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Damien Miller2e68d792010-01-26 12:51:13 +11001.\" $OpenBSD: ssh-agent.1,v 1.50 2010/01/17 21:49:09 tedu Exp $
Damien Miller32aa1441999-10-29 09:15:49 +10002.\"
3.\" Author: Tatu Ylonen <ylo@cs.hut.fi>
Damien Miller32aa1441999-10-29 09:15:49 +10004.\" Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
5.\" All rights reserved
6.\"
Damien Millere4340be2000-09-16 13:29:08 +11007.\" As far as I am concerned, the code I have written for this software
8.\" can be used freely for any purpose. Any derived versions of this
9.\" software must be clearly marked as such, and if the derived work is
10.\" incompatible with the protocol description in the RFC file, it must be
11.\" called by a name other than "ssh" or "Secure Shell".
12.\"
Ben Lindstrom92a2e382001-03-05 06:59:27 +000013.\" Copyright (c) 1999,2000 Markus Friedl. All rights reserved.
14.\" Copyright (c) 1999 Aaron Campbell. All rights reserved.
15.\" Copyright (c) 1999 Theo de Raadt. All rights reserved.
Damien Millere4340be2000-09-16 13:29:08 +110016.\"
17.\" Redistribution and use in source and binary forms, with or without
18.\" modification, are permitted provided that the following conditions
19.\" are met:
20.\" 1. Redistributions of source code must retain the above copyright
21.\" notice, this list of conditions and the following disclaimer.
22.\" 2. Redistributions in binary form must reproduce the above copyright
23.\" notice, this list of conditions and the following disclaimer in the
24.\" documentation and/or other materials provided with the distribution.
25.\"
26.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
27.\" IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
28.\" OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
29.\" IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
30.\" INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
31.\" NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
32.\" DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
33.\" THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
34.\" (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
35.\" THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
Damien Miller32aa1441999-10-29 09:15:49 +100036.\"
Damien Miller2e68d792010-01-26 12:51:13 +110037.Dd $Mdocdate: January 17 2010 $
Damien Miller32aa1441999-10-29 09:15:49 +100038.Dt SSH-AGENT 1
39.Os
40.Sh NAME
41.Nm ssh-agent
42.Nd authentication agent
43.Sh SYNOPSIS
Damien Miller22c77262000-04-13 12:26:34 +100044.Nm ssh-agent
Ben Lindstromba1fa1d2001-09-12 17:02:49 +000045.Op Fl c Li | Fl s
46.Op Fl d
Damien Miller5cbe7ca2007-09-17 16:05:50 +100047.Op Fl a Ar bind_address
48.Op Fl t Ar life
49.Op Ar command Op Ar arg ...
Ben Lindstrom14920292000-11-21 21:24:55 +000050.Nm ssh-agent
51.Op Fl c Li | Fl s
Ben Lindstrom14920292000-11-21 21:24:55 +000052.Fl k
Damien Miller22c77262000-04-13 12:26:34 +100053.Sh DESCRIPTION
Damien Miller32aa1441999-10-29 09:15:49 +100054.Nm
Damien Millerad833b32000-08-23 10:46:23 +100055is a program to hold private keys used for public key authentication
56(RSA, DSA).
Damien Miller450a7a12000-03-26 13:04:51 +100057The idea is that
Damien Miller32aa1441999-10-29 09:15:49 +100058.Nm
59is started in the beginning of an X-session or a login session, and
60all other windows or programs are started as clients to the ssh-agent
Damien Miller450a7a12000-03-26 13:04:51 +100061program.
62Through use of environment variables the agent can be located
Damien Millerad833b32000-08-23 10:46:23 +100063and automatically used for authentication when logging in to other
Damien Miller32aa1441999-10-29 09:15:49 +100064machines using
65.Xr ssh 1 .
66.Pp
67The options are as follows:
68.Bl -tag -width Ds
Ben Lindstromb7788f32002-06-06 21:46:08 +000069.It Fl a Ar bind_address
Darren Tuckerae69e1d2009-10-24 11:41:34 +110070Bind the agent to the
Darren Tucker98c9aec2009-10-24 11:42:44 +110071.Ux Ns -domain
72socket
Ben Lindstromb7788f32002-06-06 21:46:08 +000073.Ar bind_address .
74The default is
Damien Miller393821a2006-07-24 14:04:53 +100075.Pa /tmp/ssh-XXXXXXXXXX/agent.\*(Ltppid\*(Gt .
Damien Miller32aa1441999-10-29 09:15:49 +100076.It Fl c
77Generate C-shell commands on
78.Dv stdout .
79This is the default if
80.Ev SHELL
81looks like it's a csh style of shell.
Damien Miller5cbe7ca2007-09-17 16:05:50 +100082.It Fl d
83Debug mode.
84When this option is specified
85.Nm
86will not fork.
87.It Fl k
88Kill the current agent (given by the
89.Ev SSH_AGENT_PID
90environment variable).
Damien Miller32aa1441999-10-29 09:15:49 +100091.It Fl s
92Generate Bourne shell commands on
93.Dv stdout .
94This is the default if
95.Ev SHELL
96does not look like it's a csh style of shell.
Damien Miller53d81482003-01-22 11:47:19 +110097.It Fl t Ar life
Damien Miller495dca32003-04-01 21:42:14 +100098Set a default value for the maximum lifetime of identities added to the agent.
Damien Miller53d81482003-01-22 11:47:19 +110099The lifetime may be specified in seconds or in a time format specified in
Darren Tucker3a4634f2005-11-28 17:05:40 +1100100.Xr sshd_config 5 .
Damien Miller53d81482003-01-22 11:47:19 +1100101A lifetime specified for an identity with
102.Xr ssh-add 1
103overrides this value.
104Without this option the default maximum lifetime is forever.
Damien Miller32aa1441999-10-29 09:15:49 +1000105.El
106.Pp
107If a commandline is given, this is executed as a subprocess of the agent.
108When the command dies, so does the agent.
109.Pp
Damien Miller450a7a12000-03-26 13:04:51 +1000110The agent initially does not have any private keys.
111Keys are added using
Damien Miller32aa1441999-10-29 09:15:49 +1000112.Xr ssh-add 1 .
Damien Miller22c77262000-04-13 12:26:34 +1000113When executed without arguments,
Damien Miller32aa1441999-10-29 09:15:49 +1000114.Xr ssh-add 1
Damien Millerd2b8f162002-02-05 12:24:19 +1100115adds the files
Damien Miller167ea5d2005-05-26 12:04:02 +1000116.Pa ~/.ssh/id_rsa ,
117.Pa ~/.ssh/id_dsa
Damien Millerd2b8f162002-02-05 12:24:19 +1100118and
Damien Miller167ea5d2005-05-26 12:04:02 +1000119.Pa ~/.ssh/identity .
Damien Miller22c77262000-04-13 12:26:34 +1000120If the identity has a passphrase,
Damien Miller32aa1441999-10-29 09:15:49 +1000121.Xr ssh-add 1
Damien Miller2e68d792010-01-26 12:51:13 +1100122asks for the passphrase on the terminal if it has one or from a small X11
123program if running under X11.
124If neither of these is the case then the authentication will fail.
Damien Miller450a7a12000-03-26 13:04:51 +1000125It then sends the identity to the agent.
126Several identities can be stored in the
Damien Miller32aa1441999-10-29 09:15:49 +1000127agent; the agent can automatically use any of these identities.
128.Ic ssh-add -l
129displays the identities currently held by the agent.
130.Pp
131The idea is that the agent is run in the user's local PC, laptop, or
Damien Miller450a7a12000-03-26 13:04:51 +1000132terminal.
133Authentication data need not be stored on any other
Damien Miller32aa1441999-10-29 09:15:49 +1000134machine, and authentication passphrases never go over the network.
135However, the connection to the agent is forwarded over SSH
136remote logins, and the user can thus use the privileges given by the
137identities anywhere in the network in a secure way.
138.Pp
Damien Millerabbae982003-05-15 10:16:21 +1000139There are two main ways to get an agent set up:
Darren Tuckera86b4532004-05-13 16:45:46 +1000140The first is that the agent starts a new subcommand into which some environment
141variables are exported, eg
142.Cm ssh-agent xterm & .
143The second is that the agent prints the needed shell commands (either
Damien Miller32aa1441999-10-29 09:15:49 +1000144.Xr sh 1
145or
146.Xr csh 1
Darren Tucker5837b512009-06-21 17:52:27 +1000147syntax can be generated) which can be evaluated in the calling shell, eg
Darren Tuckera86b4532004-05-13 16:45:46 +1000148.Cm eval `ssh-agent -s`
149for Bourne-type shells such as
150.Xr sh 1
151or
152.Xr ksh 1
153and
Darren Tuckerfc959702004-07-17 16:12:08 +1000154.Cm eval `ssh-agent -c`
Darren Tuckera86b4532004-05-13 16:45:46 +1000155for
156.Xr csh 1
157and derivatives.
158.Pp
Damien Miller32aa1441999-10-29 09:15:49 +1000159Later
160.Xr ssh 1
Ben Lindstrom0d3e8fa2001-04-04 01:51:25 +0000161looks at these variables and uses them to establish a connection to the agent.
Damien Miller32aa1441999-10-29 09:15:49 +1000162.Pp
Ben Lindstrom11f790b2001-12-06 16:37:51 +0000163The agent will never send a private key over its request channel.
164Instead, operations that require a private key will be performed
165by the agent, and the result will be returned to the requester.
166This way, private keys are not exposed to clients using the agent.
167.Pp
Darren Tuckerae69e1d2009-10-24 11:41:34 +1100168A
Darren Tucker98c9aec2009-10-24 11:42:44 +1100169.Ux Ns -domain
170socket is created and the name of this socket is stored in the
Damien Miller32aa1441999-10-29 09:15:49 +1000171.Ev SSH_AUTH_SOCK
172environment
Damien Miller450a7a12000-03-26 13:04:51 +1000173variable.
174The socket is made accessible only to the current user.
Damien Miller32aa1441999-10-29 09:15:49 +1000175This method is easily abused by root or another instance of the same
176user.
177.Pp
178The
179.Ev SSH_AGENT_PID
Ben Lindstrom959de992002-06-23 00:35:25 +0000180environment variable holds the agent's process ID.
Damien Miller32aa1441999-10-29 09:15:49 +1000181.Pp
182The agent exits automatically when the command given on the command
183line terminates.
Damien Miller32aa1441999-10-29 09:15:49 +1000184.Sh FILES
185.Bl -tag -width Ds
Damien Miller167ea5d2005-05-26 12:04:02 +1000186.It Pa ~/.ssh/identity
Ben Lindstrom18a82ac2001-04-11 15:59:35 +0000187Contains the protocol version 1 RSA authentication identity of the user.
Damien Miller167ea5d2005-05-26 12:04:02 +1000188.It Pa ~/.ssh/id_dsa
Ben Lindstrom18a82ac2001-04-11 15:59:35 +0000189Contains the protocol version 2 DSA authentication identity of the user.
Damien Miller167ea5d2005-05-26 12:04:02 +1000190.It Pa ~/.ssh/id_rsa
Ben Lindstrom18a82ac2001-04-11 15:59:35 +0000191Contains the protocol version 2 RSA authentication identity of the user.
Damien Miller393821a2006-07-24 14:04:53 +1000192.It Pa /tmp/ssh-XXXXXXXXXX/agent.\*(Ltppid\*(Gt
Darren Tucker98c9aec2009-10-24 11:42:44 +1100193.Ux Ns -domain
194sockets used to contain the connection to the authentication agent.
Damien Miller450a7a12000-03-26 13:04:51 +1000195These sockets should only be readable by the owner.
196The sockets should get automatically removed when the agent exits.
Damien Miller37023962000-07-11 17:31:38 +1000197.El
Damien Millerf1ce5052003-06-11 22:04:39 +1000198.Sh SEE ALSO
199.Xr ssh 1 ,
200.Xr ssh-add 1 ,
201.Xr ssh-keygen 1 ,
202.Xr sshd 8
Damien Miller0bc1bd82000-11-13 22:57:25 +1100203.Sh AUTHORS
Ben Lindstrom035782e2001-01-29 08:34:16 +0000204OpenSSH is a derivative of the original and free
205ssh 1.2.12 release by Tatu Ylonen.
206Aaron Campbell, Bob Beck, Markus Friedl, Niels Provos,
207Theo de Raadt and Dug Song
208removed many bugs, re-added newer features and
209created OpenSSH.
210Markus Friedl contributed the support for SSH
211protocol versions 1.5 and 2.0.