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Diffstat (limited to 'lib/ssh/doc/src/ssh_app.xml')
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diff --git a/lib/ssh/doc/src/ssh_app.xml b/lib/ssh/doc/src/ssh_app.xml index a1d2402790..1cbbdfcf38 100644 --- a/lib/ssh/doc/src/ssh_app.xml +++ b/lib/ssh/doc/src/ssh_app.xml @@ -4,97 +4,351 @@ <appref> <header> <copyright> - <year>2012</year><year>2013</year> + <year>2012</year><year>2017</year> <holder>Ericsson AB. All Rights Reserved.</holder> </copyright> <legalnotice> - The contents of this file are subject to the Erlang Public License, - Version 1.1, (the "License"); you may not use this file except in - compliance with the License. You should have received a copy of the - Erlang Public License along with this software. If not, it can be - retrieved online at http://www.erlang.org/. - - Software distributed under the License is distributed on an "AS IS" - basis, WITHOUT WARRANTY OF ANY KIND, either express or implied. See - the License for the specific language governing rights and limitations - under the License. + Licensed under the Apache License, Version 2.0 (the "License"); + you may not use this file except in compliance with the License. + You may obtain a copy of the License at + + http://www.apache.org/licenses/LICENSE-2.0 + Unless required by applicable law or agreed to in writing, software + distributed under the License is distributed on an "AS IS" BASIS, + WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. + See the License for the specific language governing permissions and + limitations under the License. </legalnotice> <title>SSH</title> + <prepared></prepared> + <docno></docno> + <checked></checked> + <date></date> + <rev></rev> <file>ssh_app.xml</file> </header> <app>SSH</app> - <appsummary>The ssh application implements the SSH (Secure Shell) protocol and - provides an SFTP (SSH File Transfer Protocol) client and server. </appsummary> + <appsummary>The ssh application implements the Secure Shell (SSH) protocol and + provides an SSH File Transfer Protocol (SFTP) client and server.</appsummary> + <description> + <p>The <c>ssh</c> application is an implementation of the SSH protocol in Erlang. + <c>ssh</c> offers API functions to write customized SSH clients and servers as well as + making the Erlang shell available over SSH. An SFTP client, <c>ssh_sftp</c>, and server, + <c>ssh_sftpd</c>, are also included.</p> + </description> - <section> + <section> <title>DEPENDENCIES</title> - <p>The ssh application uses the Erlang applications public_key and - crypto to handle public keys and encryption, hence these - applications needs to be loaded for the ssh application to work. In - an embedded environment that means they need to be started with - application:start/[1,2] before the ssh application is started. + <p>The <c>ssh</c> application uses the applications + <seealso marker="public_key:public_key">public_key</seealso> and + <seealso marker="crypto:crypto">crypto</seealso> + to handle public keys and encryption. Hence, these + applications must be loaded for the <c>ssh</c> application to work. In + an embedded environment this means that they must be started with + <seealso marker="kernel:application#start/1">application:start/1,2</seealso> before the + <c>ssh</c> application is started. </p> </section> - <section> + <section> <title>CONFIGURATION</title> - <p>The ssh application does not currently have an application - specific configuration file as described in application(3), - however it will by default use the following configuration files - from openssh: known_hosts, authorized_keys, authorized_keys2, - id_dsa and id_rsa, ssh_host_dsa_key and ssh_host_rsa_key. By - default Erlang SSH will look for id_dsa, id_rsa, known_hosts - and authorized_keys in ~/.ssh, and the host key files in /etc/ssh - . These locations may be changed by the options user_dir and - system_dir. Public key handling may also be customized by - providing a callback module implementing the behaviors - <seealso marker="ssh_client_key_api">ssh_client_key_api</seealso> and - <seealso marker="ssh_server_key_api">ssh_server_key_api</seealso>. - </p> + <p>The <c>ssh</c> application does not have an application- + specific configuration file, as described in <seealso marker="kernel:application">application(3)</seealso>. + However, by default it use the following configuration files + from OpenSSH:</p> + <list type="bulleted"> + <item><c>known_hosts</c></item> + <item><c>authorized_keys</c></item> + <item><c>authorized_keys2</c></item> + <item><c>id_dsa</c></item> + <item><c>id_rsa</c></item> + <item><c>id_ecdsa</c></item> + <item><c>ssh_host_dsa_key</c></item> + <item><c>ssh_host_rsa_key</c></item> + <item><c>ssh_host_ecdsa_key</c></item> + </list> + <p>By default, <c>ssh</c> looks for <c>id_dsa</c>, <c>id_rsa</c>, + <c>id_ecdsa_key</c>, + <c>known_hosts</c>, and <c>authorized_keys</c> in ~/.ssh, + and for the host key files in <c>/etc/ssh</c>. These locations can be changed + by the options <c>user_dir</c> and <c>system_dir</c>. + </p> + <p>Public key handling can also be customized through a callback module that + implements the behaviors + <seealso marker="ssh_client_key_api">ssh_client_key_api</seealso> and + <seealso marker="ssh_server_key_api">ssh_server_key_api</seealso>. + </p> - <section> - <title>PUBLIC KEYS</title> - <p> - id_dsa and id_rsa are the users private key files, note that - the public key is part of the private key so the ssh - application will not use the id_<*>.pub files. These are - for the users convenience when he/she needs to convey their + </section> + <section> + <title>Public Keys</title> + <p><c>id_dsa</c>, <c>id_rsa</c> and <c>id_ecdsa</c> are the users private key files. + Notice that the public key is part of the private key so the <c>ssh</c> + application does not use the <c>id_<*>.pub</c> files. These are + for the user's convenience when it is needed to convey the user's public key. </p> - </section> - - <section> - <title>KNOW HOSTS</title> - <p>The known_hosts file contains a list of approved servers and - their public keys. Once a server is listed, it can be verified + </section> + <section> + <title>Known Hosts</title> + <p>The <c>known_hosts</c> file contains a list of approved servers and + their public keys. Once a server is listed, it can be verified without user interaction. + </p> + </section> + <section> + <title>Authorized Keys</title> + <p>The <c>authorized_key</c> file keeps track of the user's authorized + public keys. The most common use of this file is to let users + log in without entering their password, which is supported by the + Erlang <c>ssh</c> daemon. </p> - </section> + </section> + <section> + <title>Host Keys</title> + <p>RSA, DSA and ECDSA host keys are supported and are + expected to be found in files named <c>ssh_host_rsa_key</c>, + <c>ssh_host_dsa_key</c> and <c>ssh_host_ecdsa_key</c>. + </p> + </section> + <section> + <title>ERROR LOGGER AND EVENT HANDLERS</title> + <p>The <c>ssh</c> application uses the default <seealso marker="kernel:error_logger">OTP error logger</seealso> to log unexpected errors or print information about special events.</p> + </section> - <section> - <title>AUTHORIZED KEYS</title> - <p>The authorized key file keeps track of the user's authorized - public keys. The most common use of this file is to let users - log in without entering their password which is supported by the - Erlang SSH daemon. + <section> + <marker id="supported"/> + <title>SUPPORTED SPECIFICATIONS AND STANDARDS</title> + <p>The supported SSH version is 2.0.</p> + </section> + <section> + <title>Algorithms</title> + <p>The actual set of algorithms may vary depending on which OpenSSL crypto library that is installed on the machine. + For the list on a particular installation, use the command + <seealso marker="ssh:ssh#default_algorithms/0">ssh:default_algorithms/0</seealso>. + The user may override the default algorithm configuration both on the server side and the client side. + See the option <c>preferred_algorithms</c> in the <seealso marker="ssh:ssh#daemon/1">ssh:daemon/1,2,3</seealso> and + <seealso marker="ssh:ssh#connect/3">ssh:connect/3,4</seealso> functions. + </p> + + <p>Supported algorithms are:</p> + <marker id="supported_algos"></marker> + <taglist> + <tag>Key exchange algorithms</tag> + <item> + <list type="bulleted"> + <item>ecdh-sha2-nistp256</item> + <item>ecdh-sha2-nistp384</item> + <item>ecdh-sha2-nistp521</item> + <item>diffie-hellman-group-exchange-sha1</item> + <item>diffie-hellman-group-exchange-sha256</item> + <item>diffie-hellman-group14-sha1</item> + <item>diffie-hellman-group14-sha256</item> + <item>diffie-hellman-group16-sha512</item> + <item>diffie-hellman-group18-sha512</item> + <item>(diffie-hellman-group1-sha1, retired: can be enabled with the <c>preferred_algorithms</c> option)</item> + </list> + </item> + + <tag>Public key algorithms</tag> + <item> + <list type="bulleted"> + <item>ecdsa-sha2-nistp256</item> + <item>ecdsa-sha2-nistp384</item> + <item>ecdsa-sha2-nistp521</item> + <item>ssh-rsa</item> + <item>ssh-dss</item> + <item>rsa-sha2-256</item> + <item>rsa-sha2-512</item> + </list> + </item> + + <tag>MAC algorithms</tag> + <item> + <list type="bulleted"> + <item>hmac-sha2-256</item> + <item>hmac-sha2-512</item> + <item>hmac-sha1</item> + </list> + </item> + + <tag>Encryption algorithms (ciphers)</tag> + <item> + <list type="bulleted"> + <item>[email protected]</item> + <item>[email protected]</item> + <item>aes128-ctr</item> + <item>aes192-ctr</item> + <item>aes256-ctr</item> + <item>aes128-cbc</item> + <item>3des-cbc</item> + <item>(AEAD_AES_128_GCM, not enabled per default)</item> + <item>(AEAD_AES_256_GCM, not enabled per default)</item> + </list> + <p>See the text at the description of <seealso marker="#rfc5647_note">the rfc 5647 further down</seealso> + for more information regarding AEAD_AES_*_GCM. + </p> + <p>Following the internet de-facto standard, the cipher and mac algorithm AEAD_AES_128_GCM is selected when the + cipher [email protected] is negotiated. The cipher and mac algorithm AEAD_AES_256_GCM is selected when the + cipher [email protected] is negotiated. + </p> + </item> + + <tag>Compression algorithms</tag> + <item> + <list type="bulleted"> + <item>none</item> + <item>[email protected]</item> + <item>zlib</item> + </list> + </item> + </taglist> + </section> + <section> + <title>Unicode support</title> + <p>Unicode filenames are supported if the emulator and the underlaying OS support it. See section DESCRIPTION in the + <seealso marker="kernel:file">file</seealso> manual page in Kernel for information about this subject. + </p> + <p>The shell and the cli both support unicode. + </p> + </section> + + <section> + <title>Rfcs</title> + <p>The following rfc:s are supported:</p> + <list type="bulleted"> + <item><url href="https://tools.ietf.org/html/rfc4251">RFC 4251</url>, The Secure Shell (SSH) Protocol Architecture. + <p>Except</p> + <list type="bulleted"> + <item>9.4.6 Host-Based Authentication</item> + <item>9.5.2 Proxy Forwarding</item> + <item>9.5.3 X11 Forwarding</item> + </list> + <p/> + </item> + + <item><url href="https://tools.ietf.org/html/rfc4252">RFC 4252</url>, The Secure Shell (SSH) Authentication Protocol. + <p>Except</p> + <list type="bulleted"> + <item>9. Host-Based Authentication: "hostbased"</item> + </list> + <p/> + </item> + + <item><url href="https://tools.ietf.org/html/rfc4253">RFC 4253</url>, The Secure Shell (SSH) Transport Layer Protocol. + <p>Except</p> + <list type="bulleted"> + <item>8.1. diffie-hellman-group1-sha1. Disabled by default, can be enabled with the <c>preferred_algorithms</c> option.</item> + </list> + <p/> + </item> + + <item><url href="https://tools.ietf.org/html/rfc4254">RFC 4254</url>, The Secure Shell (SSH) Connection Protocol. + <p>Except</p> + <list type="bulleted"> + <item>6.3. X11 Forwarding</item> + <item>7. TCP/IP Port Forwarding</item> + </list> + <p/> + </item> + + <item><url href="https://tools.ietf.org/html/rfc4256">RFC 4256</url>, Generic Message Exchange Authentication for + the Secure Shell Protocol (SSH). + <p>Except</p> + <list type="bulleted"> + <item><c>num-prompts > 1</c></item> + <item>password changing</item> + <item>other identification methods than userid-password</item> + </list> + <p/> + </item> + + <item><url href="https://tools.ietf.org/html/rfc4419">RFC 4419</url>, Diffie-Hellman Group Exchange for + the Secure Shell (SSH) Transport Layer Protocol. + <p/> + </item> + + <item><url href="https://tools.ietf.org/html/rfc4716">RFC 4716</url>, The Secure Shell (SSH) Public Key File Format. + <p/> + </item> + + <item><url href="https://tools.ietf.org/html/rfc5647">RFC 5647</url>, AES Galois Counter Mode for + the Secure Shell Transport Layer Protocol. + <p><marker id="rfc5647_note"/>There is an ambiguity in the synchronized selection of cipher and mac algorithm. + This is resolved by OpenSSH in the ciphers [email protected] and [email protected] which are implemented. + If the explicit ciphers and macs AEAD_AES_128_GCM or AEAD_AES_256_GCM are needed, + they could be enabled with the option preferred_algorithms. + </p> + <warning> + <p> + If the client or the server is not Erlang/OTP, it is the users responsibility to check that + other implementation has the same interpretation of AEAD_AES_*_GCM as the Erlang/OTP SSH before + enabling them. The aes*[email protected] variants are always safe to use since they lack the + ambiguity. + </p> + </warning> + <p>The second paragraph in section 5.1 is resolved as:</p> + <list type="ordered"> + <item>If the negotiated cipher is AEAD_AES_128_GCM, the mac algorithm is set to AEAD_AES_128_GCM.</item> + <item>If the negotiated cipher is AEAD_AES_256_GCM, the mac algorithm is set to AEAD_AES_256_GCM.</item> + <item>If the mac algorithm is AEAD_AES_128_GCM, the cipher is set to AEAD_AES_128_GCM.</item> + <item>If the mac algorithm is AEAD_AES_256_GCM, the cipher is set to AEAD_AES_256_GCM.</item> + </list> + <p>The first rule that matches when read in order from the top is applied</p> + </item> + + <item><url href="https://tools.ietf.org/html/rfc5656">RFC 5656</url>, Elliptic Curve Algorithm Integration in + the Secure Shell Transport Layer. + <p>Except</p> + <list type="bulleted"> + <item>5. ECMQV Key Exchange</item> + <item>6.4. ECMQV Key Exchange and Verification Method Name</item> + <item>7.2. ECMQV Message Numbers</item> + <item>10.2. Recommended Curves</item> + </list> + <p/> + </item> + + <item><url href="https://tools.ietf.org/html/rfc6668">RFC 6668</url>, SHA-2 Data Integrity Verification for + the Secure Shell (SSH) Transport Layer Protocol + <p>Comment: Defines hmac-sha2-256 and hmac-sha2-512 </p> - </section> + </item> + + <item><url href="https://tools.ietf.org/html/draft-ietf-curdle-ssh-kex-sha2">Draft-ietf-curdle-ssh-kex-sha2 (work in progress)</url>, Key Exchange (KEX) Method Updates and Recommendations for Secure Shell (SSH). + <p>Deviations:</p> + <list type="bulleted"> + <item>The <c>diffie-hellman-group1-sha1</c> is not enabled by default, but is still supported and can be enabled + with the option <c>preferred-algorithms</c></item> + <item>The questionable sha1-based algorithms <c>diffie-hellman-group-exchange-sha1</c> and + <c>diffie-hellman-group14-sha1</c> are still enabled by default for compatibility with ancient clients and servers. + They can be disabled with the option <c>preferred-algorithms</c></item> + </list> + <p/> + </item> + + <item><url href="https://tools.ietf.org/html/draft-ietf-curdle-rsa-sha2">Draft-ietf-curdle-rsa-sha2 (work in progress)</url>, Use of RSA Keys with SHA-2 256 and 512 in Secure Shell (SSH). + </item> + + <item><url href="https://tools.ietf.org/html/draft-ietf-curdle-ssh-ext-info">Draft-ietf-curdle-ssh-ext-info (work in progress)</url>, Extension Negotiation in Secure Shell (SSH). + <p>Implemented are:</p> + <list type="bulleted"> + <item>The Extension Negotiation Mechanism</item> + <item>The extension <c>server-sig-algs</c></item> + </list> + <p/> + </item> + + </list> - <section> - <title>HOST KEYS</title> - <p>Currently rsa and dsa host keys are supported and are - expected to be found in files named ssh_host_rsa_key and - ssh_host_dsa_key. - </p> - </section> </section> <section> <title>SEE ALSO</title> - <p>application(3)</p> + <p><seealso marker="kernel:application">application(3)</seealso></p> </section> </appref> |