-.\" $OpenBSD: ssh-agent.1,v 1.20 2001/01/28 10:24:04 markus Exp $
+.\" $OpenBSD: ssh-agent.1,v 1.41 2004/07/11 17:48:47 deraadt Exp $
.\"
.\" Author: Tatu Ylonen <ylo@cs.hut.fi>
.\" Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
.\" incompatible with the protocol description in the RFC file, it must be
.\" called by a name other than "ssh" or "Secure Shell".
.\"
-.\" Copyright (c) 1999,2000 Markus Friedl. All rights reserved.
-.\" Copyright (c) 1999 Aaron Campbell. All rights reserved.
-.\" Copyright (c) 1999 Theo de Raadt. All rights reserved.
+.\" Copyright (c) 1999,2000 Markus Friedl. All rights reserved.
+.\" Copyright (c) 1999 Aaron Campbell. All rights reserved.
+.\" Copyright (c) 1999 Theo de Raadt. All rights reserved.
.\"
.\" Redistribution and use in source and binary forms, with or without
.\" modification, are permitted provided that the following conditions
.Nd authentication agent
.Sh SYNOPSIS
.Nm ssh-agent
-.Ar command
-.Ar args ...
-.Nm ssh-agent
+.Op Fl a Ar bind_address
.Op Fl c Li | Fl s
+.Op Fl t Ar life
+.Op Fl d
+.Op Ar command Op Ar args ...
.Nm ssh-agent
+.Op Fl c Li | Fl s
.Fl k
.Sh DESCRIPTION
.Nm
.Pp
The options are as follows:
.Bl -tag -width Ds
+.It Fl a Ar bind_address
+Bind the agent to the unix-domain socket
+.Ar bind_address .
+The default is
+.Pa /tmp/ssh-XXXXXXXX/agent.<ppid> .
.It Fl c
Generate C-shell commands on
.Dv stdout .
Kill the current agent (given by the
.Ev SSH_AGENT_PID
environment variable).
+.It Fl t Ar life
+Set a default value for the maximum lifetime of identities added to the agent.
+The lifetime may be specified in seconds or in a time format specified in
+.Xr sshd 8 .
+A lifetime specified for an identity with
+.Xr ssh-add 1
+overrides this value.
+Without this option the default maximum lifetime is forever.
+.It Fl d
+Debug mode.
+When this option is specified
+.Nm
+will not fork.
.El
.Pp
If a commandline is given, this is executed as a subprocess of the agent.
.Xr ssh-add 1 .
When executed without arguments,
.Xr ssh-add 1
-adds the
-.Pa $HOME/.ssh/identity
-file.
+adds the files
+.Pa $HOME/.ssh/id_rsa ,
+.Pa $HOME/.ssh/id_dsa
+and
+.Pa $HOME/.ssh/identity .
If the identity has a passphrase,
.Xr ssh-add 1
asks for the passphrase (using a small X11 application if running
remote logins, and the user can thus use the privileges given by the
identities anywhere in the network in a secure way.
.Pp
-There are two main ways to get an agent setup:
-Either you let the agent
-start a new subcommand into which some environment variables are exported, or
-you let the agent print the needed shell commands (either
+There are two main ways to get an agent set up:
+The first is that the agent starts a new subcommand into which some environment
+variables are exported, eg
+.Cm ssh-agent xterm & .
+The second is that the agent prints the needed shell commands (either
+.Xr sh 1
+or
+.Xr csh 1
+syntax can be generated) which can be evalled in the calling shell, eg
+.Cm eval `ssh-agent -s`
+for Bourne-type shells such as
.Xr sh 1
or
+.Xr ksh 1
+and
+.Cm eval `ssh-agent -c`
+for
.Xr csh 1
-syntax can be generated) which can be evalled in the calling shell.
+and derivatives.
+.Pp
Later
.Xr ssh 1
-look at these variables and use them to establish a connection to the agent.
+looks at these variables and uses them to establish a connection to the agent.
+.Pp
+The agent will never send a private key over its request channel.
+Instead, operations that require a private key will be performed
+by the agent, and the result will be returned to the requester.
+This way, private keys are not exposed to clients using the agent.
.Pp
A unix-domain socket is created
-.Pq Pa /tmp/ssh-XXXXXXXX/agent.<pid> ,
and the name of this socket is stored in the
.Ev SSH_AUTH_SOCK
environment
.Pp
The
.Ev SSH_AGENT_PID
-environment variable holds the agent's PID.
+environment variable holds the agent's process ID.
.Pp
The agent exits automatically when the command given on the command
line terminates.
.Sh FILES
.Bl -tag -width Ds
.It Pa $HOME/.ssh/identity
-Contains the RSA authentication identity of the user.
-This file should not be readable by anyone but the user.
-It is possible to
-specify a passphrase when generating the key; that passphrase will be
-used to encrypt the private part of this file.
-This file is not used by
-.Nm
-but is normally added to the agent using
-.Xr ssh-add 1
-at login time.
+Contains the protocol version 1 RSA authentication identity of the user.
.It Pa $HOME/.ssh/id_dsa
-Contains the DSA authentication identity of the user.
-.It Pa /tmp/ssh-XXXXXXXX/agent.<pid>
+Contains the protocol version 2 DSA authentication identity of the user.
+.It Pa $HOME/.ssh/id_rsa
+Contains the protocol version 2 RSA authentication identity of the user.
+.It Pa /tmp/ssh-XXXXXXXX/agent.<ppid>
Unix-domain sockets used to contain the connection to the
authentication agent.
These sockets should only be readable by the owner.
The sockets should get automatically removed when the agent exits.
.El
+.Sh SEE ALSO
+.Xr ssh 1 ,
+.Xr ssh-add 1 ,
+.Xr ssh-keygen 1 ,
+.Xr sshd 8
.Sh AUTHORS
OpenSSH is a derivative of the original and free
ssh 1.2.12 release by Tatu Ylonen.
created OpenSSH.
Markus Friedl contributed the support for SSH
protocol versions 1.5 and 2.0.
-.Sh SEE ALSO
-.Xr ssh 1 ,
-.Xr ssh-add 1 ,
-.Xr ssh-keygen 1 ,
-.Xr sshd 8 ,
-.Xr ssl 8
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