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DNS-over-HTTPS (DoH) client for the JVM and Android

This library implements a DNS-over-HTTPS (DoH) client for the JVM 8+ and Android 5+. By default, it connects to Cloudflare's DoH resolver, but any RFC 8484-compliant resolver can be used.

Behind the scenes, this client uses OkHTTP via KTor in order to get coroutine support and keep a connection pool.

For privacy reasons, HTTP requests are made with the POST method, but we'd welcome a PR to support GET requests optionally.

For security reasons, DNSSEC validation can't be turned off, but we're open to consider toggling DNSSEC validation if there's a good reason to do so and a PR is subsequently proposed.

Install

You can get this library from Maven Central.

Usage

The client has a very simple interface. For example, to resolve the A record(s) for example.com, you'd just do:

var aRecords : List<String>? = null
val doh = DoHClient()
doh.use {
    aRecords = doh.lookUp("example.com", "A").data
}

Make sure to wrap your code around .use { ... } or call .close() after using the client in order to release the underlying resources.

If you don't wish to use the default resolver (Cloudflare), pass the DoH resolver URL to the constructor of DoHClient.

Read the API documentation online.

Comparison with other JVM DoH clients

  • org.xbill.DNS.DohResolver is a proof-of-concept implementation with documented shortcomings that make it unsuitable for production environments.
  • dohjava is undocumented, seemed abandoned, and a cursory code review uncovered issues such as:
    • It creates a single-use, blocking HTTP client.
    • It only supports GET requests, which makes responses cacheable, but is bad for privacy.
  • okhttp3.dnsoverhttps.DnsOverHttps only supports A/AAAA records because it appears to be only meant to be used with OkHTTP.

Contributing

We love contributions! If you haven't contributed to a Relaycorp project before, please take a minute to read our guidelines first.