DNS CAA (Certificate Authority Authorization) Record

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DNS CAA

A DNS CAA (Certificate Authority Authorization) record is a DNS record that specifies which Certificate Authorities (CAs) are allowed to issue SSL/TLS certificates for a domain. It helps improve security by preventing unauthorized CAs from issuing certificates for your domain.

Example of a CAA Record:

Hostname: example.com

Record Type: CAA

Flag: 0 (critical flag, set to 0 for standard use)

Tag: issue

Value: letsencrypt.org

✅ Explanation:
This record means only Let's Encrypt can issue SSL certificates for example.com.

CAA Record Structure:

A CAA record consists of three components:

Flag:

0 = Non-critical (most common)

128 = Critical (if the CA does not understand the record, it must reject certificate issuance)

Tag:

issue: Authorizes a CA to issue certificates for the domain.

issuewild: Authorizes a CA to issue wildcard certificates (*.example.com).

iodef: Specifies an email or URL for CA to report policy violations.

Value:

Specifies the CA (e.g., letsencrypt.org, digicert.com).

Example CAA Record Setups:

✅ Allow Let's Encrypt only:

plaintext

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example.com. CAA 0 issue "letsencrypt.org"

✅ Allow Let's Encrypt for wildcard certificates:

plaintext

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example.com. CAA 0 issuewild "letsencrypt.org"

✅ Send policy violation reports:

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example.com. CAA 0 iodef "mailto:admin@example.com"

Why Use CAA Records?

Enhanced Security: Prevent unauthorized SSL certificates.

Compliance: Helps meet industry security standards.

Transparency: CAs must check CAA records before issuing certificates.