linux-kernel - Re: [PATCH v5 00/21] EVM

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Date:	Thu, 26 May 2011 15:49:07 -0400
From:	Mimi Zohar <zohar@...ux.vnet.ibm.com>
To:	Pavel Machek <pavel@....cz>
Cc:	David Safford <safford@...son.ibm.com>,
	Casey Schaufler <casey@...aufler-ca.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	linux-security-module@...r.kernel.org,
	linux-kernel@...r.kernel.org, linux-fsdevel@...r.kernel.org,
	James Morris <jmorris@...ei.org>, Greg KH <greg@...ah.com>,
	Dmitry Kasatkin <dmitry.kasatkin@...ia.com>
Subject: Re: [PATCH v5 00/21] EVM

On Thu, 2011-05-26 at 20:38 +0200, Pavel Machek wrote:
> On Thu 2011-05-26 14:11:54, David Safford wrote:
> > On Thu, 2011-05-26 at 09:34 -0700, Casey Schaufler wrote:
> > > On 5/25/2011 11:08 PM, Pavel Machek wrote:
> > > > ...
> > > > Fourthly, is it likely to find its way to the next cellphone I buy,
> > > > and will it prevent me from rooting it?
> > > 
> > > That will of course depend on the phone vendor. You are certainly
> > > going to be able to vote with your checkbook (digital wallet?) but
> > > odds are pretty good that should EVM prove effective it will be
> > > ubiquitous within the next five years on embedded devices.
> 
> Hmm. But maybe it is more effective to vote with NAKs, now? It does
> not seem to have any non-evil uses.
> 
> Phone vendors will play nasty tricks on us, but... why make it easy
> for them?
> 
> > um, not quite the right threat model...
> > 
> > Rooting is normally done through an exploit of the loader
> > or the kernel, neither of which EVM can prevent. The phones
> 
> Androids are often rooted by exploiting kernel or userspace
> security holes. G1 was rooted by shell that was left running on
> console...
> 
> > Whether or not the phone is rooted, IMA-Appraisal, EVM, and 
> > the Digital Signature Extensions help protect against remote
> > software attacks, and offline hardware attacks on individual
> > files, but not against rooting itself.
> 
> As far as I can tell, file signatures only prevent "offline hardware
> attacks"; that is  user trying to "attack" (== root) his own computer.
> 
> 								Pavel

Since when is my being able to detect and prevent unauthorized/malicious
files on my own system (eg. device - VM) from being read/executed deemed
evil?!  Are you suggesting that we're better off not knowing the
integrity or authenticity of a file?  I suggest you read Dave's
Integrity Overview whitepaper?

Becoming involved in designing when/how new EVM encrypted key(s) are
made available, determining if we need separate keyrings for EVM keys
and the keys for appraising files(IMA-appraisal signatures), or defining
the authorization mechanism required to add such keys (eg. LSM, extend
capabilities), would be welcomed.  Such discussions can take place on
either the LSM or linux-ima mailing lists.

thanks,

Mimi

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