linux-kernel - Re: Defense in depth: LSM *modules*, not a static interface

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Date:	Tue, 6 Nov 2007 20:34:45 -0800 (PST)
From:	Casey Schaufler <casey@...aufler-ca.com>
To:	Tetsuo Handa <penguin-kernel@...ove.sakura.ne.jp>,
	casey@...aufler-ca.com
Cc:	crispin@...spincowan.com, simon@...e.lp0.eu,
	linux-kernel@...r.kernel.org,
	linux-security-module@...r.kernel.org, cliffe@...net,
	oiaohm@...il.com
Subject: Re: Defense in depth: LSM *modules*, not a static interface


--- Tetsuo Handa <penguin-kernel@...ove.sakura.ne.jp> wrote:

> Hello.
> 
> Casey Schaufler wrote:
> > Fine grained capabilities are a bonus, and there are lots of
> > people who think that it would be really nifty if there were a
> > separate capability for each "if" in the kernel. I personally
> > don't see need for more than about 20. That is a matter of taste.
> > DG/UX ended up with 330 and I say that's too many.
> 
> TOMOYO Linux has own (non-POSIX) capability that can support 65536
> capabilities
> if there *were* a separate capability for each "if" in the kernel.
>
http://svn.sourceforge.jp/cgi-bin/viewcvs.cgi/trunk/2.1.x/tomoyo-lsm/patches/tomoyo-capability.diff?root=tomoyo&view=markup
> 
> The reason I don't use POSIX capability is that the maximum types are limited
> to
> bitwidth of a variable (i.e. currently 32, or are we going to extend it to
> 64).
> This leads to abuse of CAP_SYS_ADMIN capability.

That is a matter of taste. 

> In other words, it makes fine-grained privilege division impossible.

I personally believe that a finer granularity than about 20
is too fine. I understand that this is a minority opinion.


Casey Schaufler
casey@...aufler-ca.com
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