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Ben Lindstrom92a2e382001-03-05 06:59:27 +00001.\" $OpenBSD: ssh-agent.1,v 1.22 2001/03/02 18:54:31 deraadt 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
Damien Miller32aa1441999-10-29 09:15:49 +100045.Ar command
Ben Lindstrom14920292000-11-21 21:24:55 +000046.Ar args ...
47.Nm ssh-agent
48.Op Fl c Li | Fl s
49.Nm ssh-agent
50.Fl k
Damien Miller22c77262000-04-13 12:26:34 +100051.Sh DESCRIPTION
Damien Miller32aa1441999-10-29 09:15:49 +100052.Nm
Damien Millerad833b32000-08-23 10:46:23 +100053is a program to hold private keys used for public key authentication
54(RSA, DSA).
Damien Miller450a7a12000-03-26 13:04:51 +100055The idea is that
Damien Miller32aa1441999-10-29 09:15:49 +100056.Nm
57is started in the beginning of an X-session or a login session, and
58all other windows or programs are started as clients to the ssh-agent
Damien Miller450a7a12000-03-26 13:04:51 +100059program.
60Through use of environment variables the agent can be located
Damien Millerad833b32000-08-23 10:46:23 +100061and automatically used for authentication when logging in to other
Damien Miller32aa1441999-10-29 09:15:49 +100062machines using
63.Xr ssh 1 .
64.Pp
65The options are as follows:
66.Bl -tag -width Ds
67.It Fl c
68Generate C-shell commands on
69.Dv stdout .
70This is the default if
71.Ev SHELL
72looks like it's a csh style of shell.
73.It Fl s
74Generate Bourne shell commands on
75.Dv stdout .
76This is the default if
77.Ev SHELL
78does not look like it's a csh style of shell.
79.It Fl k
80Kill the current agent (given by the
81.Ev SSH_AGENT_PID
82environment variable).
83.El
84.Pp
85If a commandline is given, this is executed as a subprocess of the agent.
86When the command dies, so does the agent.
87.Pp
Damien Miller450a7a12000-03-26 13:04:51 +100088The agent initially does not have any private keys.
89Keys are added using
Damien Miller32aa1441999-10-29 09:15:49 +100090.Xr ssh-add 1 .
Damien Miller22c77262000-04-13 12:26:34 +100091When executed without arguments,
Damien Miller32aa1441999-10-29 09:15:49 +100092.Xr ssh-add 1
Damien Miller22c77262000-04-13 12:26:34 +100093adds the
Damien Miller32aa1441999-10-29 09:15:49 +100094.Pa $HOME/.ssh/identity
Damien Miller450a7a12000-03-26 13:04:51 +100095file.
Damien Miller22c77262000-04-13 12:26:34 +100096If the identity has a passphrase,
Damien Miller32aa1441999-10-29 09:15:49 +100097.Xr ssh-add 1
98asks for the passphrase (using a small X11 application if running
Damien Miller450a7a12000-03-26 13:04:51 +100099under X11, or from the terminal if running without X).
100It then sends the identity to the agent.
101Several identities can be stored in the
Damien Miller32aa1441999-10-29 09:15:49 +1000102agent; the agent can automatically use any of these identities.
103.Ic ssh-add -l
104displays the identities currently held by the agent.
105.Pp
106The idea is that the agent is run in the user's local PC, laptop, or
Damien Miller450a7a12000-03-26 13:04:51 +1000107terminal.
108Authentication data need not be stored on any other
Damien Miller32aa1441999-10-29 09:15:49 +1000109machine, and authentication passphrases never go over the network.
110However, the connection to the agent is forwarded over SSH
111remote logins, and the user can thus use the privileges given by the
112identities anywhere in the network in a secure way.
113.Pp
Damien Miller450a7a12000-03-26 13:04:51 +1000114There are two main ways to get an agent setup:
115Either you let the agent
Damien Miller32aa1441999-10-29 09:15:49 +1000116start a new subcommand into which some environment variables are exported, or
117you let the agent print the needed shell commands (either
118.Xr sh 1
119or
120.Xr csh 1
121syntax can be generated) which can be evalled in the calling shell.
122Later
123.Xr ssh 1
124look at these variables and use them to establish a connection to the agent.
125.Pp
126A unix-domain socket is created
127.Pq Pa /tmp/ssh-XXXXXXXX/agent.<pid> ,
128and the name of this socket is stored in the
129.Ev SSH_AUTH_SOCK
130environment
Damien Miller450a7a12000-03-26 13:04:51 +1000131variable.
132The socket is made accessible only to the current user.
Damien Miller32aa1441999-10-29 09:15:49 +1000133This method is easily abused by root or another instance of the same
134user.
135.Pp
136The
137.Ev SSH_AGENT_PID
138environment variable holds the agent's PID.
139.Pp
140The agent exits automatically when the command given on the command
141line terminates.
Damien Miller32aa1441999-10-29 09:15:49 +1000142.Sh FILES
143.Bl -tag -width Ds
144.It Pa $HOME/.ssh/identity
Damien Miller450a7a12000-03-26 13:04:51 +1000145Contains the RSA authentication identity of the user.
146This file should not be readable by anyone but the user.
147It is possible to
Damien Miller32aa1441999-10-29 09:15:49 +1000148specify a passphrase when generating the key; that passphrase will be
Damien Miller450a7a12000-03-26 13:04:51 +1000149used to encrypt the private part of this file.
150This file is not used by
Damien Miller32aa1441999-10-29 09:15:49 +1000151.Nm
152but is normally added to the agent using
153.Xr ssh-add 1
154at login time.
Damien Millerad833b32000-08-23 10:46:23 +1000155.It Pa $HOME/.ssh/id_dsa
156Contains the DSA authentication identity of the user.
Ben Lindstrom14920292000-11-21 21:24:55 +0000157.It Pa /tmp/ssh-XXXXXXXX/agent.<pid>
Damien Miller32aa1441999-10-29 09:15:49 +1000158Unix-domain sockets used to contain the connection to the
Damien Miller450a7a12000-03-26 13:04:51 +1000159authentication agent.
160These sockets should only be readable by the owner.
161The sockets should get automatically removed when the agent exits.
Damien Miller37023962000-07-11 17:31:38 +1000162.El
Damien Miller0bc1bd82000-11-13 22:57:25 +1100163.Sh AUTHORS
Ben Lindstrom035782e2001-01-29 08:34:16 +0000164OpenSSH is a derivative of the original and free
165ssh 1.2.12 release by Tatu Ylonen.
166Aaron Campbell, Bob Beck, Markus Friedl, Niels Provos,
167Theo de Raadt and Dug Song
168removed many bugs, re-added newer features and
169created OpenSSH.
170Markus Friedl contributed the support for SSH
171protocol versions 1.5 and 2.0.
Damien Miller32aa1441999-10-29 09:15:49 +1000172.Sh SEE ALSO
173.Xr ssh 1 ,
174.Xr ssh-add 1 ,
175.Xr ssh-keygen 1 ,
Ben Lindstrome5b3fb32001-02-10 23:56:35 +0000176.Xr sshd 8