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Re: [xmpp] IQ Handling vulnerabilities

"Joe Hildebrand (jhildebr)" <jhildebr@cisco.com> Mon, 10 February 2014 19:33 UTC

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From: "Joe Hildebrand (jhildebr)" <jhildebr@cisco.com>
To: Thijs Alkemade <thijs@xnyhps.nl>
Thread-Topic: [xmpp] IQ Handling vulnerabilities
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Date: Mon, 10 Feb 2014 19:33:31 +0000
Message-ID: <CF1E771D.38FA7%jhildebr@cisco.com>
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> <1078DA63-EB0B-4724-A4DA-BA1B5C4FE4EC@xnyhps.nl>
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Cc: Ben Campbell <ben@nostrum.com>, XMPP Working Group <xmpp@ietf.org>
Subject: Re: [xmpp] IQ Handling vulnerabilities
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On 2/10/14 12:25 PM, "Thijs Alkemade" <thijs@xnyhps.nl> wrote:

>Uhm. Maybe this email is missing a line again, but if you use those
>values as
>'id's directly, they will not be unpredictable at all, as anyone who
>receives
>an <iq/> can generate the rest of the chain.
>
>However, if you make sure the 'id' values are only half the hashes, it
>should
>be unpredictable unless an attacker is willing to spend an insane amount
>of
>work.
>
>So:
>
>start = sha1(crytpo_rand())
>start+1 = sha1(start)
>...
>
>id1 = start[0:10]
>id2 = start+1[0:10]

Or add a nonce to each round:

nonce = crytpo_rand()
start = sha1(nonce + crytpo_rand())
start+1 = sha1(nonce + start)

Regardless, there exist solutions.


-- 
Joe Hildebrand

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