11-01-2009, 05:17 PM
Bypass network security packet filters using web proxy
I've noticed that the web proxy can be used to bypass network security packet filters. Consider a gateway with three interfaces, one for the WAN, one for the LAN, and one for GUESTS. If GUESTS are normally not permitted to access web servers on the LAN, but are permitted to access the web proxy (to limit web access), than the GUESTS can make requests through the web proxy to access the LAN.
As a simple measure to prevent this, I've tried using URL Filtering to block hosts on the LAN by URL. But this won't cut it as anyone can register a domain name that does not match my URL filters and resolves to a host on my LAN. I've also tried to add network security packet filter rules that block the Astaro LAN IP from accessing any hosts on the LAN - but it seems that the web proxy is exempt from these rules.
What I'd really like is a way to limit the web proxy by destination IP address or IP range. I know how to do this with Squid (acl to_localnet dst <ip range>; http_access deny to_localnet), but is there a way to do this with Astaro?