Subject: [Uta] Warren Kumari's Discuss on draft-ietf-uta-smtp-tlsrpt-18: (with DISCUSS)

From: Warren Kumari <[email-masked]>
Date: Mon, 16 Apr 2018 10:58:09 -0700

Warren Kumari has entered the following ballot position for
draft-ietf-uta-smtp-tlsrpt-18: Discuss

When responding, please keep the subject line intact and reply to all
email addresses included in the To and CC lines. (Feel free to cut this
introductory paragraph, however.)

Please refer to https://www.ietf.org/iesg/statement/discuss-criteria.html
for more information about IESG DISCUSS and COMMENT positions.

The document, along with other ballot positions, can be found here:
https://datatracker.ietf.org/doc/draft-ietf-uta-smtp-tlsrpt/

----------------------------------------------------------------------
DISCUSS:
----------------------------------------------------------------------

I'm guessing that I'm simply misunderstanding / not understanding (reformatted
for clarity): 1: If multiple TXT records for "_smtp._tls" are returned by the
resolver, records which do not begin with "v=TLSRPTv1;" are discarded. 2: If
the number of resulting records is not one, senders MUST assume the recipient
domain does not implement TLSRPT. 3: If the resulting TXT record contains
multiple strings, then the record MUST be treated as if those strings are
concatenated together without adding spaces.

So, if I query for '_smtp._tls.example.com' and get back:
"v=TLSRPTv1;rua=mailto:[email-masked]"
"v=TLSRPTv3;rua=mailto:[email-masked]"

I throw away the one that contains 'bar', fair enough, got it. What I don't
understand is what a record would look like which is a single record (#2), but
that contains multiple strings (#3). Can you provide an example of a TXT record
with multiple strings? I don't *think* that this is just me being dense, and so
I think that the document needs to better explain this / include the example.

---

From: Viktor Dukhovni <[email-masked]>
Date: Mon, 16 Apr 2018 14:08:29 -0400

> On Apr 16, 2018, at 1:58 PM, Warren Kumari <[email-masked]> wrote:
> 

Strings in TXT records have a single-octet length field. When returning a longer
string, or when one wants to explicitly segment a TXT RDATA into multiple strings
one returns:

	txt.example. IN TXT "first string" "second string" ... "last string"

with the wire RDATA being:

	<len1>first string<len2>second string...<lenN>last string

-- 
	Viktor.

---

From: Warren Kumari <[email-masked]>
Date: Mon, 16 Apr 2018 14:24:33 -0400

>         <len1>first string<len2>second string...<lenN>last string

Ah, you mean basically do what RFC4408, S 3.1.3 says? I *completely*
didn't understand that from the above... I still think that it would
be useful to have an example of multiple strings which meet the above
(preferably in "zone file" format) but I'll accept that I was just
being dumb and clear my DISCUSS.

W

-- 
I don't think the execution is relevant when it was obviously a bad
idea in the first place.
This is like putting rabid weasels in your pants, and later expressing
regret at having chosen those particular rabid weasels and that pair
of pants.
   ---maf

---

From: Viktor Dukhovni <[email-masked]>
Date: Mon, 16 Apr 2018 14:39:43 -0400

> On Apr 16, 2018, at 2:24 PM, Warren Kumari <[email-masked]> wrote:
> 

Yes, but I'm not an author, that's just how I read that text,
so I'll let the authors confirm.  Perhaps a reference to:

   https://tools.ietf.org/html/rfc4408#section-3.1.3

i,e. "Section 3.1.3 of rfc4408" would help other readers.

-- 
	Viktor.

---

From: Binu Ramakrishnan <[email-masked]>
Date: Wed, 18 Apr 2018 21:12:22 -0700

Confirmed, and updated the doc with the RFC reference.

---

From: Warren Kumari <[email-masked]>
Date: Thu, 19 Apr 2018 09:45:15 -0400

> Confirmed, and updated the doc with the RFC reference.

Awesome, thanks!

W