Hello,
This development is exciting work in regard to allowing domain owners to limit 
which validation methods they want to allow to be used for their domains.

Unfortunately, the validation-methods extension is not compliant with RFC 6844 
(the CAA RFC), as parameter tags cannot contain hyphens.  This was originally 
pointed out on this mailing list in January 
(https://www.ietf.org/mail-archive/web/acme/current/msg02506.html). I proposed 
a fix to this issue (as well as fixing an ambiguity in the ABNF grammar in 
regard to parameter delimiters) on the LAMPS WG mailing list a few months ago 
(https://www.ietf.org/mail-archive/web/spasm/current/msg01144.html), but this 
change has not yet been incorporated into a draft of RFC 6844-bis.

Since RFC 6844 dictates that parameters have meaning specific to the issuer 
(from section 5.1: “The semantics of issuer-parameters are determined by the 
issuer alone”), I don’t believe that issuing certificates for domains whose CAA 
record sets contain non-conformant parameter syntax would constitute 
mis-issuance. However, it may present difficulties in regard to 
tooling/automation that expect all parameter tags to follow RFC 6844.

Thanks,

Corey Bonnell
Senior Software Engineer

Trustwave | SMART SECURITY ON DEMAND
www.trustwave.com<http://www.trustwave.com/>

From: Acme <[email protected]> on behalf of Daniel McCarney 
<[email protected]>
Reply-To: "[email protected]" <[email protected]>
Date: Wednesday, May 30, 2018 at 1:57 PM
To: Hugo Landau <[email protected]>, IETF ACME <[email protected]>
Subject: [Acme] Let's Encrypt ACME-CAA validation-methods support

Hi folks,

I'm happy to share that Let's Encrypt has deployed support for Hugo Landau's 
ACME-CAA "validation-methods" CAA record extension in the staging 
environment[0]. Community feedback/review would be most appreciated.

You can find more information in the associated API announcement[1].

Thanks,

- Daniel / cpu
[0] - 
https://letsencrypt.org/docs/staging-environment/<https://scanmail.trustwave.com/?c=4062&d=k-aO27uBtMDYKMre1tiXIgJYkioPrIC1cToq5JsZWQ&s=5&u=https%3a%2f%2fletsencrypt%2eorg%2fdocs%2fstaging-environment%2f>
[1] - 
https://community.letsencrypt.org/t/acme-caa-validation-methods-support/63125<https://scanmail.trustwave.com/?c=4062&d=k-aO27uBtMDYKMre1tiXIgJYkioPrIC1cWBx5cxLDw&s=5&u=https%3a%2f%2fcommunity%2eletsencrypt%2eorg%2ft%2facme-caa-validation-methods-support%2f63125>
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