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f095fcc7 | 1 | .\" $OpenBSD: ssh-agent.1,v 1.8 1999/11/16 23:59:21 deraadt Exp $ |
bf740959 | 2 | .\" |
3 | .\" -*- nroff -*- | |
4 | .\" | |
5 | .\" ssh-agent.1 | |
6 | .\" | |
7 | .\" Author: Tatu Ylonen <ylo@cs.hut.fi> | |
f095fcc7 | 8 | .\" |
bf740959 | 9 | .\" Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland |
10 | .\" All rights reserved | |
11 | .\" | |
12 | .\" Created: Sat Apr 23 20:10:43 1995 ylo | |
13 | .\" | |
14 | .Dd September 25, 1999 | |
15 | .Dt SSH-AGENT 1 | |
16 | .Os | |
17 | .Sh NAME | |
18 | .Nm ssh-agent | |
19 | .Nd authentication agent | |
20 | .Sh SYNOPSIS | |
21 | .Nm ssh-agent | |
22 | .Op Fl c Li | Fl s | |
23 | .Op Fl k | |
24 | .Oo | |
25 | .Ar command | |
26 | .Op Ar args ... | |
27 | .Oc | |
28 | .Sh DESCRIPTION | |
29 | .Nm | |
30 | is a program to hold authentication private keys. The | |
31 | idea is that | |
32 | .Nm | |
33 | is started in the beginning of an X-session or a login session, and | |
34 | all other windows or programs are started as clients to the ssh-agent | |
35 | program. Through use of environment variables the agent can be located | |
36 | and automatically used for RSA authentication when logging in to other | |
37 | machines using | |
38 | .Xr ssh 1 . | |
39 | .Pp | |
40 | The options are as follows: | |
41 | .Bl -tag -width Ds | |
42 | .It Fl c | |
43 | Generate C-shell commands on | |
44 | .Dv stdout . | |
45 | This is the default if | |
46 | .Ev SHELL | |
47 | looks like it's a csh style of shell. | |
48 | .It Fl s | |
49 | Generate Bourne shell commands on | |
50 | .Dv stdout . | |
51 | This is the default if | |
52 | .Ev SHELL | |
53 | does not look like it's a csh style of shell. | |
54 | .It Fl k | |
55 | Kill the current agent (given by the | |
56 | .Ev SSH_AGENT_PID | |
57 | environment variable). | |
58 | .El | |
59 | .Pp | |
60 | If a commandline is given, this is executed as a subprocess of the agent. | |
61 | When the command dies, so does the agent. | |
62 | .Pp | |
63 | The agent initially does not have any private keys. Keys are added | |
64 | using | |
65 | .Xr ssh-add 1 . | |
66 | When executed without arguments, | |
67 | .Xr ssh-add 1 | |
68 | adds the | |
69 | .Pa $HOME/.ssh/identity | |
70 | file. If the identity has a passphrase, | |
71 | .Xr ssh-add 1 | |
72 | asks for the passphrase (using a small X11 application if running | |
73 | under X11, or from the terminal if running without X). It then sends | |
74 | the identity to the agent. Several identities can be stored in the | |
75 | agent; the agent can automatically use any of these identities. | |
76 | .Ic ssh-add -l | |
77 | displays the identities currently held by the agent. | |
78 | .Pp | |
79 | The idea is that the agent is run in the user's local PC, laptop, or | |
80 | terminal. Authentication data need not be stored on any other | |
81 | machine, and authentication passphrases never go over the network. | |
82 | However, the connection to the agent is forwarded over SSH | |
83 | remote logins, and the user can thus use the privileges given by the | |
84 | identities anywhere in the network in a secure way. | |
85 | .Pp | |
86 | There are two main ways to get an agent setup: Either you let the agent | |
87 | start a new subcommand into which some environment variables are exported, or | |
88 | you let the agent print the needed shell commands (either | |
89 | .Xr sh 1 | |
90 | or | |
91 | .Xr csh 1 | |
92 | syntax can be generated) which can be evalled in the calling shell. | |
93 | Later | |
94 | .Xr ssh 1 | |
95 | look at these variables and use them to establish a connection to the agent. | |
96 | .Pp | |
97 | A unix-domain socket is created | |
98 | .Pq Pa /tmp/ssh-XXXXXXXX/agent.<pid> , | |
99 | and the name of this socket is stored in the | |
100 | .Ev SSH_AUTH_SOCK | |
101 | environment | |
102 | variable. The socket is made accessible only to the current user. | |
103 | This method is easily abused by root or another instance of the same | |
104 | user. | |
105 | .Pp | |
106 | The | |
107 | .Ev SSH_AGENT_PID | |
108 | environment variable holds the agent's PID. | |
109 | .Pp | |
110 | The agent exits automatically when the command given on the command | |
111 | line terminates. | |
e1a9c08d | 112 | .Pp |
113 | Here's a trick that will allow you to start this up from your .bash_profile (just put it in as the first thing that happens): | |
114 | .Sp | |
115 | .Vb 1 | |
116 | ||
117 | \& [ ! "$SSH_AGENT_PID" ] && exec ssh-agent -- bash --login | |
118 | \& ssh-add | |
119 | .Ve | |
bf740959 | 120 | .Sh FILES |
121 | .Bl -tag -width Ds | |
122 | .It Pa $HOME/.ssh/identity | |
123 | Contains the RSA authentication identity of the user. This file | |
124 | should not be readable by anyone but the user. It is possible to | |
125 | specify a passphrase when generating the key; that passphrase will be | |
126 | used to encrypt the private part of this file. This file | |
127 | is not used by | |
128 | .Nm | |
129 | but is normally added to the agent using | |
130 | .Xr ssh-add 1 | |
131 | at login time. | |
132 | .It Pa /tmp/ssh-XXXX/agent.<pid> , | |
133 | Unix-domain sockets used to contain the connection to the | |
134 | authentication agent. These sockets should only be readable by the | |
135 | owner. The sockets should get automatically removed when the agent | |
136 | exits. | |
137 | .Sh AUTHOR | |
138 | Tatu Ylonen <ylo@cs.hut.fi> | |
139 | .Pp | |
140 | OpenSSH | |
141 | is a derivative of the original (free) ssh 1.2.12 release, but with bugs | |
142 | removed and newer features re-added. Rapidly after the 1.2.12 release, | |
143 | newer versions bore successively more restrictive licenses. This version | |
144 | of OpenSSH | |
145 | .Bl -bullet | |
146 | .It | |
147 | has all components of a restrictive nature (ie. patents, see | |
148 | .Xr ssl 8 ) | |
149 | directly removed from the source code; any licensed or patented components | |
150 | are chosen from | |
151 | external libraries. | |
152 | .It | |
153 | has been updated to support ssh protocol 1.5. | |
154 | .It | |
155 | contains added support for | |
156 | .Xr kerberos 8 | |
157 | authentication and ticket passing. | |
158 | .It | |
159 | supports one-time password authentication with | |
160 | .Xr skey 1 . | |
161 | .El | |
162 | .Pp | |
163 | The libraries described in | |
164 | .Xr ssl 8 | |
165 | are required for proper operation. | |
166 | .Sh SEE ALSO | |
167 | .Xr ssh 1 , | |
168 | .Xr ssh-add 1 , | |
169 | .Xr ssh-keygen 1 , | |
170 | .Xr sshd 8 , | |
171 | .Xr ssl 8 |