Fortifying DNS Against Cache Poisoning

Overview

This recipe hardens your DNS infrastructure against cache poisoning, a type of attack where a malicious actor inserts fraudulent DNS data into a resolver's cache, causing users to be redirected to malicious sites. By implementing DNSSEC and other best practices, you can significantly reduce the risk of cache poisoning.

DNS Records and Configuration

1. DNS Security Extensions (DNSSEC)

   • Type: Multiple Record Types including DNSKEY, RRSIG, DS, NSEC/NSEC3
   • Purpose: Adds cryptographic signatures to DNS data to ensure its authenticity.
   • Details: DNSSEC provides a way for software to validate that the DNS responses are authentic and have not been tampered with. It uses public key cryptography and is outlined in RFC 4033, among others.
   • Implementation: Configure your DNS server to sign your zones, and then publish the DNSSEC keys (DNSKEY) and signatures (RRSIG) as well as Delegation Signer (DS) records with your domain registrar or parent zone. Examples: @ IN DNSKEY 256 3 13 <Key Tag> <Public Key> @ IN RRSIG A 13 2 3600 <Signature Expiration> <Signature Inception> <Key Tag> <Signer's Name> <Signature> @ IN DS <Key Tag> 13 2 <Digest>

2. Secure Delegation Utilizing CDS and CDNSKEY Records

   • Type: CDS and CDNSKEY
   • Purpose: Automates the process of updating DS records in the parent zone.
   • Details: CDS (Child Delegation Signer) and CDNSKEY (Child DNSKEY) records are used to automatically update the DS records in the parent zone without manual intervention, as described in RFC 7344.
   • Implementation: Ensure your DNS server or service provider supports CDS and CDNSKEY automatic updates to streamline DNSSEC maintenance. Examples: @ IN CDS <Key Tag> 13 2 <Digest> @ IN CDNSKEY 256 3 13 <Public Key>

Explanation and Benefits

• DNSSEC: Guarantees the validity of DNS responses, making it very difficult for an attacker to forge DNS records.
• CDS and CDNSKEY Records: Facilitate the automated management of DNSSEC's trust chain, which is critical for maintaining security without excessive administrative burden.

Implementation Tips

• Use an automated tool to check for implementation mistakes in your DNSSEC configuration, such as the VeriSign DNSSEC Debugger.
• Monitor for CDS/CDNSKEY records and ensure that automatic DS updates occur smoothly.

This recipe provides a robust defense against DNS cache poisoning, ensuring that your users reach their intended destinations on the internet without interference from malicious actors.

Created at: 2023-12-26 04:44:22