[cabfpub] "[UNVERIFIED SENDER]Re: no CAA authorizations -- RFC 6844

Thu Jun 22 19:31:43 UTC 2017

It is not clear which of us you are responding to.

Let us consider the case proposed:

*	Domain example.com has an issue entry for CA alice.com but no
issuewild
*	Certificate requested for *.example.com from bob.com

So section 5.3 does not apply. There is no issuewild to take priority. 

The request has a wildcard so the requirement to ignore issuewild records
for a non wildcard does not apply.

No issuewild properties are specified. So the second part does not apply.

From: Peter Bowen [mailto:pzb at amzn.com] 
Sent: Thursday, June 22, 2017 2:59 PM
To: Phillip <philliph at comodo.com>; CA/Browser Forum Public Discussion List
<public at cabforum.org>
Cc: ekr at rtfm.com; kathleen.moriarty.ietf at gmail.com
Subject: Re: "[UNVERIFIED SENDER]Re: [cabfpub] no CAA authorizations -- RFC
6844

I believe that this is a misreading, based on section 5.3:

 <https://tools.ietf.org/html/rfc6844#section-5.3> 5.3.  CAA issuewild
Property

   The issuewild property has the same syntax and semantics as the issue
   property except that issuewild properties only grant authorization to
   issue certificates that specify a wildcard domain and issuewild
   properties take precedence over issue properties when specified.
   Specifically:

      issuewild properties MUST be ignored when processing a request for
      a domain that is not a wildcard domain.

      If at least one issuewild property is specified in the relevant
      CAA record set, all issue properties MUST be ignored when
      processing a request for a domain that is a wildcard domain.

This makes it clear that issue property applies when a wildcard domain is
processed unless there is an issuewild property.

Thanks,

Peter

On Jun 22, 2017, at 11:46 AM, Phillip via Public <public at cabforum.org
<mailto:public at cabforum.org> > wrote:

It is my understanding that the text as drafted prohibits issue of a
wildcard certificate if the record set only contains issue records and issue
of a non wildcard certificate if the record set only contains issuewild
records.

My reasoning is as follows:

The relevant parts of the specification are:

4.  Certification Authority Processing

  Before issuing a certificate, a compliant CA MUST check for
  publication of a relevant CAA Resource Record set.  If such a record
  set exists, a CA MUST NOT issue a certificate unless the CA
  determines that 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.

  A certificate request MAY specify more than one domain name and MAY
  specify wildcard domains.  Issuers MUST verify authorization for all
  the domains and wildcard domains specified in the request.

3.  The CAA RR Type

  issue <Issuer Domain Name> [; <name>=<value> ]* :  The issue property
     entry authorizes the holder of the domain name <Issuer Domain
     Name> or a party acting under the explicit authority of the holder
     of that domain name to issue certificates for the domain in which
     the property is published.

  issuewild <Issuer Domain Name> [; <name>=<value> ]* :  The issuewild
     property entry authorizes the holder of the domain name <Issuer
     Domain Name> or a party acting under the explicit authority of the
     holder of that domain name to issue wildcard certificates for the
     domain in which the property is published.

Section 4 specifies that the CA MUST NOT issue a certificate unless... 'is
consistent'

If we were to interpret 'is consistent' as meaning that the absence of an
authorization record implies authorization than the whole specification
becomes meaningless. The argument made that silence on issue permits
issuewild would apply just as well to issue. 

Proposed resolution:

I do not believe that the text as written is ambiguous. However, 'out of an
abundance of caution and to eliminate any possible doubt, I propose an
errata to read as follows:

Existing text

4.  Certification Authority Processing

  Before issuing a certificate, a compliant CA MUST check for
  publication of a relevant CAA Resource Record set.  If such a record
  set exists, a CA MUST NOT issue a certificate unless the CA
  determines that 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.

Replacement text

4.  Certification Authority Processing

  Before issuing a certificate, a compliant CA MUST check for
  publication of a relevant CAA Resource Record set.  If such a record
  set exists, a CA MUST NOT issue a certificate unless the CA
  determines that either (1) the certificate request is consistent with
  and explicitly authorized by the applicable CAA Resource Record 
  set or (2) an exception specified in the relevant Certificate Policy 
  or Certification Practices Statement applies.

-----Original Message-----
From: Public [mailto:public-bounces at cabforum.org] On Behalf Of philliph---
via Public
Sent: Thursday, June 22, 2017 10:47 AM
To: Gervase Markham <gerv at mozilla.org <mailto:gerv at mozilla.org> >;
CA/Browser Forum Public Discussion
List <public at cabforum.org <mailto:public at cabforum.org> >
Subject: Re: [cabfpub] no CAA authorizations -- RFC 6844

It was certainly the intention that presence of an issue prevents issue of
wildcard certs.

I will re-read that section and report.

Meanwhile, I have had some comment on the discovery fixup and will rev that.

On Jun 22, 2017, at 8:34 AM, Gervase Markham via Public

<public at cabforum.org <mailto:public at cabforum.org> > wrote:

On 22/06/17 06:42, y-iida--- via Public wrote:

<C> Likewise, when there are some relevant CAA records, but no CAA 
with "issuewild" property tag at all for a certificate domain, we 
will issue wildcard certificate for that domain.

You should read RFC6844 carefully, but to my understanding, this is 
incorrect. If there is an "issue" property but no "issuewild" 
property, then the "issue" property also controls the issuance of wildcard

certs.

So you need to respect it in that case.

Gerv

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