linux-kernel - Re: [PATCH 0/4][RFC v2] Introduce the in-kernel hibernation encryption

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Message-ID: <20180724130110.GA29006@amd>
Date:   Tue, 24 Jul 2018 15:03:46 +0200
From:   Pavel Machek <pavel@....cz>
To:     Oliver Neukum <oneukum@...e.com>
Cc:     Yu Chen <yu.c.chen@...el.com>,
        "Rafael J . Wysocki" <rafael.j.wysocki@...el.com>,
        Eric Biggers <ebiggers@...gle.com>,
        "Lee, Chun-Yi" <jlee@...e.com>, Theodore Ts o <tytso@....edu>,
        Stephan Mueller <smueller@...onox.de>,
        Denis Kenzior <denkenz@...il.com>, linux-pm@...r.kernel.org,
        linux-crypto@...r.kernel.org, linux-kernel@...r.kernel.org,
        "Gu, Kookoo" <kookoo.gu@...el.com>,
        "Zhang, Rui" <rui.zhang@...el.com>
Subject: Re: [PATCH 0/4][RFC v2] Introduce the in-kernel hibernation
 encryption

On Tue 2018-07-24 14:47:54, Oliver Neukum wrote:
> On Di, 2018-07-24 at 14:01 +0200, Pavel Machek wrote:
> > Hi!
> > 
> > > > > >        "There have some functions be locked-down because
> > > > > >        there have no appropriate mechanisms to check the
> > > > > >        integrity of writing data."
> > > > > >        https://patchwork.kernel.org/patch/10476751/
> > > > > 
> > > > > So your goal is to make hibernation compatible with kernel
> > > > > lockdown? Do your patches provide sufficient security that hibernation
> > > > > can be enabled with kernel lockdown?
> > > > 
> > > > OK, maybe I am dense, but if the key comes from user space, will that
> > > > be enough?
> > > > 
> > > 
> > > Good point, we once tried to generate key in kernel, but people
> > > suggest to generate key in userspace and provide it to the
> > > kernel, which is what ecryptfs do currently, so it seems this
> > > should also be safe for encryption in kernel.
> > 
> > Safe against what kind of attack? Please describe what kind of
> > security you are trying to provide.
> 
> Unsigned code must not take over the priviledge level of signed code.
> Hence:
> 
> 1. Unsigned code must not allowed to read sensitive parts of signed
> code's memory space
> 
> 2. Unsigned code must not be able to alter the memory space of
> signed code -> snapshots that are changed must not be able to be
> resumed

Ok.

> > I don't think generating key in userspace is good enough for providing
> > guarantees for secure-boot.
> 
> Why?

Because then, userpace has both key (now) and encrypted image (after
reboot), so it can decrypt, modify, re-encrypt...?

									Pavel
-- 
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html

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