[cabfpub] Voting Begins: Ballot SC2 - version 2: Validating certificates via CAA CONTACT

Tue Jul 24 18:04:07 UTC 2018

I was out at IETF while this was being discussed. Unfortunately, the person I needed to speak to about it was not there. Thus I do not have status on:

https://tools.ietf.org/id/draft-ietf-dnsop-attrleaf-12.txt <https://tools.ietf.org/id/draft-ietf-dnsop-attrleaf-12.txt>

This is adopted as a WG item and appears to be almost ready. Problem being that it has been in this state for a while.

As to the concerns raised, I see two possible issues

1) The general mechanism is bad
2) The choice of prefix is bad.

As to the first, I really don’t see that it is an argument any longer. There have been folk in the DNS world arguing against the use of prefixes for decades now and it is an argument they have very clearly lost. See the following:

https://tools.ietf.org/html/rfc6763 <https://tools.ietf.org/html/rfc6763>

RFC6763 is how Apple has been doing service discovery for 15 years now. It is widely deployed and supported by practically every vendor large and small. The combination of SRV+TXT records is the way that service discovery is done.

The argument made in the DNS world that the way to deploy new DNS features is to introduce a new record type has been comprehensively debunked. No it isn’t any more possible today than when we had the argument over SPF. While Microsoft’s DNS server now supports arbitrary records, the vast number of ISPs servicing the community do not. Furthermore, recent proposals for different DNS discovery approaches made at IETF 102 such as resolverless DNS foreclose the issue completely.

As to the second, the worst that can happen is that at some point in the future there is a subgroup for the prefixes. So _caa_contact ends up being supplemented by _caa._report or the like.

After giving the matter considerable thought I am not that bothered by that possibility any more since if we do end up developing _contact, we are likely to end up standardizing reporting mechanisms and protocols, etc. So it is probably better if _caa_contact is separate.

I will put the CSS vote in separately.

> On Jul 19, 2018, at 11:02 AM, Tim Hollebeek via Public <public at cabforum.org> wrote:
> 
>  
> Administrivia:
>  
> 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.
> 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:domainowner at example.com <mailto:domainowner at example.com>”
> .              CAA 0 contact “tel:+1-310-555-1212 <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 <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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> Public at cabforum.org <mailto:Public at cabforum.org>
> https://cabforum.org/mailman/listinfo/public <https://cabforum.org/mailman/listinfo/public>
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