linux-kernel - Re: Hibernation considerations

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Date:	Tue, 17 Jul 2007 10:49:52 -0700 (PDT)
From:	david@...g.hm
To:	"Dr. David Alan Gilbert" <linux@...blig.org>
cc:	"Rafael J. Wysocki" <rjw@...k.pl>,
	LKML <linux-kernel@...r.kernel.org>,
	Alan Stern <stern@...land.harvard.edu>,
	Andrew Morton <akpm@...ux-foundation.org>,
	"Eric W. Biederman" <ebiederm@...ssion.com>,
	"Huang, Ying" <ying.huang@...el.com>,
	Jeremy Maitin-Shepard <jbms@....edu>,
	Kyle Moffett <mrmacman_g4@....com>,
	Nigel Cunningham <nigel@...el.suspend2.net>,
	Pavel Machek <pavel@....cz>,
	pm list <linux-pm@...ts.linux-foundation.org>,
	Al Boldi <a1426z@...ab.com>
Subject: Re: Hibernation considerations

On Tue, 17 Jul 2007, Dr. David Alan Gilbert wrote:

> * david@...g.hm (david@...g.hm) wrote:
>> On Mon, 16 Jul 2007, Rafael J. Wysocki wrote:
>
>>> Encryption is possible with both the userland hibernation (aka uswsusp) and
>>> TuxOnIce (formerly known as suspend2).  Still, I don't consider it as a
>>> "must
>>> have" feature for a framework to be generally useful (many users don't use
>>> it
>>> anyway).
>>
>> he's talking about the main system useing an encrypted device/partition,
>> not the hibernate image being stored encrypted.
>>
>> This would require the main system 'forget' the keys when it does the
>> hinbernate and prompt for it again during the wake-up phase.
>
> Indeed - although as I say I really don't know what you would do with
> apps using the mounts at that point.   Still it seems like a
> sensible requrest from the security side.

along the same lines, it would probably be a good idea to have the ability 
for a system to re-ask for the pass phrase periodicly while the system is 
running.

I see two possible approaches to these issues.

1. implement the periodic re-request capability, and when going into 
hibernate time-out any known pass phrases.

this is a lot of work overall, but the suspend portion is trivial so there 
would not be any suspend surprises.

2. flush the keyring on hibernate and have the resume process re-populate 
it (either by pokeing directly into the memory, or by providing a table 
that the resuming kernel reads from during wake-up to re-populate it)

this is less work, but it's all suspend related so it will get less 
testing.

David Lang
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