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Date:   Wed, 9 Jan 2019 23:19:28 +0100
From:   Pavel Machek <pavel@....cz>
To:     James Bottomley <James.Bottomley@...senPartnership.com>
Cc:     Andy Lutomirski <luto@...nel.org>,
        Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com>,
        Stephan Mueller <smueller@...onox.de>,
        Herbert Xu <herbert@...dor.apana.org.au>,
        "Lee, Chun-Yi" <joeyli.kernel@...il.com>,
        "Rafael J . Wysocki" <rjw@...ysocki.net>,
        LKML <linux-kernel@...r.kernel.org>, linux-pm@...r.kernel.org,
        keyrings@...r.kernel.org,
        "Rafael J. Wysocki" <rafael.j.wysocki@...el.com>,
        Chen Yu <yu.c.chen@...el.com>,
        Oliver Neukum <oneukum@...e.com>,
        Ryan Chen <yu.chen.surf@...il.com>,
        David Howells <dhowells@...hat.com>,
        Giovanni Gherdovich <ggherdovich@...e.cz>,
        Randy Dunlap <rdunlap@...radead.org>,
        Jann Horn <jannh@...gle.com>
Subject: Re: [PATCH 1/5 v2] PM / hibernate: Create snapshot keys handler

Hi!

> > > Note if someone has your laptop and the ability to boot their own
> > > kernels, they could always corrupt the kernel into decrypting the
> > > image or giving you the unsealed key, but there's no real way of
> > > preventing that even with PCR sealing or lockdown, so the basis for
> > > the threat model is very much my laptop in my possession running my
> > > kernel.
> > 
> > I'm not entirely sure I agree.  With a TPM-aware bootloader, it
> > really ought to be possible to seal to PCRs such that a corrupted
> > kernel can't restore the image.  Obviously a *compromised* but
> > otherwise valid kernel will be able to restore the image.
> 
> It is possible to seal the key so that only the same booted kernel can
> restore the image, yes.  One of the measurements that goes into the
> boot log is the hash of the kernel and you can seal to this value ...
> obviously if you upgrade your kernel RPM (or shim or grub) this value
> changes and you'd lose the ability to restore the hibernated image, but
> since the image is very kernel specific, that's probably OK.

Non-ancient kernels actually support hibernation by one kernel and
restore by another one.

But yes, normally it is same kernel binary doing hibernation and
restore.

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

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