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Date: Sun, 1 Sep 2013 17:46:37 +0100
From: Matthew Garrett <mjg59@srcf.ucam.org>
To: Florian Weimer <fw@deneb.enyo.de>
Cc: joeyli <jlee@suse.com>, linux-kernel@vger.kernel.org,
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Subject: Re: [RFC PATCH 00/18 v3] Signature verification of hibernate
 snapshot
Message-ID: <20130901164637.GA2409@srcf.ucam.org>
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On Sun, Sep 01, 2013 at 06:40:41PM +0200, Florian Weimer wrote:
> * Matthew Garrett:
> 
> > On Sun, Sep 01, 2013 at 12:41:22PM +0200, Florian Weimer wrote:
> >
> >> But if you don't generate fresh keys on every boot, the persistent
> >> keys are mor exposed to other UEFI applications.  Correct me if I'm
> >> wrong, but I don't think UEFI variables are segregated between
> >> different UEFI applications, so if anyone gets a generic UEFI variable
> >> dumper (or setter) signed by the trusted key, this cryptographic
> >> validation of hibernate snapshots is bypassable.
> >
> > If anyone can execute arbitrary code in your UEFI environment then 
> > you've already lost.
> 
> This is not about arbitrary code execution.  The problematic
> applications which conflict with this proposed functionality are not
> necessarily malicious by themselves and even potentially useful.
 
A signed application that permits the modification of arbitrary boot 
services variables *is* malicious. No implementation is designed to be 
safe in that scenario. Why bother with modifying encryption keys when 
you can just modify MOK instead?

-- 
Matthew Garrett | mjg59@srcf.ucam.org
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