linux-kernel - Re: [PATCH 3/4] security: capabilities patch (version 0.4.4), part 3/4: introduce new capabilities

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Date:	Tue, 19 Sep 2006 00:09:43 -0400
From:	Joshua Brindle <method@...too.org>
To:	casey@...aufler-ca.com
CC:	David Madore <david.madore@....fr>,
	Linux Kernel mailing-list <linux-kernel@...r.kernel.org>,
	LSM mailing-list <linux-security-module@...r.kernel.org>
Subject: Re: [PATCH 3/4] security: capabilities patch (version 0.4.4), part
 3/4: introduce new capabilities

Casey Schaufler wrote:
> --- Joshua Brindle <method@...too.org> wrote:
>   
>>> The first system I took through evaluation
>>> (that is, independent 3rd party analysis) stored
>>> security attributes in a file while the second
>>> and third systems attached the attributes
>>> directly (XFS). The 1st evaluation required
>>> 5 years, the 2nd 1 year. It is possible that
>>> I just got a lot smarter with age, but I
>>> ascribe a significant amount of the improvement
>>> to the direct association of the attributes
>>> to the file.
>>>       
>> Thats great but entirely irrelevant in this context.
>> The patch and caps 
>> in question are not attached to the file via some
>> externally observable 
>> property (eg., xattr) but instead are embedded in
>> the source code so 
>> that it can drop caps at certain points during the
>> execution or before 
>> executing another app, thus unanalyzable.
>>     
>
> Oh that. Sure, we used capability bracketing
> in the code, too. That makes it easy to
> determine when a capability is active. What,
> you don't think that it's possible to analyze
> source code? Of course it is. Refer to the
> evaluation reports if you don't believe me.
>
>   
When I see an analysis of every line of source code on an average Linux 
machine then I might believe you (if you'll grant that no software can 
ever be installed on it afterward without being analyzed) but until then 
I'll stick with a centralized policy. I doubt many others will be 
satisfied with that limitation.

Bracketing hardly makes it analyzable, how can you possibly know if the 
bracketing happened? You *believe* it will and therefore you say that 
the bracketed code is safe but in reality this is a discretionary 
mechanism and you have zero assurance that there is any security 
whatsoever, no thanks, I'll pass.
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