Web Filtering and Directory Server installation and setup

I need a linux server expert. I need to setup a 20 user office with USER AUTHENTICATION (LDAP server, I was thinking of using Zentyal ) and web filtering (this needs to be done per user level) Preferably I would like an open source linux solution. I need to block all web access except few websites (whitelist) for 10 users, Other remaining users need to have FULL internet access with maybe some sites blocked (blacklist), ALL users also need to be authenticated when they login to the system, and have access to FILE SERVER with user folders. thanks