[cabfpub] Ballot 188 - Clarify use of term "CA" in Baseline Requirements

Dimitris Zacharopoulos jimmy at it.auth.gr
Tue Feb 28 10:09:53 UTC 2017

On 27/2/2017 9:21 μμ, Ryan Sleevi wrote:
> On Mon, Feb 27, 2017 at 10:52 AM, Dimitris Zacharopoulos 
> <jimmy at it.auth.gr <mailto:jimmy at it.auth.gr>> wrote:
>>     I think this is a potentially problematic definition, in that it
>>     relates to the scope of the operations of the audit, as well as
>>     matters below that I highlight. I'm hoping the proposers and
>>     drafters can clarify (or link to previous discussions) as to the
>>     reason in which "or its Affiliate" was introduced into these
>>     definitions, or to highlight where it was already a natural and
>>     existing part of these definitions.
>     Peter already provided some clarity for this. The "Affiliate"
>     language was not introduced by this ballot. It was already
>     mentioned in several sections of the BRs ( "CA Key Pair
>     Generation", 6.1.2 "Private Key Delivery to Subscriber", 6.2.6
>     "Private Key Transfer into or from a Cryptographic Module",
> "Subordinate CA Certificate" and "Subordinate CA
>     Certificates").
> Unfortunately, I think the concern still remains that this is a subtle 
> introduction that goes from being scoped to specific sections (as 
> you've noted) to now being a foundational concept, which unfortunately 
> 'weakens' the BRs, I believe.
> I totally understand and appreciate the intent to align here, 
> especially for the cases Peter noted, but I want to especially make 
> sure to highlight the issue that "or the Affiliate" can be problematic 
> from a set of scope of audits.
> Basically, what's being asked for on this ballot is a trade-off from 
> being logically bugged (and I agree, this is an issue we should fix) 
> to something that is procedurally weaker, and I'm trying to figure out 
> what the plan is to align. From both you and Peter's response, it 
> sounds like you don't believe further changes are needed, and this is 
> concerning.

As far as this ballot is concerned, which is only to clarify the use of 
the term "CA", it does not "weaken" the BRs in any way. The use of the 
term "Affiliate" and policy around it, is already there. I personally 
(and maybe others) feel that the "Affiliate" issue needs to be further 
discussed and even be removed as a way of providing better conditions 
but this is something outside the scope of this ballot.

>     Peter's answer should cover this. Your follow-up questions
>     challenge the fact that the current BRs treat Root Operator's
>     "Affiliates" in a different way than the non-Affiliates but this
>     is a policy matter and should be discussed separately. In any
>     case, I don't think it changes the fact that all Subordinate CAs
>     (whether internally or externally operated) need to be audited. In
>     the case of Internally Operated Subordinate CAs, the audit might
>     be covered in the Root Operator audit, and this information should
>     be included in the audit scope.
> That's the intent - but my question is, where is it specified? I may 
> have missed that, and that was the point of raising these concerns: if 
> I'm misreading, and it's already addressed, fantastic. But I don't 
> believe it is, hence the concern :)

8.1: "Certificates that are capable of being used to issue new 
certificates MUST either be Technically Constrained in line with section 
7.1.5 and audited in line with section 8.7 only, or Unconstrained and 
fully audited in line with all remaining requirements from this 
section". IMO, from this reading, it is clear that all Subordinate CAs 
MUST be fully audited or self-audited (per 8.7) if they use Technically 
Constrained Subordinate CA Certificates. There is no distinction about 
whether the Subordinate CA is "Internal" or "External".

"Affiliates" in the current BRs have different policy in the following:

  * The key generation ceremony SHOULD (instead of MUST) be witnessed by
    an external auditor (
  * The Policy Identifier MAY (instead of MUST) be present in the
    Subordinate CA Certificate and the "anyPolicy" identifier MAY
    (instead of MUST NOT) be used. (

I believe that's all there is to it.

>     After several discussions within the WG, it was agreed that the
>     most accurate technical language is that "Private Keys sign
>     Certificates". Certificates, don't sign Certificates.
> I understand the "why". I'm more specifically asking three questions:
> 1) Is my interpretation correct?
> 2) Is this desired?
> 3) Is there a plan to fix it?
> From the rest of this section, I can interpret your response as "1) 
> Yes 2) No, not necessarily 3) Not really, but we could come up with 
> one". I'm not sure if that really provides the level of assurance when 
> considering whether to vote on this ballot, even though I agree and 
> understand the why, and am relieved it isn't intended.

Your interpretation for 1) is correct regarding the specific OCSP 
responder question.

For 2), the WG's desire was to use technically correct language in the 
entire BRs to describe the "signing" process. You had a very specific 
concern about the OCSP responder where RFC 6960 allows either the name 
of the responder of a hash of the responder's public key as the 
ResponderID so even that is taken care of. However, if this concern 
remains, we will move to fixing it.

For 3), if this concern remains, we will fix it. I would like to ask if 
more members have the same concern, to please speak up.

>     So, according to your example, if the ResponderID was the hash of
>     the Subordinate CA Certificate's public key, it would not be
>     prohibited even though that key would be included in two or more
>     Subordinate CA Certificates. Perhaps the multiple CA Certificates
>     with the same key-pair scenario is not entirely addressed. We
>     could update the BRs to specifically include language for the
>     ResponderID information, if you think people would be puzzled
>     about what information should be included in that field.
> Whether we address this by specifying language fro the ResponderID 
> (which seems overly specific) or by addressing the general concern, 
> I'd like to see a concrete proposal to address this, ideally before 
> voting concludes.

So far, the WG thought that the phrase "signed by the Private Key 
associated with a Root CA Certificate or a Subordinate CA Certificate" 
was technically correct and enough to clearly demonstrate a link between 
a Private Key and a Specific CA Certificate. If the corresponding public 
key to that private key is included in another Subordinate CA 
Certificate, it only adds policy requirements around that private key.

Put differently, if a Private Key is associated with Certificate 
"SubCA1" which is operated by "SubCA1 org" and for some reason the same 
private key is associated with Certificate "SubCA2" which is operated by 
"SubCA2 org", we need to determine what obligations exist for the 
handling of that Private Key for its entire lifecycle and usage, which 
is the superset of SubCA1 and SubCA2. If the requirements surrounding 
SubCA1 and SubCA1 org are "requirements A" and the requirements 
surrounding SubCA2 and SubCA2 org are "requirements B", then the Private 
Key must meet requirements A+B.

>>         In Section 4.9.10 (On-line revocation checking requirements)
>>     Was this intentional?
>     This specific change was addressed during the discussion phase
>     (https://www.mail-archive.com/public@cabforum.org/msg02652.html
>     <https://www.mail-archive.com/public@cabforum.org/msg02652.html>).
> Did you link to the right thread? I cannot find a clear answer, but 
> perhaps I'm just missing it. As it stands, I think this alone is 
> potentially grounds that we may need to vote against it, because it's 
> a clear reduction in assurance.

The link is from a thread started by Ben. Unfortunately, I couldn't find 
it in the mail-archive so it is pasted here:

-------- Forwarded Message --------
Subject:     [cabfpub] Policy Review Working Group's Pre-Ballot to 
Clarify Use of "CA"
Date:     Thu, 19 Jan 2017 16:44:46 +0000
From:     Ben Wilson via Public <public at cabforum.org>
Reply-To:     CA/Browser Forum Public Discussion List <public at cabforum.org>
To:     CABFPub <public at cabforum.org>
CC:     Ben Wilson <ben.wilson at digicert.com>


The Policy Review Working Group has completed its review of the Baseline 
Requirements for purposes of clarifying use of the term "CA" and related 
terminology.  Please review and comment on the following pre-ballot.  A 
redlined version of the Baseline Requirements is attached to facilitate 
your review and comment.

I did want to highlight one of the proposed changes that is not related 
to "CA" terminology.   That proposed change is in Section 4.9.10.  The 
current language is ambiguous, and it doesn't say what was originally 
intended when it was adopted.  The current language says, "Effective 1 
August 2013, OCSP responders for CAs which are not Technically 
Constrained in line with Section 7.1.5 MUST NOT respond with a "good" 
status for such certificates."

The proposed change would rephrase this sentence to say what was 
originally intended.  It would say, "OCSP responders for Subordinate CA 
Certificates that are Technically Constrained in accordance with Section 
7.1.5 are exempt from this prohibition on responding with a "good" to 
OCSP requests for the status for such certificates."

I don't know if anyone is relying on this provision, but its original 
intent was to address concerns by users of legacy CA software / OCSP 
responder software who complained that they could not meet this 
requirement because their OCSP responders were built to rely only on CRLs.

If this proposed change presents a problem for anybody, it will be 
removed from this ballot and put into its own separate ballot.

--- END QUOTE---

Gerv replied on January 25th that he agrees with the proposed change on 
7.1.5 which basically clears the language. It doesn't reduce the 
assurance. The assurance is already "reduced" in the current BRs. Here 
is the current language in 4.9.10:

"Effective 1 August 2013, OCSP responders for CAs which are not 
Technically Constrained in line with Section 7.1.5 MUST NOT respond with 
a "good" status for such certificates".

The new proposed language says exactly the same thing but in a more 
clear way. So, again, the ballot does not propose policy changes 
(although as we said a couple of times, the WG was very tempted to 
propose policy changes to make things better).

>     A typo indeed. It is clear in the red-lined version.
> For future reference, we should try to figure out what version is 
> being voted on, when the e-mailed ballot and Red Line disagree :) This 
> is a minor issue, but I can easily see more significant issues 
> creeping in, least of all, because I have not looked at all at the Red 
> Lined version, because that's not the balloted text :)

Agreed. I guess once we become more familiar with a github process, we 
will use one version over another as authoritative for ballots (most 
probably the github version).

>>         In Section 8.7 (Self-Audits)
>>         Replace the last paragraph with:
>>         During the period in which a Technically Constrained
>>         Externally Operated Subordinate CA issues Certificates, the
>>         Issuing CA SHALL monitor adherence to the Issuing CA's
>>         Certificate Policy and/or Certification Practice Statement
>>         and the Externally Operated Subordinate CA's Certificate
>>         Policy and/or Certification Practice Statement. On at least a
>>         quarterly basis, against a randomly selected sample of the
>>         greater of one certificate or at least three percent of the
>>         Certificates issued by the Externally Operated Subordinate
>>         CA, during the period commencing immediately after the
>>         previous audit sample was taken, the CA SHALL ensure
>>         adherence to all applicable Certificate Policies and/or
>>         Certification Practice Statements.
>>     Much like several other changes mentioned above, this limits the
>>     scope of the existing text from "internal or external" to simply
>>     "external". Thus it reduces the scope of examination for
>>     internally operated subordinate CA certificates, which may be
>>     operated by an Afilliate under a distinct CP/CPS. Is that fair to
>>     say?
>     The rest of the section remains the same. It doesn't remove the
>     obligation for the CA (this covers ALL CA organizations, including
>     affiliates) to perform quarterly self-audits.
>     The reasoning for changing the last paragraph to only "Externally
>     Operated Subordinate CAs", was that the language dictates that the
>     "Issuing CA SHALL monitor adherence...". We thought that it
>     doesn't make sense to have one organization monitor adherence to
>     it's own organization. It is already required for the Root CA
>     Operator to adhere to its own CP and/or CPS (that must cover all
>     Internally Operated Subordinate CAs), check against a randomly
>     selected sample, etc, as specified in the first paragraph of
>     section 8.7.
> So I think the point you're making is important, and I'm not cleared 
> where it's technically spelled out or required, and do hope you can 
> highlight this.
> You're asserting that all Internally Operated Subordinate CAs are 
> operated by the Root Operator AND, if I'm understanding correctly, 
> audited to the same CP/CPS as the Root CA Certificate - is this correct?

No. I am saying that it could be, under some circumstances. For example, 
if a Root Operator has an internal department (under the same 
Management) that handle issuances under a specific Subordinate CA 
Certificate, then this Internally Operated Subordinate CA could be 
covered in the audit of the Root Operator. If we're talking about two 
separate legal entities under different Management, then a separate 
audit report is needed according to Section 8.1.

> I haven't found text to normatively require either statement, and 
> that's the concern: even if it's the same organization as the Root 
> Operator, the possibility for distinct CP/CPSes to exist between the 
> Root CA Certificate's policies and the Internally Operated Subordinate 
> CA's policies (and/or independent audits) exists, and as much as 
> possible, I want to ensure the same consistent duty of care with 
> respect to policies and practices. I fear this introduces a loophole 
> for Affiliates to 'skip' audits and key protection, even if 
> unintended, so I'm curious if we can find a resolution for this within 
> the voting period.

The requirement for all Subordinate CAs to be audited comes from the 
first paragraph of Section 8.1, as stated above. It leaves no room for 
interpretations and includes ALL Subordinate CAs, Internal or External.

>     Here are the two definitions introduced:
>     *Root CA Operator:*The top-level Certification Authority (i.e. an
>     organization) whose CA Certificate (or associated Public Key) is
>     distributed by Application Software Suppliers as a trust anchor
>     *Internally Operated Subordinate CA:*A Subordinate CA Operator,
>     operated by a Root CA Operator or its Affiliate that is in
>     possession or control of the Private Key associated with the
>     Subordinate CA Certificate
>     The Root CA Operator is already -by definition- responsible for
>     all actions related to its Internally Operated Subordinate CAs and
>     Affiliates.
> I disagree, and that's the point of concern. If the Root CA Operator 
> included the definition of Affiliates - ergo bringing consistency to 
> the scope of audits and operation - then perhaps this issue would be 
> resolved (of course, it may introduce new bugs). But as it stands, an 
> Internally Operated Sub CA having the "or its Affiliate" creates a 
> loophole in which all the policies which apply to a Root CA Operator 
> _don't_ apply to the Affiliate, because IOSCAs clearly distinguish 
> Affiliate as "something other than the Root CA Operator"
> Does this make sense?

I believe it is the opposite. To the best of my knowledge and 
understanding (and I hope members can correct me if I'm wrong), IOSCAs 
are treated as "something as the Root CA Operator". That's already 
captured in the BRs today.

>     Voting ends on Thursday March 2 at 22:00 UTC but the remaining
>     issues will be tracked and addressed in a future ballot.
> My hope is something a bit more concrete than future ballot before 
> then, because I think some of these concerns are enough to prevent our 
> support

The voting ends tomorrow and I hope to have addressed some or all your 
concerns. Ben and Tim (and even Peter who attended several of the WG 
meetings) are welcome to add any comments to help addressing these 
concerns even further. I also encourage other members with the same or 
similar concerns who feel they are not properly addressed, to speak up 
so we can decide if we must proceed with amendments. Unfortunately, at 
the stage we are at, the ballot cannot be withdrawn so it can either 
pass or fail. Overall, the ballot has significant language improvements 
-as many have already stated- and it would be nice to have every 
member's support. Policy problems that pre-existed the ballot, still 
remain but that was left untouched on purpose, so we could proceed with 
policy improvements after we had a consistent language and definitions 
throughout the BRs.

Best regards,
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