[Servercert-wg] Compromised/Weak Keys Ballot Proposal

Tom Zermeno tom at ssl.com
Fri Feb 23 17:33:18 UTC 2024


Regarding the change of the Debian weak keys statement at proposed line 1701: is the statement intended to be a sub-clause of the second item in the sublist, which would then make Debian weak keys exempt from the Fermat factorization method check?  Or, more likely based on the recent discussion, was the statement meant to be a third item in the list, which would then exempt Debian weak keys from the 5th condition of the list requiring CAs to reject certificate requests?


My question stems from the abnormal line spacing and indention of the statement, which stands out from the surrounding text.






From: Servercert-wg <servercert-wg-bounces at cabforum.org> On Behalf Of Wayne Thayer via Servercert-wg
Sent: Friday, February 23, 2024 11:18 AM
To: Martijn Katerbarg <martijn.katerbarg at sectigo.com>
Cc: CA/B Forum Server Certificate WG Public Discussion List <servercert-wg at cabforum.org>
Subject: Re: [Servercert-wg] Compromised/Weak Keys Ballot Proposal




I would summarize the reasoning for removing the Debian requirements as follows:

- CAs would prefer the greater clarity that would be provided by the weak keys ballot that failed last year.

- However, some CAs were of the opinion that the prior ballot imposed more explicit requirements for Debian weak key checking rather than just clarifying existing requirements. The "new" requirements were viewed as burdensome.

- The Debian vulnerability is more than 15 years old. If an Applicant submits a Debian weak key at this point, they almost certainly have bigger security issues.

- So the cost of these requirements outweighs the benefits at this point in time.


I included a few links to the discussion during the prior balot's voting period, and there was also discussion at the last SCWG teleconference that should be captured in the minutes.






On Fri, Feb 23, 2024 at 2:19 AM Martijn Katerbarg <martijn.katerbarg at sectigo.com <mailto:martijn.katerbarg at sectigo.com> > wrote:


Apologies if I’ve missed something in discussions, but why exactly are we removing the Debian Weak Keys language, and even explicitly mentioned that CAs do not need to check for them (anymore)?




From: Servercert-wg <servercert-wg-bounces at cabforum.org <mailto:servercert-wg-bounces at cabforum.org> > on behalf of Wayne Thayer via Servercert-wg <servercert-wg at cabforum.org <mailto:servercert-wg at cabforum.org> >
Date: Thursday, 22 February 2024 at 20:01
To: CA/B Forum Server Certificate WG Public Discussion List <servercert-wg at cabforum.org <mailto:servercert-wg at cabforum.org> >
Subject: Re: [Servercert-wg] Compromised/Weak Keys Ballot Proposal

CAUTION: This email originated from outside of the organization. Do not click links or open attachments unless you recognize the sender and know the content is safe.


I am seeking a second endorser for this proposal. Below is a draft of the ballot language.






**Ballot SC-XX: Compromised / Weak Keys**

This ballot updates BR section to address two issues:

First, the requirements placed on CAs to reject a certificate request if they have been “made aware” that the key pair is compromised is vague and open-ended in regard to how CAs may be “made aware”. This ballot specifies that CAs be “made aware” via their problem reporting mechanism.

Second, this ballot reintroduces the language from [failed] ballot SC-59: Weak Key Guidance. However, based on feedback received during the discussion and voting period for that ballot, Debian weak key checks are now explicitly out of scope.

This ballot is proposed by Wayne Thayer (Fastly) and endorsed by Brittany Randall (GoDaddy) and <someone else( )>. You can view and comment on the github pull request representing this ballot here: https://github.com/wthayer/servercert/pull/1/files 

The preceding discussions can be seen here:

* This ballot: https://lists.cabforum.org/pipermail/servercert-wg/2024-February/004195.html 
* The prior weak keys ballot: https://lists.cabforum.org/pipermail/servercert-wg/2023-July/003820.html and https://lists.cabforum.org/pipermail/servercert-wg/2023-July/003857.html
* The “made aware” language in <> :  https://lists.cabforum.org/pipermail/servercert-wg/2023-July/003902.html

--- Motion Begins ---

This ballot modifies the "Baseline Requirements for the Issuance and Management of Publicly-Trusted Certificates" ("Baseline Requirements") based on Version 2.X.X

MODIFY the Baseline Requirements as specified in the following redline: <Immutable redline link>

--- Motion Ends ---

Discussion (at least 7 days):

- Start: TBD UTC
- End: TBD UTC

Vote for approval (7 days):

- Start: TBD UTC
- End: TBD UTC


On Mon, Feb 12, 2024 at 6:12 PM Wayne Thayer via Servercert-wg <servercert-wg at cabforum.org <mailto:servercert-wg at cabforum.org> > wrote:

Thank you fo the feedback Aaron. I agree with both points you made in the PR and have updated it to reflect your suggestions.


- Wayne


On Mon, Feb 12, 2024 at 12:27 PM Aaron Gable <aaron at letsencrypt.org <mailto:aaron at letsencrypt.org> > wrote:

Thank you Wayne! I think this gets close to the sweet spot for me, personally. I've left two small comments on the ballot, but on the whole I think I like this approach. 


Thanks again,



On Mon, Feb 12, 2024 at 8:18 AM Wayne Thayer via Servercert-wg <servercert-wg at cabforum.org <mailto:servercert-wg at cabforum.org> > wrote:

Following up from the last SCWG teleconference, I've reviewed the feedback from the discussion [1] and voting [2] periods for ballot SC-59 Weak Key Guidance, along with the prior discussions on the "made aware" language in section [3] and I would like to propose the following Baseline Requirements improvements:


* Scope the "made aware" language to "made aware via the CA's documented problem reporting mechanism". This addresses the concern that I raised by limiting how a CA can be "made aware". [4]


* Remove the Debian requirements from the prior weak keys ballot and replace them with language that excludes Debian weak keys. Otherwise use the language from the prior ballot, with the exception of a new effective date. This consolidates feedback that CAs do desire the clarity that would have been provided by the prior ballot, but many believe that the burden for rejecting Debian weak keys exceeds the value of doing so at this point in time.


Here's the result: https://github.com/wthayer/servercert/pull/1/files


Note that, while there has been discussion about completely removing weak key checking requirements, there does not appear to be a consensus to do so.


I would appreciate everyone's feedback on the proposal, and I am also seeking endorsers.






[1] https://lists.cabforum.org/pipermail/servercert-wg/2023-July/003820.html

[2] https://lists.cabforum.org/pipermail/servercert-wg/2023-July/003857.html

[3] https://lists.cabforum.org/pipermail/servercert-wg/2023-July/003902.html

[4] https://github.com/cabforum/servercert/issues/442


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