| .\" $OpenBSD: ssh-agent.1,v 1.25 2001/06/26 04:07:06 markus Exp $ |
| .\" |
| .\" Author: Tatu Ylonen <ylo@cs.hut.fi> |
| .\" Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland |
| .\" All rights reserved |
| .\" |
| .\" 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. |
| .\" |
| .\" 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 September 25, 1999 |
| .Dt SSH-AGENT 1 |
| .Os |
| .Sh NAME |
| .Nm ssh-agent |
| .Nd authentication agent |
| .Sh SYNOPSIS |
| .Nm ssh-agent |
| .Ar command |
| .Ar args ... |
| .Nm ssh-agent |
| .Op Fl c Li | Fl s |
| .Nm ssh-agent |
| .Fl k |
| .Nm ssh-agent |
| .Fl d |
| .Sh DESCRIPTION |
| .Nm |
| 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 authentication when logging in to other |
| machines using |
| .Xr ssh 1 . |
| .Pp |
| The options are as follows: |
| .Bl -tag -width Ds |
| .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 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 d |
| Debug mode. When this option is specified |
| .Nm |
| will fork. |
| .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 |
| .Xr ssh-add 1 . |
| When executed without arguments, |
| .Xr ssh-add 1 |
| adds the |
| .Pa $HOME/.ssh/identity |
| file. |
| 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 |
| 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 |
| 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 |
| .Xr sh 1 |
| or |
| .Xr csh 1 |
| syntax can be generated) which can be evalled in the calling shell. |
| Later |
| .Xr ssh 1 |
| looks at these variables and uses them to establish a connection to 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 |
| 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. |
| .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 protocol version 1 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 $HOME/.ssh/id_dsa |
| 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.<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. |
| .El |
| .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. |
| .Sh SEE ALSO |
| .Xr ssh 1 , |
| .Xr ssh-add 1 , |
| .Xr ssh-keygen 1 , |
| .Xr sshd 8 |