[cabfpub] Ballot 187 - Make CAA Checking Mandatory

Gervase Markham gerv at mozilla.org
Fri Mar 3 02:18:18 MST 2017

On 03/03/17 02:06, Dean Coclin wrote:

> Hi Gerv,
> Did you already publish a revised ballot somewhere? I recall seeing the original ballot but not a revised one. It would be helpful just to have a full, final ballot.

I did not, as the change was so minor. But your wish is my command :-)


*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

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.


Add the following text as a new section (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.


The procedure for approval of this Final Maintenance Guideline ballot is
as follows:



Status: Maintenance Guideline


Start time (22:00 UTC)


End time (22:00 UTC)

Discussion (7 to 14 calendar days)





Vote for approval (7 calendar days)





If vote approves ballot: Review Period (Chair to send Review Notice) (30
calendar days). 

If Exclusion Notice(s) filed, ballot approval is rescinded and PAG to be

If no Exclusion Notices filed, ballot becomes effective at end of Review


Upon filing of Review Notice by Chair


30 days after filing of Review Notice by Chair


>From Section 2.3 of the Bylaws: If the Draft Guideline Ballot is
proposing a Final Maintenance Guideline, such ballot will include a
redline or comparison showing the set of changes from the Final
Guideline section(s) intended to become a Final Maintenance Guideline,
and need not include a copy of the full set of guidelines.  Such redline
or comparison shall be made against the Final Guideline section(s) as
they exist at the time a ballot is proposed, and need not take into
consideration other ballots that may be proposed subsequently, except as
provided in Section 2.3(j) of the Bylaws.


Votes must be cast by posting an on-list reply to this thread on the
Public Mail List.  A vote in favor of the motion must indicate a clear
“yes” in the response. A vote against must indicate a clear “no” in the
response. A vote to abstain must indicate a clear “abstain” in the
response. Unclear responses will not be counted. The latest vote
received from any representative of a voting member before the close of
the voting period will be counted. Voting members are listed here:

In order for the motion to be adopted, two thirds (2/3) or more of the
votes cast by members in the CA category and greater than 50% of the
votes cast by members in the browser category must vote “yes”.  Quorum
is shown on CA/Browser Forum wiki.  Under Section 2.2(g) of the Bylaws,
at least the required quorum number of voting members must participate
in the ballot for the ballot to be valid, either by voting in favor,
voting against, or abstaining.
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