Re: [xmpp] IQ Handling vulnerabilities

Alexander Holler <holler@ahsoftware.de> Tue, 11 February 2014 16:18 UTC

Return-Path: <holler@ahsoftware.de>
X-Original-To: xmpp@ietfa.amsl.com
Delivered-To: xmpp@ietfa.amsl.com
Received: from localhost (ietfa.amsl.com [127.0.0.1]) by ietfa.amsl.com (Postfix) with ESMTP id CD2891A01A8 for <xmpp@ietfa.amsl.com>; Tue, 11 Feb 2014 08:18:05 -0800 (PST)
X-Virus-Scanned: amavisd-new at amsl.com
X-Spam-Flag: NO
X-Spam-Score: 0.209
X-Spam-Level:
X-Spam-Status: No, score=0.209 tagged_above=-999 required=5 tests=[BAYES_00=-1.9, HELO_EQ_DE=0.35, HELO_MISMATCH_DE=1.448, HOST_MISMATCH_NET=0.311, LOTS_OF_MONEY=0.001, SPF_PASS=-0.001] autolearn=no
Received: from mail.ietf.org ([4.31.198.44]) by localhost (ietfa.amsl.com [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id seYZnaJhNAze for <xmpp@ietfa.amsl.com>; Tue, 11 Feb 2014 08:17:59 -0800 (PST)
Received: from mail.ahsoftware.de (h1446028.stratoserver.net [85.214.92.142]) by ietfa.amsl.com (Postfix) with ESMTP id 269E01A061F for <xmpp@ietf.org>; Tue, 11 Feb 2014 08:17:58 -0800 (PST)
Received: by mail.ahsoftware.de (Postfix, from userid 65534) id 00478423C2A9; Tue, 11 Feb 2014 17:17:56 +0100 (CET)
Received: from eiche.ahsoftware (p57B23CD3.dip0.t-ipconnect.de [87.178.60.211]) (using TLSv1 with cipher ADH-AES256-SHA (256/256 bits)) (No client certificate requested) by mail.ahsoftware.de (Postfix) with ESMTPSA id D31E8423C256 for <xmpp@ietf.org>; Tue, 11 Feb 2014 17:17:50 +0100 (CET)
Received: by eiche.ahsoftware (Postfix, from userid 65534) id 63AD47F82C; Tue, 11 Feb 2014 17:17:38 +0100 (CET)
Received: from krabat.ahsoftware (unknown [IPv6:feee::5246:5dff:fe8b:95f8]) by eiche.ahsoftware (Postfix) with ESMTP id 76C4E7FA1B; Tue, 11 Feb 2014 16:17:06 +0000 (UTC)
Message-ID: <52FA4D02.5050907@ahsoftware.de>
Date: Tue, 11 Feb 2014 17:17:06 +0100
From: Alexander Holler <holler@ahsoftware.de>
User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:24.0) Gecko/20100101 Thunderbird/24.2.0
MIME-Version: 1.0
To: Thijs Alkemade <thijs@xnyhps.nl>
References: <CAOb_FnxS-dMT85N7LHj5M9JWk3pL85=ugrDqaT7j5d28HBr0Cw@mail.gmail.com> <CF194491.38AD3%jhildebr@cisco.com> <2F5E925F-021D-408E-91D9-3CC5BEB6BEC6@nostrum.com> <48F4D361-4403-47E6-862D-FBDDDEBCC642@xnyhps.nl> <CF1A369C.38BE2%jhildebr@cisco.com> <CAKHUCzyCwKbmnUoXLHW=XzYbiFrcg-dQsDojGUnA-_r3qK+_Vg@mail.gmail.com> <CF1A4928-54B5-4A95-9A4B-0EC572A3CDBD@cisco.com> <CF1E56C5.38F45%jhildebr@cisco.com> <B671D7DA-CE9A-4A2C-8EDE-BF94F5F6FE82@xnyhps.nl> <52FA165B.8050901@ahsoftware.de> <CAKHUCzzhxKLbkNE=WjtP9S6XWm14-5e7Ut150x4k1akegm+1Qw@mail.gmail.com> <52FA3E53.3060009@ahsoftware.de> <0C2D606F-F718-4B07-A0A8-329C547D1BD8@xnyhps.nl>
In-Reply-To: <0C2D606F-F718-4B07-A0A8-329C547D1BD8@xnyhps.nl>
Content-Type: text/plain; charset=ISO-8859-15; format=flowed
Content-Transfer-Encoding: 7bit
Cc: XMPP Working Group <xmpp@ietf.org>
Subject: Re: [xmpp] IQ Handling vulnerabilities
X-BeenThere: xmpp@ietf.org
X-Mailman-Version: 2.1.15
Precedence: list
List-Id: XMPP Working Group <xmpp.ietf.org>
List-Unsubscribe: <https://www.ietf.org/mailman/options/xmpp>, <mailto:xmpp-request@ietf.org?subject=unsubscribe>
List-Archive: <http://www.ietf.org/mail-archive/web/xmpp/>
List-Post: <mailto:xmpp@ietf.org>
List-Help: <mailto:xmpp-request@ietf.org?subject=help>
List-Subscribe: <https://www.ietf.org/mailman/listinfo/xmpp>, <mailto:xmpp-request@ietf.org?subject=subscribe>
X-List-Received-Date: Tue, 11 Feb 2014 16:18:06 -0000

Am 11.02.2014 16:33, schrieb Thijs Alkemade:
>
> On 11 feb. 2014, at 16:14, Alexander Holler <holler@ahsoftware.de> wrote:
>
>> Am 11.02.2014 13:29, schrieb Dave Cridland:
>>> On Tue, Feb 11, 2014 at 12:23 PM, Alexander Holler <holler@ahsoftware.de>wrote;wrote:
>>>
>>>> Hmm, in all these mails it was never be mentioned that IDs still have to
>>>> be unique over some time for one session. I'm not sure if such is given
>>>> with the above constructs. It might be very unlikely that the same ID will
>>>> appear twice, but someone has to take a deeper look at it when using such
>>>> constructs like above. Of course, in reality the window in time IDs must be
>>>> unique is rather small, but ...
>>>>
>>>
>>> You'd need random collisions amongst cryptographically secure hashes.
>>> You're pretty safe.
>>
>> I don't aggree. You are safe if you use the hash as intendend, but not
>> if you just use some part of the hash(-number) or hashes of hashes. I'm
>> not sure about how safe it is (in regard to collisions) if you look at
>> consequent hashes of hashes. I would assume that is not what
>> cryptographers do look for (primarily).
>>
>> At least I can't remember to have seen some discussion if the series of
>> hash(hash(hash(...))) is collision free (that is imho quiet different
>> than hash(random); hash(random)). Of course, I'm not looking that often
>> at cryptographic papers, I usually prefer if cryptographers do such. ;)
>
> You're not going to stumble upon a SHA-1 collision by accident. Even if you do
> "hashes of hashes". The esitmated cost of an intentional SHA-1 collision is
> still at least $1M:
> https://www.schneier.com/blog/archives/2012/10/when_will_we_se.html
>
> If you do happen to find one, congratulations, you are now famous. Nobody has
> published a SHA-1 collision yet.

Sorry, but you haven't understood what I've written.

Alexander Holler