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
filename contains one line per item listed. If
the item is found, then if
PAM_SUCCESS is returned, causing the authorization
request to succeed; else if
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
or a given group
This added restriction is only meaningful when used with the
tty, rhost and
Besides this last one, all arguments should be specified; do not count on any default behavior.
No credentials are awarded by this module.
What is listed in the file and should be checked for.
Action to take if found in file, if the item is NOT found in the file, then the opposite action is requested.
File containing one item per line. The file needs to be a plain file and not world writable.
What to do if something weird happens like being unable to open the file.
Restrict the user class for which the restriction apply. Note that
item=[user|ruser|group] this does not make sense,
item=[tty|rhost|shell] it have a meaning.
Do not treat service refusals or missing list files as errors that need to be logged.
Memory buffer error.
The rule does not apply to the
Error in service module.
Classic 'ftpusers' authentication can be implemented with this entry
# # 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.