NAME
pam_listfile - deny or allow services based on an arbitrary file
SYNOPSIS
pam_listfile.so item=[tty|user|rhost|ruser|group|shell]
sense=[allow|deny] file=/path/filename
onerr=[succeed|fail] [apply=[user|@group]] [quiet]
DESCRIPTION
pam_listfile is a PAM module which provides a way to deny or allow
services based on an arbitrary file.
The module gets the item of the type specified -- user specifies the
username, PAM_USER; tty specifies the name of the terminal over which
the request has been made, PAM_TTY; rhost specifies the name of the
remote host (if any) from which the request was made, PAM_RHOST; and
ruser specifies the name of the remote user (if available) who made the
request, PAM_RUSER -- and looks for an instance of that item in the
file=filename. filename contains one line per item listed. If the item
is found, then if sense=allow, PAM_SUCCESS is returned, causing the
authorization request to succeed; else if sense=deny, PAM_AUTH_ERR is
returned, causing the authorization request to fail.
If an error is encountered (for instance, if filename does not exist,
or a poorly-constructed argument is encountered), then if
onerr=succeed, PAM_SUCCESS is returned, otherwise if onerr=fail,
PAM_AUTH_ERR or PAM_SERVICE_ERR (as appropriate) will be returned.
An additional argument, apply=, can be used to restrict the application
of the above to a specific user (apply=username) or a given group
(apply=@groupname). This added restriction is only meaningful when used
with the tty, rhost and shell items.
Besides this last one, all arguments should be specified; do not count
on any default behavior.
No credentials are awarded by this module.
OPTIONS
item=[tty|user|rhost|ruser|group|shell]
What is listed in the file and should be checked for.
sense=[allow|deny]
Action to take if found in file, if the item is NOT found in the
file, then the opposite action is requested.
file=/path/filename
File containing one item per line. The file needs to be a plain
file and not world writable.
onerr=[succeed|fail]
What to do if something weird happens like being unable to open the
file.
apply=[user|@group]
Restrict the user class for which the restriction apply. Note that
with item=[user|ruser|group] this does not make sense, but for
item=[tty|rhost|shell] it have a meaning.
quiet
Do not treat service refusals or missing list files as errors that
need to be logged.
MODULE TYPES PROVIDED
All module types (auth, account, password and session) are provided.
RETURN VALUES
PAM_AUTH_ERR
Authentication failure.
PAM_BUF_ERR
Memory buffer error.
PAM_IGNORE
The rule does not apply to the apply option.
PAM_SERVICE_ERR
Error in service module.
PAM_SUCCESS
Success.
EXAMPLES
Classic 'ftpusers' authentication can be implemented with this entry in
/etc/pam.d/ftpd:
#
# deny ftp-access to users listed in the /etc/ftpusers file
#
auth required pam_listfile.so \
onerr=succeed item=user sense=deny file=/etc/ftpusers
Note, users listed in /etc/ftpusers file are (counterintuitively) not
allowed access to the ftp service.
To allow login access only for certain users, you can use a
/etc/pam.d/login entry like this:
#
# permit login to users listed in /etc/loginusers
#
auth required pam_listfile.so \
onerr=fail item=user sense=allow file=/etc/loginusers
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 su to the root
account.
SEE ALSO
pam.conf(5), pam.d(5), pam(7)
AUTHOR
pam_listfile was written by Michael K. Johnson <johnsonm@redhat.com>
and Elliot Lee <sopwith@cuc.edu>.