NAME    [Toc]    [Back]

     ssh-agent - authentication agent

SYNOPSIS    [Toc]    [Back]

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

DESCRIPTION    [Toc]    [Back]

     ssh-agent  is a program to hold private keys used for public
key authentication
 (RSA, DSA).  The idea is that ssh-agent 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
ssh(1).

     The options are as follows:

     -a bind_address
             Bind   the   agent   to   the   unix-domain   socket
bind_address.  The default
 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).

     -t 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 sshd(8).  A lifetime specified for an
             identity   with  ssh-add(1)  overrides  this  value.
Without this option
 the default maximum lifetime is forever.

     -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 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.   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 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.

     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  ssh-agent  xterm  &.   The second is that 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,  eg  eval
`ssh-agent -s` for
     Bourne-type  shells  such  as  sh(1)  or  ksh(1)  and   eval
`ssh-agent -c` for
     csh(1) and derivatives.

     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.  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.

     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 another
 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    [Toc]    [Back]

     $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 authentication
 agent.  These sockets should only be  readable by the
             owner.  The sockets should get automatically removed
when the
             agent exits.

SEE ALSO    [Toc]    [Back]

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

AUTHORS    [Toc]    [Back]

     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.

OpenBSD     3.6                       September     25,      1999