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

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Message-ID: <20090929171318.GC14405@elf.ucw.cz>
Date:	Tue, 29 Sep 2009 19:13:18 +0200
From:	Pavel Machek <pavel@....cz>
To:	Shane Wang <shane.wang@...el.com>
Cc:	"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 Tue 2009-09-29 14:34:09, Shane Wang wrote:
> Pavel Machek wrote:
>> On Mon 2009-09-28 14:11:25, H. Peter Anvin wrote:
>>> On 09/28/2009 02:07 PM, Rafael J. Wysocki wrote:
>>>>> Well, I worry that S3 support for TXT makes TXT completely useless. A
>>>>> little liquid nitrogen, remove RAM, place it in another machine,
>>>>> modify it in any way you want, more liquid nitrogen, place it back.
>>>>>
>>>>> Oops, protection provided by TXT is lost.
>>>> Ah, I see your point now.
>>>>
>>> Shane Wang sent me a patch for S3 support, but it missed the merge window:
>>>
>>> 	http://marc.info/?i=4A9CE0B2.5060608@intel.com
>>>
>>> *As far as I understand* -- and I haven't looked into it in detail yet,
>>> having just come back from Plumber's -- this provides integrity
>>> protection, not content extraction protection.

Well, documentation seems to suggest it provides content protection,
too. If not, should that be clearly documented in Doc*/intel_txt?
[Also, I'd expect threat model aka "what does it protect against there"].

>> How does it provide integrity protection? I'm free to modify RAM
>> content in the other machine....

>
> Before S3 sleep, tboot patch will MAC the memory, and after S3 resume, 
> the memory integrity will be verified according to the MAC value. So, you 
> can't modify RAM, or else you will fail on S3 resume.
>
> The current patch hpa mentioned is for userspace memory integrity. For 
> kernel memory integrity, the code is already in with the previous txt 
> patch.

Ok, and what prevents me from commenting out the MAC checking code?

									Pavel
-- 
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html
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