Enterprise Networking Planet: Pulling The Covers Off Linux PAM

“A hidden jewel–or pain in the rear, depending on your
perspective–is Linux PAM (Pluggable Authentication Module). Linux
oldtimers remember the ancient days when PAM was simple and used
but a single configuration file. It didn’t do much, and life was
easy. The modern PAM is more complex and flexible, which can be
trying for new sysadmins. But it has a number of significant
advantages.

“Back in the Linux stone age, passwords were encrypted by the
venerable crypt and the resulting hash was kept in /etc/passwd.
/etc/passwd has to be world-readable, so anyone who could glom a
copy of it could then crack the passwords at leisure. So shadow
passwords were invented; the hashed password is kept in
/etc/shadow, which only root can read…”

Complete Story