Re: [rtcweb] Security Architecture: SDES support is a MUST

Alan Johnston <alan.b.johnston@gmail.com> Fri, 20 July 2012 18:19 UTC

Return-Path: <alan.b.johnston@gmail.com>
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 A49C711E80CB for <rtcweb@ietfa.amsl.com>; Fri, 20 Jul 2012 11:19:50 -0700 (PDT)
X-Virus-Scanned: amavisd-new at amsl.com
X-Spam-Flag: NO
X-Spam-Score: -103.599
X-Spam-Level:
X-Spam-Status: No, score=-103.599 tagged_above=-999 required=5 tests=[AWL=0.000, BAYES_00=-2.599, RCVD_IN_DNSWL_LOW=-1, USER_IN_WHITELIST=-100]
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 vfqqpsFqzOI5 for <rtcweb@ietfa.amsl.com>; Fri, 20 Jul 2012 11:19:49 -0700 (PDT)
Received: from mail-lb0-f172.google.com (mail-lb0-f172.google.com [209.85.217.172]) by ietfa.amsl.com (Postfix) with ESMTP id E015211E80D5 for <rtcweb@ietf.org>; Fri, 20 Jul 2012 11:19:48 -0700 (PDT)
Received: by lbbgo11 with SMTP id go11so5882930lbb.31 for <rtcweb@ietf.org>; Fri, 20 Jul 2012 11:20:42 -0700 (PDT)
DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20120113; h=mime-version:in-reply-to:references:date:message-id:subject:from:to :cc:content-type; bh=HK6nT6HFxqvTYVlSnbGSfTBnDAmD/xACA91mBGpae10=; b=UWce+nk1sijh38QKlewhE0tzPHp+2uvIc9kbDk/3P0ZWNQUQCRliOMjhjPoHfefMZW ZzyyPLbhjtTtps1pKZZyOgJgJz9HMSqEtJY1EtltHdmCadaF1NPOVuvwBP2hsIol8UiR VWVFnZtNfk2XbTivxDIBYevpAsk7XQN/+wp3qTgRCRPg/ZwdLDl8ifWKYHJo94LLnwP2 Zx8EYfEjicvsapyfcb5AGz1WJWJFBcKAZy7E55Ta3utwRhirGr3mbeuEjYLJXQFOJAr0 TbehxHjDthycGUD+QQl7Xf2vW0p0K2XMeqlMCnrhLnQJD4LfJWujysXYtJaawQFJ3QCX B1aw==
MIME-Version: 1.0
Received: by 10.152.148.1 with SMTP id to1mr7255160lab.34.1342808442355; Fri, 20 Jul 2012 11:20:42 -0700 (PDT)
Received: by 10.112.133.130 with HTTP; Fri, 20 Jul 2012 11:20:42 -0700 (PDT)
In-Reply-To: <CABcZeBM4BwtUyr=MTft0SXSwhUO0vczWd0jOVUO=ea2SYiEcZA@mail.gmail.com>
References: <201207190742.q6J7glf6008744@vivaldi29.register.it> <500834FE.5040809@alcatel-lucent.com> <500835E1.2070502@infosecurity.ch> <50084717.7060301@alcatel-lucent.com> <BLU169-DS1488EF1F32A1EB2027582093D90@phx.gbl> <5008F7B9.7020804@infosecurity.ch> <500957ED.90807@alvestrand.no> <50095AAC.7030104@infosecurity.ch> <50095CE7.6030202@alvestrand.no> <CABcZeBM4BwtUyr=MTft0SXSwhUO0vczWd0jOVUO=ea2SYiEcZA@mail.gmail.com>
Date: Fri, 20 Jul 2012 13:20:42 -0500
Message-ID: <CAKhHsXGH4NZTO+cg3XHsBR_tZD4hXUj=+iCr8ekm3Kj76vWqNQ@mail.gmail.com>
From: Alan Johnston <alan.b.johnston@gmail.com>
To: Eric Rescorla <ekr@rtfm.com>
Content-Type: text/plain; charset=ISO-8859-1
Cc: rtcweb@ietf.org
Subject: Re: [rtcweb] Security Architecture: SDES support is a MUST
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, 20 Jul 2012 18:19:50 -0000

If we want to have usable end-to-end or human-to-human authentication,
then just displaying a 128 bit fingerprint isn't going to work.

ZRTP ( RFC 6189) uses a hash commitment to reduce this to an 8 bit
fingerprint, and has human friendly ways to exchange this, such as
base 256:

     http://en.wikipedia.org/wiki/PGP_word_list

There have been claims over the years that DTLS-SRTP could do this as
well, but I have never seen a specification or a description of how
would be done.

- Alan -

On Fri, Jul 20, 2012 at 8:50 AM, Eric Rescorla <ekr@rtfm.com> wrote:
> The draft currently states:
>
>      *  The "security characteristics" MUST include some mechanism to
>          allow an out-of-band verification of the peer, such as a
>          certificate fingerprint or an SAS.
>
> I'd be happy to have us specify a particular fingerprint algorithm (presumably
> SHA-256, potentially truncated) but I haven't seen any evidence that
> users savvy enough to inspect the fingerprint at all can't navigate more
> than one hash. For example, Chrome's SSL/TLS inspector currently displays
> MD5 and SHA-1. So I'm not sure something needs to be standardized here.
>
> -Ekr
>
>
> On Fri, Jul 20, 2012 at 6:28 AM, Harald Alvestrand <harald@alvestrand.no> wrote:
>> On 07/20/2012 03:18 PM, Fabio Pietrosanti (naif) wrote:
>>>
>>> On 7/20/12 3:06 PM, Harald Alvestrand wrote:
>>>>>
>>>>> Current security definition of WebRTC does not support end-to-end
>>>>> security.
>>>>
>>>> The current security definition of WebRTC (with DTLS) provides
>>>> fingerprints.
>>>> If the application is able to verify those fingerprints, security is end
>>>> to end; if it isn't - it isn't.
>>>
>>> The security specification already does specify how the fingerprint must
>>> be checked, against a third party system that must be trusted (unless
>>> there is some recent update i didn't still checked).
>>>
>>> The way the specification describe fingerprint must be checked, does not
>>> enforce end-to-end security but always rely on trusted third party,
>>> being IdP (identity providers).
>>>
>>> The only way to achieve end-to-end security is not to have any kind of
>>> trusted third party, as has been already discussed on
>>> http://www.ietf.org/mail-archive/web/rtcweb/current/msg04043.html .
>>
>> That link is your request to have SAS considered mandatory.
>>
>> I believe you got some support for that proposal, or at least some kind of
>> availability of digest information that can be verified independently, but I
>> do not believe that you got any support for having SAS be the one and only
>> definition of "end to end security".
>>
>> Thus, you may get support for your real request, but not for the language
>> you use to describe it.
>>
>>>
>>> Until WebRTC security architecture specification does not clearly define
>>> a peer-to-peer fingerprint verification system that does not rely on
>>> trusted third party it cannot be considered to provide end-to-end
>>> security.
>>>
>>> Fabio
>>> _______________________________________________
>>> rtcweb mailing list
>>> rtcweb@ietf.org
>>> https://www.ietf.org/mailman/listinfo/rtcweb
>>
>>
>> _______________________________________________
>> rtcweb mailing list
>> rtcweb@ietf.org
>> https://www.ietf.org/mailman/listinfo/rtcweb
> _______________________________________________
> rtcweb mailing list
> rtcweb@ietf.org
> https://www.ietf.org/mailman/listinfo/rtcweb