3 .\" Author: Tatu Ylonen <ylo@cs.hut.fi>
4 .\" Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
5 .\" All rights reserved
7 .\" As far as I am concerned, the code I have written for this software
8 .\" can be used freely for any purpose. Any derived versions of this
9 .\" software must be clearly marked as such, and if the derived work is
10 .\" incompatible with the protocol description in the RFC file, it must be
11 .\" called by a name other than "ssh" or "Secure Shell".
13 .\" Copyright (c) 1999,2000 Markus Friedl. All rights reserved.
14 .\" Copyright (c) 1999 Aaron Campbell. All rights reserved.
15 .\" Copyright (c) 1999 Theo de Raadt. All rights reserved.
17 .\" Redistribution and use in source and binary forms, with or without
18 .\" modification, are permitted provided that the following conditions
20 .\" 1. Redistributions of source code must retain the above copyright
21 .\" notice, this list of conditions and the following disclaimer.
22 .\" 2. Redistributions in binary form must reproduce the above copyright
23 .\" notice, this list of conditions and the following disclaimer in the
24 .\" documentation and/or other materials provided with the distribution.
26 .\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
27 .\" IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
28 .\" OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
29 .\" IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
30 .\" INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
31 .\" NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
32 .\" DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
33 .\" THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
34 .\" (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
35 .\" THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
37 .\" $OpenBSD: ssh_config.5,v 1.105 2007/10/29 07:48:19 jmc Exp $
38 .Dd $Mdocdate: December 2 2007 $
43 .Nd OpenSSH SSH client configuration files
46 .Nm /etc/ssh/ssh_config
49 obtains configuration data from the following sources in
52 .Bl -enum -offset indent -compact
56 user's configuration file
59 GSSAPI configuration file
60 .Pq Pa $HOME/.ssh/config.gssapi
62 Kerberos configuration file
63 .Pq Pa $HOME/.ssh/config.krb
65 system-wide configuration file
66 .Pq Pa /etc/ssh/ssh_config
69 For each parameter, the first obtained value
71 The configuration files contain sections separated by
73 specifications, and that section is only applied for hosts that
74 match one of the patterns given in the specification.
75 The matched host name is the one given on the command line.
77 Since the first obtained value for each parameter is used, more
78 host-specific declarations should be given near the beginning of the
79 file, and general defaults at the end.
81 The configuration file has the following format:
83 Empty lines and lines starting with
86 Otherwise a line is of the format
87 .Dq keyword arguments .
88 Configuration options may be separated by whitespace or
89 optional whitespace and exactly one
91 the latter format is useful to avoid the need to quote whitespace
92 when specifying configuration options using the
99 Arguments may optionally be enclosed in double quotes
101 in order to represent arguments containing spaces.
104 keywords and their meanings are as follows (note that
105 keywords are case-insensitive and arguments are case-sensitive):
108 Restricts the following declarations (up to the next
110 keyword) to be only for those hosts that match one of the patterns
111 given after the keyword.
114 as a pattern can be used to provide global
115 defaults for all hosts.
118 argument given on the command line (i.e. the name is not converted to
119 a canonicalized host name before matching).
123 for more information on patterns.
125 Specifies which address family to use when connecting.
135 passphrase/password querying will be disabled.
136 This option is useful in scripts and other batch jobs where no user
137 is present to supply the password.
145 Use the specified address on the local machine as the source address of
147 Only useful on systems with more than one address.
148 Note that this option does not work if
149 .Cm UsePrivilegedPort
152 .It Cm ChallengeResponseAuthentication
153 Specifies whether to use challenge-response authentication.
154 The argument to this keyword must be
161 If this flag is set to
164 will additionally check the host IP address in the
167 This allows ssh to detect if a host key changed due to DNS spoofing.
168 If the option is set to
170 the check will not be executed.
174 Specifies the cipher to use for encrypting the session
175 in protocol version 1.
183 is only supported in the
185 client for interoperability with legacy protocol 1 implementations
186 that do not support the
189 Its use is strongly discouraged due to cryptographic weaknesses.
193 Specifies the ciphers allowed for protocol version 2
194 in order of preference.
195 Multiple ciphers must be comma-separated.
196 The supported ciphers are
211 .Bd -literal -offset 3n
212 aes128-cbc,3des-cbc,blowfish-cbc,cast128-cbc,arcfour128,
213 arcfour256,arcfour,aes192-cbc,aes256-cbc,aes128-ctr,
214 aes192-ctr,aes256-ctr
216 .It Cm ClearAllForwardings
217 Specifies that all local, remote, and dynamic port forwardings
218 specified in the configuration files or on the command line be
220 This option is primarily useful when used from the
222 command line to clear port forwardings set in
223 configuration files, and is automatically set by
234 Specifies whether to use compression.
241 .It Cm CompressionLevel
242 Specifies the compression level to use if compression is enabled.
243 The argument must be an integer from 1 (fast) to 9 (slow, best).
244 The default level is 6, which is good for most applications.
245 The meaning of the values is the same as in
247 Note that this option applies to protocol version 1 only.
248 .It Cm ConnectionAttempts
249 Specifies the number of tries (one per second) to make before exiting.
250 The argument must be an integer.
251 This may be useful in scripts if the connection sometimes fails.
253 .It Cm ConnectTimeout
254 Specifies the timeout (in seconds) used when connecting to the
255 SSH server, instead of using the default system TCP timeout.
256 This value is used only when the target is down or really unreachable,
257 not when it refuses the connection.
259 Enables the sharing of multiple sessions over a single network connection.
263 will listen for connections on a control socket specified using the
266 Additional sessions can connect to this socket using the same
273 These sessions will try to reuse the master instance's network connection
274 rather than initiating new ones, but will fall back to connecting normally
275 if the control socket does not exist, or is not listening.
280 to listen for control connections, but require confirmation using the
282 program before they are accepted (see
288 ssh will continue without connecting to a master instance.
292 forwarding is supported over these multiplexed connections, however the
293 display and agent forwarded will be the one belonging to the master
294 connection i.e. it is not possible to forward multiple displays or agents.
296 Two additional options allow for opportunistic multiplexing: try to use a
297 master connection but fall back to creating a new one if one does not already
303 The latter requires confirmation like the
307 Specify the path to the control socket used for connection sharing as described
310 section above or the string
312 to disable connection sharing.
315 will be substituted by the local host name,
317 will be substituted by the target host name,
321 by the remote login username.
322 It is recommended that any
324 used for opportunistic connection sharing include
325 at least %h, %p, and %r.
326 This ensures that shared connections are uniquely identified.
327 .It Cm DynamicForward
328 Specifies that a TCP port on the local machine be forwarded
329 over the secure channel, and the application
330 protocol is then used to determine where to connect to from the
335 .Oo Ar bind_address : Oc Ar port .
337 IPv6 addresses can be specified by enclosing addresses in square brackets or
338 by using an alternative syntax:
339 .Oo Ar bind_address Ns / Oc Ns Ar port .
340 By default, the local port is bound in accordance with the
345 may be used to bind the connection to a specific address.
350 indicates that the listening port be bound for local use only, while an
353 indicates that the port should be available from all interfaces.
355 Currently the SOCKS4 and SOCKS5 protocols are supported, and
357 will act as a SOCKS server.
358 Multiple forwardings may be specified, and
359 additional forwardings can be given on the command line.
360 Only the superuser can forward privileged ports.
361 .It Cm EnableSSHKeysign
362 Setting this option to
364 in the global client configuration file
365 .Pa /etc/ssh/ssh_config
366 enables the use of the helper program
369 .Cm HostbasedAuthentication .
376 This option should be placed in the non-hostspecific section.
379 for more information.
381 Sets the escape character (default:
383 The escape character can also
384 be set on the command line.
385 The argument should be a single character,
387 followed by a letter, or
389 to disable the escape
390 character entirely (making the connection transparent for binary
392 .It Cm ExitOnForwardFailure
395 should terminate the connection if it cannot set up all requested
396 dynamic, tunnel, local, and remote port forwardings.
404 Specifies whether the connection to the authentication agent (if any)
405 will be forwarded to the remote machine.
413 Agent forwarding should be enabled with caution.
414 Users with the ability to bypass file permissions on the remote host
415 (for the agent's Unix-domain socket)
416 can access the local agent through the forwarded connection.
417 An attacker cannot obtain key material from the agent,
418 however they can perform operations on the keys that enable them to
419 authenticate using the identities loaded into the agent.
421 Specifies whether X11 connections will be automatically redirected
422 over the secure channel and
432 X11 forwarding should be enabled with caution.
433 Users with the ability to bypass file permissions on the remote host
434 (for the user's X11 authorization database)
435 can access the local X11 display through the forwarded connection.
436 An attacker may then be able to perform activities such as keystroke monitoring
438 .Cm ForwardX11Trusted
439 option is also enabled.
440 .It Cm ForwardX11Trusted
441 If this option is set to
443 remote X11 clients will have full access to the original X11 display.
445 If this option is set to
447 remote X11 clients will be considered untrusted and prevented
448 from stealing or tampering with data belonging to trusted X11
452 token used for the session will be set to expire after 20 minutes.
453 Remote clients will be refused access after this time.
458 See the X11 SECURITY extension specification for full details on
459 the restrictions imposed on untrusted clients.
461 Specifies whether remote hosts are allowed to connect to local
465 binds local port forwardings to the loopback address.
466 This prevents other remote hosts from connecting to forwarded ports.
468 can be used to specify that ssh
469 should bind local port forwardings to the wildcard address,
470 thus allowing remote hosts to connect to forwarded ports.
477 .It Cm GlobalKnownHostsFile
478 Specifies a file to use for the global
479 host key database instead of
480 .Pa /etc/ssh/ssh_known_hosts .
481 .It Cm GSSAPIAuthentication
482 Specifies whether user authentication based on GSSAPI is allowed.
485 Note that this option applies to protocol version 2 only.
486 .It Cm GSSAPIKeyExchange
487 Specifies whether key exchange based on GSSAPI may be used. When using
488 GSSAPI key exchange the server need not have a host key.
491 Note that this option applies to protocol version 2 only.
492 .It Cm GSSAPIDelegateCredentials
493 Forward (delegate) credentials to the server.
496 Note that this option applies to protocol version 2 only.
497 .It Cm GSSAPITrustDns
500 to indicate that the DNS is trusted to securely canonicalize
501 the name of the host being connected to. If
503 the hostname entered on the
504 command line will be passed untouched to the GSSAPI library.
507 This option only applies to protocol version 2 connections using GSSAPI.
508 .It Cm HashKnownHosts
511 should hash host names and addresses when they are added to
512 .Pa ~/.ssh/known_hosts .
513 These hashed names may be used normally by
517 but they do not reveal identifying information should the file's contents
521 Note that existing names and addresses in known hosts files
522 will not be converted automatically,
523 but may be manually hashed using
525 .It Cm HostbasedAuthentication
526 Specifies whether to try rhosts based authentication with public key
534 This option applies to protocol version 2 only and
536 .Cm RhostsRSAAuthentication .
537 .It Cm HostKeyAlgorithms
538 Specifies the protocol version 2 host key algorithms
539 that the client wants to use in order of preference.
540 The default for this option is:
541 .Dq ssh-rsa,ssh-dss .
543 Specifies an alias that should be used instead of the
544 real host name when looking up or saving the host key
545 in the host key database files.
546 This option is useful for tunneling SSH connections
547 or for multiple servers running on a single host.
549 Specifies the real host name to log into.
550 This can be used to specify nicknames or abbreviations for hosts.
551 The default is the name given on the command line.
552 Numeric IP addresses are also permitted (both on the command line and in
555 .It Cm IdentitiesOnly
558 should only use the authentication identity files configured in the
563 offers more identities.
564 The argument to this keyword must be
568 This option is intended for situations where ssh-agent
569 offers many different identities.
573 Specifies a file from which the user's RSA or DSA authentication identity
577 for protocol version 1, and
581 for protocol version 2.
582 Additionally, any identities represented by the authentication agent
583 will be used for authentication.
585 The file name may use the tilde
586 syntax to refer to a user's home directory or one of the following
589 (local user's home directory),
595 (remote host name) or
599 It is possible to have
600 multiple identity files specified in configuration files; all these
601 identities will be tried in sequence.
602 .It Cm KbdInteractiveAuthentication
603 Specifies whether to use keyboard-interactive authentication.
604 The argument to this keyword must be
610 .It Cm KbdInteractiveDevices
611 Specifies the list of methods to use in keyboard-interactive authentication.
612 Multiple method names must be comma-separated.
613 The default is to use the server specified list.
614 The methods available vary depending on what the server supports.
615 For an OpenSSH server,
616 it may be zero or more of:
622 Specifies a command to execute on the local machine after successfully
623 connecting to the server.
624 The command string extends to the end of the line, and is executed with
626 This directive is ignored unless
627 .Cm PermitLocalCommand
630 Specifies that a TCP port on the local machine be forwarded over
631 the secure channel to the specified host and port from the remote machine.
632 The first argument must be
634 .Oo Ar bind_address : Oc Ar port
636 and the second argument must be
637 .Ar host : Ns Ar hostport .
638 IPv6 addresses can be specified by enclosing addresses in square brackets or
639 by using an alternative syntax:
640 .Oo Ar bind_address Ns / Oc Ns Ar port
642 .Ar host Ns / Ns Ar hostport .
643 Multiple forwardings may be specified, and additional forwardings can be
644 given on the command line.
645 Only the superuser can forward privileged ports.
646 By default, the local port is bound in accordance with the
651 may be used to bind the connection to a specific address.
656 indicates that the listening port be bound for local use only, while an
659 indicates that the port should be available from all interfaces.
661 Gives the verbosity level that is used when logging messages from
663 The possible values are:
664 QUIET, FATAL, ERROR, INFO, VERBOSE, DEBUG, DEBUG1, DEBUG2, and DEBUG3.
666 DEBUG and DEBUG1 are equivalent.
667 DEBUG2 and DEBUG3 each specify higher levels of verbose output.
669 Specifies the MAC (message authentication code) algorithms
670 in order of preference.
671 The MAC algorithm is used in protocol version 2
672 for data integrity protection.
673 Multiple algorithms must be comma-separated.
675 .Bd -literal -offset indent
676 hmac-md5,hmac-sha1,umac-64@openssh.com,
677 hmac-ripemd160,hmac-sha1-96,hmac-md5-96
679 .It Cm NoHostAuthenticationForLocalhost
680 This option can be used if the home directory is shared across machines.
681 In this case localhost will refer to a different machine on each of
682 the machines and the user will get many warnings about changed host keys.
683 However, this option disables host authentication for localhost.
684 The argument to this keyword must be
688 The default is to check the host key for localhost.
689 .It Cm NumberOfPasswordPrompts
690 Specifies the number of password prompts before giving up.
691 The argument to this keyword must be an integer.
693 .It Cm PasswordAuthentication
694 Specifies whether to use password authentication.
695 The argument to this keyword must be
701 .It Cm PermitLocalCommand
702 Allow local command execution via the
705 .Ic !\& Ns Ar command
715 Specifies the port number to connect on the remote host.
717 .It Cm PreferredAuthentications
718 Specifies the order in which the client should try protocol 2
719 authentication methods.
720 This allows a client to prefer one method (e.g.\&
721 .Cm keyboard-interactive )
722 over another method (e.g.\&
724 The default for this option is:
730 keyboard-interactive,
734 Specifies the protocol versions
736 should support in order of preference.
737 The possible values are
741 Multiple versions must be comma-separated.
745 tries version 2 and falls back to version 1
746 if version 2 is not available.
748 Specifies the command to use to connect to the server.
750 string extends to the end of the line, and is executed with
752 In the command string,
754 will be substituted by the host name to
758 The command can be basically anything,
759 and should read from its standard input and write to its standard output.
760 It should eventually connect an
762 server running on some machine, or execute
765 Host key management will be done using the
766 HostName of the host being connected (defaulting to the name typed by
768 Setting the command to
770 disables this option entirely.
773 is not available for connects with a proxy command.
775 This directive is useful in conjunction with
777 and its proxy support.
778 For example, the following directive would connect via an HTTP proxy at
780 .Bd -literal -offset 3n
781 ProxyCommand /usr/bin/nc -X connect -x 192.0.2.0:8080 %h %p
783 .It Cm PubkeyAuthentication
784 Specifies whether to try public key authentication.
785 The argument to this keyword must be
791 This option applies to protocol version 2 only.
793 Specifies the maximum amount of data that may be transmitted before the
794 session key is renegotiated.
795 The argument is the number of bytes, with an optional suffix of
800 to indicate Kilobytes, Megabytes, or Gigabytes, respectively.
801 The default is between
805 depending on the cipher.
806 This option applies to protocol version 2 only.
808 Specifies that a TCP port on the remote machine be forwarded over
809 the secure channel to the specified host and port from the local machine.
810 The first argument must be
812 .Oo Ar bind_address : Oc Ar port
814 and the second argument must be
815 .Ar host : Ns Ar hostport .
816 IPv6 addresses can be specified by enclosing addresses in square brackets
817 or by using an alternative syntax:
818 .Oo Ar bind_address Ns / Oc Ns Ar port
820 .Ar host Ns / Ns Ar hostport .
821 Multiple forwardings may be specified, and additional
822 forwardings can be given on the command line.
823 Only the superuser can forward privileged ports.
827 is not specified, the default is to only bind to loopback addresses.
832 or an empty string, then the forwarding is requested to listen on all
836 will only succeed if the server's
838 option is enabled (see
839 .Xr sshd_config 5 ) .
840 .It Cm RhostsRSAAuthentication
841 Specifies whether to try rhosts based authentication with RSA host
849 This option applies to protocol version 1 only and requires
852 .It Cm RSAAuthentication
853 Specifies whether to try RSA authentication.
854 The argument to this keyword must be
858 RSA authentication will only be
859 attempted if the identity file exists, or an authentication agent is
863 Note that this option applies to protocol version 1 only.
865 Specifies what variables from the local
867 should be sent to the server.
868 Note that environment passing is only supported for protocol 2.
869 The server must also support it, and the server must be configured to
870 accept these environment variables.
875 for how to configure the server.
876 Variables are specified by name, which may contain wildcard characters.
877 Multiple environment variables may be separated by whitespace or spread
881 The default is not to send any environment variables.
885 for more information on patterns.
886 .It Cm ServerAliveCountMax
887 Sets the number of server alive messages (see below) which may be
890 receiving any messages back from the server.
891 If this threshold is reached while server alive messages are being sent,
892 ssh will disconnect from the server, terminating the session.
893 It is important to note that the use of server alive messages is very
897 The server alive messages are sent through the encrypted channel
898 and therefore will not be spoofable.
899 The TCP keepalive option enabled by
902 The server alive mechanism is valuable when the client or
903 server depend on knowing when a connection has become inactive.
905 The default value is 3.
907 .Cm ServerAliveInterval
908 (see below) is set to 15 and
909 .Cm ServerAliveCountMax
910 is left at the default, if the server becomes unresponsive,
911 ssh will disconnect after approximately 45 seconds.
912 This option applies to protocol version 2 only.
913 .It Cm ServerAliveInterval
914 Sets a timeout interval in seconds after which if no data has been received
917 will send a message through the encrypted
918 channel to request a response from the server.
920 is 0, indicating that these messages will not be sent to the server.
921 This option applies to protocol version 2 only.
922 .It Cm SmartcardDevice
923 Specifies which smartcard device to use.
924 The argument to this keyword is the device
926 should use to communicate with a smartcard used for storing the user's
928 By default, no device is specified and smartcard support is not activated.
929 .It Cm StrictHostKeyChecking
930 If this flag is set to
933 will never automatically add host keys to the
934 .Pa ~/.ssh/known_hosts
935 file, and refuses to connect to hosts whose host key has changed.
936 This provides maximum protection against trojan horse attacks,
937 though it can be annoying when the
938 .Pa /etc/ssh/ssh_known_hosts
939 file is poorly maintained or when connections to new hosts are
941 This option forces the user to manually
943 If this flag is set to
945 ssh will automatically add new host keys to the
946 user known hosts files.
947 If this flag is set to
950 will be added to the user known host files only after the user
951 has confirmed that is what they really want to do, and
952 ssh will refuse to connect to hosts whose host key has changed.
954 known hosts will be verified automatically in all cases.
963 Specifies whether the system should send TCP keepalive messages to the
965 If they are sent, death of the connection or crash of one
966 of the machines will be properly noticed.
967 However, this means that
968 connections will die if the route is down temporarily, and some people
973 (to send TCP keepalive messages), and the client will notice
974 if the network goes down or the remote host dies.
975 This is important in scripts, and many users want it too.
977 To disable TCP keepalive messages, the value should be set to
982 device forwarding between the client and the server.
993 requests the default tunnel mode, which is
1000 devices to open on the client
1005 The argument must be
1007 .Ar local_tun Op : Ar remote_tun .
1009 The devices may be specified by numerical ID or the keyword
1011 which uses the next available tunnel device.
1014 is not specified, it defaults to
1018 .It Cm UsePrivilegedPort
1019 Specifies whether to use a privileged port for outgoing connections.
1020 The argument must be
1029 must be setuid root.
1030 Note that this option must be set to
1033 .Cm RhostsRSAAuthentication
1036 Specifies the user to log in as.
1037 This can be useful when a different user name is used on different machines.
1038 This saves the trouble of
1039 having to remember to give the user name on the command line.
1040 .It Cm UserKnownHostsFile
1041 Specifies a file to use for the user
1042 host key database instead of
1043 .Pa ~/.ssh/known_hosts .
1044 .It Cm VerifyHostKeyDNS
1045 Specifies whether to verify the remote key using DNS and SSHFP resource
1047 If this option is set to
1049 the client will implicitly trust keys that match a secure fingerprint
1051 Insecure fingerprints will be handled as if this option was set to
1053 If this option is set to
1055 information on fingerprint match will be displayed, but the user will still
1056 need to confirm new host keys according to the
1057 .Cm StrictHostKeyChecking
1059 The argument must be
1066 Note that this option applies to protocol version 2 only.
1069 .Sx VERIFYING HOST KEYS
1072 .It Cm XAuthLocation
1073 Specifies the full pathname of the
1077 .Pa /usr/X11R6/bin/xauth .
1082 consists of zero or more non-whitespace characters,
1084 (a wildcard that matches zero or more characters),
1087 (a wildcard that matches exactly one character).
1088 For example, to specify a set of declarations for any host in the
1091 the following pattern could be used:
1095 The following pattern
1096 would match any host in the 192.168.0.[0-9] network range:
1098 .Dl Host 192.168.0.?
1102 is a comma-separated list of patterns.
1103 Patterns within pattern-lists may be negated
1104 by preceding them with an exclamation mark
1107 to allow a key to be used from anywhere within an organisation
1111 the following entry (in authorized_keys) could be used:
1113 .Dl from=\&"!*.dialup.example.com,*.example.com\&"
1116 .It Pa ~/.ssh/config
1117 This is the per-user configuration file.
1118 The format of this file is described above.
1119 This file is used by the SSH client.
1120 Because of the potential for abuse, this file must have strict permissions:
1121 read/write for the user, and not accessible by others.
1122 .It Pa /etc/ssh/ssh_config
1123 Systemwide configuration file.
1124 This file provides defaults for those
1125 values that are not specified in the user's configuration file, and
1126 for those users who do not have a configuration file.
1127 This file must be world-readable.
1132 OpenSSH is a derivative of the original and free
1133 ssh 1.2.12 release by Tatu Ylonen.
1134 Aaron Campbell, Bob Beck, Markus Friedl, Niels Provos,
1135 Theo de Raadt and Dug Song
1136 removed many bugs, re-added newer features and
1138 Markus Friedl contributed the support for SSH
1139 protocol versions 1.5 and 2.0.
andersk / gssapi-openssh.git / blob