On Apr 21, 2013, at 6:27 AM, Olle E. Johansson <[email protected]> wrote:

> Hi!
> 
> Looking at the DANE SRV draft with my SIP eyes I realize that there's a lot 
> of work to be done to get this
> to work with SIP. 

Thank you.

> 
> SIP has no StartTLS, we use NAPTR records to select transport. The NAPTR 
> points to a SRV
> name that resolves into a set of host names.
> 
> The SIP Domain certificates RFC - http://tools.ietf.org/html/rfc5922 - 
> specificies matching a 
> given SIP URI with a certificate. The matching is done on service domain 
> either with 
> a ALT name URI, like sip:ietf.org or a DNS name, like ietf.org - but not the 
> host name.
> 
> I personally agree with the policy in the DANE SRV draft that we should match 
> on the
> SRV hostname used to get A/AAAA records when using DNSsec. For this to work,
> the path from the SIP URI over NAPTR to SRV and hostnames needs to be fully
> signed in and verified in the DNS. This is going to require an update to 5922.
> 
> The final question is how to handle this without SNI. The certificates for 
> both
> DANE verification and RFC 5922 plus "old-style" verification with the sip
> domain in the CN seems like a complicated mess to manage.
> 
> Food for thought on a sunny Sunday.
> 
> The SRV draft is not clear on how to use Subject AltNames of various types,
> and doesn't mention NAPTR. I am not personally aware of other protocols using
> this setup, so maybe this requires a very SIP specfic draft,

So, when we were writing the DANE protocol document we decided to describe the 
general case and that there would likely be a whole set of "How to do DANE with 
$foo protocol" documents.

Your mail backs up that decision, and also sounds like you are volunteering to 
start the "How to do DANE with SIP" draft...

> following the wake of the
> smtp work.

or, better yet, in parallel with the smtp work? :-)

W


> 
> /O
> 
> 
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> 

--
"Go on, prove me wrong. Destroy the fabric of the universe. See if I care."  -- 
Terry Prachett 


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