This pluggable authentication module (pam) provides single sign-on using secure shell (ssh) keys: - during authentication, the user types a ssh passphrase and is authenticated
if the passphrase successfully decrypts the user's ssh private keys;
- in session phase, a ssh-agent process is started and decrypted keys are
added, and thus the user can ssh to other hosts that accept key
authentication without typing more passwords for the entire session.