blob: 20c58934add92a979b93bdaddfe5a9cff64557b2 [file] [log] [blame]
Ben Lindstrom9f049032002-06-21 00:59:05 +00001.\" -*- nroff -*-
2.\"
3.\" Author: Tatu Ylonen <ylo@cs.hut.fi>
4.\" Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
5.\" All rights reserved
6.\"
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".
12.\"
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.
16.\"
17.\" Redistribution and use in source and binary forms, with or without
18.\" modification, are permitted provided that the following conditions
19.\" are met:
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.
25.\"
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.
36.\"
Damien Miller858bb7d2006-08-05 11:34:51 +100037.\" $OpenBSD: ssh_config.5,v 1.97 2006/07/27 08:00:50 jmc Exp $
Ben Lindstrom9f049032002-06-21 00:59:05 +000038.Dd September 25, 1999
39.Dt SSH_CONFIG 5
40.Os
41.Sh NAME
42.Nm ssh_config
43.Nd OpenSSH SSH client configuration files
44.Sh SYNOPSIS
45.Bl -tag -width Ds -compact
Damien Miller167ea5d2005-05-26 12:04:02 +100046.It Pa ~/.ssh/config
Ben Lindstrom9f049032002-06-21 00:59:05 +000047.It Pa /etc/ssh/ssh_config
48.El
49.Sh DESCRIPTION
Damien Miller45ee2b92006-03-15 11:56:18 +110050.Xr ssh 1
Ben Lindstrom9f049032002-06-21 00:59:05 +000051obtains configuration data from the following sources in
52the following order:
Damien Miller5c853b52006-03-15 11:37:02 +110053.Pp
Ben Lindstrom479b4762002-08-20 19:04:51 +000054.Bl -enum -offset indent -compact
55.It
56command-line options
57.It
58user's configuration file
Damien Miller167ea5d2005-05-26 12:04:02 +100059.Pq Pa ~/.ssh/config
Ben Lindstrom479b4762002-08-20 19:04:51 +000060.It
61system-wide configuration file
62.Pq Pa /etc/ssh/ssh_config
63.El
Ben Lindstrom9f049032002-06-21 00:59:05 +000064.Pp
65For each parameter, the first obtained value
66will be used.
Darren Tucker43d8e282005-02-09 09:51:08 +110067The configuration files contain sections separated by
Ben Lindstrom9f049032002-06-21 00:59:05 +000068.Dq Host
69specifications, and that section is only applied for hosts that
70match one of the patterns given in the specification.
71The matched host name is the one given on the command line.
72.Pp
73Since the first obtained value for each parameter is used, more
74host-specific declarations should be given near the beginning of the
75file, and general defaults at the end.
76.Pp
77The configuration file has the following format:
78.Pp
79Empty lines and lines starting with
80.Ql #
81are comments.
Ben Lindstrom9f049032002-06-21 00:59:05 +000082Otherwise a line is of the format
83.Dq keyword arguments .
84Configuration options may be separated by whitespace or
85optional whitespace and exactly one
86.Ql = ;
87the latter format is useful to avoid the need to quote whitespace
88when specifying configuration options using the
89.Nm ssh ,
Damien Miller4aea9742006-03-15 11:59:39 +110090.Nm scp ,
Ben Lindstrom9f049032002-06-21 00:59:05 +000091and
92.Nm sftp
93.Fl o
94option.
Damien Miller306d1182006-03-15 12:05:59 +110095Arguments may optionally be enclosed in double quotes
96.Pq \&"
97in order to represent arguments containing spaces.
Ben Lindstrom9f049032002-06-21 00:59:05 +000098.Pp
99The possible
100keywords and their meanings are as follows (note that
101keywords are case-insensitive and arguments are case-sensitive):
102.Bl -tag -width Ds
103.It Cm Host
104Restricts the following declarations (up to the next
105.Cm Host
106keyword) to be only for those hosts that match one of the patterns
107given after the keyword.
Ben Lindstrom9f049032002-06-21 00:59:05 +0000108A single
Damien Miller208f1ed2006-03-15 11:56:03 +1100109.Ql *
Ben Lindstrom9f049032002-06-21 00:59:05 +0000110as a pattern can be used to provide global
111defaults for all hosts.
112The host is the
113.Ar hostname
Damien Miller208f1ed2006-03-15 11:56:03 +1100114argument given on the command line (i.e. the name is not converted to
Ben Lindstrom9f049032002-06-21 00:59:05 +0000115a canonicalized host name before matching).
Damien Millerf54a4b92006-03-15 11:54:36 +1100116.Pp
117See
118.Sx PATTERNS
119for more information on patterns.
Damien Miller20a8f972003-05-18 20:50:30 +1000120.It Cm AddressFamily
Damien Millerfbf486b2003-05-23 18:44:23 +1000121Specifies which address family to use when connecting.
122Valid arguments are
Damien Miller20a8f972003-05-18 20:50:30 +1000123.Dq any ,
124.Dq inet
Damien Miller45ee2b92006-03-15 11:56:18 +1100125(use IPv4 only), or
Damien Miller20a8f972003-05-18 20:50:30 +1000126.Dq inet6
Darren Tucker79a7acf2005-02-09 09:48:57 +1100127(use IPv6 only).
Ben Lindstrom9f049032002-06-21 00:59:05 +0000128.It Cm BatchMode
129If set to
130.Dq yes ,
131passphrase/password querying will be disabled.
132This option is useful in scripts and other batch jobs where no user
133is present to supply the password.
134The argument must be
135.Dq yes
136or
137.Dq no .
138The default is
139.Dq no .
140.It Cm BindAddress
Darren Tucker89f4d472005-07-14 17:06:21 +1000141Use the specified address on the local machine as the source address of
Darren Tucker6c71d202005-07-14 17:06:50 +1000142the connection.
143Only useful on systems with more than one address.
Ben Lindstrom9f049032002-06-21 00:59:05 +0000144Note that this option does not work if
145.Cm UsePrivilegedPort
146is set to
147.Dq yes .
148.It Cm ChallengeResponseAuthentication
Damien Miller1faa7132006-03-15 11:55:31 +1100149Specifies whether to use challenge-response authentication.
Ben Lindstrom9f049032002-06-21 00:59:05 +0000150The argument to this keyword must be
151.Dq yes
152or
153.Dq no .
154The default is
155.Dq yes .
156.It Cm CheckHostIP
157If this flag is set to
158.Dq yes ,
Damien Miller45ee2b92006-03-15 11:56:18 +1100159.Xr ssh 1
160will additionally check the host IP address in the
Ben Lindstrom9f049032002-06-21 00:59:05 +0000161.Pa known_hosts
162file.
163This allows ssh to detect if a host key changed due to DNS spoofing.
164If the option is set to
165.Dq no ,
166the check will not be executed.
167The default is
168.Dq yes .
169.It Cm Cipher
170Specifies the cipher to use for encrypting the session
171in protocol version 1.
172Currently,
173.Dq blowfish ,
174.Dq 3des ,
175and
176.Dq des
177are supported.
178.Ar des
179is only supported in the
Damien Miller45ee2b92006-03-15 11:56:18 +1100180.Xr ssh 1
Ben Lindstrom9f049032002-06-21 00:59:05 +0000181client for interoperability with legacy protocol 1 implementations
182that do not support the
183.Ar 3des
Damien Miller495dca32003-04-01 21:42:14 +1000184cipher.
185Its use is strongly discouraged due to cryptographic weaknesses.
Ben Lindstrom9f049032002-06-21 00:59:05 +0000186The default is
187.Dq 3des .
188.It Cm Ciphers
189Specifies the ciphers allowed for protocol version 2
190in order of preference.
191Multiple ciphers must be comma-separated.
Damien Miller05202ff2004-06-15 10:30:39 +1000192The supported ciphers are
193.Dq 3des-cbc ,
194.Dq aes128-cbc ,
195.Dq aes192-cbc ,
196.Dq aes256-cbc ,
197.Dq aes128-ctr ,
198.Dq aes192-ctr ,
199.Dq aes256-ctr ,
Damien Miller3710f272005-05-26 12:19:17 +1000200.Dq arcfour128 ,
201.Dq arcfour256 ,
Damien Miller05202ff2004-06-15 10:30:39 +1000202.Dq arcfour ,
203.Dq blowfish-cbc ,
204and
205.Dq cast128-cbc .
Damien Miller45ee2b92006-03-15 11:56:18 +1100206The default is:
207.Bd -literal -offset 3n
208aes128-cbc,3des-cbc,blowfish-cbc,cast128-cbc,arcfour128,
209arcfour256,arcfour,aes192-cbc,aes256-cbc,aes128-ctr,
210aes192-ctr,aes256-ctr
Ben Lindstrom9f049032002-06-21 00:59:05 +0000211.Ed
212.It Cm ClearAllForwardings
Damien Miller45ee2b92006-03-15 11:56:18 +1100213Specifies that all local, remote, and dynamic port forwardings
Ben Lindstrom9f049032002-06-21 00:59:05 +0000214specified in the configuration files or on the command line be
Damien Miller495dca32003-04-01 21:42:14 +1000215cleared.
216This option is primarily useful when used from the
Damien Miller45ee2b92006-03-15 11:56:18 +1100217.Xr ssh 1
Ben Lindstrom9f049032002-06-21 00:59:05 +0000218command line to clear port forwardings set in
219configuration files, and is automatically set by
220.Xr scp 1
221and
222.Xr sftp 1 .
223The argument must be
224.Dq yes
225or
226.Dq no .
227The default is
228.Dq no .
229.It Cm Compression
230Specifies whether to use compression.
231The argument must be
232.Dq yes
233or
234.Dq no .
235The default is
236.Dq no .
237.It Cm CompressionLevel
238Specifies the compression level to use if compression is enabled.
239The argument must be an integer from 1 (fast) to 9 (slow, best).
240The default level is 6, which is good for most applications.
241The meaning of the values is the same as in
242.Xr gzip 1 .
243Note that this option applies to protocol version 1 only.
244.It Cm ConnectionAttempts
245Specifies the number of tries (one per second) to make before exiting.
246The argument must be an integer.
247This may be useful in scripts if the connection sometimes fails.
248The default is 1.
Damien Millerb78d5eb2003-05-16 11:39:04 +1000249.It Cm ConnectTimeout
Damien Miller45ee2b92006-03-15 11:56:18 +1100250Specifies the timeout (in seconds) used when connecting to the
251SSH server, instead of using the default system TCP timeout.
Damien Millerfbf486b2003-05-23 18:44:23 +1000252This value is used only when the target is down or really unreachable,
253not when it refuses the connection.
Damien Miller0e220db2004-06-15 10:34:08 +1000254.It Cm ControlMaster
255Enables the sharing of multiple sessions over a single network connection.
256When set to
Damien Miller45ee2b92006-03-15 11:56:18 +1100257.Dq yes ,
258.Xr ssh 1
Damien Miller0e220db2004-06-15 10:34:08 +1000259will listen for connections on a control socket specified using the
260.Cm ControlPath
261argument.
262Additional sessions can connect to this socket using the same
263.Cm ControlPath
264with
265.Cm ControlMaster
266set to
267.Dq no
Damien Miller2234bac2004-06-30 22:38:52 +1000268(the default).
Damien Miller713de762005-11-05 15:13:49 +1100269These sessions will try to reuse the master instance's network connection
Damien Millerb3bfbb72005-11-05 15:11:48 +1100270rather than initiating new ones, but will fall back to connecting normally
271if the control socket does not exist, or is not listening.
272.Pp
Damien Miller23f07702004-06-18 01:19:03 +1000273Setting this to
274.Dq ask
Damien Miller45ee2b92006-03-15 11:56:18 +1100275will cause ssh
Damien Miller23f07702004-06-18 01:19:03 +1000276to listen for control connections, but require confirmation using the
277.Ev SSH_ASKPASS
278program before they are accepted (see
279.Xr ssh-add 1
Damien Miller2234bac2004-06-30 22:38:52 +1000280for details).
Damien Millerdadfd4d2005-05-26 12:07:13 +1000281If the
282.Cm ControlPath
Damien Miller45ee2b92006-03-15 11:56:18 +1100283cannot be opened,
284ssh will continue without connecting to a master instance.
Damien Millerd14b1e72005-06-16 13:19:41 +1000285.Pp
Damien Miller13390022005-07-06 09:44:19 +1000286X11 and
Damien Millerfd94fba2005-07-06 09:44:59 +1000287.Xr ssh-agent 1
Damien Miller13390022005-07-06 09:44:19 +1000288forwarding is supported over these multiplexed connections, however the
Darren Tucker63551872005-12-20 16:14:15 +1100289display and agent forwarded will be the one belonging to the master
Damien Millerfd94fba2005-07-06 09:44:59 +1000290connection i.e. it is not possible to forward multiple displays or agents.
Damien Miller13390022005-07-06 09:44:19 +1000291.Pp
Damien Millerd14b1e72005-06-16 13:19:41 +1000292Two additional options allow for opportunistic multiplexing: try to use a
293master connection but fall back to creating a new one if one does not already
294exist.
295These options are:
296.Dq auto
297and
298.Dq autoask .
299The latter requires confirmation like the
300.Dq ask
301option.
Damien Miller0e220db2004-06-15 10:34:08 +1000302.It Cm ControlPath
Damien Miller6476cad2005-06-16 13:18:34 +1000303Specify the path to the control socket used for connection sharing as described
304in the
Damien Miller0e220db2004-06-15 10:34:08 +1000305.Cm ControlMaster
Damien Miller8f74c8f2005-06-26 08:56:03 +1000306section above or the string
307.Dq none
308to disable connection sharing.
Damien Miller6476cad2005-06-16 13:18:34 +1000309In the path,
Damien Miller3ec54c72006-03-15 11:30:13 +1100310.Ql %l
311will be substituted by the local host name,
Damien Miller6476cad2005-06-16 13:18:34 +1000312.Ql %h
313will be substituted by the target host name,
314.Ql %p
Damien Miller45ee2b92006-03-15 11:56:18 +1100315the port, and
Damien Miller6476cad2005-06-16 13:18:34 +1000316.Ql %r
317by the remote login username.
Damien Millerd14b1e72005-06-16 13:19:41 +1000318It is recommended that any
319.Cm ControlPath
320used for opportunistic connection sharing include
Damien Miller20c2ec42006-03-15 11:31:01 +1100321at least %h, %p, and %r.
Damien Millerd14b1e72005-06-16 13:19:41 +1000322This ensures that shared connections are uniquely identified.
Damien Miller2234bac2004-06-30 22:38:52 +1000323.It Cm DynamicForward
Damien Millere9d001e2006-01-14 10:10:17 +1100324Specifies that a TCP port on the local machine be forwarded
Damien Miller2234bac2004-06-30 22:38:52 +1000325over the secure channel, and the application
326protocol is then used to determine where to connect to from the
327remote machine.
Darren Tuckerc8d64212005-10-03 18:13:42 +1000328.Pp
329The argument must be
330.Sm off
331.Oo Ar bind_address : Oc Ar port .
332.Sm on
333IPv6 addresses can be specified by enclosing addresses in square brackets or
334by using an alternative syntax:
335.Oo Ar bind_address Ns / Oc Ns Ar port .
336By default, the local port is bound in accordance with the
337.Cm GatewayPorts
338setting.
339However, an explicit
340.Ar bind_address
341may be used to bind the connection to a specific address.
342The
343.Ar bind_address
344of
345.Dq localhost
346indicates that the listening port be bound for local use only, while an
347empty address or
348.Sq *
349indicates that the port should be available from all interfaces.
350.Pp
Damien Miller2234bac2004-06-30 22:38:52 +1000351Currently the SOCKS4 and SOCKS5 protocols are supported, and
Damien Miller45ee2b92006-03-15 11:56:18 +1100352.Xr ssh 1
Damien Miller2234bac2004-06-30 22:38:52 +1000353will act as a SOCKS server.
354Multiple forwardings may be specified, and
355additional forwardings can be given on the command line.
356Only the superuser can forward privileged ports.
Darren Tucker674f71d2003-06-28 12:33:12 +1000357.It Cm EnableSSHKeysign
358Setting this option to
359.Dq yes
360in the global client configuration file
361.Pa /etc/ssh/ssh_config
362enables the use of the helper program
363.Xr ssh-keysign 8
364during
365.Cm HostbasedAuthentication .
366The argument must be
367.Dq yes
368or
369.Dq no .
370The default is
371.Dq no .
Darren Tuckerf132c672003-10-15 15:58:18 +1000372This option should be placed in the non-hostspecific section.
Darren Tucker674f71d2003-06-28 12:33:12 +1000373See
374.Xr ssh-keysign 8
375for more information.
Ben Lindstrom9f049032002-06-21 00:59:05 +0000376.It Cm EscapeChar
377Sets the escape character (default:
378.Ql ~ ) .
379The escape character can also
380be set on the command line.
381The argument should be a single character,
382.Ql ^
383followed by a letter, or
384.Dq none
385to disable the escape
386character entirely (making the connection transparent for binary
387data).
Darren Tuckere7d4b192006-07-12 22:17:10 +1000388.It Cm ExitOnForwardFailure
389Specifies whether
390.Xr ssh 1
391should terminate the connection if it cannot set up all requested
392dynamic, local, and remote port forwardings.
393The argument must be
394.Dq yes
395or
396.Dq no .
397The default is
398.Dq no .
Ben Lindstrom9f049032002-06-21 00:59:05 +0000399.It Cm ForwardAgent
400Specifies whether the connection to the authentication agent (if any)
401will be forwarded to the remote machine.
402The argument must be
403.Dq yes
404or
405.Dq no .
406The default is
407.Dq no .
Damien Milleraf653042002-09-04 16:40:37 +1000408.Pp
Damien Miller495dca32003-04-01 21:42:14 +1000409Agent forwarding should be enabled with caution.
410Users with the ability to bypass file permissions on the remote host
411(for the agent's Unix-domain socket)
412can access the local agent through the forwarded connection.
413An attacker cannot obtain key material from the agent,
Damien Milleraf653042002-09-04 16:40:37 +1000414however they can perform operations on the keys that enable them to
415authenticate using the identities loaded into the agent.
Ben Lindstrom9f049032002-06-21 00:59:05 +0000416.It Cm ForwardX11
417Specifies whether X11 connections will be automatically redirected
418over the secure channel and
419.Ev DISPLAY
420set.
421The argument must be
422.Dq yes
423or
424.Dq no .
425The default is
426.Dq no .
Damien Milleraf653042002-09-04 16:40:37 +1000427.Pp
Damien Miller495dca32003-04-01 21:42:14 +1000428X11 forwarding should be enabled with caution.
429Users with the ability to bypass file permissions on the remote host
Darren Tucker0a118da2003-10-15 15:54:32 +1000430(for the user's X11 authorization database)
Damien Miller495dca32003-04-01 21:42:14 +1000431can access the local X11 display through the forwarded connection.
Darren Tucker0a118da2003-10-15 15:54:32 +1000432An attacker may then be able to perform activities such as keystroke monitoring
433if the
434.Cm ForwardX11Trusted
435option is also enabled.
436.It Cm ForwardX11Trusted
Darren Tuckerdcf6ec42004-05-13 13:03:56 +1000437If this option is set to
Damien Miller45ee2b92006-03-15 11:56:18 +1100438.Dq yes ,
439remote X11 clients will have full access to the original X11 display.
Damien Miller1717fd42005-03-01 21:17:31 +1100440.Pp
Darren Tucker0a118da2003-10-15 15:54:32 +1000441If this option is set to
Damien Miller45ee2b92006-03-15 11:56:18 +1100442.Dq no ,
443remote X11 clients will be considered untrusted and prevented
Darren Tucker0a118da2003-10-15 15:54:32 +1000444from stealing or tampering with data belonging to trusted X11
445clients.
Damien Miller1717fd42005-03-01 21:17:31 +1100446Furthermore, the
447.Xr xauth 1
448token used for the session will be set to expire after 20 minutes.
449Remote clients will be refused access after this time.
Darren Tucker0a118da2003-10-15 15:54:32 +1000450.Pp
451The default is
452.Dq no .
453.Pp
454See the X11 SECURITY extension specification for full details on
455the restrictions imposed on untrusted clients.
Ben Lindstrom9f049032002-06-21 00:59:05 +0000456.It Cm GatewayPorts
457Specifies whether remote hosts are allowed to connect to local
458forwarded ports.
459By default,
Damien Miller45ee2b92006-03-15 11:56:18 +1100460.Xr ssh 1
Damien Miller495dca32003-04-01 21:42:14 +1000461binds local port forwardings to the loopback address.
462This prevents other remote hosts from connecting to forwarded ports.
Ben Lindstrom9f049032002-06-21 00:59:05 +0000463.Cm GatewayPorts
Damien Miller45ee2b92006-03-15 11:56:18 +1100464can be used to specify that ssh
Ben Lindstrom9f049032002-06-21 00:59:05 +0000465should bind local port forwardings to the wildcard address,
466thus allowing remote hosts to connect to forwarded ports.
467The argument must be
468.Dq yes
469or
470.Dq no .
471The default is
472.Dq no .
473.It Cm GlobalKnownHostsFile
474Specifies a file to use for the global
475host key database instead of
476.Pa /etc/ssh/ssh_known_hosts .
Darren Tucker0efd1552003-08-26 11:49:55 +1000477.It Cm GSSAPIAuthentication
Damien Millerbaafb982003-12-17 16:32:23 +1100478Specifies whether user authentication based on GSSAPI is allowed.
Damien Millerc2b98272003-09-03 12:13:30 +1000479The default is
Darren Tuckera044f472003-10-15 15:52:03 +1000480.Dq no .
Darren Tucker0efd1552003-08-26 11:49:55 +1000481Note that this option applies to protocol version 2 only.
482.It Cm GSSAPIDelegateCredentials
483Forward (delegate) credentials to the server.
484The default is
485.Dq no .
486Note that this option applies to protocol version 2 only.
Damien Millere1776152005-03-01 21:47:37 +1100487.It Cm HashKnownHosts
488Indicates that
Damien Miller45ee2b92006-03-15 11:56:18 +1100489.Xr ssh 1
Damien Millere1776152005-03-01 21:47:37 +1100490should hash host names and addresses when they are added to
Damien Miller167ea5d2005-05-26 12:04:02 +1000491.Pa ~/.ssh/known_hosts .
Damien Millere1776152005-03-01 21:47:37 +1100492These hashed names may be used normally by
Damien Miller45ee2b92006-03-15 11:56:18 +1100493.Xr ssh 1
Damien Millere1776152005-03-01 21:47:37 +1100494and
Damien Miller45ee2b92006-03-15 11:56:18 +1100495.Xr sshd 8 ,
Damien Millere1776152005-03-01 21:47:37 +1100496but they do not reveal identifying information should the file's contents
497be disclosed.
498The default is
499.Dq no .
Damien Miller858bb7d2006-08-05 11:34:51 +1000500Note that existing names and addresses in known hosts files
501will not be converted automatically,
502but may be manually hashed using
Damien Miller4b42d7f2005-03-01 21:48:35 +1100503.Xr ssh-keygen 1 .
Ben Lindstrom9f049032002-06-21 00:59:05 +0000504.It Cm HostbasedAuthentication
505Specifies whether to try rhosts based authentication with public key
506authentication.
507The argument must be
508.Dq yes
509or
510.Dq no .
511The default is
512.Dq no .
513This option applies to protocol version 2 only and
514is similar to
515.Cm RhostsRSAAuthentication .
516.It Cm HostKeyAlgorithms
517Specifies the protocol version 2 host key algorithms
518that the client wants to use in order of preference.
519The default for this option is:
520.Dq ssh-rsa,ssh-dss .
521.It Cm HostKeyAlias
522Specifies an alias that should be used instead of the
523real host name when looking up or saving the host key
524in the host key database files.
Damien Miller45ee2b92006-03-15 11:56:18 +1100525This option is useful for tunneling SSH connections
Ben Lindstrom9f049032002-06-21 00:59:05 +0000526or for multiple servers running on a single host.
527.It Cm HostName
528Specifies the real host name to log into.
529This can be used to specify nicknames or abbreviations for hosts.
Damien Miller45ee2b92006-03-15 11:56:18 +1100530The default is the name given on the command line.
Ben Lindstrom9f049032002-06-21 00:59:05 +0000531Numeric IP addresses are also permitted (both on the command line and in
532.Cm HostName
533specifications).
Damien Millerbd394c32004-03-08 23:12:36 +1100534.It Cm IdentitiesOnly
535Specifies that
Damien Miller45ee2b92006-03-15 11:56:18 +1100536.Xr ssh 1
Damien Millerbd394c32004-03-08 23:12:36 +1100537should only use the authentication identity files configured in the
Damien Miller1a812582004-04-20 20:13:32 +1000538.Nm
Damien Millerbd394c32004-03-08 23:12:36 +1100539files,
Damien Miller45ee2b92006-03-15 11:56:18 +1100540even if
541.Xr ssh-agent 1
Damien Millerbd394c32004-03-08 23:12:36 +1100542offers more identities.
543The argument to this keyword must be
544.Dq yes
545or
546.Dq no .
Damien Miller45ee2b92006-03-15 11:56:18 +1100547This option is intended for situations where ssh-agent
Damien Millerbd394c32004-03-08 23:12:36 +1100548offers many different identities.
549The default is
550.Dq no .
Damien Miller957d4e42005-12-13 19:30:45 +1100551.It Cm IdentityFile
552Specifies a file from which the user's RSA or DSA authentication identity
553is read.
554The default is
555.Pa ~/.ssh/identity
556for protocol version 1, and
557.Pa ~/.ssh/id_rsa
558and
559.Pa ~/.ssh/id_dsa
560for protocol version 2.
561Additionally, any identities represented by the authentication agent
562will be used for authentication.
Damien Miller6b1d53c2006-03-31 23:13:21 +1100563.Pp
Damien Miller957d4e42005-12-13 19:30:45 +1100564The file name may use the tilde
Damien Millerc6437cf2006-03-31 23:14:41 +1100565syntax to refer to a user's home directory or one of the following
Damien Miller6b1d53c2006-03-31 23:13:21 +1100566escape characters:
567.Ql %d
568(local user's home directory),
569.Ql %u
570(local user name),
571.Ql %l
572(local host name),
573.Ql %h
574(remote host name) or
Damien Millerdfc61832006-03-31 23:14:57 +1100575.Ql %r
Damien Miller6b1d53c2006-03-31 23:13:21 +1100576(remote user name).
577.Pp
Damien Miller957d4e42005-12-13 19:30:45 +1100578It is possible to have
579multiple identity files specified in configuration files; all these
580identities will be tried in sequence.
Darren Tucker636ca902004-11-05 20:22:00 +1100581.It Cm KbdInteractiveDevices
582Specifies the list of methods to use in keyboard-interactive authentication.
583Multiple method names must be comma-separated.
584The default is to use the server specified list.
Damien Miller9cfbaec2006-03-15 11:57:55 +1100585The methods available vary depending on what the server supports.
586For an OpenSSH server,
587it may be zero or more of:
588.Dq bsdauth ,
589.Dq pam ,
590and
591.Dq skey .
Damien Millerd27b9472005-12-13 19:29:02 +1100592.It Cm LocalCommand
593Specifies a command to execute on the local machine after successfully
594connecting to the server.
595The command string extends to the end of the line, and is executed with
596.Pa /bin/sh .
597This directive is ignored unless
598.Cm PermitLocalCommand
599has been enabled.
Ben Lindstrom9f049032002-06-21 00:59:05 +0000600.It Cm LocalForward
Damien Millere9d001e2006-01-14 10:10:17 +1100601Specifies that a TCP port on the local machine be forwarded over
Ben Lindstrom9f049032002-06-21 00:59:05 +0000602the secure channel to the specified host and port from the remote machine.
Darren Tucker5ede2ad2005-03-31 21:31:10 +1000603The first argument must be
Damien Millerf91ee4c2005-03-01 21:24:33 +1100604.Sm off
Darren Tucker5ede2ad2005-03-31 21:31:10 +1000605.Oo Ar bind_address : Oc Ar port
Damien Millerf91ee4c2005-03-01 21:24:33 +1100606.Sm on
Darren Tucker5ede2ad2005-03-31 21:31:10 +1000607and the second argument must be
608.Ar host : Ns Ar hostport .
Damien Millerf8c55462005-03-02 12:03:05 +1100609IPv6 addresses can be specified by enclosing addresses in square brackets or
Damien Millerf91ee4c2005-03-01 21:24:33 +1100610by using an alternative syntax:
Darren Tucker5ede2ad2005-03-31 21:31:10 +1000611.Oo Ar bind_address Ns / Oc Ns Ar port
612and
613.Ar host Ns / Ns Ar hostport .
Damien Millerf8c55462005-03-02 12:03:05 +1100614Multiple forwardings may be specified, and additional forwardings can be
Damien Millerf91ee4c2005-03-01 21:24:33 +1100615given on the command line.
Ben Lindstrom9f049032002-06-21 00:59:05 +0000616Only the superuser can forward privileged ports.
Damien Millerf91ee4c2005-03-01 21:24:33 +1100617By default, the local port is bound in accordance with the
618.Cm GatewayPorts
619setting.
620However, an explicit
621.Ar bind_address
622may be used to bind the connection to a specific address.
623The
624.Ar bind_address
625of
626.Dq localhost
Damien Millerf8c55462005-03-02 12:03:05 +1100627indicates that the listening port be bound for local use only, while an
628empty address or
629.Sq *
Damien Millerf91ee4c2005-03-01 21:24:33 +1100630indicates that the port should be available from all interfaces.
Ben Lindstrom9f049032002-06-21 00:59:05 +0000631.It Cm LogLevel
632Gives the verbosity level that is used when logging messages from
Damien Miller45ee2b92006-03-15 11:56:18 +1100633.Xr ssh 1 .
Ben Lindstrom9f049032002-06-21 00:59:05 +0000634The possible values are:
Damien Miller45ee2b92006-03-15 11:56:18 +1100635QUIET, FATAL, ERROR, INFO, VERBOSE, DEBUG, DEBUG1, DEBUG2, and DEBUG3.
Damien Miller495dca32003-04-01 21:42:14 +1000636The default is INFO.
637DEBUG and DEBUG1 are equivalent.
638DEBUG2 and DEBUG3 each specify higher levels of verbose output.
Ben Lindstrom9f049032002-06-21 00:59:05 +0000639.It Cm MACs
640Specifies the MAC (message authentication code) algorithms
641in order of preference.
642The MAC algorithm is used in protocol version 2
643for data integrity protection.
644Multiple algorithms must be comma-separated.
Damien Miller45ee2b92006-03-15 11:56:18 +1100645The default is:
Ben Lindstrom9f049032002-06-21 00:59:05 +0000646.Dq hmac-md5,hmac-sha1,hmac-ripemd160,hmac-sha1-96,hmac-md5-96 .
647.It Cm NoHostAuthenticationForLocalhost
648This option can be used if the home directory is shared across machines.
649In this case localhost will refer to a different machine on each of
650the machines and the user will get many warnings about changed host keys.
651However, this option disables host authentication for localhost.
652The argument to this keyword must be
653.Dq yes
654or
655.Dq no .
656The default is to check the host key for localhost.
657.It Cm NumberOfPasswordPrompts
658Specifies the number of password prompts before giving up.
659The argument to this keyword must be an integer.
Damien Miller45ee2b92006-03-15 11:56:18 +1100660The default is 3.
Ben Lindstrom9f049032002-06-21 00:59:05 +0000661.It Cm PasswordAuthentication
662Specifies whether to use password authentication.
663The argument to this keyword must be
664.Dq yes
665or
666.Dq no .
667The default is
668.Dq yes .
Damien Millerd27b9472005-12-13 19:29:02 +1100669.It Cm PermitLocalCommand
670Allow local command execution via the
671.Ic LocalCommand
672option or using the
Damien Miller4b2319f2005-12-13 19:30:27 +1100673.Ic !\& Ns Ar command
Damien Millerd27b9472005-12-13 19:29:02 +1100674escape sequence in
675.Xr ssh 1 .
676The argument must be
677.Dq yes
678or
679.Dq no .
680The default is
681.Dq no .
Damien Miller957d4e42005-12-13 19:30:45 +1100682.It Cm Port
683Specifies the port number to connect on the remote host.
Damien Miller45ee2b92006-03-15 11:56:18 +1100684The default is 22.
Ben Lindstrom9f049032002-06-21 00:59:05 +0000685.It Cm PreferredAuthentications
686Specifies the order in which the client should try protocol 2
Damien Millerfbf486b2003-05-23 18:44:23 +1000687authentication methods.
Darren Tucker1adc2bd2005-03-14 23:14:20 +1100688This allows a client to prefer one method (e.g.\&
Ben Lindstrom9f049032002-06-21 00:59:05 +0000689.Cm keyboard-interactive )
Darren Tucker1adc2bd2005-03-14 23:14:20 +1100690over another method (e.g.\&
Ben Lindstrom9f049032002-06-21 00:59:05 +0000691.Cm password )
692The default for this option is:
Damien Miller3c6ed7b2006-06-13 13:01:41 +1000693.Do gssapi-with-mic ,
694hostbased,
695publickey,
696keyboard-interactive,
697password
698.Dc .
Ben Lindstrom9f049032002-06-21 00:59:05 +0000699.It Cm Protocol
700Specifies the protocol versions
Damien Miller45ee2b92006-03-15 11:56:18 +1100701.Xr ssh 1
Ben Lindstrom9f049032002-06-21 00:59:05 +0000702should support in order of preference.
703The possible values are
Damien Miller45ee2b92006-03-15 11:56:18 +1100704.Sq 1
Ben Lindstrom9f049032002-06-21 00:59:05 +0000705and
Damien Miller45ee2b92006-03-15 11:56:18 +1100706.Sq 2 .
Ben Lindstrom9f049032002-06-21 00:59:05 +0000707Multiple versions must be comma-separated.
708The default is
709.Dq 2,1 .
Damien Miller45ee2b92006-03-15 11:56:18 +1100710This means that ssh
Ben Lindstrom9f049032002-06-21 00:59:05 +0000711tries version 2 and falls back to version 1
712if version 2 is not available.
713.It Cm ProxyCommand
714Specifies the command to use to connect to the server.
715The command
716string extends to the end of the line, and is executed with
717.Pa /bin/sh .
718In the command string,
719.Ql %h
720will be substituted by the host name to
721connect and
722.Ql %p
723by the port.
724The command can be basically anything,
725and should read from its standard input and write to its standard output.
726It should eventually connect an
727.Xr sshd 8
728server running on some machine, or execute
729.Ic sshd -i
730somewhere.
731Host key management will be done using the
732HostName of the host being connected (defaulting to the name typed by
733the user).
Damien Miller495dca32003-04-01 21:42:14 +1000734Setting the command to
735.Dq none
Damien Miller9f1e33a2003-02-24 11:57:32 +1100736disables this option entirely.
Ben Lindstrom9f049032002-06-21 00:59:05 +0000737Note that
738.Cm CheckHostIP
739is not available for connects with a proxy command.
740.Pp
Damien Millerebcfedc2005-05-26 12:13:56 +1000741This directive is useful in conjunction with
742.Xr nc 1
743and its proxy support.
Damien Millerdfec2942005-05-26 12:14:32 +1000744For example, the following directive would connect via an HTTP proxy at
Damien Millerebcfedc2005-05-26 12:13:56 +1000745192.0.2.0:
746.Bd -literal -offset 3n
747ProxyCommand /usr/bin/nc -X connect -x 192.0.2.0:8080 %h %p
748.Ed
Ben Lindstrom9f049032002-06-21 00:59:05 +0000749.It Cm PubkeyAuthentication
750Specifies whether to try public key authentication.
751The argument to this keyword must be
752.Dq yes
753or
754.Dq no .
755The default is
756.Dq yes .
757This option applies to protocol version 2 only.
Darren Tucker62388b22006-01-20 11:31:47 +1100758.It Cm RekeyLimit
759Specifies the maximum amount of data that may be transmitted before the
Damien Millerddfddf12006-01-31 21:39:03 +1100760session key is renegotiated.
Darren Tucker62388b22006-01-20 11:31:47 +1100761The argument is the number of bytes, with an optional suffix of
Damien Millerddfddf12006-01-31 21:39:03 +1100762.Sq K ,
763.Sq M ,
Darren Tucker62388b22006-01-20 11:31:47 +1100764or
Damien Millerddfddf12006-01-31 21:39:03 +1100765.Sq G
Darren Tucker62388b22006-01-20 11:31:47 +1100766to indicate Kilobytes, Megabytes, or Gigabytes, respectively.
767The default is between
Damien Miller45ee2b92006-03-15 11:56:18 +1100768.Sq 1G
Darren Tucker62388b22006-01-20 11:31:47 +1100769and
Damien Miller45ee2b92006-03-15 11:56:18 +1100770.Sq 4G ,
Darren Tucker62388b22006-01-20 11:31:47 +1100771depending on the cipher.
Damien Millerddfddf12006-01-31 21:39:03 +1100772This option applies to protocol version 2 only.
Ben Lindstrom9f049032002-06-21 00:59:05 +0000773.It Cm RemoteForward
Damien Millere9d001e2006-01-14 10:10:17 +1100774Specifies that a TCP port on the remote machine be forwarded over
Ben Lindstrom9f049032002-06-21 00:59:05 +0000775the secure channel to the specified host and port from the local machine.
Darren Tucker5ede2ad2005-03-31 21:31:10 +1000776The first argument must be
Damien Millerf91ee4c2005-03-01 21:24:33 +1100777.Sm off
Darren Tucker5ede2ad2005-03-31 21:31:10 +1000778.Oo Ar bind_address : Oc Ar port
Damien Millerf91ee4c2005-03-01 21:24:33 +1100779.Sm on
Darren Tucker5ede2ad2005-03-31 21:31:10 +1000780and the second argument must be
781.Ar host : Ns Ar hostport .
782IPv6 addresses can be specified by enclosing addresses in square brackets
783or by using an alternative syntax:
784.Oo Ar bind_address Ns / Oc Ns Ar port
785and
786.Ar host Ns / Ns Ar hostport .
Ben Lindstrom9f049032002-06-21 00:59:05 +0000787Multiple forwardings may be specified, and additional
788forwardings can be given on the command line.
789Only the superuser can forward privileged ports.
Damien Millerf91ee4c2005-03-01 21:24:33 +1100790.Pp
791If the
792.Ar bind_address
793is not specified, the default is to only bind to loopback addresses.
794If the
795.Ar bind_address
796is
797.Ql *
798or an empty string, then the forwarding is requested to listen on all
799interfaces.
800Specifying a remote
801.Ar bind_address
Damien Millerf8c55462005-03-02 12:03:05 +1100802will only succeed if the server's
803.Cm GatewayPorts
Damien Millerf91ee4c2005-03-01 21:24:33 +1100804option is enabled (see
Damien Millerf8c55462005-03-02 12:03:05 +1100805.Xr sshd_config 5 ) .
Ben Lindstrom9f049032002-06-21 00:59:05 +0000806.It Cm RhostsRSAAuthentication
807Specifies whether to try rhosts based authentication with RSA host
808authentication.
809The argument must be
810.Dq yes
811or
812.Dq no .
813The default is
814.Dq no .
815This option applies to protocol version 1 only and requires
Damien Miller45ee2b92006-03-15 11:56:18 +1100816.Xr ssh 1
Ben Lindstrom9f049032002-06-21 00:59:05 +0000817to be setuid root.
818.It Cm RSAAuthentication
819Specifies whether to try RSA authentication.
820The argument to this keyword must be
821.Dq yes
822or
823.Dq no .
824RSA authentication will only be
825attempted if the identity file exists, or an authentication agent is
826running.
827The default is
828.Dq yes .
829Note that this option applies to protocol version 1 only.
Darren Tucker46bc0752004-05-02 22:11:30 +1000830.It Cm SendEnv
831Specifies what variables from the local
832.Xr environ 7
833should be sent to the server.
Damien Miller45ee2b92006-03-15 11:56:18 +1100834Note that environment passing is only supported for protocol 2.
835The server must also support it, and the server must be configured to
Darren Tucker1e0c9bf2004-05-02 22:12:48 +1000836accept these environment variables.
Darren Tucker46bc0752004-05-02 22:11:30 +1000837Refer to
838.Cm AcceptEnv
839in
840.Xr sshd_config 5
841for how to configure the server.
Damien Miller6def5512006-03-15 11:54:05 +1100842Variables are specified by name, which may contain wildcard characters.
Darren Tucker1e0c9bf2004-05-02 22:12:48 +1000843Multiple environment variables may be separated by whitespace or spread
Darren Tucker46bc0752004-05-02 22:11:30 +1000844across multiple
845.Cm SendEnv
846directives.
847The default is not to send any environment variables.
Damien Millerf54a4b92006-03-15 11:54:36 +1100848.Pp
849See
850.Sx PATTERNS
851for more information on patterns.
Damien Miller509b0102003-12-17 16:33:10 +1100852.It Cm ServerAliveCountMax
Damien Millerb7977702006-01-03 18:47:31 +1100853Sets the number of server alive messages (see below) which may be
Damien Miller509b0102003-12-17 16:33:10 +1100854sent without
Damien Miller45ee2b92006-03-15 11:56:18 +1100855.Xr ssh 1
Damien Miller509b0102003-12-17 16:33:10 +1100856receiving any messages back from the server.
857If this threshold is reached while server alive messages are being sent,
Damien Miller45ee2b92006-03-15 11:56:18 +1100858ssh will disconnect from the server, terminating the session.
Damien Miller509b0102003-12-17 16:33:10 +1100859It is important to note that the use of server alive messages is very
860different from
861.Cm TCPKeepAlive
862(below).
863The server alive messages are sent through the encrypted channel
864and therefore will not be spoofable.
865The TCP keepalive option enabled by
866.Cm TCPKeepAlive
867is spoofable.
868The server alive mechanism is valuable when the client or
869server depend on knowing when a connection has become inactive.
870.Pp
871The default value is 3.
872If, for example,
873.Cm ServerAliveInterval
Damien Miller45ee2b92006-03-15 11:56:18 +1100874(see below) is set to 15 and
Damien Miller509b0102003-12-17 16:33:10 +1100875.Cm ServerAliveCountMax
Damien Miller45ee2b92006-03-15 11:56:18 +1100876is left at the default, if the server becomes unresponsive,
877ssh will disconnect after approximately 45 seconds.
Damien Millercc3e8ba2006-03-15 12:06:55 +1100878This option applies to protocol version 2 only.
Damien Miller957d4e42005-12-13 19:30:45 +1100879.It Cm ServerAliveInterval
880Sets a timeout interval in seconds after which if no data has been received
881from the server,
Damien Miller45ee2b92006-03-15 11:56:18 +1100882.Xr ssh 1
Damien Miller957d4e42005-12-13 19:30:45 +1100883will send a message through the encrypted
884channel to request a response from the server.
885The default
886is 0, indicating that these messages will not be sent to the server.
887This option applies to protocol version 2 only.
Ben Lindstrom9f049032002-06-21 00:59:05 +0000888.It Cm SmartcardDevice
Damien Millerfbf486b2003-05-23 18:44:23 +1000889Specifies which smartcard device to use.
890The argument to this keyword is the device
Damien Miller45ee2b92006-03-15 11:56:18 +1100891.Xr ssh 1
Ben Lindstrom9f049032002-06-21 00:59:05 +0000892should use to communicate with a smartcard used for storing the user's
Damien Millerfbf486b2003-05-23 18:44:23 +1000893private RSA key.
894By default, no device is specified and smartcard support is not activated.
Ben Lindstrom9f049032002-06-21 00:59:05 +0000895.It Cm StrictHostKeyChecking
896If this flag is set to
897.Dq yes ,
Damien Miller45ee2b92006-03-15 11:56:18 +1100898.Xr ssh 1
Ben Lindstrom9f049032002-06-21 00:59:05 +0000899will never automatically add host keys to the
Damien Miller167ea5d2005-05-26 12:04:02 +1000900.Pa ~/.ssh/known_hosts
Ben Lindstrom9f049032002-06-21 00:59:05 +0000901file, and refuses to connect to hosts whose host key has changed.
902This provides maximum protection against trojan horse attacks,
Damien Miller45ee2b92006-03-15 11:56:18 +1100903though it can be annoying when the
Ben Lindstrom9f049032002-06-21 00:59:05 +0000904.Pa /etc/ssh/ssh_known_hosts
Damien Miller45ee2b92006-03-15 11:56:18 +1100905file is poorly maintained or when connections to new hosts are
Ben Lindstrom9f049032002-06-21 00:59:05 +0000906frequently made.
907This option forces the user to manually
908add all new hosts.
909If this flag is set to
910.Dq no ,
Damien Miller45ee2b92006-03-15 11:56:18 +1100911ssh will automatically add new host keys to the
Ben Lindstrom9f049032002-06-21 00:59:05 +0000912user known hosts files.
913If this flag is set to
914.Dq ask ,
915new host keys
916will be added to the user known host files only after the user
917has confirmed that is what they really want to do, and
Damien Miller45ee2b92006-03-15 11:56:18 +1100918ssh will refuse to connect to hosts whose host key has changed.
Ben Lindstrom9f049032002-06-21 00:59:05 +0000919The host keys of
920known hosts will be verified automatically in all cases.
921The argument must be
922.Dq yes ,
Damien Miller45ee2b92006-03-15 11:56:18 +1100923.Dq no ,
Ben Lindstrom9f049032002-06-21 00:59:05 +0000924or
925.Dq ask .
926The default is
927.Dq ask .
Damien Miller12c150e2003-12-17 16:31:10 +1100928.It Cm TCPKeepAlive
929Specifies whether the system should send TCP keepalive messages to the
930other side.
931If they are sent, death of the connection or crash of one
932of the machines will be properly noticed.
933However, this means that
934connections will die if the route is down temporarily, and some people
935find it annoying.
936.Pp
937The default is
938.Dq yes
939(to send TCP keepalive messages), and the client will notice
940if the network goes down or the remote host dies.
941This is important in scripts, and many users want it too.
942.Pp
943To disable TCP keepalive messages, the value should be set to
944.Dq no .
Damien Millerd27b9472005-12-13 19:29:02 +1100945.It Cm Tunnel
Damien Miller991dba42006-07-10 20:16:27 +1000946Request
Damien Millerd27b9472005-12-13 19:29:02 +1100947.Xr tun 4
Damien Miller7746c392005-12-13 19:33:37 +1100948device forwarding between the client and the server.
Damien Millerd27b9472005-12-13 19:29:02 +1100949The argument must be
Damien Miller7b58e802005-12-13 19:33:19 +1100950.Dq yes ,
Damien Miller991dba42006-07-10 20:16:27 +1000951.Dq point-to-point
952(layer 3),
953.Dq ethernet
954(layer 2),
Damien Millerd27b9472005-12-13 19:29:02 +1100955or
956.Dq no .
Damien Miller991dba42006-07-10 20:16:27 +1000957Specifying
958.Dq yes
959requests the default tunnel mode, which is
960.Dq point-to-point .
Damien Millerd27b9472005-12-13 19:29:02 +1100961The default is
962.Dq no .
963.It Cm TunnelDevice
Damien Miller991dba42006-07-10 20:16:27 +1000964Specifies the
Damien Millerd27b9472005-12-13 19:29:02 +1100965.Xr tun 4
Damien Miller991dba42006-07-10 20:16:27 +1000966devices to open on the client
967.Pq Ar local_tun
968and the server
969.Pq Ar remote_tun .
970.Pp
971The argument must be
972.Sm off
973.Ar local_tun Op : Ar remote_tun .
974.Sm on
975The devices may be specified by numerical ID or the keyword
976.Dq any ,
977which uses the next available tunnel device.
978If
979.Ar remote_tun
980is not specified, it defaults to
981.Dq any .
982The default is
983.Dq any:any .
Damien Millere8cd7412005-12-24 14:55:47 +1100984.It Cm UsePrivilegedPort
985Specifies whether to use a privileged port for outgoing connections.
986The argument must be
987.Dq yes
988or
989.Dq no .
990The default is
991.Dq no .
992If set to
Damien Miller45ee2b92006-03-15 11:56:18 +1100993.Dq yes ,
994.Xr ssh 1
Damien Millere8cd7412005-12-24 14:55:47 +1100995must be setuid root.
996Note that this option must be set to
997.Dq yes
998for
999.Cm RhostsRSAAuthentication
1000with older servers.
Ben Lindstrom9f049032002-06-21 00:59:05 +00001001.It Cm User
1002Specifies the user to log in as.
1003This can be useful when a different user name is used on different machines.
1004This saves the trouble of
1005having to remember to give the user name on the command line.
1006.It Cm UserKnownHostsFile
1007Specifies a file to use for the user
1008host key database instead of
Damien Miller167ea5d2005-05-26 12:04:02 +10001009.Pa ~/.ssh/known_hosts .
Damien Miller37876e92003-05-15 10:19:46 +10001010.It Cm VerifyHostKeyDNS
1011Specifies whether to verify the remote key using DNS and SSHFP resource
1012records.
Damien Miller150b5572003-11-17 21:19:29 +11001013If this option is set to
1014.Dq yes ,
Damien Millerfe448472003-11-17 21:19:49 +11001015the client will implicitly trust keys that match a secure fingerprint
Damien Miller150b5572003-11-17 21:19:29 +11001016from DNS.
1017Insecure fingerprints will be handled as if this option was set to
1018.Dq ask .
1019If this option is set to
1020.Dq ask ,
1021information on fingerprint match will be displayed, but the user will still
1022need to confirm new host keys according to the
1023.Cm StrictHostKeyChecking
1024option.
1025The argument must be
1026.Dq yes ,
Damien Miller45ee2b92006-03-15 11:56:18 +11001027.Dq no ,
Damien Millerfe448472003-11-17 21:19:49 +11001028or
1029.Dq ask .
Damien Miller37876e92003-05-15 10:19:46 +10001030The default is
1031.Dq no .
Damien Millereacbb4f2003-06-02 19:10:41 +10001032Note that this option applies to protocol version 2 only.
Damien Miller45ee2b92006-03-15 11:56:18 +11001033.Pp
1034See also
1035.Sx VERIFYING HOST KEYS
1036in
1037.Xr ssh 1 .
Ben Lindstrom9f049032002-06-21 00:59:05 +00001038.It Cm XAuthLocation
Damien Miller05913ba2002-09-04 16:51:03 +10001039Specifies the full pathname of the
Ben Lindstrom9f049032002-06-21 00:59:05 +00001040.Xr xauth 1
1041program.
1042The default is
1043.Pa /usr/X11R6/bin/xauth .
1044.El
Damien Millerb5282c22006-03-15 11:59:08 +11001045.Sh PATTERNS
1046A
1047.Em pattern
1048consists of zero or more non-whitespace characters,
1049.Sq *
1050(a wildcard that matches zero or more characters),
1051or
1052.Sq ?\&
1053(a wildcard that matches exactly one character).
1054For example, to specify a set of declarations for any host in the
1055.Dq .co.uk
1056set of domains,
1057the following pattern could be used:
1058.Pp
1059.Dl Host *.co.uk
1060.Pp
1061The following pattern
1062would match any host in the 192.168.0.[0-9] network range:
1063.Pp
1064.Dl Host 192.168.0.?
1065.Pp
1066A
1067.Em pattern-list
1068is a comma-separated list of patterns.
1069Patterns within pattern-lists may be negated
1070by preceding them with an exclamation mark
1071.Pq Sq !\& .
1072For example,
1073to allow a key to be used from anywhere within an organisation
1074except from the
1075.Dq dialup
1076pool,
1077the following entry (in authorized_keys) could be used:
1078.Pp
1079.Dl from=\&"!*.dialup.example.com,*.example.com\&"
Ben Lindstrom9f049032002-06-21 00:59:05 +00001080.Sh FILES
1081.Bl -tag -width Ds
Damien Miller167ea5d2005-05-26 12:04:02 +10001082.It Pa ~/.ssh/config
Ben Lindstrom9f049032002-06-21 00:59:05 +00001083This is the per-user configuration file.
1084The format of this file is described above.
Damien Miller45ee2b92006-03-15 11:56:18 +11001085This file is used by the SSH client.
Damien Millerc970cb92004-04-20 20:12:53 +10001086Because of the potential for abuse, this file must have strict permissions:
1087read/write for the user, and not accessible by others.
Ben Lindstrom9f049032002-06-21 00:59:05 +00001088.It Pa /etc/ssh/ssh_config
1089Systemwide configuration file.
1090This file provides defaults for those
1091values that are not specified in the user's configuration file, and
1092for those users who do not have a configuration file.
1093This file must be world-readable.
1094.El
Damien Millerf1ce5052003-06-11 22:04:39 +10001095.Sh SEE ALSO
1096.Xr ssh 1
Ben Lindstrom9f049032002-06-21 00:59:05 +00001097.Sh AUTHORS
1098OpenSSH is a derivative of the original and free
1099ssh 1.2.12 release by Tatu Ylonen.
1100Aaron Campbell, Bob Beck, Markus Friedl, Niels Provos,
1101Theo de Raadt and Dug Song
1102removed many bugs, re-added newer features and
1103created OpenSSH.
1104Markus Friedl contributed the support for SSH
1105protocol versions 1.5 and 2.0.