linux-kernel - Re: [RFC PATCH 00/18 v3] Signature verification of hibernate snapshot

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Message-ID: <87vc2ksdfa.fsf@mid.deneb.enyo.de>
Date:	Sun, 01 Sep 2013 18:40:41 +0200
From:	Florian Weimer <fw@...eb.enyo.de>
To:	Matthew Garrett <mjg59@...f.ucam.org>
Cc:	joeyli <jlee@...e.com>, linux-kernel@...r.kernel.org,
	linux-security-module@...r.kernel.org, linux-efi@...r.kernel.org,
	linux-pm@...r.kernel.org, linux-crypto@...r.kernel.org,
	opensuse-kernel@...nsuse.org, David Howells <dhowells@...hat.com>,
	"Rafael J. Wysocki" <rjw@...k.pl>, Len Brown <len.brown@...el.com>,
	Pavel Machek <pavel@....cz>, Josh Boyer <jwboyer@...hat.com>,
	Vojtech Pavlik <vojtech@...e.cz>,
	Matt Fleming <matt.fleming@...el.com>,
	James Bottomley <james.bottomley@...senpartnership.com>,
	Greg KH <gregkh@...uxfoundation.org>, JKosina@...e.com,
	Rusty Russell <rusty@...tcorp.com.au>,
	Herbert Xu <herbert@...dor.apana.org.au>,
	"David S. Miller" <davem@...emloft.net>,
	"H. Peter Anvin" <hpa@...or.com>, Michal Marek <mmarek@...e.cz>,
	Gary Lin <GLin@...e.com>, Vivek Goyal <vgoyal@...hat.com>
Subject: Re: [RFC PATCH 00/18 v3] Signature verification of hibernate snapshot

* Matthew Garrett:

> On Sun, Sep 01, 2013 at 12:41:22PM +0200, Florian Weimer wrote:
>
>> But if you don't generate fresh keys on every boot, the persistent
>> keys are mor exposed to other UEFI applications.  Correct me if I'm
>> wrong, but I don't think UEFI variables are segregated between
>> different UEFI applications, so if anyone gets a generic UEFI variable
>> dumper (or setter) signed by the trusted key, this cryptographic
>> validation of hibernate snapshots is bypassable.
>
> If anyone can execute arbitrary code in your UEFI environment then 
> you've already lost.

This is not about arbitrary code execution.  The problematic
applications which conflict with this proposed functionality are not
necessarily malicious by themselves and even potentially useful.

For example, if you want to provision a bunch of machines and you have
to set certain UEFI variables, it might be helpful to do so in an
unattended fashion, just by booting from a USB stick with a suitable
UEFI application.  Is this evil?  I don't think so.
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