CA/Lessons Learned

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Since 2014, over 1,000 incidents involving Certification Authorities (CAs) have been recorded. This page aims to collect, categorize, and analyze common compliance issues, including their underlying causes and the corrective measures that CA operators have implemented. A review of these incidents has uncovered a variety of recurring problems, ranging from certificate misissuance to reporting issues. The table below provides a high-level, categorized overview of these compliance issues and sets forth a few remediation actions that CA operators can implement to address each issue. By learning from these past mistakes and adopting these recommended practices, CA operators can enhance their compliance posture and ensure the integrity and reliability of the certificates they issue.

This wiki page is an initial draft, and we invite suggestions from the Mozilla community on how it can be improved.

Incorrect Certificate Profiles and Misconfigured Certificates
Compliance Issue Corrective Measures
General Issues of Non-Compliance

(e.g. certificates that do not comply with CA/B Forum requirements or Mozilla Policy)

Closely monitor changes in requirements; conduct regular audits and reviews; provide training; implement automated compliance tools
Certificate Profile Errors

(see below - certificates issued with profiles not adhering to requirements, certificates with incorrect Subject attribute order, incorrect key usages, etc.)

Use standardized templates that have been validated against CABF and Mozilla requirements; automate the profile validation process
Duplicate Serial Numbers

Bug #s 1636140, 1677737

Unique serial number generation; database checks; eliminate the potential that certificate orders remain in the issuance queue when re-starting or re-configuring CA systems; generate the final certificate immediately upon receipt of the SCTs;
Insufficient Serial Number Entropy

Numerous bugs

Check entropy with pre-issuance linting; specify more entropy than is required; follow cryptographic best practices; keep CA software up to date; test CA software for compliance with requirements; provide developers with training on the proper calculation of entropy;
Improper Key Usage

Bug #s 1756122, 1647468, 1667448, 1703528

Pre-issuance linting; check keyUsage configuration in certificate profiles using automated tools; review section 7 of the Baseline Requirements; implement dual control for certificate template changes;
Invalid CN/SAN Entries

Bug #s 1687139, 1705187, 1716123, 1462423, 1897346

Pre-issuance linting; implement automated checks for CN and SAN matching; conduct code review and system testing;
Invalid Certificate Extensions/Non-Standard Extensions

Bug #s 1899466, 1876565, 1498463, 1524451

Implement strict validation processes to detect and reject non-standard extensions; stay updated on revisions to requirements; implement pre-issuance linting;
Invalid OrganizationIdentifier

Bug #s 1897538, 1898986, 1769240, 1900492

Write detailed specifications; conduct code review; improve training and internal communications; improve linting; update validation scheme logic; replace manual processes with automation;
Overly Long Certificate Lifetimes/Validity Periods

Bug #s 1826713, 1774418, 1676352

Keep certificate profile management system updated; review certificate profiles on system startup; implement pre-issuance linting; set maximum validity periods to much less than that allowed by the requirements; don’t give credits for early certificate renewals;
Use of Deprecated or Incorrect Algorithms

Bug #s 1648472, 1793441, 1664328,

Stay up-to-date with approved algorithms listed in requirements; conduct detailed certificate profile checks, and use automation where feasible; update system logic so that it selects the correct algorithm; implement pre-issuance linting;
Wildcard Mis-issuance

Bug #s 1446121, 1528263, 1782391, 1731939,

Block wildcards in EV certificates; ensure proper syntax and ASN.1 encoding per RFC 5280; implement pre-issuance linting;
Incorrect Certificate Subject Details
Invalid Organization Information

Bug #s 1680083, 1674886, 1838371, 1535735, 1662382, 1705647, 1746421, 1813989, 1815527, 1828105, 1826235

Implement stringent validation and pre-issuance linting; ensure that any abbreviations used are correct; cross-check with multiple authoritative databases; sanitize internal lookup databases; ensure correct domain name registrant's organization name is placed in the certificate; prevent placement of organization information in DV certificates; test system changes; automate lookups and reduce human error; do not rely on CSRs for organization information;
Incorrect Address Fields


locality names,




Automate address validation and reduce human involvement that leads to typos, etc.; cross-check with multiple authoritative databases; prevent placement of organization information in DV certificates; sanitize internal lookup databases; do not rely on CSRs for organization information; implement tools that verify locality, state, and country combinations; do not allow the pass-through of default/filler data into the certificate; use the correct abbreviations for geographic locations;
Insufficient Domain Validation
Improper Use of Domain Validation Methods (Issuance of Certificates for Unregistered Domains) Enforce use of approved methods; eliminate potential for human error; regularly update CP and CPS with allowed methods; use proper Random Values; do not use look-ups to external resources that are subject to attack;
CAA-based Misissuances

Summary search string: CAA

Automate and do not bypass CAA record checks; keep CAA verification logic up to date; communicate CAA checking requirements clearly to developers; run CAA checks immediately before certificate issuance (to avoid TTL issues with CAA records); check all domains to be contained in the certificate
Failure to Revoke and Revocation Delays
Delayed Revocations

Whiteboard search: leaf

Automated revocation systems; improved incident response procedures; reduced mis-issuance (see rows above), including pre-issuance linting, thorough review of certificate profiles, improved validation, etc.
Disclosure/Reporting Failures
Delayed, Incomplete, or Failed Disclosure of Intermediate CA Certificates in the CCADB

Whiteboard: disclosureSummary search string: intermediate

Ensure coverage; provide training on CCADB tasks, especially on staff turnover; use automated tools for timely disclosure; include CCADB disclosure in key ceremony procedures; cross-reference internal databases with information in the CCADB; conduct regular audits; monitor the activity of external intermediate/subordinate CAs;
Failure to Respond to CA Survey

Summary search string: Survey

Make sure emails are received; keep CCADB updated with communication group email addresses; provide training; document procedures; prioritize responses to root programs; set deadlines in calendaring systems
CRL and OCSP Failures
Unavailable CRLs and OCSP Service Outages

Whiteboard: crl OR ocspSummary search string: avail

Deploy high-availability solutions on redundant systems; publish to CDNs; continuous monitoring and alerts; monitor on and; make sure CRLs have the correct names and match what is in certificates;
Incorrect OCSP Responses

Whiteboard: ocspSummary search string: response

Update CA software; perform QA testing; monitor performance of internal systems; regularly check; ensure that OCSP responses are provided for pre-certificates;
Expired or Invalid CRLs

Whiteboard: crlSummary search string:expired

Implement automated CRL management; validate CRL profiles against CABF and root program requirements;
Mismatch Between CA SubjectDN and CRL Issuer SubjectDN

Bug #s 1888371,

Implement consistency checks and ensure that CRL issuer matches CA subject byte-for-byte; monitor on;
Policy and Practice Failures
Failure to Publish Annual CP or CPS Updates

Bug #s 1565494, 1769222

Summary search string: annual cps update

Schedule regular updates; involve stakeholders in review process; ensure adequate staffing;
Mistakes and erroneous information in CP or CPS

Whiteboard: policySummary search string:cps

Update CP/CPS to address CABF and root program changes to requirements (e.g. domain validation methods); implement validation processes for CP/CPS updates; conduct regular CP/CPS reviews that also checks operational behaviors (e.g. CRL issuance frequency); double-check certificate profiles published in CP/CPS; conduct peer reviews before CP/CPS publication; include CP/CPS review in operational change processes (whenever a proposed code change will introduce or change a feature);
Delayed Responses to Certificate Problem Reports (CPRs)

Whiteboard label:policy-failureSummary search string:cpr

Establish clear response time policies; use email distribution lists; designate a sufficient number of responsible individuals to answer CPRs; use automated ticketing systems; update CCADB records as soon as changes occur;
Audit Issues, Delays, and Failures
Delayed Audit Statements

Whiteboard label: audit-delay

Implement strict audit scheduling; use calendaring, monitoring and alerting; enter into engagement letters with auditors well ahead of the planned audit dates; develop contingency plans to address potential delays, disruptions, or auditor unavailability; gather documentation in advance of audit; follow up with auditor on expected delivery of audit letter;
Audit Letter Validation Failures

Summary search string: ALV

Follow all guidance on the CCADB website, including;
Missing CAs in Audit Letters

Whiteboard label:audit-failureSummary search string:intermediate

Include all intermediate and cross-certified CAs “capable of issuing” the particular kind of end entity certificate covered by the audit (TLS Capable, S/MIME Capable, etc.); use the 7MB All CA Certificates CSV list to identify all CA certificates that are “capable” of such issuance; communicate audit letter requirements to your auditor;
Auditor Qualifications

Whiteboard label: auditor-compliance

Ensure auditors are qualified and certified; review the Mozilla wikipage on Auditor Qualifications;
Test Certificates
Test Website Certificates

Summary search string: test website

Implement certificate management tools; and calendaring for replacing the certificates used on test websites; regularly check for certificate expiration for “valid” and “revoked” certificates; provide training;
Issuance of Test Certificates

Summary search string: test certificate

Use PKI hierarchies that are not publicly trusted or complete all validation and other pre-issuance steps for the test certificate;
Internal Security Issues
Logging Issues

Summary search string: log

Implement robust log management systems; log to a separate log server; leverage “big data” solutions; freeze operations if logging is not working; monitor logs in real-time with solutions that provide alerting and data analysis; regularly audit system logs;
Improper Access Control

Summary search string: access

Establish and follow strict access control policies; conduct regular reviews of access control lists;