4.3. Example configuration file entries

In this section, we give some examples of entries that can be present in the Linux-PAM configuration file. As a first attempt at configuring your system you could do worse than to implement these.

If a system is to be considered secure, it had better have a reasonably secure 'other entry. The following is a paranoid setting (which is not a bad place to start!):

# default; deny access
other   auth     required       pam_deny.so
other   account  required       pam_deny.so
other   password required       pam_deny.so
other   session  required       pam_deny.so

Whilst fundamentally a secure default, this is not very sympathetic to a misconfigured system. For example, such a system is vulnerable to locking everyone out should the rest of the file become badly written.

The module pam_deny (documented in a later section) is not very sophisticated. For example, it logs no information when it is invoked so unless the users of a system contact the administrator when failing to execute a service application, the administrator may go for a long while in ignorance of the fact that his system is misconfigured.

The addition of the following line before those in the above example would provide a suitable warning to the administrator.

# default; wake up! This application is not configured
other   auth     required       pam_warn.so
other   password required       pam_warn.so

Having two 'other auth' lines is an example of stacking.

On a system that uses the /etc/pam.d/ configuration, the corresponding default setup would be achieved with the following file:

# default configuration: /etc/pam.d/other
auth     required       pam_warn.so
auth     required       pam_deny.so
account  required       pam_deny.so
password required       pam_warn.so
password required       pam_deny.so
session  required       pam_deny.so

This is the only explicit example we give for an /etc/pam.d/ file. In general, it should be clear how to transpose the remaining examples to this configuration scheme.

On a less sensitive computer, one on which the system administrator wishes to remain ignorant of much of the power of Linux-PAM, the following selection of lines (in /etc/pam.d/other) is likely to mimic the historically familiar Linux setup.

# default; standard UN*X access
auth     required       pam_unix.so
account  required       pam_unix.so
password required       pam_unix.so
session  required       pam_unix.so

In general this will provide a starting place for most applications.