[cabfpub] Voting has started on Ballot 214 - CAA Discovery CNAME Errata

Tim Hollebeek THollebeek at trustwave.com
Mon Sep 25 19:23:59 UTC 2017 

While it is possible to implement an algorithm which is simultaneously compliant with RFC 6844 and RFC 6844 + erratum 5065, the algorithm specified in RFC 6844 is *not* that algorithm.  Erratum 5065 is a breaking change.  RFC 6844 shortcuts tree-climbing when it encounters CNAME records; erratum 5065 does not.  An algorithm that attempts to comply with both RFCs at the same time is significantly more complicated than either algorithm alone, and has not undergone as much public vetting.

So while it’s possible for CAs to implement a new dual-compliant algorithm, push it out before the deadline, and then transition again to RFC 6844 + erratum 5065 after that, that isn’t what everyone voted for.  The requirement voted on and agreed to in March was RFC 6844 compliance.  Doing so would unnecessarily force some CAs to either change their algorithm twice, or make the transition on a very specific day, instead of just transitioning from a faithful and correct implementation of RFC 6844 to a faithful and correct implementation of RFC 6844 + erratum 5065.

What makes much more sense is to allow CAs to migrate from the current situation to where we want them to be within a reasonable timeline.  That’s what the replacement ballot does, and it’s the better solution.

-Tim


From: Public [mailto:public-bounces at cabforum.org] On Behalf Of Tim Hollebeek via Public
Sent: Monday, September 25, 2017 9:33 AM
To: Jacob Hoffman-Andrews <jsha at letsencrypt.org>; CA/Browser Forum Public Discussion List <public at cabforum.org>; Doug Beattie <doug.beattie at globalsign.com>
Subject: Re: [cabfpub] Voting has started on Ballot 214 - CAA Discovery CNAME Errata

This requires a third implementation that many CAs probably do not have ready or tested.

From: Public [mailto:public-bounces at cabforum.org] On Behalf Of Jacob Hoffman-Andrews via Public
Sent: Friday, September 22, 2017 5:04 PM
To: Doug Beattie <doug.beattie at globalsign.com<mailto:doug.beattie at globalsign.com>>; CA/Browser Forum Public Discussion List <public at cabforum.org<mailto:public at cabforum.org>>
Subject: Re: [cabfpub] Voting has started on Ballot 214 - CAA Discovery CNAME Errata

I believe a transition period is not necessary, because it's entirely possible to operate the RFC 6844 algorithm and the RFC 6844 + erratum 5065 algorithm in tandem, without significantly impacting issuance.

The lookups done under erratum 5065 are a strict subset of those done under RFC 6844, so in the common case where there is no CAA record present, any RFC 6844 implementation is also compliant with erratum 5065.

The only situation where they conflict is when there is a CAA record permitting issuance on the parent of a CNAME involved in CAA lookup, but a different CAA record allowing issuance on a direct parent of the domain being validated. The simple way to handle a transition while being assured of compliance is to block issuance if either RFC 6844 or erratum 5065 says to block issuance. Due to the rarity of this scenario, this should not decrease successful issuance rates.

Given that a transition period isn't necessary, I think it would be a mistake to delay the ballot to add it in. There are clear problems with RFC 6844 that are causing live problems for many CA subscribers. The solutions have been known and agreed upon since March. Let's not delay them any further.

On Fri, Sep 22, 2017 at 10:15 AM, Doug Beattie via Public <public at cabforum.org<mailto:public at cabforum.org>> wrote:
In light of recent discussions about a phase in period, GlobalSign changes their vote to NO for Ballot 214.

From: Doug Beattie
Sent: Thursday, September 21, 2017 7:34 AM
To: 'CA/Browser Forum Public Discussion List' <public at cabforum.org<mailto:public at cabforum.org>>
Subject: RE: [cabfpub] Voting has started on Ballot 214 - CAA Discovery CNAME Errata

GlobalSign votes YES


From: Public [mailto:public-bounces at cabforum.org<mailto:public-bounces at cabforum.org>] On Behalf Of Kirk Hall via Public
Sent: Wednesday, September 20, 2017 8:56 PM
To: CA/Browser Forum Public Discussion List <public at cabforum.org<mailto:public at cabforum.org>>
Subject: Re: [cabfpub] Voting has started on Ballot 214 - CAA Discovery CNAME Errata

Correcting subject line to Ballot 214

From: Kirk Hall
Sent: Wednesday, September 20, 2017 5:55 PM
To: CA/Browser Forum Public Discussion List <public at cabforum.org<mailto:public at cabforum.org>>
Subject: Voting has started on Ballot 21 - CAA Discovery CNAME Errata

Voting has started on Ballot 214 – CAA Discovery CNAME Errata.

Technically, the Discussion period ended at 22:00 UTC today (which was 3:00 pm Pacific Time).  Josh, as the Proposer of the Ballot, accepted Gerv and Tim’s email suggestion as to a 3-month transition period, but this acceptance occurred at 5:05 pm Pacific Time, two hours after the end of the discussion period.  Also, we don’t have specific amendment language to consider, only a concept.

Regrettably, I think it’s too late for this transition period amendment, so we are voting on Ballot 214 as originally proposed (see below).  If there is a need for a transition period, I think it’s best if it’s proposed by a separate ballot with specific language.


From: Public [mailto:public-bounces at cabforum.org] On Behalf Of Jacob Hoffman-Andrews via Public
Sent: Wednesday, September 13, 2017 2:31 PM
To: CABFPub <public at cabforum.org<mailto:public at cabforum.org>>
Subject: [EXTERNAL][cabfpub] Ballot 214: CAA Discovery CNAME Errata

Kicking off the official discussion period for ballot 214 today per discussion with Phillip.

The following motion has been proposed by Phillip Hallam-Baker of Comodo Group Inc. and endorsed by Gervase Markham of Mozilla and Mads Egil Henriksveen of Buypass.

-- MOTION BEGINS --

In the Baseline Requirements v1.4.9 Section 3.2.2.8. CAA Records

Strike:

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.

Replace with:

As part of the issuance process, the CA MUST check for CAA records and follow the processing instructions for any records found, for each dNSName in the subjectAltName extension of the certificate to be issued, as specified in RFC 6844 as amended by Errata 5065 (Appendix A). If the CA issues, they MUST do so within the TTL of the CAA record, or 8 hours, whichever is greater.


In the Baseline Requirements ADD an Appendix A that reads:

Appendix A -- RFC6844 Errata 5065

The following errata report has been held for document update for RFC6844, "DNS Certification Authority Authorization (CAA) Resource Record".

--------------------------------------
You may review the report below and at:
http://www.rfc-editor.org/errata/eid5065<http://scanmail.trustwave.com/?c=4062&d=3oXJ2ZQg_1yHx8aUFsbb76X_TrvjCb4TzvMdP2t74w&s=5&u=http%3a%2f%2fwww%2erfc-editor%2eorg%2ferrata%2feid5065>

--------------------------------------
Status: Held for Document Update
Type: Technical

Reported by: Phillip Hallam-Baker <philliph at comodo.com<mailto:philliph at comodo.com>> Date Reported: 2017-07-10 Held by: EKR (IESG)

Section: 4

Original Text
-------------
   Let CAA(X) be the record set returned in response to performing a CAA
   record query on the label X, P(X) be the DNS label immediately above
   X in the DNS hierarchy, and A(X) be the target of a CNAME or DNAME
   alias record specified at the label X.

   o  If CAA(X) is not empty, R(X) = CAA (X), otherwise

   o  If A(X) is not null, and R(A(X)) is not empty, then R(X) =
      R(A(X)), otherwise

   o  If X is not a top-level domain, then R(X) = R(P(X)), otherwise

   o  R(X) is empty.

Corrected Text
--------------
   Let CAA(X) be the record set returned in response to performing a CAA
   record query on the label X, P(X) be the DNS label immediately above
   X in the DNS hierarchy, and A(X) be the target of a CNAME or DNAME
   alias record chain specified at the label X.

   o  If CAA(X) is not empty, R(X) = CAA (X), otherwise

   o  If A(X) is not null, and CAA(A(X)) is not empty, then R(X) =
      CAA(A(X)), otherwise

   o  If X is not a top-level domain, then R(X) = R(P(X)), otherwise

   o  R(X) is empty.

  Thus, when a search at node X returns a CNAME record, the CA will
  follow the CNAME record chain to its target. If the target label
  contains a CAA record, it is returned.

  Otherwise, the CA continues the search at
  the parent of node X.

  Note that the search does not include the parent of a target of a
  CNAME record (except when the CNAME points back to its own path).

  To prevent resource exhaustion attacks, CAs SHOULD limit the length of
  CNAME chains that are accepted. However CAs MUST process CNAME
  chains that contain 8 or fewer CNAME records.

--Motion Ends--

The procedure for approval of this Final Maintenance Guideline ballot is as follows (exact start and end times may be adjusted to comply with applicable Bylaws and IPR Agreement):

BALLOT 214 Status:   Final Maintenance Guideline    Start time (22:00 UTC)    End time (22:00 UTC)

Discussion begins now and ends September 20, 2017 22:00 UTC (7 days)

Vote for approval begins September 20, 2017 22:00 UTC and ends September 27, 2017 22:00 UTC (7 days)

If vote approves ballot: Review Period (Chair to send Review Notice) (30 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 Bylaw 2.3: 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 Bylaw Section 2.3(j).

Votes must be cast by posting an on-list reply to this thread on the Public 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: https://cabforum.org/members/<https://scanmail.trustwave.com/?c=4062&d=3oXJ2ZQg_1yHx8aUFsbb76X_TrvjCb4TzvIQZ24r5A&s=5&u=https%3a%2f%2fcabforum%2eorg%2fmembers%2f>

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 shown on CA/Browser Forum wiki. Under Bylaw 2.2(g), at least the required quorum number must participate in the ballot for the ballot to be valid, either by voting in favor, voting against, or abstaining.

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