snowflake/client/snowflake.go

251 lines
6 KiB
Go

// Client transport plugin for the Snowflake pluggable transport.
package main
import (
"bufio"
"errors"
"flag"
"io"
"log"
"net"
"os"
"os/signal"
"sync"
"syscall"
"time"
"git.torproject.org/pluggable-transports/goptlib.git"
"github.com/keroserene/go-webrtc"
)
var ptInfo pt.ClientInfo
const (
ReconnectTimeout = 10
DefaultSnowflakeCapacity = 1
)
var iceServers IceServerList
// When a connection handler starts, +1 is written to this channel; when it
// ends, -1 is written.
var handlerChan = make(chan int)
func copyLoop(a, b net.Conn) {
var wg sync.WaitGroup
wg.Add(2)
go func() {
io.Copy(b, a)
wg.Done()
}()
go func() {
io.Copy(a, b)
wg.Done()
}()
wg.Wait()
log.Println("copy loop ended")
}
// Maintain |SnowflakeCapacity| number of available WebRTC connections, to
// transfer to the Tor SOCKS handler when needed.
func ConnectLoop(snowflakes SnowflakeCollector) {
for {
err := snowflakes.Collect()
if nil != err {
log.Println("WebRTC Error:", err,
" Retrying in", ReconnectTimeout, "seconds...")
// Failed collections get a timeout.
<-time.After(time.Second * ReconnectTimeout)
continue
}
// Successful collection gets rate limited to once per second.
log.Println("ConnectLoop success.")
<-time.After(time.Second)
}
}
// Accept local SOCKS connections and pass them to the handler.
func acceptLoop(ln *pt.SocksListener, snowflakes SnowflakeCollector) error {
defer ln.Close()
log.Println("Started SOCKS listener.")
for {
conn, err := ln.AcceptSocks()
log.Println("SOCKS accepted ", conn.Req)
if err != nil {
if e, ok := err.(net.Error); ok && e.Temporary() {
continue
}
return err
}
err = handler(conn, snowflakes)
if err != nil {
log.Printf("handler error: %s", err)
}
}
}
// Given an accepted SOCKS connection, establish a WebRTC connection to the
// remote peer and exchange traffic.
func handler(socks SocksConnector, snowflakes SnowflakeCollector) error {
handlerChan <- 1
defer func() {
handlerChan <- -1
}()
// Obtain an available WebRTC remote. May block.
snowflake := snowflakes.Pop()
if nil == snowflake {
socks.Reject()
return errors.New("handler: Received invalid Snowflake")
}
defer socks.Close()
log.Println("handler: Snowflake assigned.")
err := socks.Grant(&net.TCPAddr{IP: net.IPv4zero, Port: 0})
if err != nil {
return err
}
// Begin exchanging data.
go copyLoop(socks, snowflake)
// When WebRTC resets, close the SOCKS connection, which induces new handler.
// TODO: Double check this / fix it.
<-snowflake.reset
log.Println("---- Closed ---")
return nil
}
// TODO: Fix since multiplexing changes access to remotes.
func readSignalingMessages(f *os.File) {
log.Printf("readSignalingMessages")
s := bufio.NewScanner(f)
for s.Scan() {
msg := s.Text()
log.Printf("readSignalingMessages loop %+q", msg)
sdp := webrtc.DeserializeSessionDescription(msg)
if sdp == nil {
log.Printf("ignoring invalid signal message %+q", msg)
continue
}
// webrtcRemotes[0].answerChannel <- sdp
}
log.Printf("close answerChannel")
// close(webrtcRemotes[0].answerChannel)
if err := s.Err(); err != nil {
log.Printf("signal FIFO: %s", err)
}
}
func main() {
webrtc.SetLoggingVerbosity(1)
logFile, err := os.OpenFile("snowflake.log",
os.O_CREATE|os.O_APPEND|os.O_WRONLY, 0600)
if err != nil {
log.Fatal(err)
}
defer logFile.Close()
log.SetOutput(logFile)
log.Println("\nStarting Snowflake Client...")
brokerURL := flag.String("url", "", "URL of signaling broker")
frontDomain := flag.String("front", "", "front domain")
flag.Var(&iceServers, "ice", "comma-separated list of ICE servers")
max := flag.Int("max", DefaultSnowflakeCapacity,
"capacity for number of multiplexed WebRTC peers")
flag.Parse()
// TODO: Maybe just get rid of copy-paste option entirely.
if "" != *brokerURL {
log.Println("Rendezvous using Broker at: ", *brokerURL)
if "" != *frontDomain {
log.Println("Domain fronting using:", *frontDomain)
}
} else {
log.Println("No HTTP signaling detected. Waiting for a \"signal\" pipe...")
// This FIFO receives signaling messages.
err := syscall.Mkfifo("signal", 0600)
if err != nil {
if err.(syscall.Errno) != syscall.EEXIST {
log.Fatal(err)
}
}
signalFile, err := os.OpenFile("signal", os.O_RDONLY, 0600)
if err != nil {
log.Fatal(err)
}
defer signalFile.Close()
go readSignalingMessages(signalFile)
}
// Prepare WebRTC SnowflakeCollector, Broker, then accumulate connections.
snowflakes := NewPeers(*max)
broker := NewBrokerChannel(*brokerURL, *frontDomain, CreateBrokerTransport())
snowflakes.Tongue = NewWebRTCDialer(broker)
// Use a real logger for traffic.
snowflakes.BytesLogger = &BytesSyncLogger{
inboundChan: make(chan int, 5), outboundChan: make(chan int, 5),
inbound: 0, outbound: 0, inEvents: 0, outEvents: 0,
}
go ConnectLoop(snowflakes)
go snowflakes.BytesLogger.Log()
ptInfo, err = pt.ClientSetup(nil)
if err != nil {
log.Fatal(err)
}
if ptInfo.ProxyURL != nil {
pt.ProxyError("proxy is not supported")
os.Exit(1)
}
listeners := make([]net.Listener, 0)
for _, methodName := range ptInfo.MethodNames {
switch methodName {
case "snowflake":
// TODO: Be able to recover when SOCKS dies.
ln, err := pt.ListenSocks("tcp", "127.0.0.1:0")
if err != nil {
pt.CmethodError(methodName, err.Error())
break
}
go acceptLoop(ln, snowflakes)
pt.Cmethod(methodName, ln.Version(), ln.Addr())
listeners = append(listeners, ln)
default:
pt.CmethodError(methodName, "no such method")
}
}
pt.CmethodsDone()
var numHandlers int = 0
var sig os.Signal
sigChan := make(chan os.Signal, 1)
signal.Notify(sigChan, syscall.SIGINT, syscall.SIGTERM)
// wait for first signal
sig = nil
for sig == nil {
select {
case n := <-handlerChan:
numHandlers += n
case sig = <-sigChan:
}
}
for _, ln := range listeners {
ln.Close()
}
snowflakes.End()
// wait for second signal or no more handlers
sig = nil
for sig == nil && numHandlers != 0 {
select {
case n := <-handlerChan:
numHandlers += n
case sig = <-sigChan:
}
}
}