22 apr 2013 kl. 23:33 skrev Warren Kumari <[email protected]>:

> 
> 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...
Well, I started with trying to map the area and gather data. The RAI area wants 
this work to be done in the
sipcore working group and there is a discussion going on (based on the same 
e-mail) in the RAI dispatch wg.

> 
>> following the wake of the
>> smtp work.
> 
> or, better yet, in parallel with the smtp work? :-)
Right. :-)
There is also work going on with XMPP that is similar to SIP, so there are many 
drafts to digest.

/O
> 
> 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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