pam_listfile - deny or allow services based on an arbitrary file

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

Linux-PAM                                          07/03/2025                                    PAM_LISTFILE(8)

       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.

       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.

       All module types (auth, account, password and session) are provided.

       pam_listfile - deny or allow services based on an arbitrary file

       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.

       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.

pam.conf(5), pam.d(5), pam(7)

pam_listfile.so item=[tty|user|rhost|ruser|group|shell] sense=[allow|deny] file=/path/filename
                       onerr=[succeed|fail] [apply=[user|@group]] [quiet]