ssh-agent [-a bind_address] [-c | -s] [-t life]  [-d]  [com-
mand [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 win-
dows or pro-
     grams are started  as  clients  to  the  ssh-agent  program.
Through use of
     environment variables the agent can be located and automati-
cally 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_ad-
dress.  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).

     -t life
             Set a default value  for  the  maximum  lifetime  of
identities added
             to the agent.  The lifetime may be specified in sec-
onds or in a
             time format specified in sshd(8).  A lifetime speci-
fied for an
             identity   with  ssh-add(1)  overrides  this  value.
Without this op-
             tion the default maximum lifetime is forever.

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

     ning  without  X).  It then sends the identity to the agent.
Several iden-
     tities can be stored in the agent; the agent  can  automati-
cally use any of
     these  identities.   ssh-add -l displays the identities cur-
rently 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.   How-
ever, 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 set up: Either the
agent starts a
     new subcommand into which some environment variables are ex-
ported, 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 con-
nection 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 per-
formed 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
     $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  read-
able by the
             owner.  The sockets should get automatically removed
when the
             agent exits.

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

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

OpenBSD     3.5                       September     25,      1999
2