[Servercert-wg] [EXTERNAL]Re: [cabfpub] Ballot SC6 - Revocation Timeline Extension
Wayne Thayer
wthayer at mozilla.com
Tue Aug 21 13:57:55 MST 2018
Thanks for the comments Mike. Based on the discussion, I would propose two
changes:
1. Regarding your second point about "The technical content or format of
the Certificate presents an unacceptable risk", my interpretation of the
language in the context of the section is that the "given period of time"
must be no more than 5 days, which doesn't make a lot of sense. Bruce's
interpretation seems more reasonable but not what the current wording
really means. If this language only comes into effect after a deadline is
set, as implied by the example, then any requirement to revoke can be
stipulated by whomever set the deadline (root program or CAB Forum ballot).
It follows that this reason for revocation (in both the Subscriber and
Subordinate CA sections) is unnecessary and can be removed.
2. Regarding the third point, add the Subscriber in addition to the "entity
reporting the Certificate Problem Report" as someone to consult when
deciding when to revoke the certificate. I think the other clarifications
you suggested are already covered.
Here are the changes I've captured from the discussion to-date:
https://github.com/wthayer/documents/commit/2d427a74f604d635609602bed2808e5d96ee03ad
I'll publish a 'version 2' of the ballot when it appears that there are no
further concerns.
- Wayne
On Tue, Aug 21, 2018 at 10:08 AM Ryan Sleevi <sleevi at google.com> wrote:
>
>
> On Tue, Aug 21, 2018 at 1:01 PM Bruce Morton via Servercert-wg <
> servercert-wg at cabforum.org> wrote:
>
>> Per Mike’s items:
>>
>>
>>
>> 1. 7 days would be preferable as this would provide a “business
>> week” for the CA to investigate the issue. It will also provide 2 extra
>> days to have reach and discuss the issue with the Reporter and the
>> Subscriber.
>>
> As Mike summarized correctly, Google felt and feels that 7 days is too
> long. We repeatedly asked for specific examples and details of where the
> additional time would be valuable, and to date, no CA has provided them. We
> had previously proposed that anything longer should require a mandatory
> public, unredacted incident report from the CA, and the concession to avoid
> such a requirement was to find a balance, while also ensuring that CAs were
> gathering and collecting concrete reports to provide that.
>
>
>> 2. Given the examples for unacceptable risk, I would assume that
>> this item would have a deadline set in the BRs. We have done this before
>> with non-registered domain name certificates. So if the certificate has not
>> been revoked by the deadline, then it must be revoked immediately. As such,
>> perhaps this requirement should be better defined and also moved to the 24
>> hour section.
>>
>> 3. I do agree that the CA should work with both the Reporter and
>> the Subscriber; however, please note that the investigation may mean that
>> the certificate will not be revoked. Also, having a preliminary report
>> within 24 hours may not be feasible to have a report with substantial
>> substance as there may not be time to discuss with the Subscriber. I do
>> suggest that within 24 hours the CA should advise the Reporter and the
>> Subscriber that an investigation has started which may result in the
>> certificate being revoked.
>>
> I don't think this is something we'd agree on. As noted above, our goal is
> to improve the transparency. There are some who've said that the best
> solution to these issues is to know what it's like by going to work for a
> CA. Absent changing employers, the next best thing is going to be to
> improve the transparency of the ecosystem, which will improve the trust
> overall. CAs are already required to conduct their activities within 24
> hours - this doesn't relax that particular item, but allows them to make it
> available as a report, while offering greater flexibility. That seems a
> meaningful compromise to balance the need for transparency while providing
> CAs and Subscribers some degree of flexibility.
>
>
>
>>
>>
>> Thanks, Bruce.
>>
>>
>>
>> *From:* Servercert-wg [mailto:servercert-wg-bounces at cabforum.org] *On
>> Behalf Of *Mike Reilly (GRC) via Servercert-wg
>> *Sent:* August 21, 2018 12:17 PM
>> *To:* Doug Beattie <doug.beattie at globalsign.com>; CA/B Forum Server
>> Certificate WG Public Discussion List <servercert-wg at cabforum.org>; Tim
>> Hollebeek <tim.hollebeek at digicert.com>; Wayne Thayer <wthayer at mozilla.com
>> >
>> *Cc:* CA/Browser Forum Public Discussion List <public at cabforum.org>
>> *Subject:* [EXTERNAL]Re: [Servercert-wg] [cabfpub] Ballot SC6 -
>> Revocation Timeline Extension
>>
>>
>>
>> Hi all. Some areas of clarification requested from the Microsoft team:
>>
>>
>>
>> - I don’t remember why 5 days was chosen vs. 7 or 3 days. I believe
>> it was we felt 7 days was too long but 5 days was reasonable. I believe we
>> also considered the scenario where an incident occurs on a Friday evening
>> of a three day weekend and the difficulty of the CA dealing with a
>> subscriber who may be unavailable over a weekend for a non-urgent
>> revocation requirement. 5 days covered that scenario without being too far
>> past 24 hours. 3 days was felt to be too short and 7 days seemed too
>> long. Correct?
>> - Regarding point 11. Will this "given period of time" means up to 5
>> days as well? Point 11 reads: *“The technical content or format of
>> the Certificate presents an unacceptable risk to Application Software
>> Suppliers or Relying Parties (e.g. the CA/Browser Forum might determine
>> that a deprecated cryptographic/signature algorithm or key size presents an
>> unacceptable risk and that such Certificates should be revoked and replaced
>> by CAs within a given period of time)”*
>> - There is also a bit of confusion about the following statement as
>> it is still governed by the 5 day requirement so we’re not sure why it’s
>> called out this way. *“Within 24 hours of receiving a problem
>> report, the CA is now required to report back to both the entity reporting
>> the problem and the Subscriber on the CA's findings, and to work with the
>> reporter to establish a date by which the CA will revoke the certificate.”*
>> Should this be clarified to include both the reporter and the Subscriber
>> included in both steps to reduce potential impact to relying parties.
>> Perhaps add more clarification in this statement:
>> - Report back the findings to reporter and the Subscriber within
>> 24 hours
>> - Work with the reporter and the Subscriber to revoke within 5 days
>>
>>
>>
>> Thanks, Mike
>>
>>
>>
>> *From:* Servercert-wg <servercert-wg-bounces at cabforum.org> *On Behalf Of
>> *Doug Beattie via Servercert-wg
>> *Sent:* Monday, August 20, 2018 1:43 PM
>> *To:* Tim Hollebeek <tim.hollebeek at digicert.com>; CA/B Forum Server
>> Certificate WG Public Discussion List <servercert-wg at cabforum.org>;
>> Wayne Thayer <wthayer at mozilla.com>
>> *Cc:* CA/Browser Forum Public Discussion List <public at cabforum.org>
>> *Subject:* Re: [Servercert-wg] [cabfpub] Ballot SC6 - Revocation
>> Timeline Extension
>>
>>
>>
>> Tim,
>>
>>
>>
>> I agree that Vulnerability is different from key compromise and the
>> actions we take should reflect that and I think we should try to keep 12
>> and 13 type events in the 5-day list.
>>
>>
>>
>> Is our strategy to have vulnerabilities fall into the 5 day list and
>> exploited vulnerabilities fall into the 24 hour list?
>>
>> *Key Compromise:* A Private Key is said to be compromised if:
>>
>> 1) its value has been disclosed to an unauthorized person
>>
>> 2) an unauthorized person has had access to the private keys
>>
>> 3) a vulnerability has been exploited to disclose private keys
>>
>> And the remainder of the definition can be removed because those are
>> examples of vulnerabilities being exploited ( Debian weak and poor key
>> generation). If we want a list of possible vulnerabilities or bad
>> practices, then we can put in an appendix.
>>
>>
>>
>> I think #13 is a special case of #12 (both vulnerabilities), so I still
>> recommend removing it. Is the distribution of a private key in in a
>> software package any different than the distribution of a private key in
>> any other (insecure) method?
>>
>>
>>
>> Here’s what I’d recommend:
>>
>>
>>
>> a) Use the new definition I listed above
>>
>>
>>
>> b) change:
>>
>> 12. The CA is made aware of a vulnerability that exposes the Subscriber's
>> Private Key to compromise; or
>>
>> to
>>
>> 12. The CA is made aware of a vulnerability that has been exploited to
>> disclose the Subscriber's Private Key; or
>>
>>
>>
>> c) Delete #13
>>
>>
>>
>> Doug
>>
>>
>>
>> *From:* Servercert-wg <servercert-wg-bounces at cabforum.org> *On Behalf Of
>> *Tim Hollebeek via Servercert-wg
>> *Sent:* Monday, August 20, 2018 3:57 PM
>> *To:* Wayne Thayer <wthayer at mozilla.com>; CA/B Forum Server Certificate
>> WG Public Discussion List <servercert-wg at cabforum.org>
>> *Cc:* CA/Browser Forum Public Discussion List <public at cabforum.org>
>> *Subject:* Re: [Servercert-wg] [cabfpub] Ballot SC6 - Revocation
>> Timeline Extension
>>
>>
>>
>> Vulnerability is different from key compromise. Replacing all the
>> heartbleed certificates within 24 hours would have been a huge fire drill.
>> It’s important to get them replaced as quickly as possible, but mandatory
>> revocations within 24 hours is going to make things worse, not better.
>>
>>
>>
>> There are potential mitigating factors for a vulnerability. For example,
>> the technical details may not be publicly known yet, or there may be no
>> public exploit available yet. The vulnerability might not affect all OS
>> versions, might be easily blocked by firewalls, and so on. The amount of
>> effort necessary to turn a vulnerability into a key compromise can vary
>> from insignificant to “lots and lots”.
>>
>>
>>
>> A compromised key, on the other hand, is clearly compromised.
>>
>>
>>
>> -Tim
>>
>>
>>
>> *From:* Servercert-wg <servercert-wg-bounces at cabforum.org> *On Behalf Of
>> *Wayne Thayer via Servercert-wg
>> *Sent:* Monday, August 20, 2018 12:52 PM
>> *To:* CA/B Forum Server Certificate WG Public Discussion List <
>> servercert-wg at cabforum.org>
>> *Cc:* CA/Browser Forum Public Discussion List <public at cabforum.org>
>> *Subject:* Re: [Servercert-wg] [cabfpub] Ballot SC6 - Revocation
>> Timeline Extension
>>
>>
>>
>> This has the potential to cause confusion, so I'd like to attempt to fix
>> it. Given that a reasonable interpretation of the existing definition of
>> key compromise encompasses reasons 12 and 13, but I want to leave those two
>> reasons in the document for the sake of clarity as Ryan suggests, maybe I
>> should just move those two up to the 24-hour section? I could also be
>> persuaded that a vulnerability is different than proof of key compromise,
>> in which case 12 could stay in the 5-day section and we could move "or
>> there exists a practical technique by which an unauthorized person may
>> discover its value" from the definition of key compromise to 12. What do
>> others think?
>>
>>
>>
>> - Wayne
>>
>>
>>
>> On Mon, Aug 20, 2018 at 7:04 AM Ryan Sleevi <sleevi at google.com> wrote:
>>
>>
>>
>> On Mon, Aug 20, 2018 at 9:17 AM Doug Beattie via Servercert-wg <
>> servercert-wg at cabforum.org> wrote:
>>
>> We’re having a hard time determining the differences between the
>> following:
>>
>>
>>
>> The CA SHALL revoke a Certificate within 24 hours if:
>>
>> 3. The CA obtains evidence that the Subscriber's Private Key
>> corresponding to the Public Key in the Certificate suffered a Key
>> Compromise; or
>>
>>
>>
>> and
>>
>>
>>
>> The CA SHOULD revoke a certificate within 24 hours and MUST revoke a
>> Certificate within 5 days if one or more of the following occurs:
>>
>>
>>
>> 12. The CA is made aware of a vulnerability that exposes the Subscriber's
>> Private Key to compromise; or
>>
>> 13. The CA is made aware that the Subscriber's Private Key is being
>> publicly distributed in a software package.
>>
>>
>>
>> If “Subscriber's Private Key is being publicly distributed in a
>> software package”, isn’t that the same as #3: “obtains evidence that the
>> Subscriber's Private Key corresponding to the Public Key in the Certificate
>> suffered a Key Compromise”?
>>
>>
>>
>> How do you see #12 in reality? What types of vulnerabilities do you
>> envision that could expose a subscribers Private Key that are not also
>> consistent with #3?
>>
>>
>>
>> While this is the same argument that I've made in the past, I think the
>> goal here is to reduce ambiguity for those that might take a tortured
>> reading of the text.
>>
>>
>>
>> For example, at least one vendor 'obfuscated' the private key within
>> their binary, requiring running the embedded private key through a
>> transformation (I hesitate to say decryption, since the passphrase was
>> itself fixed within the binary). Such a vendor might argue that the key has
>> not been compromised until someone reverses the binary. This resolves that
>> ambiguity by saying that the distribution within the binary itself
>> constitutes a compromise, regardless of whether a passphrase is used.
>>
>>
>>
>> Also, the definition of Private Key Compromise is very broad, and the
>> scenarios in #12 and #13 would appear to fall into “Key Compromise” which
>> further causes confusion about them. What constitutes a “*practical
>> technique*”? If we applied this definition to #12 and #13, wouldn’t
>> these all fall into the 24 hour rule?
>>
>>
>>
>> *Key Compromise:* A Private Key is said to be compromised if its value
>> has been disclosed to an unauthorized person, an unauthorized person has
>> had access to it, or there exists a practical technique by which an
>> unauthorized person may discover its value. A Private Key is also
>> considered compromised if methods have been developed that can easily
>> calculate it based on the Public Key (such as a Debian weak key, see
>> http://wiki.debian.org/SSLkeys
>> <https://na01.safelinks.protection.outlook.com/?url=http%3A%2F%2Fwiki.debian.org%2FSSLkeys&data=02%7C01%7CMike.reilly%40microsoft.com%7Ccc86f18ac7f1436d776808d606dd9e4f%7C72f988bf86f141af91ab2d7cd011db47%7C1%7C0%7C636703946261915965&sdata=VTjxlqVQj%2F5CEUKsG10UF2UoC75AtmFi3d51%2Fj9wdZ4%3D&reserved=0>)
>> or if there is clear evidence that the specific method used to generate the
>> Private Key was flawed.
>>
>>
>>
>>
>>
>> Doug
>>
>>
>>
>> *From:* Public <public-bounces at cabforum.org> *On Behalf Of *Wayne Thayer
>> via Public
>> *Sent:* Monday, August 13, 2018 4:58 PM
>> *To:* CA/B Forum Server Certificate WG Public Discussion List <
>> servercert-wg at cabforum.org>
>> *Cc:* CA/Browser Forum Public Discussion List <public at cabforum.org>
>> *Subject:* [cabfpub] Ballot SC6 - Revocation Timeline Extension
>>
>>
>>
>> This begins the formal discussion period for ballot SC6.
>>
>>
>>
>> ==========================================
>>
>>
>>
>> Ballot SC6: Revocation Timeline Extension
>>
>>
>>
>> Purpose of Ballot:
>>
>> Section 4.9.1.1 of the Baseline Requirements currently requires CAs to
>> revoke a Subscriber certificate within 24 hours of identifying any of 15
>> issues affecting the certificate. In cases where there is not an immediate
>> threat of misuse of the certificate, this requirement can cause undue harm
>> to a Subscriber that isn't capable of replacing the certificate prior to
>> revocation. This ballot makes a number of improvements to the revocation
>> rules imposed by the Baseline Requirements:
>>
>> * Primarily, it creates a tiered timeline for revocations. The most
>> critical "reasons" still require revocation within 24 hours, but for many
>> others 24 hours becomes a SHOULD and the CA has 5 days before they MUST
>> revoke.
>>
>> * A new "reason for revocation" was added to address the fact that there
>> is currently no requirement for CAs to revoke a certificate when requested
>> by the domain name registrant. After considering some more specific
>> language that required CAs to follow 3.2.2.4 to validate domain control, I
>> settled on the following more general "reason": "The CA obtains evidence
>> that the validation of domain authorization or control for any
>> Fully-Qualified Domain Name or IP address in the Certificate should not be
>> relied upon."
>>
>> * Reason #10 states "The CA determines that any of the information
>> appearing in the Certificate is inaccurate or misleading;" This ballot
>> removes "or misleading" because that is a subjective judgement that could
>> effectively be used to justify censorship, as discussed at length in
>> relation to the "Stripe, Inc of Kentucky" EV certificates.
>>
>> * Current reasons #11 and #13 were removed from the section on subscriber
>> certificates because they address cases where the intermediate and/or root
>> must be revoked, so there isn't much sense (and some possible harm) in
>> requiring revocation of all the leaf certs.
>>
>> * It requires CAs to disclose their problem reporting mechanisms in a
>> standard location: CPS section 1.5.2.
>>
>> * Within 24 hours of receiving a problem report, the CA is now required
>> to report back to both the entity reporting the problem and the Subscriber
>> on the CA's findings, and to work with the reporter to establish a date by
>> which the CA will revoke the certificate.
>>
>>
>>
>> The following motion has been proposed by Wayne Thayer of Mozilla and
>> endorsed by Tim Hollebeek of DigiCert and Dimitris Zacharopoulos of Harica.
>>
>>
>>
>> --- MOTION BEGINS ---
>>
>> This ballot modifies the “Baseline Requirements for the Issuance and
>> Management of Publicly-Trusted Certificates” as follows, based on Version
>> 1.6.0:
>>
>> ** Modify Section 4.9.1.1 to read as follows: **
>>
>> The CA SHALL revoke a Certificate within 24 hours if:
>>
>> 1. The Subscriber requests in writing that the CA revoke the Certificate;
>> 2. The Subscriber notifies the CA that the original certificate request
>> was not authorized and does not retroactively grant authorization;
>> 3. The CA obtains evidence that the Subscriber's Private Key
>> corresponding to the Public Key in the Certificate suffered a Key
>> Compromise; or
>> 4. The CA obtains evidence that the validation of domain authorization or
>> control for any Fully-Qualified Domain Name or IP address in the
>> Certificate should not be relied upon.
>>
>> The CA SHOULD revoke a certificate within 24 hours and MUST revoke a
>> Certificate within 5 days if one or more of the following occurs:
>>
>> 1. The Certificate no longer complies with the requirements of Sections
>> 6.1.5 and 6.1.6;
>> 2. The CA obtains evidence that the Certificate was misused;
>> 3. The CA is made aware that a Subscriber has violated one or more of its
>> material obligations under the Subscriber Agreement or Terms of Use;
>> 4. The CA is made aware of any circumstance indicating that use of a
>> Fully-Qualified Domain Name or IP address in the Certificate is no longer
>> legally permitted (e.g. a court or arbitrator has revoked a Domain Name
>> Registrant's right to use the Domain Name, a relevant licensing or services
>> agreement between the Domain Name Registrant and the Applicant has
>> terminated, or the Domain Name Registrant has failed to renew the Domain
>> Name);
>> 5. The CA is made aware that a Wildcard Certificate has been used to
>> authenticate a fraudulently misleading subordinate Fully-Qualified Domain
>> Name;
>> 6. The CA is made aware of a material change in the information contained
>> in the Certificate;
>> 7. The CA is made aware that the Certificate was not issued in accordance
>> with these Requirements or the CA's Certificate Policy or Certification
>> Practice Statement;
>> 8. The CA determines that any of the information appearing in the
>> Certificate is inaccurate;
>> 9. The CA's right to issue Certificates under these Requirements expires
>> or is revoked or terminated, unless the CA has made arrangements to
>> continue maintaining the CRL/OCSP Repository;
>> 10. Revocation is required by the CA's Certificate Policy and/or
>> Certification Practice Statement;
>> 11. The technical content or format of the Certificate presents an
>> unacceptable risk to Application Software Suppliers or Relying Parties
>> (e.g. the CA/Browser Forum might determine that a deprecated
>> cryptographic/signature algorithm or key size presents an unacceptable risk
>> and that such Certificates should be revoked and replaced by CAs within a
>> given period of time);
>> 12. The CA is made aware of a vulnerability that exposes the Subscriber's
>> Private Key to compromise; or
>> 13. The CA is made aware that the Subscriber's Private Key is being
>> publicly distributed in a software package.
>>
>> ** Modify section 4.9.3 as follows: **
>>
>> The CA SHALL provide a process for Subscribers to request revocation of
>> their own Certificates. The process MUST be described in the CA's
>> Certificate Policy or Certification Practice Statement. The CA SHALL
>> maintain a continuous 24x7 ability to accept and respond to revocation
>> requests and Certificate Problem Reports.
>>
>> The CA SHALL provide Subscribers, Relying Parties, Application Software
>> Suppliers, and other third parties with clear instructions for reporting
>> suspected Private Key Compromise, Certificate misuse, or other types of
>> fraud, compromise, misuse, inappropriate conduct, or any other matter
>> related to Certificates. The CA SHALL publicly disclose the instructions
>> through a readily accessible online means and in section 1.5.2 of their CPS.
>>
>> ** Modify section 4.9.5 to read as follows: **
>>
>> Within 24 hours after receiving a Certificate Problem Report, the CA
>> SHALL investigate the facts and circumstances related to a Certificate
>> Problem Report and provide a preliminary report on its findings to both the
>> Subscriber and the entity who filed the Certificate Problem Report.
>>
>> After reviewing the facts and circumstances, the CA SHALL work with any
>> entity reporting the Certificate Problem Report or other revocation-related
>> notice to establish a date when the CA will revoke the Certificate which
>> MUST not exceed the time frame set forth in Section 4.9.1.1. The date
>> selected by the CA SHOULD consider the following criteria:
>>
>> 1. The nature of the alleged problem (scope, context, severity,
>> magnitude, risk of harm);
>> 2. The consequences of revocation (direct and collateral impacts to
>> Subscribers and Relying Parties);
>> 3. The number of Certificate Problem Reports received about a particular
>> Certificate or Subscriber;
>> 4. The entity making the complaint (for example, a complaint from a law
>> enforcement official that a Web site is engaged in illegal activities
>> should carry more weight than a complaint from a consumer alleging that she
>> didn't receive the goods she ordered); and
>> 5. Relevant legislation.
>>
>> --- MOTION ENDS ---
>>
>> A comparison of the changes can be found at:
>> https://github.com/cabforum/documents/compare/master...wthayer:patch-1?short_path=7f6d14a#diff-7f6d14a20e7f3beb696b45e1bf8196f2
>> <https://na01.safelinks.protection.outlook.com/?url=https%3A%2F%2Fgithub.com%2Fcabforum%2Fdocuments%2Fcompare%2Fmaster...wthayer%3Apatch-1%3Fshort_path%3D7f6d14a%23diff-7f6d14a20e7f3beb696b45e1bf8196f2&data=02%7C01%7CMike.reilly%40microsoft.com%7Ccc86f18ac7f1436d776808d606dd9e4f%7C72f988bf86f141af91ab2d7cd011db47%7C1%7C0%7C636703946261925974&sdata=ZF1OJR2W60OJ9%2BA1c4BlDwDEQVzFc3ze2gI87AXrXow%3D&reserved=0>
>>
>>
>>
>> The procedure for approval of this ballot is as follows:
>>
>> Discussion (7+ days)
>>
>> Start Time: 2018-08-13 19:00 UTC
>>
>> End Time: Not before 2018-08-20 19:00 UTC
>>
>> Vote for approval (7 days)
>>
>> Start Time: TBD
>>
>> End Time: TBD
>>
>> _______________________________________________
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>>
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>
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