Re: [Ntp] Antw: Re: Details of the fragmentation attacks against NTP and port randomization

Fernando Gont <fgont@si6networks.com> Mon, 08 July 2019 22:17 UTC

Return-Path: <fgont@si6networks.com>
X-Original-To: ntp@ietfa.amsl.com
Delivered-To: ntp@ietfa.amsl.com
Received: from localhost (localhost [127.0.0.1]) by ietfa.amsl.com (Postfix) with ESMTP id 4E468120318 for <ntp@ietfa.amsl.com>; Mon, 8 Jul 2019 15:17:05 -0700 (PDT)
X-Virus-Scanned: amavisd-new at amsl.com
X-Spam-Flag: NO
X-Spam-Score: -0.307
X-Spam-Level:
X-Spam-Status: No, score=-0.307 tagged_above=-999 required=5 tests=[BAYES_00=-1.9, DATE_IN_PAST_03_06=1.592, RCVD_IN_DNSWL_NONE=-0.0001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001, URIBL_BLOCKED=0.001] autolearn=no autolearn_force=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 inajPU26VDBD for <ntp@ietfa.amsl.com>; Mon, 8 Jul 2019 15:17:03 -0700 (PDT)
Received: from fgont.go6lab.si (fgont.go6lab.si [91.239.96.14]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by ietfa.amsl.com (Postfix) with ESMTPS id F2DBC12031B for <ntp@ietf.org>; Mon, 8 Jul 2019 15:17:02 -0700 (PDT)
Received: from [192.168.1.16] (unknown [41.143.218.184]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by fgont.go6lab.si (Postfix) with ESMTPSA id 83C01838EA; Tue, 9 Jul 2019 00:16:59 +0200 (CEST)
To: Ulrich Windl <Ulrich.Windl@rz.uni-regensburg.de>, "ntp@ietf.org" <ntp@ietf.org>
References: <CAN2QdAGS20q=7+r+qMFEBBu4gNmSDR9-vYDbvgC=ZnqWLEU-6w@mail.gmail.com> <739c2eaa-05f1-0b30-4b64-fc5d3f91ce5b@pdmconsulting.net> <a3a545cf-d83d-a2c7-ad6c-3e349de78615@si6networks.com> <9f75e400-cf2f-053f-ed06-f4d6df415eaf@pdmconsulting.net> <70d86938-5d50-7732-5257-c698d7d308d6@si6networks.com> <b4a5d0ec-606e-7994-9bc9-e21e24f38def@ntp.org> <f4b5312c-b02c-ee51-1c59-f0467f51ab77@si6networks.com> <OF8F5917D8.BA274E92-ONC1258418.004C2FAF-C1258418.0052EEFB@ptb.de> <20190613100006.45108edd@rellim.com> <68186be5-764d-73e7-1631-04567edf28a7@si6networks.com> <20190613122929.0e049722@rellim.com> <3b7c6e55-b2a9-443c-e5cb-3b4c9e5bb642@si6networks.com> <20190614112522.2e5676f3@rellim.com> <73f861c1-72e0-5e01-87e1-18658cd11859@si6networks.com> <5D1B5F84020000A10003211E@gwsmtp.uni-regensburg.de>
From: Fernando Gont <fgont@si6networks.com>
Openpgp: preference=signencrypt
Autocrypt: addr=fgont@si6networks.com; prefer-encrypt=mutual; keydata= mQINBE5so2gBEACzBQBLUy8nzgAzSZn6ViXT6TmZBFNYNqTpPRvTVtUqF6+tkI+IEd9N2E8p pXUXCd0W4dkxz6o7pagnK63m4QSueggvp881RVVHOF8oTSHOdnGxLfLeLNJFKE1FOutU3vod GK/wG/Fwzkv9MebdXpMlLV8nnJuAt66XGl/lU1JrNfrKO4SoYQi4TsB/waUQcygh7OR/PEO0 EttiU8kZUbZNv58WH+PAj/rdZCrgUSiGXiWUQQKShqKnJxLuAcTcg5YRwL8se/V6ciW0QR9i /sr52gSmLLbW5N3hAoO+nv1V/9SjJAUvzXu43k8sua/XlCXkqU7uLj41CRR72JeUZ4DQsYfP LfNPC98ZGTVxbWbFtLXxpzzDDT8i3uo7w1LJ2Ij/d5ezcARqw01HGljWWxnidUrjbTpxkJ9X EllcsH94mer728j/HKzC9OcTuz6WUBP3Crgl6Q47gY5ZIiF0lsmd9/wxbaq5NiJ+lGuBRZrD v0dQx9KmyI0/pH2AF8cW897/6ypvcyD/1/11CJcN+uAGIrklwJlVpRSbKbFtGC6In592lhu7 wnK8cgyP5cTU+vva9+g6P1wehi4bylXdlKc6mMphbtSA+T3WBNP557+mh3L62l4pGaEGidcZ DLYT2Ud18eAJmxU3HnM8P3iZZgeoK7oqgb53/eg96vkONXNIOwARAQABtCVGZXJuYW5kbyBH b250IDxmZ29udEBzaTZuZXR3b3Jrcy5jb20+iQJBBBMBAgArAhsjBQkSzAMABgsJCAcDAgYV CAIJCgsEFgIDAQIeAQIXgAUCTmylpQIZAQAKCRCuJQ1VHU50kv7wD/9fuNtTfxSLk3B3Hs3p ixTy8YXVjdkVwWlnJjFd7BOWmg7sI+LDhpjGfT6+ddOiwkumnvUZpObodj4ysH0i8c7P4C5t F9yu7WjklSlrB5Rth2CGChg5bKt541z2WHkFFxys9qBLmCSYDeKQkzLqhCjIUJizY2kOJ2GI MnSFDzJjhSFEh//oW830Y8fel1xnf/NVF+lBVtRMtMOfoWUqDjvP3sJ1G4zgkDCnF0CfncLx +hq2Mv26Uq9OTzvLH9aSQQ/f067BOkKAJKsfHdborX4E96ISTz57/4xECRSMr5dVsKVm4Y// uVIsb+L5z+a32FaiBZIAKDgnJO7Z8j6CV5e5yfuBTtX52Yi9HjYYqnYJGSDxYd6igD4bWu+7 xmJPHjkdqZgGV6dQIgiUfqkU+s5Cv350vK48CMaT/ZLo2BdsMhWsmaHmb+waePUMyq6E4E9x 9Js+EJb9ZiCfxS9exgieZQpet1L36IvhiwByvkQM009ywfa30JeMOltUtfLi5V06WQWsTzPL 5C+4cpkguSuAJVDTctjCA0moIeVDOpJ8WH9voQ4IeWapQnX35OIoj1jGJqqYdx65gc1ygbyx b8vw+pJ9E5GLse5TQnYifOWpXzX9053dtbwp/2OVhU4KLlzfCPCEsoTyfu9nIZxdI2PMwiL5 M85BfjX4NmwBLmPGoLkCDQRObKNoARAAqqXCkr250BchRDmi+05F5UQFgylUh10XTAJxBeaQ UNtdxZiZRm6jgomSrqeYtricM9t9K0qb4X2ZXmAMW8o8AYW3RrQHTjcBwMnAKzUIEXXWaLfG cid/ygmvWzIHgMDQKP+MUq1AGQrnvt/MRLvZLyczAV1RTXS58qNaxtaSpc3K/yrDozh/a4pu WcUsVvIkzyx43sqcwamDSBb6U8JFoZizuLXiARLLASgyHrrCedNIZdWSx0z0iHEpZIelA2ih AGLiSMtmtikVEyrJICgO81DkKNCbBbPg+7fi23V6M24+3syHk3IdQibTtBMxinIPyLFF0byJ aGm0fmjefhnmVJyCIl/FDkCHprVhTme57G2/WdoGnUvnT7mcwDRb8XY5nNRkOJsqqLPemKjz kx8mXdQbunXtX9bKyVgd1gIl+LLsxbdzRCch773UBVoortPdK3kMyLtZ4uMeDX3comjx+6VL bztUdJ1Zc9/njwVG8fgmQ+0Kj5+bzQfUY+MmX0HTXIx3B4R1I1a8QoOwi1N+iZNdewV5Zfq+ 29NlQLnVPjCRCKbaz9k6RJ2oIti55YUI6zSsL3lmlOXsRbXN5bRswFczkNSCJxJMlDiyAUIC WOay7ymzvgzPa+BY/mYn94vRaurDQ4/ljOfj6oqgfjts+dJev4Jj89vp8MQI3KJpZPEAEQEA AYkCJQQYAQIADwUCTmyjaAIbDAUJEswDAAAKCRCuJQ1VHU50km4xEACho45PZrUjY4Zl2opR DFNo5a6roTOPpgwO9PcBb3I5F8yX2Dnew+9OhgWXbBhAFq4DCx+9Gjs43Bn60qbZTDbLGJ/m 8N4PwEiq0e5MKceYcbetEdEUWhm5L6psU9ZZ82GR3UGxPXYe+oifEoJjOXQ39avf9S8p3yKP Diil0E79rn7LbJjMcgMLyjFg9SDoJ6pHLtniJoDhEAaSSgeV7Y745+gyMIdtQmrFHfqrFdjq D6G0HE+Z68ywc5KN67YxhvhBmSycs1ZSKAXv1zLDlXdmjHDHkU3xMcB+RkuiTba8yRFYwb/n j62CC4NhFTuIKOc4ta3dJsyXTGh/hO9UjWUnmAGfd0fnzTBZF8Qlnw/8ftx5lt4/O+eqY1EN RITScnPzXE/wMOlTtdkddQ+QN6xt6jyR2XtAIi7aAFHypIqA3lLI9hF9x+lj4UQ2yA9LqpoX 6URpPOd13JhAyDe47cwsP1u9Y+OBvQTVLSvw7Liu2b4KjqL4lx++VdBi7dXsjJ6kjIRjI6Lb WVpxe8LumMCuVDepTafBZ49gr7Fgc4F9ZSCo6ChgQNLn6WDzIkqFX+42KuHz90AHWhuW+KZR 1aJylERWeTcMCGUSBptd48KniWmD6kPKpzwoMkJtEXTuO2lVuborxzwuqOTNuYg9lWDl7zKt wPI9brGzquUHy4qRrA==
Message-ID: <4f8eed9b-0ef3-84e0-01f4-c07c8a6debfd@si6networks.com>
Date: Mon, 8 Jul 2019 20:12:20 +0100
User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.7.2
MIME-Version: 1.0
In-Reply-To: <5D1B5F84020000A10003211E@gwsmtp.uni-regensburg.de>
Content-Type: text/plain; charset=utf-8
Content-Language: en-US
Content-Transfer-Encoding: 7bit
Archived-At: <https://mailarchive.ietf.org/arch/msg/ntp/ZdOcCSCZhazOt4OXtIi3fnGAV8s>
Subject: Re: [Ntp] Antw: Re: Details of the fragmentation attacks against NTP and port randomization
X-BeenThere: ntp@ietf.org
X-Mailman-Version: 2.1.29
Precedence: list
List-Id: <ntp.ietf.org>
List-Unsubscribe: <https://www.ietf.org/mailman/options/ntp>, <mailto:ntp-request@ietf.org?subject=unsubscribe>
List-Archive: <https://mailarchive.ietf.org/arch/browse/ntp/>
List-Post: <mailto:ntp@ietf.org>
List-Help: <mailto:ntp-request@ietf.org?subject=help>
List-Subscribe: <https://www.ietf.org/mailman/listinfo/ntp>, <mailto:ntp-request@ietf.org?subject=subscribe>
X-List-Received-Date: Mon, 08 Jul 2019 22:17:18 -0000

On 2/7/19 14:43, Ulrich Windl wrote:
> Hi!
> 
> Maybe the sentence "With changing port numbers there is a specific probability
> that the packet run times (transmission / reception) may change, having an
> effect on the accuracy of NTP that prefers fixed and symmetric packet run
> times." can make it into the document, making both parties happy; those for
> randomizing ports and those against ;-)
> 
> Note that in theory the effect on accuracy could be positive as well, but most
> likely not in the general case.

FWIW, the doc proposes the conservative approach of randomizing the
local port on a per-association basis, and leaves the analysis of
randomization on a per-transaction basis for future work.

Thanks!

Cheers,
-- 
Fernando Gont
SI6 Networks
e-mail: fgont@si6networks.com
PGP Fingerprint: 6666 31C6 D484 63B2 8FB1 E3C4 AE25 0D55 1D4E 7492