Forward Proxy

Use case

We intend to use the firewall as a proxy server, like a Squid web cache.


The solution is very simple, since there is a proxy class that we can use to control the traffic on the proxy level. In this case, the clients connect to Zorp that acts as a proxy server, and allows traffic flow according to the rules, but communicates with the clients “in the proxy language”.

from Zorp.Http import *

def default_instance():
    Service(name="service_http_nontransparent_inband", # <2>
            proxy_class=HttpProxyNonTransparent, # <3>
            router=InbandRouter(forge_port=TRUE, forge_addr=TRUE) # <4>
    Rule(service='service_http_nontransparent_inband', # <1>
         dst_subnet=('', ),
         src_zone=('clients', )
  1. Creates a rule which matches only, when the traffic comes from the clients zone and targets the IP address and the port 3128, which address is the address of the client side interface of the firewall.
  2. Creates a service that works like a proxy server.
  3. It uses the predefined HttpProxyNonTransparent, because this proxy class – against the HttpProxy in the code sniplet tarnsparent proxy use case – handles the traffic as a proxy server.
  4. In this case the address of the HTTP server, that the client wants to connect to, comes from the application layer traffic and not from the network layer, so the default DirectedRouter. It routes the traffic where it was originally considered to be routed, but in this case (non-transparent service) the client targets the proxy server (here, the firewall) itself. Setting InbandRouter as router can handle the situation for both the HTTP and FTP protocol.


Now the IP address and port 3128 can be set as HTTP proxy in the internet browsers.

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