// Copyright (c) 2020 Tailscale Inc & AUTHORS All rights reserved. // Use of this source code is governed by a BSD-style // license that can be found in the LICENSE file. // The derper binary is a simple DERP server. package main // import "tailscale.com/cmd/derper" import ( "context" "encoding/json" "errors" "expvar" "flag" "fmt" "io" "io/ioutil" "log" "net" "net/http" "os" "path/filepath" "regexp" "time" "github.com/tailscale/wireguard-go/wgcfg" "golang.org/x/crypto/acme/autocert" "tailscale.com/atomicfile" "tailscale.com/derp" "tailscale.com/derp/derphttp" "tailscale.com/logpolicy" "tailscale.com/stun" "tailscale.com/tsweb" "tailscale.com/types/key" ) var ( dev = flag.Bool("dev", false, "run in localhost development mode") addr = flag.String("a", ":443", "server address") configPath = flag.String("c", "", "config file path") certDir = flag.String("certdir", tsweb.DefaultCertDir("derper-certs"), "directory to store LetsEncrypt certs, if addr's port is :443") hostname = flag.String("hostname", "derp.tailscale.com", "LetsEncrypt host name, if addr's port is :443") mbps = flag.Int("mbps", 5, "Mbps (mebibit/s) per-client rate limit; 0 means unlimited") logCollection = flag.String("logcollection", "", "If non-empty, logtail collection to log to") runSTUN = flag.Bool("stun", false, "also run a STUN server") ) type config struct { PrivateKey wgcfg.PrivateKey } func loadConfig() config { if *dev { return config{PrivateKey: mustNewKey()} } if *configPath == "" { log.Fatalf("derper: -c not specified") } b, err := ioutil.ReadFile(*configPath) switch { case os.IsNotExist(err): return writeNewConfig() case err != nil: log.Fatal(err) panic("unreachable") default: var cfg config if err := json.Unmarshal(b, &cfg); err != nil { log.Fatalf("derper: config: %v", err) } return cfg } } func mustNewKey() wgcfg.PrivateKey { key, err := wgcfg.NewPrivateKey() if err != nil { log.Fatal(err) } return key } func writeNewConfig() config { key := mustNewKey() if err := os.MkdirAll(filepath.Dir(*configPath), 0777); err != nil { log.Fatal(err) } cfg := config{ PrivateKey: key, } b, err := json.MarshalIndent(cfg, "", "\t") if err != nil { log.Fatal(err) } if err := atomicfile.WriteFile(*configPath, b, 0666); err != nil { log.Fatal(err) } return cfg } func main() { flag.Parse() if *dev { *logCollection = "" *addr = ":3340" // above the keys DERP log.Printf("Running in dev mode.") } var logPol *logpolicy.Policy if *logCollection != "" { logPol = logpolicy.New(*logCollection) log.SetOutput(logPol.Logtail) } cfg := loadConfig() letsEncrypt := tsweb.IsProd443(*addr) s := derp.NewServer(key.Private(cfg.PrivateKey), log.Printf) if *mbps != 0 { s.BytesPerSecond = (*mbps << 20) / 8 } expvar.Publish("derp", s.ExpVar()) // Create our own mux so we don't expose /debug/ stuff to the world. mux := tsweb.NewMux(debugHandler(s)) mux.Handle("/derp", derphttp.Handler(s)) mux.Handle("/", http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) { w.Header().Set("Content-Type", "text/html; charset=utf-8") w.WriteHeader(200) io.WriteString(w, `

DERP

This is a Tailscale DERP server.

`) if tsweb.AllowDebugAccess(r) { io.WriteString(w, "

Debug info at /debug/.

\n") } })) if *runSTUN { go serveSTUN() } httpsrv := &http.Server{ Addr: *addr, Handler: mux, } var err error if letsEncrypt { if *certDir == "" { log.Fatalf("missing required --certdir flag") } log.Printf("derper: serving on %s with TLS", *addr) certManager := &autocert.Manager{ Prompt: autocert.AcceptTOS, HostPolicy: autocert.HostWhitelist(*hostname), Cache: autocert.DirCache(*certDir), } if *hostname == "derp.tailscale.com" { certManager.HostPolicy = prodAutocertHostPolicy } httpsrv.TLSConfig = certManager.TLSConfig() go func() { err := http.ListenAndServe(":80", certManager.HTTPHandler(tsweb.Port80Handler{mux})) if err != nil { if err != http.ErrServerClosed { log.Fatal(err) } } }() err = httpsrv.ListenAndServeTLS("", "") } else { log.Printf("derper: serving on %s", *addr) err = httpsrv.ListenAndServe() } if err != nil && err != http.ErrServerClosed { log.Fatalf("derper: %v", err) } } func debugHandler(s *derp.Server) http.Handler { return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) { f := func(format string, args ...interface{}) { fmt.Fprintf(w, format, args...) } f(`

DERP debug

Hostname: %v
Rate Limit: %v Mbps
Uptime: %v
/debug/vars
/debug/pprof/
/debug/pprof/goroutine (collapsed)
/debug/pprof/goroutine (full)

`) }) } func serveSTUN() { pc, err := net.ListenPacket("udp", ":3478") if err != nil { log.Fatalf("failed to open STUN listener: %v", err) } log.Printf("running STUN server on %v", pc.LocalAddr()) var ( stunReadErrors = expvar.NewInt("stun-read-error") stunWriteErrors = expvar.NewInt("stun-write-error") stunReadNotSTUN = expvar.NewInt("stun-read-not-stun") stunReadNotSTUNValid = expvar.NewInt("stun-read-not-stun-valid") stunReadIPv4 = expvar.NewInt("stun-read-ipv4") stunReadIPv6 = expvar.NewInt("stun-read-ipv6") stunWrite = expvar.NewInt("stun-write") ) var buf [64 << 10]byte for { n, addr, err := pc.ReadFrom(buf[:]) if err != nil { log.Printf("STUN ReadFrom: %v", err) time.Sleep(time.Second) stunReadErrors.Add(1) continue } ua, ok := addr.(*net.UDPAddr) if !ok { log.Printf("STUN unexpected address %T %v", addr, addr) stunReadErrors.Add(1) continue } pkt := buf[:n] if !stun.Is(pkt) { stunReadNotSTUN.Add(1) continue } txid, err := stun.ParseBindingRequest(pkt) if err != nil { stunReadNotSTUNValid.Add(1) continue } if ua.IP.To4() != nil { stunReadIPv4.Add(1) } else { stunReadIPv6.Add(1) } res := stun.Response(txid, ua.IP, uint16(ua.Port)) _, err = pc.WriteTo(res, addr) if err != nil { stunWriteErrors.Add(1) } else { stunWrite.Add(1) } } } var validProdHostname = regexp.MustCompile(`^derp(\d+|\-\w+)?\.tailscale\.com\.?$`) func prodAutocertHostPolicy(_ context.Context, host string) error { if validProdHostname.MatchString(host) { return nil } return errors.New("invalid hostname") }