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Damien Miller32aa1441999-10-29 09:15:49 +10001.\"
Damien Miller32aa1441999-10-29 09:15:49 +10002.\" Author: Tatu Ylonen <ylo@cs.hut.fi>
Damien Miller32aa1441999-10-29 09:15:49 +10003.\" Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
4.\" All rights reserved
5.\"
Damien Millere4340be2000-09-16 13:29:08 +11006.\" As far as I am concerned, the code I have written for this software
7.\" can be used freely for any purpose. Any derived versions of this
8.\" software must be clearly marked as such, and if the derived work is
9.\" incompatible with the protocol description in the RFC file, it must be
10.\" called by a name other than "ssh" or "Secure Shell".
Damien Miller32aa1441999-10-29 09:15:49 +100011.\"
Ben Lindstrom92a2e382001-03-05 06:59:27 +000012.\" Copyright (c) 1999,2000 Markus Friedl. All rights reserved.
13.\" Copyright (c) 1999 Aaron Campbell. All rights reserved.
14.\" Copyright (c) 1999 Theo de Raadt. All rights reserved.
Damien Millere4340be2000-09-16 13:29:08 +110015.\"
16.\" Redistribution and use in source and binary forms, with or without
17.\" modification, are permitted provided that the following conditions
18.\" are met:
19.\" 1. Redistributions of source code must retain the above copyright
20.\" notice, this list of conditions and the following disclaimer.
21.\" 2. Redistributions in binary form must reproduce the above copyright
22.\" notice, this list of conditions and the following disclaimer in the
23.\" documentation and/or other materials provided with the distribution.
24.\"
25.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
26.\" IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
27.\" OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
28.\" IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
29.\" INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
30.\" NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
31.\" DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
32.\" THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
33.\" (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
34.\" THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
Damien Miller32aa1441999-10-29 09:15:49 +100035.\"
Darren Tucker628a3fd2012-10-05 10:50:15 +100036.\" $OpenBSD: ssh.1,v 1.329 2012/09/26 16:12:13 jmc Exp $
37.Dd $Mdocdate: September 26 2012 $
Damien Miller32aa1441999-10-29 09:15:49 +100038.Dt SSH 1
39.Os
40.Sh NAME
41.Nm ssh
Ben Lindstromd58eb5f2001-03-07 06:07:22 +000042.Nd OpenSSH SSH client (remote login program)
Damien Miller32aa1441999-10-29 09:15:49 +100043.Sh SYNOPSIS
44.Nm ssh
Damien Millerbcfbc482010-07-16 13:59:11 +100045.Bk -words
Damien Millere272a5b2008-11-03 19:22:37 +110046.Op Fl 1246AaCfgKkMNnqsTtVvXxYy
Ben Lindstrome0f88042001-04-30 13:06:24 +000047.Op Fl b Ar bind_address
Damien Miller30c3d422000-05-09 11:02:59 +100048.Op Fl c Ar cipher_spec
Damien Millerbcfbc482010-07-16 13:59:11 +100049.Op Fl D Oo Ar bind_address : Oc Ns Ar port
Damien Miller32aa1441999-10-29 09:15:49 +100050.Op Fl e Ar escape_char
Ben Lindstrom14f31ab2001-09-12 17:48:04 +000051.Op Fl F Ar configfile
Damien Miller048dc932010-02-12 09:22:04 +110052.Op Fl I Ar pkcs11
Darren Tucker61776952003-10-02 16:19:47 +100053.Op Fl i Ar identity_file
Damien Millerbcfbc482010-07-16 13:59:11 +100054.Op Fl L Oo Ar bind_address : Oc Ns Ar port : Ns Ar host : Ns Ar hostport
Darren Tucker61776952003-10-02 16:19:47 +100055.Op Fl l Ar login_name
56.Op Fl m Ar mac_spec
Darren Tucker7ebfc102004-11-07 20:06:19 +110057.Op Fl O Ar ctl_cmd
Darren Tucker61776952003-10-02 16:19:47 +100058.Op Fl o Ar option
Darren Tucker61776952003-10-02 16:19:47 +100059.Op Fl p Ar port
Damien Millerbcfbc482010-07-16 13:59:11 +100060.Op Fl R Oo Ar bind_address : Oc Ns Ar port : Ns Ar host : Ns Ar hostport
Darren Tucker7ebfc102004-11-07 20:06:19 +110061.Op Fl S Ar ctl_path
Darren Tucker7ad8dd22010-01-12 19:40:27 +110062.Op Fl W Ar host : Ns Ar port
Damien Millerbcfbc482010-07-16 13:59:11 +100063.Op Fl w Ar local_tun Ns Op : Ns Ar remote_tun
Darren Tucker61776952003-10-02 16:19:47 +100064.Oo Ar user Ns @ Oc Ns Ar hostname
Damien Miller32aa1441999-10-29 09:15:49 +100065.Op Ar command
Damien Millerbcfbc482010-07-16 13:59:11 +100066.Ek
Damien Miller22c77262000-04-13 12:26:34 +100067.Sh DESCRIPTION
Damien Miller32aa1441999-10-29 09:15:49 +100068.Nm
Ben Lindstromd58eb5f2001-03-07 06:07:22 +000069(SSH client) is a program for logging into a remote machine and for
Damien Miller7684ee12000-03-17 23:40:15 +110070executing commands on a remote machine.
Darren Tucker61776952003-10-02 16:19:47 +100071It is intended to replace rlogin and rsh,
72and provide secure encrypted communications between
Damien Miller7684ee12000-03-17 23:40:15 +110073two untrusted hosts over an insecure network.
Damien Miller8bfaf932006-01-14 10:09:30 +110074X11 connections and arbitrary TCP ports
Darren Tucker61776952003-10-02 16:19:47 +100075can also be forwarded over the secure channel.
Damien Miller32aa1441999-10-29 09:15:49 +100076.Pp
77.Nm
Damien Miller22c77262000-04-13 12:26:34 +100078connects and logs into the specified
Darren Tucker61776952003-10-02 16:19:47 +100079.Ar hostname
80(with optional
81.Ar user
82name).
Damien Miller32aa1441999-10-29 09:15:49 +100083The user must prove
Damien Millere247cc42000-05-07 12:03:14 +100084his/her identity to the remote machine using one of several methods
Darren Tucker5434cfe2005-12-20 16:11:35 +110085depending on the protocol version used (see below).
Damien Millere247cc42000-05-07 12:03:14 +100086.Pp
Darren Tucker61776952003-10-02 16:19:47 +100087If
88.Ar command
89is specified,
Darren Tuckerb18c8672005-12-20 16:10:09 +110090it is executed on the remote host instead of a login shell.
Darren Tucker0b42e6d2004-08-13 21:22:40 +100091.Pp
Damien Miller0bc1bd82000-11-13 22:57:25 +110092The options are as follows:
Damien Miller32aa1441999-10-29 09:15:49 +100093.Bl -tag -width Ds
Darren Tucker61776952003-10-02 16:19:47 +100094.It Fl 1
95Forces
96.Nm
97to try protocol version 1 only.
98.It Fl 2
99Forces
100.Nm
101to try protocol version 2 only.
102.It Fl 4
103Forces
104.Nm
105to use IPv4 addresses only.
106.It Fl 6
107Forces
108.Nm
109to use IPv6 addresses only.
Damien Millerb1715dc2000-05-30 13:44:51 +1000110.It Fl A
111Enables forwarding of the authentication agent connection.
112This can also be specified on a per-host basis in a configuration file.
Damien Millerb5fdfaa2002-09-12 09:52:03 +1000113.Pp
Damien Miller495dca32003-04-01 21:42:14 +1000114Agent forwarding should be enabled with caution.
115Users with the ability to bypass file permissions on the remote host
Darren Tuckerae69e1d2009-10-24 11:41:34 +1100116(for the agent's
Darren Tucker98c9aec2009-10-24 11:42:44 +1100117.Ux Ns -domain
118socket) can access the local agent through the forwarded connection.
Damien Miller495dca32003-04-01 21:42:14 +1000119An attacker cannot obtain key material from the agent,
Damien Millerb5fdfaa2002-09-12 09:52:03 +1000120however they can perform operations on the keys that enable them to
121authenticate using the identities loaded into the agent.
Darren Tucker61776952003-10-02 16:19:47 +1000122.It Fl a
123Disables forwarding of the authentication agent connection.
Ben Lindstrome0f88042001-04-30 13:06:24 +0000124.It Fl b Ar bind_address
Darren Tuckera5cf8552005-07-14 17:04:18 +1000125Use
126.Ar bind_address
127on the local machine as the source address
128of the connection.
129Only useful on systems with more than one address.
Darren Tucker61776952003-10-02 16:19:47 +1000130.It Fl C
131Requests compression of all data (including stdin, stdout, stderr, and
Damien Miller8bfaf932006-01-14 10:09:30 +1100132data for forwarded X11 and TCP connections).
Darren Tucker61776952003-10-02 16:19:47 +1000133The compression algorithm is the same used by
134.Xr gzip 1 ,
135and the
136.Dq level
137can be controlled by the
138.Cm CompressionLevel
139option for protocol version 1.
140Compression is desirable on modem lines and other
141slow connections, but will only slow down things on fast networks.
142The default value can be set on a host-by-host basis in the
143configuration files; see the
144.Cm Compression
145option.
Damien Miller05202ff2004-06-15 10:30:39 +1000146.It Fl c Ar cipher_spec
147Selects the cipher specification for encrypting the session.
148.Pp
149Protocol version 1 allows specification of a single cipher.
Darren Tucker1e4308e2005-10-03 18:18:40 +1000150The supported values are
Damien Miller05202ff2004-06-15 10:30:39 +1000151.Dq 3des ,
Darren Tuckerff9f4842005-12-20 16:10:45 +1100152.Dq blowfish ,
Damien Miller05202ff2004-06-15 10:30:39 +1000153and
154.Dq des .
Damien Miller32aa1441999-10-29 09:15:49 +1000155.Ar 3des
156(triple-des) is an encrypt-decrypt-encrypt triple with three different keys.
Damien Miller05202ff2004-06-15 10:30:39 +1000157It is believed to be secure.
Damien Miller32aa1441999-10-29 09:15:49 +1000158.Ar blowfish
Darren Tucker61776952003-10-02 16:19:47 +1000159is a fast block cipher; it appears very secure and is much faster than
Damien Miller7684ee12000-03-17 23:40:15 +1100160.Ar 3des .
Ben Lindstromffa1dd62001-09-12 16:52:28 +0000161.Ar des
162is only supported in the
163.Nm
164client for interoperability with legacy protocol 1 implementations
165that do not support the
166.Ar 3des
Damien Miller495dca32003-04-01 21:42:14 +1000167cipher.
168Its use is strongly discouraged due to cryptographic weaknesses.
Damien Miller05202ff2004-06-15 10:30:39 +1000169The default is
170.Dq 3des .
171.Pp
Damien Miller35978212005-12-24 14:56:47 +1100172For protocol version 2,
Damien Miller05202ff2004-06-15 10:30:39 +1000173.Ar cipher_spec
174is a comma-separated list of ciphers
175listed in order of preference.
Darren Tucker3a6a51f2009-06-21 17:48:52 +1000176See the
177.Cm Ciphers
Damien Miller081f3c72010-08-03 16:05:25 +1000178keyword in
179.Xr ssh_config 5
180for more information.
Darren Tuckerc8d64212005-10-03 18:13:42 +1000181.It Fl D Xo
182.Sm off
183.Oo Ar bind_address : Oc
184.Ar port
185.Sm on
186.Xc
Darren Tucker61776952003-10-02 16:19:47 +1000187Specifies a local
188.Dq dynamic
189application-level port forwarding.
190This works by allocating a socket to listen to
191.Ar port
Darren Tuckerc8d64212005-10-03 18:13:42 +1000192on the local side, optionally bound to the specified
193.Ar bind_address .
194Whenever a connection is made to this port, the
Darren Tucker61776952003-10-02 16:19:47 +1000195connection is forwarded over the secure channel, and the application
196protocol is then used to determine where to connect to from the
197remote machine.
198Currently the SOCKS4 and SOCKS5 protocols are supported, and
199.Nm
200will act as a SOCKS server.
201Only root can forward privileged ports.
202Dynamic port forwardings can also be specified in the configuration file.
Darren Tuckerc8d64212005-10-03 18:13:42 +1000203.Pp
Damien Miller7fa96602010-08-05 13:03:13 +1000204IPv6 addresses can be specified by enclosing the address in square brackets.
Darren Tuckerc8d64212005-10-03 18:13:42 +1000205Only the superuser can forward privileged ports.
206By default, the local port is bound in accordance with the
207.Cm GatewayPorts
208setting.
209However, an explicit
210.Ar bind_address
211may be used to bind the connection to a specific address.
212The
213.Ar bind_address
214of
215.Dq localhost
216indicates that the listening port be bound for local use only, while an
217empty address or
218.Sq *
219indicates that the port should be available from all interfaces.
Damien Miller2142ba02005-12-24 14:56:29 +1100220.It Fl e Ar escape_char
Damien Miller32aa1441999-10-29 09:15:49 +1000221Sets the escape character for sessions with a pty (default:
222.Ql ~ ) .
Damien Miller7684ee12000-03-17 23:40:15 +1100223The escape character is only recognized at the beginning of a line.
224The escape character followed by a dot
Damien Miller32aa1441999-10-29 09:15:49 +1000225.Pq Ql \&.
Darren Tucker61776952003-10-02 16:19:47 +1000226closes the connection;
227followed by control-Z suspends the connection;
228and followed by itself sends the escape character once.
Damien Miller7684ee12000-03-17 23:40:15 +1100229Setting the character to
Damien Miller32aa1441999-10-29 09:15:49 +1000230.Dq none
231disables any escapes and makes the session fully transparent.
Darren Tucker61776952003-10-02 16:19:47 +1000232.It Fl F Ar configfile
233Specifies an alternative per-user configuration file.
234If a configuration file is given on the command line,
235the system-wide configuration file
236.Pq Pa /etc/ssh/ssh_config
237will be ignored.
238The default for the per-user configuration file is
Damien Miller167ea5d2005-05-26 12:04:02 +1000239.Pa ~/.ssh/config .
Damien Miller32aa1441999-10-29 09:15:49 +1000240.It Fl f
241Requests
242.Nm
Damien Miller7684ee12000-03-17 23:40:15 +1100243to go to background just before command execution.
244This is useful if
Damien Miller32aa1441999-10-29 09:15:49 +1000245.Nm
246is going to ask for passwords or passphrases, but the user
Damien Miller7684ee12000-03-17 23:40:15 +1100247wants it in the background.
Damien Miller22c77262000-04-13 12:26:34 +1000248This implies
Damien Miller32aa1441999-10-29 09:15:49 +1000249.Fl n .
250The recommended way to start X11 programs at a remote site is with
251something like
252.Ic ssh -f host xterm .
Darren Tucker9a2a6092008-07-04 12:53:50 +1000253.Pp
254If the
255.Cm ExitOnForwardFailure
256configuration option is set to
257.Dq yes ,
258then a client started with
259.Fl f
260will wait for all remote port forwards to be successfully established
261before placing itself in the background.
Damien Miller396691a2000-01-20 22:44:08 +1100262.It Fl g
263Allows remote hosts to connect to local forwarded ports.
Damien Miller7ea845e2010-02-12 09:21:02 +1100264.It Fl I Ar pkcs11
Damien Millerd400da52010-02-12 09:26:23 +1100265Specify the PKCS#11 shared library
Darren Tucker61776952003-10-02 16:19:47 +1000266.Nm
Damien Millera7618442010-02-12 09:26:02 +1100267should use to communicate with a PKCS#11 token providing the user's
Darren Tucker61776952003-10-02 16:19:47 +1000268private RSA key.
Damien Miller32aa1441999-10-29 09:15:49 +1000269.It Fl i Ar identity_file
Damien Millerfae23862002-01-22 23:32:26 +1100270Selects a file from which the identity (private key) for
Damien Millereb8b60e2010-08-31 22:41:14 +1000271public key authentication is read.
Damien Millerfae23862002-01-22 23:32:26 +1100272The default is
Damien Miller167ea5d2005-05-26 12:04:02 +1000273.Pa ~/.ssh/identity
Damien Millerfae23862002-01-22 23:32:26 +1100274for protocol version 1, and
Damien Millereb8b60e2010-08-31 22:41:14 +1000275.Pa ~/.ssh/id_dsa ,
276.Pa ~/.ssh/id_ecdsa
Damien Millerfae23862002-01-22 23:32:26 +1100277and
Damien Millereb8b60e2010-08-31 22:41:14 +1000278.Pa ~/.ssh/id_rsa
Damien Millerfae23862002-01-22 23:32:26 +1100279for protocol version 2.
Damien Miller7684ee12000-03-17 23:40:15 +1100280Identity files may also be specified on
281a per-host basis in the configuration file.
282It is possible to have multiple
Damien Miller32aa1441999-10-29 09:15:49 +1000283.Fl i
284options (and multiple identities specified in
285configuration files).
Damien Miller5059d8d2010-03-05 21:31:11 +1100286.Nm
287will also try to load certificate information from the filename obtained
288by appending
289.Pa -cert.pub
290to identity filenames.
Darren Tucker415bddc2007-06-12 23:43:16 +1000291.It Fl K
292Enables GSSAPI-based authentication and forwarding (delegation) of GSSAPI
293credentials to the server.
Damien Miller32aa1441999-10-29 09:15:49 +1000294.It Fl k
Damien Millere0113cc2003-11-24 13:10:09 +1100295Disables forwarding (delegation) of GSSAPI credentials to the server.
Darren Tucker61776952003-10-02 16:19:47 +1000296.It Fl L Xo
297.Sm off
Damien Millerf91ee4c2005-03-01 21:24:33 +1100298.Oo Ar bind_address : Oc
Darren Tucker61776952003-10-02 16:19:47 +1000299.Ar port : host : hostport
300.Sm on
301.Xc
302Specifies that the given port on the local (client) host is to be
303forwarded to the given host and port on the remote side.
304This works by allocating a socket to listen to
305.Ar port
Damien Millerf91ee4c2005-03-01 21:24:33 +1100306on the local side, optionally bound to the specified
307.Ar bind_address .
308Whenever a connection is made to this port, the
Darren Tucker61776952003-10-02 16:19:47 +1000309connection is forwarded over the secure channel, and a connection is
310made to
311.Ar host
312port
313.Ar hostport
314from the remote machine.
315Port forwardings can also be specified in the configuration file.
Damien Miller7fa96602010-08-05 13:03:13 +1000316IPv6 addresses can be specified by enclosing the address in square brackets.
Damien Millerf91ee4c2005-03-01 21:24:33 +1100317Only the superuser can forward privileged ports.
318By default, the local port is bound in accordance with the
319.Cm GatewayPorts
320setting.
321However, an explicit
322.Ar bind_address
323may be used to bind the connection to a specific address.
324The
325.Ar bind_address
326of
327.Dq localhost
Damien Miller36bf7dd2005-03-02 12:02:47 +1100328indicates that the listening port be bound for local use only, while an
329empty address or
330.Sq *
Damien Millerf91ee4c2005-03-01 21:24:33 +1100331indicates that the port should be available from all interfaces.
Damien Miller32aa1441999-10-29 09:15:49 +1000332.It Fl l Ar login_name
Damien Miller7684ee12000-03-17 23:40:15 +1100333Specifies the user to log in as on the remote machine.
334This also may be specified on a per-host basis in the configuration file.
Damien Miller0e220db2004-06-15 10:34:08 +1000335.It Fl M
336Places the
337.Nm
338client into
339.Dq master
340mode for connection sharing.
Damien Miller88b25522005-12-31 16:23:15 +1100341Multiple
342.Fl M
343options places
344.Nm
345into
346.Dq master
347mode with confirmation required before slave connections are accepted.
Damien Miller0e220db2004-06-15 10:34:08 +1000348Refer to the description of
349.Cm ControlMaster
350in
351.Xr ssh_config 5
352for details.
Damien Miller5d1eceb2004-06-30 22:37:57 +1000353.It Fl m Ar mac_spec
354Additionally, for protocol version 2 a comma-separated list of MAC
355(message authentication code) algorithms can
356be specified in order of preference.
357See the
358.Cm MACs
359keyword for more information.
Darren Tucker61776952003-10-02 16:19:47 +1000360.It Fl N
361Do not execute a remote command.
362This is useful for just forwarding ports
363(protocol version 2 only).
Damien Miller32aa1441999-10-29 09:15:49 +1000364.It Fl n
365Redirects stdin from
366.Pa /dev/null
367(actually, prevents reading from stdin).
368This must be used when
369.Nm
Damien Miller7684ee12000-03-17 23:40:15 +1100370is run in the background.
371A common trick is to use this to run X11 programs on a remote machine.
372For example,
Damien Miller32aa1441999-10-29 09:15:49 +1000373.Ic ssh -n shadows.cs.hut.fi emacs &
374will start an emacs on shadows.cs.hut.fi, and the X11
375connection will be automatically forwarded over an encrypted channel.
376The
377.Nm
378program will be put in the background.
379(This does not work if
380.Nm
381needs to ask for a password or passphrase; see also the
382.Fl f
383option.)
Darren Tuckere04644c2004-12-03 14:08:45 +1100384.It Fl O Ar ctl_cmd
385Control an active connection multiplexing master process.
386When the
387.Fl O
388option is specified, the
389.Ar ctl_cmd
390argument is interpreted and passed to the master process.
391Valid commands are:
392.Dq check
Damien Miller388f6fc2010-05-21 14:57:35 +1000393(check that the master process is running),
394.Dq forward
Damien Miller8cb1cda2011-05-05 14:16:56 +1000395(request forwardings without command execution),
Damien Miller1bcbd0a2011-09-22 21:40:45 +1000396.Dq cancel
397(cancel forwardings),
Darren Tuckere04644c2004-12-03 14:08:45 +1100398.Dq exit
Damien Miller8cb1cda2011-05-05 14:16:56 +1000399(request the master to exit), and
Damien Miller6c3eec72011-05-05 14:16:22 +1000400.Dq stop
401(request the master to stop accepting further multiplexing requests).
Damien Miller32aa1441999-10-29 09:15:49 +1000402.It Fl o Ar option
Ben Lindstrom14c62eb2001-08-15 23:25:46 +0000403Can be used to give options in the format used in the configuration file.
Damien Miller32aa1441999-10-29 09:15:49 +1000404This is useful for specifying options for which there is no separate
Damien Miller7684ee12000-03-17 23:40:15 +1100405command-line flag.
Darren Tucker61776952003-10-02 16:19:47 +1000406For full details of the options listed below, and their possible values, see
407.Xr ssh_config 5 .
408.Pp
409.Bl -tag -width Ds -offset indent -compact
410.It AddressFamily
411.It BatchMode
412.It BindAddress
413.It ChallengeResponseAuthentication
414.It CheckHostIP
415.It Cipher
416.It Ciphers
417.It ClearAllForwardings
418.It Compression
419.It CompressionLevel
420.It ConnectionAttempts
Darren Tuckeredae0ec2004-05-02 22:15:52 +1000421.It ConnectTimeout
Damien Miller0e220db2004-06-15 10:34:08 +1000422.It ControlMaster
423.It ControlPath
Damien Millerefad7272011-09-22 21:33:53 +1000424.It ControlPersist
Darren Tucker61776952003-10-02 16:19:47 +1000425.It DynamicForward
Darren Tucker61776952003-10-02 16:19:47 +1000426.It EscapeChar
Darren Tuckere7d4b192006-07-12 22:17:10 +1000427.It ExitOnForwardFailure
Darren Tucker61776952003-10-02 16:19:47 +1000428.It ForwardAgent
429.It ForwardX11
Damien Millerefad7272011-09-22 21:33:53 +1000430.It ForwardX11Timeout
Darren Tucker0a118da2003-10-15 15:54:32 +1000431.It ForwardX11Trusted
Darren Tucker61776952003-10-02 16:19:47 +1000432.It GatewayPorts
433.It GlobalKnownHostsFile
434.It GSSAPIAuthentication
435.It GSSAPIDelegateCredentials
Damien Millere1776152005-03-01 21:47:37 +1100436.It HashKnownHosts
Darren Tucker61776952003-10-02 16:19:47 +1000437.It Host
438.It HostbasedAuthentication
439.It HostKeyAlgorithms
440.It HostKeyAlias
441.It HostName
442.It IdentityFile
Damien Millerbd394c32004-03-08 23:12:36 +1100443.It IdentitiesOnly
Damien Miller0a184732010-11-20 15:21:03 +1100444.It IPQoS
Damien Millerefad7272011-09-22 21:33:53 +1000445.It KbdInteractiveAuthentication
Darren Tucker636ca902004-11-05 20:22:00 +1100446.It KbdInteractiveDevices
Damien Miller7fe2b1f2010-09-24 22:11:53 +1000447.It KexAlgorithms
Damien Millerd27b9472005-12-13 19:29:02 +1100448.It LocalCommand
Darren Tucker61776952003-10-02 16:19:47 +1000449.It LocalForward
450.It LogLevel
451.It MACs
452.It NoHostAuthenticationForLocalhost
453.It NumberOfPasswordPrompts
454.It PasswordAuthentication
Damien Millerd27b9472005-12-13 19:29:02 +1100455.It PermitLocalCommand
Damien Miller7ea845e2010-02-12 09:21:02 +1100456.It PKCS11Provider
Darren Tucker61776952003-10-02 16:19:47 +1000457.It Port
458.It PreferredAuthentications
459.It Protocol
460.It ProxyCommand
461.It PubkeyAuthentication
Darren Tucker62388b22006-01-20 11:31:47 +1100462.It RekeyLimit
Darren Tucker61776952003-10-02 16:19:47 +1000463.It RemoteForward
Damien Millerf4b32aa2011-05-15 08:47:43 +1000464.It RequestTTY
Darren Tucker61776952003-10-02 16:19:47 +1000465.It RhostsRSAAuthentication
466.It RSAAuthentication
Darren Tucker7a6c0662004-05-02 22:14:03 +1000467.It SendEnv
Damien Miller509b0102003-12-17 16:33:10 +1100468.It ServerAliveInterval
469.It ServerAliveCountMax
Darren Tucker61776952003-10-02 16:19:47 +1000470.It StrictHostKeyChecking
Damien Miller12c150e2003-12-17 16:31:10 +1100471.It TCPKeepAlive
Damien Millerd27b9472005-12-13 19:29:02 +1100472.It Tunnel
473.It TunnelDevice
Darren Tucker61776952003-10-02 16:19:47 +1000474.It UsePrivilegedPort
475.It User
476.It UserKnownHostsFile
477.It VerifyHostKeyDNS
Damien Miller86399202008-06-30 00:04:31 +1000478.It VisualHostKey
Darren Tucker61776952003-10-02 16:19:47 +1000479.It XAuthLocation
480.El
Damien Miller32aa1441999-10-29 09:15:49 +1000481.It Fl p Ar port
Damien Miller7684ee12000-03-17 23:40:15 +1100482Port to connect to on the remote host.
483This can be specified on a
Damien Miller32aa1441999-10-29 09:15:49 +1000484per-host basis in the configuration file.
Damien Miller32aa1441999-10-29 09:15:49 +1000485.It Fl q
Damien Miller7684ee12000-03-17 23:40:15 +1100486Quiet mode.
Damien Millereb602472008-02-10 22:21:28 +1100487Causes most warning and diagnostic messages to be suppressed.
Darren Tucker61776952003-10-02 16:19:47 +1000488.It Fl R Xo
489.Sm off
Damien Millerf91ee4c2005-03-01 21:24:33 +1100490.Oo Ar bind_address : Oc
Darren Tucker61776952003-10-02 16:19:47 +1000491.Ar port : host : hostport
492.Sm on
493.Xc
Damien Miller32aa1441999-10-29 09:15:49 +1000494Specifies that the given port on the remote (server) host is to be
Damien Miller7684ee12000-03-17 23:40:15 +1100495forwarded to the given host and port on the local side.
496This works by allocating a socket to listen to
Damien Miller32aa1441999-10-29 09:15:49 +1000497.Ar port
498on the remote side, and whenever a connection is made to this port, the
499connection is forwarded over the secure channel, and a connection is
500made to
Damien Miller34132e52000-01-14 15:45:46 +1100501.Ar host
502port
503.Ar hostport
Damien Miller7684ee12000-03-17 23:40:15 +1100504from the local machine.
Damien Millerf91ee4c2005-03-01 21:24:33 +1100505.Pp
Damien Miller7684ee12000-03-17 23:40:15 +1100506Port forwardings can also be specified in the configuration file.
507Privileged ports can be forwarded only when
Damien Miller32aa1441999-10-29 09:15:49 +1000508logging in as root on the remote machine.
Damien Miller70b2d552012-04-22 11:26:10 +1000509IPv6 addresses can be specified by enclosing the address in square brackets.
Damien Millerf91ee4c2005-03-01 21:24:33 +1100510.Pp
511By default, the listening socket on the server will be bound to the loopback
512interface only.
Darren Tucker63917bd2008-11-11 16:33:48 +1100513This may be overridden by specifying a
Damien Millerf91ee4c2005-03-01 21:24:33 +1100514.Ar bind_address .
Damien Miller36bf7dd2005-03-02 12:02:47 +1100515An empty
516.Ar bind_address ,
Damien Millerf91ee4c2005-03-01 21:24:33 +1100517or the address
Damien Miller36bf7dd2005-03-02 12:02:47 +1100518.Ql * ,
Damien Millerf91ee4c2005-03-01 21:24:33 +1100519indicates that the remote socket should listen on all interfaces.
520Specifying a remote
521.Ar bind_address
Damien Miller36bf7dd2005-03-02 12:02:47 +1100522will only succeed if the server's
523.Cm GatewayPorts
Damien Millerf91ee4c2005-03-01 21:24:33 +1100524option is enabled (see
Damien Miller36bf7dd2005-03-02 12:02:47 +1100525.Xr sshd_config 5 ) .
Damien Millere2f4cc52009-02-14 16:33:49 +1100526.Pp
527If the
528.Ar port
529argument is
Damien Miller65fa4ca2009-02-14 16:34:05 +1100530.Ql 0 ,
Damien Millere2f4cc52009-02-14 16:33:49 +1100531the listen port will be dynamically allocated on the server and reported
532to the client at run time.
Damien Miller388f6fc2010-05-21 14:57:35 +1000533When used together with
534.Ic -O forward
535the allocated port will be printed to the standard output.
Darren Tucker7ebfc102004-11-07 20:06:19 +1100536.It Fl S Ar ctl_path
Damien Miller67f30d72010-04-16 15:52:03 +1000537Specifies the location of a control socket for connection sharing,
Damien Miller9c60f242010-03-26 11:28:35 +1100538or the string
539.Dq none
540to disable connection sharing.
Damien Miller0e220db2004-06-15 10:34:08 +1000541Refer to the description of
Darren Tuckerba5c5922004-06-18 16:22:39 +1000542.Cm ControlPath
543and
Damien Miller0e220db2004-06-15 10:34:08 +1000544.Cm ControlMaster
545in
546.Xr ssh_config 5
547for details.
Darren Tucker61776952003-10-02 16:19:47 +1000548.It Fl s
549May be used to request invocation of a subsystem on the remote system.
550Subsystems are a feature of the SSH2 protocol which facilitate the use
551of SSH as a secure transport for other applications (eg.\&
552.Xr sftp 1 ) .
553The subsystem is specified as the remote command.
554.It Fl T
555Disable pseudo-tty allocation.
556.It Fl t
557Force pseudo-tty allocation.
558This can be used to execute arbitrary
559screen-based programs on a remote machine, which can be very useful,
Damien Miller208f1ed2006-03-15 11:56:03 +1100560e.g. when implementing menu services.
Darren Tucker61776952003-10-02 16:19:47 +1000561Multiple
562.Fl t
563options force tty allocation, even if
Ben Lindstrom19ceb172001-09-12 17:54:24 +0000564.Nm
Darren Tucker61776952003-10-02 16:19:47 +1000565has no local tty.
566.It Fl V
567Display the version number and exit.
568.It Fl v
569Verbose mode.
570Causes
Ben Lindstrom5ab6ae12001-02-10 22:08:03 +0000571.Nm
Darren Tucker61776952003-10-02 16:19:47 +1000572to print debugging messages about its progress.
573This is helpful in
574debugging connection, authentication, and configuration problems.
575Multiple
576.Fl v
577options increase the verbosity.
578The maximum is 3.
Darren Tucker7ad8dd22010-01-12 19:40:27 +1100579.It Fl W Ar host : Ns Ar port
580Requests that standard input and output on the client be forwarded to
581.Ar host
582on
583.Ar port
584over the secure channel.
585Implies
586.Fl N ,
587.Fl T ,
588.Cm ExitOnForwardFailure
589and
Damien Miller36378c62012-06-20 21:53:25 +1000590.Cm ClearAllForwardings .
591Works with Protocol version 2 only.
Damien Miller991dba42006-07-10 20:16:27 +1000592.It Fl w Xo
593.Ar local_tun Ns Op : Ns Ar remote_tun
594.Xc
595Requests
596tunnel
597device forwarding with the specified
Damien Millerd27b9472005-12-13 19:29:02 +1100598.Xr tun 4
Damien Miller991dba42006-07-10 20:16:27 +1000599devices between the client
600.Pq Ar local_tun
601and the server
602.Pq Ar remote_tun .
603.Pp
Damien Millercf1e3422005-12-24 14:56:04 +1100604The devices may be specified by numerical ID or the keyword
605.Dq any ,
606which uses the next available tunnel device.
Damien Miller991dba42006-07-10 20:16:27 +1000607If
608.Ar remote_tun
609is not specified, it defaults to
610.Dq any .
Damien Millercf1e3422005-12-24 14:56:04 +1100611See also the
Damien Millerd27b9472005-12-13 19:29:02 +1100612.Cm Tunnel
Damien Miller991dba42006-07-10 20:16:27 +1000613and
614.Cm TunnelDevice
615directives in
Damien Millerd27b9472005-12-13 19:29:02 +1100616.Xr ssh_config 5 .
Damien Miller991dba42006-07-10 20:16:27 +1000617If the
618.Cm Tunnel
619directive is unset, it is set to the default tunnel mode, which is
620.Dq point-to-point .
Darren Tucker61776952003-10-02 16:19:47 +1000621.It Fl X
622Enables X11 forwarding.
623This can also be specified on a per-host basis in a configuration file.
624.Pp
625X11 forwarding should be enabled with caution.
626Users with the ability to bypass file permissions on the remote host
627(for the user's X authorization database)
628can access the local X11 display through the forwarded connection.
629An attacker may then be able to perform activities such as keystroke monitoring.
Damien Miller947219e2005-03-02 13:22:30 +1100630.Pp
Damien Millerb022b232005-03-05 11:22:36 +1100631For this reason, X11 forwarding is subjected to X11 SECURITY extension
Damien Miller947219e2005-03-02 13:22:30 +1100632restrictions by default.
633Please refer to the
634.Nm
635.Fl Y
636option and the
637.Cm ForwardX11Trusted
638directive in
639.Xr ssh_config 5
640for more information.
Darren Tucker61776952003-10-02 16:19:47 +1000641.It Fl x
642Disables X11 forwarding.
Darren Tucker0a118da2003-10-15 15:54:32 +1000643.It Fl Y
644Enables trusted X11 forwarding.
Damien Miller947219e2005-03-02 13:22:30 +1100645Trusted X11 forwardings are not subjected to the X11 SECURITY extension
646controls.
Damien Millere272a5b2008-11-03 19:22:37 +1100647.It Fl y
648Send log information using the
649.Xr syslog 3
650system module.
651By default this information is sent to stderr.
Damien Miller32aa1441999-10-29 09:15:49 +1000652.El
Damien Millere9b333a2005-12-24 14:53:04 +1100653.Pp
654.Nm
655may additionally obtain configuration data from
656a per-user configuration file and a system-wide configuration file.
657The file format and configuration options are described in
658.Xr ssh_config 5 .
Damien Millerc93a8132005-12-24 14:52:13 +1100659.Sh AUTHENTICATION
Darren Tucker94299ec2006-01-20 11:30:14 +1100660The OpenSSH SSH client supports SSH protocols 1 and 2.
Darren Tucker7a4a7652009-10-11 21:51:40 +1100661The default is to use protocol 2 only,
662though this can be changed via the
Damien Millerc93a8132005-12-24 14:52:13 +1100663.Cm Protocol
664option in
Darren Tucker7a4a7652009-10-11 21:51:40 +1100665.Xr ssh_config 5
666or the
Damien Millerc93a8132005-12-24 14:52:13 +1100667.Fl 1
668and
669.Fl 2
670options (see above).
671Both protocols support similar authentication methods,
Darren Tucker7a4a7652009-10-11 21:51:40 +1100672but protocol 2 is the default since
Damien Millerc93a8132005-12-24 14:52:13 +1100673it provides additional mechanisms for confidentiality
674(the traffic is encrypted using AES, 3DES, Blowfish, CAST128, or Arcfour)
Damien Miller20bd4532011-08-06 06:17:30 +1000675and integrity (hmac-md5, hmac-sha1,
676hmac-sha2-256, hmac-sha2-512,
677umac-64, hmac-ripemd160).
Damien Millerc93a8132005-12-24 14:52:13 +1100678Protocol 1 lacks a strong mechanism for ensuring the
679integrity of the connection.
680.Pp
681The methods available for authentication are:
Damien Millerfbc94c82006-06-13 13:03:16 +1000682GSSAPI-based authentication,
Damien Millerc93a8132005-12-24 14:52:13 +1100683host-based authentication,
684public key authentication,
685challenge-response authentication,
686and password authentication.
687Authentication methods are tried in the order specified above,
688though protocol 2 has a configuration option to change the default order:
689.Cm PreferredAuthentications .
690.Pp
691Host-based authentication works as follows:
Darren Tuckerd3877b92005-12-20 16:09:36 +1100692If the machine the user logs in from is listed in
693.Pa /etc/hosts.equiv
694or
695.Pa /etc/shosts.equiv
696on the remote machine, and the user names are
697the same on both sides, or if the files
698.Pa ~/.rhosts
699or
700.Pa ~/.shosts
701exist in the user's home directory on the
702remote machine and contain a line containing the name of the client
703machine and the name of the user on that machine, the user is
Damien Millerc93a8132005-12-24 14:52:13 +1100704considered for login.
705Additionally, the server
706.Em must
707be able to verify the client's
708host key (see the description of
Darren Tuckerd3877b92005-12-20 16:09:36 +1100709.Pa /etc/ssh/ssh_known_hosts
710and
Damien Millerc93a8132005-12-24 14:52:13 +1100711.Pa ~/.ssh/known_hosts ,
712below)
713for login to be permitted.
Darren Tuckerd3877b92005-12-20 16:09:36 +1100714This authentication method closes security holes due to IP
Damien Millerc93a8132005-12-24 14:52:13 +1100715spoofing, DNS spoofing, and routing spoofing.
Darren Tuckerd3877b92005-12-20 16:09:36 +1100716[Note to the administrator:
717.Pa /etc/hosts.equiv ,
718.Pa ~/.rhosts ,
719and the rlogin/rsh protocol in general, are inherently insecure and should be
720disabled if security is desired.]
721.Pp
Damien Millerc93a8132005-12-24 14:52:13 +1100722Public key authentication works as follows:
723The scheme is based on public-key cryptography,
724using cryptosystems
725where encryption and decryption are done using separate keys,
726and it is unfeasible to derive the decryption key from the encryption key.
Darren Tuckerd3877b92005-12-20 16:09:36 +1100727The idea is that each user creates a public/private
728key pair for authentication purposes.
729The server knows the public key, and only the user knows the private key.
Damien Millerc93a8132005-12-24 14:52:13 +1100730.Nm
731implements public key authentication protocol automatically,
Damien Millereb8b60e2010-08-31 22:41:14 +1000732using one of the DSA, ECDSA or RSA algorithms.
Damien Millerc93a8132005-12-24 14:52:13 +1100733Protocol 1 is restricted to using only RSA keys,
Damien Millereb8b60e2010-08-31 22:41:14 +1000734but protocol 2 may use any.
Damien Millerc93a8132005-12-24 14:52:13 +1100735The
736.Sx HISTORY
737section of
738.Xr ssl 8
Damien Millerd4427902010-09-10 11:15:10 +1000739contains a brief discussion of the DSA and RSA algorithms.
Darren Tuckerd3877b92005-12-20 16:09:36 +1100740.Pp
741The file
742.Pa ~/.ssh/authorized_keys
743lists the public keys that are permitted for logging in.
744When the user logs in, the
745.Nm
746program tells the server which key pair it would like to use for
747authentication.
Damien Millerc93a8132005-12-24 14:52:13 +1100748The client proves that it has access to the private key
749and the server checks that the corresponding public key
750is authorized to accept the account.
Darren Tuckerd3877b92005-12-20 16:09:36 +1100751.Pp
Damien Millerc93a8132005-12-24 14:52:13 +1100752The user creates his/her key pair by running
Darren Tuckerd3877b92005-12-20 16:09:36 +1100753.Xr ssh-keygen 1 .
754This stores the private key in
755.Pa ~/.ssh/identity
Damien Millerc93a8132005-12-24 14:52:13 +1100756(protocol 1),
757.Pa ~/.ssh/id_dsa
758(protocol 2 DSA),
Damien Millereb8b60e2010-08-31 22:41:14 +1000759.Pa ~/.ssh/id_ecdsa
760(protocol 2 ECDSA),
Damien Millerc93a8132005-12-24 14:52:13 +1100761or
762.Pa ~/.ssh/id_rsa
763(protocol 2 RSA)
Darren Tuckerd3877b92005-12-20 16:09:36 +1100764and stores the public key in
765.Pa ~/.ssh/identity.pub
Damien Millerc93a8132005-12-24 14:52:13 +1100766(protocol 1),
767.Pa ~/.ssh/id_dsa.pub
768(protocol 2 DSA),
Damien Millereb8b60e2010-08-31 22:41:14 +1000769.Pa ~/.ssh/id_ecdsa.pub
770(protocol 2 ECDSA),
Damien Millerc93a8132005-12-24 14:52:13 +1100771or
772.Pa ~/.ssh/id_rsa.pub
773(protocol 2 RSA)
Darren Tuckerd3877b92005-12-20 16:09:36 +1100774in the user's home directory.
Damien Millerc93a8132005-12-24 14:52:13 +1100775The user should then copy the public key
Darren Tuckerd3877b92005-12-20 16:09:36 +1100776to
777.Pa ~/.ssh/authorized_keys
Damien Millerc93a8132005-12-24 14:52:13 +1100778in his/her home directory on the remote machine.
779The
Darren Tuckerd3877b92005-12-20 16:09:36 +1100780.Pa authorized_keys
781file corresponds to the conventional
782.Pa ~/.rhosts
783file, and has one key
Damien Millerc93a8132005-12-24 14:52:13 +1100784per line, though the lines can be very long.
Darren Tuckerd3877b92005-12-20 16:09:36 +1100785After this, the user can log in without giving the password.
786.Pp
Damien Miller922b5412010-03-05 21:30:54 +1100787A variation on public key authentication
788is available in the form of certificate authentication:
789instead of a set of public/private keys,
790signed certificates are used.
791This has the advantage that a single trusted certification authority
792can be used in place of many public/private keys.
793See the
794.Sx CERTIFICATES
795section of
796.Xr ssh-keygen 1
797for more information.
798.Pp
799The most convenient way to use public key or certificate authentication
800may be with an authentication agent.
Darren Tuckerd3877b92005-12-20 16:09:36 +1100801See
802.Xr ssh-agent 1
803for more information.
804.Pp
Damien Millerc93a8132005-12-24 14:52:13 +1100805Challenge-response authentication works as follows:
806The server sends an arbitrary
807.Qq challenge
808text, and prompts for a response.
809Protocol 2 allows multiple challenges and responses;
810protocol 1 is restricted to just one challenge/response.
811Examples of challenge-response authentication include
812BSD Authentication (see
813.Xr login.conf 5 )
814and PAM (some non-OpenBSD systems).
815.Pp
816Finally, if other authentication methods fail,
Darren Tuckerd3877b92005-12-20 16:09:36 +1100817.Nm
818prompts the user for a password.
819The password is sent to the remote
820host for checking; however, since all communications are encrypted,
821the password cannot be seen by someone listening on the network.
Damien Miller48c94ab2006-01-02 23:38:00 +1100822.Pp
823.Nm
824automatically maintains and checks a database containing
825identification for all hosts it has ever been used with.
826Host keys are stored in
827.Pa ~/.ssh/known_hosts
828in the user's home directory.
829Additionally, the file
830.Pa /etc/ssh/ssh_known_hosts
831is automatically checked for known hosts.
832Any new hosts are automatically added to the user's file.
833If a host's identification ever changes,
834.Nm
835warns about this and disables password authentication to prevent
836server spoofing or man-in-the-middle attacks,
837which could otherwise be used to circumvent the encryption.
838The
839.Cm StrictHostKeyChecking
840option can be used to control logins to machines whose
841host key is not known or has changed.
842.Pp
Darren Tuckerd3877b92005-12-20 16:09:36 +1100843When the user's identity has been accepted by the server, the server
844either executes the given command, or logs into the machine and gives
845the user a normal shell on the remote machine.
846All communication with
847the remote command or shell will be automatically encrypted.
848.Pp
849If a pseudo-terminal has been allocated (normal login session), the
850user may use the escape characters noted below.
851.Pp
852If no pseudo-tty has been allocated,
853the session is transparent and can be used to reliably transfer binary data.
854On most systems, setting the escape character to
855.Dq none
856will also make the session transparent even if a tty is used.
857.Pp
858The session terminates when the command or shell on the remote
Damien Miller8bfaf932006-01-14 10:09:30 +1100859machine exits and all X11 and TCP connections have been closed.
Damien Miller52d20612005-12-24 14:52:36 +1100860.Sh ESCAPE CHARACTERS
Darren Tuckerd3877b92005-12-20 16:09:36 +1100861When a pseudo-terminal has been requested,
862.Nm
863supports a number of functions through the use of an escape character.
864.Pp
865A single tilde character can be sent as
866.Ic ~~
867or by following the tilde by a character other than those described below.
868The escape character must always follow a newline to be interpreted as
869special.
870The escape character can be changed in configuration files using the
871.Cm EscapeChar
872configuration directive or on the command line by the
873.Fl e
874option.
875.Pp
876The supported escapes (assuming the default
877.Ql ~ )
878are:
879.Bl -tag -width Ds
880.It Cm ~.
881Disconnect.
882.It Cm ~^Z
883Background
Damien Miller1164c292006-01-02 23:38:37 +1100884.Nm .
Darren Tuckerd3877b92005-12-20 16:09:36 +1100885.It Cm ~#
886List forwarded connections.
887.It Cm ~&
888Background
889.Nm
890at logout when waiting for forwarded connection / X11 sessions to terminate.
891.It Cm ~?
892Display a list of escape characters.
893.It Cm ~B
894Send a BREAK to the remote system
895(only useful for SSH protocol version 2 and if the peer supports it).
896.It Cm ~C
897Open command line.
898Currently this allows the addition of port forwardings using the
Damien Miller0164cb82008-11-05 16:30:31 +1100899.Fl L ,
Darren Tuckerd3877b92005-12-20 16:09:36 +1100900.Fl R
Damien Miller0164cb82008-11-05 16:30:31 +1100901and
902.Fl D
Damien Miller329cb012005-12-24 14:53:23 +1100903options (see above).
Damien Millerff773642011-09-22 21:39:48 +1000904It also allows the cancellation of existing port-forwardings
905with
Damien Miller57e8ad32006-07-10 20:20:52 +1000906.Sm off
Damien Millerff773642011-09-22 21:39:48 +1000907.Fl KL Oo Ar bind_address : Oc Ar port
Damien Miller57e8ad32006-07-10 20:20:52 +1000908.Sm on
Damien Millerff773642011-09-22 21:39:48 +1000909for local,
910.Sm off
911.Fl KR Oo Ar bind_address : Oc Ar port
912.Sm on
913for remote and
914.Sm off
915.Fl KD Oo Ar bind_address : Oc Ar port
916.Sm on
917for dynamic port-forwardings.
Darren Tuckerd3877b92005-12-20 16:09:36 +1100918.Ic !\& Ns Ar command
919allows the user to execute a local command if the
920.Ic PermitLocalCommand
921option is enabled in
922.Xr ssh_config 5 .
923Basic help is available, using the
924.Fl h
925option.
926.It Cm ~R
927Request rekeying of the connection
928(only useful for SSH protocol version 2 and if the peer supports it).
Darren Tucker50a48d02012-09-06 21:25:37 +1000929.It Cm ~V
930Decrease the verbosity
931.Pq Ic LogLevel
932when errors are being written to stderr.
933.It Cm ~v
Darren Tucker83d0af62012-09-07 11:21:03 +1000934Increase the verbosity
Darren Tucker50a48d02012-09-06 21:25:37 +1000935.Pq Ic LogLevel
936when errors are being written to stderr.
Darren Tuckerd3877b92005-12-20 16:09:36 +1100937.El
Damien Millerf3177182006-01-14 10:09:13 +1100938.Sh TCP FORWARDING
939Forwarding of arbitrary TCP connections over the secure channel can
940be specified either on the command line or in a configuration file.
941One possible application of TCP forwarding is a secure connection to a
942mail server; another is going through firewalls.
943.Pp
944In the example below, we look at encrypting communication between
945an IRC client and server, even though the IRC server does not directly
946support encrypted communications.
947This works as follows:
948the user connects to the remote host using
949.Nm ,
950specifying a port to be used to forward connections
951to the remote server.
952After that it is possible to start the service which is to be encrypted
953on the client machine,
954connecting to the same local port,
955and
956.Nm
957will encrypt and forward the connection.
958.Pp
959The following example tunnels an IRC session from client machine
960.Dq 127.0.0.1
961(localhost)
962to remote server
963.Dq server.example.com :
964.Bd -literal -offset 4n
965$ ssh -f -L 1234:localhost:6667 server.example.com sleep 10
966$ irc -c '#users' -p 1234 pinky 127.0.0.1
967.Ed
968.Pp
969This tunnels a connection to IRC server
970.Dq server.example.com ,
971joining channel
972.Dq #users ,
973nickname
974.Dq pinky ,
975using port 1234.
976It doesn't matter which port is used,
977as long as it's greater than 1023
978(remember, only root can open sockets on privileged ports)
979and doesn't conflict with any ports already in use.
980The connection is forwarded to port 6667 on the remote server,
981since that's the standard port for IRC services.
982.Pp
983The
984.Fl f
985option backgrounds
986.Nm
987and the remote command
988.Dq sleep 10
989is specified to allow an amount of time
990(10 seconds, in the example)
991to start the service which is to be tunnelled.
992If no connections are made within the time specified,
993.Nm
994will exit.
Damien Millerf3177182006-01-14 10:09:13 +1100995.Sh X11 FORWARDING
Darren Tuckerd3877b92005-12-20 16:09:36 +1100996If the
997.Cm ForwardX11
998variable is set to
999.Dq yes
1000(or see the description of the
Damien Millerd7f308f2005-12-24 14:55:16 +11001001.Fl X ,
1002.Fl x ,
Darren Tuckerd3877b92005-12-20 16:09:36 +11001003and
Damien Millerd7f308f2005-12-24 14:55:16 +11001004.Fl Y
Damien Miller9a765b22005-12-24 14:53:44 +11001005options above)
Darren Tuckerd3877b92005-12-20 16:09:36 +11001006and the user is using X11 (the
1007.Ev DISPLAY
1008environment variable is set), the connection to the X11 display is
1009automatically forwarded to the remote side in such a way that any X11
1010programs started from the shell (or command) will go through the
1011encrypted channel, and the connection to the real X server will be made
1012from the local machine.
1013The user should not manually set
1014.Ev DISPLAY .
1015Forwarding of X11 connections can be
1016configured on the command line or in configuration files.
1017.Pp
1018The
1019.Ev DISPLAY
1020value set by
1021.Nm
1022will point to the server machine, but with a display number greater than zero.
1023This is normal, and happens because
1024.Nm
1025creates a
1026.Dq proxy
1027X server on the server machine for forwarding the
1028connections over the encrypted channel.
1029.Pp
1030.Nm
1031will also automatically set up Xauthority data on the server machine.
1032For this purpose, it will generate a random authorization cookie,
1033store it in Xauthority on the server, and verify that any forwarded
1034connections carry this cookie and replace it by the real cookie when
1035the connection is opened.
1036The real authentication cookie is never
1037sent to the server machine (and no cookies are sent in the plain).
1038.Pp
1039If the
1040.Cm ForwardAgent
1041variable is set to
1042.Dq yes
1043(or see the description of the
1044.Fl A
1045and
1046.Fl a
Damien Miller9a765b22005-12-24 14:53:44 +11001047options above) and
Darren Tuckerd3877b92005-12-20 16:09:36 +11001048the user is using an authentication agent, the connection to the agent
1049is automatically forwarded to the remote side.
Damien Millerbbc59092006-01-31 21:46:51 +11001050.Sh VERIFYING HOST KEYS
1051When connecting to a server for the first time,
1052a fingerprint of the server's public key is presented to the user
1053(unless the option
1054.Cm StrictHostKeyChecking
1055has been disabled).
1056Fingerprints can be determined using
1057.Xr ssh-keygen 1 :
1058.Pp
1059.Dl $ ssh-keygen -l -f /etc/ssh/ssh_host_rsa_key
1060.Pp
Darren Tuckerf6bffb12008-06-14 09:04:26 +10001061If the fingerprint is already known, it can be matched
1062and the key can be accepted or rejected.
1063Because of the difficulty of comparing host keys
1064just by looking at hex strings,
1065there is also support to compare host keys visually,
1066using
1067.Em random art .
1068By setting the
Damien Miller10288242008-06-30 00:04:03 +10001069.Cm VisualHostKey
Darren Tuckerf6bffb12008-06-14 09:04:26 +10001070option to
Damien Miller10288242008-06-30 00:04:03 +10001071.Dq yes ,
Darren Tuckerf6bffb12008-06-14 09:04:26 +10001072a small ASCII graphic gets displayed on every login to a server, no matter
1073if the session itself is interactive or not.
1074By learning the pattern a known server produces, a user can easily
1075find out that the host key has changed when a completely different pattern
1076is displayed.
1077Because these patterns are not unambiguous however, a pattern that looks
1078similar to the pattern remembered only gives a good probability that the
1079host key is the same, not guaranteed proof.
1080.Pp
1081To get a listing of the fingerprints along with their random art for
1082all known hosts, the following command line can be used:
1083.Pp
1084.Dl $ ssh-keygen -lv -f ~/.ssh/known_hosts
1085.Pp
Damien Millerbbc59092006-01-31 21:46:51 +11001086If the fingerprint is unknown,
1087an alternative method of verification is available:
1088SSH fingerprints verified by DNS.
1089An additional resource record (RR),
1090SSHFP,
1091is added to a zonefile
1092and the connecting client is able to match the fingerprint
1093with that of the key presented.
1094.Pp
1095In this example, we are connecting a client to a server,
1096.Dq host.example.com .
1097The SSHFP resource records should first be added to the zonefile for
1098host.example.com:
1099.Bd -literal -offset indent
Damien Millera1b3d632006-03-26 00:07:02 +11001100$ ssh-keygen -r host.example.com.
Damien Millerbbc59092006-01-31 21:46:51 +11001101.Ed
1102.Pp
1103The output lines will have to be added to the zonefile.
1104To check that the zone is answering fingerprint queries:
1105.Pp
1106.Dl $ dig -t SSHFP host.example.com
1107.Pp
1108Finally the client connects:
1109.Bd -literal -offset indent
1110$ ssh -o "VerifyHostKeyDNS ask" host.example.com
1111[...]
1112Matching host key fingerprint found in DNS.
1113Are you sure you want to continue connecting (yes/no)?
1114.Ed
1115.Pp
1116See the
1117.Cm VerifyHostKeyDNS
1118option in
1119.Xr ssh_config 5
1120for more information.
Darren Tucker248dd132006-01-20 11:30:58 +11001121.Sh SSH-BASED VIRTUAL PRIVATE NETWORKS
1122.Nm
1123contains support for Virtual Private Network (VPN) tunnelling
1124using the
1125.Xr tun 4
1126network pseudo-device,
1127allowing two networks to be joined securely.
1128The
1129.Xr sshd_config 5
1130configuration option
1131.Cm PermitTunnel
1132controls whether the server supports this,
1133and at what level (layer 2 or 3 traffic).
1134.Pp
1135The following example would connect client network 10.0.50.0/24
Damien Miller3975ee22006-11-05 05:31:33 +11001136with remote network 10.0.99.0/24 using a point-to-point connection
1137from 10.1.1.1 to 10.1.1.2,
1138provided that the SSH server running on the gateway to the remote network,
1139at 192.168.1.15, allows it.
1140.Pp
1141On the client:
Darren Tucker248dd132006-01-20 11:30:58 +11001142.Bd -literal -offset indent
1143# ssh -f -w 0:1 192.168.1.15 true
Damien Miller3975ee22006-11-05 05:31:33 +11001144# ifconfig tun0 10.1.1.1 10.1.1.2 netmask 255.255.255.252
1145# route add 10.0.99.0/24 10.1.1.2
1146.Ed
1147.Pp
1148On the server:
1149.Bd -literal -offset indent
1150# ifconfig tun1 10.1.1.2 10.1.1.1 netmask 255.255.255.252
1151# route add 10.0.50.0/24 10.1.1.1
Darren Tucker248dd132006-01-20 11:30:58 +11001152.Ed
1153.Pp
1154Client access may be more finely tuned via the
1155.Pa /root/.ssh/authorized_keys
1156file (see below) and the
1157.Cm PermitRootLogin
1158server option.
Damien Millere93eaaa2006-03-15 11:05:59 +11001159The following entry would permit connections on
Darren Tucker248dd132006-01-20 11:30:58 +11001160.Xr tun 4
Damien Millere93eaaa2006-03-15 11:05:59 +11001161device 1 from user
Darren Tucker248dd132006-01-20 11:30:58 +11001162.Dq jane
Damien Millere93eaaa2006-03-15 11:05:59 +11001163and on tun device 2 from user
Darren Tucker248dd132006-01-20 11:30:58 +11001164.Dq john ,
1165if
1166.Cm PermitRootLogin
1167is set to
1168.Dq forced-commands-only :
1169.Bd -literal -offset 2n
1170tunnel="1",command="sh /etc/netstart tun1" ssh-rsa ... jane
Damien Miller9f67a212006-03-15 11:05:35 +11001171tunnel="2",command="sh /etc/netstart tun2" ssh-rsa ... john
Darren Tucker248dd132006-01-20 11:30:58 +11001172.Ed
1173.Pp
Darren Tuckerffe88e12006-10-18 07:53:06 +10001174Since an SSH-based setup entails a fair amount of overhead,
Darren Tucker248dd132006-01-20 11:30:58 +11001175it may be more suited to temporary setups,
1176such as for wireless VPNs.
1177More permanent VPNs are better provided by tools such as
1178.Xr ipsecctl 8
1179and
1180.Xr isakmpd 8 .
Damien Miller32aa1441999-10-29 09:15:49 +10001181.Sh ENVIRONMENT
1182.Nm
1183will normally set the following environment variables:
Damien Miller6aa22902006-01-06 14:48:34 +11001184.Bl -tag -width "SSH_ORIGINAL_COMMAND"
Damien Miller32aa1441999-10-29 09:15:49 +10001185.It Ev DISPLAY
1186The
1187.Ev DISPLAY
Damien Miller7684ee12000-03-17 23:40:15 +11001188variable indicates the location of the X11 server.
Damien Miller22c77262000-04-13 12:26:34 +10001189It is automatically set by
Damien Miller32aa1441999-10-29 09:15:49 +10001190.Nm
1191to point to a value of the form
Damien Miller14af93e2006-01-02 23:38:21 +11001192.Dq hostname:n ,
1193where
1194.Dq hostname
1195indicates the host where the shell runs, and
1196.Sq n
1197is an integer \*(Ge 1.
Damien Miller7684ee12000-03-17 23:40:15 +11001198.Nm
1199uses this special value to forward X11 connections over the secure
1200channel.
Ben Lindstromc65e6a02001-04-23 13:02:16 +00001201The user should normally not set
1202.Ev DISPLAY
1203explicitly, as that
Damien Miller32aa1441999-10-29 09:15:49 +10001204will render the X11 connection insecure (and will require the user to
1205manually copy any required authorization cookies).
1206.It Ev HOME
1207Set to the path of the user's home directory.
1208.It Ev LOGNAME
1209Synonym for
1210.Ev USER ;
1211set for compatibility with systems that use this variable.
1212.It Ev MAIL
Ben Lindstrome59433d2001-09-12 16:41:37 +00001213Set to the path of the user's mailbox.
Damien Miller7684ee12000-03-17 23:40:15 +11001214.It Ev PATH
Damien Miller32aa1441999-10-29 09:15:49 +10001215Set to the default
1216.Ev PATH ,
1217as specified when compiling
Damien Miller1164c292006-01-02 23:38:37 +11001218.Nm .
Ben Lindstrom5bf5d672001-07-04 04:31:38 +00001219.It Ev SSH_ASKPASS
1220If
1221.Nm
1222needs a passphrase, it will read the passphrase from the current
1223terminal if it was run from a terminal.
1224If
1225.Nm
1226does not have a terminal associated with it but
1227.Ev DISPLAY
1228and
1229.Ev SSH_ASKPASS
1230are set, it will execute the program specified by
1231.Ev SSH_ASKPASS
1232and open an X11 window to read the passphrase.
1233This is particularly useful when calling
1234.Nm
1235from a
Darren Tucker4e4fe002004-11-05 20:01:03 +11001236.Pa .xsession
Ben Lindstrom5bf5d672001-07-04 04:31:38 +00001237or related script.
1238(Note that on some machines it
1239may be necessary to redirect the input from
1240.Pa /dev/null
1241to make this work.)
Damien Miller32aa1441999-10-29 09:15:49 +10001242.It Ev SSH_AUTH_SOCK
Damien Miller14af93e2006-01-02 23:38:21 +11001243Identifies the path of a
1244.Ux Ns -domain
1245socket used to communicate with the agent.
Damien Millerf37e2462002-09-19 11:47:55 +10001246.It Ev SSH_CONNECTION
1247Identifies the client and server ends of the connection.
Damien Miller7684ee12000-03-17 23:40:15 +11001248The variable contains
Damien Miller14af93e2006-01-02 23:38:21 +11001249four space-separated values: client IP address, client port number,
1250server IP address, and server port number.
Ben Lindstrom4dccfa52000-12-28 16:40:05 +00001251.It Ev SSH_ORIGINAL_COMMAND
Damien Miller14af93e2006-01-02 23:38:21 +11001252This variable contains the original command line if a forced command
Ben Lindstrom4dccfa52000-12-28 16:40:05 +00001253is executed.
1254It can be used to extract the original arguments.
Damien Miller32aa1441999-10-29 09:15:49 +10001255.It Ev SSH_TTY
1256This is set to the name of the tty (path to the device) associated
Damien Miller7684ee12000-03-17 23:40:15 +11001257with the current shell or command.
1258If the current session has no tty,
Damien Miller32aa1441999-10-29 09:15:49 +10001259this variable is not set.
1260.It Ev TZ
Damien Miller6dbdb6a2005-12-13 19:25:43 +11001261This variable is set to indicate the present time zone if it
Damien Miller208f1ed2006-03-15 11:56:03 +11001262was set when the daemon was started (i.e. the daemon passes the value
Damien Miller32aa1441999-10-29 09:15:49 +10001263on to new connections).
1264.It Ev USER
1265Set to the name of the user logging in.
1266.El
1267.Pp
Damien Miller22c77262000-04-13 12:26:34 +10001268Additionally,
Damien Miller32aa1441999-10-29 09:15:49 +10001269.Nm
Damien Miller22c77262000-04-13 12:26:34 +10001270reads
Damien Miller167ea5d2005-05-26 12:04:02 +10001271.Pa ~/.ssh/environment ,
Damien Miller32aa1441999-10-29 09:15:49 +10001272and adds lines of the format
1273.Dq VARNAME=value
Damien Miller14af93e2006-01-02 23:38:21 +11001274to the environment if the file exists and users are allowed to
Ben Lindstromdc7adf22002-08-20 18:38:02 +00001275change their environment.
Darren Tucker61776952003-10-02 16:19:47 +10001276For more information, see the
Ben Lindstromdc7adf22002-08-20 18:38:02 +00001277.Cm PermitUserEnvironment
Ben Lindstrombd9bf382002-08-20 18:54:20 +00001278option in
Ben Lindstromdc7adf22002-08-20 18:38:02 +00001279.Xr sshd_config 5 .
Damien Miller32aa1441999-10-29 09:15:49 +10001280.Sh FILES
Damien Miller7655f5c2006-01-06 14:48:18 +11001281.Bl -tag -width Ds -compact
Damien Millerafdae612010-08-31 22:31:14 +10001282.It Pa ~/.rhosts
Damien Miller1bcdb502006-01-06 14:49:38 +11001283This file is used for host-based authentication (see above).
Ben Lindstromebd888d2001-03-05 05:49:29 +00001284On some machines this file may need to be
Damien Miller1bcdb502006-01-06 14:49:38 +11001285world-readable if the user's home directory is on an NFS partition,
Damien Miller32aa1441999-10-29 09:15:49 +10001286because
1287.Xr sshd 8
Damien Miller7684ee12000-03-17 23:40:15 +11001288reads it as root.
1289Additionally, this file must be owned by the user,
1290and must not have write permissions for anyone else.
1291The recommended
Damien Miller32aa1441999-10-29 09:15:49 +10001292permission for most machines is read/write for the user, and not
1293accessible by others.
1294.Pp
Damien Millerafdae612010-08-31 22:31:14 +10001295.It Pa ~/.shosts
Damien Miller1bcdb502006-01-06 14:49:38 +11001296This file is used in exactly the same way as
1297.Pa .rhosts ,
1298but allows host-based authentication without permitting login with
1299rlogin/rsh.
Damien Miller7655f5c2006-01-06 14:48:18 +11001300.Pp
Damien Millerafdae612010-08-31 22:31:14 +10001301.It Pa ~/.ssh/
Damien Miller520e6152008-02-10 22:46:22 +11001302This directory is the default location for all user-specific configuration
1303and authentication information.
1304There is no general requirement to keep the entire contents of this directory
1305secret, but the recommended permissions are read/write/execute for the user,
1306and not accessible by others.
1307.Pp
Damien Millerafdae612010-08-31 22:31:14 +10001308.It Pa ~/.ssh/authorized_keys
Damien Millereb8b60e2010-08-31 22:41:14 +10001309Lists the public keys (DSA/ECDSA/RSA) that can be used for logging in as
1310this user.
Damien Millerfb8ea742006-01-06 14:48:52 +11001311The format of this file is described in the
1312.Xr sshd 8
1313manual page.
Damien Millerfb8ea742006-01-06 14:48:52 +11001314This file is not highly sensitive, but the recommended
1315permissions are read/write for the user, and not accessible by others.
1316.Pp
Damien Millerafdae612010-08-31 22:31:14 +10001317.It Pa ~/.ssh/config
Damien Millerfb8ea742006-01-06 14:48:52 +11001318This is the per-user configuration file.
1319The file format and configuration options are described in
1320.Xr ssh_config 5 .
1321Because of the potential for abuse, this file must have strict permissions:
1322read/write for the user, and not accessible by others.
1323.Pp
Damien Millerafdae612010-08-31 22:31:14 +10001324.It Pa ~/.ssh/environment
Damien Miller4c102ee2006-01-06 14:49:17 +11001325Contains additional definitions for environment variables; see
1326.Sx ENVIRONMENT ,
Damien Millerfb8ea742006-01-06 14:48:52 +11001327above.
1328.Pp
Damien Millerafdae612010-08-31 22:31:14 +10001329.It Pa ~/.ssh/identity
1330.It Pa ~/.ssh/id_dsa
Damien Millereb8b60e2010-08-31 22:41:14 +10001331.It Pa ~/.ssh/id_ecdsa
Damien Millerafdae612010-08-31 22:31:14 +10001332.It Pa ~/.ssh/id_rsa
Damien Millerfb8ea742006-01-06 14:48:52 +11001333Contains the private key for authentication.
1334These files
1335contain sensitive data and should be readable by the user but not
1336accessible by others (read/write/execute).
1337.Nm
1338will simply ignore a private key file if it is accessible by others.
1339It is possible to specify a passphrase when
1340generating the key which will be used to encrypt the
1341sensitive part of this file using 3DES.
1342.Pp
Damien Millerafdae612010-08-31 22:31:14 +10001343.It Pa ~/.ssh/identity.pub
1344.It Pa ~/.ssh/id_dsa.pub
Damien Millereb8b60e2010-08-31 22:41:14 +10001345.It Pa ~/.ssh/id_ecdsa.pub
Damien Millerafdae612010-08-31 22:31:14 +10001346.It Pa ~/.ssh/id_rsa.pub
Damien Millerfb8ea742006-01-06 14:48:52 +11001347Contains the public key for authentication.
1348These files are not
1349sensitive and can (but need not) be readable by anyone.
Damien Millerfb8ea742006-01-06 14:48:52 +11001350.Pp
Damien Millerafdae612010-08-31 22:31:14 +10001351.It Pa ~/.ssh/known_hosts
Damien Millere87eb4c2006-01-14 10:08:36 +11001352Contains a list of host keys for all hosts the user has logged into
1353that are not already in the systemwide list of known host keys.
Damien Millerfb8ea742006-01-06 14:48:52 +11001354See
Damien Millere87eb4c2006-01-14 10:08:36 +11001355.Xr sshd 8
1356for further details of the format of this file.
Damien Millerfb8ea742006-01-06 14:48:52 +11001357.Pp
Damien Millerafdae612010-08-31 22:31:14 +10001358.It Pa ~/.ssh/rc
Damien Millerfb8ea742006-01-06 14:48:52 +11001359Commands in this file are executed by
1360.Nm
Damien Miller7e76e1f2006-01-14 10:08:57 +11001361when the user logs in, just before the user's shell (or command) is
Damien Millerfb8ea742006-01-06 14:48:52 +11001362started.
1363See the
1364.Xr sshd 8
1365manual page for more information.
1366.Pp
Damien Millerafdae612010-08-31 22:31:14 +10001367.It Pa /etc/hosts.equiv
Damien Miller1bcdb502006-01-06 14:49:38 +11001368This file is for host-based authentication (see above).
1369It should only be writable by root.
Damien Miller7655f5c2006-01-06 14:48:18 +11001370.Pp
Damien Millerafdae612010-08-31 22:31:14 +10001371.It Pa /etc/shosts.equiv
Damien Miller1bcdb502006-01-06 14:49:38 +11001372This file is used in exactly the same way as
1373.Pa hosts.equiv ,
1374but allows host-based authentication without permitting login with
1375rlogin/rsh.
Damien Miller7655f5c2006-01-06 14:48:18 +11001376.Pp
Damien Millerfb8ea742006-01-06 14:48:52 +11001377.It Pa /etc/ssh/ssh_config
1378Systemwide configuration file.
1379The file format and configuration options are described in
1380.Xr ssh_config 5 .
1381.Pp
Damien Millerafdae612010-08-31 22:31:14 +10001382.It Pa /etc/ssh/ssh_host_key
1383.It Pa /etc/ssh/ssh_host_dsa_key
Damien Millereb8b60e2010-08-31 22:41:14 +10001384.It Pa /etc/ssh/ssh_host_ecdsa_key
Damien Millerafdae612010-08-31 22:31:14 +10001385.It Pa /etc/ssh/ssh_host_rsa_key
Damien Millerb9902cf2012-06-20 21:52:58 +10001386These files contain the private parts of the host keys
Damien Miller7e76e1f2006-01-14 10:08:57 +11001387and are used for host-based authentication.
1388If protocol version 1 is used,
Damien Millerfb8ea742006-01-06 14:48:52 +11001389.Nm
1390must be setuid root, since the host key is readable only by root.
1391For protocol version 2,
1392.Nm
1393uses
1394.Xr ssh-keysign 8
Damien Miller7e76e1f2006-01-14 10:08:57 +11001395to access the host keys,
1396eliminating the requirement that
Damien Millerfb8ea742006-01-06 14:48:52 +11001397.Nm
Damien Miller7e76e1f2006-01-14 10:08:57 +11001398be setuid root when host-based authentication is used.
Damien Millerfb8ea742006-01-06 14:48:52 +11001399By default
1400.Nm
1401is not setuid root.
1402.Pp
Damien Millerafdae612010-08-31 22:31:14 +10001403.It Pa /etc/ssh/ssh_known_hosts
Damien Millerfb8ea742006-01-06 14:48:52 +11001404Systemwide list of known host keys.
1405This file should be prepared by the
1406system administrator to contain the public host keys of all machines in the
1407organization.
Damien Millere87eb4c2006-01-14 10:08:36 +11001408It should be world-readable.
1409See
Damien Millerfb8ea742006-01-06 14:48:52 +11001410.Xr sshd 8
Damien Millere87eb4c2006-01-14 10:08:36 +11001411for further details of the format of this file.
Damien Millerfb8ea742006-01-06 14:48:52 +11001412.Pp
Damien Millerafdae612010-08-31 22:31:14 +10001413.It Pa /etc/ssh/sshrc
Damien Miller32aa1441999-10-29 09:15:49 +10001414Commands in this file are executed by
1415.Nm
Damien Miller7e76e1f2006-01-14 10:08:57 +11001416when the user logs in, just before the user's shell (or command) is started.
Damien Miller32aa1441999-10-29 09:15:49 +10001417See the
1418.Xr sshd 8
1419manual page for more information.
Damien Miller7b28dc52000-09-05 13:34:53 +11001420.El
Damien Millerdaa7b222010-09-10 11:19:33 +10001421.Sh EXIT STATUS
1422.Nm
1423exits with the exit status of the remote command or with 255
1424if an error occurred.
Damien Miller32aa1441999-10-29 09:15:49 +10001425.Sh SEE ALSO
Damien Miller32aa1441999-10-29 09:15:49 +10001426.Xr scp 1 ,
Damien Miller33804262001-02-04 23:20:18 +11001427.Xr sftp 1 ,
Damien Miller32aa1441999-10-29 09:15:49 +10001428.Xr ssh-add 1 ,
1429.Xr ssh-agent 1 ,
1430.Xr ssh-keygen 1 ,
Damien Miller128a0f12006-01-06 14:50:11 +11001431.Xr ssh-keyscan 1 ,
Darren Tucker248dd132006-01-20 11:30:58 +11001432.Xr tun 4 ,
Darren Tucker61776952003-10-02 16:19:47 +10001433.Xr hosts.equiv 5 ,
Ben Lindstrombf69e3b2002-06-23 00:31:24 +00001434.Xr ssh_config 5 ,
Ben Lindstromc001cd32002-06-23 00:32:11 +00001435.Xr ssh-keysign 8 ,
Ben Lindstrom5ab6ae12001-02-10 22:08:03 +00001436.Xr sshd 8
Darren Tucker628a3fd2012-10-05 10:50:15 +10001437.Sh STANDARDS
Ben Lindstrom160ec622001-04-22 17:17:46 +00001438.Rs
Darren Tucker628a3fd2012-10-05 10:50:15 +10001439.%A S. Lehtinen
1440.%A C. Lonvick
1441.%D January 2006
Damien Miller39a93a32006-03-15 11:34:45 +11001442.%R RFC 4250
Darren Tucker628a3fd2012-10-05 10:50:15 +10001443.%T The Secure Shell (SSH) Protocol Assigned Numbers
Damien Miller39a93a32006-03-15 11:34:45 +11001444.Re
Darren Tucker628a3fd2012-10-05 10:50:15 +10001445.Pp
Damien Miller39a93a32006-03-15 11:34:45 +11001446.Rs
Darren Tucker628a3fd2012-10-05 10:50:15 +10001447.%A T. Ylonen
1448.%A C. Lonvick
1449.%D January 2006
Damien Miller39a93a32006-03-15 11:34:45 +11001450.%R RFC 4251
Darren Tucker628a3fd2012-10-05 10:50:15 +10001451.%T The Secure Shell (SSH) Protocol Architecture
Damien Miller39a93a32006-03-15 11:34:45 +11001452.Re
Darren Tucker628a3fd2012-10-05 10:50:15 +10001453.Pp
Damien Miller39a93a32006-03-15 11:34:45 +11001454.Rs
Darren Tucker628a3fd2012-10-05 10:50:15 +10001455.%A T. Ylonen
1456.%A C. Lonvick
1457.%D January 2006
Damien Miller39a93a32006-03-15 11:34:45 +11001458.%R RFC 4252
Darren Tucker628a3fd2012-10-05 10:50:15 +10001459.%T The Secure Shell (SSH) Authentication Protocol
Damien Miller39a93a32006-03-15 11:34:45 +11001460.Re
Darren Tucker628a3fd2012-10-05 10:50:15 +10001461.Pp
Damien Miller39a93a32006-03-15 11:34:45 +11001462.Rs
Darren Tucker628a3fd2012-10-05 10:50:15 +10001463.%A T. Ylonen
1464.%A C. Lonvick
1465.%D January 2006
Damien Miller39a93a32006-03-15 11:34:45 +11001466.%R RFC 4253
Darren Tucker628a3fd2012-10-05 10:50:15 +10001467.%T The Secure Shell (SSH) Transport Layer Protocol
Damien Miller39a93a32006-03-15 11:34:45 +11001468.Re
Darren Tucker628a3fd2012-10-05 10:50:15 +10001469.Pp
Damien Miller39a93a32006-03-15 11:34:45 +11001470.Rs
Darren Tucker628a3fd2012-10-05 10:50:15 +10001471.%A T. Ylonen
1472.%A C. Lonvick
1473.%D January 2006
Damien Miller39a93a32006-03-15 11:34:45 +11001474.%R RFC 4254
Darren Tucker628a3fd2012-10-05 10:50:15 +10001475.%T The Secure Shell (SSH) Connection Protocol
Damien Miller39a93a32006-03-15 11:34:45 +11001476.Re
Darren Tucker628a3fd2012-10-05 10:50:15 +10001477.Pp
Damien Miller39a93a32006-03-15 11:34:45 +11001478.Rs
Darren Tucker628a3fd2012-10-05 10:50:15 +10001479.%A J. Schlyter
1480.%A W. Griffin
1481.%D January 2006
Damien Miller39a93a32006-03-15 11:34:45 +11001482.%R RFC 4255
Darren Tucker628a3fd2012-10-05 10:50:15 +10001483.%T Using DNS to Securely Publish Secure Shell (SSH) Key Fingerprints
Damien Miller39a93a32006-03-15 11:34:45 +11001484.Re
Darren Tucker628a3fd2012-10-05 10:50:15 +10001485.Pp
Damien Miller39a93a32006-03-15 11:34:45 +11001486.Rs
Darren Tucker628a3fd2012-10-05 10:50:15 +10001487.%A F. Cusack
1488.%A M. Forssen
1489.%D January 2006
Damien Miller39a93a32006-03-15 11:34:45 +11001490.%R RFC 4256
Darren Tucker628a3fd2012-10-05 10:50:15 +10001491.%T Generic Message Exchange Authentication for the Secure Shell Protocol (SSH)
Damien Miller39a93a32006-03-15 11:34:45 +11001492.Re
Darren Tucker628a3fd2012-10-05 10:50:15 +10001493.Pp
Damien Miller39a93a32006-03-15 11:34:45 +11001494.Rs
Darren Tucker628a3fd2012-10-05 10:50:15 +10001495.%A J. Galbraith
1496.%A P. Remaker
1497.%D January 2006
Damien Miller39a93a32006-03-15 11:34:45 +11001498.%R RFC 4335
Darren Tucker628a3fd2012-10-05 10:50:15 +10001499.%T The Secure Shell (SSH) Session Channel Break Extension
Damien Miller39a93a32006-03-15 11:34:45 +11001500.Re
Darren Tucker628a3fd2012-10-05 10:50:15 +10001501.Pp
Damien Miller39a93a32006-03-15 11:34:45 +11001502.Rs
Darren Tucker628a3fd2012-10-05 10:50:15 +10001503.%A M. Bellare
1504.%A T. Kohno
1505.%A C. Namprempre
1506.%D January 2006
Damien Miller39a93a32006-03-15 11:34:45 +11001507.%R RFC 4344
Darren Tucker628a3fd2012-10-05 10:50:15 +10001508.%T The Secure Shell (SSH) Transport Layer Encryption Modes
Damien Miller39a93a32006-03-15 11:34:45 +11001509.Re
Darren Tucker628a3fd2012-10-05 10:50:15 +10001510.Pp
Damien Miller39a93a32006-03-15 11:34:45 +11001511.Rs
Darren Tucker628a3fd2012-10-05 10:50:15 +10001512.%A B. Harris
1513.%D January 2006
Damien Miller39a93a32006-03-15 11:34:45 +11001514.%R RFC 4345
Darren Tucker628a3fd2012-10-05 10:50:15 +10001515.%T Improved Arcfour Modes for the Secure Shell (SSH) Transport Layer Protocol
Ben Lindstrom160ec622001-04-22 17:17:46 +00001516.Re
Darren Tucker628a3fd2012-10-05 10:50:15 +10001517.Pp
Damien Miller3e96d742006-03-25 23:39:29 +11001518.Rs
Darren Tucker628a3fd2012-10-05 10:50:15 +10001519.%A M. Friedl
1520.%A N. Provos
1521.%A W. Simpson
1522.%D March 2006
Damien Miller3e96d742006-03-25 23:39:29 +11001523.%R RFC 4419
Darren Tucker628a3fd2012-10-05 10:50:15 +10001524.%T Diffie-Hellman Group Exchange for the Secure Shell (SSH) Transport Layer Protocol
Damien Miller3e96d742006-03-25 23:39:29 +11001525.Re
Darren Tucker628a3fd2012-10-05 10:50:15 +10001526.Pp
Damien Millerc0367fb2007-01-05 16:25:46 +11001527.Rs
Darren Tucker628a3fd2012-10-05 10:50:15 +10001528.%A J. Galbraith
1529.%A R. Thayer
1530.%D November 2006
Damien Millerc0367fb2007-01-05 16:25:46 +11001531.%R RFC 4716
Darren Tucker628a3fd2012-10-05 10:50:15 +10001532.%T The Secure Shell (SSH) Public Key File Format
Damien Millerc0367fb2007-01-05 16:25:46 +11001533.Re
Darren Tucker628a3fd2012-10-05 10:50:15 +10001534.Pp
Darren Tuckerf6bffb12008-06-14 09:04:26 +10001535.Rs
Darren Tucker628a3fd2012-10-05 10:50:15 +10001536.%A D. Stebila
1537.%A J. Green
1538.%D December 2009
Damien Miller1ca94692010-09-24 22:01:22 +10001539.%R RFC 5656
Darren Tucker628a3fd2012-10-05 10:50:15 +10001540.%T Elliptic Curve Algorithm Integration in the Secure Shell Transport Layer
Damien Miller1ca94692010-09-24 22:01:22 +10001541.Re
Darren Tucker628a3fd2012-10-05 10:50:15 +10001542.Pp
Damien Miller1ca94692010-09-24 22:01:22 +10001543.Rs
Darren Tuckerf6bffb12008-06-14 09:04:26 +10001544.%A A. Perrig
1545.%A D. Song
1546.%D 1999
Darren Tucker628a3fd2012-10-05 10:50:15 +10001547.%O International Workshop on Cryptographic Techniques and E-Commerce (CrypTEC '99)
1548.%T Hash Visualization: a New Technique to improve Real-World Security
Darren Tuckerf6bffb12008-06-14 09:04:26 +10001549.Re
Damien Millerf1ce5052003-06-11 22:04:39 +10001550.Sh AUTHORS
1551OpenSSH is a derivative of the original and free
1552ssh 1.2.12 release by Tatu Ylonen.
1553Aaron Campbell, Bob Beck, Markus Friedl, Niels Provos,
1554Theo de Raadt and Dug Song
1555removed many bugs, re-added newer features and
1556created OpenSSH.
1557Markus Friedl contributed the support for SSH
1558protocol versions 1.5 and 2.0.