[cabfpub] Draft CAA motion (3)

Bruce Morton Bruce.Morton at entrustdatacard.com
Thu Jan 12 18:28:16 UTC 2017

Hi Gerv,

Thanks for pulling this together and addressing Jody’s request as I also see this helping with enterprise CAs. I do have some feedback.

There needs to be some consideration for existing agreements with Subscribers. In these cases the Subscriber may have a Certificate Approver or an Enterprise RA who have been allowed by the EV and BRs to approve the issuance of certificates. I was trying to resolve this by using the Enterprise RA which is already a defined term in the BRs. We should discuss some alternative to not remove permissions which have already been granted. Perhaps we could have an exception for one or more of these cases:

·        Only OV and EV certificates as authorization communication is required

·        Contractual relationship with a Subscriber which allows for an Enterprise RA or Certificate Approver

·        Contractual relation with a Subscriber for 1 year or more

I know there was some discussion about caching. I do think that 1 hour may be a period which is too short. For instance it does not address the case where a CA issues a certificate manually from a secure room/secure server. In these cases, the server will not be able to evaluate a CAA record. I think that this should be raised to 24 hours.

The effective time of 6 months may be too short. For many CAs, they will just start to deploy based on the new ballot. In this case with technical requirements which will impact the issuance of certificates, there should be more time allowed to ensure CAA is deployed effectively. I propose 12 months after the voting period ends.

Would be great to get some input from other CAs.

Thanks, Bruce.

From: Public [mailto:public-bounces at cabforum.org] On Behalf Of Gervase Markham via Public
Sent: Thursday, January 12, 2017 9:25 AM
To: CABFPub <public at cabforum.org>
Cc: Gervase Markham <gerv at mozilla.org>
Subject: [cabfpub] Draft CAA motion (3)

Hi everyone,

As we are trying to get ballots ready for when the ballot reforms are done, here's a third version of the draft motion to make CAA mandatory. Changes over version 2 are:

* Add a further exception: "CAA checking is optional if the domain's DNS is operated by the CA or an Affiliate."

This is an attempt to help Jody with his request to not have to check Microsoft's domains, while recognising that one part of the CA asking another part of the CA to set some DNS records so it can check them isn't really pointful.

One change I am not making is that I am not persuaded that there are compelling technical or business reasons to provide carve-outs for enterprise or other accounts. Providing such carve-outs changes CAA from "site policy" to "CA policy", and opens up loopholes which could be used by CAs to not do CAA on occasions where it would be appropriate. I feel the big benefit of CAA for sites is that it allows them to control issuance by all CAs (especially those with which they do not have a relationship) in a way which has not been possible before, and I'm keen to preserve that benefit. While I admit I have limited control over this, I'm also keen to encourage CAs to implement CAA in way which is hard or impossible for CA issuance staff to override, and if there are reasons they regularly need to override it, CAs obviously won't do that.

There are lots of ways a site owner can totally break their site by changing their DNS. Adding "adds an adverse CAA record in a situation where they need quick issuance" to that list doesn't, to my mind, change the risk profile significantly. Of course, the motion requires CAs to document problems encountered so if this analysis proves wrong, they will be able to provide evidence.

I am now seeking endorsers for this motion.

Would anyone like to suggest the appropriate section of the BRs to which the first section of text should be added?

The proposal is that the effective date of this change (written into the new section 2.2) should be six months after the voting period ends. I am proposing six months rather than three because it requires a reasonable amount of development work within a CA's infrastructure.


Ballot XXX - Make CAA Checking Mandatory

The following motion has been proposed by Gervase Markham of Mozilla and endorsed by XXX of XXX and XXX of XXX:

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 consequence, 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 one or two uncommon 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 to section XXX ("XXX") of the Baseline Requirements:
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 1 hour, whichever is greater.

This stipulation does not prevent the CA from checking CAA records at other points in the issuance process.

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 issuances that were prevented by an adverse CAA record in sufficient detail to provide feedback to the CAB Forum on the circumstances, and SHOULD report such 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 XXX, 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 review period for this ballot shall commence at 2200 UTC on XXX, and will close at 2200 UTC on XXX. Unless the motion is withdrawn during the review period, the voting period will start immediately thereafter and will close at XXX. Votes must be cast by posting an on-list reply to this thread.

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: https://cabforum.org/members/
In order for the motion to be adopted, two thirds 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 be in favor. Quorum is currently XXX members – at least that many members must participate in the ballot, either by voting in favor, voting against, or abstaining.
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