gistfile1.txt

diff --git a/client/lib/rendezvous.go b/client/lib/rendezvous.go
index 38e4620..587009b 100644
--- a/client/lib/rendezvous.go
+++ b/client/lib/rendezvous.go
@@ -44,6 +44,7 @@ type BrokerChannel struct {
 	natType            string
 	lock               sync.Mutex
 	BridgeFingerprint  string
+	hack               bool
 }
 
 // We make a copy of DefaultTransport because we want the default Dial
@@ -94,6 +95,7 @@ func newBrokerChannelFromConfig(config ClientConfig) (*BrokerChannel, error) {
 		keepLocalAddresses: config.KeepLocalAddresses,
 		natType:            nat.NATUnknown,
 		BridgeFingerprint:  config.BridgeFingerprint,
+		hack:               config.PoC,
 	}, nil
 }
 
@@ -110,6 +112,13 @@ func (bc *BrokerChannel) Negotiate(offer *webrtc.SessionDescription) (
 			SDP:  util.StripLocalAddresses(offer.SDP),
 		}
 	}
+	if bc.hack {
+		offer = &webrtc.SessionDescription{
+			Type: offer.Type,
+			SDP:  util.ChangeSetup(offer.SDP, true),
+		}
+	}
+	//log.Println("SDP offer:", offer.SDP)
 	offerSDP, err := util.SerializeSessionDescription(offer)
 	if err != nil {
 		return nil, err
@@ -143,7 +152,18 @@ func (bc *BrokerChannel) Negotiate(offer *webrtc.SessionDescription) (
 	if resp.Error != "" {
 		return nil, errors.New(resp.Error)
 	}
-	return util.DeserializeSessionDescription(resp.Answer)
+	answer, err := util.DeserializeSessionDescription(resp.Answer)
+	if err == nil && bc.hack {
+		if util.PionDetected(answer.SDP) {
+			return nil, errors.New("Hack: Pion detected.")
+		}
+		answer = &webrtc.SessionDescription{
+			Type: answer.Type,
+			SDP:  util.ChangeSetup(answer.SDP, false),
+		}
+		//log.Println("SDP answer:", answer.SDP)
+	}
+	return answer, err
 }
 
 // SetNATType sets the NAT type of the client so we can send it to the WebRTC broker.
diff --git a/client/lib/snowflake.go b/client/lib/snowflake.go
index 7231d86..af4fff1 100644
--- a/client/lib/snowflake.go
+++ b/client/lib/snowflake.go
@@ -106,6 +106,7 @@ type ClientConfig struct {
 	// BridgeFingerprint is the fingerprint of the bridge that the client will eventually
 	// connect to, as specified in the Bridge line of the torrc.
 	BridgeFingerprint string
+	PoC bool
 }
 
 // NewSnowflakeClient creates a new Snowflake transport client that can spawn multiple
diff --git a/client/snowflake.go b/client/snowflake.go
index 2cb6549..ee00c43 100644
--- a/client/snowflake.go
+++ b/client/snowflake.go
@@ -155,6 +155,7 @@ func main() {
 	logToStateDir := flag.Bool("log-to-state-dir", false, "resolve the log file relative to tor's pt state dir")
 	keepLocalAddresses := flag.Bool("keep-local-addresses", false, "keep local LAN address ICE candidates")
 	unsafeLogging := flag.Bool("unsafe-logging", false, "prevent logs from being scrubbed")
+	hack := flag.Bool("hack", false, "DTLS-connect to non-Pion proxy")
 	max := flag.Int("max", DefaultSnowflakeCapacity,
 		"capacity for number of multiplexed WebRTC peers")
 
@@ -203,6 +204,7 @@ func main() {
 		FrontDomain:        *frontDomain,
 		ICEAddresses:       iceAddresses,
 		KeepLocalAddresses: *keepLocalAddresses || *oldKeepLocalAddresses,
+		PoC:                *hack,
 		Max:                *max,
 	}
 
diff --git a/common/util/util.go b/common/util/util.go
index 00f7302..42bfd21 100644
--- a/common/util/util.go
+++ b/common/util/util.go
@@ -2,6 +2,7 @@ package util
 
 import (
 	"encoding/json"
+	"strings"
 	"errors"
 	"net"
 
@@ -97,3 +98,53 @@ func StripLocalAddresses(str string) string {
 	}
 	return string(bts)
 }
+
+func ChangeSetup(str string, client bool) string {
+	var desc sdp.SessionDescription
+	err := desc.Unmarshal([]byte(str))
+	if err != nil {
+		return str
+	}
+	for _, m := range desc.MediaDescriptions {
+		attrs := make([]sdp.Attribute, 0)
+		for _, a := range m.Attributes {
+			if a.Key == sdp.AttrKeyConnectionSetup {
+				if client {
+					a.Value = sdp.ConnectionRoleActive.String()
+				} else {
+					a.Value = sdp.ConnectionRolePassive.String()
+				}
+			}
+			attrs = append(attrs, a)
+		}
+		m.Attributes = attrs
+	}
+	bts, err := desc.Marshal()
+	if err != nil {
+		return str
+	}
+	return string(bts)
+}
+
+func PionDetected(str string) bool {
+	var pionMediaNameStr string = "application 9 UDP/DTLS/SCTP webrtc-datachannel"
+	var pionOriginStart string = "- "
+	var desc sdp.SessionDescription
+	err := desc.Unmarshal([]byte(str))
+	if err != nil {
+		return false
+	}
+	pionOrigin := strings.HasPrefix(desc.Origin.String(), pionOriginStart)
+	for _, a := range desc.Attributes {
+		if a.Key == sdp.AttrKeySendRecv || a.Key == sdp.AttrKeyMsidSemantic {
+			return false
+		}
+	}
+	for _, m := range desc.MediaDescriptions {
+		pionMediaName := m.MediaName.String() == pionMediaNameStr
+		if pionMediaName && pionOrigin {
+			return true
+		}
+	}
+	return false
+}