Re: [rtcweb] AVPF [was: Encryption mandate (and offer/answer)]

Matthew Kaufman <matthew.kaufman@skype.net> Fri, 09 September 2011 18:10 UTC

Return-Path: <matthew.kaufman@skype.net>
X-Original-To: rtcweb@ietfa.amsl.com
Delivered-To: rtcweb@ietfa.amsl.com
Received: from localhost (localhost [127.0.0.1]) by ietfa.amsl.com (Postfix) with ESMTP id CD9D721F8804 for <rtcweb@ietfa.amsl.com>; Fri, 9 Sep 2011 11:10:12 -0700 (PDT)
X-Virus-Scanned: amavisd-new at amsl.com
X-Spam-Flag: NO
X-Spam-Score: -6.599
X-Spam-Level:
X-Spam-Status: No, score=-6.599 tagged_above=-999 required=5 tests=[BAYES_00=-2.599, RCVD_IN_DNSWL_MED=-4]
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 6JqPSyJGMn8x for <rtcweb@ietfa.amsl.com>; Fri, 9 Sep 2011 11:10:12 -0700 (PDT)
Received: from mx.skype.net (mx.skype.net [78.141.177.88]) by ietfa.amsl.com (Postfix) with ESMTP id 01F2221F86A4 for <rtcweb@ietf.org>; Fri, 9 Sep 2011 11:10:12 -0700 (PDT)
Received: from mx.skype.net (localhost [127.0.0.1]) by mx.skype.net (Postfix) with ESMTP id B12D3170B; Fri, 9 Sep 2011 20:11:36 +0200 (CEST)
DKIM-Signature: v=1; a=rsa-sha1; c=relaxed; d=skype.net; h=message-id :date:from:mime-version:to:cc:subject:references:in-reply-to :content-type:content-transfer-encoding; s=mx; bh=qzo2V/Z9q5F4L5 h7HNxZzbMepHA=; b=UYM8dDt9M1Rb3Hcei5Ht+vAT6Hx62ND4PF1yBmGivUuxSs yOZFZms28s2Pmws0VzCtvYM4GhC9MlXCSNUx2/yskBVKpgaEoA0p2yZpEJAMKBN7 V+lH4X52lm941wRLli4PfzgRHF6c9MYTgMv2YYLSlSCkmJ2zeT+rfBKEiRSHk=
DomainKey-Signature: a=rsa-sha1; c=nofws; d=skype.net; h=message-id:date:from :mime-version:to:cc:subject:references:in-reply-to:content-type: content-transfer-encoding; q=dns; s=mx; b=jjO0HmZDQONzbIIkqp0CO9 IowwwCNyo4LUqwSI++oWr156ml9IkfNVFYHtoJcck8ElOd7MISSOVK72ra0BPKjd mowJMkSLOJCEH+C+VtmiJTNJPv1rXNBiD9mevKETfcqqpSDvY0NqKcgrjl8mKyor 8dtjy30UeMyTTOd5h9lOo=
Received: from zimbra.skype.net (zimbra.skype.net [78.141.177.82]) by mx.skype.net (Postfix) with ESMTP id AF8817F6; Fri, 9 Sep 2011 20:11:36 +0200 (CEST)
Received: from localhost (localhost [127.0.0.1]) by zimbra.skype.net (Postfix) with ESMTP id 7BB721672682; Fri, 9 Sep 2011 20:11:36 +0200 (CEST)
X-Virus-Scanned: amavisd-new at lu2-zimbra.skype.net
Received: from zimbra.skype.net ([127.0.0.1]) by localhost (zimbra.skype.net [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id GudvrDxvbc1J; Fri, 9 Sep 2011 20:11:35 +0200 (CEST)
Received: from Matthew-Kaufman-Air.local (unknown [131.107.200.34]) by zimbra.skype.net (Postfix) with ESMTPSA id 4AF0C1672681; Fri, 9 Sep 2011 20:11:34 +0200 (CEST)
Message-ID: <4E6A56D4.2030602@skype.net>
Date: Fri, 09 Sep 2011 11:11:32 -0700
From: Matthew Kaufman <matthew.kaufman@skype.net>
User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.6; rv:6.0.2) Gecko/20110902 Thunderbird/6.0.2
MIME-Version: 1.0
To: Alan Johnston <alan.b.johnston@gmail.com>
References: <A444A0F8084434499206E78C106220CA0B00FDB08B@MCHP058A.global-ad.net> <101C6067BEC68246B0C3F6843BCCC1E31018BF6BE2@MCHP058A.global-ad.net> <4E540FE2.7020605@alcatel-lucent.com> <2E239D6FCD033C4BAF15F386A979BF5106423F@sonusinmail02.sonusnet.com> <4E6595E7.7060503@skype.net> <4E661C83.5000103@alcatel-lucent.com> <2E239D6FCD033C4BAF15F386A979BF510F086B@sonusinmail02.sonusnet.com> <4E666926.8050705@skype.net> <43A0D702-1D1F-4B4E-B8E6-C9F1A06E3F8A@edvina.net> <033458F56EC2A64E8D2D7B759FA3E7E7020E64DC@sonusmail04.sonusnet.com> <E4EC1B17-0CC4-4F79-96DD-84E589FCC4F0@edvina.net> <4E67C3F7.7020304@jesup.org> <BE60FA11-8FFF-48E5-9F83-4D84A7FBE2BE@vidyo.com> <4E67F003.6000108@jesup.org> <7F2072F1E0DE894DA4B517B93C6A05852233E8554C@ESESSCMS0356.eemea.ericsson.se> <C3759687E4991243A1A0BD44EAC8230339CA68F054@BE235.mail.lan> <CAOJ7v-2u0UuNXh7bzmZFwiSucbsh=Ps=C3ZM5M3cJrXRmZgODA@mail.gmail.com> <CAKhHsXHXCkNdjtpxCSCk+ABbtxY15GEgouE6X6-sn-LqhnidQw@mail.gmail.com>
In-Reply-To: <CAKhHsXHXCkNdjtpxCSCk+ABbtxY15GEgouE6X6-sn-LqhnidQw@mail.gmail.com>
Content-Type: text/plain; charset=ISO-8859-1; format=flowed
Content-Transfer-Encoding: 7bit
Cc: Randell Jesup <randell-ietf@jesup.org>, Jonathan Lennox <jonathan@vidyo.com>, "rtcweb@ietf.org" <rtcweb@ietf.org>
Subject: Re: [rtcweb] AVPF [was: Encryption mandate (and offer/answer)]
X-BeenThere: rtcweb@ietf.org
X-Mailman-Version: 2.1.12
Precedence: list
List-Id: Real-Time Communication in WEB-browsers working group list <rtcweb.ietf.org>
List-Unsubscribe: <https://www.ietf.org/mailman/options/rtcweb>, <mailto:rtcweb-request@ietf.org?subject=unsubscribe>
List-Archive: <http://www.ietf.org/mail-archive/web/rtcweb>
List-Post: <mailto:rtcweb@ietf.org>
List-Help: <mailto:rtcweb-request@ietf.org?subject=help>
List-Subscribe: <https://www.ietf.org/mailman/listinfo/rtcweb>, <mailto:rtcweb-request@ietf.org?subject=subscribe>
X-List-Received-Date: Fri, 09 Sep 2011 18:10:12 -0000

On 9/9/11 10:47 AM, Alan Johnston wrote:
>    The default will be SRTP - this can be
> expressed in SDP without CapNeg.  Should the RTCWEB clients choose to
> instead negotiate RTP, then this could be done with a second SDP
> Offer/Answer exchange.

I believe you've just designed a downgrade vulnerability.

Matthew Kaufman