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

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To: "Olle E. Johansson" <oej@edvina.net>
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Subject: Re: [Sip] Using TLS in the first hop - Bug in RFC 5630
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2011/9/15 Olle E. Johansson <oej@edvina.net>et>:
>> 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>