Сервис FreeRADIUS

[gate:~] # cat /etc/radius.conf
auth server testing123 3 2

[gate:~] # cat /etc/pam.d/login
...
auth            sufficient      pam_radius.so           no_warn try_first_pass
auth            include         system             
...

root@gate:~# apt-get install libpam-radius-auth freeradius-utils

root@gate:~# cat /etc/pam_radius_auth.conf
...
server testing123 3
...

root@gate:~# cat /etc/pam.d/login
...
auth       sufficient   pam_radius_auth.so
# Standard Un*x authentication.
...