Merge pull request #588 from neilalexander/tls

Initial connection upgrade/TLS steganography

src/yggdrasil/api.go

@@ -280,7 +280,14 @@ func (c *Core) ConnDialer() (*Dialer, error) {
 // "Listen" configuration item, e.g.
 // 		tcp://a.b.c.d:e
 func (c *Core) ListenTCP(uri string) (*TcpListener, error) {
-	return c.link.tcp.listen(uri)
+	return c.link.tcp.listen(uri, nil)
+}
+
+// ListenTLS starts a new TLS listener. The input URI should match that of the
+// "Listen" configuration item, e.g.
+// 		tls://a.b.c.d:e
+func (c *Core) ListenTLS(uri string) (*TcpListener, error) {
+	return c.link.tcp.listen(uri, c.link.tcp.tls.forListener)
 }
 
 // NodeID gets the node ID. This is derived from your router encryption keys.

src/yggdrasil/link.go

@@ -93,9 +93,11 @@ func (l *link) call(uri string, sintf string) error {
 	pathtokens := strings.Split(strings.Trim(u.Path, "/"), "/")
 	switch u.Scheme {
 	case "tcp":
-		l.tcp.call(u.Host, nil, sintf)
+		l.tcp.call(u.Host, nil, sintf, nil)
 	case "socks":
-		l.tcp.call(pathtokens[0], u.Host, sintf)
+		l.tcp.call(pathtokens[0], u.Host, sintf, nil)
+	case "tls":
+		l.tcp.call(u.Host, nil, sintf, l.tcp.tls.forDialer)
 	default:
 		return errors.New("unknown call scheme: " + u.Scheme)
 	}
@@ -109,7 +111,10 @@ func (l *link) listen(uri string) error {
 	}
 	switch u.Scheme {
 	case "tcp":
-		_, err := l.tcp.listen(u.Host)
+		_, err := l.tcp.listen(u.Host, nil)
+		return err
+	case "tls":
+		_, err := l.tcp.listen(u.Host, l.tcp.tls.forListener)
 		return err
 	default:
 		return errors.New("unknown listen scheme: " + u.Scheme)

src/yggdrasil/tcp.go

@@ -39,6 +39,7 @@ type tcp struct {
 	listeners map[string]*TcpListener
 	calls     map[string]struct{}
 	conns     map[linkInfo](chan struct{})
+	tls       tcptls
 }
 
 // TcpListener is a stoppable TCP listener interface. These are typically
@@ -47,9 +48,15 @@ type tcp struct {
 // multicast interfaces.
 type TcpListener struct {
 	Listener net.Listener
+	upgrade  *TcpUpgrade
 	stop     chan struct{}
 }
 
+type TcpUpgrade struct {
+	upgrade func(c net.Conn) (net.Conn, error)
+	name    string
+}
+
 func (l *TcpListener) Stop() {
 	defer func() { recover() }()
 	close(l.stop)
@@ -81,6 +88,7 @@ func (t *tcp) getAddr() *net.TCPAddr {
 // Initializes the struct.
 func (t *tcp) init(l *link) error {
 	t.link = l
+	t.tls.init(t)
 	t.mutex.Lock()
 	t.calls = make(map[string]struct{})
 	t.conns = make(map[linkInfo](chan struct{}))
@@ -90,12 +98,17 @@ func (t *tcp) init(l *link) error {
 	t.link.core.config.Mutex.RLock()
 	defer t.link.core.config.Mutex.RUnlock()
 	for _, listenaddr := range t.link.core.config.Current.Listen {
-		if listenaddr[:6] != "tcp://" {
+		switch listenaddr[:6] {
+		case "tcp://":
+			if _, err := t.listen(listenaddr[6:], nil); err != nil {
+				return err
+			}
+		case "tls://":
+			if _, err := t.listen(listenaddr[6:], t.tls.forListener); err != nil {
+				return err
+			}
+		default:
 			t.link.core.log.Errorln("Failed to add listener: listener", listenaddr, "is not correctly formatted, ignoring")
-			continue
-		}
-		if _, err := t.listen(listenaddr[6:]); err != nil {
-			return err
 		}
 	}
 
@@ -119,18 +132,21 @@ func (t *tcp) reconfigure() {
 	t.link.core.config.Mutex.RUnlock()
 	if len(added) > 0 || len(deleted) > 0 {
 		for _, a := range added {
-			if a[:6] != "tcp://" {
+			switch a[:6] {
+			case "tcp://":
+				if _, err := t.listen(a[6:], nil); err != nil {
+					t.link.core.log.Errorln("Error adding TCP", a[6:], "listener:", err)
+				}
+			case "tls://":
+				if _, err := t.listen(a[6:], t.tls.forListener); err != nil {
+					t.link.core.log.Errorln("Error adding TLS", a[6:], "listener:", err)
+				}
+			default:
 				t.link.core.log.Errorln("Failed to add listener: listener", a, "is not correctly formatted, ignoring")
-				continue
-			}
-			if _, err := t.listen(a[6:]); err != nil {
-				t.link.core.log.Errorln("Error adding TCP", a[6:], "listener:", err)
-			} else {
-				t.link.core.log.Infoln("Started TCP listener:", a[6:])
 			}
 		}
 		for _, d := range deleted {
-			if d[:6] != "tcp://" {
+			if d[:6] != "tcp://" && d[:6] != "tls://" {
 				t.link.core.log.Errorln("Failed to delete listener: listener", d, "is not correctly formatted, ignoring")
 				continue
 			}
@@ -146,7 +162,7 @@ func (t *tcp) reconfigure() {
 	}
 }
 
-func (t *tcp) listen(listenaddr string) (*TcpListener, error) {
+func (t *tcp) listen(listenaddr string, upgrade *TcpUpgrade) (*TcpListener, error) {
 	var err error
 
 	ctx := context.Background()
@@ -157,6 +173,7 @@ func (t *tcp) listen(listenaddr string) (*TcpListener, error) {
 	if err == nil {
 		l := TcpListener{
 			Listener: listener,
+			upgrade:  upgrade,
 			stop:     make(chan struct{}),
 		}
 		t.waitgroup.Add(1)
@@ -204,7 +221,7 @@ func (t *tcp) listener(l *TcpListener, listenaddr string) {
 			return
 		}
 		t.waitgroup.Add(1)
-		go t.handler(sock, true, nil)
+		go t.handler(sock, true, nil, l.upgrade)
 	}
 }
 
@@ -222,11 +239,15 @@ func (t *tcp) startCalling(saddr string) bool {
 // If the dial is successful, it launches the handler.
 // When finished, it removes the outgoing call, so reconnection attempts can be made later.
 // This all happens in a separate goroutine that it spawns.
-func (t *tcp) call(saddr string, options interface{}, sintf string) {
+func (t *tcp) call(saddr string, options interface{}, sintf string, upgrade *TcpUpgrade) {
 	go func() {
 		callname := saddr
+		callproto := "TCP"
+		if upgrade != nil {
+			callproto = strings.ToUpper(upgrade.name)
+		}
 		if sintf != "" {
-			callname = fmt.Sprintf("%s/%s", saddr, sintf)
+			callname = fmt.Sprintf("%s/%s/%s", callproto, saddr, sintf)
 		}
 		if !t.startCalling(callname) {
 			return
@@ -261,7 +282,7 @@ func (t *tcp) call(saddr string, options interface{}, sintf string) {
 				return
 			}
 			t.waitgroup.Add(1)
-			t.handler(conn, false, saddr)
+			t.handler(conn, false, saddr, nil)
 		} else {
 			dst, err := net.ResolveTCPAddr("tcp", saddr)
 			if err != nil {
@@ -322,19 +343,29 @@ func (t *tcp) call(saddr string, options interface{}, sintf string) {
 			}
 			conn, err = dialer.Dial("tcp", dst.String())
 			if err != nil {
-				t.link.core.log.Debugln("Failed to dial TCP:", err)
+				t.link.core.log.Debugf("Failed to dial %s: %s", callproto, err)
 				return
 			}
 			t.waitgroup.Add(1)
-			t.handler(conn, false, nil)
+			t.handler(conn, false, nil, upgrade)
 		}
 	}()
 }
 
-func (t *tcp) handler(sock net.Conn, incoming bool, options interface{}) {
+func (t *tcp) handler(sock net.Conn, incoming bool, options interface{}, upgrade *TcpUpgrade) {
 	defer t.waitgroup.Done() // Happens after sock.close
 	defer sock.Close()
 	t.setExtraOptions(sock)
+	var upgraded bool
+	if upgrade != nil {
+		var err error
+		if sock, err = upgrade.upgrade(sock); err != nil {
+			t.link.core.log.Errorln("TCP handler upgrade failed:", err)
+			return
+		} else {
+			upgraded = true
+		}
+	}
 	stream := stream{}
 	stream.init(sock)
 	var name, proto, local, remote string
@@ -344,8 +375,13 @@ func (t *tcp) handler(sock net.Conn, incoming bool, options interface{}) {
 		local, _, _ = net.SplitHostPort(sock.LocalAddr().String())
 		remote, _, _ = net.SplitHostPort(socksaddr)
 	} else {
-		name = "tcp://" + sock.RemoteAddr().String()
-		proto = "tcp"
+		if upgraded {
+			proto = upgrade.name
+			name = proto + "://" + sock.RemoteAddr().String()
+		} else {
+			proto = "tcp"
+			name = proto + "://" + sock.RemoteAddr().String()
+		}
 		local, _, _ = net.SplitHostPort(sock.LocalAddr().String())
 		remote, _, _ = net.SplitHostPort(sock.RemoteAddr().String())
 	}

src/yggdrasil/tls.go

@@ -0,0 +1,93 @@
+package yggdrasil
+
+import (
+	"bytes"
+	"crypto/ed25519"
+	"crypto/rand"
+	"crypto/tls"
+	"crypto/x509"
+	"crypto/x509/pkix"
+	"encoding/hex"
+	"encoding/pem"
+	"log"
+	"math/big"
+	"net"
+	"time"
+)
+
+type tcptls struct {
+	tcp         *tcp
+	config      *tls.Config
+	forDialer   *TcpUpgrade
+	forListener *TcpUpgrade
+}
+
+func (t *tcptls) init(tcp *tcp) {
+	t.tcp = tcp
+	t.forDialer = &TcpUpgrade{
+		upgrade: t.upgradeDialer,
+		name:    "tls",
+	}
+	t.forListener = &TcpUpgrade{
+		upgrade: t.upgradeListener,
+		name:    "tls",
+	}
+
+	edpriv := make(ed25519.PrivateKey, ed25519.PrivateKeySize)
+	copy(edpriv[:], tcp.link.core.sigPriv[:])
+
+	certBuf := &bytes.Buffer{}
+
+	// TODO: because NotAfter is finite, we should add some mechanism to regenerate the certificate and restart the listeners periodically for nodes with very high uptimes. Perhaps regenerate certs and restart listeners every few months or so.
+	pubtemp := x509.Certificate{
+		SerialNumber: big.NewInt(1),
+		Subject: pkix.Name{
+			CommonName: hex.EncodeToString(tcp.link.core.sigPub[:]),
+		},
+		NotBefore:             time.Now(),
+		NotAfter:              time.Now().Add(time.Hour * 24 * 365),
+		KeyUsage:              x509.KeyUsageKeyEncipherment | x509.KeyUsageDigitalSignature,
+		ExtKeyUsage:           []x509.ExtKeyUsage{x509.ExtKeyUsageServerAuth},
+		BasicConstraintsValid: true,
+	}
+
+	derbytes, err := x509.CreateCertificate(rand.Reader, &pubtemp, &pubtemp, edpriv.Public(), edpriv)
+	if err != nil {
+		log.Fatalf("Failed to create certificate: %s", err)
+	}
+
+	if err := pem.Encode(certBuf, &pem.Block{Type: "CERTIFICATE", Bytes: derbytes}); err != nil {
+		panic("failed to encode certificate into PEM")
+	}
+
+	cpool := x509.NewCertPool()
+	cpool.AppendCertsFromPEM(derbytes)
+
+	t.config = &tls.Config{
+		RootCAs: cpool,
+		Certificates: []tls.Certificate{
+			{
+				Certificate: [][]byte{derbytes},
+				PrivateKey:  edpriv,
+			},
+		},
+		InsecureSkipVerify: true,
+		MinVersion:         tls.VersionTLS13,
+	}
+}
+
+func (t *tcptls) upgradeListener(c net.Conn) (net.Conn, error) {
+	conn := tls.Server(c, t.config)
+	if err := conn.Handshake(); err != nil {
+		return c, err
+	}
+	return conn, nil
+}
+
+func (t *tcptls) upgradeDialer(c net.Conn) (net.Conn, error) {
+	conn := tls.Client(c, t.config)
+	if err := conn.Handshake(); err != nil {
+		return c, err
+	}
+	return conn, nil
+}