Creating a proxy server with web based login
 

I am not sure if I am in the right place but I will post here anyway. I am needing to create a proxy server, that has user specific rights,I am wanting it so you can login through a web interface in order to gain internet access but I want certain IP's/MAC addresses to not have access all the time without having to login. , this is actually for my school, and we don't exactly have lots of money to spend on boxes that do this. Does anyone know of any open source tools that will do what I am trying to do here, or if there is a Distro that does all this already?