Previous Next Contents

6.13 The Password-Database module

Synopsis

Module Name:

pam_pwdb

Author:

Cristian Gafton <gafton@sorosis.ro>
and Andrew G. Morgan <morgan@parc.power.net>

Maintainer:

Authors.

Management groups provided:

account; authentication; password; session

Cryptographically sensitive:

Security rating:

Clean code base:

System dependencies:

Requires properly configured libpwdb

Network aware:

Overview of module

This module is a pluggable replacement for the pam_unix_.. modules. It uses the generic interface of the Password Database library http://parc.power.net/morgan/libpwdb/index.html.

Account component

Recognized arguments:

debug

Description:

The debug argument makes the accounting functions of this module syslog(3) more information on its actions. (Remaining arguments supported by the other functions of this module are silently ignored, but others are logged as errors through syslog(3)).

Based on the following pwdb_elements: expire; last_change; max_change; defer_change; warn_change, this module performs the task of establishing the status of the user's account and password. In the case of the latter, it may offer advice to the user on changing their password or, through the PAM_AUTHTOKEN_REQD return, delay giving service to the user until they have established a new password. The entries listed above are documented in the Password Database Library Guide (see pointer above). Should the user's record not contain one or more of these entries, the corresponding shadow check is not performed.

Examples/suggested usage:

In its accounting mode, this module can be inserted as follows:

#
# Ensure users account and password are still active
#
login   account  required       pam_pwdb.so

Authentication component

Recognized arguments:

debug; use_first_pass; try_first_pass; nullok

Description:

The debug argument makes the authentication functions of this module syslog(3) more information on its actions.

The default action of this module is to not permit the user access to a service if their official password is blank. The nullok argument overrides this default.

When given the argument try_first_pass, before prompting the user for their password, the module first tries the previous stacked auth-module's password in case that satisfies this module as well. The argument use_first_pass forces the module to use such a recalled password and will never prompt the user - if no password is available or the password is not appropriate, the user will be denied access.

Remaining arguments, supported by the other functions of this module, are silently ignored. Other arguments are logged as errors through syslog(3).

A helper binary, pwdb_chkpwd, is provided to check the user's password when it is stored in a read protected database. This binary is very simple and will only check the password of the user invoking it. It is called transparently on behalf of the user by the authenticating component of this module. In this way it is possible for applications like xlock to work without being setuid-root.

Examples/suggested usage:

The correct functionality of this module is dictated by having an appropriate /etc/pwdb.conf file, the user databases specified there dictate the source of the authenticated user's record.

Password component

Recognized arguments:

debug; nullok; not_set_pass; use_authtok; try_first_pass; use_first_pass; md5; shadow; radius

Description:

This part of the pam_pwdb module performs the task of updating the user's password. Thanks to the flexibility of libpwdb this module is able to move the user's password from one database to another, perhaps securing the user's database entry in a dynamic manner (this is very ALPHA code at the moment!) - this is the purpose of the shadow and radius arguments.

In the case of conventional unix databases (which store the password encrypted) the md5 argument is used to do the encryption with the MD5 function as opposed to the conventional crypt(3) call.

The nullok module is used to permit the changing of a password from an empty one. Without this argument, empty passwords are treated as account-locking ones.

The argument use_first_pass is used to lock the choice of old and new passwords to that dictated by the previously stacked password module. The try_first_pass argument is used to avoid the user having to re-enter an old password when pam_pwdb follows a module that possibly shared the user's old password - if this old password is not correct the user will be prompted for the correct one. The argument use_authtok is used to force this module to set the new password to the one provided by the previously stacked password module (this is used in an example of the stacking of the Cracklib module documented above).

The not_set_pass argument is used to inform the module that it is not to pay attention to/make available the old or new passwords from/to other (stacked) password modules.

The debug argument makes the password functions of this module syslog(3) more information on its actions. Other arguments may be logged as erroneous to syslog(3).

Examples/suggested usage:

An example of the stacking of this module with respect to the pluggable password checking module, pam_cracklib, is given in that modules section above.

Session component

Recognized arguments:

Description:

No arguments are recognized by this module component. Its action is simply to log the username and the service-type to syslog(3). Messages are logged at the beginning and end of the user's session.

Examples/suggested usage:

The use of the session modules is straightforward:

#
# pwdb - unix like session opening and closing
#
login   session  required       pam_pwdb.so


Previous Next Contents