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Re: [Uta] Benjamin Kaduk's Discuss on draft-ietf-uta-smtp-require-tls-08: (with DISCUSS and COMMENT)

Viktor Dukhovni <ietf-dane@dukhovni.org> Wed, 31 July 2019 09:08 UTC

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Subject: Re: [Uta] Benjamin Kaduk's Discuss on draft-ietf-uta-smtp-require-tls-08: (with DISCUSS and COMMENT)
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On Tue, Jul 30, 2019 at 11:16:25PM -0700, Jim Fenton wrote:

> The RFC 7672 definition of Reference Identifier includes the CN-ID, so it
> would be more consistent to include it when referencing 6125 as well.

For the record, RFC7672 has aged a bit since ~2014 when most of it
was written, so at some point support for CN-ID could be reconsidered.

In that light, I took a look at the certificates currently live on
MX hosts found by the DANE survey, and of 854 certificates on MX
hosts that use DANE-TA records (for which name checks are in scope)
22 have CN-ID and no SAN.  That may be too high a rate to pull the
plug just yet. :-(

One notable example is the state of Bavaria:

  bayern.de. IN MX 10 mail.bayern.de. ; NoError AD=1
  _25._tcp.mail.bayern.de. IN TLSA 2 0 1 32a2bc1d515cdbc412b62b47a1cccf2bb1b8e3ef309f982458d3a7c61797422a ; NoError AD=1
      cert sha256 [matched] <- 2 0 1 32a2bc1d515cdbc412b62b47a1cccf2bb1b8e3ef309f982458d3a7c61797422a
      cert sha256 [matched] <- 2 0 1 32a2bc1d515cdbc412b62b47a1cccf2bb1b8e3ef309f982458d3a7c61797422a

which sports a V1 cert (no extensions, hence no SANs).  The issuer
looks like a private CA:

  C = DE
  ST = Bayern
  O = Freistaat Bayern
  CN = Bayerische DANE-CA

-- 
	Viktor.

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