Quick and Dirty DNS-over-HTTPS in Go

qddoh.go

package main

import (
	"encoding/base64"
	"fmt"
	"io/ioutil"
	"log"
	"net/http"
	"os"

	"golang.org/x/net/dns/dnsmessage"
)

func main() {
	/* Roll a DNS query */
	qm, err := (&dnsmessage.Message{
		Header: dnsmessage.Header{
			RecursionDesired: true,
		},
		Questions: []dnsmessage.Question{{
			Name:  dnsmessage.MustNewName("yahoo.com."),
			Type:  dnsmessage.TypeA,
			Class: dnsmessage.ClassINET,
		}},
	}).Pack()
	if nil != err {
		log.Fatalf("Unable to marshal DNS request: %v", err)
	}

	/* Encode it and send it to the server */
	res, err := http.Get(
		"https://dns.quad9.net/dns-query?dns=" +
			base64.RawURLEncoding.EncodeToString(qm),
	)
	if nil != err {
		log.Fatalf("HTTP Error: %v", err)
	}
	if http.StatusOK != res.StatusCode {
		log.Fatalf("Non-OK HTTP response: %v", res.Status)
		os.Exit(1)
	}

	/* Unroll DNS answer */
	b, err := ioutil.ReadAll(res.Body)
	if nil != err {
		log.Fatalf("Erorr reading HTTP response: %v", err)
	}
	var am dnsmessage.Message
	if err := (&am).Unpack(b); nil != err {
		log.Fatalf("Error unpacking DNS response %q: %v", b, err)
	}

	/* Ugly-Print DNS response header and answer records */
	fmt.Printf("Response header:\n\t%+v\n", am.Header)
	if 0 == len(am.Answers) {
		fmt.Printf("No answers\n")
		return
	}
	fmt.Printf("Answer Records:\n")
	for _, a := range am.Answers {
		fmt.Printf("\t%+v\t%T:%v\n", a.Header, a.Body, a.Body)
	}
}