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Ben Lindstromb48057b2002-06-25 23:16:31 +00001.\" $OpenBSD: ssh-agent.1,v 1.35 2002/06/24 13:12:23 markus 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.\"
37.Dd September 25, 1999
38.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 Lindstromb7788f32002-06-06 21:46:08 +000045.Op Fl a Ar bind_address
Ben Lindstromba1fa1d2001-09-12 17:02:49 +000046.Op Fl c Li | Fl s
47.Op Fl d
48.Op Ar command Op Ar args ...
Ben Lindstrom14920292000-11-21 21:24:55 +000049.Nm ssh-agent
50.Op Fl c Li | Fl s
Ben Lindstrom14920292000-11-21 21:24:55 +000051.Fl k
Damien Miller22c77262000-04-13 12:26:34 +100052.Sh DESCRIPTION
Damien Miller32aa1441999-10-29 09:15:49 +100053.Nm
Damien Millerad833b32000-08-23 10:46:23 +100054is a program to hold private keys used for public key authentication
55(RSA, DSA).
Damien Miller450a7a12000-03-26 13:04:51 +100056The idea is that
Damien Miller32aa1441999-10-29 09:15:49 +100057.Nm
58is started in the beginning of an X-session or a login session, and
59all other windows or programs are started as clients to the ssh-agent
Damien Miller450a7a12000-03-26 13:04:51 +100060program.
61Through use of environment variables the agent can be located
Damien Millerad833b32000-08-23 10:46:23 +100062and automatically used for authentication when logging in to other
Damien Miller32aa1441999-10-29 09:15:49 +100063machines using
64.Xr ssh 1 .
65.Pp
66The options are as follows:
67.Bl -tag -width Ds
Ben Lindstromb7788f32002-06-06 21:46:08 +000068.It Fl a Ar bind_address
69Bind the agent to the unix-domain socket
70.Ar bind_address .
71The default is
Ben Lindstromb48057b2002-06-25 23:16:31 +000072.Pa /tmp/ssh-XXXXXXXX/agent.<ppid> .
Damien Miller32aa1441999-10-29 09:15:49 +100073.It Fl c
74Generate C-shell commands on
75.Dv stdout .
76This is the default if
77.Ev SHELL
78looks like it's a csh style of shell.
79.It Fl s
80Generate Bourne shell commands on
81.Dv stdout .
82This is the default if
83.Ev SHELL
84does not look like it's a csh style of shell.
85.It Fl k
86Kill the current agent (given by the
87.Ev SSH_AGENT_PID
88environment variable).
Ben Lindstromd94580c2001-07-04 03:48:02 +000089.It Fl d
90Debug mode. When this option is specified
91.Nm
Ben Lindstroma4a53232001-07-18 15:51:00 +000092will not fork.
Damien Miller32aa1441999-10-29 09:15:49 +100093.El
94.Pp
95If a commandline is given, this is executed as a subprocess of the agent.
96When the command dies, so does the agent.
97.Pp
Damien Miller450a7a12000-03-26 13:04:51 +100098The agent initially does not have any private keys.
99Keys are added using
Damien Miller32aa1441999-10-29 09:15:49 +1000100.Xr ssh-add 1 .
Damien Miller22c77262000-04-13 12:26:34 +1000101When executed without arguments,
Damien Miller32aa1441999-10-29 09:15:49 +1000102.Xr ssh-add 1
Damien Millerd2b8f162002-02-05 12:24:19 +1100103adds the files
104.Pa $HOME/.ssh/id_rsa ,
Ben Lindstromcb72e4f2002-06-21 00:41:51 +0000105.Pa $HOME/.ssh/id_dsa
Damien Millerd2b8f162002-02-05 12:24:19 +1100106and
107.Pa $HOME/.ssh/identity .
Damien Miller22c77262000-04-13 12:26:34 +1000108If the identity has a passphrase,
Damien Miller32aa1441999-10-29 09:15:49 +1000109.Xr ssh-add 1
110asks for the passphrase (using a small X11 application if running
Damien Miller450a7a12000-03-26 13:04:51 +1000111under X11, or from the terminal if running without X).
112It then sends the identity to the agent.
113Several identities can be stored in the
Damien Miller32aa1441999-10-29 09:15:49 +1000114agent; the agent can automatically use any of these identities.
115.Ic ssh-add -l
116displays the identities currently held by the agent.
117.Pp
118The idea is that the agent is run in the user's local PC, laptop, or
Damien Miller450a7a12000-03-26 13:04:51 +1000119terminal.
120Authentication data need not be stored on any other
Damien Miller32aa1441999-10-29 09:15:49 +1000121machine, and authentication passphrases never go over the network.
122However, the connection to the agent is forwarded over SSH
123remote logins, and the user can thus use the privileges given by the
124identities anywhere in the network in a secure way.
125.Pp
Damien Miller450a7a12000-03-26 13:04:51 +1000126There are two main ways to get an agent setup:
Ben Lindstrom594e2032001-09-12 18:35:30 +0000127Either the agent starts a new subcommand into which some environment
128variables are exported, or the agent prints the needed shell commands
129(either
Damien Miller32aa1441999-10-29 09:15:49 +1000130.Xr sh 1
131or
132.Xr csh 1
133syntax can be generated) which can be evalled in the calling shell.
134Later
135.Xr ssh 1
Ben Lindstrom0d3e8fa2001-04-04 01:51:25 +0000136looks at these variables and uses them to establish a connection to the agent.
Damien Miller32aa1441999-10-29 09:15:49 +1000137.Pp
Ben Lindstrom11f790b2001-12-06 16:37:51 +0000138The agent will never send a private key over its request channel.
139Instead, operations that require a private key will be performed
140by the agent, and the result will be returned to the requester.
141This way, private keys are not exposed to clients using the agent.
142.Pp
Damien Miller32aa1441999-10-29 09:15:49 +1000143A unix-domain socket is created
Damien Miller32aa1441999-10-29 09:15:49 +1000144and the name of this socket is stored in the
145.Ev SSH_AUTH_SOCK
146environment
Damien Miller450a7a12000-03-26 13:04:51 +1000147variable.
148The socket is made accessible only to the current user.
Damien Miller32aa1441999-10-29 09:15:49 +1000149This method is easily abused by root or another instance of the same
150user.
151.Pp
152The
153.Ev SSH_AGENT_PID
Ben Lindstrom959de992002-06-23 00:35:25 +0000154environment variable holds the agent's process ID.
Damien Miller32aa1441999-10-29 09:15:49 +1000155.Pp
156The agent exits automatically when the command given on the command
157line terminates.
Damien Miller32aa1441999-10-29 09:15:49 +1000158.Sh FILES
159.Bl -tag -width Ds
160.It Pa $HOME/.ssh/identity
Ben Lindstrom18a82ac2001-04-11 15:59:35 +0000161Contains the protocol version 1 RSA authentication identity of the user.
Damien Millerad833b32000-08-23 10:46:23 +1000162.It Pa $HOME/.ssh/id_dsa
Ben Lindstrom18a82ac2001-04-11 15:59:35 +0000163Contains the protocol version 2 DSA authentication identity of the user.
164.It Pa $HOME/.ssh/id_rsa
165Contains the protocol version 2 RSA authentication identity of the user.
Ben Lindstromb48057b2002-06-25 23:16:31 +0000166.It Pa /tmp/ssh-XXXXXXXX/agent.<ppid>
Damien Miller32aa1441999-10-29 09:15:49 +1000167Unix-domain sockets used to contain the connection to the
Damien Miller450a7a12000-03-26 13:04:51 +1000168authentication agent.
169These sockets should only be readable by the owner.
170The sockets should get automatically removed when the agent exits.
Damien Miller37023962000-07-11 17:31:38 +1000171.El
Damien Miller0bc1bd82000-11-13 22:57:25 +1100172.Sh AUTHORS
Ben Lindstrom035782e2001-01-29 08:34:16 +0000173OpenSSH is a derivative of the original and free
174ssh 1.2.12 release by Tatu Ylonen.
175Aaron Campbell, Bob Beck, Markus Friedl, Niels Provos,
176Theo de Raadt and Dug Song
177removed many bugs, re-added newer features and
178created OpenSSH.
179Markus Friedl contributed the support for SSH
180protocol versions 1.5 and 2.0.
Damien Miller32aa1441999-10-29 09:15:49 +1000181.Sh SEE ALSO
182.Xr ssh 1 ,
183.Xr ssh-add 1 ,
184.Xr ssh-keygen 1 ,
Ben Lindstrome5b3fb32001-02-10 23:56:35 +0000185.Xr sshd 8