linux-kernel - Re: [PATCH v12 0/9] LSM: Multiple concurrent LSMs

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Date:	Thu, 10 Jan 2013 00:42:53 +1100 (EST)
From:	James Morris <jmorris@...ei.org>
To:	Casey Schaufler <casey@...aufler-ca.com>
cc:	Stephen Rothwell <sfr@...b.auug.org.au>,
	LSM <linux-security-module@...r.kernel.org>,
	LKLM <linux-kernel@...r.kernel.org>,
	SE Linux <selinux@...ho.nsa.gov>,
	John Johansen <john.johansen@...onical.com>,
	Eric Paris <eparis@...hat.com>,
	Tetsuo Handa <penguin-kernel@...ove.sakura.ne.jp>,
	Kees Cook <keescook@...omium.org>,
	Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [PATCH v12 0/9] LSM: Multiple concurrent LSMs

On Tue, 8 Jan 2013, Casey Schaufler wrote:

> What I was hoping to say, and apparently didn't, is that people
> are developing "total" solutions in user space, when some of the
> work ought to be done in an LSM. Work that is appropriate to the
> kernel is being done in user space. Often badly, because the
> kernel provides too many mechanisms to circumvent user space
> based access controls.

People do stupid things all the time.  How is this particular case our 
problem to fix?  Do you have any concrete examples?

> And before we get too far, distros are no longer the driving force
> for Linux development. I suggest that "operating systems", including
> ChromiumOS, Android and Tizen are every bit as important. 

Indeed.  I was including these projects as "distros".

> > What is the UID issue and how does LSM stacking address it?
> 
> Android utilizes UIDs in a way that has often been referred to as
> "hijacking". The UID mechanism supports much of what they want,
> but clearly isn't complete. Now that Android is moving to multi-user
> support they're hitting conflicts with their use of the UID 
> attribute. They really ought to be using an LSM that implements
> the security policy they want rather than hacking around the
> behavior of UID based controls.

Right, so they implement an LSM to do what they need.  What does this have 
to do with stacking?

> > Also, are you saying that security mechanisms are inherently easier to 
> > configure if they're composed from a variety of distinct modules vs. a 
> > monolithic scheme? 
> 
> Nope. I'm saying that for specific use cases including but not limited to
> telephones, TVs and surveillance networks it is simpler and more appropriate
> to create the access control and security schemes that directly address
> the needs than to attempt to squeeze them into corsets designed in the
> 1990's.

That may be true, but we do need at least one significant user to step up 
with concrete plans for deployment.


-- 
James Morris
<jmorris@...ei.org>
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