linux-kernel - Re: [GIT PULL] Load keys from signed PE binaries

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Date:	Mon, 25 Feb 2013 15:45:49 +0000
From:	Matthew Garrett <mjg59@...f.ucam.org>
To:	Florian Weimer <fw@...eb.enyo.de>
Cc:	Linus Torvalds <torvalds@...ux-foundation.org>,
	David Howells <dhowells@...hat.com>,
	Josh Boyer <jwboyer@...hat.com>,
	Peter Jones <pjones@...hat.com>,
	Vivek Goyal <vgoyal@...hat.com>,
	Kees Cook <keescook@...omium.org>, keyrings@...ux-nfs.org,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [GIT PULL] Load keys from signed PE binaries

On Mon, Feb 25, 2013 at 03:28:32PM +0100, Florian Weimer wrote:

> But what puzzles me most is why anyone would assume that the UEFI
> application signing process somehow ensures that the embedded
> certificate is non-malicious.  We cannot even track it back to the
> submitter because the third-pary market place UEFI authority only
> issues pseudonymous proxy certificates.  This utterly useless for any
> purpose whatsoever, with the notable exception of avoding one
> additional step when setting up a dual-boot machine (which will not
> even work reliably until we switch to overwriting the Windows boot
> loader, like in the pre-UEFI days).

If your firmware trusts objects signed by Microsoft, you have to assume 
that objects signed by Microsoft are trustworthy. There's no way to 
build a security model otherwise. Are Microsoft trustworthy? We don't 
know. If you don't trust Microsoft, remove their key from db.

> Seriously, folks, can we go back one step and discuss what problem you
> are trying to solve?  Is it about allowing third-party kernel modules
> in an environment which does not allow unsigned ring 0 code execution?

The problem I'm trying to solve is "Don't permit Linux to be used as a 
bootloader for backdoored versions of other operating systems". Any 
other security benefit is a happy side effect.

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