firewall & login

[Flavio A Santos]

Dear friends.
Is it possible to configure a firewall betwen a private network and the
Internet via eth0 and eth1(a Linux box using ipfwadm or ipcchains as a
firewall) in order to permit the access to the Internet requiring any
kind of login procedure to the local users? 

Thanks in advance
Flavio Santos
Brasilia-Brazil