linux-kernel - Re: [PATCH v2 0/4] Checkpoint/Restore: Show in proc IDs of objects that can be shared between tasks

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Date:	Fri, 18 Nov 2011 15:46:35 -0800
From:	Tejun Heo <tj@...nel.org>
To:	Kyle Moffett <kyle@...fetthome.net>
Cc:	Pekka Enberg <penberg@...nel.org>,
	Cyrill Gorcunov <gorcunov@...il.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Pavel Emelyanov <xemul@...allels.com>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Glauber Costa <glommer@...allels.com>,
	Andi Kleen <andi@...stfloor.org>,
	Matt Helsley <matthltc@...ibm.com>,
	Eric Dumazet <eric.dumazet@...il.com>,
	Vasiliy Kulikov <segoon@...nwall.com>
Subject: Re: [PATCH v2 0/4] Checkpoint/Restore: Show in proc IDs of objects
 that can be shared between tasks

Hello,

On Fri, Nov 18, 2011 at 05:10:37PM -0500, Kyle Moffett wrote:
> The #1 rule of one-time pads is never use it for more than one thing,
> and you use it here for every object in the system.

The new version is using different poison for different types of
objects.

> If you actually want to be able to compare uniqueness without exposing
> anything vulnerable to various kinds of guessing, you should generate
> a random 64-bit value for each class of object and then use a proper
> cryptographic hash function on it:
>   crypto_hash(concat(object_ptr, random_value))
> 
> Even given the best possible practical attacks against SHA1 or MD5
> today both still provides more than enough security to prevent someone
> from guessing "object_ptr" in less than an absurd amount of time.

So, per-type poison + crypto hash, it is then.

Thank you very much.

-- 
tejun
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