Re: [PATCH] x86/efi: pull NV+BS variables out before we exit bootservices

From: James Bottomley
Date: Tue Mar 19 2013 - 19:00:41 EST

On Tue, 2013-03-19 at 18:50 +0000, Matthew Garrett wrote:
> On Tue, Mar 19, 2013 at 06:40:56PM +0000, James Bottomley wrote:
> > On Tue, 2013-03-19 at 18:28 +0000, Matthew Garrett wrote:
> > > It requires the key to survive the system being entirely powered down,
> > > which means it needs to be BS+NV. It shouldn't be possible for userspace
> > > to access this key.
> >
> > It requires the *public* key to survive power down, certainly. The
> > private key can be thrown away once the hibernate image is signed. I
> > think the scheme can be constructed so the private key is never in NV
> > storage ... that also makes it more secure against tampering.
> Well, that somewhat complicates implementation - we'd be encrypting the
> entire contents of memory except for the key that we're using to encrypt
> memory. Keeping the public key away from userspace avoids having to care
> about that.

I don't quite understand what you're getting at: the principle of public
key cryptography is that you can make the public key, well public. You
only need to guard the private key.


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