PAM module for password strength policy enforcement

 passwdqc is a password/passphrase strength checking and policy
 enforcement toolset, including a PAM module (libpam-passwdqc),
 command-line programs (pwqcheck and pwqgen), and a library (libpasswdqc0).
 .
 pam_passwdqc (optionally) integrates with PAM such that it gets invoked
 when users change their passwords. The module is capable of checking
 password or passphrase strength, enforcing a policy, and offering
 randomly-generated passphrases, with all of these features being
 optional and easily (re-)configurable.