linux-kernel - Re: [AppArmor 39/45] AppArmor: Profile loading and manipulation, pathname matching

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Date:	Fri, 22 Jun 2007 08:20:16 -0400
From:	Stephen Smalley <sds@...ho.nsa.gov>
To:	Crispin Cowan <crispin@...ell.com>
Cc:	James Morris <jmorris@...ei.org>,
	Chris Mason <chris.mason@...cle.com>,
	Lars Marowsky-Bree <lmb@...e.de>, Pavel Machek <pavel@....cz>,
	Greg KH <greg@...ah.com>, Andreas Gruenbacher <agruen@...e.de>,
	jjohansen@...e.de, linux-kernel@...r.kernel.org,
	linux-security-module@...r.kernel.org,
	linux-fsdevel@...r.kernel.org
Subject: Re: [AppArmor 39/45] AppArmor: Profile loading and manipulation,
	pathname matching

On Thu, 2007-06-21 at 22:17 -0600, Crispin Cowan wrote:
> James Morris wrote:
> > On Thu, 21 Jun 2007, Chris Mason wrote:  
> >>> The incomplete mediation flows from the design, since the pathname-based
> >>> mediation doesn't generalize to cover all objects unlike label- or
> >>> attribute-based mediation.  And the "use the natural abstraction for
> >>> each object type" approach likewise doesn't yield any general model or
> >>> anything that you can analyze systematically for data flow.
> >>>       
> >> This feels quite a lot like a repeat of the discussion at the kernel
> >> summit.  There are valid uses for path based security, and if they don't
> >> fit your needs, please don't use them.  But, path based semantics alone
> >> are not a valid reason to shut out AA.
> >>     
> > The validity or otherwise of pathname access control is not being 
> > discussed here.
> >
> > The point is that the pathname model does not generalize, and that 
> > AppArmor's inability to provide adequate coverage of the system is a 
> > design issue arising from this.
> >   
> The above two paragraphs appear to contradict each other.
> 
> > Recall that the question asked by Lars was whether there were any 
> > outstanding technical issues relating to AppArmor.
> >
> > AppArmor does not and can not provide the level of confinement claimed by 
> > the documentation, and its policy does not reflect its actual confinement 
> > properties.  That's kind of a technical issue, right?
> >   
> So if the document said "confinement with respect to direct file access
> and POSIX.1e capabilities" and that list got extended as AA got new
> confinement features, would that address your issue?

That would certainly help, although one might quibble with the use of
the word "confinement" at all wrt AppArmor (it has a long-established
technical meaning that implies information flow control, and that goes
beyond even complete mediation - it requires global and persistent
protection of the data based on its properties, which requires stable
and unambiguous identifiers).

-- 
Stephen Smalley
National Security Agency

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