CA/Audit Letter Validation

The Common CA Database (CCADB) uses an Audit Letter Validation (ALV) tool to automatically parse and validate audit statements. This system eliminates manual processing, but it requires audit statements to follow some basic rules in order to function properly.

• Audit Statement Requirements and Format Rules - If an audit statement fails to meet any of these requirements, the CA will be asked to work with their auditor to provide an audit statement that passes ALV.

Root Certificates

CAs are required to update the audit, CP, CPS and test website information for their certificate hierarchies at least annually. To provide this information for root certificates, create one Audit Case in the CCADB for a particular set of audits (e.g. Standard Audit, BR audit, EV Audit). Then create a set of corresponding Root Cases, one per root certificate, to tell the CCADB which Root Certificate records the audit statements in that Audit Case apply to.

• Audit Case Work Flow
• Detailed Instructions
  • Information Required to create an Audit Case
• Run ALV on Preliminary Audit Statements

Intermediate Certificates

CAs are required to update the audit and CP/CPS for their non-technically-constrained intermediate certificates chaining to root certs included in Mozilla's program at least annually. To provide this information for intermediate certificates, directly update the corresponding record in the CCADB then click on the "Audit Letter Validation [ALV]" button.

ALV on Intermediate Certificate Records

The following two fields are set by running ALV on an intermediate certificate record in the CCADB. CAs may cause ALV to be run on the record by clicking on the "Audit Letter Validation [ALV]" button. Additionally CCADB has automated processes that will regularly check for intermediate certificate records that need to have ALV run.

1. Standard Audit ALV Found Cert
   • This field will be set to PASS when ALV finds the SHA-256 Fingerprint for that certificate in the standard audit statement.
2. BR Audit ALV Found Cert
   • This field will only be set when the "Derived Trust Bits" field has 'Server Authentication' in its list.
   • This field will be set to PASS when ALV finds the SHA-256 Fingerprint for that certificate in the BR audit statement.

When ALV returns FAIL for either "Standard Audit ALV Found Cert" or "BR Audit ALV Found Cert" for one of your CA's intermediate certificate records in the CCADB, do the following.

• Check the corresponding audit statement to make sure the SHA-256 fingerprint of the certificate is correctly listed.
• If the SHA-256 fingerprint is listed in the audit statement, then make sure that it meets the format specifications, such as no colons, no spaces, no line feeds.
  • For existing audit statements (e.g. audit statements issued in 2019) add a comment to the "Standard Audit ALV Comments" or "BR Audit ALV Comments" fields indicating that the SHA-256 fingerprint of the certificate is listed but has a formatting problem that will be fixed in the next annual audit statement.
  • For new audit statements (e.g. audit statements issued in 2020 or later) have your auditor provide an updated audit statement that follows the formatting requirements for the SHA-256 Fingerprints.
• If you do not agree with the ALV results, add comments to the "Standard Audit ALV Comments" or "BR Audit ALV Comments" fields to indicate that the SHA-256 fingerprint is listed correctly in the audit statement.
• If the audit statement is indeed missing the SHA-256 fingerprint for the certificate, then file an Incident Report, and add the link to the Incident Report in Bugzilla to the "Standard Audit ALV Comments" or "BR Audit ALV Comments" fields.

Derived Trust Bits logic:

• If the certificate has an Extended Key Usage (EKU) extension, then the "Derived Trust Bits" field is set to values in that extension.
• Otherwise CCADB checks the root certificate that the certificate chains up to.
  • If the root certificate is in only one of Mozilla'a or Microsoft's root stores then the "Derived Trust Bits" field is set to the trust bits that are enabled for that root certificate by that root store.
  • If the root certificate is in both Mozilla'a and Microsoft's root stores then the "Derived Trust Bits" field is set as the union of the trust bits that are enabled for the root certificate in both programs.

Cross-Certificates are also considered intermediate certificates, which must also be audited and specifically listed in the applicable audit statements according to the "Derived Trust Bits" field.

When the "Audits Same as Parent" field is checked for an intermediate certificate record in the CCADB, the CCADB will look up the parent chain until audit statements are found, and then run ALV using those audit statements. When the "Audits Same as Parent" field is not checked, the CCADB will directly pass the audit statements in the intermediate certificate record into ALV.

Background

Subordinate CAs who operate non-technically-constrained intermediate certificates have the keys to the internet just as much as the CAs who have root certificates directly included in Mozilla's root store. Meaning that such subordinate CAs can also issue TLS certificates for any website or domain, so it is imperative that the same rules are being followed by all subordinate CAs operating non-technically-constrained intermediate certificates.

There are currently about 150 root certificates in Mozilla's root store , which leads to about 2,500 intermediate certificates that are trusted by Mozilla's root store. To help enforce the rules at the intermediate certificate level, Mozilla requires disclosure of non-technically-constrained intermediate certificates in the CCADB, which automatically runs ALV on them and reports the results to CAs and root store operators in their CCADB home page.

• Progress towards enforcement at intermediate certificate level