linux-kernel - Re: [RFC] Second attempt at kernel secure boot support

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Date:	Wed, 31 Oct 2012 15:55:03 +0000
From:	Alan Cox <alan@...rguk.ukuu.org.uk>
To:	Josh Boyer <jwboyer@...il.com>
Cc:	Jiri Kosina <jkosina@...e.cz>, Matthew Garrett <mjg@...hat.com>,
	linux-kernel@...r.kernel.org,
	linux-security-module@...r.kernel.org, linux-efi@...r.kernel.org
Subject: Re: [RFC] Second attempt at kernel secure boot support

> > is basically DMA-ing arbitrary data over the whole RAM. I am currently not
> > able to imagine a scenario how this could be made "secure" (without
> > storing private keys to sign the hibernation image on the machine itself
> > which, well, doesn't sound secure either).

That's what the TPM is for (in fact all of this stuff can be done
properly with a TPM while the 'secure' boot stuff can do little if any of
it.

> 
> I have a patch that disables that.  I imagine it will be included in the
> next submission of the patchset.
> 
> You can find it here in the meantime:
> 
> http://jwboyer.fedorapeople.org/pub/0001-hibernate-Disable-in-a-Secure-Boot-environment.patch

All this depends on your threat model. If I have physical access to
suspend/resume your machine then you already lost. If I don't have
physical access then I can't boot my unsigned OS to patch your S4 image
so it doesn't matter.

In fact the more I think about this the more it seems disabling hibernate
is basically farting in the wind.

Alan
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