[Servercert-wg] Question on BR 3.2.2.6

Pedro FUENTES pfuentes at WISEKEY.COM
Thu Feb 27 08:26:47 MST 2020


Thanks, Adriano.

You’re right, as the name constraint would appear as “.gov.XX” in the CA certificate, but in BR 7.1.5 it’s said that the DNS name constraints must be validated as mandated in 3.2.2.4, and from that is why I make the reference to 3.2.2.6, as from a validation standpoint I’d say that this type of name constraint is to be considered the same as a wildcard.

Best,
Pedro

El 27 feb 2020, a las 16:17, Adriano Santoni via Servercert-wg <servercert-wg at cabforum.org<mailto:servercert-wg at cabforum.org>> escribió:


Pedro,

in a CA certificate, one would not insert a wildcard in Name Constraints, as it's not needed (per https://tools.ietf.org/html/rfc5280#section-4.2.1.10) and probably not even allowed, although RFC5280 does not explicitly forbid it. In your example, it would suffice to include "gov.XX".

That said, I understand that domain control validation for domains listed in a CA certificate (in the Name Constraints extension) must be done by the same methods used for Subscriber certificates, per BR 3.2.2.4 (see the "Note" before 3.2.2.4.1).

Adriano


Il 27/02/2020 15:44, Pedro FUENTES via Servercert-wg ha scritto:
Dear all,
Sorry if this is not the appropriate way to do things, but I’m a newbie in the Forum, so please be indulgent.

BR 3.2.2.6 says:
“If a wildcard would fall within the label immediately to the left of a registry-controlled1 or public suffix, CAs MUST refuse issuance unless the applicant proves its rightful control of the entire Domain Namespace. (e.g. CAs MUST NOT issue “*.co.uk<http://co.uk/>” or “*.local”, but MAY issue “*.example.com<http://example.com/>” to Example Co.).”

I’ll have a comment and a question regarding the above...

Comment: In my humble opinion, the wording of that paragraph seems incorrect, as a “MUST” or "MUST NOT” that is conditioned to certain exceptions seem more appropriate to be stated as “SHOULD” or “SHOULD NOT”.

Question: Considering the allowed exception (“unless the applicant proves its rightful control of the entire Domain Namespace”), and in particular thinking on a wildcard of the type “*.gov.XX” used as a name constraint in a CA certificate (and not for a wildcard TLS certificate)... Has been discussed in the past what is an acceptable method to prove this control? Would any method allowed by BR 3.2.2.4 be enough (e.g. agreed change in DNS)?

I’d appreciate to be enlightened with positive comments on the above.

Thanks,
Pedro

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Pedro Fuentes
CSO - PM eSecurity Solutions
Office: + 41 (0) 22 594 30 00
Mobile: + 41 (0) 791 274 790
Address: 29, Rte de Pré-Bois - CP 853 | Geneva 1215 CH - Switzerland
Stay connected with WISeKey<http://www.wisekey.com>

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DISCLAIMER: WISeKey does not warrant the accuracy or completeness of this message and does not accept any liability for any errors or omissions herein as this message has been transmitted over a public network. Internet communications cannot be guaranteed to be secure or error-free as information may be intercepted, corrupted, or contain viruses. Attachments to this e-mail are checked for viruses; however, we do not accept any liability for any damage sustained by viruses and therefore you are kindly requested to check for viruses upon receipt.

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