Re: [PATCH 0/5 v2][RFC] Encryption and authentication for hibernate snapshot image

From: Pavel Machek <pavel@ucw.cz>
To: Andy Lutomirski <luto@kernel.org>
Cc: joeyli <jlee@suse.com>, "Lee, Chun-Yi" <joeyli.kernel@gmail.com>,
	"Rafael J . Wysocki" <rjw@rjwysocki.net>,
	LKML <linux-kernel@vger.kernel.org>,
	linux-pm@vger.kernel.org, keyrings@vger.kernel.org,
	"Rafael J. Wysocki" <rafael.j.wysocki@intel.com>,
	Chen Yu <yu.c.chen@intel.com>, Oliver Neukum <oneukum@suse.com>,
	Ryan Chen <yu.chen.surf@gmail.com>,
	David Howells <dhowells@redhat.com>,
	Giovanni Gherdovich <ggherdovich@suse.cz>,
	Randy Dunlap <rdunlap@infradead.org>,
	Jann Horn <jannh@google.com>
Subject: Re: [PATCH 0/5 v2][RFC] Encryption and authentication for hibernate snapshot image
Date: Wed, 9 Jan 2019 00:42:47 +0100	[thread overview]
Message-ID: <20190108234246.GA22310@amd> (raw)
In-Reply-To: <CALCETrWHjn_WN1WRc2pbFPB+H-ZL_1y=8dhhHoVqA53Q7Pj5vA@mail.gmail.com>

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Hi!

> >> Please explain your security goals.
> >
> > My security goals:
> >
> > - Encrypt and authicate hibernate snapshot image in kernel space. Userspace
> >  can only touch an encrypted and signed snapshot image.
> 
> Signed?
> 
> I’m not entirely convinced that the keyring mechanism is what you
> want. ISTM that there are two goals here:
> 
> a) Encryption: it should be as hard as can reasonably be arranged to
> extract secrets from a hibernation image.
> 
> b) Authentication part 1: it should not be possible for someone in
> possession of a turned-off machine to tamper with the hibernation
> image such that the image, when booted, will leak its secrets. This
> should protect against attackers who don’t know the encryption key.
> 
> c) Authentication part 2: it should be to verify, to the extent
> practical, that the image came from the same machine and was really
> created using hibernation.  Or maybe by the same user.

So... this looks like "security goals" I was asking in the first
place. Thanks!

Could we get something like that (with your real goals?) in the next
version of the patch?

> As far as I can tell, there is only one reason that any of this needs
> to be in the kernel: if it’s all in user code, then we lose “lockdown”
> protection against compromised user code on a secure boot system.  Is
> that, in fact, true?

And this is what I'd really like answer to. Because... I'd really like
this to be in userspace if it does not provide additional security
guarantees.

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

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