Need to deploy DNSSEC? NIST publishes its how-to

Secure and dependable use of the Internet depends on the ability of users and devices to navigate the Web using familiar domain names that are mapped to IP addresses.

“To access Internet resources by user-friendly domain names rather than IP addresses, users need a system that translates domain names to IP addresses and back,” a new security publication from the National Institute of Standards and Technology states. “This translation is the primary task of an engine called the Domain Name System.”

Because ensuring the availability and integrity of DNS is an essential element of cybersecurity, NIST has updated its “Secure Domain Name System Deployment Guide."

Revision 1 of Special Publication 800-81 provides guidelines for securing DNS within the enterprise, including the use of DNS Security Extensions (DNSSEC) for digitally signing zone information for verification. Because DNS information is meant to be public, the primary security goals for the system are data integrity and source authentication to ensure the authenticity of domain names. Preventing denial-of-service attacks to ensure availability is also critical.

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The revised document was approved in April, but publication was delayed until August to allow for additional editing and formatting. The revised version contains three new sections with guidelines for migrating to a new cryptographic algorithm for signing the DNS zone, moving to NSEC3 hashing specifications for authenticating denial-of-existence replies for domains and using DNSSEC in split-zone deployments.

The DNS infrastructure is a distributed, hierarchical system that provides domain name and IP address translation for more than 250 top-level domains and millions of secondary domains. There are millions of domain name servers in the infrastructure, each providing information about a small segment of the domain name space. The system depends on the ability of the elements to collaborate reliably, and domain name data provided by DNS is intended to be available to any computer anywhere on the Internet.

DNS presents some peculiar security challenges. A spoofed DNS node can deny access to a broad set of Internet resources for which the node provides information. If the integrity of DNS information on an authoritative server is violated, DNS' chained information-retrieval process can be broken, resulting in a denial of service for DNS name resolution or misdirection of users to illegitimate resources.

The DNS-specific recommendations in NIST's deployment guidelines include:

• Implementing appropriate system and network controls for securing the DNS hosting environment, such as operating system and application patching, process isolation and network fault tolerance.
• Protecting DNS transactions, such as updating DNS name resolution data and replicating data on enterprises' DNS nodes using hash-based message authentication codes.
• Protecting ubiquitous DNS query/response transactions by using digital signatures based on asymmetric cryptography.

“Part of those recommendations is deployment of [DNSSEC] for zone information,” the NIST document states. Basic steps for DNSSEC deployment are:

• Installing a DNSSEC-capable name server.
• Checking zone file(s) for integrity errors.
• Generating a key pair for each zone and including them in the zone file.
• Signing the zone.
• Loading the signed zone onto the server.
• Configuring the name server to turn on DNSSEC processing.

A copy of the public key also can be sent to a parent for secure delegation.