linux-kernel - Re: [RFC V4 PATCH 00/15] Signature verification of hibernate snapshot

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Message-ID: <20130926002730.GA26857@amd.pavel.ucw.cz>
Date:	Thu, 26 Sep 2013 02:27:30 +0200
From:	Pavel Machek <pavel@....cz>
To:	James Bottomley <James.Bottomley@...senPartnership.com>
Cc:	Alan Stern <stern@...land.harvard.edu>,
	David Howells <dhowells@...hat.com>,
	"Lee, Chun-Yi" <joeyli.kernel@...il.com>,
	linux-kernel@...r.kernel.org,
	linux-security-module@...r.kernel.org, linux-efi@...r.kernel.org,
	linux-pm@...r.kernel.org, linux-crypto@...r.kernel.org,
	opensuse-kernel@...nsuse.org, "Rafael J. Wysocki" <rjw@...k.pl>,
	Matthew Garrett <mjg59@...f.ucam.org>,
	Len Brown <len.brown@...el.com>,
	Josh Boyer <jwboyer@...hat.com>,
	Vojtech Pavlik <vojtech@...e.cz>,
	Matt Fleming <matt.fleming@...el.com>,
	Greg KH <gregkh@...uxfoundation.org>, JKosina@...e.com,
	Rusty Russell <rusty@...tcorp.com.au>,
	Herbert Xu <herbert@...dor.hengli.com.au>,
	"David S. Miller" <davem@...emloft.net>,
	"H. Peter Anvin" <hpa@...or.com>, Michal Marek <mmarek@...e.cz>,
	Gary Lin <GLin@...e.com>, Vivek Goyal <vgoyal@...hat.com>,
	"Lee, Chun-Yi" <jlee@...e.com>
Subject: Re: [RFC V4 PATCH 00/15] Signature verification of hibernate
 snapshot

On Wed 2013-09-25 15:16:54, James Bottomley wrote:
> On Wed, 2013-09-25 at 17:25 -0400, Alan Stern wrote:
> > On Wed, 25 Sep 2013, David Howells wrote:
> > 
> > > I have pushed some keyrings patches that will likely affect this to:
> > > 
> > > 	http://git.kernel.org/cgit/linux/kernel/git/dhowells/linux-fs.git/log/?h=keys-devel
> > > 
> > > I intend to ask James to pull these into his next branch.  If he's happy to do
> > > so, I can look at pulling at least your asymmetric keys patch on top of them.
> > 
> > This suggests a point that I raised at the Linux Plumbers conference:
> > 
> > Why are asymmetric keys used for verifying the hibernation image?  It
> > seems that a symmetric key would work just as well.  And it would be a
> > lot quicker to generate, because it wouldn't need any high-precision
> > integer computations.
> 
> The reason is the desire to validate that the previous kernel created
> something which it passed on to the current kernel (in this case, the
> hibernation image) untampered with.  To do that, something must be
> passed to the prior kernel that can be validated but *not* recreated by
> the current kernel.

I don't get this. Why is it important that current kernel can't
recreate the signature?

Current kernel is not considered malicious (if it were, you have worse
problems).

								Pavel

PS: And yes, it would be nice to have
Documentation/power/swsusp-uefi.txt (or something) explaining the
design.

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