Re: [Sip] Using TLS in the first hop - Bug in RFC 5630

Iñaki Baz Castillo <ibc@aliax.net> Thu, 15 September 2011 13:36 UTC

Return-Path: <ibc@aliax.net>
X-Original-To: sip@ietfa.amsl.com
Delivered-To: sip@ietfa.amsl.com
Received: from localhost (localhost [127.0.0.1]) by ietfa.amsl.com (Postfix) with ESMTP id E216821F84E5 for <sip@ietfa.amsl.com>; Thu, 15 Sep 2011 06:36:35 -0700 (PDT)
X-Virus-Scanned: amavisd-new at amsl.com
X-Spam-Flag: NO
X-Spam-Score: -2.35
X-Spam-Level:
X-Spam-Status: No, score=-2.35 tagged_above=-999 required=5 tests=[AWL=-0.273, BAYES_00=-2.599, FM_FORGED_GMAIL=0.622, J_CHICKENPOX_93=0.6, MIME_8BIT_HEADER=0.3, RCVD_IN_DNSWL_LOW=-1]
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 71WqqxbnuXIQ for <sip@ietfa.amsl.com>; Thu, 15 Sep 2011 06:36:35 -0700 (PDT)
Received: from mail-qy0-f172.google.com (mail-qy0-f172.google.com [209.85.216.172]) by ietfa.amsl.com (Postfix) with ESMTP id 63BF021F84DF for <sip@ietf.org>; Thu, 15 Sep 2011 06:36:35 -0700 (PDT)
Received: by qyk32 with SMTP id 32so5039237qyk.10 for <sip@ietf.org>; Thu, 15 Sep 2011 06:38:45 -0700 (PDT)
MIME-Version: 1.0
Received: by 10.229.67.166 with SMTP id r38mr869945qci.254.1316093924574; Thu, 15 Sep 2011 06:38:44 -0700 (PDT)
Received: by 10.229.79.207 with HTTP; Thu, 15 Sep 2011 06:38:44 -0700 (PDT)
In-Reply-To: <CFFC2869-C704-423E-974D-3F4B93145BBB@edvina.net>
References: <CALiegfkNfJ7McZAA=a5ajYVzYtmAjC_KQdK1P_ez2L1dia5v2g@mail.gmail.com> <CFFC2869-C704-423E-974D-3F4B93145BBB@edvina.net>
Date: Thu, 15 Sep 2011 15:38:44 +0200
Message-ID: <CALiegfnh2C3GNddnneepcVsGgtOd1pSDBVC3uH72S1KaVT_jHg@mail.gmail.com>
From: Iñaki Baz Castillo <ibc@aliax.net>
To: "Olle E. Johansson" <oej@edvina.net>
Content-Type: text/plain; charset="UTF-8"
Content-Transfer-Encoding: quoted-printable
Cc: sip@ietf.org
Subject: Re: [Sip] Using TLS in the first hop - Bug in RFC 5630
X-BeenThere: sip@ietf.org
X-Mailman-Version: 2.1.12
Precedence: list
List-Id: Session Initiation Protocol <sip.ietf.org>
List-Unsubscribe: <https://www.ietf.org/mailman/options/sip>, <mailto:sip-request@ietf.org?subject=unsubscribe>
List-Archive: <http://www.ietf.org/mail-archive/web/sip>
List-Post: <mailto:sip@ietf.org>
List-Help: <mailto:sip-request@ietf.org?subject=help>
List-Subscribe: <https://www.ietf.org/mailman/listinfo/sip>, <mailto:sip-request@ietf.org?subject=subscribe>
X-List-Received-Date: Thu, 15 Sep 2011 13:36:36 -0000

2011/9/15 Olle E. Johansson <oej@edvina.net>:
>> As a personal comment, I would like to say that nobody understands the
>> usage of "sips" schema, just nobody. And the specs do not help.
>>
> With the deprecation of "transport=tls" it becomes even more strange.

AFAIK "transport=tls" has never been deprecated. Instead, it has never
been an standard. Note for example that RFC 3261 says:

      Note that in the SIPS URI scheme, transport is independent of TLS,
      and thus "sips:alice@atlanta.com;transport=tcp" and
      "sips:alice@atlanta.com;transport=sctp" are both valid (although
      note that UDP is not a valid transport for SIPS).  The use of
      "transport=tls" has consequently been deprecated, partly because
      it was specific to a single hop of the request.  This is a change
      since RFC 2543.

"A change since RFC 2543"?? transport=tls has never been defined in
RFC 2543. Check yourself:

  http://tools.ietf.org/html/rfc2543


> We should really spend some time on a "hitch hikers guide to SIP with TLS" and write an RFC to reinstate transtport=tls, which is what we all use.

Or spend some time in a new draft that *correctly* explains how to use
TLS in the first hop (without requiring security in the whole path).
This is *very* easy:

As I've explained in my first mail:

  INVITE sip:bob@biloxi.com SIP/2.0
  Via: SIP/2.0/TLS 1.2.3.4
  From: sip:alice@atlanta.com
  Contact: sips:alice@1.2.3.4;transport=tcp

That's all. Just:
- Set TLS in Via transport.
- Use "sip" schema in every URI.
- But use "sips" schema in Contact URI.

And it works.



-- 
Iñaki Baz Castillo
<ibc@aliax.net>