Misconfigured PAM
TLDR: Misconfigured PAM (Pluggable Authentication Module), introduced in the 1990s, can result in unauthorized access, weakened authentication mechanisms, and disrupted user management processes. Issues such as improperly ordered rules, insecure module configurations, or neglected auditing policies compromise the security and functionality of systems relying on PAM for authentication and authorization.
https://en.wikipedia.org/wiki/Pluggable_authentication_module
One common issue with PAM misconfiguration is the improper ordering of rules within its configuration files. PAM processes rules sequentially, and an incorrectly ordered rule can unintentionally bypass security policies. For example, placing a permissive rule before a restrictive one can allow unauthorized users to authenticate. Another frequent problem is misconfigured modules, such as weak password policies in `pam_pwquality` or improperly secured `pam_unix`, which can expose systems to brute force or privilege escalation attacks.
https://man7.org/linux/man-pages/man8/pam.8.html
To address these challenges, administrators should thoroughly review and organize PAM configuration files to ensure rules are logically ordered and enforce strict security policies. Modules like `pam_tally2` or `pam_faillock` should be configured to limit failed login attempts, while password complexity and expiration settings should be enforced using `pam_pwquality`. Regular audits of PAM logs and configurations ensure compliance with security best practices and help identify potential vulnerabilities.