Straight bit-wise binary comparison is RECOMMENDED.) s -5 558 M -( For localization purposes, the protocol attempts to minimize the) s -5 547 M -( number of textual messages transmitted. When present, such messages) s -5 536 M -( typically relate to errors, debugging information, or some externally) s -5 525 M -( configured data. For data that is normally displayed, it SHOULD be) s -5 514 M -( possible to fetch a localized message instead of the transmitted) s -5 503 M -( message by using a numerical code. The remaining messages SHOULD be) s -5 492 M -( configurable.) s -5 470 M -(5. Data Type Representations Used in the SSH Protocols) s -5 459 M -( byte) s -5 437 M -( A byte represents an arbitrary 8-bit value \(octet\) [RFC-1700].) s -5 426 M -( Fixed length data is sometimes represented as an array of bytes,) s -5 415 M -( written byte[n], where n is the number of bytes in the array.) s -5 393 M -( boolean) s -5 371 M -( A boolean value is stored as a single byte. The value 0) s -5 360 M -( represents FALSE, and the value 1 represents TRUE. All non-zero) s -5 349 M -( values MUST be interpreted as TRUE; however, applications MUST NOT) s -5 338 M -( store values other than 0 and 1.) s -5 316 M -( uint32) s -5 294 M -( Represents a 32-bit unsigned integer. Stored as four bytes in the) s -5 283 M -( order of decreasing significance \(network byte order\). For) s -5 272 M -( example, the value 699921578 \(0x29b7f4aa\) is stored as 29 b7 f4) s -5 261 M -( aa.) s -5 239 M -( uint64) s -5 217 M -( Represents a 64-bit unsigned integer. Stored as eight bytes in) s -5 206 M -( the order of decreasing significance \(network byte order\).) s -5 129 M -(Ylonen & Moffat Expires March 31, 2004 [Page 8]) s -_R -S -PStoPSsaved restore -%%Page: (8,9) 5 -userdict/PStoPSsaved save put -PStoPSmatrix setmatrix -595.000000 0.271378 translate -90 rotate -0.706651 dup scale -userdict/PStoPSmatrix matrix currentmatrix put -userdict/PStoPSclip{0 0 moveto - 595.000000 0 rlineto 0 842.000000 rlineto -595.000000 0 rlineto - closepath}put initclip -/showpage{}def/copypage{}def/erasepage{}def -PStoPSxform concat -%%BeginPageSetup -_S -75 0 translate -/pagenum 9 def -/fname () def -/fdir () def -/ftail () def -/user_header_p false def -%%EndPageSetup -5 723 M -(Internet-Draft SSH Protocol Architecture Oct 2003) s -5 690 M -( string) s -5 668 M -( Arbitrary length binary string. Strings are allowed to contain) s -5 657 M -( arbitrary binary data, including null characters and 8-bit) s -5 646 M -( characters. They are stored as a uint32 containing its length) s -5 635 M -( \(number of bytes that follow\) and zero \(= empty string\) or more) s -5 624 M -( bytes that are the value of the string. Terminating null) s -5 613 M -( characters are not used.) s -5 591 M -( Strings are also used to store text. In that case, US-ASCII is) s -5 580 M -( used for internal names, and ISO-10646 UTF-8 for text that might) s -5 569 M -( be displayed to the user. The terminating null character SHOULD) s -5 558 M -( NOT normally be stored in the string.) s -5 536 M -( For example, the US-ASCII string "testing" is represented as 00 00) s -5 525 M -( 00 07 t e s t i n g. The UTF8 mapping does not alter the encoding) s -5 514 M -( of US-ASCII characters.) s -5 492 M -( mpint) s -5 470 M -( Represents multiple precision integers in two's complement format,) s -5 459 M -( stored as a string, 8 bits per byte, MSB first. Negative numbers) s -5 448 M -( have the value 1 as the most significant bit of the first byte of) s -5 437 M -( the data partition. If the most significant bit would be set for a) s -5 426 M -( positive number, the number MUST be preceded by a zero byte.) s -5 415 M -( Unnecessary leading bytes with the value 0 or 255 MUST NOT be) s -5 404 M -( included. The value zero MUST be stored as a string with zero) s -5 393 M -( bytes of data.) s -5 371 M -( By convention, a number that is used in modular computations in) s -5 360 M -( Z_n SHOULD be represented in the range 0 <= x < n.) s -5 338 M -( Examples:) s -5 327 M -( value \(hex\) representation \(hex\)) s -5 316 M -( ---------------------------------------------------------------) s -5 305 M -( 0 00 00 00 00) s -5 294 M -( 9a378f9b2e332a7 00 00 00 08 09 a3 78 f9 b2 e3 32 a7) s -5 283 M -( 80 00 00 00 02 00 80) s -5 272 M -( -1234 00 00 00 02 ed cc) s -5 261 M -( -deadbeef 00 00 00 05 ff 21 52 41 11) s -5 217 M -( name-list) s -5 195 M -( A string containing a comma separated list of names. A name list) s -5 184 M -( is represented as a uint32 containing its length \(number of bytes) s -5 173 M -( that follow\) followed by a comma-separated list of zero or more) s -5 129 M -(Ylonen & Moffat Expires March 31, 2004 [Page 9]) s -_R -S -PStoPSsaved restore -userdict/PStoPSsaved save put -PStoPSmatrix setmatrix -595.000000 421.271378 translate -90 rotate -0.706651 dup scale -userdict/PStoPSmatrix matrix currentmatrix put -userdict/PStoPSclip{0 0 moveto - 595.000000 0 rlineto 0 842.000000 rlineto -595.000000 0 rlineto - closepath}put initclip -PStoPSxform concat -%%BeginPageSetup -_S -75 0 translate -/pagenum 10 def -/fname () def -/fdir () def -/ftail () def -/user_header_p false def -%%EndPageSetup -5 723 M -(Internet-Draft SSH Protocol Architecture Oct 2003) s -5 690 M -( names. A name MUST be non-zero length, and it MUST NOT contain a) s -5 679 M -( comma \(','\). Context may impose additional restrictions on the) s -5 668 M -( names; for example, the names in a list may have to be valid) s -5 657 M -( algorithm identifier \(see Algorithm Naming below\), or [RFC-3066]) s -5 646 M -( language tags. The order of the names in a list may or may not be) s -5 635 M -( significant, also depending on the context where the list is is) s -5 624 M -( used. Terminating NUL characters are not used, neither for the) s -5 613 M -( individual names, nor for the list as a whole.) s -5 591 M -( Examples:) s -5 580 M -( value representation \(hex\)) s -5 569 M -( ---------------------------------------) s -5 558 M -( \(\), the empty list 00 00 00 00) s -5 547 M -( \("zlib"\) 00 00 00 04 7a 6c 69 62) s -5 536 M -( \("zlib", "none"\) 00 00 00 09 7a 6c 69 62 2c 6e 6f 6e 65) s -5 481 M -(6. Algorithm Naming) s -5 459 M -( The SSH protocols refer to particular hash, encryption, integrity,) s -5 448 M -( compression, and key exchange algorithms or protocols by names.) s -5 437 M -( There are some standard algorithms that all implementations MUST) s -5 426 M -( support. There are also algorithms that are defined in the protocol) s -5 415 M -( specification but are OPTIONAL. Furthermore, it is expected that) s -5 404 M -( some organizations will want to use their own algorithms.) s -5 382 M -( In this protocol, all algorithm identifiers MUST be printable) s -5 371 M -( US-ASCII non-empty strings no longer than 64 characters. Names MUST) s -5 360 M -( be case-sensitive.) s -5 338 M -( There are two formats for algorithm names:) s -5 327 M -( o Names that do not contain an at-sign \(@\) are reserved to be) s -5 316 M -( assigned by IETF consensus \(RFCs\). Examples include `3des-cbc',) s -5 305 M -( `sha-1', `hmac-sha1', and `zlib' \(the quotes are not part of the) s -5 294 M -( name\). Names of this format MUST NOT be used without first) s -5 283 M -( registering them. Registered names MUST NOT contain an at-sign) s -5 272 M -( \(@\) or a comma \(,\).) s -5 261 M -( o Anyone can define additional algorithms by using names in the) s -5 250 M -( format name@domainname, e.g. "[email protected]". The) s -5 239 M -( format of the part preceding the at sign is not specified; it MUST) s -5 228 M -( consist of US-ASCII characters except at-sign and comma. The part) s -5 217 M -( following the at-sign MUST be a valid fully qualified internet) s -5 206 M -( domain name [RFC-1034] controlled by the person or organization) s -5 195 M -( defining the name. It is up to each domain how it manages its) s -5 184 M -( local namespace.) s -5 129 M -(Ylonen & Moffat Expires March 31, 2004 [Page 10]) s -_R -S -PStoPSsaved restore -%%Page: (10,11) 6 -userdict/PStoPSsaved save put -PStoPSmatrix setmatrix -595.000000 0.271378 translate -90 rotate -0.706651 dup scale -userdict/PStoPSmatrix matrix currentmatrix put -userdict/PStoPSclip{0 0 moveto - 595.000000 0 rlineto 0 842.000000 rlineto -595.000000 0 rlineto - closepath}put initclip -/showpage{}def/copypage{}def/erasepage{}def -PStoPSxform concat -%%BeginPageSetup -_S -75 0 translate -/pagenum 11 def -/fname () def -/fdir () def -/ftail () def -/user_header_p false def -%%EndPageSetup -5 723 M -(Internet-Draft SSH Protocol Architecture Oct 2003) s -5 690 M -(7. Message Numbers) s -5 668 M -( SSH packets have message numbers in the range 1 to 255. These numbers) s -5 657 M -( have been allocated as follows:) s -5 624 M -( Transport layer protocol:) s -5 602 M -( 1 to 19 Transport layer generic \(e.g. disconnect, ignore, debug,) s -5 591 M -( etc.\)) s -5 580 M -( 20 to 29 Algorithm negotiation) s -5 569 M -( 30 to 49 Key exchange method specific \(numbers can be reused for) s -5 558 M -( different authentication methods\)) s -5 536 M -( User authentication protocol:) s -5 514 M -( 50 to 59 User authentication generic) s -5 503 M -( 60 to 79 User authentication method specific \(numbers can be) s -5 492 M -( reused for different authentication methods\)) s -5 470 M -( Connection protocol:) s -5 448 M -( 80 to 89 Connection protocol generic) s -5 437 M -( 90 to 127 Channel related messages) s -5 415 M -( Reserved for client protocols:) s -5 393 M -( 128 to 191 Reserved) s -5 371 M -( Local extensions:) s -5 349 M -( 192 to 255 Local extensions) s -5 305 M -(8. IANA Considerations) s -5 283 M -( The initial state of the IANA registry is detailed in [SSH-NUMBERS].) s -5 261 M -( Allocation of the following types of names in the SSH protocols is) s -5 250 M -( assigned by IETF consensus:) s -5 239 M -( o SSH encryption algorithm names,) s -5 228 M -( o SSH MAC algorithm names,) s -5 217 M -( o SSH public key algorithm names \(public key algorithm also implies) s -5 206 M -( encoding and signature/encryption capability\),) s -5 195 M -( o SSH key exchange method names, and) s -5 184 M -( o SSH protocol \(service\) names.) s -5 129 M -(Ylonen & Moffat Expires March 31, 2004 [Page 11]) s -_R -S -PStoPSsaved restore -userdict/PStoPSsaved save put -PStoPSmatrix setmatrix -595.000000 421.271378 translate -90 rotate -0.706651 dup scale -userdict/PStoPSmatrix matrix currentmatrix put -userdict/PStoPSclip{0 0 moveto - 595.000000 0 rlineto 0 842.000000 rlineto -595.000000 0 rlineto - closepath}put initclip -PStoPSxform concat -%%BeginPageSetup -_S -75 0 translate -/pagenum 12 def -/fname () def -/fdir () def -/ftail () def -/user_header_p false def -%%EndPageSetup -5 723 M -(Internet-Draft SSH Protocol Architecture Oct 2003) s -5 690 M -( These names MUST be printable US-ASCII strings, and MUST NOT contain) s -5 679 M -( the characters at-sign \('@'\), comma \(','\), or whitespace or control) s -5 668 M -( characters \(ASCII codes 32 or less\). Names are case-sensitive, and) s -5 657 M -( MUST NOT be longer than 64 characters.) s -5 635 M -( Names with the at-sign \('@'\) in them are allocated by the owner of) s -5 624 M -( DNS name after the at-sign \(hierarchical allocation in [RFC-2343]\),) s -5 613 M -( otherwise the same restrictions as above.) s -5 591 M -( Each category of names listed above has a separate namespace.) s -5 580 M -( However, using the same name in multiple categories SHOULD be avoided) s -5 569 M -( to minimize confusion.) s -5 547 M -( Message numbers \(see Section Message Numbers \(Section 7\)\) in the) s -5 536 M -( range of 0..191 are allocated via IETF consensus; message numbers in) s -5 525 M -( the 192..255 range \(the "Local extensions" set\) are reserved for) s -5 514 M -( private use.) s -5 492 M -(9. Security Considerations) s -5 470 M -( In order to make the entire body of Security Considerations more) s -5 459 M -( accessible, Security Considerations for the transport,) s -5 448 M -( authentication, and connection documents have been gathered here.) s -5 426 M -( The transport protocol [1] provides a confidential channel over an) s -5 415 M -( insecure network. It performs server host authentication, key) s -5 404 M -( exchange, encryption, and integrity protection. It also derives a) s -5 393 M -( unique session id that may be used by higher-level protocols.) s -5 371 M -( The authentication protocol [2] provides a suite of mechanisms which) s -5 360 M -( can be used to authenticate the client user to the server.) s -5 349 M -( Individual mechanisms specified in the in authentication protocol use) s -5 338 M -( the session id provided by the transport protocol and/or depend on) s -5 327 M -( the security and integrity guarantees of the transport protocol.) s -5 305 M -( The connection protocol [3] specifies a mechanism to multiplex) s -5 294 M -( multiple streams [channels] of data over the confidential and) s -5 283 M -( authenticated transport. It also specifies channels for accessing an) s -5 272 M -( interactive shell, for 'proxy-forwarding' various external protocols) s -5 261 M -( over the secure transport \(including arbitrary TCP/IP protocols\), and) s -5 250 M -( for accessing secure 'subsystems' on the server host.) s -5 228 M -(9.1 Pseudo-Random Number Generation) s -5 206 M -( This protocol binds each session key to the session by including) s -5 195 M -( random, session specific data in the hash used to produce session) s -5 184 M -( keys. Special care should be taken to ensure that all of the random) s -5 173 M -( numbers are of good quality. If the random data here \(e.g., DH) s -5 129 M -(Ylonen & Moffat Expires March 31, 2004 [Page 12]) s -_R -S -PStoPSsaved restore -%%Page: (12,13) 7 -userdict/PStoPSsaved save put -PStoPSmatrix setmatrix -595.000000 0.271378 translate -90 rotate -0.706651 dup scale -userdict/PStoPSmatrix matrix currentmatrix put -userdict/PStoPSclip{0 0 moveto - 595.000000 0 rlineto 0 842.000000 rlineto -595.000000 0 rlineto - closepath}put initclip -/showpage{}def/copypage{}def/erasepage{}def -PStoPSxform concat -%%BeginPageSetup -_S -75 0 translate -/pagenum 13 def -/fname () def -/fdir () def -/ftail () def -/user_header_p false def -%%EndPageSetup -5 723 M -(Internet-Draft SSH Protocol Architecture Oct 2003) s -5 690 M -( parameters\) are pseudo-random then the pseudo-random number generator) s -5 679 M -( should be cryptographically secure \(i.e., its next output not easily) s -5 668 M -( guessed even when knowing all previous outputs\) and, furthermore,) s -5 657 M -( proper entropy needs to be added to the pseudo-random number) s -5 646 M -( generator. RFC 1750 [1750] offers suggestions for sources of random) s -5 635 M -( numbers and entropy. Implementors should note the importance of) s -5 624 M -( entropy and the well-meant, anecdotal warning about the difficulty in) s -5 613 M -( properly implementing pseudo-random number generating functions.) s -5 591 M -( The amount of entropy available to a given client or server may) s -5 580 M -( sometimes be less than what is required. In this case one must) s -5 569 M -( either resort to pseudo-random number generation regardless of) s -5 558 M -( insufficient entropy or refuse to run the protocol. The latter is) s -5 547 M -( preferable.) s -5 525 M -(9.2 Transport) s -5 503 M -(9.2.1 Confidentiality) s -5 481 M -( It is beyond the scope of this document and the Secure Shell Working) s -5 470 M -( Group to analyze or recommend specific ciphers other than the ones) s -5 459 M -( which have been established and accepted within the industry. At the) s -5 448 M -( time of this writing, ciphers commonly in use include 3DES, ARCFOUR,) s -5 437 M -( twofish, serpent and blowfish. AES has been accepted by The) s -5 426 M -( published as a US Federal Information Processing Standards [FIPS-197]) s -5 415 M -( and the cryptographic community as being acceptable for this purpose) s -5 404 M -( as well has accepted AES. As always, implementors and users should) s -5 393 M -( check current literature to ensure that no recent vulnerabilities) s -5 382 M -( have been found in ciphers used within products. Implementors should) s -5 371 M -( also check to see which ciphers are considered to be relatively) s -5 360 M -( stronger than others and should recommend their use to users over) s -5 349 M -( relatively weaker ciphers. It would be considered good form for an) s -5 338 M -( implementation to politely and unobtrusively notify a user that a) s -5 327 M -( stronger cipher is available and should be used when a weaker one is) s -5 316 M -( actively chosen.) s -5 294 M -( The "none" cipher is provided for debugging and SHOULD NOT be used) s -5 283 M -( except for that purpose. It's cryptographic properties are) s -5 272 M -( sufficiently described in RFC 2410, which will show that its use does) s -5 261 M -( not meet the intent of this protocol.) s -5 239 M -( The relative merits of these and other ciphers may also be found in) s -5 228 M -( current literature. Two references that may provide information on) s -5 217 M -( the subject are [SCHNEIER] and [KAUFMAN,PERLMAN,SPECINER]. Both of) s -5 206 M -( these describe the CBC mode of operation of certain ciphers and the) s -5 195 M -( weakness of this scheme. Essentially, this mode is theoretically) s -5 184 M -( vulnerable to chosen cipher-text attacks because of the high) s -5 173 M -( predictability of the start of packet sequence. However, this attack) s -5 129 M -(Ylonen & Moffat Expires March 31, 2004 [Page 13]) s -_R -S -PStoPSsaved restore -userdict/PStoPSsaved save put -PStoPSmatrix setmatrix -595.000000 421.271378 translate -90 rotate -0.706651 dup scale -userdict/PStoPSmatrix matrix currentmatrix put -userdict/PStoPSclip{0 0 moveto - 595.000000 0 rlineto 0 842.000000 rlineto -595.000000 0 rlineto - closepath}put initclip -PStoPSxform concat -%%BeginPageSetup -_S -75 0 translate -/pagenum 14 def -/fname () def -/fdir () def -/ftail () def -/user_header_p false def -%%EndPageSetup -5 723 M -(Internet-Draft SSH Protocol Architecture Oct 2003) s -5 690 M -( is still deemed difficult and not considered fully practicable) s -5 679 M -( especially if relatively longer block sizes are used.) s -5 657 M -( Additionally, another CBC mode attack may be mitigated through the) s -5 646 M -( insertion of packets containing SSH_MSG_IGNORE. Without this) s -5 635 M -( technique, a specific attack may be successful. For this attack) s -5 624 M -( \(commonly known as the Rogaway attack) s -5 613 M -( [ROGAWAY],[DAI],[BELLARE,KOHNO,NAMPREMPRE]\) to work, the attacker) s -5 602 M -( would need to know the IV of the next block that is going to be) s -5 591 M -( encrypted. In CBC mode that is the output of the encryption of the) s -5 580 M -( previous block. If the attacker does not have any way to see the) s -5 569 M -( packet yet \(i.e it is in the internal buffers of the ssh) s -5 558 M -( implementation or even in the kernel\) then this attack will not work.) s -5 547 M -( If the last packet has been sent out to the network \(i.e the attacker) s -5 536 M -( has access to it\) then he can use the attack.) s -5 514 M -( In the optimal case an implementor would need to add an extra packet) s -5 503 M -( only if the packet has been sent out onto the network and there are) s -5 492 M -( no other packets waiting for transmission. Implementors may wish to) s -5 481 M -( check to see if there are any unsent packets awaiting transmission,) s -5 470 M -( but unfortunately it is not normally easy to obtain this information) s -5 459 M -( from the kernel or buffers. If there are not, then a packet) s -5 448 M -( containing SSH_MSG_IGNORE SHOULD be sent. If a new packet is added) s -5 437 M -( to the stream every time the attacker knows the IV that is supposed) s -5 426 M -( to be used for the next packet, then the attacker will not be able to) s -5 415 M -( guess the correct IV, thus the attack will never be successfull.) s -5 393 M -( As an example, consider the following case:) s -5 360 M -( Client Server) s -5 349 M -( ------ ------) s -5 338 M -( TCP\(seq=x, len=500\) ->) s -5 327 M -( contains Record 1) s -5 305 M -( [500 ms passes, no ACK]) s -5 283 M -( TCP\(seq=x, len=1000\) ->) s -5 272 M -( contains Records 1,2) s -5 250 M -( ACK) s -5 217 M -( 1. The Nagle algorithm + TCP retransmits mean that the two records) s -5 206 M -( get coalesced into a single TCP segment) s -5 195 M -( 2. Record 2 is *not* at the beginning of the TCP segment and never) s -5 184 M -( will be, since it gets ACKed.) s -5 129 M -(Ylonen & Moffat Expires March 31, 2004 [Page 14]) s -_R -S -PStoPSsaved restore -%%Page: (14,15) 8 -userdict/PStoPSsaved save put -PStoPSmatrix setmatrix -595.000000 0.271378 translate -90 rotate -0.706651 dup scale -userdict/PStoPSmatrix matrix currentmatrix put -userdict/PStoPSclip{0 0 moveto - 595.000000 0 rlineto 0 842.000000 rlineto -595.000000 0 rlineto - closepath}put initclip -/showpage{}def/copypage{}def/erasepage{}def -PStoPSxform concat -%%BeginPageSetup -_S -75 0 translate -/pagenum 15 def -/fname () def -/fdir () def -/ftail () def -/user_header_p false def -%%EndPageSetup -5 723 M -(Internet-Draft SSH Protocol Architecture Oct 2003) s -5 690 M -( 3. Yet, the attack is possible because Record 1 has already been) s -5 679 M -( seen.) s -5 657 M -( As this example indicates, it's totally unsafe to use the existence) s -5 646 M -( of unflushed data in the TCP buffers proper as a guide to whether you) s -5 635 M -( need an empty packet, since when you do the second write\(\), the) s -5 624 M -( buffers will contain the un-ACKed Record 1.) s -5 129 M -(Ylonen & Moffat Expires March 31, 2004 [Page 15]) s -_R -S -PStoPSsaved restore -userdict/PStoPSsaved save put -PStoPSmatrix setmatrix -595.000000 421.271378 translate -90 rotate -0.706651 dup scale -userdict/PStoPSmatrix matrix currentmatrix put -userdict/PStoPSclip{0 0 moveto - 595.000000 0 rlineto 0 842.000000 rlineto -595.000000 0 rlineto - closepath}put initclip -PStoPSxform concat -%%BeginPageSetup -_S -75 0 translate -/pagenum 16 def -/fname () def -/fdir () def -/ftail () def -/user_header_p false def -%%EndPageSetup -5 723 M -(Internet-Draft SSH Protocol Architecture Oct 2003) s -5 690 M -( On the other hand, it's perfectly safe to have the following) s -5 679 M -( situation:) s -5 646 M -( Client Server) s -5 635 M -( ------ ------) s -5 624 M -( TCP\(seq=x, len=500\) ->) s -5 613 M -( contains SSH_MSG_IGNORE) s -5 591 M -( TCP\(seq=y, len=500\) ->) s -5 580 M -( contains Data) s -5 558 M -( Provided that the IV for second SSH Record is fixed after the data for) s -5 547 M -( the Data packet is determined -i.e. you do:) s -5 536 M -( read from user) s -5 525 M -( encrypt null packet) s -5 514 M -( encrypt data packet) s -5 481 M -(9.2.2 Data Integrity) s -5 459 M -( This protocol does allow the Data Integrity mechanism to be disabled.) s -5 448 M -( Implementors SHOULD be wary of exposing this feature for any purpose) s -5 437 M -( other than debugging. Users and administrators SHOULD be explicitly) s -5 426 M -( warned anytime the "none" MAC is enabled.) s -5 404 M -( So long as the "none" MAC is not used, this protocol provides data) s -5 393 M -( integrity.) s -5 371 M -( Because MACs use a 32 bit sequence number, they might start to leak) s -5 360 M -( information after 2**32 packets have been sent. However, following) s -5 349 M -( the rekeying recommendations should prevent this attack. The) s -5 338 M -( transport protocol [1] recommends rekeying after one gigabyte of) s -5 327 M -( data, and the smallest possible packet is 16 bytes. Therefore,) s -5 316 M -( rekeying SHOULD happen after 2**28 packets at the very most.) s -5 294 M -(9.2.3 Replay) s -5 272 M -( The use of a MAC other than 'none' provides integrity and) s -5 261 M -( authentication. In addition, the transport protocol provides a) s -5 250 M -( unique session identifier \(bound in part to pseudo-random data that) s -5 239 M -( is part of the algorithm and key exchange process\) that can be used) s -5 228 M -( by higher level protocols to bind data to a given session and prevent) s -5 217 M -( replay of data from prior sessions. For example, the authentication) s -5 206 M -( protocol uses this to prevent replay of signatures from previous) s -5 195 M -( sessions. Because public key authentication exchanges are) s -5 184 M -( cryptographically bound to the session \(i.e., to the initial key) s -5 173 M -( exchange\) they cannot be successfully replayed in other sessions.) s -5 129 M -(Ylonen & Moffat Expires March 31, 2004 [Page 16]) s -_R -S -PStoPSsaved restore -%%Page: (16,17) 9 -userdict/PStoPSsaved save put -PStoPSmatrix setmatrix -595.000000 0.271378 translate -90 rotate -0.706651 dup scale -userdict/PStoPSmatrix matrix currentmatrix put -userdict/PStoPSclip{0 0 moveto - 595.000000 0 rlineto 0 842.000000 rlineto -595.000000 0 rlineto - closepath}put initclip -/showpage{}def/copypage{}def/erasepage{}def -PStoPSxform concat -%%BeginPageSetup -_S -75 0 translate -/pagenum 17 def -/fname () def -/fdir () def -/ftail () def -/user_header_p false def -%%EndPageSetup -5 723 M -(Internet-Draft SSH Protocol Architecture Oct 2003) s -5 690 M -( Note that the session ID can be made public without harming the) s -5 679 M -( security of the protocol.) s -5 657 M -( If two session happen to have the same session ID [hash of key) s -5 646 M -( exchanges] then packets from one can be replayed against the other.) s -5 635 M -( It must be stressed that the chances of such an occurrence are,) s -5 624 M -( needless to say, minimal when using modern cryptographic methods.) s -5 613 M -( This is all the more so true when specifying larger hash function) s -5 602 M -( outputs and DH parameters.) s -5 580 M -( Replay detection using monotonically increasing sequence numbers as) s -5 569 M -( input to the MAC, or HMAC in some cases, is described in [RFC2085] />) s -5 558 M -( [RFC2246], [RFC2743], [RFC1964], [RFC2025], and [RFC1510]. The) s -5 547 M -( underlying construct is discussed in [RFC2104]. Essentially a) s -5 536 M -( different sequence number in each packet ensures that at least this) s -5 525 M -( one input to the MAC function will be unique and will provide a) s -5 514 M -( nonrecurring MAC output that is not predictable to an attacker. If) s -5 503 M -( the session stays active long enough, however, this sequence number) s -5 492 M -( will wrap. This event may provide an attacker an opportunity to) s -5 481 M -( replay a previously recorded packet with an identical sequence number) s -5 470 M -( but only if the peers have not rekeyed since the transmission of the) s -5 459 M -( first packet with that sequence number. If the peers have rekeyed,) s -5 448 M -( then the replay will be detected as the MAC check will fail. For) s -5 437 M -( this reason, it must be emphasized that peers MUST rekey before a) s -5 426 M -( wrap of the sequence numbers. Naturally, if an attacker does attempt) s -5 415 M -( to replay a captured packet before the peers have rekeyed, then the) s -5 404 M -( receiver of the duplicate packet will not be able to validate the MAC) s -5 393 M -( and it will be discarded. The reason that the MAC will fail is) s -5 382 M -( because the receiver will formulate a MAC based upon the packet) s -5 371 M -( contents, the shared secret, and the expected sequence number. Since) s -5 360 M -( the replayed packet will not be using that expected sequence number) s -5 349 M -( \(the sequence number of the replayed packet will have already been) s -5 338 M -( passed by the receiver\) then the calculated MAC will not match the) s -5 327 M -( MAC received with the packet.) s -5 305 M -(9.2.4 Man-in-the-middle) s -5 283 M -( This protocol makes no assumptions nor provisions for an) s -5 272 M -( infrastructure or means for distributing the public keys of hosts. It) s -5 261 M -( is expected that this protocol will sometimes be used without first) s -5 250 M -( verifying the association between the server host key and the server) s -5 239 M -( host name. Such usage is vulnerable to man-in-the-middle attacks.) s -5 228 M -( This section describes this and encourages administrators and users) s -5 217 M -( to understand the importance of verifying this association before any) s -5 206 M -( session is initiated.) s -5 184 M -( There are three cases of man-in-the-middle attacks to consider. The) s -5 173 M -( first is where an attacker places a device between the client and the) s -5 129 M -(Ylonen & Moffat Expires March 31, 2004 [Page 17]) s -_R -S -PStoPSsaved restore -userdict/PStoPSsaved save put -PStoPSmatrix setmatrix -595.000000 421.271378 translate -90 rotate -0.706651 dup scale -userdict/PStoPSmatrix matrix currentmatrix put -userdict/PStoPSclip{0 0 moveto - 595.000000 0 rlineto 0 842.000000 rlineto -595.000000 0 rlineto - closepath}put initclip -PStoPSxform concat -%%BeginPageSetup -_S -75 0 translate -/pagenum 18 def -/fname () def -/fdir () def -/ftail () def -/user_header_p false def -%%EndPageSetup -5 723 M -(Internet-Draft SSH Protocol Architecture Oct 2003) s -5 690 M -( server before the session is initiated. In this case, the attack) s -5 679 M -( device is trying to mimic the legitimate server and will offer its) s -5 668 M -( public key to the client when the client initiates a session. If it) s -5 657 M -( were to offer the public key of the server, then it would not be able) s -5 646 M -( to decrypt or sign the transmissions between the legitimate server) s -5 635 M -( and the client unless it also had access to the private-key of the) s -5 624 M -( host. The attack device will also, simultaneously to this, initiate) s -5 613 M -( a session to the legitimate server masquerading itself as the client.) s -5 602 M -( If the public key of the server had been securely distributed to the) s -5 591 M -( client prior to that session initiation, the key offered to the) s -5 580 M -( client by the attack device will not match the key stored on the) s -5 569 M -( client. In that case, the user SHOULD be given a warning that the) s -5 558 M -( offered host key does not match the host key cached on the client.) s -5 547 M -( As described in Section 3.1 of [ARCH], the user may be free to accept) s -5 536 M -( the new key and continue the session. It is RECOMMENDED that the) s -5 525 M -( warning provide sufficient information to the user of the client) s -5 514 M -( device so they may make an informed decision. If the user chooses to) s -5 503 M -( continue the session with the stored public-key of the server \(not) s -5 492 M -( the public-key offered at the start of the session\), then the session) s -5 481 M -( specific data between the attacker and server will be different) s -5 470 M -( between the client-to-attacker session and the attacker-to-server) s -5 459 M -( sessions due to the randomness discussed above. From this, the) s -5 448 M -( attacker will not be able to make this attack work since the attacker) s -5 437 M -( will not be able to correctly sign packets containing this session) s -5 426 M -( specific data from the server since he does not have the private key) s -5 415 M -( of that server.) s -5 393 M -( The second case that should be considered is similar to the first) s -5 382 M -( case in that it also happens at the time of connection but this case) s -5 371 M -( points out the need for the secure distribution of server public) s -5 360 M -( keys. If the server public keys are not securely distributed then) s -5 349 M -( the client cannot know if it is talking to the intended server. An) s -5 338 M -( attacker may use social engineering techniques to pass off server) s -5 327 M -( keys to unsuspecting users and may then place a man-in-the-middle) s -5 316 M -( attack device between the legitimate server and the clients. If this) s -5 305 M -( is allowed to happen then the clients will form client-to-attacker) s -5 294 M -( sessions and the attacker will form attacker-to-server sessions and) s -5 283 M -( will be able to monitor and manipulate all of the traffic between the) s -5 272 M -( clients and the legitimate servers. Server administrators are) s -5 261 M -( encouraged to make host key fingerprints available for checking by) s -5 250 M -( some means whose security does not rely on the integrity of the) s -5 239 M -( actual host keys. Possible mechanisms are discussed in Section 3.1) s -5 228 M -( of [SSH-ARCH] and may also include secured Web pages, physical pieces) s -5 217 M -( of paper, etc. Implementors SHOULD provide recommendations on how) s -5 206 M -( best to do this with their implementation. Because the protocol is) s -5 195 M -( extensible, future extensions to the protocol may provide better) s -5 184 M -( mechanisms for dealing with the need to know the server's host key) s -5 173 M -( before connecting. For example, making the host key fingerprint) s -5 129 M -(Ylonen & Moffat Expires March 31, 2004 [Page 18]) s -_R -S -PStoPSsaved restore -%%Page: (18,19) 10 -userdict/PStoPSsaved save put -PStoPSmatrix setmatrix -595.000000 0.271378 translate -90 rotate -0.706651 dup scale -userdict/PStoPSmatrix matrix currentmatrix put -userdict/PStoPSclip{0 0 moveto - 595.000000 0 rlineto 0 842.000000 rlineto -595.000000 0 rlineto - closepath}put initclip -/showpage{}def/copypage{}def/erasepage{}def -PStoPSxform concat -%%BeginPageSetup -_S -75 0 translate -/pagenum 19 def -/fname () def -/fdir () def -/ftail () def -/user_header_p false def -%%EndPageSetup -5 723 M -(Internet-Draft SSH Protocol Architecture Oct 2003) s -5 690 M -( available through a secure DNS lookup, or using kerberos over gssapi) s -5 679 M -( during key exchange to authenticate the server are possibilities.) s -5 657 M -( In the third man-in-the-middle case, attackers may attempt to) s -5 646 M -( manipulate packets in transit between peers after the session has) s -5 635 M -( been established. As described in the Replay part of this section, a) s -5 624 M -( successful attack of this nature is very improbable. As in the) s -5 613 M -( Replay section, this reasoning does assume that the MAC is secure and) s -5 602 M -( that it is infeasible to construct inputs to a MAC algorithm to give) s -5 591 M -( a known output. This is discussed in much greater detail in Section) s -5 580 M -( 6 of RFC 2104. If the MAC algorithm has a vulnerability or is weak) s -5 569 M -( enough, then the attacker may be able to specify certain inputs to) s -5 558 M -( yield a known MAC. With that they may be able to alter the contents) s -5 547 M -( of a packet in transit. Alternatively the attacker may be able to) s -5 536 M -( exploit the algorithm vulnerability or weakness to find the shared) s -5 525 M -( secret by reviewing the MACs from captured packets. In either of) s -5 514 M -( those cases, an attacker could construct a packet or packets that) s -5 503 M -( could be inserted into an SSH stream. To prevent that, implementors) s -5 492 M -( are encouraged to utilize commonly accepted MAC algorithms and) s -5 481 M -( administrators are encouraged to watch current literature and) s -5 470 M -( discussions of cryptography to ensure that they are not using a MAC) s -5 459 M -( algorithm that has a recently found vulnerability or weakness.) s -5 437 M -( In summary, the use of this protocol without a reliable association) s -5 426 M -( of the binding between a host and its host keys is inherently) s -5 415 M -( insecure and is NOT RECOMMENDED. It may however be necessary in) s -5 404 M -( non-security critical environments, and will still provide protection) s -5 393 M -( against passive attacks. Implementors of protocols and applications) s -5 382 M -( running on top of this protocol should keep this possibility in mind.) s -5 360 M -(9.2.5 Denial-of-service) s -5 338 M -( This protocol is designed to be used over a reliable transport. If) s -5 327 M -( transmission errors or message manipulation occur, the connection is) s -5 316 M -( closed. The connection SHOULD be re-established if this occurs.) s -5 305 M -( Denial of service attacks of this type \("wire cutter"\) are almost) s -5 294 M -( impossible to avoid.) s -5 272 M -( In addition, this protocol is vulnerable to Denial of Service attacks) s -5 261 M -( because an attacker can force the server to go through the CPU and) s -5 250 M -( memory intensive tasks of connection setup and key exchange without) s -5 239 M -( authenticating. Implementors SHOULD provide features that make this) s -5 228 M -( more difficult. For example, only allowing connections from a subset) s -5 217 M -( of IPs known to have valid users.) s -5 195 M -(9.2.6 Covert Channels) s -5 173 M -( The protocol was not designed to eliminate covert channels. For) s -5 129 M -(Ylonen & Moffat Expires March 31, 2004 [Page 19]) s -_R -S -PStoPSsaved restore -userdict/PStoPSsaved save put -PStoPSmatrix setmatrix -595.000000 421.271378 translate -90 rotate -0.706651 dup scale -userdict/PStoPSmatrix matrix currentmatrix put -userdict/PStoPSclip{0 0 moveto - 595.000000 0 rlineto 0 842.000000 rlineto -595.000000 0 rlineto - closepath}put initclip -PStoPSxform concat -%%BeginPageSetup -_S -75 0 translate -/pagenum 20 def -/fname () def -/fdir () def -/ftail () def -/user_header_p false def -%%EndPageSetup -5 723 M -(Internet-Draft SSH Protocol Architecture Oct 2003) s -5 690 M -( example, the padding, SSH_MSG_IGNORE messages, and several other) s -5 679 M -( places in the protocol can be used to pass covert information, and) s -5 668 M -( the recipient has no reliable way to verify whether such information) s -5 657 M -( is being sent.) s -5 635 M -(9.2.7 Forward Secrecy) s -5 613 M -( It should be noted that the Diffie-Hellman key exchanges may provide) s -5 602 M -( perfect forward secrecy \(PFS\). PFS is essentially defined as the) s -5 591 M -( cryptographic property of a key-establishment protocol in which the) s -5 580 M -( compromise of a session key or long-term private key after a given) s -5 569 M -( session does not cause the compromise of any earlier session. [ANSI) s -5 558 M -( T1.523-2001] SSHv2 sessions resulting from a key exchange using) s -5 547 M -( diffie-hellman-group1-sha1 are secure even if private keying/) s -5 536 M -( authentication material is later revealed, but not if the session) s -5 525 M -( keys are revealed. So, given this definition of PFS, SSHv2 does have) s -5 514 M -( PFS. It is hoped that all other key exchange mechanisms proposed and) s -5 503 M -( used in the future will also provide PFS. This property is not) s -5 492 M -( commuted to any of the applications or protocols using SSH as a) s -5 481 M -( transport however. The transport layer of SSH provides) s -5 470 M -( confidentiality for password authentication and other methods that) s -5 459 M -( rely on secret data.) s -5 437 M -( Of course, if the DH private parameters for the client and server are) s -5 426 M -( revealed then the session key is revealed, but these items can be) s -5 415 M -( thrown away after the key exchange completes. It's worth pointing) s -5 404 M -( out that these items should not be allowed to end up on swap space) s -5 393 M -( and that they should be erased from memory as soon as the key) s -5 382 M -( exchange completes.) s -5 360 M -(9.3 Authentication Protocol) s -5 338 M -( The purpose of this protocol is to perform client user) s -5 327 M -( authentication. It assumes that this run over a secure transport) s -5 316 M -( layer protocol, which has already authenticated the server machine,) s -5 305 M -( established an encrypted communications channel, and computed a) s -5 294 M -( unique session identifier for this session.) s -5 272 M -( Several authentication methods with different security) s -5 261 M -( characteristics are allowed. It is up to the server's local policy) s -5 250 M -( to decide which methods \(or combinations of methods\) it is willing to) s -5 239 M -( accept for each user. Authentication is no stronger than the weakest) s -5 228 M -( combination allowed.) s -5 206 M -( The server may go into a "sleep" period after repeated unsuccessful) s -5 195 M -( authentication attempts to make key search more difficult for) s -5 184 M -( attackers. Care should be taken so that this doesn't become a) s -5 173 M -( self-denial of service vector.) s -5 129 M -(Ylonen & Moffat Expires March 31, 2004 [Page 20]) s -_R -S -PStoPSsaved restore -%%Page: (20,21) 11 -userdict/PStoPSsaved save put -PStoPSmatrix setmatrix -595.000000 0.271378 translate -90 rotate -0.706651 dup scale -userdict/PStoPSmatrix matrix currentmatrix put -userdict/PStoPSclip{0 0 moveto - 595.000000 0 rlineto 0 842.000000 rlineto -595.000000 0 rlineto - closepath}put initclip -/showpage{}def/copypage{}def/erasepage{}def -PStoPSxform concat -%%BeginPageSetup -_S -75 0 translate -/pagenum 21 def -/fname () def -/fdir () def -/ftail () def -/user_header_p false def -%%EndPageSetup -5 723 M -(Internet-Draft SSH Protocol Architecture Oct 2003) s -5 690 M -(9.3.1 Weak Transport) s -5 668 M -( If the transport layer does not provide confidentiality,) s -5 657 M -( authentication methods that rely on secret data SHOULD be disabled.) s -5 646 M -( If it does not provide strong integrity protection, requests to) s -5 635 M -( change authentication data \(e.g. a password change\) SHOULD be) s -5 624 M -( disabled to prevent an attacker from modifying the ciphertext) s -5 613 M -( without being noticed, or rendering the new authentication data) s -5 602 M -( unusable \(denial of service\).) s -5 580 M -( The assumption as stated above that the Authentication Protocol only) s -5 569 M -( run over a secure transport that has previously authenticated the) s -5 558 M -( server is very important to note. People deploying SSH are reminded) s -5 547 M -( of the consequences of man-in-the-middle attacks if the client does) s -5 536 M -( not have a very strong a priori association of the server with the) s -5 525 M -( host key of that server. Specifically for the case of the) s -5 514 M -( Authentication Protocol the client may form a session to a) s -5 503 M -( man-in-the-middle attack device and divulge user credentials such as) s -5 492 M -( their username and password. Even in the cases of authentication) s -5 481 M -( where no user credentials are divulged, an attacker may still gain) s -5 470 M -( information they shouldn't have by capturing key-strokes in much the) s -5 459 M -( same way that a honeypot works.) s -5 437 M -(9.3.2 Debug messages) s -5 415 M -( Special care should be taken when designing debug messages. These) s -5 404 M -( messages may reveal surprising amounts of information about the host) s -5 393 M -( if not properly designed. Debug messages can be disabled \(during) s -5 382 M -( user authentication phase\) if high security is required.) s -5 371 M -( Administrators of host machines should make all attempts to) s -5 360 M -( compartmentalize all event notification messages and protect them) s -5 349 M -( from unwarranted observation. Developers should be aware of the) s -5 338 M -( sensitive nature of some of the normal event messages and debug) s -5 327 M -( messages and may want to provide guidance to administrators on ways) s -5 316 M -( to keep this information away from unauthorized people. Developers) s -5 305 M -( should consider minimizing the amount of sensitive information) s -5 294 M -( obtainable by users during the authentication phase in accordance) s -5 283 M -( with the local policies. For this reason, it is RECOMMENDED that) s -5 272 M -( debug messages be initially disabled at the time of deployment and) s -5 261 M -( require an active decision by an administrator to allow them to be) s -5 250 M -( enabled. It is also RECOMMENDED that a message expressing this) s -5 239 M -( concern be presented to the administrator of a system when the action) s -5 228 M -( is taken to enable debugging messages.) s -5 206 M -(9.3.3 Local security policy) s -5 184 M -( Implementer MUST ensure that the credentials provided validate the) s -5 173 M -( professed user and also MUST ensure that the local policy of the) s -5 129 M -(Ylonen & Moffat Expires March 31, 2004 [Page 21]) s -_R -S -PStoPSsaved restore -userdict/PStoPSsaved save put -PStoPSmatrix setmatrix -595.000000 421.271378 translate -90 rotate -0.706651 dup scale -userdict/PStoPSmatrix matrix currentmatrix put -userdict/PStoPSclip{0 0 moveto - 595.000000 0 rlineto 0 842.000000 rlineto -595.000000 0 rlineto - closepath}put initclip -PStoPSxform concat -%%BeginPageSetup -_S -75 0 translate -/pagenum 22 def -/fname () def -/fdir () def -/ftail () def -/user_header_p false def -%%EndPageSetup -5 723 M -(Internet-Draft SSH Protocol Architecture Oct 2003) s -5 690 M -( server permits the user the access requested. In particular, because) s -5 679 M -( of the flexible nature of the SSH connection protocol, it may not be) s -5 668 M -( possible to determine the local security policy, if any, that should) s -5 657 M -( apply at the time of authentication because the kind of service being) s -5 646 M -( requested is not clear at that instant. For example, local policy) s -5 635 M -( might allow a user to access files on the server, but not start an) s -5 624 M -( interactive shell. However, during the authentication protocol, it is) s -5 613 M -( not known whether the user will be accessing files or attempting to) s -5 602 M -( use an interactive shell, or even both. In any event, where local) s -5 591 M -( security policy for the server host exists, it MUST be applied and) s -5 580 M -( enforced correctly.) s -5 558 M -( Implementors are encouraged to provide a default local policy and) s -5 547 M -( make its parameters known to administrators and users. At the) s -5 536 M -( discretion of the implementors, this default policy may be along the) s -5 525 M -( lines of 'anything goes' where there are no restrictions placed upon) s -5 514 M -( users, or it may be along the lines of 'excessively restrictive' in) s -5 503 M -( which case the administrators will have to actively make changes to) s -5 492 M -( this policy to meet their needs. Alternatively, it may be some) s -5 481 M -( attempt at providing something practical and immediately useful to) s -5 470 M -( the administrators of the system so they don't have to put in much) s -5 459 M -( effort to get SSH working. Whatever choice is made MUST be applied) s -5 448 M -( and enforced as required above.) s -5 426 M -(9.3.4 Public key authentication) s -5 404 M -( The use of public-key authentication assumes that the client host has) s -5 393 M -( not been compromised. It also assumes that the private-key of the) s -5 382 M -( server host has not been compromised.) s -5 360 M -( This risk can be mitigated by the use of passphrases on private keys;) s -5 349 M -( however, this is not an enforceable policy. The use of smartcards,) s -5 338 M -( or other technology to make passphrases an enforceable policy is) s -5 327 M -( suggested.) s -5 305 M -( The server could require both password and public-key authentication,) s -5 294 M -( however, this requires the client to expose its password to the) s -5 283 M -( server \(see section on password authentication below.\)) s -5 261 M -(9.3.5 Password authentication) s -5 239 M -( The password mechanism as specified in the authentication protocol) s -5 228 M -( assumes that the server has not been compromised. If the server has) s -5 217 M -( been compromised, using password authentication will reveal a valid) s -5 206 M -( username / password combination to the attacker, which may lead to) s -5 195 M -( further compromises.) s -5 173 M -( This vulnerability can be mitigated by using an alternative form of) s -5 129 M -(Ylonen & Moffat Expires March 31, 2004 [Page 22]) s -_R -S -PStoPSsaved restore -%%Page: (22,23) 12 -userdict/PStoPSsaved save put -PStoPSmatrix setmatrix -595.000000 0.271378 translate -90 rotate -0.706651 dup scale -userdict/PStoPSmatrix matrix currentmatrix put -userdict/PStoPSclip{0 0 moveto - 595.000000 0 rlineto 0 842.000000 rlineto -595.000000 0 rlineto - closepath}put initclip -/showpage{}def/copypage{}def/erasepage{}def -PStoPSxform concat -%%BeginPageSetup -_S -75 0 translate -/pagenum 23 def -/fname () def -/fdir () def -/ftail () def -/user_header_p false def -%%EndPageSetup -5 723 M -(Internet-Draft SSH Protocol Architecture Oct 2003) s -5 690 M -( authentication. For example, public-key authentication makes no) s -5 679 M -( assumptions about security on the server.) s -5 657 M -(9.3.6 Host based authentication) s -5 635 M -( Host based authentication assumes that the client has not been) s -5 624 M -( compromised. There are no mitigating strategies, other than to use) s -5 613 M -( host based authentication in combination with another authentication) s -5 602 M -( method.) s -5 580 M -(9.4 Connection protocol) s -5 558 M -(9.4.1 End point security) s -5 536 M -( End point security is assumed by the connection protocol. If the) s -5 525 M -( server has been compromised, any terminal sessions, port forwarding,) s -5 514 M -( or systems accessed on the host are compromised. There are no) s -5 503 M -( mitigating factors for this.) s -5 481 M -( If the client end point has been compromised, and the server fails to) s -5 470 M -( stop the attacker at the authentication protocol, all services) s -5 459 M -( exposed \(either as subsystems or through forwarding\) will be) s -5 448 M -( vulnerable to attack. Implementors SHOULD provide mechanisms for) s -5 437 M -( administrators to control which services are exposed to limit the) s -5 426 M -( vulnerability of other services.) s -5 404 M -( These controls might include controlling which machines and ports can) s -5 393 M -( be target in 'port-forwarding' operations, which users are allowed to) s -5 382 M -( use interactive shell facilities, or which users are allowed to use) s -5 371 M -( exposed subsystems.) s -5 349 M -(9.4.2 Proxy forwarding) s -5 327 M -( The SSH connection protocol allows for proxy forwarding of other) s -5 316 M -( protocols such as SNMP, POP3, and HTTP. This may be a concern for) s -5 305 M -( network administrators who wish to control the access of certain) s -5 294 M -( applications by users located outside of their physical location.) s -5 283 M -( Essentially, the forwarding of these protocols may violate site) s -5 272 M -( specific security policies as they may be undetectably tunneled) s -5 261 M -( through a firewall. Implementors SHOULD provide an administrative) s -5 250 M -( mechanism to control the proxy forwarding functionality so that site) s -5 239 M -( specific security policies may be upheld.) s -5 217 M -( In addition, a reverse proxy forwarding functionality is available,) s -5 206 M -( which again can be used to bypass firewall controls.) s -5 184 M -( As indicated above, end-point security is assumed during proxy) s -5 173 M -( forwarding operations. Failure of end-point security will compromise) s -5 129 M -(Ylonen & Moffat Expires March 31, 2004 [Page 23]) s -_R -S -PStoPSsaved restore -userdict/PStoPSsaved save put -PStoPSmatrix setmatrix -595.000000 421.271378 translate -90 rotate -0.706651 dup scale -userdict/PStoPSmatrix matrix currentmatrix put -userdict/PStoPSclip{0 0 moveto - 595.000000 0 rlineto 0 842.000000 rlineto -595.000000 0 rlineto - closepath}put initclip -PStoPSxform concat -%%BeginPageSetup -_S -75 0 translate -/pagenum 24 def -/fname () def -/fdir () def -/ftail () def -/user_header_p false def -%%EndPageSetup -5 723 M -(Internet-Draft SSH Protocol Architecture Oct 2003) s -5 690 M -( all data passed over proxy forwarding.) s -5 668 M -(9.4.3 X11 forwarding) s -5 646 M -( Another form of proxy forwarding provided by the ssh connection) s -5 635 M -( protocol is the forwarding of the X11 protocol. If end-point) s -5 624 M -( security has been compromised, X11 forwarding may allow attacks) s -5 613 M -( against the X11 server. Users and administrators should, as a matter) s -5 602 M -( of course, use appropriate X11 security mechanisms to prevent) s -5 591 M -( unauthorized use of the X11 server. Implementors, administrators and) s -5 580 M -( users who wish to further explore the security mechanisms of X11 are) s -5 569 M -( invited to read [SCHEIFLER] and analyze previously reported problems) s -5 558 M -( with the interactions between SSH forwarding and X11 in CERT) s -5 547 M -( vulnerabilities VU#363181 and VU#118892 [CERT].) s -5 525 M -( X11 display forwarding with SSH, by itself, is not sufficient to) s -5 514 M -( correct well known problems with X11 security [VENEMA]. However, X11) s -5 503 M -( display forwarding in SSHv2 \(or other, secure protocols\), combined) s -5 492 M -( with actual and pseudo-displays which accept connections only over) s -5 481 M -( local IPC mechanisms authorized by permissions or ACLs, does correct) s -5 470 M -( many X11 security problems as long as the "none" MAC is not used. It) s -5 459 M -( is RECOMMENDED that X11 display implementations default to allowing) s -5 448 M -( display opens only over local IPC. It is RECOMMENDED that SSHv2) s -5 437 M -( server implementations that support X11 forwarding default to) s -5 426 M -( allowing display opens only over local IPC. On single-user systems) s -5 415 M -( it might be reasonable to default to allowing local display opens) s -5 404 M -( over TCP/IP.) s -5 382 M -( Implementors of the X11 forwarding protocol SHOULD implement the) s -5 371 M -( magic cookie access checking spoofing mechanism as described in) s -5 360 M -( [ssh-connect] as an additional mechanism to prevent unauthorized use) s -5 349 M -( of the proxy.) s -5 327 M -(Normative References) s -5 305 M -( [SSH-ARCH]) s -5 294 M -( Ylonen, T., "SSH Protocol Architecture", I-D) s -5 283 M -( draft-ietf-architecture-15.txt, Oct 2003.) s -5 261 M -( [SSH-TRANS]) s -5 250 M -( Ylonen, T., "SSH Transport Layer Protocol", I-D) s -5 239 M -( draft-ietf-transport-17.txt, Oct 2003.) s -5 217 M -( [SSH-USERAUTH]) s -5 206 M -( Ylonen, T., "SSH Authentication Protocol", I-D) s -5 195 M -( draft-ietf-userauth-18.txt, Oct 2003.) s -5 173 M -( [SSH-CONNECT]) s -5 129 M -(Ylonen & Moffat Expires March 31, 2004 [Page 24]) s -_R -S -PStoPSsaved restore -%%Page: (24,25) 13 -userdict/PStoPSsaved save put -PStoPSmatrix setmatrix -595.000000 0.271378 translate -90 rotate -0.706651 dup scale -userdict/PStoPSmatrix matrix currentmatrix put -userdict/PStoPSclip{0 0 moveto - 595.000000 0 rlineto 0 842.000000 rlineto -595.000000 0 rlineto - closepath}put initclip -/showpage{}def/copypage{}def/erasepage{}def -PStoPSxform concat -%%BeginPageSetup -_S -75 0 translate -/pagenum 25 def -/fname () def -/fdir () def -/ftail () def -/user_header_p false def -%%EndPageSetup -5 723 M -(Internet-Draft SSH Protocol Architecture Oct 2003) s -5 690 M -( Ylonen, T., "SSH Connection Protocol", I-D) s -5 679 M -( draft-ietf-connect-18.txt, Oct 2003.) s -5 657 M -( [SSH-NUMBERS]) s -5 646 M -( Lehtinen, S. and D. Moffat, "SSH Protocol Assigned) s -5 635 M -( Numbers", I-D draft-ietf-secsh-assignednumbers-05.txt, Oct) s -5 624 M -( 2003.) s -5 602 M -( [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate) s -5 591 M -( Requirement Levels", BCP 14, RFC 2119, March 1997.) s -5 569 M -(Informative References) s -5 547 M -( [FIPS-186]) s -5 536 M -( Federal Information Processing Standards Publication,) s -5 525 M -( "FIPS PUB 186, Digital Signature Standard", May 1994.) s -5 503 M -( [FIPS-197]) s -5 492 M -( National Institue of Standards and Technology, "FIPS 197,) s -5 481 M -( Specification for the Advanced Encryption Standard",) s -5 470 M -( November 2001.) s -5 448 M -( [ANSI T1.523-2001]) s -5 437 M -( American National Standards Insitute, Inc., "Telecom) s -5 426 M -( Glossary 2000", February 2001.) s -5 404 M -( [SCHEIFLER]) s -5 393 M -( Scheifler, R., "X Window System : The Complete Reference) s -5 382 M -( to Xlib, X Protocol, Icccm, Xlfd, 3rd edition.", Digital) s -5 371 M -( Press ISBN 1555580882, Feburary 1992.) s -5 349 M -( [RFC0854] Postel, J. and J. Reynolds, "Telnet Protocol) s -5 338 M -( Specification", STD 8, RFC 854, May 1983.) s -5 316 M -( [RFC0894] Hornig, C., "Standard for the transmission of IP datagrams) s -5 305 M -( over Ethernet networks", STD 41, RFC 894, April 1984.) s -5 283 M -( [RFC1034] Mockapetris, P., "Domain names - concepts and facilities",) s -5 272 M -( STD 13, RFC 1034, November 1987.) s -5 250 M -( [RFC1134] Perkins, D., "Point-to-Point Protocol: A proposal for) s -5 239 M -( multi-protocol transmission of datagrams over) s -5 228 M -( Point-to-Point links", RFC 1134, November 1989.) s -5 206 M -( [RFC1282] Kantor, B., "BSD Rlogin", RFC 1282, December 1991.) s -5 184 M -( [RFC1510] Kohl, J. and B. Neuman, "The Kerberos Network) s -5 173 M -( Authentication Service \(V5\)", RFC 1510, September 1993.) s -5 129 M -(Ylonen & Moffat Expires March 31, 2004 [Page 25]) s -_R -S -PStoPSsaved restore -userdict/PStoPSsaved save put -PStoPSmatrix setmatrix -595.000000 421.271378 translate -90 rotate -0.706651 dup scale -userdict/PStoPSmatrix matrix currentmatrix put -userdict/PStoPSclip{0 0 moveto - 595.000000 0 rlineto 0 842.000000 rlineto -595.000000 0 rlineto - closepath}put initclip -PStoPSxform concat -%%BeginPageSetup -_S -75 0 translate -/pagenum 26 def -/fname () def -/fdir () def -/ftail () def -/user_header_p false def -%%EndPageSetup -5 723 M -(Internet-Draft SSH Protocol Architecture Oct 2003) s -5 690 M -( [RFC1700] Reynolds, J. and J. Postel, "Assigned Numbers", RFC 1700,) s -5 679 M -( October 1994.) s -5 657 M -( [RFC1750] Eastlake, D., Crocker, S. and J. Schiller, "Randomness) s -5 646 M -( Recommendations for Security", RFC 1750, December 1994.) s -5 624 M -( [RFC3066] Alvestrand, H., "Tags for the Identification of) s -5 613 M -( Languages", BCP 47, RFC 3066, January 2001.) s -5 591 M -( [RFC1964] Linn, J., "The Kerberos Version 5 GSS-API Mechanism", RFC) s -5 580 M -( 1964, June 1996.) s -5 558 M -( [RFC2025] Adams, C., "The Simple Public-Key GSS-API Mechanism) s -5 547 M -( \(SPKM\)", RFC 2025, October 1996.) s -5 525 M -( [RFC2085] Oehler, M. and R. Glenn, "HMAC-MD5 IP Authentication with) s -5 514 M -( Replay Prevention", RFC 2085, February 1997.) s -5 492 M -( [RFC2104] Krawczyk, H., Bellare, M. and R. Canetti, "HMAC:) s -5 481 M -( Keyed-Hashing for Message Authentication", RFC 2104,) s -5 470 M -( February 1997.) s -5 448 M -( [RFC2246] Dierks, T., Allen, C., Treese, W., Karlton, P., Freier, A.) s -5 437 M -( and P. Kocher, "The TLS Protocol Version 1.0", RFC 2246,) s -5 426 M -( January 1999.) s -5 404 M -( [RFC2279] Yergeau, F., "UTF-8, a transformation format of ISO) s -5 393 M -( 10646", RFC 2279, January 1998.) s -5 371 M -( [RFC2410] Glenn, R. and S. Kent, "The NULL Encryption Algorithm and) s -5 360 M -( Its Use With IPsec", RFC 2410, November 1998.) s -5 338 M -( [RFC2434] Narten, T. and H. Alvestrand, "Guidelines for Writing an) s -5 327 M -( IANA Considerations Section in RFCs", BCP 26, RFC 2434,) s -5 316 M -( October 1998.) s -5 294 M -( [RFC2743] Linn, J., "Generic Security Service Application Program) s -5 283 M -( Interface Version 2, Update 1", RFC 2743, January 2000.) s -5 261 M -( [SCHNEIER]) s -5 250 M -( Schneier, B., "Applied Cryptography Second Edition:) s -5 239 M -( protocols algorithms and source in code in C", 1996.) s -5 217 M -( [KAUFMAN,PERLMAN,SPECINER]) s -5 206 M -( Kaufman, C., Perlman, R. and M. Speciner, "Network) s -5 195 M -( Security: PRIVATE Communication in a PUBLIC World", 1995.) s -5 173 M -( [CERT] CERT Coordination Center, The., "http://www.cert.org/nav/) s -5 129 M -(Ylonen & Moffat Expires March 31, 2004 [Page 26]) s -_R -S -PStoPSsaved restore -%%Page: (26,27) 14 -userdict/PStoPSsaved save put -PStoPSmatrix setmatrix -595.000000 0.271378 translate -90 rotate -0.706651 dup scale -userdict/PStoPSmatrix matrix currentmatrix put -userdict/PStoPSclip{0 0 moveto - 595.000000 0 rlineto 0 842.000000 rlineto -595.000000 0 rlineto - closepath}put initclip -/showpage{}def/copypage{}def/erasepage{}def -PStoPSxform concat -%%BeginPageSetup -_S -75 0 translate -/pagenum 27 def -/fname () def -/fdir () def -/ftail () def -/user_header_p false def -%%EndPageSetup -5 723 M -(Internet-Draft SSH Protocol Architecture Oct 2003) s -5 690 M -( index_red.html".) s -5 668 M -( [VENEMA] Venema, W., "Murphy's Law and Computer Security",) s -5 657 M -( Proceedings of 6th USENIX Security Symposium, San Jose CA) s -5 646 M -( http://www.usenix.org/publications/library/proceedings/) s -5 635 M -( sec96/venema.html, July 1996.) s -5 613 M -( [ROGAWAY] Rogaway, P., "Problems with Proposed IP Cryptography",) s -5 602 M -( Unpublished paper http://www.cs.ucdavis.edu/~rogaway/) s -5 591 M -( papers/draft-rogaway-ipsec-comments-00.txt, 1996.) s -5 569 M -( [DAI] Dai, W., "An attack against SSH2 protocol", Email to the) s -5 558 M -( SECSH Working Group [email protected] ftp://) s -5 547 M -( ftp.ietf.org/ietf-mail-archive/secsh/2002-02.mail, Feb) s -5 536 M -( 2002.) s -5 514 M -( [BELLARE,KOHNO,NAMPREMPRE]) s -5 503 M -( Bellaire, M., Kohno, T. and C. Namprempre, "Authenticated) s -5 492 M -( Encryption in SSH: Fixing the SSH Binary Packet Protocol",) s -5 481 M -( , Sept 2002.) s -5 448 M -(Authors' Addresses) s -5 426 M -( Tatu Ylonen) s -5 415 M -( SSH Communications Security Corp) s -5 404 M -( Fredrikinkatu 42) s -5 393 M -( HELSINKI FIN-00100) s -5 382 M -( Finland) s -5 360 M -( EMail: [email protected]) s -5 327 M -( Darren J. Moffat \(editor\)) s -5 316 M -( Sun Microsystems, Inc) s -5 305 M -( 17 Network Circle) s -5 294 M -( Menlo Park CA 94025) s -5 283 M -( USA) s -5 261 M -( EMail: [email protected]) s -5 129 M -(Ylonen & Moffat Expires March 31, 2004 [Page 27]) s -_R -S -PStoPSsaved restore -userdict/PStoPSsaved save put -PStoPSmatrix setmatrix -595.000000 421.271378 translate -90 rotate -0.706651 dup scale -userdict/PStoPSmatrix matrix currentmatrix put -userdict/PStoPSclip{0 0 moveto - 595.000000 0 rlineto 0 842.000000 rlineto -595.000000 0 rlineto - closepath}put initclip -PStoPSxform concat -%%BeginPageSetup -_S -75 0 translate -/pagenum 28 def -/fname () def -/fdir () def -/ftail () def -/user_header_p false def -%%EndPageSetup -5 723 M -(Internet-Draft SSH Protocol Architecture Oct 2003) s -5 690 M -(Intellectual Property Statement) s -5 668 M -( The IETF takes no position regarding the validity or scope of any) s -5 657 M -( intellectual property or other rights that might be claimed to) s -5 646 M -( pertain to the implementation or use of the technology described in) s -5 635 M -( this document or the extent to which any license under such rights) s -5 624 M -( might or might not be available; neither does it represent that it) s -5 613 M -( has made any effort to identify any such rights. Information on the) s -5 602 M -( IETF's procedures with respect to rights in standards-track and) s -5 591 M -( standards-related documentation can be found in BCP-11. Copies of) s -5 580 M -( claims of rights made available for publication and any assurances of) s -5 569 M -( licenses to be made available, or the result of an attempt made to) s -5 558 M -( obtain a general license or permission for the use of such) s -5 547 M -( proprietary rights by implementors or users of this specification can) s -5 536 M -( be obtained from the IETF Secretariat.) s -5 514 M -( The IETF invites any interested party to bring to its attention any) s -5 503 M -( copyrights, patents or patent applications, or other proprietary) s -5 492 M -( rights which may cover technology that may be required to practice) s -5 481 M -( this standard. Please address the information to the IETF Executive) s -5 470 M -( Director.) s -5 448 M -( The IETF has been notified of intellectual property rights claimed in) s -5 437 M -( regard to some or all of the specification contained in this) s -5 426 M -( document. For more information consult the online list of claimed) s -5 415 M -( rights.) s -5 382 M -(Full Copyright Statement) s -5 360 M -( Copyright \(C\) The Internet Society \(2003\). All Rights Reserved.) s -5 338 M -( This document and translations of it may be copied and furnished to) s -5 327 M -( others, and derivative works that comment on or otherwise explain it) s -5 316 M -( or assist in its implementation may be prepared, copied, published) s -5 305 M -( and distributed, in whole or in part, without restriction of any) s -5 294 M -( kind, provided that the above copyright notice and this paragraph are) s -5 283 M -( included on all such copies and derivative works. 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Ylonen -Internet-Draft SSH Communications Security Corp -Expires: March 31, 2004 D. Moffat, Ed. - Sun Microsystems, Inc - Oct 2003 - - - SSH Protocol Architecture - draft-ietf-secsh-architecture-15.txt - -Status of this Memo - - This document is an Internet-Draft and is in full conformance with - all provisions of Section 10 of RFC2026. - - Internet-Drafts are working documents of the Internet Engineering - Task Force (IETF), its areas, and its working groups. Note that other - groups may also distribute working documents as Internet-Drafts. - - Internet-Drafts are draft documents valid for a maximum of six months - and may be updated, replaced, or obsoleted by other documents at any - time. It is inappropriate to use Internet-Drafts as reference - material or to cite them other than as "work in progress." - - The list of current Internet-Drafts can be accessed at http:// - www.ietf.org/ietf/1id-abstracts.txt. - - The list of Internet-Draft Shadow Directories can be accessed at - http://www.ietf.org/shadow.html. - - This Internet-Draft will expire on March 31, 2004. - -Copyright Notice - - Copyright (C) The Internet Society (2003). All Rights Reserved. - -Abstract - - SSH is a protocol for secure remote login and other secure network - services over an insecure network. This document describes the - architecture of the SSH protocol, as well as the notation and - terminology used in SSH protocol documents. It also discusses the SSH - algorithm naming system that allows local extensions. The SSH - protocol consists of three major components: The Transport Layer - Protocol provides server authentication, confidentiality, and - integrity with perfect forward secrecy. The User Authentication - Protocol authenticates the client to the server. The Connection - Protocol multiplexes the encrypted tunnel into several logical - channels. Details of these protocols are described in separate - - - -Ylonen & Moffat Expires March 31, 2004 [Page 1] - -Internet-Draft SSH Protocol Architecture Oct 2003 - - - documents. - -Table of Contents - - 1. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 3 - 2. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 - 3. Specification of Requirements . . . . . . . . . . . . . . . 3 - 4. Architecture . . . . . . . . . . . . . . . . . . . . . . . . 3 - 4.1 Host Keys . . . . . . . . . . . . . . . . . . . . . . . . . 4 - 4.2 Extensibility . . . . . . . . . . . . . . . . . . . . . . . 5 - 4.3 Policy Issues . . . . . . . . . . . . . . . . . . . . . . . 5 - 4.4 Security Properties . . . . . . . . . . . . . . . . . . . . 6 - 4.5 Packet Size and Overhead . . . . . . . . . . . . . . . . . . 6 - 4.6 Localization and Character Set Support . . . . . . . . . . . 7 - 5. Data Type Representations Used in the SSH Protocols . . . . 8 - 6. Algorithm Naming . . . . . . . . . . . . . . . . . . . . . . 10 - 7. Message Numbers . . . . . . . . . . . . . . . . . . . . . . 11 - 8. IANA Considerations . . . . . . . . . . . . . . . . . . . . 11 - 9. Security Considerations . . . . . . . . . . . . . . . . . . 12 - 9.1 Pseudo-Random Number Generation . . . . . . . . . . . . . . 12 - 9.2 Transport . . . . . . . . . . . . . . . . . . . . . . . . . 13 - 9.2.1 Confidentiality . . . . . . . . . . . . . . . . . . . . . . 13 - 9.2.2 Data Integrity . . . . . . . . . . . . . . . . . . . . . . . 16 - 9.2.3 Replay . . . . . . . . . . . . . . . . . . . . . . . . . . . 16 - 9.2.4 Man-in-the-middle . . . . . . . . . . . . . . . . . . . . . 17 - 9.2.5 Denial-of-service . . . . . . . . . . . . . . . . . . . . . 19 - 9.2.6 Covert Channels . . . . . . . . . . . . . . . . . . . . . . 19 - 9.2.7 Forward Secrecy . . . . . . . . . . . . . . . . . . . . . . 20 - 9.3 Authentication Protocol . . . . . . . . . . . . . . . . . . 20 - 9.3.1 Weak Transport . . . . . . . . . . . . . . . . . . . . . . . 21 - 9.3.2 Debug messages . . . . . . . . . . . . . . . . . . . . . . . 21 - 9.3.3 Local security policy . . . . . . . . . . . . . . . . . . . 21 - 9.3.4 Public key authentication . . . . . . . . . . . . . . . . . 22 - 9.3.5 Password authentication . . . . . . . . . . . . . . . . . . 22 - 9.3.6 Host based authentication . . . . . . . . . . . . . . . . . 23 - 9.4 Connection protocol . . . . . . . . . . . . . . . . . . . . 23 - 9.4.1 End point security . . . . . . . . . . . . . . . . . . . . . 23 - 9.4.2 Proxy forwarding . . . . . . . . . . . . . . . . . . . . . . 23 - 9.4.3 X11 forwarding . . . . . . . . . . . . . . . . . . . . . . . 24 - Normative References . . . . . . . . . . . . . . . . . . . . 24 - Informative References . . . . . . . . . . . . . . . . . . . 25 - Authors' Addresses . . . . . . . . . . . . . . . . . . . . . 27 - Intellectual Property and Copyright Statements . . . . . . . 28 - - - - - - - - -Ylonen & Moffat Expires March 31, 2004 [Page 2] - -Internet-Draft SSH Protocol Architecture Oct 2003 - - -1. Contributors - - The major original contributors of this document were: Tatu Ylonen, - Tero Kivinen, Timo J. Rinne, Sami Lehtinen (all of SSH Communications - Security Corp), and Markku-Juhani O. Saarinen (University of - Jyvaskyla) - - The document editor is: [email protected]. Comments on this - internet draft should be sent to the IETF SECSH working group, - details at: http://ietf.org/html.charters/secsh-charter.html - -2. Introduction - - SSH is a protocol for secure remote login and other secure network - services over an insecure network. It consists of three major - components: - o The Transport Layer Protocol [SSH-TRANS] provides server - authentication, confidentiality, and integrity. It may optionally - also provide compression. The transport layer will typically be - run over a TCP/IP connection, but might also be used on top of any - other reliable data stream. - o The User Authentication Protocol [SSH-USERAUTH] authenticates the - client-side user to the server. It runs over the transport layer - protocol. - o The Connection Protocol [SSH-CONNECT] multiplexes the encrypted - tunnel into several logical channels. It runs over the user - authentication protocol. - - The client sends a service request once a secure transport layer - connection has been established. A second service request is sent - after user authentication is complete. This allows new protocols to - be defined and coexist with the protocols listed above. - - The connection protocol provides channels that can be used for a wide - range of purposes. Standard methods are provided for setting up - secure interactive shell sessions and for forwarding ("tunneling") - arbitrary TCP/IP ports and X11 connections. - -3. Specification of Requirements - - All documents related to the SSH protocols shall use the keywords - "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", - "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" to describe - requirements. They are to be interpreted as described in [RFC2119]. - -4. Architecture - - - - - -Ylonen & Moffat Expires March 31, 2004 [Page 3] - -Internet-Draft SSH Protocol Architecture Oct 2003 - - -4.1 Host Keys - - Each server host SHOULD have a host key. Hosts MAY have multiple - host keys using multiple different algorithms. Multiple hosts MAY - share the same host key. If a host has keys at all, it MUST have at - least one key using each REQUIRED public key algorithm (DSS - [FIPS-186]). - - The server host key is used during key exchange to verify that the - client is really talking to the correct server. For this to be - possible, the client must have a priori knowledge of the server's - public host key. - - Two different trust models can be used: - o The client has a local database that associates each host name (as - typed by the user) with the corresponding public host key. This - method requires no centrally administered infrastructure, and no - third-party coordination. The downside is that the database of - name-to-key associations may become burdensome to maintain. - o The host name-to-key association is certified by some trusted - certification authority. The client only knows the CA root key, - and can verify the validity of all host keys certified by accepted - CAs. - - The second alternative eases the maintenance problem, since - ideally only a single CA key needs to be securely stored on the - client. On the other hand, each host key must be appropriately - certified by a central authority before authorization is possible. - Also, a lot of trust is placed on the central infrastructure. - - The protocol provides the option that the server name - host key - association is not checked when connecting to the host for the first - time. This allows communication without prior communication of host - keys or certification. The connection still provides protection - against passive listening; however, it becomes vulnerable to active - man-in-the-middle attacks. Implementations SHOULD NOT normally allow - such connections by default, as they pose a potential security - problem. However, as there is no widely deployed key infrastructure - available on the Internet yet, this option makes the protocol much - more usable during the transition time until such an infrastructure - emerges, while still providing a much higher level of security than - that offered by older solutions (e.g. telnet [RFC-854] and rlogin - [RFC-1282]). - - Implementations SHOULD try to make the best effort to check host - keys. An example of a possible strategy is to only accept a host key - without checking the first time a host is connected, save the key in - a local database, and compare against that key on all future - - - -Ylonen & Moffat Expires March 31, 2004 [Page 4] - -Internet-Draft SSH Protocol Architecture Oct 2003 - - - connections to that host. - - Implementations MAY provide additional methods for verifying the - correctness of host keys, e.g. a hexadecimal fingerprint derived from - the SHA-1 hash of the public key. Such fingerprints can easily be - verified by using telephone or other external communication channels. - - All implementations SHOULD provide an option to not accept host keys - that cannot be verified. - - We believe that ease of use is critical to end-user acceptance of - security solutions, and no improvement in security is gained if the - new solutions are not used. Thus, providing the option not to check - the server host key is believed to improve the overall security of - the Internet, even though it reduces the security of the protocol in - configurations where it is allowed. - -4.2 Extensibility - - We believe that the protocol will evolve over time, and some - organizations will want to use their own encryption, authentication - and/or key exchange methods. Central registration of all extensions - is cumbersome, especially for experimental or classified features. - On the other hand, having no central registration leads to conflicts - in method identifiers, making interoperability difficult. - - We have chosen to identify algorithms, methods, formats, and - extension protocols with textual names that are of a specific format. - DNS names are used to create local namespaces where experimental or - classified extensions can be defined without fear of conflicts with - other implementations. - - One design goal has been to keep the base protocol as simple as - possible, and to require as few algorithms as possible. However, all - implementations MUST support a minimal set of algorithms to ensure - interoperability (this does not imply that the local policy on all - hosts would necessary allow these algorithms). The mandatory - algorithms are specified in the relevant protocol documents. - - Additional algorithms, methods, formats, and extension protocols can - be defined in separate drafts. See Section Algorithm Naming (Section - 6) for more information. - -4.3 Policy Issues - - The protocol allows full negotiation of encryption, integrity, key - exchange, compression, and public key algorithms and formats. - Encryption, integrity, public key, and compression algorithms can be - - - -Ylonen & Moffat Expires March 31, 2004 [Page 5] - -Internet-Draft SSH Protocol Architecture Oct 2003 - - - different for each direction. - - The following policy issues SHOULD be addressed in the configuration - mechanisms of each implementation: - o Encryption, integrity, and compression algorithms, separately for - each direction. The policy MUST specify which is the preferred - algorithm (e.g. the first algorithm listed in each category). - o Public key algorithms and key exchange method to be used for host - authentication. The existence of trusted host keys for different - public key algorithms also affects this choice. - o The authentication methods that are to be required by the server - for each user. The server's policy MAY require multiple - authentication for some or all users. The required algorithms MAY - depend on the location where the user is trying to log in from. - o The operations that the user is allowed to perform using the - connection protocol. Some issues are related to security; for - example, the policy SHOULD NOT allow the server to start sessions - or run commands on the client machine, and MUST NOT allow - connections to the authentication agent unless forwarding such - connections has been requested. Other issues, such as which TCP/ - IP ports can be forwarded and by whom, are clearly issues of local - policy. Many of these issues may involve traversing or bypassing - firewalls, and are interrelated with the local security policy. - -4.4 Security Properties - - The primary goal of the SSH protocol is improved security on the - Internet. It attempts to do this in a way that is easy to deploy, - even at the cost of absolute security. - o All encryption, integrity, and public key algorithms used are - well-known, well-established algorithms. - o All algorithms are used with cryptographically sound key sizes - that are believed to provide protection against even the strongest - cryptanalytic attacks for decades. - o All algorithms are negotiated, and in case some algorithm is - broken, it is easy to switch to some other algorithm without - modifying the base protocol. - - Specific concessions were made to make wide-spread fast deployment - easier. The particular case where this comes up is verifying that - the server host key really belongs to the desired host; the protocol - allows the verification to be left out (but this is NOT RECOMMENDED). - This is believed to significantly improve usability in the short - term, until widespread Internet public key infrastructures emerge. - -4.5 Packet Size and Overhead - - Some readers will worry about the increase in packet size due to new - - - -Ylonen & Moffat Expires March 31, 2004 [Page 6] - -Internet-Draft SSH Protocol Architecture Oct 2003 - - - headers, padding, and MAC. The minimum packet size is in the order - of 28 bytes (depending on negotiated algorithms). The increase is - negligible for large packets, but very significant for one-byte - packets (telnet-type sessions). There are, however, several factors - that make this a non-issue in almost all cases: - o The minimum size of a TCP/IP header is 32 bytes. Thus, the - increase is actually from 33 to 51 bytes (roughly). - o The minimum size of the data field of an Ethernet packet is 46 - bytes [RFC-894]. Thus, the increase is no more than 5 bytes. When - Ethernet headers are considered, the increase is less than 10 - percent. - o The total fraction of telnet-type data in the Internet is - negligible, even with increased packet sizes. - - The only environment where the packet size increase is likely to have - a significant effect is PPP [RFC-1134] over slow modem lines (PPP - compresses the TCP/IP headers, emphasizing the increase in packet - size). However, with modern modems, the time needed to transfer is in - the order of 2 milliseconds, which is a lot faster than people can - type. - - There are also issues related to the maximum packet size. To - minimize delays in screen updates, one does not want excessively - large packets for interactive sessions. The maximum packet size is - negotiated separately for each channel. - -4.6 Localization and Character Set Support - - For the most part, the SSH protocols do not directly pass text that - would be displayed to the user. However, there are some places where - such data might be passed. When applicable, the character set for the - data MUST be explicitly specified. In most places, ISO 10646 with - UTF-8 encoding is used [RFC-2279]. When applicable, a field is also - provided for a language tag [RFC-3066]. - - One big issue is the character set of the interactive session. There - is no clear solution, as different applications may display data in - different formats. Different types of terminal emulation may also be - employed in the client, and the character set to be used is - effectively determined by the terminal emulation. Thus, no place is - provided for directly specifying the character set or encoding for - terminal session data. However, the terminal emulation type (e.g. - "vt100") is transmitted to the remote site, and it implicitly - specifies the character set and encoding. Applications typically use - the terminal type to determine what character set they use, or the - character set is determined using some external means. The terminal - emulation may also allow configuring the default character set. In - any case, the character set for the terminal session is considered - - - -Ylonen & Moffat Expires March 31, 2004 [Page 7] - -Internet-Draft SSH Protocol Architecture Oct 2003 - - - primarily a client local issue. - - Internal names used to identify algorithms or protocols are normally - never displayed to users, and must be in US-ASCII. - - The client and server user names are inherently constrained by what - the server is prepared to accept. They might, however, occasionally - be displayed in logs, reports, etc. They MUST be encoded using ISO - 10646 UTF-8, but other encodings may be required in some cases. It - is up to the server to decide how to map user names to accepted user - names. Straight bit-wise binary comparison is RECOMMENDED. - - For localization purposes, the protocol attempts to minimize the - number of textual messages transmitted. When present, such messages - typically relate to errors, debugging information, or some externally - configured data. For data that is normally displayed, it SHOULD be - possible to fetch a localized message instead of the transmitted - message by using a numerical code. The remaining messages SHOULD be - configurable. - -5. Data Type Representations Used in the SSH Protocols - byte - - A byte represents an arbitrary 8-bit value (octet) [RFC-1700]. - Fixed length data is sometimes represented as an array of bytes, - written byte[n], where n is the number of bytes in the array. - - boolean - - A boolean value is stored as a single byte. The value 0 - represents FALSE, and the value 1 represents TRUE. All non-zero - values MUST be interpreted as TRUE; however, applications MUST NOT - store values other than 0 and 1. - - uint32 - - Represents a 32-bit unsigned integer. Stored as four bytes in the - order of decreasing significance (network byte order). For - example, the value 699921578 (0x29b7f4aa) is stored as 29 b7 f4 - aa. - - uint64 - - Represents a 64-bit unsigned integer. Stored as eight bytes in - the order of decreasing significance (network byte order). - - - - - - -Ylonen & Moffat Expires March 31, 2004 [Page 8] - -Internet-Draft SSH Protocol Architecture Oct 2003 - - - string - - Arbitrary length binary string. Strings are allowed to contain - arbitrary binary data, including null characters and 8-bit - characters. They are stored as a uint32 containing its length - (number of bytes that follow) and zero (= empty string) or more - bytes that are the value of the string. Terminating null - characters are not used. - - Strings are also used to store text. In that case, US-ASCII is - used for internal names, and ISO-10646 UTF-8 for text that might - be displayed to the user. The terminating null character SHOULD - NOT normally be stored in the string. - - For example, the US-ASCII string "testing" is represented as 00 00 - 00 07 t e s t i n g. The UTF8 mapping does not alter the encoding - of US-ASCII characters. - - mpint - - Represents multiple precision integers in two's complement format, - stored as a string, 8 bits per byte, MSB first. Negative numbers - have the value 1 as the most significant bit of the first byte of - the data partition. If the most significant bit would be set for a - positive number, the number MUST be preceded by a zero byte. - Unnecessary leading bytes with the value 0 or 255 MUST NOT be - included. The value zero MUST be stored as a string with zero - bytes of data. - - By convention, a number that is used in modular computations in - Z_n SHOULD be represented in the range 0 <= x < n. - - Examples: - value (hex) representation (hex) - --------------------------------------------------------------- - 0 00 00 00 00 - 9a378f9b2e332a7 00 00 00 08 09 a3 78 f9 b2 e3 32 a7 - 80 00 00 00 02 00 80 - -1234 00 00 00 02 ed cc - -deadbeef 00 00 00 05 ff 21 52 41 11 - - - - name-list - - A string containing a comma separated list of names. A name list - is represented as a uint32 containing its length (number of bytes - that follow) followed by a comma-separated list of zero or more - - - -Ylonen & Moffat Expires March 31, 2004 [Page 9] - -Internet-Draft SSH Protocol Architecture Oct 2003 - - - names. A name MUST be non-zero length, and it MUST NOT contain a - comma (','). Context may impose additional restrictions on the - names; for example, the names in a list may have to be valid - algorithm identifier (see Algorithm Naming below), or [RFC-3066] - language tags. The order of the names in a list may or may not be - significant, also depending on the context where the list is is - used. Terminating NUL characters are not used, neither for the - individual names, nor for the list as a whole. - - Examples: - value representation (hex) - --------------------------------------- - (), the empty list 00 00 00 00 - ("zlib") 00 00 00 04 7a 6c 69 62 - ("zlib", "none") 00 00 00 09 7a 6c 69 62 2c 6e 6f 6e 65 - - - - -6. Algorithm Naming - - The SSH protocols refer to particular hash, encryption, integrity, - compression, and key exchange algorithms or protocols by names. - There are some standard algorithms that all implementations MUST - support. There are also algorithms that are defined in the protocol - specification but are OPTIONAL. Furthermore, it is expected that - some organizations will want to use their own algorithms. - - In this protocol, all algorithm identifiers MUST be printable - US-ASCII non-empty strings no longer than 64 characters. Names MUST - be case-sensitive. - - There are two formats for algorithm names: - o Names that do not contain an at-sign (@) are reserved to be - assigned by IETF consensus (RFCs). Examples include `3des-cbc', - `sha-1', `hmac-sha1', and `zlib' (the quotes are not part of the - name). Names of this format MUST NOT be used without first - registering them. Registered names MUST NOT contain an at-sign - (@) or a comma (,). - o Anyone can define additional algorithms by using names in the - format name@domainname, e.g. "[email protected]". The - format of the part preceding the at sign is not specified; it MUST - consist of US-ASCII characters except at-sign and comma. The part - following the at-sign MUST be a valid fully qualified internet - domain name [RFC-1034] controlled by the person or organization - defining the name. It is up to each domain how it manages its - local namespace. - - - - -Ylonen & Moffat Expires March 31, 2004 [Page 10] - -Internet-Draft SSH Protocol Architecture Oct 2003 - - -7. Message Numbers - - SSH packets have message numbers in the range 1 to 255. These numbers - have been allocated as follows: - - - Transport layer protocol: - - 1 to 19 Transport layer generic (e.g. disconnect, ignore, debug, - etc.) - 20 to 29 Algorithm negotiation - 30 to 49 Key exchange method specific (numbers can be reused for - different authentication methods) - - User authentication protocol: - - 50 to 59 User authentication generic - 60 to 79 User authentication method specific (numbers can be - reused for different authentication methods) - - Connection protocol: - - 80 to 89 Connection protocol generic - 90 to 127 Channel related messages - - Reserved for client protocols: - - 128 to 191 Reserved - - Local extensions: - - 192 to 255 Local extensions - - - -8. IANA Considerations - - The initial state of the IANA registry is detailed in [SSH-NUMBERS]. - - Allocation of the following types of names in the SSH protocols is - assigned by IETF consensus: - o SSH encryption algorithm names, - o SSH MAC algorithm names, - o SSH public key algorithm names (public key algorithm also implies - encoding and signature/encryption capability), - o SSH key exchange method names, and - o SSH protocol (service) names. - - - - -Ylonen & Moffat Expires March 31, 2004 [Page 11] - -Internet-Draft SSH Protocol Architecture Oct 2003 - - - These names MUST be printable US-ASCII strings, and MUST NOT contain - the characters at-sign ('@'), comma (','), or whitespace or control - characters (ASCII codes 32 or less). Names are case-sensitive, and - MUST NOT be longer than 64 characters. - - Names with the at-sign ('@') in them are allocated by the owner of - DNS name after the at-sign (hierarchical allocation in [RFC-2343]), - otherwise the same restrictions as above. - - Each category of names listed above has a separate namespace. - However, using the same name in multiple categories SHOULD be avoided - to minimize confusion. - - Message numbers (see Section Message Numbers (Section 7)) in the - range of 0..191 are allocated via IETF consensus; message numbers in - the 192..255 range (the "Local extensions" set) are reserved for - private use. - -9. Security Considerations - - In order to make the entire body of Security Considerations more - accessible, Security Considerations for the transport, - authentication, and connection documents have been gathered here. - - The transport protocol [1] provides a confidential channel over an - insecure network. It performs server host authentication, key - exchange, encryption, and integrity protection. It also derives a - unique session id that may be used by higher-level protocols. - - The authentication protocol [2] provides a suite of mechanisms which - can be used to authenticate the client user to the server. - Individual mechanisms specified in the in authentication protocol use - the session id provided by the transport protocol and/or depend on - the security and integrity guarantees of the transport protocol. - - The connection protocol [3] specifies a mechanism to multiplex - multiple streams [channels] of data over the confidential and - authenticated transport. It also specifies channels for accessing an - interactive shell, for 'proxy-forwarding' various external protocols - over the secure transport (including arbitrary TCP/IP protocols), and - for accessing secure 'subsystems' on the server host. - -9.1 Pseudo-Random Number Generation - - This protocol binds each session key to the session by including - random, session specific data in the hash used to produce session - keys. Special care should be taken to ensure that all of the random - numbers are of good quality. If the random data here (e.g., DH - - - -Ylonen & Moffat Expires March 31, 2004 [Page 12] - -Internet-Draft SSH Protocol Architecture Oct 2003 - - - parameters) are pseudo-random then the pseudo-random number generator - should be cryptographically secure (i.e., its next output not easily - guessed even when knowing all previous outputs) and, furthermore, - proper entropy needs to be added to the pseudo-random number - generator. RFC 1750 [1750] offers suggestions for sources of random - numbers and entropy. Implementors should note the importance of - entropy and the well-meant, anecdotal warning about the difficulty in - properly implementing pseudo-random number generating functions. - - The amount of entropy available to a given client or server may - sometimes be less than what is required. In this case one must - either resort to pseudo-random number generation regardless of - insufficient entropy or refuse to run the protocol. The latter is - preferable. - -9.2 Transport - -9.2.1 Confidentiality - - It is beyond the scope of this document and the Secure Shell Working - Group to analyze or recommend specific ciphers other than the ones - which have been established and accepted within the industry. At the - time of this writing, ciphers commonly in use include 3DES, ARCFOUR, - twofish, serpent and blowfish. AES has been accepted by The - published as a US Federal Information Processing Standards [FIPS-197] - and the cryptographic community as being acceptable for this purpose - as well has accepted AES. As always, implementors and users should - check current literature to ensure that no recent vulnerabilities - have been found in ciphers used within products. Implementors should - also check to see which ciphers are considered to be relatively - stronger than others and should recommend their use to users over - relatively weaker ciphers. It would be considered good form for an - implementation to politely and unobtrusively notify a user that a - stronger cipher is available and should be used when a weaker one is - actively chosen. - - The "none" cipher is provided for debugging and SHOULD NOT be used - except for that purpose. It's cryptographic properties are - sufficiently described in RFC 2410, which will show that its use does - not meet the intent of this protocol. - - The relative merits of these and other ciphers may also be found in - current literature. Two references that may provide information on - the subject are [SCHNEIER] and [KAUFMAN,PERLMAN,SPECINER]. Both of - these describe the CBC mode of operation of certain ciphers and the - weakness of this scheme. Essentially, this mode is theoretically - vulnerable to chosen cipher-text attacks because of the high - predictability of the start of packet sequence. However, this attack - - - -Ylonen & Moffat Expires March 31, 2004 [Page 13] - -Internet-Draft SSH Protocol Architecture Oct 2003 - - - is still deemed difficult and not considered fully practicable - especially if relatively longer block sizes are used. - - Additionally, another CBC mode attack may be mitigated through the - insertion of packets containing SSH_MSG_IGNORE. Without this - technique, a specific attack may be successful. For this attack - (commonly known as the Rogaway attack - [ROGAWAY],[DAI],[BELLARE,KOHNO,NAMPREMPRE]) to work, the attacker - would need to know the IV of the next block that is going to be - encrypted. In CBC mode that is the output of the encryption of the - previous block. If the attacker does not have any way to see the - packet yet (i.e it is in the internal buffers of the ssh - implementation or even in the kernel) then this attack will not work. - If the last packet has been sent out to the network (i.e the attacker - has access to it) then he can use the attack. - - In the optimal case an implementor would need to add an extra packet - only if the packet has been sent out onto the network and there are - no other packets waiting for transmission. Implementors may wish to - check to see if there are any unsent packets awaiting transmission, - but unfortunately it is not normally easy to obtain this information - from the kernel or buffers. If there are not, then a packet - containing SSH_MSG_IGNORE SHOULD be sent. If a new packet is added - to the stream every time the attacker knows the IV that is supposed - to be used for the next packet, then the attacker will not be able to - guess the correct IV, thus the attack will never be successfull. - - As an example, consider the following case: - - - Client Server - ------ ------ - TCP(seq=x, len=500) -> - contains Record 1 - - [500 ms passes, no ACK] - - TCP(seq=x, len=1000) -> - contains Records 1,2 - - ACK - - - 1. The Nagle algorithm + TCP retransmits mean that the two records - get coalesced into a single TCP segment - 2. Record 2 is *not* at the beginning of the TCP segment and never - will be, since it gets ACKed. - - - - -Ylonen & Moffat Expires March 31, 2004 [Page 14] - -Internet-Draft SSH Protocol Architecture Oct 2003 - - - 3. Yet, the attack is possible because Record 1 has already been - seen. - - As this example indicates, it's totally unsafe to use the existence - of unflushed data in the TCP buffers proper as a guide to whether you - need an empty packet, since when you do the second write(), the - buffers will contain the un-ACKed Record 1. - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -Ylonen & Moffat Expires March 31, 2004 [Page 15] - -Internet-Draft SSH Protocol Architecture Oct 2003 - - - On the other hand, it's perfectly safe to have the following - situation: - - - Client Server - ------ ------ - TCP(seq=x, len=500) -> - contains SSH_MSG_IGNORE - - TCP(seq=y, len=500) -> - contains Data - - Provided that the IV for second SSH Record is fixed after the data for - the Data packet is determined -i.e. you do: - read from user - encrypt null packet - encrypt data packet - - -9.2.2 Data Integrity - - This protocol does allow the Data Integrity mechanism to be disabled. - Implementors SHOULD be wary of exposing this feature for any purpose - other than debugging. Users and administrators SHOULD be explicitly - warned anytime the "none" MAC is enabled. - - So long as the "none" MAC is not used, this protocol provides data - integrity. - - Because MACs use a 32 bit sequence number, they might start to leak - information after 2**32 packets have been sent. However, following - the rekeying recommendations should prevent this attack. The - transport protocol [1] recommends rekeying after one gigabyte of - data, and the smallest possible packet is 16 bytes. Therefore, - rekeying SHOULD happen after 2**28 packets at the very most. - -9.2.3 Replay - - The use of a MAC other than 'none' provides integrity and - authentication. In addition, the transport protocol provides a - unique session identifier (bound in part to pseudo-random data that - is part of the algorithm and key exchange process) that can be used - by higher level protocols to bind data to a given session and prevent - replay of data from prior sessions. For example, the authentication - protocol uses this to prevent replay of signatures from previous - sessions. Because public key authentication exchanges are - cryptographically bound to the session (i.e., to the initial key - exchange) they cannot be successfully replayed in other sessions. - - - -Ylonen & Moffat Expires March 31, 2004 [Page 16] - -Internet-Draft SSH Protocol Architecture Oct 2003 - - - Note that the session ID can be made public without harming the - security of the protocol. - - If two session happen to have the same session ID [hash of key - exchanges] then packets from one can be replayed against the other. - It must be stressed that the chances of such an occurrence are, - needless to say, minimal when using modern cryptographic methods. - This is all the more so true when specifying larger hash function - outputs and DH parameters. - - Replay detection using monotonically increasing sequence numbers as - input to the MAC, or HMAC in some cases, is described in [RFC2085] /> - [RFC2246], [RFC2743], [RFC1964], [RFC2025], and [RFC1510]. The - underlying construct is discussed in [RFC2104]. Essentially a - different sequence number in each packet ensures that at least this - one input to the MAC function will be unique and will provide a - nonrecurring MAC output that is not predictable to an attacker. If - the session stays active long enough, however, this sequence number - will wrap. This event may provide an attacker an opportunity to - replay a previously recorded packet with an identical sequence number - but only if the peers have not rekeyed since the transmission of the - first packet with that sequence number. If the peers have rekeyed, - then the replay will be detected as the MAC check will fail. For - this reason, it must be emphasized that peers MUST rekey before a - wrap of the sequence numbers. Naturally, if an attacker does attempt - to replay a captured packet before the peers have rekeyed, then the - receiver of the duplicate packet will not be able to validate the MAC - and it will be discarded. The reason that the MAC will fail is - because the receiver will formulate a MAC based upon the packet - contents, the shared secret, and the expected sequence number. Since - the replayed packet will not be using that expected sequence number - (the sequence number of the replayed packet will have already been - passed by the receiver) then the calculated MAC will not match the - MAC received with the packet. - -9.2.4 Man-in-the-middle - - This protocol makes no assumptions nor provisions for an - infrastructure or means for distributing the public keys of hosts. It - is expected that this protocol will sometimes be used without first - verifying the association between the server host key and the server - host name. Such usage is vulnerable to man-in-the-middle attacks. - This section describes this and encourages administrators and users - to understand the importance of verifying this association before any - session is initiated. - - There are three cases of man-in-the-middle attacks to consider. The - first is where an attacker places a device between the client and the - - - -Ylonen & Moffat Expires March 31, 2004 [Page 17] - -Internet-Draft SSH Protocol Architecture Oct 2003 - - - server before the session is initiated. In this case, the attack - device is trying to mimic the legitimate server and will offer its - public key to the client when the client initiates a session. If it - were to offer the public key of the server, then it would not be able - to decrypt or sign the transmissions between the legitimate server - and the client unless it also had access to the private-key of the - host. The attack device will also, simultaneously to this, initiate - a session to the legitimate server masquerading itself as the client. - If the public key of the server had been securely distributed to the - client prior to that session initiation, the key offered to the - client by the attack device will not match the key stored on the - client. In that case, the user SHOULD be given a warning that the - offered host key does not match the host key cached on the client. - As described in Section 3.1 of [ARCH], the user may be free to accept - the new key and continue the session. It is RECOMMENDED that the - warning provide sufficient information to the user of the client - device so they may make an informed decision. If the user chooses to - continue the session with the stored public-key of the server (not - the public-key offered at the start of the session), then the session - specific data between the attacker and server will be different - between the client-to-attacker session and the attacker-to-server - sessions due to the randomness discussed above. From this, the - attacker will not be able to make this attack work since the attacker - will not be able to correctly sign packets containing this session - specific data from the server since he does not have the private key - of that server. - - The second case that should be considered is similar to the first - case in that it also happens at the time of connection but this case - points out the need for the secure distribution of server public - keys. If the server public keys are not securely distributed then - the client cannot know if it is talking to the intended server. An - attacker may use social engineering techniques to pass off server - keys to unsuspecting users and may then place a man-in-the-middle - attack device between the legitimate server and the clients. If this - is allowed to happen then the clients will form client-to-attacker - sessions and the attacker will form attacker-to-server sessions and - will be able to monitor and manipulate all of the traffic between the - clients and the legitimate servers. Server administrators are - encouraged to make host key fingerprints available for checking by - some means whose security does not rely on the integrity of the - actual host keys. Possible mechanisms are discussed in Section 3.1 - of [SSH-ARCH] and may also include secured Web pages, physical pieces - of paper, etc. Implementors SHOULD provide recommendations on how - best to do this with their implementation. Because the protocol is - extensible, future extensions to the protocol may provide better - mechanisms for dealing with the need to know the server's host key - before connecting. For example, making the host key fingerprint - - - -Ylonen & Moffat Expires March 31, 2004 [Page 18] - -Internet-Draft SSH Protocol Architecture Oct 2003 - - - available through a secure DNS lookup, or using kerberos over gssapi - during key exchange to authenticate the server are possibilities. - - In the third man-in-the-middle case, attackers may attempt to - manipulate packets in transit between peers after the session has - been established. As described in the Replay part of this section, a - successful attack of this nature is very improbable. As in the - Replay section, this reasoning does assume that the MAC is secure and - that it is infeasible to construct inputs to a MAC algorithm to give - a known output. This is discussed in much greater detail in Section - 6 of RFC 2104. If the MAC algorithm has a vulnerability or is weak - enough, then the attacker may be able to specify certain inputs to - yield a known MAC. With that they may be able to alter the contents - of a packet in transit. Alternatively the attacker may be able to - exploit the algorithm vulnerability or weakness to find the shared - secret by reviewing the MACs from captured packets. In either of - those cases, an attacker could construct a packet or packets that - could be inserted into an SSH stream. To prevent that, implementors - are encouraged to utilize commonly accepted MAC algorithms and - administrators are encouraged to watch current literature and - discussions of cryptography to ensure that they are not using a MAC - algorithm that has a recently found vulnerability or weakness. - - In summary, the use of this protocol without a reliable association - of the binding between a host and its host keys is inherently - insecure and is NOT RECOMMENDED. It may however be necessary in - non-security critical environments, and will still provide protection - against passive attacks. Implementors of protocols and applications - running on top of this protocol should keep this possibility in mind. - -9.2.5 Denial-of-service - - This protocol is designed to be used over a reliable transport. If - transmission errors or message manipulation occur, the connection is - closed. The connection SHOULD be re-established if this occurs. - Denial of service attacks of this type ("wire cutter") are almost - impossible to avoid. - - In addition, this protocol is vulnerable to Denial of Service attacks - because an attacker can force the server to go through the CPU and - memory intensive tasks of connection setup and key exchange without - authenticating. Implementors SHOULD provide features that make this - more difficult. For example, only allowing connections from a subset - of IPs known to have valid users. - -9.2.6 Covert Channels - - The protocol was not designed to eliminate covert channels. For - - - -Ylonen & Moffat Expires March 31, 2004 [Page 19] - -Internet-Draft SSH Protocol Architecture Oct 2003 - - - example, the padding, SSH_MSG_IGNORE messages, and several other - places in the protocol can be used to pass covert information, and - the recipient has no reliable way to verify whether such information - is being sent. - -9.2.7 Forward Secrecy - - It should be noted that the Diffie-Hellman key exchanges may provide - perfect forward secrecy (PFS). PFS is essentially defined as the - cryptographic property of a key-establishment protocol in which the - compromise of a session key or long-term private key after a given - session does not cause the compromise of any earlier session. [ANSI - T1.523-2001] SSHv2 sessions resulting from a key exchange using - diffie-hellman-group1-sha1 are secure even if private keying/ - authentication material is later revealed, but not if the session - keys are revealed. So, given this definition of PFS, SSHv2 does have - PFS. It is hoped that all other key exchange mechanisms proposed and - used in the future will also provide PFS. This property is not - commuted to any of the applications or protocols using SSH as a - transport however. The transport layer of SSH provides - confidentiality for password authentication and other methods that - rely on secret data. - - Of course, if the DH private parameters for the client and server are - revealed then the session key is revealed, but these items can be - thrown away after the key exchange completes. It's worth pointing - out that these items should not be allowed to end up on swap space - and that they should be erased from memory as soon as the key - exchange completes. - -9.3 Authentication Protocol - - The purpose of this protocol is to perform client user - authentication. It assumes that this run over a secure transport - layer protocol, which has already authenticated the server machine, - established an encrypted communications channel, and computed a - unique session identifier for this session. - - Several authentication methods with different security - characteristics are allowed. It is up to the server's local policy - to decide which methods (or combinations of methods) it is willing to - accept for each user. Authentication is no stronger than the weakest - combination allowed. - - The server may go into a "sleep" period after repeated unsuccessful - authentication attempts to make key search more difficult for - attackers. Care should be taken so that this doesn't become a - self-denial of service vector. - - - -Ylonen & Moffat Expires March 31, 2004 [Page 20] - -Internet-Draft SSH Protocol Architecture Oct 2003 - - -9.3.1 Weak Transport - - If the transport layer does not provide confidentiality, - authentication methods that rely on secret data SHOULD be disabled. - If it does not provide strong integrity protection, requests to - change authentication data (e.g. a password change) SHOULD be - disabled to prevent an attacker from modifying the ciphertext - without being noticed, or rendering the new authentication data - unusable (denial of service). - - The assumption as stated above that the Authentication Protocol only - run over a secure transport that has previously authenticated the - server is very important to note. People deploying SSH are reminded - of the consequences of man-in-the-middle attacks if the client does - not have a very strong a priori association of the server with the - host key of that server. Specifically for the case of the - Authentication Protocol the client may form a session to a - man-in-the-middle attack device and divulge user credentials such as - their username and password. Even in the cases of authentication - where no user credentials are divulged, an attacker may still gain - information they shouldn't have by capturing key-strokes in much the - same way that a honeypot works. - -9.3.2 Debug messages - - Special care should be taken when designing debug messages. These - messages may reveal surprising amounts of information about the host - if not properly designed. Debug messages can be disabled (during - user authentication phase) if high security is required. - Administrators of host machines should make all attempts to - compartmentalize all event notification messages and protect them - from unwarranted observation. Developers should be aware of the - sensitive nature of some of the normal event messages and debug - messages and may want to provide guidance to administrators on ways - to keep this information away from unauthorized people. Developers - should consider minimizing the amount of sensitive information - obtainable by users during the authentication phase in accordance - with the local policies. For this reason, it is RECOMMENDED that - debug messages be initially disabled at the time of deployment and - require an active decision by an administrator to allow them to be - enabled. It is also RECOMMENDED that a message expressing this - concern be presented to the administrator of a system when the action - is taken to enable debugging messages. - -9.3.3 Local security policy - - Implementer MUST ensure that the credentials provided validate the - professed user and also MUST ensure that the local policy of the - - - -Ylonen & Moffat Expires March 31, 2004 [Page 21] - -Internet-Draft SSH Protocol Architecture Oct 2003 - - - server permits the user the access requested. In particular, because - of the flexible nature of the SSH connection protocol, it may not be - possible to determine the local security policy, if any, that should - apply at the time of authentication because the kind of service being - requested is not clear at that instant. For example, local policy - might allow a user to access files on the server, but not start an - interactive shell. However, during the authentication protocol, it is - not known whether the user will be accessing files or attempting to - use an interactive shell, or even both. In any event, where local - security policy for the server host exists, it MUST be applied and - enforced correctly. - - Implementors are encouraged to provide a default local policy and - make its parameters known to administrators and users. At the - discretion of the implementors, this default policy may be along the - lines of 'anything goes' where there are no restrictions placed upon - users, or it may be along the lines of 'excessively restrictive' in - which case the administrators will have to actively make changes to - this policy to meet their needs. Alternatively, it may be some - attempt at providing something practical and immediately useful to - the administrators of the system so they don't have to put in much - effort to get SSH working. Whatever choice is made MUST be applied - and enforced as required above. - -9.3.4 Public key authentication - - The use of public-key authentication assumes that the client host has - not been compromised. It also assumes that the private-key of the - server host has not been compromised. - - This risk can be mitigated by the use of passphrases on private keys; - however, this is not an enforceable policy. The use of smartcards, - or other technology to make passphrases an enforceable policy is - suggested. - - The server could require both password and public-key authentication, - however, this requires the client to expose its password to the - server (see section on password authentication below.) - -9.3.5 Password authentication - - The password mechanism as specified in the authentication protocol - assumes that the server has not been compromised. If the server has - been compromised, using password authentication will reveal a valid - username / password combination to the attacker, which may lead to - further compromises. - - This vulnerability can be mitigated by using an alternative form of - - - -Ylonen & Moffat Expires March 31, 2004 [Page 22] - -Internet-Draft SSH Protocol Architecture Oct 2003 - - - authentication. For example, public-key authentication makes no - assumptions about security on the server. - -9.3.6 Host based authentication - - Host based authentication assumes that the client has not been - compromised. There are no mitigating strategies, other than to use - host based authentication in combination with another authentication - method. - -9.4 Connection protocol - -9.4.1 End point security - - End point security is assumed by the connection protocol. If the - server has been compromised, any terminal sessions, port forwarding, - or systems accessed on the host are compromised. There are no - mitigating factors for this. - - If the client end point has been compromised, and the server fails to - stop the attacker at the authentication protocol, all services - exposed (either as subsystems or through forwarding) will be - vulnerable to attack. Implementors SHOULD provide mechanisms for - administrators to control which services are exposed to limit the - vulnerability of other services. - - These controls might include controlling which machines and ports can - be target in 'port-forwarding' operations, which users are allowed to - use interactive shell facilities, or which users are allowed to use - exposed subsystems. - -9.4.2 Proxy forwarding - - The SSH connection protocol allows for proxy forwarding of other - protocols such as SNMP, POP3, and HTTP. This may be a concern for - network administrators who wish to control the access of certain - applications by users located outside of their physical location. - Essentially, the forwarding of these protocols may violate site - specific security policies as they may be undetectably tunneled - through a firewall. Implementors SHOULD provide an administrative - mechanism to control the proxy forwarding functionality so that site - specific security policies may be upheld. - - In addition, a reverse proxy forwarding functionality is available, - which again can be used to bypass firewall controls. - - As indicated above, end-point security is assumed during proxy - forwarding operations. Failure of end-point security will compromise - - - -Ylonen & Moffat Expires March 31, 2004 [Page 23] - -Internet-Draft SSH Protocol Architecture Oct 2003 - - - all data passed over proxy forwarding. - -9.4.3 X11 forwarding - - Another form of proxy forwarding provided by the ssh connection - protocol is the forwarding of the X11 protocol. If end-point - security has been compromised, X11 forwarding may allow attacks - against the X11 server. Users and administrators should, as a matter - of course, use appropriate X11 security mechanisms to prevent - unauthorized use of the X11 server. Implementors, administrators and - users who wish to further explore the security mechanisms of X11 are - invited to read [SCHEIFLER] and analyze previously reported problems - with the interactions between SSH forwarding and X11 in CERT - vulnerabilities VU#363181 and VU#118892 [CERT]. - - X11 display forwarding with SSH, by itself, is not sufficient to - correct well known problems with X11 security [VENEMA]. However, X11 - display forwarding in SSHv2 (or other, secure protocols), combined - with actual and pseudo-displays which accept connections only over - local IPC mechanisms authorized by permissions or ACLs, does correct - many X11 security problems as long as the "none" MAC is not used. It - is RECOMMENDED that X11 display implementations default to allowing - display opens only over local IPC. It is RECOMMENDED that SSHv2 - server implementations that support X11 forwarding default to - allowing display opens only over local IPC. On single-user systems - it might be reasonable to default to allowing local display opens - over TCP/IP. - - Implementors of the X11 forwarding protocol SHOULD implement the - magic cookie access checking spoofing mechanism as described in - [ssh-connect] as an additional mechanism to prevent unauthorized use - of the proxy. - -Normative References - - [SSH-ARCH] - Ylonen, T., "SSH Protocol Architecture", I-D - draft-ietf-architecture-15.txt, Oct 2003. - - [SSH-TRANS] - Ylonen, T., "SSH Transport Layer Protocol", I-D - draft-ietf-transport-17.txt, Oct 2003. - - [SSH-USERAUTH] - Ylonen, T., "SSH Authentication Protocol", I-D - draft-ietf-userauth-18.txt, Oct 2003. - - [SSH-CONNECT] - - - -Ylonen & Moffat Expires March 31, 2004 [Page 24] - -Internet-Draft SSH Protocol Architecture Oct 2003 - - - Ylonen, T., "SSH Connection Protocol", I-D - draft-ietf-connect-18.txt, Oct 2003. - - [SSH-NUMBERS] - Lehtinen, S. and D. Moffat, "SSH Protocol Assigned - Numbers", I-D draft-ietf-secsh-assignednumbers-05.txt, Oct - 2003. - - [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate - Requirement Levels", BCP 14, RFC 2119, March 1997. - -Informative References - - [FIPS-186] - Federal Information Processing Standards Publication, - "FIPS PUB 186, Digital Signature Standard", May 1994. - - [FIPS-197] - National Institue of Standards and Technology, "FIPS 197, - Specification for the Advanced Encryption Standard", - November 2001. - - [ANSI T1.523-2001] - American National Standards Insitute, Inc., "Telecom - Glossary 2000", February 2001. - - [SCHEIFLER] - Scheifler, R., "X Window System : The Complete Reference - to Xlib, X Protocol, Icccm, Xlfd, 3rd edition.", Digital - Press ISBN 1555580882, Feburary 1992. - - [RFC0854] Postel, J. and J. Reynolds, "Telnet Protocol - Specification", STD 8, RFC 854, May 1983. - - [RFC0894] Hornig, C., "Standard for the transmission of IP datagrams - over Ethernet networks", STD 41, RFC 894, April 1984. - - [RFC1034] Mockapetris, P., "Domain names - concepts and facilities", - STD 13, RFC 1034, November 1987. - - [RFC1134] Perkins, D., "Point-to-Point Protocol: A proposal for - multi-protocol transmission of datagrams over - Point-to-Point links", RFC 1134, November 1989. - - [RFC1282] Kantor, B., "BSD Rlogin", RFC 1282, December 1991. - - [RFC1510] Kohl, J. and B. Neuman, "The Kerberos Network - Authentication Service (V5)", RFC 1510, September 1993. - - - -Ylonen & Moffat Expires March 31, 2004 [Page 25] - -Internet-Draft SSH Protocol Architecture Oct 2003 - - - [RFC1700] Reynolds, J. and J. Postel, "Assigned Numbers", RFC 1700, - October 1994. - - [RFC1750] Eastlake, D., Crocker, S. and J. Schiller, "Randomness - Recommendations for Security", RFC 1750, December 1994. - - [RFC3066] Alvestrand, H., "Tags for the Identification of - Languages", BCP 47, RFC 3066, January 2001. - - [RFC1964] Linn, J., "The Kerberos Version 5 GSS-API Mechanism", RFC - 1964, June 1996. - - [RFC2025] Adams, C., "The Simple Public-Key GSS-API Mechanism - (SPKM)", RFC 2025, October 1996. - - [RFC2085] Oehler, M. and R. Glenn, "HMAC-MD5 IP Authentication with - Replay Prevention", RFC 2085, February 1997. - - [RFC2104] Krawczyk, H., Bellare, M. and R. Canetti, "HMAC: - Keyed-Hashing for Message Authentication", RFC 2104, - February 1997. - - [RFC2246] Dierks, T., Allen, C., Treese, W., Karlton, P., Freier, A. - and P. Kocher, "The TLS Protocol Version 1.0", RFC 2246, - January 1999. - - [RFC2279] Yergeau, F., "UTF-8, a transformation format of ISO - 10646", RFC 2279, January 1998. - - [RFC2410] Glenn, R. and S. Kent, "The NULL Encryption Algorithm and - Its Use With IPsec", RFC 2410, November 1998. - - [RFC2434] Narten, T. and H. Alvestrand, "Guidelines for Writing an - IANA Considerations Section in RFCs", BCP 26, RFC 2434, - October 1998. - - [RFC2743] Linn, J., "Generic Security Service Application Program - Interface Version 2, Update 1", RFC 2743, January 2000. - - [SCHNEIER] - Schneier, B., "Applied Cryptography Second Edition: - protocols algorithms and source in code in C", 1996. - - [KAUFMAN,PERLMAN,SPECINER] - Kaufman, C., Perlman, R. and M. Speciner, "Network - Security: PRIVATE Communication in a PUBLIC World", 1995. - - [CERT] CERT Coordination Center, The., "http://www.cert.org/nav/ - - - -Ylonen & Moffat Expires March 31, 2004 [Page 26] - -Internet-Draft SSH Protocol Architecture Oct 2003 - - - index_red.html". - - [VENEMA] Venema, W., "Murphy's Law and Computer Security", - Proceedings of 6th USENIX Security Symposium, San Jose CA - http://www.usenix.org/publications/library/proceedings/ - sec96/venema.html, July 1996. - - [ROGAWAY] Rogaway, P., "Problems with Proposed IP Cryptography", - Unpublished paper http://www.cs.ucdavis.edu/~rogaway/ - papers/draft-rogaway-ipsec-comments-00.txt, 1996. - - [DAI] Dai, W., "An attack against SSH2 protocol", Email to the - SECSH Working Group [email protected] ftp:// - ftp.ietf.org/ietf-mail-archive/secsh/2002-02.mail, Feb - 2002. - - [BELLARE,KOHNO,NAMPREMPRE] - Bellaire, M., Kohno, T. and C. Namprempre, "Authenticated - Encryption in SSH: Fixing the SSH Binary Packet Protocol", - , Sept 2002. - - -Authors' Addresses - - Tatu Ylonen - SSH Communications Security Corp - Fredrikinkatu 42 - HELSINKI FIN-00100 - Finland - - EMail: [email protected] - - - Darren J. Moffat (editor) - Sun Microsystems, Inc - 17 Network Circle - Menlo Park CA 94025 - USA - - EMail: [email protected] - - - - - - - - - - - -Ylonen & Moffat Expires March 31, 2004 [Page 27] - -Internet-Draft SSH Protocol Architecture Oct 2003 - - -Intellectual Property Statement - - The IETF takes no position regarding the validity or scope of any - intellectual property or other rights that might be claimed to - pertain to the implementation or use of the technology described in - this document or the extent to which any license under such rights - might or might not be available; neither does it represent that it - has made any effort to identify any such rights. Information on the - IETF's procedures with respect to rights in standards-track and - standards-related documentation can be found in BCP-11. Copies of - claims of rights made available for publication and any assurances of - licenses to be made available, or the result of an attempt made to - obtain a general license or permission for the use of such - proprietary rights by implementors or users of this specification can - be obtained from the IETF Secretariat. - - The IETF invites any interested party to bring to its attention any - copyrights, patents or patent applications, or other proprietary - rights which may cover technology that may be required to practice - this standard. Please address the information to the IETF Executive - Director. - - The IETF has been notified of intellectual property rights claimed in - regard to some or all of the specification contained in this - document. For more information consult the online list of claimed - rights. - - -Full Copyright Statement - - Copyright (C) The Internet Society (2003). All Rights Reserved. - - This document and translations of it may be copied and furnished to - others, and derivative works that comment on or otherwise explain it - or assist in its implementation may be prepared, copied, published - and distributed, in whole or in part, without restriction of any - kind, provided that the above copyright notice and this paragraph are - included on all such copies and derivative works. However, this - document itself may not be modified in any way, such as by removing - the copyright notice or references to the Internet Society or other - Internet organizations, except as needed for the purpose of - developing Internet standards in which case the procedures for - copyrights defined in the Internet Standards process must be - followed, or as required to translate it into languages other than - English. - - The limited permissions granted above are perpetual and will not be - revoked by the Internet Society or its successors or assignees. - - - -Ylonen & Moffat Expires March 31, 2004 [Page 28] - -Internet-Draft SSH Protocol Architecture Oct 2003 - - - This document and the information contained herein is provided on an - "AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING - TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING - BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION - HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF - MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE. - - -Acknowledgment - - Funding for the RFC Editor function is currently provided by the - Internet Society. - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -Ylonen & Moffat Expires March 31, 2004 [Page 29]
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matrix invertmatrix matrix concatmatrix - matrix invertmatrix put -%%EndSetup -%%Page: (0,1) 1 -userdict/PStoPSsaved save put -PStoPSmatrix setmatrix -595.000000 0.271378 translate -90 rotate -0.706651 dup scale -userdict/PStoPSmatrix matrix currentmatrix put -userdict/PStoPSclip{0 0 moveto - 595.000000 0 rlineto 0 842.000000 rlineto -595.000000 0 rlineto - closepath}put initclip -/showpage{}def/copypage{}def/erasepage{}def -PStoPSxform concat -%%BeginPageSetup -_S -75 0 translate -/pagenum 1 def -/fname () def -/fdir () def -/ftail () def -/user_header_p false def -%%EndPageSetup -5 701 M -(Network Working Group T. Ylonen) s -5 690 M -(Internet-Draft SSH Communications Security Corp) s -5 679 M -(Expires: March 31, 2004 D. Moffat, Editor, Ed.) s -5 668 M -( Sun Microsystems, Inc) s -5 657 M -( Oct 2003) s -5 624 M -( SSH Connection Protocol) s -5 613 M -( draft-ietf-secsh-connect-18.txt) s -5 591 M -(Status of this Memo) s -5 569 M -( This document is an Internet-Draft and is in full conformance with) s -5 558 M -( all provisions of Section 10 of RFC2026.) s -5 536 M -( Internet-Drafts are working documents of the Internet Engineering) s -5 525 M -( Task Force \(IETF\), its areas, and its working groups. Note that other) s -5 514 M -( groups may also distribute working documents as Internet-Drafts.) s -5 492 M -( Internet-Drafts are draft documents valid for a maximum of six months) s -5 481 M -( and may be updated, replaced, or obsoleted by other documents at any) s -5 470 M -( time. It is inappropriate to use Internet-Drafts as reference) s -5 459 M -( material or to cite them other than as "work in progress.") s -5 437 M -( The list of current Internet-Drafts can be accessed at http://) s -5 426 M -( www.ietf.org/ietf/1id-abstracts.txt.) s -5 404 M -( The list of Internet-Draft Shadow Directories can be accessed at) s -5 393 M -( http://www.ietf.org/shadow.html.) s -5 371 M -( This Internet-Draft will expire on March 31, 2004.) s -5 349 M -(Copyright Notice) s -5 327 M -( Copyright \(C\) The Internet Society \(2003\). All Rights Reserved.) s -5 305 M -(Abstract) s -5 283 M -( SSH is a protocol for secure remote login and other secure network) s -5 272 M -( services over an insecure network.) s -5 250 M -( This document describes the SSH Connection Protocol. It provides) s -5 239 M -( interactive login sessions, remote execution of commands, forwarded) s -5 228 M -( TCP/IP connections, and forwarded X11 connections. All of these) s -5 217 M -( channels are multiplexed into a single encrypted tunnel.) s -5 195 M -( The SSH Connection Protocol has been designed to run on top of the) s -5 184 M -( SSH transport layer and user authentication protocols.) s -5 129 M -(Ylonen & Moffat, Editor Expires March 31, 2004 [Page 1]) s -_R -S -PStoPSsaved restore -userdict/PStoPSsaved save put -PStoPSmatrix setmatrix -595.000000 421.271378 translate -90 rotate -0.706651 dup scale -userdict/PStoPSmatrix matrix currentmatrix put -userdict/PStoPSclip{0 0 moveto - 595.000000 0 rlineto 0 842.000000 rlineto -595.000000 0 rlineto - closepath}put initclip -PStoPSxform concat -%%BeginPageSetup -_S -75 0 translate -/pagenum 2 def -/fname () def -/fdir () def -/ftail () def -/user_header_p false def -%%EndPageSetup -5 723 M -(Internet-Draft SSH Connection Protocol Oct 2003) s -5 690 M -(Table of Contents) s -5 668 M -( 1. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 3) s -5 657 M -( 2. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3) s -5 646 M -( 3. Conventions Used in This Document . . . . . . . . . . . . . 3) s -5 635 M -( 4. Global Requests . . . . . . . . . . . . . . . . . . . . . . 3) s -5 624 M -( 5. Channel Mechanism . . . . . . . . . . . . . . . . . . . . . 4) s -5 613 M -( 5.1 Opening a Channel . . . . . . . . . . . . . . . . . . . . . 4) s -5 602 M -( 5.2 Data Transfer . . . . . . . . . . . . . . . . . . . . . . . 5) s -5 591 M -( 5.3 Closing a Channel . . . . . . . . . . . . . . . . . . . . . 6) s -5 580 M -( 5.4 Channel-Specific Requests . . . . . . . . . . . . . . . . . 7) s -5 569 M -( 6. Interactive Sessions . . . . . . . . . . . . . . . . . . . . 8) s -5 558 M -( 6.1 Opening a Session . . . . . . . . . . . . . . . . . . . . . 8) s -5 547 M -( 6.2 Requesting a Pseudo-Terminal . . . . . . . . . . . . . . . . 8) s -5 536 M -( 6.3 X11 Forwarding . . . . . . . . . . . . . . . . . . . . . . . 9) s -5 525 M -( 6.3.1 Requesting X11 Forwarding . . . . . . . . . . . . . . . . . 9) s -5 514 M -( 6.3.2 X11 Channels . . . . . . . . . . . . . . . . . . . . . . . . 10) s -5 503 M -( 6.4 Environment Variable Passing . . . . . . . . . . . . . . . . 10) s -5 492 M -( 6.5 Starting a Shell or a Command . . . . . . . . . . . . . . . 10) s -5 481 M -( 6.6 Session Data Transfer . . . . . . . . . . . . . . . . . . . 11) s -5 470 M -( 6.7 Window Dimension Change Message . . . . . . . . . . . . . . 12) s -5 459 M -( 6.8 Local Flow Control . . . . . . . . . . . . . . . . . . . . . 12) s -5 448 M -( 6.9 Signals . . . . . . . . . . . . . . . . . . . . . . . . . . 12) s -5 437 M -( 6.10 Returning Exit Status . . . . . . . . . . . . . . . . . . . 13) s -5 426 M -( 7. TCP/IP Port Forwarding . . . . . . . . . . . . . . . . . . . 14) s -5 415 M -( 7.1 Requesting Port Forwarding . . . . . . . . . . . . . . . . . 14) s -5 404 M -( 7.2 TCP/IP Forwarding Channels . . . . . . . . . . . . . . . . . 15) s -5 393 M -( 8. Encoding of Terminal Modes . . . . . . . . . . . . . . . . . 16) s -5 382 M -( 9. Summary of Message Numbers . . . . . . . . . . . . . . . . . 18) s -5 371 M -( 10. Security Considerations . . . . . . . . . . . . . . . . . . 18) s -5 360 M -( 11. iana cONSiderations . . . . . . . . . . . . . . . . . . . . 19) s -5 349 M -( 12. Intellectual Property . . . . . . . . . . . . . . . . . . . 19) s -5 338 M -( Normative References . . . . . . . . . . . . . . . . . . . . 19) s -5 327 M -( Informative References . . . . . . . . . . . . . . . . . . . 20) s -5 316 M -( Authors' Addresses . . . . . . . . . . . . . . . . . . . . . 20) s -5 305 M -( Intellectual Property and Copyright Statements . . . . . . . 21) s -5 129 M -(Ylonen & Moffat, Editor Expires March 31, 2004 [Page 2]) s -_R -S -PStoPSsaved restore -%%Page: (2,3) 2 -userdict/PStoPSsaved save put -PStoPSmatrix setmatrix -595.000000 0.271378 translate -90 rotate -0.706651 dup scale -userdict/PStoPSmatrix matrix currentmatrix put -userdict/PStoPSclip{0 0 moveto - 595.000000 0 rlineto 0 842.000000 rlineto -595.000000 0 rlineto - closepath}put initclip -/showpage{}def/copypage{}def/erasepage{}def -PStoPSxform concat -%%BeginPageSetup -_S -75 0 translate -/pagenum 3 def -/fname () def -/fdir () def -/ftail () def -/user_header_p false def -%%EndPageSetup -5 723 M -(Internet-Draft SSH Connection Protocol Oct 2003) s -5 690 M -(1. Contributors) s -5 668 M -( The major original contributors of this document were: Tatu Ylonen,) s -5 657 M -( Tero Kivinen, Timo J. Rinne, Sami Lehtinen \(all of SSH Communications) s -5 646 M -( Security Corp\), and Markku-Juhani O. Saarinen \(University of) s -5 635 M -( Jyvaskyla\)) s -5 613 M -( The document editor is: [email protected]. Comments on this) s -5 602 M -( internet draft should be sent to the IETF SECSH working group,) s -5 591 M -( details at: http://ietf.org/html.charters/secsh-charter.html) s -5 569 M -(2. Introduction) s -5 547 M -( The SSH Connection Protocol has been designed to run on top of the) s -5 536 M -( SSH transport layer and user authentication protocols. It provides) s -5 525 M -( interactive login sessions, remote execution of commands, forwarded) s -5 514 M -( TCP/IP connections, and forwarded X11 connections. The service name) s -5 503 M -( for this protocol is "ssh-connection".) s -5 481 M -( This document should be read only after reading the SSH architecture) s -5 470 M -( document [SSH-ARCH]. This document freely uses terminology and) s -5 459 M -( notation from the architecture document without reference or further) s -5 448 M -( explanation.) s -5 426 M -(3. Conventions Used in This Document) s -5 404 M -( The keywords "MUST", "MUST NOT", "REQUIRED", "SHOULD", "SHOULD NOT",) s -5 393 M -( and "MAY" that appear in this document are to be interpreted as) s -5 382 M -( described in [RFC2119].) s -5 360 M -( The used data types and terminology are specified in the architecture) s -5 349 M -( document [SSH-ARCH].) s -5 327 M -( The architecture document also discusses the algorithm naming) s -5 316 M -( conventions that MUST be used with the SSH protocols.) s -5 294 M -(4. Global Requests) s -5 272 M -( There are several kinds of requests that affect the state of the) s -5 261 M -( remote end "globally", independent of any channels. An example is a) s -5 250 M -( request to start TCP/IP forwarding for a specific port. All such) s -5 239 M -( requests use the following format.) s -5 217 M -( byte SSH_MSG_GLOBAL_REQUEST) s -5 206 M -( string request name \(restricted to US-ASCII\)) s -5 195 M -( boolean want reply) s -5 184 M -( ... request-specific data follows) s -5 129 M -(Ylonen & Moffat, Editor Expires March 31, 2004 [Page 3]) s -_R -S -PStoPSsaved restore -userdict/PStoPSsaved save put -PStoPSmatrix setmatrix -595.000000 421.271378 translate -90 rotate -0.706651 dup scale -userdict/PStoPSmatrix matrix currentmatrix put -userdict/PStoPSclip{0 0 moveto - 595.000000 0 rlineto 0 842.000000 rlineto -595.000000 0 rlineto - closepath}put initclip -PStoPSxform concat -%%BeginPageSetup -_S -75 0 translate -/pagenum 4 def -/fname () def -/fdir () def -/ftail () def -/user_header_p false def -%%EndPageSetup -5 723 M -(Internet-Draft SSH Connection Protocol Oct 2003) s -5 690 M -( Request names follow the DNS extensibility naming convention outlined) s -5 679 M -( in [SSH-ARCH].) s -5 657 M -( The recipient will respond to this message with) s -5 646 M -( SSH_MSG_REQUEST_SUCCESS or SSH_MSG_REQUEST_FAILURE if `want reply' is) s -5 635 M -( TRUE.) s -5 613 M -( byte SSH_MSG_REQUEST_SUCCESS) s -5 602 M -( ..... response specific data) s -5 580 M -( Usually the response specific data is non-existent.) s -5 558 M -( If the recipient does not recognize or support the request, it simply) s -5 547 M -( responds with SSH_MSG_REQUEST_FAILURE.) s -5 525 M -( byte SSH_MSG_REQUEST_FAILURE) s -5 492 M -(5. Channel Mechanism) s -5 470 M -( All terminal sessions, forwarded connections, etc. are channels.) s -5 459 M -( Either side may open a channel. Multiple channels are multiplexed) s -5 448 M -( into a single connection.) s -5 426 M -( Channels are identified by numbers at each end. The number referring) s -5 415 M -( to a channel may be different on each side. Requests to open a) s -5 404 M -( channel contain the sender's channel number. Any other) s -5 393 M -( channel-related messages contain the recipient's channel number for) s -5 382 M -( the channel.) s -5 360 M -( Channels are flow-controlled. No data may be sent to a channel until) s -5 349 M -( a message is received to indicate that window space is available.) s -5 327 M -(5.1 Opening a Channel) s -5 305 M -( When either side wishes to open a new channel, it allocates a local) s -5 294 M -( number for the channel. It then sends the following message to the) s -5 283 M -( other side, and includes the local channel number and initial window) s -5 272 M -( size in the message.) s -5 250 M -( byte SSH_MSG_CHANNEL_OPEN) s -5 239 M -( string channel type \(restricted to US-ASCII\)) s -5 228 M -( uint32 sender channel) s -5 217 M -( uint32 initial window size) s -5 206 M -( uint32 maximum packet size) s -5 195 M -( ... channel type specific data follows) s -5 173 M -( The channel type is a name as described in the SSH architecture) s -5 129 M -(Ylonen & Moffat, Editor Expires March 31, 2004 [Page 4]) s -_R -S -PStoPSsaved restore -%%Page: (4,5) 3 -userdict/PStoPSsaved save put -PStoPSmatrix setmatrix -595.000000 0.271378 translate -90 rotate -0.706651 dup scale -userdict/PStoPSmatrix matrix currentmatrix put -userdict/PStoPSclip{0 0 moveto - 595.000000 0 rlineto 0 842.000000 rlineto -595.000000 0 rlineto - closepath}put initclip -/showpage{}def/copypage{}def/erasepage{}def -PStoPSxform concat -%%BeginPageSetup -_S -75 0 translate -/pagenum 5 def -/fname () def -/fdir () def -/ftail () def -/user_header_p false def -%%EndPageSetup -5 723 M -(Internet-Draft SSH Connection Protocol Oct 2003) s -5 690 M -( document, with similar extension mechanisms. `sender channel' is a) s -5 679 M -( local identifier for the channel used by the sender of this message.) s -5 668 M -( `initial window size' specifies how many bytes of channel data can be) s -5 657 M -( sent to the sender of this message without adjusting the window.) s -5 646 M -( `Maximum packet size' specifies the maximum size of an individual) s -5 635 M -( data packet that can be sent to the sender \(for example, one might) s -5 624 M -( want to use smaller packets for interactive connections to get better) s -5 613 M -( interactive response on slow links\).) s -5 591 M -( The remote side then decides whether it can open the channel, and) s -5 580 M -( responds with either) s -5 558 M -( byte SSH_MSG_CHANNEL_OPEN_CONFIRMATION) s -5 547 M -( uint32 recipient channel) s -5 536 M -( uint32 sender channel) s -5 525 M -( uint32 initial window size) s -5 514 M -( uint32 maximum packet size) s -5 503 M -( ... channel type specific data follows) s -5 481 M -( where `recipient channel' is the channel number given in the original) s -5 470 M -( open request, and `sender channel' is the channel number allocated by) s -5 459 M -( the other side, or) s -5 437 M -( byte SSH_MSG_CHANNEL_OPEN_FAILURE) s -5 426 M -( uint32 recipient channel) s -5 415 M -( uint32 reason code) s -5 404 M -( string additional textual information \(ISO-10646 UTF-8 [RFC2279]\)) s -5 393 M -( string language tag \(as defined in [RFC3066]\)) s -5 371 M -( If the recipient of the SSH_MSG_CHANNEL_OPEN message does not support) s -5 360 M -( the specified channel type, it simply responds with) s -5 349 M -( SSH_MSG_CHANNEL_OPEN_FAILURE. The client MAY show the additional) s -5 338 M -( information to the user. If this is done, the client software should) s -5 327 M -( take the precautions discussed in [SSH-ARCH].) s -5 305 M -( The following reason codes are defined:) s -5 283 M -( #define SSH_OPEN_ADMINISTRATIVELY_PROHIBITED 1) s -5 272 M -( #define SSH_OPEN_CONNECT_FAILED 2) s -5 261 M -( #define SSH_OPEN_UNKNOWN_CHANNEL_TYPE 3) s -5 250 M -( #define SSH_OPEN_RESOURCE_SHORTAGE 4) s -5 217 M -(5.2 Data Transfer) s -5 195 M -( The window size specifies how many bytes the other party can send) s -5 184 M -( before it must wait for the window to be adjusted. Both parties use) s -5 173 M -( the following message to adjust the window.) s -5 129 M -(Ylonen & Moffat, Editor Expires March 31, 2004 [Page 5]) s -_R -S -PStoPSsaved restore -userdict/PStoPSsaved save put -PStoPSmatrix setmatrix -595.000000 421.271378 translate -90 rotate -0.706651 dup scale -userdict/PStoPSmatrix matrix currentmatrix put -userdict/PStoPSclip{0 0 moveto - 595.000000 0 rlineto 0 842.000000 rlineto -595.000000 0 rlineto - closepath}put initclip -PStoPSxform concat -%%BeginPageSetup -_S -75 0 translate -/pagenum 6 def -/fname () def -/fdir () def -/ftail () def -/user_header_p false def -%%EndPageSetup -5 723 M -(Internet-Draft SSH Connection Protocol Oct 2003) s -5 690 M -( byte SSH_MSG_CHANNEL_WINDOW_ADJUST) s -5 679 M -( uint32 recipient channel) s -5 668 M -( uint32 bytes to add) s -5 646 M -( After receiving this message, the recipient MAY send the given number) s -5 635 M -( of bytes more than it was previously allowed to send; the window size) s -5 624 M -( is incremented.) s -5 602 M -( Data transfer is done with messages of the following type.) s -5 580 M -( byte SSH_MSG_CHANNEL_DATA) s -5 569 M -( uint32 recipient channel) s -5 558 M -( string data) s -5 536 M -( The maximum amount of data allowed is the current window size. The) s -5 525 M -( window size is decremented by the amount of data sent. Both parties) s -5 514 M -( MAY ignore all extra data sent after the allowed window is empty.) s -5 492 M -( Additionally, some channels can transfer several types of data. An) s -5 481 M -( example of this is stderr data from interactive sessions. Such data) s -5 470 M -( can be passed with SSH_MSG_CHANNEL_EXTENDED_DATA messages, where a) s -5 459 M -( separate integer specifies the type of the data. The available types) s -5 448 M -( and their interpretation depend on the type of the channel.) s -5 426 M -( byte SSH_MSG_CHANNEL_EXTENDED_DATA) s -5 415 M -( uint32 recipient_channel) s -5 404 M -( uint32 data_type_code) s -5 393 M -( string data) s -5 371 M -( Data sent with these messages consumes the same window as ordinary) s -5 360 M -( data.) s -5 338 M -( Currently, only the following type is defined.) s -5 316 M -( #define SSH_EXTENDED_DATA_STDERR 1) s -5 283 M -(5.3 Closing a Channel) s -5 261 M -( When a party will no longer send more data to a channel, it SHOULD) s -5 250 M -( send SSH_MSG_CHANNEL_EOF.) s -5 228 M -( byte SSH_MSG_CHANNEL_EOF) s -5 217 M -( uint32 recipient_channel) s -5 195 M -( No explicit response is sent to this message; however, the) s -5 184 M -( application may send EOF to whatever is at the other end of the) s -5 173 M -( channel. Note that the channel remains open after this message, and) s -5 129 M -(Ylonen & Moffat, Editor Expires March 31, 2004 [Page 6]) s -_R -S -PStoPSsaved restore -%%Page: (6,7) 4 -userdict/PStoPSsaved save put -PStoPSmatrix setmatrix -595.000000 0.271378 translate -90 rotate -0.706651 dup scale -userdict/PStoPSmatrix matrix currentmatrix put -userdict/PStoPSclip{0 0 moveto - 595.000000 0 rlineto 0 842.000000 rlineto -595.000000 0 rlineto - closepath}put initclip -/showpage{}def/copypage{}def/erasepage{}def -PStoPSxform concat -%%BeginPageSetup -_S -75 0 translate -/pagenum 7 def -/fname () def -/fdir () def -/ftail () def -/user_header_p false def -%%EndPageSetup -5 723 M -(Internet-Draft SSH Connection Protocol Oct 2003) s -5 690 M -( more data may still be sent in the other direction. This message) s -5 679 M -( does not consume window space and can be sent even if no window space) s -5 668 M -( is available.) s -5 646 M -( When either party wishes to terminate the channel, it sends) s -5 635 M -( SSH_MSG_CHANNEL_CLOSE. Upon receiving this message, a party MUST) s -5 624 M -( send back a SSH_MSG_CHANNEL_CLOSE unless it has already sent this) s -5 613 M -( message for the channel. The channel is considered closed for a) s -5 602 M -( party when it has both sent and received SSH_MSG_CHANNEL_CLOSE, and) s -5 591 M -( the party may then reuse the channel number. A party MAY send) s -5 580 M -( SSH_MSG_CHANNEL_CLOSE without having sent or received) s -5 569 M -( SSH_MSG_CHANNEL_EOF.) s -5 547 M -( byte SSH_MSG_CHANNEL_CLOSE) s -5 536 M -( uint32 recipient_channel) s -5 514 M -( This message does not consume window space and can be sent even if no) s -5 503 M -( window space is available.) s -5 481 M -( It is recommended that any data sent before this message is delivered) s -5 470 M -( to the actual destination, if possible.) s -5 448 M -(5.4 Channel-Specific Requests) s -5 426 M -( Many channel types have extensions that are specific to that) s -5 415 M -( particular channel type. An example is requesting a pty \(pseudo) s -5 404 M -( terminal\) for an interactive session.) s -5 382 M -( All channel-specific requests use the following format.) s -5 360 M -( byte SSH_MSG_CHANNEL_REQUEST) s -5 349 M -( uint32 recipient channel) s -5 338 M -( string request type \(restricted to US-ASCII\)) s -5 327 M -( boolean want reply) s -5 316 M -( ... type-specific data) s -5 294 M -( If want reply is FALSE, no response will be sent to the request.) s -5 283 M -( Otherwise, the recipient responds with either SSH_MSG_CHANNEL_SUCCESS) s -5 272 M -( or SSH_MSG_CHANNEL_FAILURE, or request-specific continuation) s -5 261 M -( messages. If the request is not recognized or is not supported for) s -5 250 M -( the channel, SSH_MSG_CHANNEL_FAILURE is returned.) s -5 228 M -( This message does not consume window space and can be sent even if no) s -5 217 M -( window space is available. Request types are local to each channel) s -5 206 M -( type.) s -5 184 M -( The client is allowed to send further messages without waiting for) s -5 173 M -( the response to the request.) s -5 129 M -(Ylonen & Moffat, Editor Expires March 31, 2004 [Page 7]) s -_R -S -PStoPSsaved restore -userdict/PStoPSsaved save put -PStoPSmatrix setmatrix -595.000000 421.271378 translate -90 rotate -0.706651 dup scale -userdict/PStoPSmatrix matrix currentmatrix put -userdict/PStoPSclip{0 0 moveto - 595.000000 0 rlineto 0 842.000000 rlineto -595.000000 0 rlineto - closepath}put initclip -PStoPSxform concat -%%BeginPageSetup -_S -75 0 translate -/pagenum 8 def -/fname () def -/fdir () def -/ftail () def -/user_header_p false def -%%EndPageSetup -5 723 M -(Internet-Draft SSH Connection Protocol Oct 2003) s -5 690 M -( request type names follow the DNS extensibility naming convention) s -5 679 M -( outlined in [SSH-ARCH]) s -5 657 M -( byte SSH_MSG_CHANNEL_SUCCESS) s -5 646 M -( uint32 recipient_channel) s -5 613 M -( byte SSH_MSG_CHANNEL_FAILURE) s -5 602 M -( uint32 recipient_channel) s -5 580 M -( These messages do not consume window space and can be sent even if no) s -5 569 M -( window space is available.) s -5 547 M -(6. Interactive Sessions) s -5 525 M -( A session is a remote execution of a program. The program may be a) s -5 514 M -( shell, an application, a system command, or some built-in subsystem.) s -5 503 M -( It may or may not have a tty, and may or may not involve X11) s -5 492 M -( forwarding. Multiple sessions can be active simultaneously.) s -5 470 M -(6.1 Opening a Session) s -5 448 M -( A session is started by sending the following message.) s -5 426 M -( byte SSH_MSG_CHANNEL_OPEN) s -5 415 M -( string "session") s -5 404 M -( uint32 sender channel) s -5 393 M -( uint32 initial window size) s -5 382 M -( uint32 maximum packet size) s -5 360 M -( Client implementations SHOULD reject any session channel open) s -5 349 M -( requests to make it more difficult for a corrupt server to attack the) s -5 338 M -( client.) s -5 316 M -(6.2 Requesting a Pseudo-Terminal) s -5 294 M -( A pseudo-terminal can be allocated for the session by sending the) s -5 283 M -( following message.) s -5 261 M -( byte SSH_MSG_CHANNEL_REQUEST) s -5 250 M -( uint32 recipient_channel) s -5 239 M -( string "pty-req") s -5 228 M -( boolean want_reply) s -5 217 M -( string TERM environment variable value \(e.g., vt100\)) s -5 206 M -( uint32 terminal width, characters \(e.g., 80\)) s -5 195 M -( uint32 terminal height, rows \(e.g., 24\)) s -5 184 M -( uint32 terminal width, pixels \(e.g., 640\)) s -5 173 M -( uint32 terminal height, pixels \(e.g., 480\)) s -5 129 M -(Ylonen & Moffat, Editor Expires March 31, 2004 [Page 8]) s -_R -S -PStoPSsaved restore -%%Page: (8,9) 5 -userdict/PStoPSsaved save put -PStoPSmatrix setmatrix -595.000000 0.271378 translate -90 rotate -0.706651 dup scale -userdict/PStoPSmatrix matrix currentmatrix put -userdict/PStoPSclip{0 0 moveto - 595.000000 0 rlineto 0 842.000000 rlineto -595.000000 0 rlineto - closepath}put initclip -/showpage{}def/copypage{}def/erasepage{}def -PStoPSxform concat -%%BeginPageSetup -_S -75 0 translate -/pagenum 9 def -/fname () def -/fdir () def -/ftail () def -/user_header_p false def -%%EndPageSetup -5 723 M -(Internet-Draft SSH Connection Protocol Oct 2003) s -5 690 M -( string encoded terminal modes) s -5 668 M -( The encoding of terminal modes is described in Section Encoding of) s -5 657 M -( Terminal Modes \(Section 8\). Zero dimension parameters MUST be) s -5 646 M -( ignored. The character/row dimensions override the pixel dimensions) s -5 635 M -( \(when nonzero\). Pixel dimensions refer to the drawable area of the) s -5 624 M -( window.) s -5 602 M -( The dimension parameters are only informational.) s -5 580 M -( The client SHOULD ignore pty requests.) s -5 558 M -(6.3 X11 Forwarding) s -5 536 M -(6.3.1 Requesting X11 Forwarding) s -5 514 M -( X11 forwarding may be requested for a session by sending) s -5 492 M -( byte SSH_MSG_CHANNEL_REQUEST) s -5 481 M -( uint32 recipient channel) s -5 470 M -( string "x11-req") s -5 459 M -( boolean want reply) s -5 448 M -( boolean single connection) s -5 437 M -( string x11 authentication protocol) s -5 426 M -( string x11 authentication cookie) s -5 415 M -( uint32 x11 screen number) s -5 393 M -( It is recommended that the authentication cookie that is sent be a) s -5 382 M -( fake, random cookie, and that the cookie is checked and replaced by) s -5 371 M -( the real cookie when a connection request is received.) s -5 349 M -( X11 connection forwarding should stop when the session channel is) s -5 338 M -( closed; however, already opened forwardings should not be) s -5 327 M -( automatically closed when the session channel is closed.) s -5 305 M -( If `single connection' is TRUE, only a single connection should be) s -5 294 M -( forwarded. No more connections will be forwarded after the first, or) s -5 283 M -( after the session channel has been closed.) s -5 261 M -( The "x11 authentication protocol" is the name of the X11) s -5 250 M -( authentication method used, e.g. "MIT-MAGIC-COOKIE-1".) s -5 228 M -( The x11 authentication cookie MUST be hexadecimal encoded.) s -5 206 M -( X Protocol is documented in [SCHEIFLER].) s -5 129 M -(Ylonen & Moffat, Editor Expires March 31, 2004 [Page 9]) s -_R -S -PStoPSsaved restore -userdict/PStoPSsaved save put -PStoPSmatrix setmatrix -595.000000 421.271378 translate -90 rotate -0.706651 dup scale -userdict/PStoPSmatrix matrix currentmatrix put -userdict/PStoPSclip{0 0 moveto - 595.000000 0 rlineto 0 842.000000 rlineto -595.000000 0 rlineto - closepath}put initclip -PStoPSxform concat -%%BeginPageSetup -_S -75 0 translate -/pagenum 10 def -/fname () def -/fdir () def -/ftail () def -/user_header_p false def -%%EndPageSetup -5 723 M -(Internet-Draft SSH Connection Protocol Oct 2003) s -5 690 M -(6.3.2 X11 Channels) s -5 668 M -( X11 channels are opened with a channel open request. The resulting) s -5 657 M -( channels are independent of the session, and closing the session) s -5 646 M -( channel does not close the forwarded X11 channels.) s -5 624 M -( byte SSH_MSG_CHANNEL_OPEN) s -5 613 M -( string "x11") s -5 602 M -( uint32 sender channel) s -5 591 M -( uint32 initial window size) s -5 580 M -( uint32 maximum packet size) s -5 569 M -( string originator address \(e.g. "192.168.7.38"\)) s -5 558 M -( uint32 originator port) s -5 536 M -( The recipient should respond with SSH_MSG_CHANNEL_OPEN_CONFIRMATION) s -5 525 M -( or SSH_MSG_CHANNEL_OPEN_FAILURE.) s -5 503 M -( Implementations MUST reject any X11 channel open requests if they) s -5 492 M -( have not requested X11 forwarding.) s -5 470 M -(6.4 Environment Variable Passing) s -5 448 M -( Environment variables may be passed to the shell/command to be) s -5 437 M -( started later. Uncontrolled setting of environment variables in a) s -5 426 M -( privileged process can be a security hazard. It is recommended that) s -5 415 M -( implementations either maintain a list of allowable variable names or) s -5 404 M -( only set environment variables after the server process has dropped) s -5 393 M -( sufficient privileges.) s -5 371 M -( byte SSH_MSG_CHANNEL_REQUEST) s -5 360 M -( uint32 recipient channel) s -5 349 M -( string "env") s -5 338 M -( boolean want reply) s -5 327 M -( string variable name) s -5 316 M -( string variable value) s -5 283 M -(6.5 Starting a Shell or a Command) s -5 261 M -( Once the session has been set up, a program is started at the remote) s -5 250 M -( end. The program can be a shell, an application program or a) s -5 239 M -( subsystem with a host-independent name. Only one of these requests) s -5 228 M -( can succeed per channel.) s -5 206 M -( byte SSH_MSG_CHANNEL_REQUEST) s -5 195 M -( uint32 recipient channel) s -5 184 M -( string "shell") s -5 173 M -( boolean want reply) s -5 129 M -(Ylonen & Moffat, Editor Expires March 31, 2004 [Page 10]) s -_R -S -PStoPSsaved restore -%%Page: (10,11) 6 -userdict/PStoPSsaved save put -PStoPSmatrix setmatrix -595.000000 0.271378 translate -90 rotate -0.706651 dup scale -userdict/PStoPSmatrix matrix currentmatrix put -userdict/PStoPSclip{0 0 moveto - 595.000000 0 rlineto 0 842.000000 rlineto -595.000000 0 rlineto - closepath}put initclip -/showpage{}def/copypage{}def/erasepage{}def -PStoPSxform concat -%%BeginPageSetup -_S -75 0 translate -/pagenum 11 def -/fname () def -/fdir () def -/ftail () def -/user_header_p false def -%%EndPageSetup -5 723 M -(Internet-Draft SSH Connection Protocol Oct 2003) s -5 690 M -( This message will request the user's default shell \(typically defined) s -5 679 M -( in /etc/passwd in UNIX systems\) to be started at the other end.) s -5 657 M -( byte SSH_MSG_CHANNEL_REQUEST) s -5 646 M -( uint32 recipient channel) s -5 635 M -( string "exec") s -5 624 M -( boolean want reply) s -5 613 M -( string command) s -5 591 M -( This message will request the server to start the execution of the) s -5 580 M -( given command. The command string may contain a path. Normal) s -5 569 M -( precautions MUST be taken to prevent the execution of unauthorized) s -5 558 M -( commands.) s -5 536 M -( byte SSH_MSG_CHANNEL_REQUEST) s -5 525 M -( uint32 recipient channel) s -5 514 M -( string "subsystem") s -5 503 M -( boolean want reply) s -5 492 M -( string subsystem name) s -5 470 M -( This last form executes a predefined subsystem. It is expected that) s -5 459 M -( these will include a general file transfer mechanism, and possibly) s -5 448 M -( other features. Implementations may also allow configuring more such) s -5 437 M -( mechanisms. As the user's shell is usually used to execute the) s -5 426 M -( subsystem, it is advisable for the subsystem protocol to have a) s -5 415 M -( "magic cookie" at the beginning of the protocol transaction to) s -5 404 M -( distinguish it from arbitrary output generated by shell) s -5 393 M -( initialization scripts etc. This spurious output from the shell may) s -5 382 M -( be filtered out either at the server or at the client.) s -5 360 M -( The server SHOULD not halt the execution of the protocol stack when) s -5 349 M -( starting a shell or a program. All input and output from these SHOULD) s -5 338 M -( be redirected to the channel or to the encrypted tunnel.) s -5 316 M -( It is RECOMMENDED to request and check the reply for these messages.) s -5 305 M -( The client SHOULD ignore these messages.) s -5 283 M -( Subsystem names follow the DNS extensibility naming convention) s -5 272 M -( outlined in [SSH-ARCH].) s -5 250 M -(6.6 Session Data Transfer) s -5 228 M -( Data transfer for a session is done using SSH_MSG_CHANNEL_DATA and) s -5 217 M -( SSH_MSG_CHANNEL_EXTENDED_DATA packets and the window mechanism. The) s -5 206 M -( extended data type SSH_EXTENDED_DATA_STDERR has been defined for) s -5 195 M -( stderr data.) s -5 129 M -(Ylonen & Moffat, Editor Expires March 31, 2004 [Page 11]) s -_R -S -PStoPSsaved restore -userdict/PStoPSsaved save put -PStoPSmatrix setmatrix -595.000000 421.271378 translate -90 rotate -0.706651 dup scale -userdict/PStoPSmatrix matrix currentmatrix put -userdict/PStoPSclip{0 0 moveto - 595.000000 0 rlineto 0 842.000000 rlineto -595.000000 0 rlineto - closepath}put initclip -PStoPSxform concat -%%BeginPageSetup -_S -75 0 translate -/pagenum 12 def -/fname () def -/fdir () def -/ftail () def -/user_header_p false def -%%EndPageSetup -5 723 M -(Internet-Draft SSH Connection Protocol Oct 2003) s -5 690 M -(6.7 Window Dimension Change Message) s -5 668 M -( When the window \(terminal\) size changes on the client side, it MAY) s -5 657 M -( send a message to the other side to inform it of the new dimensions.) s -5 635 M -( byte SSH_MSG_CHANNEL_REQUEST) s -5 624 M -( uint32 recipient_channel) s -5 613 M -( string "window-change") s -5 602 M -( boolean FALSE) s -5 591 M -( uint32 terminal width, columns) s -5 580 M -( uint32 terminal height, rows) s -5 569 M -( uint32 terminal width, pixels) s -5 558 M -( uint32 terminal height, pixels) s -5 536 M -( No response SHOULD be sent to this message.) s -5 514 M -(6.8 Local Flow Control) s -5 492 M -( On many systems, it is possible to determine if a pseudo-terminal is) s -5 481 M -( using control-S/control-Q flow control. When flow control is) s -5 470 M -( allowed, it is often desirable to do the flow control at the client) s -5 459 M -( end to speed up responses to user requests. This is facilitated by) s -5 448 M -( the following notification. Initially, the server is responsible for) s -5 437 M -( flow control. \(Here, again, client means the side originating the) s -5 426 M -( session, and server means the other side.\)) s -5 404 M -( The message below is used by the server to inform the client when it) s -5 393 M -( can or cannot perform flow control \(control-S/control-Q processing\).) s -5 382 M -( If `client can do' is TRUE, the client is allowed to do flow control) s -5 371 M -( using control-S and control-Q. The client MAY ignore this message.) s -5 349 M -( byte SSH_MSG_CHANNEL_REQUEST) s -5 338 M -( uint32 recipient channel) s -5 327 M -( string "xon-xoff") s -5 316 M -( boolean FALSE) s -5 305 M -( boolean client can do) s -5 283 M -( No response is sent to this message.) s -5 261 M -(6.9 Signals) s -5 239 M -( A signal can be delivered to the remote process/service using the) s -5 228 M -( following message. Some systems may not implement signals, in which) s -5 217 M -( case they SHOULD ignore this message.) s -5 195 M -( byte SSH_MSG_CHANNEL_REQUEST) s -5 184 M -( uint32 recipient channel) s -5 173 M -( string "signal") s -5 129 M -(Ylonen & Moffat, Editor Expires March 31, 2004 [Page 12]) s -_R -S -PStoPSsaved restore -%%Page: (12,13) 7 -userdict/PStoPSsaved save put -PStoPSmatrix setmatrix -595.000000 0.271378 translate -90 rotate -0.706651 dup scale -userdict/PStoPSmatrix matrix currentmatrix put -userdict/PStoPSclip{0 0 moveto - 595.000000 0 rlineto 0 842.000000 rlineto -595.000000 0 rlineto - closepath}put initclip -/showpage{}def/copypage{}def/erasepage{}def -PStoPSxform concat -%%BeginPageSetup -_S -75 0 translate -/pagenum 13 def -/fname () def -/fdir () def -/ftail () def -/user_header_p false def -%%EndPageSetup -5 723 M -(Internet-Draft SSH Connection Protocol Oct 2003) s -5 690 M -( boolean FALSE) s -5 679 M -( string signal name without the "SIG" prefix.) s -5 657 M -( Signal names will be encoded as discussed in the "exit-signal") s -5 646 M -( SSH_MSG_CHANNEL_REQUEST.) s -5 624 M -(6.10 Returning Exit Status) s -5 602 M -( When the command running at the other end terminates, the following) s -5 591 M -( message can be sent to return the exit status of the command.) s -5 580 M -( Returning the status is RECOMMENDED. No acknowledgment is sent for) s -5 569 M -( this message. The channel needs to be closed with) s -5 558 M -( SSH_MSG_CHANNEL_CLOSE after this message.) s -5 536 M -( The client MAY ignore these messages.) s -5 514 M -( byte SSH_MSG_CHANNEL_REQUEST) s -5 503 M -( uint32 recipient_channel) s -5 492 M -( string "exit-status") s -5 481 M -( boolean FALSE) s -5 470 M -( uint32 exit_status) s -5 448 M -( The remote command may also terminate violently due to a signal.) s -5 437 M -( Such a condition can be indicated by the following message. A zero) s -5 426 M -( exit_status usually means that the command terminated successfully.) s -5 404 M -( byte SSH_MSG_CHANNEL_REQUEST) s -5 393 M -( uint32 recipient channel) s -5 382 M -( string "exit-signal") s -5 371 M -( boolean FALSE) s -5 360 M -( string signal name without the "SIG" prefix.) s -5 349 M -( boolean core dumped) s -5 338 M -( string error message \(ISO-10646 UTF-8\)) s -5 327 M -( string language tag \(as defined in [RFC3066]\)) s -5 305 M -( The signal name is one of the following \(these are from [POSIX]\)) s -5 283 M -( ABRT) s -5 272 M -( ALRM) s -5 261 M -( FPE) s -5 250 M -( HUP) s -5 239 M -( ILL) s -5 228 M -( INT) s -5 217 M -( KILL) s -5 206 M -( PIPE) s -5 195 M -( QUIT) s -5 184 M -( SEGV) s -5 173 M -( TERM) s -5 129 M -(Ylonen & Moffat, Editor Expires March 31, 2004 [Page 13]) s -_R -S -PStoPSsaved restore -userdict/PStoPSsaved save put -PStoPSmatrix setmatrix -595.000000 421.271378 translate -90 rotate -0.706651 dup scale -userdict/PStoPSmatrix matrix currentmatrix put -userdict/PStoPSclip{0 0 moveto - 595.000000 0 rlineto 0 842.000000 rlineto -595.000000 0 rlineto - closepath}put initclip -PStoPSxform concat -%%BeginPageSetup -_S -75 0 translate -/pagenum 14 def -/fname () def -/fdir () def -/ftail () def -/user_header_p false def -%%EndPageSetup -5 723 M -(Internet-Draft SSH Connection Protocol Oct 2003) s -5 690 M -( USR1) s -5 679 M -( USR2) s -5 657 M -( Additional signal names MAY be sent in the format "sig-name@xyz",) s -5 646 M -( where `sig-name' and `xyz' may be anything a particular implementor) s -5 635 M -( wants \(except the `@' sign\). However, it is suggested that if a) s -5 624 M -( `configure' script is used, the non-standard signal names it finds be) s -5 613 M -( encoded as "[email protected]", where `SIG' is the signal name) s -5 602 M -( without the "SIG" prefix, and `xyz' be the host type, as determined) s -5 591 M -( by `config.guess'.) s -5 569 M -( The `error message' contains an additional explanation of the error) s -5 558 M -( message. The message may consist of multiple lines. The client) s -5 547 M -( software MAY display this message to the user. If this is done, the) s -5 536 M -( client software should take the precautions discussed in [SSH-ARCH].) s -5 514 M -(7. TCP/IP Port Forwarding) s -5 492 M -(7.1 Requesting Port Forwarding) s -5 470 M -( A party need not explicitly request forwardings from its own end to) s -5 459 M -( the other direction. However, if it wishes that connections to a) s -5 448 M -( port on the other side be forwarded to the local side, it must) s -5 437 M -( explicitly request this.) s -5 404 M -( byte SSH_MSG_GLOBAL_REQUEST) s -5 393 M -( string "tcpip-forward") s -5 382 M -( boolean want reply) s -5 371 M -( string address to bind \(e.g. "0.0.0.0"\)) s -5 360 M -( uint32 port number to bind) s -5 338 M -( `Address to bind' and `port number to bind' specify the IP address) s -5 327 M -( and port to which the socket to be listened is bound. The address) s -5 316 M -( should be "0.0.0.0" if connections are allowed from anywhere. \(Note) s -5 305 M -( that the client can still filter connections based on information) s -5 294 M -( passed in the open request.\)) s -5 272 M -( Implementations should only allow forwarding privileged ports if the) s -5 261 M -( user has been authenticated as a privileged user.) s -5 239 M -( Client implementations SHOULD reject these messages; they are) s -5 228 M -( normally only sent by the client.) s -5 195 M -( If a client passes 0 as port number to bind and has want reply TRUE) s -5 184 M -( then the server allocates the next available unprivileged port number) s -5 173 M -( and replies with the following message, otherwise there is no) s -5 129 M -(Ylonen & Moffat, Editor Expires March 31, 2004 [Page 14]) s -_R -S -PStoPSsaved restore -%%Page: (14,15) 8 -userdict/PStoPSsaved save put -PStoPSmatrix setmatrix -595.000000 0.271378 translate -90 rotate -0.706651 dup scale -userdict/PStoPSmatrix matrix currentmatrix put -userdict/PStoPSclip{0 0 moveto - 595.000000 0 rlineto 0 842.000000 rlineto -595.000000 0 rlineto - closepath}put initclip -/showpage{}def/copypage{}def/erasepage{}def -PStoPSxform concat -%%BeginPageSetup -_S -75 0 translate -/pagenum 15 def -/fname () def -/fdir () def -/ftail () def -/user_header_p false def -%%EndPageSetup -5 723 M -(Internet-Draft SSH Connection Protocol Oct 2003) s -5 690 M -( response specific data.) s -5 657 M -( byte SSH_MSG_GLOBAL_REQUEST_SUCCESS) s -5 646 M -( uint32 port that was bound on the server) s -5 624 M -( A port forwarding can be cancelled with the following message. Note) s -5 613 M -( that channel open requests may be received until a reply to this) s -5 602 M -( message is received.) s -5 580 M -( byte SSH_MSG_GLOBAL_REQUEST) s -5 569 M -( string "cancel-tcpip-forward") s -5 558 M -( boolean want reply) s -5 547 M -( string address_to_bind \(e.g. "127.0.0.1"\)) s -5 536 M -( uint32 port number to bind) s -5 514 M -( Client implementations SHOULD reject these messages; they are) s -5 503 M -( normally only sent by the client.) s -5 481 M -(7.2 TCP/IP Forwarding Channels) s -5 459 M -( When a connection comes to a port for which remote forwarding has) s -5 448 M -( been requested, a channel is opened to forward the port to the other) s -5 437 M -( side.) s -5 415 M -( byte SSH_MSG_CHANNEL_OPEN) s -5 404 M -( string "forwarded-tcpip") s -5 393 M -( uint32 sender channel) s -5 382 M -( uint32 initial window size) s -5 371 M -( uint32 maximum packet size) s -5 360 M -( string address that was connected) s -5 349 M -( uint32 port that was connected) s -5 338 M -( string originator IP address) s -5 327 M -( uint32 originator port) s -5 305 M -( Implementations MUST reject these messages unless they have) s -5 294 M -( previously requested a remote TCP/IP port forwarding with the given) s -5 283 M -( port number.) s -5 261 M -( When a connection comes to a locally forwarded TCP/IP port, the) s -5 250 M -( following packet is sent to the other side. Note that these messages) s -5 239 M -( MAY be sent also for ports for which no forwarding has been) s -5 228 M -( explicitly requested. The receiving side must decide whether to) s -5 217 M -( allow the forwarding.) s -5 195 M -( byte SSH_MSG_CHANNEL_OPEN) s -5 184 M -( string "direct-tcpip") s -5 173 M -( uint32 sender channel) s -5 129 M -(Ylonen & Moffat, Editor Expires March 31, 2004 [Page 15]) s -_R -S -PStoPSsaved restore -userdict/PStoPSsaved save put -PStoPSmatrix setmatrix -595.000000 421.271378 translate -90 rotate -0.706651 dup scale -userdict/PStoPSmatrix matrix currentmatrix put -userdict/PStoPSclip{0 0 moveto - 595.000000 0 rlineto 0 842.000000 rlineto -595.000000 0 rlineto - closepath}put initclip -PStoPSxform concat -%%BeginPageSetup -_S -75 0 translate -/pagenum 16 def -/fname () def -/fdir () def -/ftail () def -/user_header_p false def -%%EndPageSetup -5 723 M -(Internet-Draft SSH Connection Protocol Oct 2003) s -5 690 M -( uint32 initial window size) s -5 679 M -( uint32 maximum packet size) s -5 668 M -( string host to connect) s -5 657 M -( uint32 port to connect) s -5 646 M -( string originator IP address) s -5 635 M -( uint32 originator port) s -5 613 M -( `Host to connect' and `port to connect' specify the TCP/IP host and) s -5 602 M -( port where the recipient should connect the channel. `Host to) s -5 591 M -( connect' may be either a domain name or a numeric IP address.) s -5 569 M -( `Originator IP address' is the numeric IP address of the machine) s -5 558 M -( where the connection request comes from, and `originator port' is the) s -5 547 M -( port on the originator host from where the connection came from.) s -5 525 M -( Forwarded TCP/IP channels are independent of any sessions, and) s -5 514 M -( closing a session channel does not in any way imply that forwarded) s -5 503 M -( connections should be closed.) s -5 481 M -( Client implementations SHOULD reject direct TCP/IP open requests for) s -5 470 M -( security reasons.) s -5 448 M -(8. Encoding of Terminal Modes) s -5 426 M -( Terminal modes \(as passed in a pty request\) are encoded into a byte) s -5 415 M -( stream. It is intended that the coding be portable across different) s -5 404 M -( environments.) s -5 382 M -( The tty mode description is a stream of bytes. The stream consists) s -5 371 M -( of opcode-argument pairs. It is terminated by opcode TTY_OP_END \(0\).) s -5 360 M -( Opcodes 1 to 159 have a single uint32 argument. Opcodes 160 to 255) s -5 349 M -( are not yet defined, and cause parsing to stop \(they should only be) s -5 338 M -( used after any other data\).) s -5 316 M -( The client SHOULD put in the stream any modes it knows about, and the) s -5 305 M -( server MAY ignore any modes it does not know about. This allows some) s -5 294 M -( degree of machine-independence, at least between systems that use a) s -5 283 M -( POSIX-like tty interface. The protocol can support other systems as) s -5 272 M -( well, but the client may need to fill reasonable values for a number) s -5 261 M -( of parameters so the server pty gets set to a reasonable mode \(the) s -5 250 M -( server leaves all unspecified mode bits in their default values, and) s -5 239 M -( only some combinations make sense\).) s -5 217 M -( The following opcodes have been defined. The naming of opcodes) s -5 206 M -( mostly follows the POSIX terminal mode flags.) s -5 184 M -( 0 TTY_OP_END Indicates end of options.) s -5 173 M -( 1 VINTR Interrupt character; 255 if none. Similarly for the) s -5 129 M -(Ylonen & Moffat, Editor Expires March 31, 2004 [Page 16]) s -_R -S -PStoPSsaved restore -%%Page: (16,17) 9 -userdict/PStoPSsaved save put -PStoPSmatrix setmatrix -595.000000 0.271378 translate -90 rotate -0.706651 dup scale -userdict/PStoPSmatrix matrix currentmatrix put -userdict/PStoPSclip{0 0 moveto - 595.000000 0 rlineto 0 842.000000 rlineto -595.000000 0 rlineto - closepath}put initclip -/showpage{}def/copypage{}def/erasepage{}def -PStoPSxform concat -%%BeginPageSetup -_S -75 0 translate -/pagenum 17 def -/fname () def -/fdir () def -/ftail () def -/user_header_p false def -%%EndPageSetup -5 723 M -(Internet-Draft SSH Connection Protocol Oct 2003) s -5 690 M -( other characters. Not all of these characters are) s -5 679 M -( supported on all systems.) s -5 668 M -( 2 VQUIT The quit character \(sends SIGQUIT signal on POSIX) s -5 657 M -( systems\).) s -5 646 M -( 3 VERASE Erase the character to left of the cursor.) s -5 635 M -( 4 VKILL Kill the current input line.) s -5 624 M -( 5 VEOF End-of-file character \(sends EOF from the terminal\).) s -5 613 M -( 6 VEOL End-of-line character in addition to carriage return) s -5 602 M -( and/or linefeed.) s -5 591 M -( 7 VEOL2 Additional end-of-line character.) s -5 580 M -( 8 VSTART Continues paused output \(normally control-Q\).) s -5 569 M -( 9 VSTOP Pauses output \(normally control-S\).) s -5 558 M -( 10 VSUSP Suspends the current program.) s -5 547 M -( 11 VDSUSP Another suspend character.) s -5 536 M -( 12 VREPRINT Reprints the current input line.) s -5 525 M -( 13 VWERASE Erases a word left of cursor.) s -5 514 M -( 14 VLNEXT Enter the next character typed literally, even if it) s -5 503 M -( is a special character) s -5 492 M -( 15 VFLUSH Character to flush output.) s -5 481 M -( 16 VSWTCH Switch to a different shell layer.) s -5 470 M -( 17 VSTATUS Prints system status line \(load, command, pid etc\).) s -5 459 M -( 18 VDISCARD Toggles the flushing of terminal output.) s -5 448 M -( 30 IGNPAR The ignore parity flag. The parameter SHOULD be 0 if) s -5 437 M -( this flag is FALSE set, and 1 if it is TRUE.) s -5 426 M -( 31 PARMRK Mark parity and framing errors.) s -5 415 M -( 32 INPCK Enable checking of parity errors.) s -5 404 M -( 33 ISTRIP Strip 8th bit off characters.) s -5 393 M -( 34 INLCR Map NL into CR on input.) s -5 382 M -( 35 IGNCR Ignore CR on input.) s -5 371 M -( 36 ICRNL Map CR to NL on input.) s -5 360 M -( 37 IUCLC Translate uppercase characters to lowercase.) s -5 349 M -( 38 IXON Enable output flow control.) s -5 338 M -( 39 IXANY Any char will restart after stop.) s -5 327 M -( 40 IXOFF Enable input flow control.) s -5 316 M -( 41 IMAXBEL Ring bell on input queue full.) s -5 305 M -( 50 ISIG Enable signals INTR, QUIT, [D]SUSP.) s -5 294 M -( 51 ICANON Canonicalize input lines.) s -5 283 M -( 52 XCASE Enable input and output of uppercase characters by) s -5 272 M -( preceding their lowercase equivalents with `\\'.) s -5 261 M -( 53 ECHO Enable echoing.) s -5 250 M -( 54 ECHOE Visually erase chars.) s -5 239 M -( 55 ECHOK Kill character discards current line.) s -5 228 M -( 56 ECHONL Echo NL even if ECHO is off.) s -5 217 M -( 57 NOFLSH Don't flush after interrupt.) s -5 206 M -( 58 TOSTOP Stop background jobs from output.) s -5 195 M -( 59 IEXTEN Enable extensions.) s -5 184 M -( 60 ECHOCTL Echo control characters as ^\(Char\).) s -5 173 M -( 61 ECHOKE Visual erase for line kill.) s -5 129 M -(Ylonen & Moffat, Editor Expires March 31, 2004 [Page 17]) s -_R -S -PStoPSsaved restore -userdict/PStoPSsaved save put -PStoPSmatrix setmatrix -595.000000 421.271378 translate -90 rotate -0.706651 dup scale -userdict/PStoPSmatrix matrix currentmatrix put -userdict/PStoPSclip{0 0 moveto - 595.000000 0 rlineto 0 842.000000 rlineto -595.000000 0 rlineto - closepath}put initclip -PStoPSxform concat -%%BeginPageSetup -_S -75 0 translate -/pagenum 18 def -/fname () def -/fdir () def -/ftail () def -/user_header_p false def -%%EndPageSetup -5 723 M -(Internet-Draft SSH Connection Protocol Oct 2003) s -5 690 M -( 62 PENDIN Retype pending input.) s -5 679 M -( 70 OPOST Enable output processing.) s -5 668 M -( 71 OLCUC Convert lowercase to uppercase.) s -5 657 M -( 72 ONLCR Map NL to CR-NL.) s -5 646 M -( 73 OCRNL Translate carriage return to newline \(output\).) s -5 635 M -( 74 ONOCR Translate newline to carriage return-newline) s -5 624 M -( \(output\).) s -5 613 M -( 75 ONLRET Newline performs a carriage return \(output\).) s -5 602 M -( 90 CS7 7 bit mode.) s -5 591 M -( 91 CS8 8 bit mode.) s -5 580 M -( 92 PARENB Parity enable.) s -5 569 M -( 93 PARODD Odd parity, else even.) s -5 547 M -( 128 TTY_OP_ISPEED Specifies the input baud rate in bits per second.) s -5 536 M -( 129 TTY_OP_OSPEED Specifies the output baud rate in bits per second.) s -5 503 M -(9. Summary of Message Numbers) s -5 481 M -( #define SSH_MSG_GLOBAL_REQUEST 80) s -5 470 M -( #define SSH_MSG_REQUEST_SUCCESS 81) s -5 459 M -( #define SSH_MSG_REQUEST_FAILURE 82) s -5 448 M -( #define SSH_MSG_CHANNEL_OPEN 90) s -5 437 M -( #define SSH_MSG_CHANNEL_OPEN_CONFIRMATION 91) s -5 426 M -( #define SSH_MSG_CHANNEL_OPEN_FAILURE 92) s -5 415 M -( #define SSH_MSG_CHANNEL_WINDOW_ADJUST 93) s -5 404 M -( #define SSH_MSG_CHANNEL_DATA 94) s -5 393 M -( #define SSH_MSG_CHANNEL_EXTENDED_DATA 95) s -5 382 M -( #define SSH_MSG_CHANNEL_EOF 96) s -5 371 M -( #define SSH_MSG_CHANNEL_CLOSE 97) s -5 360 M -( #define SSH_MSG_CHANNEL_REQUEST 98) s -5 349 M -( #define SSH_MSG_CHANNEL_SUCCESS 99) s -5 338 M -( #define SSH_MSG_CHANNEL_FAILURE 100) s -5 305 M -(10. Security Considerations) s -5 283 M -( This protocol is assumed to run on top of a secure, authenticated) s -5 272 M -( transport. User authentication and protection against network-level) s -5 261 M -( attacks are assumed to be provided by the underlying protocols.) s -5 239 M -( It is RECOMMENDED that implementations disable all the potentially) s -5 228 M -( dangerous features \(e.g. agent forwarding, X11 forwarding, and TCP/IP) s -5 217 M -( forwarding\) if the host key has changed.) s -5 195 M -( Full security considerations for this protocol are provided in) s -5 184 M -( Section 8 of [SSH-ARCH]) s -5 129 M -(Ylonen & Moffat, Editor Expires March 31, 2004 [Page 18]) s -_R -S -PStoPSsaved restore -%%Page: (18,19) 10 -userdict/PStoPSsaved save put -PStoPSmatrix setmatrix -595.000000 0.271378 translate -90 rotate -0.706651 dup scale -userdict/PStoPSmatrix matrix currentmatrix put -userdict/PStoPSclip{0 0 moveto - 595.000000 0 rlineto 0 842.000000 rlineto -595.000000 0 rlineto - closepath}put initclip -/showpage{}def/copypage{}def/erasepage{}def -PStoPSxform concat -%%BeginPageSetup -_S -75 0 translate -/pagenum 19 def -/fname () def -/fdir () def -/ftail () def -/user_header_p false def -%%EndPageSetup -5 723 M -(Internet-Draft SSH Connection Protocol Oct 2003) s -5 690 M -(11. iana cONSiderations) s -5 668 M -( This document is part of a set, the IANA considerations for the SSH) s -5 657 M -( protocol as defined in [SSH-ARCH], [SSH-TRANS], [SSH-USERAUTH],) s -5 646 M -( [SSH-CONNECT] are detailed in [SSH-NUMBERS].) s -5 624 M -(12. Intellectual Property) s -5 602 M -( The IETF takes no position regarding the validity or scope of any) s -5 591 M -( intellectual property or other rights that might be claimed to) s -5 580 M -( pertain to the implementation or use of the technology described in) s -5 569 M -( this document or the extent to which any license under such rights) s -5 558 M -( might or might not be available; neither does it represent that it) s -5 547 M -( has made any effort to identify any such rights. Information on the) s -5 536 M -( IETF's procedures with respect to rights in standards-track and) s -5 525 M -( standards-related documentation can be found in BCP-11. Copies of) s -5 514 M -( claims of rights made available for publication and any assurances of) s -5 503 M -( licenses to be made available, or the result of an attempt made to) s -5 492 M -( obtain a general license or permission for the use of such) s -5 481 M -( proprietary rights by implementers or users of this specification can) s -5 470 M -( be obtained from the IETF Secretariat.) s -5 448 M -( The IETF has been notified of intellectual property rights claimed in) s -5 437 M -( regard to some or all of the specification contained in this) s -5 426 M -( document. For more information consult the online list of claimed) s -5 415 M -( rights.) s -5 393 M -(Normative References) s -5 371 M -( [SSH-ARCH]) s -5 360 M -( Ylonen, T., "SSH Protocol Architecture", I-D) s -5 349 M -( draft-ietf-architecture-15.txt, Oct 2003.) s -5 327 M -( [SSH-TRANS]) s -5 316 M -( Ylonen, T., "SSH Transport Layer Protocol", I-D) s -5 305 M -( draft-ietf-transport-17.txt, Oct 2003.) s -5 283 M -( [SSH-USERAUTH]) s -5 272 M -( Ylonen, T., "SSH Authentication Protocol", I-D) s -5 261 M -( draft-ietf-userauth-18.txt, Oct 2003.) s -5 239 M -( [SSH-CONNECT]) s -5 228 M -( Ylonen, T., "SSH Connection Protocol", I-D) s -5 217 M -( draft-ietf-connect-18.txt, Oct 2003.) s -5 195 M -( [SSH-NUMBERS]) s -5 184 M -( Lehtinen, S. and D. Moffat, "SSH Protocol Assigned) s -5 173 M -( Numbers", I-D draft-ietf-secsh-assignednumbers-05.txt, Oct) s -5 129 M -(Ylonen & Moffat, Editor Expires March 31, 2004 [Page 19]) s -_R -S -PStoPSsaved restore -userdict/PStoPSsaved save put -PStoPSmatrix setmatrix -595.000000 421.271378 translate -90 rotate -0.706651 dup scale -userdict/PStoPSmatrix matrix currentmatrix put -userdict/PStoPSclip{0 0 moveto - 595.000000 0 rlineto 0 842.000000 rlineto -595.000000 0 rlineto - closepath}put initclip -PStoPSxform concat -%%BeginPageSetup -_S -75 0 translate -/pagenum 20 def -/fname () def -/fdir () def -/ftail () def -/user_header_p false def -%%EndPageSetup -5 723 M -(Internet-Draft SSH Connection Protocol Oct 2003) s -5 690 M -( 2003.) s -5 668 M -( [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate) s -5 657 M -( Requirement Levels", BCP 14, RFC 2119, March 1997.) s -5 635 M -(Informative References) s -5 613 M -( [RFC3066] Alvestrand, H., "Tags for the Identification of) s -5 602 M -( Languages", BCP 47, RFC 3066, January 2001.) s -5 580 M -( [RFC1884] Hinden, R. and S. Deering, "IP Version 6 Addressing) s -5 569 M -( Architecture", RFC 1884, December 1995.) s -5 547 M -( [RFC2279] Yergeau, F., "UTF-8, a transformation format of ISO) s -5 536 M -( 10646", RFC 2279, January 1998.) s -5 514 M -( [SCHEIFLER]) s -5 503 M -( Scheifler, R., "X Window System : The Complete Reference) s -5 492 M -( to Xlib, X Protocol, Icccm, Xlfd, 3rd edition.", Digital) s -5 481 M -( Press ISBN 1555580882, Feburary 1992.) s -5 459 M -( [POSIX] ISO/IEC, 9945-1., "Information technology -- Portable) s -5 448 M -( Operating System Interface \(POSIX\)-Part 1: System) s -5 437 M -( Application Program Interface \(API\) C Language", ANSI/IEE) s -5 426 M -( Std 1003.1, July 1996.) s -5 393 M -(Authors' Addresses) s -5 371 M -( Tatu Ylonen) s -5 360 M -( SSH Communications Security Corp) s -5 349 M -( Fredrikinkatu 42) s -5 338 M -( HELSINKI FIN-00100) s -5 327 M -( Finland) s -5 305 M -( EMail: [email protected]) s -5 272 M -( Darren J. Moffat \(editor\)) s -5 261 M -( Sun Microsystems, Inc) s -5 250 M -( 17 Network Circle) s -5 239 M -( Menlo Park CA 94025) s -5 228 M -( USA) s -5 206 M -( EMail: [email protected]) s -5 129 M -(Ylonen & Moffat, Editor Expires March 31, 2004 [Page 20]) s -_R -S -PStoPSsaved restore -%%Page: (20,21) 11 -userdict/PStoPSsaved save put -PStoPSmatrix setmatrix -595.000000 0.271378 translate -90 rotate -0.706651 dup scale -userdict/PStoPSmatrix matrix currentmatrix put -userdict/PStoPSclip{0 0 moveto - 595.000000 0 rlineto 0 842.000000 rlineto -595.000000 0 rlineto - closepath}put initclip -/showpage{}def/copypage{}def/erasepage{}def -PStoPSxform concat -%%BeginPageSetup -_S -75 0 translate -/pagenum 21 def -/fname () def -/fdir () def -/ftail () def -/user_header_p false def -%%EndPageSetup -5 723 M -(Internet-Draft SSH Connection Protocol Oct 2003) s -5 690 M -(Intellectual Property Statement) s -5 668 M -( The IETF takes no position regarding the validity or scope of any) s -5 657 M -( intellectual property or other rights that might be claimed to) s -5 646 M -( pertain to the implementation or use of the technology described in) s -5 635 M -( this document or the extent to which any license under such rights) s -5 624 M -( might or might not be available; neither does it represent that it) s -5 613 M -( has made any effort to identify any such rights. Information on the) s -5 602 M -( IETF's procedures with respect to rights in standards-track and) s -5 591 M -( standards-related documentation can be found in BCP-11. Copies of) s -5 580 M -( claims of rights made available for publication and any assurances of) s -5 569 M -( licenses to be made available, or the result of an attempt made to) s -5 558 M -( obtain a general license or permission for the use of such) s -5 547 M -( proprietary rights by implementors or users of this specification can) s -5 536 M -( be obtained from the IETF Secretariat.) s -5 514 M -( The IETF invites any interested party to bring to its attention any) s -5 503 M -( copyrights, patents or patent applications, or other proprietary) s -5 492 M -( rights which may cover technology that may be required to practice) s -5 481 M -( this standard. Please address the information to the IETF Executive) s -5 470 M -( Director.) s -5 448 M -( The IETF has been notified of intellectual property rights claimed in) s -5 437 M -( regard to some or all of the specification contained in this) s -5 426 M -( document. For more information consult the online list of claimed) s -5 415 M -( rights.) s -5 382 M -(Full Copyright Statement) s -5 360 M -( Copyright \(C\) The Internet Society \(2003\). All Rights Reserved.) s -5 338 M -( This document and translations of it may be copied and furnished to) s -5 327 M -( others, and derivative works that comment on or otherwise explain it) s -5 316 M -( or assist in its implementation may be prepared, copied, published) s -5 305 M -( and distributed, in whole or in part, without restriction of any) s -5 294 M -( kind, provided that the above copyright notice and this paragraph are) s -5 283 M -( included on all such copies and derivative works. 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Ylonen -Internet-Draft SSH Communications Security Corp -Expires: March 31, 2004 D. Moffat, Editor, Ed. - Sun Microsystems, Inc - Oct 2003 - - - SSH Connection Protocol - draft-ietf-secsh-connect-18.txt - -Status of this Memo - - This document is an Internet-Draft and is in full conformance with - all provisions of Section 10 of RFC2026. - - Internet-Drafts are working documents of the Internet Engineering - Task Force (IETF), its areas, and its working groups. Note that other - groups may also distribute working documents as Internet-Drafts. - - Internet-Drafts are draft documents valid for a maximum of six months - and may be updated, replaced, or obsoleted by other documents at any - time. It is inappropriate to use Internet-Drafts as reference - material or to cite them other than as "work in progress." - - The list of current Internet-Drafts can be accessed at http:// - www.ietf.org/ietf/1id-abstracts.txt. - - The list of Internet-Draft Shadow Directories can be accessed at - http://www.ietf.org/shadow.html. - - This Internet-Draft will expire on March 31, 2004. - -Copyright Notice - - Copyright (C) The Internet Society (2003). All Rights Reserved. - -Abstract - - SSH is a protocol for secure remote login and other secure network - services over an insecure network. - - This document describes the SSH Connection Protocol. It provides - interactive login sessions, remote execution of commands, forwarded - TCP/IP connections, and forwarded X11 connections. All of these - channels are multiplexed into a single encrypted tunnel. - - The SSH Connection Protocol has been designed to run on top of the - SSH transport layer and user authentication protocols. - - - - -Ylonen & Moffat, Editor Expires March 31, 2004 [Page 1] - -Internet-Draft SSH Connection Protocol Oct 2003 - - -Table of Contents - - 1. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 3 - 2. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 - 3. Conventions Used in This Document . . . . . . . . . . . . . 3 - 4. Global Requests . . . . . . . . . . . . . . . . . . . . . . 3 - 5. Channel Mechanism . . . . . . . . . . . . . . . . . . . . . 4 - 5.1 Opening a Channel . . . . . . . . . . . . . . . . . . . . . 4 - 5.2 Data Transfer . . . . . . . . . . . . . . . . . . . . . . . 5 - 5.3 Closing a Channel . . . . . . . . . . . . . . . . . . . . . 6 - 5.4 Channel-Specific Requests . . . . . . . . . . . . . . . . . 7 - 6. Interactive Sessions . . . . . . . . . . . . . . . . . . . . 8 - 6.1 Opening a Session . . . . . . . . . . . . . . . . . . . . . 8 - 6.2 Requesting a Pseudo-Terminal . . . . . . . . . . . . . . . . 8 - 6.3 X11 Forwarding . . . . . . . . . . . . . . . . . . . . . . . 9 - 6.3.1 Requesting X11 Forwarding . . . . . . . . . . . . . . . . . 9 - 6.3.2 X11 Channels . . . . . . . . . . . . . . . . . . . . . . . . 10 - 6.4 Environment Variable Passing . . . . . . . . . . . . . . . . 10 - 6.5 Starting a Shell or a Command . . . . . . . . . . . . . . . 10 - 6.6 Session Data Transfer . . . . . . . . . . . . . . . . . . . 11 - 6.7 Window Dimension Change Message . . . . . . . . . . . . . . 12 - 6.8 Local Flow Control . . . . . . . . . . . . . . . . . . . . . 12 - 6.9 Signals . . . . . . . . . . . . . . . . . . . . . . . . . . 12 - 6.10 Returning Exit Status . . . . . . . . . . . . . . . . . . . 13 - 7. TCP/IP Port Forwarding . . . . . . . . . . . . . . . . . . . 14 - 7.1 Requesting Port Forwarding . . . . . . . . . . . . . . . . . 14 - 7.2 TCP/IP Forwarding Channels . . . . . . . . . . . . . . . . . 15 - 8. Encoding of Terminal Modes . . . . . . . . . . . . . . . . . 16 - 9. Summary of Message Numbers . . . . . . . . . . . . . . . . . 18 - 10. Security Considerations . . . . . . . . . . . . . . . . . . 18 - 11. iana cONSiderations . . . . . . . . . . . . . . . . . . . . 19 - 12. Intellectual Property . . . . . . . . . . . . . . . . . . . 19 - Normative References . . . . . . . . . . . . . . . . . . . . 19 - Informative References . . . . . . . . . . . . . . . . . . . 20 - Authors' Addresses . . . . . . . . . . . . . . . . . . . . . 20 - Intellectual Property and Copyright Statements . . . . . . . 21 - - - - - - - - - - - - - - - -Ylonen & Moffat, Editor Expires March 31, 2004 [Page 2] - -Internet-Draft SSH Connection Protocol Oct 2003 - - -1. Contributors - - The major original contributors of this document were: Tatu Ylonen, - Tero Kivinen, Timo J. Rinne, Sami Lehtinen (all of SSH Communications - Security Corp), and Markku-Juhani O. Saarinen (University of - Jyvaskyla) - - The document editor is: [email protected]. Comments on this - internet draft should be sent to the IETF SECSH working group, - details at: http://ietf.org/html.charters/secsh-charter.html - -2. Introduction - - The SSH Connection Protocol has been designed to run on top of the - SSH transport layer and user authentication protocols. It provides - interactive login sessions, remote execution of commands, forwarded - TCP/IP connections, and forwarded X11 connections. The service name - for this protocol is "ssh-connection". - - This document should be read only after reading the SSH architecture - document [SSH-ARCH]. This document freely uses terminology and - notation from the architecture document without reference or further - explanation. - -3. Conventions Used in This Document - - The keywords "MUST", "MUST NOT", "REQUIRED", "SHOULD", "SHOULD NOT", - and "MAY" that appear in this document are to be interpreted as - described in [RFC2119]. - - The used data types and terminology are specified in the architecture - document [SSH-ARCH]. - - The architecture document also discusses the algorithm naming - conventions that MUST be used with the SSH protocols. - -4. Global Requests - - There are several kinds of requests that affect the state of the - remote end "globally", independent of any channels. An example is a - request to start TCP/IP forwarding for a specific port. All such - requests use the following format. - - byte SSH_MSG_GLOBAL_REQUEST - string request name (restricted to US-ASCII) - boolean want reply - ... request-specific data follows - - - - -Ylonen & Moffat, Editor Expires March 31, 2004 [Page 3] - -Internet-Draft SSH Connection Protocol Oct 2003 - - - Request names follow the DNS extensibility naming convention outlined - in [SSH-ARCH]. - - The recipient will respond to this message with - SSH_MSG_REQUEST_SUCCESS or SSH_MSG_REQUEST_FAILURE if `want reply' is - TRUE. - - byte SSH_MSG_REQUEST_SUCCESS - ..... response specific data - - Usually the response specific data is non-existent. - - If the recipient does not recognize or support the request, it simply - responds with SSH_MSG_REQUEST_FAILURE. - - byte SSH_MSG_REQUEST_FAILURE - - -5. Channel Mechanism - - All terminal sessions, forwarded connections, etc. are channels. - Either side may open a channel. Multiple channels are multiplexed - into a single connection. - - Channels are identified by numbers at each end. The number referring - to a channel may be different on each side. Requests to open a - channel contain the sender's channel number. Any other - channel-related messages contain the recipient's channel number for - the channel. - - Channels are flow-controlled. No data may be sent to a channel until - a message is received to indicate that window space is available. - -5.1 Opening a Channel - - When either side wishes to open a new channel, it allocates a local - number for the channel. It then sends the following message to the - other side, and includes the local channel number and initial window - size in the message. - - byte SSH_MSG_CHANNEL_OPEN - string channel type (restricted to US-ASCII) - uint32 sender channel - uint32 initial window size - uint32 maximum packet size - ... channel type specific data follows - - The channel type is a name as described in the SSH architecture - - - -Ylonen & Moffat, Editor Expires March 31, 2004 [Page 4] - -Internet-Draft SSH Connection Protocol Oct 2003 - - - document, with similar extension mechanisms. `sender channel' is a - local identifier for the channel used by the sender of this message. - `initial window size' specifies how many bytes of channel data can be - sent to the sender of this message without adjusting the window. - `Maximum packet size' specifies the maximum size of an individual - data packet that can be sent to the sender (for example, one might - want to use smaller packets for interactive connections to get better - interactive response on slow links). - - The remote side then decides whether it can open the channel, and - responds with either - - byte SSH_MSG_CHANNEL_OPEN_CONFIRMATION - uint32 recipient channel - uint32 sender channel - uint32 initial window size - uint32 maximum packet size - ... channel type specific data follows - - where `recipient channel' is the channel number given in the original - open request, and `sender channel' is the channel number allocated by - the other side, or - - byte SSH_MSG_CHANNEL_OPEN_FAILURE - uint32 recipient channel - uint32 reason code - string additional textual information (ISO-10646 UTF-8 [RFC2279]) - string language tag (as defined in [RFC3066]) - - If the recipient of the SSH_MSG_CHANNEL_OPEN message does not support - the specified channel type, it simply responds with - SSH_MSG_CHANNEL_OPEN_FAILURE. The client MAY show the additional - information to the user. If this is done, the client software should - take the precautions discussed in [SSH-ARCH]. - - The following reason codes are defined: - - #define SSH_OPEN_ADMINISTRATIVELY_PROHIBITED 1 - #define SSH_OPEN_CONNECT_FAILED 2 - #define SSH_OPEN_UNKNOWN_CHANNEL_TYPE 3 - #define SSH_OPEN_RESOURCE_SHORTAGE 4 - - -5.2 Data Transfer - - The window size specifies how many bytes the other party can send - before it must wait for the window to be adjusted. Both parties use - the following message to adjust the window. - - - -Ylonen & Moffat, Editor Expires March 31, 2004 [Page 5] - -Internet-Draft SSH Connection Protocol Oct 2003 - - - byte SSH_MSG_CHANNEL_WINDOW_ADJUST - uint32 recipient channel - uint32 bytes to add - - After receiving this message, the recipient MAY send the given number - of bytes more than it was previously allowed to send; the window size - is incremented. - - Data transfer is done with messages of the following type. - - byte SSH_MSG_CHANNEL_DATA - uint32 recipient channel - string data - - The maximum amount of data allowed is the current window size. The - window size is decremented by the amount of data sent. Both parties - MAY ignore all extra data sent after the allowed window is empty. - - Additionally, some channels can transfer several types of data. An - example of this is stderr data from interactive sessions. Such data - can be passed with SSH_MSG_CHANNEL_EXTENDED_DATA messages, where a - separate integer specifies the type of the data. The available types - and their interpretation depend on the type of the channel. - - byte SSH_MSG_CHANNEL_EXTENDED_DATA - uint32 recipient_channel - uint32 data_type_code - string data - - Data sent with these messages consumes the same window as ordinary - data. - - Currently, only the following type is defined. - - #define SSH_EXTENDED_DATA_STDERR 1 - - -5.3 Closing a Channel - - When a party will no longer send more data to a channel, it SHOULD - send SSH_MSG_CHANNEL_EOF. - - byte SSH_MSG_CHANNEL_EOF - uint32 recipient_channel - - No explicit response is sent to this message; however, the - application may send EOF to whatever is at the other end of the - channel. Note that the channel remains open after this message, and - - - -Ylonen & Moffat, Editor Expires March 31, 2004 [Page 6] - -Internet-Draft SSH Connection Protocol Oct 2003 - - - more data may still be sent in the other direction. This message - does not consume window space and can be sent even if no window space - is available. - - When either party wishes to terminate the channel, it sends - SSH_MSG_CHANNEL_CLOSE. Upon receiving this message, a party MUST - send back a SSH_MSG_CHANNEL_CLOSE unless it has already sent this - message for the channel. The channel is considered closed for a - party when it has both sent and received SSH_MSG_CHANNEL_CLOSE, and - the party may then reuse the channel number. A party MAY send - SSH_MSG_CHANNEL_CLOSE without having sent or received - SSH_MSG_CHANNEL_EOF. - - byte SSH_MSG_CHANNEL_CLOSE - uint32 recipient_channel - - This message does not consume window space and can be sent even if no - window space is available. - - It is recommended that any data sent before this message is delivered - to the actual destination, if possible. - -5.4 Channel-Specific Requests - - Many channel types have extensions that are specific to that - particular channel type. An example is requesting a pty (pseudo - terminal) for an interactive session. - - All channel-specific requests use the following format. - - byte SSH_MSG_CHANNEL_REQUEST - uint32 recipient channel - string request type (restricted to US-ASCII) - boolean want reply - ... type-specific data - - If want reply is FALSE, no response will be sent to the request. - Otherwise, the recipient responds with either SSH_MSG_CHANNEL_SUCCESS - or SSH_MSG_CHANNEL_FAILURE, or request-specific continuation - messages. If the request is not recognized or is not supported for - the channel, SSH_MSG_CHANNEL_FAILURE is returned. - - This message does not consume window space and can be sent even if no - window space is available. Request types are local to each channel - type. - - The client is allowed to send further messages without waiting for - the response to the request. - - - -Ylonen & Moffat, Editor Expires March 31, 2004 [Page 7] - -Internet-Draft SSH Connection Protocol Oct 2003 - - - request type names follow the DNS extensibility naming convention - outlined in [SSH-ARCH] - - byte SSH_MSG_CHANNEL_SUCCESS - uint32 recipient_channel - - - byte SSH_MSG_CHANNEL_FAILURE - uint32 recipient_channel - - These messages do not consume window space and can be sent even if no - window space is available. - -6. Interactive Sessions - - A session is a remote execution of a program. The program may be a - shell, an application, a system command, or some built-in subsystem. - It may or may not have a tty, and may or may not involve X11 - forwarding. Multiple sessions can be active simultaneously. - -6.1 Opening a Session - - A session is started by sending the following message. - - byte SSH_MSG_CHANNEL_OPEN - string "session" - uint32 sender channel - uint32 initial window size - uint32 maximum packet size - - Client implementations SHOULD reject any session channel open - requests to make it more difficult for a corrupt server to attack the - client. - -6.2 Requesting a Pseudo-Terminal - - A pseudo-terminal can be allocated for the session by sending the - following message. - - byte SSH_MSG_CHANNEL_REQUEST - uint32 recipient_channel - string "pty-req" - boolean want_reply - string TERM environment variable value (e.g., vt100) - uint32 terminal width, characters (e.g., 80) - uint32 terminal height, rows (e.g., 24) - uint32 terminal width, pixels (e.g., 640) - uint32 terminal height, pixels (e.g., 480) - - - -Ylonen & Moffat, Editor Expires March 31, 2004 [Page 8] - -Internet-Draft SSH Connection Protocol Oct 2003 - - - string encoded terminal modes - - The encoding of terminal modes is described in Section Encoding of - Terminal Modes (Section 8). Zero dimension parameters MUST be - ignored. The character/row dimensions override the pixel dimensions - (when nonzero). Pixel dimensions refer to the drawable area of the - window. - - The dimension parameters are only informational. - - The client SHOULD ignore pty requests. - -6.3 X11 Forwarding - -6.3.1 Requesting X11 Forwarding - - X11 forwarding may be requested for a session by sending - - byte SSH_MSG_CHANNEL_REQUEST - uint32 recipient channel - string "x11-req" - boolean want reply - boolean single connection - string x11 authentication protocol - string x11 authentication cookie - uint32 x11 screen number - - It is recommended that the authentication cookie that is sent be a - fake, random cookie, and that the cookie is checked and replaced by - the real cookie when a connection request is received. - - X11 connection forwarding should stop when the session channel is - closed; however, already opened forwardings should not be - automatically closed when the session channel is closed. - - If `single connection' is TRUE, only a single connection should be - forwarded. No more connections will be forwarded after the first, or - after the session channel has been closed. - - The "x11 authentication protocol" is the name of the X11 - authentication method used, e.g. "MIT-MAGIC-COOKIE-1". - - The x11 authentication cookie MUST be hexadecimal encoded. - - X Protocol is documented in [SCHEIFLER]. - - - - - - -Ylonen & Moffat, Editor Expires March 31, 2004 [Page 9] - -Internet-Draft SSH Connection Protocol Oct 2003 - - -6.3.2 X11 Channels - - X11 channels are opened with a channel open request. The resulting - channels are independent of the session, and closing the session - channel does not close the forwarded X11 channels. - - byte SSH_MSG_CHANNEL_OPEN - string "x11" - uint32 sender channel - uint32 initial window size - uint32 maximum packet size - string originator address (e.g. "192.168.7.38") - uint32 originator port - - The recipient should respond with SSH_MSG_CHANNEL_OPEN_CONFIRMATION - or SSH_MSG_CHANNEL_OPEN_FAILURE. - - Implementations MUST reject any X11 channel open requests if they - have not requested X11 forwarding. - -6.4 Environment Variable Passing - - Environment variables may be passed to the shell/command to be - started later. Uncontrolled setting of environment variables in a - privileged process can be a security hazard. It is recommended that - implementations either maintain a list of allowable variable names or - only set environment variables after the server process has dropped - sufficient privileges. - - byte SSH_MSG_CHANNEL_REQUEST - uint32 recipient channel - string "env" - boolean want reply - string variable name - string variable value - - -6.5 Starting a Shell or a Command - - Once the session has been set up, a program is started at the remote - end. The program can be a shell, an application program or a - subsystem with a host-independent name. Only one of these requests - can succeed per channel. - - byte SSH_MSG_CHANNEL_REQUEST - uint32 recipient channel - string "shell" - boolean want reply - - - -Ylonen & Moffat, Editor Expires March 31, 2004 [Page 10] - -Internet-Draft SSH Connection Protocol Oct 2003 - - - This message will request the user's default shell (typically defined - in /etc/passwd in UNIX systems) to be started at the other end. - - byte SSH_MSG_CHANNEL_REQUEST - uint32 recipient channel - string "exec" - boolean want reply - string command - - This message will request the server to start the execution of the - given command. The command string may contain a path. Normal - precautions MUST be taken to prevent the execution of unauthorized - commands. - - byte SSH_MSG_CHANNEL_REQUEST - uint32 recipient channel - string "subsystem" - boolean want reply - string subsystem name - - This last form executes a predefined subsystem. It is expected that - these will include a general file transfer mechanism, and possibly - other features. Implementations may also allow configuring more such - mechanisms. As the user's shell is usually used to execute the - subsystem, it is advisable for the subsystem protocol to have a - "magic cookie" at the beginning of the protocol transaction to - distinguish it from arbitrary output generated by shell - initialization scripts etc. This spurious output from the shell may - be filtered out either at the server or at the client. - - The server SHOULD not halt the execution of the protocol stack when - starting a shell or a program. All input and output from these SHOULD - be redirected to the channel or to the encrypted tunnel. - - It is RECOMMENDED to request and check the reply for these messages. - The client SHOULD ignore these messages. - - Subsystem names follow the DNS extensibility naming convention - outlined in [SSH-ARCH]. - -6.6 Session Data Transfer - - Data transfer for a session is done using SSH_MSG_CHANNEL_DATA and - SSH_MSG_CHANNEL_EXTENDED_DATA packets and the window mechanism. The - extended data type SSH_EXTENDED_DATA_STDERR has been defined for - stderr data. - - - - - -Ylonen & Moffat, Editor Expires March 31, 2004 [Page 11] - -Internet-Draft SSH Connection Protocol Oct 2003 - - -6.7 Window Dimension Change Message - - When the window (terminal) size changes on the client side, it MAY - send a message to the other side to inform it of the new dimensions. - - byte SSH_MSG_CHANNEL_REQUEST - uint32 recipient_channel - string "window-change" - boolean FALSE - uint32 terminal width, columns - uint32 terminal height, rows - uint32 terminal width, pixels - uint32 terminal height, pixels - - No response SHOULD be sent to this message. - -6.8 Local Flow Control - - On many systems, it is possible to determine if a pseudo-terminal is - using control-S/control-Q flow control. When flow control is - allowed, it is often desirable to do the flow control at the client - end to speed up responses to user requests. This is facilitated by - the following notification. Initially, the server is responsible for - flow control. (Here, again, client means the side originating the - session, and server means the other side.) - - The message below is used by the server to inform the client when it - can or cannot perform flow control (control-S/control-Q processing). - If `client can do' is TRUE, the client is allowed to do flow control - using control-S and control-Q. The client MAY ignore this message. - - byte SSH_MSG_CHANNEL_REQUEST - uint32 recipient channel - string "xon-xoff" - boolean FALSE - boolean client can do - - No response is sent to this message. - -6.9 Signals - - A signal can be delivered to the remote process/service using the - following message. Some systems may not implement signals, in which - case they SHOULD ignore this message. - - byte SSH_MSG_CHANNEL_REQUEST - uint32 recipient channel - string "signal" - - - -Ylonen & Moffat, Editor Expires March 31, 2004 [Page 12] - -Internet-Draft SSH Connection Protocol Oct 2003 - - - boolean FALSE - string signal name without the "SIG" prefix. - - Signal names will be encoded as discussed in the "exit-signal" - SSH_MSG_CHANNEL_REQUEST. - -6.10 Returning Exit Status - - When the command running at the other end terminates, the following - message can be sent to return the exit status of the command. - Returning the status is RECOMMENDED. No acknowledgment is sent for - this message. The channel needs to be closed with - SSH_MSG_CHANNEL_CLOSE after this message. - - The client MAY ignore these messages. - - byte SSH_MSG_CHANNEL_REQUEST - uint32 recipient_channel - string "exit-status" - boolean FALSE - uint32 exit_status - - The remote command may also terminate violently due to a signal. - Such a condition can be indicated by the following message. A zero - exit_status usually means that the command terminated successfully. - - byte SSH_MSG_CHANNEL_REQUEST - uint32 recipient channel - string "exit-signal" - boolean FALSE - string signal name without the "SIG" prefix. - boolean core dumped - string error message (ISO-10646 UTF-8) - string language tag (as defined in [RFC3066]) - - The signal name is one of the following (these are from [POSIX]) - - ABRT - ALRM - FPE - HUP - ILL - INT - KILL - PIPE - QUIT - SEGV - TERM - - - -Ylonen & Moffat, Editor Expires March 31, 2004 [Page 13] - -Internet-Draft SSH Connection Protocol Oct 2003 - - - USR1 - USR2 - - Additional signal names MAY be sent in the format "sig-name@xyz", - where `sig-name' and `xyz' may be anything a particular implementor - wants (except the `@' sign). However, it is suggested that if a - `configure' script is used, the non-standard signal names it finds be - encoded as "[email protected]", where `SIG' is the signal name - without the "SIG" prefix, and `xyz' be the host type, as determined - by `config.guess'. - - The `error message' contains an additional explanation of the error - message. The message may consist of multiple lines. The client - software MAY display this message to the user. If this is done, the - client software should take the precautions discussed in [SSH-ARCH]. - -7. TCP/IP Port Forwarding - -7.1 Requesting Port Forwarding - - A party need not explicitly request forwardings from its own end to - the other direction. However, if it wishes that connections to a - port on the other side be forwarded to the local side, it must - explicitly request this. - - - byte SSH_MSG_GLOBAL_REQUEST - string "tcpip-forward" - boolean want reply - string address to bind (e.g. "0.0.0.0") - uint32 port number to bind - - `Address to bind' and `port number to bind' specify the IP address - and port to which the socket to be listened is bound. The address - should be "0.0.0.0" if connections are allowed from anywhere. (Note - that the client can still filter connections based on information - passed in the open request.) - - Implementations should only allow forwarding privileged ports if the - user has been authenticated as a privileged user. - - Client implementations SHOULD reject these messages; they are - normally only sent by the client. - - - If a client passes 0 as port number to bind and has want reply TRUE - then the server allocates the next available unprivileged port number - and replies with the following message, otherwise there is no - - - -Ylonen & Moffat, Editor Expires March 31, 2004 [Page 14] - -Internet-Draft SSH Connection Protocol Oct 2003 - - - response specific data. - - - byte SSH_MSG_GLOBAL_REQUEST_SUCCESS - uint32 port that was bound on the server - - A port forwarding can be cancelled with the following message. Note - that channel open requests may be received until a reply to this - message is received. - - byte SSH_MSG_GLOBAL_REQUEST - string "cancel-tcpip-forward" - boolean want reply - string address_to_bind (e.g. "127.0.0.1") - uint32 port number to bind - - Client implementations SHOULD reject these messages; they are - normally only sent by the client. - -7.2 TCP/IP Forwarding Channels - - When a connection comes to a port for which remote forwarding has - been requested, a channel is opened to forward the port to the other - side. - - byte SSH_MSG_CHANNEL_OPEN - string "forwarded-tcpip" - uint32 sender channel - uint32 initial window size - uint32 maximum packet size - string address that was connected - uint32 port that was connected - string originator IP address - uint32 originator port - - Implementations MUST reject these messages unless they have - previously requested a remote TCP/IP port forwarding with the given - port number. - - When a connection comes to a locally forwarded TCP/IP port, the - following packet is sent to the other side. Note that these messages - MAY be sent also for ports for which no forwarding has been - explicitly requested. The receiving side must decide whether to - allow the forwarding. - - byte SSH_MSG_CHANNEL_OPEN - string "direct-tcpip" - uint32 sender channel - - - -Ylonen & Moffat, Editor Expires March 31, 2004 [Page 15] - -Internet-Draft SSH Connection Protocol Oct 2003 - - - uint32 initial window size - uint32 maximum packet size - string host to connect - uint32 port to connect - string originator IP address - uint32 originator port - - `Host to connect' and `port to connect' specify the TCP/IP host and - port where the recipient should connect the channel. `Host to - connect' may be either a domain name or a numeric IP address. - - `Originator IP address' is the numeric IP address of the machine - where the connection request comes from, and `originator port' is the - port on the originator host from where the connection came from. - - Forwarded TCP/IP channels are independent of any sessions, and - closing a session channel does not in any way imply that forwarded - connections should be closed. - - Client implementations SHOULD reject direct TCP/IP open requests for - security reasons. - -8. Encoding of Terminal Modes - - Terminal modes (as passed in a pty request) are encoded into a byte - stream. It is intended that the coding be portable across different - environments. - - The tty mode description is a stream of bytes. The stream consists - of opcode-argument pairs. It is terminated by opcode TTY_OP_END (0). - Opcodes 1 to 159 have a single uint32 argument. Opcodes 160 to 255 - are not yet defined, and cause parsing to stop (they should only be - used after any other data). - - The client SHOULD put in the stream any modes it knows about, and the - server MAY ignore any modes it does not know about. This allows some - degree of machine-independence, at least between systems that use a - POSIX-like tty interface. The protocol can support other systems as - well, but the client may need to fill reasonable values for a number - of parameters so the server pty gets set to a reasonable mode (the - server leaves all unspecified mode bits in their default values, and - only some combinations make sense). - - The following opcodes have been defined. The naming of opcodes - mostly follows the POSIX terminal mode flags. - - 0 TTY_OP_END Indicates end of options. - 1 VINTR Interrupt character; 255 if none. Similarly for the - - - -Ylonen & Moffat, Editor Expires March 31, 2004 [Page 16] - -Internet-Draft SSH Connection Protocol Oct 2003 - - - other characters. Not all of these characters are - supported on all systems. - 2 VQUIT The quit character (sends SIGQUIT signal on POSIX - systems). - 3 VERASE Erase the character to left of the cursor. - 4 VKILL Kill the current input line. - 5 VEOF End-of-file character (sends EOF from the terminal). - 6 VEOL End-of-line character in addition to carriage return - and/or linefeed. - 7 VEOL2 Additional end-of-line character. - 8 VSTART Continues paused output (normally control-Q). - 9 VSTOP Pauses output (normally control-S). - 10 VSUSP Suspends the current program. - 11 VDSUSP Another suspend character. - 12 VREPRINT Reprints the current input line. - 13 VWERASE Erases a word left of cursor. - 14 VLNEXT Enter the next character typed literally, even if it - is a special character - 15 VFLUSH Character to flush output. - 16 VSWTCH Switch to a different shell layer. - 17 VSTATUS Prints system status line (load, command, pid etc). - 18 VDISCARD Toggles the flushing of terminal output. - 30 IGNPAR The ignore parity flag. The parameter SHOULD be 0 if - this flag is FALSE set, and 1 if it is TRUE. - 31 PARMRK Mark parity and framing errors. - 32 INPCK Enable checking of parity errors. - 33 ISTRIP Strip 8th bit off characters. - 34 INLCR Map NL into CR on input. - 35 IGNCR Ignore CR on input. - 36 ICRNL Map CR to NL on input. - 37 IUCLC Translate uppercase characters to lowercase. - 38 IXON Enable output flow control. - 39 IXANY Any char will restart after stop. - 40 IXOFF Enable input flow control. - 41 IMAXBEL Ring bell on input queue full. - 50 ISIG Enable signals INTR, QUIT, [D]SUSP. - 51 ICANON Canonicalize input lines. - 52 XCASE Enable input and output of uppercase characters by - preceding their lowercase equivalents with `\'. - 53 ECHO Enable echoing. - 54 ECHOE Visually erase chars. - 55 ECHOK Kill character discards current line. - 56 ECHONL Echo NL even if ECHO is off. - 57 NOFLSH Don't flush after interrupt. - 58 TOSTOP Stop background jobs from output. - 59 IEXTEN Enable extensions. - 60 ECHOCTL Echo control characters as ^(Char). - 61 ECHOKE Visual erase for line kill. - - - -Ylonen & Moffat, Editor Expires March 31, 2004 [Page 17] - -Internet-Draft SSH Connection Protocol Oct 2003 - - - 62 PENDIN Retype pending input. - 70 OPOST Enable output processing. - 71 OLCUC Convert lowercase to uppercase. - 72 ONLCR Map NL to CR-NL. - 73 OCRNL Translate carriage return to newline (output). - 74 ONOCR Translate newline to carriage return-newline - (output). - 75 ONLRET Newline performs a carriage return (output). - 90 CS7 7 bit mode. - 91 CS8 8 bit mode. - 92 PARENB Parity enable. - 93 PARODD Odd parity, else even. - - 128 TTY_OP_ISPEED Specifies the input baud rate in bits per second. - 129 TTY_OP_OSPEED Specifies the output baud rate in bits per second. - - -9. Summary of Message Numbers - - #define SSH_MSG_GLOBAL_REQUEST 80 - #define SSH_MSG_REQUEST_SUCCESS 81 - #define SSH_MSG_REQUEST_FAILURE 82 - #define SSH_MSG_CHANNEL_OPEN 90 - #define SSH_MSG_CHANNEL_OPEN_CONFIRMATION 91 - #define SSH_MSG_CHANNEL_OPEN_FAILURE 92 - #define SSH_MSG_CHANNEL_WINDOW_ADJUST 93 - #define SSH_MSG_CHANNEL_DATA 94 - #define SSH_MSG_CHANNEL_EXTENDED_DATA 95 - #define SSH_MSG_CHANNEL_EOF 96 - #define SSH_MSG_CHANNEL_CLOSE 97 - #define SSH_MSG_CHANNEL_REQUEST 98 - #define SSH_MSG_CHANNEL_SUCCESS 99 - #define SSH_MSG_CHANNEL_FAILURE 100 - - -10. Security Considerations - - This protocol is assumed to run on top of a secure, authenticated - transport. User authentication and protection against network-level - attacks are assumed to be provided by the underlying protocols. - - It is RECOMMENDED that implementations disable all the potentially - dangerous features (e.g. agent forwarding, X11 forwarding, and TCP/IP - forwarding) if the host key has changed. - - Full security considerations for this protocol are provided in - Section 8 of [SSH-ARCH] - - - - -Ylonen & Moffat, Editor Expires March 31, 2004 [Page 18] - -Internet-Draft SSH Connection Protocol Oct 2003 - - -11. iana cONSiderations - - This document is part of a set, the IANA considerations for the SSH - protocol as defined in [SSH-ARCH], [SSH-TRANS], [SSH-USERAUTH], - [SSH-CONNECT] are detailed in [SSH-NUMBERS]. - -12. Intellectual Property - - The IETF takes no position regarding the validity or scope of any - intellectual property or other rights that might be claimed to - pertain to the implementation or use of the technology described in - this document or the extent to which any license under such rights - might or might not be available; neither does it represent that it - has made any effort to identify any such rights. Information on the - IETF's procedures with respect to rights in standards-track and - standards-related documentation can be found in BCP-11. Copies of - claims of rights made available for publication and any assurances of - licenses to be made available, or the result of an attempt made to - obtain a general license or permission for the use of such - proprietary rights by implementers or users of this specification can - be obtained from the IETF Secretariat. - - The IETF has been notified of intellectual property rights claimed in - regard to some or all of the specification contained in this - document. For more information consult the online list of claimed - rights. - -Normative References - - [SSH-ARCH] - Ylonen, T., "SSH Protocol Architecture", I-D - draft-ietf-architecture-15.txt, Oct 2003. - - [SSH-TRANS] - Ylonen, T., "SSH Transport Layer Protocol", I-D - draft-ietf-transport-17.txt, Oct 2003. - - [SSH-USERAUTH] - Ylonen, T., "SSH Authentication Protocol", I-D - draft-ietf-userauth-18.txt, Oct 2003. - - [SSH-CONNECT] - Ylonen, T., "SSH Connection Protocol", I-D - draft-ietf-connect-18.txt, Oct 2003. - - [SSH-NUMBERS] - Lehtinen, S. and D. Moffat, "SSH Protocol Assigned - Numbers", I-D draft-ietf-secsh-assignednumbers-05.txt, Oct - - - -Ylonen & Moffat, Editor Expires March 31, 2004 [Page 19] - -Internet-Draft SSH Connection Protocol Oct 2003 - - - 2003. - - [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate - Requirement Levels", BCP 14, RFC 2119, March 1997. - -Informative References - - [RFC3066] Alvestrand, H., "Tags for the Identification of - Languages", BCP 47, RFC 3066, January 2001. - - [RFC1884] Hinden, R. and S. Deering, "IP Version 6 Addressing - Architecture", RFC 1884, December 1995. - - [RFC2279] Yergeau, F., "UTF-8, a transformation format of ISO - 10646", RFC 2279, January 1998. - - [SCHEIFLER] - Scheifler, R., "X Window System : The Complete Reference - to Xlib, X Protocol, Icccm, Xlfd, 3rd edition.", Digital - Press ISBN 1555580882, Feburary 1992. - - [POSIX] ISO/IEC, 9945-1., "Information technology -- Portable - Operating System Interface (POSIX)-Part 1: System - Application Program Interface (API) C Language", ANSI/IEE - Std 1003.1, July 1996. - - -Authors' Addresses - - Tatu Ylonen - SSH Communications Security Corp - Fredrikinkatu 42 - HELSINKI FIN-00100 - Finland - - EMail: [email protected] - - - Darren J. Moffat (editor) - Sun Microsystems, Inc - 17 Network Circle - Menlo Park CA 94025 - USA - - EMail: [email protected] - - - - - - -Ylonen & Moffat, Editor Expires March 31, 2004 [Page 20] - -Internet-Draft SSH Connection Protocol Oct 2003 - - -Intellectual Property Statement - - The IETF takes no position regarding the validity or scope of any - intellectual property or other rights that might be claimed to - pertain to the implementation or use of the technology described in - this document or the extent to which any license under such rights - might or might not be available; neither does it represent that it - has made any effort to identify any such rights. Information on the - IETF's procedures with respect to rights in standards-track and - standards-related documentation can be found in BCP-11. Copies of - claims of rights made available for publication and any assurances of - licenses to be made available, or the result of an attempt made to - obtain a general license or permission for the use of such - proprietary rights by implementors or users of this specification can - be obtained from the IETF Secretariat. - - The IETF invites any interested party to bring to its attention any - copyrights, patents or patent applications, or other proprietary - rights which may cover technology that may be required to practice - this standard. Please address the information to the IETF Executive - Director. - - The IETF has been notified of intellectual property rights claimed in - regard to some or all of the specification contained in this - document. For more information consult the online list of claimed - rights. - - -Full Copyright Statement - - Copyright (C) The Internet Society (2003). All Rights Reserved. - - This document and translations of it may be copied and furnished to - others, and derivative works that comment on or otherwise explain it - or assist in its implementation may be prepared, copied, published - and distributed, in whole or in part, without restriction of any - kind, provided that the above copyright notice and this paragraph are - included on all such copies and derivative works. However, this - document itself may not be modified in any way, such as by removing - the copyright notice or references to the Internet Society or other - Internet organizations, except as needed for the purpose of - developing Internet standards in which case the procedures for - copyrights defined in the Internet Standards process must be - followed, or as required to translate it into languages other than - English. - - The limited permissions granted above are perpetual and will not be - revoked by the Internet Society or its successors or assignees. - - - -Ylonen & Moffat, Editor Expires March 31, 2004 [Page 21] - -Internet-Draft SSH Connection Protocol Oct 2003 - - - This document and the information contained herein is provided on an - "AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING - TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING - BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION - HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF - MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE. - - -Acknowledgment - - Funding for the RFC Editor function is currently provided by the - Internet Society. - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -Ylonen & Moffat, Editor Expires March 31, 2004 [Page 22]
\ No newline at end of file diff --git a/lib/ssh/doc/standard/draft-ietf-secsh-filexfer-02.2.ps b/lib/ssh/doc/standard/draft-ietf-secsh-filexfer-02.2.ps deleted file mode 100644 index 06c91bf8cd..0000000000 --- a/lib/ssh/doc/standard/draft-ietf-secsh-filexfer-02.2.ps +++ /dev/null @@ -1,2853 +0,0 @@ -%!PS-Adobe-3.0 -%%BoundingBox: 75 0 595 747 -%%Title: Enscript Output -%%For: Magnus Thoang -%%Creator: GNU enscript 1.6.1 -%%CreationDate: Wed Nov 12 12:26:07 2003 -%%Orientation: Portrait -%%Pages: 15 0 -%%DocumentMedia: A4 595 842 0 () () -%%DocumentNeededResources: (atend) -%%EndComments -%%BeginProlog -%%BeginProcSet: PStoPS 1 15 -userdict begin -[/showpage/erasepage/copypage]{dup where{pop dup load - type/operatortype eq{1 array cvx dup 0 3 index cvx put - bind def}{pop}ifelse}{pop}ifelse}forall -[/letter/legal/executivepage/a4/a4small/b5/com10envelope - /monarchenvelope/c5envelope/dlenvelope/lettersmall/note - /folio/quarto/a5]{dup where{dup wcheck{exch{}put} - {pop{}def}ifelse}{pop}ifelse}forall -/setpagedevice {pop}bind 1 index where{dup wcheck{3 1 roll put} - 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matrix invertmatrix matrix concatmatrix - matrix invertmatrix put -%%EndSetup -%%Page: (0,1) 1 -userdict/PStoPSsaved save put -PStoPSmatrix setmatrix -595.000000 0.271378 translate -90 rotate -0.706651 dup scale -userdict/PStoPSmatrix matrix currentmatrix put -userdict/PStoPSclip{0 0 moveto - 595.000000 0 rlineto 0 842.000000 rlineto -595.000000 0 rlineto - closepath}put initclip -/showpage{}def/copypage{}def/erasepage{}def -PStoPSxform concat -%%BeginPageSetup -_S -75 0 translate -/pagenum 1 def -/fname () def -/fdir () def -/ftail () def -/user_header_p false def -%%EndPageSetup -5 701 M -(Network Working Group T. Ylonen) s -5 690 M -(Internet-Draft S. Lehtinen) s -5 679 M -(Expires: April 1, 2002 SSH Communications Security Corp) s -5 668 M -( October 2001) s -5 635 M -( SSH File Transfer Protocol) s -5 624 M -( draft-ietf-secsh-filexfer-02.txt) s -5 602 M -(Status of this Memo) s -5 580 M -( This document is an Internet-Draft and is in full conformance with) s -5 569 M -( all provisions of Section 10 of RFC2026.) s -5 547 M -( Internet-Drafts are working documents of the Internet Engineering) s -5 536 M -( Task Force \(IETF\), its areas, and its working groups. Note that) s -5 525 M -( other groups may also distribute working documents as Internet-) s -5 514 M -( Drafts.) s -5 492 M -( Internet-Drafts are draft documents valid for a maximum of six months) s -5 481 M -( and may be updated, replaced, or obsoleted by other documents at any) s -5 470 M -( time. It is inappropriate to use Internet-Drafts as reference) s -5 459 M -( material or to cite them other than as "work in progress.") s -5 437 M -( The list of current Internet-Drafts can be accessed at http://) s -5 426 M -( www.ietf.org/ietf/1id-abstracts.txt.) s -5 404 M -( The list of Internet-Draft Shadow Directories can be accessed at) s -5 393 M -( http://www.ietf.org/shadow.html.) s -5 371 M -( This Internet-Draft will expire on April 1, 2002.) s -5 349 M -(Copyright Notice) s -5 327 M -( Copyright \(C\) The Internet Society \(2001\). All Rights Reserved.) s -5 305 M -(Abstract) s -5 283 M -( The SSH File Transfer Protocol provides secure file transfer) s -5 272 M -( functionality over any reliable data stream. It is the standard file) s -5 261 M -( transfer protocol for use with the SSH2 protocol. This document) s -5 250 M -( describes the file transfer protocol and its interface to the SSH2) s -5 239 M -( protocol suite.) s -5 129 M -(Ylonen & Lehtinen Expires April 1, 2002 [Page 1]) s -_R -S -PStoPSsaved restore -userdict/PStoPSsaved save put -PStoPSmatrix setmatrix -595.000000 421.271378 translate -90 rotate -0.706651 dup scale -userdict/PStoPSmatrix matrix currentmatrix put -userdict/PStoPSclip{0 0 moveto - 595.000000 0 rlineto 0 842.000000 rlineto -595.000000 0 rlineto - closepath}put initclip -PStoPSxform concat -%%BeginPageSetup -_S -75 0 translate -/pagenum 2 def -/fname () def -/fdir () def -/ftail () def -/user_header_p false def -%%EndPageSetup -5 723 M -(Internet-Draft SSH File Transfer Protocol October 2001) s -5 690 M -(Table of Contents) s -5 668 M -( 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3) s -5 657 M -( 2. Use with the SSH Connection Protocol . . . . . . . . . . . . 4) s -5 646 M -( 3. General Packet Format . . . . . . . . . . . . . . . . . . . 5) s -5 635 M -( 4. Protocol Initialization . . . . . . . . . . . . . . . . . . 7) s -5 624 M -( 5. File Attributes . . . . . . . . . . . . . . . . . . . . . . 8) s -5 613 M -( 6. Requests From the Client to the Server . . . . . . . . . . . 10) s -5 602 M -( 6.1 Request Synchronization and Reordering . . . . . . . . . . . 10) s -5 591 M -( 6.2 File Names . . . . . . . . . . . . . . . . . . . . . . . . . 11) s -5 580 M -( 6.3 Opening, Creating, and Closing Files . . . . . . . . . . . . 11) s -5 569 M -( 6.4 Reading and Writing . . . . . . . . . . . . . . . . . . . . 13) s -5 558 M -( 6.5 Removing and Renaming Files . . . . . . . . . . . . . . . . 14) s -5 547 M -( 6.6 Creating and Deleting Directories . . . . . . . . . . . . . 15) s -5 536 M -( 6.7 Scanning Directories . . . . . . . . . . . . . . . . . . . . 15) s -5 525 M -( 6.8 Retrieving File Attributes . . . . . . . . . . . . . . . . . 16) s -5 514 M -( 6.9 Setting File Attributes . . . . . . . . . . . . . . . . . . 17) s -5 503 M -( 6.10 Dealing with Symbolic links . . . . . . . . . . . . . . . . 18) s -5 492 M -( 6.11 Canonicalizing the Server-Side Path Name . . . . . . . . . . 18) s -5 481 M -( 7. Responses from the Server to the Client . . . . . . . . . . 20) s -5 470 M -( 8. Vendor-Specific Extensions . . . . . . . . . . . . . . . . . 24) s -5 459 M -( 9. Security Considerations . . . . . . . . . . . . . . . . . . 25) s -5 448 M -( 10. Changes from previous protocol versions . . . . . . . . . . 26) s -5 437 M -( 10.1 Changes between versions 3 and 2 . . . . . . . . . . . . . . 26) s -5 426 M -( 10.2 Changes between versions 2 and 1 . . . . . . . . . . . . . . 26) s -5 415 M -( 10.3 Changes between versions 1 and 0 . . . . . . . . . . . . . . 26) s -5 404 M -( 11. Trademark Issues . . . . . . . . . . . . . . . . . . . . . . 27) s -5 393 M -( References . . . . . . . . . . . . . . . . . . . . . . . . . 28) s -5 382 M -( Authors' Addresses . . . . . . . . . . . . . . . . . . . . . 28) s -5 371 M -( Full Copyright Statement . . . . . . . . . . . . . . . . . . 29) s -5 129 M -(Ylonen & Lehtinen Expires April 1, 2002 [Page 2]) s -_R -S -PStoPSsaved restore -%%Page: (2,3) 2 -userdict/PStoPSsaved save put -PStoPSmatrix setmatrix -595.000000 0.271378 translate -90 rotate -0.706651 dup scale -userdict/PStoPSmatrix matrix currentmatrix put -userdict/PStoPSclip{0 0 moveto - 595.000000 0 rlineto 0 842.000000 rlineto -595.000000 0 rlineto - closepath}put initclip -/showpage{}def/copypage{}def/erasepage{}def -PStoPSxform concat -%%BeginPageSetup -_S -75 0 translate -/pagenum 3 def -/fname () def -/fdir () def -/ftail () def -/user_header_p false def -%%EndPageSetup -5 723 M -(Internet-Draft SSH File Transfer Protocol October 2001) s -5 690 M -(1. Introduction) s -5 668 M -( This protocol provides secure file transfer \(and more generally file) s -5 657 M -( system access\) functionality over a reliable data stream, such as a) s -5 646 M -( channel in the SSH2 protocol [3].) s -5 624 M -( This protocol is designed so that it could be used to implement a) s -5 613 M -( secure remote file system service, as well as a secure file transfer) s -5 602 M -( service.) s -5 580 M -( This protocol assumes that it runs over a secure channel, and that) s -5 569 M -( the server has already authenticated the user at the client end, and) s -5 558 M -( that the identity of the client user is externally available to the) s -5 547 M -( server implementation.) s -5 525 M -( In general, this protocol follows a simple request-response model.) s -5 514 M -( Each request and response contains a sequence number and multiple) s -5 503 M -( requests may be pending simultaneously. There are a relatively large) s -5 492 M -( number of different request messages, but a small number of possible) s -5 481 M -( response messages. Each request has one or more response messages) s -5 470 M -( that may be returned in result \(e.g., a read either returns data or) s -5 459 M -( reports error status\).) s -5 437 M -( The packet format descriptions in this specification follow the) s -5 426 M -( notation presented in the secsh architecture draft.[3].) s -5 404 M -( Even though this protocol is described in the context of the SSH2) s -5 393 M -( protocol, this protocol is general and independent of the rest of the) s -5 382 M -( SSH2 protocol suite. It could be used in a number of different) s -5 371 M -( applications, such as secure file transfer over TLS RFC 2246 [1] and) s -5 360 M -( transfer of management information in VPN applications.) s -5 129 M -(Ylonen & Lehtinen Expires April 1, 2002 [Page 3]) s -_R -S -PStoPSsaved restore -userdict/PStoPSsaved save put -PStoPSmatrix setmatrix -595.000000 421.271378 translate -90 rotate -0.706651 dup scale -userdict/PStoPSmatrix matrix currentmatrix put -userdict/PStoPSclip{0 0 moveto - 595.000000 0 rlineto 0 842.000000 rlineto -595.000000 0 rlineto - closepath}put initclip -PStoPSxform concat -%%BeginPageSetup -_S -75 0 translate -/pagenum 4 def -/fname () def -/fdir () def -/ftail () def -/user_header_p false def -%%EndPageSetup -5 723 M -(Internet-Draft SSH File Transfer Protocol October 2001) s -5 690 M -(2. Use with the SSH Connection Protocol) s -5 668 M -( When used with the SSH2 Protocol suite, this protocol is intended to) s -5 657 M -( be used from the SSH Connection Protocol [5] as a subsystem, as) s -5 646 M -( described in section ``Starting a Shell or a Command''. The) s -5 635 M -( subsystem name used with this protocol is "sftp".) s -5 129 M -(Ylonen & Lehtinen Expires April 1, 2002 [Page 4]) s -_R -S -PStoPSsaved restore -%%Page: (4,5) 3 -userdict/PStoPSsaved save put -PStoPSmatrix setmatrix -595.000000 0.271378 translate -90 rotate -0.706651 dup scale -userdict/PStoPSmatrix matrix currentmatrix put -userdict/PStoPSclip{0 0 moveto - 595.000000 0 rlineto 0 842.000000 rlineto -595.000000 0 rlineto - closepath}put initclip -/showpage{}def/copypage{}def/erasepage{}def -PStoPSxform concat -%%BeginPageSetup -_S -75 0 translate -/pagenum 5 def -/fname () def -/fdir () def -/ftail () def -/user_header_p false def -%%EndPageSetup -5 723 M -(Internet-Draft SSH File Transfer Protocol October 2001) s -5 690 M -(3. General Packet Format) s -5 668 M -( All packets transmitted over the secure connection are of the) s -5 657 M -( following format:) s -5 635 M -( uint32 length) s -5 624 M -( byte type) s -5 613 M -( byte[length - 1] data payload) s -5 591 M -( That is, they are just data preceded by 32-bit length and 8-bit type) s -5 580 M -( fields. The `length' is the length of the data area, and does not) s -5 569 M -( include the `length' field itself. The format and interpretation of) s -5 558 M -( the data area depends on the packet type.) s -5 536 M -( All packet descriptions below only specify the packet type and the) s -5 525 M -( data that goes into the data field. Thus, they should be prefixed by) s -5 514 M -( the `length' and `type' fields.) s -5 492 M -( The maximum size of a packet is in practice determined by the client) s -5 481 M -( \(the maximum size of read or write requests that it sends, plus a few) s -5 470 M -( bytes of packet overhead\). All servers SHOULD support packets of at) s -5 459 M -( least 34000 bytes \(where the packet size refers to the full length,) s -5 448 M -( including the header above\). This should allow for reads and writes) s -5 437 M -( of at most 32768 bytes.) s -5 415 M -( There is no limit on the number of outstanding \(non-acknowledged\)) s -5 404 M -( requests that the client may send to the server. In practice this is) s -5 393 M -( limited by the buffering available on the data stream and the queuing) s -5 382 M -( performed by the server. If the server's queues are full, it should) s -5 371 M -( not read any more data from the stream, and flow control will prevent) s -5 360 M -( the client from sending more requests. Note, however, that while) s -5 349 M -( there is no restriction on the protocol level, the client's API may) s -5 338 M -( provide a limit in order to prevent infinite queuing of outgoing) s -5 327 M -( requests at the client.) s -5 129 M -(Ylonen & Lehtinen Expires April 1, 2002 [Page 5]) s -_R -S -PStoPSsaved restore -userdict/PStoPSsaved save put -PStoPSmatrix setmatrix -595.000000 421.271378 translate -90 rotate -0.706651 dup scale -userdict/PStoPSmatrix matrix currentmatrix put -userdict/PStoPSclip{0 0 moveto - 595.000000 0 rlineto 0 842.000000 rlineto -595.000000 0 rlineto - closepath}put initclip -PStoPSxform concat -%%BeginPageSetup -_S -75 0 translate -/pagenum 6 def -/fname () def -/fdir () def -/ftail () def -/user_header_p false def -%%EndPageSetup -5 723 M -(Internet-Draft SSH File Transfer Protocol October 2001) s -5 690 M -( The following values are defined for packet types.) s -5 668 M -( #define SSH_FXP_INIT 1) s -5 657 M -( #define SSH_FXP_VERSION 2) s -5 646 M -( #define SSH_FXP_OPEN 3) s -5 635 M -( #define SSH_FXP_CLOSE 4) s -5 624 M -( #define SSH_FXP_READ 5) s -5 613 M -( #define SSH_FXP_WRITE 6) s -5 602 M -( #define SSH_FXP_LSTAT 7) s -5 591 M -( #define SSH_FXP_FSTAT 8) s -5 580 M -( #define SSH_FXP_SETSTAT 9) s -5 569 M -( #define SSH_FXP_FSETSTAT 10) s -5 558 M -( #define SSH_FXP_OPENDIR 11) s -5 547 M -( #define SSH_FXP_READDIR 12) s -5 536 M -( #define SSH_FXP_REMOVE 13) s -5 525 M -( #define SSH_FXP_MKDIR 14) s -5 514 M -( #define SSH_FXP_RMDIR 15) s -5 503 M -( #define SSH_FXP_REALPATH 16) s -5 492 M -( #define SSH_FXP_STAT 17) s -5 481 M -( #define SSH_FXP_RENAME 18) s -5 470 M -( #define SSH_FXP_READLINK 19) s -5 459 M -( #define SSH_FXP_SYMLINK 20) s -5 448 M -( #define SSH_FXP_STATUS 101) s -5 437 M -( #define SSH_FXP_HANDLE 102) s -5 426 M -( #define SSH_FXP_DATA 103) s -5 415 M -( #define SSH_FXP_NAME 104) s -5 404 M -( #define SSH_FXP_ATTRS 105) s -5 393 M -( #define SSH_FXP_EXTENDED 200) s -5 382 M -( #define SSH_FXP_EXTENDED_REPLY 201) s -5 360 M -( Additional packet types should only be defined if the protocol) s -5 349 M -( version number \(see Section ``Protocol Initialization''\) is) s -5 338 M -( incremented, and their use MUST be negotiated using the version) s -5 327 M -( number. However, the SSH_FXP_EXTENDED and SSH_FXP_EXTENDED_REPLY) s -5 316 M -( packets can be used to implement vendor-specific extensions. See) s -5 305 M -( Section ``Vendor-Specific-Extensions'' for more details.) s -5 129 M -(Ylonen & Lehtinen Expires April 1, 2002 [Page 6]) s -_R -S -PStoPSsaved restore -%%Page: (6,7) 4 -userdict/PStoPSsaved save put -PStoPSmatrix setmatrix -595.000000 0.271378 translate -90 rotate -0.706651 dup scale -userdict/PStoPSmatrix matrix currentmatrix put -userdict/PStoPSclip{0 0 moveto - 595.000000 0 rlineto 0 842.000000 rlineto -595.000000 0 rlineto - closepath}put initclip -/showpage{}def/copypage{}def/erasepage{}def -PStoPSxform concat -%%BeginPageSetup -_S -75 0 translate -/pagenum 7 def -/fname () def -/fdir () def -/ftail () def -/user_header_p false def -%%EndPageSetup -5 723 M -(Internet-Draft SSH File Transfer Protocol October 2001) s -5 690 M -(4. Protocol Initialization) s -5 668 M -( When the file transfer protocol starts, it first sends a SSH_FXP_INIT) s -5 657 M -( \(including its version number\) packet to the server. The server) s -5 646 M -( responds with a SSH_FXP_VERSION packet, supplying the lowest of its) s -5 635 M -( own and the client's version number. Both parties should from then) s -5 624 M -( on adhere to particular version of the protocol.) s -5 602 M -( The SSH_FXP_INIT packet \(from client to server\) has the following) s -5 591 M -( data:) s -5 569 M -( uint32 version) s -5 558 M -( <extension data>) s -5 536 M -( The SSH_FXP_VERSION packet \(from server to client\) has the following) s -5 525 M -( data:) s -5 503 M -( uint32 version) s -5 492 M -( <extension data>) s -5 470 M -( The version number of the protocol specified in this document is 3.) s -5 459 M -( The version number should be incremented for each incompatible) s -5 448 M -( revision of this protocol.) s -5 426 M -( The extension data in the above packets may be empty, or may be a) s -5 415 M -( sequence of) s -5 393 M -( string extension_name) s -5 382 M -( string extension_data) s -5 360 M -( pairs \(both strings MUST always be present if one is, but the) s -5 349 M -( `extension_data' string may be of zero length\). If present, these) s -5 338 M -( strings indicate extensions to the baseline protocol. The) s -5 327 M -( `extension_name' field\(s\) identify the name of the extension. The) s -5 316 M -( name should be of the form "name@domain", where the domain is the DNS) s -5 305 M -( domain name of the organization defining the extension. Additional) s -5 294 M -( names that are not of this format may be defined later by the IETF.) s -5 283 M -( Implementations MUST silently ignore any extensions whose name they) s -5 272 M -( do not recognize.) s -5 129 M -(Ylonen & Lehtinen Expires April 1, 2002 [Page 7]) s -_R -S -PStoPSsaved restore -userdict/PStoPSsaved save put -PStoPSmatrix setmatrix -595.000000 421.271378 translate -90 rotate -0.706651 dup scale -userdict/PStoPSmatrix matrix currentmatrix put -userdict/PStoPSclip{0 0 moveto - 595.000000 0 rlineto 0 842.000000 rlineto -595.000000 0 rlineto - closepath}put initclip -PStoPSxform concat -%%BeginPageSetup -_S -75 0 translate -/pagenum 8 def -/fname () def -/fdir () def -/ftail () def -/user_header_p false def -%%EndPageSetup -5 723 M -(Internet-Draft SSH File Transfer Protocol October 2001) s -5 690 M -(5. File Attributes) s -5 668 M -( A new compound data type is defined for encoding file attributes. It) s -5 657 M -( is basically just a combination of elementary types, but is defined) s -5 646 M -( once because of the non-trivial description of the fields and to) s -5 635 M -( ensure maintainability.) s -5 613 M -( The same encoding is used both when returning file attributes from) s -5 602 M -( the server and when sending file attributes to the server. When) s -5 591 M -( sending it to the server, the flags field specifies which attributes) s -5 580 M -( are included, and the server will use default values for the) s -5 569 M -( remaining attributes \(or will not modify the values of remaining) s -5 558 M -( attributes\). When receiving attributes from the server, the flags) s -5 547 M -( specify which attributes are included in the returned data. The) s -5 536 M -( server normally returns all attributes it knows about.) s -5 514 M -( uint32 flags) s -5 503 M -( uint64 size present only if flag SSH_FILEXFER_ATTR_SIZE) s -5 492 M -( uint32 uid present only if flag SSH_FILEXFER_ATTR_UIDGID) s -5 481 M -( uint32 gid present only if flag SSH_FILEXFER_ATTR_UIDGID) s -5 470 M -( uint32 permissions present only if flag SSH_FILEXFER_ATTR_PERMISSIONS) s -5 459 M -( uint32 atime present only if flag SSH_FILEXFER_ACMODTIME) s -5 448 M -( uint32 mtime present only if flag SSH_FILEXFER_ACMODTIME) s -5 437 M -( uint32 extended_count present only if flag SSH_FILEXFER_ATTR_EXTENDED) s -5 426 M -( string extended_type) s -5 415 M -( string extended_data) s -5 404 M -( ... more extended data \(extended_type - extended_data pairs\),) s -5 393 M -( so that number of pairs equals extended_count) s -5 371 M -( The `flags' specify which of the fields are present. Those fields) s -5 360 M -( for which the corresponding flag is not set are not present \(not) s -5 349 M -( included in the packet\). New flags can only be added by incrementing) s -5 338 M -( the protocol version number \(or by using the extension mechanism) s -5 327 M -( described below\).) s -5 305 M -( The `size' field specifies the size of the file in bytes.) s -5 283 M -( The `uid' and `gid' fields contain numeric Unix-like user and group) s -5 272 M -( identifiers, respectively.) s -5 250 M -( The `permissions' field contains a bit mask of file permissions as) s -5 239 M -( defined by posix [1].) s -5 217 M -( The `atime' and `mtime' contain the access and modification times of) s -5 206 M -( the files, respectively. They are represented as seconds from Jan 1,) s -5 195 M -( 1970 in UTC.) s -5 173 M -( The SSH_FILEXFER_ATTR_EXTENDED flag provides a general extension) s -5 129 M -(Ylonen & Lehtinen Expires April 1, 2002 [Page 8]) s -_R -S -PStoPSsaved restore -%%Page: (8,9) 5 -userdict/PStoPSsaved save put -PStoPSmatrix setmatrix -595.000000 0.271378 translate -90 rotate -0.706651 dup scale -userdict/PStoPSmatrix matrix currentmatrix put -userdict/PStoPSclip{0 0 moveto - 595.000000 0 rlineto 0 842.000000 rlineto -595.000000 0 rlineto - closepath}put initclip -/showpage{}def/copypage{}def/erasepage{}def -PStoPSxform concat -%%BeginPageSetup -_S -75 0 translate -/pagenum 9 def -/fname () def -/fdir () def -/ftail () def -/user_header_p false def -%%EndPageSetup -5 723 M -(Internet-Draft SSH File Transfer Protocol October 2001) s -5 690 M -( mechanism for vendor-specific extensions. If the flag is specified,) s -5 679 M -( then the `extended_count' field is present. It specifies the number) s -5 668 M -( of extended_type-extended_data pairs that follow. Each of these) s -5 657 M -( pairs specifies an extended attribute. For each of the attributes,) s -5 646 M -( the extended_type field should be a string of the format) s -5 635 M -( "name@domain", where "domain" is a valid, registered domain name and) s -5 624 M -( "name" identifies the method. The IETF may later standardize certain) s -5 613 M -( names that deviate from this format \(e.g., that do not contain the) s -5 602 M -( "@" sign\). The interpretation of `extended_data' depends on the) s -5 591 M -( type. Implementations SHOULD ignore extended data fields that they) s -5 580 M -( do not understand.) s -5 558 M -( Additional fields can be added to the attributes by either defining) s -5 547 M -( additional bits to the flags field to indicate their presence, or by) s -5 536 M -( defining extended attributes for them. The extended attributes) s -5 525 M -( mechanism is recommended for most purposes; additional flags bits) s -5 514 M -( should only be defined by an IETF standards action that also) s -5 503 M -( increments the protocol version number. The use of such new fields) s -5 492 M -( MUST be negotiated by the version number in the protocol exchange.) s -5 481 M -( It is a protocol error if a packet with unsupported protocol bits is) s -5 470 M -( received.) s -5 448 M -( The flags bits are defined to have the following values:) s -5 426 M -( #define SSH_FILEXFER_ATTR_SIZE 0x00000001) s -5 415 M -( #define SSH_FILEXFER_ATTR_UIDGID 0x00000002) s -5 404 M -( #define SSH_FILEXFER_ATTR_PERMISSIONS 0x00000004) s -5 393 M -( #define SSH_FILEXFER_ATTR_ACMODTIME 0x00000008) s -5 382 M -( #define SSH_FILEXFER_ATTR_EXTENDED 0x80000000) s -5 129 M -(Ylonen & Lehtinen Expires April 1, 2002 [Page 9]) s -_R -S -PStoPSsaved restore -userdict/PStoPSsaved save put -PStoPSmatrix setmatrix -595.000000 421.271378 translate -90 rotate -0.706651 dup scale -userdict/PStoPSmatrix matrix currentmatrix put -userdict/PStoPSclip{0 0 moveto - 595.000000 0 rlineto 0 842.000000 rlineto -595.000000 0 rlineto - closepath}put initclip -PStoPSxform concat -%%BeginPageSetup -_S -75 0 translate -/pagenum 10 def -/fname () def -/fdir () def -/ftail () def -/user_header_p false def -%%EndPageSetup -5 723 M -(Internet-Draft SSH File Transfer Protocol October 2001) s -5 690 M -(6. Requests From the Client to the Server) s -5 668 M -( Requests from the client to the server represent the various file) s -5 657 M -( system operations. Each request begins with an `id' field, which is) s -5 646 M -( a 32-bit identifier identifying the request \(selected by the client\).) s -5 635 M -( The same identifier will be returned in the response to the request.) s -5 624 M -( One possible implementation of it is a monotonically increasing) s -5 613 M -( request sequence number \(modulo 2^32\).) s -5 591 M -( Many operations in the protocol operate on open files. The) s -5 580 M -( SSH_FXP_OPEN request can return a file handle \(which is an opaque) s -5 569 M -( variable-length string\) which may be used to access the file later) s -5 558 M -( \(e.g. in a read operation\). The client MUST NOT send requests the) s -5 547 M -( server with bogus or closed handles. However, the server MUST) s -5 536 M -( perform adequate checks on the handle in order to avoid security) s -5 525 M -( risks due to fabricated handles.) s -5 503 M -( This design allows either stateful and stateless server) s -5 492 M -( implementation, as well as an implementation which caches state) s -5 481 M -( between requests but may also flush it. The contents of the file) s -5 470 M -( handle string are entirely up to the server and its design. The) s -5 459 M -( client should not modify or attempt to interpret the file handle) s -5 448 M -( strings.) s -5 426 M -( The file handle strings MUST NOT be longer than 256 bytes.) s -5 404 M -(6.1 Request Synchronization and Reordering) s -5 382 M -( The protocol and implementations MUST process requests relating to) s -5 371 M -( the same file in the order in which they are received. In other) s -5 360 M -( words, if an application submits multiple requests to the server, the) s -5 349 M -( results in the responses will be the same as if it had sent the) s -5 338 M -( requests one at a time and waited for the response in each case. For) s -5 327 M -( example, the server may process non-overlapping read/write requests) s -5 316 M -( to the same file in parallel, but overlapping reads and writes cannot) s -5 305 M -( be reordered or parallelized. However, there are no ordering) s -5 294 M -( restrictions on the server for processing requests from two different) s -5 283 M -( file transfer connections. The server may interleave and parallelize) s -5 272 M -( them at will.) s -5 250 M -( There are no restrictions on the order in which responses to) s -5 239 M -( outstanding requests are delivered to the client, except that the) s -5 228 M -( server must ensure fairness in the sense that processing of no) s -5 217 M -( request will be indefinitely delayed even if the client is sending) s -5 206 M -( other requests so that there are multiple outstanding requests all) s -5 195 M -( the time.) s -5 129 M -(Ylonen & Lehtinen Expires April 1, 2002 [Page 10]) s -_R -S -PStoPSsaved restore -%%Page: (10,11) 6 -userdict/PStoPSsaved save put -PStoPSmatrix setmatrix -595.000000 0.271378 translate -90 rotate -0.706651 dup scale -userdict/PStoPSmatrix matrix currentmatrix put -userdict/PStoPSclip{0 0 moveto - 595.000000 0 rlineto 0 842.000000 rlineto -595.000000 0 rlineto - closepath}put initclip -/showpage{}def/copypage{}def/erasepage{}def -PStoPSxform concat -%%BeginPageSetup -_S -75 0 translate -/pagenum 11 def -/fname () def -/fdir () def -/ftail () def -/user_header_p false def -%%EndPageSetup -5 723 M -(Internet-Draft SSH File Transfer Protocol October 2001) s -5 690 M -(6.2 File Names) s -5 668 M -( This protocol represents file names as strings. File names are) s -5 657 M -( assumed to use the slash \('/'\) character as a directory separator.) s -5 635 M -( File names starting with a slash are "absolute", and are relative to) s -5 624 M -( the root of the file system. Names starting with any other character) s -5 613 M -( are relative to the user's default directory \(home directory\). Note) s -5 602 M -( that identifying the user is assumed to take place outside of this) s -5 591 M -( protocol.) s -5 569 M -( Servers SHOULD interpret a path name component ".." as referring to) s -5 558 M -( the parent directory, and "." as referring to the current directory.) s -5 547 M -( If the server implementation limits access to certain parts of the) s -5 536 M -( file system, it must be extra careful in parsing file names when) s -5 525 M -( enforcing such restrictions. There have been numerous reported) s -5 514 M -( security bugs where a ".." in a path name has allowed access outside) s -5 503 M -( the intended area.) s -5 481 M -( An empty path name is valid, and it refers to the user's default) s -5 470 M -( directory \(usually the user's home directory\).) s -5 448 M -( Otherwise, no syntax is defined for file names by this specification.) s -5 437 M -( Clients should not make any other assumptions; however, they can) s -5 426 M -( splice path name components returned by SSH_FXP_READDIR together) s -5 415 M -( using a slash \('/'\) as the separator, and that will work as expected.) s -5 393 M -( It is understood that the lack of well-defined semantics for file) s -5 382 M -( names may cause interoperability problems between clients and servers) s -5 371 M -( using radically different operating systems. However, this approach) s -5 360 M -( is known to work acceptably with most systems, and alternative) s -5 349 M -( approaches that e.g. treat file names as sequences of structured) s -5 338 M -( components are quite complicated.) s -5 316 M -(6.3 Opening, Creating, and Closing Files) s -5 294 M -( Files are opened and created using the SSH_FXP_OPEN message, whose) s -5 283 M -( data part is as follows:) s -5 261 M -( uint32 id) s -5 250 M -( string filename) s -5 239 M -( uint32 pflags) s -5 228 M -( ATTRS attrs) s -5 206 M -( The `id' field is the request identifier as for all requests.) s -5 184 M -( The `filename' field specifies the file name. See Section ``File) s -5 173 M -( Names'' for more information.) s -5 129 M -(Ylonen & Lehtinen Expires April 1, 2002 [Page 11]) s -_R -S -PStoPSsaved restore -userdict/PStoPSsaved save put -PStoPSmatrix setmatrix -595.000000 421.271378 translate -90 rotate -0.706651 dup scale -userdict/PStoPSmatrix matrix currentmatrix put -userdict/PStoPSclip{0 0 moveto - 595.000000 0 rlineto 0 842.000000 rlineto -595.000000 0 rlineto - closepath}put initclip -PStoPSxform concat -%%BeginPageSetup -_S -75 0 translate -/pagenum 12 def -/fname () def -/fdir () def -/ftail () def -/user_header_p false def -%%EndPageSetup -5 723 M -(Internet-Draft SSH File Transfer Protocol October 2001) s -5 690 M -( The `pflags' field is a bitmask. The following bits have been) s -5 679 M -( defined.) s -5 657 M -( #define SSH_FXF_READ 0x00000001) s -5 646 M -( #define SSH_FXF_WRITE 0x00000002) s -5 635 M -( #define SSH_FXF_APPEND 0x00000004) s -5 624 M -( #define SSH_FXF_CREAT 0x00000008) s -5 613 M -( #define SSH_FXF_TRUNC 0x00000010) s -5 602 M -( #define SSH_FXF_EXCL 0x00000020) s -5 580 M -( These have the following meanings:) s -5 558 M -( SSH_FXF_READ) s -5 547 M -( Open the file for reading.) s -5 525 M -( SSH_FXF_WRITE) s -5 514 M -( Open the file for writing. If both this and SSH_FXF_READ are) s -5 503 M -( specified, the file is opened for both reading and writing.) s -5 481 M -( SSH_FXF_APPEND) s -5 470 M -( Force all writes to append data at the end of the file.) s -5 448 M -( SSH_FXF_CREAT) s -5 437 M -( If this flag is specified, then a new file will be created if one) s -5 426 M -( does not already exist \(if O_TRUNC is specified, the new file will) s -5 415 M -( be truncated to zero length if it previously exists\).) s -5 393 M -( SSH_FXF_TRUNC) s -5 382 M -( Forces an existing file with the same name to be truncated to zero) s -5 371 M -( length when creating a file by specifying SSH_FXF_CREAT.) s -5 360 M -( SSH_FXF_CREAT MUST also be specified if this flag is used.) s -5 338 M -( SSH_FXF_EXCL) s -5 327 M -( Causes the request to fail if the named file already exists.) s -5 316 M -( SSH_FXF_CREAT MUST also be specified if this flag is used.) s -5 294 M -( The `attrs' field specifies the initial attributes for the file.) s -5 283 M -( Default values will be used for those attributes that are not) s -5 272 M -( specified. See Section ``File Attributes'' for more information.) s -5 250 M -( Regardless the server operating system, the file will always be) s -5 239 M -( opened in "binary" mode \(i.e., no translations between different) s -5 228 M -( character sets and newline encodings\).) s -5 206 M -( The response to this message will be either SSH_FXP_HANDLE \(if the) s -5 195 M -( operation is successful\) or SSH_FXP_STATUS \(if the operation fails\).) s -5 129 M -(Ylonen & Lehtinen Expires April 1, 2002 [Page 12]) s -_R -S -PStoPSsaved restore -%%Page: (12,13) 7 -userdict/PStoPSsaved save put -PStoPSmatrix setmatrix -595.000000 0.271378 translate -90 rotate -0.706651 dup scale -userdict/PStoPSmatrix matrix currentmatrix put -userdict/PStoPSclip{0 0 moveto - 595.000000 0 rlineto 0 842.000000 rlineto -595.000000 0 rlineto - closepath}put initclip -/showpage{}def/copypage{}def/erasepage{}def -PStoPSxform concat -%%BeginPageSetup -_S -75 0 translate -/pagenum 13 def -/fname () def -/fdir () def -/ftail () def -/user_header_p false def -%%EndPageSetup -5 723 M -(Internet-Draft SSH File Transfer Protocol October 2001) s -5 690 M -( A file is closed by using the SSH_FXP_CLOSE request. Its data field) s -5 679 M -( has the following format:) s -5 657 M -( uint32 id) s -5 646 M -( string handle) s -5 624 M -( where `id' is the request identifier, and `handle' is a handle) s -5 613 M -( previously returned in the response to SSH_FXP_OPEN or) s -5 602 M -( SSH_FXP_OPENDIR. The handle becomes invalid immediately after this) s -5 591 M -( request has been sent.) s -5 569 M -( The response to this request will be a SSH_FXP_STATUS message. One) s -5 558 M -( should note that on some server platforms even a close can fail.) s -5 547 M -( This can happen e.g. if the server operating system caches writes,) s -5 536 M -( and an error occurs while flushing cached writes during the close.) s -5 514 M -(6.4 Reading and Writing) s -5 492 M -( Once a file has been opened, it can be read using the SSH_FXP_READ) s -5 481 M -( message, which has the following format:) s -5 459 M -( uint32 id) s -5 448 M -( string handle) s -5 437 M -( uint64 offset) s -5 426 M -( uint32 len) s -5 404 M -( where `id' is the request identifier, `handle' is an open file handle) s -5 393 M -( returned by SSH_FXP_OPEN, `offset' is the offset \(in bytes\) relative) s -5 382 M -( to the beginning of the file from where to start reading, and `len') s -5 371 M -( is the maximum number of bytes to read.) s -5 349 M -( In response to this request, the server will read as many bytes as it) s -5 338 M -( can from the file \(up to `len'\), and return them in a SSH_FXP_DATA) s -5 327 M -( message. If an error occurs or EOF is encountered before reading any) s -5 316 M -( data, the server will respond with SSH_FXP_STATUS. For normal disk) s -5 305 M -( files, it is guaranteed that this will read the specified number of) s -5 294 M -( bytes, or up to end of file. For e.g. device files this may return) s -5 283 M -( fewer bytes than requested.) s -5 261 M -( Writing to a file is achieved using the SSH_FXP_WRITE message, which) s -5 250 M -( has the following format:) s -5 228 M -( uint32 id) s -5 217 M -( string handle) s -5 206 M -( uint64 offset) s -5 195 M -( string data) s -5 173 M -( where `id' is a request identifier, `handle' is a file handle) s -5 129 M -(Ylonen & Lehtinen Expires April 1, 2002 [Page 13]) s -_R -S -PStoPSsaved restore -userdict/PStoPSsaved save put -PStoPSmatrix setmatrix -595.000000 421.271378 translate -90 rotate -0.706651 dup scale -userdict/PStoPSmatrix matrix currentmatrix put -userdict/PStoPSclip{0 0 moveto - 595.000000 0 rlineto 0 842.000000 rlineto -595.000000 0 rlineto - closepath}put initclip -PStoPSxform concat -%%BeginPageSetup -_S -75 0 translate -/pagenum 14 def -/fname () def -/fdir () def -/ftail () def -/user_header_p false def -%%EndPageSetup -5 723 M -(Internet-Draft SSH File Transfer Protocol October 2001) s -5 690 M -( returned by SSH_FXP_OPEN, `offset' is the offset \(in bytes\) from the) s -5 679 M -( beginning of the file where to start writing, and `data' is the data) s -5 668 M -( to be written.) s -5 646 M -( The write will extend the file if writing beyond the end of the file.) s -5 635 M -( It is legal to write way beyond the end of the file; the semantics) s -5 624 M -( are to write zeroes from the end of the file to the specified offset) s -5 613 M -( and then the data. On most operating systems, such writes do not) s -5 602 M -( allocate disk space but instead leave "holes" in the file.) s -5 580 M -( The server responds to a write request with a SSH_FXP_STATUS message.) s -5 558 M -(6.5 Removing and Renaming Files) s -5 536 M -( Files can be removed using the SSH_FXP_REMOVE message. It has the) s -5 525 M -( following format:) s -5 503 M -( uint32 id) s -5 492 M -( string filename) s -5 470 M -( where `id' is the request identifier and `filename' is the name of) s -5 459 M -( the file to be removed. See Section ``File Names'' for more) s -5 448 M -( information. This request cannot be used to remove directories.) s -5 426 M -( The server will respond to this request with a SSH_FXP_STATUS) s -5 415 M -( message.) s -5 393 M -( Files \(and directories\) can be renamed using the SSH_FXP_RENAME) s -5 382 M -( message. Its data is as follows:) s -5 360 M -( uint32 id) s -5 349 M -( string oldpath) s -5 338 M -( string newpath) s -5 316 M -( where `id' is the request identifier, `oldpath' is the name of an) s -5 305 M -( existing file or directory, and `newpath' is the new name for the) s -5 294 M -( file or directory. It is an error if there already exists a file) s -5 283 M -( with the name specified by newpath. The server may also fail rename) s -5 272 M -( requests in other situations, for example if `oldpath' and `newpath') s -5 261 M -( point to different file systems on the server.) s -5 239 M -( The server will respond to this request with a SSH_FXP_STATUS) s -5 228 M -( message.) s -5 129 M -(Ylonen & Lehtinen Expires April 1, 2002 [Page 14]) s -_R -S -PStoPSsaved restore -%%Page: (14,15) 8 -userdict/PStoPSsaved save put -PStoPSmatrix setmatrix -595.000000 0.271378 translate -90 rotate -0.706651 dup scale -userdict/PStoPSmatrix matrix currentmatrix put -userdict/PStoPSclip{0 0 moveto - 595.000000 0 rlineto 0 842.000000 rlineto -595.000000 0 rlineto - closepath}put initclip -/showpage{}def/copypage{}def/erasepage{}def -PStoPSxform concat -%%BeginPageSetup -_S -75 0 translate -/pagenum 15 def -/fname () def -/fdir () def -/ftail () def -/user_header_p false def -%%EndPageSetup -5 723 M -(Internet-Draft SSH File Transfer Protocol October 2001) s -5 690 M -(6.6 Creating and Deleting Directories) s -5 668 M -( New directories can be created using the SSH_FXP_MKDIR request. It) s -5 657 M -( has the following format:) s -5 635 M -( uint32 id) s -5 624 M -( string path) s -5 613 M -( ATTRS attrs) s -5 591 M -( where `id' is the request identifier, `path' and `attrs' specifies) s -5 580 M -( the modifications to be made to its attributes. See Section ``File) s -5 569 M -( Names'' for more information on file names. Attributes are discussed) s -5 558 M -( in more detail in Section ``File Attributes''. specifies the) s -5 547 M -( directory to be created. An error will be returned if a file or) s -5 536 M -( directory with the specified path already exists. The server will) s -5 525 M -( respond to this request with a SSH_FXP_STATUS message.) s -5 503 M -( Directories can be removed using the SSH_FXP_RMDIR request, which) s -5 492 M -( has the following format:) s -5 470 M -( uint32 id) s -5 459 M -( string path) s -5 437 M -( where `id' is the request identifier, and `path' specifies the) s -5 426 M -( directory to be removed. See Section ``File Names'' for more) s -5 415 M -( information on file names. An error will be returned if no directory) s -5 404 M -( with the specified path exists, or if the specified directory is not) s -5 393 M -( empty, or if the path specified a file system object other than a) s -5 382 M -( directory. The server responds to this request with a SSH_FXP_STATUS) s -5 371 M -( message.) s -5 349 M -(6.7 Scanning Directories) s -5 327 M -( The files in a directory can be listed using the SSH_FXP_OPENDIR and) s -5 316 M -( SSH_FXP_READDIR requests. Each SSH_FXP_READDIR request returns one) s -5 305 M -( or more file names with full file attributes for each file. The) s -5 294 M -( client should call SSH_FXP_READDIR repeatedly until it has found the) s -5 283 M -( file it is looking for or until the server responds with a) s -5 272 M -( SSH_FXP_STATUS message indicating an error \(normally SSH_FX_EOF if) s -5 261 M -( there are no more files in the directory\). The client should then) s -5 250 M -( close the handle using the SSH_FXP_CLOSE request.) s -5 129 M -(Ylonen & Lehtinen Expires April 1, 2002 [Page 15]) s -_R -S -PStoPSsaved restore -userdict/PStoPSsaved save put -PStoPSmatrix setmatrix -595.000000 421.271378 translate -90 rotate -0.706651 dup scale -userdict/PStoPSmatrix matrix currentmatrix put -userdict/PStoPSclip{0 0 moveto - 595.000000 0 rlineto 0 842.000000 rlineto -595.000000 0 rlineto - closepath}put initclip -PStoPSxform concat -%%BeginPageSetup -_S -75 0 translate -/pagenum 16 def -/fname () def -/fdir () def -/ftail () def -/user_header_p false def -%%EndPageSetup -5 723 M -(Internet-Draft SSH File Transfer Protocol October 2001) s -5 690 M -( The SSH_FXP_OPENDIR opens a directory for reading. It has the) s -5 679 M -( following format:) s -5 657 M -( uint32 id) s -5 646 M -( string path) s -5 624 M -( where `id' is the request identifier and `path' is the path name of) s -5 613 M -( the directory to be listed \(without any trailing slash\). See Section) s -5 602 M -( ``File Names'' for more information on file names. This will return) s -5 591 M -( an error if the path does not specify a directory or if the directory) s -5 580 M -( is not readable. The server will respond to this request with either) s -5 569 M -( a SSH_FXP_HANDLE or a SSH_FXP_STATUS message.) s -5 547 M -( Once the directory has been successfully opened, files \(and) s -5 536 M -( directories\) contained in it can be listed using SSH_FXP_READDIR) s -5 525 M -( requests. These are of the format) s -5 503 M -( uint32 id) s -5 492 M -( string handle) s -5 470 M -( where `id' is the request identifier, and `handle' is a handle) s -5 459 M -( returned by SSH_FXP_OPENDIR. \(It is a protocol error to attempt to) s -5 448 M -( use an ordinary file handle returned by SSH_FXP_OPEN.\)) s -5 426 M -( The server responds to this request with either a SSH_FXP_NAME or a) s -5 415 M -( SSH_FXP_STATUS message. One or more names may be returned at a time.) s -5 404 M -( Full status information is returned for each name in order to speed) s -5 393 M -( up typical directory listings.) s -5 371 M -( When the client no longer wishes to read more names from the) s -5 360 M -( directory, it SHOULD call SSH_FXP_CLOSE for the handle. The handle) s -5 349 M -( should be closed regardless of whether an error has occurred or not.) s -5 327 M -(6.8 Retrieving File Attributes) s -5 305 M -( Very often, file attributes are automatically returned by) s -5 294 M -( SSH_FXP_READDIR. However, sometimes there is need to specifically) s -5 283 M -( retrieve the attributes for a named file. This can be done using the) s -5 272 M -( SSH_FXP_STAT, SSH_FXP_LSTAT and SSH_FXP_FSTAT requests.) s -5 250 M -( SSH_FXP_STAT and SSH_FXP_LSTAT only differ in that SSH_FXP_STAT) s -5 239 M -( follows symbolic links on the server, whereas SSH_FXP_LSTAT does not) s -5 228 M -( follow symbolic links. Both have the same format:) s -5 206 M -( uint32 id) s -5 195 M -( string path) s -5 173 M -( where `id' is the request identifier, and `path' specifies the file) s -5 129 M -(Ylonen & Lehtinen Expires April 1, 2002 [Page 16]) s -_R -S -PStoPSsaved restore -%%Page: (16,17) 9 -userdict/PStoPSsaved save put -PStoPSmatrix setmatrix -595.000000 0.271378 translate -90 rotate -0.706651 dup scale -userdict/PStoPSmatrix matrix currentmatrix put -userdict/PStoPSclip{0 0 moveto - 595.000000 0 rlineto 0 842.000000 rlineto -595.000000 0 rlineto - closepath}put initclip -/showpage{}def/copypage{}def/erasepage{}def -PStoPSxform concat -%%BeginPageSetup -_S -75 0 translate -/pagenum 17 def -/fname () def -/fdir () def -/ftail () def -/user_header_p false def -%%EndPageSetup -5 723 M -(Internet-Draft SSH File Transfer Protocol October 2001) s -5 690 M -( system object for which status is to be returned. The server) s -5 679 M -( responds to this request with either SSH_FXP_ATTRS or SSH_FXP_STATUS.) s -5 657 M -( SSH_FXP_FSTAT differs from the others in that it returns status) s -5 646 M -( information for an open file \(identified by the file handle\). Its) s -5 635 M -( format is as follows:) s -5 613 M -( uint32 id) s -5 602 M -( string handle) s -5 580 M -( where `id' is the request identifier and `handle' is a file handle) s -5 569 M -( returned by SSH_FXP_OPEN. The server responds to this request with) s -5 558 M -( SSH_FXP_ATTRS or SSH_FXP_STATUS.) s -5 536 M -(6.9 Setting File Attributes) s -5 514 M -( File attributes may be modified using the SSH_FXP_SETSTAT and) s -5 503 M -( SSH_FXP_FSETSTAT requests. These requests are used for operations) s -5 492 M -( such as changing the ownership, permissions or access times, as well) s -5 481 M -( as for truncating a file.) s -5 459 M -( The SSH_FXP_SETSTAT request is of the following format:) s -5 437 M -( uint32 id) s -5 426 M -( string path) s -5 415 M -( ATTRS attrs) s -5 393 M -( where `id' is the request identifier, `path' specifies the file) s -5 382 M -( system object \(e.g. file or directory\) whose attributes are to be) s -5 371 M -( modified, and `attrs' specifies the modifications to be made to its) s -5 360 M -( attributes. Attributes are discussed in more detail in Section) s -5 349 M -( ``File Attributes''.) s -5 327 M -( An error will be returned if the specified file system object does) s -5 316 M -( not exist or the user does not have sufficient rights to modify the) s -5 305 M -( specified attributes. The server responds to this request with a) s -5 294 M -( SSH_FXP_STATUS message.) s -5 272 M -( The SSH_FXP_FSETSTAT request modifies the attributes of a file which) s -5 261 M -( is already open. It has the following format:) s -5 239 M -( uint32 id) s -5 228 M -( string handle) s -5 217 M -( ATTRS attrs) s -5 195 M -( where `id' is the request identifier, `handle' \(MUST be returned by) s -5 184 M -( SSH_FXP_OPEN\) identifies the file whose attributes are to be) s -5 173 M -( modified, and `attrs' specifies the modifications to be made to its) s -5 129 M -(Ylonen & Lehtinen Expires April 1, 2002 [Page 17]) s -_R -S -PStoPSsaved restore -userdict/PStoPSsaved save put -PStoPSmatrix setmatrix -595.000000 421.271378 translate -90 rotate -0.706651 dup scale -userdict/PStoPSmatrix matrix currentmatrix put -userdict/PStoPSclip{0 0 moveto - 595.000000 0 rlineto 0 842.000000 rlineto -595.000000 0 rlineto - closepath}put initclip -PStoPSxform concat -%%BeginPageSetup -_S -75 0 translate -/pagenum 18 def -/fname () def -/fdir () def -/ftail () def -/user_header_p false def -%%EndPageSetup -5 723 M -(Internet-Draft SSH File Transfer Protocol October 2001) s -5 690 M -( attributes. Attributes are discussed in more detail in Section) s -5 679 M -( ``File Attributes''. The server will respond to this request with) s -5 668 M -( SSH_FXP_STATUS.) s -5 646 M -(6.10 Dealing with Symbolic links) s -5 624 M -( The SSH_FXP_READLINK request may be used to read the target of a) s -5 613 M -( symbolic link. It would have a data part as follows:) s -5 591 M -( uint32 id) s -5 580 M -( string path) s -5 558 M -( where `id' is the request identifier and `path' specifies the path) s -5 547 M -( name of the symlink to be read.) s -5 525 M -( The server will respond with a SSH_FXP_NAME packet containing only) s -5 514 M -( one name and a dummy attributes value. The name in the returned) s -5 503 M -( packet contains the target of the link. If an error occurs, the) s -5 492 M -( server may respond with SSH_FXP_STATUS.) s -5 470 M -( The SSH_FXP_SYMLINK request will create a symbolic link on the) s -5 459 M -( server. It is of the following format) s -5 437 M -( uint32 id) s -5 426 M -( string linkpath) s -5 415 M -( string targetpath) s -5 393 M -( where `id' is the request identifier, `linkpath' specifies the path) s -5 382 M -( name of the symlink to be created and `targetpath' specifies the) s -5 371 M -( target of the symlink. The server shall respond with a) s -5 360 M -( SSH_FXP_STATUS indicating either success \(SSH_FX_OK\) or an error) s -5 349 M -( condition.) s -5 327 M -(6.11 Canonicalizing the Server-Side Path Name) s -5 305 M -( The SSH_FXP_REALPATH request can be used to have the server) s -5 294 M -( canonicalize any given path name to an absolute path. This is useful) s -5 283 M -( for converting path names containing ".." components or relative) s -5 272 M -( pathnames without a leading slash into absolute paths. The format of) s -5 261 M -( the request is as follows:) s -5 239 M -( uint32 id) s -5 228 M -( string path) s -5 206 M -( where `id' is the request identifier and `path' specifies the path) s -5 195 M -( name to be canonicalized. The server will respond with a) s -5 184 M -( SSH_FXP_NAME packet containing only one name and a dummy attributes) s -5 173 M -( value. The name is the returned packet will be in canonical form.) s -5 129 M -(Ylonen & Lehtinen Expires April 1, 2002 [Page 18]) s -_R -S -PStoPSsaved restore -%%Page: (18,19) 10 -userdict/PStoPSsaved save put -PStoPSmatrix setmatrix -595.000000 0.271378 translate -90 rotate -0.706651 dup scale -userdict/PStoPSmatrix matrix currentmatrix put -userdict/PStoPSclip{0 0 moveto - 595.000000 0 rlineto 0 842.000000 rlineto -595.000000 0 rlineto - closepath}put initclip -/showpage{}def/copypage{}def/erasepage{}def -PStoPSxform concat -%%BeginPageSetup -_S -75 0 translate -/pagenum 19 def -/fname () def -/fdir () def -/ftail () def -/user_header_p false def -%%EndPageSetup -5 723 M -(Internet-Draft SSH File Transfer Protocol October 2001) s -5 690 M -( If an error occurs, the server may also respond with SSH_FXP_STATUS.) s -5 129 M -(Ylonen & Lehtinen Expires April 1, 2002 [Page 19]) s -_R -S -PStoPSsaved restore -userdict/PStoPSsaved save put -PStoPSmatrix setmatrix -595.000000 421.271378 translate -90 rotate -0.706651 dup scale -userdict/PStoPSmatrix matrix currentmatrix put -userdict/PStoPSclip{0 0 moveto - 595.000000 0 rlineto 0 842.000000 rlineto -595.000000 0 rlineto - closepath}put initclip -PStoPSxform concat -%%BeginPageSetup -_S -75 0 translate -/pagenum 20 def -/fname () def -/fdir () def -/ftail () def -/user_header_p false def -%%EndPageSetup -5 723 M -(Internet-Draft SSH File Transfer Protocol October 2001) s -5 690 M -(7. Responses from the Server to the Client) s -5 668 M -( The server responds to the client using one of a few response) s -5 657 M -( packets. All requests can return a SSH_FXP_STATUS response upon) s -5 646 M -( failure. When the operation is successful, any of the responses may) s -5 635 M -( be returned \(depending on the operation\). If no data needs to be) s -5 624 M -( returned to the client, the SSH_FXP_STATUS response with SSH_FX_OK) s -5 613 M -( status is appropriate. Otherwise, the SSH_FXP_HANDLE message is used) s -5 602 M -( to return a file handle \(for SSH_FXP_OPEN and SSH_FXP_OPENDIR) s -5 591 M -( requests\), SSH_FXP_DATA is used to return data from SSH_FXP_READ,) s -5 580 M -( SSH_FXP_NAME is used to return one or more file names from a) s -5 569 M -( SSH_FXP_READDIR or SSH_FXP_REALPATH request, and SSH_FXP_ATTRS is) s -5 558 M -( used to return file attributes from SSH_FXP_STAT, SSH_FXP_LSTAT, and) s -5 547 M -( SSH_FXP_FSTAT requests.) s -5 525 M -( Exactly one response will be returned for each request. Each) s -5 514 M -( response packet contains a request identifier which can be used to) s -5 503 M -( match each response with the corresponding request. Note that it is) s -5 492 M -( legal to have several requests outstanding simultaneously, and the) s -5 481 M -( server is allowed to send responses to them in a different order from) s -5 470 M -( the order in which the requests were sent \(the result of their) s -5 459 M -( execution, however, is guaranteed to be as if they had been processed) s -5 448 M -( one at a time in the order in which the requests were sent\).) s -5 426 M -( Response packets are of the same general format as request packets.) s -5 415 M -( Each response packet begins with the request identifier.) s -5 393 M -( The format of the data portion of the SSH_FXP_STATUS response is as) s -5 382 M -( follows:) s -5 360 M -( uint32 id) s -5 349 M -( uint32 error/status code) s -5 338 M -( string error message \(ISO-10646 UTF-8 [RFC-2279]\)) s -5 327 M -( string language tag \(as defined in [RFC-1766]\)) s -5 305 M -( where `id' is the request identifier, and `error/status code') s -5 294 M -( indicates the result of the requested operation. The value SSH_FX_OK) s -5 283 M -( indicates success, and all other values indicate failure.) s -5 129 M -(Ylonen & Lehtinen Expires April 1, 2002 [Page 20]) s -_R -S -PStoPSsaved restore -%%Page: (20,21) 11 -userdict/PStoPSsaved save put -PStoPSmatrix setmatrix -595.000000 0.271378 translate -90 rotate -0.706651 dup scale -userdict/PStoPSmatrix matrix currentmatrix put -userdict/PStoPSclip{0 0 moveto - 595.000000 0 rlineto 0 842.000000 rlineto -595.000000 0 rlineto - closepath}put initclip -/showpage{}def/copypage{}def/erasepage{}def -PStoPSxform concat -%%BeginPageSetup -_S -75 0 translate -/pagenum 21 def -/fname () def -/fdir () def -/ftail () def -/user_header_p false def -%%EndPageSetup -5 723 M -(Internet-Draft SSH File Transfer Protocol October 2001) s -5 690 M -( Currently, the following values are defined \(other values may be) s -5 679 M -( defined by future versions of this protocol\):) s -5 657 M -( #define SSH_FX_OK 0) s -5 646 M -( #define SSH_FX_EOF 1) s -5 635 M -( #define SSH_FX_NO_SUCH_FILE 2) s -5 624 M -( #define SSH_FX_PERMISSION_DENIED 3) s -5 613 M -( #define SSH_FX_FAILURE 4) s -5 602 M -( #define SSH_FX_BAD_MESSAGE 5) s -5 591 M -( #define SSH_FX_NO_CONNECTION 6) s -5 580 M -( #define SSH_FX_CONNECTION_LOST 7) s -5 569 M -( #define SSH_FX_OP_UNSUPPORTED 8) s -5 547 M -( SSH_FX_OK) s -5 536 M -( Indicates successful completion of the operation.) s -5 514 M -( SSH_FX_EOF) s -5 503 M -( indicates end-of-file condition; for SSH_FX_READ it means that no) s -5 492 M -( more data is available in the file, and for SSH_FX_READDIR it) s -5 481 M -( indicates that no more files are contained in the directory.) s -5 459 M -( SSH_FX_NO_SUCH_FILE) s -5 448 M -( is returned when a reference is made to a file which should exist) s -5 437 M -( but doesn't.) s -5 415 M -( SSH_FX_PERMISSION_DENIED) s -5 404 M -( is returned when the authenticated user does not have sufficient) s -5 393 M -( permissions to perform the operation.) s -5 371 M -( SSH_FX_FAILURE) s -5 360 M -( is a generic catch-all error message; it should be returned if an) s -5 349 M -( error occurs for which there is no more specific error code) s -5 338 M -( defined.) s -5 316 M -( SSH_FX_BAD_MESSAGE) s -5 305 M -( may be returned if a badly formatted packet or protocol) s -5 294 M -( incompatibility is detected.) s -5 272 M -( SSH_FX_NO_CONNECTION) s -5 261 M -( is a pseudo-error which indicates that the client has no) s -5 250 M -( connection to the server \(it can only be generated locally by the) s -5 239 M -( client, and MUST NOT be returned by servers\).) s -5 217 M -( SSH_FX_CONNECTION_LOST) s -5 206 M -( is a pseudo-error which indicates that the connection to the) s -5 195 M -( server has been lost \(it can only be generated locally by the) s -5 184 M -( client, and MUST NOT be returned by servers\).) s -5 129 M -(Ylonen & Lehtinen Expires April 1, 2002 [Page 21]) s -_R -S -PStoPSsaved restore -userdict/PStoPSsaved save put -PStoPSmatrix setmatrix -595.000000 421.271378 translate -90 rotate -0.706651 dup scale -userdict/PStoPSmatrix matrix currentmatrix put -userdict/PStoPSclip{0 0 moveto - 595.000000 0 rlineto 0 842.000000 rlineto -595.000000 0 rlineto - closepath}put initclip -PStoPSxform concat -%%BeginPageSetup -_S -75 0 translate -/pagenum 22 def -/fname () def -/fdir () def -/ftail () def -/user_header_p false def -%%EndPageSetup -5 723 M -(Internet-Draft SSH File Transfer Protocol October 2001) s -5 690 M -( SSH_FX_OP_UNSUPPORTED) s -5 679 M -( indicates that an attempt was made to perform an operation which) s -5 668 M -( is not supported for the server \(it may be generated locally by) s -5 657 M -( the client if e.g. the version number exchange indicates that a) s -5 646 M -( required feature is not supported by the server, or it may be) s -5 635 M -( returned by the server if the server does not implement an) s -5 624 M -( operation\).) s -5 602 M -( The SSH_FXP_HANDLE response has the following format:) s -5 580 M -( uint32 id) s -5 569 M -( string handle) s -5 547 M -( where `id' is the request identifier, and `handle' is an arbitrary) s -5 536 M -( string that identifies an open file or directory on the server. The) s -5 525 M -( handle is opaque to the client; the client MUST NOT attempt to) s -5 514 M -( interpret or modify it in any way. The length of the handle string) s -5 503 M -( MUST NOT exceed 256 data bytes.) s -5 481 M -( The SSH_FXP_DATA response has the following format:) s -5 459 M -( uint32 id) s -5 448 M -( string data) s -5 426 M -( where `id' is the request identifier, and `data' is an arbitrary byte) s -5 415 M -( string containing the requested data. The data string may be at most) s -5 404 M -( the number of bytes requested in a SSH_FXP_READ request, but may also) s -5 393 M -( be shorter if end of file is reached or if the read is from something) s -5 382 M -( other than a regular file.) s -5 360 M -( The SSH_FXP_NAME response has the following format:) s -5 338 M -( uint32 id) s -5 327 M -( uint32 count) s -5 316 M -( repeats count times:) s -5 305 M -( string filename) s -5 294 M -( string longname) s -5 283 M -( ATTRS attrs) s -5 261 M -( where `id' is the request identifier, `count' is the number of names) s -5 250 M -( returned in this response, and the remaining fields repeat `count') s -5 239 M -( times \(so that all three fields are first included for the first) s -5 228 M -( file, then for the second file, etc\). In the repeated part,) s -5 217 M -( `filename' is a file name being returned \(for SSH_FXP_READDIR, it) s -5 206 M -( will be a relative name within the directory, without any path) s -5 195 M -( components; for SSH_FXP_REALPATH it will be an absolute path name\),) s -5 184 M -( `longname' is an expanded format for the file name, similar to what) s -5 173 M -( is returned by "ls -l" on Unix systems, and `attrs' is the attributes) s -5 129 M -(Ylonen & Lehtinen Expires April 1, 2002 [Page 22]) s -_R -S -PStoPSsaved restore -%%Page: (22,23) 12 -userdict/PStoPSsaved save put -PStoPSmatrix setmatrix -595.000000 0.271378 translate -90 rotate -0.706651 dup scale -userdict/PStoPSmatrix matrix currentmatrix put -userdict/PStoPSclip{0 0 moveto - 595.000000 0 rlineto 0 842.000000 rlineto -595.000000 0 rlineto - closepath}put initclip -/showpage{}def/copypage{}def/erasepage{}def -PStoPSxform concat -%%BeginPageSetup -_S -75 0 translate -/pagenum 23 def -/fname () def -/fdir () def -/ftail () def -/user_header_p false def -%%EndPageSetup -5 723 M -(Internet-Draft SSH File Transfer Protocol October 2001) s -5 690 M -( of the file as described in Section ``File Attributes''.) s -5 668 M -( The format of the `longname' field is unspecified by this protocol.) s -5 657 M -( It MUST be suitable for use in the output of a directory listing) s -5 646 M -( command \(in fact, the recommended operation for a directory listing) s -5 635 M -( command is to simply display this data\). However, clients SHOULD NOT) s -5 624 M -( attempt to parse the longname field for file attributes; they SHOULD) s -5 613 M -( use the attrs field instead.) s -5 591 M -( The recommended format for the longname field is as follows:) s -5 569 M -( -rwxr-xr-x 1 mjos staff 348911 Mar 25 14:29 t-filexfer) s -5 558 M -( 1234567890 123 12345678 12345678 12345678 123456789012) s -5 536 M -( Here, the first line is sample output, and the second field indicates) s -5 525 M -( widths of the various fields. Fields are separated by spaces. The) s -5 514 M -( first field lists file permissions for user, group, and others; the) s -5 503 M -( second field is link count; the third field is the name of the user) s -5 492 M -( who owns the file; the fourth field is the name of the group that) s -5 481 M -( owns the file; the fifth field is the size of the file in bytes; the) s -5 470 M -( sixth field \(which actually may contain spaces, but is fixed to 12) s -5 459 M -( characters\) is the file modification time, and the seventh field is) s -5 448 M -( the file name. Each field is specified to be a minimum of certain) s -5 437 M -( number of character positions \(indicated by the second line above\),) s -5 426 M -( but may also be longer if the data does not fit in the specified) s -5 415 M -( length.) s -5 393 M -( The SSH_FXP_ATTRS response has the following format:) s -5 371 M -( uint32 id) s -5 360 M -( ATTRS attrs) s -5 338 M -( where `id' is the request identifier, and `attrs' is the returned) s -5 327 M -( file attributes as described in Section ``File Attributes''.) s -5 129 M -(Ylonen & Lehtinen Expires April 1, 2002 [Page 23]) s -_R -S -PStoPSsaved restore -userdict/PStoPSsaved save put -PStoPSmatrix setmatrix -595.000000 421.271378 translate -90 rotate -0.706651 dup scale -userdict/PStoPSmatrix matrix currentmatrix put -userdict/PStoPSclip{0 0 moveto - 595.000000 0 rlineto 0 842.000000 rlineto -595.000000 0 rlineto - closepath}put initclip -PStoPSxform concat -%%BeginPageSetup -_S -75 0 translate -/pagenum 24 def -/fname () def -/fdir () def -/ftail () def -/user_header_p false def -%%EndPageSetup -5 723 M -(Internet-Draft SSH File Transfer Protocol October 2001) s -5 690 M -(8. Vendor-Specific Extensions) s -5 668 M -( The SSH_FXP_EXTENDED request provides a generic extension mechanism) s -5 657 M -( for adding vendor-specific commands. The request has the following) s -5 646 M -( format:) s -5 624 M -( uint32 id) s -5 613 M -( string extended-request) s -5 602 M -( ... any request-specific data ...) s -5 580 M -( where `id' is the request identifier, and `extended-request' is a) s -5 569 M -( string of the format "name@domain", where domain is an internet) s -5 558 M -( domain name of the vendor defining the request. The rest of the) s -5 547 M -( request is completely vendor-specific, and servers should only) s -5 536 M -( attempt to interpret it if they recognize the `extended-request') s -5 525 M -( name.) s -5 503 M -( The server may respond to such requests using any of the response) s -5 492 M -( packets defined in Section ``Responses from the Server to the) s -5 481 M -( Client''. Additionally, the server may also respond with a) s -5 470 M -( SSH_FXP_EXTENDED_REPLY packet, as defined below. If the server does) s -5 459 M -( not recognize the `extended-request' name, then the server MUST) s -5 448 M -( respond with SSH_FXP_STATUS with error/status set to) s -5 437 M -( SSH_FX_OP_UNSUPPORTED.) s -5 415 M -( The SSH_FXP_EXTENDED_REPLY packet can be used to carry arbitrary) s -5 404 M -( extension-specific data from the server to the client. It is of the) s -5 393 M -( following format:) s -5 371 M -( uint32 id) s -5 360 M -( ... any request-specific data ...) s -5 129 M -(Ylonen & Lehtinen Expires April 1, 2002 [Page 24]) s -_R -S -PStoPSsaved restore -%%Page: (24,25) 13 -userdict/PStoPSsaved save put -PStoPSmatrix setmatrix -595.000000 0.271378 translate -90 rotate -0.706651 dup scale -userdict/PStoPSmatrix matrix currentmatrix put -userdict/PStoPSclip{0 0 moveto - 595.000000 0 rlineto 0 842.000000 rlineto -595.000000 0 rlineto - closepath}put initclip -/showpage{}def/copypage{}def/erasepage{}def -PStoPSxform concat -%%BeginPageSetup -_S -75 0 translate -/pagenum 25 def -/fname () def -/fdir () def -/ftail () def -/user_header_p false def -%%EndPageSetup -5 723 M -(Internet-Draft SSH File Transfer Protocol October 2001) s -5 690 M -(9. Security Considerations) s -5 668 M -( This protocol assumes that it is run over a secure channel and that) s -5 657 M -( the endpoints of the channel have been authenticated. Thus, this) s -5 646 M -( protocol assumes that it is externally protected from network-level) s -5 635 M -( attacks.) s -5 613 M -( This protocol provides file system access to arbitrary files on the) s -5 602 M -( server \(only constrained by the server implementation\). It is the) s -5 591 M -( responsibility of the server implementation to enforce any access) s -5 580 M -( controls that may be required to limit the access allowed for any) s -5 569 M -( particular user \(the user being authenticated externally to this) s -5 558 M -( protocol, typically using the SSH User Authentication Protocol [6].) s -5 536 M -( Care must be taken in the server implementation to check the validity) s -5 525 M -( of received file handle strings. The server should not rely on them) s -5 514 M -( directly; it MUST check the validity of each handle before relying on) s -5 503 M -( it.) s -5 129 M -(Ylonen & Lehtinen Expires April 1, 2002 [Page 25]) s -_R -S -PStoPSsaved restore -userdict/PStoPSsaved save put -PStoPSmatrix setmatrix -595.000000 421.271378 translate -90 rotate -0.706651 dup scale -userdict/PStoPSmatrix matrix currentmatrix put -userdict/PStoPSclip{0 0 moveto - 595.000000 0 rlineto 0 842.000000 rlineto -595.000000 0 rlineto - closepath}put initclip -PStoPSxform concat -%%BeginPageSetup -_S -75 0 translate -/pagenum 26 def -/fname () def -/fdir () def -/ftail () def -/user_header_p false def -%%EndPageSetup -5 723 M -(Internet-Draft SSH File Transfer Protocol October 2001) s -5 690 M -(10. Changes from previous protocol versions) s -5 668 M -( The SSH File Transfer Protocol has changed over time, before it's) s -5 657 M -( standardization. The following is a description of the incompatible) s -5 646 M -( changes between different versions.) s -5 624 M -(10.1 Changes between versions 3 and 2) s -5 602 M -( o The SSH_FXP_READLINK and SSH_FXP_SYMLINK messages were added.) s -5 580 M -( o The SSH_FXP_EXTENDED and SSH_FXP_EXTENDED_REPLY messages were) s -5 569 M -( added.) s -5 547 M -( o The SSH_FXP_STATUS message was changed to include fields `error) s -5 536 M -( message' and `language tag'.) s -5 503 M -(10.2 Changes between versions 2 and 1) s -5 481 M -( o The SSH_FXP_RENAME message was added.) s -5 448 M -(10.3 Changes between versions 1 and 0) s -5 426 M -( o Implementation changes, no actual protocol changes.) s -5 129 M -(Ylonen & Lehtinen Expires April 1, 2002 [Page 26]) s -_R -S -PStoPSsaved restore -%%Page: (26,27) 14 -userdict/PStoPSsaved save put -PStoPSmatrix setmatrix -595.000000 0.271378 translate -90 rotate -0.706651 dup scale -userdict/PStoPSmatrix matrix currentmatrix put -userdict/PStoPSclip{0 0 moveto - 595.000000 0 rlineto 0 842.000000 rlineto -595.000000 0 rlineto - closepath}put initclip -/showpage{}def/copypage{}def/erasepage{}def -PStoPSxform concat -%%BeginPageSetup -_S -75 0 translate -/pagenum 27 def -/fname () def -/fdir () def -/ftail () def -/user_header_p false def -%%EndPageSetup -5 723 M -(Internet-Draft SSH File Transfer Protocol October 2001) s -5 690 M -(11. Trademark Issues) s -5 668 M -( "ssh" is a registered trademark of SSH Communications Security Corp) s -5 657 M -( in the United States and/or other countries.) s -5 129 M -(Ylonen & Lehtinen Expires April 1, 2002 [Page 27]) s -_R -S -PStoPSsaved restore -userdict/PStoPSsaved save put -PStoPSmatrix setmatrix -595.000000 421.271378 translate -90 rotate -0.706651 dup scale -userdict/PStoPSmatrix matrix currentmatrix put -userdict/PStoPSclip{0 0 moveto - 595.000000 0 rlineto 0 842.000000 rlineto -595.000000 0 rlineto - closepath}put initclip -PStoPSxform concat -%%BeginPageSetup -_S -75 0 translate -/pagenum 28 def -/fname () def -/fdir () def -/ftail () def -/user_header_p false def -%%EndPageSetup -5 723 M -(Internet-Draft SSH File Transfer Protocol October 2001) s -5 690 M -(References) s -5 668 M -( [1] Dierks, T., Allen, C., Treese, W., Karlton, P., Freier, A. and) s -5 657 M -( P. Kocher, "The TLS Protocol Version 1.0", RFC 2246, January) s -5 646 M -( 1999.) s -5 624 M -( [2] Institute of Electrical and Electronics Engineers, "Information) s -5 613 M -( Technology - Portable Operating System Interface \(POSIX\) - Part) s -5 602 M -( 1: System Application Program Interface \(API\) [C Language]",) s -5 591 M -( IEEE Standard 1003.2, 1996.) s -5 569 M -( [3] Rinne, T., Ylonen, T., Kivinen, T., Saarinen, M. and S.) s -5 558 M -( Lehtinen, "SSH Protocol Architecture", draft-ietf-secsh-) s -5 547 M -( architecture-09 \(work in progress\), July 2001.) s -5 525 M -( [4] Rinne, T., Ylonen, T., Kivinen, T., Saarinen, M. and S.) s -5 514 M -( Lehtinen, "SSH Protocol Transport Protocol", draft-ietf-secsh-) s -5 503 M -( architecture-09 \(work in progress\), July 2001.) s -5 481 M -( [5] Rinne, T., Ylonen, T., Kivinen, T., Saarinen, M. and S.) s -5 470 M -( Lehtinen, "SSH Connection Protocol", draft-ietf-secsh-connect-11) s -5 459 M -( \(work in progress\), July 2001.) s -5 437 M -( [6] Rinne, T., Ylonen, T., Kivinen, T., Saarinen, M. and S.) s -5 426 M -( Lehtinen, "SSH Authentication Protocol", draft-ietf-secsh-) s -5 415 M -( userauth-11 \(work in progress\), July 2001.) s -5 382 M -(Authors' Addresses) s -5 360 M -( Tatu Ylonen) s -5 349 M -( SSH Communications Security Corp) s -5 338 M -( Fredrikinkatu 42) s -5 327 M -( HELSINKI FIN-00100) s -5 316 M -( Finland) s -5 294 M -( EMail: [email protected]) s -5 261 M -( Sami Lehtinen) s -5 250 M -( SSH Communications Security Corp) s -5 239 M -( Fredrikinkatu 42) s -5 228 M -( HELSINKI FIN-00100) s -5 217 M -( Finland) s -5 195 M -( EMail: [email protected]) s -5 129 M -(Ylonen & Lehtinen Expires April 1, 2002 [Page 28]) s -_R -S -PStoPSsaved restore -%%Page: (28,29) 15 -userdict/PStoPSsaved save put -PStoPSmatrix setmatrix -595.000000 0.271378 translate -90 rotate -0.706651 dup scale -userdict/PStoPSmatrix matrix currentmatrix put -userdict/PStoPSclip{0 0 moveto - 595.000000 0 rlineto 0 842.000000 rlineto -595.000000 0 rlineto - closepath}put initclip -/showpage{}def/copypage{}def/erasepage{}def -PStoPSxform concat -%%BeginPageSetup -_S -75 0 translate -/pagenum 29 def -/fname () def -/fdir () def -/ftail () def -/user_header_p false def -%%EndPageSetup -5 723 M -(Internet-Draft SSH File Transfer Protocol October 2001) s -5 690 M -(Full Copyright Statement) s -5 668 M -( Copyright \(C\) The Internet Society \(2001\). All Rights Reserved.) s -5 646 M -( This document and translations of it may be copied and furnished to) s -5 635 M -( others, and derivative works that comment on or otherwise explain it) s -5 624 M -( or assist in its implementation may be prepared, copied, published) s -5 613 M -( and distributed, in whole or in part, without restriction of any) s -5 602 M -( kind, provided that the above copyright notice and this paragraph are) s -5 591 M -( included on all such copies and derivative works. However, this) s -5 580 M -( document itself may not be modified in any way, such as by removing) s -5 569 M -( the copyright notice or references to the Internet Society or other) s -5 558 M -( Internet organizations, except as needed for the purpose of) s -5 547 M -( developing Internet standards in which case the procedures for) s -5 536 M -( copyrights defined in the Internet Standards process must be) s -5 525 M -( followed, or as required to translate it into languages other than) s -5 514 M -( English.) s -5 492 M -( The limited permissions granted above are perpetual and will not be) s -5 481 M -( revoked by the Internet Society or its successors or assigns.) s -5 459 M -( This document and the information contained herein is provided on an) s -5 448 M -( "AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING) s -5 437 M -( TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING) s -5 426 M -( BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION) s -5 415 M -( HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF) s -5 404 M -( MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.) s -5 382 M -(Acknowledgement) s -5 360 M -( Funding for the RFC Editor function is currently provided by the) s -5 349 M -( Internet Society.) s -5 129 M -(Ylonen & Lehtinen Expires April 1, 2002 [Page 29]) s -_R -S -PStoPSsaved restore -userdict/PStoPSsaved save put -PStoPSmatrix setmatrix -595.000000 421.271378 translate -90 rotate -0.706651 dup scale -userdict/PStoPSmatrix matrix currentmatrix put -userdict/PStoPSclip{0 0 moveto - 595.000000 0 rlineto 0 842.000000 rlineto -595.000000 0 rlineto - closepath}put initclip -PStoPSxform concat -%%BeginPageSetup -_S -75 0 translate -/pagenum 30 def -/fname () def -/fdir () def -/ftail () def -/user_header_p false def -%%EndPageSetup -_R -S -PStoPSsaved restore -%%Trailer -%%Pages: 30 -%%DocumentNeededResources: font Courier-Bold Courier -%%EOF diff --git a/lib/ssh/doc/standard/draft-ietf-secsh-filexfer-02.txt b/lib/ssh/doc/standard/draft-ietf-secsh-filexfer-02.txt deleted file mode 100644 index c4ec8c1125..0000000000 --- a/lib/ssh/doc/standard/draft-ietf-secsh-filexfer-02.txt +++ /dev/null @@ -1,1627 +0,0 @@ - - - -Network Working Group T. Ylonen -Internet-Draft S. Lehtinen -Expires: April 1, 2002 SSH Communications Security Corp - October 2001 - - - SSH File Transfer Protocol - draft-ietf-secsh-filexfer-02.txt - -Status of this Memo - - This document is an Internet-Draft and is in full conformance with - all provisions of Section 10 of RFC2026. - - Internet-Drafts are working documents of the Internet Engineering - Task Force (IETF), its areas, and its working groups. Note that - other groups may also distribute working documents as Internet- - Drafts. - - Internet-Drafts are draft documents valid for a maximum of six months - and may be updated, replaced, or obsoleted by other documents at any - time. It is inappropriate to use Internet-Drafts as reference - material or to cite them other than as "work in progress." - - The list of current Internet-Drafts can be accessed at http:// - www.ietf.org/ietf/1id-abstracts.txt. - - The list of Internet-Draft Shadow Directories can be accessed at - http://www.ietf.org/shadow.html. - - This Internet-Draft will expire on April 1, 2002. - -Copyright Notice - - Copyright (C) The Internet Society (2001). All Rights Reserved. - -Abstract - - The SSH File Transfer Protocol provides secure file transfer - functionality over any reliable data stream. It is the standard file - transfer protocol for use with the SSH2 protocol. This document - describes the file transfer protocol and its interface to the SSH2 - protocol suite. - - - - - - - - - -Ylonen & Lehtinen Expires April 1, 2002 [Page 1] - -Internet-Draft SSH File Transfer Protocol October 2001 - - -Table of Contents - - 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 - 2. Use with the SSH Connection Protocol . . . . . . . . . . . . 4 - 3. General Packet Format . . . . . . . . . . . . . . . . . . . 5 - 4. Protocol Initialization . . . . . . . . . . . . . . . . . . 7 - 5. File Attributes . . . . . . . . . . . . . . . . . . . . . . 8 - 6. Requests From the Client to the Server . . . . . . . . . . . 10 - 6.1 Request Synchronization and Reordering . . . . . . . . . . . 10 - 6.2 File Names . . . . . . . . . . . . . . . . . . . . . . . . . 11 - 6.3 Opening, Creating, and Closing Files . . . . . . . . . . . . 11 - 6.4 Reading and Writing . . . . . . . . . . . . . . . . . . . . 13 - 6.5 Removing and Renaming Files . . . . . . . . . . . . . . . . 14 - 6.6 Creating and Deleting Directories . . . . . . . . . . . . . 15 - 6.7 Scanning Directories . . . . . . . . . . . . . . . . . . . . 15 - 6.8 Retrieving File Attributes . . . . . . . . . . . . . . . . . 16 - 6.9 Setting File Attributes . . . . . . . . . . . . . . . . . . 17 - 6.10 Dealing with Symbolic links . . . . . . . . . . . . . . . . 18 - 6.11 Canonicalizing the Server-Side Path Name . . . . . . . . . . 18 - 7. Responses from the Server to the Client . . . . . . . . . . 20 - 8. Vendor-Specific Extensions . . . . . . . . . . . . . . . . . 24 - 9. Security Considerations . . . . . . . . . . . . . . . . . . 25 - 10. Changes from previous protocol versions . . . . . . . . . . 26 - 10.1 Changes between versions 3 and 2 . . . . . . . . . . . . . . 26 - 10.2 Changes between versions 2 and 1 . . . . . . . . . . . . . . 26 - 10.3 Changes between versions 1 and 0 . . . . . . . . . . . . . . 26 - 11. Trademark Issues . . . . . . . . . . . . . . . . . . . . . . 27 - References . . . . . . . . . . . . . . . . . . . . . . . . . 28 - Authors' Addresses . . . . . . . . . . . . . . . . . . . . . 28 - Full Copyright Statement . . . . . . . . . . . . . . . . . . 29 - - - - - - - - - - - - - - - - - - - - - -Ylonen & Lehtinen Expires April 1, 2002 [Page 2] - -Internet-Draft SSH File Transfer Protocol October 2001 - - -1. Introduction - - This protocol provides secure file transfer (and more generally file - system access) functionality over a reliable data stream, such as a - channel in the SSH2 protocol [3]. - - This protocol is designed so that it could be used to implement a - secure remote file system service, as well as a secure file transfer - service. - - This protocol assumes that it runs over a secure channel, and that - the server has already authenticated the user at the client end, and - that the identity of the client user is externally available to the - server implementation. - - In general, this protocol follows a simple request-response model. - Each request and response contains a sequence number and multiple - requests may be pending simultaneously. There are a relatively large - number of different request messages, but a small number of possible - response messages. Each request has one or more response messages - that may be returned in result (e.g., a read either returns data or - reports error status). - - The packet format descriptions in this specification follow the - notation presented in the secsh architecture draft.[3]. - - Even though this protocol is described in the context of the SSH2 - protocol, this protocol is general and independent of the rest of the - SSH2 protocol suite. It could be used in a number of different - applications, such as secure file transfer over TLS RFC 2246 [1] and - transfer of management information in VPN applications. - - - - - - - - - - - - - - - - - - - - -Ylonen & Lehtinen Expires April 1, 2002 [Page 3] - -Internet-Draft SSH File Transfer Protocol October 2001 - - -2. Use with the SSH Connection Protocol - - When used with the SSH2 Protocol suite, this protocol is intended to - be used from the SSH Connection Protocol [5] as a subsystem, as - described in section ``Starting a Shell or a Command''. The - subsystem name used with this protocol is "sftp". - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -Ylonen & Lehtinen Expires April 1, 2002 [Page 4] - -Internet-Draft SSH File Transfer Protocol October 2001 - - -3. General Packet Format - - All packets transmitted over the secure connection are of the - following format: - - uint32 length - byte type - byte[length - 1] data payload - - That is, they are just data preceded by 32-bit length and 8-bit type - fields. The `length' is the length of the data area, and does not - include the `length' field itself. The format and interpretation of - the data area depends on the packet type. - - All packet descriptions below only specify the packet type and the - data that goes into the data field. Thus, they should be prefixed by - the `length' and `type' fields. - - The maximum size of a packet is in practice determined by the client - (the maximum size of read or write requests that it sends, plus a few - bytes of packet overhead). All servers SHOULD support packets of at - least 34000 bytes (where the packet size refers to the full length, - including the header above). This should allow for reads and writes - of at most 32768 bytes. - - There is no limit on the number of outstanding (non-acknowledged) - requests that the client may send to the server. In practice this is - limited by the buffering available on the data stream and the queuing - performed by the server. If the server's queues are full, it should - not read any more data from the stream, and flow control will prevent - the client from sending more requests. Note, however, that while - there is no restriction on the protocol level, the client's API may - provide a limit in order to prevent infinite queuing of outgoing - requests at the client. - - - - - - - - - - - - - - - - - -Ylonen & Lehtinen Expires April 1, 2002 [Page 5] - -Internet-Draft SSH File Transfer Protocol October 2001 - - - The following values are defined for packet types. - - #define SSH_FXP_INIT 1 - #define SSH_FXP_VERSION 2 - #define SSH_FXP_OPEN 3 - #define SSH_FXP_CLOSE 4 - #define SSH_FXP_READ 5 - #define SSH_FXP_WRITE 6 - #define SSH_FXP_LSTAT 7 - #define SSH_FXP_FSTAT 8 - #define SSH_FXP_SETSTAT 9 - #define SSH_FXP_FSETSTAT 10 - #define SSH_FXP_OPENDIR 11 - #define SSH_FXP_READDIR 12 - #define SSH_FXP_REMOVE 13 - #define SSH_FXP_MKDIR 14 - #define SSH_FXP_RMDIR 15 - #define SSH_FXP_REALPATH 16 - #define SSH_FXP_STAT 17 - #define SSH_FXP_RENAME 18 - #define SSH_FXP_READLINK 19 - #define SSH_FXP_SYMLINK 20 - #define SSH_FXP_STATUS 101 - #define SSH_FXP_HANDLE 102 - #define SSH_FXP_DATA 103 - #define SSH_FXP_NAME 104 - #define SSH_FXP_ATTRS 105 - #define SSH_FXP_EXTENDED 200 - #define SSH_FXP_EXTENDED_REPLY 201 - - Additional packet types should only be defined if the protocol - version number (see Section ``Protocol Initialization'') is - incremented, and their use MUST be negotiated using the version - number. However, the SSH_FXP_EXTENDED and SSH_FXP_EXTENDED_REPLY - packets can be used to implement vendor-specific extensions. See - Section ``Vendor-Specific-Extensions'' for more details. - - - - - - - - - - - - - - - -Ylonen & Lehtinen Expires April 1, 2002 [Page 6] - -Internet-Draft SSH File Transfer Protocol October 2001 - - -4. Protocol Initialization - - When the file transfer protocol starts, it first sends a SSH_FXP_INIT - (including its version number) packet to the server. The server - responds with a SSH_FXP_VERSION packet, supplying the lowest of its - own and the client's version number. Both parties should from then - on adhere to particular version of the protocol. - - The SSH_FXP_INIT packet (from client to server) has the following - data: - - uint32 version - <extension data> - - The SSH_FXP_VERSION packet (from server to client) has the following - data: - - uint32 version - <extension data> - - The version number of the protocol specified in this document is 3. - The version number should be incremented for each incompatible - revision of this protocol. - - The extension data in the above packets may be empty, or may be a - sequence of - - string extension_name - string extension_data - - pairs (both strings MUST always be present if one is, but the - `extension_data' string may be of zero length). If present, these - strings indicate extensions to the baseline protocol. The - `extension_name' field(s) identify the name of the extension. The - name should be of the form "name@domain", where the domain is the DNS - domain name of the organization defining the extension. Additional - names that are not of this format may be defined later by the IETF. - Implementations MUST silently ignore any extensions whose name they - do not recognize. - - - - - - - - - - - - -Ylonen & Lehtinen Expires April 1, 2002 [Page 7] - -Internet-Draft SSH File Transfer Protocol October 2001 - - -5. File Attributes - - A new compound data type is defined for encoding file attributes. It - is basically just a combination of elementary types, but is defined - once because of the non-trivial description of the fields and to - ensure maintainability. - - The same encoding is used both when returning file attributes from - the server and when sending file attributes to the server. When - sending it to the server, the flags field specifies which attributes - are included, and the server will use default values for the - remaining attributes (or will not modify the values of remaining - attributes). When receiving attributes from the server, the flags - specify which attributes are included in the returned data. The - server normally returns all attributes it knows about. - - uint32 flags - uint64 size present only if flag SSH_FILEXFER_ATTR_SIZE - uint32 uid present only if flag SSH_FILEXFER_ATTR_UIDGID - uint32 gid present only if flag SSH_FILEXFER_ATTR_UIDGID - uint32 permissions present only if flag SSH_FILEXFER_ATTR_PERMISSIONS - uint32 atime present only if flag SSH_FILEXFER_ACMODTIME - uint32 mtime present only if flag SSH_FILEXFER_ACMODTIME - uint32 extended_count present only if flag SSH_FILEXFER_ATTR_EXTENDED - string extended_type - string extended_data - ... more extended data (extended_type - extended_data pairs), - so that number of pairs equals extended_count - - The `flags' specify which of the fields are present. Those fields - for which the corresponding flag is not set are not present (not - included in the packet). New flags can only be added by incrementing - the protocol version number (or by using the extension mechanism - described below). - - The `size' field specifies the size of the file in bytes. - - The `uid' and `gid' fields contain numeric Unix-like user and group - identifiers, respectively. - - The `permissions' field contains a bit mask of file permissions as - defined by posix [1]. - - The `atime' and `mtime' contain the access and modification times of - the files, respectively. They are represented as seconds from Jan 1, - 1970 in UTC. - - The SSH_FILEXFER_ATTR_EXTENDED flag provides a general extension - - - -Ylonen & Lehtinen Expires April 1, 2002 [Page 8] - -Internet-Draft SSH File Transfer Protocol October 2001 - - - mechanism for vendor-specific extensions. If the flag is specified, - then the `extended_count' field is present. It specifies the number - of extended_type-extended_data pairs that follow. Each of these - pairs specifies an extended attribute. For each of the attributes, - the extended_type field should be a string of the format - "name@domain", where "domain" is a valid, registered domain name and - "name" identifies the method. The IETF may later standardize certain - names that deviate from this format (e.g., that do not contain the - "@" sign). The interpretation of `extended_data' depends on the - type. Implementations SHOULD ignore extended data fields that they - do not understand. - - Additional fields can be added to the attributes by either defining - additional bits to the flags field to indicate their presence, or by - defining extended attributes for them. The extended attributes - mechanism is recommended for most purposes; additional flags bits - should only be defined by an IETF standards action that also - increments the protocol version number. The use of such new fields - MUST be negotiated by the version number in the protocol exchange. - It is a protocol error if a packet with unsupported protocol bits is - received. - - The flags bits are defined to have the following values: - - #define SSH_FILEXFER_ATTR_SIZE 0x00000001 - #define SSH_FILEXFER_ATTR_UIDGID 0x00000002 - #define SSH_FILEXFER_ATTR_PERMISSIONS 0x00000004 - #define SSH_FILEXFER_ATTR_ACMODTIME 0x00000008 - #define SSH_FILEXFER_ATTR_EXTENDED 0x80000000 - - - - - - - - - - - - - - - - - - - - - - -Ylonen & Lehtinen Expires April 1, 2002 [Page 9] - -Internet-Draft SSH File Transfer Protocol October 2001 - - -6. Requests From the Client to the Server - - Requests from the client to the server represent the various file - system operations. Each request begins with an `id' field, which is - a 32-bit identifier identifying the request (selected by the client). - The same identifier will be returned in the response to the request. - One possible implementation of it is a monotonically increasing - request sequence number (modulo 2^32). - - Many operations in the protocol operate on open files. The - SSH_FXP_OPEN request can return a file handle (which is an opaque - variable-length string) which may be used to access the file later - (e.g. in a read operation). The client MUST NOT send requests the - server with bogus or closed handles. However, the server MUST - perform adequate checks on the handle in order to avoid security - risks due to fabricated handles. - - This design allows either stateful and stateless server - implementation, as well as an implementation which caches state - between requests but may also flush it. The contents of the file - handle string are entirely up to the server and its design. The - client should not modify or attempt to interpret the file handle - strings. - - The file handle strings MUST NOT be longer than 256 bytes. - -6.1 Request Synchronization and Reordering - - The protocol and implementations MUST process requests relating to - the same file in the order in which they are received. In other - words, if an application submits multiple requests to the server, the - results in the responses will be the same as if it had sent the - requests one at a time and waited for the response in each case. For - example, the server may process non-overlapping read/write requests - to the same file in parallel, but overlapping reads and writes cannot - be reordered or parallelized. However, there are no ordering - restrictions on the server for processing requests from two different - file transfer connections. The server may interleave and parallelize - them at will. - - There are no restrictions on the order in which responses to - outstanding requests are delivered to the client, except that the - server must ensure fairness in the sense that processing of no - request will be indefinitely delayed even if the client is sending - other requests so that there are multiple outstanding requests all - the time. - - - - - -Ylonen & Lehtinen Expires April 1, 2002 [Page 10] - -Internet-Draft SSH File Transfer Protocol October 2001 - - -6.2 File Names - - This protocol represents file names as strings. File names are - assumed to use the slash ('/') character as a directory separator. - - File names starting with a slash are "absolute", and are relative to - the root of the file system. Names starting with any other character - are relative to the user's default directory (home directory). Note - that identifying the user is assumed to take place outside of this - protocol. - - Servers SHOULD interpret a path name component ".." as referring to - the parent directory, and "." as referring to the current directory. - If the server implementation limits access to certain parts of the - file system, it must be extra careful in parsing file names when - enforcing such restrictions. There have been numerous reported - security bugs where a ".." in a path name has allowed access outside - the intended area. - - An empty path name is valid, and it refers to the user's default - directory (usually the user's home directory). - - Otherwise, no syntax is defined for file names by this specification. - Clients should not make any other assumptions; however, they can - splice path name components returned by SSH_FXP_READDIR together - using a slash ('/') as the separator, and that will work as expected. - - It is understood that the lack of well-defined semantics for file - names may cause interoperability problems between clients and servers - using radically different operating systems. However, this approach - is known to work acceptably with most systems, and alternative - approaches that e.g. treat file names as sequences of structured - components are quite complicated. - -6.3 Opening, Creating, and Closing Files - - Files are opened and created using the SSH_FXP_OPEN message, whose - data part is as follows: - - uint32 id - string filename - uint32 pflags - ATTRS attrs - - The `id' field is the request identifier as for all requests. - - The `filename' field specifies the file name. See Section ``File - Names'' for more information. - - - -Ylonen & Lehtinen Expires April 1, 2002 [Page 11] - -Internet-Draft SSH File Transfer Protocol October 2001 - - - The `pflags' field is a bitmask. The following bits have been - defined. - - #define SSH_FXF_READ 0x00000001 - #define SSH_FXF_WRITE 0x00000002 - #define SSH_FXF_APPEND 0x00000004 - #define SSH_FXF_CREAT 0x00000008 - #define SSH_FXF_TRUNC 0x00000010 - #define SSH_FXF_EXCL 0x00000020 - - These have the following meanings: - - SSH_FXF_READ - Open the file for reading. - - SSH_FXF_WRITE - Open the file for writing. If both this and SSH_FXF_READ are - specified, the file is opened for both reading and writing. - - SSH_FXF_APPEND - Force all writes to append data at the end of the file. - - SSH_FXF_CREAT - If this flag is specified, then a new file will be created if one - does not already exist (if O_TRUNC is specified, the new file will - be truncated to zero length if it previously exists). - - SSH_FXF_TRUNC - Forces an existing file with the same name to be truncated to zero - length when creating a file by specifying SSH_FXF_CREAT. - SSH_FXF_CREAT MUST also be specified if this flag is used. - - SSH_FXF_EXCL - Causes the request to fail if the named file already exists. - SSH_FXF_CREAT MUST also be specified if this flag is used. - - The `attrs' field specifies the initial attributes for the file. - Default values will be used for those attributes that are not - specified. See Section ``File Attributes'' for more information. - - Regardless the server operating system, the file will always be - opened in "binary" mode (i.e., no translations between different - character sets and newline encodings). - - The response to this message will be either SSH_FXP_HANDLE (if the - operation is successful) or SSH_FXP_STATUS (if the operation fails). - - - - - -Ylonen & Lehtinen Expires April 1, 2002 [Page 12] - -Internet-Draft SSH File Transfer Protocol October 2001 - - - A file is closed by using the SSH_FXP_CLOSE request. Its data field - has the following format: - - uint32 id - string handle - - where `id' is the request identifier, and `handle' is a handle - previously returned in the response to SSH_FXP_OPEN or - SSH_FXP_OPENDIR. The handle becomes invalid immediately after this - request has been sent. - - The response to this request will be a SSH_FXP_STATUS message. One - should note that on some server platforms even a close can fail. - This can happen e.g. if the server operating system caches writes, - and an error occurs while flushing cached writes during the close. - -6.4 Reading and Writing - - Once a file has been opened, it can be read using the SSH_FXP_READ - message, which has the following format: - - uint32 id - string handle - uint64 offset - uint32 len - - where `id' is the request identifier, `handle' is an open file handle - returned by SSH_FXP_OPEN, `offset' is the offset (in bytes) relative - to the beginning of the file from where to start reading, and `len' - is the maximum number of bytes to read. - - In response to this request, the server will read as many bytes as it - can from the file (up to `len'), and return them in a SSH_FXP_DATA - message. If an error occurs or EOF is encountered before reading any - data, the server will respond with SSH_FXP_STATUS. For normal disk - files, it is guaranteed that this will read the specified number of - bytes, or up to end of file. For e.g. device files this may return - fewer bytes than requested. - - Writing to a file is achieved using the SSH_FXP_WRITE message, which - has the following format: - - uint32 id - string handle - uint64 offset - string data - - where `id' is a request identifier, `handle' is a file handle - - - -Ylonen & Lehtinen Expires April 1, 2002 [Page 13] - -Internet-Draft SSH File Transfer Protocol October 2001 - - - returned by SSH_FXP_OPEN, `offset' is the offset (in bytes) from the - beginning of the file where to start writing, and `data' is the data - to be written. - - The write will extend the file if writing beyond the end of the file. - It is legal to write way beyond the end of the file; the semantics - are to write zeroes from the end of the file to the specified offset - and then the data. On most operating systems, such writes do not - allocate disk space but instead leave "holes" in the file. - - The server responds to a write request with a SSH_FXP_STATUS message. - -6.5 Removing and Renaming Files - - Files can be removed using the SSH_FXP_REMOVE message. It has the - following format: - - uint32 id - string filename - - where `id' is the request identifier and `filename' is the name of - the file to be removed. See Section ``File Names'' for more - information. This request cannot be used to remove directories. - - The server will respond to this request with a SSH_FXP_STATUS - message. - - Files (and directories) can be renamed using the SSH_FXP_RENAME - message. Its data is as follows: - - uint32 id - string oldpath - string newpath - - where `id' is the request identifier, `oldpath' is the name of an - existing file or directory, and `newpath' is the new name for the - file or directory. It is an error if there already exists a file - with the name specified by newpath. The server may also fail rename - requests in other situations, for example if `oldpath' and `newpath' - point to different file systems on the server. - - The server will respond to this request with a SSH_FXP_STATUS - message. - - - - - - - - -Ylonen & Lehtinen Expires April 1, 2002 [Page 14] - -Internet-Draft SSH File Transfer Protocol October 2001 - - -6.6 Creating and Deleting Directories - - New directories can be created using the SSH_FXP_MKDIR request. It - has the following format: - - uint32 id - string path - ATTRS attrs - - where `id' is the request identifier, `path' and `attrs' specifies - the modifications to be made to its attributes. See Section ``File - Names'' for more information on file names. Attributes are discussed - in more detail in Section ``File Attributes''. specifies the - directory to be created. An error will be returned if a file or - directory with the specified path already exists. The server will - respond to this request with a SSH_FXP_STATUS message. - - Directories can be removed using the SSH_FXP_RMDIR request, which - has the following format: - - uint32 id - string path - - where `id' is the request identifier, and `path' specifies the - directory to be removed. See Section ``File Names'' for more - information on file names. An error will be returned if no directory - with the specified path exists, or if the specified directory is not - empty, or if the path specified a file system object other than a - directory. The server responds to this request with a SSH_FXP_STATUS - message. - -6.7 Scanning Directories - - The files in a directory can be listed using the SSH_FXP_OPENDIR and - SSH_FXP_READDIR requests. Each SSH_FXP_READDIR request returns one - or more file names with full file attributes for each file. The - client should call SSH_FXP_READDIR repeatedly until it has found the - file it is looking for or until the server responds with a - SSH_FXP_STATUS message indicating an error (normally SSH_FX_EOF if - there are no more files in the directory). The client should then - close the handle using the SSH_FXP_CLOSE request. - - - - - - - - - - -Ylonen & Lehtinen Expires April 1, 2002 [Page 15] - -Internet-Draft SSH File Transfer Protocol October 2001 - - - The SSH_FXP_OPENDIR opens a directory for reading. It has the - following format: - - uint32 id - string path - - where `id' is the request identifier and `path' is the path name of - the directory to be listed (without any trailing slash). See Section - ``File Names'' for more information on file names. This will return - an error if the path does not specify a directory or if the directory - is not readable. The server will respond to this request with either - a SSH_FXP_HANDLE or a SSH_FXP_STATUS message. - - Once the directory has been successfully opened, files (and - directories) contained in it can be listed using SSH_FXP_READDIR - requests. These are of the format - - uint32 id - string handle - - where `id' is the request identifier, and `handle' is a handle - returned by SSH_FXP_OPENDIR. (It is a protocol error to attempt to - use an ordinary file handle returned by SSH_FXP_OPEN.) - - The server responds to this request with either a SSH_FXP_NAME or a - SSH_FXP_STATUS message. One or more names may be returned at a time. - Full status information is returned for each name in order to speed - up typical directory listings. - - When the client no longer wishes to read more names from the - directory, it SHOULD call SSH_FXP_CLOSE for the handle. The handle - should be closed regardless of whether an error has occurred or not. - -6.8 Retrieving File Attributes - - Very often, file attributes are automatically returned by - SSH_FXP_READDIR. However, sometimes there is need to specifically - retrieve the attributes for a named file. This can be done using the - SSH_FXP_STAT, SSH_FXP_LSTAT and SSH_FXP_FSTAT requests. - - SSH_FXP_STAT and SSH_FXP_LSTAT only differ in that SSH_FXP_STAT - follows symbolic links on the server, whereas SSH_FXP_LSTAT does not - follow symbolic links. Both have the same format: - - uint32 id - string path - - where `id' is the request identifier, and `path' specifies the file - - - -Ylonen & Lehtinen Expires April 1, 2002 [Page 16] - -Internet-Draft SSH File Transfer Protocol October 2001 - - - system object for which status is to be returned. The server - responds to this request with either SSH_FXP_ATTRS or SSH_FXP_STATUS. - - SSH_FXP_FSTAT differs from the others in that it returns status - information for an open file (identified by the file handle). Its - format is as follows: - - uint32 id - string handle - - where `id' is the request identifier and `handle' is a file handle - returned by SSH_FXP_OPEN. The server responds to this request with - SSH_FXP_ATTRS or SSH_FXP_STATUS. - -6.9 Setting File Attributes - - File attributes may be modified using the SSH_FXP_SETSTAT and - SSH_FXP_FSETSTAT requests. These requests are used for operations - such as changing the ownership, permissions or access times, as well - as for truncating a file. - - The SSH_FXP_SETSTAT request is of the following format: - - uint32 id - string path - ATTRS attrs - - where `id' is the request identifier, `path' specifies the file - system object (e.g. file or directory) whose attributes are to be - modified, and `attrs' specifies the modifications to be made to its - attributes. Attributes are discussed in more detail in Section - ``File Attributes''. - - An error will be returned if the specified file system object does - not exist or the user does not have sufficient rights to modify the - specified attributes. The server responds to this request with a - SSH_FXP_STATUS message. - - The SSH_FXP_FSETSTAT request modifies the attributes of a file which - is already open. It has the following format: - - uint32 id - string handle - ATTRS attrs - - where `id' is the request identifier, `handle' (MUST be returned by - SSH_FXP_OPEN) identifies the file whose attributes are to be - modified, and `attrs' specifies the modifications to be made to its - - - -Ylonen & Lehtinen Expires April 1, 2002 [Page 17] - -Internet-Draft SSH File Transfer Protocol October 2001 - - - attributes. Attributes are discussed in more detail in Section - ``File Attributes''. The server will respond to this request with - SSH_FXP_STATUS. - -6.10 Dealing with Symbolic links - - The SSH_FXP_READLINK request may be used to read the target of a - symbolic link. It would have a data part as follows: - - uint32 id - string path - - where `id' is the request identifier and `path' specifies the path - name of the symlink to be read. - - The server will respond with a SSH_FXP_NAME packet containing only - one name and a dummy attributes value. The name in the returned - packet contains the target of the link. If an error occurs, the - server may respond with SSH_FXP_STATUS. - - The SSH_FXP_SYMLINK request will create a symbolic link on the - server. It is of the following format - - uint32 id - string linkpath - string targetpath - - where `id' is the request identifier, `linkpath' specifies the path - name of the symlink to be created and `targetpath' specifies the - target of the symlink. The server shall respond with a - SSH_FXP_STATUS indicating either success (SSH_FX_OK) or an error - condition. - -6.11 Canonicalizing the Server-Side Path Name - - The SSH_FXP_REALPATH request can be used to have the server - canonicalize any given path name to an absolute path. This is useful - for converting path names containing ".." components or relative - pathnames without a leading slash into absolute paths. The format of - the request is as follows: - - uint32 id - string path - - where `id' is the request identifier and `path' specifies the path - name to be canonicalized. The server will respond with a - SSH_FXP_NAME packet containing only one name and a dummy attributes - value. The name is the returned packet will be in canonical form. - - - -Ylonen & Lehtinen Expires April 1, 2002 [Page 18] - -Internet-Draft SSH File Transfer Protocol October 2001 - - - If an error occurs, the server may also respond with SSH_FXP_STATUS. - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -Ylonen & Lehtinen Expires April 1, 2002 [Page 19] - -Internet-Draft SSH File Transfer Protocol October 2001 - - -7. Responses from the Server to the Client - - The server responds to the client using one of a few response - packets. All requests can return a SSH_FXP_STATUS response upon - failure. When the operation is successful, any of the responses may - be returned (depending on the operation). If no data needs to be - returned to the client, the SSH_FXP_STATUS response with SSH_FX_OK - status is appropriate. Otherwise, the SSH_FXP_HANDLE message is used - to return a file handle (for SSH_FXP_OPEN and SSH_FXP_OPENDIR - requests), SSH_FXP_DATA is used to return data from SSH_FXP_READ, - SSH_FXP_NAME is used to return one or more file names from a - SSH_FXP_READDIR or SSH_FXP_REALPATH request, and SSH_FXP_ATTRS is - used to return file attributes from SSH_FXP_STAT, SSH_FXP_LSTAT, and - SSH_FXP_FSTAT requests. - - Exactly one response will be returned for each request. Each - response packet contains a request identifier which can be used to - match each response with the corresponding request. Note that it is - legal to have several requests outstanding simultaneously, and the - server is allowed to send responses to them in a different order from - the order in which the requests were sent (the result of their - execution, however, is guaranteed to be as if they had been processed - one at a time in the order in which the requests were sent). - - Response packets are of the same general format as request packets. - Each response packet begins with the request identifier. - - The format of the data portion of the SSH_FXP_STATUS response is as - follows: - - uint32 id - uint32 error/status code - string error message (ISO-10646 UTF-8 [RFC-2279]) - string language tag (as defined in [RFC-1766]) - - where `id' is the request identifier, and `error/status code' - indicates the result of the requested operation. The value SSH_FX_OK - indicates success, and all other values indicate failure. - - - - - - - - - - - - - -Ylonen & Lehtinen Expires April 1, 2002 [Page 20] - -Internet-Draft SSH File Transfer Protocol October 2001 - - - Currently, the following values are defined (other values may be - defined by future versions of this protocol): - - #define SSH_FX_OK 0 - #define SSH_FX_EOF 1 - #define SSH_FX_NO_SUCH_FILE 2 - #define SSH_FX_PERMISSION_DENIED 3 - #define SSH_FX_FAILURE 4 - #define SSH_FX_BAD_MESSAGE 5 - #define SSH_FX_NO_CONNECTION 6 - #define SSH_FX_CONNECTION_LOST 7 - #define SSH_FX_OP_UNSUPPORTED 8 - - SSH_FX_OK - Indicates successful completion of the operation. - - SSH_FX_EOF - indicates end-of-file condition; for SSH_FX_READ it means that no - more data is available in the file, and for SSH_FX_READDIR it - indicates that no more files are contained in the directory. - - SSH_FX_NO_SUCH_FILE - is returned when a reference is made to a file which should exist - but doesn't. - - SSH_FX_PERMISSION_DENIED - is returned when the authenticated user does not have sufficient - permissions to perform the operation. - - SSH_FX_FAILURE - is a generic catch-all error message; it should be returned if an - error occurs for which there is no more specific error code - defined. - - SSH_FX_BAD_MESSAGE - may be returned if a badly formatted packet or protocol - incompatibility is detected. - - SSH_FX_NO_CONNECTION - is a pseudo-error which indicates that the client has no - connection to the server (it can only be generated locally by the - client, and MUST NOT be returned by servers). - - SSH_FX_CONNECTION_LOST - is a pseudo-error which indicates that the connection to the - server has been lost (it can only be generated locally by the - client, and MUST NOT be returned by servers). - - - - -Ylonen & Lehtinen Expires April 1, 2002 [Page 21] - -Internet-Draft SSH File Transfer Protocol October 2001 - - - SSH_FX_OP_UNSUPPORTED - indicates that an attempt was made to perform an operation which - is not supported for the server (it may be generated locally by - the client if e.g. the version number exchange indicates that a - required feature is not supported by the server, or it may be - returned by the server if the server does not implement an - operation). - - The SSH_FXP_HANDLE response has the following format: - - uint32 id - string handle - - where `id' is the request identifier, and `handle' is an arbitrary - string that identifies an open file or directory on the server. The - handle is opaque to the client; the client MUST NOT attempt to - interpret or modify it in any way. The length of the handle string - MUST NOT exceed 256 data bytes. - - The SSH_FXP_DATA response has the following format: - - uint32 id - string data - - where `id' is the request identifier, and `data' is an arbitrary byte - string containing the requested data. The data string may be at most - the number of bytes requested in a SSH_FXP_READ request, but may also - be shorter if end of file is reached or if the read is from something - other than a regular file. - - The SSH_FXP_NAME response has the following format: - - uint32 id - uint32 count - repeats count times: - string filename - string longname - ATTRS attrs - - where `id' is the request identifier, `count' is the number of names - returned in this response, and the remaining fields repeat `count' - times (so that all three fields are first included for the first - file, then for the second file, etc). In the repeated part, - `filename' is a file name being returned (for SSH_FXP_READDIR, it - will be a relative name within the directory, without any path - components; for SSH_FXP_REALPATH it will be an absolute path name), - `longname' is an expanded format for the file name, similar to what - is returned by "ls -l" on Unix systems, and `attrs' is the attributes - - - -Ylonen & Lehtinen Expires April 1, 2002 [Page 22] - -Internet-Draft SSH File Transfer Protocol October 2001 - - - of the file as described in Section ``File Attributes''. - - The format of the `longname' field is unspecified by this protocol. - It MUST be suitable for use in the output of a directory listing - command (in fact, the recommended operation for a directory listing - command is to simply display this data). However, clients SHOULD NOT - attempt to parse the longname field for file attributes; they SHOULD - use the attrs field instead. - - The recommended format for the longname field is as follows: - - -rwxr-xr-x 1 mjos staff 348911 Mar 25 14:29 t-filexfer - 1234567890 123 12345678 12345678 12345678 123456789012 - - Here, the first line is sample output, and the second field indicates - widths of the various fields. Fields are separated by spaces. The - first field lists file permissions for user, group, and others; the - second field is link count; the third field is the name of the user - who owns the file; the fourth field is the name of the group that - owns the file; the fifth field is the size of the file in bytes; the - sixth field (which actually may contain spaces, but is fixed to 12 - characters) is the file modification time, and the seventh field is - the file name. Each field is specified to be a minimum of certain - number of character positions (indicated by the second line above), - but may also be longer if the data does not fit in the specified - length. - - The SSH_FXP_ATTRS response has the following format: - - uint32 id - ATTRS attrs - - where `id' is the request identifier, and `attrs' is the returned - file attributes as described in Section ``File Attributes''. - - - - - - - - - - - - - - - - - -Ylonen & Lehtinen Expires April 1, 2002 [Page 23] - -Internet-Draft SSH File Transfer Protocol October 2001 - - -8. Vendor-Specific Extensions - - The SSH_FXP_EXTENDED request provides a generic extension mechanism - for adding vendor-specific commands. The request has the following - format: - - uint32 id - string extended-request - ... any request-specific data ... - - where `id' is the request identifier, and `extended-request' is a - string of the format "name@domain", where domain is an internet - domain name of the vendor defining the request. The rest of the - request is completely vendor-specific, and servers should only - attempt to interpret it if they recognize the `extended-request' - name. - - The server may respond to such requests using any of the response - packets defined in Section ``Responses from the Server to the - Client''. Additionally, the server may also respond with a - SSH_FXP_EXTENDED_REPLY packet, as defined below. If the server does - not recognize the `extended-request' name, then the server MUST - respond with SSH_FXP_STATUS with error/status set to - SSH_FX_OP_UNSUPPORTED. - - The SSH_FXP_EXTENDED_REPLY packet can be used to carry arbitrary - extension-specific data from the server to the client. It is of the - following format: - - uint32 id - ... any request-specific data ... - - - - - - - - - - - - - - - - - - - - -Ylonen & Lehtinen Expires April 1, 2002 [Page 24] - -Internet-Draft SSH File Transfer Protocol October 2001 - - -9. Security Considerations - - This protocol assumes that it is run over a secure channel and that - the endpoints of the channel have been authenticated. Thus, this - protocol assumes that it is externally protected from network-level - attacks. - - This protocol provides file system access to arbitrary files on the - server (only constrained by the server implementation). It is the - responsibility of the server implementation to enforce any access - controls that may be required to limit the access allowed for any - particular user (the user being authenticated externally to this - protocol, typically using the SSH User Authentication Protocol [6]. - - Care must be taken in the server implementation to check the validity - of received file handle strings. The server should not rely on them - directly; it MUST check the validity of each handle before relying on - it. - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -Ylonen & Lehtinen Expires April 1, 2002 [Page 25] - -Internet-Draft SSH File Transfer Protocol October 2001 - - -10. Changes from previous protocol versions - - The SSH File Transfer Protocol has changed over time, before it's - standardization. The following is a description of the incompatible - changes between different versions. - -10.1 Changes between versions 3 and 2 - - o The SSH_FXP_READLINK and SSH_FXP_SYMLINK messages were added. - - o The SSH_FXP_EXTENDED and SSH_FXP_EXTENDED_REPLY messages were - added. - - o The SSH_FXP_STATUS message was changed to include fields `error - message' and `language tag'. - - -10.2 Changes between versions 2 and 1 - - o The SSH_FXP_RENAME message was added. - - -10.3 Changes between versions 1 and 0 - - o Implementation changes, no actual protocol changes. - - - - - - - - - - - - - - - - - - - - - - - - - - -Ylonen & Lehtinen Expires April 1, 2002 [Page 26] - -Internet-Draft SSH File Transfer Protocol October 2001 - - -11. Trademark Issues - - "ssh" is a registered trademark of SSH Communications Security Corp - in the United States and/or other countries. - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -Ylonen & Lehtinen Expires April 1, 2002 [Page 27] - -Internet-Draft SSH File Transfer Protocol October 2001 - - -References - - [1] Dierks, T., Allen, C., Treese, W., Karlton, P., Freier, A. and - P. Kocher, "The TLS Protocol Version 1.0", RFC 2246, January - 1999. - - [2] Institute of Electrical and Electronics Engineers, "Information - Technology - Portable Operating System Interface (POSIX) - Part - 1: System Application Program Interface (API) [C Language]", - IEEE Standard 1003.2, 1996. - - [3] Rinne, T., Ylonen, T., Kivinen, T., Saarinen, M. and S. - Lehtinen, "SSH Protocol Architecture", draft-ietf-secsh- - architecture-09 (work in progress), July 2001. - - [4] Rinne, T., Ylonen, T., Kivinen, T., Saarinen, M. and S. - Lehtinen, "SSH Protocol Transport Protocol", draft-ietf-secsh- - architecture-09 (work in progress), July 2001. - - [5] Rinne, T., Ylonen, T., Kivinen, T., Saarinen, M. and S. - Lehtinen, "SSH Connection Protocol", draft-ietf-secsh-connect-11 - (work in progress), July 2001. - - [6] Rinne, T., Ylonen, T., Kivinen, T., Saarinen, M. and S. - Lehtinen, "SSH Authentication Protocol", draft-ietf-secsh- - userauth-11 (work in progress), July 2001. - - -Authors' Addresses - - Tatu Ylonen - SSH Communications Security Corp - Fredrikinkatu 42 - HELSINKI FIN-00100 - Finland - - EMail: [email protected] - - - Sami Lehtinen - SSH Communications Security Corp - Fredrikinkatu 42 - HELSINKI FIN-00100 - Finland - - EMail: [email protected] - - - - - -Ylonen & Lehtinen Expires April 1, 2002 [Page 28] - -Internet-Draft SSH File Transfer Protocol October 2001 - - -Full Copyright Statement - - Copyright (C) The Internet Society (2001). All Rights Reserved. - - This document and translations of it may be copied and furnished to - others, and derivative works that comment on or otherwise explain it - or assist in its implementation may be prepared, copied, published - and distributed, in whole or in part, without restriction of any - kind, provided that the above copyright notice and this paragraph are - included on all such copies and derivative works. However, this - document itself may not be modified in any way, such as by removing - the copyright notice or references to the Internet Society or other - Internet organizations, except as needed for the purpose of - developing Internet standards in which case the procedures for - copyrights defined in the Internet Standards process must be - followed, or as required to translate it into languages other than - English. - - The limited permissions granted above are perpetual and will not be - revoked by the Internet Society or its successors or assigns. - - This document and the information contained herein is provided on an - "AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING - TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING - BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION - HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF - MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE. - -Acknowledgement - - Funding for the RFC Editor function is currently provided by the - Internet Society. - - - - - - - - - - - - - - - - - - - -Ylonen & Lehtinen Expires April 1, 2002 [Page 29] - - - diff --git a/lib/ssh/doc/standard/draft-ietf-secsh-filexfer-03.2.ps b/lib/ssh/doc/standard/draft-ietf-secsh-filexfer-03.2.ps deleted file mode 100644 index 6a40cd6067..0000000000 --- a/lib/ssh/doc/standard/draft-ietf-secsh-filexfer-03.2.ps +++ /dev/null @@ -1,3511 +0,0 @@ -%!PS-Adobe-3.0 -%%BoundingBox: 75 0 595 747 -%%Title: Enscript Output -%%For: Magnus Thoang -%%Creator: GNU enscript 1.6.1 -%%CreationDate: Wed Nov 12 12:18:50 2003 -%%Orientation: Portrait -%%Pages: 18 0 -%%DocumentMedia: A4 595 842 0 () () -%%DocumentNeededResources: (atend) -%%EndComments -%%BeginProlog -%%BeginProcSet: PStoPS 1 15 -userdict begin -[/showpage/erasepage/copypage]{dup where{pop dup load - type/operatortype eq{1 array cvx dup 0 3 index cvx put - bind def}{pop}ifelse}{pop}ifelse}forall -[/letter/legal/executivepage/a4/a4small/b5/com10envelope - /monarchenvelope/c5envelope/dlenvelope/lettersmall/note - 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matrix invertmatrix matrix concatmatrix - matrix invertmatrix put -%%EndSetup -%%Page: (0,1) 1 -userdict/PStoPSsaved save put -PStoPSmatrix setmatrix -595.000000 0.271378 translate -90 rotate -0.706651 dup scale -userdict/PStoPSmatrix matrix currentmatrix put -userdict/PStoPSclip{0 0 moveto - 595.000000 0 rlineto 0 842.000000 rlineto -595.000000 0 rlineto - closepath}put initclip -/showpage{}def/copypage{}def/erasepage{}def -PStoPSxform concat -%%BeginPageSetup -_S -75 0 translate -/pagenum 1 def -/fname () def -/fdir () def -/ftail () def -/user_header_p false def -%%EndPageSetup -5 701 M -(Secure Shell Working Group J. Galbraith) s -5 690 M -(Internet-Draft VanDyke Software) s -5 679 M -(Expires: April 16, 2003 T. Ylonen) s -5 668 M -( S. Lehtinen) s -5 657 M -( SSH Communications Security Corp) s -5 646 M -( October 16, 2002) s -5 613 M -( SSH File Transfer Protocol) s -5 602 M -( draft-ietf-secsh-filexfer-03.txt) s -5 580 M -(Status of this Memo) s -5 558 M -( This document is an Internet-Draft and is in full conformance with) s -5 547 M -( all provisions of Section 10 of RFC2026.) s -5 525 M -( Internet-Drafts are working documents of the Internet Engineering) s -5 514 M -( Task Force \(IETF\), its areas, and its working groups. Note that) s -5 503 M -( other groups may also distribute working documents as Internet-) s -5 492 M -( Drafts.) s -5 470 M -( Internet-Drafts are draft documents valid for a maximum of six months) s -5 459 M -( and may be updated, replaced, or obsoleted by other documents at any) s -5 448 M -( time. It is inappropriate to use Internet-Drafts as reference) s -5 437 M -( material or to cite them other than as "work in progress.") s -5 415 M -( The list of current Internet-Drafts can be accessed at http://) s -5 404 M -( www.ietf.org/ietf/1id-abstracts.txt.) s -5 382 M -( The list of Internet-Draft Shadow Directories can be accessed at) s -5 371 M -( http://www.ietf.org/shadow.html.) s -5 349 M -( This Internet-Draft will expire on April 16, 2003.) s -5 327 M -(Copyright Notice) s -5 305 M -( Copyright \(C\) The Internet Society \(2002\). All Rights Reserved.) s -5 283 M -(Abstract) s -5 261 M -( The SSH File Transfer Protocol provides secure file transfer) s -5 250 M -( functionality over any reliable data stream. It is the standard file) s -5 239 M -( transfer protocol for use with the SSH2 protocol. This document) s -5 228 M -( describes the file transfer protocol and its interface to the SSH2) s -5 217 M -( protocol suite.) s -5 129 M -(Galbraith, et al. Expires April 16, 2003 [Page 1]) s -_R -S -PStoPSsaved restore -userdict/PStoPSsaved save put -PStoPSmatrix setmatrix -595.000000 421.271378 translate -90 rotate -0.706651 dup scale -userdict/PStoPSmatrix matrix currentmatrix put -userdict/PStoPSclip{0 0 moveto - 595.000000 0 rlineto 0 842.000000 rlineto -595.000000 0 rlineto - closepath}put initclip -PStoPSxform concat -%%BeginPageSetup -_S -75 0 translate -/pagenum 2 def -/fname () def -/fdir () def -/ftail () def -/user_header_p false def -%%EndPageSetup -5 723 M -(Internet-Draft SSH File Transfer Protocol October 2002) s -5 690 M -(Table of Contents) s -5 668 M -( 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . 3) s -5 657 M -( 2. Use with the SSH Connection Protocol . . . . . . . . . . . 4) s -5 646 M -( 3. General Packet Format . . . . . . . . . . . . . . . . . . 5) s -5 635 M -( 4. Protocol Initialization . . . . . . . . . . . . . . . . . 7) s -5 624 M -( 4.1 Client Initialization . . . . . . . . . . . . . . . . . . 7) s -5 613 M -( 4.2 Server Initialization . . . . . . . . . . . . . . . . . . 7) s -5 602 M -( 4.3 Determining Server Newline Convention . . . . . . . . . . 8) s -5 591 M -( 5. File Attributes . . . . . . . . . . . . . . . . . . . . . 9) s -5 580 M -( 5.1 Flags . . . . . . . . . . . . . . . . . . . . . . . . . . 9) s -5 569 M -( 5.2 Type . . . . . . . . . . . . . . . . . . . . . . . . . . . 10) s -5 558 M -( 5.3 Size . . . . . . . . . . . . . . . . . . . . . . . . . . . 10) s -5 547 M -( 5.4 Owner and Group . . . . . . . . . . . . . . . . . . . . . 10) s -5 536 M -( 5.5 Permissions . . . . . . . . . . . . . . . . . . . . . . . 11) s -5 525 M -( 5.6 Times . . . . . . . . . . . . . . . . . . . . . . . . . . 11) s -5 514 M -( 5.7 ACL . . . . . . . . . . . . . . . . . . . . . . . . . . . 11) s -5 503 M -( 5.8 Extended attributes . . . . . . . . . . . . . . . . . . . 12) s -5 492 M -( 6. Requests From the Client to the Server . . . . . . . . . . 13) s -5 481 M -( 6.1 Request Synchronization and Reordering . . . . . . . . . . 13) s -5 470 M -( 6.2 File Names . . . . . . . . . . . . . . . . . . . . . . . . 14) s -5 459 M -( 6.3 Opening, Creating, and Closing Files . . . . . . . . . . . 14) s -5 448 M -( 6.4 Reading and Writing . . . . . . . . . . . . . . . . . . . 17) s -5 437 M -( 6.5 Removing and Renaming Files . . . . . . . . . . . . . . . 18) s -5 426 M -( 6.6 Creating and Deleting Directories . . . . . . . . . . . . 19) s -5 415 M -( 6.7 Scanning Directories . . . . . . . . . . . . . . . . . . . 19) s -5 404 M -( 6.8 Retrieving File Attributes . . . . . . . . . . . . . . . . 20) s -5 393 M -( 6.9 Setting File Attributes . . . . . . . . . . . . . . . . . 21) s -5 382 M -( 6.10 Dealing with Symbolic links . . . . . . . . . . . . . . . 22) s -5 371 M -( 6.11 Canonicalizing the Server-Side Path Name . . . . . . . . . 23) s -5 360 M -( 6.11.1 Best practice for dealing with paths . . . . . . . . . . . 23) s -5 349 M -( 7. Responses from the Server to the Client . . . . . . . . . 24) s -5 338 M -( 8. Vendor-Specific Extensions . . . . . . . . . . . . . . . . 28) s -5 327 M -( 9. Security Considerations . . . . . . . . . . . . . . . . . 29) s -5 316 M -( 10. Changes from previous protocol versions . . . . . . . . . 30) s -5 305 M -( 10.1 Changes between versions 4 and 3 . . . . . . . . . . . . . 30) s -5 294 M -( 10.2 Changes between versions 3 and 2 . . . . . . . . . . . . . 31) s -5 283 M -( 10.3 Changes between versions 2 and 1 . . . . . . . . . . . . . 31) s -5 272 M -( 10.4 Changes between versions 1 and 0 . . . . . . . . . . . . . 31) s -5 261 M -( 11. Trademark Issues . . . . . . . . . . . . . . . . . . . . . 32) s -5 250 M -( References . . . . . . . . . . . . . . . . . . . . . . . . 33) s -5 239 M -( Authors' Addresses . . . . . . . . . . . . . . . . . . . . 33) s -5 228 M -( Full Copyright Statement . . . . . . . . . . . . . . . . . 35) s -5 129 M -(Galbraith, et al. Expires April 16, 2003 [Page 2]) s -_R -S -PStoPSsaved restore -%%Page: (2,3) 2 -userdict/PStoPSsaved save put -PStoPSmatrix setmatrix -595.000000 0.271378 translate -90 rotate -0.706651 dup scale -userdict/PStoPSmatrix matrix currentmatrix put -userdict/PStoPSclip{0 0 moveto - 595.000000 0 rlineto 0 842.000000 rlineto -595.000000 0 rlineto - closepath}put initclip -/showpage{}def/copypage{}def/erasepage{}def -PStoPSxform concat -%%BeginPageSetup -_S -75 0 translate -/pagenum 3 def -/fname () def -/fdir () def -/ftail () def -/user_header_p false def -%%EndPageSetup -5 723 M -(Internet-Draft SSH File Transfer Protocol October 2002) s -5 690 M -(1. Introduction) s -5 668 M -( This protocol provides secure file transfer \(and more generally file) s -5 657 M -( system access\) functionality over a reliable data stream, such as a) s -5 646 M -( channel in the SSH2 protocol [5].) s -5 624 M -( This protocol is designed so that it could be used to implement a) s -5 613 M -( secure remote file system service, as well as a secure file transfer) s -5 602 M -( service.) s -5 580 M -( This protocol assumes that it runs over a secure channel, and that) s -5 569 M -( the server has already authenticated the user at the client end, and) s -5 558 M -( that the identity of the client user is externally available to the) s -5 547 M -( server implementation.) s -5 525 M -( In general, this protocol follows a simple request-response model.) s -5 514 M -( Each request and response contains a sequence number and multiple) s -5 503 M -( requests may be pending simultaneously. There are a relatively large) s -5 492 M -( number of different request messages, but a small number of possible) s -5 481 M -( response messages. Each request has one or more response messages) s -5 470 M -( that may be returned in result \(e.g., a read either returns data or) s -5 459 M -( reports error status\).) s -5 437 M -( The packet format descriptions in this specification follow the) s -5 426 M -( notation presented in the secsh architecture draft. [5]) s -5 404 M -( Even though this protocol is described in the context of the SSH2) s -5 393 M -( protocol, this protocol is general and independent of the rest of the) s -5 382 M -( SSH2 protocol suite. It could be used in a number of different) s -5 371 M -( applications, such as secure file transfer over TLS RFC 2246 [1] and) s -5 360 M -( transfer of management information in VPN applications.) s -5 129 M -(Galbraith, et al. Expires April 16, 2003 [Page 3]) s -_R -S -PStoPSsaved restore -userdict/PStoPSsaved save put -PStoPSmatrix setmatrix -595.000000 421.271378 translate -90 rotate -0.706651 dup scale -userdict/PStoPSmatrix matrix currentmatrix put -userdict/PStoPSclip{0 0 moveto - 595.000000 0 rlineto 0 842.000000 rlineto -595.000000 0 rlineto - closepath}put initclip -PStoPSxform concat -%%BeginPageSetup -_S -75 0 translate -/pagenum 4 def -/fname () def -/fdir () def -/ftail () def -/user_header_p false def -%%EndPageSetup -5 723 M -(Internet-Draft SSH File Transfer Protocol October 2002) s -5 690 M -(2. Use with the SSH Connection Protocol) s -5 668 M -( When used with the SSH2 Protocol suite, this protocol is intended to) s -5 657 M -( be used from the SSH Connection Protocol [7] as a subsystem, as) s -5 646 M -( described in section ``Starting a Shell or a Command''. The) s -5 635 M -( subsystem name used with this protocol is "sftp".) s -5 129 M -(Galbraith, et al. Expires April 16, 2003 [Page 4]) s -_R -S -PStoPSsaved restore -%%Page: (4,5) 3 -userdict/PStoPSsaved save put -PStoPSmatrix setmatrix -595.000000 0.271378 translate -90 rotate -0.706651 dup scale -userdict/PStoPSmatrix matrix currentmatrix put -userdict/PStoPSclip{0 0 moveto - 595.000000 0 rlineto 0 842.000000 rlineto -595.000000 0 rlineto - closepath}put initclip -/showpage{}def/copypage{}def/erasepage{}def -PStoPSxform concat -%%BeginPageSetup -_S -75 0 translate -/pagenum 5 def -/fname () def -/fdir () def -/ftail () def -/user_header_p false def -%%EndPageSetup -5 723 M -(Internet-Draft SSH File Transfer Protocol October 2002) s -5 690 M -(3. General Packet Format) s -5 668 M -( All packets transmitted over the secure connection are of the) s -5 657 M -( following format:) s -5 635 M -( uint32 length) s -5 624 M -( byte type) s -5 613 M -( byte[length - 1] data payload) s -5 591 M -( That is, they are just data preceded by 32-bit length and 8-bit type) s -5 580 M -( fields. The `length' is the length of the data area, and does not) s -5 569 M -( include the `length' field itself. The format and interpretation of) s -5 558 M -( the data area depends on the packet type.) s -5 536 M -( All packet descriptions below only specify the packet type and the) s -5 525 M -( data that goes into the data field. Thus, they should be prefixed by) s -5 514 M -( the `length' and `type' fields.) s -5 492 M -( The maximum size of a packet is in practice determined by the client) s -5 481 M -( \(the maximum size of read or write requests that it sends, plus a few) s -5 470 M -( bytes of packet overhead\). All servers SHOULD support packets of at) s -5 459 M -( least 34000 bytes \(where the packet size refers to the full length,) s -5 448 M -( including the header above\). This should allow for reads and writes) s -5 437 M -( of at most 32768 bytes.) s -5 415 M -( There is no limit on the number of outstanding \(non-acknowledged\)) s -5 404 M -( requests that the client may send to the server. In practice this is) s -5 393 M -( limited by the buffering available on the data stream and the queuing) s -5 382 M -( performed by the server. If the server's queues are full, it should) s -5 371 M -( not read any more data from the stream, and flow control will prevent) s -5 360 M -( the client from sending more requests. Note, however, that while) s -5 349 M -( there is no restriction on the protocol level, the client's API may) s -5 338 M -( provide a limit in order to prevent infinite queuing of outgoing) s -5 327 M -( requests at the client.) s -5 305 M -( The following values are defined for packet types.) s -5 129 M -(Galbraith, et al. Expires April 16, 2003 [Page 5]) s -_R -S -PStoPSsaved restore -userdict/PStoPSsaved save put -PStoPSmatrix setmatrix -595.000000 421.271378 translate -90 rotate -0.706651 dup scale -userdict/PStoPSmatrix matrix currentmatrix put -userdict/PStoPSclip{0 0 moveto - 595.000000 0 rlineto 0 842.000000 rlineto -595.000000 0 rlineto - closepath}put initclip -PStoPSxform concat -%%BeginPageSetup -_S -75 0 translate -/pagenum 6 def -/fname () def -/fdir () def -/ftail () def -/user_header_p false def -%%EndPageSetup -5 723 M -(Internet-Draft SSH File Transfer Protocol October 2002) s -5 690 M -( #define SSH_FXP_INIT 1) s -5 679 M -( #define SSH_FXP_VERSION 2) s -5 668 M -( #define SSH_FXP_OPEN 3) s -5 657 M -( #define SSH_FXP_CLOSE 4) s -5 646 M -( #define SSH_FXP_READ 5) s -5 635 M -( #define SSH_FXP_WRITE 6) s -5 624 M -( #define SSH_FXP_LSTAT 7) s -5 613 M -( #define SSH_FXP_FSTAT 8) s -5 602 M -( #define SSH_FXP_SETSTAT 9) s -5 591 M -( #define SSH_FXP_FSETSTAT 10) s -5 580 M -( #define SSH_FXP_OPENDIR 11) s -5 569 M -( #define SSH_FXP_READDIR 12) s -5 558 M -( #define SSH_FXP_REMOVE 13) s -5 547 M -( #define SSH_FXP_MKDIR 14) s -5 536 M -( #define SSH_FXP_RMDIR 15) s -5 525 M -( #define SSH_FXP_REALPATH 16) s -5 514 M -( #define SSH_FXP_STAT 17) s -5 503 M -( #define SSH_FXP_RENAME 18) s -5 492 M -( #define SSH_FXP_READLINK 19) s -5 481 M -( #define SSH_FXP_SYMLINK 20) s -5 459 M -( #define SSH_FXP_STATUS 101) s -5 448 M -( #define SSH_FXP_HANDLE 102) s -5 437 M -( #define SSH_FXP_DATA 103) s -5 426 M -( #define SSH_FXP_NAME 104) s -5 415 M -( #define SSH_FXP_ATTRS 105) s -5 393 M -( #define SSH_FXP_EXTENDED 200) s -5 382 M -( #define SSH_FXP_EXTENDED_REPLY 201) s -5 360 M -( RESERVED_FOR_EXTENSIONS 210-255) s -5 338 M -( Additional packet types should only be defined if the protocol) s -5 327 M -( version number \(see Section ``Protocol Initialization''\) is) s -5 316 M -( incremented, and their use MUST be negotiated using the version) s -5 305 M -( number. However, the SSH_FXP_EXTENDED and SSH_FXP_EXTENDED_REPLY) s -5 294 M -( packets can be used to implement vendor-specific extensions. See) s -5 283 M -( Section ``Vendor-Specific-Extensions'' for more details.) s -5 129 M -(Galbraith, et al. Expires April 16, 2003 [Page 6]) s -_R -S -PStoPSsaved restore -%%Page: (6,7) 4 -userdict/PStoPSsaved save put -PStoPSmatrix setmatrix -595.000000 0.271378 translate -90 rotate -0.706651 dup scale -userdict/PStoPSmatrix matrix currentmatrix put -userdict/PStoPSclip{0 0 moveto - 595.000000 0 rlineto 0 842.000000 rlineto -595.000000 0 rlineto - closepath}put initclip -/showpage{}def/copypage{}def/erasepage{}def -PStoPSxform concat -%%BeginPageSetup -_S -75 0 translate -/pagenum 7 def -/fname () def -/fdir () def -/ftail () def -/user_header_p false def -%%EndPageSetup -5 723 M -(Internet-Draft SSH File Transfer Protocol October 2002) s -5 690 M -(4. Protocol Initialization) s -5 668 M -( When the file transfer protocol starts, the client first sends a) s -5 657 M -( SSH_FXP_INIT \(including its version number\) packet to the server.) s -5 646 M -( The server responds with a SSH_FXP_VERSION packet, supplying the) s -5 635 M -( lowest of its own and the client's version number. Both parties) s -5 624 M -( should from then on adhere to particular version of the protocol.) s -5 602 M -( The version number of the protocol specified in this document is 4.) s -5 591 M -( The version number should be incremented for each incompatible) s -5 580 M -( revision of this protocol.) s -5 558 M -(4.1 Client Initialization) s -5 536 M -( The SSH_FXP_INIT packet \(from client to server\) has the following) s -5 525 M -( data:) s -5 503 M -( uint32 version) s -5 481 M -( Version 3 of this protocol allowed clients to include extensions in) s -5 470 M -( the SSH_FXP_INIT packet; however, this can cause interoperability) s -5 459 M -( problems with version 1 and version 2 servers because the client must) s -5 448 M -( send this packet before knowing the servers version.) s -5 426 M -( In this version of the protocol, clients MUST use the) s -5 415 M -( SSH_FXP_EXTENDED packet to send extensions to the server after) s -5 404 M -( version exchange has completed. Clients MUST NOT include extensions) s -5 393 M -( in the version packet. This will prevent interoperability problems) s -5 382 M -( with older servers) s -5 360 M -(4.2 Server Initialization) s -5 338 M -( The SSH_FXP_VERSION packet \(from server to client\) has the following) s -5 327 M -( data:) s -5 305 M -( uint32 version) s -5 294 M -( <extension data>) s -5 272 M -( 'version' is the lower of the protocol version supported by the) s -5 261 M -( server and the version number received from the client.) s -5 239 M -( The extension data may be empty, or may be a sequence of) s -5 217 M -( string extension_name) s -5 206 M -( string extension_data) s -5 184 M -( pairs \(both strings MUST always be present if one is, but the) s -5 173 M -( `extension_data' string may be of zero length\). If present, these) s -5 129 M -(Galbraith, et al. Expires April 16, 2003 [Page 7]) s -_R -S -PStoPSsaved restore -userdict/PStoPSsaved save put -PStoPSmatrix setmatrix -595.000000 421.271378 translate -90 rotate -0.706651 dup scale -userdict/PStoPSmatrix matrix currentmatrix put -userdict/PStoPSclip{0 0 moveto - 595.000000 0 rlineto 0 842.000000 rlineto -595.000000 0 rlineto - closepath}put initclip -PStoPSxform concat -%%BeginPageSetup -_S -75 0 translate -/pagenum 8 def -/fname () def -/fdir () def -/ftail () def -/user_header_p false def -%%EndPageSetup -5 723 M -(Internet-Draft SSH File Transfer Protocol October 2002) s -5 690 M -( strings indicate extensions to the baseline protocol. The) s -5 679 M -( `extension_name' field\(s\) identify the name of the extension. The) s -5 668 M -( name should be of the form "name@domain", where the domain is the DNS) s -5 657 M -( domain name of the organization defining the extension. Additional) s -5 646 M -( names that are not of this format may be defined later by the IETF.) s -5 635 M -( Implementations MUST silently ignore any extensions whose name they) s -5 624 M -( do not recognize.) s -5 602 M -(4.3 Determining Server Newline Convention) s -5 580 M -( In order to correctly process text files in a cross platform) s -5 569 M -( compatible way, the newline convention must be converted from that of) s -5 558 M -( the server to that of the client, or, during an upload, from that of) s -5 547 M -( the client to that of the server.) s -5 525 M -( Versions 3 and prior of this protocol made no provisions for) s -5 514 M -( processing text files. Many clients implemented some sort of) s -5 503 M -( conversion algorithm, but without either a 'canonical' on the wire) s -5 492 M -( format or knowledge of the servers newline convention, correct) s -5 481 M -( conversion was not always possible.) s -5 459 M -( Starting with Version 4, the SSH_FXF_TEXT file open flag \(Section) s -5 448 M -( 6.3\) makes it possible to request that the server translate a file to) s -5 437 M -( a 'canonical' on the wire format. This format uses \\r\\n as the line) s -5 426 M -( separator.) s -5 404 M -( Servers for systems using multiple newline characters \(for example,) s -5 393 M -( Mac OS X or VMS\) or systems using counted records, MUST translate to) s -5 382 M -( the canonical form.) s -5 360 M -( However, to ease the burden of implementation on servers that use a) s -5 349 M -( single, simple separator sequence, the following extension allows the) s -5 338 M -( canonical format to be changed.) s -5 316 M -( string "newline") s -5 305 M -( string new-canonical-separator \(usually "\\r" or "\\n" or "\\r\\n"\)) s -5 283 M -( All clients MUST support this extension.) s -5 261 M -( When processing text files, clients SHOULD NOT translate any) s -5 250 M -( character or sequence that is not an exact match of the servers) s -5 239 M -( newline separator.) s -5 217 M -( In particular, if the newline sequence being used is the canonical) s -5 206 M -( "\\r\\n" sequence, a lone \\r or a lone \\n SHOULD be written through) s -5 195 M -( without change.) s -5 129 M -(Galbraith, et al. Expires April 16, 2003 [Page 8]) s -_R -S -PStoPSsaved restore -%%Page: (8,9) 5 -userdict/PStoPSsaved save put -PStoPSmatrix setmatrix -595.000000 0.271378 translate -90 rotate -0.706651 dup scale -userdict/PStoPSmatrix matrix currentmatrix put -userdict/PStoPSclip{0 0 moveto - 595.000000 0 rlineto 0 842.000000 rlineto -595.000000 0 rlineto - closepath}put initclip -/showpage{}def/copypage{}def/erasepage{}def -PStoPSxform concat -%%BeginPageSetup -_S -75 0 translate -/pagenum 9 def -/fname () def -/fdir () def -/ftail () def -/user_header_p false def -%%EndPageSetup -5 723 M -(Internet-Draft SSH File Transfer Protocol October 2002) s -5 690 M -(5. File Attributes) s -5 668 M -( A new compound data type is defined for encoding file attributes.) s -5 657 M -( The same encoding is used both when returning file attributes from) s -5 646 M -( the server and when sending file attributes to the server. When) s -5 635 M -( sending it to the server, the flags field specifies which attributes) s -5 624 M -( are included, and the server will use default values for the) s -5 613 M -( remaining attributes \(or will not modify the values of remaining) s -5 602 M -( attributes\). When receiving attributes from the server, the flags) s -5 591 M -( specify which attributes are included in the returned data. The) s -5 580 M -( server normally returns all attributes it knows about.) s -5 558 M -( uint32 flags) s -5 547 M -( byte type always present) s -5 536 M -( uint64 size present only if flag SSH_FILEXFER_ATTR_SIZE) s -5 525 M -( string owner present only if flag SSH_FILEXFER_ATTR_OWNERGROUP) s -5 514 M -( string group present only if flag SSH_FILEXFER_ATTR_OWNERGROUP) s -5 503 M -( uint32 permissions present only if flag SSH_FILEXFER_ATTR_PERMISSIONS) s -5 492 M -( uint32 atime present only if flag SSH_FILEXFER_ATTR_ACCESSTIME) s -5 481 M -( uint32 createtime present only if flag SSH_FILEXFER_ATTR_CREATETIME) s -5 470 M -( uint32 mtime present only if flag SSH_FILEXFER_ATTR_MODIFYTIME) s -5 459 M -( string acl present only if flag SSH_FILEXFER_ATTR_ACL) s -5 448 M -( uint32 extended_count present only if flag SSH_FILEXFER_ATTR_EXTENDED) s -5 437 M -( string extended_type) s -5 426 M -( string extended_data) s -5 415 M -( ... more extended data \(extended_type - extended_data pairs\),) s -5 404 M -( so that number of pairs equals extended_count) s -5 371 M -(5.1 Flags) s -5 349 M -( The `flags' specify which of the fields are present. Those fields) s -5 338 M -( for which the corresponding flag is not set are not present \(not) s -5 327 M -( included in the packet\). New flags can only be added by incrementing) s -5 316 M -( the protocol version number \(or by using the extension mechanism) s -5 305 M -( described below\).) s -5 283 M -( The flags bits are defined to have the following values:) s -5 261 M -( #define SSH_FILEXFER_ATTR_SIZE 0x00000001) s -5 250 M -( #define SSH_FILEXFER_ATTR_PERMISSIONS 0x00000004) s -5 239 M -( #define SSH_FILEXFER_ATTR_ACCESSTIME 0x00000008) s -5 228 M -( #define SSH_FILEXFER_ATTR_CREATETIME 0x00000010) s -5 217 M -( #define SSH_FILEXFER_ATTR_MODIFYTIME 0x00000020) s -5 206 M -( #define SSH_FILEXFER_ATTR_ACL 0x00000040) s -5 195 M -( #define SSH_FILEXFER_ATTR_OWNERGROUP 0x00000080) s -5 184 M -( #define SSH_FILEXFER_ATTR_EXTENDED 0x80000000) s -5 129 M -(Galbraith, et al. Expires April 16, 2003 [Page 9]) s -_R -S -PStoPSsaved restore -userdict/PStoPSsaved save put -PStoPSmatrix setmatrix -595.000000 421.271378 translate -90 rotate -0.706651 dup scale -userdict/PStoPSmatrix matrix currentmatrix put -userdict/PStoPSclip{0 0 moveto - 595.000000 0 rlineto 0 842.000000 rlineto -595.000000 0 rlineto - closepath}put initclip -PStoPSxform concat -%%BeginPageSetup -_S -75 0 translate -/pagenum 10 def -/fname () def -/fdir () def -/ftail () def -/user_header_p false def -%%EndPageSetup -5 723 M -(Internet-Draft SSH File Transfer Protocol October 2002) s -5 690 M -( In previous versions of this protocol flags value 0x00000002 was) s -5 679 M -( SSH_FILEXFER_ATTR_UIDGID. This value is now unused, and OWNERGROUP) s -5 668 M -( was given a new value in order to ease implementation burden.) s -5 657 M -( 0x00000002 MUST NOT appear in the mask. Some future version of this) s -5 646 M -( protocol may reuse flag 0x00000002.) s -5 624 M -(5.2 Type) s -5 602 M -( The type field is always present. The following types are defined:) s -5 580 M -( #define SSH_FILEXFER_TYPE_REGULAR 1) s -5 569 M -( #define SSH_FILEXFER_TYPE_DIRECTORY 2) s -5 558 M -( #define SSH_FILEXFER_TYPE_SYMLINK 3) s -5 547 M -( #define SSH_FILEXFER_TYPE_SPECIAL 4) s -5 536 M -( #define SSH_FILEXFER_TYPE_UNKNOWN 5) s -5 514 M -( On a POSIX system, these values would be derived from the permission) s -5 503 M -( field.) s -5 481 M -(5.3 Size) s -5 459 M -( The `size' field specifies the size of the file on disk, in bytes.) s -5 448 M -( If it is present during file creation, it should be considered a hint) s -5 437 M -( as to the files eventual size.) s -5 415 M -( Files opened with the SSH_FXF_TEXT flag may have a size that is) s -5 404 M -( greater or less than the value of the size field.) s -5 382 M -(5.4 Owner and Group) s -5 360 M -( The `owner' and `group' fields are represented as UTF-8 strings; this) s -5 349 M -( is the form used by NFS v4. See NFS version 4 Protocol. [3] The) s -5 338 M -( following text is selected quotations from section 5.6.) s -5 316 M -( To avoid a representation that is tied to a particular underlying) s -5 305 M -( implementation at the client or server, the use of UTF-8 strings has) s -5 294 M -( been chosen. The string should be of the form user@dns_domain".) s -5 283 M -( This will allow for a client and server that do not use the same) s -5 272 M -( local representation the ability to translate to a common syntax that) s -5 261 M -( can be interpreted by both. In the case where there is no) s -5 250 M -( translation available to the client or server, the attribute value) s -5 239 M -( must be constructed without the "@". Therefore, the absence of the @) s -5 228 M -( from the owner or owner_group attribute signifies that no translation) s -5 217 M -( was available and the receiver of the attribute should not place any) s -5 206 M -( special meaning with the attribute value. Even though the attribute) s -5 195 M -( value can not be translated, it may still be useful. In the case of) s -5 184 M -( a client, the attribute string may be used for local display of) s -5 173 M -( ownership.) s -5 129 M -(Galbraith, et al. Expires April 16, 2003 [Page 10]) s -_R -S -PStoPSsaved restore -%%Page: (10,11) 6 -userdict/PStoPSsaved save put -PStoPSmatrix setmatrix -595.000000 0.271378 translate -90 rotate -0.706651 dup scale -userdict/PStoPSmatrix matrix currentmatrix put -userdict/PStoPSclip{0 0 moveto - 595.000000 0 rlineto 0 842.000000 rlineto -595.000000 0 rlineto - closepath}put initclip -/showpage{}def/copypage{}def/erasepage{}def -PStoPSxform concat -%%BeginPageSetup -_S -75 0 translate -/pagenum 11 def -/fname () def -/fdir () def -/ftail () def -/user_header_p false def -%%EndPageSetup -5 723 M -(Internet-Draft SSH File Transfer Protocol October 2002) s -5 690 M -(5.5 Permissions) s -5 668 M -( The `permissions' field contains a bit mask of file permissions as) s -5 657 M -( defined by POSIX [1].) s -5 635 M -(5.6 Times) s -5 613 M -( The 'atime', 'createtime', and 'mtime' contain the access, creation,) s -5 602 M -( and modification times of the files, respectively. They are) s -5 591 M -( represented as seconds from Jan 1, 1970 in UTC.) s -5 569 M -(5.7 ACL) s -5 547 M -( The 'ACL' field contains an ACL similar to that defined in section) s -5 536 M -( 5.9 of NFS version 4 Protocol [3].) s -5 514 M -( uint32 ace-count) s -5 492 M -( repeated ace-count time:) s -5 481 M -( uint32 ace-type) s -5 470 M -( uint32 ace-flag) s -5 459 M -( uint32 ace-mask) s -5 448 M -( string who [UTF-8]) s -5 426 M -( ace-type is one of the following four values \(taken from NFS Version) s -5 415 M -( 4 Protocol [3]:) s -5 393 M -( const ACE4_ACCESS_ALLOWED_ACE_TYPE = 0x00000000;) s -5 382 M -( const ACE4_ACCESS_DENIED_ACE_TYPE = 0x00000001;) s -5 371 M -( const ACE4_SYSTEM_AUDIT_ACE_TYPE = 0x00000002;) s -5 360 M -( const ACE4_SYSTEM_ALARM_ACE_TYPE = 0x00000003;) s -5 338 M -( ace-flag is a combination of the following flag values. See NFS) s -5 327 M -( Version 4 Protocol [3] section 5.9.2:) s -5 305 M -( const ACE4_FILE_INHERIT_ACE = 0x00000001;) s -5 294 M -( const ACE4_DIRECTORY_INHERIT_ACE = 0x00000002;) s -5 283 M -( const ACE4_NO_PROPAGATE_INHERIT_ACE = 0x00000004;) s -5 272 M -( const ACE4_INHERIT_ONLY_ACE = 0x00000008;) s -5 261 M -( const ACE4_SUCCESSFUL_ACCESS_ACE_FLAG = 0x00000010;) s -5 250 M -( const ACE4_FAILED_ACCESS_ACE_FLAG = 0x00000020;) s -5 239 M -( const ACE4_IDENTIFIER_GROUP = 0x00000040;) s -5 217 M -( ace-mask is any combination of the following flags \(taken from NFS) s -5 206 M -( Version 4 Protocol [3] section 5.9.3:) s -5 129 M -(Galbraith, et al. Expires April 16, 2003 [Page 11]) s -_R -S -PStoPSsaved restore -userdict/PStoPSsaved save put -PStoPSmatrix setmatrix -595.000000 421.271378 translate -90 rotate -0.706651 dup scale -userdict/PStoPSmatrix matrix currentmatrix put -userdict/PStoPSclip{0 0 moveto - 595.000000 0 rlineto 0 842.000000 rlineto -595.000000 0 rlineto - closepath}put initclip -PStoPSxform concat -%%BeginPageSetup -_S -75 0 translate -/pagenum 12 def -/fname () def -/fdir () def -/ftail () def -/user_header_p false def -%%EndPageSetup -5 723 M -(Internet-Draft SSH File Transfer Protocol October 2002) s -5 690 M -( const ACE4_READ_DATA = 0x00000001;) s -5 679 M -( const ACE4_LIST_DIRECTORY = 0x00000001;) s -5 668 M -( const ACE4_WRITE_DATA = 0x00000002;) s -5 657 M -( const ACE4_ADD_FILE = 0x00000002;) s -5 646 M -( const ACE4_APPEND_DATA = 0x00000004;) s -5 635 M -( const ACE4_ADD_SUBDIRECTORY = 0x00000004;) s -5 624 M -( const ACE4_READ_NAMED_ATTRS = 0x00000008;) s -5 613 M -( const ACE4_WRITE_NAMED_ATTRS = 0x00000010;) s -5 602 M -( const ACE4_EXECUTE = 0x00000020;) s -5 591 M -( const ACE4_DELETE_CHILD = 0x00000040;) s -5 580 M -( const ACE4_READ_ATTRIBUTES = 0x00000080;) s -5 569 M -( const ACE4_WRITE_ATTRIBUTES = 0x00000100;) s -5 558 M -( const ACE4_DELETE = 0x00010000;) s -5 547 M -( const ACE4_READ_ACL = 0x00020000;) s -5 536 M -( const ACE4_WRITE_ACL = 0x00040000;) s -5 525 M -( const ACE4_WRITE_OWNER = 0x00080000;) s -5 514 M -( const ACE4_SYNCHRONIZE = 0x00100000;) s -5 492 M -( who is a UTF-8 string of the form described in 'Owner and Group') s -5 481 M -( \(Section 5.4\)) s -5 459 M -(5.8 Extended attributes) s -5 437 M -( The SSH_FILEXFER_ATTR_EXTENDED flag provides a general extension) s -5 426 M -( mechanism for vendor-specific extensions. If the flag is specified,) s -5 415 M -( then the `extended_count' field is present. It specifies the number) s -5 404 M -( of extended_type-extended_data pairs that follow. Each of these) s -5 393 M -( pairs specifies an extended attribute. For each of the attributes,) s -5 382 M -( the extended_type field should be a string of the format) s -5 371 M -( "name@domain", where "domain" is a valid, registered domain name and) s -5 360 M -( "name" identifies the method. The IETF may later standardize certain) s -5 349 M -( names that deviate from this format \(e.g., that do not contain the) s -5 338 M -( "@" sign\). The interpretation of `extended_data' depends on the) s -5 327 M -( type. Implementations SHOULD ignore extended data fields that they) s -5 316 M -( do not understand.) s -5 294 M -( Additional fields can be added to the attributes by either defining) s -5 283 M -( additional bits to the flags field to indicate their presence, or by) s -5 272 M -( defining extended attributes for them. The extended attributes) s -5 261 M -( mechanism is recommended for most purposes; additional flags bits) s -5 250 M -( should only be defined by an IETF standards action that also) s -5 239 M -( increments the protocol version number. The use of such new fields) s -5 228 M -( MUST be negotiated by the version number in the protocol exchange.) s -5 217 M -( It is a protocol error if a packet with unsupported protocol bits is) s -5 206 M -( received.) s -5 129 M -(Galbraith, et al. Expires April 16, 2003 [Page 12]) s -_R -S -PStoPSsaved restore -%%Page: (12,13) 7 -userdict/PStoPSsaved save put -PStoPSmatrix setmatrix -595.000000 0.271378 translate -90 rotate -0.706651 dup scale -userdict/PStoPSmatrix matrix currentmatrix put -userdict/PStoPSclip{0 0 moveto - 595.000000 0 rlineto 0 842.000000 rlineto -595.000000 0 rlineto - closepath}put initclip -/showpage{}def/copypage{}def/erasepage{}def -PStoPSxform concat -%%BeginPageSetup -_S -75 0 translate -/pagenum 13 def -/fname () def -/fdir () def -/ftail () def -/user_header_p false def -%%EndPageSetup -5 723 M -(Internet-Draft SSH File Transfer Protocol October 2002) s -5 690 M -(6. Requests From the Client to the Server) s -5 668 M -( Requests from the client to the server represent the various file) s -5 657 M -( system operations. Each request begins with an `id' field, which is) s -5 646 M -( a 32-bit identifier identifying the request \(selected by the client\).) s -5 635 M -( The same identifier will be returned in the response to the request.) s -5 624 M -( One possible implementation is a monotonically increasing request) s -5 613 M -( sequence number \(modulo 2^32\).) s -5 591 M -( Many operations in the protocol operate on open files. The) s -5 580 M -( SSH_FXP_OPEN request can return a file handle \(which is an opaque) s -5 569 M -( variable-length string\) which may be used to access the file later) s -5 558 M -( \(e.g. in a read operation\). The client MUST NOT send requests the) s -5 547 M -( server with bogus or closed handles. However, the server MUST) s -5 536 M -( perform adequate checks on the handle in order to avoid security) s -5 525 M -( risks due to fabricated handles.) s -5 503 M -( This design allows either stateful and stateless server) s -5 492 M -( implementation, as well as an implementation which caches state) s -5 481 M -( between requests but may also flush it. The contents of the file) s -5 470 M -( handle string are entirely up to the server and its design. The) s -5 459 M -( client should not modify or attempt to interpret the file handle) s -5 448 M -( strings.) s -5 426 M -( The file handle strings MUST NOT be longer than 256 bytes.) s -5 404 M -(6.1 Request Synchronization and Reordering) s -5 382 M -( The protocol and implementations MUST process requests relating to) s -5 371 M -( the same file in the order in which they are received. In other) s -5 360 M -( words, if an application submits multiple requests to the server, the) s -5 349 M -( results in the responses will be the same as if it had sent the) s -5 338 M -( requests one at a time and waited for the response in each case. For) s -5 327 M -( example, the server may process non-overlapping read/write requests) s -5 316 M -( to the same file in parallel, but overlapping reads and writes cannot) s -5 305 M -( be reordered or parallelized. However, there are no ordering) s -5 294 M -( restrictions on the server for processing requests from two different) s -5 283 M -( file transfer connections. The server may interleave and parallelize) s -5 272 M -( them at will.) s -5 250 M -( There are no restrictions on the order in which responses to) s -5 239 M -( outstanding requests are delivered to the client, except that the) s -5 228 M -( server must ensure fairness in the sense that processing of no) s -5 217 M -( request will be indefinitely delayed even if the client is sending) s -5 206 M -( other requests so that there are multiple outstanding requests all) s -5 195 M -( the time.) s -5 129 M -(Galbraith, et al. Expires April 16, 2003 [Page 13]) s -_R -S -PStoPSsaved restore -userdict/PStoPSsaved save put -PStoPSmatrix setmatrix -595.000000 421.271378 translate -90 rotate -0.706651 dup scale -userdict/PStoPSmatrix matrix currentmatrix put -userdict/PStoPSclip{0 0 moveto - 595.000000 0 rlineto 0 842.000000 rlineto -595.000000 0 rlineto - closepath}put initclip -PStoPSxform concat -%%BeginPageSetup -_S -75 0 translate -/pagenum 14 def -/fname () def -/fdir () def -/ftail () def -/user_header_p false def -%%EndPageSetup -5 723 M -(Internet-Draft SSH File Transfer Protocol October 2002) s -5 690 M -(6.2 File Names) s -5 668 M -( This protocol represents file names as strings. File names are) s -5 657 M -( assumed to use the slash \('/'\) character as a directory separator.) s -5 635 M -( File names starting with a slash are "absolute", and are relative to) s -5 624 M -( the root of the file system. Names starting with any other character) s -5 613 M -( are relative to the user's default directory \(home directory\). Note) s -5 602 M -( that identifying the user is assumed to take place outside of this) s -5 591 M -( protocol.) s -5 569 M -( Servers SHOULD interpret a path name component ".." as referring to) s -5 558 M -( the parent directory, and "." as referring to the current directory.) s -5 547 M -( If the server implementation limits access to certain parts of the) s -5 536 M -( file system, it must be extra careful in parsing file names when) s -5 525 M -( enforcing such restrictions. There have been numerous reported) s -5 514 M -( security bugs where a ".." in a path name has allowed access outside) s -5 503 M -( the intended area.) s -5 481 M -( An empty path name is valid, and it refers to the user's default) s -5 470 M -( directory \(usually the user's home directory\).) s -5 448 M -( Otherwise, no syntax is defined for file names by this specification.) s -5 437 M -( Clients should not make any other assumptions; however, they can) s -5 426 M -( splice path name components returned by SSH_FXP_READDIR together) s -5 415 M -( using a slash \('/'\) as the separator, and that will work as expected.) s -5 393 M -( In order to comply with IETF Policy on Character Sets and Languages) s -5 382 M -( [2], all filenames are to be encoded in UTF-8. The shortest valid) s -5 371 M -( UTF-8 encoding of the UNICODE data MUST be used. The server is) s -5 360 M -( responsible for converting the UNICODE data to whatever canonical) s -5 349 M -( form it requires.) s -5 327 M -( For example, if the server requires that precomposed characters) s -5 316 M -( always be used, the server MUST NOT assume the filename as sent by) s -5 305 M -( the client has this attribute, but must do this normalization itself.) s -5 283 M -( It is understood that the lack of well-defined semantics for file) s -5 272 M -( names may cause interoperability problems between clients and servers) s -5 261 M -( using radically different operating systems. However, this approach) s -5 250 M -( is known to work acceptably with most systems, and alternative) s -5 239 M -( approaches that e.g. treat file names as sequences of structured) s -5 228 M -( components are quite complicated.) s -5 206 M -(6.3 Opening, Creating, and Closing Files) s -5 184 M -( Files are opened and created using the SSH_FXP_OPEN message, whose) s -5 173 M -( data part is as follows:) s -5 129 M -(Galbraith, et al. Expires April 16, 2003 [Page 14]) s -_R -S -PStoPSsaved restore -%%Page: (14,15) 8 -userdict/PStoPSsaved save put -PStoPSmatrix setmatrix -595.000000 0.271378 translate -90 rotate -0.706651 dup scale -userdict/PStoPSmatrix matrix currentmatrix put -userdict/PStoPSclip{0 0 moveto - 595.000000 0 rlineto 0 842.000000 rlineto -595.000000 0 rlineto - closepath}put initclip -/showpage{}def/copypage{}def/erasepage{}def -PStoPSxform concat -%%BeginPageSetup -_S -75 0 translate -/pagenum 15 def -/fname () def -/fdir () def -/ftail () def -/user_header_p false def -%%EndPageSetup -5 723 M -(Internet-Draft SSH File Transfer Protocol October 2002) s -5 690 M -( uint32 id) s -5 679 M -( string filename [UTF-8]) s -5 668 M -( uint32 pflags) s -5 657 M -( ATTRS attrs) s -5 635 M -( The `id' field is the request identifier as for all requests.) s -5 613 M -( The `filename' field specifies the file name. See Section ``File) s -5 602 M -( Names'' for more information.) s -5 580 M -( The `pflags' field is a bitmask. The following bits have been) s -5 569 M -( defined.) s -5 547 M -( #define SSH_FXF_READ 0x00000001) s -5 536 M -( #define SSH_FXF_WRITE 0x00000002) s -5 525 M -( #define SSH_FXF_APPEND 0x00000004) s -5 514 M -( #define SSH_FXF_CREAT 0x00000008) s -5 503 M -( #define SSH_FXF_TRUNC 0x00000010) s -5 492 M -( #define SSH_FXF_EXCL 0x00000020) s -5 481 M -( #define SSH_FXF_TEXT 0x00000040) s -5 459 M -( These have the following meanings:) s -5 437 M -( SSH_FXF_READ) s -5 426 M -( Open the file for reading.) s -5 404 M -( SSH_FXF_WRITE) s -5 393 M -( Open the file for writing. If both this and SSH_FXF_READ are) s -5 382 M -( specified, the file is opened for both reading and writing.) s -5 360 M -( SSH_FXF_APPEND) s -5 349 M -( Force all writes to append data at the end of the file. The) s -5 338 M -( offset parameter to write will be ignored.) s -5 316 M -( SSH_FXF_CREAT) s -5 305 M -( If this flag is specified, then a new file will be created if one) s -5 294 M -( does not already exist \(if O_TRUNC is specified, the new file will) s -5 283 M -( be truncated to zero length if it previously exists\).) s -5 261 M -( SSH_FXF_TRUNC) s -5 250 M -( Forces an existing file with the same name to be truncated to zero) s -5 239 M -( length when creating a file by specifying SSH_FXF_CREAT.) s -5 228 M -( SSH_FXF_CREAT MUST also be specified if this flag is used.) s -5 206 M -( SSH_FXF_EXCL) s -5 195 M -( Causes the request to fail if the named file already exists.) s -5 184 M -( SSH_FXF_CREAT MUST also be specified if this flag is used.) s -5 129 M -(Galbraith, et al. Expires April 16, 2003 [Page 15]) s -_R -S -PStoPSsaved restore -userdict/PStoPSsaved save put -PStoPSmatrix setmatrix -595.000000 421.271378 translate -90 rotate -0.706651 dup scale -userdict/PStoPSmatrix matrix currentmatrix put -userdict/PStoPSclip{0 0 moveto - 595.000000 0 rlineto 0 842.000000 rlineto -595.000000 0 rlineto - closepath}put initclip -PStoPSxform concat -%%BeginPageSetup -_S -75 0 translate -/pagenum 16 def -/fname () def -/fdir () def -/ftail () def -/user_header_p false def -%%EndPageSetup -5 723 M -(Internet-Draft SSH File Transfer Protocol October 2002) s -5 690 M -( SSH_FXF_TEXT) s -5 679 M -( Indicates that the server should treat the file as text and) s -5 668 M -( convert it to the canonical newline convention in use. \(See) s -5 657 M -( Determining Server Newline Convention. \(Section 4.3\)) s -5 635 M -( When a file is opened with the FXF_TEXT flag, the offset field in) s -5 624 M -( both the read and write function are ignored.) s -5 602 M -( Servers MUST correctly process multiple parallel reads and writes) s -5 591 M -( correctly in this mode. Naturally, it is permissible for them to) s -5 580 M -( do this by serializing the requests. It would not be possible for) s -5 569 M -( a client to reliably detect a server that does not implement) s -5 558 M -( parallel writes in time to prevent damage.) s -5 536 M -( Clients SHOULD use the SSH_FXF_APPEND flag to append data to a) s -5 525 M -( text file rather then using write with a calculated offset.) s -5 503 M -( To support seeks on text file the following SSH_FXP_EXTENDED) s -5 492 M -( packet is defined.) s -5 448 M -( string "text-seek") s -5 437 M -( string file-handle) s -5 426 M -( uint64 line-number) s -5 404 M -( line-number is the index of the line number to seek to, where byte) s -5 393 M -( 0 in the file is line number 0, and the byte directly following) s -5 382 M -( the first newline sequence in the file is line number 1 and so on.) s -5 360 M -( The response to a "text-seek" request is an SSH_FXP_STATUS) s -5 349 M -( message.) s -5 327 M -( An attempt to seek past the end-of-file should result in a) s -5 316 M -( SSH_FX_EOF status.) s -5 294 M -( Servers SHOULD support at least one "text-seek" in order to) s -5 283 M -( support resume. However, a client MUST be prepared to receive) s -5 272 M -( SSH_FX_OP_UNSUPPORTED when attempting a "text-seek" operation.) s -5 261 M -( The client can then try a fall-back strategy, if it has one.) s -5 239 M -( Clients MUST be prepared to handle SSH_FX_OP_UNSUPPORTED returned) s -5 228 M -( for read or write operations that are not sequential.) s -5 206 M -( The `attrs' field specifies the initial attributes for the file.) s -5 195 M -( Default values will be used for those attributes that are not) s -5 184 M -( specified. See Section ``File Attributes'' for more information.) s -5 129 M -(Galbraith, et al. Expires April 16, 2003 [Page 16]) s -_R -S -PStoPSsaved restore -%%Page: (16,17) 9 -userdict/PStoPSsaved save put -PStoPSmatrix setmatrix -595.000000 0.271378 translate -90 rotate -0.706651 dup scale -userdict/PStoPSmatrix matrix currentmatrix put -userdict/PStoPSclip{0 0 moveto - 595.000000 0 rlineto 0 842.000000 rlineto -595.000000 0 rlineto - closepath}put initclip -/showpage{}def/copypage{}def/erasepage{}def -PStoPSxform concat -%%BeginPageSetup -_S -75 0 translate -/pagenum 17 def -/fname () def -/fdir () def -/ftail () def -/user_header_p false def -%%EndPageSetup -5 723 M -(Internet-Draft SSH File Transfer Protocol October 2002) s -5 690 M -( The response to this message will be either SSH_FXP_HANDLE \(if the) s -5 679 M -( operation is successful\) or SSH_FXP_STATUS \(if the operation fails\).) s -5 657 M -( A file is closed by using the SSH_FXP_CLOSE request. Its data field) s -5 646 M -( has the following format:) s -5 624 M -( uint32 id) s -5 613 M -( string handle) s -5 591 M -( where `id' is the request identifier, and `handle' is a handle) s -5 580 M -( previously returned in the response to SSH_FXP_OPEN or) s -5 569 M -( SSH_FXP_OPENDIR. The handle becomes invalid immediately after this) s -5 558 M -( request has been sent.) s -5 536 M -( The response to this request will be a SSH_FXP_STATUS message. One) s -5 525 M -( should note that on some server platforms even a close can fail.) s -5 514 M -( This can happen e.g. if the server operating system caches writes,) s -5 503 M -( and an error occurs while flushing cached writes during the close.) s -5 481 M -(6.4 Reading and Writing) s -5 459 M -( Once a file has been opened, it can be read using the SSH_FXP_READ) s -5 448 M -( message, which has the following format:) s -5 426 M -( uint32 id) s -5 415 M -( string handle) s -5 404 M -( uint64 offset) s -5 393 M -( uint32 len) s -5 371 M -( where `id' is the request identifier, `handle' is an open file handle) s -5 360 M -( returned by SSH_FXP_OPEN, `offset' is the offset \(in bytes\) relative) s -5 349 M -( to the beginning of the file from where to start reading, and `len') s -5 338 M -( is the maximum number of bytes to read.) s -5 316 M -( In response to this request, the server will read as many bytes as it) s -5 305 M -( can from the file \(up to `len'\), and return them in a SSH_FXP_DATA) s -5 294 M -( message. If an error occurs or EOF is encountered before reading any) s -5 283 M -( data, the server will respond with SSH_FXP_STATUS. For normal disk) s -5 272 M -( files, it is guaranteed that this will read the specified number of) s -5 261 M -( bytes, or up to end of file. For e.g. device files this may return) s -5 250 M -( fewer bytes than requested.) s -5 228 M -( Writing to a file is achieved using the SSH_FXP_WRITE message, which) s -5 217 M -( has the following format:) s -5 129 M -(Galbraith, et al. Expires April 16, 2003 [Page 17]) s -_R -S -PStoPSsaved restore -userdict/PStoPSsaved save put -PStoPSmatrix setmatrix -595.000000 421.271378 translate -90 rotate -0.706651 dup scale -userdict/PStoPSmatrix matrix currentmatrix put -userdict/PStoPSclip{0 0 moveto - 595.000000 0 rlineto 0 842.000000 rlineto -595.000000 0 rlineto - closepath}put initclip -PStoPSxform concat -%%BeginPageSetup -_S -75 0 translate -/pagenum 18 def -/fname () def -/fdir () def -/ftail () def -/user_header_p false def -%%EndPageSetup -5 723 M -(Internet-Draft SSH File Transfer Protocol October 2002) s -5 690 M -( uint32 id) s -5 679 M -( string handle) s -5 668 M -( uint64 offset) s -5 657 M -( string data) s -5 635 M -( where `id' is a request identifier, `handle' is a file handle) s -5 624 M -( returned by SSH_FXP_OPEN, `offset' is the offset \(in bytes\) from the) s -5 613 M -( beginning of the file where to start writing, and `data' is the data) s -5 602 M -( to be written.) s -5 580 M -( The write will extend the file if writing beyond the end of the file.) s -5 569 M -( It is legal to write way beyond the end of the file; the semantics) s -5 558 M -( are to write zeroes from the end of the file to the specified offset) s -5 547 M -( and then the data. On most operating systems, such writes do not) s -5 536 M -( allocate disk space but instead leave "holes" in the file.) s -5 514 M -( The server responds to a write request with a SSH_FXP_STATUS message.) s -5 492 M -(6.5 Removing and Renaming Files) s -5 470 M -( Files can be removed using the SSH_FXP_REMOVE message. It has the) s -5 459 M -( following format:) s -5 437 M -( uint32 id) s -5 426 M -( string filename [UTF-8]) s -5 404 M -( where `id' is the request identifier and `filename' is the name of) s -5 393 M -( the file to be removed. See Section ``File Names'' for more) s -5 382 M -( information. This request cannot be used to remove directories.) s -5 360 M -( The server will respond to this request with a SSH_FXP_STATUS) s -5 349 M -( message.) s -5 327 M -( Files \(and directories\) can be renamed using the SSH_FXP_RENAME) s -5 316 M -( message. Its data is as follows:) s -5 294 M -( uint32 id) s -5 283 M -( string oldpath [UTF-8]) s -5 272 M -( string newpath [UTF-8]) s -5 250 M -( where `id' is the request identifier, `oldpath' is the name of an) s -5 239 M -( existing file or directory, and `newpath' is the new name for the) s -5 228 M -( file or directory. It is an error if there already exists a file) s -5 217 M -( with the name specified by newpath. The server may also fail rename) s -5 206 M -( requests in other situations, for example if `oldpath' and `newpath') s -5 195 M -( point to different file systems on the server.) s -5 173 M -( The server will respond to this request with a SSH_FXP_STATUS) s -5 129 M -(Galbraith, et al. Expires April 16, 2003 [Page 18]) s -_R -S -PStoPSsaved restore -%%Page: (18,19) 10 -userdict/PStoPSsaved save put -PStoPSmatrix setmatrix -595.000000 0.271378 translate -90 rotate -0.706651 dup scale -userdict/PStoPSmatrix matrix currentmatrix put -userdict/PStoPSclip{0 0 moveto - 595.000000 0 rlineto 0 842.000000 rlineto -595.000000 0 rlineto - closepath}put initclip -/showpage{}def/copypage{}def/erasepage{}def -PStoPSxform concat -%%BeginPageSetup -_S -75 0 translate -/pagenum 19 def -/fname () def -/fdir () def -/ftail () def -/user_header_p false def -%%EndPageSetup -5 723 M -(Internet-Draft SSH File Transfer Protocol October 2002) s -5 690 M -( message.) s -5 668 M -(6.6 Creating and Deleting Directories) s -5 646 M -( New directories can be created using the SSH_FXP_MKDIR request. It) s -5 635 M -( has the following format:) s -5 613 M -( uint32 id) s -5 602 M -( string path [UTF-8]) s -5 591 M -( ATTRS attrs) s -5 569 M -( where `id' is the request identifier.) s -5 547 M -( `path' specifies the directory to be created. See Section ``File) s -5 536 M -( Names'' for more information on file names.) s -5 514 M -( `attrs' specifies the attributes that should be applied to it upon) s -5 503 M -( creation. Attributes are discussed in more detail in Section ``File) s -5 492 M -( Attributes''.) s -5 470 M -( The server will respond to this request with a SSH_FXP_STATUS) s -5 459 M -( message. If a file or directory with the specified path already) s -5 448 M -( exists, an error will be returned.) s -5 426 M -( Directories can be removed using the SSH_FXP_RMDIR request, which has) s -5 415 M -( the following format:) s -5 393 M -( uint32 id) s -5 382 M -( string path [UTF-8]) s -5 360 M -( where `id' is the request identifier, and `path' specifies the) s -5 349 M -( directory to be removed. See Section ``File Names'' for more) s -5 338 M -( information on file names.) s -5 316 M -( The server responds to this request with a SSH_FXP_STATUS message.) s -5 305 M -( Errors may be returned from this operation for various reasons,) s -5 294 M -( including, but not limited to, the path does not exist, the path does) s -5 283 M -( not refer to a directory object, the directory is not empty, or the) s -5 272 M -( user has insufficient access or permission to perform the requested) s -5 261 M -( operation.) s -5 239 M -(6.7 Scanning Directories) s -5 217 M -( The files in a directory can be listed using the SSH_FXP_OPENDIR and) s -5 206 M -( SSH_FXP_READDIR requests. Each SSH_FXP_READDIR request returns one) s -5 195 M -( or more file names with full file attributes for each file. The) s -5 184 M -( client should call SSH_FXP_READDIR repeatedly until it has found the) s -5 173 M -( file it is looking for or until the server responds with a) s -5 129 M -(Galbraith, et al. Expires April 16, 2003 [Page 19]) s -_R -S -PStoPSsaved restore -userdict/PStoPSsaved save put -PStoPSmatrix setmatrix -595.000000 421.271378 translate -90 rotate -0.706651 dup scale -userdict/PStoPSmatrix matrix currentmatrix put -userdict/PStoPSclip{0 0 moveto - 595.000000 0 rlineto 0 842.000000 rlineto -595.000000 0 rlineto - closepath}put initclip -PStoPSxform concat -%%BeginPageSetup -_S -75 0 translate -/pagenum 20 def -/fname () def -/fdir () def -/ftail () def -/user_header_p false def -%%EndPageSetup -5 723 M -(Internet-Draft SSH File Transfer Protocol October 2002) s -5 690 M -( SSH_FXP_STATUS message indicating an error \(normally SSH_FX_EOF if) s -5 679 M -( there are no more files in the directory\). The client should then) s -5 668 M -( close the handle using the SSH_FXP_CLOSE request.) s -5 646 M -( The SSH_FXP_OPENDIR opens a directory for reading. It has the) s -5 635 M -( following format:) s -5 613 M -( uint32 id) s -5 602 M -( string path [UTF-8]) s -5 580 M -( where `id' is the request identifier and `path' is the path name of) s -5 569 M -( the directory to be listed \(without any trailing slash\). See Section) s -5 558 M -( ``File Names'' for more information on file names. This will return) s -5 547 M -( an error if the path does not specify a directory or if the directory) s -5 536 M -( is not readable. The server will respond to this request with either) s -5 525 M -( a SSH_FXP_HANDLE or a SSH_FXP_STATUS message.) s -5 503 M -( Once the directory has been successfully opened, files \(and) s -5 492 M -( directories\) contained in it can be listed using SSH_FXP_READDIR) s -5 481 M -( requests. These are of the format) s -5 459 M -( uint32 id) s -5 448 M -( string handle) s -5 426 M -( where `id' is the request identifier, and `handle' is a handle) s -5 415 M -( returned by SSH_FXP_OPENDIR. \(It is a protocol error to attempt to) s -5 404 M -( use an ordinary file handle returned by SSH_FXP_OPEN.\)) s -5 382 M -( The server responds to this request with either a SSH_FXP_NAME or a) s -5 371 M -( SSH_FXP_STATUS message. One or more names may be returned at a time.) s -5 360 M -( Full status information is returned for each name in order to speed) s -5 349 M -( up typical directory listings.) s -5 327 M -( If there are no more names available to be read, the server MUST) s -5 316 M -( respond with a SSH_FXP_STATUS message with error code of SSH_FX_EOF.) s -5 294 M -( When the client no longer wishes to read more names from the) s -5 283 M -( directory, it SHOULD call SSH_FXP_CLOSE for the handle. The handle) s -5 272 M -( should be closed regardless of whether an error has occurred or not.) s -5 250 M -(6.8 Retrieving File Attributes) s -5 228 M -( Very often, file attributes are automatically returned by) s -5 217 M -( SSH_FXP_READDIR. However, sometimes there is need to specifically) s -5 206 M -( retrieve the attributes for a named file. This can be done using the) s -5 195 M -( SSH_FXP_STAT, SSH_FXP_LSTAT and SSH_FXP_FSTAT requests.) s -5 173 M -( SSH_FXP_STAT and SSH_FXP_LSTAT only differ in that SSH_FXP_STAT) s -5 129 M -(Galbraith, et al. Expires April 16, 2003 [Page 20]) s -_R -S -PStoPSsaved restore -%%Page: (20,21) 11 -userdict/PStoPSsaved save put -PStoPSmatrix setmatrix -595.000000 0.271378 translate -90 rotate -0.706651 dup scale -userdict/PStoPSmatrix matrix currentmatrix put -userdict/PStoPSclip{0 0 moveto - 595.000000 0 rlineto 0 842.000000 rlineto -595.000000 0 rlineto - closepath}put initclip -/showpage{}def/copypage{}def/erasepage{}def -PStoPSxform concat -%%BeginPageSetup -_S -75 0 translate -/pagenum 21 def -/fname () def -/fdir () def -/ftail () def -/user_header_p false def -%%EndPageSetup -5 723 M -(Internet-Draft SSH File Transfer Protocol October 2002) s -5 690 M -( follows symbolic links on the server, whereas SSH_FXP_LSTAT does not) s -5 679 M -( follow symbolic links. Both have the same format:) s -5 657 M -( uint32 id) s -5 646 M -( string path [UTF-8]) s -5 635 M -( uint32 flags) s -5 613 M -( where `id' is the request identifier, and `path' specifies the file) s -5 602 M -( system object for which status is to be returned. The server) s -5 591 M -( responds to this request with either SSH_FXP_ATTRS or SSH_FXP_STATUS.) s -5 569 M -( The flags field specify the attribute flags in which the client has) s -5 558 M -( particular interest. This is a hint to the server. For example,) s -5 547 M -( because retrieving owner / group and acl information can be an) s -5 536 M -( expensive operation under some operating systems, the server may) s -5 525 M -( choose not to retrieve this information unless the client expresses a) s -5 514 M -( specific interest in it.) s -5 492 M -( The client has no guarantee the server will provide all the fields) s -5 481 M -( that it has expressed an interest in.) s -5 459 M -( SSH_FXP_FSTAT differs from the others in that it returns status) s -5 448 M -( information for an open file \(identified by the file handle\). Its) s -5 437 M -( format is as follows:) s -5 415 M -( uint32 id) s -5 404 M -( string handle) s -5 393 M -( uint32 flags) s -5 371 M -( where `id' is the request identifier and `handle' is a file handle) s -5 360 M -( returned by SSH_FXP_OPEN. The server responds to this request with) s -5 349 M -( SSH_FXP_ATTRS or SSH_FXP_STATUS.) s -5 327 M -(6.9 Setting File Attributes) s -5 305 M -( File attributes may be modified using the SSH_FXP_SETSTAT and) s -5 294 M -( SSH_FXP_FSETSTAT requests. These requests are used for operations) s -5 283 M -( such as changing the ownership, permissions or access times, as well) s -5 272 M -( as for truncating a file.) s -5 250 M -( The SSH_FXP_SETSTAT request is of the following format:) s -5 228 M -( uint32 id) s -5 217 M -( string path [UTF-8]) s -5 206 M -( ATTRS attrs) s -5 184 M -( where `id' is the request identifier, `path' specifies the file) s -5 173 M -( system object \(e.g. file or directory\) whose attributes are to be) s -5 129 M -(Galbraith, et al. Expires April 16, 2003 [Page 21]) s -_R -S -PStoPSsaved restore -userdict/PStoPSsaved save put -PStoPSmatrix setmatrix -595.000000 421.271378 translate -90 rotate -0.706651 dup scale -userdict/PStoPSmatrix matrix currentmatrix put -userdict/PStoPSclip{0 0 moveto - 595.000000 0 rlineto 0 842.000000 rlineto -595.000000 0 rlineto - closepath}put initclip -PStoPSxform concat -%%BeginPageSetup -_S -75 0 translate -/pagenum 22 def -/fname () def -/fdir () def -/ftail () def -/user_header_p false def -%%EndPageSetup -5 723 M -(Internet-Draft SSH File Transfer Protocol October 2002) s -5 690 M -( modified, and `attrs' specifies the modifications to be made to its) s -5 679 M -( attributes. Attributes are discussed in more detail in Section) s -5 668 M -( ``File Attributes''.) s -5 646 M -( An error will be returned if the specified file system object does) s -5 635 M -( not exist or the user does not have sufficient rights to modify the) s -5 624 M -( specified attributes. The server responds to this request with a) s -5 613 M -( SSH_FXP_STATUS message.) s -5 591 M -( The SSH_FXP_FSETSTAT request modifies the attributes of a file which) s -5 580 M -( is already open. It has the following format:) s -5 558 M -( uint32 id) s -5 547 M -( string handle) s -5 536 M -( ATTRS attrs) s -5 514 M -( where `id' is the request identifier, `handle' \(MUST be returned by) s -5 503 M -( SSH_FXP_OPEN\) identifies the file whose attributes are to be) s -5 492 M -( modified, and `attrs' specifies the modifications to be made to its) s -5 481 M -( attributes. Attributes are discussed in more detail in Section) s -5 470 M -( ``File Attributes''. The server will respond to this request with) s -5 459 M -( SSH_FXP_STATUS.) s -5 437 M -(6.10 Dealing with Symbolic links) s -5 415 M -( The SSH_FXP_READLINK request may be used to read the target of a) s -5 404 M -( symbolic link. It would have a data part as follows:) s -5 382 M -( uint32 id) s -5 371 M -( string path [UTF-8]) s -5 349 M -( where `id' is the request identifier and `path' specifies the path) s -5 338 M -( name of the symlink to be read.) s -5 316 M -( The server will respond with a SSH_FXP_NAME packet containing only) s -5 305 M -( one name and a dummy attributes value. The name in the returned) s -5 294 M -( packet contains the target of the link. If an error occurs, the) s -5 283 M -( server may respond with SSH_FXP_STATUS.) s -5 261 M -( The SSH_FXP_SYMLINK request will create a symbolic link on the) s -5 250 M -( server. It is of the following format) s -5 228 M -( uint32 id) s -5 217 M -( string linkpath [UTF-8]) s -5 206 M -( string targetpath [UTF-8]) s -5 184 M -( where `id' is the request identifier, `linkpath' specifies the path) s -5 173 M -( name of the symlink to be created and `targetpath' specifies the) s -5 129 M -(Galbraith, et al. Expires April 16, 2003 [Page 22]) s -_R -S -PStoPSsaved restore -%%Page: (22,23) 12 -userdict/PStoPSsaved save put -PStoPSmatrix setmatrix -595.000000 0.271378 translate -90 rotate -0.706651 dup scale -userdict/PStoPSmatrix matrix currentmatrix put -userdict/PStoPSclip{0 0 moveto - 595.000000 0 rlineto 0 842.000000 rlineto -595.000000 0 rlineto - closepath}put initclip -/showpage{}def/copypage{}def/erasepage{}def -PStoPSxform concat -%%BeginPageSetup -_S -75 0 translate -/pagenum 23 def -/fname () def -/fdir () def -/ftail () def -/user_header_p false def -%%EndPageSetup -5 723 M -(Internet-Draft SSH File Transfer Protocol October 2002) s -5 690 M -( target of the symlink. The server shall respond with a) s -5 679 M -( SSH_FXP_STATUS indicating either success \(SSH_FX_OK\) or an error) s -5 668 M -( condition.) s -5 646 M -(6.11 Canonicalizing the Server-Side Path Name) s -5 624 M -( The SSH_FXP_REALPATH request can be used to have the server) s -5 613 M -( canonicalize any given path name to an absolute path. This is useful) s -5 602 M -( for converting path names containing ".." components or relative) s -5 591 M -( pathnames without a leading slash into absolute paths. The format of) s -5 580 M -( the request is as follows:) s -5 558 M -( uint32 id) s -5 547 M -( string path [UTF-8]) s -5 525 M -( where `id' is the request identifier and `path' specifies the path) s -5 514 M -( name to be canonicalized. The server will respond with a) s -5 503 M -( SSH_FXP_NAME packet containing the name in canonical form and a dummy) s -5 492 M -( attributes value. If an error occurs, the server may also respond) s -5 481 M -( with SSH_FXP_STATUS.) s -5 459 M -(6.11.1 Best practice for dealing with paths) s -5 437 M -( The client SHOULD treat the results of SSH_FXP_REALPATH as a) s -5 426 M -( canonical absolute path, even if the path does not appear to be) s -5 415 M -( absolute. A client that use REALPATH\("."\) and treats the result as) s -5 404 M -( absolute, even if there is no leading slash, will continue to) s -5 393 M -( function correctly, even when talking to a Windows NT or VMS style) s -5 382 M -( system, where absolute paths may not begin with a slash.) s -5 360 M -( For example, if the client wishes to change directory up, and the) s -5 349 M -( server has returned "c:/x/y/z" from REALPATH, the client SHOULD use) s -5 338 M -( "c:/x/y/z/..".) s -5 316 M -( As a second example, if the client wishes to open the file "x.txt" in) s -5 305 M -( the current directory, and server has returned "dka100:/x/y/z" as the) s -5 294 M -( canonical path of the directory, the client SHOULD open "dka100:/x/y/) s -5 283 M -( z/x.txt") s -5 129 M -(Galbraith, et al. Expires April 16, 2003 [Page 23]) s -_R -S -PStoPSsaved restore -userdict/PStoPSsaved save put -PStoPSmatrix setmatrix -595.000000 421.271378 translate -90 rotate -0.706651 dup scale -userdict/PStoPSmatrix matrix currentmatrix put -userdict/PStoPSclip{0 0 moveto - 595.000000 0 rlineto 0 842.000000 rlineto -595.000000 0 rlineto - closepath}put initclip -PStoPSxform concat -%%BeginPageSetup -_S -75 0 translate -/pagenum 24 def -/fname () def -/fdir () def -/ftail () def -/user_header_p false def -%%EndPageSetup -5 723 M -(Internet-Draft SSH File Transfer Protocol October 2002) s -5 690 M -(7. Responses from the Server to the Client) s -5 668 M -( The server responds to the client using one of a few response) s -5 657 M -( packets. All requests can return a SSH_FXP_STATUS response upon) s -5 646 M -( failure. When the operation is successful, any of the responses may) s -5 635 M -( be returned \(depending on the operation\). If no data needs to be) s -5 624 M -( returned to the client, the SSH_FXP_STATUS response with SSH_FX_OK) s -5 613 M -( status is appropriate. Otherwise, the SSH_FXP_HANDLE message is used) s -5 602 M -( to return a file handle \(for SSH_FXP_OPEN and SSH_FXP_OPENDIR) s -5 591 M -( requests\), SSH_FXP_DATA is used to return data from SSH_FXP_READ,) s -5 580 M -( SSH_FXP_NAME is used to return one or more file names from a) s -5 569 M -( SSH_FXP_READDIR or SSH_FXP_REALPATH request, and SSH_FXP_ATTRS is) s -5 558 M -( used to return file attributes from SSH_FXP_STAT, SSH_FXP_LSTAT, and) s -5 547 M -( SSH_FXP_FSTAT requests.) s -5 525 M -( Exactly one response will be returned for each request. Each) s -5 514 M -( response packet contains a request identifier which can be used to) s -5 503 M -( match each response with the corresponding request. Note that it is) s -5 492 M -( legal to have several requests outstanding simultaneously, and the) s -5 481 M -( server is allowed to send responses to them in a different order from) s -5 470 M -( the order in which the requests were sent \(the result of their) s -5 459 M -( execution, however, is guaranteed to be as if they had been processed) s -5 448 M -( one at a time in the order in which the requests were sent\).) s -5 426 M -( Response packets are of the same general format as request packets.) s -5 415 M -( Each response packet begins with the request identifier.) s -5 393 M -( The format of the data portion of the SSH_FXP_STATUS response is as) s -5 382 M -( follows:) s -5 360 M -( uint32 id) s -5 349 M -( uint32 error/status code) s -5 338 M -( string error message \(ISO-10646 UTF-8 [RFC-2279]\)) s -5 327 M -( string language tag \(as defined in [RFC-1766]\)) s -5 305 M -( where `id' is the request identifier, and `error/status code') s -5 294 M -( indicates the result of the requested operation. The value SSH_FX_OK) s -5 283 M -( indicates success, and all other values indicate failure.) s -5 261 M -( Currently, the following values are defined \(other values may be) s -5 250 M -( defined by future versions of this protocol\):) s -5 129 M -(Galbraith, et al. Expires April 16, 2003 [Page 24]) s -_R -S -PStoPSsaved restore -%%Page: (24,25) 13 -userdict/PStoPSsaved save put -PStoPSmatrix setmatrix -595.000000 0.271378 translate -90 rotate -0.706651 dup scale -userdict/PStoPSmatrix matrix currentmatrix put -userdict/PStoPSclip{0 0 moveto - 595.000000 0 rlineto 0 842.000000 rlineto -595.000000 0 rlineto - closepath}put initclip -/showpage{}def/copypage{}def/erasepage{}def -PStoPSxform concat -%%BeginPageSetup -_S -75 0 translate -/pagenum 25 def -/fname () def -/fdir () def -/ftail () def -/user_header_p false def -%%EndPageSetup -5 723 M -(Internet-Draft SSH File Transfer Protocol October 2002) s -5 690 M -( #define SSH_FX_OK 0) s -5 679 M -( #define SSH_FX_EOF 1) s -5 668 M -( #define SSH_FX_NO_SUCH_FILE 2) s -5 657 M -( #define SSH_FX_PERMISSION_DENIED 3) s -5 646 M -( #define SSH_FX_FAILURE 4) s -5 635 M -( #define SSH_FX_BAD_MESSAGE 5) s -5 624 M -( #define SSH_FX_NO_CONNECTION 6) s -5 613 M -( #define SSH_FX_CONNECTION_LOST 7) s -5 602 M -( #define SSH_FX_OP_UNSUPPORTED 8) s -5 591 M -( #define SSH_FX_INVALID_HANDLE 9) s -5 580 M -( #define SSH_FX_NO_SUCH_PATH 10) s -5 569 M -( #define SSH_FX_FILE_ALREADY_EXISTS 11) s -5 558 M -( #define SSH_FX_WRITE_PROTECT 12) s -5 536 M -( SSH_FX_OK) s -5 525 M -( Indicates successful completion of the operation.) s -5 503 M -( SSH_FX_EOF) s -5 492 M -( indicates end-of-file condition; for SSH_FX_READ it means that no) s -5 481 M -( more data is available in the file, and for SSH_FX_READDIR it) s -5 470 M -( indicates that no more files are contained in the directory.) s -5 448 M -( SSH_FX_NO_SUCH_FILE) s -5 437 M -( is returned when a reference is made to a file which does not) s -5 426 M -( exist.) s -5 404 M -( SSH_FX_PERMISSION_DENIED) s -5 393 M -( is returned when the authenticated user does not have sufficient) s -5 382 M -( permissions to perform the operation.) s -5 360 M -( SSH_FX_FAILURE) s -5 349 M -( is a generic catch-all error message; it should be returned if an) s -5 338 M -( error occurs for which there is no more specific error code) s -5 327 M -( defined.) s -5 305 M -( SSH_FX_BAD_MESSAGE) s -5 294 M -( may be returned if a badly formatted packet or protocol) s -5 283 M -( incompatibility is detected.) s -5 261 M -( SSH_FX_NO_CONNECTION) s -5 250 M -( is a pseudo-error which indicates that the client has no) s -5 239 M -( connection to the server \(it can only be generated locally by the) s -5 228 M -( client, and MUST NOT be returned by servers\).) s -5 206 M -( SSH_FX_CONNECTION_LOST) s -5 195 M -( is a pseudo-error which indicates that the connection to the) s -5 184 M -( server has been lost \(it can only be generated locally by the) s -5 173 M -( client, and MUST NOT be returned by servers\).) s -5 129 M -(Galbraith, et al. Expires April 16, 2003 [Page 25]) s -_R -S -PStoPSsaved restore -userdict/PStoPSsaved save put -PStoPSmatrix setmatrix -595.000000 421.271378 translate -90 rotate -0.706651 dup scale -userdict/PStoPSmatrix matrix currentmatrix put -userdict/PStoPSclip{0 0 moveto - 595.000000 0 rlineto 0 842.000000 rlineto -595.000000 0 rlineto - closepath}put initclip -PStoPSxform concat -%%BeginPageSetup -_S -75 0 translate -/pagenum 26 def -/fname () def -/fdir () def -/ftail () def -/user_header_p false def -%%EndPageSetup -5 723 M -(Internet-Draft SSH File Transfer Protocol October 2002) s -5 690 M -( SSH_FX_OP_UNSUPPORTED) s -5 679 M -( indicates that an attempt was made to perform an operation which) s -5 668 M -( is not supported for the server \(it may be generated locally by) s -5 657 M -( the client if e.g. the version number exchange indicates that a) s -5 646 M -( required feature is not supported by the server, or it may be) s -5 635 M -( returned by the server if the server does not implement an) s -5 624 M -( operation\).) s -5 602 M -( SSH_FX_INVALID_HANDLE) s -5 591 M -( The handle value was invalid.) s -5 569 M -( SSH_FX_NO_SUCH_PATH) s -5 558 M -( The file path does not exist or is invalid.) s -5 536 M -( SSH_FX_FILE_ALREADY_EXISTS) s -5 525 M -( The file already exists.) s -5 503 M -( SSH_FX_WRITE_PROTECT) s -5 492 M -( The file is on read only media, or the media is write protected.) s -5 470 M -( The SSH_FXP_HANDLE response has the following format:) s -5 448 M -( uint32 id) s -5 437 M -( string handle) s -5 415 M -( where `id' is the request identifier, and `handle' is an arbitrary) s -5 404 M -( string that identifies an open file or directory on the server. The) s -5 393 M -( handle is opaque to the client; the client MUST NOT attempt to) s -5 382 M -( interpret or modify it in any way. The length of the handle string) s -5 371 M -( MUST NOT exceed 256 data bytes.) s -5 349 M -( The SSH_FXP_DATA response has the following format:) s -5 327 M -( uint32 id) s -5 316 M -( string data) s -5 294 M -( where `id' is the request identifier, and `data' is an arbitrary byte) s -5 283 M -( string containing the requested data. The data string may be at most) s -5 272 M -( the number of bytes requested in a SSH_FXP_READ request, but may also) s -5 261 M -( be shorter if end of file is reached or if the read is from something) s -5 250 M -( other than a regular file.) s -5 228 M -( The SSH_FXP_NAME response has the following format:) s -5 129 M -(Galbraith, et al. Expires April 16, 2003 [Page 26]) s -_R -S -PStoPSsaved restore -%%Page: (26,27) 14 -userdict/PStoPSsaved save put -PStoPSmatrix setmatrix -595.000000 0.271378 translate -90 rotate -0.706651 dup scale -userdict/PStoPSmatrix matrix currentmatrix put -userdict/PStoPSclip{0 0 moveto - 595.000000 0 rlineto 0 842.000000 rlineto -595.000000 0 rlineto - closepath}put initclip -/showpage{}def/copypage{}def/erasepage{}def -PStoPSxform concat -%%BeginPageSetup -_S -75 0 translate -/pagenum 27 def -/fname () def -/fdir () def -/ftail () def -/user_header_p false def -%%EndPageSetup -5 723 M -(Internet-Draft SSH File Transfer Protocol October 2002) s -5 690 M -( uint32 id) s -5 679 M -( uint32 count) s -5 668 M -( repeats count times:) s -5 657 M -( string filename [UTF-8]) s -5 646 M -( ATTRS attrs) s -5 624 M -( where `id' is the request identifier, `count' is the number of names) s -5 613 M -( returned in this response, and the remaining fields repeat `count') s -5 602 M -( times \(so that all three fields are first included for the first) s -5 591 M -( file, then for the second file, etc\). In the repeated part,) s -5 580 M -( `filename' is a file name being returned \(for SSH_FXP_READDIR, it) s -5 569 M -( will be a relative name within the directory, without any path) s -5 558 M -( components; for SSH_FXP_REALPATH it will be an absolute path name\),) s -5 547 M -( and `attrs' is the attributes of the file as described in Section) s -5 536 M -( ``File Attributes''.) s -5 514 M -( The SSH_FXP_ATTRS response has the following format:) s -5 492 M -( uint32 id) s -5 481 M -( ATTRS attrs) s -5 459 M -( where `id' is the request identifier, and `attrs' is the returned) s -5 448 M -( file attributes as described in Section ``File Attributes''.) s -5 129 M -(Galbraith, et al. Expires April 16, 2003 [Page 27]) s -_R -S -PStoPSsaved restore -userdict/PStoPSsaved save put -PStoPSmatrix setmatrix -595.000000 421.271378 translate -90 rotate -0.706651 dup scale -userdict/PStoPSmatrix matrix currentmatrix put -userdict/PStoPSclip{0 0 moveto - 595.000000 0 rlineto 0 842.000000 rlineto -595.000000 0 rlineto - closepath}put initclip -PStoPSxform concat -%%BeginPageSetup -_S -75 0 translate -/pagenum 28 def -/fname () def -/fdir () def -/ftail () def -/user_header_p false def -%%EndPageSetup -5 723 M -(Internet-Draft SSH File Transfer Protocol October 2002) s -5 690 M -(8. Vendor-Specific Extensions) s -5 668 M -( The SSH_FXP_EXTENDED request provides a generic extension mechanism) s -5 657 M -( for adding vendor-specific commands. The request has the following) s -5 646 M -( format:) s -5 624 M -( uint32 id) s -5 613 M -( string extended-request) s -5 602 M -( ... any request-specific data ...) s -5 580 M -( where `id' is the request identifier, and `extended-request' is a) s -5 569 M -( string of the format "name@domain", where domain is an internet) s -5 558 M -( domain name of the vendor defining the request. The rest of the) s -5 547 M -( request is completely vendor-specific, and servers should only) s -5 536 M -( attempt to interpret it if they recognize the `extended-request') s -5 525 M -( name.) s -5 503 M -( The server may respond to such requests using any of the response) s -5 492 M -( packets defined in Section ``Responses from the Server to the) s -5 481 M -( Client''. Additionally, the server may also respond with a) s -5 470 M -( SSH_FXP_EXTENDED_REPLY packet, as defined below. If the server does) s -5 459 M -( not recognize the `extended-request' name, then the server MUST) s -5 448 M -( respond with SSH_FXP_STATUS with error/status set to) s -5 437 M -( SSH_FX_OP_UNSUPPORTED.) s -5 415 M -( The SSH_FXP_EXTENDED_REPLY packet can be used to carry arbitrary) s -5 404 M -( extension-specific data from the server to the client. It is of the) s -5 393 M -( following format:) s -5 371 M -( uint32 id) s -5 360 M -( ... any request-specific data ...) s -5 338 M -( There is a range of packet types reserved for use by extensions. In) s -5 327 M -( order to avoid collision, extensions that turn on the use of) s -5 316 M -( additional packet types should determine those numbers dynamically.) s -5 294 M -( The suggested way of doing this is have an extension request from the) s -5 283 M -( client to the server that enables the extension; the extension) s -5 272 M -( response from the server to the client would specify the actual type) s -5 261 M -( values to use, in additional to any other data.) s -5 239 M -( Extension authors should be mindful of the limited range of packet) s -5 228 M -( types available \(there are only 45 values available\) and avoid) s -5 217 M -( requiring a new packet type where possible.) s -5 129 M -(Galbraith, et al. Expires April 16, 2003 [Page 28]) s -_R -S -PStoPSsaved restore -%%Page: (28,29) 15 -userdict/PStoPSsaved save put -PStoPSmatrix setmatrix -595.000000 0.271378 translate -90 rotate -0.706651 dup scale -userdict/PStoPSmatrix matrix currentmatrix put -userdict/PStoPSclip{0 0 moveto - 595.000000 0 rlineto 0 842.000000 rlineto -595.000000 0 rlineto - closepath}put initclip -/showpage{}def/copypage{}def/erasepage{}def -PStoPSxform concat -%%BeginPageSetup -_S -75 0 translate -/pagenum 29 def -/fname () def -/fdir () def -/ftail () def -/user_header_p false def -%%EndPageSetup -5 723 M -(Internet-Draft SSH File Transfer Protocol October 2002) s -5 690 M -(9. Security Considerations) s -5 668 M -( This protocol assumes that it is run over a secure channel and that) s -5 657 M -( the endpoints of the channel have been authenticated. Thus, this) s -5 646 M -( protocol assumes that it is externally protected from network-level) s -5 635 M -( attacks.) s -5 613 M -( This protocol provides file system access to arbitrary files on the) s -5 602 M -( server \(only constrained by the server implementation\). It is the) s -5 591 M -( responsibility of the server implementation to enforce any access) s -5 580 M -( controls that may be required to limit the access allowed for any) s -5 569 M -( particular user \(the user being authenticated externally to this) s -5 558 M -( protocol, typically using the SSH User Authentication Protocol [8].) s -5 536 M -( Care must be taken in the server implementation to check the validity) s -5 525 M -( of received file handle strings. The server should not rely on them) s -5 514 M -( directly; it MUST check the validity of each handle before relying on) s -5 503 M -( it.) s -5 129 M -(Galbraith, et al. Expires April 16, 2003 [Page 29]) s -_R -S -PStoPSsaved restore -userdict/PStoPSsaved save put -PStoPSmatrix setmatrix -595.000000 421.271378 translate -90 rotate -0.706651 dup scale -userdict/PStoPSmatrix matrix currentmatrix put -userdict/PStoPSclip{0 0 moveto - 595.000000 0 rlineto 0 842.000000 rlineto -595.000000 0 rlineto - closepath}put initclip -PStoPSxform concat -%%BeginPageSetup -_S -75 0 translate -/pagenum 30 def -/fname () def -/fdir () def -/ftail () def -/user_header_p false def -%%EndPageSetup -5 723 M -(Internet-Draft SSH File Transfer Protocol October 2002) s -5 690 M -(10. Changes from previous protocol versions) s -5 668 M -( The SSH File Transfer Protocol has changed over time, before it's) s -5 657 M -( standardization. The following is a description of the incompatible) s -5 646 M -( changes between different versions.) s -5 624 M -(10.1 Changes between versions 4 and 3) s -5 602 M -( Many of the changes between version 4 and version 3 are to the) s -5 591 M -( attribute structure to make it more flexible for non-unix platforms.) s -5 569 M -( o Make all filenames UTF-8.) s -5 547 M -( o Added 'newline' extension.) s -5 525 M -( o Made file attribute owner and group strings so they can actually) s -5 514 M -( be used on disparate systems.) s -5 492 M -( o Added createtime field, and added separate flags for atime,) s -5 481 M -( createtime, and mtime so they can be set separately.) s -5 459 M -( o Split the file type out of the permissions field and into it's own) s -5 448 M -( field \(which is always present.\)) s -5 426 M -( o Added acl attribute.) s -5 404 M -( o Added SSH_FXF_TEXT file open flag.) s -5 382 M -( o Added flags field to the get stat commands so that the client can) s -5 371 M -( specifically request information the server might not normally) s -5 360 M -( included for performance reasons.) s -5 338 M -( o Removed the long filename from the names structure-- it can now be) s -5 327 M -( built from information available in the attrs structure.) s -5 305 M -( o Added reserved range of packet numbers for extensions.) s -5 283 M -( o Added several additional error codes.) s -5 261 M -( o Change the way version negotiate works slightly. Previously, if) s -5 250 M -( the client version were higher than the server version, the server) s -5 239 M -( was supposed to 'echo back' the clients version. The server now) s -5 228 M -( sends it's own version and the lower of the two is considered to) s -5 217 M -( be the one in use.) s -5 129 M -(Galbraith, et al. Expires April 16, 2003 [Page 30]) s -_R -S -PStoPSsaved restore -%%Page: (30,31) 16 -userdict/PStoPSsaved save put -PStoPSmatrix setmatrix -595.000000 0.271378 translate -90 rotate -0.706651 dup scale -userdict/PStoPSmatrix matrix currentmatrix put -userdict/PStoPSclip{0 0 moveto - 595.000000 0 rlineto 0 842.000000 rlineto -595.000000 0 rlineto - closepath}put initclip -/showpage{}def/copypage{}def/erasepage{}def -PStoPSxform concat -%%BeginPageSetup -_S -75 0 translate -/pagenum 31 def -/fname () def -/fdir () def -/ftail () def -/user_header_p false def -%%EndPageSetup -5 723 M -(Internet-Draft SSH File Transfer Protocol October 2002) s -5 690 M -(10.2 Changes between versions 3 and 2) s -5 668 M -( o The SSH_FXP_READLINK and SSH_FXP_SYMLINK messages were added.) s -5 646 M -( o The SSH_FXP_EXTENDED and SSH_FXP_EXTENDED_REPLY messages were) s -5 635 M -( added.) s -5 613 M -( o The SSH_FXP_STATUS message was changed to include fields `error) s -5 602 M -( message' and `language tag'.) s -5 569 M -(10.3 Changes between versions 2 and 1) s -5 547 M -( o The SSH_FXP_RENAME message was added.) s -5 514 M -(10.4 Changes between versions 1 and 0) s -5 492 M -( o Implementation changes, no actual protocol changes.) s -5 129 M -(Galbraith, et al. Expires April 16, 2003 [Page 31]) s -_R -S -PStoPSsaved restore -userdict/PStoPSsaved save put -PStoPSmatrix setmatrix -595.000000 421.271378 translate -90 rotate -0.706651 dup scale -userdict/PStoPSmatrix matrix currentmatrix put -userdict/PStoPSclip{0 0 moveto - 595.000000 0 rlineto 0 842.000000 rlineto -595.000000 0 rlineto - closepath}put initclip -PStoPSxform concat -%%BeginPageSetup -_S -75 0 translate -/pagenum 32 def -/fname () def -/fdir () def -/ftail () def -/user_header_p false def -%%EndPageSetup -5 723 M -(Internet-Draft SSH File Transfer Protocol October 2002) s -5 690 M -(11. Trademark Issues) s -5 668 M -( "ssh" is a registered trademark of SSH Communications Security Corp) s -5 657 M -( in the United States and/or other countries.) s -5 129 M -(Galbraith, et al. Expires April 16, 2003 [Page 32]) s -_R -S -PStoPSsaved restore -%%Page: (32,33) 17 -userdict/PStoPSsaved save put -PStoPSmatrix setmatrix -595.000000 0.271378 translate -90 rotate -0.706651 dup scale -userdict/PStoPSmatrix matrix currentmatrix put -userdict/PStoPSclip{0 0 moveto - 595.000000 0 rlineto 0 842.000000 rlineto -595.000000 0 rlineto - closepath}put initclip -/showpage{}def/copypage{}def/erasepage{}def -PStoPSxform concat -%%BeginPageSetup -_S -75 0 translate -/pagenum 33 def -/fname () def -/fdir () def -/ftail () def -/user_header_p false def -%%EndPageSetup -5 723 M -(Internet-Draft SSH File Transfer Protocol October 2002) s -5 690 M -(References) s -5 668 M -( [1] Dierks, T., Allen, C., Treese, W., Karlton, P., Freier, A. and) s -5 657 M -( P. Kocher, "The TLS Protocol Version 1.0", RFC 2246, January) s -5 646 M -( 1999.) s -5 624 M -( [2] Alvestrand, H., "IETF Policy on Character Sets and Languages",) s -5 613 M -( BCP 18, RFC 2277, January 1998.) s -5 591 M -( [3] Shepler, S., Callaghan, B., Robinson, D., Thurlow, R., Beame,) s -5 580 M -( C., Eisler, M. and D. Noveck, "NFS version 4 Protocol", RFC) s -5 569 M -( 3010, December 2000.) s -5 547 M -( [4] Institute of Electrical and Electronics Engineers, "Information) s -5 536 M -( Technology - Portable Operating System Interface \(POSIX\) - Part) s -5 525 M -( 1: System Application Program Interface \(API\) [C Language]",) s -5 514 M -( IEEE Standard 1003.2, 1996.) s -5 492 M -( [5] Rinne, T., Ylonen, T., Kivinen, T., Saarinen, M. and S.) s -5 481 M -( Lehtinen, "SSH Protocol Architecture", draft-ietf-secsh-) s -5 470 M -( architecture-13 \(work in progress\), September 2002.) s -5 448 M -( [6] Rinne, T., Ylonen, T., Kivinen, T., Saarinen, M. and S.) s -5 437 M -( Lehtinen, "SSH Protocol Transport Protocol", draft-ietf-secsh-) s -5 426 M -( transport-15 \(work in progress\), September 2002.) s -5 404 M -( [7] Rinne, T., Ylonen, T., Kivinen, T., Saarinen, M. and S.) s -5 393 M -( Lehtinen, "SSH Connection Protocol", draft-ietf-secsh-connect-16) s -5 382 M -( \(work in progress\), September 2002.) s -5 360 M -( [8] Rinne, T., Ylonen, T., Kivinen, T., Saarinen, M. and S.) s -5 349 M -( Lehtinen, "SSH Authentication Protocol", draft-ietf-secsh-) s -5 338 M -( userauth-16 \(work in progress\), September 2002.) s -5 305 M -(Authors' Addresses) s -5 283 M -( Joseph Galbraith) s -5 272 M -( VanDyke Software) s -5 261 M -( 4848 Tramway Ridge Blvd) s -5 250 M -( Suite 101) s -5 239 M -( Albuquerque, NM 87111) s -5 228 M -( US) s -5 206 M -( Phone: +1 505 332 5700) s -5 195 M -( EMail: [email protected]) s -5 129 M -(Galbraith, et al. Expires April 16, 2003 [Page 33]) s -_R -S -PStoPSsaved restore -userdict/PStoPSsaved save put -PStoPSmatrix setmatrix -595.000000 421.271378 translate -90 rotate -0.706651 dup scale -userdict/PStoPSmatrix matrix currentmatrix put -userdict/PStoPSclip{0 0 moveto - 595.000000 0 rlineto 0 842.000000 rlineto -595.000000 0 rlineto - closepath}put initclip -PStoPSxform concat -%%BeginPageSetup -_S -75 0 translate -/pagenum 34 def -/fname () def -/fdir () def -/ftail () def -/user_header_p false def -%%EndPageSetup -5 723 M -(Internet-Draft SSH File Transfer Protocol October 2002) s -5 690 M -( Tatu Ylonen) s -5 679 M -( SSH Communications Security Corp) s -5 668 M -( Fredrikinkatu 42) s -5 657 M -( HELSINKI FIN-00100) s -5 646 M -( Finland) s -5 624 M -( EMail: [email protected]) s -5 591 M -( Sami Lehtinen) s -5 580 M -( SSH Communications Security Corp) s -5 569 M -( Fredrikinkatu 42) s -5 558 M -( HELSINKI FIN-00100) s -5 547 M -( Finland) s -5 525 M -( EMail: [email protected]) s -5 129 M -(Galbraith, et al. Expires April 16, 2003 [Page 34]) s -_R -S -PStoPSsaved restore -%%Page: (34,35) 18 -userdict/PStoPSsaved save put -PStoPSmatrix setmatrix -595.000000 0.271378 translate -90 rotate -0.706651 dup scale -userdict/PStoPSmatrix matrix currentmatrix put -userdict/PStoPSclip{0 0 moveto - 595.000000 0 rlineto 0 842.000000 rlineto -595.000000 0 rlineto - closepath}put initclip -/showpage{}def/copypage{}def/erasepage{}def -PStoPSxform concat -%%BeginPageSetup -_S -75 0 translate -/pagenum 35 def -/fname () def -/fdir () def -/ftail () def -/user_header_p false def -%%EndPageSetup -5 723 M -(Internet-Draft SSH File Transfer Protocol October 2002) s -5 690 M -(Full Copyright Statement) s -5 668 M -( Copyright \(C\) The Internet Society \(2002\). All Rights Reserved.) s -5 646 M -( This document and translations of it may be copied and furnished to) s -5 635 M -( others, and derivative works that comment on or otherwise explain it) s -5 624 M -( or assist in its implementation may be prepared, copied, published) s -5 613 M -( and distributed, in whole or in part, without restriction of any) s -5 602 M -( kind, provided that the above copyright notice and this paragraph are) s -5 591 M -( included on all such copies and derivative works. However, this) s -5 580 M -( document itself may not be modified in any way, such as by removing) s -5 569 M -( the copyright notice or references to the Internet Society or other) s -5 558 M -( Internet organizations, except as needed for the purpose of) s -5 547 M -( developing Internet standards in which case the procedures for) s -5 536 M -( copyrights defined in the Internet Standards process must be) s -5 525 M -( followed, or as required to translate it into languages other than) s -5 514 M -( English.) s -5 492 M -( The limited permissions granted above are perpetual and will not be) s -5 481 M -( revoked by the Internet Society or its successors or assigns.) s -5 459 M -( This document and the information contained herein is provided on an) s -5 448 M -( "AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING) s -5 437 M -( TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING) s -5 426 M -( BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION) s -5 415 M -( HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF) s -5 404 M -( MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.) s -5 382 M -(Acknowledgement) s -5 360 M -( Funding for the RFC Editor function is currently provided by the) s -5 349 M -( Internet Society.) s -5 129 M -(Galbraith, et al. Expires April 16, 2003 [Page 35]) s -_R -S -PStoPSsaved restore -userdict/PStoPSsaved save put -PStoPSmatrix setmatrix -595.000000 421.271378 translate -90 rotate -0.706651 dup scale -userdict/PStoPSmatrix matrix currentmatrix put -userdict/PStoPSclip{0 0 moveto - 595.000000 0 rlineto 0 842.000000 rlineto -595.000000 0 rlineto - closepath}put initclip -PStoPSxform concat -%%BeginPageSetup -_S -75 0 translate -/pagenum 36 def -/fname () def -/fdir () def -/ftail () def -/user_header_p false def -%%EndPageSetup -_R -S -PStoPSsaved restore -%%Trailer -%%Pages: 36 -%%DocumentNeededResources: font Courier-Bold Courier -%%EOF diff --git a/lib/ssh/doc/standard/draft-ietf-secsh-filexfer-03.txt b/lib/ssh/doc/standard/draft-ietf-secsh-filexfer-03.txt deleted file mode 100644 index 83960ae976..0000000000 --- a/lib/ssh/doc/standard/draft-ietf-secsh-filexfer-03.txt +++ /dev/null @@ -1,1962 +0,0 @@ - - - -Secure Shell Working Group J. Galbraith -Internet-Draft VanDyke Software -Expires: April 16, 2003 T. Ylonen - S. Lehtinen - SSH Communications Security Corp - October 16, 2002 - - - SSH File Transfer Protocol - draft-ietf-secsh-filexfer-03.txt - -Status of this Memo - - This document is an Internet-Draft and is in full conformance with - all provisions of Section 10 of RFC2026. - - Internet-Drafts are working documents of the Internet Engineering - Task Force (IETF), its areas, and its working groups. Note that - other groups may also distribute working documents as Internet- - Drafts. - - Internet-Drafts are draft documents valid for a maximum of six months - and may be updated, replaced, or obsoleted by other documents at any - time. It is inappropriate to use Internet-Drafts as reference - material or to cite them other than as "work in progress." - - The list of current Internet-Drafts can be accessed at http:// - www.ietf.org/ietf/1id-abstracts.txt. - - The list of Internet-Draft Shadow Directories can be accessed at - http://www.ietf.org/shadow.html. - - This Internet-Draft will expire on April 16, 2003. - -Copyright Notice - - Copyright (C) The Internet Society (2002). All Rights Reserved. - -Abstract - - The SSH File Transfer Protocol provides secure file transfer - functionality over any reliable data stream. It is the standard file - transfer protocol for use with the SSH2 protocol. This document - describes the file transfer protocol and its interface to the SSH2 - protocol suite. - - - - - - - -Galbraith, et al. Expires April 16, 2003 [Page 1] - -Internet-Draft SSH File Transfer Protocol October 2002 - - -Table of Contents - - 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . 3 - 2. Use with the SSH Connection Protocol . . . . . . . . . . . 4 - 3. General Packet Format . . . . . . . . . . . . . . . . . . 5 - 4. Protocol Initialization . . . . . . . . . . . . . . . . . 7 - 4.1 Client Initialization . . . . . . . . . . . . . . . . . . 7 - 4.2 Server Initialization . . . . . . . . . . . . . . . . . . 7 - 4.3 Determining Server Newline Convention . . . . . . . . . . 8 - 5. File Attributes . . . . . . . . . . . . . . . . . . . . . 9 - 5.1 Flags . . . . . . . . . . . . . . . . . . . . . . . . . . 9 - 5.2 Type . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 - 5.3 Size . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 - 5.4 Owner and Group . . . . . . . . . . . . . . . . . . . . . 10 - 5.5 Permissions . . . . . . . . . . . . . . . . . . . . . . . 11 - 5.6 Times . . . . . . . . . . . . . . . . . . . . . . . . . . 11 - 5.7 ACL . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 - 5.8 Extended attributes . . . . . . . . . . . . . . . . . . . 12 - 6. Requests From the Client to the Server . . . . . . . . . . 13 - 6.1 Request Synchronization and Reordering . . . . . . . . . . 13 - 6.2 File Names . . . . . . . . . . . . . . . . . . . . . . . . 14 - 6.3 Opening, Creating, and Closing Files . . . . . . . . . . . 14 - 6.4 Reading and Writing . . . . . . . . . . . . . . . . . . . 17 - 6.5 Removing and Renaming Files . . . . . . . . . . . . . . . 18 - 6.6 Creating and Deleting Directories . . . . . . . . . . . . 19 - 6.7 Scanning Directories . . . . . . . . . . . . . . . . . . . 19 - 6.8 Retrieving File Attributes . . . . . . . . . . . . . . . . 20 - 6.9 Setting File Attributes . . . . . . . . . . . . . . . . . 21 - 6.10 Dealing with Symbolic links . . . . . . . . . . . . . . . 22 - 6.11 Canonicalizing the Server-Side Path Name . . . . . . . . . 23 - 6.11.1 Best practice for dealing with paths . . . . . . . . . . . 23 - 7. Responses from the Server to the Client . . . . . . . . . 24 - 8. Vendor-Specific Extensions . . . . . . . . . . . . . . . . 28 - 9. Security Considerations . . . . . . . . . . . . . . . . . 29 - 10. Changes from previous protocol versions . . . . . . . . . 30 - 10.1 Changes between versions 4 and 3 . . . . . . . . . . . . . 30 - 10.2 Changes between versions 3 and 2 . . . . . . . . . . . . . 31 - 10.3 Changes between versions 2 and 1 . . . . . . . . . . . . . 31 - 10.4 Changes between versions 1 and 0 . . . . . . . . . . . . . 31 - 11. Trademark Issues . . . . . . . . . . . . . . . . . . . . . 32 - References . . . . . . . . . . . . . . . . . . . . . . . . 33 - Authors' Addresses . . . . . . . . . . . . . . . . . . . . 33 - Full Copyright Statement . . . . . . . . . . . . . . . . . 35 - - - - - - - - -Galbraith, et al. Expires April 16, 2003 [Page 2] - -Internet-Draft SSH File Transfer Protocol October 2002 - - -1. Introduction - - This protocol provides secure file transfer (and more generally file - system access) functionality over a reliable data stream, such as a - channel in the SSH2 protocol [5]. - - This protocol is designed so that it could be used to implement a - secure remote file system service, as well as a secure file transfer - service. - - This protocol assumes that it runs over a secure channel, and that - the server has already authenticated the user at the client end, and - that the identity of the client user is externally available to the - server implementation. - - In general, this protocol follows a simple request-response model. - Each request and response contains a sequence number and multiple - requests may be pending simultaneously. There are a relatively large - number of different request messages, but a small number of possible - response messages. Each request has one or more response messages - that may be returned in result (e.g., a read either returns data or - reports error status). - - The packet format descriptions in this specification follow the - notation presented in the secsh architecture draft. [5] - - Even though this protocol is described in the context of the SSH2 - protocol, this protocol is general and independent of the rest of the - SSH2 protocol suite. It could be used in a number of different - applications, such as secure file transfer over TLS RFC 2246 [1] and - transfer of management information in VPN applications. - - - - - - - - - - - - - - - - - - - - -Galbraith, et al. Expires April 16, 2003 [Page 3] - -Internet-Draft SSH File Transfer Protocol October 2002 - - -2. Use with the SSH Connection Protocol - - When used with the SSH2 Protocol suite, this protocol is intended to - be used from the SSH Connection Protocol [7] as a subsystem, as - described in section ``Starting a Shell or a Command''. The - subsystem name used with this protocol is "sftp". - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -Galbraith, et al. Expires April 16, 2003 [Page 4] - -Internet-Draft SSH File Transfer Protocol October 2002 - - -3. General Packet Format - - All packets transmitted over the secure connection are of the - following format: - - uint32 length - byte type - byte[length - 1] data payload - - That is, they are just data preceded by 32-bit length and 8-bit type - fields. The `length' is the length of the data area, and does not - include the `length' field itself. The format and interpretation of - the data area depends on the packet type. - - All packet descriptions below only specify the packet type and the - data that goes into the data field. Thus, they should be prefixed by - the `length' and `type' fields. - - The maximum size of a packet is in practice determined by the client - (the maximum size of read or write requests that it sends, plus a few - bytes of packet overhead). All servers SHOULD support packets of at - least 34000 bytes (where the packet size refers to the full length, - including the header above). This should allow for reads and writes - of at most 32768 bytes. - - There is no limit on the number of outstanding (non-acknowledged) - requests that the client may send to the server. In practice this is - limited by the buffering available on the data stream and the queuing - performed by the server. If the server's queues are full, it should - not read any more data from the stream, and flow control will prevent - the client from sending more requests. Note, however, that while - there is no restriction on the protocol level, the client's API may - provide a limit in order to prevent infinite queuing of outgoing - requests at the client. - - The following values are defined for packet types. - - - - - - - - - - - - - - - -Galbraith, et al. Expires April 16, 2003 [Page 5] - -Internet-Draft SSH File Transfer Protocol October 2002 - - - #define SSH_FXP_INIT 1 - #define SSH_FXP_VERSION 2 - #define SSH_FXP_OPEN 3 - #define SSH_FXP_CLOSE 4 - #define SSH_FXP_READ 5 - #define SSH_FXP_WRITE 6 - #define SSH_FXP_LSTAT 7 - #define SSH_FXP_FSTAT 8 - #define SSH_FXP_SETSTAT 9 - #define SSH_FXP_FSETSTAT 10 - #define SSH_FXP_OPENDIR 11 - #define SSH_FXP_READDIR 12 - #define SSH_FXP_REMOVE 13 - #define SSH_FXP_MKDIR 14 - #define SSH_FXP_RMDIR 15 - #define SSH_FXP_REALPATH 16 - #define SSH_FXP_STAT 17 - #define SSH_FXP_RENAME 18 - #define SSH_FXP_READLINK 19 - #define SSH_FXP_SYMLINK 20 - - #define SSH_FXP_STATUS 101 - #define SSH_FXP_HANDLE 102 - #define SSH_FXP_DATA 103 - #define SSH_FXP_NAME 104 - #define SSH_FXP_ATTRS 105 - - #define SSH_FXP_EXTENDED 200 - #define SSH_FXP_EXTENDED_REPLY 201 - - RESERVED_FOR_EXTENSIONS 210-255 - - Additional packet types should only be defined if the protocol - version number (see Section ``Protocol Initialization'') is - incremented, and their use MUST be negotiated using the version - number. However, the SSH_FXP_EXTENDED and SSH_FXP_EXTENDED_REPLY - packets can be used to implement vendor-specific extensions. See - Section ``Vendor-Specific-Extensions'' for more details. - - - - - - - - - - - - - -Galbraith, et al. Expires April 16, 2003 [Page 6] - -Internet-Draft SSH File Transfer Protocol October 2002 - - -4. Protocol Initialization - - When the file transfer protocol starts, the client first sends a - SSH_FXP_INIT (including its version number) packet to the server. - The server responds with a SSH_FXP_VERSION packet, supplying the - lowest of its own and the client's version number. Both parties - should from then on adhere to particular version of the protocol. - - The version number of the protocol specified in this document is 4. - The version number should be incremented for each incompatible - revision of this protocol. - -4.1 Client Initialization - - The SSH_FXP_INIT packet (from client to server) has the following - data: - - uint32 version - - Version 3 of this protocol allowed clients to include extensions in - the SSH_FXP_INIT packet; however, this can cause interoperability - problems with version 1 and version 2 servers because the client must - send this packet before knowing the servers version. - - In this version of the protocol, clients MUST use the - SSH_FXP_EXTENDED packet to send extensions to the server after - version exchange has completed. Clients MUST NOT include extensions - in the version packet. This will prevent interoperability problems - with older servers - -4.2 Server Initialization - - The SSH_FXP_VERSION packet (from server to client) has the following - data: - - uint32 version - <extension data> - - 'version' is the lower of the protocol version supported by the - server and the version number received from the client. - - The extension data may be empty, or may be a sequence of - - string extension_name - string extension_data - - pairs (both strings MUST always be present if one is, but the - `extension_data' string may be of zero length). If present, these - - - -Galbraith, et al. Expires April 16, 2003 [Page 7] - -Internet-Draft SSH File Transfer Protocol October 2002 - - - strings indicate extensions to the baseline protocol. The - `extension_name' field(s) identify the name of the extension. The - name should be of the form "name@domain", where the domain is the DNS - domain name of the organization defining the extension. Additional - names that are not of this format may be defined later by the IETF. - Implementations MUST silently ignore any extensions whose name they - do not recognize. - -4.3 Determining Server Newline Convention - - In order to correctly process text files in a cross platform - compatible way, the newline convention must be converted from that of - the server to that of the client, or, during an upload, from that of - the client to that of the server. - - Versions 3 and prior of this protocol made no provisions for - processing text files. Many clients implemented some sort of - conversion algorithm, but without either a 'canonical' on the wire - format or knowledge of the servers newline convention, correct - conversion was not always possible. - - Starting with Version 4, the SSH_FXF_TEXT file open flag (Section - 6.3) makes it possible to request that the server translate a file to - a 'canonical' on the wire format. This format uses \r\n as the line - separator. - - Servers for systems using multiple newline characters (for example, - Mac OS X or VMS) or systems using counted records, MUST translate to - the canonical form. - - However, to ease the burden of implementation on servers that use a - single, simple separator sequence, the following extension allows the - canonical format to be changed. - - string "newline" - string new-canonical-separator (usually "\r" or "\n" or "\r\n") - - All clients MUST support this extension. - - When processing text files, clients SHOULD NOT translate any - character or sequence that is not an exact match of the servers - newline separator. - - In particular, if the newline sequence being used is the canonical - "\r\n" sequence, a lone \r or a lone \n SHOULD be written through - without change. - - - - - -Galbraith, et al. Expires April 16, 2003 [Page 8] - -Internet-Draft SSH File Transfer Protocol October 2002 - - -5. File Attributes - - A new compound data type is defined for encoding file attributes. - The same encoding is used both when returning file attributes from - the server and when sending file attributes to the server. When - sending it to the server, the flags field specifies which attributes - are included, and the server will use default values for the - remaining attributes (or will not modify the values of remaining - attributes). When receiving attributes from the server, the flags - specify which attributes are included in the returned data. The - server normally returns all attributes it knows about. - - uint32 flags - byte type always present - uint64 size present only if flag SSH_FILEXFER_ATTR_SIZE - string owner present only if flag SSH_FILEXFER_ATTR_OWNERGROUP - string group present only if flag SSH_FILEXFER_ATTR_OWNERGROUP - uint32 permissions present only if flag SSH_FILEXFER_ATTR_PERMISSIONS - uint32 atime present only if flag SSH_FILEXFER_ATTR_ACCESSTIME - uint32 createtime present only if flag SSH_FILEXFER_ATTR_CREATETIME - uint32 mtime present only if flag SSH_FILEXFER_ATTR_MODIFYTIME - string acl present only if flag SSH_FILEXFER_ATTR_ACL - uint32 extended_count present only if flag SSH_FILEXFER_ATTR_EXTENDED - string extended_type - string extended_data - ... more extended data (extended_type - extended_data pairs), - so that number of pairs equals extended_count - - -5.1 Flags - - The `flags' specify which of the fields are present. Those fields - for which the corresponding flag is not set are not present (not - included in the packet). New flags can only be added by incrementing - the protocol version number (or by using the extension mechanism - described below). - - The flags bits are defined to have the following values: - - #define SSH_FILEXFER_ATTR_SIZE 0x00000001 - #define SSH_FILEXFER_ATTR_PERMISSIONS 0x00000004 - #define SSH_FILEXFER_ATTR_ACCESSTIME 0x00000008 - #define SSH_FILEXFER_ATTR_CREATETIME 0x00000010 - #define SSH_FILEXFER_ATTR_MODIFYTIME 0x00000020 - #define SSH_FILEXFER_ATTR_ACL 0x00000040 - #define SSH_FILEXFER_ATTR_OWNERGROUP 0x00000080 - #define SSH_FILEXFER_ATTR_EXTENDED 0x80000000 - - - - -Galbraith, et al. Expires April 16, 2003 [Page 9] - -Internet-Draft SSH File Transfer Protocol October 2002 - - - In previous versions of this protocol flags value 0x00000002 was - SSH_FILEXFER_ATTR_UIDGID. This value is now unused, and OWNERGROUP - was given a new value in order to ease implementation burden. - 0x00000002 MUST NOT appear in the mask. Some future version of this - protocol may reuse flag 0x00000002. - -5.2 Type - - The type field is always present. The following types are defined: - - #define SSH_FILEXFER_TYPE_REGULAR 1 - #define SSH_FILEXFER_TYPE_DIRECTORY 2 - #define SSH_FILEXFER_TYPE_SYMLINK 3 - #define SSH_FILEXFER_TYPE_SPECIAL 4 - #define SSH_FILEXFER_TYPE_UNKNOWN 5 - - On a POSIX system, these values would be derived from the permission - field. - -5.3 Size - - The `size' field specifies the size of the file on disk, in bytes. - If it is present during file creation, it should be considered a hint - as to the files eventual size. - - Files opened with the SSH_FXF_TEXT flag may have a size that is - greater or less than the value of the size field. - -5.4 Owner and Group - - The `owner' and `group' fields are represented as UTF-8 strings; this - is the form used by NFS v4. See NFS version 4 Protocol. [3] The - following text is selected quotations from section 5.6. - - To avoid a representation that is tied to a particular underlying - implementation at the client or server, the use of UTF-8 strings has - been chosen. The string should be of the form user@dns_domain". - This will allow for a client and server that do not use the same - local representation the ability to translate to a common syntax that - can be interpreted by both. In the case where there is no - translation available to the client or server, the attribute value - must be constructed without the "@". Therefore, the absence of the @ - from the owner or owner_group attribute signifies that no translation - was available and the receiver of the attribute should not place any - special meaning with the attribute value. Even though the attribute - value can not be translated, it may still be useful. In the case of - a client, the attribute string may be used for local display of - ownership. - - - -Galbraith, et al. Expires April 16, 2003 [Page 10] - -Internet-Draft SSH File Transfer Protocol October 2002 - - -5.5 Permissions - - The `permissions' field contains a bit mask of file permissions as - defined by POSIX [1]. - -5.6 Times - - The 'atime', 'createtime', and 'mtime' contain the access, creation, - and modification times of the files, respectively. They are - represented as seconds from Jan 1, 1970 in UTC. - -5.7 ACL - - The 'ACL' field contains an ACL similar to that defined in section - 5.9 of NFS version 4 Protocol [3]. - - uint32 ace-count - - repeated ace-count time: - uint32 ace-type - uint32 ace-flag - uint32 ace-mask - string who [UTF-8] - - ace-type is one of the following four values (taken from NFS Version - 4 Protocol [3]: - - const ACE4_ACCESS_ALLOWED_ACE_TYPE = 0x00000000; - const ACE4_ACCESS_DENIED_ACE_TYPE = 0x00000001; - const ACE4_SYSTEM_AUDIT_ACE_TYPE = 0x00000002; - const ACE4_SYSTEM_ALARM_ACE_TYPE = 0x00000003; - - ace-flag is a combination of the following flag values. See NFS - Version 4 Protocol [3] section 5.9.2: - - const ACE4_FILE_INHERIT_ACE = 0x00000001; - const ACE4_DIRECTORY_INHERIT_ACE = 0x00000002; - const ACE4_NO_PROPAGATE_INHERIT_ACE = 0x00000004; - const ACE4_INHERIT_ONLY_ACE = 0x00000008; - const ACE4_SUCCESSFUL_ACCESS_ACE_FLAG = 0x00000010; - const ACE4_FAILED_ACCESS_ACE_FLAG = 0x00000020; - const ACE4_IDENTIFIER_GROUP = 0x00000040; - - ace-mask is any combination of the following flags (taken from NFS - Version 4 Protocol [3] section 5.9.3: - - - - - - -Galbraith, et al. Expires April 16, 2003 [Page 11] - -Internet-Draft SSH File Transfer Protocol October 2002 - - - const ACE4_READ_DATA = 0x00000001; - const ACE4_LIST_DIRECTORY = 0x00000001; - const ACE4_WRITE_DATA = 0x00000002; - const ACE4_ADD_FILE = 0x00000002; - const ACE4_APPEND_DATA = 0x00000004; - const ACE4_ADD_SUBDIRECTORY = 0x00000004; - const ACE4_READ_NAMED_ATTRS = 0x00000008; - const ACE4_WRITE_NAMED_ATTRS = 0x00000010; - const ACE4_EXECUTE = 0x00000020; - const ACE4_DELETE_CHILD = 0x00000040; - const ACE4_READ_ATTRIBUTES = 0x00000080; - const ACE4_WRITE_ATTRIBUTES = 0x00000100; - const ACE4_DELETE = 0x00010000; - const ACE4_READ_ACL = 0x00020000; - const ACE4_WRITE_ACL = 0x00040000; - const ACE4_WRITE_OWNER = 0x00080000; - const ACE4_SYNCHRONIZE = 0x00100000; - - who is a UTF-8 string of the form described in 'Owner and Group' - (Section 5.4) - -5.8 Extended attributes - - The SSH_FILEXFER_ATTR_EXTENDED flag provides a general extension - mechanism for vendor-specific extensions. If the flag is specified, - then the `extended_count' field is present. It specifies the number - of extended_type-extended_data pairs that follow. Each of these - pairs specifies an extended attribute. For each of the attributes, - the extended_type field should be a string of the format - "name@domain", where "domain" is a valid, registered domain name and - "name" identifies the method. The IETF may later standardize certain - names that deviate from this format (e.g., that do not contain the - "@" sign). The interpretation of `extended_data' depends on the - type. Implementations SHOULD ignore extended data fields that they - do not understand. - - Additional fields can be added to the attributes by either defining - additional bits to the flags field to indicate their presence, or by - defining extended attributes for them. The extended attributes - mechanism is recommended for most purposes; additional flags bits - should only be defined by an IETF standards action that also - increments the protocol version number. The use of such new fields - MUST be negotiated by the version number in the protocol exchange. - It is a protocol error if a packet with unsupported protocol bits is - received. - - - - - - -Galbraith, et al. Expires April 16, 2003 [Page 12] - -Internet-Draft SSH File Transfer Protocol October 2002 - - -6. Requests From the Client to the Server - - Requests from the client to the server represent the various file - system operations. Each request begins with an `id' field, which is - a 32-bit identifier identifying the request (selected by the client). - The same identifier will be returned in the response to the request. - One possible implementation is a monotonically increasing request - sequence number (modulo 2^32). - - Many operations in the protocol operate on open files. The - SSH_FXP_OPEN request can return a file handle (which is an opaque - variable-length string) which may be used to access the file later - (e.g. in a read operation). The client MUST NOT send requests the - server with bogus or closed handles. However, the server MUST - perform adequate checks on the handle in order to avoid security - risks due to fabricated handles. - - This design allows either stateful and stateless server - implementation, as well as an implementation which caches state - between requests but may also flush it. The contents of the file - handle string are entirely up to the server and its design. The - client should not modify or attempt to interpret the file handle - strings. - - The file handle strings MUST NOT be longer than 256 bytes. - -6.1 Request Synchronization and Reordering - - The protocol and implementations MUST process requests relating to - the same file in the order in which they are received. In other - words, if an application submits multiple requests to the server, the - results in the responses will be the same as if it had sent the - requests one at a time and waited for the response in each case. For - example, the server may process non-overlapping read/write requests - to the same file in parallel, but overlapping reads and writes cannot - be reordered or parallelized. However, there are no ordering - restrictions on the server for processing requests from two different - file transfer connections. The server may interleave and parallelize - them at will. - - There are no restrictions on the order in which responses to - outstanding requests are delivered to the client, except that the - server must ensure fairness in the sense that processing of no - request will be indefinitely delayed even if the client is sending - other requests so that there are multiple outstanding requests all - the time. - - - - - -Galbraith, et al. Expires April 16, 2003 [Page 13] - -Internet-Draft SSH File Transfer Protocol October 2002 - - -6.2 File Names - - This protocol represents file names as strings. File names are - assumed to use the slash ('/') character as a directory separator. - - File names starting with a slash are "absolute", and are relative to - the root of the file system. Names starting with any other character - are relative to the user's default directory (home directory). Note - that identifying the user is assumed to take place outside of this - protocol. - - Servers SHOULD interpret a path name component ".." as referring to - the parent directory, and "." as referring to the current directory. - If the server implementation limits access to certain parts of the - file system, it must be extra careful in parsing file names when - enforcing such restrictions. There have been numerous reported - security bugs where a ".." in a path name has allowed access outside - the intended area. - - An empty path name is valid, and it refers to the user's default - directory (usually the user's home directory). - - Otherwise, no syntax is defined for file names by this specification. - Clients should not make any other assumptions; however, they can - splice path name components returned by SSH_FXP_READDIR together - using a slash ('/') as the separator, and that will work as expected. - - In order to comply with IETF Policy on Character Sets and Languages - [2], all filenames are to be encoded in UTF-8. The shortest valid - UTF-8 encoding of the UNICODE data MUST be used. The server is - responsible for converting the UNICODE data to whatever canonical - form it requires. - - For example, if the server requires that precomposed characters - always be used, the server MUST NOT assume the filename as sent by - the client has this attribute, but must do this normalization itself. - - It is understood that the lack of well-defined semantics for file - names may cause interoperability problems between clients and servers - using radically different operating systems. However, this approach - is known to work acceptably with most systems, and alternative - approaches that e.g. treat file names as sequences of structured - components are quite complicated. - -6.3 Opening, Creating, and Closing Files - - Files are opened and created using the SSH_FXP_OPEN message, whose - data part is as follows: - - - -Galbraith, et al. Expires April 16, 2003 [Page 14] - -Internet-Draft SSH File Transfer Protocol October 2002 - - - uint32 id - string filename [UTF-8] - uint32 pflags - ATTRS attrs - - The `id' field is the request identifier as for all requests. - - The `filename' field specifies the file name. See Section ``File - Names'' for more information. - - The `pflags' field is a bitmask. The following bits have been - defined. - - #define SSH_FXF_READ 0x00000001 - #define SSH_FXF_WRITE 0x00000002 - #define SSH_FXF_APPEND 0x00000004 - #define SSH_FXF_CREAT 0x00000008 - #define SSH_FXF_TRUNC 0x00000010 - #define SSH_FXF_EXCL 0x00000020 - #define SSH_FXF_TEXT 0x00000040 - - These have the following meanings: - - SSH_FXF_READ - Open the file for reading. - - SSH_FXF_WRITE - Open the file for writing. If both this and SSH_FXF_READ are - specified, the file is opened for both reading and writing. - - SSH_FXF_APPEND - Force all writes to append data at the end of the file. The - offset parameter to write will be ignored. - - SSH_FXF_CREAT - If this flag is specified, then a new file will be created if one - does not already exist (if O_TRUNC is specified, the new file will - be truncated to zero length if it previously exists). - - SSH_FXF_TRUNC - Forces an existing file with the same name to be truncated to zero - length when creating a file by specifying SSH_FXF_CREAT. - SSH_FXF_CREAT MUST also be specified if this flag is used. - - SSH_FXF_EXCL - Causes the request to fail if the named file already exists. - SSH_FXF_CREAT MUST also be specified if this flag is used. - - - - -Galbraith, et al. Expires April 16, 2003 [Page 15] - -Internet-Draft SSH File Transfer Protocol October 2002 - - - SSH_FXF_TEXT - Indicates that the server should treat the file as text and - convert it to the canonical newline convention in use. (See - Determining Server Newline Convention. (Section 4.3) - - When a file is opened with the FXF_TEXT flag, the offset field in - both the read and write function are ignored. - - Servers MUST correctly process multiple parallel reads and writes - correctly in this mode. Naturally, it is permissible for them to - do this by serializing the requests. It would not be possible for - a client to reliably detect a server that does not implement - parallel writes in time to prevent damage. - - Clients SHOULD use the SSH_FXF_APPEND flag to append data to a - text file rather then using write with a calculated offset. - - To support seeks on text file the following SSH_FXP_EXTENDED - packet is defined. - - - - string "text-seek" - string file-handle - uint64 line-number - - line-number is the index of the line number to seek to, where byte - 0 in the file is line number 0, and the byte directly following - the first newline sequence in the file is line number 1 and so on. - - The response to a "text-seek" request is an SSH_FXP_STATUS - message. - - An attempt to seek past the end-of-file should result in a - SSH_FX_EOF status. - - Servers SHOULD support at least one "text-seek" in order to - support resume. However, a client MUST be prepared to receive - SSH_FX_OP_UNSUPPORTED when attempting a "text-seek" operation. - The client can then try a fall-back strategy, if it has one. - - Clients MUST be prepared to handle SSH_FX_OP_UNSUPPORTED returned - for read or write operations that are not sequential. - - The `attrs' field specifies the initial attributes for the file. - Default values will be used for those attributes that are not - specified. See Section ``File Attributes'' for more information. - - - - -Galbraith, et al. Expires April 16, 2003 [Page 16] - -Internet-Draft SSH File Transfer Protocol October 2002 - - - The response to this message will be either SSH_FXP_HANDLE (if the - operation is successful) or SSH_FXP_STATUS (if the operation fails). - - A file is closed by using the SSH_FXP_CLOSE request. Its data field - has the following format: - - uint32 id - string handle - - where `id' is the request identifier, and `handle' is a handle - previously returned in the response to SSH_FXP_OPEN or - SSH_FXP_OPENDIR. The handle becomes invalid immediately after this - request has been sent. - - The response to this request will be a SSH_FXP_STATUS message. One - should note that on some server platforms even a close can fail. - This can happen e.g. if the server operating system caches writes, - and an error occurs while flushing cached writes during the close. - -6.4 Reading and Writing - - Once a file has been opened, it can be read using the SSH_FXP_READ - message, which has the following format: - - uint32 id - string handle - uint64 offset - uint32 len - - where `id' is the request identifier, `handle' is an open file handle - returned by SSH_FXP_OPEN, `offset' is the offset (in bytes) relative - to the beginning of the file from where to start reading, and `len' - is the maximum number of bytes to read. - - In response to this request, the server will read as many bytes as it - can from the file (up to `len'), and return them in a SSH_FXP_DATA - message. If an error occurs or EOF is encountered before reading any - data, the server will respond with SSH_FXP_STATUS. For normal disk - files, it is guaranteed that this will read the specified number of - bytes, or up to end of file. For e.g. device files this may return - fewer bytes than requested. - - Writing to a file is achieved using the SSH_FXP_WRITE message, which - has the following format: - - - - - - - -Galbraith, et al. Expires April 16, 2003 [Page 17] - -Internet-Draft SSH File Transfer Protocol October 2002 - - - uint32 id - string handle - uint64 offset - string data - - where `id' is a request identifier, `handle' is a file handle - returned by SSH_FXP_OPEN, `offset' is the offset (in bytes) from the - beginning of the file where to start writing, and `data' is the data - to be written. - - The write will extend the file if writing beyond the end of the file. - It is legal to write way beyond the end of the file; the semantics - are to write zeroes from the end of the file to the specified offset - and then the data. On most operating systems, such writes do not - allocate disk space but instead leave "holes" in the file. - - The server responds to a write request with a SSH_FXP_STATUS message. - -6.5 Removing and Renaming Files - - Files can be removed using the SSH_FXP_REMOVE message. It has the - following format: - - uint32 id - string filename [UTF-8] - - where `id' is the request identifier and `filename' is the name of - the file to be removed. See Section ``File Names'' for more - information. This request cannot be used to remove directories. - - The server will respond to this request with a SSH_FXP_STATUS - message. - - Files (and directories) can be renamed using the SSH_FXP_RENAME - message. Its data is as follows: - - uint32 id - string oldpath [UTF-8] - string newpath [UTF-8] - - where `id' is the request identifier, `oldpath' is the name of an - existing file or directory, and `newpath' is the new name for the - file or directory. It is an error if there already exists a file - with the name specified by newpath. The server may also fail rename - requests in other situations, for example if `oldpath' and `newpath' - point to different file systems on the server. - - The server will respond to this request with a SSH_FXP_STATUS - - - -Galbraith, et al. Expires April 16, 2003 [Page 18] - -Internet-Draft SSH File Transfer Protocol October 2002 - - - message. - -6.6 Creating and Deleting Directories - - New directories can be created using the SSH_FXP_MKDIR request. It - has the following format: - - uint32 id - string path [UTF-8] - ATTRS attrs - - where `id' is the request identifier. - - `path' specifies the directory to be created. See Section ``File - Names'' for more information on file names. - - `attrs' specifies the attributes that should be applied to it upon - creation. Attributes are discussed in more detail in Section ``File - Attributes''. - - The server will respond to this request with a SSH_FXP_STATUS - message. If a file or directory with the specified path already - exists, an error will be returned. - - Directories can be removed using the SSH_FXP_RMDIR request, which has - the following format: - - uint32 id - string path [UTF-8] - - where `id' is the request identifier, and `path' specifies the - directory to be removed. See Section ``File Names'' for more - information on file names. - - The server responds to this request with a SSH_FXP_STATUS message. - Errors may be returned from this operation for various reasons, - including, but not limited to, the path does not exist, the path does - not refer to a directory object, the directory is not empty, or the - user has insufficient access or permission to perform the requested - operation. - -6.7 Scanning Directories - - The files in a directory can be listed using the SSH_FXP_OPENDIR and - SSH_FXP_READDIR requests. Each SSH_FXP_READDIR request returns one - or more file names with full file attributes for each file. The - client should call SSH_FXP_READDIR repeatedly until it has found the - file it is looking for or until the server responds with a - - - -Galbraith, et al. Expires April 16, 2003 [Page 19] - -Internet-Draft SSH File Transfer Protocol October 2002 - - - SSH_FXP_STATUS message indicating an error (normally SSH_FX_EOF if - there are no more files in the directory). The client should then - close the handle using the SSH_FXP_CLOSE request. - - The SSH_FXP_OPENDIR opens a directory for reading. It has the - following format: - - uint32 id - string path [UTF-8] - - where `id' is the request identifier and `path' is the path name of - the directory to be listed (without any trailing slash). See Section - ``File Names'' for more information on file names. This will return - an error if the path does not specify a directory or if the directory - is not readable. The server will respond to this request with either - a SSH_FXP_HANDLE or a SSH_FXP_STATUS message. - - Once the directory has been successfully opened, files (and - directories) contained in it can be listed using SSH_FXP_READDIR - requests. These are of the format - - uint32 id - string handle - - where `id' is the request identifier, and `handle' is a handle - returned by SSH_FXP_OPENDIR. (It is a protocol error to attempt to - use an ordinary file handle returned by SSH_FXP_OPEN.) - - The server responds to this request with either a SSH_FXP_NAME or a - SSH_FXP_STATUS message. One or more names may be returned at a time. - Full status information is returned for each name in order to speed - up typical directory listings. - - If there are no more names available to be read, the server MUST - respond with a SSH_FXP_STATUS message with error code of SSH_FX_EOF. - - When the client no longer wishes to read more names from the - directory, it SHOULD call SSH_FXP_CLOSE for the handle. The handle - should be closed regardless of whether an error has occurred or not. - -6.8 Retrieving File Attributes - - Very often, file attributes are automatically returned by - SSH_FXP_READDIR. However, sometimes there is need to specifically - retrieve the attributes for a named file. This can be done using the - SSH_FXP_STAT, SSH_FXP_LSTAT and SSH_FXP_FSTAT requests. - - SSH_FXP_STAT and SSH_FXP_LSTAT only differ in that SSH_FXP_STAT - - - -Galbraith, et al. Expires April 16, 2003 [Page 20] - -Internet-Draft SSH File Transfer Protocol October 2002 - - - follows symbolic links on the server, whereas SSH_FXP_LSTAT does not - follow symbolic links. Both have the same format: - - uint32 id - string path [UTF-8] - uint32 flags - - where `id' is the request identifier, and `path' specifies the file - system object for which status is to be returned. The server - responds to this request with either SSH_FXP_ATTRS or SSH_FXP_STATUS. - - The flags field specify the attribute flags in which the client has - particular interest. This is a hint to the server. For example, - because retrieving owner / group and acl information can be an - expensive operation under some operating systems, the server may - choose not to retrieve this information unless the client expresses a - specific interest in it. - - The client has no guarantee the server will provide all the fields - that it has expressed an interest in. - - SSH_FXP_FSTAT differs from the others in that it returns status - information for an open file (identified by the file handle). Its - format is as follows: - - uint32 id - string handle - uint32 flags - - where `id' is the request identifier and `handle' is a file handle - returned by SSH_FXP_OPEN. The server responds to this request with - SSH_FXP_ATTRS or SSH_FXP_STATUS. - -6.9 Setting File Attributes - - File attributes may be modified using the SSH_FXP_SETSTAT and - SSH_FXP_FSETSTAT requests. These requests are used for operations - such as changing the ownership, permissions or access times, as well - as for truncating a file. - - The SSH_FXP_SETSTAT request is of the following format: - - uint32 id - string path [UTF-8] - ATTRS attrs - - where `id' is the request identifier, `path' specifies the file - system object (e.g. file or directory) whose attributes are to be - - - -Galbraith, et al. Expires April 16, 2003 [Page 21] - -Internet-Draft SSH File Transfer Protocol October 2002 - - - modified, and `attrs' specifies the modifications to be made to its - attributes. Attributes are discussed in more detail in Section - ``File Attributes''. - - An error will be returned if the specified file system object does - not exist or the user does not have sufficient rights to modify the - specified attributes. The server responds to this request with a - SSH_FXP_STATUS message. - - The SSH_FXP_FSETSTAT request modifies the attributes of a file which - is already open. It has the following format: - - uint32 id - string handle - ATTRS attrs - - where `id' is the request identifier, `handle' (MUST be returned by - SSH_FXP_OPEN) identifies the file whose attributes are to be - modified, and `attrs' specifies the modifications to be made to its - attributes. Attributes are discussed in more detail in Section - ``File Attributes''. The server will respond to this request with - SSH_FXP_STATUS. - -6.10 Dealing with Symbolic links - - The SSH_FXP_READLINK request may be used to read the target of a - symbolic link. It would have a data part as follows: - - uint32 id - string path [UTF-8] - - where `id' is the request identifier and `path' specifies the path - name of the symlink to be read. - - The server will respond with a SSH_FXP_NAME packet containing only - one name and a dummy attributes value. The name in the returned - packet contains the target of the link. If an error occurs, the - server may respond with SSH_FXP_STATUS. - - The SSH_FXP_SYMLINK request will create a symbolic link on the - server. It is of the following format - - uint32 id - string linkpath [UTF-8] - string targetpath [UTF-8] - - where `id' is the request identifier, `linkpath' specifies the path - name of the symlink to be created and `targetpath' specifies the - - - -Galbraith, et al. Expires April 16, 2003 [Page 22] - -Internet-Draft SSH File Transfer Protocol October 2002 - - - target of the symlink. The server shall respond with a - SSH_FXP_STATUS indicating either success (SSH_FX_OK) or an error - condition. - -6.11 Canonicalizing the Server-Side Path Name - - The SSH_FXP_REALPATH request can be used to have the server - canonicalize any given path name to an absolute path. This is useful - for converting path names containing ".." components or relative - pathnames without a leading slash into absolute paths. The format of - the request is as follows: - - uint32 id - string path [UTF-8] - - where `id' is the request identifier and `path' specifies the path - name to be canonicalized. The server will respond with a - SSH_FXP_NAME packet containing the name in canonical form and a dummy - attributes value. If an error occurs, the server may also respond - with SSH_FXP_STATUS. - -6.11.1 Best practice for dealing with paths - - The client SHOULD treat the results of SSH_FXP_REALPATH as a - canonical absolute path, even if the path does not appear to be - absolute. A client that use REALPATH(".") and treats the result as - absolute, even if there is no leading slash, will continue to - function correctly, even when talking to a Windows NT or VMS style - system, where absolute paths may not begin with a slash. - - For example, if the client wishes to change directory up, and the - server has returned "c:/x/y/z" from REALPATH, the client SHOULD use - "c:/x/y/z/..". - - As a second example, if the client wishes to open the file "x.txt" in - the current directory, and server has returned "dka100:/x/y/z" as the - canonical path of the directory, the client SHOULD open "dka100:/x/y/ - z/x.txt" - - - - - - - - - - - - - -Galbraith, et al. Expires April 16, 2003 [Page 23] - -Internet-Draft SSH File Transfer Protocol October 2002 - - -7. Responses from the Server to the Client - - The server responds to the client using one of a few response - packets. All requests can return a SSH_FXP_STATUS response upon - failure. When the operation is successful, any of the responses may - be returned (depending on the operation). If no data needs to be - returned to the client, the SSH_FXP_STATUS response with SSH_FX_OK - status is appropriate. Otherwise, the SSH_FXP_HANDLE message is used - to return a file handle (for SSH_FXP_OPEN and SSH_FXP_OPENDIR - requests), SSH_FXP_DATA is used to return data from SSH_FXP_READ, - SSH_FXP_NAME is used to return one or more file names from a - SSH_FXP_READDIR or SSH_FXP_REALPATH request, and SSH_FXP_ATTRS is - used to return file attributes from SSH_FXP_STAT, SSH_FXP_LSTAT, and - SSH_FXP_FSTAT requests. - - Exactly one response will be returned for each request. Each - response packet contains a request identifier which can be used to - match each response with the corresponding request. Note that it is - legal to have several requests outstanding simultaneously, and the - server is allowed to send responses to them in a different order from - the order in which the requests were sent (the result of their - execution, however, is guaranteed to be as if they had been processed - one at a time in the order in which the requests were sent). - - Response packets are of the same general format as request packets. - Each response packet begins with the request identifier. - - The format of the data portion of the SSH_FXP_STATUS response is as - follows: - - uint32 id - uint32 error/status code - string error message (ISO-10646 UTF-8 [RFC-2279]) - string language tag (as defined in [RFC-1766]) - - where `id' is the request identifier, and `error/status code' - indicates the result of the requested operation. The value SSH_FX_OK - indicates success, and all other values indicate failure. - - Currently, the following values are defined (other values may be - defined by future versions of this protocol): - - - - - - - - - - -Galbraith, et al. Expires April 16, 2003 [Page 24] - -Internet-Draft SSH File Transfer Protocol October 2002 - - - #define SSH_FX_OK 0 - #define SSH_FX_EOF 1 - #define SSH_FX_NO_SUCH_FILE 2 - #define SSH_FX_PERMISSION_DENIED 3 - #define SSH_FX_FAILURE 4 - #define SSH_FX_BAD_MESSAGE 5 - #define SSH_FX_NO_CONNECTION 6 - #define SSH_FX_CONNECTION_LOST 7 - #define SSH_FX_OP_UNSUPPORTED 8 - #define SSH_FX_INVALID_HANDLE 9 - #define SSH_FX_NO_SUCH_PATH 10 - #define SSH_FX_FILE_ALREADY_EXISTS 11 - #define SSH_FX_WRITE_PROTECT 12 - - SSH_FX_OK - Indicates successful completion of the operation. - - SSH_FX_EOF - indicates end-of-file condition; for SSH_FX_READ it means that no - more data is available in the file, and for SSH_FX_READDIR it - indicates that no more files are contained in the directory. - - SSH_FX_NO_SUCH_FILE - is returned when a reference is made to a file which does not - exist. - - SSH_FX_PERMISSION_DENIED - is returned when the authenticated user does not have sufficient - permissions to perform the operation. - - SSH_FX_FAILURE - is a generic catch-all error message; it should be returned if an - error occurs for which there is no more specific error code - defined. - - SSH_FX_BAD_MESSAGE - may be returned if a badly formatted packet or protocol - incompatibility is detected. - - SSH_FX_NO_CONNECTION - is a pseudo-error which indicates that the client has no - connection to the server (it can only be generated locally by the - client, and MUST NOT be returned by servers). - - SSH_FX_CONNECTION_LOST - is a pseudo-error which indicates that the connection to the - server has been lost (it can only be generated locally by the - client, and MUST NOT be returned by servers). - - - -Galbraith, et al. Expires April 16, 2003 [Page 25] - -Internet-Draft SSH File Transfer Protocol October 2002 - - - SSH_FX_OP_UNSUPPORTED - indicates that an attempt was made to perform an operation which - is not supported for the server (it may be generated locally by - the client if e.g. the version number exchange indicates that a - required feature is not supported by the server, or it may be - returned by the server if the server does not implement an - operation). - - SSH_FX_INVALID_HANDLE - The handle value was invalid. - - SSH_FX_NO_SUCH_PATH - The file path does not exist or is invalid. - - SSH_FX_FILE_ALREADY_EXISTS - The file already exists. - - SSH_FX_WRITE_PROTECT - The file is on read only media, or the media is write protected. - - The SSH_FXP_HANDLE response has the following format: - - uint32 id - string handle - - where `id' is the request identifier, and `handle' is an arbitrary - string that identifies an open file or directory on the server. The - handle is opaque to the client; the client MUST NOT attempt to - interpret or modify it in any way. The length of the handle string - MUST NOT exceed 256 data bytes. - - The SSH_FXP_DATA response has the following format: - - uint32 id - string data - - where `id' is the request identifier, and `data' is an arbitrary byte - string containing the requested data. The data string may be at most - the number of bytes requested in a SSH_FXP_READ request, but may also - be shorter if end of file is reached or if the read is from something - other than a regular file. - - The SSH_FXP_NAME response has the following format: - - - - - - - - -Galbraith, et al. Expires April 16, 2003 [Page 26] - -Internet-Draft SSH File Transfer Protocol October 2002 - - - uint32 id - uint32 count - repeats count times: - string filename [UTF-8] - ATTRS attrs - - where `id' is the request identifier, `count' is the number of names - returned in this response, and the remaining fields repeat `count' - times (so that all three fields are first included for the first - file, then for the second file, etc). In the repeated part, - `filename' is a file name being returned (for SSH_FXP_READDIR, it - will be a relative name within the directory, without any path - components; for SSH_FXP_REALPATH it will be an absolute path name), - and `attrs' is the attributes of the file as described in Section - ``File Attributes''. - - The SSH_FXP_ATTRS response has the following format: - - uint32 id - ATTRS attrs - - where `id' is the request identifier, and `attrs' is the returned - file attributes as described in Section ``File Attributes''. - - - - - - - - - - - - - - - - - - - - - - - - - - - - -Galbraith, et al. Expires April 16, 2003 [Page 27] - -Internet-Draft SSH File Transfer Protocol October 2002 - - -8. Vendor-Specific Extensions - - The SSH_FXP_EXTENDED request provides a generic extension mechanism - for adding vendor-specific commands. The request has the following - format: - - uint32 id - string extended-request - ... any request-specific data ... - - where `id' is the request identifier, and `extended-request' is a - string of the format "name@domain", where domain is an internet - domain name of the vendor defining the request. The rest of the - request is completely vendor-specific, and servers should only - attempt to interpret it if they recognize the `extended-request' - name. - - The server may respond to such requests using any of the response - packets defined in Section ``Responses from the Server to the - Client''. Additionally, the server may also respond with a - SSH_FXP_EXTENDED_REPLY packet, as defined below. If the server does - not recognize the `extended-request' name, then the server MUST - respond with SSH_FXP_STATUS with error/status set to - SSH_FX_OP_UNSUPPORTED. - - The SSH_FXP_EXTENDED_REPLY packet can be used to carry arbitrary - extension-specific data from the server to the client. It is of the - following format: - - uint32 id - ... any request-specific data ... - - There is a range of packet types reserved for use by extensions. In - order to avoid collision, extensions that turn on the use of - additional packet types should determine those numbers dynamically. - - The suggested way of doing this is have an extension request from the - client to the server that enables the extension; the extension - response from the server to the client would specify the actual type - values to use, in additional to any other data. - - Extension authors should be mindful of the limited range of packet - types available (there are only 45 values available) and avoid - requiring a new packet type where possible. - - - - - - - -Galbraith, et al. Expires April 16, 2003 [Page 28] - -Internet-Draft SSH File Transfer Protocol October 2002 - - -9. Security Considerations - - This protocol assumes that it is run over a secure channel and that - the endpoints of the channel have been authenticated. Thus, this - protocol assumes that it is externally protected from network-level - attacks. - - This protocol provides file system access to arbitrary files on the - server (only constrained by the server implementation). It is the - responsibility of the server implementation to enforce any access - controls that may be required to limit the access allowed for any - particular user (the user being authenticated externally to this - protocol, typically using the SSH User Authentication Protocol [8]. - - Care must be taken in the server implementation to check the validity - of received file handle strings. The server should not rely on them - directly; it MUST check the validity of each handle before relying on - it. - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -Galbraith, et al. Expires April 16, 2003 [Page 29] - -Internet-Draft SSH File Transfer Protocol October 2002 - - -10. Changes from previous protocol versions - - The SSH File Transfer Protocol has changed over time, before it's - standardization. The following is a description of the incompatible - changes between different versions. - -10.1 Changes between versions 4 and 3 - - Many of the changes between version 4 and version 3 are to the - attribute structure to make it more flexible for non-unix platforms. - - o Make all filenames UTF-8. - - o Added 'newline' extension. - - o Made file attribute owner and group strings so they can actually - be used on disparate systems. - - o Added createtime field, and added separate flags for atime, - createtime, and mtime so they can be set separately. - - o Split the file type out of the permissions field and into it's own - field (which is always present.) - - o Added acl attribute. - - o Added SSH_FXF_TEXT file open flag. - - o Added flags field to the get stat commands so that the client can - specifically request information the server might not normally - included for performance reasons. - - o Removed the long filename from the names structure-- it can now be - built from information available in the attrs structure. - - o Added reserved range of packet numbers for extensions. - - o Added several additional error codes. - - o Change the way version negotiate works slightly. Previously, if - the client version were higher than the server version, the server - was supposed to 'echo back' the clients version. The server now - sends it's own version and the lower of the two is considered to - be the one in use. - - - - - - - -Galbraith, et al. Expires April 16, 2003 [Page 30] - -Internet-Draft SSH File Transfer Protocol October 2002 - - -10.2 Changes between versions 3 and 2 - - o The SSH_FXP_READLINK and SSH_FXP_SYMLINK messages were added. - - o The SSH_FXP_EXTENDED and SSH_FXP_EXTENDED_REPLY messages were - added. - - o The SSH_FXP_STATUS message was changed to include fields `error - message' and `language tag'. - - -10.3 Changes between versions 2 and 1 - - o The SSH_FXP_RENAME message was added. - - -10.4 Changes between versions 1 and 0 - - o Implementation changes, no actual protocol changes. - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -Galbraith, et al. Expires April 16, 2003 [Page 31] - -Internet-Draft SSH File Transfer Protocol October 2002 - - -11. Trademark Issues - - "ssh" is a registered trademark of SSH Communications Security Corp - in the United States and/or other countries. - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -Galbraith, et al. Expires April 16, 2003 [Page 32] - -Internet-Draft SSH File Transfer Protocol October 2002 - - -References - - [1] Dierks, T., Allen, C., Treese, W., Karlton, P., Freier, A. and - P. Kocher, "The TLS Protocol Version 1.0", RFC 2246, January - 1999. - - [2] Alvestrand, H., "IETF Policy on Character Sets and Languages", - BCP 18, RFC 2277, January 1998. - - [3] Shepler, S., Callaghan, B., Robinson, D., Thurlow, R., Beame, - C., Eisler, M. and D. Noveck, "NFS version 4 Protocol", RFC - 3010, December 2000. - - [4] Institute of Electrical and Electronics Engineers, "Information - Technology - Portable Operating System Interface (POSIX) - Part - 1: System Application Program Interface (API) [C Language]", - IEEE Standard 1003.2, 1996. - - [5] Rinne, T., Ylonen, T., Kivinen, T., Saarinen, M. and S. - Lehtinen, "SSH Protocol Architecture", draft-ietf-secsh- - architecture-13 (work in progress), September 2002. - - [6] Rinne, T., Ylonen, T., Kivinen, T., Saarinen, M. and S. - Lehtinen, "SSH Protocol Transport Protocol", draft-ietf-secsh- - transport-15 (work in progress), September 2002. - - [7] Rinne, T., Ylonen, T., Kivinen, T., Saarinen, M. and S. - Lehtinen, "SSH Connection Protocol", draft-ietf-secsh-connect-16 - (work in progress), September 2002. - - [8] Rinne, T., Ylonen, T., Kivinen, T., Saarinen, M. and S. - Lehtinen, "SSH Authentication Protocol", draft-ietf-secsh- - userauth-16 (work in progress), September 2002. - - -Authors' Addresses - - Joseph Galbraith - VanDyke Software - 4848 Tramway Ridge Blvd - Suite 101 - Albuquerque, NM 87111 - US - - Phone: +1 505 332 5700 - EMail: [email protected] - - - - - -Galbraith, et al. Expires April 16, 2003 [Page 33] - -Internet-Draft SSH File Transfer Protocol October 2002 - - - Tatu Ylonen - SSH Communications Security Corp - Fredrikinkatu 42 - HELSINKI FIN-00100 - Finland - - EMail: [email protected] - - - Sami Lehtinen - SSH Communications Security Corp - Fredrikinkatu 42 - HELSINKI FIN-00100 - Finland - - EMail: [email protected] - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -Galbraith, et al. Expires April 16, 2003 [Page 34] - -Internet-Draft SSH File Transfer Protocol October 2002 - - -Full Copyright Statement - - Copyright (C) The Internet Society (2002). All Rights Reserved. - - This document and translations of it may be copied and furnished to - others, and derivative works that comment on or otherwise explain it - or assist in its implementation may be prepared, copied, published - and distributed, in whole or in part, without restriction of any - kind, provided that the above copyright notice and this paragraph are - included on all such copies and derivative works. However, this - document itself may not be modified in any way, such as by removing - the copyright notice or references to the Internet Society or other - Internet organizations, except as needed for the purpose of - developing Internet standards in which case the procedures for - copyrights defined in the Internet Standards process must be - followed, or as required to translate it into languages other than - English. - - The limited permissions granted above are perpetual and will not be - revoked by the Internet Society or its successors or assigns. - - This document and the information contained herein is provided on an - "AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING - TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING - BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION - HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF - MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE. - -Acknowledgement - - Funding for the RFC Editor function is currently provided by the - Internet Society. - - - - - - - - - - - - - - - - - - - -Galbraith, et al. Expires April 16, 2003 [Page 35] - - diff --git a/lib/ssh/doc/standard/draft-ietf-secsh-filexfer-04.txt b/lib/ssh/doc/standard/draft-ietf-secsh-filexfer-04.txt deleted file mode 100644 index 9f51883cd2..0000000000 --- a/lib/ssh/doc/standard/draft-ietf-secsh-filexfer-04.txt +++ /dev/null @@ -1,2130 +0,0 @@ - - - -Secure Shell Working Group J. Galbraith -Internet-Draft VanDyke Software -Expires: June 18, 2003 T. Ylonen - S. Lehtinen - SSH Communications Security Corp - December 18, 2002 - - - SSH File Transfer Protocol - draft-ietf-secsh-filexfer-04.txt - -Status of this Memo - - This document is an Internet-Draft and is in full conformance with - all provisions of Section 10 of RFC2026. - - Internet-Drafts are working documents of the Internet Engineering - Task Force (IETF), its areas, and its working groups. Note that - other groups may also distribute working documents as - Internet-Drafts. - - Internet-Drafts are draft documents valid for a maximum of six months - and may be updated, replaced, or obsoleted by other documents at any - time. It is inappropriate to use Internet-Drafts as reference - material or to cite them other than as "work in progress." - - The list of current Internet-Drafts can be accessed at http:// - www.ietf.org/ietf/1id-abstracts.txt. - - The list of Internet-Draft Shadow Directories can be accessed at - http://www.ietf.org/shadow.html. - - This Internet-Draft will expire on June 18, 2003. - -Copyright Notice - - Copyright (C) The Internet Society (2002). All Rights Reserved. - -Abstract - - The SSH File Transfer Protocol provides secure file transfer - functionality over any reliable data stream. It is the standard file - transfer protocol for use with the SSH2 protocol. This document - describes the file transfer protocol and its interface to the SSH2 - protocol suite. - - - - - - - -Galbraith, et al. Expires June 18, 2003 [Page 1] - -Internet-Draft SSH File Transfer Protocol December 2002 - - -Table of Contents - - 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . 3 - 2. Use with the SSH Connection Protocol . . . . . . . . . . . 4 - 3. General Packet Format . . . . . . . . . . . . . . . . . . 5 - 3.1 The use of stderr in the server . . . . . . . . . . . . . 6 - 4. Protocol Initialization . . . . . . . . . . . . . . . . . 8 - 4.1 Client Initialization . . . . . . . . . . . . . . . . . . 8 - 4.2 Server Initialization . . . . . . . . . . . . . . . . . . 8 - 4.3 Determining Server Newline Convention . . . . . . . . . . 9 - 5. File Attributes . . . . . . . . . . . . . . . . . . . . . 10 - 5.1 Flags . . . . . . . . . . . . . . . . . . . . . . . . . . 10 - 5.2 Type . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 - 5.3 Size . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 - 5.4 Owner and Group . . . . . . . . . . . . . . . . . . . . . 11 - 5.5 Permissions . . . . . . . . . . . . . . . . . . . . . . . 12 - 5.6 Times . . . . . . . . . . . . . . . . . . . . . . . . . . 12 - 5.7 ACL . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 - 5.8 Extended attributes . . . . . . . . . . . . . . . . . . . 14 - 6. Requests From the Client to the Server . . . . . . . . . . 15 - 6.1 Request Synchronization and Reordering . . . . . . . . . . 15 - 6.2 File Names . . . . . . . . . . . . . . . . . . . . . . . . 16 - 6.3 Opening, Creating, and Closing Files . . . . . . . . . . . 16 - 6.4 Reading and Writing . . . . . . . . . . . . . . . . . . . 19 - 6.5 Removing and Renaming Files . . . . . . . . . . . . . . . 20 - 6.6 Creating and Deleting Directories . . . . . . . . . . . . 21 - 6.7 Scanning Directories . . . . . . . . . . . . . . . . . . . 21 - 6.8 Retrieving File Attributes . . . . . . . . . . . . . . . . 22 - 6.9 Setting File Attributes . . . . . . . . . . . . . . . . . 23 - 6.10 Dealing with Symbolic links . . . . . . . . . . . . . . . 24 - 6.11 Canonicalizing the Server-Side Path Name . . . . . . . . . 25 - 6.11.1 Best practice for dealing with paths . . . . . . . . . . . 25 - 7. Responses from the Server to the Client . . . . . . . . . 26 - 8. Vendor-Specific Extensions . . . . . . . . . . . . . . . . 30 - 9. Security Considerations . . . . . . . . . . . . . . . . . 31 - 10. Changes from previous protocol versions . . . . . . . . . 32 - 10.1 Changes between versions 4 and 3 . . . . . . . . . . . . . 32 - 10.2 Changes between versions 3 and 2 . . . . . . . . . . . . . 33 - 10.3 Changes between versions 2 and 1 . . . . . . . . . . . . . 33 - 10.4 Changes between versions 1 and 0 . . . . . . . . . . . . . 33 - 11. Trademark Issues . . . . . . . . . . . . . . . . . . . . . 34 - References . . . . . . . . . . . . . . . . . . . . . . . . 35 - Authors' Addresses . . . . . . . . . . . . . . . . . . . . 35 - Intellectual Property and Copyright Statements . . . . . . 37 - - - - - - - -Galbraith, et al. Expires June 18, 2003 [Page 2] - -Internet-Draft SSH File Transfer Protocol December 2002 - - -1. Introduction - - This protocol provides secure file transfer (and more generally file - system access) functionality over a reliable data stream, such as a - channel in the SSH2 protocol [5]. - - This protocol is designed so that it could be used to implement a - secure remote file system service, as well as a secure file transfer - service. - - This protocol assumes that it runs over a secure channel, and that - the server has already authenticated the user at the client end, and - that the identity of the client user is externally available to the - server implementation. - - In general, this protocol follows a simple request-response model. - Each request and response contains a sequence number and multiple - requests may be pending simultaneously. There are a relatively large - number of different request messages, but a small number of possible - response messages. Each request has one or more response messages - that may be returned in result (e.g., a read either returns data or - reports error status). - - The packet format descriptions in this specification follow the - notation presented in the secsh architecture draft. [5] - - Even though this protocol is described in the context of the SSH2 - protocol, this protocol is general and independent of the rest of the - SSH2 protocol suite. It could be used in a number of different - applications, such as secure file transfer over TLS RFC 2246 [1] and - transfer of management information in VPN applications. - - - - - - - - - - - - - - - - - - - - -Galbraith, et al. Expires June 18, 2003 [Page 3] - -Internet-Draft SSH File Transfer Protocol December 2002 - - -2. Use with the SSH Connection Protocol - - When used with the SSH2 Protocol suite, this protocol is intended to - be used from the SSH Connection Protocol [7] as a subsystem, as - described in section ``Starting a Shell or a Command''. The - subsystem name used with this protocol is "sftp". - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -Galbraith, et al. Expires June 18, 2003 [Page 4] - -Internet-Draft SSH File Transfer Protocol December 2002 - - -3. General Packet Format - - All packets transmitted over the secure connection are of the - following format: - - uint32 length - byte type - byte[length - 1] data payload - - That is, they are just data preceded by 32-bit length and 8-bit type - fields. The `length' is the length of the data area, and does not - include the `length' field itself. The format and interpretation of - the data area depends on the packet type. - - All packet descriptions below only specify the packet type and the - data that goes into the data field. Thus, they should be prefixed by - the `length' and `type' fields. - - The maximum size of a packet is in practice determined by the client - (the maximum size of read or write requests that it sends, plus a few - bytes of packet overhead). All servers SHOULD support packets of at - least 34000 bytes (where the packet size refers to the full length, - including the header above). This should allow for reads and writes - of at most 32768 bytes. - - There is no limit on the number of outstanding (non-acknowledged) - requests that the client may send to the server. In practice this is - limited by the buffering available on the data stream and the queuing - performed by the server. If the server's queues are full, it should - not read any more data from the stream, and flow control will prevent - the client from sending more requests. Note, however, that while - there is no restriction on the protocol level, the client's API may - provide a limit in order to prevent infinite queuing of outgoing - requests at the client. - - The following values are defined for packet types. - - - - - - - - - - - - - - - -Galbraith, et al. Expires June 18, 2003 [Page 5] - -Internet-Draft SSH File Transfer Protocol December 2002 - - - #define SSH_FXP_INIT 1 - #define SSH_FXP_VERSION 2 - #define SSH_FXP_OPEN 3 - #define SSH_FXP_CLOSE 4 - #define SSH_FXP_READ 5 - #define SSH_FXP_WRITE 6 - #define SSH_FXP_LSTAT 7 - #define SSH_FXP_FSTAT 8 - #define SSH_FXP_SETSTAT 9 - #define SSH_FXP_FSETSTAT 10 - #define SSH_FXP_OPENDIR 11 - #define SSH_FXP_READDIR 12 - #define SSH_FXP_REMOVE 13 - #define SSH_FXP_MKDIR 14 - #define SSH_FXP_RMDIR 15 - #define SSH_FXP_REALPATH 16 - #define SSH_FXP_STAT 17 - #define SSH_FXP_RENAME 18 - #define SSH_FXP_READLINK 19 - #define SSH_FXP_SYMLINK 20 - - #define SSH_FXP_STATUS 101 - #define SSH_FXP_HANDLE 102 - #define SSH_FXP_DATA 103 - #define SSH_FXP_NAME 104 - #define SSH_FXP_ATTRS 105 - - #define SSH_FXP_EXTENDED 200 - #define SSH_FXP_EXTENDED_REPLY 201 - - RESERVED_FOR_EXTENSIONS 210-255 - - Additional packet types should only be defined if the protocol - version number (see Section ``Protocol Initialization'') is - incremented, and their use MUST be negotiated using the version - number. However, the SSH_FXP_EXTENDED and SSH_FXP_EXTENDED_REPLY - packets can be used to implement vendor-specific extensions. See - Section ``Vendor-Specific-Extensions'' for more details. - -3.1 The use of stderr in the server - - Packets are sent and received on stdout and stdin. Data sent on - stderr by the server SHOULD be considered debug or supplemental error - information, and MAY be displayed to the user. - - For example, during initialization, there is no client request - active, so errors or warning information cannot be sent to the client - as part of the SFTP protocol at this early stage. However, the - - - -Galbraith, et al. Expires June 18, 2003 [Page 6] - -Internet-Draft SSH File Transfer Protocol December 2002 - - - errors or warnings MAY be sent as stderr text. - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -Galbraith, et al. Expires June 18, 2003 [Page 7] - -Internet-Draft SSH File Transfer Protocol December 2002 - - -4. Protocol Initialization - - When the file transfer protocol starts, the client first sends a - SSH_FXP_INIT (including its version number) packet to the server. - The server responds with a SSH_FXP_VERSION packet, supplying the - lowest of its own and the client's version number. Both parties - should from then on adhere to particular version of the protocol. - - The version number of the protocol specified in this document is 4. - The version number should be incremented for each incompatible - revision of this protocol. - -4.1 Client Initialization - - The SSH_FXP_INIT packet (from client to server) has the following - data: - - uint32 version - - Version 3 of this protocol allowed clients to include extensions in - the SSH_FXP_INIT packet; however, this can cause interoperability - problems with version 1 and version 2 servers because the client must - send this packet before knowing the servers version. - - In this version of the protocol, clients MUST use the - SSH_FXP_EXTENDED packet to send extensions to the server after - version exchange has completed. Clients MUST NOT include extensions - in the version packet. This will prevent interoperability problems - with older servers - -4.2 Server Initialization - - The SSH_FXP_VERSION packet (from server to client) has the following - data: - - uint32 version - <extension data> - - 'version' is the lower of the protocol version supported by the - server and the version number received from the client. - - The extension data may be empty, or may be a sequence of - - string extension_name - string extension_data - - pairs (both strings MUST always be present if one is, but the - `extension_data' string may be of zero length). If present, these - - - -Galbraith, et al. Expires June 18, 2003 [Page 8] - -Internet-Draft SSH File Transfer Protocol December 2002 - - - strings indicate extensions to the baseline protocol. The - `extension_name' field(s) identify the name of the extension. The - name should be of the form "name@domain", where the domain is the DNS - domain name of the organization defining the extension. Additional - names that are not of this format may be defined later by the IETF. - Implementations MUST silently ignore any extensions whose name they - do not recognize. - -4.3 Determining Server Newline Convention - - In order to correctly process text files in a cross platform - compatible way, the newline convention must be converted from that of - the server to that of the client, or, during an upload, from that of - the client to that of the server. - - Versions 3 and prior of this protocol made no provisions for - processing text files. Many clients implemented some sort of - conversion algorithm, but without either a 'canonical' on the wire - format or knowledge of the servers newline convention, correct - conversion was not always possible. - - Starting with Version 4, the SSH_FXF_TEXT file open flag (Section - 6.3) makes it possible to request that the server translate a file to - a 'canonical' on the wire format. This format uses \r\n as the line - separator. - - Servers for systems using multiple newline characters (for example, - Mac OS X or VMS) or systems using counted records, MUST translate to - the canonical form. - - However, to ease the burden of implementation on servers that use a - single, simple separator sequence, the following extension allows the - canonical format to be changed. - - string "newline" - string new-canonical-separator (usually "\r" or "\n" or "\r\n") - - All clients MUST support this extension. - - When processing text files, clients SHOULD NOT translate any - character or sequence that is not an exact match of the servers - newline separator. - - In particular, if the newline sequence being used is the canonical - "\r\n" sequence, a lone \r or a lone \n SHOULD be written through - without change. - - - - - -Galbraith, et al. Expires June 18, 2003 [Page 9] - -Internet-Draft SSH File Transfer Protocol December 2002 - - -5. File Attributes - - A new compound data type is defined for encoding file attributes. - The same encoding is used both when returning file attributes from - the server and when sending file attributes to the server. When - sending it to the server, the flags field specifies which attributes - are included, and the server will use default values for the - remaining attributes (or will not modify the values of remaining - attributes). When receiving attributes from the server, the flags - specify which attributes are included in the returned data. The - server normally returns all attributes it knows about. - - uint32 flags - byte type always present - uint64 size present only if flag SIZE - string owner present only if flag OWNERGROUP - string group present only if flag OWNERGROUP - uint32 permissions present only if flag PERMISSIONS - uint64 atime present only if flag ACCESSTIME - uint32 atime_nseconds present only if flag SUBSECOND_TIMES - uint64 createtime present only if flag CREATETIME - uint32 createtime_nseconds present only if flag SUBSECOND_TIMES - uint64 mtime present only if flag MODIFYTIME - uint32 mtime_nseconds present only if flag SUBSECOND_TIMES - string acl present only if flag ACL - uint32 extended_count present only if flag EXTENDED - string extended_type - string extended_data - ... more extended data (extended_type - extended_data pairs), - so that number of pairs equals extended_count - - -5.1 Flags - - The `flags' specify which of the fields are present. Those fields - for which the corresponding flag is not set are not present (not - included in the packet). New flags can only be added by incrementing - the protocol version number (or by using the extension mechanism - described below). - - The flags bits are defined to have the following values: - - - - - - - - - - -Galbraith, et al. Expires June 18, 2003 [Page 10] - -Internet-Draft SSH File Transfer Protocol December 2002 - - - #define SSH_FILEXFER_ATTR_SIZE 0x00000001 - #define SSH_FILEXFER_ATTR_PERMISSIONS 0x00000040 - #define SSH_FILEXFER_ATTR_ACCESSTIME 0x00000008 - #define SSH_FILEXFER_ATTR_CREATETIME 0x00000010 - #define SSH_FILEXFER_ATTR_MODIFYTIME 0x00000020 - #define SSH_FILEXFER_ATTR_ACL 0x00000040 - #define SSH_FILEXFER_ATTR_OWNERGROUP 0x00000080 - #define SSH_FILEXFER_ATTR_SUBSECOND_TIMES 0x00000100 - #define SSH_FILEXFER_ATTR_EXTENDED 0x80000000 - - In previous versions of this protocol flags value 0x00000002 was - SSH_FILEXFER_ATTR_UIDGID. This value is now unused, and OWNERGROUP - was given a new value in order to ease implementation burden. - 0x00000002 MUST NOT appear in the mask. Some future version of this - protocol may reuse flag 0x00000002. - -5.2 Type - - The type field is always present. The following types are defined: - - #define SSH_FILEXFER_TYPE_REGULAR 1 - #define SSH_FILEXFER_TYPE_DIRECTORY 2 - #define SSH_FILEXFER_TYPE_SYMLINK 3 - #define SSH_FILEXFER_TYPE_SPECIAL 4 - #define SSH_FILEXFER_TYPE_UNKNOWN 5 - - On a POSIX system, these values would be derived from the permission - field. - -5.3 Size - - The `size' field specifies the size of the file on disk, in bytes. - If it is present during file creation, it should be considered a hint - as to the files eventual size. - - Files opened with the SSH_FXF_TEXT flag may have a size that is - greater or less than the value of the size field. - -5.4 Owner and Group - - The `owner' and `group' fields are represented as UTF-8 strings; this - is the form used by NFS v4. See NFS version 4 Protocol. [3] The - following text is selected quotations from section 5.6. - - To avoid a representation that is tied to a particular underlying - implementation at the client or server, the use of UTF-8 strings has - been chosen. The string should be of the form user@dns_domain". - This will allow for a client and server that do not use the same - - - -Galbraith, et al. Expires June 18, 2003 [Page 11] - -Internet-Draft SSH File Transfer Protocol December 2002 - - - local representation the ability to translate to a common syntax that - can be interpreted by both. In the case where there is no - translation available to the client or server, the attribute value - must be constructed without the "@". Therefore, the absence of the @ - from the owner or owner_group attribute signifies that no translation - was available and the receiver of the attribute should not place any - special meaning with the attribute value. Even though the attribute - value can not be translated, it may still be useful. In the case of - a client, the attribute string may be used for local display of - ownership. - -5.5 Permissions - - The `permissions' field contains a bit mask of file permissions as - defined by POSIX [1]. - -5.6 Times - - The 'atime', 'createtime', and 'mtime' contain the access, creation, - and modification times of the files, respectively. They are - represented as seconds from Jan 1, 1970 in UTC. - - A negative value indicates number of seconds before Jan 1, 1970. In - both cases, if the SSH_FILEXFER_ATTR_SUBSECOND_TIMES flag is set, the - nseconds field is to be added to the seconds field for the final time - representation. For example, if the time to be represented is - one-half second before 0 hour January 1, 1970, the seconds field - would have a value of negative one (-1) and the nseconds fields would - have a value of one-half second (500000000). Values greater than - 999,999,999 for nseconds are considered invalid. - -5.7 ACL - - The 'ACL' field contains an ACL similar to that defined in section - 5.9 of NFS version 4 Protocol [3]. - - uint32 ace-count - - repeated ace-count time: - uint32 ace-type - uint32 ace-flag - uint32 ace-mask - string who [UTF-8] - - ace-type is one of the following four values (taken from NFS Version - 4 Protocol [3]: - - - - - -Galbraith, et al. Expires June 18, 2003 [Page 12] - -Internet-Draft SSH File Transfer Protocol December 2002 - - - const ACE4_ACCESS_ALLOWED_ACE_TYPE = 0x00000000; - const ACE4_ACCESS_DENIED_ACE_TYPE = 0x00000001; - const ACE4_SYSTEM_AUDIT_ACE_TYPE = 0x00000002; - const ACE4_SYSTEM_ALARM_ACE_TYPE = 0x00000003; - - ace-flag is a combination of the following flag values. See NFS - Version 4 Protocol [3] section 5.9.2: - - const ACE4_FILE_INHERIT_ACE = 0x00000001; - const ACE4_DIRECTORY_INHERIT_ACE = 0x00000002; - const ACE4_NO_PROPAGATE_INHERIT_ACE = 0x00000004; - const ACE4_INHERIT_ONLY_ACE = 0x00000008; - const ACE4_SUCCESSFUL_ACCESS_ACE_FLAG = 0x00000010; - const ACE4_FAILED_ACCESS_ACE_FLAG = 0x00000020; - const ACE4_IDENTIFIER_GROUP = 0x00000040; - - ace-mask is any combination of the following flags (taken from NFS - Version 4 Protocol [3] section 5.9.3: - - const ACE4_READ_DATA = 0x00000001; - const ACE4_LIST_DIRECTORY = 0x00000001; - const ACE4_WRITE_DATA = 0x00000002; - const ACE4_ADD_FILE = 0x00000002; - const ACE4_APPEND_DATA = 0x00000004; - const ACE4_ADD_SUBDIRECTORY = 0x00000004; - const ACE4_READ_NAMED_ATTRS = 0x00000008; - const ACE4_WRITE_NAMED_ATTRS = 0x00000010; - const ACE4_EXECUTE = 0x00000020; - const ACE4_DELETE_CHILD = 0x00000040; - const ACE4_READ_ATTRIBUTES = 0x00000080; - const ACE4_WRITE_ATTRIBUTES = 0x00000100; - const ACE4_DELETE = 0x00010000; - const ACE4_READ_ACL = 0x00020000; - const ACE4_WRITE_ACL = 0x00040000; - const ACE4_WRITE_OWNER = 0x00080000; - const ACE4_SYNCHRONIZE = 0x00100000; - - who is a UTF-8 string of the form described in 'Owner and Group' - (Section 5.4) - - Also, as per '5.9.4 ACE who' [3] there are several identifiers that - need to be understood universally. Some of these identifiers cannot - be understood when an client access the server, but have meaning when - a local process accesses the file. The ability to display and modify - these permissions is permitted over SFTP. - - OWNER The owner of the file. - - - - -Galbraith, et al. Expires June 18, 2003 [Page 13] - -Internet-Draft SSH File Transfer Protocol December 2002 - - - GROUP The group associated with the file. - - EVERYONE The world. - - INTERACTIVE Accessed from an interactive terminal. - - NETWORK Accessed via the network. - - DIALUP Accessed as a dialup user to the server. - - BATCH Accessed from a batch job. - - ANONYMOUS Accessed without any authentication. - - AUTHENTICATED Any authenticated user (opposite of ANONYMOUS). - - SERVICE Access from a system service. - - To avoid conflict, these special identifiers are distinguish by an - appended "@" and should appear in the form "xxxx@" (note: no domain - name after the "@"). For example: ANONYMOUS@. - -5.8 Extended attributes - - The SSH_FILEXFER_ATTR_EXTENDED flag provides a general extension - mechanism for vendor-specific extensions. If the flag is specified, - then the `extended_count' field is present. It specifies the number - of extended_type-extended_data pairs that follow. Each of these - pairs specifies an extended attribute. For each of the attributes, - the extended_type field should be a string of the format - "name@domain", where "domain" is a valid, registered domain name and - "name" identifies the method. The IETF may later standardize certain - names that deviate from this format (e.g., that do not contain the - "@" sign). The interpretation of `extended_data' depends on the - type. Implementations SHOULD ignore extended data fields that they - do not understand. - - Additional fields can be added to the attributes by either defining - additional bits to the flags field to indicate their presence, or by - defining extended attributes for them. The extended attributes - mechanism is recommended for most purposes; additional flags bits - should only be defined by an IETF standards action that also - increments the protocol version number. The use of such new fields - MUST be negotiated by the version number in the protocol exchange. - It is a protocol error if a packet with unsupported protocol bits is - received. - - - - - -Galbraith, et al. Expires June 18, 2003 [Page 14] - -Internet-Draft SSH File Transfer Protocol December 2002 - - -6. Requests From the Client to the Server - - Requests from the client to the server represent the various file - system operations. Each request begins with an `id' field, which is - a 32-bit identifier identifying the request (selected by the client). - The same identifier will be returned in the response to the request. - One possible implementation is a monotonically increasing request - sequence number (modulo 2^32). - - Many operations in the protocol operate on open files. The - SSH_FXP_OPEN request can return a file handle (which is an opaque - variable-length string) which may be used to access the file later - (e.g. in a read operation). The client MUST NOT send requests the - server with bogus or closed handles. However, the server MUST - perform adequate checks on the handle in order to avoid security - risks due to fabricated handles. - - This design allows either stateful and stateless server - implementation, as well as an implementation which caches state - between requests but may also flush it. The contents of the file - handle string are entirely up to the server and its design. The - client should not modify or attempt to interpret the file handle - strings. - - The file handle strings MUST NOT be longer than 256 bytes. - -6.1 Request Synchronization and Reordering - - The protocol and implementations MUST process requests relating to - the same file in the order in which they are received. In other - words, if an application submits multiple requests to the server, the - results in the responses will be the same as if it had sent the - requests one at a time and waited for the response in each case. For - example, the server may process non-overlapping read/write requests - to the same file in parallel, but overlapping reads and writes cannot - be reordered or parallelized. However, there are no ordering - restrictions on the server for processing requests from two different - file transfer connections. The server may interleave and parallelize - them at will. - - There are no restrictions on the order in which responses to - outstanding requests are delivered to the client, except that the - server must ensure fairness in the sense that processing of no - request will be indefinitely delayed even if the client is sending - other requests so that there are multiple outstanding requests all - the time. - - - - - -Galbraith, et al. Expires June 18, 2003 [Page 15] - -Internet-Draft SSH File Transfer Protocol December 2002 - - -6.2 File Names - - This protocol represents file names as strings. File names are - assumed to use the slash ('/') character as a directory separator. - - File names starting with a slash are "absolute", and are relative to - the root of the file system. Names starting with any other character - are relative to the user's default directory (home directory). Note - that identifying the user is assumed to take place outside of this - protocol. - - Servers SHOULD interpret a path name component ".." as referring to - the parent directory, and "." as referring to the current directory. - If the server implementation limits access to certain parts of the - file system, it must be extra careful in parsing file names when - enforcing such restrictions. There have been numerous reported - security bugs where a ".." in a path name has allowed access outside - the intended area. - - An empty path name is valid, and it refers to the user's default - directory (usually the user's home directory). - - Otherwise, no syntax is defined for file names by this specification. - Clients should not make any other assumptions; however, they can - splice path name components returned by SSH_FXP_READDIR together - using a slash ('/') as the separator, and that will work as expected. - - In order to comply with IETF Policy on Character Sets and Languages - [2], all filenames are to be encoded in UTF-8. The shortest valid - UTF-8 encoding of the UNICODE data MUST be used. The server is - responsible for converting the UNICODE data to whatever canonical - form it requires. - - For example, if the server requires that precomposed characters - always be used, the server MUST NOT assume the filename as sent by - the client has this attribute, but must do this normalization itself. - - It is understood that the lack of well-defined semantics for file - names may cause interoperability problems between clients and servers - using radically different operating systems. However, this approach - is known to work acceptably with most systems, and alternative - approaches that e.g. treat file names as sequences of structured - components are quite complicated. - -6.3 Opening, Creating, and Closing Files - - Files are opened and created using the SSH_FXP_OPEN message, whose - data part is as follows: - - - -Galbraith, et al. Expires June 18, 2003 [Page 16] - -Internet-Draft SSH File Transfer Protocol December 2002 - - - uint32 id - string filename [UTF-8] - uint32 pflags - ATTRS attrs - - The `id' field is the request identifier as for all requests. - - The `filename' field specifies the file name. See Section ``File - Names'' for more information. - - The `pflags' field is a bitmask. The following bits have been - defined. - - #define SSH_FXF_READ 0x00000001 - #define SSH_FXF_WRITE 0x00000002 - #define SSH_FXF_APPEND 0x00000004 - #define SSH_FXF_CREAT 0x00000008 - #define SSH_FXF_TRUNC 0x00000010 - #define SSH_FXF_EXCL 0x00000020 - #define SSH_FXF_TEXT 0x00000040 - - These have the following meanings: - - SSH_FXF_READ - Open the file for reading. - - SSH_FXF_WRITE - Open the file for writing. If both this and SSH_FXF_READ are - specified, the file is opened for both reading and writing. - - SSH_FXF_APPEND - Force all writes to append data at the end of the file. The - offset parameter to write will be ignored. - - SSH_FXF_CREAT - If this flag is specified, then a new file will be created if one - does not already exist (if O_TRUNC is specified, the new file will - be truncated to zero length if it previously exists). - - SSH_FXF_TRUNC - Forces an existing file with the same name to be truncated to zero - length when creating a file by specifying SSH_FXF_CREAT. - SSH_FXF_CREAT MUST also be specified if this flag is used. - - SSH_FXF_EXCL - Causes the request to fail if the named file already exists. - SSH_FXF_CREAT MUST also be specified if this flag is used. - - - - -Galbraith, et al. Expires June 18, 2003 [Page 17] - -Internet-Draft SSH File Transfer Protocol December 2002 - - - SSH_FXF_TEXT - Indicates that the server should treat the file as text and - convert it to the canonical newline convention in use. (See - Determining Server Newline Convention. (Section 4.3) - - When a file is opened with the FXF_TEXT flag, the offset field in - both the read and write function are ignored. - - Servers MUST correctly process multiple parallel reads and writes - correctly in this mode. Naturally, it is permissible for them to - do this by serializing the requests. It would not be possible for - a client to reliably detect a server that does not implement - parallel writes in time to prevent damage. - - Clients SHOULD use the SSH_FXF_APPEND flag to append data to a - text file rather then using write with a calculated offset. - - To support seeks on text file the following SSH_FXP_EXTENDED - packet is defined. - - - - string "text-seek" - string file-handle - uint64 line-number - - line-number is the index of the line number to seek to, where byte - 0 in the file is line number 0, and the byte directly following - the first newline sequence in the file is line number 1 and so on. - - The response to a "text-seek" request is an SSH_FXP_STATUS - message. - - An attempt to seek past the end-of-file should result in a - SSH_FX_EOF status. - - Servers SHOULD support at least one "text-seek" in order to - support resume. However, a client MUST be prepared to receive - SSH_FX_OP_UNSUPPORTED when attempting a "text-seek" operation. - The client can then try a fall-back strategy, if it has one. - - Clients MUST be prepared to handle SSH_FX_OP_UNSUPPORTED returned - for read or write operations that are not sequential. - - The `attrs' field specifies the initial attributes for the file. - Default values will be used for those attributes that are not - specified. See Section ``File Attributes'' for more information. - - - - -Galbraith, et al. Expires June 18, 2003 [Page 18] - -Internet-Draft SSH File Transfer Protocol December 2002 - - - The response to this message will be either SSH_FXP_HANDLE (if the - operation is successful) or SSH_FXP_STATUS (if the operation fails). - - A file is closed by using the SSH_FXP_CLOSE request. Its data field - has the following format: - - uint32 id - string handle - - where `id' is the request identifier, and `handle' is a handle - previously returned in the response to SSH_FXP_OPEN or - SSH_FXP_OPENDIR. The handle becomes invalid immediately after this - request has been sent. - - The response to this request will be a SSH_FXP_STATUS message. One - should note that on some server platforms even a close can fail. - This can happen e.g. if the server operating system caches writes, - and an error occurs while flushing cached writes during the close. - -6.4 Reading and Writing - - Once a file has been opened, it can be read using the following - message: - - byte SSH_FXP_READ - uint32 id - string handle - uint64 offset - uint32 len - - where `id' is the request identifier, `handle' is an open file handle - returned by SSH_FXP_OPEN, `offset' is the offset (in bytes) relative - to the beginning of the file from where to start reading, and `len' - is the maximum number of bytes to read. - - In response to this request, the server will read as many bytes as it - can from the file (up to `len'), and return them in a SSH_FXP_DATA - message. If an error occurs or EOF is encountered before reading any - data, the server will respond with SSH_FXP_STATUS. - - For normal disk files, it is normally guaranteed that this will read - the specified number of bytes, or up to end of file. However, if the - read length is very long, the server may truncate it if it doesn't - support packets of that length. See General Packet Format (Section - 3). - - For e.g. device files this may return fewer bytes than requested. - - - - -Galbraith, et al. Expires June 18, 2003 [Page 19] - -Internet-Draft SSH File Transfer Protocol December 2002 - - - Writing to a file is achieved using the following message: - - byte SSH_FXP_WRITE - uint32 id - string handle - uint64 offset - string data - - where `id' is a request identifier, `handle' is a file handle - returned by SSH_FXP_OPEN, `offset' is the offset (in bytes) from the - beginning of the file where to start writing, and `data' is the data - to be written. - - The write will extend the file if writing beyond the end of the file. - It is legal to write way beyond the end of the file; the semantics - are to write zeroes from the end of the file to the specified offset - and then the data. On most operating systems, such writes do not - allocate disk space but instead leave "holes" in the file. - - The server responds to a write request with a SSH_FXP_STATUS message. - -6.5 Removing and Renaming Files - - Files can be removed using the SSH_FXP_REMOVE message. It has the - following format: - - uint32 id - string filename [UTF-8] - - where `id' is the request identifier and `filename' is the name of - the file to be removed. See Section ``File Names'' for more - information. This request cannot be used to remove directories. - - The server will respond to this request with a SSH_FXP_STATUS - message. - - Files (and directories) can be renamed using the SSH_FXP_RENAME - message. Its data is as follows: - - uint32 id - string oldpath [UTF-8] - string newpath [UTF-8] - - where `id' is the request identifier, `oldpath' is the name of an - existing file or directory, and `newpath' is the new name for the - file or directory. It is an error if there already exists a file - with the name specified by newpath. The server may also fail rename - requests in other situations, for example if `oldpath' and `newpath' - - - -Galbraith, et al. Expires June 18, 2003 [Page 20] - -Internet-Draft SSH File Transfer Protocol December 2002 - - - point to different file systems on the server. - - The server will respond to this request with a SSH_FXP_STATUS - message. - -6.6 Creating and Deleting Directories - - New directories can be created using the SSH_FXP_MKDIR request. It - has the following format: - - uint32 id - string path [UTF-8] - ATTRS attrs - - where `id' is the request identifier. - - `path' specifies the directory to be created. See Section ``File - Names'' for more information on file names. - - `attrs' specifies the attributes that should be applied to it upon - creation. Attributes are discussed in more detail in Section ``File - Attributes''. - - The server will respond to this request with a SSH_FXP_STATUS - message. If a file or directory with the specified path already - exists, an error will be returned. - - Directories can be removed using the SSH_FXP_RMDIR request, which has - the following format: - - uint32 id - string path [UTF-8] - - where `id' is the request identifier, and `path' specifies the - directory to be removed. See Section ``File Names'' for more - information on file names. - - The server responds to this request with a SSH_FXP_STATUS message. - Errors may be returned from this operation for various reasons, - including, but not limited to, the path does not exist, the path does - not refer to a directory object, the directory is not empty, or the - user has insufficient access or permission to perform the requested - operation. - -6.7 Scanning Directories - - The files in a directory can be listed using the SSH_FXP_OPENDIR and - SSH_FXP_READDIR requests. Each SSH_FXP_READDIR request returns one - - - -Galbraith, et al. Expires June 18, 2003 [Page 21] - -Internet-Draft SSH File Transfer Protocol December 2002 - - - or more file names with full file attributes for each file. The - client should call SSH_FXP_READDIR repeatedly until it has found the - file it is looking for or until the server responds with a - SSH_FXP_STATUS message indicating an error (normally SSH_FX_EOF if - there are no more files in the directory). The client should then - close the handle using the SSH_FXP_CLOSE request. - - The SSH_FXP_OPENDIR opens a directory for reading. It has the - following format: - - uint32 id - string path [UTF-8] - - where `id' is the request identifier and `path' is the path name of - the directory to be listed (without any trailing slash). See Section - ``File Names'' for more information on file names. This will return - an error if the path does not specify a directory or if the directory - is not readable. The server will respond to this request with either - a SSH_FXP_HANDLE or a SSH_FXP_STATUS message. - - Once the directory has been successfully opened, files (and - directories) contained in it can be listed using SSH_FXP_READDIR - requests. These are of the format - - uint32 id - string handle - - where `id' is the request identifier, and `handle' is a handle - returned by SSH_FXP_OPENDIR. (It is a protocol error to attempt to - use an ordinary file handle returned by SSH_FXP_OPEN.) - - The server responds to this request with either a SSH_FXP_NAME or a - SSH_FXP_STATUS message. One or more names may be returned at a time. - Full status information is returned for each name in order to speed - up typical directory listings. - - If there are no more names available to be read, the server MUST - respond with a SSH_FXP_STATUS message with error code of SSH_FX_EOF. - - When the client no longer wishes to read more names from the - directory, it SHOULD call SSH_FXP_CLOSE for the handle. The handle - should be closed regardless of whether an error has occurred or not. - -6.8 Retrieving File Attributes - - Very often, file attributes are automatically returned by - SSH_FXP_READDIR. However, sometimes there is need to specifically - retrieve the attributes for a named file. This can be done using the - - - -Galbraith, et al. Expires June 18, 2003 [Page 22] - -Internet-Draft SSH File Transfer Protocol December 2002 - - - SSH_FXP_STAT, SSH_FXP_LSTAT and SSH_FXP_FSTAT requests. - - SSH_FXP_STAT and SSH_FXP_LSTAT only differ in that SSH_FXP_STAT - follows symbolic links on the server, whereas SSH_FXP_LSTAT does not - follow symbolic links. Both have the same format: - - uint32 id - string path [UTF-8] - uint32 flags - - where `id' is the request identifier, and `path' specifies the file - system object for which status is to be returned. The server - responds to this request with either SSH_FXP_ATTRS or SSH_FXP_STATUS. - - The flags field specify the attribute flags in which the client has - particular interest. This is a hint to the server. For example, - because retrieving owner / group and acl information can be an - expensive operation under some operating systems, the server may - choose not to retrieve this information unless the client expresses a - specific interest in it. - - The client has no guarantee the server will provide all the fields - that it has expressed an interest in. - - SSH_FXP_FSTAT differs from the others in that it returns status - information for an open file (identified by the file handle). Its - format is as follows: - - uint32 id - string handle - uint32 flags - - where `id' is the request identifier and `handle' is a file handle - returned by SSH_FXP_OPEN. The server responds to this request with - SSH_FXP_ATTRS or SSH_FXP_STATUS. - -6.9 Setting File Attributes - - File attributes may be modified using the SSH_FXP_SETSTAT and - SSH_FXP_FSETSTAT requests. These requests are used for operations - such as changing the ownership, permissions or access times, as well - as for truncating a file. - - The SSH_FXP_SETSTAT request is of the following format: - - - - - - - -Galbraith, et al. Expires June 18, 2003 [Page 23] - -Internet-Draft SSH File Transfer Protocol December 2002 - - - uint32 id - string path [UTF-8] - ATTRS attrs - - where `id' is the request identifier, `path' specifies the file - system object (e.g. file or directory) whose attributes are to be - modified, and `attrs' specifies the modifications to be made to its - attributes. Attributes are discussed in more detail in Section - ``File Attributes''. - - An error will be returned if the specified file system object does - not exist or the user does not have sufficient rights to modify the - specified attributes. The server responds to this request with a - SSH_FXP_STATUS message. - - The SSH_FXP_FSETSTAT request modifies the attributes of a file which - is already open. It has the following format: - - uint32 id - string handle - ATTRS attrs - - where `id' is the request identifier, `handle' (MUST be returned by - SSH_FXP_OPEN) identifies the file whose attributes are to be - modified, and `attrs' specifies the modifications to be made to its - attributes. Attributes are discussed in more detail in Section - ``File Attributes''. The server will respond to this request with - SSH_FXP_STATUS. - -6.10 Dealing with Symbolic links - - The SSH_FXP_READLINK request may be used to read the target of a - symbolic link. It would have a data part as follows: - - uint32 id - string path [UTF-8] - - where `id' is the request identifier and `path' specifies the path - name of the symlink to be read. - - The server will respond with a SSH_FXP_NAME packet containing only - one name and a dummy attributes value. The name in the returned - packet contains the target of the link. If an error occurs, the - server may respond with SSH_FXP_STATUS. - - The SSH_FXP_SYMLINK request will create a symbolic link on the - server. It is of the following format - - - - -Galbraith, et al. Expires June 18, 2003 [Page 24] - -Internet-Draft SSH File Transfer Protocol December 2002 - - - uint32 id - string linkpath [UTF-8] - string targetpath [UTF-8] - - where `id' is the request identifier, `linkpath' specifies the path - name of the symlink to be created and `targetpath' specifies the - target of the symlink. The server shall respond with a - SSH_FXP_STATUS indicating either success (SSH_FX_OK) or an error - condition. - -6.11 Canonicalizing the Server-Side Path Name - - The SSH_FXP_REALPATH request can be used to have the server - canonicalize any given path name to an absolute path. This is useful - for converting path names containing ".." components or relative - pathnames without a leading slash into absolute paths. The format of - the request is as follows: - - uint32 id - string path [UTF-8] - - where `id' is the request identifier and `path' specifies the path - name to be canonicalized. The server will respond with a - SSH_FXP_NAME packet containing the name in canonical form and a dummy - attributes value. If an error occurs, the server may also respond - with SSH_FXP_STATUS. - -6.11.1 Best practice for dealing with paths - - The client SHOULD treat the results of SSH_FXP_REALPATH as a - canonical absolute path, even if the path does not appear to be - absolute. A client that use REALPATH(".") and treats the result as - absolute, even if there is no leading slash, will continue to - function correctly, even when talking to a Windows NT or VMS style - system, where absolute paths may not begin with a slash. - - For example, if the client wishes to change directory up, and the - server has returned "c:/x/y/z" from REALPATH, the client SHOULD use - "c:/x/y/z/..". - - As a second example, if the client wishes to open the file "x.txt" in - the current directory, and server has returned "dka100:/x/y/z" as the - canonical path of the directory, the client SHOULD open "dka100:/x/y/ - z/x.txt" - - - - - - - -Galbraith, et al. Expires June 18, 2003 [Page 25] - -Internet-Draft SSH File Transfer Protocol December 2002 - - -7. Responses from the Server to the Client - - The server responds to the client using one of a few response - packets. All requests can return a SSH_FXP_STATUS response upon - failure. When the operation is successful, any of the responses may - be returned (depending on the operation). If no data needs to be - returned to the client, the SSH_FXP_STATUS response with SSH_FX_OK - status is appropriate. Otherwise, the SSH_FXP_HANDLE message is used - to return a file handle (for SSH_FXP_OPEN and SSH_FXP_OPENDIR - requests), SSH_FXP_DATA is used to return data from SSH_FXP_READ, - SSH_FXP_NAME is used to return one or more file names from a - SSH_FXP_READDIR or SSH_FXP_REALPATH request, and SSH_FXP_ATTRS is - used to return file attributes from SSH_FXP_STAT, SSH_FXP_LSTAT, and - SSH_FXP_FSTAT requests. - - Exactly one response will be returned for each request. Each - response packet contains a request identifier which can be used to - match each response with the corresponding request. Note that it is - legal to have several requests outstanding simultaneously, and the - server is allowed to send responses to them in a different order from - the order in which the requests were sent (the result of their - execution, however, is guaranteed to be as if they had been processed - one at a time in the order in which the requests were sent). - - Response packets are of the same general format as request packets. - Each response packet begins with the request identifier. - - The format of the data portion of the SSH_FXP_STATUS response is as - follows: - - uint32 id - uint32 error/status code - string error message (ISO-10646 UTF-8 [RFC-2279]) - string language tag (as defined in [RFC-1766]) - - where `id' is the request identifier, and `error/status code' - indicates the result of the requested operation. The value SSH_FX_OK - indicates success, and all other values indicate failure. - - Currently, the following values are defined (other values may be - defined by future versions of this protocol): - - - - - - - - - - -Galbraith, et al. Expires June 18, 2003 [Page 26] - -Internet-Draft SSH File Transfer Protocol December 2002 - - - #define SSH_FX_OK 0 - #define SSH_FX_EOF 1 - #define SSH_FX_NO_SUCH_FILE 2 - #define SSH_FX_PERMISSION_DENIED 3 - #define SSH_FX_FAILURE 4 - #define SSH_FX_BAD_MESSAGE 5 - #define SSH_FX_NO_CONNECTION 6 - #define SSH_FX_CONNECTION_LOST 7 - #define SSH_FX_OP_UNSUPPORTED 8 - #define SSH_FX_INVALID_HANDLE 9 - #define SSH_FX_NO_SUCH_PATH 10 - #define SSH_FX_FILE_ALREADY_EXISTS 11 - #define SSH_FX_WRITE_PROTECT 12 - #define SSH_FX_NO_MEDIA 13 - - SSH_FX_OK - Indicates successful completion of the operation. - - SSH_FX_EOF - indicates end-of-file condition; for SSH_FX_READ it means that no - more data is available in the file, and for SSH_FX_READDIR it - indicates that no more files are contained in the directory. - - SSH_FX_NO_SUCH_FILE - is returned when a reference is made to a file which does not - exist. - - SSH_FX_PERMISSION_DENIED - is returned when the authenticated user does not have sufficient - permissions to perform the operation. - - SSH_FX_FAILURE - is a generic catch-all error message; it should be returned if an - error occurs for which there is no more specific error code - defined. - - SSH_FX_BAD_MESSAGE - may be returned if a badly formatted packet or protocol - incompatibility is detected. - - SSH_FX_NO_CONNECTION - is a pseudo-error which indicates that the client has no - connection to the server (it can only be generated locally by the - client, and MUST NOT be returned by servers). - - SSH_FX_CONNECTION_LOST - is a pseudo-error which indicates that the connection to the - server has been lost (it can only be generated locally by the - - - -Galbraith, et al. Expires June 18, 2003 [Page 27] - -Internet-Draft SSH File Transfer Protocol December 2002 - - - client, and MUST NOT be returned by servers). - - SSH_FX_OP_UNSUPPORTED - indicates that an attempt was made to perform an operation which - is not supported for the server (it may be generated locally by - the client if e.g. the version number exchange indicates that a - required feature is not supported by the server, or it may be - returned by the server if the server does not implement an - operation). - - SSH_FX_INVALID_HANDLE - The handle value was invalid. - - SSH_FX_NO_SUCH_PATH - The file path does not exist or is invalid. - - SSH_FX_FILE_ALREADY_EXISTS - The file already exists. - - SSH_FX_WRITE_PROTECT - The file is on read only media, or the media is write protected. - - SSH_FX_NO_MEDIA - The requested operation can not be completed because there is no - media available in the drive. - - The SSH_FXP_HANDLE response has the following format: - - uint32 id - string handle - - where `id' is the request identifier, and `handle' is an arbitrary - string that identifies an open file or directory on the server. The - handle is opaque to the client; the client MUST NOT attempt to - interpret or modify it in any way. The length of the handle string - MUST NOT exceed 256 data bytes. - - The SSH_FXP_DATA response has the following format: - - uint32 id - string data - - where `id' is the request identifier, and `data' is an arbitrary byte - string containing the requested data. The data string may be at most - the number of bytes requested in a SSH_FXP_READ request, but may also - be shorter if end of file is reached or if the read is from something - other than a regular file. - - - - -Galbraith, et al. Expires June 18, 2003 [Page 28] - -Internet-Draft SSH File Transfer Protocol December 2002 - - - The SSH_FXP_NAME response has the following format: - - uint32 id - uint32 count - repeats count times: - string filename [UTF-8] - ATTRS attrs - - where `id' is the request identifier, `count' is the number of names - returned in this response, and the remaining fields repeat `count' - times (so that all three fields are first included for the first - file, then for the second file, etc). In the repeated part, - `filename' is a file name being returned (for SSH_FXP_READDIR, it - will be a relative name within the directory, without any path - components; for SSH_FXP_REALPATH it will be an absolute path name), - and `attrs' is the attributes of the file as described in Section - ``File Attributes''. - - The SSH_FXP_ATTRS response has the following format: - - uint32 id - ATTRS attrs - - where `id' is the request identifier, and `attrs' is the returned - file attributes as described in Section ``File Attributes''. - - - - - - - - - - - - - - - - - - - - - - - - - - -Galbraith, et al. Expires June 18, 2003 [Page 29] - -Internet-Draft SSH File Transfer Protocol December 2002 - - -8. Vendor-Specific Extensions - - The SSH_FXP_EXTENDED request provides a generic extension mechanism - for adding vendor-specific commands. The request has the following - format: - - uint32 id - string extended-request - ... any request-specific data ... - - where `id' is the request identifier, and `extended-request' is a - string of the format "name@domain", where domain is an internet - domain name of the vendor defining the request. The rest of the - request is completely vendor-specific, and servers should only - attempt to interpret it if they recognize the `extended-request' - name. - - The server may respond to such requests using any of the response - packets defined in Section ``Responses from the Server to the - Client''. Additionally, the server may also respond with a - SSH_FXP_EXTENDED_REPLY packet, as defined below. If the server does - not recognize the `extended-request' name, then the server MUST - respond with SSH_FXP_STATUS with error/status set to - SSH_FX_OP_UNSUPPORTED. - - The SSH_FXP_EXTENDED_REPLY packet can be used to carry arbitrary - extension-specific data from the server to the client. It is of the - following format: - - uint32 id - ... any request-specific data ... - - There is a range of packet types reserved for use by extensions. In - order to avoid collision, extensions that turn on the use of - additional packet types should determine those numbers dynamically. - - The suggested way of doing this is have an extension request from the - client to the server that enables the extension; the extension - response from the server to the client would specify the actual type - values to use, in additional to any other data. - - Extension authors should be mindful of the limited range of packet - types available (there are only 45 values available) and avoid - requiring a new packet type where possible. - - - - - - - -Galbraith, et al. Expires June 18, 2003 [Page 30] - -Internet-Draft SSH File Transfer Protocol December 2002 - - -9. Security Considerations - - This protocol assumes that it is run over a secure channel and that - the endpoints of the channel have been authenticated. Thus, this - protocol assumes that it is externally protected from network-level - attacks. - - This protocol provides file system access to arbitrary files on the - server (only constrained by the server implementation). It is the - responsibility of the server implementation to enforce any access - controls that may be required to limit the access allowed for any - particular user (the user being authenticated externally to this - protocol, typically using the SSH User Authentication Protocol [8]. - - Care must be taken in the server implementation to check the validity - of received file handle strings. The server should not rely on them - directly; it MUST check the validity of each handle before relying on - it. - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -Galbraith, et al. Expires June 18, 2003 [Page 31] - -Internet-Draft SSH File Transfer Protocol December 2002 - - -10. Changes from previous protocol versions - - The SSH File Transfer Protocol has changed over time, before it's - standardization. The following is a description of the incompatible - changes between different versions. - -10.1 Changes between versions 4 and 3 - - Many of the changes between version 4 and version 3 are to the - attribute structure to make it more flexible for non-unix platforms. - - o Clarify the use of stderr by the server. - - o Clarify handling of very large read requests by the server. - - o Make all filenames UTF-8. - - o Added 'newline' extension. - - o Made time fields 64 bit, and optionally have nanosecond resultion. - - o Made file attribute owner and group strings so they can actually - be used on disparate systems. - - o Added createtime field, and added separate flags for atime, - createtime, and mtime so they can be set separately. - - o Split the file type out of the permissions field and into it's own - field (which is always present.) - - o Added acl attribute. - - o Added SSH_FXF_TEXT file open flag. - - o Added flags field to the get stat commands so that the client can - specifically request information the server might not normally - included for performance reasons. - - o Removed the long filename from the names structure-- it can now be - built from information available in the attrs structure. - - o Added reserved range of packet numbers for extensions. - - o Added several additional error codes. - - - - - - - -Galbraith, et al. Expires June 18, 2003 [Page 32] - -Internet-Draft SSH File Transfer Protocol December 2002 - - -10.2 Changes between versions 3 and 2 - - o The SSH_FXP_READLINK and SSH_FXP_SYMLINK messages were added. - - o The SSH_FXP_EXTENDED and SSH_FXP_EXTENDED_REPLY messages were - added. - - o The SSH_FXP_STATUS message was changed to include fields `error - message' and `language tag'. - - -10.3 Changes between versions 2 and 1 - - o The SSH_FXP_RENAME message was added. - - -10.4 Changes between versions 1 and 0 - - o Implementation changes, no actual protocol changes. - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -Galbraith, et al. Expires June 18, 2003 [Page 33] - -Internet-Draft SSH File Transfer Protocol December 2002 - - -11. Trademark Issues - - "ssh" is a registered trademark of SSH Communications Security Corp - in the United States and/or other countries. - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -Galbraith, et al. Expires June 18, 2003 [Page 34] - -Internet-Draft SSH File Transfer Protocol December 2002 - - -References - - [1] Dierks, T., Allen, C., Treese, W., Karlton, P., Freier, A. and - P. Kocher, "The TLS Protocol Version 1.0", RFC 2246, January - 1999. - - [2] Alvestrand, H., "IETF Policy on Character Sets and Languages", - BCP 18, RFC 2277, January 1998. - - [3] Shepler, S., Callaghan, B., Robinson, D., Thurlow, R., Beame, - C., Eisler, M. and D. Noveck, "NFS version 4 Protocol", RFC - 3010, December 2000. - - [4] Institute of Electrical and Electronics Engineers, "Information - Technology - Portable Operating System Interface (POSIX) - Part - 1: System Application Program Interface (API) [C Language]", - IEEE Standard 1003.2, 1996. - - [5] Rinne, T., Ylonen, T., Kivinen, T., Saarinen, M. and S. - Lehtinen, "SSH Protocol Architecture", - draft-ietf-secsh-architecture-13 (work in progress), September - 2002. - - [6] Rinne, T., Ylonen, T., Kivinen, T., Saarinen, M. and S. - Lehtinen, "SSH Protocol Transport Protocol", - draft-ietf-secsh-transport-15 (work in progress), September - 2002. - - [7] Rinne, T., Ylonen, T., Kivinen, T., Saarinen, M. and S. - Lehtinen, "SSH Connection Protocol", draft-ietf-secsh-connect-16 - (work in progress), September 2002. - - [8] Rinne, T., Ylonen, T., Kivinen, T., Saarinen, M. and S. - Lehtinen, "SSH Authentication Protocol", - draft-ietf-secsh-userauth-16 (work in progress), September 2002. - - -Authors' Addresses - - Joseph Galbraith - VanDyke Software - 4848 Tramway Ridge Blvd - Suite 101 - Albuquerque, NM 87111 - US - - Phone: +1 505 332 5700 - EMail: [email protected] - - - -Galbraith, et al. Expires June 18, 2003 [Page 35] - -Internet-Draft SSH File Transfer Protocol December 2002 - - - Tatu Ylonen - SSH Communications Security Corp - Fredrikinkatu 42 - HELSINKI FIN-00100 - Finland - - EMail: [email protected] - - - Sami Lehtinen - SSH Communications Security Corp - Fredrikinkatu 42 - HELSINKI FIN-00100 - Finland - - EMail: [email protected] - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -Galbraith, et al. Expires June 18, 2003 [Page 36] - -Internet-Draft SSH File Transfer Protocol December 2002 - - -Intellectual Property Statement - - The IETF takes no position regarding the validity or scope of any - intellectual property or other rights that might be claimed to - pertain to the implementation or use of the technology described in - this document or the extent to which any license under such rights - might or might not be available; neither does it represent that it - has made any effort to identify any such rights. Information on the - IETF's procedures with respect to rights in standards-track and - standards-related documentation can be found in BCP-11. Copies of - claims of rights made available for publication and any assurances of - licenses to be made available, or the result of an attempt made to - obtain a general license or permission for the use of such - proprietary rights by implementors or users of this specification can - be obtained from the IETF Secretariat. - - The IETF invites any interested party to bring to its attention any - copyrights, patents or patent applications, or other proprietary - rights which may cover technology that may be required to practice - this standard. Please address the information to the IETF Executive - Director. - - -Full Copyright Statement - - Copyright (C) The Internet Society (2002). All Rights Reserved. - - This document and translations of it may be copied and furnished to - others, and derivative works that comment on or otherwise explain it - or assist in its implementation may be prepared, copied, published - and distributed, in whole or in part, without restriction of any - kind, provided that the above copyright notice and this paragraph are - included on all such copies and derivative works. However, this - document itself may not be modified in any way, such as by removing - the copyright notice or references to the Internet Society or other - Internet organizations, except as needed for the purpose of - developing Internet standards in which case the procedures for - copyrights defined in the Internet Standards process must be - followed, or as required to translate it into languages other than - English. - - The limited permissions granted above are perpetual and will not be - revoked by the Internet Society or its successors or assignees. - - This document and the information contained herein is provided on an - "AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING - TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING - BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION - - - -Galbraith, et al. Expires June 18, 2003 [Page 37] - -Internet-Draft SSH File Transfer Protocol December 2002 - - - HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF - MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE. - - -Acknowledgement - - Funding for the RFC Editor function is currently provided by the - Internet Society. - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -Galbraith, et al. Expires June 18, 2003 [Page 38] - - diff --git a/lib/ssh/doc/standard/draft-ietf-secsh-transport-17.2.ps b/lib/ssh/doc/standard/draft-ietf-secsh-transport-17.2.ps deleted file mode 100644 index d692285b4e..0000000000 --- a/lib/ssh/doc/standard/draft-ietf-secsh-transport-17.2.ps +++ /dev/null @@ -1,3205 +0,0 @@ -%!PS-Adobe-3.0 -%%BoundingBox: 75 0 595 747 -%%Title: Enscript Output -%%For: Magnus Thoang -%%Creator: GNU enscript 1.6.1 -%%CreationDate: Fri Oct 31 13:35:14 2003 -%%Orientation: Portrait -%%Pages: 15 0 -%%DocumentMedia: A4 595 842 0 () () -%%DocumentNeededResources: (atend) -%%EndComments -%%BeginProlog -%%BeginProcSet: PStoPS 1 15 -userdict begin -[/showpage/erasepage/copypage]{dup where{pop dup load - type/operatortype eq{1 array cvx dup 0 3 index cvx put - bind def}{pop}ifelse}{pop}ifelse}forall -[/letter/legal/executivepage/a4/a4small/b5/com10envelope - /monarchenvelope/c5envelope/dlenvelope/lettersmall/note - /folio/quarto/a5]{dup where{dup wcheck{exch{}put} - {pop{}def}ifelse}{pop}ifelse}forall -/setpagedevice {pop}bind 1 index where{dup wcheck{3 1 roll put} - 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matrix invertmatrix matrix concatmatrix - matrix invertmatrix put -%%EndSetup -%%Page: (0,1) 1 -userdict/PStoPSsaved save put -PStoPSmatrix setmatrix -595.000000 0.271378 translate -90 rotate -0.706651 dup scale -userdict/PStoPSmatrix matrix currentmatrix put -userdict/PStoPSclip{0 0 moveto - 595.000000 0 rlineto 0 842.000000 rlineto -595.000000 0 rlineto - closepath}put initclip -/showpage{}def/copypage{}def/erasepage{}def -PStoPSxform concat -%%BeginPageSetup -_S -75 0 translate -/pagenum 1 def -/fname () def -/fdir () def -/ftail () def -/user_header_p false def -%%EndPageSetup -5 701 M -(Network Working Group T. Ylonen) s -5 690 M -(Internet-Draft SSH Communications Security Corp) s -5 679 M -(Expires: March 31, 2004 D. Moffat, Editor, Ed.) s -5 668 M -( Sun Microsystems, Inc) s -5 657 M -( Oct 2003) s -5 624 M -( SSH Transport Layer Protocol) s -5 613 M -( draft-ietf-secsh-transport-17.txt) s -5 591 M -(Status of this Memo) s -5 569 M -( This document is an Internet-Draft and is in full conformance with) s -5 558 M -( all provisions of Section 10 of RFC2026.) s -5 536 M -( Internet-Drafts are working documents of the Internet Engineering) s -5 525 M -( Task Force \(IETF\), its areas, and its working groups. Note that other) s -5 514 M -( groups may also distribute working documents as Internet-Drafts.) s -5 492 M -( Internet-Drafts are draft documents valid for a maximum of six months) s -5 481 M -( and may be updated, replaced, or obsoleted by other documents at any) s -5 470 M -( time. It is inappropriate to use Internet-Drafts as reference) s -5 459 M -( material or to cite them other than as "work in progress.") s -5 437 M -( The list of current Internet-Drafts can be accessed at http://) s -5 426 M -( www.ietf.org/ietf/1id-abstracts.txt.) s -5 404 M -( The list of Internet-Draft Shadow Directories can be accessed at) s -5 393 M -( http://www.ietf.org/shadow.html.) s -5 371 M -( This Internet-Draft will expire on March 31, 2004.) s -5 349 M -(Copyright Notice) s -5 327 M -( Copyright \(C\) The Internet Society \(2003\). All Rights Reserved.) s -5 305 M -(Abstract) s -5 283 M -( SSH is a protocol for secure remote login and other secure network) s -5 272 M -( services over an insecure network.) s -5 250 M -( This document describes the SSH transport layer protocol which) s -5 239 M -( typically runs on top of TCP/IP. The protocol can be used as a basis) s -5 228 M -( for a number of secure network services. It provides strong) s -5 217 M -( encryption, server authentication, and integrity protection. It may) s -5 206 M -( also provide compression.) s -5 184 M -( Key exchange method, public key algorithm, symmetric encryption) s -5 173 M -( algorithm, message authentication algorithm, and hash algorithm are) s -5 129 M -(Ylonen & Moffat, Editor Expires March 31, 2004 [Page 1]) s -_R -S -PStoPSsaved restore -userdict/PStoPSsaved save put -PStoPSmatrix setmatrix -595.000000 421.271378 translate -90 rotate -0.706651 dup scale -userdict/PStoPSmatrix matrix currentmatrix put -userdict/PStoPSclip{0 0 moveto - 595.000000 0 rlineto 0 842.000000 rlineto -595.000000 0 rlineto - closepath}put initclip -PStoPSxform concat -%%BeginPageSetup -_S -75 0 translate -/pagenum 2 def -/fname () def -/fdir () def -/ftail () def -/user_header_p false def -%%EndPageSetup -5 723 M -(Internet-Draft SSH Transport Layer Protocol Oct 2003) s -5 690 M -( all negotiated.) s -5 668 M -( This document also describes the Diffie-Hellman key exchange method) s -5 657 M -( and the minimal set of algorithms that are needed to implement the) s -5 646 M -( SSH transport layer protocol.) s -5 624 M -(Table of Contents) s -5 602 M -( 1. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 3) s -5 591 M -( 2. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3) s -5 580 M -( 3. Conventions Used in This Document . . . . . . . . . . . . . 3) s -5 569 M -( 4. Connection Setup . . . . . . . . . . . . . . . . . . . . . . 3) s -5 558 M -( 4.1 Use over TCP/IP . . . . . . . . . . . . . . . . . . . . . . 4) s -5 547 M -( 4.2 Protocol Version Exchange . . . . . . . . . . . . . . . . . 4) s -5 536 M -( 4.3 Compatibility With Old SSH Versions . . . . . . . . . . . . 4) s -5 525 M -( 4.3.1 Old Client, New Server . . . . . . . . . . . . . . . . . . . 5) s -5 514 M -( 4.3.2 New Client, Old Server . . . . . . . . . . . . . . . . . . . 5) s -5 503 M -( 5. Binary Packet Protocol . . . . . . . . . . . . . . . . . . . 5) s -5 492 M -( 5.1 Maximum Packet Length . . . . . . . . . . . . . . . . . . . 6) s -5 481 M -( 5.2 Compression . . . . . . . . . . . . . . . . . . . . . . . . 7) s -5 470 M -( 5.3 Encryption . . . . . . . . . . . . . . . . . . . . . . . . . 7) s -5 459 M -( 5.4 Data Integrity . . . . . . . . . . . . . . . . . . . . . . . 9) s -5 448 M -( 5.5 Key Exchange Methods . . . . . . . . . . . . . . . . . . . . 10) s -5 437 M -( 5.6 Public Key Algorithms . . . . . . . . . . . . . . . . . . . 11) s -5 426 M -( 6. Key Exchange . . . . . . . . . . . . . . . . . . . . . . . . 13) s -5 415 M -( 6.1 Algorithm Negotiation . . . . . . . . . . . . . . . . . . . 13) s -5 404 M -( 6.2 Output from Key Exchange . . . . . . . . . . . . . . . . . . 16) s -5 393 M -( 6.3 Taking Keys Into Use . . . . . . . . . . . . . . . . . . . . 17) s -5 382 M -( 7. Diffie-Hellman Key Exchange . . . . . . . . . . . . . . . . 18) s -5 371 M -( 7.1 diffie-hellman-group1-sha1 . . . . . . . . . . . . . . . . . 19) s -5 360 M -( 8. Key Re-Exchange . . . . . . . . . . . . . . . . . . . . . . 20) s -5 349 M -( 9. Service Request . . . . . . . . . . . . . . . . . . . . . . 21) s -5 338 M -( 10. Additional Messages . . . . . . . . . . . . . . . . . . . . 21) s -5 327 M -( 10.1 Disconnection Message . . . . . . . . . . . . . . . . . . . 22) s -5 316 M -( 10.2 Ignored Data Message . . . . . . . . . . . . . . . . . . . . 22) s -5 305 M -( 10.3 Debug Message . . . . . . . . . . . . . . . . . . . . . . . 23) s -5 294 M -( 10.4 Reserved Messages . . . . . . . . . . . . . . . . . . . . . 23) s -5 283 M -( 11. Summary of Message Numbers . . . . . . . . . . . . . . . . . 23) s -5 272 M -( 12. IANA Considerations . . . . . . . . . . . . . . . . . . . . 24) s -5 261 M -( 13. Security Considerations . . . . . . . . . . . . . . . . . . 24) s -5 250 M -( 14. Intellectual Property . . . . . . . . . . . . . . . . . . . 24) s -5 239 M -( 15. Additional Information . . . . . . . . . . . . . . . . . . . 24) s -5 228 M -( Authors' Addresses . . . . . . . . . . . . . . . . . . . . . 26) s -5 217 M -( Normative . . . . . . . . . . . . . . . . . . . . . . . . . 25) s -5 206 M -( Informative . . . . . . . . . . . . . . . . . . . . . . . . 25) s -5 195 M -( A. Contibutors . . . . . . . . . . . . . . . . . . . . . . . . 27) s -5 184 M -( Intellectual Property and Copyright Statements . . . . . . . 28) s -5 129 M -(Ylonen & Moffat, Editor Expires March 31, 2004 [Page 2]) s -_R -S -PStoPSsaved restore -%%Page: (2,3) 2 -userdict/PStoPSsaved save put -PStoPSmatrix setmatrix -595.000000 0.271378 translate -90 rotate -0.706651 dup scale -userdict/PStoPSmatrix matrix currentmatrix put -userdict/PStoPSclip{0 0 moveto - 595.000000 0 rlineto 0 842.000000 rlineto -595.000000 0 rlineto - closepath}put initclip -/showpage{}def/copypage{}def/erasepage{}def -PStoPSxform concat -%%BeginPageSetup -_S -75 0 translate -/pagenum 3 def -/fname () def -/fdir () def -/ftail () def -/user_header_p false def -%%EndPageSetup -5 723 M -(Internet-Draft SSH Transport Layer Protocol Oct 2003) s -5 690 M -(1. Contributors) s -5 668 M -( The major original contributors of this document were: Tatu Ylonen,) s -5 657 M -( Tero Kivinen, Timo J. Rinne, Sami Lehtinen \(all of SSH Communications) s -5 646 M -( Security Corp\), and Markku-Juhani O. Saarinen \(University of) s -5 635 M -( Jyvaskyla\)) s -5 613 M -( The document editor is: [email protected]. Comments on this) s -5 602 M -( internet draft should be sent to the IETF SECSH working group,) s -5 591 M -( details at: http://ietf.org/html.charters/secsh-charter.html) s -5 569 M -(2. Introduction) s -5 547 M -( The SSH transport layer is a secure low level transport protocol. It) s -5 536 M -( provides strong encryption, cryptographic host authentication, and) s -5 525 M -( integrity protection.) s -5 503 M -( Authentication in this protocol level is host-based; this protocol) s -5 492 M -( does not perform user authentication. A higher level protocol for) s -5 481 M -( user authentication can be designed on top of this protocol.) s -5 459 M -( The protocol has been designed to be simple, flexible, to allow) s -5 448 M -( parameter negotiation, and to minimize the number of round-trips.) s -5 437 M -( Key exchange method, public key algorithm, symmetric encryption) s -5 426 M -( algorithm, message authentication algorithm, and hash algorithm are) s -5 415 M -( all negotiated. It is expected that in most environments, only 2) s -5 404 M -( round-trips will be needed for full key exchange, server) s -5 393 M -( authentication, service request, and acceptance notification of) s -5 382 M -( service request. The worst case is 3 round-trips.) s -5 360 M -(3. Conventions Used in This Document) s -5 338 M -( The keywords "MUST", "MUST NOT", "REQUIRED", "SHOULD", "SHOULD NOT",) s -5 327 M -( and "MAY" that appear in this document are to be interpreted as) s -5 316 M -( described in [RFC2119].) s -5 294 M -( The used data types and terminology are specified in the architecture) s -5 283 M -( document [SSH-ARCH].) s -5 261 M -( The architecture document also discusses the algorithm naming) s -5 250 M -( conventions that MUST be used with the SSH protocols.) s -5 228 M -(4. Connection Setup) s -5 206 M -( SSH works over any 8-bit clean, binary-transparent transport. The) s -5 195 M -( underlying transport SHOULD protect against transmission errors as) s -5 184 M -( such errors cause the SSH connection to terminate.) s -5 129 M -(Ylonen & Moffat, Editor Expires March 31, 2004 [Page 3]) s -_R -S -PStoPSsaved restore -userdict/PStoPSsaved save put -PStoPSmatrix setmatrix -595.000000 421.271378 translate -90 rotate -0.706651 dup scale -userdict/PStoPSmatrix matrix currentmatrix put -userdict/PStoPSclip{0 0 moveto - 595.000000 0 rlineto 0 842.000000 rlineto -595.000000 0 rlineto - closepath}put initclip -PStoPSxform concat -%%BeginPageSetup -_S -75 0 translate -/pagenum 4 def -/fname () def -/fdir () def -/ftail () def -/user_header_p false def -%%EndPageSetup -5 723 M -(Internet-Draft SSH Transport Layer Protocol Oct 2003) s -5 690 M -( The client initiates the connection.) s -5 668 M -(4.1 Use over TCP/IP) s -5 646 M -( When used over TCP/IP, the server normally listens for connections on) s -5 635 M -( port 22. This port number has been registered with the IANA, and has) s -5 624 M -( been officially assigned for SSH.) s -5 602 M -(4.2 Protocol Version Exchange) s -5 580 M -( When the connection has been established, both sides MUST send an) s -5 569 M -( identification string of the form "SSH-protoversion-softwareversion) s -5 558 M -( comments", followed by carriage return and newline characters \(ASCII) s -5 547 M -( 13 and 10, respectively\). Both sides MUST be able to process) s -5 536 M -( identification strings without carriage return character. No null) s -5 525 M -( character is sent. The maximum length of the string is 255) s -5 514 M -( characters, including the carriage return and newline.) s -5 492 M -( The part of the identification string preceding carriage return and) s -5 481 M -( newline is used in the Diffie-Hellman key exchange \(see Section) s -5 470 M -( Section 7\).) s -5 448 M -( The server MAY send other lines of data before sending the version) s -5 437 M -( string. Each line SHOULD be terminated by a carriage return and) s -5 426 M -( newline. Such lines MUST NOT begin with "SSH-", and SHOULD be) s -5 415 M -( encoded in ISO-10646 UTF-8 [RFC2279] \(language is not specified\).) s -5 404 M -( Clients MUST be able to process such lines; they MAY be silently) s -5 393 M -( ignored, or MAY be displayed to the client user; if they are) s -5 382 M -( displayed, control character filtering discussed in [SSH-ARCH] SHOULD) s -5 371 M -( be used. The primary use of this feature is to allow TCP-wrappers to) s -5 360 M -( display an error message before disconnecting.) s -5 338 M -( Version strings MUST consist of printable US-ASCII characters, not) s -5 327 M -( including whitespaces or a minus sign \(-\). The version string is) s -5 316 M -( primarily used to trigger compatibility extensions and to indicate) s -5 305 M -( the capabilities of an implementation. The comment string should) s -5 294 M -( contain additional information that might be useful in solving user) s -5 283 M -( problems.) s -5 261 M -( The protocol version described in this document is 2.0.) s -5 239 M -( Key exchange will begin immediately after sending this identifier.) s -5 228 M -( All packets following the identification string SHALL use the binary) s -5 217 M -( packet protocol, to be described below.) s -5 195 M -(4.3 Compatibility With Old SSH Versions) s -5 173 M -( During the transition period, it is important to be able to work in a) s -5 129 M -(Ylonen & Moffat, Editor Expires March 31, 2004 [Page 4]) s -_R -S -PStoPSsaved restore -%%Page: (4,5) 3 -userdict/PStoPSsaved save put -PStoPSmatrix setmatrix -595.000000 0.271378 translate -90 rotate -0.706651 dup scale -userdict/PStoPSmatrix matrix currentmatrix put -userdict/PStoPSclip{0 0 moveto - 595.000000 0 rlineto 0 842.000000 rlineto -595.000000 0 rlineto - closepath}put initclip -/showpage{}def/copypage{}def/erasepage{}def -PStoPSxform concat -%%BeginPageSetup -_S -75 0 translate -/pagenum 5 def -/fname () def -/fdir () def -/ftail () def -/user_header_p false def -%%EndPageSetup -5 723 M -(Internet-Draft SSH Transport Layer Protocol Oct 2003) s -5 690 M -( way that is compatible with the installed SSH clients and servers) s -5 679 M -( that use an older version of the protocol. Information in this) s -5 668 M -( section is only relevant for implementations supporting compatibility) s -5 657 M -( with SSH versions 1.x. There is no standards track or informational) s -5 646 M -( draft available that defines the SSH 1.x protocol. The only known) s -5 635 M -( documentation of the 1.x protocol is contained in README files that) s -5 624 M -( are shipped along with the source code.) s -5 602 M -(4.3.1 Old Client, New Server) s -5 580 M -( Server implementations MAY support a configurable "compatibility") s -5 569 M -( flag that enables compatibility with old versions. When this flag is) s -5 558 M -( on, the server SHOULD identify its protocol version as "1.99".) s -5 547 M -( Clients using protocol 2.0 MUST be able to identify this as identical) s -5 536 M -( to "2.0". In this mode the server SHOULD NOT send the carriage) s -5 525 M -( return character \(ASCII 13\) after the version identification string.) s -5 503 M -( In the compatibility mode the server SHOULD NOT send any further data) s -5 492 M -( after its initialization string until it has received an) s -5 481 M -( identification string from the client. The server can then determine) s -5 470 M -( whether the client is using an old protocol, and can revert to the) s -5 459 M -( old protocol if required. In the compatibility mode, the server MUST) s -5 448 M -( NOT send additional data before the version string.) s -5 426 M -( When compatibility with old clients is not needed, the server MAY) s -5 415 M -( send its initial key exchange data immediately after the) s -5 404 M -( identification string.) s -5 382 M -(4.3.2 New Client, Old Server) s -5 360 M -( Since the new client MAY immediately send additional data after its) s -5 349 M -( identification string \(before receiving server's identification\), the) s -5 338 M -( old protocol may already have been corrupted when the client learns) s -5 327 M -( that the server is old. When this happens, the client SHOULD close) s -5 316 M -( the connection to the server, and reconnect using the old protocol.) s -5 294 M -(5. Binary Packet Protocol) s -5 272 M -( Each packet is in the following format:) s -5 250 M -( uint32 packet_length) s -5 239 M -( byte padding_length) s -5 228 M -( byte[n1] payload; n1 = packet_length - padding_length - 1) s -5 217 M -( byte[n2] random padding; n2 = padding_length) s -5 206 M -( byte[m] mac \(message authentication code\); m = mac_length) s -5 184 M -( packet_length) s -5 129 M -(Ylonen & Moffat, Editor Expires March 31, 2004 [Page 5]) s -_R -S -PStoPSsaved restore -userdict/PStoPSsaved save put -PStoPSmatrix setmatrix -595.000000 421.271378 translate -90 rotate -0.706651 dup scale -userdict/PStoPSmatrix matrix currentmatrix put -userdict/PStoPSclip{0 0 moveto - 595.000000 0 rlineto 0 842.000000 rlineto -595.000000 0 rlineto - closepath}put initclip -PStoPSxform concat -%%BeginPageSetup -_S -75 0 translate -/pagenum 6 def -/fname () def -/fdir () def -/ftail () def -/user_header_p false def -%%EndPageSetup -5 723 M -(Internet-Draft SSH Transport Layer Protocol Oct 2003) s -5 690 M -( The length of the packet \(bytes\), not including MAC or the) s -5 679 M -( packet_length field itself.) s -5 657 M -( padding_length) s -5 646 M -( Length of padding \(bytes\).) s -5 624 M -( payload) s -5 613 M -( The useful contents of the packet. If compression has been) s -5 602 M -( negotiated, this field is compressed. Initially, compression) s -5 591 M -( MUST be "none".) s -5 569 M -( random padding) s -5 558 M -( Arbitrary-length padding, such that the total length of) s -5 547 M -( \(packet_length || padding_length || payload || padding\) is a) s -5 536 M -( multiple of the cipher block size or 8, whichever is larger.) s -5 525 M -( There MUST be at least four bytes of padding. The padding) s -5 514 M -( SHOULD consist of random bytes. The maximum amount of padding) s -5 503 M -( is 255 bytes.) s -5 481 M -( mac) s -5 470 M -( Message authentication code. If message authentication has) s -5 459 M -( been negotiated, this field contains the MAC bytes. Initially,) s -5 448 M -( the MAC algorithm MUST be "none".) s -5 415 M -( Note that length of the concatenation of packet length, padding) s -5 404 M -( length, payload, and padding MUST be a multiple of the cipher block) s -5 393 M -( size or 8, whichever is larger. This constraint MUST be enforced) s -5 382 M -( even when using stream ciphers. Note that the packet length field is) s -5 371 M -( also encrypted, and processing it requires special care when sending) s -5 360 M -( or receiving packets.) s -5 338 M -( The minimum size of a packet is 16 \(or the cipher block size,) s -5 327 M -( whichever is larger\) bytes \(plus MAC\); implementations SHOULD decrypt) s -5 316 M -( the length after receiving the first 8 \(or cipher block size,) s -5 305 M -( whichever is larger\) bytes of a packet.) s -5 283 M -(5.1 Maximum Packet Length) s -5 261 M -( All implementations MUST be able to process packets with uncompressed) s -5 250 M -( payload length of 32768 bytes or less and total packet size of 35000) s -5 239 M -( bytes or less \(including length, padding length, payload, padding,) s -5 228 M -( and MAC.\). The maximum of 35000 bytes is an arbitrary chosen value) s -5 217 M -( larger than uncompressed size. Implementations SHOULD support longer) s -5 206 M -( packets, where they might be needed, e.g. if an implementation wants) s -5 195 M -( to send a very large number of certificates. Such packets MAY be) s -5 184 M -( sent if the version string indicates that the other party is able to) s -5 173 M -( process them. However, implementations SHOULD check that the packet) s -5 129 M -(Ylonen & Moffat, Editor Expires March 31, 2004 [Page 6]) s -_R -S -PStoPSsaved restore -%%Page: (6,7) 4 -userdict/PStoPSsaved save put -PStoPSmatrix setmatrix -595.000000 0.271378 translate -90 rotate -0.706651 dup scale -userdict/PStoPSmatrix matrix currentmatrix put -userdict/PStoPSclip{0 0 moveto - 595.000000 0 rlineto 0 842.000000 rlineto -595.000000 0 rlineto - closepath}put initclip -/showpage{}def/copypage{}def/erasepage{}def -PStoPSxform concat -%%BeginPageSetup -_S -75 0 translate -/pagenum 7 def -/fname () def -/fdir () def -/ftail () def -/user_header_p false def -%%EndPageSetup -5 723 M -(Internet-Draft SSH Transport Layer Protocol Oct 2003) s -5 690 M -( length is reasonable for the implementation to avoid) s -5 679 M -( denial-of-service and/or buffer overflow attacks.) s -5 657 M -(5.2 Compression) s -5 635 M -( If compression has been negotiated, the payload field \(and only it\)) s -5 624 M -( will be compressed using the negotiated algorithm. The length field) s -5 613 M -( and MAC will be computed from the compressed payload. Encryption will) s -5 602 M -( be done after compression.) s -5 580 M -( Compression MAY be stateful, depending on the method. Compression) s -5 569 M -( MUST be independent for each direction, and implementations MUST) s -5 558 M -( allow independently choosing the algorithm for each direction.) s -5 536 M -( The following compression methods are currently defined:) s -5 514 M -( none REQUIRED no compression) s -5 503 M -( zlib OPTIONAL ZLIB \(LZ77\) compression) s -5 481 M -( The "zlib" compression is described in [RFC1950] and in [RFC1951].) s -5 470 M -( The compression context is initialized after each key exchange, and) s -5 459 M -( is passed from one packet to the next with only a partial flush being) s -5 448 M -( performed at the end of each packet. A partial flush means that the) s -5 437 M -( current compressed block is ended and all data will be output. If the) s -5 426 M -( current block is not a stored block, one or more empty blocks are) s -5 415 M -( added after the current block to ensure that there are at least 8) s -5 404 M -( bits counting from the start of the end-of-block code of the current) s -5 393 M -( block to the end of the packet payload.) s -5 371 M -( Additional methods may be defined as specified in [SSH-ARCH].) s -5 349 M -(5.3 Encryption) s -5 327 M -( An encryption algorithm and a key will be negotiated during the key) s -5 316 M -( exchange. When encryption is in effect, the packet length, padding) s -5 305 M -( length, payload and padding fields of each packet MUST be encrypted) s -5 294 M -( with the given algorithm.) s -5 272 M -( The encrypted data in all packets sent in one direction SHOULD be) s -5 261 M -( considered a single data stream. For example, initialization vectors) s -5 250 M -( SHOULD be passed from the end of one packet to the beginning of the) s -5 239 M -( next packet. All ciphers SHOULD use keys with an effective key length) s -5 228 M -( of 128 bits or more.) s -5 206 M -( The ciphers in each direction MUST run independently of each other,) s -5 195 M -( and implementations MUST allow independently choosing the algorithm) s -5 184 M -( for each direction \(if multiple algorithms are allowed by local) s -5 173 M -( policy\).) s -5 129 M -(Ylonen & Moffat, Editor Expires March 31, 2004 [Page 7]) s -_R -S -PStoPSsaved restore -userdict/PStoPSsaved save put -PStoPSmatrix setmatrix -595.000000 421.271378 translate -90 rotate -0.706651 dup scale -userdict/PStoPSmatrix matrix currentmatrix put -userdict/PStoPSclip{0 0 moveto - 595.000000 0 rlineto 0 842.000000 rlineto -595.000000 0 rlineto - closepath}put initclip -PStoPSxform concat -%%BeginPageSetup -_S -75 0 translate -/pagenum 8 def -/fname () def -/fdir () def -/ftail () def -/user_header_p false def -%%EndPageSetup -5 723 M -(Internet-Draft SSH Transport Layer Protocol Oct 2003) s -5 690 M -( The following ciphers are currently defined:) s -5 668 M -( 3des-cbc REQUIRED three-key 3DES in CBC mode) s -5 657 M -( blowfish-cbc OPTIONALi Blowfish in CBC mode) s -5 646 M -( twofish256-cbc OPTIONAL Twofish in CBC mode,) s -5 635 M -( with 256-bit key) s -5 624 M -( twofish-cbc OPTIONAL alias for "twofish256-cbc" \(this) s -5 613 M -( is being retained for) s -5 602 M -( historical reasons\)) s -5 591 M -( twofish192-cbc OPTIONAL Twofish with 192-bit key) s -5 580 M -( twofish128-cbc OPTIONAL Twofish with 128-bit key) s -5 569 M -( aes256-cbc OPTIONAL AES \(Rijndael\) in CBC mode,) s -5 558 M -( with 256-bit key) s -5 547 M -( aes192-cbc OPTIONAL AES with 192-bit key) s -5 536 M -( aes128-cbc RECOMMENDED AES with 128-bit key) s -5 525 M -( serpent256-cbc OPTIONAL Serpent in CBC mode, with) s -5 514 M -( 256-bit key) s -5 503 M -( serpent192-cbc OPTIONAL Serpent with 192-bit key) s -5 492 M -( serpent128-cbc OPTIONAL Serpent with 128-bit key) s -5 481 M -( arcfour OPTIONAL the ARCFOUR stream cipher) s -5 470 M -( idea-cbc OPTIONAL IDEA in CBC mode) s -5 459 M -( cast128-cbc OPTIONAL CAST-128 in CBC mode) s -5 448 M -( none OPTIONAL no encryption; NOT RECOMMENDED) s -5 426 M -( The "3des-cbc" cipher is three-key triple-DES) s -5 415 M -( \(encrypt-decrypt-encrypt\), where the first 8 bytes of the key are) s -5 404 M -( used for the first encryption, the next 8 bytes for the decryption,) s -5 393 M -( and the following 8 bytes for the final encryption. This requires 24) s -5 382 M -( bytes of key data \(of which 168 bits are actually used\). To) s -5 371 M -( implement CBC mode, outer chaining MUST be used \(i.e., there is only) s -5 360 M -( one initialization vector\). This is a block cipher with 8 byte) s -5 349 M -( blocks. This algorithm is defined in [FIPS-46-3]) s -5 327 M -( The "blowfish-cbc" cipher is Blowfish in CBC mode, with 128 bit keys) s -5 316 M -( [SCHNEIER]. This is a block cipher with 8 byte blocks.) s -5 294 M -( The "twofish-cbc" or "twofish256-cbc" cipher is Twofish in CBC mode,) s -5 283 M -( with 256 bit keys as described [TWOFISH]. This is a block cipher with) s -5 272 M -( 16 byte blocks.) s -5 250 M -( The "twofish192-cbc" cipher. Same as above but with 192-bit key.) s -5 228 M -( The "twofish128-cbc" cipher. Same as above but with 128-bit key.) s -5 206 M -( The "aes256-cbc" cipher is AES \(Advanced Encryption Standard\)) s -5 195 M -( [FIPS-197], formerly Rijndael, in CBC mode. This version uses 256-bit) s -5 184 M -( key.) s -5 129 M -(Ylonen & Moffat, Editor Expires March 31, 2004 [Page 8]) s -_R -S -PStoPSsaved restore -%%Page: (8,9) 5 -userdict/PStoPSsaved save put -PStoPSmatrix setmatrix -595.000000 0.271378 translate -90 rotate -0.706651 dup scale -userdict/PStoPSmatrix matrix currentmatrix put -userdict/PStoPSclip{0 0 moveto - 595.000000 0 rlineto 0 842.000000 rlineto -595.000000 0 rlineto - closepath}put initclip -/showpage{}def/copypage{}def/erasepage{}def -PStoPSxform concat -%%BeginPageSetup -_S -75 0 translate -/pagenum 9 def -/fname () def -/fdir () def -/ftail () def -/user_header_p false def -%%EndPageSetup -5 723 M -(Internet-Draft SSH Transport Layer Protocol Oct 2003) s -5 690 M -( The "aes192-cbc" cipher. Same as above but with 192-bit key.) s -5 668 M -( The "aes128-cbc" cipher. Same as above but with 128-bit key.) s -5 646 M -( The "serpent256-cbc" cipher in CBC mode, with 256-bit key as) s -5 635 M -( described in the Serpent AES submission.) s -5 613 M -( The "serpent192-cbc" cipher. Same as above but with 192-bit key.) s -5 591 M -( The "serpent128-cbc" cipher. Same as above but with 128-bit key.) s -5 569 M -( The "arcfour" is the Arcfour stream cipher with 128 bit keys. The) s -5 558 M -( Arcfour cipher is believed to be compatible with the RC4 cipher) s -5 547 M -( [SCHNEIER]. RC4 is a registered trademark of RSA Data Security Inc.) s -5 536 M -( Arcfour \(and RC4\) has problems with weak keys, and should be used) s -5 525 M -( with caution.) s -5 503 M -( The "idea-cbc" cipher is the IDEA cipher in CBC mode [SCHNEIER].) s -5 481 M -( The "cast128-cbc" cipher is the CAST-128 cipher in CBC mode) s -5 470 M -( [RFC2144].) s -5 448 M -( The "none" algorithm specifies that no encryption is to be done.) s -5 437 M -( Note that this method provides no confidentiality protection, and it) s -5 426 M -( is not recommended. Some functionality \(e.g. password) s -5 415 M -( authentication\) may be disabled for security reasons if this cipher) s -5 404 M -( is chosen.) s -5 382 M -( Additional methods may be defined as specified in [SSH-ARCH].) s -5 360 M -(5.4 Data Integrity) s -5 338 M -( Data integrity is protected by including with each packet a message) s -5 327 M -( authentication code \(MAC\) that is computed from a shared secret,) s -5 316 M -( packet sequence number, and the contents of the packet.) s -5 294 M -( The message authentication algorithm and key are negotiated during) s -5 283 M -( key exchange. Initially, no MAC will be in effect, and its length) s -5 272 M -( MUST be zero. After key exchange, the selected MAC will be computed) s -5 261 M -( before encryption from the concatenation of packet data:) s -5 239 M -( mac = MAC\(key, sequence_number || unencrypted_packet\)) s -5 217 M -( where unencrypted_packet is the entire packet without MAC \(the length) s -5 206 M -( fields, payload and padding\), and sequence_number is an implicit) s -5 195 M -( packet sequence number represented as uint32. The sequence number is) s -5 184 M -( initialized to zero for the first packet, and is incremented after) s -5 173 M -( every packet \(regardless of whether encryption or MAC is in use\). It) s -5 129 M -(Ylonen & Moffat, Editor Expires March 31, 2004 [Page 9]) s -_R -S -PStoPSsaved restore -userdict/PStoPSsaved save put -PStoPSmatrix setmatrix -595.000000 421.271378 translate -90 rotate -0.706651 dup scale -userdict/PStoPSmatrix matrix currentmatrix put -userdict/PStoPSclip{0 0 moveto - 595.000000 0 rlineto 0 842.000000 rlineto -595.000000 0 rlineto - closepath}put initclip -PStoPSxform concat -%%BeginPageSetup -_S -75 0 translate -/pagenum 10 def -/fname () def -/fdir () def -/ftail () def -/user_header_p false def -%%EndPageSetup -5 723 M -(Internet-Draft SSH Transport Layer Protocol Oct 2003) s -5 690 M -( is never reset, even if keys/algorithms are renegotiated later. It) s -5 679 M -( wraps around to zero after every 2^32 packets. The packet sequence) s -5 668 M -( number itself is not included in the packet sent over the wire.) s -5 646 M -( The MAC algorithms for each direction MUST run independently, and) s -5 635 M -( implementations MUST allow choosing the algorithm independently for) s -5 624 M -( both directions.) s -5 602 M -( The MAC bytes resulting from the MAC algorithm MUST be transmitted) s -5 591 M -( without encryption as the last part of the packet. The number of MAC) s -5 580 M -( bytes depends on the algorithm chosen.) s -5 558 M -( The following MAC algorithms are currently defined:) s -5 536 M -( hmac-sha1 REQUIRED HMAC-SHA1 \(digest length = key) s -5 525 M -( length = 20\)) s -5 514 M -( hmac-sha1-96 RECOMMENDED first 96 bits of HMAC-SHA1 \(digest) s -5 503 M -( length = 12, key length = 20\)) s -5 492 M -( hmac-md5 OPTIONAL HMAC-MD5 \(digest length = key) s -5 481 M -( length = 16\)) s -5 470 M -( hmac-md5-96 OPTIONAL first 96 bits of HMAC-MD5 \(digest) s -5 459 M -( length = 12, key length = 16\)) s -5 448 M -( none OPTIONAL no MAC; NOT RECOMMENDED) s -5 426 M -( Figure 1) s -5 404 M -( The "hmac-*" algorithms are described in [RFC2104] The "*-n" MACs use) s -5 393 M -( only the first n bits of the resulting value.) s -5 371 M -( The hash algorithms are described in [SCHNEIER].) s -5 349 M -( Additional methods may be defined as specified in [SSH-ARCH].) s -5 327 M -(5.5 Key Exchange Methods) s -5 305 M -( The key exchange method specifies how one-time session keys are) s -5 294 M -( generated for encryption and for authentication, and how the server) s -5 283 M -( authentication is done.) s -5 261 M -( Only one REQUIRED key exchange method has been defined:) s -5 239 M -( diffie-hellman-group1-sha1 REQUIRED) s -5 217 M -( This method is described later in this document.) s -5 195 M -( Additional methods may be defined as specified in [SSH-ARCH].) s -5 129 M -(Ylonen & Moffat, Editor Expires March 31, 2004 [Page 10]) s -_R -S -PStoPSsaved restore -%%Page: (10,11) 6 -userdict/PStoPSsaved save put -PStoPSmatrix setmatrix -595.000000 0.271378 translate -90 rotate -0.706651 dup scale -userdict/PStoPSmatrix matrix currentmatrix put -userdict/PStoPSclip{0 0 moveto - 595.000000 0 rlineto 0 842.000000 rlineto -595.000000 0 rlineto - closepath}put initclip -/showpage{}def/copypage{}def/erasepage{}def -PStoPSxform concat -%%BeginPageSetup -_S -75 0 translate -/pagenum 11 def -/fname () def -/fdir () def -/ftail () def -/user_header_p false def -%%EndPageSetup -5 723 M -(Internet-Draft SSH Transport Layer Protocol Oct 2003) s -5 690 M -(5.6 Public Key Algorithms) s -5 668 M -( This protocol has been designed to be able to operate with almost any) s -5 657 M -( public key format, encoding, and algorithm \(signature and/or) s -5 646 M -( encryption\).) s -5 624 M -( There are several aspects that define a public key type:) s -5 613 M -( o Key format: how is the key encoded and how are certificates) s -5 602 M -( represented. The key blobs in this protocol MAY contain) s -5 591 M -( certificates in addition to keys.) s -5 580 M -( o Signature and/or encryption algorithms. Some key types may not) s -5 569 M -( support both signing and encryption. Key usage may also be) s -5 558 M -( restricted by policy statements in e.g. certificates. In this) s -5 547 M -( case, different key types SHOULD be defined for the different) s -5 536 M -( policy alternatives.) s -5 525 M -( o Encoding of signatures and/or encrypted data. This includes but is) s -5 514 M -( not limited to padding, byte order, and data formats.) s -5 492 M -( The following public key and/or certificate formats are currently defined:) s -5 470 M -( ssh-dss REQUIRED sign Raw DSS Key) s -5 459 M -( ssh-rsa RECOMMENDED sign Raw RSA Key) s -5 448 M -( x509v3-sign-rsa OPTIONAL sign X.509 certificates \(RSA key\)) s -5 437 M -( x509v3-sign-dss OPTIONAL sign X.509 certificates \(DSS key\)) s -5 426 M -( spki-sign-rsa OPTIONAL sign SPKI certificates \(RSA key\)) s -5 415 M -( spki-sign-dss OPTIONAL sign SPKI certificates \(DSS key\)) s -5 404 M -( pgp-sign-rsa OPTIONAL sign OpenPGP certificates \(RSA key\)) s -5 393 M -( pgp-sign-dss OPTIONAL sign OpenPGP certificates \(DSS key\)) s -5 371 M -( Additional key types may be defined as specified in [SSH-ARCH].) s -5 349 M -( The key type MUST always be explicitly known \(from algorithm) s -5 338 M -( negotiation or some other source\). It is not normally included in) s -5 327 M -( the key blob.) s -5 305 M -( Certificates and public keys are encoded as follows:) s -5 283 M -( string certificate or public key format identifier) s -5 272 M -( byte[n] key/certificate data) s -5 250 M -( The certificate part may have be a zero length string, but a public) s -5 239 M -( key is required. This is the public key that will be used for) s -5 228 M -( authentication; the certificate sequence contained in the certificate) s -5 217 M -( blob can be used to provide authorization.) s -5 195 M -( Public key / certifcate formats that do not explicitly specify a) s -5 184 M -( signature format identifier MUST use the public key / certificate) s -5 173 M -( format identifier as the signature identifier.) s -5 129 M -(Ylonen & Moffat, Editor Expires March 31, 2004 [Page 11]) s -_R -S -PStoPSsaved restore -userdict/PStoPSsaved save put -PStoPSmatrix setmatrix -595.000000 421.271378 translate -90 rotate -0.706651 dup scale -userdict/PStoPSmatrix matrix currentmatrix put -userdict/PStoPSclip{0 0 moveto - 595.000000 0 rlineto 0 842.000000 rlineto -595.000000 0 rlineto - closepath}put initclip -PStoPSxform concat -%%BeginPageSetup -_S -75 0 translate -/pagenum 12 def -/fname () def -/fdir () def -/ftail () def -/user_header_p false def -%%EndPageSetup -5 723 M -(Internet-Draft SSH Transport Layer Protocol Oct 2003) s -5 690 M -( Signatures are encoded as follows:) s -5 679 M -( string signature format identifier \(as specified by the) s -5 668 M -( public key / cert format\)) s -5 657 M -( byte[n] signature blob in format specific encoding.) s -5 624 M -( The "ssh-dss" key format has the following specific encoding:) s -5 602 M -( string "ssh-dss") s -5 591 M -( mpint p) s -5 580 M -( mpint q) s -5 569 M -( mpint g) s -5 558 M -( mpint y) s -5 536 M -( Here the p, q, g, and y parameters form the signature key blob.) s -5 514 M -( Signing and verifying using this key format is done according to the) s -5 503 M -( Digital Signature Standard [FIPS-186] using the SHA-1 hash. A) s -5 492 M -( description can also be found in [SCHNEIER].) s -5 470 M -( The resulting signature is encoded as follows:) s -5 448 M -( string "ssh-dss") s -5 437 M -( string dss_signature_blob) s -5 415 M -( dss_signature_blob is encoded as a string containing r followed by s) s -5 404 M -( \(which are 160 bits long integers, without lengths or padding,) s -5 393 M -( unsigned and in network byte order\).) s -5 371 M -( The "ssh-rsa" key format has the following specific encoding:) s -5 349 M -( string "ssh-rsa") s -5 338 M -( mpint e) s -5 327 M -( mpint n) s -5 305 M -( Here the e and n parameters form the signature key blob.) s -5 283 M -( Signing and verifying using this key format is done according to) s -5 272 M -( [SCHNEIER] and [PKCS1] using the SHA-1 hash.) s -5 250 M -( The resulting signature is encoded as follows:) s -5 228 M -( string "ssh-rsa") s -5 217 M -( string rsa_signature_blob) s -5 195 M -( rsa_signature_blob is encoded as a string containing s \(which is an) s -5 184 M -( integer, without lengths or padding, unsigned and in network byte) s -5 173 M -( order\).) s -5 129 M -(Ylonen & Moffat, Editor Expires March 31, 2004 [Page 12]) s -_R -S -PStoPSsaved restore -%%Page: (12,13) 7 -userdict/PStoPSsaved save put -PStoPSmatrix setmatrix -595.000000 0.271378 translate -90 rotate -0.706651 dup scale -userdict/PStoPSmatrix matrix currentmatrix put -userdict/PStoPSclip{0 0 moveto - 595.000000 0 rlineto 0 842.000000 rlineto -595.000000 0 rlineto - closepath}put initclip -/showpage{}def/copypage{}def/erasepage{}def -PStoPSxform concat -%%BeginPageSetup -_S -75 0 translate -/pagenum 13 def -/fname () def -/fdir () def -/ftail () def -/user_header_p false def -%%EndPageSetup -5 723 M -(Internet-Draft SSH Transport Layer Protocol Oct 2003) s -5 690 M -( The "spki-sign-rsa" method indicates that the certificate blob) s -5 679 M -( contains a sequence of SPKI certificates. The format of SPKI) s -5 668 M -( certificates is described in [RFC2693]. This method indicates that) s -5 657 M -( the key \(or one of the keys in the certificate\) is an RSA-key.) s -5 635 M -( The "spki-sign-dss". As above, but indicates that the key \(or one of) s -5 624 M -( the keys in the certificate\) is a DSS-key.) s -5 602 M -( The "pgp-sign-rsa" method indicates the certificates, the public key,) s -5 591 M -( and the signature are in OpenPGP compatible binary format) s -5 580 M -( \([RFC2440]\). This method indicates that the key is an RSA-key.) s -5 558 M -( The "pgp-sign-dss". As above, but indicates that the key is a) s -5 547 M -( DSS-key.) s -5 525 M -(6. Key Exchange) s -5 503 M -( Key exchange begins by each side sending lists of supported) s -5 492 M -( algorithms. Each side has a preferred algorithm in each category, and) s -5 481 M -( it is assumed that most implementations at any given time will use) s -5 470 M -( the same preferred algorithm. Each side MAY guess which algorithm) s -5 459 M -( the other side is using, and MAY send an initial key exchange packet) s -5 448 M -( according to the algorithm if appropriate for the preferred method.) s -5 426 M -( Guess is considered wrong, if:) s -5 415 M -( o the kex algorithm and/or the host key algorithm is guessed wrong) s -5 404 M -( \(server and client have different preferred algorithm\), or) s -5 393 M -( o if any of the other algorithms cannot be agreed upon \(the) s -5 382 M -( procedure is defined below in Section Section 6.1\).) s -5 360 M -( Otherwise, the guess is considered to be right and the optimistically) s -5 349 M -( sent packet MUST be handled as the first key exchange packet.) s -5 327 M -( However, if the guess was wrong, and a packet was optimistically sent) s -5 316 M -( by one or both parties, such packets MUST be ignored \(even if the) s -5 305 M -( error in the guess would not affect the contents of the initial) s -5 294 M -( packet\(s\)\), and the appropriate side MUST send the correct initial) s -5 283 M -( packet.) s -5 261 M -( Server authentication in the key exchange MAY be implicit. After a) s -5 250 M -( key exchange with implicit server authentication, the client MUST) s -5 239 M -( wait for response to its service request message before sending any) s -5 228 M -( further data.) s -5 206 M -(6.1 Algorithm Negotiation) s -5 184 M -( Key exchange begins by each side sending the following packet:) s -5 129 M -(Ylonen & Moffat, Editor Expires March 31, 2004 [Page 13]) s -_R -S -PStoPSsaved restore -userdict/PStoPSsaved save put -PStoPSmatrix setmatrix -595.000000 421.271378 translate -90 rotate -0.706651 dup scale -userdict/PStoPSmatrix matrix currentmatrix put -userdict/PStoPSclip{0 0 moveto - 595.000000 0 rlineto 0 842.000000 rlineto -595.000000 0 rlineto - closepath}put initclip -PStoPSxform concat -%%BeginPageSetup -_S -75 0 translate -/pagenum 14 def -/fname () def -/fdir () def -/ftail () def -/user_header_p false def -%%EndPageSetup -5 723 M -(Internet-Draft SSH Transport Layer Protocol Oct 2003) s -5 690 M -( byte SSH_MSG_KEXINIT) s -5 679 M -( byte[16] cookie \(random bytes\)) s -5 668 M -( string kex_algorithms) s -5 657 M -( string server_host_key_algorithms) s -5 646 M -( string encryption_algorithms_client_to_server) s -5 635 M -( string encryption_algorithms_server_to_client) s -5 624 M -( string mac_algorithms_client_to_server) s -5 613 M -( string mac_algorithms_server_to_client) s -5 602 M -( string compression_algorithms_client_to_server) s -5 591 M -( string compression_algorithms_server_to_client) s -5 580 M -( string languages_client_to_server) s -5 569 M -( string languages_server_to_client) s -5 558 M -( boolean first_kex_packet_follows) s -5 547 M -( uint32 0 \(reserved for future extension\)) s -5 525 M -( Each of the algorithm strings MUST be a comma-separated list of) s -5 514 M -( algorithm names \(see ''Algorithm Naming'' in [SSH-ARCH]\). Each) s -5 503 M -( supported \(allowed\) algorithm MUST be listed in order of preference.) s -5 481 M -( The first algorithm in each list MUST be the preferred \(guessed\)) s -5 470 M -( algorithm. Each string MUST contain at least one algorithm name.) s -5 437 M -( cookie) s -5 426 M -( The cookie MUST be a random value generated by the sender. Its) s -5 415 M -( purpose is to make it impossible for either side to fully) s -5 404 M -( determine the keys and the session identifier.) s -5 382 M -( kex_algorithms) s -5 371 M -( Key exchange algorithms were defined above. The first) s -5 360 M -( algorithm MUST be the preferred \(and guessed\) algorithm. If) s -5 349 M -( both sides make the same guess, that algorithm MUST be used.) s -5 338 M -( Otherwise, the following algorithm MUST be used to choose a key) s -5 327 M -( exchange method: iterate over client's kex algorithms, one at a) s -5 316 M -( time. Choose the first algorithm that satisfies the following) s -5 305 M -( conditions:) s -5 294 M -( + the server also supports the algorithm,) s -5 283 M -( + if the algorithm requires an encryption-capable host key,) s -5 272 M -( there is an encryption-capable algorithm on the server's) s -5 261 M -( server_host_key_algorithms that is also supported by the) s -5 250 M -( client, and) s -5 239 M -( + if the algorithm requires a signature-capable host key,) s -5 228 M -( there is a signature-capable algorithm on the server's) s -5 217 M -( server_host_key_algorithms that is also supported by the) s -5 206 M -( client.) s -5 195 M -( + If no algorithm satisfying all these conditions can be) s -5 184 M -( found, the connection fails, and both sides MUST disconnect.) s -5 129 M -(Ylonen & Moffat, Editor Expires March 31, 2004 [Page 14]) s -_R -S -PStoPSsaved restore -%%Page: (14,15) 8 -userdict/PStoPSsaved save put -PStoPSmatrix setmatrix -595.000000 0.271378 translate -90 rotate -0.706651 dup scale -userdict/PStoPSmatrix matrix currentmatrix put -userdict/PStoPSclip{0 0 moveto - 595.000000 0 rlineto 0 842.000000 rlineto -595.000000 0 rlineto - closepath}put initclip -/showpage{}def/copypage{}def/erasepage{}def -PStoPSxform concat -%%BeginPageSetup -_S -75 0 translate -/pagenum 15 def -/fname () def -/fdir () def -/ftail () def -/user_header_p false def -%%EndPageSetup -5 723 M -(Internet-Draft SSH Transport Layer Protocol Oct 2003) s -5 690 M -( server_host_key_algorithms) s -5 679 M -( List of the algorithms supported for the server host key. The) s -5 668 M -( server lists the algorithms for which it has host keys; the) s -5 657 M -( client lists the algorithms that it is willing to accept.) s -5 646 M -( \(There MAY be multiple host keys for a host, possibly with) s -5 635 M -( different algorithms.\)) s -5 613 M -( Some host keys may not support both signatures and encryption) s -5 602 M -( \(this can be determined from the algorithm\), and thus not all) s -5 591 M -( host keys are valid for all key exchange methods.) s -5 569 M -( Algorithm selection depends on whether the chosen key exchange) s -5 558 M -( algorithm requires a signature or encryption capable host key.) s -5 547 M -( It MUST be possible to determine this from the public key) s -5 536 M -( algorithm name. The first algorithm on the client's list that) s -5 525 M -( satisfies the requirements and is also supported by the server) s -5 514 M -( MUST be chosen. If there is no such algorithm, both sides MUST) s -5 503 M -( disconnect.) s -5 481 M -( encryption_algorithms) s -5 470 M -( Lists the acceptable symmetric encryption algorithms in order) s -5 459 M -( of preference. The chosen encryption algorithm to each) s -5 448 M -( direction MUST be the first algorithm on the client's list) s -5 437 M -( that is also on the server's list. If there is no such) s -5 426 M -( algorithm, both sides MUST disconnect.) s -5 404 M -( Note that "none" must be explicitly listed if it is to be) s -5 393 M -( acceptable. The defined algorithm names are listed in Section) s -5 382 M -( Section 5.3.) s -5 360 M -( mac_algorithms) s -5 349 M -( Lists the acceptable MAC algorithms in order of preference.) s -5 338 M -( The chosen MAC algorithm MUST be the first algorithm on the) s -5 327 M -( client's list that is also on the server's list. If there is) s -5 316 M -( no such algorithm, both sides MUST disconnect.) s -5 294 M -( Note that "none" must be explicitly listed if it is to be) s -5 283 M -( acceptable. The MAC algorithm names are listed in Section) s -5 272 M -( Figure 1.) s -5 250 M -( compression_algorithms) s -5 239 M -( Lists the acceptable compression algorithms in order of) s -5 228 M -( preference. The chosen compression algorithm MUST be the first) s -5 217 M -( algorithm on the client's list that is also on the server's) s -5 206 M -( list. If there is no such algorithm, both sides MUST) s -5 195 M -( disconnect.) s -5 129 M -(Ylonen & Moffat, Editor Expires March 31, 2004 [Page 15]) s -_R -S -PStoPSsaved restore -userdict/PStoPSsaved save put -PStoPSmatrix setmatrix -595.000000 421.271378 translate -90 rotate -0.706651 dup scale -userdict/PStoPSmatrix matrix currentmatrix put -userdict/PStoPSclip{0 0 moveto - 595.000000 0 rlineto 0 842.000000 rlineto -595.000000 0 rlineto - closepath}put initclip -PStoPSxform concat -%%BeginPageSetup -_S -75 0 translate -/pagenum 16 def -/fname () def -/fdir () def -/ftail () def -/user_header_p false def -%%EndPageSetup -5 723 M -(Internet-Draft SSH Transport Layer Protocol Oct 2003) s -5 690 M -( Note that "none" must be explicitly listed if it is to be) s -5 679 M -( acceptable. The compression algorithm names are listed in) s -5 668 M -( Section Section 5.2.) s -5 646 M -( languages) s -5 635 M -( This is a comma-separated list of language tags in order of) s -5 624 M -( preference [RFC3066]. Both parties MAY ignore this list. If) s -5 613 M -( there are no language preferences, this list SHOULD be empty.) s -5 602 M -( Language tags SHOULD NOT be present unless they are known to be) s -5 591 M -( needed by the sending party.) s -5 569 M -( first_kex_packet_follows) s -5 558 M -( Indicates whether a guessed key exchange packet follows. If a) s -5 547 M -( guessed packet will be sent, this MUST be TRUE. If no guessed) s -5 536 M -( packet will be sent, this MUST be FALSE.) s -5 514 M -( After receiving the SSH_MSG_KEXINIT packet from the other side,) s -5 503 M -( each party will know whether their guess was right. If the) s -5 492 M -( other party's guess was wrong, and this field was TRUE, the) s -5 481 M -( next packet MUST be silently ignored, and both sides MUST then) s -5 470 M -( act as determined by the negotiated key exchange method. If) s -5 459 M -( the guess was right, key exchange MUST continue using the) s -5 448 M -( guessed packet.) s -5 426 M -( After the KEXINIT packet exchange, the key exchange algorithm is run.) s -5 415 M -( It may involve several packet exchanges, as specified by the key) s -5 404 M -( exchange method.) s -5 382 M -(6.2 Output from Key Exchange) s -5 360 M -( The key exchange produces two values: a shared secret K, and an) s -5 349 M -( exchange hash H. Encryption and authentication keys are derived from) s -5 338 M -( these. The exchange hash H from the first key exchange is) s -5 327 M -( additionally used as the session identifier, which is a unique) s -5 316 M -( identifier for this connection. It is used by authentication methods) s -5 305 M -( as a part of the data that is signed as a proof of possession of a) s -5 294 M -( private key. Once computed, the session identifier is not changed,) s -5 283 M -( even if keys are later re-exchanged.) s -5 250 M -( Each key exchange method specifies a hash function that is used in) s -5 239 M -( the key exchange. The same hash algorithm MUST be used in key) s -5 228 M -( derivation. Here, we'll call it HASH.) s -5 195 M -( Encryption keys MUST be computed as HASH of a known value and K as) s -5 184 M -( follows:) s -5 129 M -(Ylonen & Moffat, Editor Expires March 31, 2004 [Page 16]) s -_R -S -PStoPSsaved restore -%%Page: (16,17) 9 -userdict/PStoPSsaved save put -PStoPSmatrix setmatrix -595.000000 0.271378 translate -90 rotate -0.706651 dup scale -userdict/PStoPSmatrix matrix currentmatrix put -userdict/PStoPSclip{0 0 moveto - 595.000000 0 rlineto 0 842.000000 rlineto -595.000000 0 rlineto - closepath}put initclip -/showpage{}def/copypage{}def/erasepage{}def -PStoPSxform concat -%%BeginPageSetup -_S -75 0 translate -/pagenum 17 def -/fname () def -/fdir () def -/ftail () def -/user_header_p false def -%%EndPageSetup -5 723 M -(Internet-Draft SSH Transport Layer Protocol Oct 2003) s -5 690 M -( o Initial IV client to server: HASH\(K || H || "A" || session_id\)) s -5 679 M -( \(Here K is encoded as mpint and "A" as byte and session_id as raw) s -5 668 M -( data."A" means the single character A, ASCII 65\).) s -5 657 M -( o Initial IV server to client: HASH\(K || H || "B" || session_id\)) s -5 646 M -( o Encryption key client to server: HASH\(K || H || "C" || session_id\)) s -5 635 M -( o Encryption key server to client: HASH\(K || H || "D" || session_id\)) s -5 624 M -( o Integrity key client to server: HASH\(K || H || "E" || session_id\)) s -5 613 M -( o Integrity key server to client: HASH\(K || H || "F" || session_id\)) s -5 591 M -( Key data MUST be taken from the beginning of the hash output. 128) s -5 580 M -( bits \(16 bytes\) MUST be used for algorithms with variable-length) s -5 569 M -( keys. The only variable key length algorithm defined in this document) s -5 558 M -( is arcfour\). For other algorithms, as many bytes as are needed are) s -5 547 M -( taken from the beginning of the hash value. If the key length needed) s -5 536 M -( is longer than the output of the HASH, the key is extended by) s -5 525 M -( computing HASH of the concatenation of K and H and the entire key so) s -5 514 M -( far, and appending the resulting bytes \(as many as HASH generates\) to) s -5 503 M -( the key. This process is repeated until enough key material is) s -5 492 M -( available; the key is taken from the beginning of this value. In) s -5 481 M -( other words:) s -5 459 M -( K1 = HASH\(K || H || X || session_id\) \(X is e.g. "A"\)) s -5 448 M -( K2 = HASH\(K || H || K1\)) s -5 437 M -( K3 = HASH\(K || H || K1 || K2\)) s -5 426 M -( ...) s -5 415 M -( key = K1 || K2 || K3 || ...) s -5 393 M -( This process will lose entropy if the amount of entropy in K is) s -5 382 M -( larger than the internal state size of HASH.) s -5 360 M -(6.3 Taking Keys Into Use) s -5 338 M -( Key exchange ends by each side sending an SSH_MSG_NEWKEYS message.) s -5 327 M -( This message is sent with the old keys and algorithms. All messages) s -5 316 M -( sent after this message MUST use the new keys and algorithms.) s -5 283 M -( When this message is received, the new keys and algorithms MUST be) s -5 272 M -( taken into use for receiving.) s -5 239 M -( This message is the only valid message after key exchange, in) s -5 228 M -( addition to SSH_MSG_DEBUG, SSH_MSG_DISCONNECT and SSH_MSG_IGNORE) s -5 217 M -( messages. The purpose of this message is to ensure that a party is) s -5 206 M -( able to respond with a disconnect message that the other party can) s -5 195 M -( understand if something goes wrong with the key exchange.) s -5 184 M -( Implementations MUST NOT accept any other messages after key exchange) s -5 173 M -( before receiving SSH_MSG_NEWKEYS.) s -5 129 M -(Ylonen & Moffat, Editor Expires March 31, 2004 [Page 17]) s -_R -S -PStoPSsaved restore -userdict/PStoPSsaved save put -PStoPSmatrix setmatrix -595.000000 421.271378 translate -90 rotate -0.706651 dup scale -userdict/PStoPSmatrix matrix currentmatrix put -userdict/PStoPSclip{0 0 moveto - 595.000000 0 rlineto 0 842.000000 rlineto -595.000000 0 rlineto - closepath}put initclip -PStoPSxform concat -%%BeginPageSetup -_S -75 0 translate -/pagenum 18 def -/fname () def -/fdir () def -/ftail () def -/user_header_p false def -%%EndPageSetup -5 723 M -(Internet-Draft SSH Transport Layer Protocol Oct 2003) s -5 690 M -( byte SSH_MSG_NEWKEYS) s -5 657 M -(7. Diffie-Hellman Key Exchange) s -5 635 M -( The Diffie-Hellman key exchange provides a shared secret that can not) s -5 624 M -( be determined by either party alone. The key exchange is combined) s -5 613 M -( with a signature with the host key to provide host authentication.) s -5 580 M -( In the following description \(C is the client, S is the server; p is) s -5 569 M -( a large safe prime, g is a generator for a subgroup of GF\(p\), and q) s -5 558 M -( is the order of the subgroup; V_S is S's version string; V_C is C's) s -5 547 M -( version string; K_S is S's public host key; I_C is C's KEXINIT) s -5 536 M -( message and I_S S's KEXINIT message which have been exchanged before) s -5 525 M -( this part begins\):) s -5 492 M -( 1. C generates a random number x \(1 < x < q\) and computes e = g^x) s -5 481 M -( mod p. C sends "e" to S.) s -5 459 M -( 2. S generates a random number y \(0 < y < q\) and computes f = g^y) s -5 448 M -( mod p. S receives "e". It computes K = e^y mod p, H = hash\(V_C) s -5 437 M -( || V_S || I_C || I_S || K_S || e || f || K\) \(these elements are) s -5 426 M -( encoded according to their types; see below\), and signature s on) s -5 415 M -( H with its private host key. S sends "K_S || f || s" to C. The) s -5 404 M -( signing operation may involve a second hashing operation.) s -5 382 M -( 3. C verifies that K_S really is the host key for S \(e.g. using) s -5 371 M -( certificates or a local database\). C is also allowed to accept) s -5 360 M -( the key without verification; however, doing so will render the) s -5 349 M -( protocol insecure against active attacks \(but may be desirable) s -5 338 M -( for practical reasons in the short term in many environments\). C) s -5 327 M -( then computes K = f^x mod p, H = hash\(V_C || V_S || I_C || I_S ||) s -5 316 M -( K_S || e || f || K\), and verifies the signature s on H.) s -5 294 M -( Either side MUST NOT send or accept e or f values that are not in the) s -5 283 M -( range [1, p-1]. If this condition is violated, the key exchange) s -5 272 M -( fails.) s -5 239 M -( This is implemented with the following messages. The hash algorithm) s -5 228 M -( for computing the exchange hash is defined by the method name, and is) s -5 217 M -( called HASH. The public key algorithm for signing is negotiated with) s -5 206 M -( the KEXINIT messages.) s -5 184 M -( First, the client sends the following:) s -5 129 M -(Ylonen & Moffat, Editor Expires March 31, 2004 [Page 18]) s -_R -S -PStoPSsaved restore -%%Page: (18,19) 10 -userdict/PStoPSsaved save put -PStoPSmatrix setmatrix -595.000000 0.271378 translate -90 rotate -0.706651 dup scale -userdict/PStoPSmatrix matrix currentmatrix put -userdict/PStoPSclip{0 0 moveto - 595.000000 0 rlineto 0 842.000000 rlineto -595.000000 0 rlineto - closepath}put initclip -/showpage{}def/copypage{}def/erasepage{}def -PStoPSxform concat -%%BeginPageSetup -_S -75 0 translate -/pagenum 19 def -/fname () def -/fdir () def -/ftail () def -/user_header_p false def -%%EndPageSetup -5 723 M -(Internet-Draft SSH Transport Layer Protocol Oct 2003) s -5 690 M -( byte SSH_MSG_KEXDH_INIT) s -5 679 M -( mpint e) s -5 646 M -( The server responds with the following:) s -5 624 M -( byte SSH_MSG_KEXDH_REPLY) s -5 613 M -( string server public host key and certificates \(K_S\)) s -5 602 M -( mpint f) s -5 591 M -( string signature of H) s -5 569 M -( The hash H is computed as the HASH hash of the concatenation of the) s -5 558 M -( following:) s -5 536 M -( string V_C, the client's version string \(CR and NL excluded\)) s -5 525 M -( string V_S, the server's version string \(CR and NL excluded\)) s -5 514 M -( string I_C, the payload of the client's SSH_MSG_KEXINIT) s -5 503 M -( string I_S, the payload of the server's SSH_MSG_KEXINIT) s -5 492 M -( string K_S, the host key) s -5 481 M -( mpint e, exchange value sent by the client) s -5 470 M -( mpint f, exchange value sent by the server) s -5 459 M -( mpint K, the shared secret) s -5 437 M -( This value is called the exchange hash, and it is used to) s -5 426 M -( authenticate the key exchange. The exchange hash SHOULD be kept) s -5 415 M -( secret.) s -5 382 M -( The signature algorithm MUST be applied over H, not the original) s -5 371 M -( data. Most signature algorithms include hashing and additional) s -5 360 M -( padding. For example, "ssh-dss" specifies SHA-1 hashing; in that) s -5 349 M -( case, the data is first hashed with HASH to compute H, and H is then) s -5 338 M -( hashed with SHA-1 as part of the signing operation.) s -5 316 M -(7.1 diffie-hellman-group1-sha1) s -5 294 M -( The "diffie-hellman-group1-sha1" method specifies Diffie-Hellman key) s -5 283 M -( exchange with SHA-1 as HASH, and Oakley group 14 [RFC3526] \(2048-bit) s -5 272 M -( MODP Group\). It is included below in hexadecimal and decimal.) s -5 250 M -( The prime p is equal to 2^1024 - 2^960 - 1 + 2^64 * floor\( 2^894 Pi +) s -5 239 M -( 129093 \). Its hexadecimal value is:) s -5 217 M -( FFFFFFFF FFFFFFFF C90FDAA2 2168C234 C4C6628B 80DC1CD1) s -5 206 M -( 29024E08 8A67CC74 020BBEA6 3B139B22 514A0879 8E3404DD) s -5 195 M -( EF9519B3 CD3A431B 302B0A6D F25F1437 4FE1356D 6D51C245) s -5 184 M -( E485B576 625E7EC6 F44C42E9 A637ED6B 0BFF5CB6 F406B7ED) s -5 173 M -( EE386BFB 5A899FA5 AE9F2411 7C4B1FE6 49286651 ECE65381) s -5 129 M -(Ylonen & Moffat, Editor Expires March 31, 2004 [Page 19]) s -_R -S -PStoPSsaved restore -userdict/PStoPSsaved save put -PStoPSmatrix setmatrix -595.000000 421.271378 translate -90 rotate -0.706651 dup scale -userdict/PStoPSmatrix matrix currentmatrix put -userdict/PStoPSclip{0 0 moveto - 595.000000 0 rlineto 0 842.000000 rlineto -595.000000 0 rlineto - closepath}put initclip -PStoPSxform concat -%%BeginPageSetup -_S -75 0 translate -/pagenum 20 def -/fname () def -/fdir () def -/ftail () def -/user_header_p false def -%%EndPageSetup -5 723 M -(Internet-Draft SSH Transport Layer Protocol Oct 2003) s -5 690 M -( FFFFFFFF FFFFFFFF.) s -5 668 M -( In decimal, this value is:) s -5 646 M -( 179769313486231590770839156793787453197860296048756011706444) s -5 635 M -( 423684197180216158519368947833795864925541502180565485980503) s -5 624 M -( 646440548199239100050792877003355816639229553136239076508735) s -5 613 M -( 759914822574862575007425302077447712589550957937778424442426) s -5 602 M -( 617334727629299387668709205606050270810842907692932019128194) s -5 591 M -( 467627007.) s -5 569 M -( The generator used with this prime is g = 2. The group order q is \(p) s -5 558 M -( - 1\) / 2.) s -5 536 M -(8. Key Re-Exchange) s -5 514 M -( Key re-exchange is started by sending an SSH_MSG_KEXINIT packet when) s -5 503 M -( not already doing a key exchange \(as described in Section Section) s -5 492 M -( 6.1\). When this message is received, a party MUST respond with its) s -5 481 M -( own SSH_MSG_KEXINIT message except when the received SSH_MSG_KEXINIT) s -5 470 M -( already was a reply. Either party MAY initiate the re-exchange, but) s -5 459 M -( roles MUST NOT be changed \(i.e., the server remains the server, and) s -5 448 M -( the client remains the client\).) s -5 415 M -( Key re-exchange is performed using whatever encryption was in effect) s -5 404 M -( when the exchange was started. Encryption, compression, and MAC) s -5 393 M -( methods are not changed before a new SSH_MSG_NEWKEYS is sent after) s -5 382 M -( the key exchange \(as in the initial key exchange\). Re-exchange is) s -5 371 M -( processed identically to the initial key exchange, except for the) s -5 360 M -( session identifier that will remain unchanged. It is permissible to) s -5 349 M -( change some or all of the algorithms during the re-exchange. Host) s -5 338 M -( keys can also change. All keys and initialization vectors are) s -5 327 M -( recomputed after the exchange. Compression and encryption contexts) s -5 316 M -( are reset.) s -5 283 M -( It is recommended that the keys are changed after each gigabyte of) s -5 272 M -( transmitted data or after each hour of connection time, whichever) s -5 261 M -( comes sooner. However, since the re-exchange is a public key) s -5 250 M -( operation, it requires a fair amount of processing power and should) s -5 239 M -( not be performed too often.) s -5 206 M -( More application data may be sent after the SSH_MSG_NEWKEYS packet) s -5 195 M -( has been sent; key exchange does not affect the protocols that lie) s -5 184 M -( above the SSH transport layer.) s -5 129 M -(Ylonen & Moffat, Editor Expires March 31, 2004 [Page 20]) s -_R -S -PStoPSsaved restore -%%Page: (20,21) 11 -userdict/PStoPSsaved save put -PStoPSmatrix setmatrix -595.000000 0.271378 translate -90 rotate -0.706651 dup scale -userdict/PStoPSmatrix matrix currentmatrix put -userdict/PStoPSclip{0 0 moveto - 595.000000 0 rlineto 0 842.000000 rlineto -595.000000 0 rlineto - closepath}put initclip -/showpage{}def/copypage{}def/erasepage{}def -PStoPSxform concat -%%BeginPageSetup -_S -75 0 translate -/pagenum 21 def -/fname () def -/fdir () def -/ftail () def -/user_header_p false def -%%EndPageSetup -5 723 M -(Internet-Draft SSH Transport Layer Protocol Oct 2003) s -5 690 M -(9. Service Request) s -5 668 M -( After the key exchange, the client requests a service. The service is) s -5 657 M -( identified by a name. The format of names and procedures for defining) s -5 646 M -( new names are defined in [SSH-ARCH].) s -5 613 M -( Currently, the following names have been reserved:) s -5 591 M -( ssh-userauth) s -5 580 M -( ssh-connection) s -5 558 M -( Similar local naming policy is applied to the service names, as is) s -5 547 M -( applied to the algorithm names; a local service should use the) s -5 536 M -( "servicename@domain" syntax.) s -5 514 M -( byte SSH_MSG_SERVICE_REQUEST) s -5 503 M -( string service name) s -5 481 M -( If the server rejects the service request, it SHOULD send an) s -5 470 M -( appropriate SSH_MSG_DISCONNECT message and MUST disconnect.) s -5 437 M -( When the service starts, it may have access to the session identifier) s -5 426 M -( generated during the key exchange.) s -5 393 M -( If the server supports the service \(and permits the client to use) s -5 382 M -( it\), it MUST respond with the following:) s -5 360 M -( byte SSH_MSG_SERVICE_ACCEPT) s -5 349 M -( string service name) s -5 327 M -( Message numbers used by services should be in the area reserved for) s -5 316 M -( them \(see Section 6 in [SSH-ARCH]\). The transport level will) s -5 305 M -( continue to process its own messages.) s -5 272 M -( Note that after a key exchange with implicit server authentication,) s -5 261 M -( the client MUST wait for response to its service request message) s -5 250 M -( before sending any further data.) s -5 228 M -(10. Additional Messages) s -5 206 M -( Either party may send any of the following messages at any time.) s -5 129 M -(Ylonen & Moffat, Editor Expires March 31, 2004 [Page 21]) s -_R -S -PStoPSsaved restore -userdict/PStoPSsaved save put -PStoPSmatrix setmatrix -595.000000 421.271378 translate -90 rotate -0.706651 dup scale -userdict/PStoPSmatrix matrix currentmatrix put -userdict/PStoPSclip{0 0 moveto - 595.000000 0 rlineto 0 842.000000 rlineto -595.000000 0 rlineto - closepath}put initclip -PStoPSxform concat -%%BeginPageSetup -_S -75 0 translate -/pagenum 22 def -/fname () def -/fdir () def -/ftail () def -/user_header_p false def -%%EndPageSetup -5 723 M -(Internet-Draft SSH Transport Layer Protocol Oct 2003) s -5 690 M -(10.1 Disconnection Message) s -5 668 M -( byte SSH_MSG_DISCONNECT) s -5 657 M -( uint32 reason code) s -5 646 M -( string description [RFC2279]) s -5 635 M -( string language tag [RFC3066]) s -5 613 M -( This message causes immediate termination of the connection. All) s -5 602 M -( implementations MUST be able to process this message; they SHOULD be) s -5 591 M -( able to send this message.) s -5 569 M -( The sender MUST NOT send or receive any data after this message, and) s -5 558 M -( the recipient MUST NOT accept any data after receiving this message.) s -5 547 M -( The description field gives a more specific explanation in a) s -5 536 M -( human-readable form. The error code gives the reason in a more) s -5 525 M -( machine-readable format \(suitable for localization\), and can have the) s -5 514 M -( following values:) s -5 492 M -( #define SSH_DISCONNECT_HOST_NOT_ALLOWED_TO_CONNECT 1) s -5 481 M -( #define SSH_DISCONNECT_PROTOCOL_ERROR 2) s -5 470 M -( #define SSH_DISCONNECT_KEY_EXCHANGE_FAILED 3) s -5 459 M -( #define SSH_DISCONNECT_RESERVED 4) s -5 448 M -( #define SSH_DISCONNECT_MAC_ERROR 5) s -5 437 M -( #define SSH_DISCONNECT_COMPRESSION_ERROR 6) s -5 426 M -( #define SSH_DISCONNECT_SERVICE_NOT_AVAILABLE 7) s -5 415 M -( #define SSH_DISCONNECT_PROTOCOL_VERSION_NOT_SUPPORTED 8) s -5 404 M -( #define SSH_DISCONNECT_HOST_KEY_NOT_VERIFIABLE 9) s -5 393 M -( #define SSH_DISCONNECT_CONNECTION_LOST 10) s -5 382 M -( #define SSH_DISCONNECT_BY_APPLICATION 11) s -5 371 M -( #define SSH_DISCONNECT_TOO_MANY_CONNECTIONS 12) s -5 360 M -( #define SSH_DISCONNECT_AUTH_CANCELLED_BY_USER 13) s -5 349 M -( #define SSH_DISCONNECT_NO_MORE_AUTH_METHODS_AVAILABLE 14) s -5 338 M -( #define SSH_DISCONNECT_ILLEGAL_USER_NAME 15) s -5 316 M -( If the description string is displayed, control character filtering) s -5 305 M -( discussed in [SSH-ARCH] should be used to avoid attacks by sending) s -5 294 M -( terminal control characters.) s -5 272 M -(10.2 Ignored Data Message) s -5 250 M -( byte SSH_MSG_IGNORE) s -5 239 M -( string data) s -5 217 M -( All implementations MUST understand \(and ignore\) this message at any) s -5 206 M -( time \(after receiving the protocol version\). No implementation is) s -5 195 M -( required to send them. This message can be used as an additional) s -5 184 M -( protection measure against advanced traffic analysis techniques.) s -5 129 M -(Ylonen & Moffat, Editor Expires March 31, 2004 [Page 22]) s -_R -S -PStoPSsaved restore -%%Page: (22,23) 12 -userdict/PStoPSsaved save put -PStoPSmatrix setmatrix -595.000000 0.271378 translate -90 rotate -0.706651 dup scale -userdict/PStoPSmatrix matrix currentmatrix put -userdict/PStoPSclip{0 0 moveto - 595.000000 0 rlineto 0 842.000000 rlineto -595.000000 0 rlineto - closepath}put initclip -/showpage{}def/copypage{}def/erasepage{}def -PStoPSxform concat -%%BeginPageSetup -_S -75 0 translate -/pagenum 23 def -/fname () def -/fdir () def -/ftail () def -/user_header_p false def -%%EndPageSetup -5 723 M -(Internet-Draft SSH Transport Layer Protocol Oct 2003) s -5 690 M -(10.3 Debug Message) s -5 668 M -( byte SSH_MSG_DEBUG) s -5 657 M -( boolean always_display) s -5 646 M -( string message [RFC2279]) s -5 635 M -( string language tag [RFC3066]) s -5 613 M -( All implementations MUST understand this message, but they are) s -5 602 M -( allowed to ignore it. This message is used to pass the other side) s -5 591 M -( information that may help debugging. If always_display is TRUE, the) s -5 580 M -( message SHOULD be displayed. Otherwise, it SHOULD NOT be displayed) s -5 569 M -( unless debugging information has been explicitly requested by the) s -5 558 M -( user.) s -5 525 M -( The message doesn't need to contain a newline. It is, however,) s -5 514 M -( allowed to consist of multiple lines separated by CRLF \(Carriage) s -5 503 M -( Return - Line Feed\) pairs.) s -5 470 M -( If the message string is displayed, terminal control character) s -5 459 M -( filtering discussed in [SSH-ARCH] should be used to avoid attacks by) s -5 448 M -( sending terminal control characters.) s -5 426 M -(10.4 Reserved Messages) s -5 404 M -( An implementation MUST respond to all unrecognized messages with an) s -5 393 M -( SSH_MSG_UNIMPLEMENTED message in the order in which the messages were) s -5 382 M -( received. Such messages MUST be otherwise ignored. Later protocol) s -5 371 M -( versions may define other meanings for these message types.) s -5 349 M -( byte SSH_MSG_UNIMPLEMENTED) s -5 338 M -( uint32 packet sequence number of rejected message) s -5 305 M -(11. Summary of Message Numbers) s -5 283 M -( The following message numbers have been defined in this protocol:) s -5 261 M -( #define SSH_MSG_DISCONNECT 1) s -5 250 M -( #define SSH_MSG_IGNORE 2) s -5 239 M -( #define SSH_MSG_UNIMPLEMENTED 3) s -5 228 M -( #define SSH_MSG_DEBUG 4) s -5 217 M -( #define SSH_MSG_SERVICE_REQUEST 5) s -5 206 M -( #define SSH_MSG_SERVICE_ACCEPT 6) s -5 184 M -( #define SSH_MSG_KEXINIT 20) s -5 173 M -( #define SSH_MSG_NEWKEYS 21) s -5 129 M -(Ylonen & Moffat, Editor Expires March 31, 2004 [Page 23]) s -_R -S -PStoPSsaved restore -userdict/PStoPSsaved save put -PStoPSmatrix setmatrix -595.000000 421.271378 translate -90 rotate -0.706651 dup scale -userdict/PStoPSmatrix matrix currentmatrix put -userdict/PStoPSclip{0 0 moveto - 595.000000 0 rlineto 0 842.000000 rlineto -595.000000 0 rlineto - closepath}put initclip -PStoPSxform concat -%%BeginPageSetup -_S -75 0 translate -/pagenum 24 def -/fname () def -/fdir () def -/ftail () def -/user_header_p false def -%%EndPageSetup -5 723 M -(Internet-Draft SSH Transport Layer Protocol Oct 2003) s -5 690 M -( /* Numbers 30-49 used for kex packets.) s -5 679 M -( Different kex methods may reuse message numbers in) s -5 668 M -( this range. */) s -5 646 M -( #define SSH_MSG_KEXDH_INIT 30) s -5 635 M -( #define SSH_MSG_KEXDH_REPLY 31) s -5 602 M -(12. IANA Considerations) s -5 580 M -( This document is part of a set, the IANA considerations for the SSH) s -5 569 M -( protocol as defined in [SSH-ARCH], [SSH-TRANS], [SSH-USERAUTH],) s -5 558 M -( [SSH-CONNECT] are detailed in [SSH-NUMBERS].) s -5 536 M -(13. Security Considerations) s -5 514 M -( This protocol provides a secure encrypted channel over an insecure) s -5 503 M -( network. It performs server host authentication, key exchange,) s -5 492 M -( encryption, and integrity protection. It also derives a unique) s -5 481 M -( session id that may be used by higher-level protocols.) s -5 459 M -( Full security considerations for this protocol are provided in) s -5 448 M -( Section 8 of [SSH-ARCH]) s -5 426 M -(14. Intellectual Property) s -5 404 M -( The IETF takes no position regarding the validity or scope of any) s -5 393 M -( intellectual property or other rights that might be claimed to) s -5 382 M -( pertain to the implementation or use of the technology described in) s -5 371 M -( this document or the extent to which any license under such rights) s -5 360 M -( might or might not be available; neither does it represent that it) s -5 349 M -( has made any effort to identify any such rights. Information on the) s -5 338 M -( IETF's procedures with respect to rights in standards-track and) s -5 327 M -( standards-related documentation can be found in BCP-11. Copies of) s -5 316 M -( claims of rights made available for publication and any assurances of) s -5 305 M -( licenses to be made available, or the result of an attempt made to) s -5 294 M -( obtain a general license or permission for the use of such) s -5 283 M -( proprietary rights by implementers or users of this specification can) s -5 272 M -( be obtained from the IETF Secretariat.) s -5 250 M -( The IETF has been notified of intellectual property rights claimed in) s -5 239 M -( regard to some or all of the specification contained in this) s -5 228 M -( document. For more information consult the online list of claimed) s -5 217 M -( rights.) s -5 195 M -(15. Additional Information) s -5 173 M -( The current document editor is: [email protected]. Comments on) s -5 129 M -(Ylonen & Moffat, Editor Expires March 31, 2004 [Page 24]) s -_R -S -PStoPSsaved restore -%%Page: (24,25) 13 -userdict/PStoPSsaved save put -PStoPSmatrix setmatrix -595.000000 0.271378 translate -90 rotate -0.706651 dup scale -userdict/PStoPSmatrix matrix currentmatrix put -userdict/PStoPSclip{0 0 moveto - 595.000000 0 rlineto 0 842.000000 rlineto -595.000000 0 rlineto - closepath}put initclip -/showpage{}def/copypage{}def/erasepage{}def -PStoPSxform concat -%%BeginPageSetup -_S -75 0 translate -/pagenum 25 def -/fname () def -/fdir () def -/ftail () def -/user_header_p false def -%%EndPageSetup -5 723 M -(Internet-Draft SSH Transport Layer Protocol Oct 2003) s -5 690 M -( this internet draft should be sent to the IETF SECSH working group,) s -5 679 M -( details at: http://ietf.org/html.charters/secsh-charter.html) s -5 657 M -(Normative) s -5 635 M -( [SSH-ARCH]) s -5 624 M -( Ylonen, T., "SSH Protocol Architecture", I-D) s -5 613 M -( draft-ietf-architecture-15.txt, Oct 2003.) s -5 591 M -( [SSH-TRANS]) s -5 580 M -( Ylonen, T., "SSH Transport Layer Protocol", I-D) s -5 569 M -( draft-ietf-transport-17.txt, Oct 2003.) s -5 547 M -( [SSH-USERAUTH]) s -5 536 M -( Ylonen, T., "SSH Authentication Protocol", I-D) s -5 525 M -( draft-ietf-userauth-18.txt, Oct 2003.) s -5 503 M -( [SSH-CONNECT]) s -5 492 M -( Ylonen, T., "SSH Connection Protocol", I-D) s -5 481 M -( draft-ietf-connect-18.txt, Oct 2003.) s -5 459 M -( [SSH-NUMBERS]) s -5 448 M -( Lehtinen, S. and D. Moffat, "SSH Protocol Assigned) s -5 437 M -( Numbers", I-D draft-ietf-secsh-assignednumbers-05.txt, Oct) s -5 426 M -( 2003.) s -5 404 M -( [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate) s -5 393 M -( Requirement Levels", BCP 14, RFC 2119, March 1997.) s -5 371 M -(Informative) s -5 349 M -( [FIPS-186]) s -5 338 M -( Federal Information Processing Standards Publication,) s -5 327 M -( "FIPS PUB 186, Digital Signature Standard", May 1994.) s -5 305 M -( [FIPS-197]) s -5 294 M -( NIST, "FIPS PUB 197 Advanced Encryption Standard \(AES\)",) s -5 283 M -( November 2001.) s -5 261 M -( [FIPS-46-3]) s -5 250 M -( U.S. Dept. of Commerce, "FIPS PUB 46-3, Data Encryption) s -5 239 M -( Standard \(DES\)", October 1999.) s -5 217 M -( [RFC2459] Housley, R., Ford, W., Polk, T. and D. Solo, "Internet) s -5 206 M -( X.509 Public Key Infrastructure Certificate and CRL) s -5 195 M -( Profile", RFC 2459, January 1999.) s -5 173 M -( [RFC1034] Mockapetris, P., "Domain names - concepts and facilities",) s -5 129 M -(Ylonen & Moffat, Editor Expires March 31, 2004 [Page 25]) s -_R -S -PStoPSsaved restore -userdict/PStoPSsaved save put -PStoPSmatrix setmatrix -595.000000 421.271378 translate -90 rotate -0.706651 dup scale -userdict/PStoPSmatrix matrix currentmatrix put -userdict/PStoPSclip{0 0 moveto - 595.000000 0 rlineto 0 842.000000 rlineto -595.000000 0 rlineto - closepath}put initclip -PStoPSxform concat -%%BeginPageSetup -_S -75 0 translate -/pagenum 26 def -/fname () def -/fdir () def -/ftail () def -/user_header_p false def -%%EndPageSetup -5 723 M -(Internet-Draft SSH Transport Layer Protocol Oct 2003) s -5 690 M -( STD 13, RFC 1034, November 1987.) s -5 668 M -( [RFC3066] Alvestrand, H., "Tags for the Identification of) s -5 657 M -( Languages", BCP 47, RFC 3066, January 2001.) s -5 635 M -( [RFC1950] Deutsch, L. and J-L. Gailly, "ZLIB Compressed Data Format) s -5 624 M -( Specification version 3.3", RFC 1950, May 1996.) s -5 602 M -( [RFC1951] Deutsch, P., "DEFLATE Compressed Data Format Specification) s -5 591 M -( version 1.3", RFC 1951, May 1996.) s -5 569 M -( [RFC2279] Yergeau, F., "UTF-8, a transformation format of ISO) s -5 558 M -( 10646", RFC 2279, January 1998.) s -5 536 M -( [RFC2104] Krawczyk, H., Bellare, M. and R. Canetti, "HMAC:) s -5 525 M -( Keyed-Hashing for Message Authentication", RFC 2104,) s -5 514 M -( February 1997.) s -5 492 M -( [RFC2144] Adams, C., "The CAST-128 Encryption Algorithm", RFC 2144,) s -5 481 M -( May 1997.) s -5 459 M -( [RFC2440] Callas, J., Donnerhacke, L., Finney, H. and R. Thayer,) s -5 448 M -( "OpenPGP Message Format", RFC 2440, November 1998.) s -5 426 M -( [RFC2693] Ellison, C., Frantz, B., Lampson, B., Rivest, R., Thomas,) s -5 415 M -( B. and T. Ylonen, "SPKI Certificate Theory", RFC 2693,) s -5 404 M -( September 1999.) s -5 382 M -( [RFC3526] Kivinen, T. and M. Kojo, "More Modular Exponential \(MODP\)) s -5 371 M -( Diffie-Hellman groups for Internet Key Exchange \(IKE\)",) s -5 360 M -( RFC 3526, May 2003.) s -5 338 M -( [SCHNEIER]) s -5 327 M -( Schneier, B., "Applied Cryptography Second Edition:) s -5 316 M -( protocols algorithms and source in code in C", 1996.) s -5 294 M -( [TWOFISH] Schneier, B., "The Twofish Encryptions Algorithm: A) s -5 283 M -( 128-Bit Block Cipher, 1st Edition", March 1999.) s -5 129 M -(Ylonen & Moffat, Editor Expires March 31, 2004 [Page 26]) s -_R -S -PStoPSsaved restore -%%Page: (26,27) 14 -userdict/PStoPSsaved save put -PStoPSmatrix setmatrix -595.000000 0.271378 translate -90 rotate -0.706651 dup scale -userdict/PStoPSmatrix matrix currentmatrix put -userdict/PStoPSclip{0 0 moveto - 595.000000 0 rlineto 0 842.000000 rlineto -595.000000 0 rlineto - closepath}put initclip -/showpage{}def/copypage{}def/erasepage{}def -PStoPSxform concat -%%BeginPageSetup -_S -75 0 translate -/pagenum 27 def -/fname () def -/fdir () def -/ftail () def -/user_header_p false def -%%EndPageSetup -5 723 M -(Internet-Draft SSH Transport Layer Protocol Oct 2003) s -5 690 M -(Authors' Addresses) s -5 668 M -( Tatu Ylonen) s -5 657 M -( SSH Communications Security Corp) s -5 646 M -( Fredrikinkatu 42) s -5 635 M -( HELSINKI FIN-00100) s -5 624 M -( Finland) s -5 602 M -( EMail: [email protected]) s -5 569 M -( Darren J. Moffat \(editor\)) s -5 558 M -( Sun Microsystems, Inc) s -5 547 M -( 17 Network Circle) s -5 536 M -( Menlo Park 95025) s -5 525 M -( USA) s -5 503 M -( EMail: [email protected]) s -5 481 M -(Appendix A. Contibutors) s -5 129 M -(Ylonen & Moffat, Editor Expires March 31, 2004 [Page 27]) s -_R -S -PStoPSsaved restore -userdict/PStoPSsaved save put -PStoPSmatrix setmatrix -595.000000 421.271378 translate -90 rotate -0.706651 dup scale -userdict/PStoPSmatrix matrix currentmatrix put -userdict/PStoPSclip{0 0 moveto - 595.000000 0 rlineto 0 842.000000 rlineto -595.000000 0 rlineto - closepath}put initclip -PStoPSxform concat -%%BeginPageSetup -_S -75 0 translate -/pagenum 28 def -/fname () def -/fdir () def -/ftail () def -/user_header_p false def -%%EndPageSetup -5 723 M -(Internet-Draft SSH Transport Layer Protocol Oct 2003) s -5 690 M -(Intellectual Property Statement) s -5 668 M -( The IETF takes no position regarding the validity or scope of any) s -5 657 M -( intellectual property or other rights that might be claimed to) s -5 646 M -( pertain to the implementation or use of the technology described in) s -5 635 M -( this document or the extent to which any license under such rights) s -5 624 M -( might or might not be available; neither does it represent that it) s -5 613 M -( has made any effort to identify any such rights. Information on the) s -5 602 M -( IETF's procedures with respect to rights in standards-track and) s -5 591 M -( standards-related documentation can be found in BCP-11. Copies of) s -5 580 M -( claims of rights made available for publication and any assurances of) s -5 569 M -( licenses to be made available, or the result of an attempt made to) s -5 558 M -( obtain a general license or permission for the use of such) s -5 547 M -( proprietary rights by implementors or users of this specification can) s -5 536 M -( be obtained from the IETF Secretariat.) s -5 514 M -( The IETF invites any interested party to bring to its attention any) s -5 503 M -( copyrights, patents or patent applications, or other proprietary) s -5 492 M -( rights which may cover technology that may be required to practice) s -5 481 M -( this standard. Please address the information to the IETF Executive) s -5 470 M -( Director.) s -5 448 M -( The IETF has been notified of intellectual property rights claimed in) s -5 437 M -( regard to some or all of the specification contained in this) s -5 426 M -( document. For more information consult the online list of claimed) s -5 415 M -( rights.) s -5 382 M -(Full Copyright Statement) s -5 360 M -( Copyright \(C\) The Internet Society \(2003\). All Rights Reserved.) s -5 338 M -( This document and translations of it may be copied and furnished to) s -5 327 M -( others, and derivative works that comment on or otherwise explain it) s -5 316 M -( or assist in its implementation may be prepared, copied, published) s -5 305 M -( and distributed, in whole or in part, without restriction of any) s -5 294 M -( kind, provided that the above copyright notice and this paragraph are) s -5 283 M -( included on all such copies and derivative works. However, this) s -5 272 M -( document itself may not be modified in any way, such as by removing) s -5 261 M -( the copyright notice or references to the Internet Society or other) s -5 250 M -( Internet organizations, except as needed for the purpose of) s -5 239 M -( developing Internet standards in which case the procedures for) s -5 228 M -( copyrights defined in the Internet Standards process must be) s -5 217 M -( followed, or as required to translate it into languages other than) s -5 206 M -( English.) s -5 184 M -( The limited permissions granted above are perpetual and will not be) s -5 173 M -( revoked by the Internet Society or its successors or assignees.) s -5 129 M -(Ylonen & Moffat, Editor Expires March 31, 2004 [Page 28]) s -_R -S -PStoPSsaved restore -%%Page: (28,29) 15 -userdict/PStoPSsaved save put -PStoPSmatrix setmatrix -595.000000 0.271378 translate -90 rotate -0.706651 dup scale -userdict/PStoPSmatrix matrix currentmatrix put -userdict/PStoPSclip{0 0 moveto - 595.000000 0 rlineto 0 842.000000 rlineto -595.000000 0 rlineto - closepath}put initclip -/showpage{}def/copypage{}def/erasepage{}def -PStoPSxform concat -%%BeginPageSetup -_S -75 0 translate -/pagenum 29 def -/fname () def -/fdir () def -/ftail () def -/user_header_p false def -%%EndPageSetup -5 723 M -(Internet-Draft SSH Transport Layer Protocol Oct 2003) s -5 690 M -( This document and the information contained herein is provided on an) s -5 679 M -( "AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING) s -5 668 M -( TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING) s -5 657 M -( BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION) s -5 646 M -( HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF) s -5 635 M -( MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.) s -5 602 M -(Acknowledgment) s -5 580 M -( Funding for the RFC Editor function is currently provided by the) s -5 569 M -( Internet Society.) s -5 129 M -(Ylonen & Moffat, Editor Expires March 31, 2004 [Page 29]) s -_R -S -PStoPSsaved restore -userdict/PStoPSsaved save put -PStoPSmatrix setmatrix -595.000000 421.271378 translate -90 rotate -0.706651 dup scale -userdict/PStoPSmatrix matrix currentmatrix put -userdict/PStoPSclip{0 0 moveto - 595.000000 0 rlineto 0 842.000000 rlineto -595.000000 0 rlineto - closepath}put initclip -PStoPSxform concat -showpage -PStoPSsaved restore -%%Trailer -%%Pages: 29 -%%DocumentNeededResources: font Courier-Bold Courier -%%EOF diff --git a/lib/ssh/doc/standard/draft-ietf-secsh-transport-17.txt b/lib/ssh/doc/standard/draft-ietf-secsh-transport-17.txt deleted file mode 100644 index 9073ea52b2..0000000000 --- a/lib/ssh/doc/standard/draft-ietf-secsh-transport-17.txt +++ /dev/null @@ -1,1624 +0,0 @@ - - - -Network Working Group T. Ylonen -Internet-Draft SSH Communications Security Corp -Expires: March 31, 2004 D. Moffat, Editor, Ed. - Sun Microsystems, Inc - Oct 2003 - - - SSH Transport Layer Protocol - draft-ietf-secsh-transport-17.txt - -Status of this Memo - - This document is an Internet-Draft and is in full conformance with - all provisions of Section 10 of RFC2026. - - Internet-Drafts are working documents of the Internet Engineering - Task Force (IETF), its areas, and its working groups. Note that other - groups may also distribute working documents as Internet-Drafts. - - Internet-Drafts are draft documents valid for a maximum of six months - and may be updated, replaced, or obsoleted by other documents at any - time. It is inappropriate to use Internet-Drafts as reference - material or to cite them other than as "work in progress." - - The list of current Internet-Drafts can be accessed at http:// - www.ietf.org/ietf/1id-abstracts.txt. - - The list of Internet-Draft Shadow Directories can be accessed at - http://www.ietf.org/shadow.html. - - This Internet-Draft will expire on March 31, 2004. - -Copyright Notice - - Copyright (C) The Internet Society (2003). All Rights Reserved. - -Abstract - - SSH is a protocol for secure remote login and other secure network - services over an insecure network. - - This document describes the SSH transport layer protocol which - typically runs on top of TCP/IP. The protocol can be used as a basis - for a number of secure network services. It provides strong - encryption, server authentication, and integrity protection. It may - also provide compression. - - Key exchange method, public key algorithm, symmetric encryption - algorithm, message authentication algorithm, and hash algorithm are - - - -Ylonen & Moffat, Editor Expires March 31, 2004 [Page 1] - -Internet-Draft SSH Transport Layer Protocol Oct 2003 - - - all negotiated. - - This document also describes the Diffie-Hellman key exchange method - and the minimal set of algorithms that are needed to implement the - SSH transport layer protocol. - -Table of Contents - - 1. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 3 - 2. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 - 3. Conventions Used in This Document . . . . . . . . . . . . . 3 - 4. Connection Setup . . . . . . . . . . . . . . . . . . . . . . 3 - 4.1 Use over TCP/IP . . . . . . . . . . . . . . . . . . . . . . 4 - 4.2 Protocol Version Exchange . . . . . . . . . . . . . . . . . 4 - 4.3 Compatibility With Old SSH Versions . . . . . . . . . . . . 4 - 4.3.1 Old Client, New Server . . . . . . . . . . . . . . . . . . . 5 - 4.3.2 New Client, Old Server . . . . . . . . . . . . . . . . . . . 5 - 5. Binary Packet Protocol . . . . . . . . . . . . . . . . . . . 5 - 5.1 Maximum Packet Length . . . . . . . . . . . . . . . . . . . 6 - 5.2 Compression . . . . . . . . . . . . . . . . . . . . . . . . 7 - 5.3 Encryption . . . . . . . . . . . . . . . . . . . . . . . . . 7 - 5.4 Data Integrity . . . . . . . . . . . . . . . . . . . . . . . 9 - 5.5 Key Exchange Methods . . . . . . . . . . . . . . . . . . . . 10 - 5.6 Public Key Algorithms . . . . . . . . . . . . . . . . . . . 11 - 6. Key Exchange . . . . . . . . . . . . . . . . . . . . . . . . 13 - 6.1 Algorithm Negotiation . . . . . . . . . . . . . . . . . . . 13 - 6.2 Output from Key Exchange . . . . . . . . . . . . . . . . . . 16 - 6.3 Taking Keys Into Use . . . . . . . . . . . . . . . . . . . . 17 - 7. Diffie-Hellman Key Exchange . . . . . . . . . . . . . . . . 18 - 7.1 diffie-hellman-group1-sha1 . . . . . . . . . . . . . . . . . 19 - 8. Key Re-Exchange . . . . . . . . . . . . . . . . . . . . . . 20 - 9. Service Request . . . . . . . . . . . . . . . . . . . . . . 21 - 10. Additional Messages . . . . . . . . . . . . . . . . . . . . 21 - 10.1 Disconnection Message . . . . . . . . . . . . . . . . . . . 22 - 10.2 Ignored Data Message . . . . . . . . . . . . . . . . . . . . 22 - 10.3 Debug Message . . . . . . . . . . . . . . . . . . . . . . . 23 - 10.4 Reserved Messages . . . . . . . . . . . . . . . . . . . . . 23 - 11. Summary of Message Numbers . . . . . . . . . . . . . . . . . 23 - 12. IANA Considerations . . . . . . . . . . . . . . . . . . . . 24 - 13. Security Considerations . . . . . . . . . . . . . . . . . . 24 - 14. Intellectual Property . . . . . . . . . . . . . . . . . . . 24 - 15. Additional Information . . . . . . . . . . . . . . . . . . . 24 - Authors' Addresses . . . . . . . . . . . . . . . . . . . . . 26 - Normative . . . . . . . . . . . . . . . . . . . . . . . . . 25 - Informative . . . . . . . . . . . . . . . . . . . . . . . . 25 - A. Contibutors . . . . . . . . . . . . . . . . . . . . . . . . 27 - Intellectual Property and Copyright Statements . . . . . . . 28 - - - - -Ylonen & Moffat, Editor Expires March 31, 2004 [Page 2] - -Internet-Draft SSH Transport Layer Protocol Oct 2003 - - -1. Contributors - - The major original contributors of this document were: Tatu Ylonen, - Tero Kivinen, Timo J. Rinne, Sami Lehtinen (all of SSH Communications - Security Corp), and Markku-Juhani O. Saarinen (University of - Jyvaskyla) - - The document editor is: [email protected]. Comments on this - internet draft should be sent to the IETF SECSH working group, - details at: http://ietf.org/html.charters/secsh-charter.html - -2. Introduction - - The SSH transport layer is a secure low level transport protocol. It - provides strong encryption, cryptographic host authentication, and - integrity protection. - - Authentication in this protocol level is host-based; this protocol - does not perform user authentication. A higher level protocol for - user authentication can be designed on top of this protocol. - - The protocol has been designed to be simple, flexible, to allow - parameter negotiation, and to minimize the number of round-trips. - Key exchange method, public key algorithm, symmetric encryption - algorithm, message authentication algorithm, and hash algorithm are - all negotiated. It is expected that in most environments, only 2 - round-trips will be needed for full key exchange, server - authentication, service request, and acceptance notification of - service request. The worst case is 3 round-trips. - -3. Conventions Used in This Document - - The keywords "MUST", "MUST NOT", "REQUIRED", "SHOULD", "SHOULD NOT", - and "MAY" that appear in this document are to be interpreted as - described in [RFC2119]. - - The used data types and terminology are specified in the architecture - document [SSH-ARCH]. - - The architecture document also discusses the algorithm naming - conventions that MUST be used with the SSH protocols. - -4. Connection Setup - - SSH works over any 8-bit clean, binary-transparent transport. The - underlying transport SHOULD protect against transmission errors as - such errors cause the SSH connection to terminate. - - - - -Ylonen & Moffat, Editor Expires March 31, 2004 [Page 3] - -Internet-Draft SSH Transport Layer Protocol Oct 2003 - - - The client initiates the connection. - -4.1 Use over TCP/IP - - When used over TCP/IP, the server normally listens for connections on - port 22. This port number has been registered with the IANA, and has - been officially assigned for SSH. - -4.2 Protocol Version Exchange - - When the connection has been established, both sides MUST send an - identification string of the form "SSH-protoversion-softwareversion - comments", followed by carriage return and newline characters (ASCII - 13 and 10, respectively). Both sides MUST be able to process - identification strings without carriage return character. No null - character is sent. The maximum length of the string is 255 - characters, including the carriage return and newline. - - The part of the identification string preceding carriage return and - newline is used in the Diffie-Hellman key exchange (see Section - Section 7). - - The server MAY send other lines of data before sending the version - string. Each line SHOULD be terminated by a carriage return and - newline. Such lines MUST NOT begin with "SSH-", and SHOULD be - encoded in ISO-10646 UTF-8 [RFC2279] (language is not specified). - Clients MUST be able to process such lines; they MAY be silently - ignored, or MAY be displayed to the client user; if they are - displayed, control character filtering discussed in [SSH-ARCH] SHOULD - be used. The primary use of this feature is to allow TCP-wrappers to - display an error message before disconnecting. - - Version strings MUST consist of printable US-ASCII characters, not - including whitespaces or a minus sign (-). The version string is - primarily used to trigger compatibility extensions and to indicate - the capabilities of an implementation. The comment string should - contain additional information that might be useful in solving user - problems. - - The protocol version described in this document is 2.0. - - Key exchange will begin immediately after sending this identifier. - All packets following the identification string SHALL use the binary - packet protocol, to be described below. - -4.3 Compatibility With Old SSH Versions - - During the transition period, it is important to be able to work in a - - - -Ylonen & Moffat, Editor Expires March 31, 2004 [Page 4] - -Internet-Draft SSH Transport Layer Protocol Oct 2003 - - - way that is compatible with the installed SSH clients and servers - that use an older version of the protocol. Information in this - section is only relevant for implementations supporting compatibility - with SSH versions 1.x. There is no standards track or informational - draft available that defines the SSH 1.x protocol. The only known - documentation of the 1.x protocol is contained in README files that - are shipped along with the source code. - -4.3.1 Old Client, New Server - - Server implementations MAY support a configurable "compatibility" - flag that enables compatibility with old versions. When this flag is - on, the server SHOULD identify its protocol version as "1.99". - Clients using protocol 2.0 MUST be able to identify this as identical - to "2.0". In this mode the server SHOULD NOT send the carriage - return character (ASCII 13) after the version identification string. - - In the compatibility mode the server SHOULD NOT send any further data - after its initialization string until it has received an - identification string from the client. The server can then determine - whether the client is using an old protocol, and can revert to the - old protocol if required. In the compatibility mode, the server MUST - NOT send additional data before the version string. - - When compatibility with old clients is not needed, the server MAY - send its initial key exchange data immediately after the - identification string. - -4.3.2 New Client, Old Server - - Since the new client MAY immediately send additional data after its - identification string (before receiving server's identification), the - old protocol may already have been corrupted when the client learns - that the server is old. When this happens, the client SHOULD close - the connection to the server, and reconnect using the old protocol. - -5. Binary Packet Protocol - - Each packet is in the following format: - - uint32 packet_length - byte padding_length - byte[n1] payload; n1 = packet_length - padding_length - 1 - byte[n2] random padding; n2 = padding_length - byte[m] mac (message authentication code); m = mac_length - - packet_length - - - - -Ylonen & Moffat, Editor Expires March 31, 2004 [Page 5] - -Internet-Draft SSH Transport Layer Protocol Oct 2003 - - - The length of the packet (bytes), not including MAC or the - packet_length field itself. - - padding_length - Length of padding (bytes). - - payload - The useful contents of the packet. If compression has been - negotiated, this field is compressed. Initially, compression - MUST be "none". - - random padding - Arbitrary-length padding, such that the total length of - (packet_length || padding_length || payload || padding) is a - multiple of the cipher block size or 8, whichever is larger. - There MUST be at least four bytes of padding. The padding - SHOULD consist of random bytes. The maximum amount of padding - is 255 bytes. - - mac - Message authentication code. If message authentication has - been negotiated, this field contains the MAC bytes. Initially, - the MAC algorithm MUST be "none". - - - Note that length of the concatenation of packet length, padding - length, payload, and padding MUST be a multiple of the cipher block - size or 8, whichever is larger. This constraint MUST be enforced - even when using stream ciphers. Note that the packet length field is - also encrypted, and processing it requires special care when sending - or receiving packets. - - The minimum size of a packet is 16 (or the cipher block size, - whichever is larger) bytes (plus MAC); implementations SHOULD decrypt - the length after receiving the first 8 (or cipher block size, - whichever is larger) bytes of a packet. - -5.1 Maximum Packet Length - - All implementations MUST be able to process packets with uncompressed - payload length of 32768 bytes or less and total packet size of 35000 - bytes or less (including length, padding length, payload, padding, - and MAC.). The maximum of 35000 bytes is an arbitrary chosen value - larger than uncompressed size. Implementations SHOULD support longer - packets, where they might be needed, e.g. if an implementation wants - to send a very large number of certificates. Such packets MAY be - sent if the version string indicates that the other party is able to - process them. However, implementations SHOULD check that the packet - - - -Ylonen & Moffat, Editor Expires March 31, 2004 [Page 6] - -Internet-Draft SSH Transport Layer Protocol Oct 2003 - - - length is reasonable for the implementation to avoid - denial-of-service and/or buffer overflow attacks. - -5.2 Compression - - If compression has been negotiated, the payload field (and only it) - will be compressed using the negotiated algorithm. The length field - and MAC will be computed from the compressed payload. Encryption will - be done after compression. - - Compression MAY be stateful, depending on the method. Compression - MUST be independent for each direction, and implementations MUST - allow independently choosing the algorithm for each direction. - - The following compression methods are currently defined: - - none REQUIRED no compression - zlib OPTIONAL ZLIB (LZ77) compression - - The "zlib" compression is described in [RFC1950] and in [RFC1951]. - The compression context is initialized after each key exchange, and - is passed from one packet to the next with only a partial flush being - performed at the end of each packet. A partial flush means that the - current compressed block is ended and all data will be output. If the - current block is not a stored block, one or more empty blocks are - added after the current block to ensure that there are at least 8 - bits counting from the start of the end-of-block code of the current - block to the end of the packet payload. - - Additional methods may be defined as specified in [SSH-ARCH]. - -5.3 Encryption - - An encryption algorithm and a key will be negotiated during the key - exchange. When encryption is in effect, the packet length, padding - length, payload and padding fields of each packet MUST be encrypted - with the given algorithm. - - The encrypted data in all packets sent in one direction SHOULD be - considered a single data stream. For example, initialization vectors - SHOULD be passed from the end of one packet to the beginning of the - next packet. All ciphers SHOULD use keys with an effective key length - of 128 bits or more. - - The ciphers in each direction MUST run independently of each other, - and implementations MUST allow independently choosing the algorithm - for each direction (if multiple algorithms are allowed by local - policy). - - - -Ylonen & Moffat, Editor Expires March 31, 2004 [Page 7] - -Internet-Draft SSH Transport Layer Protocol Oct 2003 - - - The following ciphers are currently defined: - - 3des-cbc REQUIRED three-key 3DES in CBC mode - blowfish-cbc OPTIONALi Blowfish in CBC mode - twofish256-cbc OPTIONAL Twofish in CBC mode, - with 256-bit key - twofish-cbc OPTIONAL alias for "twofish256-cbc" (this - is being retained for - historical reasons) - twofish192-cbc OPTIONAL Twofish with 192-bit key - twofish128-cbc OPTIONAL Twofish with 128-bit key - aes256-cbc OPTIONAL AES (Rijndael) in CBC mode, - with 256-bit key - aes192-cbc OPTIONAL AES with 192-bit key - aes128-cbc RECOMMENDED AES with 128-bit key - serpent256-cbc OPTIONAL Serpent in CBC mode, with - 256-bit key - serpent192-cbc OPTIONAL Serpent with 192-bit key - serpent128-cbc OPTIONAL Serpent with 128-bit key - arcfour OPTIONAL the ARCFOUR stream cipher - idea-cbc OPTIONAL IDEA in CBC mode - cast128-cbc OPTIONAL CAST-128 in CBC mode - none OPTIONAL no encryption; NOT RECOMMENDED - - The "3des-cbc" cipher is three-key triple-DES - (encrypt-decrypt-encrypt), where the first 8 bytes of the key are - used for the first encryption, the next 8 bytes for the decryption, - and the following 8 bytes for the final encryption. This requires 24 - bytes of key data (of which 168 bits are actually used). To - implement CBC mode, outer chaining MUST be used (i.e., there is only - one initialization vector). This is a block cipher with 8 byte - blocks. This algorithm is defined in [FIPS-46-3] - - The "blowfish-cbc" cipher is Blowfish in CBC mode, with 128 bit keys - [SCHNEIER]. This is a block cipher with 8 byte blocks. - - The "twofish-cbc" or "twofish256-cbc" cipher is Twofish in CBC mode, - with 256 bit keys as described [TWOFISH]. This is a block cipher with - 16 byte blocks. - - The "twofish192-cbc" cipher. Same as above but with 192-bit key. - - The "twofish128-cbc" cipher. Same as above but with 128-bit key. - - The "aes256-cbc" cipher is AES (Advanced Encryption Standard) - [FIPS-197], formerly Rijndael, in CBC mode. This version uses 256-bit - key. - - - - -Ylonen & Moffat, Editor Expires March 31, 2004 [Page 8] - -Internet-Draft SSH Transport Layer Protocol Oct 2003 - - - The "aes192-cbc" cipher. Same as above but with 192-bit key. - - The "aes128-cbc" cipher. Same as above but with 128-bit key. - - The "serpent256-cbc" cipher in CBC mode, with 256-bit key as - described in the Serpent AES submission. - - The "serpent192-cbc" cipher. Same as above but with 192-bit key. - - The "serpent128-cbc" cipher. Same as above but with 128-bit key. - - The "arcfour" is the Arcfour stream cipher with 128 bit keys. The - Arcfour cipher is believed to be compatible with the RC4 cipher - [SCHNEIER]. RC4 is a registered trademark of RSA Data Security Inc. - Arcfour (and RC4) has problems with weak keys, and should be used - with caution. - - The "idea-cbc" cipher is the IDEA cipher in CBC mode [SCHNEIER]. - - The "cast128-cbc" cipher is the CAST-128 cipher in CBC mode - [RFC2144]. - - The "none" algorithm specifies that no encryption is to be done. - Note that this method provides no confidentiality protection, and it - is not recommended. Some functionality (e.g. password - authentication) may be disabled for security reasons if this cipher - is chosen. - - Additional methods may be defined as specified in [SSH-ARCH]. - -5.4 Data Integrity - - Data integrity is protected by including with each packet a message - authentication code (MAC) that is computed from a shared secret, - packet sequence number, and the contents of the packet. - - The message authentication algorithm and key are negotiated during - key exchange. Initially, no MAC will be in effect, and its length - MUST be zero. After key exchange, the selected MAC will be computed - before encryption from the concatenation of packet data: - - mac = MAC(key, sequence_number || unencrypted_packet) - - where unencrypted_packet is the entire packet without MAC (the length - fields, payload and padding), and sequence_number is an implicit - packet sequence number represented as uint32. The sequence number is - initialized to zero for the first packet, and is incremented after - every packet (regardless of whether encryption or MAC is in use). It - - - -Ylonen & Moffat, Editor Expires March 31, 2004 [Page 9] - -Internet-Draft SSH Transport Layer Protocol Oct 2003 - - - is never reset, even if keys/algorithms are renegotiated later. It - wraps around to zero after every 2^32 packets. The packet sequence - number itself is not included in the packet sent over the wire. - - The MAC algorithms for each direction MUST run independently, and - implementations MUST allow choosing the algorithm independently for - both directions. - - The MAC bytes resulting from the MAC algorithm MUST be transmitted - without encryption as the last part of the packet. The number of MAC - bytes depends on the algorithm chosen. - - The following MAC algorithms are currently defined: - - hmac-sha1 REQUIRED HMAC-SHA1 (digest length = key - length = 20) - hmac-sha1-96 RECOMMENDED first 96 bits of HMAC-SHA1 (digest - length = 12, key length = 20) - hmac-md5 OPTIONAL HMAC-MD5 (digest length = key - length = 16) - hmac-md5-96 OPTIONAL first 96 bits of HMAC-MD5 (digest - length = 12, key length = 16) - none OPTIONAL no MAC; NOT RECOMMENDED - - Figure 1 - - The "hmac-*" algorithms are described in [RFC2104] The "*-n" MACs use - only the first n bits of the resulting value. - - The hash algorithms are described in [SCHNEIER]. - - Additional methods may be defined as specified in [SSH-ARCH]. - -5.5 Key Exchange Methods - - The key exchange method specifies how one-time session keys are - generated for encryption and for authentication, and how the server - authentication is done. - - Only one REQUIRED key exchange method has been defined: - - diffie-hellman-group1-sha1 REQUIRED - - This method is described later in this document. - - Additional methods may be defined as specified in [SSH-ARCH]. - - - - - -Ylonen & Moffat, Editor Expires March 31, 2004 [Page 10] - -Internet-Draft SSH Transport Layer Protocol Oct 2003 - - -5.6 Public Key Algorithms - - This protocol has been designed to be able to operate with almost any - public key format, encoding, and algorithm (signature and/or - encryption). - - There are several aspects that define a public key type: - o Key format: how is the key encoded and how are certificates - represented. The key blobs in this protocol MAY contain - certificates in addition to keys. - o Signature and/or encryption algorithms. Some key types may not - support both signing and encryption. Key usage may also be - restricted by policy statements in e.g. certificates. In this - case, different key types SHOULD be defined for the different - policy alternatives. - o Encoding of signatures and/or encrypted data. This includes but is - not limited to padding, byte order, and data formats. - - The following public key and/or certificate formats are currently defined: - - ssh-dss REQUIRED sign Raw DSS Key - ssh-rsa RECOMMENDED sign Raw RSA Key - x509v3-sign-rsa OPTIONAL sign X.509 certificates (RSA key) - x509v3-sign-dss OPTIONAL sign X.509 certificates (DSS key) - spki-sign-rsa OPTIONAL sign SPKI certificates (RSA key) - spki-sign-dss OPTIONAL sign SPKI certificates (DSS key) - pgp-sign-rsa OPTIONAL sign OpenPGP certificates (RSA key) - pgp-sign-dss OPTIONAL sign OpenPGP certificates (DSS key) - - Additional key types may be defined as specified in [SSH-ARCH]. - - The key type MUST always be explicitly known (from algorithm - negotiation or some other source). It is not normally included in - the key blob. - - Certificates and public keys are encoded as follows: - - string certificate or public key format identifier - byte[n] key/certificate data - - The certificate part may have be a zero length string, but a public - key is required. This is the public key that will be used for - authentication; the certificate sequence contained in the certificate - blob can be used to provide authorization. - - Public key / certifcate formats that do not explicitly specify a - signature format identifier MUST use the public key / certificate - format identifier as the signature identifier. - - - -Ylonen & Moffat, Editor Expires March 31, 2004 [Page 11] - -Internet-Draft SSH Transport Layer Protocol Oct 2003 - - - Signatures are encoded as follows: - string signature format identifier (as specified by the - public key / cert format) - byte[n] signature blob in format specific encoding. - - - The "ssh-dss" key format has the following specific encoding: - - string "ssh-dss" - mpint p - mpint q - mpint g - mpint y - - Here the p, q, g, and y parameters form the signature key blob. - - Signing and verifying using this key format is done according to the - Digital Signature Standard [FIPS-186] using the SHA-1 hash. A - description can also be found in [SCHNEIER]. - - The resulting signature is encoded as follows: - - string "ssh-dss" - string dss_signature_blob - - dss_signature_blob is encoded as a string containing r followed by s - (which are 160 bits long integers, without lengths or padding, - unsigned and in network byte order). - - The "ssh-rsa" key format has the following specific encoding: - - string "ssh-rsa" - mpint e - mpint n - - Here the e and n parameters form the signature key blob. - - Signing and verifying using this key format is done according to - [SCHNEIER] and [PKCS1] using the SHA-1 hash. - - The resulting signature is encoded as follows: - - string "ssh-rsa" - string rsa_signature_blob - - rsa_signature_blob is encoded as a string containing s (which is an - integer, without lengths or padding, unsigned and in network byte - order). - - - -Ylonen & Moffat, Editor Expires March 31, 2004 [Page 12] - -Internet-Draft SSH Transport Layer Protocol Oct 2003 - - - The "spki-sign-rsa" method indicates that the certificate blob - contains a sequence of SPKI certificates. The format of SPKI - certificates is described in [RFC2693]. This method indicates that - the key (or one of the keys in the certificate) is an RSA-key. - - The "spki-sign-dss". As above, but indicates that the key (or one of - the keys in the certificate) is a DSS-key. - - The "pgp-sign-rsa" method indicates the certificates, the public key, - and the signature are in OpenPGP compatible binary format - ([RFC2440]). This method indicates that the key is an RSA-key. - - The "pgp-sign-dss". As above, but indicates that the key is a - DSS-key. - -6. Key Exchange - - Key exchange begins by each side sending lists of supported - algorithms. Each side has a preferred algorithm in each category, and - it is assumed that most implementations at any given time will use - the same preferred algorithm. Each side MAY guess which algorithm - the other side is using, and MAY send an initial key exchange packet - according to the algorithm if appropriate for the preferred method. - - Guess is considered wrong, if: - o the kex algorithm and/or the host key algorithm is guessed wrong - (server and client have different preferred algorithm), or - o if any of the other algorithms cannot be agreed upon (the - procedure is defined below in Section Section 6.1). - - Otherwise, the guess is considered to be right and the optimistically - sent packet MUST be handled as the first key exchange packet. - - However, if the guess was wrong, and a packet was optimistically sent - by one or both parties, such packets MUST be ignored (even if the - error in the guess would not affect the contents of the initial - packet(s)), and the appropriate side MUST send the correct initial - packet. - - Server authentication in the key exchange MAY be implicit. After a - key exchange with implicit server authentication, the client MUST - wait for response to its service request message before sending any - further data. - -6.1 Algorithm Negotiation - - Key exchange begins by each side sending the following packet: - - - - -Ylonen & Moffat, Editor Expires March 31, 2004 [Page 13] - -Internet-Draft SSH Transport Layer Protocol Oct 2003 - - - byte SSH_MSG_KEXINIT - byte[16] cookie (random bytes) - string kex_algorithms - string server_host_key_algorithms - string encryption_algorithms_client_to_server - string encryption_algorithms_server_to_client - string mac_algorithms_client_to_server - string mac_algorithms_server_to_client - string compression_algorithms_client_to_server - string compression_algorithms_server_to_client - string languages_client_to_server - string languages_server_to_client - boolean first_kex_packet_follows - uint32 0 (reserved for future extension) - - Each of the algorithm strings MUST be a comma-separated list of - algorithm names (see ''Algorithm Naming'' in [SSH-ARCH]). Each - supported (allowed) algorithm MUST be listed in order of preference. - - The first algorithm in each list MUST be the preferred (guessed) - algorithm. Each string MUST contain at least one algorithm name. - - - cookie - The cookie MUST be a random value generated by the sender. Its - purpose is to make it impossible for either side to fully - determine the keys and the session identifier. - - kex_algorithms - Key exchange algorithms were defined above. The first - algorithm MUST be the preferred (and guessed) algorithm. If - both sides make the same guess, that algorithm MUST be used. - Otherwise, the following algorithm MUST be used to choose a key - exchange method: iterate over client's kex algorithms, one at a - time. Choose the first algorithm that satisfies the following - conditions: - + the server also supports the algorithm, - + if the algorithm requires an encryption-capable host key, - there is an encryption-capable algorithm on the server's - server_host_key_algorithms that is also supported by the - client, and - + if the algorithm requires a signature-capable host key, - there is a signature-capable algorithm on the server's - server_host_key_algorithms that is also supported by the - client. - + If no algorithm satisfying all these conditions can be - found, the connection fails, and both sides MUST disconnect. - - - - -Ylonen & Moffat, Editor Expires March 31, 2004 [Page 14] - -Internet-Draft SSH Transport Layer Protocol Oct 2003 - - - server_host_key_algorithms - List of the algorithms supported for the server host key. The - server lists the algorithms for which it has host keys; the - client lists the algorithms that it is willing to accept. - (There MAY be multiple host keys for a host, possibly with - different algorithms.) - - Some host keys may not support both signatures and encryption - (this can be determined from the algorithm), and thus not all - host keys are valid for all key exchange methods. - - Algorithm selection depends on whether the chosen key exchange - algorithm requires a signature or encryption capable host key. - It MUST be possible to determine this from the public key - algorithm name. The first algorithm on the client's list that - satisfies the requirements and is also supported by the server - MUST be chosen. If there is no such algorithm, both sides MUST - disconnect. - - encryption_algorithms - Lists the acceptable symmetric encryption algorithms in order - of preference. The chosen encryption algorithm to each - direction MUST be the first algorithm on the client's list - that is also on the server's list. If there is no such - algorithm, both sides MUST disconnect. - - Note that "none" must be explicitly listed if it is to be - acceptable. The defined algorithm names are listed in Section - Section 5.3. - - mac_algorithms - Lists the acceptable MAC algorithms in order of preference. - The chosen MAC algorithm MUST be the first algorithm on the - client's list that is also on the server's list. If there is - no such algorithm, both sides MUST disconnect. - - Note that "none" must be explicitly listed if it is to be - acceptable. The MAC algorithm names are listed in Section - Figure 1. - - compression_algorithms - Lists the acceptable compression algorithms in order of - preference. The chosen compression algorithm MUST be the first - algorithm on the client's list that is also on the server's - list. If there is no such algorithm, both sides MUST - disconnect. - - - - - -Ylonen & Moffat, Editor Expires March 31, 2004 [Page 15] - -Internet-Draft SSH Transport Layer Protocol Oct 2003 - - - Note that "none" must be explicitly listed if it is to be - acceptable. The compression algorithm names are listed in - Section Section 5.2. - - languages - This is a comma-separated list of language tags in order of - preference [RFC3066]. Both parties MAY ignore this list. If - there are no language preferences, this list SHOULD be empty. - Language tags SHOULD NOT be present unless they are known to be - needed by the sending party. - - first_kex_packet_follows - Indicates whether a guessed key exchange packet follows. If a - guessed packet will be sent, this MUST be TRUE. If no guessed - packet will be sent, this MUST be FALSE. - - After receiving the SSH_MSG_KEXINIT packet from the other side, - each party will know whether their guess was right. If the - other party's guess was wrong, and this field was TRUE, the - next packet MUST be silently ignored, and both sides MUST then - act as determined by the negotiated key exchange method. If - the guess was right, key exchange MUST continue using the - guessed packet. - - After the KEXINIT packet exchange, the key exchange algorithm is run. - It may involve several packet exchanges, as specified by the key - exchange method. - -6.2 Output from Key Exchange - - The key exchange produces two values: a shared secret K, and an - exchange hash H. Encryption and authentication keys are derived from - these. The exchange hash H from the first key exchange is - additionally used as the session identifier, which is a unique - identifier for this connection. It is used by authentication methods - as a part of the data that is signed as a proof of possession of a - private key. Once computed, the session identifier is not changed, - even if keys are later re-exchanged. - - - Each key exchange method specifies a hash function that is used in - the key exchange. The same hash algorithm MUST be used in key - derivation. Here, we'll call it HASH. - - - Encryption keys MUST be computed as HASH of a known value and K as - follows: - - - - -Ylonen & Moffat, Editor Expires March 31, 2004 [Page 16] - -Internet-Draft SSH Transport Layer Protocol Oct 2003 - - - o Initial IV client to server: HASH(K || H || "A" || session_id) - (Here K is encoded as mpint and "A" as byte and session_id as raw - data."A" means the single character A, ASCII 65). - o Initial IV server to client: HASH(K || H || "B" || session_id) - o Encryption key client to server: HASH(K || H || "C" || session_id) - o Encryption key server to client: HASH(K || H || "D" || session_id) - o Integrity key client to server: HASH(K || H || "E" || session_id) - o Integrity key server to client: HASH(K || H || "F" || session_id) - - Key data MUST be taken from the beginning of the hash output. 128 - bits (16 bytes) MUST be used for algorithms with variable-length - keys. The only variable key length algorithm defined in this document - is arcfour). For other algorithms, as many bytes as are needed are - taken from the beginning of the hash value. If the key length needed - is longer than the output of the HASH, the key is extended by - computing HASH of the concatenation of K and H and the entire key so - far, and appending the resulting bytes (as many as HASH generates) to - the key. This process is repeated until enough key material is - available; the key is taken from the beginning of this value. In - other words: - - K1 = HASH(K || H || X || session_id) (X is e.g. "A") - K2 = HASH(K || H || K1) - K3 = HASH(K || H || K1 || K2) - ... - key = K1 || K2 || K3 || ... - - This process will lose entropy if the amount of entropy in K is - larger than the internal state size of HASH. - -6.3 Taking Keys Into Use - - Key exchange ends by each side sending an SSH_MSG_NEWKEYS message. - This message is sent with the old keys and algorithms. All messages - sent after this message MUST use the new keys and algorithms. - - - When this message is received, the new keys and algorithms MUST be - taken into use for receiving. - - - This message is the only valid message after key exchange, in - addition to SSH_MSG_DEBUG, SSH_MSG_DISCONNECT and SSH_MSG_IGNORE - messages. The purpose of this message is to ensure that a party is - able to respond with a disconnect message that the other party can - understand if something goes wrong with the key exchange. - Implementations MUST NOT accept any other messages after key exchange - before receiving SSH_MSG_NEWKEYS. - - - -Ylonen & Moffat, Editor Expires March 31, 2004 [Page 17] - -Internet-Draft SSH Transport Layer Protocol Oct 2003 - - - byte SSH_MSG_NEWKEYS - - -7. Diffie-Hellman Key Exchange - - The Diffie-Hellman key exchange provides a shared secret that can not - be determined by either party alone. The key exchange is combined - with a signature with the host key to provide host authentication. - - - In the following description (C is the client, S is the server; p is - a large safe prime, g is a generator for a subgroup of GF(p), and q - is the order of the subgroup; V_S is S's version string; V_C is C's - version string; K_S is S's public host key; I_C is C's KEXINIT - message and I_S S's KEXINIT message which have been exchanged before - this part begins): - - - 1. C generates a random number x (1 < x < q) and computes e = g^x - mod p. C sends "e" to S. - - 2. S generates a random number y (0 < y < q) and computes f = g^y - mod p. S receives "e". It computes K = e^y mod p, H = hash(V_C - || V_S || I_C || I_S || K_S || e || f || K) (these elements are - encoded according to their types; see below), and signature s on - H with its private host key. S sends "K_S || f || s" to C. The - signing operation may involve a second hashing operation. - - 3. C verifies that K_S really is the host key for S (e.g. using - certificates or a local database). C is also allowed to accept - the key without verification; however, doing so will render the - protocol insecure against active attacks (but may be desirable - for practical reasons in the short term in many environments). C - then computes K = f^x mod p, H = hash(V_C || V_S || I_C || I_S || - K_S || e || f || K), and verifies the signature s on H. - - Either side MUST NOT send or accept e or f values that are not in the - range [1, p-1]. If this condition is violated, the key exchange - fails. - - - This is implemented with the following messages. The hash algorithm - for computing the exchange hash is defined by the method name, and is - called HASH. The public key algorithm for signing is negotiated with - the KEXINIT messages. - - First, the client sends the following: - - - - -Ylonen & Moffat, Editor Expires March 31, 2004 [Page 18] - -Internet-Draft SSH Transport Layer Protocol Oct 2003 - - - byte SSH_MSG_KEXDH_INIT - mpint e - - - The server responds with the following: - - byte SSH_MSG_KEXDH_REPLY - string server public host key and certificates (K_S) - mpint f - string signature of H - - The hash H is computed as the HASH hash of the concatenation of the - following: - - string V_C, the client's version string (CR and NL excluded) - string V_S, the server's version string (CR and NL excluded) - string I_C, the payload of the client's SSH_MSG_KEXINIT - string I_S, the payload of the server's SSH_MSG_KEXINIT - string K_S, the host key - mpint e, exchange value sent by the client - mpint f, exchange value sent by the server - mpint K, the shared secret - - This value is called the exchange hash, and it is used to - authenticate the key exchange. The exchange hash SHOULD be kept - secret. - - - The signature algorithm MUST be applied over H, not the original - data. Most signature algorithms include hashing and additional - padding. For example, "ssh-dss" specifies SHA-1 hashing; in that - case, the data is first hashed with HASH to compute H, and H is then - hashed with SHA-1 as part of the signing operation. - -7.1 diffie-hellman-group1-sha1 - - The "diffie-hellman-group1-sha1" method specifies Diffie-Hellman key - exchange with SHA-1 as HASH, and Oakley group 14 [RFC3526] (2048-bit - MODP Group). It is included below in hexadecimal and decimal. - - The prime p is equal to 2^1024 - 2^960 - 1 + 2^64 * floor( 2^894 Pi + - 129093 ). Its hexadecimal value is: - - FFFFFFFF FFFFFFFF C90FDAA2 2168C234 C4C6628B 80DC1CD1 - 29024E08 8A67CC74 020BBEA6 3B139B22 514A0879 8E3404DD - EF9519B3 CD3A431B 302B0A6D F25F1437 4FE1356D 6D51C245 - E485B576 625E7EC6 F44C42E9 A637ED6B 0BFF5CB6 F406B7ED - EE386BFB 5A899FA5 AE9F2411 7C4B1FE6 49286651 ECE65381 - - - -Ylonen & Moffat, Editor Expires March 31, 2004 [Page 19] - -Internet-Draft SSH Transport Layer Protocol Oct 2003 - - - FFFFFFFF FFFFFFFF. - - In decimal, this value is: - - 179769313486231590770839156793787453197860296048756011706444 - 423684197180216158519368947833795864925541502180565485980503 - 646440548199239100050792877003355816639229553136239076508735 - 759914822574862575007425302077447712589550957937778424442426 - 617334727629299387668709205606050270810842907692932019128194 - 467627007. - - The generator used with this prime is g = 2. The group order q is (p - - 1) / 2. - -8. Key Re-Exchange - - Key re-exchange is started by sending an SSH_MSG_KEXINIT packet when - not already doing a key exchange (as described in Section Section - 6.1). When this message is received, a party MUST respond with its - own SSH_MSG_KEXINIT message except when the received SSH_MSG_KEXINIT - already was a reply. Either party MAY initiate the re-exchange, but - roles MUST NOT be changed (i.e., the server remains the server, and - the client remains the client). - - - Key re-exchange is performed using whatever encryption was in effect - when the exchange was started. Encryption, compression, and MAC - methods are not changed before a new SSH_MSG_NEWKEYS is sent after - the key exchange (as in the initial key exchange). Re-exchange is - processed identically to the initial key exchange, except for the - session identifier that will remain unchanged. It is permissible to - change some or all of the algorithms during the re-exchange. Host - keys can also change. All keys and initialization vectors are - recomputed after the exchange. Compression and encryption contexts - are reset. - - - It is recommended that the keys are changed after each gigabyte of - transmitted data or after each hour of connection time, whichever - comes sooner. However, since the re-exchange is a public key - operation, it requires a fair amount of processing power and should - not be performed too often. - - - More application data may be sent after the SSH_MSG_NEWKEYS packet - has been sent; key exchange does not affect the protocols that lie - above the SSH transport layer. - - - - -Ylonen & Moffat, Editor Expires March 31, 2004 [Page 20] - -Internet-Draft SSH Transport Layer Protocol Oct 2003 - - -9. Service Request - - After the key exchange, the client requests a service. The service is - identified by a name. The format of names and procedures for defining - new names are defined in [SSH-ARCH]. - - - Currently, the following names have been reserved: - - ssh-userauth - ssh-connection - - Similar local naming policy is applied to the service names, as is - applied to the algorithm names; a local service should use the - "servicename@domain" syntax. - - byte SSH_MSG_SERVICE_REQUEST - string service name - - If the server rejects the service request, it SHOULD send an - appropriate SSH_MSG_DISCONNECT message and MUST disconnect. - - - When the service starts, it may have access to the session identifier - generated during the key exchange. - - - If the server supports the service (and permits the client to use - it), it MUST respond with the following: - - byte SSH_MSG_SERVICE_ACCEPT - string service name - - Message numbers used by services should be in the area reserved for - them (see Section 6 in [SSH-ARCH]). The transport level will - continue to process its own messages. - - - Note that after a key exchange with implicit server authentication, - the client MUST wait for response to its service request message - before sending any further data. - -10. Additional Messages - - Either party may send any of the following messages at any time. - - - - - - -Ylonen & Moffat, Editor Expires March 31, 2004 [Page 21] - -Internet-Draft SSH Transport Layer Protocol Oct 2003 - - -10.1 Disconnection Message - - byte SSH_MSG_DISCONNECT - uint32 reason code - string description [RFC2279] - string language tag [RFC3066] - - This message causes immediate termination of the connection. All - implementations MUST be able to process this message; they SHOULD be - able to send this message. - - The sender MUST NOT send or receive any data after this message, and - the recipient MUST NOT accept any data after receiving this message. - The description field gives a more specific explanation in a - human-readable form. The error code gives the reason in a more - machine-readable format (suitable for localization), and can have the - following values: - - #define SSH_DISCONNECT_HOST_NOT_ALLOWED_TO_CONNECT 1 - #define SSH_DISCONNECT_PROTOCOL_ERROR 2 - #define SSH_DISCONNECT_KEY_EXCHANGE_FAILED 3 - #define SSH_DISCONNECT_RESERVED 4 - #define SSH_DISCONNECT_MAC_ERROR 5 - #define SSH_DISCONNECT_COMPRESSION_ERROR 6 - #define SSH_DISCONNECT_SERVICE_NOT_AVAILABLE 7 - #define SSH_DISCONNECT_PROTOCOL_VERSION_NOT_SUPPORTED 8 - #define SSH_DISCONNECT_HOST_KEY_NOT_VERIFIABLE 9 - #define SSH_DISCONNECT_CONNECTION_LOST 10 - #define SSH_DISCONNECT_BY_APPLICATION 11 - #define SSH_DISCONNECT_TOO_MANY_CONNECTIONS 12 - #define SSH_DISCONNECT_AUTH_CANCELLED_BY_USER 13 - #define SSH_DISCONNECT_NO_MORE_AUTH_METHODS_AVAILABLE 14 - #define SSH_DISCONNECT_ILLEGAL_USER_NAME 15 - - If the description string is displayed, control character filtering - discussed in [SSH-ARCH] should be used to avoid attacks by sending - terminal control characters. - -10.2 Ignored Data Message - - byte SSH_MSG_IGNORE - string data - - All implementations MUST understand (and ignore) this message at any - time (after receiving the protocol version). No implementation is - required to send them. This message can be used as an additional - protection measure against advanced traffic analysis techniques. - - - - -Ylonen & Moffat, Editor Expires March 31, 2004 [Page 22] - -Internet-Draft SSH Transport Layer Protocol Oct 2003 - - -10.3 Debug Message - - byte SSH_MSG_DEBUG - boolean always_display - string message [RFC2279] - string language tag [RFC3066] - - All implementations MUST understand this message, but they are - allowed to ignore it. This message is used to pass the other side - information that may help debugging. If always_display is TRUE, the - message SHOULD be displayed. Otherwise, it SHOULD NOT be displayed - unless debugging information has been explicitly requested by the - user. - - - The message doesn't need to contain a newline. It is, however, - allowed to consist of multiple lines separated by CRLF (Carriage - Return - Line Feed) pairs. - - - If the message string is displayed, terminal control character - filtering discussed in [SSH-ARCH] should be used to avoid attacks by - sending terminal control characters. - -10.4 Reserved Messages - - An implementation MUST respond to all unrecognized messages with an - SSH_MSG_UNIMPLEMENTED message in the order in which the messages were - received. Such messages MUST be otherwise ignored. Later protocol - versions may define other meanings for these message types. - - byte SSH_MSG_UNIMPLEMENTED - uint32 packet sequence number of rejected message - - -11. Summary of Message Numbers - - The following message numbers have been defined in this protocol: - - #define SSH_MSG_DISCONNECT 1 - #define SSH_MSG_IGNORE 2 - #define SSH_MSG_UNIMPLEMENTED 3 - #define SSH_MSG_DEBUG 4 - #define SSH_MSG_SERVICE_REQUEST 5 - #define SSH_MSG_SERVICE_ACCEPT 6 - - #define SSH_MSG_KEXINIT 20 - #define SSH_MSG_NEWKEYS 21 - - - -Ylonen & Moffat, Editor Expires March 31, 2004 [Page 23] - -Internet-Draft SSH Transport Layer Protocol Oct 2003 - - - /* Numbers 30-49 used for kex packets. - Different kex methods may reuse message numbers in - this range. */ - - #define SSH_MSG_KEXDH_INIT 30 - #define SSH_MSG_KEXDH_REPLY 31 - - -12. IANA Considerations - - This document is part of a set, the IANA considerations for the SSH - protocol as defined in [SSH-ARCH], [SSH-TRANS], [SSH-USERAUTH], - [SSH-CONNECT] are detailed in [SSH-NUMBERS]. - -13. Security Considerations - - This protocol provides a secure encrypted channel over an insecure - network. It performs server host authentication, key exchange, - encryption, and integrity protection. It also derives a unique - session id that may be used by higher-level protocols. - - Full security considerations for this protocol are provided in - Section 8 of [SSH-ARCH] - -14. Intellectual Property - - The IETF takes no position regarding the validity or scope of any - intellectual property or other rights that might be claimed to - pertain to the implementation or use of the technology described in - this document or the extent to which any license under such rights - might or might not be available; neither does it represent that it - has made any effort to identify any such rights. Information on the - IETF's procedures with respect to rights in standards-track and - standards-related documentation can be found in BCP-11. Copies of - claims of rights made available for publication and any assurances of - licenses to be made available, or the result of an attempt made to - obtain a general license or permission for the use of such - proprietary rights by implementers or users of this specification can - be obtained from the IETF Secretariat. - - The IETF has been notified of intellectual property rights claimed in - regard to some or all of the specification contained in this - document. For more information consult the online list of claimed - rights. - -15. Additional Information - - The current document editor is: [email protected]. Comments on - - - -Ylonen & Moffat, Editor Expires March 31, 2004 [Page 24] - -Internet-Draft SSH Transport Layer Protocol Oct 2003 - - - this internet draft should be sent to the IETF SECSH working group, - details at: http://ietf.org/html.charters/secsh-charter.html - -Normative - - [SSH-ARCH] - Ylonen, T., "SSH Protocol Architecture", I-D - draft-ietf-architecture-15.txt, Oct 2003. - - [SSH-TRANS] - Ylonen, T., "SSH Transport Layer Protocol", I-D - draft-ietf-transport-17.txt, Oct 2003. - - [SSH-USERAUTH] - Ylonen, T., "SSH Authentication Protocol", I-D - draft-ietf-userauth-18.txt, Oct 2003. - - [SSH-CONNECT] - Ylonen, T., "SSH Connection Protocol", I-D - draft-ietf-connect-18.txt, Oct 2003. - - [SSH-NUMBERS] - Lehtinen, S. and D. Moffat, "SSH Protocol Assigned - Numbers", I-D draft-ietf-secsh-assignednumbers-05.txt, Oct - 2003. - - [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate - Requirement Levels", BCP 14, RFC 2119, March 1997. - -Informative - - [FIPS-186] - Federal Information Processing Standards Publication, - "FIPS PUB 186, Digital Signature Standard", May 1994. - - [FIPS-197] - NIST, "FIPS PUB 197 Advanced Encryption Standard (AES)", - November 2001. - - [FIPS-46-3] - U.S. Dept. of Commerce, "FIPS PUB 46-3, Data Encryption - Standard (DES)", October 1999. - - [RFC2459] Housley, R., Ford, W., Polk, T. and D. Solo, "Internet - X.509 Public Key Infrastructure Certificate and CRL - Profile", RFC 2459, January 1999. - - [RFC1034] Mockapetris, P., "Domain names - concepts and facilities", - - - -Ylonen & Moffat, Editor Expires March 31, 2004 [Page 25] - -Internet-Draft SSH Transport Layer Protocol Oct 2003 - - - STD 13, RFC 1034, November 1987. - - [RFC3066] Alvestrand, H., "Tags for the Identification of - Languages", BCP 47, RFC 3066, January 2001. - - [RFC1950] Deutsch, L. and J-L. Gailly, "ZLIB Compressed Data Format - Specification version 3.3", RFC 1950, May 1996. - - [RFC1951] Deutsch, P., "DEFLATE Compressed Data Format Specification - version 1.3", RFC 1951, May 1996. - - [RFC2279] Yergeau, F., "UTF-8, a transformation format of ISO - 10646", RFC 2279, January 1998. - - [RFC2104] Krawczyk, H., Bellare, M. and R. Canetti, "HMAC: - Keyed-Hashing for Message Authentication", RFC 2104, - February 1997. - - [RFC2144] Adams, C., "The CAST-128 Encryption Algorithm", RFC 2144, - May 1997. - - [RFC2440] Callas, J., Donnerhacke, L., Finney, H. and R. Thayer, - "OpenPGP Message Format", RFC 2440, November 1998. - - [RFC2693] Ellison, C., Frantz, B., Lampson, B., Rivest, R., Thomas, - B. and T. Ylonen, "SPKI Certificate Theory", RFC 2693, - September 1999. - - [RFC3526] Kivinen, T. and M. Kojo, "More Modular Exponential (MODP) - Diffie-Hellman groups for Internet Key Exchange (IKE)", - RFC 3526, May 2003. - - [SCHNEIER] - Schneier, B., "Applied Cryptography Second Edition: - protocols algorithms and source in code in C", 1996. - - [TWOFISH] Schneier, B., "The Twofish Encryptions Algorithm: A - 128-Bit Block Cipher, 1st Edition", March 1999. - - - - - - - - - - - - - -Ylonen & Moffat, Editor Expires March 31, 2004 [Page 26] - -Internet-Draft SSH Transport Layer Protocol Oct 2003 - - -Authors' Addresses - - Tatu Ylonen - SSH Communications Security Corp - Fredrikinkatu 42 - HELSINKI FIN-00100 - Finland - - EMail: [email protected] - - - Darren J. Moffat (editor) - Sun Microsystems, Inc - 17 Network Circle - Menlo Park 95025 - USA - - EMail: [email protected] - -Appendix A. Contibutors - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -Ylonen & Moffat, Editor Expires March 31, 2004 [Page 27] - -Internet-Draft SSH Transport Layer Protocol Oct 2003 - - -Intellectual Property Statement - - The IETF takes no position regarding the validity or scope of any - intellectual property or other rights that might be claimed to - pertain to the implementation or use of the technology described in - this document or the extent to which any license under such rights - might or might not be available; neither does it represent that it - has made any effort to identify any such rights. Information on the - IETF's procedures with respect to rights in standards-track and - standards-related documentation can be found in BCP-11. Copies of - claims of rights made available for publication and any assurances of - licenses to be made available, or the result of an attempt made to - obtain a general license or permission for the use of such - proprietary rights by implementors or users of this specification can - be obtained from the IETF Secretariat. - - The IETF invites any interested party to bring to its attention any - copyrights, patents or patent applications, or other proprietary - rights which may cover technology that may be required to practice - this standard. Please address the information to the IETF Executive - Director. - - The IETF has been notified of intellectual property rights claimed in - regard to some or all of the specification contained in this - document. For more information consult the online list of claimed - rights. - - -Full Copyright Statement - - Copyright (C) The Internet Society (2003). All Rights Reserved. - - This document and translations of it may be copied and furnished to - others, and derivative works that comment on or otherwise explain it - or assist in its implementation may be prepared, copied, published - and distributed, in whole or in part, without restriction of any - kind, provided that the above copyright notice and this paragraph are - included on all such copies and derivative works. However, this - document itself may not be modified in any way, such as by removing - the copyright notice or references to the Internet Society or other - Internet organizations, except as needed for the purpose of - developing Internet standards in which case the procedures for - copyrights defined in the Internet Standards process must be - followed, or as required to translate it into languages other than - English. - - The limited permissions granted above are perpetual and will not be - revoked by the Internet Society or its successors or assignees. - - - -Ylonen & Moffat, Editor Expires March 31, 2004 [Page 28] - -Internet-Draft SSH Transport Layer Protocol Oct 2003 - - - This document and the information contained herein is provided on an - "AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING - TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING - BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION - HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF - MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE. - - -Acknowledgment - - Funding for the RFC Editor function is currently provided by the - Internet Society. - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -Ylonen & Moffat, Editor Expires March 31, 2004 [Page 29]
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matrix invertmatrix matrix concatmatrix - matrix invertmatrix put -%%EndSetup -%%Page: (0,1) 1 -userdict/PStoPSsaved save put -PStoPSmatrix setmatrix -595.000000 0.271378 translate -90 rotate -0.706651 dup scale -userdict/PStoPSmatrix matrix currentmatrix put -userdict/PStoPSclip{0 0 moveto - 595.000000 0 rlineto 0 842.000000 rlineto -595.000000 0 rlineto - closepath}put initclip -/showpage{}def/copypage{}def/erasepage{}def -PStoPSxform concat -%%BeginPageSetup -_S -75 0 translate -/pagenum 1 def -/fname () def -/fdir () def -/ftail () def -/user_header_p false def -%%EndPageSetup -5 701 M -(Network Working Group T. Ylonen) s -5 690 M -(Internet-Draft SSH Communications Security Corp) s -5 679 M -(Expires: March 2, 2003 D. Moffat, Ed.) s -5 668 M -( Sun Microsystems, Inc) s -5 657 M -( September 2002) s -5 624 M -( SSH Authentication Protocol) s -5 613 M -( draft-ietf-secsh-userauth-18.txt) s -5 591 M -(Status of this Memo) s -5 569 M -( This document is an Internet-Draft and is in full conformance with) s -5 558 M -( all provisions of Section 10 of RFC2026.) s -5 536 M -( Internet-Drafts are working documents of the Internet Engineering) s -5 525 M -( Task Force \(IETF\), its areas, and its working groups. Note that other) s -5 514 M -( groups may also distribute working documents as Internet-Drafts.) s -5 492 M -( Internet-Drafts are draft documents valid for a maximum of six months) s -5 481 M -( and may be updated, replaced, or obsoleted by other documents at any) s -5 470 M -( time. It is inappropriate to use Internet-Drafts as reference) s -5 459 M -( material or to cite them other than as "work in progress.") s -5 437 M -( The list of current Internet-Drafts can be accessed at http://) s -5 426 M -( www.ietf.org/ietf/1id-abstracts.txt.) s -5 404 M -( The list of Internet-Draft Shadow Directories can be accessed at) s -5 393 M -( http://www.ietf.org/shadow.html.) s -5 371 M -( This Internet-Draft will expire on March 2, 2003.) s -5 349 M -(Copyright Notice) s -5 327 M -( Copyright \(C\) The Internet Society \(2002\). All Rights Reserved.) s -5 305 M -(Abstract) s -5 283 M -( SSH is a protocol for secure remote login and other secure network) s -5 272 M -( services over an insecure network. This document describes the SSH) s -5 261 M -( authentication protocol framework and public key, password, and) s -5 250 M -( host-based client authentication methods. Additional authentication) s -5 239 M -( methods are described in separate documents. The SSH authentication) s -5 228 M -( protocol runs on top of the SSH transport layer protocol and provides) s -5 217 M -( a single authenticated tunnel for the SSH connection protocol.) s -5 129 M -(Ylonen & Moffat Expires March 2, 2003 [Page 1]) s -_R -S -PStoPSsaved restore -userdict/PStoPSsaved save put -PStoPSmatrix setmatrix -595.000000 421.271378 translate -90 rotate -0.706651 dup scale -userdict/PStoPSmatrix matrix currentmatrix put -userdict/PStoPSclip{0 0 moveto - 595.000000 0 rlineto 0 842.000000 rlineto -595.000000 0 rlineto - closepath}put initclip -PStoPSxform concat -%%BeginPageSetup -_S -75 0 translate -/pagenum 2 def -/fname () def -/fdir () def -/ftail () def -/user_header_p false def -%%EndPageSetup -5 723 M -(Internet-Draft SSH Authentication Protocol September 2002) s -5 690 M -(Table of Contents) s -5 668 M -( 1. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 3) s -5 657 M -( 2. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3) s -5 646 M -( 3. Conventions Used in This Document . . . . . . . . . . . . . 3) s -5 635 M -( 3.1 The Authentication Protocol Framework . . . . . . . . . . . 3) s -5 624 M -( 3.1.1 Authentication Requests . . . . . . . . . . . . . . . . . . 4) s -5 613 M -( 3.1.2 Responses to Authentication Requests . . . . . . . . . . . . 5) s -5 602 M -( 3.1.3 The "none" Authentication Request . . . . . . . . . . . . . 6) s -5 591 M -( 3.1.4 Completion of User Authentication . . . . . . . . . . . . . 6) s -5 580 M -( 3.1.5 Banner Message . . . . . . . . . . . . . . . . . . . . . . . 7) s -5 569 M -( 3.2 Authentication Protocol Message Numbers . . . . . . . . . . 7) s -5 558 M -( 3.3 Public Key Authentication Method: publickey . . . . . . . . 8) s -5 547 M -( 3.4 Password Authentication Method: password . . . . . . . . . . 10) s -5 536 M -( 3.5 Host-Based Authentication: hostbased . . . . . . . . . . . . 11) s -5 525 M -( 4. Security Considerations . . . . . . . . . . . . . . . . . . 12) s -5 514 M -( Normative . . . . . . . . . . . . . . . . . . . . . . . . . 13) s -5 503 M -( Informative . . . . . . . . . . . . . . . . . . . . . . . . 13) s -5 492 M -( Authors' Addresses . . . . . . . . . . . . . . . . . . . . . 14) s -5 481 M -( Intellectual Property and Copyright Statements . . . . . . . 15) s -5 129 M -(Ylonen & Moffat Expires March 2, 2003 [Page 2]) s -_R -S -PStoPSsaved restore -%%Page: (2,3) 2 -userdict/PStoPSsaved save put -PStoPSmatrix setmatrix -595.000000 0.271378 translate -90 rotate -0.706651 dup scale -userdict/PStoPSmatrix matrix currentmatrix put -userdict/PStoPSclip{0 0 moveto - 595.000000 0 rlineto 0 842.000000 rlineto -595.000000 0 rlineto - closepath}put initclip -/showpage{}def/copypage{}def/erasepage{}def -PStoPSxform concat -%%BeginPageSetup -_S -75 0 translate -/pagenum 3 def -/fname () def -/fdir () def -/ftail () def -/user_header_p false def -%%EndPageSetup -5 723 M -(Internet-Draft SSH Authentication Protocol September 2002) s -5 690 M -(1. Contributors) s -5 668 M -( The major original contributors of this document were: Tatu Ylonen,) s -5 657 M -( Tero Kivinen, Timo J. Rinne, Sami Lehtinen \(all of SSH Communications) s -5 646 M -( Security Corp\), and Markku-Juhani O. Saarinen \(University of) s -5 635 M -( Jyvaskyla\)) s -5 613 M -( The document editor is: [email protected]. Comments on this) s -5 602 M -( internet draft should be sent to the IETF SECSH working group,) s -5 591 M -( details at: http://ietf.org/html.charters/secsh-charter.html) s -5 569 M -(2. Introduction) s -5 547 M -( The SSH authentication protocol is a general-purpose user) s -5 536 M -( authentication protocol. It is intended to be run over the SSH) s -5 525 M -( transport layer protocol [SSH-TRANS]. This protocol assumes that the) s -5 514 M -( underlying protocols provide integrity and confidentiality) s -5 503 M -( protection.) s -5 481 M -( This document should be read only after reading the SSH architecture) s -5 470 M -( document [SSH-ARCH]. This document freely uses terminology and) s -5 459 M -( notation from the architecture document without reference or further) s -5 448 M -( explanation.) s -5 426 M -( The service name for this protocol is "ssh-userauth".) s -5 404 M -( When this protocol starts, it receives the session identifier from) s -5 393 M -( the lower-level protocol \(this is the exchange hash H from the first) s -5 382 M -( key exchange\). The session identifier uniquely identifies this) s -5 371 M -( session and is suitable for signing in order to prove ownership of a) s -5 360 M -( private key. This protocol also needs to know whether the lower-level) s -5 349 M -( protocol provides confidentiality protection.) s -5 327 M -(3. Conventions Used in This Document) s -5 305 M -( The keywords "MUST", "MUST NOT", "REQUIRED", "SHOULD", "SHOULD NOT",) s -5 294 M -( and "MAY" that appear in this document are to be interpreted as) s -5 283 M -( described in [RFC2119]) s -5 261 M -( The used data types and terminology are specified in the architecture) s -5 250 M -( document [SSH-ARCH]) s -5 228 M -( The architecture document also discusses the algorithm naming) s -5 217 M -( conventions that MUST be used with the SSH protocols.) s -5 195 M -(3.1 The Authentication Protocol Framework) s -5 173 M -( The server drives the authentication by telling the client which) s -5 129 M -(Ylonen & Moffat Expires March 2, 2003 [Page 3]) s -_R -S -PStoPSsaved restore -userdict/PStoPSsaved save put -PStoPSmatrix setmatrix -595.000000 421.271378 translate -90 rotate -0.706651 dup scale -userdict/PStoPSmatrix matrix currentmatrix put -userdict/PStoPSclip{0 0 moveto - 595.000000 0 rlineto 0 842.000000 rlineto -595.000000 0 rlineto - closepath}put initclip -PStoPSxform concat -%%BeginPageSetup -_S -75 0 translate -/pagenum 4 def -/fname () def -/fdir () def -/ftail () def -/user_header_p false def -%%EndPageSetup -5 723 M -(Internet-Draft SSH Authentication Protocol September 2002) s -5 690 M -( authentication methods can be used to continue the exchange at any) s -5 679 M -( given time. The client has the freedom to try the methods listed by) s -5 668 M -( the server in any order. This gives the server complete control over) s -5 657 M -( the authentication process if desired, but also gives enough) s -5 646 M -( flexibility for the client to use the methods it supports or that are) s -5 635 M -( most convenient for the user, when multiple methods are offered by) s -5 624 M -( the server.) s -5 602 M -( Authentication methods are identified by their name, as defined in) s -5 591 M -( [SSH-ARCH]. The "none" method is reserved, and MUST NOT be listed as) s -5 580 M -( supported. However, it MAY be sent by the client. The server MUST) s -5 569 M -( always reject this request, unless the client is to be allowed in) s -5 558 M -( without any authentication, in which case the server MUST accept this) s -5 547 M -( request. The main purpose of sending this request is to get the list) s -5 536 M -( of supported methods from the server.) s -5 514 M -( The server SHOULD have a timeout for authentication, and disconnect) s -5 503 M -( if the authentication has not been accepted within the timeout) s -5 492 M -( period. The RECOMMENDED timeout period is 10 minutes. Additionally,) s -5 481 M -( the implementation SHOULD limit the number of failed authentication) s -5 470 M -( attempts a client may perform in a single session \(the RECOMMENDED) s -5 459 M -( limit is 20 attempts\). If the threshold is exceeded, the server) s -5 448 M -( SHOULD disconnect.) s -5 426 M -(3.1.1 Authentication Requests) s -5 404 M -( All authentication requests MUST use the following message format.) s -5 393 M -( Only the first few fields are defined; the remaining fields depend on) s -5 382 M -( the authentication method.) s -5 360 M -( byte SSH_MSG_USERAUTH_REQUEST) s -5 349 M -( string user name \(in ISO-10646 UTF-8 encoding [RFC2279]\)) s -5 338 M -( string service name \(in US-ASCII\)) s -5 327 M -( string method name \(US-ASCII\)) s -5 316 M -( The rest of the packet is method-specific.) s -5 294 M -( The user name and service are repeated in every new authentication) s -5 283 M -( attempt, and MAY change. The server implementation MUST carefully) s -5 272 M -( check them in every message, and MUST flush any accumulated) s -5 261 M -( authentication states if they change. If it is unable to flush some) s -5 250 M -( authentication state, it MUST disconnect if the user or service name) s -5 239 M -( changes.) s -5 217 M -( The service name specifies the service to start after authentication.) s -5 206 M -( There may be several different authenticated services provided. If) s -5 195 M -( the requested service is not available, the server MAY disconnect) s -5 184 M -( immediately or at any later time. Sending a proper disconnect) s -5 173 M -( message is RECOMMENDED. In any case, if the service does not exist,) s -5 129 M -(Ylonen & Moffat Expires March 2, 2003 [Page 4]) s -_R -S -PStoPSsaved restore -%%Page: (4,5) 3 -userdict/PStoPSsaved save put -PStoPSmatrix setmatrix -595.000000 0.271378 translate -90 rotate -0.706651 dup scale -userdict/PStoPSmatrix matrix currentmatrix put -userdict/PStoPSclip{0 0 moveto - 595.000000 0 rlineto 0 842.000000 rlineto -595.000000 0 rlineto - closepath}put initclip -/showpage{}def/copypage{}def/erasepage{}def -PStoPSxform concat -%%BeginPageSetup -_S -75 0 translate -/pagenum 5 def -/fname () def -/fdir () def -/ftail () def -/user_header_p false def -%%EndPageSetup -5 723 M -(Internet-Draft SSH Authentication Protocol September 2002) s -5 690 M -( authentication MUST NOT be accepted.) s -5 668 M -( If the requested user does not exist, the server MAY disconnect, or) s -5 657 M -( MAY send a bogus list of acceptable authentication methods, but never) s -5 646 M -( accept any. This makes it possible for the server to avoid) s -5 635 M -( disclosing information on which accounts exist. In any case, if the) s -5 624 M -( user does not exist, the authentication request MUST NOT be accepted.) s -5 602 M -( While there is usually little point for clients to send requests that) s -5 591 M -( the server does not list as acceptable, sending such requests is not) s -5 580 M -( an error, and the server SHOULD simply reject requests that it does) s -5 569 M -( not recognize.) s -5 547 M -( An authentication request MAY result in a further exchange of) s -5 536 M -( messages. All such messages depend on the authentication method) s -5 525 M -( used, and the client MAY at any time continue with a new) s -5 514 M -( SSH_MSG_USERAUTH_REQUEST message, in which case the server MUST) s -5 503 M -( abandon the previous authentication attempt and continue with the new) s -5 492 M -( one.) s -5 470 M -(3.1.2 Responses to Authentication Requests) s -5 448 M -( If the server rejects the authentication request, it MUST respond) s -5 437 M -( with the following:) s -5 415 M -( byte SSH_MSG_USERAUTH_FAILURE) s -5 404 M -( string authentications that can continue) s -5 393 M -( boolean partial success) s -5 371 M -( "Authentications that can continue" is a comma-separated list of) s -5 360 M -( authentication method names that may productively continue the) s -5 349 M -( authentication dialog.) s -5 327 M -( It is RECOMMENDED that servers only include those methods in the list) s -5 316 M -( that are actually useful. However, it is not illegal to include) s -5 305 M -( methods that cannot be used to authenticate the user.) s -5 283 M -( Already successfully completed authentications SHOULD NOT be included) s -5 272 M -( in the list, unless they really should be performed again for some) s -5 261 M -( reason.) s -5 239 M -( "Partial success" MUST be TRUE if the authentication request to which) s -5 228 M -( this is a response was successful. It MUST be FALSE if the request) s -5 217 M -( was not successfully processed.) s -5 195 M -( When the server accepts authentication, it MUST respond with the) s -5 184 M -( following:) s -5 129 M -(Ylonen & Moffat Expires March 2, 2003 [Page 5]) s -_R -S -PStoPSsaved restore -userdict/PStoPSsaved save put -PStoPSmatrix setmatrix -595.000000 421.271378 translate -90 rotate -0.706651 dup scale -userdict/PStoPSmatrix matrix currentmatrix put -userdict/PStoPSclip{0 0 moveto - 595.000000 0 rlineto 0 842.000000 rlineto -595.000000 0 rlineto - closepath}put initclip -PStoPSxform concat -%%BeginPageSetup -_S -75 0 translate -/pagenum 6 def -/fname () def -/fdir () def -/ftail () def -/user_header_p false def -%%EndPageSetup -5 723 M -(Internet-Draft SSH Authentication Protocol September 2002) s -5 690 M -( byte SSH_MSG_USERAUTH_SUCCESS) s -5 668 M -( Note that this is not sent after each step in a multi-method) s -5 657 M -( authentication sequence, but only when the authentication is) s -5 646 M -( complete.) s -5 624 M -( The client MAY send several authentication requests without waiting) s -5 613 M -( for responses from previous requests. The server MUST process each) s -5 602 M -( request completely and acknowledge any failed requests with a) s -5 591 M -( SSH_MSG_USERAUTH_FAILURE message before processing the next request.) s -5 569 M -( A request that results in further exchange of messages will be) s -5 558 M -( aborted by a second request. It is not possible to send a second) s -5 547 M -( request without waiting for a response from the server, if the first) s -5 536 M -( request will result in further exchange of messages. No) s -5 525 M -( SSH_MSG_USERAUTH_FAILURE message will be sent for the aborted method.) s -5 503 M -( SSH_MSG_USERAUTH_SUCCESS MUST be sent only once. When) s -5 492 M -( SSH_MSG_USERAUTH_SUCCESS has been sent, any further authentication) s -5 481 M -( requests received after that SHOULD be silently ignored.) s -5 459 M -( Any non-authentication messages sent by the client after the request) s -5 448 M -( that resulted in SSH_MSG_USERAUTH_SUCCESS being sent MUST be passed) s -5 437 M -( to the service being run on top of this protocol. Such messages can) s -5 426 M -( be identified by their message numbers \(see Section Message Numbers) s -5 415 M -( \(Section 3.2\)\).) s -5 393 M -(3.1.3 The "none" Authentication Request) s -5 371 M -( A client may request a list of authentication methods that may) s -5 360 M -( continue by using the "none" authentication method.) s -5 338 M -( If no authentication at all is needed for the user, the server MUST) s -5 327 M -( return SSH_MSG_USERAUTH_SUCCESS. Otherwise, the server MUST return) s -5 316 M -( SSH_MSG_USERAUTH_FAILURE and MAY return with it a list of) s -5 305 M -( authentication methods that can continue.) s -5 283 M -( This method MUST NOT be listed as supported by the server.) s -5 261 M -(3.1.4 Completion of User Authentication) s -5 239 M -( Authentication is complete when the server has responded with) s -5 228 M -( SSH_MSG_USERAUTH_SUCCESS; all authentication related messages) s -5 217 M -( received after sending this message SHOULD be silently ignored.) s -5 195 M -( After sending SSH_MSG_USERAUTH_SUCCESS, the server starts the) s -5 184 M -( requested service.) s -5 129 M -(Ylonen & Moffat Expires March 2, 2003 [Page 6]) s -_R -S -PStoPSsaved restore -%%Page: (6,7) 4 -userdict/PStoPSsaved save put -PStoPSmatrix setmatrix -595.000000 0.271378 translate -90 rotate -0.706651 dup scale -userdict/PStoPSmatrix matrix currentmatrix put -userdict/PStoPSclip{0 0 moveto - 595.000000 0 rlineto 0 842.000000 rlineto -595.000000 0 rlineto - closepath}put initclip -/showpage{}def/copypage{}def/erasepage{}def -PStoPSxform concat -%%BeginPageSetup -_S -75 0 translate -/pagenum 7 def -/fname () def -/fdir () def -/ftail () def -/user_header_p false def -%%EndPageSetup -5 723 M -(Internet-Draft SSH Authentication Protocol September 2002) s -5 690 M -(3.1.5 Banner Message) s -5 668 M -( In some jurisdictions, sending a warning message before) s -5 657 M -( authentication may be relevant for getting legal protection. Many) s -5 646 M -( UNIX machines, for example, normally display text from `/etc/issue',) s -5 635 M -( or use "tcp wrappers" or similar software to display a banner before) s -5 624 M -( issuing a login prompt.) s -5 602 M -( The SSH server may send a SSH_MSG_USERAUTH_BANNER message at any time) s -5 591 M -( before authentication is successful. This message contains text to) s -5 580 M -( be displayed to the client user before authentication is attempted.) s -5 569 M -( The format is as follows:) s -5 547 M -( byte SSH_MSG_USERAUTH_BANNER) s -5 536 M -( string message \(ISO-10646 UTF-8\)) s -5 525 M -( string language tag \(as defined in [RFC3066]\)) s -5 503 M -( The client SHOULD by default display the message on the screen.) s -5 492 M -( However, since the message is likely to be sent for every login) s -5 481 M -( attempt, and since some client software will need to open a separate) s -5 470 M -( window for this warning, the client software may allow the user to) s -5 459 M -( explicitly disable the display of banners from the server. The) s -5 448 M -( message may consist of multiple lines.) s -5 426 M -( If the message string is displayed, control character filtering) s -5 415 M -( discussed in [SSH-ARCH] SHOULD be used to avoid attacks by sending) s -5 404 M -( terminal control characters.) s -5 382 M -(3.2 Authentication Protocol Message Numbers) s -5 360 M -( All message numbers used by this authentication protocol are in the) s -5 349 M -( range from 50 to 79, which is part of the range reserved for) s -5 338 M -( protocols running on top of the SSH transport layer protocol.) s -5 316 M -( Message numbers of 80 and higher are reserved for protocols running) s -5 305 M -( after this authentication protocol, so receiving one of them before) s -5 294 M -( authentication is complete is an error, to which the server MUST) s -5 283 M -( respond by disconnecting \(preferably with a proper disconnect message) s -5 272 M -( sent first to ease troubleshooting\).) s -5 250 M -( After successful authentication, such messages are passed to the) s -5 239 M -( higher-level service.) s -5 217 M -( These are the general authentication message codes:) s -5 195 M -( #define SSH_MSG_USERAUTH_REQUEST 50) s -5 184 M -( #define SSH_MSG_USERAUTH_FAILURE 51) s -5 173 M -( #define SSH_MSG_USERAUTH_SUCCESS 52) s -5 129 M -(Ylonen & Moffat Expires March 2, 2003 [Page 7]) s -_R -S -PStoPSsaved restore -userdict/PStoPSsaved save put -PStoPSmatrix setmatrix -595.000000 421.271378 translate -90 rotate -0.706651 dup scale -userdict/PStoPSmatrix matrix currentmatrix put -userdict/PStoPSclip{0 0 moveto - 595.000000 0 rlineto 0 842.000000 rlineto -595.000000 0 rlineto - closepath}put initclip -PStoPSxform concat -%%BeginPageSetup -_S -75 0 translate -/pagenum 8 def -/fname () def -/fdir () def -/ftail () def -/user_header_p false def -%%EndPageSetup -5 723 M -(Internet-Draft SSH Authentication Protocol September 2002) s -5 690 M -( #define SSH_MSG_USERAUTH_BANNER 53) s -5 668 M -( In addition to the above, there is a range of message numbers) s -5 657 M -( \(60..79\) reserved for method-specific messages. These messages are) s -5 646 M -( only sent by the server \(client sends only SSH_MSG_USERAUTH_REQUEST) s -5 635 M -( messages\). Different authentication methods reuse the same message) s -5 624 M -( numbers.) s -5 602 M -(3.3 Public Key Authentication Method: publickey) s -5 580 M -( The only REQUIRED authentication method is public key authentication.) s -5 569 M -( All implementations MUST support this method; however, not all users) s -5 558 M -( need to have public keys, and most local policies are not likely to) s -5 547 M -( require public key authentication for all users in the near future.) s -5 525 M -( With this method, the possession of a private key serves as) s -5 514 M -( authentication. This method works by sending a signature created) s -5 503 M -( with a private key of the user. The server MUST check that the key) s -5 492 M -( is a valid authenticator for the user, and MUST check that the) s -5 481 M -( signature is valid. If both hold, the authentication request MUST be) s -5 470 M -( accepted; otherwise it MUST be rejected. \(Note that the server MAY) s -5 459 M -( require additional authentications after successful authentication.\)) s -5 437 M -( Private keys are often stored in an encrypted form at the client) s -5 426 M -( host, and the user must supply a passphrase before the signature can) s -5 415 M -( be generated. Even if they are not, the signing operation involves) s -5 404 M -( some expensive computation. To avoid unnecessary processing and user) s -5 393 M -( interaction, the following message is provided for querying whether) s -5 382 M -( authentication using the key would be acceptable.) s -5 360 M -( byte SSH_MSG_USERAUTH_REQUEST) s -5 349 M -( string user name) s -5 338 M -( string service) s -5 327 M -( string "publickey") s -5 316 M -( boolean FALSE) s -5 305 M -( string public key algorithm name) s -5 294 M -( string public key blob) s -5 272 M -( Public key algorithms are defined in the transport layer) s -5 261 M -( specification [SSH-TRANS]. The public key blob may contain) s -5 250 M -( certificates.) s -5 228 M -( Any public key algorithm may be offered for use in authentication.) s -5 217 M -( In particular, the list is not constrained by what was negotiated) s -5 206 M -( during key exchange. If the server does not support some algorithm,) s -5 195 M -( it MUST simply reject the request.) s -5 173 M -( The server MUST respond to this message with either) s -5 129 M -(Ylonen & Moffat Expires March 2, 2003 [Page 8]) s -_R -S -PStoPSsaved restore -%%Page: (8,9) 5 -userdict/PStoPSsaved save put -PStoPSmatrix setmatrix -595.000000 0.271378 translate -90 rotate -0.706651 dup scale -userdict/PStoPSmatrix matrix currentmatrix put -userdict/PStoPSclip{0 0 moveto - 595.000000 0 rlineto 0 842.000000 rlineto -595.000000 0 rlineto - closepath}put initclip -/showpage{}def/copypage{}def/erasepage{}def -PStoPSxform concat -%%BeginPageSetup -_S -75 0 translate -/pagenum 9 def -/fname () def -/fdir () def -/ftail () def -/user_header_p false def -%%EndPageSetup -5 723 M -(Internet-Draft SSH Authentication Protocol September 2002) s -5 690 M -( SSH_MSG_USERAUTH_FAILURE or with the following:) s -5 668 M -( byte SSH_MSG_USERAUTH_PK_OK) s -5 657 M -( string public key algorithm name from the request) s -5 646 M -( string public key blob from the request) s -5 624 M -( To perform actual authentication, the client MAY then send a) s -5 613 M -( signature generated using the private key. The client MAY send the) s -5 602 M -( signature directly without first verifying whether the key is) s -5 591 M -( acceptable. The signature is sent using the following packet:) s -5 569 M -( byte SSH_MSG_USERAUTH_REQUEST) s -5 558 M -( string user name) s -5 547 M -( string service) s -5 536 M -( string "publickey") s -5 525 M -( boolean TRUE) s -5 514 M -( string public key algorithm name) s -5 503 M -( string public key to be used for authentication) s -5 492 M -( string signature) s -5 470 M -( Signature is a signature by the corresponding private key over the) s -5 459 M -( following data, in the following order:) s -5 437 M -( string session identifier) s -5 426 M -( byte SSH_MSG_USERAUTH_REQUEST) s -5 415 M -( string user name) s -5 404 M -( string service) s -5 393 M -( string "publickey") s -5 382 M -( boolean TRUE) s -5 371 M -( string public key algorithm name) s -5 360 M -( string public key to be used for authentication) s -5 338 M -( When the server receives this message, it MUST check whether the) s -5 327 M -( supplied key is acceptable for authentication, and if so, it MUST) s -5 316 M -( check whether the signature is correct.) s -5 294 M -( If both checks succeed, this method is successful. Note that the) s -5 283 M -( server may require additional authentications. The server MUST) s -5 272 M -( respond with SSH_MSG_USERAUTH_SUCCESS \(if no more authentications are) s -5 261 M -( needed\), or SSH_MSG_USERAUTH_FAILURE \(if the request failed, or more) s -5 250 M -( authentications are needed\).) s -5 228 M -( The following method-specific message numbers are used by the) s -5 217 M -( publickey authentication method.) s -5 195 M -( /* Key-based */) s -5 184 M -( #define SSH_MSG_USERAUTH_PK_OK 60) s -5 129 M -(Ylonen & Moffat Expires March 2, 2003 [Page 9]) s -_R -S -PStoPSsaved restore -userdict/PStoPSsaved save put -PStoPSmatrix setmatrix -595.000000 421.271378 translate -90 rotate -0.706651 dup scale -userdict/PStoPSmatrix matrix currentmatrix put -userdict/PStoPSclip{0 0 moveto - 595.000000 0 rlineto 0 842.000000 rlineto -595.000000 0 rlineto - closepath}put initclip -PStoPSxform concat -%%BeginPageSetup -_S -75 0 translate -/pagenum 10 def -/fname () def -/fdir () def -/ftail () def -/user_header_p false def -%%EndPageSetup -5 723 M -(Internet-Draft SSH Authentication Protocol September 2002) s -5 690 M -(3.4 Password Authentication Method: password) s -5 668 M -( Password authentication uses the following packets. Note that a) s -5 657 M -( server MAY request the user to change the password. All) s -5 646 M -( implementations SHOULD support password authentication.) s -5 624 M -( byte SSH_MSG_USERAUTH_REQUEST) s -5 613 M -( string user name) s -5 602 M -( string service) s -5 591 M -( string "password") s -5 580 M -( boolean FALSE) s -5 569 M -( string plaintext password \(ISO-10646 UTF-8\)) s -5 547 M -( Note that the password is encoded in ISO-10646 UTF-8. It is up to) s -5 536 M -( the server how it interprets the password and validates it against) s -5 525 M -( the password database. However, if the client reads the password in) s -5 514 M -( some other encoding \(e.g., ISO 8859-1 \(ISO Latin1\)\), it MUST convert) s -5 503 M -( the password to ISO-10646 UTF-8 before transmitting, and the server) s -5 492 M -( MUST convert the password to the encoding used on that system for) s -5 481 M -( passwords.) s -5 459 M -( Note that even though the cleartext password is transmitted in the) s -5 448 M -( packet, the entire packet is encrypted by the transport layer. Both) s -5 437 M -( the server and the client should check whether the underlying) s -5 426 M -( transport layer provides confidentiality \(i.e., if encryption is) s -5 415 M -( being used\). If no confidentiality is provided \(none cipher\),) s -5 404 M -( password authentication SHOULD be disabled. If there is no) s -5 393 M -( confidentiality or no MAC, password change SHOULD be disabled.) s -5 371 M -( Normally, the server responds to this message with success or) s -5 360 M -( failure. However, if the password has expired the server SHOULD) s -5 349 M -( indicate this by responding with SSH_MSG_USERAUTH_PASSWD_CHANGEREQ.) s -5 338 M -( In anycase the server MUST NOT allow an expired password to be used) s -5 327 M -( for authentication.) s -5 305 M -( byte SSH_MSG_USERAUTH_PASSWD_CHANGEREQ) s -5 294 M -( string prompt \(ISO-10646 UTF-8\)) s -5 283 M -( string language tag \(as defined in [RFC3066]\)) s -5 261 M -( In this case, the client MAY continue with a different authentication) s -5 250 M -( method, or request a new password from the user and retry password) s -5 239 M -( authentication using the following message. The client MAY also send) s -5 228 M -( this message instead of the normal password authentication request) s -5 217 M -( without the server asking for it.) s -5 195 M -( byte SSH_MSG_USERAUTH_REQUEST) s -5 184 M -( string user name) s -5 173 M -( string service) s -5 129 M -(Ylonen & Moffat Expires March 2, 2003 [Page 10]) s -_R -S -PStoPSsaved restore -%%Page: (10,11) 6 -userdict/PStoPSsaved save put -PStoPSmatrix setmatrix -595.000000 0.271378 translate -90 rotate -0.706651 dup scale -userdict/PStoPSmatrix matrix currentmatrix put -userdict/PStoPSclip{0 0 moveto - 595.000000 0 rlineto 0 842.000000 rlineto -595.000000 0 rlineto - closepath}put initclip -/showpage{}def/copypage{}def/erasepage{}def -PStoPSxform concat -%%BeginPageSetup -_S -75 0 translate -/pagenum 11 def -/fname () def -/fdir () def -/ftail () def -/user_header_p false def -%%EndPageSetup -5 723 M -(Internet-Draft SSH Authentication Protocol September 2002) s -5 690 M -( string "password") s -5 679 M -( boolean TRUE) s -5 668 M -( string plaintext old password \(ISO-10646 UTF-8\)) s -5 657 M -( string plaintext new password \(ISO-10646 UTF-8\)) s -5 635 M -( The server must reply to request message with) s -5 624 M -( SSH_MSG_USERAUTH_SUCCESS, SSH_MSG_USERAUTH_FAILURE, or another) s -5 613 M -( SSH_MSG_USERAUTH_PASSWD_CHANGEREQ. The meaning of these is as) s -5 602 M -( follows:) s -5 580 M -( SSH_MSG_USERAUTH_SUCCESS The password has been changed, and) s -5 569 M -( authentication has been successfully completed.) s -5 547 M -( SSH_MSG_USERAUTH_FAILURE with partial success The password has) s -5 536 M -( been changed, but more authentications are needed.) s -5 514 M -( SSH_MSG_USERAUTH_FAILURE without partial success The password has) s -5 503 M -( not been changed. Either password changing was not supported, or) s -5 492 M -( the old password was bad. Note that if the server has already) s -5 481 M -( sent SSH_MSG_USERAUTH_PASSWD_CHANGEREQ, we know that it supports) s -5 470 M -( changing the password.) s -5 448 M -( SSH_MSG_USERAUTH_CHANGEREQ The password was not changed because) s -5 437 M -( the new password was not acceptable \(e.g. too easy to guess\).) s -5 415 M -( The following method-specific message numbers are used by the) s -5 404 M -( password authentication method.) s -5 382 M -( #define SSH_MSG_USERAUTH_PASSWD_CHANGEREQ 60) s -5 349 M -(3.5 Host-Based Authentication: hostbased) s -5 327 M -( Some sites wish to allow authentication based on the host where the) s -5 316 M -( user is coming from, and the user name on the remote host. While) s -5 305 M -( this form of authentication is not suitable for high-security sites,) s -5 294 M -( it can be very convenient in many environments. This form of) s -5 283 M -( authentication is OPTIONAL. When used, special care SHOULD be taken) s -5 272 M -( to prevent a regular user from obtaining the private host key.) s -5 250 M -( The client requests this form of authentication by sending the) s -5 239 M -( following message. It is similar to the UNIX "rhosts" and) s -5 228 M -( "hosts.equiv" styles of authentication, except that the identity of) s -5 217 M -( the client host is checked more rigorously.) s -5 195 M -( This method works by having the client send a signature created with) s -5 184 M -( the private key of the client host, which the server checks with that) s -5 173 M -( host's public key. Once the client host's identity is established,) s -5 129 M -(Ylonen & Moffat Expires March 2, 2003 [Page 11]) s -_R -S -PStoPSsaved restore -userdict/PStoPSsaved save put -PStoPSmatrix setmatrix -595.000000 421.271378 translate -90 rotate -0.706651 dup scale -userdict/PStoPSmatrix matrix currentmatrix put -userdict/PStoPSclip{0 0 moveto - 595.000000 0 rlineto 0 842.000000 rlineto -595.000000 0 rlineto - closepath}put initclip -PStoPSxform concat -%%BeginPageSetup -_S -75 0 translate -/pagenum 12 def -/fname () def -/fdir () def -/ftail () def -/user_header_p false def -%%EndPageSetup -5 723 M -(Internet-Draft SSH Authentication Protocol September 2002) s -5 690 M -( authorization \(but no further authentication\) is performed based on) s -5 679 M -( the user names on the server and the client, and the client host) s -5 668 M -( name.) s -5 646 M -( byte SSH_MSG_USERAUTH_REQUEST) s -5 635 M -( string user name) s -5 624 M -( string service) s -5 613 M -( string "hostbased") s -5 602 M -( string public key algorithm for host key) s -5 591 M -( string public host key and certificates for client host) s -5 580 M -( string client host name \(FQDN; US-ASCII\)) s -5 569 M -( string user name on the client host \(ISO-10646 UTF-8\)) s -5 558 M -( string signature) s -5 536 M -( Public key algorithm names for use in "public key algorithm for host) s -5 525 M -( key" are defined in the transport layer specification. The "public) s -5 514 M -( host key for client host" may include certificates.) s -5 492 M -( Signature is a signature with the private host key of the following) s -5 481 M -( data, in this order:) s -5 459 M -( string session identifier) s -5 448 M -( byte SSH_MSG_USERAUTH_REQUEST) s -5 437 M -( string user name) s -5 426 M -( string service) s -5 415 M -( string "hostbased") s -5 404 M -( string public key algorithm for host key) s -5 393 M -( string public host key and certificates for client host) s -5 382 M -( string client host name \(FQDN; US-ASCII\)) s -5 371 M -( string user name on the client host\(ISO-10646 UTF-8\)) s -5 349 M -( The server MUST verify that the host key actually belongs to the) s -5 338 M -( client host named in the message, that the given user on that host is) s -5 327 M -( allowed to log in, and that the signature is a valid signature on the) s -5 316 M -( appropriate value by the given host key. The server MAY ignore the) s -5 305 M -( client user name, if it wants to authenticate only the client host.) s -5 283 M -( It is RECOMMENDED that whenever possible, the server perform) s -5 272 M -( additional checks to verify that the network address obtained from) s -5 261 M -( the \(untrusted\) network matches the given client host name. This) s -5 250 M -( makes exploiting compromised host keys more difficult. Note that) s -5 239 M -( this may require special handling for connections coming through a) s -5 228 M -( firewall.) s -5 206 M -(4. Security Considerations) s -5 184 M -( The purpose of this protocol is to perform client user) s -5 173 M -( authentication. It assumed that this runs over a secure transport) s -5 129 M -(Ylonen & Moffat Expires March 2, 2003 [Page 12]) s -_R -S -PStoPSsaved restore -%%Page: (12,13) 7 -userdict/PStoPSsaved save put -PStoPSmatrix setmatrix -595.000000 0.271378 translate -90 rotate -0.706651 dup scale -userdict/PStoPSmatrix matrix currentmatrix put -userdict/PStoPSclip{0 0 moveto - 595.000000 0 rlineto 0 842.000000 rlineto -595.000000 0 rlineto - closepath}put initclip -/showpage{}def/copypage{}def/erasepage{}def -PStoPSxform concat -%%BeginPageSetup -_S -75 0 translate -/pagenum 13 def -/fname () def -/fdir () def -/ftail () def -/user_header_p false def -%%EndPageSetup -5 723 M -(Internet-Draft SSH Authentication Protocol September 2002) s -5 690 M -( layer protocol, which has already authenticated the server machine,) s -5 679 M -( established an encrypted communications channel, and computed a) s -5 668 M -( unique session identifier for this session. The transport layer) s -5 657 M -( provides forward secrecy for password authentication and other) s -5 646 M -( methods that rely on secret data.) s -5 624 M -( Full security considerations for this protocol are provided in) s -5 613 M -( Section 8 of [SSH-ARCH]) s -5 591 M -(Normative) s -5 569 M -( [SSH-ARCH]) s -5 558 M -( Ylonen, T., "SSH Protocol Architecture", I-D) s -5 547 M -( draft-ietf-architecture-15.txt, Oct 2003.) s -5 525 M -( [SSH-TRANS]) s -5 514 M -( Ylonen, T., "SSH Transport Layer Protocol", I-D) s -5 503 M -( draft-ietf-transport-17.txt, Oct 2003.) s -5 481 M -( [SSH-USERAUTH]) s -5 470 M -( Ylonen, T., "SSH Authentication Protocol", I-D) s -5 459 M -( draft-ietf-userauth-18.txt, Oct 2003.) s -5 437 M -( [SSH-CONNECT]) s -5 426 M -( Ylonen, T., "SSH Connection Protocol", I-D) s -5 415 M -( draft-ietf-connect-18.txt, Oct 2003.) s -5 393 M -( [SSH-NUMBERS]) s -5 382 M -( Lehtinen, S. and D. Moffat, "SSH Protocol Assigned) s -5 371 M -( Numbers", I-D draft-ietf-secsh-assignednumbers-05.txt, Oct) s -5 360 M -( 2003.) s -5 338 M -( [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate) s -5 327 M -( Requirement Levels", BCP 14, RFC 2119, March 1997.) s -5 305 M -(Informative) s -5 283 M -( [RFC3066] Alvestrand, H., "Tags for the Identification of) s -5 272 M -( Languages", BCP 47, RFC 3066, January 2001.) s -5 250 M -( [RFC2279] Yergeau, F., "UTF-8, a transformation format of ISO) s -5 239 M -( 10646", RFC 2279, January 1998.) s -5 129 M -(Ylonen & Moffat Expires March 2, 2003 [Page 13]) s -_R -S -PStoPSsaved restore -userdict/PStoPSsaved save put -PStoPSmatrix setmatrix -595.000000 421.271378 translate -90 rotate -0.706651 dup scale -userdict/PStoPSmatrix matrix currentmatrix put -userdict/PStoPSclip{0 0 moveto - 595.000000 0 rlineto 0 842.000000 rlineto -595.000000 0 rlineto - closepath}put initclip -PStoPSxform concat -%%BeginPageSetup -_S -75 0 translate -/pagenum 14 def -/fname () def -/fdir () def -/ftail () def -/user_header_p false def -%%EndPageSetup -5 723 M -(Internet-Draft SSH Authentication Protocol September 2002) s -5 690 M -(Authors' Addresses) s -5 668 M -( Tatu Ylonen) s -5 657 M -( SSH Communications Security Corp) s -5 646 M -( Fredrikinkatu 42) s -5 635 M -( HELSINKI FIN-00100) s -5 624 M -( Finland) s -5 602 M -( EMail: [email protected]) s -5 569 M -( Darren J. Moffat \(editor\)) s -5 558 M -( Sun Microsystems, Inc) s -5 547 M -( 17 Network Circle) s -5 536 M -( Menlo Park 95025) s -5 525 M -( USA) s -5 503 M -( EMail: [email protected]) s -5 129 M -(Ylonen & Moffat Expires March 2, 2003 [Page 14]) s -_R -S -PStoPSsaved restore -%%Page: (14,15) 8 -userdict/PStoPSsaved save put -PStoPSmatrix setmatrix -595.000000 0.271378 translate -90 rotate -0.706651 dup scale -userdict/PStoPSmatrix matrix currentmatrix put -userdict/PStoPSclip{0 0 moveto - 595.000000 0 rlineto 0 842.000000 rlineto -595.000000 0 rlineto - closepath}put initclip -/showpage{}def/copypage{}def/erasepage{}def -PStoPSxform concat -%%BeginPageSetup -_S -75 0 translate -/pagenum 15 def -/fname () def -/fdir () def -/ftail () def -/user_header_p false def -%%EndPageSetup -5 723 M -(Internet-Draft SSH Authentication Protocol September 2002) s -5 690 M -(Intellectual Property Statement) s -5 668 M -( The IETF takes no position regarding the validity or scope of any) s -5 657 M -( intellectual property or other rights that might be claimed to) s -5 646 M -( pertain to the implementation or use of the technology described in) s -5 635 M -( this document or the extent to which any license under such rights) s -5 624 M -( might or might not be available; neither does it represent that it) s -5 613 M -( has made any effort to identify any such rights. Information on the) s -5 602 M -( IETF's procedures with respect to rights in standards-track and) s -5 591 M -( standards-related documentation can be found in BCP-11. Copies of) s -5 580 M -( claims of rights made available for publication and any assurances of) s -5 569 M -( licenses to be made available, or the result of an attempt made to) s -5 558 M -( obtain a general license or permission for the use of such) s -5 547 M -( proprietary rights by implementors or users of this specification can) s -5 536 M -( be obtained from the IETF Secretariat.) s -5 514 M -( The IETF invites any interested party to bring to its attention any) s -5 503 M -( copyrights, patents or patent applications, or other proprietary) s -5 492 M -( rights which may cover technology that may be required to practice) s -5 481 M -( this standard. Please address the information to the IETF Executive) s -5 470 M -( Director.) s -5 448 M -( The IETF has been notified of intellectual property rights claimed in) s -5 437 M -( regard to some or all of the specification contained in this) s -5 426 M -( document. For more information consult the online list of claimed) s -5 415 M -( rights.) s -5 382 M -(Full Copyright Statement) s -5 360 M -( Copyright \(C\) The Internet Society \(2002\). All Rights Reserved.) s -5 338 M -( This document and translations of it may be copied and furnished to) s -5 327 M -( others, and derivative works that comment on or otherwise explain it) s -5 316 M -( or assist in its implementation may be prepared, copied, published) s -5 305 M -( and distributed, in whole or in part, without restriction of any) s -5 294 M -( kind, provided that the above copyright notice and this paragraph are) s -5 283 M -( included on all such copies and derivative works. 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Ylonen -Internet-Draft SSH Communications Security Corp -Expires: March 2, 2003 D. Moffat, Ed. - Sun Microsystems, Inc - September 2002 - - - SSH Authentication Protocol - draft-ietf-secsh-userauth-18.txt - -Status of this Memo - - This document is an Internet-Draft and is in full conformance with - all provisions of Section 10 of RFC2026. - - Internet-Drafts are working documents of the Internet Engineering - Task Force (IETF), its areas, and its working groups. Note that other - groups may also distribute working documents as Internet-Drafts. - - Internet-Drafts are draft documents valid for a maximum of six months - and may be updated, replaced, or obsoleted by other documents at any - time. It is inappropriate to use Internet-Drafts as reference - material or to cite them other than as "work in progress." - - The list of current Internet-Drafts can be accessed at http:// - www.ietf.org/ietf/1id-abstracts.txt. - - The list of Internet-Draft Shadow Directories can be accessed at - http://www.ietf.org/shadow.html. - - This Internet-Draft will expire on March 2, 2003. - -Copyright Notice - - Copyright (C) The Internet Society (2002). All Rights Reserved. - -Abstract - - SSH is a protocol for secure remote login and other secure network - services over an insecure network. This document describes the SSH - authentication protocol framework and public key, password, and - host-based client authentication methods. Additional authentication - methods are described in separate documents. The SSH authentication - protocol runs on top of the SSH transport layer protocol and provides - a single authenticated tunnel for the SSH connection protocol. - - - - - - - -Ylonen & Moffat Expires March 2, 2003 [Page 1] - -Internet-Draft SSH Authentication Protocol September 2002 - - -Table of Contents - - 1. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 3 - 2. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 - 3. Conventions Used in This Document . . . . . . . . . . . . . 3 - 3.1 The Authentication Protocol Framework . . . . . . . . . . . 3 - 3.1.1 Authentication Requests . . . . . . . . . . . . . . . . . . 4 - 3.1.2 Responses to Authentication Requests . . . . . . . . . . . . 5 - 3.1.3 The "none" Authentication Request . . . . . . . . . . . . . 6 - 3.1.4 Completion of User Authentication . . . . . . . . . . . . . 6 - 3.1.5 Banner Message . . . . . . . . . . . . . . . . . . . . . . . 7 - 3.2 Authentication Protocol Message Numbers . . . . . . . . . . 7 - 3.3 Public Key Authentication Method: publickey . . . . . . . . 8 - 3.4 Password Authentication Method: password . . . . . . . . . . 10 - 3.5 Host-Based Authentication: hostbased . . . . . . . . . . . . 11 - 4. Security Considerations . . . . . . . . . . . . . . . . . . 12 - Normative . . . . . . . . . . . . . . . . . . . . . . . . . 13 - Informative . . . . . . . . . . . . . . . . . . . . . . . . 13 - Authors' Addresses . . . . . . . . . . . . . . . . . . . . . 14 - Intellectual Property and Copyright Statements . . . . . . . 15 - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -Ylonen & Moffat Expires March 2, 2003 [Page 2] - -Internet-Draft SSH Authentication Protocol September 2002 - - -1. Contributors - - The major original contributors of this document were: Tatu Ylonen, - Tero Kivinen, Timo J. Rinne, Sami Lehtinen (all of SSH Communications - Security Corp), and Markku-Juhani O. Saarinen (University of - Jyvaskyla) - - The document editor is: [email protected]. Comments on this - internet draft should be sent to the IETF SECSH working group, - details at: http://ietf.org/html.charters/secsh-charter.html - -2. Introduction - - The SSH authentication protocol is a general-purpose user - authentication protocol. It is intended to be run over the SSH - transport layer protocol [SSH-TRANS]. This protocol assumes that the - underlying protocols provide integrity and confidentiality - protection. - - This document should be read only after reading the SSH architecture - document [SSH-ARCH]. This document freely uses terminology and - notation from the architecture document without reference or further - explanation. - - The service name for this protocol is "ssh-userauth". - - When this protocol starts, it receives the session identifier from - the lower-level protocol (this is the exchange hash H from the first - key exchange). The session identifier uniquely identifies this - session and is suitable for signing in order to prove ownership of a - private key. This protocol also needs to know whether the lower-level - protocol provides confidentiality protection. - -3. Conventions Used in This Document - - The keywords "MUST", "MUST NOT", "REQUIRED", "SHOULD", "SHOULD NOT", - and "MAY" that appear in this document are to be interpreted as - described in [RFC2119] - - The used data types and terminology are specified in the architecture - document [SSH-ARCH] - - The architecture document also discusses the algorithm naming - conventions that MUST be used with the SSH protocols. - -3.1 The Authentication Protocol Framework - - The server drives the authentication by telling the client which - - - -Ylonen & Moffat Expires March 2, 2003 [Page 3] - -Internet-Draft SSH Authentication Protocol September 2002 - - - authentication methods can be used to continue the exchange at any - given time. The client has the freedom to try the methods listed by - the server in any order. This gives the server complete control over - the authentication process if desired, but also gives enough - flexibility for the client to use the methods it supports or that are - most convenient for the user, when multiple methods are offered by - the server. - - Authentication methods are identified by their name, as defined in - [SSH-ARCH]. The "none" method is reserved, and MUST NOT be listed as - supported. However, it MAY be sent by the client. The server MUST - always reject this request, unless the client is to be allowed in - without any authentication, in which case the server MUST accept this - request. The main purpose of sending this request is to get the list - of supported methods from the server. - - The server SHOULD have a timeout for authentication, and disconnect - if the authentication has not been accepted within the timeout - period. The RECOMMENDED timeout period is 10 minutes. Additionally, - the implementation SHOULD limit the number of failed authentication - attempts a client may perform in a single session (the RECOMMENDED - limit is 20 attempts). If the threshold is exceeded, the server - SHOULD disconnect. - -3.1.1 Authentication Requests - - All authentication requests MUST use the following message format. - Only the first few fields are defined; the remaining fields depend on - the authentication method. - - byte SSH_MSG_USERAUTH_REQUEST - string user name (in ISO-10646 UTF-8 encoding [RFC2279]) - string service name (in US-ASCII) - string method name (US-ASCII) - The rest of the packet is method-specific. - - The user name and service are repeated in every new authentication - attempt, and MAY change. The server implementation MUST carefully - check them in every message, and MUST flush any accumulated - authentication states if they change. If it is unable to flush some - authentication state, it MUST disconnect if the user or service name - changes. - - The service name specifies the service to start after authentication. - There may be several different authenticated services provided. If - the requested service is not available, the server MAY disconnect - immediately or at any later time. Sending a proper disconnect - message is RECOMMENDED. In any case, if the service does not exist, - - - -Ylonen & Moffat Expires March 2, 2003 [Page 4] - -Internet-Draft SSH Authentication Protocol September 2002 - - - authentication MUST NOT be accepted. - - If the requested user does not exist, the server MAY disconnect, or - MAY send a bogus list of acceptable authentication methods, but never - accept any. This makes it possible for the server to avoid - disclosing information on which accounts exist. In any case, if the - user does not exist, the authentication request MUST NOT be accepted. - - While there is usually little point for clients to send requests that - the server does not list as acceptable, sending such requests is not - an error, and the server SHOULD simply reject requests that it does - not recognize. - - An authentication request MAY result in a further exchange of - messages. All such messages depend on the authentication method - used, and the client MAY at any time continue with a new - SSH_MSG_USERAUTH_REQUEST message, in which case the server MUST - abandon the previous authentication attempt and continue with the new - one. - -3.1.2 Responses to Authentication Requests - - If the server rejects the authentication request, it MUST respond - with the following: - - byte SSH_MSG_USERAUTH_FAILURE - string authentications that can continue - boolean partial success - - "Authentications that can continue" is a comma-separated list of - authentication method names that may productively continue the - authentication dialog. - - It is RECOMMENDED that servers only include those methods in the list - that are actually useful. However, it is not illegal to include - methods that cannot be used to authenticate the user. - - Already successfully completed authentications SHOULD NOT be included - in the list, unless they really should be performed again for some - reason. - - "Partial success" MUST be TRUE if the authentication request to which - this is a response was successful. It MUST be FALSE if the request - was not successfully processed. - - When the server accepts authentication, it MUST respond with the - following: - - - - -Ylonen & Moffat Expires March 2, 2003 [Page 5] - -Internet-Draft SSH Authentication Protocol September 2002 - - - byte SSH_MSG_USERAUTH_SUCCESS - - Note that this is not sent after each step in a multi-method - authentication sequence, but only when the authentication is - complete. - - The client MAY send several authentication requests without waiting - for responses from previous requests. The server MUST process each - request completely and acknowledge any failed requests with a - SSH_MSG_USERAUTH_FAILURE message before processing the next request. - - A request that results in further exchange of messages will be - aborted by a second request. It is not possible to send a second - request without waiting for a response from the server, if the first - request will result in further exchange of messages. No - SSH_MSG_USERAUTH_FAILURE message will be sent for the aborted method. - - SSH_MSG_USERAUTH_SUCCESS MUST be sent only once. When - SSH_MSG_USERAUTH_SUCCESS has been sent, any further authentication - requests received after that SHOULD be silently ignored. - - Any non-authentication messages sent by the client after the request - that resulted in SSH_MSG_USERAUTH_SUCCESS being sent MUST be passed - to the service being run on top of this protocol. Such messages can - be identified by their message numbers (see Section Message Numbers - (Section 3.2)). - -3.1.3 The "none" Authentication Request - - A client may request a list of authentication methods that may - continue by using the "none" authentication method. - - If no authentication at all is needed for the user, the server MUST - return SSH_MSG_USERAUTH_SUCCESS. Otherwise, the server MUST return - SSH_MSG_USERAUTH_FAILURE and MAY return with it a list of - authentication methods that can continue. - - This method MUST NOT be listed as supported by the server. - -3.1.4 Completion of User Authentication - - Authentication is complete when the server has responded with - SSH_MSG_USERAUTH_SUCCESS; all authentication related messages - received after sending this message SHOULD be silently ignored. - - After sending SSH_MSG_USERAUTH_SUCCESS, the server starts the - requested service. - - - - -Ylonen & Moffat Expires March 2, 2003 [Page 6] - -Internet-Draft SSH Authentication Protocol September 2002 - - -3.1.5 Banner Message - - In some jurisdictions, sending a warning message before - authentication may be relevant for getting legal protection. Many - UNIX machines, for example, normally display text from `/etc/issue', - or use "tcp wrappers" or similar software to display a banner before - issuing a login prompt. - - The SSH server may send a SSH_MSG_USERAUTH_BANNER message at any time - before authentication is successful. This message contains text to - be displayed to the client user before authentication is attempted. - The format is as follows: - - byte SSH_MSG_USERAUTH_BANNER - string message (ISO-10646 UTF-8) - string language tag (as defined in [RFC3066]) - - The client SHOULD by default display the message on the screen. - However, since the message is likely to be sent for every login - attempt, and since some client software will need to open a separate - window for this warning, the client software may allow the user to - explicitly disable the display of banners from the server. The - message may consist of multiple lines. - - If the message string is displayed, control character filtering - discussed in [SSH-ARCH] SHOULD be used to avoid attacks by sending - terminal control characters. - -3.2 Authentication Protocol Message Numbers - - All message numbers used by this authentication protocol are in the - range from 50 to 79, which is part of the range reserved for - protocols running on top of the SSH transport layer protocol. - - Message numbers of 80 and higher are reserved for protocols running - after this authentication protocol, so receiving one of them before - authentication is complete is an error, to which the server MUST - respond by disconnecting (preferably with a proper disconnect message - sent first to ease troubleshooting). - - After successful authentication, such messages are passed to the - higher-level service. - - These are the general authentication message codes: - - #define SSH_MSG_USERAUTH_REQUEST 50 - #define SSH_MSG_USERAUTH_FAILURE 51 - #define SSH_MSG_USERAUTH_SUCCESS 52 - - - -Ylonen & Moffat Expires March 2, 2003 [Page 7] - -Internet-Draft SSH Authentication Protocol September 2002 - - - #define SSH_MSG_USERAUTH_BANNER 53 - - In addition to the above, there is a range of message numbers - (60..79) reserved for method-specific messages. These messages are - only sent by the server (client sends only SSH_MSG_USERAUTH_REQUEST - messages). Different authentication methods reuse the same message - numbers. - -3.3 Public Key Authentication Method: publickey - - The only REQUIRED authentication method is public key authentication. - All implementations MUST support this method; however, not all users - need to have public keys, and most local policies are not likely to - require public key authentication for all users in the near future. - - With this method, the possession of a private key serves as - authentication. This method works by sending a signature created - with a private key of the user. The server MUST check that the key - is a valid authenticator for the user, and MUST check that the - signature is valid. If both hold, the authentication request MUST be - accepted; otherwise it MUST be rejected. (Note that the server MAY - require additional authentications after successful authentication.) - - Private keys are often stored in an encrypted form at the client - host, and the user must supply a passphrase before the signature can - be generated. Even if they are not, the signing operation involves - some expensive computation. To avoid unnecessary processing and user - interaction, the following message is provided for querying whether - authentication using the key would be acceptable. - - byte SSH_MSG_USERAUTH_REQUEST - string user name - string service - string "publickey" - boolean FALSE - string public key algorithm name - string public key blob - - Public key algorithms are defined in the transport layer - specification [SSH-TRANS]. The public key blob may contain - certificates. - - Any public key algorithm may be offered for use in authentication. - In particular, the list is not constrained by what was negotiated - during key exchange. If the server does not support some algorithm, - it MUST simply reject the request. - - The server MUST respond to this message with either - - - -Ylonen & Moffat Expires March 2, 2003 [Page 8] - -Internet-Draft SSH Authentication Protocol September 2002 - - - SSH_MSG_USERAUTH_FAILURE or with the following: - - byte SSH_MSG_USERAUTH_PK_OK - string public key algorithm name from the request - string public key blob from the request - - To perform actual authentication, the client MAY then send a - signature generated using the private key. The client MAY send the - signature directly without first verifying whether the key is - acceptable. The signature is sent using the following packet: - - byte SSH_MSG_USERAUTH_REQUEST - string user name - string service - string "publickey" - boolean TRUE - string public key algorithm name - string public key to be used for authentication - string signature - - Signature is a signature by the corresponding private key over the - following data, in the following order: - - string session identifier - byte SSH_MSG_USERAUTH_REQUEST - string user name - string service - string "publickey" - boolean TRUE - string public key algorithm name - string public key to be used for authentication - - When the server receives this message, it MUST check whether the - supplied key is acceptable for authentication, and if so, it MUST - check whether the signature is correct. - - If both checks succeed, this method is successful. Note that the - server may require additional authentications. The server MUST - respond with SSH_MSG_USERAUTH_SUCCESS (if no more authentications are - needed), or SSH_MSG_USERAUTH_FAILURE (if the request failed, or more - authentications are needed). - - The following method-specific message numbers are used by the - publickey authentication method. - - /* Key-based */ - #define SSH_MSG_USERAUTH_PK_OK 60 - - - - -Ylonen & Moffat Expires March 2, 2003 [Page 9] - -Internet-Draft SSH Authentication Protocol September 2002 - - -3.4 Password Authentication Method: password - - Password authentication uses the following packets. Note that a - server MAY request the user to change the password. All - implementations SHOULD support password authentication. - - byte SSH_MSG_USERAUTH_REQUEST - string user name - string service - string "password" - boolean FALSE - string plaintext password (ISO-10646 UTF-8) - - Note that the password is encoded in ISO-10646 UTF-8. It is up to - the server how it interprets the password and validates it against - the password database. However, if the client reads the password in - some other encoding (e.g., ISO 8859-1 (ISO Latin1)), it MUST convert - the password to ISO-10646 UTF-8 before transmitting, and the server - MUST convert the password to the encoding used on that system for - passwords. - - Note that even though the cleartext password is transmitted in the - packet, the entire packet is encrypted by the transport layer. Both - the server and the client should check whether the underlying - transport layer provides confidentiality (i.e., if encryption is - being used). If no confidentiality is provided (none cipher), - password authentication SHOULD be disabled. If there is no - confidentiality or no MAC, password change SHOULD be disabled. - - Normally, the server responds to this message with success or - failure. However, if the password has expired the server SHOULD - indicate this by responding with SSH_MSG_USERAUTH_PASSWD_CHANGEREQ. - In anycase the server MUST NOT allow an expired password to be used - for authentication. - - byte SSH_MSG_USERAUTH_PASSWD_CHANGEREQ - string prompt (ISO-10646 UTF-8) - string language tag (as defined in [RFC3066]) - - In this case, the client MAY continue with a different authentication - method, or request a new password from the user and retry password - authentication using the following message. The client MAY also send - this message instead of the normal password authentication request - without the server asking for it. - - byte SSH_MSG_USERAUTH_REQUEST - string user name - string service - - - -Ylonen & Moffat Expires March 2, 2003 [Page 10] - -Internet-Draft SSH Authentication Protocol September 2002 - - - string "password" - boolean TRUE - string plaintext old password (ISO-10646 UTF-8) - string plaintext new password (ISO-10646 UTF-8) - - The server must reply to request message with - SSH_MSG_USERAUTH_SUCCESS, SSH_MSG_USERAUTH_FAILURE, or another - SSH_MSG_USERAUTH_PASSWD_CHANGEREQ. The meaning of these is as - follows: - - SSH_MSG_USERAUTH_SUCCESS The password has been changed, and - authentication has been successfully completed. - - SSH_MSG_USERAUTH_FAILURE with partial success The password has - been changed, but more authentications are needed. - - SSH_MSG_USERAUTH_FAILURE without partial success The password has - not been changed. Either password changing was not supported, or - the old password was bad. Note that if the server has already - sent SSH_MSG_USERAUTH_PASSWD_CHANGEREQ, we know that it supports - changing the password. - - SSH_MSG_USERAUTH_CHANGEREQ The password was not changed because - the new password was not acceptable (e.g. too easy to guess). - - The following method-specific message numbers are used by the - password authentication method. - - #define SSH_MSG_USERAUTH_PASSWD_CHANGEREQ 60 - - -3.5 Host-Based Authentication: hostbased - - Some sites wish to allow authentication based on the host where the - user is coming from, and the user name on the remote host. While - this form of authentication is not suitable for high-security sites, - it can be very convenient in many environments. This form of - authentication is OPTIONAL. When used, special care SHOULD be taken - to prevent a regular user from obtaining the private host key. - - The client requests this form of authentication by sending the - following message. It is similar to the UNIX "rhosts" and - "hosts.equiv" styles of authentication, except that the identity of - the client host is checked more rigorously. - - This method works by having the client send a signature created with - the private key of the client host, which the server checks with that - host's public key. Once the client host's identity is established, - - - -Ylonen & Moffat Expires March 2, 2003 [Page 11] - -Internet-Draft SSH Authentication Protocol September 2002 - - - authorization (but no further authentication) is performed based on - the user names on the server and the client, and the client host - name. - - byte SSH_MSG_USERAUTH_REQUEST - string user name - string service - string "hostbased" - string public key algorithm for host key - string public host key and certificates for client host - string client host name (FQDN; US-ASCII) - string user name on the client host (ISO-10646 UTF-8) - string signature - - Public key algorithm names for use in "public key algorithm for host - key" are defined in the transport layer specification. The "public - host key for client host" may include certificates. - - Signature is a signature with the private host key of the following - data, in this order: - - string session identifier - byte SSH_MSG_USERAUTH_REQUEST - string user name - string service - string "hostbased" - string public key algorithm for host key - string public host key and certificates for client host - string client host name (FQDN; US-ASCII) - string user name on the client host(ISO-10646 UTF-8) - - The server MUST verify that the host key actually belongs to the - client host named in the message, that the given user on that host is - allowed to log in, and that the signature is a valid signature on the - appropriate value by the given host key. The server MAY ignore the - client user name, if it wants to authenticate only the client host. - - It is RECOMMENDED that whenever possible, the server perform - additional checks to verify that the network address obtained from - the (untrusted) network matches the given client host name. This - makes exploiting compromised host keys more difficult. Note that - this may require special handling for connections coming through a - firewall. - -4. Security Considerations - - The purpose of this protocol is to perform client user - authentication. It assumed that this runs over a secure transport - - - -Ylonen & Moffat Expires March 2, 2003 [Page 12] - -Internet-Draft SSH Authentication Protocol September 2002 - - - layer protocol, which has already authenticated the server machine, - established an encrypted communications channel, and computed a - unique session identifier for this session. The transport layer - provides forward secrecy for password authentication and other - methods that rely on secret data. - - Full security considerations for this protocol are provided in - Section 8 of [SSH-ARCH] - -Normative - - [SSH-ARCH] - Ylonen, T., "SSH Protocol Architecture", I-D - draft-ietf-architecture-15.txt, Oct 2003. - - [SSH-TRANS] - Ylonen, T., "SSH Transport Layer Protocol", I-D - draft-ietf-transport-17.txt, Oct 2003. - - [SSH-USERAUTH] - Ylonen, T., "SSH Authentication Protocol", I-D - draft-ietf-userauth-18.txt, Oct 2003. - - [SSH-CONNECT] - Ylonen, T., "SSH Connection Protocol", I-D - draft-ietf-connect-18.txt, Oct 2003. - - [SSH-NUMBERS] - Lehtinen, S. and D. Moffat, "SSH Protocol Assigned - Numbers", I-D draft-ietf-secsh-assignednumbers-05.txt, Oct - 2003. - - [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate - Requirement Levels", BCP 14, RFC 2119, March 1997. - -Informative - - [RFC3066] Alvestrand, H., "Tags for the Identification of - Languages", BCP 47, RFC 3066, January 2001. - - [RFC2279] Yergeau, F., "UTF-8, a transformation format of ISO - 10646", RFC 2279, January 1998. - - - - - - - - - -Ylonen & Moffat Expires March 2, 2003 [Page 13] - -Internet-Draft SSH Authentication Protocol September 2002 - - -Authors' Addresses - - Tatu Ylonen - SSH Communications Security Corp - Fredrikinkatu 42 - HELSINKI FIN-00100 - Finland - - EMail: [email protected] - - - Darren J. Moffat (editor) - Sun Microsystems, Inc - 17 Network Circle - Menlo Park 95025 - USA - - EMail: [email protected] - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -Ylonen & Moffat Expires March 2, 2003 [Page 14] - -Internet-Draft SSH Authentication Protocol September 2002 - - -Intellectual Property Statement - - The IETF takes no position regarding the validity or scope of any - intellectual property or other rights that might be claimed to - pertain to the implementation or use of the technology described in - this document or the extent to which any license under such rights - might or might not be available; neither does it represent that it - has made any effort to identify any such rights. Information on the - IETF's procedures with respect to rights in standards-track and - standards-related documentation can be found in BCP-11. 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