[cabfpub] Start of Review Period for Ballot 187 - Make CAA Checking Mandatory

Wed Mar 8 22:00:54 UTC 2017

NOTICE OF REVIEW PERIOD

This Review Notice is sent pursuant to Section 4.1 of the CA/Browser Forum’s Intellectual Property Rights Policy (v1.2).  This Review Period is for Final Maintenance Guidelines (30 day Review Period).  A complete draft of the Draft Guideline that is the subject of this Review Notice is attached below.

Date Review Notice Sent:        March 8, 2017

Ballot for Review:                    Ballot 187 – Make CAA Checking Mandatory

Start of Review Period:           March 8, 2017 at 22:00 UTC

End of Review Period:             April 7, 2017 at 22:00 UTC

Please forward any Exclusion Notice relating to Essential Claims to the Chair by email to kirk.hall at entrustdatacard.com<mailto:kirk.hall at entrustdatacard.com> before the end of the Review Period.  See current version of CA/Browser Forum Intellectual Property Rights Policy for details.

Ballot 187 v2 - Make CAA Checking Mandatory

The following motion has been proposed by Gervase Markham of Mozilla and endorsed by Jeremy Rowley of DigiCert and Ryan Sleevi of Google:

Statement of Intent
Certificate Authority Authorization (CAA) is a DNS Resource Record defined in RFC 6844 - https://datatracker.ietf.org/doc/rfc6844/ , published in January 2013. It allows a DNS domain name holder to specify one or more Certification Authorities (CAs) authorized to issue certificates for that domain and, by implication, that no other CAs are authorized.

The intent of this motion is to make it mandatory for CAs to check CAA records at issuance time for all certificates issued (except in a few special cases), and to prevent issuance if a CAA record is found which does not permit issuance by that CA. This therefore allows domain owners to set an issuance policy which will be respected by all publicly-trusted CAs, and allows them to mitigate the problem that the public CA trust system is only as strong as its weakest CA.

Note that CAA is already a defined term in the BRs and so does not need definitional text to be provided by this motion.

-- MOTION BEGINS --
Add the following text as a new section 3.2.2.8 (titled "CAA Records") of the Baseline Requirements:
This section is effective as of 8 September 2017.

As part of the issuance process, the CA must check for a CAA record for each dNSName in the subjectAltName extension of the certificate to be issued, according to the procedure in RFC 6844, following the processing instructions set down in RFC 6844 for any records found. If the CA issues, they must do so within the TTL of the CAA record, or 8 hours, whichever is greater.

This stipulation does not prevent the CA from checking CAA records at any other time.
When processing CAA records, CAs MUST process the issue, issuewild, and iodef property tags as specified in RFC 6844. Additional property tags MAY be supported, but MUST NOT conflict with or supersede the mandatory property tags set out in this document. CAs MUST respect the critical flag and reject any unrecognized properties with this flag set.

RFC 6844 requires that CAs "MUST NOT issue a certificate unless either (1) the certificate request is consistent with the applicable CAA Resource Record set or (2) an exception specified in the relevant Certificate Policy or Certification Practices Statement applies." For issuances conforming to these Baseline Requirements, CAs MUST NOT rely on any exceptions specified in their CP or CPS unless they are one of the following:

  *   CAA checking is optional for certificates for which a Certificate Transparency pre-certificate was created and logged in at least two public logs, and for which CAA was checked.
  *   CAA checking is optional for certificates issued by an Technically Constrained Subordinate CA Certificate as set out in Baseline Requirements section 7.1.5, where the lack of CAA checking is an explicit contractual provision in the contract with the Applicant.
  *   CAA checking is optional if the CA or an Affiliate of the CA is the DNS Operator (as defined in RFC 7719<https://tools.ietf.org/html/rfc7719>) of the domain's DNS.
CAs are permitted to treat a record lookup failure as permission to issue if:

  *   the failure is outside the CA's infrastructure;
  *   the lookup has been retried at least once; and
  *   the domain's zone does not have a DNSSEC validation chain to the ICANN root.
CAs MUST document potential issuances that were prevented by a CAA record in sufficient detail to provide feedback to the CAB Forum on the circumstances, and SHOULD dispatch reports of such issuance requests to the contact(s) stipulated in the CAA iodef record(s), if present. CAs are not expected to support URL schemes in the iodef record other than mailto: or https:.
Update section 2.2 ("Publication of Information") of the Baseline Requirements, to remove the following text:

    Effective as of 15 April 2015, section 4.2 of a CA's Certificate Policy and/or Certification

    Practice Statement (section 4.1 for CAs still conforming to RFC 2527) SHALL state whether

    the CA reviews CAA Records, and if so, the CA’s policy or practice on processing CAA Records

    for Fully Qualified Domain Names. The CA SHALL log all actions taken, if any, consistent with

    its processing practice.
and replace it with:

    Effective as of 8 September 2017, section 4.2 of a CA's Certificate Policy and/or Certification

    Practice Statement (section 4.1 for CAs still conforming to RFC 2527) SHALL state the CA’s policy or

    practice on processing CAA Records for Fully Qualified Domain Names; that policy shall be consistent

    with these Requirements. It shall clearly specify the set of Issuer Domain Names that the CA

    recognises in CAA "issue" or "issuewild" records as permitting it to issue. The CA SHALL log all actions

    taken, if any, consistent with its processing practice.

Add the following text to the appropriate place in section 1.6.3 ("References"):
RFC6844, Request for Comments: 6844, DNS Certification Authority Authorization (CAA) Resource Record, Hallam-Baker, Stradling, January 2013.
-- MOTION ENDS --

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