.\" Adopted for Linux by Ilya Evseev at Jan 2004.
.\"
.\" Copyright (c) 2002 Brian Fundakowski Feldman
.\" All rights reserved.
.\" Copyright (c) 2002 Networks Associates Technologies, Inc.
.\" All rights reserved.
.\"
.\" Portions of this software were 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.
.\"
.\" Redistribution and use in source and binary forms, with or without
.\" modification, are permitted provided that the following conditions
.\" are met:
.\" 1. Redistributions of source code must retain the above copyright
.\"    notice, this list of conditions and the following disclaimer.
.\" 2. Redistributions in binary form must reproduce the above copyright
.\"    notice, this list of conditions and the following disclaimer in the
.\"    documentation and/or other materials provided with the distribution.
.\" 3. The name of the author may not be used to endorse or promote
.\"    products derived from this software without specific prior written
.\"    permission.
.\"
.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
.\" ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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.\" SUCH DAMAGE.
.\"
.\" $ Id: pam_alreadyloggedin.8,v 1.2 2002/03/07 16:54:40 green Exp $
.\"
.Dd January 30, 2004
.Dt PAM_ALREADYLOGGEDIN 8
.Os Linux-PAM
.ds Xr-font \f[B]
.Sh NAME
.Nm pam_alreadyloggedin
.Nd Already-logged-in PAM module
.Sh SYNOPSIS
.Op Ar service-name
.Ar module-type
.Ar control-flag
.Pa pam_alreadyloggedin
.Op Ar options
.Sh DESCRIPTION
The Already-logged-in authentication service module for PAM,
.Nm
provides functionality for only one PAM category:
authentication.
In terms of the
.Ar module-type
parameter, this is the
.Dq Li auth
feature.
It also provides null functions for other PAM categories.
.Ss Already-logged-in Authentication Module
The Already-logged-in authentication component
.Pq Fn pam_sm_authenticate ,
returns success if and only if the target user's ID is identical to a current login specified in the
.Xr utmp 5
database and verified with matching permissions on that login's respective terminal in
.Pa /dev .
If a user shows up in
.Xr w 8
output, they will generally be allowed to authenticate using this method.
.Pp
The following options may be passed to the authentication module:
.Bl -tag -width ".Cm restrict_loggedin_tty Ns = Ns Ar ttyglob*"
.It Cm debug
Enable verbose output to syslog at LOG_DEBUG level.
.It Cm no_debug
Disable verbose output to syslog even it's enabled at compile time.
.It Cm no_root
Never allow login with a target user ID of zero.
.It Cm restrict_tty Ns = Ns Ar ttyglob*
Only allow login if the terminal device currently being authenticated on matches
.Ar ttyglob* .
The
.Ar ttyglob*
argument is specified as a shell glob, and checked using the
.Xr fnmatch 3 
function. For example,
.Cm restrict_tty=/dev/tty[1-6]
allows logging from text consoles of physical terminal only.
.It Cm restrict_loggedin_tty Ns = Ns Ar ttyglob*
Disallow recognition that the user is already logged in unless the terminal device logged in upon matches
.Ar ttyglob* .
.El
.Sh EXAMPLE
Modify
.Cd auth
section of the
.Pa /etc/pam.d/login
file like following:
.Lp
.Bd -unfilled -offset indent
auth required   /lib/security/pam_securetty.so
auth sufficient /lib/security/pam_alreadyloggedin.so no_root
auth required   /lib/security/pam_stack.so service=system-auth
.Ed
.Sh BUGS
FreeBSD version expects
.Pa /dev/
prefix in
.Cm restrict_tty
value, but value of
.Cm restrict_loggedin_tty
should be without them.
Linux version expects
.Pa /dev/
in both cases.
.Sh SEE ALSO
.Xr fnmatch 3 ,
.Xr getuid 2 ,
.Xr stat 2 ,
.Xr utmp 5 ,
.Xr w 8 ,
.Xr pam.conf 5 ,
.Xr pam 8
.Sh AUTHORS
Adopted for Linux PAM by Ilya Evseev at Jan 2004.
.Lp
The original
.Nm
module and this manual page were developed for the FreeBSD Project by
NAI Labs and ThinkSec AS, 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.