PolarDNS: Open-source DNS server tailored for security evaluations

PolarDNS is a specialized authoritative DNS server that allows the operator to produce custom DNS responses suitable for DNS protocol testing purposes.

What can you do with PolarDNS?

PolarDNS can be used for testing of:

• DNS resolvers (server-side)
• DNS clients
• DNS libraries
• DNS parsers and dissectors
• Any software handling DNS information

Some examples of DNS responses that PolarDNS can produce include:

• Alias (CNAME) chains and alias loops
• DNS header malformations (ID, Flags, number of sections)
• Injection of unsolicited records (cache poisoning)
• Injection of arbitrary bytes of arbitrary lengths
• Incomplete / empty / NULL byte(s) responses
• Compression issues (loops, invalid pointers)
• Slowly transmitted chunked responses
• Illegal labels or domain name lengths
• An arbitrary number of TXT records of arbitrary size
• Packet length manipulations (TCP)

These can lead to the discovery of various vulnerabilities, such as:

• Sloth domain attacks
• Phantom domain attacks
• Domain lock-up attacks
• Cache poisoning
• Resource exhaustion
• Crashes, DoS

What makes PolarDNS unique?

To learn more about PolarDNS, we talked with Sumit Dhar, CEO at OryxLabs, who provided insight into the tool.

“To address our requirements, the internal security team at OryxLabs decided to create PolarDNS – a tool that could provide a more comprehensive and versatile set of capabilities. Some of the unique features include:

• Ability to act as a rogue authoritative DNS server for server-side attack scenarios
• Ability to craft custom DNS responses
• Ability to have complete control over the DNS layer as well as the underlying UDP and TCP protocols to have a comprehensive coverage of the essential functionalities

There are many built-in features and modifiers to produce various DNS responses. Combining them makes it possible to produce countless variants of a given response.

These features allow PolarDNS to produce highly unusual, abnormal, and even malformed DNS responses, enabling the operators to see how the receiving side handles such situations and whether the receiving side is technically robust and mature.

If you are testing DNS products/protocol, I strongly recommend you check this page for a comprehensive list of features and differentiators.”

Future plans

“Our key focus areas over the next year will be to build a community, drive a collaborative roadmap for additional features and continuously enhance the product. Against this backdrop of broad objectives, we will also evaluate potential integrations with other cybersecurity platforms/tools and support additional user awareness/trainings,” Dhar concluded.

PolarDNS is available for free download at GitHub.

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