-.\" $OpenBSD: ssh-agent.1,v 1.7 1999/10/28 08:43:10 markus Exp $
-.\"
-.\" -*- nroff -*-
-.\"
-.\" ssh-agent.1
+.\" $OpenBSD: ssh-agent.1,v 1.50 2010/01/17 21:49:09 tedu Exp $
.\"
.\" Author: Tatu Ylonen <ylo@cs.hut.fi>
-pp.\"
.\" Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
.\" All rights reserved
.\"
-.\" Created: Sat Apr 23 20:10:43 1995 ylo
+.\" As far as I am concerned, the code I have written for this software
+.\" can be used freely for any purpose. Any derived versions of this
+.\" software must be clearly marked as such, and if the derived work is
+.\" 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.
+.\"
+.\" Redistribution and use in source and binary forms, with or without
+.\" modification, are permitted provided that the following conditions
+.\" are met:
+.\" 1. Redistributions of source code must retain the above copyright
+.\" notice, this list of conditions and the following disclaimer.
+.\" 2. Redistributions in binary form must reproduce the above copyright
+.\" notice, this list of conditions and the following disclaimer in the
+.\" documentation and/or other materials provided with the distribution.
.\"
-.Dd September 25, 1999
+.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
+.\" IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
+.\" OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
+.\" IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
+.\" INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
+.\" NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+.\" DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+.\" THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+.\" (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
+.\" THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+.\"
+.Dd $Mdocdate$
.Dt SSH-AGENT 1
.Os
.Sh NAME
.Nm ssh-agent
.Nd authentication agent
.Sh SYNOPSIS
-.Nm ssh-agent
+.Nm ssh-agent
+.Op Fl c Li | Fl s
+.Op Fl d
+.Op Fl a Ar bind_address
+.Op Fl t Ar life
+.Op Ar command Op Ar arg ...
+.Nm ssh-agent
.Op Fl c Li | Fl s
-.Op Fl k
-.Oo
-.Ar command
-.Op Ar args ...
-.Oc
-.Sh DESCRIPTION
+.Fl k
+.Sh DESCRIPTION
.Nm
-is a program to hold authentication private keys. The
-idea is that
+is a program to hold private keys used for public key authentication
+(RSA, DSA).
+The idea is that
.Nm
is started in the beginning of an X-session or a login session, and
all other windows or programs are started as clients to the ssh-agent
-program. Through use of environment variables the agent can be located
-and automatically used for RSA authentication when logging in to other
+program.
+Through use of environment variables the agent can be located
+and automatically used for authentication when logging in to other
machines using
.Xr ssh 1 .
.Pp
The options are as follows:
.Bl -tag -width Ds
+.It Fl a Ar bind_address
+Bind the agent to the
+.Ux Ns -domain
+socket
+.Ar bind_address .
+The default is
+.Pa /tmp/ssh-XXXXXXXXXX/agent.\*(Ltppid\*(Gt .
.It Fl c
Generate C-shell commands on
.Dv stdout .
This is the default if
.Ev SHELL
looks like it's a csh style of shell.
+.It Fl d
+Debug mode.
+When this option is specified
+.Nm
+will not fork.
+.It Fl k
+Kill the current agent (given by the
+.Ev SSH_AGENT_PID
+environment variable).
.It Fl s
Generate Bourne shell commands on
.Dv stdout .
This is the default if
.Ev SHELL
does not look like it's a csh style of shell.
-.It Fl k
-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_config 5 .
+A lifetime specified for an identity with
+.Xr ssh-add 1
+overrides this value.
+Without this option the default maximum lifetime is forever.
.El
.Pp
If a commandline is given, this is executed as a subprocess of the agent.
When the command dies, so does the agent.
.Pp
-The agent initially does not have any private keys. Keys are added
-using
+The agent initially does not have any private keys.
+Keys are added using
.Xr ssh-add 1 .
-When executed without arguments,
+When executed without arguments,
.Xr ssh-add 1
-adds the
-.Pa $HOME/.ssh/identity
-file. If the identity has a passphrase,
+adds the files
+.Pa ~/.ssh/id_rsa ,
+.Pa ~/.ssh/id_dsa
+and
+.Pa ~/.ssh/identity .
+If the identity has a passphrase,
.Xr ssh-add 1
-asks for the passphrase (using a small X11 application if running
-under X11, or from the terminal if running without X). It then sends
-the identity to the agent. Several identities can be stored in the
+asks for the passphrase on the terminal if it has one or from a small X11
+program if running under X11.
+If neither of these is the case then the authentication will fail.
+It then sends the identity to the agent.
+Several identities can be stored in the
agent; the agent can automatically use any of these identities.
.Ic ssh-add -l
displays the identities currently held by the agent.
.Pp
The idea is that the agent is run in the user's local PC, laptop, or
-terminal. Authentication data need not be stored on any other
+terminal.
+Authentication data need not be stored on any other
machine, and authentication passphrases never go over the network.
However, the connection to the agent is forwarded over SSH
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 evaluated 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
+A
+.Ux Ns -domain
+socket is created and the name of this socket is stored in the
.Ev SSH_AUTH_SOCK
environment
-variable. The socket is made accessible only to the current user.
+variable.
+The socket is made accessible only to the current user.
This method is easily abused by root or another instance of the same
user.
.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.
-.It Pa /tmp/ssh-XXXX/agent.<pid> ,
-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.
-.Sh AUTHOR
-Tatu Ylonen <ylo@cs.hut.fi>
-.Pp
-OpenSSH
-is a derivative of the original (free) ssh 1.2.12 release, but with bugs
-removed and newer features re-added. Rapidly after the 1.2.12 release,
-newer versions bore successively more restrictive licenses. This version
-of OpenSSH
-.Bl -bullet
-.It
-has all components of a restrictive nature (ie. patents, see
-.Xr ssl 8 )
-directly removed from the source code; any licensed or patented components
-are chosen from
-external libraries.
-.It
-has been updated to support ssh protocol 1.5.
-.It
-contains added support for
-.Xr kerberos 8
-authentication and ticket passing.
-.It
-supports one-time password authentication with
-.Xr skey 1 .
+.It Pa ~/.ssh/identity
+Contains the protocol version 1 RSA authentication identity of the user.
+.It Pa ~/.ssh/id_dsa
+Contains the protocol version 2 DSA authentication identity of the user.
+.It Pa ~/.ssh/id_rsa
+Contains the protocol version 2 RSA authentication identity of the user.
+.It Pa /tmp/ssh-XXXXXXXXXX/agent.\*(Ltppid\*(Gt
+.Ux Ns -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
-.Pp
-The libraries described in
-.Xr ssl 8
-are required for proper operation.
.Sh SEE ALSO
.Xr ssh 1 ,
.Xr ssh-add 1 ,
.Xr ssh-keygen 1 ,
-.Xr sshd 8 ,
-.Xr ssl 8
+.Xr sshd 8
+.Sh AUTHORS
+OpenSSH is a derivative of the original and free
+ssh 1.2.12 release by Tatu Ylonen.
+Aaron Campbell, Bob Beck, Markus Friedl, Niels Provos,
+Theo de Raadt and Dug Song
+removed many bugs, re-added newer features and
+created OpenSSH.
+Markus Friedl contributed the support for SSH
+protocol versions 1.5 and 2.0.
andersk / openssh.git / blobdiff