Add support for plain DNS over 53 (udp/tcp)

Refectored the _dnsExchange to create reusable udpExchange & tcpExchange
Also added support for a "." forward rule

dnscrypt-proxy/dnsutils.go

@@ -434,46 +434,79 @@ func _dnsExchange(
 		if err != nil {
 			return DNSExchangeResponse{err: err}
 		}
-		udpAddr, err := net.ResolveUDPAddr("udp", serverAddress)
+		packet, rtt, err = udpExchange(proxy, serverAddress, relay, binQuery)
 		if err != nil {
 			return DNSExchangeResponse{err: err}
 		}
-		upstreamAddr := udpAddr
-		if relay != nil {
-			proxy.prepareForRelay(udpAddr.IP, udpAddr.Port, &binQuery)
-			upstreamAddr = relay.RelayUDPAddr
-		}
-		now := time.Now()
-		pc, err := net.DialUDP("udp", nil, upstreamAddr)
-		if err != nil {
-			return DNSExchangeResponse{err: err}
-		}
-		defer pc.Close()
-		if err := pc.SetDeadline(time.Now().Add(proxy.timeout)); err != nil {
-			return DNSExchangeResponse{err: err}
-		}
-		if _, err := pc.Write(binQuery); err != nil {
-			return DNSExchangeResponse{err: err}
-		}
-		packet = make([]byte, MaxDNSPacketSize)
-		length, err := pc.Read(packet)
-		if err != nil {
-			return DNSExchangeResponse{err: err}
-		}
-		rtt = time.Since(now)
-		packet = packet[:length]
 	} else {
 		binQuery, err := query.Pack()
 		if err != nil {
 			return DNSExchangeResponse{err: err}
 		}
-		tcpAddr, err := net.ResolveTCPAddr("tcp", serverAddress)
+		packet, rtt, err = tcpExchange(proxy, serverAddress, relay, binQuery)
 		if err != nil {
 			return DNSExchangeResponse{err: err}
 		}
+	}
+	msg := dns.Msg{}
+	if err := msg.Unpack(packet); err != nil {
+		return DNSExchangeResponse{err: err}
+	}
+	return DNSExchangeResponse{response: &msg, rtt: rtt, err: nil}
+}
+
+func udpExchange(proxy *Proxy, serverAddress string, relay *DNSCryptRelay, query []byte) ([]byte, time.Duration, error) {
+	var rtt time.Duration
+	packet := []byte{}
+	udpAddr, err := net.ResolveUDPAddr("udp", serverAddress)
+	if err != nil {
+		return packet, rtt, err
+	}
+	upstreamAddr := udpAddr
+	if relay != nil {
+		proxy.prepareForRelay(udpAddr.IP, udpAddr.Port, &query)
+		upstreamAddr = relay.RelayUDPAddr
+	}
+	now := time.Now()
+	lAddr, err := net.ResolveUDPAddr("udp", ":0")
+	if err != nil {
+		return packet, rtt, err
+	}
+	pc, err := net.ListenUDP("udp", lAddr)
+	if err != nil {
+		return packet, rtt, err
+	}
+	defer pc.Close()
+	if err = pc.SetReadBuffer(MaxDNSPacketSize); err != nil {
+		return packet, rtt, err
+	}
+	if err = pc.SetDeadline(time.Now().Add(proxy.timeout)); err != nil {
+		return packet, rtt, err
+	}
+	if _, err = pc.WriteToUDPAddrPort(query, upstreamAddr.AddrPort()); err != nil {
+		return packet, rtt, err
+	}
+	packet = make([]byte, MaxDNSPacketSize)
+	length, _, err := pc.ReadFromUDPAddrPort(packet)
+	if err != nil {
+		return packet, rtt, err
+	}
+
+	rtt = time.Since(now)
+	packet = packet[:length]
+	return packet, rtt, err
+}
+
+func tcpExchange(proxy *Proxy, serverAddress string, relay *DNSCryptRelay, query []byte) ([]byte, time.Duration, error) {
+	var rtt time.Duration
+	packet := []byte{}
+	tcpAddr, err := net.ResolveTCPAddr("tcp", serverAddress)
+	if err != nil {
+		return packet, rtt, err
+	}
 	upstreamAddr := tcpAddr
 	if relay != nil {
-			proxy.prepareForRelay(tcpAddr.IP, tcpAddr.Port, &binQuery)
+		proxy.prepareForRelay(tcpAddr.IP, tcpAddr.Port, &query)
 		upstreamAddr = relay.RelayTCPAddr
 	}
 	now := time.Now()
@@ -485,28 +518,23 @@ func _dnsExchange(
 		pc, err = (*proxyDialer).Dial("tcp", tcpAddr.String())
 	}
 	if err != nil {
-			return DNSExchangeResponse{err: err}
+		return packet, rtt, err
 	}
 	defer pc.Close()
 	if err := pc.SetDeadline(time.Now().Add(proxy.timeout)); err != nil {
-			return DNSExchangeResponse{err: err}
+		return packet, rtt, err
 	}
-		binQuery, err = PrefixWithSize(binQuery)
+	query, err = PrefixWithSize(query)
 	if err != nil {
-			return DNSExchangeResponse{err: err}
+		return packet, rtt, err
 	}
-		if _, err := pc.Write(binQuery); err != nil {
-			return DNSExchangeResponse{err: err}
+	if _, err := pc.Write(query); err != nil {
+		return packet, rtt, err
 	}
 	packet, err = ReadPrefixed(&pc)
 	if err != nil {
-			return DNSExchangeResponse{err: err}
+		return packet, rtt, err
 	}
 	rtt = time.Since(now)
-	}
-	msg := dns.Msg{}
-	if err := msg.Unpack(packet); err != nil {
-		return DNSExchangeResponse{err: err}
-	}
-	return DNSExchangeResponse{response: &msg, rtt: rtt, err: nil}
+	return packet, rtt, err
 }

dnscrypt-proxy/dnsutils_test.go

@@ -0,0 +1,197 @@
+package main
+
+import (
+	"net"
+	"strings"
+	"sync"
+	"testing"
+	"time"
+
+	"github.com/jedisct1/dlog"
+	"github.com/miekg/dns"
+	"github.com/powerman/check"
+)
+
+func TestUDPExchangeIPv4(tt *testing.T) {
+	if testing.Verbose() {
+		dlog.SetLogLevel(dlog.SeverityDebug)
+		dlog.UseSyslog(false)
+	}
+	t := check.T(tt)
+
+	us, err := startServerUDP(t, "udp4", dns.HandlerFunc(FakeServer1))
+	t.Nil(err)
+	defer us.Shutdown()
+
+	var relay *DNSCryptRelay
+	proxy := Proxy{timeout: 2 * time.Second}
+
+	msg := dns.Msg{}
+	msg.SetQuestion("example.com.", dns.TypeA)
+
+	query, err := msg.Pack()
+	t.Nil(err)
+	serverAddr, err := toServerAddr(us)
+	t.Nil(err)
+	r, rtt, err := udpExchange(&proxy, serverAddr, relay, query)
+
+	t.Nil(err)
+	t.Must(len(r) > 0)
+	t.Must(rtt > 0)
+	resp := dns.Msg{}
+	resp.Unpack(r)
+	t.Must(resp.Rcode == dns.RcodeSuccess)
+}
+
+func TestUDPExchangeIPv6(tt *testing.T) {
+	if testing.Verbose() {
+		dlog.SetLogLevel(dlog.SeverityDebug)
+		dlog.UseSyslog(false)
+	}
+	t := check.T(tt)
+
+	us, err := startServerUDP(t, "udp6", dns.HandlerFunc(FakeServer1))
+	t.Nil(err)
+	defer us.Shutdown()
+
+	var relay *DNSCryptRelay
+	proxy := Proxy{timeout: 2 * time.Second}
+
+	msg := dns.Msg{}
+	msg.SetQuestion("example.com.", dns.TypeA)
+
+	query, err := msg.Pack()
+	t.Nil(err)
+	serverAddr, err := toServerAddr(us)
+	t.Nil(err)
+	r, rtt, err := udpExchange(&proxy, serverAddr, relay, query)
+
+	t.Nil(err)
+	t.Must(len(r) > 0)
+	t.Must(rtt > 0)
+	resp := dns.Msg{}
+	resp.Unpack(r)
+	t.Must(resp.Rcode == dns.RcodeSuccess)
+}
+
+func TestTCPExchangeIPv4(tt *testing.T) {
+	if testing.Verbose() {
+		dlog.SetLogLevel(dlog.SeverityDebug)
+		dlog.UseSyslog(false)
+	}
+	t := check.T(tt)
+
+	us, err := startServerTCP(t, "tcp4", dns.HandlerFunc(FakeServer1))
+	t.Nil(err)
+	defer us.Shutdown()
+
+	var relay *DNSCryptRelay
+	proxy := Proxy{timeout: 2 * time.Second, xTransport: &XTransport{proxyDialer: nil}}
+
+	msg := dns.Msg{}
+	msg.SetQuestion("example.com.", dns.TypeA)
+
+	query, err := msg.Pack()
+	t.Nil(err)
+	serverAddr, err := toServerAddr(us)
+	t.Nil(err)
+	r, rtt, err := tcpExchange(&proxy, serverAddr, relay, query)
+
+	t.Nil(err)
+	t.Must(len(r) > 0)
+	t.Must(rtt > 0)
+	resp := dns.Msg{}
+	resp.Unpack(r)
+	t.Must(resp.Rcode == dns.RcodeSuccess)
+}
+
+func TestTCPExchangeIPv6(tt *testing.T) {
+	if testing.Verbose() {
+		dlog.SetLogLevel(dlog.SeverityDebug)
+		dlog.UseSyslog(false)
+	}
+	t := check.T(tt)
+
+	us, err := startServerTCP(t, "tcp6", dns.HandlerFunc(FakeServer1))
+	t.Nil(err)
+	defer us.Shutdown()
+
+	var relay *DNSCryptRelay
+	proxy := Proxy{timeout: 2 * time.Second, xTransport: &XTransport{proxyDialer: nil}}
+
+	msg := dns.Msg{}
+	msg.SetQuestion("example.com.", dns.TypeA)
+
+	query, err := msg.Pack()
+	t.Nil(err)
+	serverAddr, err := toServerAddr(us)
+	t.Nil(err)
+	r, rtt, err := tcpExchange(&proxy, serverAddr, relay, query)
+
+	t.Nil(err)
+	t.Must(len(r) > 0)
+	t.Must(rtt > 0)
+	resp := dns.Msg{}
+	resp.Unpack(r)
+	t.Must(resp.Rcode == dns.RcodeSuccess)
+}
+
+func toServerAddr(s *dns.Server) (string, error) {
+	var h, p string
+	var err error
+	if strings.HasPrefix(s.Net, "udp") {
+		h, p, err = net.SplitHostPort(s.PacketConn.LocalAddr().String())
+	} else {
+		h, p, err = net.SplitHostPort(s.Listener.Addr().String())
+	}
+	if err != nil {
+		return "", err
+	}
+	if net.ParseIP(h).To4() == nil {
+		return "[::1]:" + p, nil
+	}
+	return "127.0.0.1:" + p, nil
+}
+
+func startServerUDP(t *check.C, proto string, h dns.Handler) (*dns.Server, error) {
+	waitLock := sync.Mutex{}
+	addr := ":0"
+	if proto == "udp6" {
+		addr = "[::]:0"
+	}
+	server := &dns.Server{Addr: addr, Net: proto, ReadTimeout: time.Hour, WriteTimeout: time.Hour, NotifyStartedFunc: waitLock.Unlock, Handler: h}
+	waitLock.Lock()
+
+	go func() {
+		err := server.ListenAndServe()
+		t.Nil(err)
+	}()
+	waitLock.Lock()
+	return server, nil
+}
+
+func startServerTCP(t *check.C, proto string, h dns.Handler) (*dns.Server, error) {
+	waitLock := sync.Mutex{}
+	addr := ":0"
+	if proto == "tcp6" {
+		addr = "[::]:0"
+	}
+	server := &dns.Server{Addr: addr, Net: proto, ReadTimeout: time.Hour, WriteTimeout: time.Hour, NotifyStartedFunc: waitLock.Unlock, Handler: h}
+	waitLock.Lock()
+
+	go func() {
+		err := server.ListenAndServe()
+		t.Nil(err)
+	}()
+	waitLock.Lock()
+	return server, nil
+}
+
+func FakeServer1(w dns.ResponseWriter, req *dns.Msg) {
+	m := new(dns.Msg)
+	m.SetReply(req)
+
+	m.Extra = make([]dns.RR, 1)
+	m.Extra[0] = &dns.TXT{Hdr: dns.RR_Header{Name: m.Question[0].Name, Rrtype: dns.TypeTXT, Class: dns.ClassINET, Ttl: 0}, Txt: []string{"Hello world"}}
+	w.WriteMsg(m)
+}

dnscrypt-proxy/plugin_forward.go

@@ -94,6 +94,10 @@ func (plugin *PluginForward) Eval(pluginsState *PluginsState, msg *dns.Msg) erro
 			servers = candidate.servers
 			break
 		}
+		if "." == candidate.domain {
+			servers = candidate.servers
+			break
+		}
 	}
 	if len(servers) == 0 {
 		return nil

dnscrypt-proxy/proxy.go

@@ -630,6 +630,10 @@ func (proxy *Proxy) processIncomingQuery(
 	if serverInfo != nil {
 		serverName = serverInfo.Name
 		needsEDNS0Padding = (serverInfo.Proto == stamps.StampProtoTypeDoH || serverInfo.Proto == stamps.StampProtoTypeTLS)
+
+		if serverInfo.Proto == stamps.StampProtoTypePlain && serverInfo.knownBugs.fragmentsBlocked {
+			pluginsState.maxPayloadSize = pluginsState.maxUnencryptedUDPSafePayloadSize
+		}
 	}
 	query, _ = pluginsState.ApplyQueryPlugins(&proxy.pluginsGlobals, query, needsEDNS0Padding)
 	if len(query) < MinDNSPacketSize || len(query) > MaxDNSPacketSize {
@@ -786,6 +790,31 @@ func (proxy *Proxy) processIncomingQuery(
 				serverInfo.noticeFailure(proxy)
 				return response
 			}
+		} else if serverInfo.Proto == stamps.StampProtoTypePlain {
+			serverInfo.noticeBegin(proxy)
+			var relay *DNSCryptRelay
+			if serverInfo.Relay != nil && serverInfo.Relay.Dnscrypt != nil {
+				relay = serverInfo.Relay.Dnscrypt
+			}
+			truncated := false
+			if clientProto == "udp" {
+				response, _, err = udpExchange(proxy, serverInfo.UDPAddr.String(), relay, query)
+				if err != nil {
+					dlog.Warnf("Failed to exchange query with plain server [%v] %v", serverName, err)
+					response = nil
+				}
+				if len(response) >= MinDNSPacketSize {
+					truncated = HasTCFlag(response)
+				}
+			}
+
+			if truncated || clientProto == "tcp" {
+				response, _, err = tcpExchange(proxy, serverInfo.TCPAddr.String(), relay, query)
+				if err != nil {
+					dlog.Warnf("Failed to exchange query with plain server [%v] %v", serverName, err)
+					response = nil
+				}
+			}
 		} else {
 			dlog.Fatal("Unsupported protocol")
 		}

dnscrypt-proxy/serversInfo.go

@@ -325,6 +325,8 @@ func fetchServerInfo(proxy *Proxy, name string, stamp stamps.ServerStamp, isNew
 		return fetchDoHServerInfo(proxy, name, stamp, isNew)
 	} else if stamp.Proto == stamps.StampProtoTypeODoHTarget {
 		return fetchODoHTargetInfo(proxy, name, stamp, isNew)
+	} else if stamp.Proto == stamps.StampProtoTypePlain {
+		return fetchPlainServerInfo(proxy, name, stamp, isNew)
 	}
 	return ServerInfo{}, fmt.Errorf("Unsupported protocol for [%s]: [%s]", name, stamp.Proto.String())
 }
@@ -944,6 +946,49 @@ func fetchODoHTargetInfo(proxy *Proxy, name string, stamp stamps.ServerStamp, is
 	return serverInfo, err
 }
 
+func fetchPlainServerInfo(proxy *Proxy, name string, stamp stamps.ServerStamp, isNew bool) (ServerInfo, error) {
+	relay, err := route(proxy, name, stamp.Proto)
+	if err != nil {
+		return ServerInfo{}, err
+	}
+	if relay != nil {
+		return ServerInfo{}, errors.New("Relay is not supported by plain DNS")
+	}
+
+	remoteUDPAddr, err := net.ResolveUDPAddr("udp", stamp.ServerAddrStr)
+	if err != nil {
+		return ServerInfo{}, err
+	}
+	remoteTCPAddr, err := net.ResolveTCPAddr("tcp", stamp.ServerAddrStr)
+	if err != nil {
+		return ServerInfo{}, err
+	}
+
+	testQuery := dns.Msg{}
+	testQuery.SetQuestion(".", dns.TypeNS)
+	testQuery.Id = 0xcafe
+	testQuery.MsgHdr.RecursionDesired = true
+	in, rtt, fragmentsBlocked, err := DNSExchange(proxy, "udp", &testQuery, stamp.ServerAddrStr,
+		nil, &name, false)
+
+	if in != nil && in.Rcode != dns.RcodeSuccess {
+		dlog.Warnf("Plain Server Target Test Rcode: %v", in.Rcode)
+	}
+	if err != nil {
+		return ServerInfo{}, err
+	}
+	return ServerInfo{
+		Proto:      stamps.StampProtoTypePlain,
+		Name:       name,
+		Timeout:    proxy.timeout,
+		UDPAddr:    remoteUDPAddr,
+		TCPAddr:    remoteTCPAddr,
+		Relay:      relay,
+		initialRtt: int(rtt.Nanoseconds() / 1000000),
+		knownBugs:  ServerBugs{fragmentsBlocked: fragmentsBlocked},
+	}, nil
+}
+
 func (serverInfo *ServerInfo) noticeFailure(proxy *Proxy) {
 	proxy.serversInfo.Lock()
 	serverInfo.rtt.Add(float64(proxy.timeout.Nanoseconds() / 1000000))