CA/Subordinate CA Checklist

In considering a root CA for inclusion, Mozilla must also evaluate the current subordinate CAs as described in this wiki page.

If Mozilla accepts and includes a root certificate, then we have to assume that we also accept any of that root's future sub-CAs and their sub-CAs. Therefore, the selection criteria for sub-CAs and their sub-CAs is considered a critical decision factor. The CP/CPS should clearly explain the types of organizations that apply to operate a sub-CA (at any level), the selection/approval process for sub-CAs and their sub-CAs, the verification procedures applied to sub-CAs and their sub-CAs, what restrictions (legal and technical) are placed on all sub-CAs (eg constraints to issuing certs within certain domains), and how the sub-CAs are monitored/audited.

In the situation where the root CA functions as kind of a super CA and their CA policies don't apply to the subordinate CAs (including auditing), then the subordinate CAs must apply for inclusion themselves, as separate trust anchors.

Terminology

The following terminology will be used in this wiki page regarding subordinate CAs.

In-House: The subordinate CA is operated by the same organization operating the root CA.

Third-Party: The subordinate CA is operated by a third party external to the root CA organization.

Private: The subordinate CA issues certificates to entities affiliated with the sub-CA organization.

Public: The subordinate CA issues certificates to entities not affiliated with the sub-CA organization.

There are four possible combinations:

1. In-house public subordinate CAs: This is the case where a commercial CA establishes one or more internally-operated subordinates to offer certificates of a particular type (e.g., EV vs. non-EV certificates, or SSL certificates vs. email certificates) to the general public.
   • For this case, the standard root inclusion process applies, and it will be verified that the sub-CAs are sufficiently covered by the CP/CPS and audits.
2. In-house private subordinate CAs: This case would cover CA organizations that establish subordinate CAs for internal testing or other internal purposes.
   • For this case, the standard root inclusion process applies, and it will be verified that the sub-CAs are sufficiently covered by the CP/CPS and audits.
3. Third-party public subordinate CAs: In this case the root signs subordinate CAs for organizations who operate the sub-CA to sign certificates for other entities not affiliated with their organization. One example is a commercial CA which establishes one or more subordinate CAs to be operated by third-party organizations acting as Certificate Service Providers (CSP). Another example is a government-sponsored root CA where the organization running the root CA delegates to other organizations the task of issuing end entity certificates to the general public. For example, there might be a separate organization authorized to issue certificates for general business purposes, another organization issuing certificates specifically within a vertical industry sector like financial services, a third organization to issue certificates to individuals, and so on.
   • A typical Mozilla user is likely to encounter certificates issued by these third parties in the course of typical activities like web browsing. Hence we need assurances that these third parties are required to follow practices that satisfy the Mozilla CA Certificate Policy, and we need to ensure that these third parties are under an acceptable audit regime.
   • The root CA is required to disclose the identity of these third parties, because they are essentially functioning as public CAs.
   • Please see the section below which outlines the additional information that must be provided for third-party public subordinate CAs.
4. Third-party private (or enterprise) subordinate CAs: This is the case where a commercial CA has enterprise customers who want to operate their own CAs for internal purposes, e.g., to issue SSL server certificates to systems running intranet applications, to issue individual SSL client certificates for employees or contractors for use in authenticating to such applications, and so on.
   • These sub-CAs are not functioning as public CAs, so typical Mozilla users would not encounter certificates issued by these sub-CAs in their normal activities.
   • For these sub-CAs we need assurance that they are not going to start functioning as public CAs. Currently the only assurances available for this case it to ensure that these third parties are required to follow practices that satisfy the Mozilla CA Certificate Policy, and that these third parties are under an acceptable audit regime.
     • Note: Mozilla is investigating ways to programmatically ensure that these types of sub-CAs are only able to issue certificates within their domain.
   • Please see the section below which outlines the additional information that must be provided for third-party private (or enterprise) subordinate CAs.

Third-Party Private (or Enterprise) Subordinate CAs

When your root signs subordinate CAs for enterprises/companies who operate the sub-CA for their own use, the following information needs to be provided and publicly available.

1. General description of the sub-CAs operated by third parties.
2. The CP/CPS that the sub-CAs are required to follow.
3. Requirements (technical and contractual) for sub-CAs in regards to whether or not sub-CAs are constrained to issue certificates only within certain domains, and whether or not sub-CAs can create their own subordinates.
4. Requirements (typically in the CP or CPS) for sub-CAs to take reasonable measures to verify the ownership of the domain name and email address for end-entity certificates chaining up to the root, as per section 7 of our Mozilla CA certificate policy.
   • domain ownership/control
   • email address ownership/control
   • digitally signing code objects -- entity submitting the certificate signing request is the same entity referenced in the certificate
5. Description of audit requirements for sub-CAs (typically in the CP or CPS)
   • Whether or not the root CA audit includes the sub-CAs.
   • Who can perform the audits for sub-CAs.
   • Frequency of the audits for sub-CAs.

Third-Party Public Subordinate CAs

This section applies when your root signs subordinate CAs for companies who use the sub-CA to sign other sub-CAs or certificates for other companies or individuals not affiliated with their company. For instance, this section applies to you if your root issues sub-CAs that are used by Certificate Service Providers (CSP).

In addition to the information listed above, you will also need to provide the following information for each CSP.

1. Sub-CA Company Name
2. Sub-CA Corporate URL
3. Sub-CA cert download URL
4. General CA hierarchy under the sub-CA.
5. Sub-CA CP/CPS Links
6. The section numbers and text (in English) in the CP/CPS that demonstrate that reasonable measures are taken to verify the ownership of the domain name and email address for end-entity certificates chaining up to the root, as per section 7 of our Mozilla CA certificate policy.
   • domain ownership/control
   • email address ownership/control
   • digitally signing code objects -- entity submitting the certificate signing request is the same entity referenced in the certificate
7. Identify if the SSL certificates chaining up to the sub-CA are DV and/or OV. Some of the potentially problematic practices, only apply to DV certificates.
   • DV: Organization attribute is not verified. Only the Domain Name referenced in the certificate is verified to be owned/controlled by the subscriber.
   • OV: Both the Organization and the ownership/control of the Domain Name are verified.
8. Review the CP/CPS for Potentially Problematic Practices. Provide further info when a potentially problematic practice is found.
9. If the root CA audit does not include this sub-CA, then for this sub-CA provide a publishable statement or letter from an auditor that meets the requirements of sections 8, 9, and 10 of our Mozilla CA certificate policy.
10. Provide information about the CRL update frequency for end-entity certificates. There should be a statement in the CP/CPS that the sub-CA must follow to the effect that the CRL for end-entity certs is updated whenever a cert is revoked, and at least every 24 or 36 hours.
11. If this sub-CA provides OCSP, then a test must be done to make sure that their OCSP responder works within the Firefox browser. Provide the url to a website whose SSL cert chains up to this sub-CA and has the AIA extension referencing the OCSP responder. The Mozilla representative will perform the following check:
    • Enforce OCSP in Firefox: Tools->Options…->Advanced->Encryption->Validation
    • Select the box for “When an OCSP server connection fails, treat the certificate as invalid”
    • Browse to the given url. Ensure that the website loads without error into Firefox, and that it's SSL cert chains up to the sub-CA and references the OCSP responder in the AIA extension.