Re: [Sip] A proposal for breaking the DTLS-SRTP vs RFC4474 gateway deadlock

[Eric Rescorla <ekr at networkresonance.com>]

Dean,

This sounds like an excellent way to proceed. I'll generate some candidate text
and send it to the list in the next few days.

-Ekr

On Tue, Jun 24, 2008 at 10:21 AM, Dean Willis <dean.willis at softarmor.com> wrote:
>
> We've gotten stuck on a fine point in DTLS-SRTP.
>
> The current draft-ietf-sip-dtls-srtp-framework-01 uses an RFC 4474 Identity
> header to preserve the integrity of the media key's fingerprint, thereby
> detecting a certain class of MITM attack.
>
> However, RFC 4474 Identity headers are of questionable validity when used
> with protocol gateways or B2BUAs.  More or less, they're capable of
> asserting the identity of the gateway, not the identity of the calling
> party. But the recipient has no real way to figure out which is which.
>
> We've debated at some length, and with no good result, about whether we
> should try and fix RFC 4474. We've had some suggestions that may work for
> B2BUAs, and some other suggestions that may work for gateways, but we
> certainly don't have a consensus.
>
> That leaves our chartered deliverable of DTLS-SRTP hanging, and the
> milestone has gone past months ago.
>
> Here's a proposal:
>
> We add a caveat about the limitation of RFC 4474 to
> draft-ietf-sip-dtls-srtp-framework and go ahead and advance that
> specification. If somebody later decides to fix RFC 4474, they can do so,
> and if necessary update DTLS-SRTP if needed.
>
>
> Does that work for everybody?
>
> If we agree to it, I suggest that we move the date for WGLC of
> draft-ietf-sip-dtls-srtp-framework to July 2008, and move the milestone for
> delivery of that doc to the IESG into September.
>
> --
> Dean
>

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