[Servercert-wg] [cabfpub] Ballot SC6 - Revocation Timeline Extension

[Ryan Sleevi]

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) 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
>
>
>
> 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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