PAM (Pluggable Authentication Modules)
The library that login, su, sudo, sshd and passwd hand user checks to: a stack of modules from /etc/pam.d decides whether to let the user in, which new password to accept and what to do at login.
The library that login, su, sudo, sshd and passwd hand user checks to: a stack of modules from /etc/pam.d decides whether to let the user in, which new password to accept and what to do at login.