1SSH-AGENT(1)               OpenBSD Reference Manual               SSH-AGENT(1)
2
3NAME
4     ssh-agent - authentication agent
5
6SYNOPSIS
7     ssh-agent [-c | -s] [-d] [-a bind_address] [-t life] [command [arg ...]]
8     ssh-agent [-c | -s] -k
9
10DESCRIPTION
11     ssh-agent is a program to hold private keys used for public key
12     authentication (RSA, DSA, ECDSA, ED25519).  The idea is that ssh-agent is
13     started in the beginning of an X-session or a login session, and all
14     other windows or programs are started as clients to the ssh-agent
15     program.  Through use of environment variables the agent can be located
16     and automatically used for authentication when logging in to other
17     machines using ssh(1).
18
19     The options are as follows:
20
21     -a bind_address
22             Bind the agent to the UNIX-domain socket bind_address.  The
23             default is $TMPDIR/ssh-XXXXXXXXXX/agent.<ppid>.
24
25     -c      Generate C-shell commands on stdout.  This is the default if
26             SHELL looks like it's a csh style of shell.
27
28     -d      Debug mode.  When this option is specified ssh-agent will not
29             fork.
30
31     -k      Kill the current agent (given by the SSH_AGENT_PID environment
32             variable).
33
34     -s      Generate Bourne shell commands on stdout.  This is the default if
35             SHELL does not look like it's a csh style of shell.
36
37     -t life
38             Set a default value for the maximum lifetime of identities added
39             to the agent.  The lifetime may be specified in seconds or in a
40             time format specified in sshd_config(5).  A lifetime specified
41             for an identity with ssh-add(1) overrides this value.  Without
42             this option the default maximum lifetime is forever.
43
44     If a commandline is given, this is executed as a subprocess of the agent.
45     When the command dies, so does the agent.
46
47     The agent initially does not have any private keys.  Keys are added using
48     ssh-add(1).  When executed without arguments, ssh-add(1) adds the files
49     ~/.ssh/id_rsa, ~/.ssh/id_dsa, ~/.ssh/id_ecdsa, ~/.ssh/id_ed25519 and
50     ~/.ssh/identity.  If the identity has a passphrase, ssh-add(1) asks for
51     the passphrase on the terminal if it has one or from a small X11 program
52     if running under X11.  If neither of these is the case then the
53     authentication will fail.  It then sends the identity to the agent.
54     Several identities can be stored in the agent; the agent can
55     automatically use any of these identities.  ssh-add -l displays the
56     identities currently held by the agent.
57
58     The idea is that the agent is run in the user's local PC, laptop, or
59     terminal.  Authentication data need not be stored on any other machine,
60     and authentication passphrases never go over the network.  However, the
61     connection to the agent is forwarded over SSH remote logins, and the user
62     can thus use the privileges given by the identities anywhere in the
63     network in a secure way.
64
65     There are two main ways to get an agent set up: The first is that the
66     agent starts a new subcommand into which some environment variables are
67     exported, eg ssh-agent xterm &.  The second is that the agent prints the
68     needed shell commands (either sh(1) or csh(1) syntax can be generated)
69     which can be evaluated in the calling shell, eg eval `ssh-agent -s` for
70     Bourne-type shells such as sh(1) or ksh(1) and eval `ssh-agent -c` for
71     csh(1) and derivatives.
72
73     Later ssh(1) looks at these variables and uses them to establish a
74     connection to the agent.
75
76     The agent will never send a private key over its request channel.
77     Instead, operations that require a private key will be performed by the
78     agent, and the result will be returned to the requester.  This way,
79     private keys are not exposed to clients using the agent.
80
81     A UNIX-domain socket is created and the name of this socket is stored in
82     the SSH_AUTH_SOCK environment variable.  The socket is made accessible
83     only to the current user.  This method is easily abused by root or
84     another instance of the same user.
85
86     The SSH_AGENT_PID environment variable holds the agent's process ID.
87
88     The agent exits automatically when the command given on the command line
89     terminates.
90
91FILES
92     ~/.ssh/identity
93             Contains the protocol version 1 RSA authentication identity of
94             the user.
95
96     ~/.ssh/id_dsa
97             Contains the protocol version 2 DSA authentication identity of
98             the user.
99
100     ~/.ssh/id_ecdsa
101             Contains the protocol version 2 ECDSA authentication identity of
102             the user.
103
104     ~/.ssh/id_ed25519
105             Contains the protocol version 2 ED25519 authentication identity
106             of the user.
107
108     ~/.ssh/id_rsa
109             Contains the protocol version 2 RSA authentication identity of
110             the user.
111
112     $TMPDIR/ssh-XXXXXXXXXX/agent.<ppid>
113             UNIX-domain sockets used to contain the connection to the
114             authentication agent.  These sockets should only be readable by
115             the owner.  The sockets should get automatically removed when the
116             agent exits.
117
118SEE ALSO
119     ssh(1), ssh-add(1), ssh-keygen(1), sshd(8)
120
121AUTHORS
122     OpenSSH is a derivative of the original and free ssh 1.2.12 release by
123     Tatu Ylonen.  Aaron Campbell, Bob Beck, Markus Friedl, Niels Provos, Theo
124     de Raadt and Dug Song removed many bugs, re-added newer features and
125     created OpenSSH.  Markus Friedl contributed the support for SSH protocol
126     versions 1.5 and 2.0.
127
128OpenBSD 5.5                    December 7, 2013                    OpenBSD 5.5
129