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// Copyright (c) Tailscale Inc & AUTHORS
// SPDX-License-Identifier: BSD-3-Clause
// The sniproxy is an outbound SNI proxy. It receives TLS connections over
// Tailscale on one or more TCP ports and sends them out to the same SNI
// hostname & port on the internet. It only does TCP.
package main
import (
"context"
"flag"
"log"
"net"
"net/http"
"strings"
"time"
"golang.org/x/net/dns/dnsmessage"
"inet.af/tcpproxy"
"tailscale.com/client/tailscale"
"tailscale.com/hostinfo"
"tailscale.com/net/netutil"
"tailscale.com/tsnet"
"tailscale.com/types/nettype"
"tailscale.com/util/clientmetric"
)
var (
ports = flag.String("ports", "443", "comma-separated list of ports to proxy")
wgPort = flag.Int("wg-listen-port", 0, "UDP port to listen on for WireGuard and peer-to-peer traffic; 0 means automatically select")
promoteHTTPS = flag.Bool("promote-https", true, "promote HTTP to HTTPS")
)
var tsMBox = dnsmessage.MustNewName("support.tailscale.com.")
var (
numSessions = clientmetric.NewCounter("sniproxy_sessions")
numBadAddrPort = clientmetric.NewCounter("sniproxy_bad_addrport")
dnsResponses = clientmetric.NewCounter("sniproxy_dns_responses")
dnsFailures = clientmetric.NewCounter("sniproxy_dns_failed")
httpPromoted = clientmetric.NewCounter("sniproxy_http_promoted")
)
func main() {
flag.Parse()
if *ports == "" {
log.Fatal("no ports")
}
hostinfo.SetApp("sniproxy")
var s server
s.ts.Port = uint16(*wgPort)
defer s.ts.Close()
lc, err := s.ts.LocalClient()
if err != nil {
log.Fatal(err)
}
s.lc = lc
for _, portStr := range strings.Split(*ports, ",") {
ln, err := s.ts.Listen("tcp", ":"+portStr)
if err != nil {
log.Fatal(err)
}
log.Printf("Serving on port %v ...", portStr)
go s.serve(ln)
}
ln, err := s.ts.Listen("udp", ":53")
if err != nil {
log.Fatal(err)
}
go s.serveDNS(ln)
if *promoteHTTPS {
ln, err := s.ts.Listen("tcp", ":80")
if err != nil {
log.Fatal(err)
}
log.Printf("Promoting HTTP to HTTPS ...")
go s.promoteHTTPS(ln)
}
select {}
}
type server struct {
ts tsnet.Server
lc *tailscale.LocalClient
}
func (s *server) serve(ln net.Listener) {
for {
c, err := ln.Accept()
if err != nil {
log.Fatal(err)
}
go s.serveConn(c)
}
}
func (s *server) serveDNS(ln net.Listener) {
for {
c, err := ln.Accept()
if err != nil {
log.Fatal(err)
}
go s.serveDNSConn(c.(nettype.ConnPacketConn))
}
}
func (s *server) serveDNSConn(c nettype.ConnPacketConn) {
defer c.Close()
c.SetReadDeadline(time.Now().Add(5 * time.Second))
buf := make([]byte, 1500)
n, err := c.Read(buf)
if err != nil {
log.Printf("c.Read failed: %v\n ", err)
dnsFailures.Add(1)
return
}
var msg dnsmessage.Message
err = msg.Unpack(buf[:n])
if err != nil {
log.Printf("dnsmessage unpack failed: %v\n ", err)
dnsFailures.Add(1)
return
}
buf, err = s.dnsResponse(&msg)
if err != nil {
log.Printf("s.dnsResponse failed: %v\n", err)
dnsFailures.Add(1)
return
}
_, err = c.Write(buf)
if err != nil {
log.Printf("c.Write failed: %v\n", err)
dnsFailures.Add(1)
return
}
dnsResponses.Add(1)
}
func (s *server) serveConn(c net.Conn) {
addrPortStr := c.LocalAddr().String()
_, port, err := net.SplitHostPort(addrPortStr)
if err != nil {
log.Printf("bogus addrPort %q", addrPortStr)
numBadAddrPort.Add(1)
c.Close()
return
}
var dialer net.Dialer
dialer.Timeout = 5 * time.Second
var p tcpproxy.Proxy
p.ListenFunc = func(net, laddr string) (net.Listener, error) {
return netutil.NewOneConnListener(c, nil), nil
}
p.AddSNIRouteFunc(addrPortStr, func(ctx context.Context, sniName string) (t tcpproxy.Target, ok bool) {
numSessions.Add(1)
return &tcpproxy.DialProxy{
Addr: net.JoinHostPort(sniName, port),
DialContext: dialer.DialContext,
}, true
})
p.Start()
}
func (s *server) dnsResponse(req *dnsmessage.Message) (buf []byte, err error) {
resp := dnsmessage.NewBuilder(buf,
dnsmessage.Header{
ID: req.Header.ID,
Response: true,
Authoritative: true,
})
resp.EnableCompression()
if len(req.Questions) == 0 {
buf, _ = resp.Finish()
return
}
q := req.Questions[0]
err = resp.StartQuestions()
if err != nil {
return
}
resp.Question(q)
ip4, ip6 := s.ts.TailscaleIPs()
err = resp.StartAnswers()
if err != nil {
return
}
switch q.Type {
case dnsmessage.TypeAAAA:
err = resp.AAAAResource(
dnsmessage.ResourceHeader{Name: q.Name, Class: q.Class, TTL: 120},
dnsmessage.AAAAResource{AAAA: ip6.As16()},
)
case dnsmessage.TypeA:
err = resp.AResource(
dnsmessage.ResourceHeader{Name: q.Name, Class: q.Class, TTL: 120},
dnsmessage.AResource{A: ip4.As4()},
)
case dnsmessage.TypeSOA:
err = resp.SOAResource(
dnsmessage.ResourceHeader{Name: q.Name, Class: q.Class, TTL: 120},
dnsmessage.SOAResource{NS: q.Name, MBox: tsMBox, Serial: 2023030600,
Refresh: 120, Retry: 120, Expire: 120, MinTTL: 60},
)
case dnsmessage.TypeNS:
err = resp.NSResource(
dnsmessage.ResourceHeader{Name: q.Name, Class: q.Class, TTL: 120},
dnsmessage.NSResource{NS: tsMBox},
)
}
if err != nil {
return
}
return resp.Finish()
}
func (s *server) promoteHTTPS(ln net.Listener) {
err := http.Serve(ln, http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
httpPromoted.Add(1)
http.Redirect(w, r, "https://"+r.Host+r.RequestURI, http.StatusFound)
}))
log.Fatalf("promoteHTTPS http.Serve: %v", err)
}
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