.\" -*- nroff -*- .\" .\" ssh-agent.1 .\" .\" Author: Tatu Ylonen .\" .\" Copyright (c) 1995 Tatu Ylonen , Espoo, Finland .\" All rights reserved .\" .\" Created: Sat Apr 23 20:10:43 1995 ylo .\" .\" $Id: ssh-agent.1,v 1.5 1999/10/16 20:47:14 markus Exp $ .\" .Dd September 25, 1999 .Dt SSH-AGENT 1 .Os .Sh NAME .Nm ssh-agent .Nd authentication agent .Sh SYNOPSIS .Nm ssh-agent .Ar command .Sh DESCRIPTION .Nm is a program to hold authentication private keys. 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 children of the ssh-agent program (the .Ar command normally starts X or is the user shell). Programs started under the agent inherit a connection to the agent, and the agent is automatically used for RSA authentication when logging to other machines using .Xr ssh 1 . .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 A connection to the agent is inherited by child programs: A unix-domain socket is created .Pq Pa /tmp/ssh-XXXX/agent. , 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 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. , 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 .Pp This version of .Nm is a derivative of the original 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. In this version, all components of a restrictive nature (ie. patents) have been directly removed from the source code; any licensed or patented components are chosen from external libraries. 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