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// Client transport plugin for the Snowflake pluggable transport.
package main
import (
"flag"
"io"
"io/ioutil"
"log"
"net"
"os"
"os/signal"
"path/filepath"
"strings"
"syscall"
"time"
pt "git.torproject.org/pluggable-transports/goptlib.git"
sf "git.torproject.org/pluggable-transports/snowflake.git/client/lib"
"git.torproject.org/pluggable-transports/snowflake.git/common/safelog"
"github.com/pion/webrtc"
)
const (
DefaultSnowflakeCapacity = 1
)
// Maintain |SnowflakeCapacity| number of available WebRTC connections, to
// transfer to the Tor SOCKS handler when needed.
func ConnectLoop(snowflakes sf.SnowflakeCollector) {
for {
// Check if ending is necessary.
_, err := snowflakes.Collect()
if err != nil {
log.Printf("WebRTC: %v Retrying in %v...",
err, sf.ReconnectTimeout)
}
select {
case <-time.After(sf.ReconnectTimeout):
continue
case <-snowflakes.Melted():
log.Println("ConnectLoop: stopped.")
return
}
}
}
// Accept local SOCKS connections and pass them to the handler.
func socksAcceptLoop(ln *pt.SocksListener, snowflakes sf.SnowflakeCollector) {
defer ln.Close()
for {
conn, err := ln.AcceptSocks()
if err != nil {
if err, ok := err.(net.Error); ok && err.Temporary() {
continue
}
log.Printf("SOCKS accept error: %s", err)
break
}
log.Printf("SOCKS accepted: %v", conn.Req)
go func() {
defer conn.Close()
err := conn.Grant(&net.TCPAddr{IP: net.IPv4zero, Port: 0})
if err != nil {
log.Printf("conn.Grant error: %s", err)
return
}
err = sf.Handler(conn, snowflakes)
if err != nil {
log.Printf("handler error: %s", err)
return
}
}()
}
}
// s is a comma-separated list of ICE server URLs.
func parseIceServers(s string) []webrtc.ICEServer {
var servers []webrtc.ICEServer
s = strings.TrimSpace(s)
if len(s) == 0 {
return nil
}
urls := strings.Split(s, ",")
for _, url := range urls {
url = strings.TrimSpace(url)
servers = append(servers, webrtc.ICEServer{
URLs: []string{url},
})
}
return servers
}
func main() {
iceServersCommas := flag.String("ice", "", "comma-separated list of ICE servers")
brokerURL := flag.String("url", "", "URL of signaling broker")
frontDomain := flag.String("front", "", "front domain")
logFilename := flag.String("log", "", "name of log file")
logToStateDir := flag.Bool("logToStateDir", false, "resolve the log file relative to tor's pt state dir")
max := flag.Int("max", DefaultSnowflakeCapacity,
"capacity for number of multiplexed WebRTC peers")
flag.Parse()
log.SetFlags(log.LstdFlags | log.LUTC)
// Don't write to stderr; versions of tor earlier than about 0.3.5.6 do
// not read from the pipe, and eventually we will deadlock because the
// buffer is full.
// https://bugs.torproject.org/26360
// https://bugs.torproject.org/25600#comment:14
var logOutput = ioutil.Discard
if *logFilename != "" {
if *logToStateDir {
stateDir, err := pt.MakeStateDir()
if err != nil {
log.Fatal(err)
}
*logFilename = filepath.Join(stateDir, *logFilename)
}
logFile, err := os.OpenFile(*logFilename,
os.O_CREATE|os.O_APPEND|os.O_WRONLY, 0600)
if err != nil {
log.Fatal(err)
}
defer logFile.Close()
logOutput = logFile
}
// We want to send the log output through our scrubber first
log.SetOutput(&safelog.LogScrubber{Output: logOutput})
log.Println("\n\n\n --- Starting Snowflake Client ---")
iceServers := parseIceServers(*iceServersCommas)
log.Printf("Using ICE servers:")
for _, server := range iceServers {
log.Printf("url: %v", strings.Join(server.URLs, " "))
}
// Prepare to collect remote WebRTC peers.
snowflakes := sf.NewPeers(*max)
// Use potentially domain-fronting broker to rendezvous.
broker, err := sf.NewBrokerChannel(*brokerURL, *frontDomain, sf.CreateBrokerTransport())
if err != nil {
log.Fatalf("parsing broker URL: %v", err)
}
snowflakes.Tongue = sf.NewWebRTCDialer(broker, iceServers)
// Use a real logger to periodically output how much traffic is happening.
snowflakes.BytesLogger = &sf.BytesSyncLogger{
InboundChan: make(chan int, 5),
OutboundChan: make(chan int, 5),
Inbound: 0,
Outbound: 0,
InEvents: 0,
OutEvents: 0,
}
go snowflakes.BytesLogger.Log()
go ConnectLoop(snowflakes)
// Begin goptlib client process.
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
}
log.Printf("Started SOCKS listener at %v.", ln.Addr())
go socksAcceptLoop(ln, snowflakes)
pt.Cmethod(methodName, ln.Version(), ln.Addr())
listeners = append(listeners, ln)
default:
pt.CmethodError(methodName, "no such method")
}
}
pt.CmethodsDone()
sigChan := make(chan os.Signal, 1)
signal.Notify(sigChan, syscall.SIGTERM)
if os.Getenv("TOR_PT_EXIT_ON_STDIN_CLOSE") == "1" {
// This environment variable means we should treat EOF on stdin
// just like SIGTERM: https://bugs.torproject.org/15435.
go func() {
if _, err := io.Copy(ioutil.Discard, os.Stdin); err != nil {
log.Printf("calling io.Copy(ioutil.Discard, os.Stdin) returned error: %v", err)
}
log.Printf("synthesizing SIGTERM because of stdin close")
sigChan <- syscall.SIGTERM
}()
}
// Wait for a signal.
<-sigChan
// Signal received, shut down.
for _, ln := range listeners {
ln.Close()
}
snowflakes.End()
log.Println("snowflake is done.")
}
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