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

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Date:   Wed, 8 Aug 2018 19:50:36 +0200
From:   Pavel Machek <pavel@....cz>
To:     Yu Chen <yu.c.chen@...el.com>
Cc:     Ryan Chen <yu.chen.surf@...il.com>, jlee@...e.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!

> > > > 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

Define unsafe.

If you want security against bad people resuming your machines, please
take a look at existing uswsusp solutions. It defends against that.

If you want security against bad people tampering with your machines
physically, sorry, there's no way to defend against that.

But I thought you were trying to do something for secure boot, and "bad
person resumes your machine" is out of scope there.

So please always explain security against _what kind of attack_ you
are trying to improve; intelligent communication is not possible
without that.

								Pavel

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

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