Re: CRL Issuance Frequency for non-published CRLs

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Rob Stradling

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Sep 21, 2022, 4:21:14 PM (6 days ago) Sep 21
to Ben Wilson, Clint Wilson, Christophe Bonjean, MDSP
AIUI, the latest published version of a root store policy always takes precedence over (1) draft updates to that policy, (2) language proposed for public discussion by the policy's owner, and (3) expressions of intent by the policy's owner that are at odds with the latest published policy language.  With that in mind...

Clint, thanks for confirming that Ben's proposed language matches the intent of the similar Apple Root Program requirement.  Do you plan to update https://www.apple.com/certificateauthority/ca_program.html before October 1st, so that the Apple Root Program's effective policy for CRL URL disclosures matches your intent?
The current language - "for each included CA Certificate and each CA Certificate chaining up to an included CA Certificate in the Apple Root Program" - leaves no room for a "before the CA signs certificates" carve-out, and there's also no permission for any delay between the issuance of a Subordinate CA Certificate and the disclosure of its CRL URL(s).

Ben, thanks for proposing some language for discussion.  Do you plan to (quoting you) "modify MRSP section 4.1 to more clearly indicate when full CRLs need to be added to the CCADB" before October 1st?
The current language in https://www.mozilla.org/en-US/about/governance/policies/security-group/certs/policy/#41-additional-requirements leaves no room for a "before the CA signs certificates" carve-out, and there's no permission for any delay between the issuance of a Subordinate CA Certificate and the disclosure of its CRL URL(s).

Alternatively...
If Mozilla's and Apple's intended policies are aligned on these matters, would it be better to add the language to https://www.ccadb.org/policy#4-intermediate-certificates and then update both the MRSP and https://www.apple.com/certificateauthority/ca_program.html to defer to the CCADB Policy?


From: 'Clint Wilson' via dev-secur...@mozilla.org
Sent: Thursday, August 25, 2022 18:31
To: Ben Wilson
Cc: Christophe Bonjean; MDSP
Subject: Re: CRL Issuance Frequency for non-published CRLs

Hi all,

FWIW, the below language also matches the intent of the similar Apple Root Program requirement.

Thanks,
-Clint

On Aug 25, 2022, at 10:20 AM, Ben Wilson <bwi...@mozilla.com> wrote:

Hi Christophe,

We do want to maintain some flexibility here and to mirror current practices without creating new unnecessary requirements.  We could modify MRSP section 4.1 to more clearly indicate when full CRLs need to be added to the CCADB.  For discussion, the language could be something like, "Full CRL URLs MUST be provided in the CCADB before the CA signs certificates, or if it is already signing certificates, then within 7 days of disclosing the CA certificate in the CCADB." 

Thoughts?

Ben



On Tue, Aug 23, 2022 at 12:33 PM Christophe Bonjean <christoph...@globalsign.com> wrote:

Hi Ben,

 

There’s a few CA and CRL lifecycle events linked to this change:

  1. T= 0 : CA creation
  2. T= 0 + a: CRL URL assignment (not yet publishing CRLs)
  3. T = max 7 days: CA disclosure in CCADB (section 5.3.2)
  4. T = 7 days + b: CRL disclosure in CCADB (section 4.1)
  5. T = 7 days + c: First CRL published
  6. T = d: First certificate issued from CA (with CRL in certificate profile)

 

The proposed change to section 4.1 means that CRLs need to be published as soon as they are being disclosed in CCADB. 

 

In some cases, CAs are generated a while before they are used, for example TLS CAs that we rotate on a quarterly basis. In that case, CRLs will only be published close to the when the CA becomes operational.

 

It seems the timeline to populate the CRL information in CCADB is currently flexible and supports this approach (i.e. populating and publishing the CRL a while after the CA is disclosed). 

 

Is this the correct understanding? If there’s a different interpretation or intention to restrict this timeline in the future, we would like to further discuss.

 

Thanks

 

Christophe

 

From: dev-secur...@mozilla.org <dev-secur...@mozilla.org> On Behalf Of Ben Wilson
Sent: Thursday, 11 August 2022 17:03
To: Corey Bonnell <Corey....@digicert.com>
Cc: Aaron Gable <aa...@letsencrypt.org>; dev-secur...@mozilla.org <dev-secur...@mozilla.org>
Subject: Re: CRL Issuance Frequency for non-published CRLs

 

All,

 

Mozilla's position is that adding CRL URLs to the CCADB (as required effective Oct. 1, 2022, by MRSP section 4.1) will be considered "publishing" them because we will be relying on that information in the CCADB to operate CRLite. I have added Issue #251 to GitHub to address this issue more precisely in the next version of the Mozilla Root Store Policy. For this, we will use the timeframes from section 4.9.7 of the Baseline Requirements, "the CA SHALL update and reissue CRLs at least once every seven days ...." (In the future, we might want to see that time frame shortened.)  

 

Thanks,

 

Ben Wilson

Mozilla Root Store Program

 

 

On Fri, Aug 5, 2022 at 1:08 PM 'Corey Bonnell' via dev-secur...@mozilla.org <dev-secur...@mozilla.org> wrote:

Hi Aaron,

 

> As long as we do not publish the CRLs, they are not required to be updated on specific timetables.

 

My understanding is that absent the inclusion of a URI in a CRLDP extension of a Certificate that is subject to the BRs or some other Root Program requirement, there is no obligation by the CA to publish and update CRL-based revocation information on any specific cadence.

 

Given this, I believe that it’s compliant to not publish CRLs that are signed by the CA.

 

Thanks,

Corey

 

From: 'Aaron Gable' via dev-secur...@mozilla.org <dev-secur...@mozilla.org> 
Sent: Thursday, August 4, 2022 4:10 PM
To: dev-secur...@mozilla.org <dev-secur...@mozilla.org>
Subject: CRL Issuance Frequency for non-published CRLs

 

Hi MDSP,

 

Section 4.9.7 of the Baseline Requirements says (emphasis added):

 

> If the CA publishes a CRL, then the CA SHALL update and reissue CRLs at least once every seven days, and the value of the nextUpdate field MUST NOT be more than ten days beyond the value of the thisUpdate field.

 

Let's Encrypt is currently in the final stages of standing up infrastructure to issue and publish CRLs, in compliance with the upcoming Apple and Mozilla root program requirements that go into effect on October 1st.

 

As with many systems, we would like to test this as thoroughly as possible prior to making it fully available. Of course we're already running it in our non-production environment with an untrusted hierarchy of issuers. But there's a risk that, if we were to run the new infrastructure in our production environment and discover some sort of fault, we would not be able to turn it off again due to the reissuance and update requirements.

 

It is our interpretation of the above-quoted text from Section 4.9.7 that this risk does not actually exist. As long as we do not publish the CRLs, they are not required to be updated on specific timetables.

 

Does anyone disagree with this interpretation? Are there other requirements that I'm missing that would prevent us from turning the new infrastructure off?

 

Thanks,

Aaron

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Clint Wilson

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Sep 21, 2022, 4:36:32 PM (6 days ago) Sep 21
to Rob Stradling, Ben Wilson, Christophe Bonjean, MDSP
Hi Rob,

It’s possible, but not guaranteed at this moment, that the policy update will be published prior to October 1st, however an official communication was sent to CAs (earlier this month) participating in the Apple Root Program clarifying interpretation of this requirement. If that is insufficient in the interim in the view of CAs or other interested parties to be comfortable with their own compliance, I would appreciate that feedback and will certainly work with any impacted CAs in this regard.

Thank you!
-Clint

Rob Stradling

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Sep 21, 2022, 5:32:28 PM (6 days ago) Sep 21
to Clint Wilson, Ben Wilson, Christophe Bonjean, MDSP
Thanks Clint.  Your interpretation of the Apple Root Program's CRL URL disclosure requirement is crystal clear to me, thanks to your comments here and in the official communication you mentioned.  Sectigo's compliance to this requirement in Apple's eyes is actually the least of my concerns, TBH.

It's the second order effects of this sort of situation that bother me.  If a document that purports to be "the root store policy" is in reality "most of the root store policy, with some bits that are (at best) misleading or (at worst) wrong", then how can we expect CAs' auditors and the wider community to accurately interpret the actual policy?  CAs are expected to read every MDSP message, but auditors and the wider community are not.  CAs receive official communications from root programs, but auditors and the wider community do not.


From: 'Clint Wilson' via dev-secur...@mozilla.org
Sent: Wednesday, September 21, 2022 21:36
To: Rob Stradling
Cc: Ben Wilson; Christophe Bonjean; MDSP

Ben Wilson

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Sep 21, 2022, 7:45:48 PM (6 days ago) Sep 21
to Rob Stradling, Clint Wilson, Christophe Bonjean, MDSP
Hi Rob,

Your message is well-received. I'll see what we can do to clarify this in the MRSP soon. I have tagged Issue #251 in Github for an interim MRSP version 2.8.1, but I certainly won't be able to make any MRSP changes before October 1.

Also, I need to work on the previously proposed language--"Full CRL URLs MUST be provided in the CCADB before the CA signs certificates, or if it is already signing certificates, then within 7 days of disclosing the CA certificate in the CCADB."--to make it more clear. With that wording, it seems to contradict the October 1 deadline, and it doesn't seem to address all scenarios. I'll need to work on language that makes more sense.

Thanks,

Ben

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