Great Circle Associates Firewalls
(March 1994)
 

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Subject: Re: INN on a Firewall vs Socks proxy NNTP
From: Marcus J Ranum <mjr @ tis . com>
Date: Wed, 30 Mar 94 19:08:45 EST
To: firewalls @ greatcircle . com, howard . b . owen @ octel . com, socks @ syl . dl . nec . com

>    1: How insecure is the inn software?

	One could do worse than INN. INN is very nicely configured to
do all its work as the news owner. That's good design. The server
process is cleanly written and well-designed. The bad news is that
there are a number of shell scripts that are useful for processing
news, which means that chrooting the whole thing would be tough,
since you've got expire and all that stuff to worry about. Just
chrooting innd doesn't buy you anything if someone can get you
with a data-driven attack of some sort (like the recent '~' problem
in the control message handler)  We looked at hacking on INN enough
to make it run entirely under chroot, but that seemed like a lot
of effort.

>    2: In light of the answer to the previous question, where should
>       we run this puppy, if at all? Inside? Outside?

	We run our news on our fileserver inside, and use a simple
plug-board relay to "tunnel" all our NNTP traffic through our firewall
to the internal host that runs news. There are some advantages and
disadvantages to this approach, namely:

	+ News running on an internal machine is a lot easier to
		manage -- if disk overflows or expiry needs to be
		tweaked, there's no need to log into the firewall
		bastion host every time you need to do news stuff.

	- News running on an internal machine means that if there
		is a data-driven attack that lets someone do something,
		they have done it on the internal machine.
		This has its own pros and cons:
		Pro: At least the firewall bastion host hasn't been
			compromised! If that happened we'd really be
			in trouble!
		Con: Our internal machine is not exactly "disposable"
			and having someone do something bad to it is
			not pleasant to contemplate.
		Pro: Even if the attacker can do something to the
			internal machine, there's still a firewall
			between them and it, and hopefully that'll
			make the attack harder to exploit.

	+ News running on an internal machine means the firewall
		remains a "black box" that you don't have to spend
		much time managing.


>    3: Has anyone done this??

mjr.


Follow-Ups:
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From: pcc @ sanjose . ssds . com (Philip Cox (San Jose))
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From: Edward Chien <edward @ tss . com>
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From: pcc @ sanjose . ssds . com (Philip Cox (San Jose))
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From: Randy Bias <randyb @ kalpana . com>

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