Certificate Validation & CAA (Certificate Authority Authorization)

Complete Guide to Certificate Security - Ensuring Certificates Are Authentic and Properly Authorized

What is Certificate Validation?

Certificate validation is the process by which browsers verify that SSL/TLS certificates are valid, trusted, and properly configured. Validation ensures:

• Trust Chain: Certificate is signed by a trusted Certificate Authority
• Validity: Certificate is not expired
• Domain Match: Certificate matches the domain name
• Signature: Certificate signature is valid
• Public Key: Public key is valid

Certificate Trust Chain

The trust chain is the hierarchy of certificates that links your server certificate to a trusted root Certificate Authority:

1. Root Certificate: Trusted root CA certificate (built into browsers)
2. Intermediate Certificate: Intermediate CA certificate (issued by root, issues server certificates)
3. Server Certificate: Your website's certificate (issued by intermediate CA)

If any link in the chain is missing or invalid, browsers will show certificate errors and users may not be able to access your website.

What is CAA?

CAA (Certificate Authority Authorization) is a DNS record type that specifies which Certificate Authorities are authorized to issue certificates for your domain. This prevents unauthorized certificate issuance.

Without CAA records, any Certificate Authority can issue a certificate for your domain. This allows attackers to obtain fraudulent certificates if they can convince a CA to issue them (through social engineering or compromised CA systems).

CAA records specify:

• Authorized CAs: Which Certificate Authorities can issue certificates
• Policy Flags: Additional restrictions (e.g., wildcard certificates, validation methods)
• Contact Information: Email address for certificate issuance notifications

How CAA Works

When a Certificate Authority is asked to issue a certificate for your domain:

1. CA Checks DNS: CA looks up CAA records for your domain
2. Authorization Check: CA verifies it's authorized in the CAA record
3. Certificate Issuance: CA only issues certificate if authorized
4. Rejection: CA rejects request if not authorized

This prevents unauthorized certificate issuance, even if attackers can compromise CA systems or use social engineering.

CAA Record Format

CAA records are DNS records with the following format:

example.gov. IN CAA 0 issue "letsencrypt.org"
example.gov. IN CAA 0 issuewild "letsencrypt.org"
example.gov. IN CAA 0 iodef "mailto:security@example.gov"

CAA record fields:

• Flags (0 or 128): Critical flag (0 = non-critical, 128 = critical)
• Tag: Record type (issue, issuewild, iodef)
• Value: CA domain name or email address

CAA Record Tags

CAA records support several tags:

• issue: Authorizes CA to issue certificates (required)
• issuewild: Authorizes CA to issue wildcard certificates
• iodef: Specifies email address for certificate issuance notifications

Why Certificate Validation & CAA is Critical

For government agencies, proper certificate validation and CAA records are critical:

1. Prevents Unauthorized Certificate Issuance

CAA records prevent attackers from obtaining fraudulent certificates for your domain. Without CAA, attackers can obtain certificates through:

• Social engineering of Certificate Authorities
• Compromised CA systems
• Misconfigured CA processes

2. Prevents Man-in-the-Middle Attacks

Fraudulent certificates allow attackers to perform man-in-the-middle attacks. With a fraudulent certificate, attackers can intercept HTTPS traffic, making it appear legitimate to users.

3. Ensures Browser Trust

Proper certificate validation ensures browsers trust your certificates. Invalid certificates cause browser warnings, reducing user trust and potentially blocking access.

4. Required for CISA Compliance

The Cybersecurity and Infrastructure Security Agency (CISA) mandates proper certificate validation and CAA records for government domains. Failure to implement CAA exposes your agency to liability.

Common Certificate Validation Issues

Several common issues can cause certificate validation problems:

1. Missing Intermediate Certificates

If intermediate certificates are missing, browsers cannot complete the trust chain, causing certificate errors.

Solution: Ensure all intermediate certificates are included in the certificate chain.

2. Expired Certificates

Expired certificates cause browsers to show security warnings and may block access.

Solution: Renew certificates before expiration and implement automatic renewal.

3. Domain Name Mismatch

If the certificate doesn't match the domain name (CN or SAN), browsers show certificate errors.

Solution: Ensure certificates match the exact domain name and include all subdomains if needed.

4. Missing CAA Records

Without CAA records, any Certificate Authority can issue certificates for your domain.

Solution: Create CAA records authorizing only trusted Certificate Authorities.

How to Implement CAA

Implementing CAA requires:

Step 1: Identify Authorized CAs

Identify which Certificate Authorities you want to authorize (e.g., Let's Encrypt, DigiCert, Sectigo).

Step 2: Create CAA Records

Create CAA records authorizing the selected Certificate Authorities:

example.gov. IN CAA 0 issue "letsencrypt.org"
example.gov. IN CAA 0 issue "digicert.com"

Step 3: Configure iodef (Optional)

Configure iodef to receive notifications about certificate issuance attempts:

example.gov. IN CAA 0 iodef "mailto:security@example.gov"

How YesGov Ensures Certificate Validation & CAA is Properly Configured

YesGov handles all aspects of certificate validation and CAA for government agencies:

• Complete Validation: We verify certificate trust chains, validity, and domain matching
• CAA Configuration: We create CAA records authorizing only trusted Certificate Authorities
• Certificate Management: We ensure certificates are valid, not expired, and properly configured
• Automatic Renewal: We implement automatic certificate renewal to prevent expiration
• Monitoring: We monitor certificate status and CAA records continuously
• Documentation: All certificate and CAA configuration is documented for compliance and insurance purposes

How YesGov Ensures Complete Certificate Validation & CAA Protection

At YesGov, we don't just check if certificates are valid—we perform comprehensive validation of your entire certificate and CAA setup:

• Trust Chain Verification: We verify the complete certificate chain to trusted root CAs
• Domain Matching: We ensure certificates match your domain names correctly
• Expiration Monitoring: We monitor certificate expiration and renew before expiry
• CAA Configuration: We create CAA records authorizing only trusted Certificate Authorities
• Certificate Validation: We verify certificates are valid, not revoked, and properly configured
• Ongoing Monitoring: We continuously monitor certificate status and CAA records
• Documentation: All certificate and CAA configuration is documented for compliance

When you host with YesGov, certificate validation and CAA are properly configured, continuously monitored, and automatically maintained. We handle trust chain verification, CAA record management, and certificate renewal so you don't have to worry about unauthorized certificate issuance. This is one of our comprehensive security checks that ensures your agency meets and exceeds federal, state, and industry standards.

Additional Resources

• Back to Learn Home
• SSL/TLS Certificates
• HSTS (HTTP Strict Transport Security)
• TLS Configuration
• Check Your Domain's Certificate & CAA Status
• Website Security Overview
• Contact YesGov for Services

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