Re: [Ntp] A simpler way to secure PTP

Miroslav Lichvar <mlichvar@redhat.com> Tue, 11 May 2021 08:24 UTC

Return-Path: <mlichvar@redhat.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 7E8363A0121 for <ntp@ietfa.amsl.com>; Tue, 11 May 2021 01:24:29 -0700 (PDT)
X-Virus-Scanned: amavisd-new at amsl.com
X-Spam-Flag: NO
X-Spam-Score: -2.795
X-Spam-Level:
X-Spam-Status: No, score=-2.795 tagged_above=-999 required=5 tests=[BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.698, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_BLOCKED=0.001, RCVD_IN_MSPIKE_H4=0.001, RCVD_IN_MSPIKE_WL=0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001] autolearn=ham autolearn_force=no
Authentication-Results: ietfa.amsl.com (amavisd-new); dkim=pass (1024-bit key) header.d=redhat.com
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 Rb4jQOEVF2-G for <ntp@ietfa.amsl.com>; Tue, 11 May 2021 01:24:27 -0700 (PDT)
Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [216.205.24.124]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by ietfa.amsl.com (Postfix) with ESMTPS id E85D83A011D for <ntp@ietf.org>; Tue, 11 May 2021 01:24:26 -0700 (PDT)
DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1620721465; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=o0vKaEEVNTpsWuflvOhxxsY98QvYdfxt1wtDoCpLPHk=; b=DW1WHFD28MU8Fu++zxhkVl9/AFOz4iheNrld4J9Kn8gZkfry9KYamM416Yx+E9xYHshQ0y woNx555ylU+DOSXq0FvHrgM4D02n6nV4su2jX4DOjb/wS87/U7q8AEVLo6DEgu2mtBn9Sd FaNwjvKMzwbtf2sMZV5EtbLgnvbnkII=
Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-597-TjEg2EHgOeaQDxikseSsjQ-1; Tue, 11 May 2021 04:24:24 -0400
X-MC-Unique: TjEg2EHgOeaQDxikseSsjQ-1
Received: from smtp.corp.redhat.com (int-mx05.intmail.prod.int.phx2.redhat.com [10.5.11.15]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 1C118107ACE4; Tue, 11 May 2021 08:24:23 +0000 (UTC)
Received: from localhost (holly.tpb.lab.eng.brq.redhat.com [10.43.134.11]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 7B8DF6268E; Tue, 11 May 2021 08:24:21 +0000 (UTC)
Date: Tue, 11 May 2021 10:24:19 +0200
From: Miroslav Lichvar <mlichvar@redhat.com>
To: Heiko Gerstung <heiko.gerstung=40meinberg.de@dmarc.ietf.org>
Cc: Daniel Franke <dfoxfranke@gmail.com>, NTP WG <ntp@ietf.org>
Message-ID: <YJo/M6TdqqrmrVyP@localhost>
References: <CAJm83bCpio5WwigY6nc9Y0Gt_XSdjUV=sHUz04dOQ0zELPwZxw@mail.gmail.com> <886DDD0D-AB9A-43A1-999B-FC296D680434@meinberg.de>
MIME-Version: 1.0
In-Reply-To: <886DDD0D-AB9A-43A1-999B-FC296D680434@meinberg.de>
X-Scanned-By: MIMEDefang 2.79 on 10.5.11.15
Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=mlichvar@redhat.com
X-Mimecast-Spam-Score: 0
X-Mimecast-Originator: redhat.com
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
Archived-At: <https://mailarchive.ietf.org/arch/msg/ntp/QWEPmmXJCXlI6HkbBKQ3iIEVtXk>
Subject: Re: [Ntp] A simpler way to secure PTP
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: Tue, 11 May 2021 08:24:30 -0000

On Tue, May 11, 2021 at 09:14:55AM +0200, Heiko Gerstung wrote:
>PTP is different from NTP on multiple levels and offers a number of features that you do not find in NTP, for example higher packet rates to increase the number of samples you feed into your statistics.

Isn't this the other way around? The maximum rate of delay requests is
limited by the TX HW timestamping rate. The few PTP appliances I saw
supported only a very small number of clients. This can exploited for
a DoS attack. The same applies to NTP using HW timestamps+xleave, but
at least it can fall back to SW timestamps and clients should handle
that well.

> It also offers hardware timestamping in the network infrastructure components, i.e. switches and routers, which can improve your sync performance dramatically.

Would you expect the network devices to gain support for the new
security protocol quickly, or is it more likely the leaf clocks would
need to bypass them and send their secured requests to new designated
clocks (avoiding the benefits of the hardware support)?

> However, especially unicast PTP is a great traffic amplification tool, maybe one of the biggest traffic amplification machines of all times. And I also believe that it would be great to (re)use the general concepts of NTS to secure the other popular time transfer protocol out there. 

Yes, the near infinite amplification factor of the unicast PTP mode is
a major concern, but I don't see what can be reused from NTS to fix
that. NTS in NTP avoids amplification by the protocol design, not by a
security mechanism.

-- 
Miroslav Lichvar