Re: [RFC V4 PATCH 00/15] Signature verification of hibernatesnapshot

From: Pavel Machek
Date: Wed Sep 25 2013 - 20:27:38 EST

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:
> > >
> > >
> > >
> > > 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


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

(cesky, pictures)
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