linux-kernel - Re: LSM conversion to static interface

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Message-ID: <471DBB75.9020605@debian.org>
Date:	Tue, 23 Oct 2007 11:14:29 +0200
From:	"Giacomo A. Catenazzi" <cate@...ian.org>
To:	Jan Engelhardt <jengelh@...putergmbh.de>
CC:	Linus Torvalds <torvalds@...ux-foundation.org>,
	Andreas Gruenbacher <agruen@...e.de>,
	Thomas Fricaccia <thomas_fricacci@...oo.com>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	James Morris <jmorris@...ei.org>
Subject: Re: LSM conversion to static interface

Jan Engelhardt wrote:
> On Oct 23 2007 07:44, Giacomo Catenazzi wrote:
>>> I do have a pseudo LSM called "multiadm" at 
>>> http://freshmeat.net/p/multiadm/ , quoting:
>>> Policy is dead simple since it is based on UIDs. The UID ranges can be 
>>> set on module load time or during runtime (sysfs params). This LSM is 
>>> basically grants extra rights unlike most other LSMs[1], which is why 
>>> modprobe makes much more sense here. (It also does not have to do any 
>>> security labelling that would require it to be loaded at boot time 
>>> already.)
>> But his is against LSM design (and first agreements about LSM):
>> LSM can deny rights, but it should not give extra permissions
>> or bypass standard unix permissions.
> 
> It is just not feasible to add ACLs to all million files in /home,
> also because ACLs are limited to around 25 entries.
> And it is obvious I do not want <prof> to have UID 0, because
> then you cannot distinguish who created what file.
> So the requirement to the task is to have unique UIDs.
> The next logical step would be to give capabilities to those UIDs.
> 
> *Is that wrong*? Who says that only UID 0 is allowed to have
> all 31 capability bits turned on, and that all non-UID 0 users
> need to have all 31 capability bits turned off?
> 
> So, we give caps to the subadmins (which is IMHO a natural task),
> and then, as per LSM design (wonder where that is written) deny
> some of the rights that the capabilities raised for subadmins grant,
> because that is obviously too much.

Nothing wrong.  I only said that it was against (IIRC) the
principle of LSM in kernel (we should only remove capacities).
I've nothing against the changing the design or rules.
It was only a commentary, to be sure that we know what we do ;-)

ciao
	cate
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