linux-kernel - Re: [PATCH] x86/efi: pull NV+BS variables out before we exit boot services

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Message-ID: <1363734031.2377.77.camel@dabdike.int.hansenpartnership.com>
Date:	Tue, 19 Mar 2013 23:00:31 +0000
From:	James Bottomley <James.Bottomley@...senPartnership.com>
To:	Matthew Garrett <mjg59@...f.ucam.org>
Cc:	linux-efi@...r.kernel.org,
	linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] x86/efi: pull NV+BS variables out before we exit boot
 services

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.

James



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