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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.\"
Darren Tuckerdcc1ab52008-06-13 04:44:25 +100037.\" $OpenBSD: ssh_config.5,v 1.108 2008/06/11 23:03:56 grunk Exp $
Darren Tucker9c16ac92008-06-13 04:40:35 +100038.Dd $Mdocdate: June 11 2008 $
Ben Lindstrom9f049032002-06-21 00:59:05 +000039.Dt SSH_CONFIG 5
40.Os
41.Sh NAME
42.Nm ssh_config
43.Nd OpenSSH SSH client configuration files
44.Sh SYNOPSIS
Darren Tuckerbf6b3282007-02-19 22:08:17 +110045.Nm ~/.ssh/config
46.Nm /etc/ssh/ssh_config
Ben Lindstrom9f049032002-06-21 00:59:05 +000047.Sh DESCRIPTION
Damien Miller45ee2b92006-03-15 11:56:18 +110048.Xr ssh 1
Ben Lindstrom9f049032002-06-21 00:59:05 +000049obtains configuration data from the following sources in
50the following order:
Damien Miller5c853b52006-03-15 11:37:02 +110051.Pp
Ben Lindstrom479b4762002-08-20 19:04:51 +000052.Bl -enum -offset indent -compact
53.It
54command-line options
55.It
56user's configuration file
Damien Miller167ea5d2005-05-26 12:04:02 +100057.Pq Pa ~/.ssh/config
Ben Lindstrom479b4762002-08-20 19:04:51 +000058.It
59system-wide configuration file
60.Pq Pa /etc/ssh/ssh_config
61.El
Ben Lindstrom9f049032002-06-21 00:59:05 +000062.Pp
63For each parameter, the first obtained value
64will be used.
Darren Tucker43d8e282005-02-09 09:51:08 +110065The configuration files contain sections separated by
Ben Lindstrom9f049032002-06-21 00:59:05 +000066.Dq Host
67specifications, and that section is only applied for hosts that
68match one of the patterns given in the specification.
69The matched host name is the one given on the command line.
70.Pp
71Since the first obtained value for each parameter is used, more
72host-specific declarations should be given near the beginning of the
73file, and general defaults at the end.
74.Pp
75The configuration file has the following format:
76.Pp
77Empty lines and lines starting with
78.Ql #
79are comments.
Ben Lindstrom9f049032002-06-21 00:59:05 +000080Otherwise a line is of the format
81.Dq keyword arguments .
82Configuration options may be separated by whitespace or
83optional whitespace and exactly one
84.Ql = ;
85the latter format is useful to avoid the need to quote whitespace
86when specifying configuration options using the
87.Nm ssh ,
Damien Miller4aea9742006-03-15 11:59:39 +110088.Nm scp ,
Ben Lindstrom9f049032002-06-21 00:59:05 +000089and
90.Nm sftp
91.Fl o
92option.
Damien Miller306d1182006-03-15 12:05:59 +110093Arguments may optionally be enclosed in double quotes
94.Pq \&"
95in order to represent arguments containing spaces.
Ben Lindstrom9f049032002-06-21 00:59:05 +000096.Pp
97The possible
98keywords and their meanings are as follows (note that
99keywords are case-insensitive and arguments are case-sensitive):
100.Bl -tag -width Ds
101.It Cm Host
102Restricts the following declarations (up to the next
103.Cm Host
104keyword) to be only for those hosts that match one of the patterns
105given after the keyword.
Darren Tuckerc9807e82008-06-11 09:33:01 +1000106If more than one pattern is provided, they should be separated by whitepsace.
Ben Lindstrom9f049032002-06-21 00:59:05 +0000107A single
Damien Miller208f1ed2006-03-15 11:56:03 +1100108.Ql *
Ben Lindstrom9f049032002-06-21 00:59:05 +0000109as a pattern can be used to provide global
110defaults for all hosts.
111The host is the
112.Ar hostname
Damien Miller208f1ed2006-03-15 11:56:03 +1100113argument given on the command line (i.e. the name is not converted to
Ben Lindstrom9f049032002-06-21 00:59:05 +0000114a canonicalized host name before matching).
Damien Millerf54a4b92006-03-15 11:54:36 +1100115.Pp
116See
117.Sx PATTERNS
118for more information on patterns.
Damien Miller20a8f972003-05-18 20:50:30 +1000119.It Cm AddressFamily
Damien Millerfbf486b2003-05-23 18:44:23 +1000120Specifies which address family to use when connecting.
121Valid arguments are
Damien Miller20a8f972003-05-18 20:50:30 +1000122.Dq any ,
123.Dq inet
Damien Miller45ee2b92006-03-15 11:56:18 +1100124(use IPv4 only), or
Damien Miller20a8f972003-05-18 20:50:30 +1000125.Dq inet6
Darren Tucker79a7acf2005-02-09 09:48:57 +1100126(use IPv6 only).
Ben Lindstrom9f049032002-06-21 00:59:05 +0000127.It Cm BatchMode
128If set to
129.Dq yes ,
130passphrase/password querying will be disabled.
131This option is useful in scripts and other batch jobs where no user
132is present to supply the password.
133The argument must be
134.Dq yes
135or
136.Dq no .
137The default is
138.Dq no .
139.It Cm BindAddress
Darren Tucker89f4d472005-07-14 17:06:21 +1000140Use the specified address on the local machine as the source address of
Darren Tucker6c71d202005-07-14 17:06:50 +1000141the connection.
142Only useful on systems with more than one address.
Ben Lindstrom9f049032002-06-21 00:59:05 +0000143Note that this option does not work if
144.Cm UsePrivilegedPort
145is set to
146.Dq yes .
147.It Cm ChallengeResponseAuthentication
Damien Miller1faa7132006-03-15 11:55:31 +1100148Specifies whether to use challenge-response authentication.
Ben Lindstrom9f049032002-06-21 00:59:05 +0000149The argument to this keyword must be
150.Dq yes
151or
152.Dq no .
153The default is
154.Dq yes .
155.It Cm CheckHostIP
156If this flag is set to
157.Dq yes ,
Damien Miller45ee2b92006-03-15 11:56:18 +1100158.Xr ssh 1
159will additionally check the host IP address in the
Ben Lindstrom9f049032002-06-21 00:59:05 +0000160.Pa known_hosts
161file.
162This allows ssh to detect if a host key changed due to DNS spoofing.
163If the option is set to
Darren Tucker9c16ac92008-06-13 04:40:35 +1000164.Dq fingerprint ,
Darren Tuckerdcc1ab52008-06-13 04:44:25 +1000165not only the host IP address will be checked, but also a fingerprint
166along with an ASCII art
Darren Tucker9c16ac92008-06-13 04:40:35 +1000167representation of the key will be printed.
168If the option is set to
Ben Lindstrom9f049032002-06-21 00:59:05 +0000169.Dq no ,
170the check will not be executed.
171The default is
172.Dq yes .
173.It Cm Cipher
174Specifies the cipher to use for encrypting the session
175in protocol version 1.
176Currently,
177.Dq blowfish ,
178.Dq 3des ,
179and
180.Dq des
181are supported.
182.Ar des
183is only supported in the
Damien Miller45ee2b92006-03-15 11:56:18 +1100184.Xr ssh 1
Ben Lindstrom9f049032002-06-21 00:59:05 +0000185client for interoperability with legacy protocol 1 implementations
186that do not support the
187.Ar 3des
Damien Miller495dca32003-04-01 21:42:14 +1000188cipher.
189Its use is strongly discouraged due to cryptographic weaknesses.
Ben Lindstrom9f049032002-06-21 00:59:05 +0000190The default is
191.Dq 3des .
192.It Cm Ciphers
193Specifies the ciphers allowed for protocol version 2
194in order of preference.
195Multiple ciphers must be comma-separated.
Damien Miller05202ff2004-06-15 10:30:39 +1000196The supported ciphers are
197.Dq 3des-cbc ,
198.Dq aes128-cbc ,
199.Dq aes192-cbc ,
200.Dq aes256-cbc ,
201.Dq aes128-ctr ,
202.Dq aes192-ctr ,
203.Dq aes256-ctr ,
Damien Miller3710f272005-05-26 12:19:17 +1000204.Dq arcfour128 ,
205.Dq arcfour256 ,
Damien Miller05202ff2004-06-15 10:30:39 +1000206.Dq arcfour ,
207.Dq blowfish-cbc ,
208and
209.Dq cast128-cbc .
Damien Miller45ee2b92006-03-15 11:56:18 +1100210The default is:
211.Bd -literal -offset 3n
212aes128-cbc,3des-cbc,blowfish-cbc,cast128-cbc,arcfour128,
213arcfour256,arcfour,aes192-cbc,aes256-cbc,aes128-ctr,
214aes192-ctr,aes256-ctr
Ben Lindstrom9f049032002-06-21 00:59:05 +0000215.Ed
216.It Cm ClearAllForwardings
Damien Miller45ee2b92006-03-15 11:56:18 +1100217Specifies that all local, remote, and dynamic port forwardings
Ben Lindstrom9f049032002-06-21 00:59:05 +0000218specified in the configuration files or on the command line be
Damien Miller495dca32003-04-01 21:42:14 +1000219cleared.
220This option is primarily useful when used from the
Damien Miller45ee2b92006-03-15 11:56:18 +1100221.Xr ssh 1
Ben Lindstrom9f049032002-06-21 00:59:05 +0000222command line to clear port forwardings set in
223configuration files, and is automatically set by
224.Xr scp 1
225and
226.Xr sftp 1 .
227The argument must be
228.Dq yes
229or
230.Dq no .
231The default is
232.Dq no .
233.It Cm Compression
234Specifies whether to use compression.
235The argument must be
236.Dq yes
237or
238.Dq no .
239The default is
240.Dq no .
241.It Cm CompressionLevel
242Specifies the compression level to use if compression is enabled.
243The argument must be an integer from 1 (fast) to 9 (slow, best).
244The default level is 6, which is good for most applications.
245The meaning of the values is the same as in
246.Xr gzip 1 .
247Note that this option applies to protocol version 1 only.
248.It Cm ConnectionAttempts
249Specifies the number of tries (one per second) to make before exiting.
250The argument must be an integer.
251This may be useful in scripts if the connection sometimes fails.
252The default is 1.
Damien Millerb78d5eb2003-05-16 11:39:04 +1000253.It Cm ConnectTimeout
Damien Miller45ee2b92006-03-15 11:56:18 +1100254Specifies the timeout (in seconds) used when connecting to the
255SSH server, instead of using the default system TCP timeout.
Damien Millerfbf486b2003-05-23 18:44:23 +1000256This value is used only when the target is down or really unreachable,
257not when it refuses the connection.
Damien Miller0e220db2004-06-15 10:34:08 +1000258.It Cm ControlMaster
259Enables the sharing of multiple sessions over a single network connection.
260When set to
Damien Miller45ee2b92006-03-15 11:56:18 +1100261.Dq yes ,
262.Xr ssh 1
Damien Miller0e220db2004-06-15 10:34:08 +1000263will listen for connections on a control socket specified using the
264.Cm ControlPath
265argument.
266Additional sessions can connect to this socket using the same
267.Cm ControlPath
268with
269.Cm ControlMaster
270set to
271.Dq no
Damien Miller2234bac2004-06-30 22:38:52 +1000272(the default).
Damien Miller713de762005-11-05 15:13:49 +1100273These sessions will try to reuse the master instance's network connection
Damien Millerb3bfbb72005-11-05 15:11:48 +1100274rather than initiating new ones, but will fall back to connecting normally
275if the control socket does not exist, or is not listening.
276.Pp
Damien Miller23f07702004-06-18 01:19:03 +1000277Setting this to
278.Dq ask
Damien Miller45ee2b92006-03-15 11:56:18 +1100279will cause ssh
Damien Miller23f07702004-06-18 01:19:03 +1000280to listen for control connections, but require confirmation using the
281.Ev SSH_ASKPASS
282program before they are accepted (see
283.Xr ssh-add 1
Damien Miller2234bac2004-06-30 22:38:52 +1000284for details).
Damien Millerdadfd4d2005-05-26 12:07:13 +1000285If the
286.Cm ControlPath
Damien Miller45ee2b92006-03-15 11:56:18 +1100287cannot be opened,
288ssh will continue without connecting to a master instance.
Damien Millerd14b1e72005-06-16 13:19:41 +1000289.Pp
Damien Miller13390022005-07-06 09:44:19 +1000290X11 and
Damien Millerfd94fba2005-07-06 09:44:59 +1000291.Xr ssh-agent 1
Damien Miller13390022005-07-06 09:44:19 +1000292forwarding is supported over these multiplexed connections, however the
Darren Tucker63551872005-12-20 16:14:15 +1100293display and agent forwarded will be the one belonging to the master
Damien Millerfd94fba2005-07-06 09:44:59 +1000294connection i.e. it is not possible to forward multiple displays or agents.
Damien Miller13390022005-07-06 09:44:19 +1000295.Pp
Damien Millerd14b1e72005-06-16 13:19:41 +1000296Two additional options allow for opportunistic multiplexing: try to use a
297master connection but fall back to creating a new one if one does not already
298exist.
299These options are:
300.Dq auto
301and
302.Dq autoask .
303The latter requires confirmation like the
304.Dq ask
305option.
Damien Miller0e220db2004-06-15 10:34:08 +1000306.It Cm ControlPath
Damien Miller6476cad2005-06-16 13:18:34 +1000307Specify the path to the control socket used for connection sharing as described
308in the
Damien Miller0e220db2004-06-15 10:34:08 +1000309.Cm ControlMaster
Damien Miller8f74c8f2005-06-26 08:56:03 +1000310section above or the string
311.Dq none
312to disable connection sharing.
Damien Miller6476cad2005-06-16 13:18:34 +1000313In the path,
Damien Miller3ec54c72006-03-15 11:30:13 +1100314.Ql %l
315will be substituted by the local host name,
Damien Miller6476cad2005-06-16 13:18:34 +1000316.Ql %h
317will be substituted by the target host name,
318.Ql %p
Damien Miller45ee2b92006-03-15 11:56:18 +1100319the port, and
Damien Miller6476cad2005-06-16 13:18:34 +1000320.Ql %r
321by the remote login username.
Damien Millerd14b1e72005-06-16 13:19:41 +1000322It is recommended that any
323.Cm ControlPath
324used for opportunistic connection sharing include
Damien Miller20c2ec42006-03-15 11:31:01 +1100325at least %h, %p, and %r.
Damien Millerd14b1e72005-06-16 13:19:41 +1000326This ensures that shared connections are uniquely identified.
Damien Miller2234bac2004-06-30 22:38:52 +1000327.It Cm DynamicForward
Damien Millere9d001e2006-01-14 10:10:17 +1100328Specifies that a TCP port on the local machine be forwarded
Damien Miller2234bac2004-06-30 22:38:52 +1000329over the secure channel, and the application
330protocol is then used to determine where to connect to from the
331remote machine.
Darren Tuckerc8d64212005-10-03 18:13:42 +1000332.Pp
333The argument must be
334.Sm off
335.Oo Ar bind_address : Oc Ar port .
336.Sm on
337IPv6 addresses can be specified by enclosing addresses in square brackets or
338by using an alternative syntax:
339.Oo Ar bind_address Ns / Oc Ns Ar port .
340By default, the local port is bound in accordance with the
341.Cm GatewayPorts
342setting.
343However, an explicit
344.Ar bind_address
345may be used to bind the connection to a specific address.
346The
347.Ar bind_address
348of
349.Dq localhost
350indicates that the listening port be bound for local use only, while an
351empty address or
352.Sq *
353indicates that the port should be available from all interfaces.
354.Pp
Damien Miller2234bac2004-06-30 22:38:52 +1000355Currently the SOCKS4 and SOCKS5 protocols are supported, and
Damien Miller45ee2b92006-03-15 11:56:18 +1100356.Xr ssh 1
Damien Miller2234bac2004-06-30 22:38:52 +1000357will act as a SOCKS server.
358Multiple forwardings may be specified, and
359additional forwardings can be given on the command line.
360Only the superuser can forward privileged ports.
Darren Tucker674f71d2003-06-28 12:33:12 +1000361.It Cm EnableSSHKeysign
362Setting this option to
363.Dq yes
364in the global client configuration file
365.Pa /etc/ssh/ssh_config
366enables the use of the helper program
367.Xr ssh-keysign 8
368during
369.Cm HostbasedAuthentication .
370The argument must be
371.Dq yes
372or
373.Dq no .
374The default is
375.Dq no .
Darren Tuckerf132c672003-10-15 15:58:18 +1000376This option should be placed in the non-hostspecific section.
Darren Tucker674f71d2003-06-28 12:33:12 +1000377See
378.Xr ssh-keysign 8
379for more information.
Ben Lindstrom9f049032002-06-21 00:59:05 +0000380.It Cm EscapeChar
381Sets the escape character (default:
382.Ql ~ ) .
383The escape character can also
384be set on the command line.
385The argument should be a single character,
386.Ql ^
387followed by a letter, or
388.Dq none
389to disable the escape
390character entirely (making the connection transparent for binary
391data).
Darren Tuckere7d4b192006-07-12 22:17:10 +1000392.It Cm ExitOnForwardFailure
393Specifies whether
394.Xr ssh 1
395should terminate the connection if it cannot set up all requested
Darren Tuckerfc5d1882007-08-15 22:20:22 +1000396dynamic, tunnel, local, and remote port forwardings.
Darren Tuckere7d4b192006-07-12 22:17:10 +1000397The argument must be
398.Dq yes
399or
400.Dq no .
401The default is
402.Dq no .
Ben Lindstrom9f049032002-06-21 00:59:05 +0000403.It Cm ForwardAgent
404Specifies whether the connection to the authentication agent (if any)
405will be forwarded to the remote machine.
406The argument must be
407.Dq yes
408or
409.Dq no .
410The default is
411.Dq no .
Damien Milleraf653042002-09-04 16:40:37 +1000412.Pp
Damien Miller495dca32003-04-01 21:42:14 +1000413Agent forwarding should be enabled with caution.
414Users with the ability to bypass file permissions on the remote host
415(for the agent's Unix-domain socket)
416can access the local agent through the forwarded connection.
417An attacker cannot obtain key material from the agent,
Damien Milleraf653042002-09-04 16:40:37 +1000418however they can perform operations on the keys that enable them to
419authenticate using the identities loaded into the agent.
Ben Lindstrom9f049032002-06-21 00:59:05 +0000420.It Cm ForwardX11
421Specifies whether X11 connections will be automatically redirected
422over the secure channel and
423.Ev DISPLAY
424set.
425The argument must be
426.Dq yes
427or
428.Dq no .
429The default is
430.Dq no .
Damien Milleraf653042002-09-04 16:40:37 +1000431.Pp
Damien Miller495dca32003-04-01 21:42:14 +1000432X11 forwarding should be enabled with caution.
433Users with the ability to bypass file permissions on the remote host
Darren Tucker0a118da2003-10-15 15:54:32 +1000434(for the user's X11 authorization database)
Damien Miller495dca32003-04-01 21:42:14 +1000435can access the local X11 display through the forwarded connection.
Darren Tucker0a118da2003-10-15 15:54:32 +1000436An attacker may then be able to perform activities such as keystroke monitoring
437if the
438.Cm ForwardX11Trusted
439option is also enabled.
440.It Cm ForwardX11Trusted
Darren Tuckerdcf6ec42004-05-13 13:03:56 +1000441If this option is set to
Damien Miller45ee2b92006-03-15 11:56:18 +1100442.Dq yes ,
443remote X11 clients will have full access to the original X11 display.
Damien Miller1717fd42005-03-01 21:17:31 +1100444.Pp
Darren Tucker0a118da2003-10-15 15:54:32 +1000445If this option is set to
Damien Miller45ee2b92006-03-15 11:56:18 +1100446.Dq no ,
447remote X11 clients will be considered untrusted and prevented
Darren Tucker0a118da2003-10-15 15:54:32 +1000448from stealing or tampering with data belonging to trusted X11
449clients.
Damien Miller1717fd42005-03-01 21:17:31 +1100450Furthermore, the
451.Xr xauth 1
452token used for the session will be set to expire after 20 minutes.
453Remote clients will be refused access after this time.
Darren Tucker0a118da2003-10-15 15:54:32 +1000454.Pp
455The default is
456.Dq no .
457.Pp
458See the X11 SECURITY extension specification for full details on
459the restrictions imposed on untrusted clients.
Ben Lindstrom9f049032002-06-21 00:59:05 +0000460.It Cm GatewayPorts
461Specifies whether remote hosts are allowed to connect to local
462forwarded ports.
463By default,
Damien Miller45ee2b92006-03-15 11:56:18 +1100464.Xr ssh 1
Damien Miller495dca32003-04-01 21:42:14 +1000465binds local port forwardings to the loopback address.
466This prevents other remote hosts from connecting to forwarded ports.
Ben Lindstrom9f049032002-06-21 00:59:05 +0000467.Cm GatewayPorts
Damien Miller45ee2b92006-03-15 11:56:18 +1100468can be used to specify that ssh
Ben Lindstrom9f049032002-06-21 00:59:05 +0000469should bind local port forwardings to the wildcard address,
470thus allowing remote hosts to connect to forwarded ports.
471The argument must be
472.Dq yes
473or
474.Dq no .
475The default is
476.Dq no .
477.It Cm GlobalKnownHostsFile
478Specifies a file to use for the global
479host key database instead of
480.Pa /etc/ssh/ssh_known_hosts .
Darren Tucker0efd1552003-08-26 11:49:55 +1000481.It Cm GSSAPIAuthentication
Damien Millerbaafb982003-12-17 16:32:23 +1100482Specifies whether user authentication based on GSSAPI is allowed.
Damien Millerc2b98272003-09-03 12:13:30 +1000483The default is
Darren Tuckera044f472003-10-15 15:52:03 +1000484.Dq no .
Darren Tucker0efd1552003-08-26 11:49:55 +1000485Note that this option applies to protocol version 2 only.
486.It Cm GSSAPIDelegateCredentials
487Forward (delegate) credentials to the server.
488The default is
489.Dq no .
490Note that this option applies to protocol version 2 only.
Damien Millere1776152005-03-01 21:47:37 +1100491.It Cm HashKnownHosts
492Indicates that
Damien Miller45ee2b92006-03-15 11:56:18 +1100493.Xr ssh 1
Damien Millere1776152005-03-01 21:47:37 +1100494should hash host names and addresses when they are added to
Damien Miller167ea5d2005-05-26 12:04:02 +1000495.Pa ~/.ssh/known_hosts .
Damien Millere1776152005-03-01 21:47:37 +1100496These hashed names may be used normally by
Damien Miller45ee2b92006-03-15 11:56:18 +1100497.Xr ssh 1
Damien Millere1776152005-03-01 21:47:37 +1100498and
Damien Miller45ee2b92006-03-15 11:56:18 +1100499.Xr sshd 8 ,
Damien Millere1776152005-03-01 21:47:37 +1100500but they do not reveal identifying information should the file's contents
501be disclosed.
502The default is
503.Dq no .
Damien Miller858bb7d2006-08-05 11:34:51 +1000504Note that existing names and addresses in known hosts files
505will not be converted automatically,
506but may be manually hashed using
Damien Miller4b42d7f2005-03-01 21:48:35 +1100507.Xr ssh-keygen 1 .
Ben Lindstrom9f049032002-06-21 00:59:05 +0000508.It Cm HostbasedAuthentication
509Specifies whether to try rhosts based authentication with public key
510authentication.
511The argument must be
512.Dq yes
513or
514.Dq no .
515The default is
516.Dq no .
517This option applies to protocol version 2 only and
518is similar to
519.Cm RhostsRSAAuthentication .
520.It Cm HostKeyAlgorithms
521Specifies the protocol version 2 host key algorithms
522that the client wants to use in order of preference.
523The default for this option is:
524.Dq ssh-rsa,ssh-dss .
525.It Cm HostKeyAlias
526Specifies an alias that should be used instead of the
527real host name when looking up or saving the host key
528in the host key database files.
Damien Miller45ee2b92006-03-15 11:56:18 +1100529This option is useful for tunneling SSH connections
Ben Lindstrom9f049032002-06-21 00:59:05 +0000530or for multiple servers running on a single host.
531.It Cm HostName
532Specifies the real host name to log into.
533This can be used to specify nicknames or abbreviations for hosts.
Damien Miller45ee2b92006-03-15 11:56:18 +1100534The default is the name given on the command line.
Ben Lindstrom9f049032002-06-21 00:59:05 +0000535Numeric IP addresses are also permitted (both on the command line and in
536.Cm HostName
537specifications).
Damien Millerbd394c32004-03-08 23:12:36 +1100538.It Cm IdentitiesOnly
539Specifies that
Damien Miller45ee2b92006-03-15 11:56:18 +1100540.Xr ssh 1
Damien Millerbd394c32004-03-08 23:12:36 +1100541should only use the authentication identity files configured in the
Damien Miller1a812582004-04-20 20:13:32 +1000542.Nm
Damien Millerbd394c32004-03-08 23:12:36 +1100543files,
Damien Miller45ee2b92006-03-15 11:56:18 +1100544even if
545.Xr ssh-agent 1
Damien Millerbd394c32004-03-08 23:12:36 +1100546offers more identities.
547The argument to this keyword must be
548.Dq yes
549or
550.Dq no .
Damien Miller45ee2b92006-03-15 11:56:18 +1100551This option is intended for situations where ssh-agent
Damien Millerbd394c32004-03-08 23:12:36 +1100552offers many different identities.
553The default is
554.Dq no .
Damien Miller957d4e42005-12-13 19:30:45 +1100555.It Cm IdentityFile
556Specifies a file from which the user's RSA or DSA authentication identity
557is read.
558The default is
559.Pa ~/.ssh/identity
560for protocol version 1, and
561.Pa ~/.ssh/id_rsa
562and
563.Pa ~/.ssh/id_dsa
564for protocol version 2.
565Additionally, any identities represented by the authentication agent
566will be used for authentication.
Damien Miller6b1d53c2006-03-31 23:13:21 +1100567.Pp
Damien Miller957d4e42005-12-13 19:30:45 +1100568The file name may use the tilde
Damien Millerc6437cf2006-03-31 23:14:41 +1100569syntax to refer to a user's home directory or one of the following
Damien Miller6b1d53c2006-03-31 23:13:21 +1100570escape characters:
571.Ql %d
572(local user's home directory),
573.Ql %u
574(local user name),
575.Ql %l
576(local host name),
577.Ql %h
578(remote host name) or
Damien Millerdfc61832006-03-31 23:14:57 +1100579.Ql %r
Damien Miller6b1d53c2006-03-31 23:13:21 +1100580(remote user name).
581.Pp
Damien Miller957d4e42005-12-13 19:30:45 +1100582It is possible to have
583multiple identity files specified in configuration files; all these
584identities will be tried in sequence.
Damien Millercfb606c2007-10-26 14:24:48 +1000585.It Cm KbdInteractiveAuthentication
586Specifies whether to use keyboard-interactive authentication.
587The argument to this keyword must be
588.Dq yes
589or
590.Dq no .
591The default is
592.Dq yes .
Darren Tucker636ca902004-11-05 20:22:00 +1100593.It Cm KbdInteractiveDevices
594Specifies the list of methods to use in keyboard-interactive authentication.
595Multiple method names must be comma-separated.
596The default is to use the server specified list.
Damien Miller9cfbaec2006-03-15 11:57:55 +1100597The methods available vary depending on what the server supports.
598For an OpenSSH server,
599it may be zero or more of:
600.Dq bsdauth ,
601.Dq pam ,
602and
603.Dq skey .
Damien Millerd27b9472005-12-13 19:29:02 +1100604.It Cm LocalCommand
605Specifies a command to execute on the local machine after successfully
606connecting to the server.
607The command string extends to the end of the line, and is executed with
Darren Tucker63b31cb2007-12-02 23:09:30 +1100608the user's shell.
Damien Millerd27b9472005-12-13 19:29:02 +1100609This directive is ignored unless
610.Cm PermitLocalCommand
611has been enabled.
Ben Lindstrom9f049032002-06-21 00:59:05 +0000612.It Cm LocalForward
Damien Millere9d001e2006-01-14 10:10:17 +1100613Specifies that a TCP port on the local machine be forwarded over
Ben Lindstrom9f049032002-06-21 00:59:05 +0000614the secure channel to the specified host and port from the remote machine.
Darren Tucker5ede2ad2005-03-31 21:31:10 +1000615The first argument must be
Damien Millerf91ee4c2005-03-01 21:24:33 +1100616.Sm off
Darren Tucker5ede2ad2005-03-31 21:31:10 +1000617.Oo Ar bind_address : Oc Ar port
Damien Millerf91ee4c2005-03-01 21:24:33 +1100618.Sm on
Darren Tucker5ede2ad2005-03-31 21:31:10 +1000619and the second argument must be
620.Ar host : Ns Ar hostport .
Damien Millerf8c55462005-03-02 12:03:05 +1100621IPv6 addresses can be specified by enclosing addresses in square brackets or
Damien Millerf91ee4c2005-03-01 21:24:33 +1100622by using an alternative syntax:
Darren Tucker5ede2ad2005-03-31 21:31:10 +1000623.Oo Ar bind_address Ns / Oc Ns Ar port
624and
625.Ar host Ns / Ns Ar hostport .
Damien Millerf8c55462005-03-02 12:03:05 +1100626Multiple forwardings may be specified, and additional forwardings can be
Damien Millerf91ee4c2005-03-01 21:24:33 +1100627given on the command line.
Ben Lindstrom9f049032002-06-21 00:59:05 +0000628Only the superuser can forward privileged ports.
Damien Millerf91ee4c2005-03-01 21:24:33 +1100629By default, the local port is bound in accordance with the
630.Cm GatewayPorts
631setting.
632However, an explicit
633.Ar bind_address
634may be used to bind the connection to a specific address.
635The
636.Ar bind_address
637of
638.Dq localhost
Damien Millerf8c55462005-03-02 12:03:05 +1100639indicates that the listening port be bound for local use only, while an
640empty address or
641.Sq *
Damien Millerf91ee4c2005-03-01 21:24:33 +1100642indicates that the port should be available from all interfaces.
Ben Lindstrom9f049032002-06-21 00:59:05 +0000643.It Cm LogLevel
644Gives the verbosity level that is used when logging messages from
Damien Miller45ee2b92006-03-15 11:56:18 +1100645.Xr ssh 1 .
Ben Lindstrom9f049032002-06-21 00:59:05 +0000646The possible values are:
Damien Miller45ee2b92006-03-15 11:56:18 +1100647QUIET, FATAL, ERROR, INFO, VERBOSE, DEBUG, DEBUG1, DEBUG2, and DEBUG3.
Damien Miller495dca32003-04-01 21:42:14 +1000648The default is INFO.
649DEBUG and DEBUG1 are equivalent.
650DEBUG2 and DEBUG3 each specify higher levels of verbose output.
Ben Lindstrom9f049032002-06-21 00:59:05 +0000651.It Cm MACs
652Specifies the MAC (message authentication code) algorithms
653in order of preference.
654The MAC algorithm is used in protocol version 2
655for data integrity protection.
656Multiple algorithms must be comma-separated.
Damien Miller45ee2b92006-03-15 11:56:18 +1100657The default is:
Damien Miller5e7c30b2007-06-11 14:06:32 +1000658.Bd -literal -offset indent
659hmac-md5,hmac-sha1,umac-64@openssh.com,
660hmac-ripemd160,hmac-sha1-96,hmac-md5-96
661.Ed
Ben Lindstrom9f049032002-06-21 00:59:05 +0000662.It Cm NoHostAuthenticationForLocalhost
663This option can be used if the home directory is shared across machines.
664In this case localhost will refer to a different machine on each of
665the machines and the user will get many warnings about changed host keys.
666However, this option disables host authentication for localhost.
667The argument to this keyword must be
668.Dq yes
669or
670.Dq no .
671The default is to check the host key for localhost.
672.It Cm NumberOfPasswordPrompts
673Specifies the number of password prompts before giving up.
674The argument to this keyword must be an integer.
Damien Miller45ee2b92006-03-15 11:56:18 +1100675The default is 3.
Ben Lindstrom9f049032002-06-21 00:59:05 +0000676.It Cm PasswordAuthentication
677Specifies whether to use password authentication.
678The argument to this keyword must be
679.Dq yes
680or
681.Dq no .
682The default is
683.Dq yes .
Damien Millerd27b9472005-12-13 19:29:02 +1100684.It Cm PermitLocalCommand
685Allow local command execution via the
686.Ic LocalCommand
687option or using the
Damien Miller4b2319f2005-12-13 19:30:27 +1100688.Ic !\& Ns Ar command
Damien Millerd27b9472005-12-13 19:29:02 +1100689escape sequence in
690.Xr ssh 1 .
691The argument must be
692.Dq yes
693or
694.Dq no .
695The default is
696.Dq no .
Damien Miller957d4e42005-12-13 19:30:45 +1100697.It Cm Port
698Specifies the port number to connect on the remote host.
Damien Miller45ee2b92006-03-15 11:56:18 +1100699The default is 22.
Ben Lindstrom9f049032002-06-21 00:59:05 +0000700.It Cm PreferredAuthentications
701Specifies the order in which the client should try protocol 2
Damien Millerfbf486b2003-05-23 18:44:23 +1000702authentication methods.
Darren Tucker1adc2bd2005-03-14 23:14:20 +1100703This allows a client to prefer one method (e.g.\&
Ben Lindstrom9f049032002-06-21 00:59:05 +0000704.Cm keyboard-interactive )
Darren Tucker1adc2bd2005-03-14 23:14:20 +1100705over another method (e.g.\&
Ben Lindstrom9f049032002-06-21 00:59:05 +0000706.Cm password )
707The default for this option is:
Damien Miller3c6ed7b2006-06-13 13:01:41 +1000708.Do gssapi-with-mic ,
709hostbased,
710publickey,
711keyboard-interactive,
712password
713.Dc .
Ben Lindstrom9f049032002-06-21 00:59:05 +0000714.It Cm Protocol
715Specifies the protocol versions
Damien Miller45ee2b92006-03-15 11:56:18 +1100716.Xr ssh 1
Ben Lindstrom9f049032002-06-21 00:59:05 +0000717should support in order of preference.
718The possible values are
Damien Miller45ee2b92006-03-15 11:56:18 +1100719.Sq 1
Ben Lindstrom9f049032002-06-21 00:59:05 +0000720and
Damien Miller45ee2b92006-03-15 11:56:18 +1100721.Sq 2 .
Ben Lindstrom9f049032002-06-21 00:59:05 +0000722Multiple versions must be comma-separated.
723The default is
724.Dq 2,1 .
Damien Miller45ee2b92006-03-15 11:56:18 +1100725This means that ssh
Ben Lindstrom9f049032002-06-21 00:59:05 +0000726tries version 2 and falls back to version 1
727if version 2 is not available.
728.It Cm ProxyCommand
729Specifies the command to use to connect to the server.
730The command
731string extends to the end of the line, and is executed with
Darren Tucker63b31cb2007-12-02 23:09:30 +1100732the user's shell.
Ben Lindstrom9f049032002-06-21 00:59:05 +0000733In the command string,
734.Ql %h
735will be substituted by the host name to
736connect and
737.Ql %p
738by the port.
739The command can be basically anything,
740and should read from its standard input and write to its standard output.
741It should eventually connect an
742.Xr sshd 8
743server running on some machine, or execute
744.Ic sshd -i
745somewhere.
746Host key management will be done using the
747HostName of the host being connected (defaulting to the name typed by
748the user).
Damien Miller495dca32003-04-01 21:42:14 +1000749Setting the command to
750.Dq none
Damien Miller9f1e33a2003-02-24 11:57:32 +1100751disables this option entirely.
Ben Lindstrom9f049032002-06-21 00:59:05 +0000752Note that
753.Cm CheckHostIP
754is not available for connects with a proxy command.
755.Pp
Damien Millerebcfedc2005-05-26 12:13:56 +1000756This directive is useful in conjunction with
757.Xr nc 1
758and its proxy support.
Damien Millerdfec2942005-05-26 12:14:32 +1000759For example, the following directive would connect via an HTTP proxy at
Damien Millerebcfedc2005-05-26 12:13:56 +1000760192.0.2.0:
761.Bd -literal -offset 3n
762ProxyCommand /usr/bin/nc -X connect -x 192.0.2.0:8080 %h %p
763.Ed
Ben Lindstrom9f049032002-06-21 00:59:05 +0000764.It Cm PubkeyAuthentication
765Specifies whether to try public key authentication.
766The argument to this keyword must be
767.Dq yes
768or
769.Dq no .
770The default is
771.Dq yes .
772This option applies to protocol version 2 only.
Darren Tucker62388b22006-01-20 11:31:47 +1100773.It Cm RekeyLimit
774Specifies the maximum amount of data that may be transmitted before the
Damien Millerddfddf12006-01-31 21:39:03 +1100775session key is renegotiated.
Darren Tucker62388b22006-01-20 11:31:47 +1100776The argument is the number of bytes, with an optional suffix of
Damien Millerddfddf12006-01-31 21:39:03 +1100777.Sq K ,
778.Sq M ,
Darren Tucker62388b22006-01-20 11:31:47 +1100779or
Damien Millerddfddf12006-01-31 21:39:03 +1100780.Sq G
Darren Tucker62388b22006-01-20 11:31:47 +1100781to indicate Kilobytes, Megabytes, or Gigabytes, respectively.
782The default is between
Damien Miller45ee2b92006-03-15 11:56:18 +1100783.Sq 1G
Darren Tucker62388b22006-01-20 11:31:47 +1100784and
Damien Miller45ee2b92006-03-15 11:56:18 +1100785.Sq 4G ,
Darren Tucker62388b22006-01-20 11:31:47 +1100786depending on the cipher.
Damien Millerddfddf12006-01-31 21:39:03 +1100787This option applies to protocol version 2 only.
Ben Lindstrom9f049032002-06-21 00:59:05 +0000788.It Cm RemoteForward
Damien Millere9d001e2006-01-14 10:10:17 +1100789Specifies that a TCP port on the remote machine be forwarded over
Ben Lindstrom9f049032002-06-21 00:59:05 +0000790the secure channel to the specified host and port from the local machine.
Darren Tucker5ede2ad2005-03-31 21:31:10 +1000791The first argument must be
Damien Millerf91ee4c2005-03-01 21:24:33 +1100792.Sm off
Darren Tucker5ede2ad2005-03-31 21:31:10 +1000793.Oo Ar bind_address : Oc Ar port
Damien Millerf91ee4c2005-03-01 21:24:33 +1100794.Sm on
Darren Tucker5ede2ad2005-03-31 21:31:10 +1000795and the second argument must be
796.Ar host : Ns Ar hostport .
797IPv6 addresses can be specified by enclosing addresses in square brackets
798or by using an alternative syntax:
799.Oo Ar bind_address Ns / Oc Ns Ar port
800and
801.Ar host Ns / Ns Ar hostport .
Ben Lindstrom9f049032002-06-21 00:59:05 +0000802Multiple forwardings may be specified, and additional
803forwardings can be given on the command line.
804Only the superuser can forward privileged ports.
Damien Millerf91ee4c2005-03-01 21:24:33 +1100805.Pp
806If the
807.Ar bind_address
808is not specified, the default is to only bind to loopback addresses.
809If the
810.Ar bind_address
811is
812.Ql *
813or an empty string, then the forwarding is requested to listen on all
814interfaces.
815Specifying a remote
816.Ar bind_address
Damien Millerf8c55462005-03-02 12:03:05 +1100817will only succeed if the server's
818.Cm GatewayPorts
Damien Millerf91ee4c2005-03-01 21:24:33 +1100819option is enabled (see
Damien Millerf8c55462005-03-02 12:03:05 +1100820.Xr sshd_config 5 ) .
Ben Lindstrom9f049032002-06-21 00:59:05 +0000821.It Cm RhostsRSAAuthentication
822Specifies whether to try rhosts based authentication with RSA host
823authentication.
824The argument must be
825.Dq yes
826or
827.Dq no .
828The default is
829.Dq no .
830This option applies to protocol version 1 only and requires
Damien Miller45ee2b92006-03-15 11:56:18 +1100831.Xr ssh 1
Ben Lindstrom9f049032002-06-21 00:59:05 +0000832to be setuid root.
833.It Cm RSAAuthentication
834Specifies whether to try RSA authentication.
835The argument to this keyword must be
836.Dq yes
837or
838.Dq no .
839RSA authentication will only be
840attempted if the identity file exists, or an authentication agent is
841running.
842The default is
843.Dq yes .
844Note that this option applies to protocol version 1 only.
Darren Tucker46bc0752004-05-02 22:11:30 +1000845.It Cm SendEnv
846Specifies what variables from the local
847.Xr environ 7
848should be sent to the server.
Damien Miller45ee2b92006-03-15 11:56:18 +1100849Note that environment passing is only supported for protocol 2.
850The server must also support it, and the server must be configured to
Darren Tucker1e0c9bf2004-05-02 22:12:48 +1000851accept these environment variables.
Darren Tucker46bc0752004-05-02 22:11:30 +1000852Refer to
853.Cm AcceptEnv
854in
855.Xr sshd_config 5
856for how to configure the server.
Damien Miller6def5512006-03-15 11:54:05 +1100857Variables are specified by name, which may contain wildcard characters.
Darren Tucker1e0c9bf2004-05-02 22:12:48 +1000858Multiple environment variables may be separated by whitespace or spread
Darren Tucker46bc0752004-05-02 22:11:30 +1000859across multiple
860.Cm SendEnv
861directives.
862The default is not to send any environment variables.
Damien Millerf54a4b92006-03-15 11:54:36 +1100863.Pp
864See
865.Sx PATTERNS
866for more information on patterns.
Damien Miller509b0102003-12-17 16:33:10 +1100867.It Cm ServerAliveCountMax
Damien Millerb7977702006-01-03 18:47:31 +1100868Sets the number of server alive messages (see below) which may be
Damien Miller509b0102003-12-17 16:33:10 +1100869sent without
Damien Miller45ee2b92006-03-15 11:56:18 +1100870.Xr ssh 1
Damien Miller509b0102003-12-17 16:33:10 +1100871receiving any messages back from the server.
872If this threshold is reached while server alive messages are being sent,
Damien Miller45ee2b92006-03-15 11:56:18 +1100873ssh will disconnect from the server, terminating the session.
Damien Miller509b0102003-12-17 16:33:10 +1100874It is important to note that the use of server alive messages is very
875different from
876.Cm TCPKeepAlive
877(below).
878The server alive messages are sent through the encrypted channel
879and therefore will not be spoofable.
880The TCP keepalive option enabled by
881.Cm TCPKeepAlive
882is spoofable.
883The server alive mechanism is valuable when the client or
884server depend on knowing when a connection has become inactive.
885.Pp
886The default value is 3.
887If, for example,
888.Cm ServerAliveInterval
Damien Miller45ee2b92006-03-15 11:56:18 +1100889(see below) is set to 15 and
Damien Miller509b0102003-12-17 16:33:10 +1100890.Cm ServerAliveCountMax
Damien Miller45ee2b92006-03-15 11:56:18 +1100891is left at the default, if the server becomes unresponsive,
892ssh will disconnect after approximately 45 seconds.
Damien Millercc3e8ba2006-03-15 12:06:55 +1100893This option applies to protocol version 2 only.
Damien Miller957d4e42005-12-13 19:30:45 +1100894.It Cm ServerAliveInterval
895Sets a timeout interval in seconds after which if no data has been received
896from the server,
Damien Miller45ee2b92006-03-15 11:56:18 +1100897.Xr ssh 1
Damien Miller957d4e42005-12-13 19:30:45 +1100898will send a message through the encrypted
899channel to request a response from the server.
900The default
901is 0, indicating that these messages will not be sent to the server.
902This option applies to protocol version 2 only.
Ben Lindstrom9f049032002-06-21 00:59:05 +0000903.It Cm SmartcardDevice
Damien Millerfbf486b2003-05-23 18:44:23 +1000904Specifies which smartcard device to use.
905The argument to this keyword is the device
Damien Miller45ee2b92006-03-15 11:56:18 +1100906.Xr ssh 1
Ben Lindstrom9f049032002-06-21 00:59:05 +0000907should use to communicate with a smartcard used for storing the user's
Damien Millerfbf486b2003-05-23 18:44:23 +1000908private RSA key.
909By default, no device is specified and smartcard support is not activated.
Ben Lindstrom9f049032002-06-21 00:59:05 +0000910.It Cm StrictHostKeyChecking
911If this flag is set to
912.Dq yes ,
Damien Miller45ee2b92006-03-15 11:56:18 +1100913.Xr ssh 1
Ben Lindstrom9f049032002-06-21 00:59:05 +0000914will never automatically add host keys to the
Damien Miller167ea5d2005-05-26 12:04:02 +1000915.Pa ~/.ssh/known_hosts
Ben Lindstrom9f049032002-06-21 00:59:05 +0000916file, and refuses to connect to hosts whose host key has changed.
917This provides maximum protection against trojan horse attacks,
Damien Miller45ee2b92006-03-15 11:56:18 +1100918though it can be annoying when the
Ben Lindstrom9f049032002-06-21 00:59:05 +0000919.Pa /etc/ssh/ssh_known_hosts
Damien Miller45ee2b92006-03-15 11:56:18 +1100920file is poorly maintained or when connections to new hosts are
Ben Lindstrom9f049032002-06-21 00:59:05 +0000921frequently made.
922This option forces the user to manually
923add all new hosts.
924If this flag is set to
925.Dq no ,
Damien Miller45ee2b92006-03-15 11:56:18 +1100926ssh will automatically add new host keys to the
Ben Lindstrom9f049032002-06-21 00:59:05 +0000927user known hosts files.
928If this flag is set to
929.Dq ask ,
930new host keys
931will be added to the user known host files only after the user
932has confirmed that is what they really want to do, and
Damien Miller45ee2b92006-03-15 11:56:18 +1100933ssh will refuse to connect to hosts whose host key has changed.
Ben Lindstrom9f049032002-06-21 00:59:05 +0000934The host keys of
935known hosts will be verified automatically in all cases.
936The argument must be
937.Dq yes ,
Damien Miller45ee2b92006-03-15 11:56:18 +1100938.Dq no ,
Ben Lindstrom9f049032002-06-21 00:59:05 +0000939or
940.Dq ask .
941The default is
942.Dq ask .
Damien Miller12c150e2003-12-17 16:31:10 +1100943.It Cm TCPKeepAlive
944Specifies whether the system should send TCP keepalive messages to the
945other side.
946If they are sent, death of the connection or crash of one
947of the machines will be properly noticed.
948However, this means that
949connections will die if the route is down temporarily, and some people
950find it annoying.
951.Pp
952The default is
953.Dq yes
954(to send TCP keepalive messages), and the client will notice
955if the network goes down or the remote host dies.
956This is important in scripts, and many users want it too.
957.Pp
958To disable TCP keepalive messages, the value should be set to
959.Dq no .
Damien Millerd27b9472005-12-13 19:29:02 +1100960.It Cm Tunnel
Damien Miller991dba42006-07-10 20:16:27 +1000961Request
Damien Millerd27b9472005-12-13 19:29:02 +1100962.Xr tun 4
Damien Miller7746c392005-12-13 19:33:37 +1100963device forwarding between the client and the server.
Damien Millerd27b9472005-12-13 19:29:02 +1100964The argument must be
Damien Miller7b58e802005-12-13 19:33:19 +1100965.Dq yes ,
Damien Miller991dba42006-07-10 20:16:27 +1000966.Dq point-to-point
967(layer 3),
968.Dq ethernet
969(layer 2),
Damien Millerd27b9472005-12-13 19:29:02 +1100970or
971.Dq no .
Damien Miller991dba42006-07-10 20:16:27 +1000972Specifying
973.Dq yes
974requests the default tunnel mode, which is
975.Dq point-to-point .
Damien Millerd27b9472005-12-13 19:29:02 +1100976The default is
977.Dq no .
978.It Cm TunnelDevice
Damien Miller991dba42006-07-10 20:16:27 +1000979Specifies the
Damien Millerd27b9472005-12-13 19:29:02 +1100980.Xr tun 4
Damien Miller991dba42006-07-10 20:16:27 +1000981devices to open on the client
982.Pq Ar local_tun
983and the server
984.Pq Ar remote_tun .
985.Pp
986The argument must be
987.Sm off
988.Ar local_tun Op : Ar remote_tun .
989.Sm on
990The devices may be specified by numerical ID or the keyword
991.Dq any ,
992which uses the next available tunnel device.
993If
994.Ar remote_tun
995is not specified, it defaults to
996.Dq any .
997The default is
998.Dq any:any .
Damien Millere8cd7412005-12-24 14:55:47 +1100999.It Cm UsePrivilegedPort
1000Specifies whether to use a privileged port for outgoing connections.
1001The argument must be
1002.Dq yes
1003or
1004.Dq no .
1005The default is
1006.Dq no .
1007If set to
Damien Miller45ee2b92006-03-15 11:56:18 +11001008.Dq yes ,
1009.Xr ssh 1
Damien Millere8cd7412005-12-24 14:55:47 +11001010must be setuid root.
1011Note that this option must be set to
1012.Dq yes
1013for
1014.Cm RhostsRSAAuthentication
1015with older servers.
Ben Lindstrom9f049032002-06-21 00:59:05 +00001016.It Cm User
1017Specifies the user to log in as.
1018This can be useful when a different user name is used on different machines.
1019This saves the trouble of
1020having to remember to give the user name on the command line.
1021.It Cm UserKnownHostsFile
1022Specifies a file to use for the user
1023host key database instead of
Damien Miller167ea5d2005-05-26 12:04:02 +10001024.Pa ~/.ssh/known_hosts .
Damien Miller37876e92003-05-15 10:19:46 +10001025.It Cm VerifyHostKeyDNS
1026Specifies whether to verify the remote key using DNS and SSHFP resource
1027records.
Damien Miller150b5572003-11-17 21:19:29 +11001028If this option is set to
1029.Dq yes ,
Damien Millerfe448472003-11-17 21:19:49 +11001030the client will implicitly trust keys that match a secure fingerprint
Damien Miller150b5572003-11-17 21:19:29 +11001031from DNS.
1032Insecure fingerprints will be handled as if this option was set to
1033.Dq ask .
1034If this option is set to
1035.Dq ask ,
1036information on fingerprint match will be displayed, but the user will still
1037need to confirm new host keys according to the
1038.Cm StrictHostKeyChecking
1039option.
1040The argument must be
1041.Dq yes ,
Damien Miller45ee2b92006-03-15 11:56:18 +11001042.Dq no ,
Damien Millerfe448472003-11-17 21:19:49 +11001043or
1044.Dq ask .
Damien Miller37876e92003-05-15 10:19:46 +10001045The default is
1046.Dq no .
Damien Millereacbb4f2003-06-02 19:10:41 +10001047Note that this option applies to protocol version 2 only.
Damien Miller45ee2b92006-03-15 11:56:18 +11001048.Pp
1049See also
1050.Sx VERIFYING HOST KEYS
1051in
1052.Xr ssh 1 .
Ben Lindstrom9f049032002-06-21 00:59:05 +00001053.It Cm XAuthLocation
Damien Miller05913ba2002-09-04 16:51:03 +10001054Specifies the full pathname of the
Ben Lindstrom9f049032002-06-21 00:59:05 +00001055.Xr xauth 1
1056program.
1057The default is
1058.Pa /usr/X11R6/bin/xauth .
1059.El
Damien Millerb5282c22006-03-15 11:59:08 +11001060.Sh PATTERNS
1061A
1062.Em pattern
1063consists of zero or more non-whitespace characters,
1064.Sq *
1065(a wildcard that matches zero or more characters),
1066or
1067.Sq ?\&
1068(a wildcard that matches exactly one character).
1069For example, to specify a set of declarations for any host in the
1070.Dq .co.uk
1071set of domains,
1072the following pattern could be used:
1073.Pp
1074.Dl Host *.co.uk
1075.Pp
1076The following pattern
1077would match any host in the 192.168.0.[0-9] network range:
1078.Pp
1079.Dl Host 192.168.0.?
1080.Pp
1081A
1082.Em pattern-list
1083is a comma-separated list of patterns.
1084Patterns within pattern-lists may be negated
1085by preceding them with an exclamation mark
1086.Pq Sq !\& .
1087For example,
1088to allow a key to be used from anywhere within an organisation
1089except from the
1090.Dq dialup
1091pool,
1092the following entry (in authorized_keys) could be used:
1093.Pp
1094.Dl from=\&"!*.dialup.example.com,*.example.com\&"
Ben Lindstrom9f049032002-06-21 00:59:05 +00001095.Sh FILES
1096.Bl -tag -width Ds
Damien Miller167ea5d2005-05-26 12:04:02 +10001097.It Pa ~/.ssh/config
Ben Lindstrom9f049032002-06-21 00:59:05 +00001098This is the per-user configuration file.
1099The format of this file is described above.
Damien Miller45ee2b92006-03-15 11:56:18 +11001100This file is used by the SSH client.
Damien Millerc970cb92004-04-20 20:12:53 +10001101Because of the potential for abuse, this file must have strict permissions:
1102read/write for the user, and not accessible by others.
Ben Lindstrom9f049032002-06-21 00:59:05 +00001103.It Pa /etc/ssh/ssh_config
1104Systemwide configuration file.
1105This file provides defaults for those
1106values that are not specified in the user's configuration file, and
1107for those users who do not have a configuration file.
1108This file must be world-readable.
1109.El
Damien Millerf1ce5052003-06-11 22:04:39 +10001110.Sh SEE ALSO
1111.Xr ssh 1
Ben Lindstrom9f049032002-06-21 00:59:05 +00001112.Sh AUTHORS
1113OpenSSH is a derivative of the original and free
1114ssh 1.2.12 release by Tatu Ylonen.
1115Aaron Campbell, Bob Beck, Markus Friedl, Niels Provos,
1116Theo de Raadt and Dug Song
1117removed many bugs, re-added newer features and
1118created OpenSSH.
1119Markus Friedl contributed the support for SSH
1120protocol versions 1.5 and 2.0.