begin meek-webrtc signalling channel for client (issue #1)

client/meek-webrtc.go

@@ -0,0 +1,84 @@
+// Exchange WebRTC SessionDescriptions over meek.
+// Much of this source is extracted from meek-client.go.
+package main
+
+import (
+	"bytes"
+	"io/ioutil"
+	"net/http"
+	"net/url"
+
+	"github.com/keroserene/go-webrtc"
+)
+
+// RequestInfo encapsulates all the configuration used for a request–response
+// roundtrip, including variables that may come from SOCKS args or from the
+// command line.
+type RequestInfo struct {
+	// What to put in the X-Session-ID header.
+	// SessionID string
+	// The URL to request.
+	URL *url.URL
+	// The Host header to put in the HTTP request (optional and may be
+	// different from the host name in URL).
+	Host string
+}
+
+func NewRequestInfo(meekUrl string, front string) *RequestInfo {
+	info := new(RequestInfo)
+	requestUrl, err := url.Parse(meekUrl)
+	if nil != err {
+		return nil
+	}
+	info.URL = requestUrl
+	info.Host = info.URL.Host
+	info.URL.Host = front
+	return info
+}
+
+// Meek Signalling Channel
+type MeekChannel struct {
+	info *RequestInfo
+	// Used to make all requests.
+	transport http.Transport
+}
+
+func NewMeekChannel(info *RequestInfo) *MeekChannel {
+	m := new(MeekChannel)
+	// We make a copy of DefaultTransport because we want the default Dial
+	// and TLSHandshakeTimeout settings. But we want to disable the default
+	// ProxyFromEnvironment setting. Proxy is overridden below if
+	// options.ProxyURL is set.
+	m.transport = *http.DefaultTransport.(*http.Transport)
+	m.transport.Proxy = nil
+	m.info = info
+	return m
+}
+
+// Do an HTTP roundtrip using the payload data in buf.
+func (m *MeekChannel) roundTripHTTP(buf []byte) (*http.Response, error) {
+	req, err := http.NewRequest("POST", m.info.URL.String(), bytes.NewReader(buf))
+	if nil != err {
+		return nil, err
+	}
+	if "" != m.info.Host {
+		req.Host = m.info.Host
+	}
+	// req.Header.Set("X-Session-Id", m.info.SessionID)
+	return m.transport.RoundTrip(req)
+}
+
+// Send an SDP offer to the meek facilitator, and wait for an SDP answer from
+// the assigned proxy in the response.
+func (m *MeekChannel) Negotiate(offer *webrtc.SessionDescription) (
+	*webrtc.SessionDescription, error) {
+	buf := []byte(offer.Serialize())
+	resp, err := m.roundTripHTTP(buf)
+	if nil != err {
+		return nil, err
+	}
+	defer resp.Body.Close()
+	body, err := ioutil.ReadAll(resp.Body)
+	answer := webrtc.DeserializeSessionDescription(string(body))
+	return answer, nil
+}

client/snowflake.go

@@ -1,3 +1,6 @@
+// Client transport plugin for the snowflake pluggable transport.
+//
+// TODO: Use meek for signalling.
 package main
 
 import (
@@ -18,6 +21,13 @@ import (
 	"git.torproject.org/pluggable-transports/goptlib.git"
 )
 
+// Hard-coded meek signalling channel for now.
+// TODO: expose as param
+const (
+	MEEK_URL     = "not implemented yet"
+	FRONT_DOMAIN = "www.google.com"
+)
+
 var ptInfo pt.ClientInfo
 var logFile *os.File
 
@@ -89,8 +99,10 @@ func (c *webRTCConn) SetWriteDeadline(t time.Time) error {
 	return fmt.Errorf("SetWriteDeadline not implemented")
 }
 
-func dialWebRTC(config *webrtc.Configuration) (*webRTCConn, error) {
-	blobChan := make(chan string)
+func dialWebRTC(config *webrtc.Configuration, meek *MeekChannel) (
+	*webRTCConn, error) {
+
+	offerChan := make(chan *webrtc.SessionDescription)
 	errChan := make(chan error)
 	openChan := make(chan bool)
 
@@ -123,7 +135,7 @@ func dialWebRTC(config *webrtc.Configuration) (*webRTCConn, error) {
 	// TODO: This may soon be deprecated, consider OnIceGatheringStateChange.
 	pc.OnIceComplete = func() {
 		log.Printf("OnIceComplete")
-		blobChan <- pc.LocalDescription().Serialize()
+		offerChan <- pc.LocalDescription()
 	}
 	pc.OnDataChannel = func(channel *data.Channel) {
 		log.Println("OnDataChannel")
@@ -162,10 +174,22 @@ func dialWebRTC(config *webrtc.Configuration) (*webRTCConn, error) {
 	case err := <-errChan:
 		pc.Close()
 		return nil, err
-	case offer := <-blobChan:
+	case offer := <-offerChan:
 		log.Printf("----------------")
-		fmt.Fprintln(logFile, "\n"+offer+"\n")
+		fmt.Fprintln(logFile, "\n"+offer.Serialize()+"\n")
 		log.Printf("----------------")
+		go func() {
+			log.Printf("Sending offer via meek...")
+			answer, err := meek.Negotiate(pc.LocalDescription())
+			if nil != err {
+				log.Printf("Signalling error: %s", err)
+			}
+			if nil == answer {
+				log.Printf("No answer received from meek channel.")
+			} else {
+				signalChan <- answer
+			}
+		}()
 	}
 
 	log.Printf("waiting for answer")
@@ -184,6 +208,7 @@ func dialWebRTC(config *webrtc.Configuration) (*webRTCConn, error) {
 
 	// Wait until data channel is open; otherwise for example sends may get
 	// lost.
+	// TODO: Buffering *should* work though.
 	_, ok = <-openChan
 	if !ok {
 		pc.Close()
@@ -215,8 +240,16 @@ func handler(conn *pt.SocksConn) error {
 	}()
 	defer conn.Close()
 
-	config := webrtc.NewConfiguration(webrtc.OptionIceServer("stun:stun.l.google.com:19302"))
-	remote, err := dialWebRTC(config)
+	// go func() {
+	// }()
+	// Prepare meek signalling channel.
+	info := NewRequestInfo(MEEK_URL, FRONT_DOMAIN)
+	meek := NewMeekChannel(info)
+
+	config := webrtc.NewConfiguration(
+		webrtc.OptionIceServer("stun:stun.l.google.com:19302"))
+	// remote, err := dialWebRTC(config, nil)
+	remote, err := dialWebRTC(config, meek)
 	if err != nil {
 		conn.Reject()
 		return err