path: root/modules/pam_listfile/pam_listfile.8

'\" t
.\"     Title: pam_listfile
.\"    Author: [see the "AUTHOR" section]
.\" Generator: DocBook XSL Stylesheets v1.79.1 <http://docbook.sf.net/>
.\"      Date: 06/08/2020
.\"    Manual: Linux-PAM Manual
.\"    Source: Linux-PAM Manual
.\"  Language: English
.\"
.TH "PAM_LISTFILE" "8" "06/08/2020" "Linux-PAM Manual" "Linux\-PAM Manual"
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.ie \n(.g .ds Aq \(aq
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.SH "NAME"
pam_listfile \- deny or allow services based on an arbitrary file
.SH "SYNOPSIS"
.HP \w'\fBpam_listfile\&.so\fR\ 'u
\fBpam_listfile\&.so\fR item=[tty|user|rhost|ruser|group|shell] sense=[allow|deny] file=\fI/path/filename\fR onerr=[succeed|fail] [apply=[\fIuser\fR|\fI@group\fR]] [quiet]
.SH "DESCRIPTION"
.PP
pam_listfile is a PAM module which provides a way to deny or allow services based on an arbitrary file\&.
.PP
The module gets the
\fBitem\fR
of the type specified \-\-
\fIuser\fR
specifies the username,
\fIPAM_USER\fR; tty specifies the name of the terminal over which the request has been made,
\fIPAM_TTY\fR; rhost specifies the name of the remote host (if any) from which the request was made,
\fIPAM_RHOST\fR; and ruser specifies the name of the remote user (if available) who made the request,
\fIPAM_RUSER\fR
\-\- and looks for an instance of that item in the
\fBfile=\fR\fB\fIfilename\fR\fR\&.
filename
contains one line per item listed\&. If the item is found, then if
\fBsense=\fR\fB\fIallow\fR\fR,
\fIPAM_SUCCESS\fR
is returned, causing the authorization request to succeed; else if
\fBsense=\fR\fB\fIdeny\fR\fR,
\fIPAM_AUTH_ERR\fR
is returned, causing the authorization request to fail\&.
.PP
If an error is encountered (for instance, if
filename
does not exist, or a poorly\-constructed argument is encountered), then if
\fIonerr=succeed\fR,
\fIPAM_SUCCESS\fR
is returned, otherwise if
\fIonerr=fail\fR,
\fIPAM_AUTH_ERR\fR
or
\fIPAM_SERVICE_ERR\fR
(as appropriate) will be returned\&.
.PP
An additional argument,
\fBapply=\fR, can be used to restrict the application of the above to a specific user (\fBapply=\fR\fB\fIusername\fR\fR) or a given group (\fBapply=\fR\fB\fI@groupname\fR\fR)\&. This added restriction is only meaningful when used with the
\fItty\fR,
\fIrhost\fR
and
\fIshell\fR
items\&.
.PP
Besides this last one, all arguments should be specified; do not count on any default behavior\&.
.PP
No credentials are awarded by this module\&.
.SH "OPTIONS"
.PP
.PP
\fBitem=[tty|user|rhost|ruser|group|shell]\fR
.RS 4
What is listed in the file and should be checked for\&.
.RE
.PP
\fBsense=[allow|deny]\fR
.RS 4
Action to take if found in file, if the item is NOT found in the file, then the opposite action is requested\&.
.RE
.PP
\fBfile=\fR\fB\fI/path/filename\fR\fR
.RS 4
File containing one item per line\&. The file needs to be a plain file and not world writable\&.
.RE
.PP
\fBonerr=[succeed|fail]\fR
.RS 4
What to do if something weird happens like being unable to open the file\&.
.RE
.PP
\fBapply=[\fR\fB\fIuser\fR\fR\fB|\fR\fB\fI@group\fR\fR\fB]\fR
.RS 4
Restrict the user class for which the restriction apply\&. Note that with
\fBitem=[user|ruser|group]\fR
this does not make sense, but for
\fBitem=[tty|rhost|shell]\fR
it have a meaning\&.
.RE
.PP
\fBquiet\fR
.RS 4
Do not treat service refusals or missing list files as errors that need to be logged\&.
.RE
.SH "MODULE TYPES PROVIDED"
.PP
All module types (\fBauth\fR,
\fBaccount\fR,
\fBpassword\fR
and
\fBsession\fR) are provided\&.
.SH "RETURN VALUES"
.PP
.PP
PAM_AUTH_ERR
.RS 4
Authentication failure\&.
.RE
.PP
PAM_BUF_ERR
.RS 4
Memory buffer error\&.
.RE
.PP
PAM_IGNORE
.RS 4
The rule does not apply to the
\fBapply\fR
option\&.
.RE
.PP
PAM_SERVICE_ERR
.RS 4
Error in service module\&.
.RE
.PP
PAM_SUCCESS
.RS 4
Success\&.
.RE
.SH "EXAMPLES"
.PP
Classic \*(Aqftpusers\*(Aq authentication can be implemented with this entry in
/etc/pam\&.d/ftpd:
.sp
.if n \{\
.RS 4
.\}
.nf
#
# deny ftp\-access to users listed in the /etc/ftpusers file
#
auth    required       pam_listfile\&.so \e
        onerr=succeed item=user sense=deny file=/etc/ftpusers
      
.fi
.if n \{\
.RE
.\}
.sp
Note, users listed in
/etc/ftpusers
file are (counterintuitively)
\fInot\fR
allowed access to the ftp service\&.
.PP
To allow login access only for certain users, you can use a
/etc/pam\&.d/login
entry like this:
.sp
.if n \{\
.RS 4
.\}
.nf
#
# permit login to users listed in /etc/loginusers
#
auth    required       pam_listfile\&.so \e
        onerr=fail item=user sense=allow file=/etc/loginusers
      
.fi
.if n \{\
.RE
.\}
.sp
For this example to work, all users who are allowed to use the login service should be listed in the file
/etc/loginusers\&. Unless you are explicitly trying to lock out root, make sure that when you do this, you leave a way for root to log in, either by listing root in
/etc/loginusers, or by listing a user who is able to
\fIsu\fR
to the root account\&.
.SH "SEE ALSO"
.PP
\fBpam.conf\fR(5),
\fBpam.d\fR(5),
\fBpam\fR(8)
.SH "AUTHOR"
.PP
pam_listfile was written by Michael K\&. Johnson <johnsonm@redhat\&.com> and Elliot Lee <sopwith@cuc\&.edu>\&.