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 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: Darren.Moffat@Sun.COM. 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 "SIG@xyz.config.guess", 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: ylo@ssh.com Darren J. Moffat (editor) Sun Microsystems, Inc 17 Network Circle Menlo Park CA 94025 USA EMail: Darren.Moffat@Sun.COM 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]