Re: [dtn-security] Including fragment offset in the correlator doesn't prevent all fragment collisions.

Stephen Farrell <stephen.farrell@cs.tcd.ie> Wed, 20 March 2013 09:00 UTC

Return-Path: <stephen.farrell@cs.tcd.ie>
X-Original-To: dtn-security@ietfa.amsl.com
Delivered-To: dtn-security@ietfa.amsl.com
Received: from localhost (localhost [127.0.0.1]) by ietfa.amsl.com (Postfix) with ESMTP id 4995721F8A64 for <dtn-security@ietfa.amsl.com>; Wed, 20 Mar 2013 02:00:11 -0700 (PDT)
X-Virus-Scanned: amavisd-new at amsl.com
X-Spam-Flag: NO
X-Spam-Score: -102.6
X-Spam-Level:
X-Spam-Status: No, score=-102.6 tagged_above=-999 required=5 tests=[AWL=-0.000, BAYES_00=-2.599, USER_IN_WHITELIST=-100]
Received: from mail.ietf.org ([12.22.58.30]) by localhost (ietfa.amsl.com [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id EHWkLxpGJvsg for <dtn-security@ietfa.amsl.com>; Wed, 20 Mar 2013 02:00:10 -0700 (PDT)
Received: from mercury.scss.tcd.ie (mercury.scss.tcd.ie [134.226.56.6]) by ietfa.amsl.com (Postfix) with ESMTP id D5D0821F89FB for <dtn-security@irtf.org>; Wed, 20 Mar 2013 02:00:09 -0700 (PDT)
Received: from localhost (localhost [127.0.0.1]) by mercury.scss.tcd.ie (Postfix) with ESMTP id D3863BE5F; Wed, 20 Mar 2013 08:59:43 +0000 (GMT)
X-Virus-Scanned: Debian amavisd-new at scss.tcd.ie
Received: from mercury.scss.tcd.ie ([127.0.0.1]) by localhost (mercury.scss.tcd.ie [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id 5ngjSGlyYghw; Wed, 20 Mar 2013 08:59:41 +0000 (GMT)
Received: from [10.87.48.10] (unknown [86.45.51.139]) by mercury.scss.tcd.ie (Postfix) with ESMTPSA id 72252BE4C; Wed, 20 Mar 2013 08:59:41 +0000 (GMT)
Message-ID: <51497A7D.2040707@cs.tcd.ie>
Date: Wed, 20 Mar 2013 08:59:41 +0000
From: Stephen Farrell <stephen.farrell@cs.tcd.ie>
User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:17.0) Gecko/20130308 Thunderbird/17.0.4
MIME-Version: 1.0
To: "Ivancic, William D. (GRC-RHN0)" <william.d.ivancic@nasa.gov>
References: <CD6E8AB6.11FDB%william.d.ivancic@nasa.gov>
In-Reply-To: <CD6E8AB6.11FDB%william.d.ivancic@nasa.gov>
X-Enigmail-Version: 1.5.1
Content-Type: text/plain; charset=ISO-8859-1
Content-Transfer-Encoding: 7bit
Cc: dtn-security <dtn-security@irtf.org>
Subject: Re: [dtn-security] Including fragment offset in the correlator doesn't prevent all fragment collisions.
X-BeenThere: dtn-security@irtf.org
X-Mailman-Version: 2.1.12
Precedence: list
List-Id: "The Delay-Tolerant Networking Research Group \(DTNRG\) - Security." <dtn-security.irtf.org>
List-Unsubscribe: <https://www.irtf.org/mailman/options/dtn-security>, <mailto:dtn-security-request@irtf.org?subject=unsubscribe>
List-Archive: <http://www.irtf.org/mail-archive/web/dtn-security>
List-Post: <mailto:dtn-security@irtf.org>
List-Help: <mailto:dtn-security-request@irtf.org?subject=help>
List-Subscribe: <https://www.irtf.org/mailman/listinfo/dtn-security>, <mailto:dtn-security-request@irtf.org?subject=subscribe>
X-List-Received-Date: Wed, 20 Mar 2013 09:00:11 -0000

On 03/20/2013 01:35 AM, Ivancic, William D. (GRC-RHN0) wrote:
> Amy,
> 
> I do not believe RFC5050 was designed with secure reactive fragmentation in
> mind.  

I don't believe anything has ever been designed with secure reactive
fragmentation in mind;-) But I may be forgetting - if there has been
something like that done then it'd be good to look at.

> RFC5050 is fine for research.  Hopefully we are learning a lot and
> will fix what doesn't work very well on a second or third iteration.

Tend to agree, at least in this respect but I'd put it differently.
I think 5050 is mostly fine, but not wrt security which was added
after the fact in what was required to be a pretty ugly manner.

I do recall the fragmentation issue being discussed when DTNRG met
in Dublin some years ago, if someone found the notes from that those
might be useful. (I've not following the details of this conversation
sorry.)

S.

> 
> -- Will 
> 
> 
>> From: Peter Lovell <plovell@mac.com>
>> Date: Tue, 19 Mar 2013 20:11:14 -0500
>> To: Amy Alford <aloomis@sarn.org>rg>, dtn-security <dtn-security@irtf.org>
>> Subject: Re: [dtn-security] Including fragment offset in the correlator
>> doesn't prevent all fragment collisions.
>>
>> Amy Alford <aloomis@sarn.org> wrote:
>>
>>> A bundle can be fragmented multiple times independently, so a node may
>>> receive multiple fragments with the same offset and length that have
>>> traveled different paths (and accumulated different BSP blocks along the
>>> way).  Collisions in the correlator values once the bundle is reassembled
>>> are inevitable.
>>> - Amy
>>
>> Hi Amy,
>>
>> my thought is that we have covered the problem of multiple-fragmentation and
>> multi-path, but perhaps not.
>>
>> Can you describe a bundle scenario that exemplifies the issue you see, so we
>> can think about it.
>>
>> Thanks.....Peter
>>
>> _______________________________________________
>> dtn-security mailing list
>> dtn-security@irtf.org
>> https://www.irtf.org/mailman/listinfo/dtn-security
> 
> _______________________________________________
> dtn-security mailing list
> dtn-security@irtf.org
> https://www.irtf.org/mailman/listinfo/dtn-security
> 
>