Internet sharing authentication

[Gareth Bailey]

Greetings,

I have set up a FreeBSD gateway/firewall with ipf and ipnat in the
past, but I am now confronted with a new challenge. I need to setup
the firewall to only allow internet (www) access to users who
successfully authenticate themselves with a username/password
combination.

Ideally, a user will open their web browser and be confronted with a
authentication popup before gaining access to browse the web. Users
should be able to access mail without authentication.

Please advise on what I might use to do this.

Thanks,
Gareth