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 a work in progress, and we invite suggestions from the Mozilla community on how it can be improved.

Incorrect Certificate Profiles and Misconfigured Certificates
Compliance Issue Bug References 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, 1907667 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 streetAddress,

locality names,

stateOrProvinceName,

postalCode,

country

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 and Issuance of Certificates for Unregistered Domains Summary contains "domain validation method" or "unregistered" 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 Reduced mis-issuance (see rows above), including pre-issuance linting, thorough review of certificate profiles, and improved validation; detailed changes to policies and procedures to ensure timely revocation, including improved incident response procedures, new guidelines, checklists, approval processes, and clearer subscriber communications; and automation and technological improvements to the infrastructure, including monitoring, auditing, and alerting, for faster detection and response to incidents requiring revocation and to quickly identify lapses in compliance with such policies and procedures
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 https://sslmate.com/labs/crl_watch/ and https://sslmate.com/labs/ocsp_watch/; 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 https://sslmate.com/labs/ocsp_watch/; 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 https://sslmate.com/labs/crl_watch/
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 https://www.ccadb.org/cas/alv
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