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Date: Tue, 19 Mar 2013 18:50:03 +0000
From: Matthew Garrett <mjg59@srcf.ucam.org>
To: James Bottomley <James.Bottomley@HansenPartnership.com>
Cc: linux-efi@vger.kernel.org, linux-kernel <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH] x86/efi: pull NV+BS variables out before we exit boot
 services
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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.

-- 
Matthew Garrett | mjg59@srcf.ucam.org

From mboxrd@z Thu Jan  1 00:00:00 1970
From: Matthew Garrett <mjg59-1xO5oi07KQx4cg9Nei1l7Q@public.gmane.org>
Subject: Re: [PATCH] x86/efi: pull NV+BS variables out before we exit boot
 services
Date: Tue, 19 Mar 2013 18:50:03 +0000
Message-ID: <20130319185003.GA13301@srcf.ucam.org>
References: <1363596014.2412.8.camel@dabdike.int.hansenpartnership.com>
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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.

-- 
Matthew Garrett | mjg59-1xO5oi07KQx4cg9Nei1l7Q@public.gmane.org