pam_tty_audit.so

The pam_tty_audit.so module in Linux is used to enable or configure session auditing for TTY (teletypewriter) sessions. This module is part of the Pluggable Authentication Modules (PAM) framework, which allows for flexible authentication and session management on Linux systems. Here’s an overview of pam_tty_audit.so and its functionality:

Purpose of pam_tty_audit.so

The main purpose of pam_tty_audit.so is to facilitate auditing of user sessions that occur on TTY devices. TTY sessions include interactions such as local console logins, serial port logins, or any virtual terminal sessions (e.g., SSH sessions if they allocate a TTY).

Functionality

1. Auditing Sessions: When pam_tty_audit.so is configured in the PAM stack, it ensures that all sessions on TTY devices are audited. This means that user actions and commands executed during these sessions are logged into the system's audit log (/var/log/audit/audit.log).

2. Integration with Audit Framework: The module works in conjunction with the Linux Audit Framework (auditd) to capture audit events related to TTY sessions. This enhances security monitoring and provides a detailed record of user activities on the system.

3. Configuration Options: pam_tty_audit.so can be configured with various options to control the auditing behavior, such as:

   • perm: Specifies the auditing permission mask.

   • dir: Specifies the directory for storing audit logs.

   • call_pam: Determines whether to call the underlying PAM stack.

Typical Use Cases

• Compliance Auditing: Helps organizations meet compliance requirements (e.g., PCI DSS, HIPAA) by ensuring all user sessions on TTY devices are audited.

• Security Monitoring: Provides visibility into user activities on local consoles, serial ports, or virtual terminals, aiding in incident detection and response.

Example Configuration

To configure pam_tty_audit.so, you typically edit the PAM configuration file associated with session management (e.g., /etc/pam.d/sshd for SSH sessions) and include or modify the line related to session auditing. Here’s an example:

session required pam_tty_audit.so enable=* dir=/var/log/audit/

• required: Specifies that the module is mandatory for session auditing.

• enable=*: Enables auditing for all TTY sessions.

• dir=/var/log/audit/: Specifies the directory where audit logs should be stored.

Security Considerations

• Ensure that pam_tty_audit.so is correctly configured and enabled in the PAM stack to capture all relevant TTY sessions.

• Regularly review audit logs (/var/log/audit/audit.log) for unauthorized activities or security incidents.

Conclusion

pam_tty_audit.so is a crucial component for enhancing security and compliance on Linux systems by auditing user sessions on TTY devices. By configuring and utilizing this module effectively, administrators can strengthen their ability to monitor and manage user activities across various session types.