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

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Message-ID: <20180809034320.GB21364@chenyu-desktop>
Date:   Thu, 9 Aug 2018 11:43:20 +0800
From:   Yu Chen <yu.c.chen@...el.com>
To:     Pavel Machek <pavel@....cz>
Cc:     joeyli <jlee@...e.com>, Ryan Chen <yu.chen.surf@...il.com>,
        oneukum@...e.com, "Rafael J. Wysocki" <rafael.j.wysocki@...el.com>,
        ebiggers@...gle.com, Theodore Ts'o <tytso@....edu>,
        smueller@...onox.de, denkenz@...il.com,
        Linux PM list <linux-pm@...r.kernel.org>,
        linux-crypto@...r.kernel.org,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        kookoo.gu@...el.com, Zhang Rui <rui.zhang@...el.com>
Subject: Re: [PATCH 0/4][RFC v2] Introduce the in-kernel hibernation
 encryption

Hi,
On Wed, Aug 08, 2018 at 07:58:45PM +0200, Pavel Machek wrote:
> On Mon 2018-08-06 18:39:58, joeyli wrote:
> > On Mon, Aug 06, 2018 at 04:45:34PM +0800, Yu Chen wrote:
> > > Hi Pavel,
> > > On Sun, Aug 05, 2018 at 12:02:00PM +0200, Pavel Machek wrote:
> > > > Hi!
> > > > 
> > > > > > User space doesn't need to involve. The EFI root key is generated by
> > > > > > EFI boot stub and be transfer to kernel. It's stored in EFI boot service
> > > > > > variable that it can only be accessed by trusted EFI binary when
> > > > > > secure boot is enabled.
> > > > > >
> > > > > Okay, this apply to the 'suspend' phase, right?
> > > > > I'm still a little confused about the 'resume' phase.
> > > > > Taking encryption as example(not signature),
> > > > > the purpose of doing hibernation encryption is to prevent other users
> > > > > from stealing ram content. Say, user A uses a  passphrase to generate the
> > > > 
> > > > No, I don't think that's purpose here.
> > > > 
> > > > Purpose here is to prevent user from reading/modifying kernel memory
> > > > content on machine he owns.
> > > >
> > > Say, A puts his laptop into hibernation and walks away,
> > > and B walks by, and opens A's laptop and wakes up the system and he
> > > can do what he wants. Although EFI key/TPM trusted key is enabled,
> > > currently there's no certification during resume, which sounds
> > > unsafe to me. Afterall, the original requirement is to probe
> > > user for password during resume, which sounds more natural.
> > 
> > OK, I saw your case. This is a physical accessing.
> > 
> > I have a question: The suspend to memory also has the same behavior
> > and more people are using suspend. Should we think a common solution
> > to cover S3 and S4? 
> 
> Well, we have similar problem during runtime, too ;-).
> 
> Anyway, I don't think we should encrypt memory during S3 in kernel.
> 
It seems that Joey was talking about certification(something like login)
rather than encryption?

Best,
Yu
> If you wanted to do that, you could use uswsusp to take snapshot,
> store it in ram, encrypt, erase originals (new API might be
> needed... hmm. does not exactly sound easy... kexec?), trigger S3, decrypt,
> resume from snapshot...
> 
> Sounds like a bit of work...
> 
> Best regards,
> 
> 									Pavel
> -- 
> (english) http://www.livejournal.com/~pavelmachek
> (cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html