[Servercert-wg] SC-59 Weak Key Guidance

Thu Jun 1 13:43:29 UTC 2023

[back to discussing the ballot]

Hi all,

I raised the following question during the January 19th
<https://cabforum.org/2023/01/19/2023-01-19-minutes-of-the-server-certificate-working-group/>
SCWG meeting, but I recognize only some group members can participate in
our regularly scheduled meetings.

Do participants in this Forum feel that weak-key checks should be removed
from the scope of a CA’s set of mandatory responsibilities?

While I appreciate the work carried out by ecosystem members to produce
this ballot, primarily led by the SSL.com <http://ssl.com> team, I struggle
with the demonstrated security value of these checks compared to the
overall effort they represent.

In a recent Validation Subcommittee meeting where we focused on delegating
parts of the domain validation process, we discussed that subscribers often
make security decisions that can have considerable consequences but are
ultimately beyond the CA’s scope of responsibility (for example, delegating
domain validation to an insecure third-party service). Wouldn’t we consider
using an outdated software application/library to generate key-pairs along
the same lines?

Beyond perceived security value, I also struggle with the opportunity cost
of time spent evaluating weak keys and responding to weak key incidents. It
seems to me that something like requiring pre-/post-issuance linting
instead of weak-key checks is a better tradeoff and would be more valuable
for the ecosystem (e.g., reducing the likelihood of unexpected customer
impact due to prescribed revocations timelines in the BRs related to
mis-issuance).

As this is now in discussion, I wanted to again offer the perspective that
maybe weak-key checks should not be in scope of a CA’s responsibilities in
case others share the same opinion.

- Ryan

On Mon, May 29, 2023 at 1:18 AM Dimitris Zacharopoulos (HARICA) via
Servercert-wg <servercert-wg at cabforum.org> wrote:

> Hi Clint,
>
> On 26/5/2023 6:45 μ.μ., Clint Wilson wrote:
>
> Hi Tom, Dimitris,
>
> I continue to be opposed to the SCWG trying to limit effective dates to 2
> per year. I think it’s entirely reasonable to align on a day of the month
> (I think the 15th has broadly been the only one I’ve heard proposed). I
> think it’s reasonable to try to avoid January and December. I also think
> there may be value in trying to reduce the overall number of effective
> dates somewhat. The dates I’m personally in favor of aligning on are
> February, April, June, August, and October 15th.
>
> If there’s a particular penchant towards March and September, however,
> then I’d be unopposed to March, May, July, September, and November 15th.
>
> For this ballot in particular, I think October 15 or November 15 2023 are
> feasible targets for implementing these changes and would greatly prefer
> closing this issue (open now for *more than 3 years*) sooner than later,
> especially given the number of incidents we’ve seen in the last years
> related to weak key vulnerabilities and CAs issuing certificates with weak
> keys.
>
>
> It's fine for me also to close this issue sooner than later which is why I
> recommended even the September 15, 2023 effective date.
>
> On the 2 document releases per year issue, this is a preliminary result
> after having long discussions. I was not aware of any opposition until now,
> but perhaps your opposition didn't consider the emergency options of the
> proposal? The "standardized release cycle for Guidelines" proposal
> addresses a series of concerns about the frequency and number of document
> updates, as highlighted in the presentation shared in my previous reply. If
> you recall, the proposal still allows the release of "Emergency Guidelines"
> that bypasses the 6-month regular release cycle. We still need to work on
> the details which I hope to make progress on after passing the first Bylaws
> updates that are already prepared, but I'm confident that all concerns will
> be addressed.
>
> If we use this ballot as an example for applying the "standardized release
> cycle for Guidelines", Apple would propose that this is an Emergency
> Guideline and specify an effective date that would not be one of March 15
> or September 15. If there was no opposition, we would proceed with a ballot
> that would result in an emergency guideline release and the proposed
> effective date exactly as we normally do today.
>
> I plan to start a separate thread to continue this discussion at the Forum
> level after we make some progress with the recently proposed Bylaws changes.
>
>
> Thanks,
> Dimitris.
>
>
> Thanks,
> -Clint
>
> On May 26, 2023, at 7:37 AM, Tom Zermeno via Servercert-wg
> <servercert-wg at cabforum.org> <servercert-wg at cabforum.org> wrote:
>
> Hello Dimitris,
>
> Thank you for the input.  We feel that September 15th does not provide
> enough time for CAs to implement these changes, but we are not against the
> March 15,  2024 effective date, if there is consensus from the Community.
>
> Thank you,
>
> Tom
> SSL.com <http://ssl.com/>
>
> *From:* Servercert-wg <servercert-wg-bounces at cabforum.org> *On Behalf Of *Dimitris
> Zacharopoulos (HARICA) via Servercert-wg
> *Sent:* Friday, May 26, 2023 1:54 AM
> *To:* servercert-wg at cabforum.org
> *Subject:* Re: [Servercert-wg] SC-59 Weak Key Guidance
>
>
>
> Hi Tom,
>
> Historically, the SCWG has been trying to avoid effective dates during
> January or December. I recommend using September 15, 2023 or March 15, 2024
> as possible effective dates. These two dates seem to be more favorable
> <https://docs.google.com/presentation/d/1oTGVYqggQpQMR4Lktbu_L6DhuBVJzeuiFGd9EAU1zsE>
>  than others.
>
>
> Thanks,
> Dimitris.
> On 25/5/2023 10:51 μ.μ., Tom Zermeno via Servercert-wg wrote:
>
> Purpose of Ballot SC-059 V3
>
> Several events within the community have led to concerns that the Baseline
> Requirements for the Issuance and Management of Publicly-Trusted
> Certificates (BRs) lacked a specificity required to properly guide CAs on
> matters dealing with the identification and processing of digital
> certificates based on private keys considered weak, or easy to ascertain.
> In the hopes that elaboration and clarity on the subject would be
> beneficial to the community, we are presenting updates to §4.9.1.1(“Reasons
> for Revoking a Subscriber Certificate) and §6.1.1.3 (Subscriber Key Pair
> Generation) of the BRs.
>
> The first update is to §4.9.1.1 and is made to expand the scope of easily
> computable Private Keys from “Debian weak keys” to “those listed in section
> 6.1.1.3(5)”.  While the initial language in the BRs did not exclude other
> concerns, the use of a single example could be interpreted to mean that
> other easily computable Private Keys are few and far between.  The next
> update was to §6.1.1.3(5), wherein we added specific actions to be taken
> for ROCA vulnerability, Debian weak keys - both RSA and ECDSA – and Close
> Primes vulnerability.  We also added a link to suggested tools to be used
> for checking weak keys. Finally, an implementation date of December 1, 2023
> was added to allow CAs time to update processes to meet the requirements.
>
>
> The following motion has been proposed by Thomas Zermeno of SSL.com
> <http://ssl.com/> and endorsed by Ben Wilson of Mozilla and Martijn
> Katerbarg of Sectigo.
>
> --Motion Begins—
>
> This ballot is intended to clarify CA responsibilities regarding weak key
> vulnerabilities, including specific guidance for Debian weak key, ROCA and
> Close Primes attack vulnerabilities, and modifies the “Baseline
> Requirements for the Issuance and Management of Publicly-Trusted
> Certificates” as follows, based on Version 2.0.0.
>
> Notes: Upon beginning discussion for SC-59, the then-current version of
> the BRs was 1.8.4; since that time several ballots have been approved,
> leading to the increment of the version to 1.8.7 and eventually 2.0.0,
> which is the latest approved version of the BRs.  The changes introduced in
> SC-59 do not conflict with any of the recent ballots. As observed with
> other ballots in the past, minor administrative updates must be made to the
> proposed ballot text before publication such that the appropriate Version #
> and Change History are accurately represented (e.g., to indicate these
> changes will be represented in Version 2.0.1).
>
>
>
> MODIFY the Baseline Requirements as specified in the following Redline:
> https://github.com/cabforum/servercert/compare/a0360b61e73476959220dc328e3b68d0224fa0b3...SSLcom:servercert:3b0c6de32595d02fbd96762cda98cdc88addef00
>
>
>
>
> --Motion Ends—
>
> This ballot proposes a Final Maintenance Guideline. The procedure for
> approval of this ballot is as follows:
>
> Discussion (11+ days) • Start time: 2023-05-25 19:00:00 UTC • End time:
> 2023-06-08 18:59:00 UTC
> Vote for approval (7 days) • Start time: TBD • End time: TBD
>
>
>
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>
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>
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>
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>
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