Re: [Acme] CAA in draft-ietf-acme-client-01.txt

Kathleen Moriarty <> Tue, 28 July 2020 14:57 UTC

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From: Kathleen Moriarty <>
Date: Tue, 28 Jul 2020 10:56:45 -0400
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To: Carl Mehner <>
Cc: IETF ACME <>, "Moriarty, Kathleen" <>
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Subject: Re: [Acme] CAA in draft-ietf-acme-client-01.txt
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Hello Carl,

Thank you for your review and I apologize for my extremely tardy response.

On Mon, May 18, 2020 at 11:41 AM Carl Mehner <> wrote:

> Looking at the latest draft for acme-client, I noticed that it mentions
> CAA:
>    CAA helps as anyone verifying a certificate used for code signing can
>    verify that the CA used has been authorized to issue certificates for
>    that organization.
> However, in the CAA RFC it states:
>    Relying Applications MUST
>    NOT use CAA records as part of certificate validation.
> I propose removing the statement in acme-client about CAA that is quoted
> above.

I recall having gone through this conversation before to wind up where the
draft is now.  RFC8555 has the following:

      caaIdentities (optional, array of string):  The hostnames that the
      ACME server recognizes as referring to itself for the purposes of
      CAA record validation as defined in [RFC6844
<>].  Each string MUST
      represent the same sequence of ASCII code points that the server
      will expect to see as the "Issuer Domain Name" in a CAA issue or
      issuewild property tag.  This allows clients to determine the
      correct issuer domain name to use when configuring CAA records.

 Section 9.7.8 has the following:

   Validation methods do not have to be compatible with ACME in order to

   be registered.  For example, a CA might wish to register a validation
   method to support its use with the ACME extensions to CAA [ACME-CAA

Section 11.2 has the following:

   An ACME-based CA must only use a resolver if it trusts the resolver
   and every component of the network route by which it is accessed.
   Therefore, it is RECOMMENDED that ACME-based CAs operate their own
   DNSSEC-validating resolvers within their trusted network and use
   these resolvers both for CAA record lookups and all record lookups in

       furtherance of a challenge scheme (A, AAAA, TXT, etc.).

As you point out,, advises against its

I am happy to edit to consensus.  If a change is needed, I can turn that
around quickly.

Best regards,

-carl mehner
> _______________________________________________
> Acme mailing list


Best regards,