Understanding CAA Records

Learn how CAA records help control which Certificate Authorities can issue SSL/TLS certificates for your domain

What is a CAA Record?

A CAA (Certificate Authority Authorization) record specifies which Certificate Authorities (CAs) are allowed to issue SSL/TLS certificates for your domain. It's like having a list of trusted locksmiths who are allowed to make keys for your house.

Format:

domain.com.    IN    CAA    flag tag "value"

Examples:

# Allow Let's Encrypt to issue certificates
example.com.    IN    CAA    0 issue "letsencrypt.org"

# Specify email for violation reports
example.com.    IN    CAA    0 iodef "mailto:security@example.com"

# Only allow specific CA and wildcards
example.com.    IN    CAA    0 issue "sectigo.com"
example.com.    IN    CAA    0 issuewild "sectigo.com"

Simple Explanation

Think of CAA records like a VIP guest list for your domain's security:

Just like a bouncer checks a guest list, CAA records tell CAs if they're allowed to issue certificates
Like having specific doors for specific keys, you can control which CAs can issue different types of certificates
Similar to having a security office to report to, you can specify where to send reports if someone tries to break the rules

Common Uses

✓
Restrict Certificate Issuance
Control which CAs can issue certificates for your domain and subdomains.
✓
Prevent Unauthorized Certificates
Stop unauthorized CAs from issuing certificates for your domain.
✓
Monitor Certificate Activity
Receive notifications when someone attempts to issue unauthorized certificates.

Common Pitfalls

⚠️
Too Restrictive
Setting overly restrictive CAA records can prevent legitimate certificate issuance.
⚠️
Missing Wildcard Rules
Forgetting to set issuewild tags when wildcard certificates are needed.

Best Practices

✓
Set Reporting Address
Always include an iodef record to receive violation reports.
✓
Regular Review
Periodically review and update your CAA records to match your certificate needs.
✓
Test Before Deployment
Verify CAA records work as expected before deploying to production.

Security Considerations

🔒
DNSSEC Protection
Implement DNSSEC to prevent tampering with CAA records.
🔒
Regular Monitoring
Monitor CAA records and certificate issuance attempts.
🔒
Incident Response
Have a plan for responding to unauthorized certificate issuance attempts.

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