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// Copyright 2016 Google Inc.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
package main
import (
"bytes"
"flag"
"fmt"
"io"
"log"
"net"
"sync"
"time"
)
var (
cfgFile = flag.String("conf", "", "configuration file")
listen = flag.String("listen", ":443", "listening port")
helloTimeout = flag.Duration("hello-timeout", 3*time.Second, "how long to wait for the TLS ClientHello")
)
var config Config
func main() {
flag.Parse()
if err := config.ReadFile(*cfgFile); err != nil {
log.Fatalf("Failed to read config %q: %s", *cfgFile, err)
}
l, err := net.Listen("tcp", *listen)
if err != nil {
log.Fatalf("Failed to listen: %s", err)
}
for {
c, err := l.Accept()
if err != nil {
log.Fatalf("Error while accepting: %s", err)
}
conn := &Conn{TCPConn: c.(*net.TCPConn)}
go conn.proxy()
}
}
// A Conn handles the TLS proxying of one user connection.
type Conn struct {
*net.TCPConn
tlsMinor int
hostname string
backend string
backendConn *net.TCPConn
}
func (c *Conn) logf(msg string, args ...interface{}) {
msg = fmt.Sprintf(msg, args...)
log.Printf("%s <> %s: %s", c.RemoteAddr(), c.LocalAddr(), msg)
}
func (c *Conn) abort(alert byte, msg string, args ...interface{}) {
c.logf(msg, args...)
alertMsg := []byte{21, 3, byte(c.tlsMinor), 0, 2, 2, alert}
if err := c.SetWriteDeadline(time.Now().Add(*helloTimeout)); err != nil {
c.logf("error while setting write deadline during abort: %s", err)
// Do NOT send the alert if we can't set a write deadline,
// that could result in leaking a connection for an extended
// period.
return
}
if _, err := c.Write(alertMsg); err != nil {
c.logf("error while sending alert: %s", err)
}
}
func (c *Conn) internalError(msg string, args ...interface{}) { c.abort(80, msg, args...) }
func (c *Conn) sniFailed(msg string, args ...interface{}) { c.abort(112, msg, args...) }
func (c *Conn) proxy() {
defer c.Close()
if err := c.SetReadDeadline(time.Now().Add(*helloTimeout)); err != nil {
c.internalError("Setting read deadline for ClientHello: %s", err)
return
}
var (
err error
handshakeBuf bytes.Buffer
)
c.hostname, c.tlsMinor, err = extractSNI(io.TeeReader(c, &handshakeBuf))
if err != nil {
c.internalError("Extracting SNI: %s", err)
return
}
if err = c.SetReadDeadline(time.Time{}); err != nil {
c.internalError("Clearing read deadline for ClientHello: %s", err)
return
}
c.backend = config.Match(c.hostname)
if c.backend == "" {
c.sniFailed("no backend found for %q", c.hostname)
return
}
c.logf("routing %q to %q", c.hostname, c.backend)
backend, err := net.DialTimeout("tcp", c.backend, 10*time.Second)
if err != nil {
c.internalError("failed to dial backend %q for %q: %s", c.backend, c.hostname, err)
return
}
defer backend.Close()
c.backendConn = backend.(*net.TCPConn)
// Replay the piece of the handshake we had to read to do the
// routing, then blindly proxy any other bytes.
if _, err = io.Copy(c.backendConn, &handshakeBuf); err != nil {
c.internalError("failed to replay handshake to %q: %s", c.backend, err)
return
}
var wg sync.WaitGroup
wg.Add(2)
go proxy(&wg, c.TCPConn, c.backendConn)
go proxy(&wg, c.backendConn, c.TCPConn)
wg.Wait()
}
func proxy(wg *sync.WaitGroup, a, b net.Conn) {
defer wg.Done()
atcp, btcp := a.(*net.TCPConn), b.(*net.TCPConn)
if _, err := io.Copy(atcp, btcp); err != nil {
log.Printf("%s<>%s -> %s<>%s: %s", atcp.RemoteAddr(), atcp.LocalAddr(), btcp.LocalAddr(), btcp.RemoteAddr(), err)
}
btcp.CloseWrite()
atcp.CloseRead()
}
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