Manual Pages: ssh-agent

## Manual Pages

    SSH-AGENT(1)               OpenBSD Reference Manual               SSH-AGENT(1)

    NAME
         ssh-agent - authentication agent

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

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

         -a bind_address
                 Bind the agent to the unix-domain socket bind_address. The de-
                 fault is /tmp/ssh-XXXXXXXX/agent._ppid_.

         -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 files
         $HOME/.ssh/id_rsa, $HOME/.ssh/id_dsa and $HOME/.ssh/identity. 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 run-
         ning without X).  It then sends the identity to the agent.  Several iden-
         tities 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 ter-
         minal.  Authentication data need not be stored on any other machine, and
         authentication passphrases never go over the network.  However, the con-
         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 net-
         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.

         The agent will never send a private key over its request channel.  In-
         stead, operations that require a private key will be performed by the
         agent, and the result will be returned to the requester.  This way, pri-
         vate keys are not exposed to clients using the agent.

         A unix-domain socket is created 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 anoth-
         er instance of the same user.

         The SSH_AGENT_PID environment variable holds the agent's process ID.

         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.

         $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.<ppid>
                 Unix-domain sockets used to contain the connection to the authen-
                 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 cre-
         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)

    OpenBSD 3.1                   September 25, 1999                             2

NAME | SYNOPSIS | DESCRIPTION | FILES | AUTHORS | SEE ALSO