DoH resolver implementation

go.mod

@@ -0,0 +1,10 @@
+module github.com/libp2p/go-doh-resolver
+
+go 1.15
+
+require (
+	github.com/ipfs/go-log/v2 v2.1.3
+	github.com/miekg/dns v1.1.41
+	github.com/multiformats/go-multiaddr-dns v0.3.0
+	golang.org/x/tools v0.0.0-20210106214847-113979e3529a // indirect
+)

go.sum

@@ -0,0 +1,93 @@
+github.com/BurntSushi/toml v0.3.1 h1:WXkYYl6Yr3qBf1K79EBnL4mak0OimBfB0XUf9Vl28OQ=
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request.go

@@ -0,0 +1,135 @@
+package doh
+
+import (
+	"bytes"
+	"context"
+	"fmt"
+	"io"
+	"net"
+	"net/http"
+
+	"github.com/miekg/dns"
+
+	logging "github.com/ipfs/go-log/v2"
+)
+
+const (
+	dohMimeType = "application/dns-message"
+)
+
+var log = logging.Logger("doh")
+
+func doRequest(ctx context.Context, url string, m *dns.Msg) (*dns.Msg, error) {
+	data, err := m.Pack()
+	if err != nil {
+		return nil, err
+	}
+
+	req, err := http.NewRequest(http.MethodPost, url, bytes.NewReader(data))
+	if err != nil {
+		return nil, err
+	}
+
+	req.Header.Set("Content-Type", dohMimeType)
+	req.Header.Set("Accept", dohMimeType)
+
+	req = req.WithContext(ctx)
+
+	resp, err := http.DefaultClient.Do(req)
+	if err != nil {
+		return nil, err
+	}
+	defer resp.Body.Close()
+
+	if resp.StatusCode != http.StatusOK {
+		return nil, fmt.Errorf("HTTP error: %q [%d]", resp.Status, resp.StatusCode)
+	}
+
+	if ct := resp.Header.Get("Content-Type"); ct != dohMimeType {
+		return nil, fmt.Errorf("unexpected Content-Type %q", ct)
+	}
+
+	body, err := io.ReadAll(resp.Body)
+	if err != nil {
+		return nil, err
+	}
+
+	r := new(dns.Msg)
+	if err := r.Unpack(body); err != nil {
+		return nil, err
+	}
+
+	return r, nil
+}
+
+func doRequestA(ctx context.Context, url string, domain string) ([]net.IPAddr, error) {
+	fqdn := dns.Fqdn(domain)
+
+	m := new(dns.Msg)
+	m.SetQuestion(fqdn, dns.TypeA)
+
+	r, err := doRequest(ctx, url, m)
+	if err != nil {
+		return nil, err
+	}
+
+	result := make([]net.IPAddr, 0, len(r.Answer))
+	for _, rr := range r.Answer {
+		switch v := rr.(type) {
+		case *dns.A:
+			result = append(result, net.IPAddr{IP: v.A})
+		default:
+			log.Warnf("unexpected DNS resource record %+v", rr)
+		}
+	}
+
+	return result, nil
+}
+
+func doRequestAAAA(ctx context.Context, url string, domain string) ([]net.IPAddr, error) {
+	fqdn := dns.Fqdn(domain)
+
+	m := new(dns.Msg)
+	m.SetQuestion(fqdn, dns.TypeAAAA)
+
+	r, err := doRequest(ctx, url, m)
+	if err != nil {
+		return nil, err
+	}
+
+	result := make([]net.IPAddr, 0, len(r.Answer))
+	for _, rr := range r.Answer {
+		switch v := rr.(type) {
+		case *dns.AAAA:
+			result = append(result, net.IPAddr{IP: v.AAAA})
+		default:
+			log.Warnf("unexpected DNS resource record %+v", rr)
+		}
+	}
+
+	return result, nil
+}
+
+func doRequestTXT(ctx context.Context, url string, domain string) ([]string, error) {
+	fqdn := dns.Fqdn(domain)
+
+	m := new(dns.Msg)
+	m.SetQuestion(fqdn, dns.TypeTXT)
+
+	r, err := doRequest(ctx, url, m)
+	if err != nil {
+		return nil, err
+	}
+
+	var result []string
+	for _, rr := range r.Answer {
+		switch v := rr.(type) {
+		case *dns.TXT:
+			result = append(result, v.Txt...)
+		default:
+			log.Warnf("unexpected DNS resource record %+v", rr)
+		}
+	}
+
+	return result, nil
+}

resolver.go

@@ -0,0 +1,56 @@
+package doh
+
+import (
+	"context"
+	"net"
+	"strings"
+
+	madns "github.com/multiformats/go-multiaddr-dns"
+)
+
+type Resolver struct {
+	url string
+}
+
+func NewResolver(url string) *Resolver {
+	if !strings.HasPrefix(url, "https://") {
+		url = "https://" + url
+	}
+
+	return &Resolver{url: url}
+}
+
+var _ madns.BasicResolver = (*Resolver)(nil)
+
+func (r *Resolver) LookupIPAddr(ctx context.Context, domain string) (result []net.IPAddr, err error) {
+	type response struct {
+		ips []net.IPAddr
+		err error
+	}
+
+	resch := make(chan response, 2)
+	go func() {
+		ip4, err := doRequestA(ctx, r.url, domain)
+		resch <- response{ip4, err}
+	}()
+
+	go func() {
+		ip6, err := doRequestAAAA(ctx, r.url, domain)
+		resch <- response{ip6, err}
+	}()
+
+	for i := 0; i < 2; i++ {
+		r := <-resch
+		if r.err != nil {
+			return nil, r.err
+		}
+
+		result = append(result, r.ips...)
+	}
+
+	return result, nil
+}
+
+func (r *Resolver) LookupTXT(ctx context.Context, domain string) ([]string, error) {
+	return doRequestTXT(ctx, r.url, domain)
+}

resolver_test.go

@@ -0,0 +1,30 @@
+package doh
+
+import (
+	"context"
+	"testing"
+)
+
+func TestLookupIPAddr(t *testing.T) {
+	r := NewResolver("https://cloudflare-dns.com/dns-query")
+
+	ips, err := r.LookupIPAddr(context.Background(), "ewr-1.bootstrap.libp2p.io")
+	if err != nil {
+		t.Fatal(err)
+	}
+	if len(ips) == 0 {
+		t.Fatal("got no IPs")
+	}
+}
+
+func TestLookupTXT(t *testing.T) {
+	r := NewResolver("https://cloudflare-dns.com/dns-query")
+
+	txt, err := r.LookupTXT(context.Background(), "_dnsaddr.bootstrap.libp2p.io")
+	if err != nil {
+		t.Fatal(err)
+	}
+	if len(txt) == 0 {
+		t.Fatal("got no TXT entries")
+	}
+}