pam_listfile -- deny or allow services based on an arbitrary file
     __________________________________________________________________

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 (if any)
   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 the item is found in the 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 has a meaning.

   quiet
          Do not treat service refusals or missing list files as errors
          that need to be logged.

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.

AUTHOR

   pam_listfile was written by Michael K. Johnson <johnsonm@redhat.com>
   and Elliot Lee <sopwith@cuc.edu>.
