On Feb 14, 2014, at 2:50 PM, James Cloos <[email protected]> wrote:

> The only real question is whether dane-srv and dane-smtp-with-dane
> should be published as two rfcs or combined into one?
> (I’m leaning towards two, numerically adjacent.)

With all due respect, there are other real questions, much more significant 
than that one.

One of the biggest questions that needs to be asked is not whether DANE can be 
used for opportunistic protocols, because of course it can, but whether DANE 
can be used to determine whether a server at a domain name "should" be speaking 
TLS at the time that a client tries to connect. Viktor makes a strong case that 
it does for SMTP. During the early discussions of TLSA, many people thought it 
should not.

Viktor's view gives us good MITM protection if the DNS channel is not broken 
and the client knows the DNSSEC status of its query. It also causes messages to 
be lost if there is an operational problem or even an unexpected mis-match on 
the crypto desires of the client and server. It also assumes that the person 
running the DNS server for a name is in active contact with the person 
operating the SMTP server.

Personally, I don't care about MITM protection if it comes at the cost of 
getting more organizations to turn on opportunistic crypto. I think DANE still 
has an important role in that it gives the SMTP server operator a logging 
capability to see if there is an MITM. Others prefer more protection against 
MITMs even in the face of preventable communication failures.

And, to be blunt, if we think that Viktor is right about DANE for SMTP, 
shouldn't DANE for HTTP have the same MITM protection and operational downsides?

--Paul Hoffman
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