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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.\"
djm@openbsd.org7a2cb182019-01-22 11:51:25 +000036.\" $OpenBSD: ssh.1,v 1.400 2019/01/22 11:51:25 djm Exp $
37.Dd $Mdocdate: January 22 2019 $
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
djm@openbsd.org788ac792017-04-30 23:18:22 +000045.Op Fl 46AaCfGgKkMNnqsTtVvXxYy
djm@openbsd.orgac2e3022018-02-23 02:34:33 +000046.Op Fl B Ar bind_interface
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 Miller03d4d7e2013-04-23 15:21:06 +100050.Op Fl E Ar log_file
Damien Miller32aa1441999-10-29 09:15:49 +100051.Op Fl e Ar escape_char
Ben Lindstrom14f31ab2001-09-12 17:48:04 +000052.Op Fl F Ar configfile
Damien Miller048dc932010-02-12 09:22:04 +110053.Op Fl I Ar pkcs11
Darren Tucker61776952003-10-02 16:19:47 +100054.Op Fl i Ar identity_file
millert@openbsd.org887669e2017-10-21 23:06:24 +000055.Op Fl J Ar destination
millert@openbsd.org79ec2142015-07-20 15:39:52 +000056.Op Fl L Ar address
Darren Tucker61776952003-10-02 16:19:47 +100057.Op Fl l Ar login_name
58.Op Fl m Ar mac_spec
Darren Tucker7ebfc102004-11-07 20:06:19 +110059.Op Fl O Ar ctl_cmd
Darren Tucker61776952003-10-02 16:19:47 +100060.Op Fl o Ar option
Darren Tucker61776952003-10-02 16:19:47 +100061.Op Fl p Ar port
djm@openbsd.orgc0f55db2015-09-11 03:42:32 +000062.Op Fl Q Ar query_option
millert@openbsd.org79ec2142015-07-20 15:39:52 +000063.Op Fl R Ar address
Darren Tucker7ebfc102004-11-07 20:06:19 +110064.Op Fl S Ar ctl_path
Darren Tucker7ad8dd22010-01-12 19:40:27 +110065.Op Fl W Ar host : Ns Ar port
Damien Millerbcfbc482010-07-16 13:59:11 +100066.Op Fl w Ar local_tun Ns Op : Ns Ar remote_tun
millert@openbsd.org887669e2017-10-21 23:06:24 +000067.Ar destination
Damien Miller32aa1441999-10-29 09:15:49 +100068.Op Ar command
Damien Miller22c77262000-04-13 12:26:34 +100069.Sh DESCRIPTION
Damien Miller32aa1441999-10-29 09:15:49 +100070.Nm
Ben Lindstromd58eb5f2001-03-07 06:07:22 +000071(SSH client) is a program for logging into a remote machine and for
Damien Miller7684ee12000-03-17 23:40:15 +110072executing commands on a remote machine.
mmcc@openbsd.org5e288922015-11-06 00:31:41 +000073It is intended to provide secure encrypted communications between
Damien Miller7684ee12000-03-17 23:40:15 +110074two untrusted hosts over an insecure network.
Damien Millera8a0f652014-07-30 12:32:28 +100075X11 connections, arbitrary TCP ports and
76.Ux Ns -domain
77sockets can also be forwarded over the secure channel.
Damien Miller32aa1441999-10-29 09:15:49 +100078.Pp
79.Nm
Damien Miller22c77262000-04-13 12:26:34 +100080connects and logs into the specified
jmc@openbsd.org@openbsd.org0b2e2892017-10-25 06:19:46 +000081.Ar destination ,
millert@openbsd.org887669e2017-10-21 23:06:24 +000082which may be specified as either
jmc@openbsd.org@openbsd.org0b2e2892017-10-25 06:19:46 +000083.Sm off
84.Oo user @ Oc hostname
85.Sm on
86or a URI of the form
87.Sm off
88.No ssh:// Oo user @ Oc hostname Op : port .
89.Sm on
Damien Miller32aa1441999-10-29 09:15:49 +100090The user must prove
Damien Millere247cc42000-05-07 12:03:14 +100091his/her identity to the remote machine using one of several methods
mmcc@openbsd.org5e288922015-11-06 00:31:41 +000092(see below).
Damien Millere247cc42000-05-07 12:03:14 +100093.Pp
millert@openbsd.org887669e2017-10-21 23:06:24 +000094If a
Darren Tucker61776952003-10-02 16:19:47 +100095.Ar command
96is specified,
Darren Tuckerb18c8672005-12-20 16:10:09 +110097it is executed on the remote host instead of a login shell.
Darren Tucker0b42e6d2004-08-13 21:22:40 +100098.Pp
Damien Miller0bc1bd82000-11-13 22:57:25 +110099The options are as follows:
millert@openbsd.org79ec2142015-07-20 15:39:52 +0000100.Pp
millert@openbsd.orgebe27eb2015-07-20 18:44:12 +0000101.Bl -tag -width Ds -compact
Darren Tucker61776952003-10-02 16:19:47 +1000102.It Fl 4
103Forces
104.Nm
105to use IPv4 addresses only.
millert@openbsd.org79ec2142015-07-20 15:39:52 +0000106.Pp
Darren Tucker61776952003-10-02 16:19:47 +1000107.It Fl 6
108Forces
109.Nm
110to use IPv6 addresses only.
millert@openbsd.org79ec2142015-07-20 15:39:52 +0000111.Pp
Damien Millerb1715dc2000-05-30 13:44:51 +1000112.It Fl A
113Enables forwarding of the authentication agent connection.
114This can also be specified on a per-host basis in a configuration file.
Damien Millerb5fdfaa2002-09-12 09:52:03 +1000115.Pp
Damien Miller495dca32003-04-01 21:42:14 +1000116Agent forwarding should be enabled with caution.
117Users with the ability to bypass file permissions on the remote host
Darren Tuckerae69e1d2009-10-24 11:41:34 +1100118(for the agent's
Darren Tucker98c9aec2009-10-24 11:42:44 +1100119.Ux Ns -domain
120socket) can access the local agent through the forwarded connection.
Damien Miller495dca32003-04-01 21:42:14 +1000121An attacker cannot obtain key material from the agent,
Damien Millerb5fdfaa2002-09-12 09:52:03 +1000122however they can perform operations on the keys that enable them to
123authenticate using the identities loaded into the agent.
millert@openbsd.org79ec2142015-07-20 15:39:52 +0000124.Pp
Darren Tucker61776952003-10-02 16:19:47 +1000125.It Fl a
126Disables forwarding of the authentication agent connection.
millert@openbsd.org79ec2142015-07-20 15:39:52 +0000127.Pp
jmc@openbsd.org7d330a12018-02-23 07:38:09 +0000128.It Fl B Ar bind_interface
djm@openbsd.orgac2e3022018-02-23 02:34:33 +0000129Bind to the address of
jmc@openbsd.org7d330a12018-02-23 07:38:09 +0000130.Ar bind_interface
djm@openbsd.orgac2e3022018-02-23 02:34:33 +0000131before attempting to connect to the destination host.
132This is only useful on systems with more than one address.
133.Pp
Ben Lindstrome0f88042001-04-30 13:06:24 +0000134.It Fl b Ar bind_address
Darren Tuckera5cf8552005-07-14 17:04:18 +1000135Use
136.Ar bind_address
137on the local machine as the source address
138of the connection.
139Only useful on systems with more than one address.
millert@openbsd.org79ec2142015-07-20 15:39:52 +0000140.Pp
Darren Tucker61776952003-10-02 16:19:47 +1000141.It Fl C
142Requests compression of all data (including stdin, stdout, stderr, and
Damien Millera8a0f652014-07-30 12:32:28 +1000143data for forwarded X11, TCP and
144.Ux Ns -domain
145connections).
Darren Tucker61776952003-10-02 16:19:47 +1000146The compression algorithm is the same used by
djm@openbsd.org788ac792017-04-30 23:18:22 +0000147.Xr gzip 1 .
Darren Tucker61776952003-10-02 16:19:47 +1000148Compression is desirable on modem lines and other
149slow connections, but will only slow down things on fast networks.
150The default value can be set on a host-by-host basis in the
151configuration files; see the
152.Cm Compression
153option.
millert@openbsd.org79ec2142015-07-20 15:39:52 +0000154.Pp
Damien Miller05202ff2004-06-15 10:30:39 +1000155.It Fl c Ar cipher_spec
156Selects the cipher specification for encrypting the session.
Damien Miller05202ff2004-06-15 10:30:39 +1000157.Ar cipher_spec
158is a comma-separated list of ciphers
159listed in order of preference.
Darren Tucker3a6a51f2009-06-21 17:48:52 +1000160See the
161.Cm Ciphers
Damien Miller081f3c72010-08-03 16:05:25 +1000162keyword in
163.Xr ssh_config 5
164for more information.
millert@openbsd.org79ec2142015-07-20 15:39:52 +0000165.Pp
Darren Tuckerc8d64212005-10-03 18:13:42 +1000166.It Fl D Xo
167.Sm off
168.Oo Ar bind_address : Oc
169.Ar port
170.Sm on
171.Xc
Darren Tucker61776952003-10-02 16:19:47 +1000172Specifies a local
173.Dq dynamic
174application-level port forwarding.
175This works by allocating a socket to listen to
176.Ar port
Darren Tuckerc8d64212005-10-03 18:13:42 +1000177on the local side, optionally bound to the specified
178.Ar bind_address .
179Whenever a connection is made to this port, the
Darren Tucker61776952003-10-02 16:19:47 +1000180connection is forwarded over the secure channel, and the application
181protocol is then used to determine where to connect to from the
182remote machine.
183Currently the SOCKS4 and SOCKS5 protocols are supported, and
184.Nm
185will act as a SOCKS server.
186Only root can forward privileged ports.
187Dynamic port forwardings can also be specified in the configuration file.
Darren Tuckerc8d64212005-10-03 18:13:42 +1000188.Pp
Damien Miller7fa96602010-08-05 13:03:13 +1000189IPv6 addresses can be specified by enclosing the address in square brackets.
Darren Tuckerc8d64212005-10-03 18:13:42 +1000190Only the superuser can forward privileged ports.
191By default, the local port is bound in accordance with the
192.Cm GatewayPorts
193setting.
194However, an explicit
195.Ar bind_address
196may be used to bind the connection to a specific address.
197The
198.Ar bind_address
199of
200.Dq localhost
201indicates that the listening port be bound for local use only, while an
202empty address or
203.Sq *
204indicates that the port should be available from all interfaces.
millert@openbsd.org79ec2142015-07-20 15:39:52 +0000205.Pp
Damien Miller03d4d7e2013-04-23 15:21:06 +1000206.It Fl E Ar log_file
207Append debug logs to
208.Ar log_file
209instead of standard error.
millert@openbsd.org79ec2142015-07-20 15:39:52 +0000210.Pp
Damien Miller2142ba02005-12-24 14:56:29 +1100211.It Fl e Ar escape_char
Damien Miller32aa1441999-10-29 09:15:49 +1000212Sets the escape character for sessions with a pty (default:
213.Ql ~ ) .
Damien Miller7684ee12000-03-17 23:40:15 +1100214The escape character is only recognized at the beginning of a line.
215The escape character followed by a dot
Damien Miller32aa1441999-10-29 09:15:49 +1000216.Pq Ql \&.
Darren Tucker61776952003-10-02 16:19:47 +1000217closes the connection;
218followed by control-Z suspends the connection;
219and followed by itself sends the escape character once.
Damien Miller7684ee12000-03-17 23:40:15 +1100220Setting the character to
Damien Miller32aa1441999-10-29 09:15:49 +1000221.Dq none
222disables any escapes and makes the session fully transparent.
millert@openbsd.org79ec2142015-07-20 15:39:52 +0000223.Pp
Darren Tucker61776952003-10-02 16:19:47 +1000224.It Fl F Ar configfile
225Specifies an alternative per-user configuration file.
226If a configuration file is given on the command line,
227the system-wide configuration file
228.Pq Pa /etc/ssh/ssh_config
229will be ignored.
230The default for the per-user configuration file is
Damien Miller167ea5d2005-05-26 12:04:02 +1000231.Pa ~/.ssh/config .
millert@openbsd.org79ec2142015-07-20 15:39:52 +0000232.Pp
Damien Miller32aa1441999-10-29 09:15:49 +1000233.It Fl f
234Requests
235.Nm
Damien Miller7684ee12000-03-17 23:40:15 +1100236to go to background just before command execution.
237This is useful if
Damien Miller32aa1441999-10-29 09:15:49 +1000238.Nm
239is going to ask for passwords or passphrases, but the user
Damien Miller7684ee12000-03-17 23:40:15 +1100240wants it in the background.
Damien Miller22c77262000-04-13 12:26:34 +1000241This implies
Damien Miller32aa1441999-10-29 09:15:49 +1000242.Fl n .
243The recommended way to start X11 programs at a remote site is with
244something like
245.Ic ssh -f host xterm .
Darren Tucker9a2a6092008-07-04 12:53:50 +1000246.Pp
247If the
248.Cm ExitOnForwardFailure
249configuration option is set to
250.Dq yes ,
251then a client started with
252.Fl f
253will wait for all remote port forwards to be successfully established
254before placing itself in the background.
millert@openbsd.org79ec2142015-07-20 15:39:52 +0000255.Pp
djm@openbsd.org957fbce2014-10-08 22:20:25 +0000256.It Fl G
257Causes
258.Nm
259to print its configuration after evaluating
260.Cm Host
261and
262.Cm Match
263blocks and exit.
millert@openbsd.org79ec2142015-07-20 15:39:52 +0000264.Pp
Damien Miller396691a2000-01-20 22:44:08 +1100265.It Fl g
266Allows remote hosts to connect to local forwarded ports.
Damien Miller49d9bfe2014-07-03 21:26:42 +1000267If used on a multiplexed connection, then this option must be specified
268on the master process.
millert@openbsd.org79ec2142015-07-20 15:39:52 +0000269.Pp
Damien Miller7ea845e2010-02-12 09:21:02 +1100270.It Fl I Ar pkcs11
Damien Millerd400da52010-02-12 09:26:23 +1100271Specify the PKCS#11 shared library
Darren Tucker61776952003-10-02 16:19:47 +1000272.Nm
Damien Millera7618442010-02-12 09:26:02 +1100273should use to communicate with a PKCS#11 token providing the user's
Darren Tucker61776952003-10-02 16:19:47 +1000274private RSA key.
millert@openbsd.org79ec2142015-07-20 15:39:52 +0000275.Pp
Damien Miller32aa1441999-10-29 09:15:49 +1000276.It Fl i Ar identity_file
Damien Millerfae23862002-01-22 23:32:26 +1100277Selects a file from which the identity (private key) for
Damien Millereb8b60e2010-08-31 22:41:14 +1000278public key authentication is read.
Damien Millerfae23862002-01-22 23:32:26 +1100279The default is
Damien Millereb8b60e2010-08-31 22:41:14 +1000280.Pa ~/.ssh/id_dsa ,
Damien Miller8ba0ead2013-12-18 17:46:27 +1100281.Pa ~/.ssh/id_ecdsa ,
282.Pa ~/.ssh/id_ed25519
Damien Millerfae23862002-01-22 23:32:26 +1100283and
naddy@openbsd.org2e9c3242017-05-05 10:41:58 +0000284.Pa ~/.ssh/id_rsa .
Damien Miller7684ee12000-03-17 23:40:15 +1100285Identity files may also be specified on
286a per-host basis in the configuration file.
287It is possible to have multiple
Damien Miller32aa1441999-10-29 09:15:49 +1000288.Fl i
289options (and multiple identities specified in
290configuration files).
jmc@openbsd.orgc5f7c082015-09-25 18:19:54 +0000291If no certificates have been explicitly specified by the
djm@openbsd.org4e44a792015-09-24 06:15:11 +0000292.Cm CertificateFile
293directive,
Damien Miller5059d8d2010-03-05 21:31:11 +1100294.Nm
295will also try to load certificate information from the filename obtained
296by appending
297.Pa -cert.pub
298to identity filenames.
millert@openbsd.org79ec2142015-07-20 15:39:52 +0000299.Pp
millert@openbsd.org887669e2017-10-21 23:06:24 +0000300.It Fl J Ar destination
djm@openbsd.orged877ef2016-07-15 00:24:30 +0000301Connect to the target host by first making a
302.Nm
millert@openbsd.org887669e2017-10-21 23:06:24 +0000303connection to the jump host described by
304.Ar destination
jmc@openbsd.orge4eb7d92016-07-16 06:57:55 +0000305and then establishing a TCP forwarding to the ultimate destination from
djm@openbsd.orged877ef2016-07-15 00:24:30 +0000306there.
307Multiple jump hops may be specified separated by comma characters.
308This is a shortcut to specify a
309.Cm ProxyJump
310configuration directive.
djm@openbsd.org7a2cb182019-01-22 11:51:25 +0000311Note that configuration directives supplied on the command-line generally
312apply to the destination host and not any specified jump hosts.
313Use
314.Pa ~/.ssh/config
315to specify configuration for jump hosts.
djm@openbsd.orged877ef2016-07-15 00:24:30 +0000316.Pp
Darren Tucker415bddc2007-06-12 23:43:16 +1000317.It Fl K
318Enables GSSAPI-based authentication and forwarding (delegation) of GSSAPI
319credentials to the server.
millert@openbsd.org79ec2142015-07-20 15:39:52 +0000320.Pp
Damien Miller32aa1441999-10-29 09:15:49 +1000321.It Fl k
Damien Millere0113cc2003-11-24 13:10:09 +1100322Disables forwarding (delegation) of GSSAPI credentials to the server.
millert@openbsd.org79ec2142015-07-20 15:39:52 +0000323.Pp
Darren Tucker61776952003-10-02 16:19:47 +1000324.It Fl L Xo
325.Sm off
Damien Millerf91ee4c2005-03-01 21:24:33 +1100326.Oo Ar bind_address : Oc
Darren Tucker61776952003-10-02 16:19:47 +1000327.Ar port : host : hostport
328.Sm on
329.Xc
millert@openbsd.org79ec2142015-07-20 15:39:52 +0000330.It Fl L Xo
331.Sm off
332.Oo Ar bind_address : Oc
333.Ar port : remote_socket
334.Sm on
335.Xc
336.It Fl L Xo
337.Sm off
338.Ar local_socket : host : hostport
339.Sm on
340.Xc
341.It Fl L Xo
342.Sm off
343.Ar local_socket : remote_socket
344.Sm on
345.Xc
346Specifies that connections to the given TCP port or Unix socket on the local
347(client) host are to be forwarded to the given host and port, or Unix socket,
348on the remote side.
349This works by allocating a socket to listen to either a TCP
Darren Tucker61776952003-10-02 16:19:47 +1000350.Ar port
Damien Millerf91ee4c2005-03-01 21:24:33 +1100351on the local side, optionally bound to the specified
millert@openbsd.org79ec2142015-07-20 15:39:52 +0000352.Ar bind_address ,
353or to a Unix socket.
354Whenever a connection is made to the local port or socket, the
Darren Tucker61776952003-10-02 16:19:47 +1000355connection is forwarded over the secure channel, and a connection is
millert@openbsd.org79ec2142015-07-20 15:39:52 +0000356made to either
Darren Tucker61776952003-10-02 16:19:47 +1000357.Ar host
358port
millert@openbsd.org79ec2142015-07-20 15:39:52 +0000359.Ar hostport ,
360or the Unix socket
361.Ar remote_socket ,
Darren Tucker61776952003-10-02 16:19:47 +1000362from the remote machine.
millert@openbsd.org79ec2142015-07-20 15:39:52 +0000363.Pp
Darren Tucker61776952003-10-02 16:19:47 +1000364Port forwardings can also be specified in the configuration file.
Damien Millerf91ee4c2005-03-01 21:24:33 +1100365Only the superuser can forward privileged ports.
millert@openbsd.org79ec2142015-07-20 15:39:52 +0000366IPv6 addresses can be specified by enclosing the address in square brackets.
367.Pp
Damien Millerf91ee4c2005-03-01 21:24:33 +1100368By default, the local port is bound in accordance with the
369.Cm GatewayPorts
370setting.
371However, an explicit
372.Ar bind_address
373may be used to bind the connection to a specific address.
374The
375.Ar bind_address
376of
377.Dq localhost
Damien Miller36bf7dd2005-03-02 12:02:47 +1100378indicates that the listening port be bound for local use only, while an
379empty address or
380.Sq *
Damien Millerf91ee4c2005-03-01 21:24:33 +1100381indicates that the port should be available from all interfaces.
millert@openbsd.org79ec2142015-07-20 15:39:52 +0000382.Pp
Damien Miller32aa1441999-10-29 09:15:49 +1000383.It Fl l Ar login_name
Damien Miller7684ee12000-03-17 23:40:15 +1100384Specifies the user to log in as on the remote machine.
385This also may be specified on a per-host basis in the configuration file.
millert@openbsd.org79ec2142015-07-20 15:39:52 +0000386.Pp
Damien Miller0e220db2004-06-15 10:34:08 +1000387.It Fl M
388Places the
389.Nm
390client into
391.Dq master
392mode for connection sharing.
Damien Miller88b25522005-12-31 16:23:15 +1100393Multiple
394.Fl M
395options places
396.Nm
397into
398.Dq master
djm@openbsd.org247766c2018-09-07 01:42:54 +0000399mode but with confirmation required using
400.Xr ssh-askpass 1
401before each operation that changes the multiplexing state
402(e.g. opening a new session).
Damien Miller0e220db2004-06-15 10:34:08 +1000403Refer to the description of
404.Cm ControlMaster
405in
406.Xr ssh_config 5
407for details.
millert@openbsd.org79ec2142015-07-20 15:39:52 +0000408.Pp
Damien Miller5d1eceb2004-06-30 22:37:57 +1000409.It Fl m Ar mac_spec
jmc@openbsd.orga685ae82016-02-17 07:38:19 +0000410A comma-separated list of MAC (message authentication code) algorithms,
411specified in order of preference.
Damien Miller5d1eceb2004-06-30 22:37:57 +1000412See the
413.Cm MACs
414keyword for more information.
millert@openbsd.org79ec2142015-07-20 15:39:52 +0000415.Pp
Darren Tucker61776952003-10-02 16:19:47 +1000416.It Fl N
417Do not execute a remote command.
jmc@openbsd.orga685ae82016-02-17 07:38:19 +0000418This is useful for just forwarding ports.
millert@openbsd.org79ec2142015-07-20 15:39:52 +0000419.Pp
Damien Miller32aa1441999-10-29 09:15:49 +1000420.It Fl n
421Redirects stdin from
422.Pa /dev/null
423(actually, prevents reading from stdin).
424This must be used when
425.Nm
Damien Miller7684ee12000-03-17 23:40:15 +1100426is run in the background.
427A common trick is to use this to run X11 programs on a remote machine.
428For example,
Damien Miller32aa1441999-10-29 09:15:49 +1000429.Ic ssh -n shadows.cs.hut.fi emacs &
430will start an emacs on shadows.cs.hut.fi, and the X11
431connection will be automatically forwarded over an encrypted channel.
432The
433.Nm
434program will be put in the background.
435(This does not work if
436.Nm
437needs to ask for a password or passphrase; see also the
438.Fl f
439option.)
millert@openbsd.org79ec2142015-07-20 15:39:52 +0000440.Pp
Darren Tuckere04644c2004-12-03 14:08:45 +1100441.It Fl O Ar ctl_cmd
442Control an active connection multiplexing master process.
443When the
444.Fl O
445option is specified, the
446.Ar ctl_cmd
447argument is interpreted and passed to the master process.
448Valid commands are:
449.Dq check
Damien Miller388f6fc2010-05-21 14:57:35 +1000450(check that the master process is running),
451.Dq forward
Damien Miller8cb1cda2011-05-05 14:16:56 +1000452(request forwardings without command execution),
Damien Miller1bcbd0a2011-09-22 21:40:45 +1000453.Dq cancel
454(cancel forwardings),
Darren Tuckere04644c2004-12-03 14:08:45 +1100455.Dq exit
Damien Miller8cb1cda2011-05-05 14:16:56 +1000456(request the master to exit), and
Damien Miller6c3eec72011-05-05 14:16:22 +1000457.Dq stop
458(request the master to stop accepting further multiplexing requests).
millert@openbsd.org79ec2142015-07-20 15:39:52 +0000459.Pp
Damien Miller32aa1441999-10-29 09:15:49 +1000460.It Fl o Ar option
Ben Lindstrom14c62eb2001-08-15 23:25:46 +0000461Can be used to give options in the format used in the configuration file.
Damien Miller32aa1441999-10-29 09:15:49 +1000462This is useful for specifying options for which there is no separate
Damien Miller7684ee12000-03-17 23:40:15 +1100463command-line flag.
Darren Tucker61776952003-10-02 16:19:47 +1000464For full details of the options listed below, and their possible values, see
465.Xr ssh_config 5 .
466.Pp
467.Bl -tag -width Ds -offset indent -compact
jcs@openbsd.orgf361df42015-11-15 22:26:49 +0000468.It AddKeysToAgent
Darren Tucker61776952003-10-02 16:19:47 +1000469.It AddressFamily
470.It BatchMode
471.It BindAddress
Damien Miller0faf7472013-10-17 11:47:23 +1100472.It CanonicalDomains
Damien Miller38505592013-10-17 11:48:13 +1100473.It CanonicalizeFallbackLocal
474.It CanonicalizeHostname
475.It CanonicalizeMaxDots
476.It CanonicalizePermittedCNAMEs
jmc@openbsd.orge6933a22018-09-20 06:58:48 +0000477.It CASignatureAlgorithms
djm@openbsd.org4e44a792015-09-24 06:15:11 +0000478.It CertificateFile
Darren Tucker61776952003-10-02 16:19:47 +1000479.It ChallengeResponseAuthentication
480.It CheckHostIP
Darren Tucker61776952003-10-02 16:19:47 +1000481.It Ciphers
482.It ClearAllForwardings
483.It Compression
naddy@openbsd.org9a82e242017-05-03 21:49:18 +0000484.It ConnectionAttempts
Darren Tuckeredae0ec2004-05-02 22:15:52 +1000485.It ConnectTimeout
Damien Miller0e220db2004-06-15 10:34:08 +1000486.It ControlMaster
487.It ControlPath
Damien Millerefad7272011-09-22 21:33:53 +1000488.It ControlPersist
Darren Tucker61776952003-10-02 16:19:47 +1000489.It DynamicForward
Darren Tucker61776952003-10-02 16:19:47 +1000490.It EscapeChar
Darren Tuckere7d4b192006-07-12 22:17:10 +1000491.It ExitOnForwardFailure
jmc@openbsd.org8abd8032014-12-22 09:26:31 +0000492.It FingerprintHash
Darren Tucker61776952003-10-02 16:19:47 +1000493.It ForwardAgent
494.It ForwardX11
Damien Millerefad7272011-09-22 21:33:53 +1000495.It ForwardX11Timeout
Darren Tucker0a118da2003-10-15 15:54:32 +1000496.It ForwardX11Trusted
Darren Tucker61776952003-10-02 16:19:47 +1000497.It GatewayPorts
498.It GlobalKnownHostsFile
499.It GSSAPIAuthentication
500.It GSSAPIDelegateCredentials
Damien Millere1776152005-03-01 21:47:37 +1100501.It HashKnownHosts
Darren Tucker61776952003-10-02 16:19:47 +1000502.It Host
503.It HostbasedAuthentication
djm@openbsd.org46347ed2015-01-30 11:43:14 +0000504.It HostbasedKeyTypes
Darren Tucker61776952003-10-02 16:19:47 +1000505.It HostKeyAlgorithms
506.It HostKeyAlias
507.It HostName
jmc@openbsd.org772e6ce2016-06-29 17:14:28 +0000508.It IdentitiesOnly
markus@openbsd.orgb02ad1c2016-05-04 12:21:53 +0000509.It IdentityAgent
Darren Tucker61776952003-10-02 16:19:47 +1000510.It IdentityFile
Damien Miller0a184732010-11-20 15:21:03 +1100511.It IPQoS
Damien Millerefad7272011-09-22 21:33:53 +1000512.It KbdInteractiveAuthentication
Darren Tucker636ca902004-11-05 20:22:00 +1100513.It KbdInteractiveDevices
Damien Miller7fe2b1f2010-09-24 22:11:53 +1000514.It KexAlgorithms
Damien Millerd27b9472005-12-13 19:29:02 +1100515.It LocalCommand
Darren Tucker61776952003-10-02 16:19:47 +1000516.It LocalForward
517.It LogLevel
518.It MACs
Damien Millerd77b81f2013-10-17 11:39:00 +1100519.It Match
Darren Tucker61776952003-10-02 16:19:47 +1000520.It NoHostAuthenticationForLocalhost
521.It NumberOfPasswordPrompts
522.It PasswordAuthentication
Damien Millerd27b9472005-12-13 19:29:02 +1100523.It PermitLocalCommand
Damien Miller7ea845e2010-02-12 09:21:02 +1100524.It PKCS11Provider
Darren Tucker61776952003-10-02 16:19:47 +1000525.It Port
526.It PreferredAuthentications
Darren Tucker61776952003-10-02 16:19:47 +1000527.It ProxyCommand
djm@openbsd.orged877ef2016-07-15 00:24:30 +0000528.It ProxyJump
Damien Millerf2f6c312013-08-21 02:44:58 +1000529.It ProxyUseFdpass
markus@openbsd.org3a1638d2015-07-10 06:21:53 +0000530.It PubkeyAcceptedKeyTypes
Darren Tucker61776952003-10-02 16:19:47 +1000531.It PubkeyAuthentication
Darren Tucker62388b22006-01-20 11:31:47 +1100532.It RekeyLimit
bluhm@openbsd.org1112b532017-05-30 18:58:37 +0000533.It RemoteCommand
Darren Tucker61776952003-10-02 16:19:47 +1000534.It RemoteForward
Damien Millerf4b32aa2011-05-15 08:47:43 +1000535.It RequestTTY
Darren Tucker7a6c0662004-05-02 22:14:03 +1000536.It SendEnv
Damien Miller509b0102003-12-17 16:33:10 +1100537.It ServerAliveInterval
538.It ServerAliveCountMax
jmc@openbsd.orgacf42602018-06-09 06:36:31 +0000539.It SetEnv
Damien Miller6d576562014-07-18 15:02:06 +1000540.It StreamLocalBindMask
541.It StreamLocalBindUnlink
Darren Tucker61776952003-10-02 16:19:47 +1000542.It StrictHostKeyChecking
Damien Miller12c150e2003-12-17 16:31:10 +1100543.It TCPKeepAlive
Damien Millerd27b9472005-12-13 19:29:02 +1100544.It Tunnel
545.It TunnelDevice
djm@openbsd.org1d1092b2015-01-26 12:16:36 +0000546.It UpdateHostKeys
Darren Tucker61776952003-10-02 16:19:47 +1000547.It User
548.It UserKnownHostsFile
549.It VerifyHostKeyDNS
Damien Miller86399202008-06-30 00:04:31 +1000550.It VisualHostKey
Darren Tucker61776952003-10-02 16:19:47 +1000551.It XAuthLocation
552.El
millert@openbsd.org79ec2142015-07-20 15:39:52 +0000553.Pp
Damien Miller32aa1441999-10-29 09:15:49 +1000554.It Fl p Ar port
Damien Miller7684ee12000-03-17 23:40:15 +1100555Port to connect to on the remote host.
556This can be specified on a
Damien Miller32aa1441999-10-29 09:15:49 +1000557per-host basis in the configuration file.
millert@openbsd.org79ec2142015-07-20 15:39:52 +0000558.Pp
djm@openbsd.orgc0f55db2015-09-11 03:42:32 +0000559.It Fl Q Ar query_option
Damien Millerea111192013-04-23 19:24:32 +1000560Queries
561.Nm
Damien Millerd937dc02013-12-05 10:19:54 +1100562for the algorithms supported for the specified version 2.
563The available features are:
564.Ar cipher
Damien Millerea111192013-04-23 19:24:32 +1000565(supported symmetric ciphers),
Damien Millerd937dc02013-12-05 10:19:54 +1100566.Ar cipher-auth
Damien Miller0fde8ac2013-11-21 14:12:23 +1100567(supported symmetric ciphers that support authenticated encryption),
djm@openbsd.org357128a2018-09-12 01:30:10 +0000568.Ar help
569(supported query terms for use with the
570.Fl Q
571flag),
Damien Millerd937dc02013-12-05 10:19:54 +1100572.Ar mac
Damien Millerea111192013-04-23 19:24:32 +1000573(supported message integrity codes),
Damien Millerd937dc02013-12-05 10:19:54 +1100574.Ar kex
Damien Millerea111192013-04-23 19:24:32 +1000575(key exchange algorithms),
Damien Millerd937dc02013-12-05 10:19:54 +1100576.Ar key
djm@openbsd.orgc0f55db2015-09-11 03:42:32 +0000577(key types),
578.Ar key-cert
579(certificate key types),
580.Ar key-plain
djm@openbsd.org357128a2018-09-12 01:30:10 +0000581(non-certificate key types),
djm@openbsd.org68d2dfc2015-03-03 06:48:58 +0000582.Ar protocol-version
djm@openbsd.org357128a2018-09-12 01:30:10 +0000583(supported SSH protocol versions), and
584.Ar sig
585(supported signature algorithms).
millert@openbsd.org79ec2142015-07-20 15:39:52 +0000586.Pp
Damien Miller32aa1441999-10-29 09:15:49 +1000587.It Fl q
Damien Miller7684ee12000-03-17 23:40:15 +1100588Quiet mode.
Damien Millereb602472008-02-10 22:21:28 +1100589Causes most warning and diagnostic messages to be suppressed.
millert@openbsd.org79ec2142015-07-20 15:39:52 +0000590.Pp
Darren Tucker61776952003-10-02 16:19:47 +1000591.It Fl R Xo
592.Sm off
Damien Millerf91ee4c2005-03-01 21:24:33 +1100593.Oo Ar bind_address : Oc
Darren Tucker61776952003-10-02 16:19:47 +1000594.Ar port : host : hostport
595.Sm on
596.Xc
millert@openbsd.org79ec2142015-07-20 15:39:52 +0000597.It Fl R Xo
598.Sm off
599.Oo Ar bind_address : Oc
600.Ar port : local_socket
601.Sm on
602.Xc
603.It Fl R Xo
604.Sm off
605.Ar remote_socket : host : hostport
606.Sm on
607.Xc
608.It Fl R Xo
609.Sm off
610.Ar remote_socket : local_socket
611.Sm on
612.Xc
markus@openbsd.org609d7a62017-09-21 19:16:53 +0000613.It Fl R Xo
614.Sm off
615.Oo Ar bind_address : Oc
616.Ar port
617.Sm on
618.Xc
millert@openbsd.org79ec2142015-07-20 15:39:52 +0000619Specifies that connections to the given TCP port or Unix socket on the remote
markus@openbsd.org609d7a62017-09-21 19:16:53 +0000620(server) host are to be forwarded to the local side.
621.Pp
millert@openbsd.org79ec2142015-07-20 15:39:52 +0000622This works by allocating a socket to listen to either a TCP
Damien Miller32aa1441999-10-29 09:15:49 +1000623.Ar port
millert@openbsd.org79ec2142015-07-20 15:39:52 +0000624or to a Unix socket on the remote side.
625Whenever a connection is made to this port or Unix socket, the
626connection is forwarded over the secure channel, and a connection
markus@openbsd.org609d7a62017-09-21 19:16:53 +0000627is made from the local machine to either an explicit destination specified by
Damien Miller34132e52000-01-14 15:45:46 +1100628.Ar host
629port
millert@openbsd.org79ec2142015-07-20 15:39:52 +0000630.Ar hostport ,
631or
632.Ar local_socket ,
markus@openbsd.org609d7a62017-09-21 19:16:53 +0000633or, if no explicit destination was specified,
634.Nm
635will act as a SOCKS 4/5 proxy and forward connections to the destinations
636requested by the remote SOCKS client.
Damien Millerf91ee4c2005-03-01 21:24:33 +1100637.Pp
Damien Miller7684ee12000-03-17 23:40:15 +1100638Port forwardings can also be specified in the configuration file.
639Privileged ports can be forwarded only when
Damien Miller32aa1441999-10-29 09:15:49 +1000640logging in as root on the remote machine.
Damien Miller70b2d552012-04-22 11:26:10 +1000641IPv6 addresses can be specified by enclosing the address in square brackets.
Damien Millerf91ee4c2005-03-01 21:24:33 +1100642.Pp
millert@openbsd.org79ec2142015-07-20 15:39:52 +0000643By default, TCP listening sockets on the server will be bound to the loopback
Damien Millerf91ee4c2005-03-01 21:24:33 +1100644interface only.
Darren Tucker63917bd2008-11-11 16:33:48 +1100645This may be overridden by specifying a
Damien Millerf91ee4c2005-03-01 21:24:33 +1100646.Ar bind_address .
Damien Miller36bf7dd2005-03-02 12:02:47 +1100647An empty
648.Ar bind_address ,
Damien Millerf91ee4c2005-03-01 21:24:33 +1100649or the address
Damien Miller36bf7dd2005-03-02 12:02:47 +1100650.Ql * ,
Damien Millerf91ee4c2005-03-01 21:24:33 +1100651indicates that the remote socket should listen on all interfaces.
652Specifying a remote
653.Ar bind_address
Damien Miller36bf7dd2005-03-02 12:02:47 +1100654will only succeed if the server's
655.Cm GatewayPorts
Damien Millerf91ee4c2005-03-01 21:24:33 +1100656option is enabled (see
Damien Miller36bf7dd2005-03-02 12:02:47 +1100657.Xr sshd_config 5 ) .
Damien Millere2f4cc52009-02-14 16:33:49 +1100658.Pp
659If the
660.Ar port
661argument is
Damien Miller65fa4ca2009-02-14 16:34:05 +1100662.Ql 0 ,
Damien Millere2f4cc52009-02-14 16:33:49 +1100663the listen port will be dynamically allocated on the server and reported
664to the client at run time.
Damien Miller388f6fc2010-05-21 14:57:35 +1000665When used together with
666.Ic -O forward
667the allocated port will be printed to the standard output.
millert@openbsd.org79ec2142015-07-20 15:39:52 +0000668.Pp
Darren Tucker7ebfc102004-11-07 20:06:19 +1100669.It Fl S Ar ctl_path
Damien Miller67f30d72010-04-16 15:52:03 +1000670Specifies the location of a control socket for connection sharing,
Damien Miller9c60f242010-03-26 11:28:35 +1100671or the string
672.Dq none
673to disable connection sharing.
Damien Miller0e220db2004-06-15 10:34:08 +1000674Refer to the description of
Darren Tuckerba5c5922004-06-18 16:22:39 +1000675.Cm ControlPath
676and
Damien Miller0e220db2004-06-15 10:34:08 +1000677.Cm ControlMaster
678in
679.Xr ssh_config 5
680for details.
millert@openbsd.org79ec2142015-07-20 15:39:52 +0000681.Pp
Darren Tucker61776952003-10-02 16:19:47 +1000682.It Fl s
683May be used to request invocation of a subsystem on the remote system.
jmc@openbsd.orga685ae82016-02-17 07:38:19 +0000684Subsystems facilitate the use of SSH
685as a secure transport for other applications (e.g.\&
Darren Tucker61776952003-10-02 16:19:47 +1000686.Xr sftp 1 ) .
687The subsystem is specified as the remote command.
millert@openbsd.org79ec2142015-07-20 15:39:52 +0000688.Pp
Darren Tucker61776952003-10-02 16:19:47 +1000689.It Fl T
dtucker@openbsd.orgf8484da2015-05-06 05:45:17 +0000690Disable pseudo-terminal allocation.
millert@openbsd.org79ec2142015-07-20 15:39:52 +0000691.Pp
Darren Tucker61776952003-10-02 16:19:47 +1000692.It Fl t
dtucker@openbsd.orgf8484da2015-05-06 05:45:17 +0000693Force pseudo-terminal allocation.
Darren Tucker61776952003-10-02 16:19:47 +1000694This can be used to execute arbitrary
695screen-based programs on a remote machine, which can be very useful,
Damien Miller208f1ed2006-03-15 11:56:03 +1100696e.g. when implementing menu services.
Darren Tucker61776952003-10-02 16:19:47 +1000697Multiple
698.Fl t
699options force tty allocation, even if
Ben Lindstrom19ceb172001-09-12 17:54:24 +0000700.Nm
Darren Tucker61776952003-10-02 16:19:47 +1000701has no local tty.
millert@openbsd.org79ec2142015-07-20 15:39:52 +0000702.Pp
Darren Tucker61776952003-10-02 16:19:47 +1000703.It Fl V
704Display the version number and exit.
millert@openbsd.org79ec2142015-07-20 15:39:52 +0000705.Pp
Darren Tucker61776952003-10-02 16:19:47 +1000706.It Fl v
707Verbose mode.
708Causes
Ben Lindstrom5ab6ae12001-02-10 22:08:03 +0000709.Nm
Darren Tucker61776952003-10-02 16:19:47 +1000710to print debugging messages about its progress.
711This is helpful in
712debugging connection, authentication, and configuration problems.
713Multiple
714.Fl v
715options increase the verbosity.
716The maximum is 3.
millert@openbsd.org79ec2142015-07-20 15:39:52 +0000717.Pp
Darren Tucker7ad8dd22010-01-12 19:40:27 +1100718.It Fl W Ar host : Ns Ar port
719Requests that standard input and output on the client be forwarded to
720.Ar host
721on
722.Ar port
723over the secure channel.
724Implies
725.Fl N ,
726.Fl T ,
727.Cm ExitOnForwardFailure
728and
jmc@openbsd.org6915f162016-06-03 06:44:12 +0000729.Cm ClearAllForwardings ,
730though these can be overridden in the configuration file or using
dtucker@openbsd.org0cb2f4c2016-06-03 04:09:38 +0000731.Fl o
732command line options.
millert@openbsd.org79ec2142015-07-20 15:39:52 +0000733.Pp
Damien Miller991dba42006-07-10 20:16:27 +1000734.It Fl w Xo
735.Ar local_tun Ns Op : Ns Ar remote_tun
736.Xc
737Requests
738tunnel
739device forwarding with the specified
Damien Millerd27b9472005-12-13 19:29:02 +1100740.Xr tun 4
Damien Miller991dba42006-07-10 20:16:27 +1000741devices between the client
742.Pq Ar local_tun
743and the server
744.Pq Ar remote_tun .
745.Pp
Damien Millercf1e3422005-12-24 14:56:04 +1100746The devices may be specified by numerical ID or the keyword
747.Dq any ,
748which uses the next available tunnel device.
Damien Miller991dba42006-07-10 20:16:27 +1000749If
750.Ar remote_tun
751is not specified, it defaults to
752.Dq any .
Damien Millercf1e3422005-12-24 14:56:04 +1100753See also the
Damien Millerd27b9472005-12-13 19:29:02 +1100754.Cm Tunnel
Damien Miller991dba42006-07-10 20:16:27 +1000755and
756.Cm TunnelDevice
757directives in
Damien Millerd27b9472005-12-13 19:29:02 +1100758.Xr ssh_config 5 .
djm@openbsd.orgf18bc972018-05-11 04:01:11 +0000759.Pp
Damien Miller991dba42006-07-10 20:16:27 +1000760If the
761.Cm Tunnel
djm@openbsd.orgf18bc972018-05-11 04:01:11 +0000762directive is unset, it will be set to the default tunnel mode, which is
Damien Miller991dba42006-07-10 20:16:27 +1000763.Dq point-to-point .
djm@openbsd.orgf18bc972018-05-11 04:01:11 +0000764If a different
765.Cm Tunnel
766forwarding mode it desired, then it should be specified before
767.Fl w .
millert@openbsd.org79ec2142015-07-20 15:39:52 +0000768.Pp
Darren Tucker61776952003-10-02 16:19:47 +1000769.It Fl X
770Enables X11 forwarding.
771This can also be specified on a per-host basis in a configuration file.
772.Pp
773X11 forwarding should be enabled with caution.
774Users with the ability to bypass file permissions on the remote host
775(for the user's X authorization database)
776can access the local X11 display through the forwarded connection.
777An attacker may then be able to perform activities such as keystroke monitoring.
Damien Miller947219e2005-03-02 13:22:30 +1100778.Pp
Damien Millerb022b232005-03-05 11:22:36 +1100779For this reason, X11 forwarding is subjected to X11 SECURITY extension
Damien Miller947219e2005-03-02 13:22:30 +1100780restrictions by default.
781Please refer to the
782.Nm
783.Fl Y
784option and the
785.Cm ForwardX11Trusted
786directive in
787.Xr ssh_config 5
788for more information.
millert@openbsd.org79ec2142015-07-20 15:39:52 +0000789.Pp
Darren Tucker61776952003-10-02 16:19:47 +1000790.It Fl x
791Disables X11 forwarding.
millert@openbsd.org79ec2142015-07-20 15:39:52 +0000792.Pp
Darren Tucker0a118da2003-10-15 15:54:32 +1000793.It Fl Y
794Enables trusted X11 forwarding.
Damien Miller947219e2005-03-02 13:22:30 +1100795Trusted X11 forwardings are not subjected to the X11 SECURITY extension
796controls.
millert@openbsd.org79ec2142015-07-20 15:39:52 +0000797.Pp
Damien Millere272a5b2008-11-03 19:22:37 +1100798.It Fl y
799Send log information using the
800.Xr syslog 3
801system module.
802By default this information is sent to stderr.
Damien Miller32aa1441999-10-29 09:15:49 +1000803.El
Damien Millere9b333a2005-12-24 14:53:04 +1100804.Pp
805.Nm
806may additionally obtain configuration data from
807a per-user configuration file and a system-wide configuration file.
808The file format and configuration options are described in
809.Xr ssh_config 5 .
Damien Millerc93a8132005-12-24 14:52:13 +1100810.Sh AUTHENTICATION
djm@openbsd.org788ac792017-04-30 23:18:22 +0000811The OpenSSH SSH client supports SSH protocol 2.
Damien Millerc93a8132005-12-24 14:52:13 +1100812.Pp
813The methods available for authentication are:
Damien Millerfbc94c82006-06-13 13:03:16 +1000814GSSAPI-based authentication,
Damien Millerc93a8132005-12-24 14:52:13 +1100815host-based authentication,
816public key authentication,
817challenge-response authentication,
818and password authentication.
819Authentication methods are tried in the order specified above,
jmc@openbsd.orga685ae82016-02-17 07:38:19 +0000820though
821.Cm PreferredAuthentications
822can be used to change the default order.
Damien Millerc93a8132005-12-24 14:52:13 +1100823.Pp
824Host-based authentication works as follows:
Darren Tuckerd3877b92005-12-20 16:09:36 +1100825If the machine the user logs in from is listed in
826.Pa /etc/hosts.equiv
827or
828.Pa /etc/shosts.equiv
829on the remote machine, and the user names are
830the same on both sides, or if the files
831.Pa ~/.rhosts
832or
833.Pa ~/.shosts
834exist in the user's home directory on the
835remote machine and contain a line containing the name of the client
836machine and the name of the user on that machine, the user is
Damien Millerc93a8132005-12-24 14:52:13 +1100837considered for login.
838Additionally, the server
839.Em must
840be able to verify the client's
841host key (see the description of
Darren Tuckerd3877b92005-12-20 16:09:36 +1100842.Pa /etc/ssh/ssh_known_hosts
843and
Damien Millerc93a8132005-12-24 14:52:13 +1100844.Pa ~/.ssh/known_hosts ,
845below)
846for login to be permitted.
Darren Tuckerd3877b92005-12-20 16:09:36 +1100847This authentication method closes security holes due to IP
Damien Millerc93a8132005-12-24 14:52:13 +1100848spoofing, DNS spoofing, and routing spoofing.
Darren Tuckerd3877b92005-12-20 16:09:36 +1100849[Note to the administrator:
850.Pa /etc/hosts.equiv ,
851.Pa ~/.rhosts ,
852and the rlogin/rsh protocol in general, are inherently insecure and should be
853disabled if security is desired.]
854.Pp
Damien Millerc93a8132005-12-24 14:52:13 +1100855Public key authentication works as follows:
856The scheme is based on public-key cryptography,
857using cryptosystems
858where encryption and decryption are done using separate keys,
859and it is unfeasible to derive the decryption key from the encryption key.
Darren Tuckerd3877b92005-12-20 16:09:36 +1100860The idea is that each user creates a public/private
861key pair for authentication purposes.
862The server knows the public key, and only the user knows the private key.
Damien Millerc93a8132005-12-24 14:52:13 +1100863.Nm
864implements public key authentication protocol automatically,
sobrado@openbsd.orgf70b22b2014-08-30 15:33:50 +0000865using one of the DSA, ECDSA, Ed25519 or RSA algorithms.
Damien Millerfecfd112013-07-18 16:11:50 +1000866The HISTORY section of
Damien Millerc93a8132005-12-24 14:52:13 +1100867.Xr ssl 8
Damien Millerd4427902010-09-10 11:15:10 +1000868contains a brief discussion of the DSA and RSA algorithms.
Darren Tuckerd3877b92005-12-20 16:09:36 +1100869.Pp
870The file
871.Pa ~/.ssh/authorized_keys
872lists the public keys that are permitted for logging in.
873When the user logs in, the
874.Nm
875program tells the server which key pair it would like to use for
876authentication.
Damien Millerc93a8132005-12-24 14:52:13 +1100877The client proves that it has access to the private key
878and the server checks that the corresponding public key
879is authorized to accept the account.
Darren Tuckerd3877b92005-12-20 16:09:36 +1100880.Pp
djm@openbsd.org7f5637c2017-06-09 06:43:01 +0000881The server may inform the client of errors that prevented public key
882authentication from succeeding after authentication completes using a
883different method.
884These may be viewed by increasing the
885.Cm LogLevel
886to
887.Cm DEBUG
888or higher (e.g. by using the
889.Fl v
890flag).
891.Pp
Damien Millerc93a8132005-12-24 14:52:13 +1100892The user creates his/her key pair by running
Darren Tuckerd3877b92005-12-20 16:09:36 +1100893.Xr ssh-keygen 1 .
894This stores the private key in
Damien Millerc93a8132005-12-24 14:52:13 +1100895.Pa ~/.ssh/id_dsa
jmc@openbsd.orga685ae82016-02-17 07:38:19 +0000896(DSA),
Damien Millereb8b60e2010-08-31 22:41:14 +1000897.Pa ~/.ssh/id_ecdsa
jmc@openbsd.orga685ae82016-02-17 07:38:19 +0000898(ECDSA),
Damien Miller8ba0ead2013-12-18 17:46:27 +1100899.Pa ~/.ssh/id_ed25519
jmc@openbsd.orga685ae82016-02-17 07:38:19 +0000900(Ed25519),
Damien Millerc93a8132005-12-24 14:52:13 +1100901or
902.Pa ~/.ssh/id_rsa
jmc@openbsd.orga685ae82016-02-17 07:38:19 +0000903(RSA)
Darren Tuckerd3877b92005-12-20 16:09:36 +1100904and stores the public key in
Damien Millerc93a8132005-12-24 14:52:13 +1100905.Pa ~/.ssh/id_dsa.pub
jmc@openbsd.orga685ae82016-02-17 07:38:19 +0000906(DSA),
Damien Millereb8b60e2010-08-31 22:41:14 +1000907.Pa ~/.ssh/id_ecdsa.pub
jmc@openbsd.orga685ae82016-02-17 07:38:19 +0000908(ECDSA),
Damien Miller8ba0ead2013-12-18 17:46:27 +1100909.Pa ~/.ssh/id_ed25519.pub
jmc@openbsd.orga685ae82016-02-17 07:38:19 +0000910(Ed25519),
Damien Millerc93a8132005-12-24 14:52:13 +1100911or
912.Pa ~/.ssh/id_rsa.pub
jmc@openbsd.orga685ae82016-02-17 07:38:19 +0000913(RSA)
Darren Tuckerd3877b92005-12-20 16:09:36 +1100914in the user's home directory.
Damien Millerc93a8132005-12-24 14:52:13 +1100915The user should then copy the public key
Darren Tuckerd3877b92005-12-20 16:09:36 +1100916to
917.Pa ~/.ssh/authorized_keys
Damien Millerc93a8132005-12-24 14:52:13 +1100918in his/her home directory on the remote machine.
919The
Darren Tuckerd3877b92005-12-20 16:09:36 +1100920.Pa authorized_keys
921file corresponds to the conventional
922.Pa ~/.rhosts
923file, and has one key
Damien Millerc93a8132005-12-24 14:52:13 +1100924per line, though the lines can be very long.
Darren Tuckerd3877b92005-12-20 16:09:36 +1100925After this, the user can log in without giving the password.
926.Pp
Damien Miller922b5412010-03-05 21:30:54 +1100927A variation on public key authentication
928is available in the form of certificate authentication:
929instead of a set of public/private keys,
930signed certificates are used.
931This has the advantage that a single trusted certification authority
932can be used in place of many public/private keys.
Damien Millerfecfd112013-07-18 16:11:50 +1000933See the CERTIFICATES section of
Damien Miller922b5412010-03-05 21:30:54 +1100934.Xr ssh-keygen 1
935for more information.
936.Pp
937The most convenient way to use public key or certificate authentication
938may be with an authentication agent.
Darren Tuckerd3877b92005-12-20 16:09:36 +1100939See
940.Xr ssh-agent 1
jcs@openbsd.orgf361df42015-11-15 22:26:49 +0000941and (optionally) the
942.Cm AddKeysToAgent
943directive in
944.Xr ssh_config 5
Darren Tuckerd3877b92005-12-20 16:09:36 +1100945for more information.
946.Pp
Damien Millerc93a8132005-12-24 14:52:13 +1100947Challenge-response authentication works as follows:
948The server sends an arbitrary
949.Qq challenge
950text, and prompts for a response.
Damien Millerc93a8132005-12-24 14:52:13 +1100951Examples of challenge-response authentication include
Damien Millerb7727df2013-08-21 02:43:49 +1000952.Bx
953Authentication (see
Damien Millerc93a8132005-12-24 14:52:13 +1100954.Xr login.conf 5 )
Damien Millerb7727df2013-08-21 02:43:49 +1000955and PAM (some
956.Pf non- Ox
957systems).
Damien Millerc93a8132005-12-24 14:52:13 +1100958.Pp
959Finally, if other authentication methods fail,
Darren Tuckerd3877b92005-12-20 16:09:36 +1100960.Nm
961prompts the user for a password.
962The password is sent to the remote
963host for checking; however, since all communications are encrypted,
964the password cannot be seen by someone listening on the network.
Damien Miller48c94ab2006-01-02 23:38:00 +1100965.Pp
966.Nm
967automatically maintains and checks a database containing
968identification for all hosts it has ever been used with.
969Host keys are stored in
970.Pa ~/.ssh/known_hosts
971in the user's home directory.
972Additionally, the file
973.Pa /etc/ssh/ssh_known_hosts
974is automatically checked for known hosts.
975Any new hosts are automatically added to the user's file.
976If a host's identification ever changes,
977.Nm
978warns about this and disables password authentication to prevent
979server spoofing or man-in-the-middle attacks,
980which could otherwise be used to circumvent the encryption.
981The
982.Cm StrictHostKeyChecking
983option can be used to control logins to machines whose
984host key is not known or has changed.
985.Pp
Darren Tuckerd3877b92005-12-20 16:09:36 +1100986When the user's identity has been accepted by the server, the server
dtucker@openbsd.orgf8484da2015-05-06 05:45:17 +0000987either executes the given command in a non-interactive session or,
988if no command has been specified, logs into the machine and gives
989the user a normal shell as an interactive session.
Darren Tuckerd3877b92005-12-20 16:09:36 +1100990All communication with
991the remote command or shell will be automatically encrypted.
992.Pp
dtucker@openbsd.orgf8484da2015-05-06 05:45:17 +0000993If an interactive session is requested
994.Nm
995by default will only request a pseudo-terminal (pty) for interactive
996sessions when the client has one.
997The flags
998.Fl T
999and
1000.Fl t
1001can be used to override this behaviour.
1002.Pp
1003If a pseudo-terminal has been allocated the
Darren Tuckerd3877b92005-12-20 16:09:36 +11001004user may use the escape characters noted below.
1005.Pp
dtucker@openbsd.orgf8484da2015-05-06 05:45:17 +00001006If no pseudo-terminal has been allocated,
Darren Tuckerd3877b92005-12-20 16:09:36 +11001007the session is transparent and can be used to reliably transfer binary data.
1008On most systems, setting the escape character to
1009.Dq none
1010will also make the session transparent even if a tty is used.
1011.Pp
1012The session terminates when the command or shell on the remote
Damien Miller8bfaf932006-01-14 10:09:30 +11001013machine exits and all X11 and TCP connections have been closed.
Damien Miller52d20612005-12-24 14:52:36 +11001014.Sh ESCAPE CHARACTERS
Darren Tuckerd3877b92005-12-20 16:09:36 +11001015When a pseudo-terminal has been requested,
1016.Nm
1017supports a number of functions through the use of an escape character.
1018.Pp
1019A single tilde character can be sent as
1020.Ic ~~
1021or by following the tilde by a character other than those described below.
1022The escape character must always follow a newline to be interpreted as
1023special.
1024The escape character can be changed in configuration files using the
1025.Cm EscapeChar
1026configuration directive or on the command line by the
1027.Fl e
1028option.
1029.Pp
1030The supported escapes (assuming the default
1031.Ql ~ )
1032are:
1033.Bl -tag -width Ds
1034.It Cm ~.
1035Disconnect.
1036.It Cm ~^Z
1037Background
Damien Miller1164c292006-01-02 23:38:37 +11001038.Nm .
Darren Tuckerd3877b92005-12-20 16:09:36 +11001039.It Cm ~#
1040List forwarded connections.
1041.It Cm ~&
1042Background
1043.Nm
1044at logout when waiting for forwarded connection / X11 sessions to terminate.
1045.It Cm ~?
1046Display a list of escape characters.
1047.It Cm ~B
1048Send a BREAK to the remote system
jmc@openbsd.orga685ae82016-02-17 07:38:19 +00001049(only useful if the peer supports it).
Darren Tuckerd3877b92005-12-20 16:09:36 +11001050.It Cm ~C
1051Open command line.
1052Currently this allows the addition of port forwardings using the
Damien Miller0164cb82008-11-05 16:30:31 +11001053.Fl L ,
Darren Tuckerd3877b92005-12-20 16:09:36 +11001054.Fl R
Damien Miller0164cb82008-11-05 16:30:31 +11001055and
1056.Fl D
Damien Miller329cb012005-12-24 14:53:23 +11001057options (see above).
Damien Millerff773642011-09-22 21:39:48 +10001058It also allows the cancellation of existing port-forwardings
1059with
Damien Miller57e8ad32006-07-10 20:20:52 +10001060.Sm off
Damien Millerff773642011-09-22 21:39:48 +10001061.Fl KL Oo Ar bind_address : Oc Ar port
Damien Miller57e8ad32006-07-10 20:20:52 +10001062.Sm on
Damien Millerff773642011-09-22 21:39:48 +10001063for local,
1064.Sm off
1065.Fl KR Oo Ar bind_address : Oc Ar port
1066.Sm on
1067for remote and
1068.Sm off
1069.Fl KD Oo Ar bind_address : Oc Ar port
1070.Sm on
1071for dynamic port-forwardings.
Darren Tuckerd3877b92005-12-20 16:09:36 +11001072.Ic !\& Ns Ar command
1073allows the user to execute a local command if the
1074.Ic PermitLocalCommand
1075option is enabled in
1076.Xr ssh_config 5 .
1077Basic help is available, using the
1078.Fl h
1079option.
1080.It Cm ~R
1081Request rekeying of the connection
jmc@openbsd.orga685ae82016-02-17 07:38:19 +00001082(only useful if the peer supports it).
Darren Tucker50a48d02012-09-06 21:25:37 +10001083.It Cm ~V
1084Decrease the verbosity
1085.Pq Ic LogLevel
1086when errors are being written to stderr.
1087.It Cm ~v
Darren Tucker83d0af62012-09-07 11:21:03 +10001088Increase the verbosity
Darren Tucker50a48d02012-09-06 21:25:37 +10001089.Pq Ic LogLevel
1090when errors are being written to stderr.
Darren Tuckerd3877b92005-12-20 16:09:36 +11001091.El
Damien Millerf3177182006-01-14 10:09:13 +11001092.Sh TCP FORWARDING
1093Forwarding of arbitrary TCP connections over the secure channel can
1094be specified either on the command line or in a configuration file.
1095One possible application of TCP forwarding is a secure connection to a
1096mail server; another is going through firewalls.
1097.Pp
1098In the example below, we look at encrypting communication between
1099an IRC client and server, even though the IRC server does not directly
1100support encrypted communications.
1101This works as follows:
1102the user connects to the remote host using
1103.Nm ,
1104specifying a port to be used to forward connections
1105to the remote server.
1106After that it is possible to start the service which is to be encrypted
1107on the client machine,
1108connecting to the same local port,
1109and
1110.Nm
1111will encrypt and forward the connection.
1112.Pp
1113The following example tunnels an IRC session from client machine
1114.Dq 127.0.0.1
1115(localhost)
1116to remote server
1117.Dq server.example.com :
1118.Bd -literal -offset 4n
1119$ ssh -f -L 1234:localhost:6667 server.example.com sleep 10
1120$ irc -c '#users' -p 1234 pinky 127.0.0.1
1121.Ed
1122.Pp
1123This tunnels a connection to IRC server
1124.Dq server.example.com ,
1125joining channel
1126.Dq #users ,
1127nickname
1128.Dq pinky ,
1129using port 1234.
1130It doesn't matter which port is used,
1131as long as it's greater than 1023
1132(remember, only root can open sockets on privileged ports)
1133and doesn't conflict with any ports already in use.
1134The connection is forwarded to port 6667 on the remote server,
1135since that's the standard port for IRC services.
1136.Pp
1137The
1138.Fl f
1139option backgrounds
1140.Nm
1141and the remote command
1142.Dq sleep 10
1143is specified to allow an amount of time
1144(10 seconds, in the example)
1145to start the service which is to be tunnelled.
1146If no connections are made within the time specified,
1147.Nm
1148will exit.
Damien Millerf3177182006-01-14 10:09:13 +11001149.Sh X11 FORWARDING
Darren Tuckerd3877b92005-12-20 16:09:36 +11001150If the
1151.Cm ForwardX11
1152variable is set to
1153.Dq yes
1154(or see the description of the
Damien Millerd7f308f2005-12-24 14:55:16 +11001155.Fl X ,
1156.Fl x ,
Darren Tuckerd3877b92005-12-20 16:09:36 +11001157and
Damien Millerd7f308f2005-12-24 14:55:16 +11001158.Fl Y
Damien Miller9a765b22005-12-24 14:53:44 +11001159options above)
Darren Tuckerd3877b92005-12-20 16:09:36 +11001160and the user is using X11 (the
1161.Ev DISPLAY
1162environment variable is set), the connection to the X11 display is
1163automatically forwarded to the remote side in such a way that any X11
1164programs started from the shell (or command) will go through the
1165encrypted channel, and the connection to the real X server will be made
1166from the local machine.
1167The user should not manually set
1168.Ev DISPLAY .
1169Forwarding of X11 connections can be
1170configured on the command line or in configuration files.
1171.Pp
1172The
1173.Ev DISPLAY
1174value set by
1175.Nm
1176will point to the server machine, but with a display number greater than zero.
1177This is normal, and happens because
1178.Nm
1179creates a
1180.Dq proxy
1181X server on the server machine for forwarding the
1182connections over the encrypted channel.
1183.Pp
1184.Nm
1185will also automatically set up Xauthority data on the server machine.
1186For this purpose, it will generate a random authorization cookie,
1187store it in Xauthority on the server, and verify that any forwarded
1188connections carry this cookie and replace it by the real cookie when
1189the connection is opened.
1190The real authentication cookie is never
1191sent to the server machine (and no cookies are sent in the plain).
1192.Pp
1193If the
1194.Cm ForwardAgent
1195variable is set to
1196.Dq yes
1197(or see the description of the
1198.Fl A
1199and
1200.Fl a
Damien Miller9a765b22005-12-24 14:53:44 +11001201options above) and
Darren Tuckerd3877b92005-12-20 16:09:36 +11001202the user is using an authentication agent, the connection to the agent
1203is automatically forwarded to the remote side.
Damien Millerbbc59092006-01-31 21:46:51 +11001204.Sh VERIFYING HOST KEYS
1205When connecting to a server for the first time,
1206a fingerprint of the server's public key is presented to the user
1207(unless the option
1208.Cm StrictHostKeyChecking
1209has been disabled).
1210Fingerprints can be determined using
1211.Xr ssh-keygen 1 :
1212.Pp
1213.Dl $ ssh-keygen -l -f /etc/ssh/ssh_host_rsa_key
1214.Pp
Darren Tuckerf6bffb12008-06-14 09:04:26 +10001215If the fingerprint is already known, it can be matched
1216and the key can be accepted or rejected.
djm@openbsd.orgf9487372015-05-22 05:28:45 +00001217If only legacy (MD5) fingerprints for the server are available, the
1218.Xr ssh-keygen 1
1219.Fl E
1220option may be used to downgrade the fingerprint algorithm to match.
1221.Pp
Darren Tuckerf6bffb12008-06-14 09:04:26 +10001222Because of the difficulty of comparing host keys
djm@openbsd.org56d1c832014-12-21 22:27:55 +00001223just by looking at fingerprint strings,
Darren Tuckerf6bffb12008-06-14 09:04:26 +10001224there is also support to compare host keys visually,
1225using
1226.Em random art .
1227By setting the
Damien Miller10288242008-06-30 00:04:03 +10001228.Cm VisualHostKey
Darren Tuckerf6bffb12008-06-14 09:04:26 +10001229option to
Damien Miller10288242008-06-30 00:04:03 +10001230.Dq yes ,
Darren Tuckerf6bffb12008-06-14 09:04:26 +10001231a small ASCII graphic gets displayed on every login to a server, no matter
1232if the session itself is interactive or not.
1233By learning the pattern a known server produces, a user can easily
1234find out that the host key has changed when a completely different pattern
1235is displayed.
1236Because these patterns are not unambiguous however, a pattern that looks
1237similar to the pattern remembered only gives a good probability that the
1238host key is the same, not guaranteed proof.
1239.Pp
1240To get a listing of the fingerprints along with their random art for
1241all known hosts, the following command line can be used:
1242.Pp
1243.Dl $ ssh-keygen -lv -f ~/.ssh/known_hosts
1244.Pp
Damien Millerbbc59092006-01-31 21:46:51 +11001245If the fingerprint is unknown,
1246an alternative method of verification is available:
1247SSH fingerprints verified by DNS.
1248An additional resource record (RR),
1249SSHFP,
1250is added to a zonefile
1251and the connecting client is able to match the fingerprint
1252with that of the key presented.
1253.Pp
1254In this example, we are connecting a client to a server,
1255.Dq host.example.com .
1256The SSHFP resource records should first be added to the zonefile for
1257host.example.com:
1258.Bd -literal -offset indent
Damien Millera1b3d632006-03-26 00:07:02 +11001259$ ssh-keygen -r host.example.com.
Damien Millerbbc59092006-01-31 21:46:51 +11001260.Ed
1261.Pp
1262The output lines will have to be added to the zonefile.
1263To check that the zone is answering fingerprint queries:
1264.Pp
1265.Dl $ dig -t SSHFP host.example.com
1266.Pp
1267Finally the client connects:
1268.Bd -literal -offset indent
1269$ ssh -o "VerifyHostKeyDNS ask" host.example.com
1270[...]
1271Matching host key fingerprint found in DNS.
1272Are you sure you want to continue connecting (yes/no)?
1273.Ed
1274.Pp
1275See the
1276.Cm VerifyHostKeyDNS
1277option in
1278.Xr ssh_config 5
1279for more information.
Darren Tucker248dd132006-01-20 11:30:58 +11001280.Sh SSH-BASED VIRTUAL PRIVATE NETWORKS
1281.Nm
1282contains support for Virtual Private Network (VPN) tunnelling
1283using the
1284.Xr tun 4
1285network pseudo-device,
1286allowing two networks to be joined securely.
1287The
1288.Xr sshd_config 5
1289configuration option
1290.Cm PermitTunnel
1291controls whether the server supports this,
1292and at what level (layer 2 or 3 traffic).
1293.Pp
1294The following example would connect client network 10.0.50.0/24
Damien Miller3975ee22006-11-05 05:31:33 +11001295with remote network 10.0.99.0/24 using a point-to-point connection
1296from 10.1.1.1 to 10.1.1.2,
1297provided that the SSH server running on the gateway to the remote network,
1298at 192.168.1.15, allows it.
1299.Pp
1300On the client:
Darren Tucker248dd132006-01-20 11:30:58 +11001301.Bd -literal -offset indent
1302# ssh -f -w 0:1 192.168.1.15 true
Damien Miller3975ee22006-11-05 05:31:33 +11001303# ifconfig tun0 10.1.1.1 10.1.1.2 netmask 255.255.255.252
1304# route add 10.0.99.0/24 10.1.1.2
1305.Ed
1306.Pp
1307On the server:
1308.Bd -literal -offset indent
1309# ifconfig tun1 10.1.1.2 10.1.1.1 netmask 255.255.255.252
1310# route add 10.0.50.0/24 10.1.1.1
Darren Tucker248dd132006-01-20 11:30:58 +11001311.Ed
1312.Pp
1313Client access may be more finely tuned via the
1314.Pa /root/.ssh/authorized_keys
1315file (see below) and the
1316.Cm PermitRootLogin
1317server option.
Damien Millere93eaaa2006-03-15 11:05:59 +11001318The following entry would permit connections on
Darren Tucker248dd132006-01-20 11:30:58 +11001319.Xr tun 4
Damien Millere93eaaa2006-03-15 11:05:59 +11001320device 1 from user
Darren Tucker248dd132006-01-20 11:30:58 +11001321.Dq jane
Damien Millere93eaaa2006-03-15 11:05:59 +11001322and on tun device 2 from user
Darren Tucker248dd132006-01-20 11:30:58 +11001323.Dq john ,
1324if
1325.Cm PermitRootLogin
1326is set to
1327.Dq forced-commands-only :
1328.Bd -literal -offset 2n
1329tunnel="1",command="sh /etc/netstart tun1" ssh-rsa ... jane
Damien Miller9f67a212006-03-15 11:05:35 +11001330tunnel="2",command="sh /etc/netstart tun2" ssh-rsa ... john
Darren Tucker248dd132006-01-20 11:30:58 +11001331.Ed
1332.Pp
Darren Tuckerffe88e12006-10-18 07:53:06 +10001333Since an SSH-based setup entails a fair amount of overhead,
Darren Tucker248dd132006-01-20 11:30:58 +11001334it may be more suited to temporary setups,
1335such as for wireless VPNs.
1336More permanent VPNs are better provided by tools such as
1337.Xr ipsecctl 8
1338and
1339.Xr isakmpd 8 .
Damien Miller32aa1441999-10-29 09:15:49 +10001340.Sh ENVIRONMENT
1341.Nm
1342will normally set the following environment variables:
Damien Miller6aa22902006-01-06 14:48:34 +11001343.Bl -tag -width "SSH_ORIGINAL_COMMAND"
Damien Miller32aa1441999-10-29 09:15:49 +10001344.It Ev DISPLAY
1345The
1346.Ev DISPLAY
Damien Miller7684ee12000-03-17 23:40:15 +11001347variable indicates the location of the X11 server.
Damien Miller22c77262000-04-13 12:26:34 +10001348It is automatically set by
Damien Miller32aa1441999-10-29 09:15:49 +10001349.Nm
1350to point to a value of the form
Damien Miller14af93e2006-01-02 23:38:21 +11001351.Dq hostname:n ,
1352where
1353.Dq hostname
1354indicates the host where the shell runs, and
1355.Sq n
1356is an integer \*(Ge 1.
Damien Miller7684ee12000-03-17 23:40:15 +11001357.Nm
1358uses this special value to forward X11 connections over the secure
1359channel.
Ben Lindstromc65e6a02001-04-23 13:02:16 +00001360The user should normally not set
1361.Ev DISPLAY
1362explicitly, as that
Damien Miller32aa1441999-10-29 09:15:49 +10001363will render the X11 connection insecure (and will require the user to
1364manually copy any required authorization cookies).
1365.It Ev HOME
1366Set to the path of the user's home directory.
1367.It Ev LOGNAME
1368Synonym for
1369.Ev USER ;
1370set for compatibility with systems that use this variable.
1371.It Ev MAIL
Ben Lindstrome59433d2001-09-12 16:41:37 +00001372Set to the path of the user's mailbox.
Damien Miller7684ee12000-03-17 23:40:15 +11001373.It Ev PATH
Damien Miller32aa1441999-10-29 09:15:49 +10001374Set to the default
1375.Ev PATH ,
1376as specified when compiling
Damien Miller1164c292006-01-02 23:38:37 +11001377.Nm .
Ben Lindstrom5bf5d672001-07-04 04:31:38 +00001378.It Ev SSH_ASKPASS
1379If
1380.Nm
1381needs a passphrase, it will read the passphrase from the current
1382terminal if it was run from a terminal.
1383If
1384.Nm
1385does not have a terminal associated with it but
1386.Ev DISPLAY
1387and
1388.Ev SSH_ASKPASS
1389are set, it will execute the program specified by
1390.Ev SSH_ASKPASS
1391and open an X11 window to read the passphrase.
1392This is particularly useful when calling
1393.Nm
1394from a
Darren Tucker4e4fe002004-11-05 20:01:03 +11001395.Pa .xsession
Ben Lindstrom5bf5d672001-07-04 04:31:38 +00001396or related script.
1397(Note that on some machines it
1398may be necessary to redirect the input from
1399.Pa /dev/null
1400to make this work.)
Damien Miller32aa1441999-10-29 09:15:49 +10001401.It Ev SSH_AUTH_SOCK
Damien Miller14af93e2006-01-02 23:38:21 +11001402Identifies the path of a
1403.Ux Ns -domain
1404socket used to communicate with the agent.
Damien Millerf37e2462002-09-19 11:47:55 +10001405.It Ev SSH_CONNECTION
1406Identifies the client and server ends of the connection.
Damien Miller7684ee12000-03-17 23:40:15 +11001407The variable contains
Damien Miller14af93e2006-01-02 23:38:21 +11001408four space-separated values: client IP address, client port number,
1409server IP address, and server port number.
Ben Lindstrom4dccfa52000-12-28 16:40:05 +00001410.It Ev SSH_ORIGINAL_COMMAND
Damien Miller14af93e2006-01-02 23:38:21 +11001411This variable contains the original command line if a forced command
Ben Lindstrom4dccfa52000-12-28 16:40:05 +00001412is executed.
1413It can be used to extract the original arguments.
Damien Miller32aa1441999-10-29 09:15:49 +10001414.It Ev SSH_TTY
1415This is set to the name of the tty (path to the device) associated
Damien Miller7684ee12000-03-17 23:40:15 +11001416with the current shell or command.
1417If the current session has no tty,
Damien Miller32aa1441999-10-29 09:15:49 +10001418this variable is not set.
djm@openbsd.orgb7548b12017-10-23 05:08:00 +00001419.It Ev SSH_TUNNEL
1420Optionally set by
1421.Xr sshd 8
1422to contain the interface names assigned if tunnel forwarding was
1423requested by the client.
djm@openbsd.org10727482017-10-13 06:45:18 +00001424.It Ev SSH_USER_AUTH
1425Optionally set by
1426.Xr sshd 8 ,
1427this variable may contain a pathname to a file that lists the authentication
1428methods successfully used when the session was established, including any
1429public keys that were used.
Damien Miller32aa1441999-10-29 09:15:49 +10001430.It Ev TZ
Damien Miller6dbdb6a2005-12-13 19:25:43 +11001431This variable is set to indicate the present time zone if it
Damien Miller208f1ed2006-03-15 11:56:03 +11001432was set when the daemon was started (i.e. the daemon passes the value
Damien Miller32aa1441999-10-29 09:15:49 +10001433on to new connections).
1434.It Ev USER
1435Set to the name of the user logging in.
1436.El
1437.Pp
Damien Miller22c77262000-04-13 12:26:34 +10001438Additionally,
Damien Miller32aa1441999-10-29 09:15:49 +10001439.Nm
Damien Miller22c77262000-04-13 12:26:34 +10001440reads
Damien Miller167ea5d2005-05-26 12:04:02 +10001441.Pa ~/.ssh/environment ,
Damien Miller32aa1441999-10-29 09:15:49 +10001442and adds lines of the format
1443.Dq VARNAME=value
Damien Miller14af93e2006-01-02 23:38:21 +11001444to the environment if the file exists and users are allowed to
Ben Lindstromdc7adf22002-08-20 18:38:02 +00001445change their environment.
Darren Tucker61776952003-10-02 16:19:47 +10001446For more information, see the
Ben Lindstromdc7adf22002-08-20 18:38:02 +00001447.Cm PermitUserEnvironment
Ben Lindstrombd9bf382002-08-20 18:54:20 +00001448option in
Ben Lindstromdc7adf22002-08-20 18:38:02 +00001449.Xr sshd_config 5 .
Damien Miller32aa1441999-10-29 09:15:49 +10001450.Sh FILES
Damien Miller7655f5c2006-01-06 14:48:18 +11001451.Bl -tag -width Ds -compact
Damien Millerafdae612010-08-31 22:31:14 +10001452.It Pa ~/.rhosts
Damien Miller1bcdb502006-01-06 14:49:38 +11001453This file is used for host-based authentication (see above).
Ben Lindstromebd888d2001-03-05 05:49:29 +00001454On some machines this file may need to be
Damien Miller1bcdb502006-01-06 14:49:38 +11001455world-readable if the user's home directory is on an NFS partition,
Damien Miller32aa1441999-10-29 09:15:49 +10001456because
1457.Xr sshd 8
Damien Miller7684ee12000-03-17 23:40:15 +11001458reads it as root.
1459Additionally, this file must be owned by the user,
1460and must not have write permissions for anyone else.
1461The recommended
Damien Miller32aa1441999-10-29 09:15:49 +10001462permission for most machines is read/write for the user, and not
1463accessible by others.
1464.Pp
Damien Millerafdae612010-08-31 22:31:14 +10001465.It Pa ~/.shosts
Damien Miller1bcdb502006-01-06 14:49:38 +11001466This file is used in exactly the same way as
1467.Pa .rhosts ,
1468but allows host-based authentication without permitting login with
1469rlogin/rsh.
Damien Miller7655f5c2006-01-06 14:48:18 +11001470.Pp
Damien Millerafdae612010-08-31 22:31:14 +10001471.It Pa ~/.ssh/
Damien Miller520e6152008-02-10 22:46:22 +11001472This directory is the default location for all user-specific configuration
1473and authentication information.
1474There is no general requirement to keep the entire contents of this directory
1475secret, but the recommended permissions are read/write/execute for the user,
1476and not accessible by others.
1477.Pp
Damien Millerafdae612010-08-31 22:31:14 +10001478.It Pa ~/.ssh/authorized_keys
sobrado@openbsd.orgf70b22b2014-08-30 15:33:50 +00001479Lists the public keys (DSA, ECDSA, Ed25519, RSA)
Damien Miller8ba0ead2013-12-18 17:46:27 +11001480that can be used for logging in as this user.
Damien Millerfb8ea742006-01-06 14:48:52 +11001481The format of this file is described in the
1482.Xr sshd 8
1483manual page.
Damien Millerfb8ea742006-01-06 14:48:52 +11001484This file is not highly sensitive, but the recommended
1485permissions are read/write for the user, and not accessible by others.
1486.Pp
Damien Millerafdae612010-08-31 22:31:14 +10001487.It Pa ~/.ssh/config
Damien Millerfb8ea742006-01-06 14:48:52 +11001488This is the per-user configuration file.
1489The file format and configuration options are described in
1490.Xr ssh_config 5 .
1491Because of the potential for abuse, this file must have strict permissions:
Damien Millerd93340c2013-07-18 16:14:34 +10001492read/write for the user, and not writable by others.
Damien Millerfb8ea742006-01-06 14:48:52 +11001493.Pp
Damien Millerafdae612010-08-31 22:31:14 +10001494.It Pa ~/.ssh/environment
Damien Miller4c102ee2006-01-06 14:49:17 +11001495Contains additional definitions for environment variables; see
1496.Sx ENVIRONMENT ,
Damien Millerfb8ea742006-01-06 14:48:52 +11001497above.
1498.Pp
Damien Millerafdae612010-08-31 22:31:14 +10001499.It Pa ~/.ssh/id_dsa
Damien Millereb8b60e2010-08-31 22:41:14 +10001500.It Pa ~/.ssh/id_ecdsa
Damien Miller8ba0ead2013-12-18 17:46:27 +11001501.It Pa ~/.ssh/id_ed25519
Damien Millerafdae612010-08-31 22:31:14 +10001502.It Pa ~/.ssh/id_rsa
Damien Millerfb8ea742006-01-06 14:48:52 +11001503Contains the private key for authentication.
1504These files
1505contain sensitive data and should be readable by the user but not
1506accessible by others (read/write/execute).
1507.Nm
1508will simply ignore a private key file if it is accessible by others.
1509It is possible to specify a passphrase when
1510generating the key which will be used to encrypt the
djm@openbsd.org@openbsd.orgecbf0052017-11-03 02:29:17 +00001511sensitive part of this file using AES-128.
Damien Millerfb8ea742006-01-06 14:48:52 +11001512.Pp
Damien Millerafdae612010-08-31 22:31:14 +10001513.It Pa ~/.ssh/id_dsa.pub
Damien Millereb8b60e2010-08-31 22:41:14 +10001514.It Pa ~/.ssh/id_ecdsa.pub
Damien Miller8ba0ead2013-12-18 17:46:27 +11001515.It Pa ~/.ssh/id_ed25519.pub
Damien Millerafdae612010-08-31 22:31:14 +10001516.It Pa ~/.ssh/id_rsa.pub
Damien Millerfb8ea742006-01-06 14:48:52 +11001517Contains the public key for authentication.
1518These files are not
1519sensitive and can (but need not) be readable by anyone.
Damien Millerfb8ea742006-01-06 14:48:52 +11001520.Pp
Damien Millerafdae612010-08-31 22:31:14 +10001521.It Pa ~/.ssh/known_hosts
Damien Millere87eb4c2006-01-14 10:08:36 +11001522Contains a list of host keys for all hosts the user has logged into
1523that are not already in the systemwide list of known host keys.
Damien Millerfb8ea742006-01-06 14:48:52 +11001524See
Damien Millere87eb4c2006-01-14 10:08:36 +11001525.Xr sshd 8
1526for further details of the format of this file.
Damien Millerfb8ea742006-01-06 14:48:52 +11001527.Pp
Damien Millerafdae612010-08-31 22:31:14 +10001528.It Pa ~/.ssh/rc
Damien Millerfb8ea742006-01-06 14:48:52 +11001529Commands in this file are executed by
1530.Nm
Damien Miller7e76e1f2006-01-14 10:08:57 +11001531when the user logs in, just before the user's shell (or command) is
Damien Millerfb8ea742006-01-06 14:48:52 +11001532started.
1533See the
1534.Xr sshd 8
1535manual page for more information.
1536.Pp
Damien Millerafdae612010-08-31 22:31:14 +10001537.It Pa /etc/hosts.equiv
Damien Miller1bcdb502006-01-06 14:49:38 +11001538This file is for host-based authentication (see above).
1539It should only be writable by root.
Damien Miller7655f5c2006-01-06 14:48:18 +11001540.Pp
Damien Millerafdae612010-08-31 22:31:14 +10001541.It Pa /etc/shosts.equiv
Damien Miller1bcdb502006-01-06 14:49:38 +11001542This file is used in exactly the same way as
1543.Pa hosts.equiv ,
1544but allows host-based authentication without permitting login with
1545rlogin/rsh.
Damien Miller7655f5c2006-01-06 14:48:18 +11001546.Pp
Damien Millerfb8ea742006-01-06 14:48:52 +11001547.It Pa /etc/ssh/ssh_config
1548Systemwide configuration file.
1549The file format and configuration options are described in
1550.Xr ssh_config 5 .
1551.Pp
Damien Millerafdae612010-08-31 22:31:14 +10001552.It Pa /etc/ssh/ssh_host_key
1553.It Pa /etc/ssh/ssh_host_dsa_key
Damien Millereb8b60e2010-08-31 22:41:14 +10001554.It Pa /etc/ssh/ssh_host_ecdsa_key
Damien Miller8ba0ead2013-12-18 17:46:27 +11001555.It Pa /etc/ssh/ssh_host_ed25519_key
Damien Millerafdae612010-08-31 22:31:14 +10001556.It Pa /etc/ssh/ssh_host_rsa_key
Damien Millerb9902cf2012-06-20 21:52:58 +10001557These files contain the private parts of the host keys
Damien Miller7e76e1f2006-01-14 10:08:57 +11001558and are used for host-based authentication.
Damien Millerfb8ea742006-01-06 14:48:52 +11001559.Pp
Damien Millerafdae612010-08-31 22:31:14 +10001560.It Pa /etc/ssh/ssh_known_hosts
Damien Millerfb8ea742006-01-06 14:48:52 +11001561Systemwide list of known host keys.
1562This file should be prepared by the
1563system administrator to contain the public host keys of all machines in the
1564organization.
Damien Millere87eb4c2006-01-14 10:08:36 +11001565It should be world-readable.
1566See
Damien Millerfb8ea742006-01-06 14:48:52 +11001567.Xr sshd 8
Damien Millere87eb4c2006-01-14 10:08:36 +11001568for further details of the format of this file.
Damien Millerfb8ea742006-01-06 14:48:52 +11001569.Pp
Damien Millerafdae612010-08-31 22:31:14 +10001570.It Pa /etc/ssh/sshrc
Damien Miller32aa1441999-10-29 09:15:49 +10001571Commands in this file are executed by
1572.Nm
Damien Miller7e76e1f2006-01-14 10:08:57 +11001573when the user logs in, just before the user's shell (or command) is started.
Damien Miller32aa1441999-10-29 09:15:49 +10001574See the
1575.Xr sshd 8
1576manual page for more information.
Damien Miller7b28dc52000-09-05 13:34:53 +11001577.El
Damien Millerdaa7b222010-09-10 11:19:33 +10001578.Sh EXIT STATUS
1579.Nm
1580exits with the exit status of the remote command or with 255
1581if an error occurred.
Damien Miller32aa1441999-10-29 09:15:49 +10001582.Sh SEE ALSO
Damien Miller32aa1441999-10-29 09:15:49 +10001583.Xr scp 1 ,
Damien Miller33804262001-02-04 23:20:18 +11001584.Xr sftp 1 ,
Damien Miller32aa1441999-10-29 09:15:49 +10001585.Xr ssh-add 1 ,
1586.Xr ssh-agent 1 ,
1587.Xr ssh-keygen 1 ,
Damien Miller128a0f12006-01-06 14:50:11 +11001588.Xr ssh-keyscan 1 ,
Darren Tucker248dd132006-01-20 11:30:58 +11001589.Xr tun 4 ,
Ben Lindstrombf69e3b2002-06-23 00:31:24 +00001590.Xr ssh_config 5 ,
Ben Lindstromc001cd32002-06-23 00:32:11 +00001591.Xr ssh-keysign 8 ,
Ben Lindstrom5ab6ae12001-02-10 22:08:03 +00001592.Xr sshd 8
Darren Tucker628a3fd2012-10-05 10:50:15 +10001593.Sh STANDARDS
Ben Lindstrom160ec622001-04-22 17:17:46 +00001594.Rs
Darren Tucker628a3fd2012-10-05 10:50:15 +10001595.%A S. Lehtinen
1596.%A C. Lonvick
1597.%D January 2006
Damien Miller39a93a32006-03-15 11:34:45 +11001598.%R RFC 4250
Darren Tucker628a3fd2012-10-05 10:50:15 +10001599.%T The Secure Shell (SSH) Protocol Assigned Numbers
Damien Miller39a93a32006-03-15 11:34:45 +11001600.Re
Darren Tucker628a3fd2012-10-05 10:50:15 +10001601.Pp
Damien Miller39a93a32006-03-15 11:34:45 +11001602.Rs
Darren Tucker628a3fd2012-10-05 10:50:15 +10001603.%A T. Ylonen
1604.%A C. Lonvick
1605.%D January 2006
Damien Miller39a93a32006-03-15 11:34:45 +11001606.%R RFC 4251
Darren Tucker628a3fd2012-10-05 10:50:15 +10001607.%T The Secure Shell (SSH) Protocol Architecture
Damien Miller39a93a32006-03-15 11:34:45 +11001608.Re
Darren Tucker628a3fd2012-10-05 10:50:15 +10001609.Pp
Damien Miller39a93a32006-03-15 11:34:45 +11001610.Rs
Darren Tucker628a3fd2012-10-05 10:50:15 +10001611.%A T. Ylonen
1612.%A C. Lonvick
1613.%D January 2006
Damien Miller39a93a32006-03-15 11:34:45 +11001614.%R RFC 4252
Darren Tucker628a3fd2012-10-05 10:50:15 +10001615.%T The Secure Shell (SSH) Authentication Protocol
Damien Miller39a93a32006-03-15 11:34:45 +11001616.Re
Darren Tucker628a3fd2012-10-05 10:50:15 +10001617.Pp
Damien Miller39a93a32006-03-15 11:34:45 +11001618.Rs
Darren Tucker628a3fd2012-10-05 10:50:15 +10001619.%A T. Ylonen
1620.%A C. Lonvick
1621.%D January 2006
Damien Miller39a93a32006-03-15 11:34:45 +11001622.%R RFC 4253
Darren Tucker628a3fd2012-10-05 10:50:15 +10001623.%T The Secure Shell (SSH) Transport Layer Protocol
Damien Miller39a93a32006-03-15 11:34:45 +11001624.Re
Darren Tucker628a3fd2012-10-05 10:50:15 +10001625.Pp
Damien Miller39a93a32006-03-15 11:34:45 +11001626.Rs
Darren Tucker628a3fd2012-10-05 10:50:15 +10001627.%A T. Ylonen
1628.%A C. Lonvick
1629.%D January 2006
Damien Miller39a93a32006-03-15 11:34:45 +11001630.%R RFC 4254
Darren Tucker628a3fd2012-10-05 10:50:15 +10001631.%T The Secure Shell (SSH) Connection Protocol
Damien Miller39a93a32006-03-15 11:34:45 +11001632.Re
Darren Tucker628a3fd2012-10-05 10:50:15 +10001633.Pp
Damien Miller39a93a32006-03-15 11:34:45 +11001634.Rs
Darren Tucker628a3fd2012-10-05 10:50:15 +10001635.%A J. Schlyter
1636.%A W. Griffin
1637.%D January 2006
Damien Miller39a93a32006-03-15 11:34:45 +11001638.%R RFC 4255
Darren Tucker628a3fd2012-10-05 10:50:15 +10001639.%T Using DNS to Securely Publish Secure Shell (SSH) Key Fingerprints
Damien Miller39a93a32006-03-15 11:34:45 +11001640.Re
Darren Tucker628a3fd2012-10-05 10:50:15 +10001641.Pp
Damien Miller39a93a32006-03-15 11:34:45 +11001642.Rs
Darren Tucker628a3fd2012-10-05 10:50:15 +10001643.%A F. Cusack
1644.%A M. Forssen
1645.%D January 2006
Damien Miller39a93a32006-03-15 11:34:45 +11001646.%R RFC 4256
Darren Tucker628a3fd2012-10-05 10:50:15 +10001647.%T Generic Message Exchange Authentication for the Secure Shell Protocol (SSH)
Damien Miller39a93a32006-03-15 11:34:45 +11001648.Re
Darren Tucker628a3fd2012-10-05 10:50:15 +10001649.Pp
Damien Miller39a93a32006-03-15 11:34:45 +11001650.Rs
Darren Tucker628a3fd2012-10-05 10:50:15 +10001651.%A J. Galbraith
1652.%A P. Remaker
1653.%D January 2006
Damien Miller39a93a32006-03-15 11:34:45 +11001654.%R RFC 4335
Darren Tucker628a3fd2012-10-05 10:50:15 +10001655.%T The Secure Shell (SSH) Session Channel Break Extension
Damien Miller39a93a32006-03-15 11:34:45 +11001656.Re
Darren Tucker628a3fd2012-10-05 10:50:15 +10001657.Pp
Damien Miller39a93a32006-03-15 11:34:45 +11001658.Rs
Darren Tucker628a3fd2012-10-05 10:50:15 +10001659.%A M. Bellare
1660.%A T. Kohno
1661.%A C. Namprempre
1662.%D January 2006
Damien Miller39a93a32006-03-15 11:34:45 +11001663.%R RFC 4344
Darren Tucker628a3fd2012-10-05 10:50:15 +10001664.%T The Secure Shell (SSH) Transport Layer Encryption Modes
Damien Miller39a93a32006-03-15 11:34:45 +11001665.Re
Darren Tucker628a3fd2012-10-05 10:50:15 +10001666.Pp
Damien Miller39a93a32006-03-15 11:34:45 +11001667.Rs
Darren Tucker628a3fd2012-10-05 10:50:15 +10001668.%A B. Harris
1669.%D January 2006
Damien Miller39a93a32006-03-15 11:34:45 +11001670.%R RFC 4345
Darren Tucker628a3fd2012-10-05 10:50:15 +10001671.%T Improved Arcfour Modes for the Secure Shell (SSH) Transport Layer Protocol
Ben Lindstrom160ec622001-04-22 17:17:46 +00001672.Re
Darren Tucker628a3fd2012-10-05 10:50:15 +10001673.Pp
Damien Miller3e96d742006-03-25 23:39:29 +11001674.Rs
Darren Tucker628a3fd2012-10-05 10:50:15 +10001675.%A M. Friedl
1676.%A N. Provos
1677.%A W. Simpson
1678.%D March 2006
Damien Miller3e96d742006-03-25 23:39:29 +11001679.%R RFC 4419
Darren Tucker628a3fd2012-10-05 10:50:15 +10001680.%T Diffie-Hellman Group Exchange for the Secure Shell (SSH) Transport Layer Protocol
Damien Miller3e96d742006-03-25 23:39:29 +11001681.Re
Darren Tucker628a3fd2012-10-05 10:50:15 +10001682.Pp
Damien Millerc0367fb2007-01-05 16:25:46 +11001683.Rs
Darren Tucker628a3fd2012-10-05 10:50:15 +10001684.%A J. Galbraith
1685.%A R. Thayer
1686.%D November 2006
Damien Millerc0367fb2007-01-05 16:25:46 +11001687.%R RFC 4716
Darren Tucker628a3fd2012-10-05 10:50:15 +10001688.%T The Secure Shell (SSH) Public Key File Format
Damien Millerc0367fb2007-01-05 16:25:46 +11001689.Re
Darren Tucker628a3fd2012-10-05 10:50:15 +10001690.Pp
Darren Tuckerf6bffb12008-06-14 09:04:26 +10001691.Rs
Darren Tucker628a3fd2012-10-05 10:50:15 +10001692.%A D. Stebila
1693.%A J. Green
1694.%D December 2009
Damien Miller1ca94692010-09-24 22:01:22 +10001695.%R RFC 5656
Darren Tucker628a3fd2012-10-05 10:50:15 +10001696.%T Elliptic Curve Algorithm Integration in the Secure Shell Transport Layer
Damien Miller1ca94692010-09-24 22:01:22 +10001697.Re
Darren Tucker628a3fd2012-10-05 10:50:15 +10001698.Pp
Damien Miller1ca94692010-09-24 22:01:22 +10001699.Rs
Darren Tuckerf6bffb12008-06-14 09:04:26 +10001700.%A A. Perrig
1701.%A D. Song
1702.%D 1999
Darren Tucker628a3fd2012-10-05 10:50:15 +10001703.%O International Workshop on Cryptographic Techniques and E-Commerce (CrypTEC '99)
1704.%T Hash Visualization: a New Technique to improve Real-World Security
Darren Tuckerf6bffb12008-06-14 09:04:26 +10001705.Re
Damien Millerf1ce5052003-06-11 22:04:39 +10001706.Sh AUTHORS
1707OpenSSH is a derivative of the original and free
1708ssh 1.2.12 release by Tatu Ylonen.
1709Aaron Campbell, Bob Beck, Markus Friedl, Niels Provos,
1710Theo de Raadt and Dug Song
1711removed many bugs, re-added newer features and
1712created OpenSSH.
1713Markus Friedl contributed the support for SSH
1714protocol versions 1.5 and 2.0.