Understanding DNSSEC: How to Deploy and Secure Your Domain's DNS Print

Pre-requirements

• Access to your domain registrar's DNS management interface.
• Administrator access to your DNS infrastructure (if signing domains).
• Understanding of cryptographic keys, digital signatures, and DNS architecture.

DNSSEC Overview: What You Need to Know

DNSSEC (Domain Name System Security Extensions) is a set of protocols that adds an authentication layer to DNS, ensuring data integrity and origin authenticity. While DNSSEC does not provide confidentiality, it validates DNS responses to prevent attacks such as DNS spoofing or cache poisoning.

DNSSEC Key Features

• Authenticity: DNSSEC allows DNS servers to provide cryptographically signed data, proving that the response is from a legitimate source.
• Data Integrity: DNSSEC guarantees that the DNS data was not altered during transit.
• Chain of Trust: DNSSEC builds a hierarchy of trust from the root domain down to your domain using DS (Delegation Signer) and DNSKEY records.
• Proof of Non-Existence: DNSSEC enables authoritative servers to prove the non-existence of a domain or record, preventing certain types of denial-of-service (DoS) attacks.

Steps to Deploy DNSSEC

1. DNSSEC Validation (Recursive)

1. Choose a DNS service provider that supports DNSSEC validation. Many public DNS providers like Google Public DNS and Cloudflare's 1.1.1.1 already support it.
2. If you're managing your own DNS infrastructure, enable DNSSEC validation by configuring your recursive DNS servers to validate DNSSEC signatures.
3. For Linux, use BIND to configure DNSSEC validation:

   options {
       dnssec-enable yes;
       dnssec-validation auto;
   };

4. Test your configuration by querying a DNSSEC-enabled domain:

   dig +dnssec example.com

5. If the domain supports DNSSEC, you should see DNSSEC-related records (RRSIG, DNSKEY, etc.) in the output.

2. DNSSEC Signing with PowerDNS (Authoritative)

PowerDNS offers DNSSEC support and integrates well with cPanel and other control panels. Here's how to enable DNSSEC for authoritative zones in PowerDNS:

1. Ensure PowerDNS is compiled with DNSSEC support (this is the default in most distributions).
2. Enable DNSSEC in the PowerDNS configuration. Open the pdns.conf file and set the following:

   launch=gmysql
   dnssec=on

3. To sign a zone, use the pdnsutil tool:

   pdnsutil secure-zone example.com

4. Generate DS records to be uploaded to your domain registrar:

   pdnsutil show-zone example.com

   This will display the DNSSEC-related records, including the DS record.
5. Upload the DS record to your registrar to complete the DNSSEC setup.
6. Once DNSSEC is active, monitor PowerDNS logs for any DNSSEC-related errors or issues.

Verifying DNSSEC with PowerDNS

After DNSSEC is enabled and the zone is signed, you can verify DNSSEC functionality by querying the zone with:

dig +dnssec example.com

This command should return the DNSSEC RRSIG and other relevant records, confirming that the zone is signed and DNSSEC is properly configured.

3. DNSSEC Signing (Authoritative)

Deploying DNSSEC for authoritative domains requires coordination with your domain registrar and your DNS infrastructure. Follow these steps:

1. Generate DNSSEC keys (KSK and ZSK) on your authoritative DNS servers. For example, with BIND:

   dnssec-keygen -a RSASHA256 -b 2048 -n ZONE example.com

2. Sign the zone using the DNSSEC keys:

   dnssec-signzone -A -3 randomsalt -N increment -o example.com -t db.example.com

3. Upload the DS Record to your domain registrar. This record connects your signed domain to the parent zone, establishing the chain of trust.
4. Once DNSSEC is enabled, monitor the logs for any validation or signing issues.

DNSSEC Responses

• Secure: The domain is DNSSEC-enabled, and the validating resolver verified the response. The response is flagged with an authenticated data (AD) flag.
• Insecure: The domain does not support DNSSEC, so the resolver falls back to traditional DNS resolution.
• Bogus: The domain supports DNSSEC, but the resolver found an issue during validation, which means the response is invalid or the domain is misconfigured.

Gotchas to Avoid

• Ensure your DNS software and libraries are current, as older versions may not fully support DNSSEC.
• Do not sign internal private namespaces, as dynamic updates require re-signing the entire zone.
• When generating DNSSEC keys, choose appropriate algorithms and key lengths (e.g., RSASHA256) to balance security and performance.
• Monitor for configuration errors such as mismatched keys, invalid DS records, or missing chain-of-trust links, which can result in SERVFAIL responses.

Linux Commands for DNSSEC Validation

To test DNSSEC on your local Linux machine, use the following commands:

dig +dnssec example.com
dig +dnssec +short example.com

These commands will display DNSSEC-related information, such as RRSIG and DNSKEY records, ensuring that DNSSEC works correctly.

DNSSEC is essential for ensuring the integrity and authenticity of DNS responses. While DNSSEC deployment on the validation side can be simple, deploying it on the authoritative side requires careful planning and cooperation with domain registrars. Implement DNSSEC in stages, starting with validation, and progressing to signing your authoritative zones to enhance your domain's security.