Subject: [Uta] Oppurtunistic DANE TLS

From: "Olle E. Johansson" <[email-masked]>
Date: Mon, 10 Feb 2014 07:45:47 +0100

Hi!

The DANE working group has a draft about Oppurtunistic DANE TLS. As Paul has a draft that defines Oppurtunistic TLS, I thought it would be a good thing to be aware of in this group. Here's the author's definition:

"opportunistic DANE TLS:  Best-effort use of TLS, resistant to
      downgrade attacks for destinations with DNSSEC-validated TLSA
      records.  When opportunistic DANE TLS is determined to be
      unavailable, clients should fall back to opportunistic TLS below.
      Opportunistic DANE TLS requires support for DNSSEC, DANE and
      STARTTLS on the client side and STARTTLS plus a DNSSEC published
      TLSA record on the server side."

http://tools.ietf.org/html/draft-ietf-dane-smtp-with-dane-05

/O

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From: "Olle E. Johansson" <[email-masked]>
Date: Mon, 10 Feb 2014 07:51:04 +0100

> http://tools.ietf.org/html/draft-ietf-dane-smtp-with-dane-05
Missed copy/paste of the second part:

"  (pre-DANE) opportunistic TLS:  Best-effort use of TLS that is
      generally vulnerable to DNS forgery and STARTTLS downgrade
      attacks.  When a TLS-encrypted communication channel is not
      available, message transmission takes place in the clear.  MX
      record indirection generally precludes authentication even when
      TLS is available."

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From: Paul Hoffman <[email-masked]>
Date: Mon, 10 Feb 2014 08:40:26 -0800

FWIW, I chatted with Viktor over the weekend, and that definition changed somewhat based on the conversation. It is important to note that the definition might change again during WG Last Call, given that the DANE WG has not been reading the draft all that carefully.

--Paul Hoffman