Great Circle Associates Firewalls
(January 1996)
 

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Subject: RE: NT Firewalls
From: "Russ . Cooper @ RC . Toronto . on . ca" <Russ . Cooper @ RC . Toronto . on . ca>
Date: Wed, 24 Jan 1996 06:09:32 -0500
To: "'A. Padgett Peterson, P.E. Information Security'" <PADGETT @ hobbes . orl . mmc . com>
Cc: "'Firewalls'" <firewalls @ GreatCircle . COM>

Padgett,

As I have stated numerous times, I have not seen an implementation of a 
Firewall under Windows NT myself as yet.

However, if, as you state,

"Thusfar what I have seen uses NT to load the firewall program after which 
the OS is politely
but quitely shunted to one side and all critical operations are performed 
with direct hardware access (why only certain specified peripherals/NICs 
are supported).

Now if Raptor (or anyone I trust) were to say "we make all hardware calls 
through the NT operating system which is left in control of the machine 
while the firewall is running" then I would feel less skeptical."

Firewall-1, for example, does implement code at the driver level in order 
to get around certain code that Microsoft has included in NT for their own 
protocols (probably SMS functionality), which could not be redirected at 
anything other than the driver level. This does not mean the OS is being 
shunted to one side, but merely that packets are being picked up at an e  
arlier point to allow their redirection, if necessary, based on the rules 
in place. For a lot of reasons, that I won't get into here, you cannot 
simply "shunt the OS to one side" in NT if you still want to do things like 
interact with a user via a UI. Unlike DOS, or even Windows, NT's components 
are all tied together in the Kernel and cannot be run independently by a 
driver.

There are known issues with Microsoft's TCP/IP stack that would force 
anyone trying to do anything substantial with IP on NT to do certain things 
to avoid some of the pitfalls present in their stack. WebSite, from 
O'Reilly and Associates, found a timing issue with the stack and had to 
write a workaround of their own to ensure the performance of the Webserver. 
As we all know, Microsoft's commitment to the Internet is evolving, rather 
more quickly now than before, but having to start life from the perspective 
"our strategic protocol of choice is IPX", means that Internet-related 
Microsoft Product Manager's are pulling their hair out.

So implementing hardware drivers, or even their own TCP/IP stack, does not 
detract from their use of NT in my opinion. To me, the bigger question is 
how they interact with the Security Reference Monitor, which is used by all 
applications running on NT to determine whether or not they can interact 
with any other aspect of NT based on rights granted to the 
user/service/thread. I'm more concerned that if improperly implemented, an 
application could simply step around the security rules and go directly to 
the HAL or another driver itself.

It really is too bad that no Raptor or Firewall-1 representative is willing 
to speak out on this topic. I'm sure that some might think it marketing to 
talk about their product, but if done at a technical level, I believe the 
list would be interested. Correct me if I'm wrong list!

Cheers,
Russ Cooper, Senior Consultant - Internet
SHL/Computer Innovations - Consulting Services
Russ .
 Cooper @
 RC .
 Toronto .
 On .
 Ca - RWCooper @
 SHL .
 Com
"can someone tell me where to go today to get the money to go to where I 
want to go today"



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