PAM_SSH(8)						    BSD System Manager's Manual 						PAM_SSH(8)

NAME

     pam_ssh -- authentication and session management with SSH private keys

SYNOPSIS

     [service-name] module-type control-flag pam_ssh [options]

DESCRIPTION

     The SSH authentication service module for PAM provides functionality for two PAM categories: authentication and session management.  In terms
     of the module-type parameter, they are the ``auth'' and ``session'' features.

   SSH Authentication Module
     The SSH authentication component provides a function to verify the identity of a user (pam_sm_authenticate()), by prompting the user for a
     passphrase and verifying that it can decrypt the target user's SSH key using that passphrase.

     The following options may be passed to the authentication module:

     use_first_pass  If the authentication module is not the first in the stack, and a previous module obtained the user's password, that password
		     is used to authenticate the user.	If this fails, the authentication module returns failure without prompting the user for a
		     password.	This option has no effect if the authentication module is the first in the stack, or if no previous modules
		     obtained the user's password.

     try_first_pass  This option is similar to the use_first_pass option, except that if the previously obtained password fails, the user is
		     prompted for another password.

     nullok	     Normally, keys with no passphrase are ignored for authentication purposes.  If this option is set, keys with no passphrase
		     will be taken into consideration, allowing the user to log in with a blank password.

   SSH Session Management Module
     The SSH session management component provides functions to initiate (pam_sm_open_session()) and terminate (pam_sm_close_session()) sessions.
     The pam_sm_open_session() function starts an SSH agent, passing it any private keys it decrypted during the authentication phase, and sets
     the environment variables the agent specifies.  The pam_sm_close_session() function kills the previously started SSH agent by sending it a
     SIGTERM.

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

     want_agent  Start an agent even if no keys were decrypted during the authentication phase.

FILES

     $HOME/.ssh/identity  SSH1 RSA key
     $HOME/.ssh/id_rsa	  SSH2 RSA key
     $HOME/.ssh/id_dsa	  SSH2 DSA key
     $HOME/.ssh/id_ecdsa  SSH2 ECDSA key

SEE ALSO

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

AUTHORS

     The pam_ssh module was originally written by Andrew J. Korty <ajk@iu.edu>.  The current implementation was developed for the FreeBSD Project
     by ThinkSec AS and NAI Labs, the Security Research Division of Network Associates, Inc. under DARPA/SPAWAR contract N66001-01-C-8035
     (``CBOSS''), as part of the DARPA CHATS research program.	This manual page was written by Mark R V Murray <markm@FreeBSD.org>.

SECURITY CONSIDERATIONS

     The pam_ssh module implements what is fundamentally a password authentication scheme.  Care should be taken to only use this module over a
     secure session (secure TTY, encrypted session, etc.), otherwise the user's SSH passphrase could be compromised.

     Additional consideration should be given to the use of pam_ssh.  Users often assume that file permissions are sufficient to protect their SSH
     keys, and thus use weak or no passphrases.  Since the system administrator has no effective means of enforcing SSH passphrase quality, this
     has the potential to expose the system to security risks.

BSD
								 December 16, 2011							       BSD