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Date:      Tue, 27 Jul 1999 11:18:02 -0600
From:      Nate Williams <nate@mt.sri.com>
To:        Matthew Dillon <dillon@apollo.backplane.com>
Cc:        "Brian F. Feldman" <green@FreeBSD.ORG>, Joe Greco <jgreco@ns.sol.net>, hackers@FreeBSD.ORG, freebsd-ipfw@FreeBSD.ORG
Subject:   Re: securelevel and ipfw zero
Message-ID:  <199907271718.LAA25910@mt.sri.com>
In-Reply-To: <199907270348.UAA49943@apollo.backplane.com>
References:  <Pine.BSF.4.10.9907262322120.35843-100000@janus.syracuse.net> <199907270348.UAA49943@apollo.backplane.com>

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>     ipfw allows you to clear counters.  It is a feature that already exists.
> 
>     However, it does not allow you to do it if you are sitting at secure
>     level 3.
> 
>     Why not?  I can't think of any good reason why clearing the counters 
>     should be disallowed when sitting at a higher secure level.  The counters
>     are nothing more then statistics.  Clearing statistics is not a security
>     threat.

I just thought of a bad thing.  If you allowed the counters to be zero'd
(or advanced) at securelevel == 3, then a 'malicious user' could write a
cronjob to continually reset them and cause a DoS attack on the system
(or in the case of advance, reset them to ridiculously high values),
thus filling up the disk.

However, one could argue that *IF* they have root, they could just as
easily fill the disk with garbage and cause the same attack, ie;

# dd if=/dev/zero of=/var/log/misc

>     The discussion should simply be about that.  Not all this garbage
>     about adding new features.  There's a feature that does not seem
>     to impact security, secure level disallows it, why?

I'm not convinced there aren't other security implications from zero'ing
(or advancing) the counters.


Nate


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