Subject: [dane] Possible ambiguity in -19

From: Andrew Sullivan <[email-masked]>
Date: Mon, 16 Apr 2012 14:46:09 -0400

Hi all,

I was trying to draw a diagram of TLS using DANE and TLSA the other
day, and I realised that there's a small ambiguity in -19.

It is not clear from the text whether the client initiating the TLS
connection needs to perform the TLSA lookup before the TLS negotiation
starts, or once the certificate is presented by the server.

The answer is, I believe, that it's up to the client.  It might be
nice to add a sentence to this effect, however.  (This is a pretty
minor addition and could be done any time, I think.)

Best,

A

-- 
Andrew Sullivan
[email-masked]

---

From: Paul Wouters <[email-masked]>
Date: Mon, 16 Apr 2012 16:20:26 -0400 (EDT)

On Mon, 16 Apr 2012, Andrew Sullivan wrote:

> The answer is, I believe, that it's up to the client.

Yes. A client might fire of TLSA and HASTLS requests while it already
attempts to initiate to port 443. I would hope the browser would do
some caching of these records (and lack of these records!) to reduce
the number of failed port 443 attempts.

But in light of how browsers do pre-emptive look-ups of all DNS entries
in links to the current page, it could also request TLSA and HASTLS and
actually already know before it needs to connect to the remote server
whether or not it can do TLS. Of course the same applies if the links it
found were https:// instead of http:// but I believe the idea of HASTLS
was that it would override any presented http:// to https:// if such a
HASTLS record would be found (and validated) and was stating it did not
run a service on port 80.

Paul

---

From: Paul Hoffman <[email-masked]>
Date: Mon, 16 Apr 2012 14:37:42 -0700

> minor addition and could be done any time, I think.)

Arrgh. I thought we had done that in an earlier version, but we didn't.

Proposal to add at the end of Section 4:

   The application can perform the TLSA lookup before initiating the
   TLS handshake, or do it during the TLS handshake: the choice is
   up to the client.

--Paul Hoffman

---

From: Ondřej Surý <[email-masked]>
Date: Tue, 17 Apr 2012 01:12:05 +0200

>   TLS handshake, or do it during the TLS handshake: the choice is

lgtm

--
 Ondřej Surý
 vedoucí výzkumu/Head of R&D department
 -------------------------------------------
 CZ.NIC, z.s.p.o.    --    Laboratoře CZ.NIC
 Americka 23, 120 00 Praha 2, Czech Republic
 mailto:[email-masked]    http://nic.cz/
 tel:+420.222745110       fax:+420.222745112
 -------------------------------------------