Dansguardian, nat, & ipfw

[Freddie Cash]

On Mon, Nov 16, 2009 at 8:51 PM, Brian <bbayorgeon at charter.net> wrote:
> Trying to configure my gateway box running FBSD 7.2 to provide content
> filtering services for some or all clients on a my network.
>
> The box is configured with natd and running IPFW.  I like this combination
> and have been using it successfully for years.  Not real interested to
> changing to squid or pf or whatever else may be known (or better documented)
> to work with dansguardian.

Dansguardian does not do any pages fetches on its own, it just scans
pages returned by a proxy server.  You cannot run Dansguardian without
some kind of web proxy server.  By default, the port will install
Squid, but it has been shown to work with TinyProxy.

> Dansguardian seems to be the preferred option for content filtering as near
> as I can tell.  There is lots of documentation out there for configuring
> dans with squid.  I can't find much of anything for IPFW / NAT
>
> So, the question is, can this be done?  I've seen one or two suggestions out
> there giving a brief description of how to use the fwd command to send
> packets to dans but unfortunately I am not smart enough to implement that
> here.

You can use IPFW to fwd packet to Dansguardian quite easily:
  ipfw add fwd 127.0.0.1:8080 tcp from $local_subnet to any 80 in recv
$local_nic
  ipfw add allow tcp from me to any 80 out xmit $public_nic
  ipfw add allow tcp from any 80 to me in recv $public_nic established

The first rule redirects all HTTP traffic from the local subnet to
Dansguardian.  Dansguardian will then pass the packets off to a local
install of Squid (uses 127.0.0.1:3128 by default).  Squid will then
connect out to the remote web server to grab the pages (the next two
rules).

You *MUST* have a web proxy server installed somewhere, that
Dansguardian will forward the requests to, and receive the responses
from.

-- 
Freddie Cash
fjwcash at gmail.com