cf-doh

Typed Cloudflare DNS Over HTTPS Resolver

Motivation

This lib is a type safe resolver that uses cloudflare's DNS Over HTTP service to resolve DNS records. It is primarily useful in contexts that do not have access to libc's dns resolver (e.g. non-node javascript like v8 isolates or the browser).

Usage

npm --save install cf-doh

import {}

Usage in node.js

If you have access to the node stdlib, you probably want to use node's dns library rather than this one, as it will use the system's native resolver. If you explicitly want to use cloudflare's DoH resolver, you can still use this library in node, but you'll need to provide a fetch implementation. JakeChampion's fetch polyfill is the preferred implmementation.

Install it in your local package.json npm install whatwg-fetch --save

Then provide it to this library:

import { queryDNS, setFetch } from "cf-doh";
import { fetch } from "whatwg-fetch";
setFetch(fetch);

// Use queryDNS normally

API

queryDNS(hostname: string, recordType: DNSRecordType | keyof typeof DNSRecordType): Promise<string[]>

Queries Cloudflare DoH for the provided hostname. If you want to query a named record, pass the hostname including it. recordType may be a DNS record type (e.g. CNAME, TXT) or the numeric value of a type as per the spec (e.g. 5, 16).

This returns an array of all values of that type found at this hostname.

If cloudflare returns a non-200 response or a Status other than NoError, this will throw with a status message or the response from cloudflare.

import { queryDNS } from "cf-doh";

const records = await queryDNS("_verification.jesseditson.com", "TXT");

records.forEach((r) => console.log(r));

queryDNSRecords(hostname: string, recordType: DNSRecordType | keyof typeof DNSRecordType): Promise<DOHResponse>

Queries Cloudflare DoH for the provided hostname. If you want to query a named record, pass the hostname including it. recordType may be a DNS record type (e.g. CNAME, TXT) or the numeric value of a type as per the spec (e.g. 5, 16).

This returns a DOHResponse, which is a typed version of the JSON returned from cloudflare: https://developers.cloudflare.com/1.1.1.1/encryption/dns-over-https/make-api-requests/dns-json/

If cloudflare returns a non-200 response, this will throw.

import { queryDNSRecords, DOHStatus } from "cf-doh";

const response = await queryDNSRecords("_verification.jesseditson.com", "TXT");

if (response.status === DOHStatus.NoError) {
  const records = r.Answer.map((r) => JSON.parse(r.data));
}

Caveats and Notes

Cloudflare returns quoted strings for standardized record types, and hex values for unknown record types. This means that for most records, the string you get back will include double quotes. queryDNS uses JSON.parse() to strip these quotes before returning them, so if you're using queryDNSRecords directly, you'll need to process these values to use them as strings.