RE: PIX -> ISA -> OWA Configuration

[Mark Tinberg <mtinberg () securepipe com>]

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On Tue, 3 May 2005, Ben Nagy wrote:

> > -----Original Message-----
> [Jason Gomes]
> [...]
> > What is the preferred placement for a OWA front-end server 
> > given these two possible network configurations and why?
> >
> > 1) [Internet] <==> [PIX Firewall] <==> [ISA Proxy] <==> [PIX 
> > Firewall] <==> [OWA] <==> [Internal Net w/Exchange Svr]
> >
> > 2) [Internet] <==> [PIX Firewall] <==> [ISA Proxy] <==> [OWA] 
> > <==> [PIX Firewall] <==> [Internal Net w/Exchange Svr]

> I always internally parse these diagrams as:
>
> [spaghetti] --> [hackable box] --> [pot of gold]
>
> In 1) there are no controls at all between the hackable box and the pot of
> gold. In 2) there is.

I ask the question, are the security controls between OWA -> Internal 
DC/Exchange really helpful?  Depending on the filtering you have available 
there may be very little benefit to having the OWA box on one of the other 
side of the PIX, as the OWA box needs to be a domain member and have legit 
access to the "pot of gold".  Without an MS-RPC proxy you're basically 
giving OWA full access to Exchange and the DC anyway, but you are making a 
lot of pomp and circumstance with a bunch of firewall rules to support it.

It'd be better (although the original poster probably can't sell this to 
his management) to drop the "requirement" for OWA in the first place.  
Find out what the users really _need_ to do, if they don't need remote 
access then it's easy, if all they really really need is mail then find 
another (better) webmail client that runs over IMAP which may be easier to 
proxy and monitor.

- -- 
Mark Tinberg <MTinberg () securepipe com>
Network Administrator, SecurePipe Inc.
Key fingerprint = FAEF 15E4 FEB3 08E8 66D5  A1A1 16EE C5E4 E523 6C67
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