.\" Copyright (c) 2001 Mark R V Murray
.\" Copyright (c) 2001-2003 Networks Associates Technology, Inc.
.\" Copyright (c) 2004-2011 Dag-Erling Smørgrav
.\" All rights reserved.
.\"
.\" This software 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.
.\"
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.Dd October 7, 2011
.Dt PAM_SSH 8
.Os
.Sh NAME
.Nm pam_ssh
.Nd authentication and session management with SSH private keys
.Sh SYNOPSIS
.Op Ar service-name
.Ar module-type
.Ar control-flag
.Pa pam_ssh
.Op Ar options
.Sh DESCRIPTION
The
SSH
authentication service module for PAM,
.Nm
provides functionality for two PAM categories:
authentication
and session management.
In terms of the
.Ar module-type
parameter, they are the
.Dq Li auth
and
.Dq Li session
features.
.Ss SSH Authentication Module
The
SSH
authentication component
provides a function to verify the identity of a user
.Pq Fn 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.
.Pp
The following options may be passed to the authentication module:
.Bl -tag -width ".Cm use_first_pass"
.It Cm 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.
.It Cm try_first_pass
This option is similar to the
.Cm use_first_pass
option,
except that if the previously obtained password fails,
the user is prompted for another password.
.It Cm 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.
.El
.Ss SSH Session Management Module
The
SSH
session management component
provides functions to initiate
.Pq Fn pam_sm_open_session
and terminate
.Pq Fn pam_sm_close_session
sessions.
The
.Fn 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
.Fn pam_sm_close_session
function kills the previously started SSH agent
by sending it a
.Dv SIGTERM .
.Pp
The following options may be passed to the session management module:
.Bl -tag -width ".Cm want_agent"
.It Cm want_agent
Start an agent even if no keys were decrypted during the
authentication phase.
.El
.Sh FILES
.Bl -tag -width ".Pa $HOME/.ssh/id_ed25519" -compact
.It Pa $HOME/.ssh/id_rsa
SSH2 RSA key
.It Pa $HOME/.ssh/id_dsa
SSH2 DSA key
.It Pa $HOME/.ssh/id_ecdsa
SSH2 ECDSA key
.It Pa $HOME/.ssh/id_ed25519
SSH2 Ed25519 key
.El
.Sh SEE ALSO
.Xr ssh-agent 1 ,
.Xr pam.conf 5 ,
.Xr pam 3
.Sh AUTHORS
The
.Nm
module was originally written by
.An -nosplit
.An Andrew J. Korty Aq Mt ajk@iu.edu .
The current implementation was developed for the
.Fx
Project by
ThinkSec AS and NAI Labs, the Security Research Division of Network
Associates, Inc.\& under DARPA/SPAWAR contract N66001-01-C-8035
.Pq Dq CBOSS ,
as part of the DARPA CHATS research program.
This manual page was written by
.An Mark R V Murray Aq Mt markm@FreeBSD.org .