You left out the fact that Bruce posted very similar text to the validation 
mailing list well before London.  This is not a new idea, and concrete 
proposals have been floating around for quite a while.  And nowhere in our 
Bylaws does it say that discussion periods can’t happen during IETF.  I think 
Devon and I were the only two relevant people there anyway.

 

It’s not a serious misrepresentation to say I was surprised, because I was in 
fact very surprised.  That’s an objective fact.  In fact I think your false 
accusation of a serious misrepresentation is a code of conduct violation.

 

You indicated that you were going to be unavailable for follow up, and that if 
I made the changes we discussed, you guys could support it.  I still have the 
paper right here on my desk with the notes.  I told you I was planning on doing 
exactly what I did, including the fact that I was planning on posting a ballot 
before I left for IETF, so there should have been no surprises there as far as 
the timing.  The only thing that didn’t happen as planned was the IETF draft, 
which I keep poking Tomofumi about and should be up soon.

 

Do you have concrete proposals for improvements that would allow you to support 
TXT?  Having it be phased out over time is actually something that has been 
explicitly discussed among the proposers.  And I’m not going to accept vague 
hand-waving about attacks.  If you guys have actual attack scenarios you want 
to discuss, post them for discussion and analysis.  We’re talking about someone 
who has the ability to modify DNS records for the domain being validated, after 
all.

 

I actually discussed the need for TXT records with several DNS experts at IETF. 
 They all agreed that it’s the only record type that actually works reliably, 
and while its ubiquity of use is undesirable, that’s the world we actually live 
in …

 

I would suggest that the more reasonable root programs vote in favor of this 
perfectly reasonable ballot.

 

-Tim

 

From: Ryan Sleevi <[email protected]> 
Sent: Monday, July 23, 2018 1:26 PM
To: Tim Hollebeek <[email protected]>; [email protected]
Cc: Devon O'Brien <[email protected]>; CABFPub <[email protected]>
Subject: Re: [Servercert-wg] Voting Begins: Ballot SC2 - version 2: Validating 
certificates via CAA CONTACT

 

Hi Tim,

 

The first message to the public/ list was 
https://cabforum.org/pipermail/public/2018-July/013678.html . As Ben can 
attest, there were some issues getting folks registered to the servercert-wg 
list - including all the Google representatives - but the first text of this 
ballot was proposed at 
https://cabforum.org/pipermail/servercert-wg/2018-July/000003.html

 

You're correct that we did have a fairly productive call on July 9, which lead 
to that improvement, but I'm having trouble finding earlier versions of your 
drafts that incorporated that feedback. As you also recall from these 
discussions, we raised concerns about supporting TXT at all, and indicated it 
would be challenging and require care. During those conversations, we 
highlighted similar concerns to what are expressed here - namely, that unlike 
special reservations like /.well-known/, TXT opens up new security risks that 
CAA expressions don't.

 

While you mention it having been discussed for several months, the only mention 
I can find for actual, concrete text - not just the idea of something - is 
https://cabforum.org/pipermail/validation/2018-July/000955.html - which Google 
raised a number of concerns with, resulting in our call, since these concerns 
had also been expressed during the Validation meeting in London as issues that 
would need to be addressed.

 

As mentioned - during London and during our phone call - this further 
normalizes a risk in which delegating the ability to create a TXT record 
effectively delegates control to issue certificates. As mentioned during those 
discussions, we acknowledge that 3.2.2.4.7 similarly suffers such a weakness - 
and that's been identified as a weakness of .7 for quite some time (as is the 
lack of the ability to specify and opt-in/opt-out of particular validation 
methods). However, introducing a new method should not rely on the existing 
weaknesses and ambiguities - we should work to do better.

 

We discussed several proposals for ways you could incorporate such within your 
ballot - ranging from requiring CAA to explicitly opt-in to such a method to 
requiring having a documented process for allowing TXT, treating it as an 
exception (similar to SHA-1), as it represents a legacy system which should be 
aggressively phased out within the CA ecosystem for more structured, less 
ambiguous representations.

 

As best I can tell, 
https://cabforum.org/pipermail/servercert-wg/2018-July/000003.html was posted a 
day after our conversation, with no feedback or follow-up from you regarding 
these concerns shared, and promptly moved straight to vote, even with the 
acknowledged concerns about the upcoming IETF delaying responses and review. In 
that regard, I think it's a serious misrepresentation to suggest that this is 
somehow surprising. As mentioned in the feedback, we tried to offer productive 
ways forward to allow some relief for CAs who found themselves relying on 
methods that are now impaired by the ICANN-EU discussions around GDPR and WHOIS 
- such as decoupling the CAA and TXT ballots - but I don't think it's at all 
reasonable to suggest we did not offer many ways in which these concerns could 
be addressed, or spend time trying to highlight these concerns in advance of 
pursuing a vote.

On Mon, Jul 23, 2018 at 11:11 AM Tim Hollebeek via Servercert-wg 
<[email protected] <mailto:[email protected]> > wrote:

This is very ironic, because the new “_caa_contact” label was added because 
Google requested it.

 

The proposal has been discussed for several months now, and as you are well 
aware, I made every effort to satisfy all of Google’s requests for improvements 
to the ballot, including a long phone conversation.

 

Please describe in detail the attacks on TXT records you envision, so that 
adequate safeguards can be added.

 

-Tim

 

From: Devon O'Brien <[email protected] <mailto:[email protected]> > 
Sent: Monday, July 23, 2018 1:00 AM
To: Tim Hollebeek <[email protected] 
<mailto:[email protected]> >; [email protected] 
<mailto:[email protected]> 
Cc: CA/Browser Forum Public Discussion List <[email protected] 
<mailto:[email protected]> >
Subject: Re: [Servercert-wg] Voting Begins: Ballot SC2 - version 2: Validating 
certificates via CAA CONTACT

 

Google votes NO

 

While supportive of efforts to offer CAs flexibility in light of ICANN policy 
changes, we're concerned that the amount of time to review concrete efforts to 
improve this has been limited. We do not feel confident in the security 
considerations of this method, in particular, the introduction of a new 
privileged label (_caa_contact) that does not have any pre-existing security 
advice surrounding it.

 

These concerns are due to the support of the TXT record, something which is 
also problematic in existing validation methods, but we don't feel confident 
that it is appropriate to introduce something 'insecure' and 'fix it later'. If 
this were scoped just to CAA, we believe it appropriate to ratify. Separate 
discussions on the necessity of TXT, when and how TXT is used in favor of CAA 
by CAs, and how site operators can secure themselves appropriately could all be 
used to develop an appropriate specification. Customers who wish to issue 
certificates this method can set CAA records, which may require work from their 
DNS provider to support standards from 6 years ago, but is still strictly an 
improvement over introducing known-insecure methods.

 

 

On Thu, Jul 19, 2018 at 11:02 AM Tim Hollebeek via Servercert-wg 
<[email protected] <mailto:[email protected]> > wrote:

 

Administrivia:

 

1.      This ballot is being cross-posted to the CABF public mailing in line 
with the consensus from last Thursday’s call that it is important everyone is 
aware of the ballot, and that not everyone is on the SCWG list yet.
2.      I promised an IETF independent stream draft for the same proposal, so 
it can get feedback from those at IETF.  I still intend to do so, but I am 
working with a colleague on setting up a github account for DigiCert IETF 
efforts to make it easier for others to collaborate with us on IETF 
submissions.  I anticipate we will have that set up and the draft submitted 
some time next week.  The IETF draft will allow IETF to review the method and 
make suggested improvements.  It should not block adoption of the current 
proposal by CABF.  DigiCert intends to submit a ballot to adopt IETF’s 
improvements once the IETF process is complete.

 

Ballot SC2: CAA Contact Property and Associated Validation Methods

Purpose of Ballot: Increasingly, contact information is not available in WHOIS 
due to concerns about potential GDPR violations.  This ballot specifies a 
method by which domain holders can publish their contact information via DNS, 
and how CAs can use that information for validating domain control.

The following motion has been proposed by Tim Hollebeek of DigiCert and 
endorsed by Bruce Morton of Entrust and Doug Beattie of GlobalSign.

--- MOTION BEGINS ---

This ballot modifies the “Baseline Requirements for the Issuance and Management 
of Publicly-Trusted Certificates” as follows, based on Version 1.5.7:

Add Section 3.2.2.4.13: Domain Owner Email published in DNS

Confirm the Applicant's control over the FQDN by (i) sending an email to a DNS 
domain name holder, (ii) including a Random Value in the email, and (iii) 
receiving a confirming response utilizing the Random Value. The CA MUST send 
the email to an email address found in the CAA Contact property record as 
defined in Appendix B.

 

Each email MAY confirm control of multiple FQDNs, provided the email address 
used is a DNS contact email address for each FQDN being confirmed. 

 

The Random Value SHALL be unique in each email. The email MAY be re-sent in its 
entirety, including the re-use of the Random Value, provided that its entire 
contents and recipient SHALL remain unchanged. The Random Value SHALL remain 
valid for use in a confirming response for no more than 30 days from its 
creation. The CPS MAY specify a shorter validity period for Random Values.

Note: Once the FQDN has been validated using this method, the CA MAY also issue 
Certificates for other FQDNs that end with all the labels of the validated 
FQDN. This method is suitable for validating Wildcard Domain Names.

Add Section 3.2.2.4.14: Domain Owner Phone published in DNS

 

Confirm the Applicant's control over the FQDN by calling the DNS domain name 
holder phone number and obtaining a response confirming the Applicant's request 
for validation of the FQDN. The CA MUST place the call to a phone number 
identified in the CAA Contact property record as defined in Appendix B.

 

Each phone call SHALL be made to a single number and MAY confirm control of 
multiple FQDNs, provided that the phone number is identified by the DNS contact 
as a valid contact method for every Base Domain Name being verified using the 
phone call.

Note: Once the FQDN has been validated using this method, the CA MAY also issue 
Certificates for other FQDNs that end with all the labels of the validated 
FQDN. This method is suitable for validating Wildcard Domain Names.

 

Add Section 3.2.2.4.15: Domain Owner Email published in TXT record

 

Confirm the Applicant's control over the FQDN by (i) sending an email to a DNS 
domain name holder, (ii) including a Random Value in the email, and (iii) 
receiving a confirming response utilizing the Random Value. The CA MUST send 
the email to an email address found in the DNS TXT record as defined in 
Appendix B.

 

Each email MAY confirm control of multiple FQDNs, provided the email address 
used is a DNS contact email address for each FQDN being confirmed. 

 

The Random Value SHALL be unique in each email. The email MAY be re-sent in its 
entirety, including the re-use of the Random Value, provided that its entire 
contents and recipient SHALL remain unchanged. The Random Value SHALL remain 
valid for use in a confirming response for no more than 30 days from its 
creation. The CPS MAY specify a shorter validity period for Random Values.

Note: Once the FQDN has been validated using this method, the CA MAY also issue 
Certificates for other FQDNs that end with all the labels of the validated 
FQDN. This method is suitable for validating Wildcard Domain Names.

 

##### 3.2.2.4.16 Domain Owner Phone published in TXT record

 

Confirm the Applicant's control over the FQDN by calling the DNS domain name 
holder phone number and obtaining a response confirming the Applicant's request 
for validation of the FQDN. The CA MUST place the call to a phone number 
identified in the DNS TXT record defined in Appendix B.

 

Each phone call SHALL be made to a single number and MAY confirm control of 
multiple FQDNs, provided that the phone number is identified by the DNS contact 
as a valid contact method for every Base Domain Name being verified using the 
phone call.

Note: Once the FQDN has been validated using this method, the CA MAY also issue 
Certificates for other FQDNs that end with all the labels of the validated 
FQDN. This method is suitable for validating Wildcard Domain Names.

Add Appendix B: CAA Contact Tag

The syntax for the contact property is similar to the iodef property.  It 
allows domain owners to publish contact information in DNS in addition to WHOIS 
for the purpose of validating domain control.

CAA contact Property

 

contact <URL> :  The contact property entry specifies the authorized means of 
contacting the holder of the domain or another party who is authorized to 
approve issuance of certificates for the domain.

 

The contact property specifies a means of contacting the domain holder, or 
another party that is authorized to approve issuance of certificates for the 
domain in question.

The contact property takes a URL as its parameter.  The following URL scheme 
types SHOULD be implemented:

mailto: An SMTP email address where the domain holder or other authorized party 
can be contacted.

tel: A telephone number where the domain holder or other authorized party can 
be contacted.

 

Schemes other than "mailto:"; or "tel:" MUST NOT be used.  Telephone numbers 
MUST include the country code and be global phone numbers as defined by RFC 
3966.

 

The following is an example where the holder of the domain specified the 
contact property using both an email address and a phone number.

 

$ORIGIN example.com <http://example.com> 

.              CAA 0 issue “ca.example.net <http://ca.example.net> ”

.              CAA 0 contact “mailto:[email protected] 
<mailto:[email protected]> ”

.              CAA 0 contact “tel:+1-310-555-1212”

 

## Support for Legacy Systems

 

Some systems still do not have sufficient support for CAA records.  To allow 
users of those systems to specify contact information, a legacy format using 
text records is allowed.  The CAA contact property SHOULD be used instead of 
TXT records, where feasible.

               

The DNS TXT record MUST be placed on the "_caa_contact" subdomain of the domain 
being validated.  The DNS record MUST be named "domain-authorization-email" or 
"domain-authorization-phone".  The value of "domain-authorization-email" MUST 
contain a valid email address, or it cannot be used.  The value of 
"domain-authorization-phone" must be a global phone number, including country 
code, as defined in RFC 3966 or it cannot be used. 

--- MOTION ENDS ---

A comparison of the changes can be found at: 
https://github.com/cabforum/documents/compare/SC2-CAA-Contact?expand=1

The procedure for approval of this ballot is as follows:

Discussion (7+ days)

Start Time: 2018-07-11 10:30am EST

End Time: 2018-07-19 11:00am EST

Vote for approval (7 days)

Start Time: 2018-07-19 11:00am EST

End Time: 2018-07-26 11:00am EST

 

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