[Servercert-wg] Critical Name Constraints (Was: Re:Question on BR 3.2.2.6)

[Dimitris Zacharopoulos (HARICA)]

On 3/3/2020 10:46 π.μ., Tadahiko Ito wrote:
> I was not aware of that thread, but I agree Dimitris that we need to treat that issue carefully.
>
> First of all, I personally know existence of IoT devices which access webserver.
>   # they are not our customer nor my acquaintance. I am not sure such usage exist for our customer or not.
> I am not sure if those devices can handle that" critical" (or even firmware update), because of constraint resource.
> I feel such practices should not done with webPKI, but they just exist, so I believe we need to care influences.
>
> In the other hand, many intermediate cert has EKU of client-auth and server-auth.
> don't we need to check certificate consumer of client-auth?
>
> Regards Tadahiko Ito

Hello Tadahiko,

Did you have any experience that clientAuth Certificates are affected by 
dNSName values in the nameConstraints extension? I may be 
misunderstanding your last statement.


Dimitris.

>
> -----------------------------------------------------------------------
>
> Date: Tue, 3 Mar 2020 09:19:38 +0200
> From: "Dimitris Zacharopoulos (HARICA)" <dzacharo at harica.gr>
> To: Ryan Sleevi <sleevi at google.com>
> Cc: CA/B Forum Server Certificate WG Public Discussion List
> 	<servercert-wg at cabforum.org>
> Subject: Re: [Servercert-wg] Critical Name Constraints (Was: Re:
> 	Question on BR 3.2.2.6)
> Message-ID: <af175960-5fdc-f107-8e04-e9ad650e8b17 at harica.gr>
> Content-Type: text/plain; charset="utf-8"; Format="flowed"
>
>
>
> On 2020-02-29 12:30 ?.?., Ryan Sleevi wrote:
>> I see. That was answered on the original thread. The short answer: No,
>> it does not, except where it's explicitly designed to break (i.e. why
>> you make them critical).
>>
>> If you have data to believe otherwise, different from that shared on
>> the thread from last year, that would be great to share to be mindful of.
> I'd first like to remind people about the previous thread
> (https://cabforum.org/pipermail/servercert-wg/2019-October/001196.html).
> It was a rather short thread, comparing to other much longer discussions
> :-) Most Members have been silent on this topic and I'm still trying to
> figure out which of the following is true:
>
>   1. CAs are just not using name constraints so they don't care about the
>      outcome
>   2. CAs are using name constraints and are ok with forcing the extension
>      to be "critical".
>
> Having been involved with name constraints for years, I find it very
> difficult to see the latter being true.
>
> HARICA uses name constraints for several subCAs. Over the years we have
> seen implementations in opensource tools/applications/services that
> would break if the extension was critical. We still see legacy systems
> and unsupported software using TLS Certificates. Some of our Subscribers
> complain that certain Relying Parties with old and unsupported devices
> can't browse sites. These are all cases that would have availability
> issues with TLS.
>
> On the other hand, Certificate Consumers that account for the majority
> of the webPKI (those participating in the SCWG), already honor and use
> this extension, thus the majority of the webPKI Relying Parties are
> currently protected. What benefit would the WebPKI have if this
> extension was forced to be "critical", other than just removing an
> "exception" to an RFC?
>
>
> Dimitris.
>
>