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Date:      Fri, 23 Sep 2005 15:59:13 -0700
From:      Eli Dart <dart@es.net>
To:        freebsd-security@freebsd.org
Subject:   Re: mounting filesystems with "noexec"
Message-ID:  <433488C1.5030906@es.net>
In-Reply-To: <43347BC3.7000308@ucsb.edu>
References:  <F02FC593-8F19-40D4-B1E7-63B78F1E5300@sarenet.es>	<43332CD7.4070107@romab.com>	<726F1E71-D4D9-4C34-848D-868C1158834E@sarenet.es>	<43345736.3090602@gugol.ru>	<20050923215556.GB72838@logik.internal.network> <43347BC3.7000308@ucsb.edu>

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randall s. ehren wrote:
>> With all that has been said so far, what is the actual point of
>> the noexec flag? 
> 
> 
> it prevents executables from being executed on a specific partition.
> 
> for instance, you can mount /var with the noexec flag and if you then
> try to run any binaries (executables) from /var they simply will not
> execute.

Note that while there may be many ways to circumvent noexec in many
circumstances, it still raises the bar.  If attempts to execute on a
filesystem mounted noexec can be logged (and the logs are sent off-box)
you have a chance of seeing something.  Also, if the execution is part
of an automated tool, noexec can cause the tool to fail.

It may not be perfect, but I don't consider it useless.

		--eli
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