linux-kernel - Re: [GIT PULL] x86/txt for v2.6.32

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Message-ID: <20091003215653.GA4011@khazad-dum.debian.net>
Date:	Sat, 3 Oct 2009 18:56:53 -0300
From:	Henrique de Moraes Holschuh <hmh@....eng.br>
To:	Arjan van de Ven <arjan@...radead.org>
Cc:	Pavel Machek <pavel@....cz>, "Wang, Shane" <shane.wang@...el.com>,
	"H. Peter Anvin" <hpa@...or.com>,
	"Rafael J. Wysocki" <rjw@...k.pl>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Ingo Molnar <mingo@...e.hu>,
	Thomas Gleixner <tglx@...utronix.de>,
	"Cihula, Joseph" <joseph.cihula@...el.com>
Subject: Re: [GIT PULL] x86/txt for v2.6.32

On Sat, 03 Oct 2009, Arjan van de Ven wrote:
> On Sat, 3 Oct 2009 17:36:20 -0300
> Henrique de Moraes Holschuh <hmh@....eng.br> wrote:
> > On Sat, 03 Oct 2009, Pavel Machek wrote:
> > > On Sat 2009-10-03 01:02:52, Wang, Shane wrote:
> > > > > So I modify the RAM content so that BIOS does not think measured
> > > > > environment existed before suspend?
> > > > > 									Pavel
> > > > 
> > > > Hi Pavel, what do you mean on this question? 
> > > > When do you modify the RAM? before S3 sleep?
> > > 
> > > During the sleep, using something cold and second machine.
> > 
> > And it is ridiculously easy to pull off, too:
> > http://www.engadget.com/2008/02/21/cold-boot-disk-encryption-attack-is-shockingly-effective/
> > 
> > Shows the attack being used to read sensitive keys, but you can use
> > it also to *modify* system running state (it will be more difficult,
> > as you need to remove and replace the RAM while on S3 instead of S5,
> > but it should be doable by someone who knows what he is doing).
> 
> that assumes all state is in ram, and not some bit in the TPM..

Indeed, it does.

> (and as for that "we can steal the content"... that's confusing DRM
> with TXT. TXT is integrity, DRM is. well evil ;-)

Agreed :)  But TXT itself (or the BIOS, but not the kernel) needs to recheck
RAM content signatures on resume.  Does it?  If it doesn't, it is easy to
"fix" too, just drop all previous atestation before suspend/restart/shutdown
:P

-- 
  "One disk to rule them all, One disk to find them. One disk to bring
  them all and in the darkness grind them. In the Land of Redmond
  where the shadows lie." -- The Silicon Valley Tarot
  Henrique Holschuh
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