Subject: Re: [AppArmor 39/45] AppArmor: Profile loading and manipulation,
	pathname matching
From: Stephen Smalley <sds@tycho.nsa.gov>
To: Karl MacMillan <kmacmill@redhat.com>
Cc: Greg KH <greg@kroah.com>, Casey Schaufler <casey@schaufler-ca.com>,
       Crispin Cowan <crispin@novell.com>,
       Andreas Gruenbacher <agruen@suse.de>, Pavel Machek <pavel@ucw.cz>,
       jjohansen@suse.de, linux-kernel@vger.kernel.org,
       linux-security-module@vger.kernel.org, linux-fsdevel@vger.kernel.org
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Content-Type: text/plain
Organization: National Security Agency
Date: Mon, 18 Jun 2007 09:33:05 -0400
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On Fri, 2007-06-15 at 18:24 -0400, Karl MacMillan wrote:
> On Fri, 2007-06-15 at 14:44 -0700, Greg KH wrote:
> > On Fri, Jun 15, 2007 at 05:28:35PM -0400, Karl MacMillan wrote:
> > > On Fri, 2007-06-15 at 14:14 -0700, Greg KH wrote:
> > > > On Fri, Jun 15, 2007 at 01:43:31PM -0700, Casey Schaufler wrote:
> > > > > 
> > > > > Yup, I see that once you accept the notion that it is OK for a
> > > > > file to be misslabeled for a bit and that having a fixxerupperd
> > > > > is sufficient it all falls out.
> > > > > 
> > > > > My point is that there is a segment of the security community
> > > > > that had not found this acceptable, even under the conditions
> > > > > outlined. If it meets your needs, I say run with it.
> > > > 
> > > > If that segment feels that way, then I imagine AA would not meet their
> > > > requirements today due to file handles and other ways of passing around
> > > > open files, right?
> > > > 
> > > > So, would SELinux today (without this AA-like daemon) fit the
> > > > requirements of this segment?
> > > > 
> > > 
> > > Yes - RHEL 5 is going through CC evaluations for LSPP, CAPP, and RBAC
> > > using the features of SELinux where appropriate.
> > 
> > Great, but is there the requirement in the CC stuff such that this type
> > of "delayed re-label" that an AA-like daemon would need to do cause that
> > model to not be able to be certified like your SELinux implementation
> > is?
> > 
> 
> There are two things:
> 
> 1) relabeling (non-tranquility) is very problematic in general because
> revocation is hard (and non-solved in Linux). So you would have to
> address concerns about that.

I think we need to distinguish between relying on restorecond-like
mechanisms for the security of SELinux vs. relying on them for emulating
pathname-based security.  The former would be a problem.  The latter is
no worse than pathname-based security already, because pathname-based
security is inherently ambiguous and non-tranquil, and revocation isn't
addressed fully in AA either.

> 
> 2) Whether this would pass certification depends on a lot of factors
> (like the specific requirements - CC is just a process not a single set
> of requirements). I don't know enough to really guess.
> 
> More to the point, though, the requirements in those documents are
> outdated at best. I don't think it is worth worrying over.
> 
> > As I'm guessing the default "label" for things like this already work
> > properly for SELinux, I figure we should be safe, but I don't know those
> > requirements at all.
> > 
> 
> Probably not - you would likely want it to be a label that can't be read
> or written by anything, only relabeled by the daemon.
> 
> Karl
> 
-- 
Stephen Smalley
National Security Agency

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