Hi Dimitris,

I was thinking more along the line: What if we had TLS leaf certificates with 
e.g. the country field missing. Such a cert would not comply to the TLS BR and 
since the ICA signed such a non-complying cert, it would need to be revoked 
too… Which IMHO makes no sense at all. 😊

Rgds
Roman

From: Servercert-wg <[email protected]> On Behalf Of Dimitris 
Zacharopoulos (HARICA) via Servercert-wg
Sent: Mittwoch, 15. Mai 2024 07:20
To: [email protected]
Subject: Re: [Servercert-wg] Discussion about single-purpose client 
authentication leaf certificates issued from a server TLS Issuing CA


On 15/5/2024 7:35 π.μ., Roman Fischer via Servercert-wg wrote:
Dear Aaron,

Interesting line of argumentation. Wouldn’t that conclude that -every- 
mis-issuance of a leaf certificate would be a violation of "all certificates 
that it issues MUST comply with one of the following certificate profiles" and 
thus would require the ICA to be revoked? That can’t be the intent of the 
regulation, right?


Roman,

TC non-TLS subCAs already have a defined certificate profile described in the 
BRs so there is no need to revoke such an ICA. I think you might be referring 
to non-TLS Subscriber Certificates issued by those TC non-TLS SubCAs?


Dimitris.


Rgds
Roman

From: Servercert-wg 
<[email protected]><mailto:[email protected]> 
On Behalf Of Aaron Gable via Servercert-wg
Sent: Dienstag, 14. Mai 2024 16:59
To: Dimitris Zacharopoulos (HARICA) 
<[email protected]><mailto:[email protected]>; CA/B Forum Server Certificate 
WG Public Discussion List 
<[email protected]><mailto:[email protected]>
Subject: Re: [Servercert-wg] Discussion about single-purpose client 
authentication leaf certificates issued from a server TLS Issuing CA

On Tue, May 14, 2024, 02:33 Dimitris Zacharopoulos (HARICA) via Servercert-wg 
<[email protected]<mailto:[email protected]>> wrote:

Is it ok for such an Issuing CA to create a single-purpose client 
authentication TLS Certificate, one that is structured according to RFC 5280 
(thus can be successfully parsed by Relying Party RFC 5280-conformant 
software), contains an extKeyUsage extension which contains the 
id-kp-clientAuth and DOES NOT include the id-kp-serverAuth KeyPurposeId?

Speaking in a personal capacity, it is my opinion that no, such issuance is not 
acceptable.

I agree that the resulting end-entity client-auth-only certificate is out of 
scope of the BRs, and is not in and of itself misissued. However, the issuing 
intermediate itself is still in scope of the BRs, and its behavior can be 
contained by them. By virtue of issuing the clientAuth cert, the issuing 
intermediate has violated the BRs requirement that "all certificates that it 
issues MUST comply with one of the following certificate profiles".

One could even argue that, having issued a certificate which does not comply 
with a BR profile, the issuing intermediate must be revoked within 7 days, per 
BRs Section 4.9.1.2 (5): "The Issuing CA SHALL revoke a Subordinate CA 
Certificate [if...] the Issuing CA is made aware that the... Subordinate CA has 
not complied with this document".

Aaron



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