[cabfpub] Ballot 187 - Make CAA Checking Mandatory
jimmy at it.auth.gr
Thu Feb 23 17:36:44 UTC 2017
Just a short comment on the following statement:
"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".
As we have discussed several times, Certificates are not issued by
Certificates so it would be more accurate to re-use some language of the
BRs around TC SubCAs and say:
"CAA checking is optional for certificates issued by a Technically
Constrained Subordinate CA in line with Section 7.1.5, where the lack of
CAA checking is an explicit contractual provision in the contract with
I am also not sure how "the domain's zone does not have a DNSSEC
validation chain to the ICANN root" comes into play. I went through the
cabforum archive and found some discussions about how DNSSEC affects
CAA. I suppose more reading is in order but if anyone could provide some
background and how it is expected to be implemented, it would be
helpful. I guess my ignorant questions is, what happens if a domain does
not use DNSSEC (which applies for most domains out there) that chain to
an ICANN root? CAA fails and automatically grants permission for issuance?
On 22/2/2017 11:34 μμ, Gervase Markham via Public wrote:
> Hi everyone,
> This ballot is now entering its seven-day discussion period. My
> sincere thanks to everyone who helped shape the text into what it is
> Changes from draft 3:
> * 1 hour changed to 8 hours as minimum caching time, to make manual
> issuance easier.
> * Added text from Ryan, at Doug's suggestion, of exactly which
> properties need to be supported.
> * Marked Jeremy and Ryan as endorsers (assuming they don't object to
> the above changes).
> *Ballot 187 - 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 126.96.36.199 (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 domain's DNS is operated by
> the CA or an Affiliate of the CA.
> 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 --
> The procedure for approval of this Final Maintenance Guideline ballot
> is as follows:
> BALLOT 187
> 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 created.
> If no Exclusion Notices filed, ballot becomes effective at end of
> Review Period.
> 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,
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> subsequently, except as provided in Section 2.3(j) of the Bylaws.
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