pam_warn

pam_warn.so [debug] [no_warn]

debug
    Enables debug mode, which outputs more verbose information to the system log.

no_warn
    Suppresses the default warning message logged by the module. This can be useful to prevent redundant or unnecessary log entries.

The pam_warn module is a standard PAM module that logs messages to the system log (syslog). It's typically used within a PAM configuration file to record events, errors, or other information related to authentication and authorization processes.

This module doesn't inherently grant or deny access; its primary function is logging. By logging PAM events, administrators can monitor system security, troubleshoot authentication issues, and audit user access attempts. The severity and content of the logged messages can be customized using various options.

The specific behavior of pam_warn depends heavily on the context in which it is used within a PAM configuration file. Its impact is limited to logging messages; it does not directly control authentication or authorization decisions.

A common usage scenario is to include pam_warn in the 'auth' and 'account' sections of a PAM configuration file. For example, you might use it to log failed authentication attempts or account expiration warnings.

Example Configuration:
auth required pam_warn.so

This line in /etc/pam.d/login will log any authentication event for the login service.

The content of the log messages generated by pam_warn includes information about the user, the service being accessed, and the specific PAM module involved.

The default message is that a module is being called. If other modules log specific events, pam_warn can provide context.

The pam_warn module is a standard component of the Pluggable Authentication Modules (PAM) framework. PAM was developed to provide a flexible and modular approach to authentication and authorization. pam_warn has been a fundamental tool for logging events during these authentication procedures across Unix-like systems.

syslog(3), pam.conf(5), pam(8)