linux-kernel - Re: [RFC][PATCH 0a/3] TXT: Intel(R) Trusted Execution Technologysupport for Linux

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Date:	Thu, 9 Oct 2008 20:45:52 +0200
From:	Pavel Machek <pavel@...e.cz>
To:	"Cihula, Joseph" <joseph.cihula@...el.com>
Cc:	Chris Wright <chrisw@...s-sol.org>, linux-kernel@...r.kernel.org,
	"Wang, Shane" <shane.wang@...el.com>,
	"Wei, Gang" <gang.wei@...el.com>,
	"Van De Ven, Arjan" <arjan.van.de.ven@...el.com>,
	"Mallick, Asit K" <asit.k.mallick@...el.com>,
	"Nakajima, Jun" <jun.nakajima@...el.com>,
	Chris Wright <chrisw@...hat.com>,
	Jan Beulich <jbeulich@...ell.com>, mingo@...e.hu, tytso@....edu
Subject: Re: [RFC][PATCH 0a/3] TXT: Intel(R) Trusted Execution
	Technologysupport for Linux - Overview


> > > > You exit/reenter the trusted mode accross sleep... so any
> guarantees
> > > > "trusted" mode does are void, right?
> > >
> > > You exit from kernel to tboot on any shutdown, which handles the
> proper
> > > teardown of the measured env (meaning you also come back on via
> tboot).
> > > So things like saving tpm state, scrubbing secrets from memory, etc.
> > 
> > Aha, so instead sleep mode is useless because I'll have to remount all
> > the crypto filesystems and restart all the apps...
> 
> Sleep mode works the same as it does today (caveat S4 issue which we
> will fix), it just goes through the tboot code before putting the
> platform HW into the appropriate state.  What this process is adding is
> that on resume, tboot will get control from BIOS instead of the kernel.
> Then tboot will re-launch the TXT environment before going back to the
> kernel at the kernel's expected S3 resume vector.  The re-establishing
> of the protected environment won't disrupt the subsequent kernel resume
> process.

No, I don't get it. So presumably useful thing to do is to seal my
crypto partition so that only known-good kernel can access it?

But then, the crypto keys will be in ram during suspend/resume
(because I have the filesystem mounted) => I loose any guarantees?

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