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// Copyright (c) Tailscale Inc & contributors
// SPDX-License-Identifier: BSD-3-Clause
//go:build !ts_omit_outboundproxy
// HTTP proxy code
package main
import (
"context"
"flag"
"io"
"log"
"net"
"net/http"
"net/http/httputil"
"strings"
"tailscale.com/feature"
"tailscale.com/net/proxymux"
"tailscale.com/net/socks5"
"tailscale.com/net/tsdial"
"tailscale.com/types/logger"
)
func init() {
hookRegisterOutboundProxyFlags.Set(registerOutboundProxyFlags)
hookOutboundProxyListen.Set(outboundProxyListen)
}
func registerOutboundProxyFlags() {
flag.StringVar(&args.socksAddr, "socks5-server", "", `optional [ip]:port to run a SOCK5 server (e.g. "localhost:1080")`)
flag.StringVar(&args.httpProxyAddr, "outbound-http-proxy-listen", "", `optional [ip]:port to run an outbound HTTP proxy (e.g. "localhost:8080")`)
}
// outboundProxyListen creates listeners for local SOCKS and HTTP proxies, if
// the respective addresses are not empty. args.socksAddr and args.httpProxyAddr
// can be the same, in which case the SOCKS5 Listener will receive connections
// that look like they're speaking SOCKS and httpListener will receive
// everything else.
//
// socksListener and httpListener can be nil, if their respective addrs are
// empty.
//
// The returned func closes over those two (possibly nil) listeners and
// starts the respective servers on the listener when called.
func outboundProxyListen() proxyStartFunc {
socksAddr, httpAddr := args.socksAddr, args.httpProxyAddr
if socksAddr == httpAddr && socksAddr != "" && !strings.HasSuffix(socksAddr, ":0") {
ln, err := net.Listen("tcp", socksAddr)
if err != nil {
log.Fatalf("proxy listener: %v", err)
}
return mkProxyStartFunc(proxymux.SplitSOCKSAndHTTP(ln))
}
var socksListener, httpListener net.Listener
var err error
if socksAddr != "" {
socksListener, err = net.Listen("tcp", socksAddr)
if err != nil {
log.Fatalf("SOCKS5 listener: %v", err)
}
if strings.HasSuffix(socksAddr, ":0") {
// Log kernel-selected port number so integration tests
// can find it portably.
log.Printf("SOCKS5 listening on %v", socksListener.Addr())
}
}
if httpAddr != "" {
httpListener, err = net.Listen("tcp", httpAddr)
if err != nil {
log.Fatalf("HTTP proxy listener: %v", err)
}
if strings.HasSuffix(httpAddr, ":0") {
// Log kernel-selected port number so integration tests
// can find it portably.
log.Printf("HTTP proxy listening on %v", httpListener.Addr())
}
}
return mkProxyStartFunc(socksListener, httpListener)
}
func mkProxyStartFunc(socksListener, httpListener net.Listener) proxyStartFunc {
return func(logf logger.Logf, dialer *tsdial.Dialer) {
var addrs []string
if httpListener != nil {
hs := &http.Server{Handler: httpProxyHandler(dialer.UserDial)}
go func() {
log.Fatalf("HTTP proxy exited: %v", hs.Serve(httpListener))
}()
addrs = append(addrs, httpListener.Addr().String())
}
if socksListener != nil {
ss := &socks5.Server{
Logf: logger.WithPrefix(logf, "socks5: "),
Dialer: dialer.UserDial,
}
go func() {
log.Fatalf("SOCKS5 server exited: %v", ss.Serve(socksListener))
}()
addrs = append(addrs, socksListener.Addr().String())
}
if set, ok := feature.HookProxySetSelfProxy.GetOk(); ok {
set(addrs...)
}
}
}
// httpProxyHandler returns an HTTP proxy http.Handler using the
// provided backend dialer.
func httpProxyHandler(dialer func(ctx context.Context, netw, addr string) (net.Conn, error)) http.Handler {
rp := &httputil.ReverseProxy{
Director: func(r *http.Request) {}, // no change
Transport: &http.Transport{
DialContext: dialer,
},
}
return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
if r.Method != "CONNECT" {
backURL := r.RequestURI
if strings.HasPrefix(backURL, "/") || backURL == "*" {
http.Error(w, "bogus RequestURI; must be absolute URL or CONNECT", 400)
return
}
rp.ServeHTTP(w, r)
return
}
// CONNECT support:
dst := r.RequestURI
c, err := dialer(r.Context(), "tcp", dst)
if err != nil {
w.Header().Set("Tailscale-Connect-Error", err.Error())
http.Error(w, err.Error(), 500)
return
}
defer c.Close()
cc, ccbuf, err := w.(http.Hijacker).Hijack()
if err != nil {
http.Error(w, err.Error(), 500)
return
}
defer cc.Close()
io.WriteString(cc, "HTTP/1.1 200 OK\r\n\r\n")
var clientSrc io.Reader = ccbuf
if ccbuf.Reader.Buffered() == 0 {
// In the common case (with no
// buffered data), read directly from
// the underlying client connection to
// save some memory, letting the
// bufio.Reader/Writer get GC'ed.
clientSrc = cc
}
errc := make(chan error, 1)
go func() {
_, err := io.Copy(cc, c)
errc <- err
}()
go func() {
_, err := io.Copy(c, clientSrc)
errc <- err
}()
<-errc
})
}
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