linux-kernel - Re: A basic question about the security

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Message-Id: <201001032112.17975.paul.moore@hp.com>
Date:	Sun, 3 Jan 2010 21:12:17 -0500
From:	Paul Moore <paul.moore@...com>
To:	"Eric W. Biederman" <ebiederm@...ssion.com>
Cc:	Casey Schaufler <casey@...aufler-ca.com>,
	Michael Stone <michael@...top.org>,
	linux-kernel@...r.kernel.org,
	linux-security-module@...r.kernel.org,
	Andi Kleen <andi@...stfloor.org>, David Lang <david@...g.hm>,
	Oliver Hartkopp <socketcan@...tkopp.net>,
	Alan Cox <alan@...rguk.ukuu.org.uk>,
	Herbert Xu <herbert@...dor.apana.org.au>,
	Valdis Kletnieks <Valdis.Kletnieks@...edu>,
	Bryan Donlan <bdonlan@...il.com>,
	Evgeniy Polyakov <zbr@...emap.net>,
	"C. Scott Ananian" <cscott@...ott.net>,
	James Morris <jmorris@...ei.org>,
	Bernie Innocenti <bernie@...ewiz.org>,
	Mark Seaborn <mrs@...hic-beasts.com>,
	Randy Dunlap <randy.dunlap@...cle.com>,
	Américo Wang <xiyou.wangcong@...il.com>
Subject: Re: A basic question about the security_* hooks

On Thursday 24 December 2009 07:53:35 am Eric W. Biederman wrote:
> Casey Schaufler <casey@...aufler-ca.com> writes:
> > I'm behind you 100%. Use the LSM. Your module is exactly why we have
> > the blessed thing. Once we get a collection of otherwise unrelated
> > LSMs the need for a stacker will be sufficiently evident that we'll
> > be able to get one done properly.
> 
> My immediate impression is that the big limitation today is the
> sharing of the void * security data members of strucutres.
> 
> Otherwise multiple security modules could be as simple as.
> list_for_each(mod)
>         if (mod->op(...) != 0)
> 		return -EPERM.
> 
> It isn't hard to multiplex a single data field into several with a
> nice little abstraction.

Just another quick point that I didn't see covered yet in this thread ... 
while many of the kernel entities have void pointers to track the security 
blobs, there are several places where a single u32/int or character string is 
used to represent the security label of an entity (look at the per-packet 
labeling for an example).  While it would be relatively easy to multiple 
multiple security blobs on top of a void pointer, multiplexing multiple 
security labels/tokens on top of a string/int is a little more difficult.

-- 
paul moore
linux @ hp
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