Add outbound proxy configuration propagation

7 files changed, 139 insertions, 37 deletions

diff --git a/client/lib/rendezvous.go b/client/lib/rendezvous.go
index ea6ab39..a9d810e 100644
--- a/client/lib/rendezvous.go
+++ b/client/lib/rendezvous.go
@@ -7,6 +7,7 @@ import (
 	"crypto/tls"
 	"errors"
 	"fmt"
+	"net/url"
 
 	"log"
 	"net/http"
@@ -51,12 +52,15 @@ type BrokerChannel struct {
 // We make a copy of DefaultTransport because we want the default Dial
 // and TLSHandshakeTimeout settings. But we want to disable the default
 // ProxyFromEnvironment setting.
-func createBrokerTransport() http.RoundTripper {
+func createBrokerTransport(proxy *url.URL) http.RoundTripper {
 	tlsConfig := &tls.Config{
 		RootCAs: certs.GetRootCAs(),
 	}
 	transport := &http.Transport{TLSClientConfig: tlsConfig}
 	transport.Proxy = nil
+	if proxy != nil {
+		transport.Proxy = http.ProxyURL(proxy)
+	}
 	transport.ResponseHeaderTimeout = 15 * time.Second
 	return transport
 }
@@ -68,7 +72,7 @@ func newBrokerChannelFromConfig(config ClientConfig) (*BrokerChannel, error) {
 		log.Printf("Domain fronting using a randomly selected domain from: %v", config.FrontDomains)
 	}
 
-	brokerTransport := createBrokerTransport()
+	brokerTransport := createBrokerTransport(config.CommunicationProxy)
 
 	if config.UTLSClientID != "" {
 		utlsClientHelloID, err := utlsutil.NameToUTLSID(config.UTLSClientID)
@@ -78,7 +82,8 @@ func newBrokerChannelFromConfig(config ClientConfig) (*BrokerChannel, error) {
 		utlsConfig := &utls.Config{
 			RootCAs: certs.GetRootCAs(),
 		}
-		brokerTransport = utlsutil.NewUTLSHTTPRoundTripper(utlsClientHelloID, utlsConfig, brokerTransport, config.UTLSRemoveSNI)
+		brokerTransport = utlsutil.NewUTLSHTTPRoundTripperWithProxy(utlsClientHelloID, utlsConfig, brokerTransport,
+			config.UTLSRemoveSNI, config.CommunicationProxy)
 	}
 
 	var rendezvous RendezvousMethod
@@ -168,14 +173,22 @@ type WebRTCDialer struct {
 	max          int
 
 	eventLogger event.SnowflakeEventReceiver
+	proxy       *url.URL
 }
 
+// Deprecated: Use NewWebRTCDialerWithEventsAndProxy instead
 func NewWebRTCDialer(broker *BrokerChannel, iceServers []webrtc.ICEServer, max int) *WebRTCDialer {
-	return NewWebRTCDialerWithEvents(broker, iceServers, max, nil)
+	return NewWebRTCDialerWithEventsAndProxy(broker, iceServers, max, nil, nil)
 }
 
-// NewWebRTCDialerWithEvents constructs a new WebRTCDialer.
+// Deprecated: Use NewWebRTCDialerWithEventsAndProxy instead
 func NewWebRTCDialerWithEvents(broker *BrokerChannel, iceServers []webrtc.ICEServer, max int, eventLogger event.SnowflakeEventReceiver) *WebRTCDialer {
+	return NewWebRTCDialerWithEventsAndProxy(broker, iceServers, max, eventLogger, nil)
+}
+
+// NewWebRTCDialerWithEventsAndProxy constructs a new WebRTCDialer.
+func NewWebRTCDialerWithEventsAndProxy(broker *BrokerChannel, iceServers []webrtc.ICEServer, max int,
+	eventLogger event.SnowflakeEventReceiver, proxy *url.URL) *WebRTCDialer {
 	config := webrtc.Configuration{
 		ICEServers: iceServers,
 	}
@@ -186,6 +199,7 @@ func NewWebRTCDialerWithEvents(broker *BrokerChannel, iceServers []webrtc.ICESer
 		max:           max,
 
 		eventLogger: eventLogger,
+		proxy:       proxy,
 	}
 }
 
@@ -193,7 +207,7 @@ func NewWebRTCDialerWithEvents(broker *BrokerChannel, iceServers []webrtc.ICESer
 func (w WebRTCDialer) Catch() (*WebRTCPeer, error) {
 	// TODO: [#25591] Fetch ICE server information from Broker.
 	// TODO: [#25596] Consider TURN servers here too.
-	return NewWebRTCPeerWithEvents(w.webrtcConfig, w.BrokerChannel, w.eventLogger)
+	return NewWebRTCPeerWithEventsAndProxy(w.webrtcConfig, w.BrokerChannel, w.eventLogger, w.proxy)
 }
 
 // GetMax returns the maximum number of snowflakes to collect.
diff --git a/client/lib/snowflake.go b/client/lib/snowflake.go
index 453b42b..daa8b4a 100644
--- a/client/lib/snowflake.go
+++ b/client/lib/snowflake.go
@@ -110,6 +110,8 @@ 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
+	// CommunicationProxy is the proxy address for network communication
+	CommunicationProxy *url.URL
 }
 
 // NewSnowflakeClient creates a new Snowflake transport client that can spawn multiple
@@ -147,14 +149,14 @@ func NewSnowflakeClient(config ClientConfig) (*Transport, error) {
 	if err != nil {
 		return nil, err
 	}
-	go updateNATType(iceServers, broker)
+	go updateNATType(iceServers, broker, config.CommunicationProxy)
 
 	max := 1
 	if config.Max > max {
 		max = config.Max
 	}
 	eventsLogger := event.NewSnowflakeEventDispatcher()
-	transport := &Transport{dialer: NewWebRTCDialerWithEvents(broker, iceServers, max, eventsLogger), eventDispatcher: eventsLogger}
+	transport := &Transport{dialer: NewWebRTCDialerWithEventsAndProxy(broker, iceServers, max, eventsLogger, config.CommunicationProxy), eventDispatcher: eventsLogger}
 
 	return transport, nil
 }
@@ -247,13 +249,13 @@ func (conn *SnowflakeConn) Close() error {
 
 // loop through all provided STUN servers until we exhaust the list or find
 // one that is compatible with RFC 5780
-func updateNATType(servers []webrtc.ICEServer, broker *BrokerChannel) {
+func updateNATType(servers []webrtc.ICEServer, broker *BrokerChannel, proxy *url.URL) {
 
 	var restrictedNAT bool
 	var err error
 	for _, server := range servers {
 		addr := strings.TrimPrefix(server.URLs[0], "stun:")
-		restrictedNAT, err = nat.CheckIfRestrictedNAT(addr)
+		restrictedNAT, err = nat.CheckIfRestrictedNATWithProxy(addr, proxy)
 
 		if err != nil {
 			log.Printf("Warning: NAT checking failed for server at %s: %s", addr, err)
diff --git a/client/lib/webrtc.go b/client/lib/webrtc.go
index fedf299..2b46ef6 100644
--- a/client/lib/webrtc.go
+++ b/client/lib/webrtc.go
@@ -5,8 +5,11 @@ import (
 	"encoding/hex"
 	"errors"
 	"fmt"
+	"github.com/pion/transport/v2"
+	"gitlab.torproject.org/tpo/anti-censorship/pluggable-transports/snowflake/v2/common/proxy"
 	"io"
 	"log"
+	"net/url"
 	"strings"
 	"sync"
 	"time"
@@ -38,20 +41,28 @@ type WebRTCPeer struct {
 
 	bytesLogger  bytesLogger
 	eventsLogger event.SnowflakeEventReceiver
+	proxy        *url.URL
 }
 
+// Deprecated: Use NewWebRTCPeerWithEventsAndProxy Instead.
 func NewWebRTCPeer(config *webrtc.Configuration,
 	broker *BrokerChannel) (*WebRTCPeer, error) {
-	return NewWebRTCPeerWithEvents(config, broker, nil)
+	return NewWebRTCPeerWithEventsAndProxy(config, broker, nil, nil)
 }
 
-// NewWebRTCPeerWithEvents constructs a WebRTC PeerConnection to a snowflake proxy.
+// Deprecated: Use NewWebRTCPeerWithEventsAndProxy Instead.
+func NewWebRTCPeerWithEvents(config *webrtc.Configuration,
+	broker *BrokerChannel, eventsLogger event.SnowflakeEventReceiver) (*WebRTCPeer, error) {
+	return NewWebRTCPeerWithEventsAndProxy(config, broker, eventsLogger, nil)
+}
+
+// NewWebRTCPeerWithEventsAndProxy constructs a WebRTC PeerConnection to a snowflake proxy.
 //
 // The creation of the peer handles the signaling to the Snowflake broker, including
 // the exchange of SDP information, the creation of a PeerConnection, and the establishment
 // of a DataChannel to the Snowflake proxy.
-func NewWebRTCPeerWithEvents(config *webrtc.Configuration,
-	broker *BrokerChannel, eventsLogger event.SnowflakeEventReceiver) (*WebRTCPeer, error) {
+func NewWebRTCPeerWithEventsAndProxy(config *webrtc.Configuration,
+	broker *BrokerChannel, eventsLogger event.SnowflakeEventReceiver, proxy *url.URL) (*WebRTCPeer, error) {
 	if eventsLogger == nil {
 		eventsLogger = event.NewSnowflakeEventDispatcher()
 	}
@@ -73,6 +84,7 @@ func NewWebRTCPeerWithEvents(config *webrtc.Configuration,
 	connection.recvPipe, connection.writePipe = io.Pipe()
 
 	connection.eventsLogger = eventsLogger
+	connection.proxy = proxy
 
 	err := connection.connect(config, broker)
 	if err != nil {
@@ -199,7 +211,17 @@ func (c *WebRTCPeer) preparePeerConnection(config *webrtc.Configuration) error {
 	// to get snowflake working in shadow (where the AF_NETLINK family is not implemented).
 	// These two lines of code functionally revert a new change in pion by silently ignoring
 	// when net.Interfaces() fails, rather than throwing an error
-	vnet, _ := stdnet.NewNet()
+	var vnet transport.Net
+	vnet, _ = stdnet.NewNet()
+
+	if c.proxy != nil {
+		if err = proxy.CheckProxyProtocolSupport(c.proxy); err != nil {
+			return err
+		}
+		socksClient := proxy.NewSocks5UDPClient(c.proxy)
+		vnet = proxy.NewTransportWrapper(&socksClient, vnet)
+	}
+
 	s.SetNet(vnet)
 	api := webrtc.NewAPI(webrtc.WithSettingEngine(s))
 	c.pc, err = api.NewPeerConnection(*config)
diff --git a/client/snowflake.go b/client/snowflake.go
index f4d9c5f..6d4b05c 100644
--- a/client/snowflake.go
+++ b/client/snowflake.go
@@ -4,6 +4,7 @@ package main
 import (
 	"flag"
 	"fmt"
+	"gitlab.torproject.org/tpo/anti-censorship/pluggable-transports/snowflake/v2/common/proxy"
 	"io"
 	"io/ioutil"
 	"log"
@@ -231,8 +232,20 @@ func main() {
 		log.Fatal(err)
 	}
 	if ptInfo.ProxyURL != nil {
-		pt.ProxyError("proxy is not supported")
-		os.Exit(1)
+		if err := proxy.CheckProxyProtocolSupport(ptInfo.ProxyURL); err != nil {
+			pt.ProxyError("proxy is not supported:" + err.Error())
+			os.Exit(1)
+		} else {
+			config.CommunicationProxy = ptInfo.ProxyURL
+			client := proxy.NewSocks5UDPClient(config.CommunicationProxy)
+			conn, err := client.ListenPacket("udp", nil)
+			if err != nil {
+				pt.ProxyError("proxy test failure:" + err.Error())
+				os.Exit(1)
+			}
+			conn.Close()
+			pt.ProxyDone()
+		}
 	}
 	listeners := make([]net.Listener, 0)
 	shutdown := make(chan struct{})
diff --git a/common/nat/nat.go b/common/nat/nat.go
index 81a82bc..cfadcdb 100644
--- a/common/nat/nat.go
+++ b/common/nat/nat.go
@@ -16,8 +16,10 @@ package nat
 import (
 	"errors"
 	"fmt"
+	"gitlab.torproject.org/tpo/anti-censorship/pluggable-transports/snowflake/v2/common/proxy"
 	"log"
 	"net"
+	"net/url"
 	"time"
 
 	"github.com/pion/stun"
@@ -31,23 +33,28 @@ const (
 	NATUnrestricted = "unrestricted"
 )
 
-// This function checks the NAT mapping and filtering
+// Deprecated: Use CheckIfRestrictedNATWithProxy Instead.
+func CheckIfRestrictedNAT(server string) (bool, error) {
+	return CheckIfRestrictedNATWithProxy(server, nil)
+}
+
+// CheckIfRestrictedNATWithProxy checks the NAT mapping and filtering
 // behaviour and returns true if the NAT is restrictive
 // (address-dependent mapping and/or port-dependent filtering)
 // and false if the NAT is unrestrictive (meaning it
 // will work with most other NATs),
-func CheckIfRestrictedNAT(server string) (bool, error) {
-	return isRestrictedMapping(server)
+func CheckIfRestrictedNATWithProxy(server string, proxy *url.URL) (bool, error) {
+	return isRestrictedMapping(server, proxy)
 }
 
 // Performs two tests from RFC 5780 to determine whether the mapping type
 // of the client's NAT is address-independent or address-dependent
 // Returns true if the mapping is address-dependent and false otherwise
-func isRestrictedMapping(addrStr string) (bool, error) {
+func isRestrictedMapping(addrStr string, proxy *url.URL) (bool, error) {
 	var xorAddr1 stun.XORMappedAddress
 	var xorAddr2 stun.XORMappedAddress
 
-	mapTestConn, err := connect(addrStr)
+	mapTestConn, err := connect(addrStr, proxy)
 	if err != nil {
 		return false, fmt.Errorf("Error creating STUN connection: %w", err)
 	}
@@ -98,10 +105,10 @@ func isRestrictedMapping(addrStr string) (bool, error) {
 // Note: This function is no longer used because a client's NAT type is
 // determined only by their mapping type, but the functionality might
 // be useful in the future and remains here.
-func isRestrictedFiltering(addrStr string) (bool, error) {
+func isRestrictedFiltering(addrStr string, proxy *url.URL) (bool, error) {
 	var xorAddr stun.XORMappedAddress
 
-	mapTestConn, err := connect(addrStr)
+	mapTestConn, err := connect(addrStr, proxy)
 	if err != nil {
 		log.Printf("Error creating STUN connection: %s", err.Error())
 		return false, err
@@ -142,23 +149,41 @@ func isRestrictedFiltering(addrStr string) (bool, error) {
 }
 
 // Given an address string, returns a StunServerConn
-func connect(addrStr string) (*StunServerConn, error) {
+func connect(addrStr string, proxyAddr *url.URL) (*StunServerConn, error) {
 	// Creating a "connection" to STUN server.
-	addr, err := net.ResolveUDPAddr("udp4", addrStr)
+	var conn net.PacketConn
+
+	ResolveUDPAddr := net.ResolveUDPAddr
+	if proxyAddr != nil {
+		socksClient := proxy.NewSocks5UDPClient(proxyAddr)
+		ResolveUDPAddr = socksClient.ResolveUDPAddr
+	}
+
+	addr, err := ResolveUDPAddr("udp4", addrStr)
 	if err != nil {
 		log.Printf("Error resolving address: %s\n", err.Error())
 		return nil, err
 	}
 
-	c, err := net.ListenUDP("udp4", nil)
-	if err != nil {
-		return nil, err
+	if proxyAddr == nil {
+		c, err := net.ListenUDP("udp4", nil)
+		if err != nil {
+			return nil, err
+		}
+		conn = c
+	} else {
+		socksClient := proxy.NewSocks5UDPClient(proxyAddr)
+		c, err := socksClient.ListenPacket("udp", nil)
+		if err != nil {
+			return nil, err
+		}
+		conn = c
 	}
 
-	mChan := listen(c)
+	mChan := listen(conn)
 
 	return &StunServerConn{
-		conn:        c,
+		conn:        conn,
 		PrimaryAddr: addr,
 		messageChan: mChan,
 	}, nil
@@ -203,13 +228,13 @@ func (c *StunServerConn) AddOtherAddr(addrStr string) error {
 }
 
 // taken from https://github.com/pion/stun/blob/master/cmd/stun-traversal/main.go
-func listen(conn *net.UDPConn) chan *stun.Message {
+func listen(conn net.PacketConn) chan *stun.Message {
 	messages := make(chan *stun.Message)
 	go func() {
 		for {
 			buf := make([]byte, 1024)
 
-			n, _, err := conn.ReadFromUDP(buf)
+			n, _, err := conn.ReadFrom(buf)
 			if err != nil {
 				close(messages)
 				return
diff --git a/common/proxy/client.go b/common/proxy/client.go
index eb062f8..689bf59 100644
--- a/common/proxy/client.go
+++ b/common/proxy/client.go
@@ -261,6 +261,10 @@ type transportWrapper struct {
 	sc *SocksClient
 }
 
+func (t *transportWrapper) ListenUDP(network string, locAddr *net.UDPAddr) (transport.UDPConn, error) {
+	return t.sc.ListenPacket(network, nil)
+}
+
 func (t *transportWrapper) ListenPacket(network string, address string) (net.PacketConn, error) {
 	return t.sc.ListenPacket(network, nil)
 }
diff --git a/common/utls/roundtripper.go b/common/utls/roundtripper.go
index 5b74aec..10c9155 100644
--- a/common/utls/roundtripper.go
+++ b/common/utls/roundtripper.go
@@ -5,8 +5,10 @@ import (
 	"crypto/tls"
 	"errors"
 	"fmt"
+	"golang.org/x/net/proxy"
 	"net"
 	"net/http"
+	"net/url"
 	"sync"
 	"time"
 
@@ -14,7 +16,13 @@ import (
 	"golang.org/x/net/http2"
 )
 
-// NewUTLSHTTPRoundTripper creates an instance of RoundTripper that dial to remote HTTPS endpoint with
+// Deprecated: use NewUTLSHTTPRoundTripperWithProxy instead
+func NewUTLSHTTPRoundTripper(clientHelloID utls.ClientHelloID, uTlsConfig *utls.Config,
+	backdropTransport http.RoundTripper, removeSNI bool) http.RoundTripper {
+	return NewUTLSHTTPRoundTripperWithProxy(clientHelloID, uTlsConfig, backdropTransport, removeSNI, nil)
+}
+
+// NewUTLSHTTPRoundTripperWithProxy creates an instance of RoundTripper that dial to remote HTTPS endpoint with
 // an alternative version of TLS implementation that attempts to imitate browsers' fingerprint.
 // clientHelloID is the clientHello that uTLS attempts to imitate
 // uTlsConfig is the TLS Configuration template
@@ -22,8 +30,8 @@ import (
 // removeSNI indicates not to send Server Name Indication Extension
 // returns a RoundTripper: its behaviour is documented at
 // https://gitlab.torproject.org/tpo/anti-censorship/pluggable-transports/snowflake/-/merge_requests/76#note_2777161
-func NewUTLSHTTPRoundTripper(clientHelloID utls.ClientHelloID, uTlsConfig *utls.Config,
-	backdropTransport http.RoundTripper, removeSNI bool) http.RoundTripper {
+func NewUTLSHTTPRoundTripperWithProxy(clientHelloID utls.ClientHelloID, uTlsConfig *utls.Config,
+	backdropTransport http.RoundTripper, removeSNI bool, proxy *url.URL) http.RoundTripper {
 	rtImpl := &uTLSHTTPRoundTripperImpl{
 		clientHelloID:     clientHelloID,
 		config:            uTlsConfig,
@@ -31,6 +39,7 @@ func NewUTLSHTTPRoundTripper(clientHelloID utls.ClientHelloID, uTlsConfig *utls.
 		backdropTransport: backdropTransport,
 		pendingConn:       map[pendingConnKey]*unclaimedConnection{},
 		removeSNI:         removeSNI,
+		proxyAddr:         proxy,
 	}
 	rtImpl.init()
 	return rtImpl
@@ -51,6 +60,7 @@ type uTLSHTTPRoundTripperImpl struct {
 	pendingConn             map[pendingConnKey]*unclaimedConnection
 
 	removeSNI bool
+	proxyAddr *url.URL
 }
 
 type pendingConnKey struct {
@@ -174,7 +184,19 @@ func (r *uTLSHTTPRoundTripperImpl) dialTLS(ctx context.Context, addr string) (*u
 	}
 	config.ServerName = host
 
-	dialer := &net.Dialer{}
+	systemDialer := &net.Dialer{}
+
+	var dialer proxy.ContextDialer
+	dialer = systemDialer
+
+	if r.proxyAddr != nil {
+		proxyDialer, err := proxy.FromURL(r.proxyAddr, systemDialer)
+		if err != nil {
+			return nil, err
+		}
+		dialer = proxyDialer.(proxy.ContextDialer)
+	}
+
 	conn, err := dialer.DialContext(ctx, "tcp", addr)
 	if err != nil {
 		return nil, err