ssh-agent.0   [plain text]


SSH-AGENT(1)            System General Commands Manual            SSH-AGENT(1)

NAME
     ssh-agent - authentication agent

SYNOPSIS
     ssh-agent [-c | -s] [-d] [command [args ...]]
     ssh-agent [-c | -s] -k

DESCRIPTION
     ssh-agent is a program to hold private keys used for public key authentiM--
     cation (RSA, DSA).  The idea is that ssh-agent is started in the beginM--
     ning of an X-session or a login session, and all other windows or proM--
     grams 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 ssh(1).

     The options are as follows:

     -c      Generate C-shell commands on stdout.  This is the default if
             SHELL looks like it's a csh style of shell.

     -s      Generate Bourne shell commands on stdout.  This is the default if
             SHELL does not look like it's a csh style of shell.

     -k      Kill the current agent (given by the SSH_AGENT_PID environment
             variable).

     -d      Debug mode.  When this option is specified ssh-agent will not
             fork.

     If a commandline is given, this is executed as a subprocess of the agent.
     When the command dies, so does the agent.

     The agent initially does not have any private keys.  Keys are added using
     ssh-add(1).  When executed without arguments, ssh-add(1) adds the
     $HOME/.ssh/identity file.  If the identity has a passphrase, 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 idenM--
     tity to the agent.  Several identities can be stored in the agent; the
     agent can automatically use any of these identities.  ssh-add -l displays
     the identities currently held by the agent.

     The idea is that the agent is run in the user's local PC, laptop, or terM--
     minal.  Authentication data need not be stored on any other machine, and
     authentication passphrases never go over the network.  However, the conM--
     nection to the agent is forwarded over SSH remote logins, and the user
     can thus use the privileges given by the identities anywhere in the netM--
     work in a secure way.

     There are two main ways to get an agent setup: Either the agent starts a
     new subcommand into which some environment variables are exported, or the
     agent prints the needed shell commands (either sh(1) or csh(1) syntax can
     be generated) which can be evalled in the calling shell.  Later ssh(1)
     looks at these variables and uses them to establish a connection to the
     agent.

     A unix-domain socket is created (/tmp/ssh-XXXXXXXX/agent.<pid>), and the
     name of this socket is stored in the 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.

     The SSH_AGENT_PID environment variable holds the agent's PID.

     The agent exits automatically when the command given on the command line
     terminates.

FILES
     $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 ssh-agent but is normally
             added to the agent using ssh-add(1) at login time.

     $HOME/.ssh/id_dsa
             Contains the protocol version 2 DSA authentication identity of
             the user.

     $HOME/.ssh/id_rsa
             Contains the protocol version 2 RSA authentication identity of
             the user.

     /tmp/ssh-XXXXXXXX/agent.<pid>
             Unix-domain sockets used to contain the connection to the authenM--
             tication agent.  These sockets should only be readable by the
             owner.  The sockets should get automatically removed when the
             agent exits.

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 creM--
     ated OpenSSH.  Markus Friedl contributed the support for SSH protocol
     versions 1.5 and 2.0.

SEE ALSO
     ssh(1), ssh-add(1), ssh-keygen(1), sshd(8)

BSD                           September 25, 1999                           BSD