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     pam_ssh - authentication and session management with SSH private keys


     The SSH authentication service module for PAM, pam_ssh provides
     functionality for two PAM categories: authentication and session

   SSH Authentication Module
     The SSH authentication component verifies the identity of a user by
     prompting the user for a passphrase and verifying that it can decrypt at
     least one of the user’s SSH login keys using that passphrase.

     The following options may be passed to the authentication module:

     debug                   syslog(3) debugging information at LOG_DEBUG

     use_first_pass          If the authentication module is not the first in
                             the stack, and a previous module obtained the
                             user’s password, then that password is used to
                             decrypt the user’s SSH login keys.  If this
                             fails, then the authentication module returns
                             failure without prompting the user for a

     try_first_pass          Similar to the use_first_pass option, except that
                             if the previously obtained password fails to
                             decrypt any of the SSH login keys, then the user
                             is prompted for an SSH passphrase.

                             try_first_pass has no effect if pam_ssh is the
                             first module on the stack, or if no previous
                             modules obtained the user’s password.

     allow_blank_passphrase  Allow SSH keys with no passphrase.

     If neither use_first_pass nor try_first_pass is specified, pam_ssh will
     unconditionally ask for an SSH passphrase.

     In addition to the above authentication procedure, all standard SSH keys
     (identity, id_rsa, id_dsa) for which the obtained password matches will
     be decrypted.

   SSH Session Management Module
     The SSH session management component initiates sessions by starting an
     SSH agent, passing it any SSH login keys it decrypted during the
     authentication phase, and sets the environment variables accordingly.

     The SSH session management component terminates the session by killing
     the previously started SSH agent by sending it a SIGTERM.

     The following options may be passed to the session management module:

     debug           syslog(3) debugging information at LOG_DEBUG level.


     Be careful with the using the try_first_pass option when pam_ssh is the
     first authentication module because it will then leak information about
     existing users without login keys: such users will not be asked for a
     specific SSH passphrase, whereas non-existing users and existing users
     with login keys will be asked for a passphrase.


     $HOME/.ssh/id_dsa         OpenSSH DSA/RSA keys decrypted by pam_ssh.
     $HOME/.ssh/login-keys.d/  Location of (possibly symbolic links to)
                               OpenSSH DSA/RSA keys used for authentication
                               and decrypted by pam_ssh.
     /var/log/auth.log         Usual log file for syslog(3)


     ssh-agent(1), syslog(3), pam.conf(5), pam(8).


     Andrew J. Korty 〈〉 wrote pam_ssh.  Dag-Erling Smorgrav wrote
     the original OpenPAM support code.  Mark R V Murray wrote the original
     version of this manual page.  Jens Peter Secher introduced the login-key