mirror of
https://github.com/tailscale/tailscale.git
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34176432d6
So we can use it in trunkd to quiet down the logs there. Updates #5563 Signed-off-by: Andrew Dunham <andrew@du.nham.ca> Change-Id: Ie3177dc33f5ad103db832aab5a3e0e4f128f973f
455 lines
15 KiB
Go
455 lines
15 KiB
Go
// Copyright (c) Tailscale Inc & AUTHORS
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// SPDX-License-Identifier: BSD-3-Clause
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// The derper binary is a simple DERP server.
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package main // import "tailscale.com/cmd/derper"
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import (
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"cmp"
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"context"
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"crypto/tls"
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"encoding/json"
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"errors"
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"expvar"
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"flag"
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"fmt"
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"io"
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"log"
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"math"
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"net"
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"net/http"
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"os"
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"os/signal"
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"path/filepath"
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"regexp"
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"strings"
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"syscall"
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"time"
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"golang.org/x/time/rate"
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"tailscale.com/atomicfile"
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"tailscale.com/derp"
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"tailscale.com/derp/derphttp"
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"tailscale.com/metrics"
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"tailscale.com/net/ktimeout"
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"tailscale.com/net/stunserver"
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"tailscale.com/tsweb"
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"tailscale.com/types/key"
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"tailscale.com/types/logger"
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)
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var (
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dev = flag.Bool("dev", false, "run in localhost development mode (overrides -a)")
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addr = flag.String("a", ":443", "server HTTP/HTTPS listen address, in form \":port\", \"ip:port\", or for IPv6 \"[ip]:port\". If the IP is omitted, it defaults to all interfaces. Serves HTTPS if the port is 443 and/or -certmode is manual, otherwise HTTP.")
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httpPort = flag.Int("http-port", 80, "The port on which to serve HTTP. Set to -1 to disable. The listener is bound to the same IP (if any) as specified in the -a flag.")
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stunPort = flag.Int("stun-port", 3478, "The UDP port on which to serve STUN. The listener is bound to the same IP (if any) as specified in the -a flag.")
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configPath = flag.String("c", "", "config file path")
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certMode = flag.String("certmode", "letsencrypt", "mode for getting a cert. possible options: manual, letsencrypt")
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certDir = flag.String("certdir", tsweb.DefaultCertDir("derper-certs"), "directory to store LetsEncrypt certs, if addr's port is :443")
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hostname = flag.String("hostname", "derp.tailscale.com", "LetsEncrypt host name, if addr's port is :443")
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runSTUN = flag.Bool("stun", true, "whether to run a STUN server. It will bind to the same IP (if any) as the --addr flag value.")
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runDERP = flag.Bool("derp", true, "whether to run a DERP server. The only reason to set this false is if you're decommissioning a server but want to keep its bootstrap DNS functionality still running.")
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meshPSKFile = flag.String("mesh-psk-file", defaultMeshPSKFile(), "if non-empty, path to file containing the mesh pre-shared key file. It should contain some hex string; whitespace is trimmed.")
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meshWith = flag.String("mesh-with", "", "optional comma-separated list of hostnames to mesh with; the server's own hostname can be in the list")
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bootstrapDNS = flag.String("bootstrap-dns-names", "", "optional comma-separated list of hostnames to make available at /bootstrap-dns")
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unpublishedDNS = flag.String("unpublished-bootstrap-dns-names", "", "optional comma-separated list of hostnames to make available at /bootstrap-dns and not publish in the list")
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verifyClients = flag.Bool("verify-clients", false, "verify clients to this DERP server through a local tailscaled instance.")
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verifyClientURL = flag.String("verify-client-url", "", "if non-empty, an admission controller URL for permitting client connections; see tailcfg.DERPAdmitClientRequest")
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verifyFailOpen = flag.Bool("verify-client-url-fail-open", true, "whether we fail open if --verify-client-url is unreachable")
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acceptConnLimit = flag.Float64("accept-connection-limit", math.Inf(+1), "rate limit for accepting new connection")
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acceptConnBurst = flag.Int("accept-connection-burst", math.MaxInt, "burst limit for accepting new connection")
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// tcpKeepAlive is intentionally long, to reduce battery cost. There is an L7 keepalive on a higher frequency schedule.
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tcpKeepAlive = flag.Duration("tcp-keepalive-time", 10*time.Minute, "TCP keepalive time")
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// tcpUserTimeout is intentionally short, so that hung connections are cleaned up promptly. DERPs should be nearby users.
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tcpUserTimeout = flag.Duration("tcp-user-timeout", 15*time.Second, "TCP user timeout")
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)
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var (
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tlsRequestVersion = &metrics.LabelMap{Label: "version"}
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tlsActiveVersion = &metrics.LabelMap{Label: "version"}
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)
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func init() {
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expvar.Publish("derper_tls_request_version", tlsRequestVersion)
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expvar.Publish("gauge_derper_tls_active_version", tlsActiveVersion)
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}
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type config struct {
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PrivateKey key.NodePrivate
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}
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func loadConfig() config {
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if *dev {
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return config{PrivateKey: key.NewNode()}
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}
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if *configPath == "" {
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if os.Getuid() == 0 {
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*configPath = "/var/lib/derper/derper.key"
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} else {
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log.Fatalf("derper: -c <config path> not specified")
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}
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log.Printf("no config path specified; using %s", *configPath)
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}
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b, err := os.ReadFile(*configPath)
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switch {
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case errors.Is(err, os.ErrNotExist):
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return writeNewConfig()
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case err != nil:
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log.Fatal(err)
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panic("unreachable")
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default:
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var cfg config
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if err := json.Unmarshal(b, &cfg); err != nil {
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log.Fatalf("derper: config: %v", err)
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}
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return cfg
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}
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}
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func writeNewConfig() config {
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k := key.NewNode()
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if err := os.MkdirAll(filepath.Dir(*configPath), 0777); err != nil {
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log.Fatal(err)
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}
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cfg := config{
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PrivateKey: k,
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}
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b, err := json.MarshalIndent(cfg, "", "\t")
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if err != nil {
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log.Fatal(err)
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}
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if err := atomicfile.WriteFile(*configPath, b, 0600); err != nil {
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log.Fatal(err)
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}
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return cfg
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}
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func main() {
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flag.Parse()
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ctx, cancel := signal.NotifyContext(context.Background(), syscall.SIGINT, syscall.SIGTERM)
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defer cancel()
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if *dev {
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*addr = ":3340" // above the keys DERP
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log.Printf("Running in dev mode.")
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tsweb.DevMode = true
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}
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listenHost, _, err := net.SplitHostPort(*addr)
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if err != nil {
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log.Fatalf("invalid server address: %v", err)
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}
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if *runSTUN {
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ss := stunserver.New(ctx)
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go ss.ListenAndServe(net.JoinHostPort(listenHost, fmt.Sprint(*stunPort)))
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}
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cfg := loadConfig()
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serveTLS := tsweb.IsProd443(*addr) || *certMode == "manual"
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s := derp.NewServer(cfg.PrivateKey, log.Printf)
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s.SetVerifyClient(*verifyClients)
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s.SetVerifyClientURL(*verifyClientURL)
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s.SetVerifyClientURLFailOpen(*verifyFailOpen)
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if *meshPSKFile != "" {
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b, err := os.ReadFile(*meshPSKFile)
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if err != nil {
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log.Fatal(err)
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}
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key := strings.TrimSpace(string(b))
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if matched, _ := regexp.MatchString(`(?i)^[0-9a-f]{64,}$`, key); !matched {
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log.Fatalf("key in %s must contain 64+ hex digits", *meshPSKFile)
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}
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s.SetMeshKey(key)
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log.Printf("DERP mesh key configured")
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}
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if err := startMesh(s); err != nil {
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log.Fatalf("startMesh: %v", err)
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}
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expvar.Publish("derp", s.ExpVar())
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mux := http.NewServeMux()
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if *runDERP {
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derpHandler := derphttp.Handler(s)
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derpHandler = addWebSocketSupport(s, derpHandler)
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mux.Handle("/derp", derpHandler)
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} else {
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mux.Handle("/derp", http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
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http.Error(w, "derp server disabled", http.StatusNotFound)
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}))
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}
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mux.HandleFunc("/derp/probe", probeHandler)
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go refreshBootstrapDNSLoop()
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mux.HandleFunc("/bootstrap-dns", tsweb.BrowserHeaderHandlerFunc(handleBootstrapDNS))
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mux.Handle("/", http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
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tsweb.AddBrowserHeaders(w)
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w.Header().Set("Content-Type", "text/html; charset=utf-8")
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w.WriteHeader(200)
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io.WriteString(w, `<html><body>
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<h1>DERP</h1>
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<p>
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This is a
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<a href="https://tailscale.com/">Tailscale</a>
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<a href="https://pkg.go.dev/tailscale.com/derp">DERP</a>
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server.
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</p>
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`)
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if !*runDERP {
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io.WriteString(w, `<p>Status: <b>disabled</b></p>`)
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}
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if tsweb.AllowDebugAccess(r) {
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io.WriteString(w, "<p>Debug info at <a href='/debug/'>/debug/</a>.</p>\n")
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}
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}))
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mux.Handle("/robots.txt", http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
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tsweb.AddBrowserHeaders(w)
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io.WriteString(w, "User-agent: *\nDisallow: /\n")
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}))
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mux.Handle("/generate_204", http.HandlerFunc(serveNoContent))
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debug := tsweb.Debugger(mux)
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debug.KV("TLS hostname", *hostname)
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debug.KV("Mesh key", s.HasMeshKey())
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debug.Handle("check", "Consistency check", http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
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err := s.ConsistencyCheck()
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if err != nil {
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http.Error(w, err.Error(), 500)
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} else {
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io.WriteString(w, "derp.Server ConsistencyCheck okay")
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}
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}))
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debug.Handle("traffic", "Traffic check", http.HandlerFunc(s.ServeDebugTraffic))
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// Longer lived DERP connections send an application layer keepalive. Note
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// if the keepalive is hit, the user timeout will take precedence over the
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// keepalive counter, so the probe if unanswered will take effect promptly,
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// this is less tolerant of high loss, but high loss is unexpected.
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lc := net.ListenConfig{
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Control: ktimeout.UserTimeout(*tcpUserTimeout),
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KeepAlive: *tcpKeepAlive,
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}
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quietLogger := log.New(logger.HTTPServerLogFilter{Inner: log.Printf}, "", 0)
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httpsrv := &http.Server{
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Addr: *addr,
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Handler: mux,
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ErrorLog: quietLogger,
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// Set read/write timeout. For derper, this basically
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// only affects TLS setup, as read/write deadlines are
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// cleared on Hijack, which the DERP server does. But
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// without this, we slowly accumulate stuck TLS
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// handshake goroutines forever. This also affects
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// /debug/ traffic, but 30 seconds is plenty for
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// Prometheus/etc scraping.
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ReadTimeout: 30 * time.Second,
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WriteTimeout: 30 * time.Second,
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}
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go func() {
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<-ctx.Done()
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httpsrv.Shutdown(ctx)
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}()
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if serveTLS {
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log.Printf("derper: serving on %s with TLS", *addr)
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var certManager certProvider
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certManager, err = certProviderByCertMode(*certMode, *certDir, *hostname)
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if err != nil {
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log.Fatalf("derper: can not start cert provider: %v", err)
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}
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httpsrv.TLSConfig = certManager.TLSConfig()
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getCert := httpsrv.TLSConfig.GetCertificate
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httpsrv.TLSConfig.GetCertificate = func(hi *tls.ClientHelloInfo) (*tls.Certificate, error) {
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cert, err := getCert(hi)
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if err != nil {
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return nil, err
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}
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cert.Certificate = append(cert.Certificate, s.MetaCert())
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return cert, nil
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}
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// Disable TLS 1.0 and 1.1, which are obsolete and have security issues.
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httpsrv.TLSConfig.MinVersion = tls.VersionTLS12
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httpsrv.Handler = http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
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if r.TLS != nil {
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label := "unknown"
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switch r.TLS.Version {
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case tls.VersionTLS10:
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label = "1.0"
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case tls.VersionTLS11:
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label = "1.1"
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case tls.VersionTLS12:
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label = "1.2"
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case tls.VersionTLS13:
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label = "1.3"
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}
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tlsRequestVersion.Add(label, 1)
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tlsActiveVersion.Add(label, 1)
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defer tlsActiveVersion.Add(label, -1)
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}
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mux.ServeHTTP(w, r)
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})
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if *httpPort > -1 {
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go func() {
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port80mux := http.NewServeMux()
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port80mux.HandleFunc("/generate_204", serveNoContent)
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port80mux.Handle("/", certManager.HTTPHandler(tsweb.Port80Handler{Main: mux}))
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port80srv := &http.Server{
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Addr: net.JoinHostPort(listenHost, fmt.Sprintf("%d", *httpPort)),
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Handler: port80mux,
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ErrorLog: quietLogger,
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ReadTimeout: 30 * time.Second,
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// Crank up WriteTimeout a bit more than usually
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// necessary just so we can do long CPU profiles
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// and not hit net/http/pprof's "profile
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// duration exceeds server's WriteTimeout".
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WriteTimeout: 5 * time.Minute,
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}
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ln, err := lc.Listen(context.Background(), "tcp", port80srv.Addr)
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if err != nil {
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log.Fatal(err)
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}
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defer ln.Close()
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err = port80srv.Serve(ln)
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if err != nil {
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if err != http.ErrServerClosed {
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log.Fatal(err)
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}
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}
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}()
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}
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err = rateLimitedListenAndServeTLS(httpsrv, &lc)
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} else {
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log.Printf("derper: serving on %s", *addr)
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var ln net.Listener
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ln, err = lc.Listen(context.Background(), "tcp", httpsrv.Addr)
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if err != nil {
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log.Fatal(err)
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}
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err = httpsrv.Serve(ln)
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}
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if err != nil && err != http.ErrServerClosed {
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log.Fatalf("derper: %v", err)
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}
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}
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const (
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noContentChallengeHeader = "X-Tailscale-Challenge"
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noContentResponseHeader = "X-Tailscale-Response"
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)
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// For captive portal detection
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func serveNoContent(w http.ResponseWriter, r *http.Request) {
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if challenge := r.Header.Get(noContentChallengeHeader); challenge != "" {
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badChar := strings.IndexFunc(challenge, func(r rune) bool {
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return !isChallengeChar(r)
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}) != -1
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if len(challenge) <= 64 && !badChar {
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w.Header().Set(noContentResponseHeader, "response "+challenge)
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}
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}
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w.WriteHeader(http.StatusNoContent)
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}
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func isChallengeChar(c rune) bool {
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// Semi-randomly chosen as a limited set of valid characters
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return ('a' <= c && c <= 'z') || ('A' <= c && c <= 'Z') ||
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('0' <= c && c <= '9') ||
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c == '.' || c == '-' || c == '_'
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}
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// probeHandler is the endpoint that js/wasm clients hit to measure
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// DERP latency, since they can't do UDP STUN queries.
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func probeHandler(w http.ResponseWriter, r *http.Request) {
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switch r.Method {
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case "HEAD", "GET":
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w.Header().Set("Access-Control-Allow-Origin", "*")
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default:
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http.Error(w, "bogus probe method", http.StatusMethodNotAllowed)
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}
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}
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var validProdHostname = regexp.MustCompile(`^derp([^.]*)\.tailscale\.com\.?$`)
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func prodAutocertHostPolicy(_ context.Context, host string) error {
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if validProdHostname.MatchString(host) {
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return nil
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}
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return errors.New("invalid hostname")
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}
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func defaultMeshPSKFile() string {
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try := []string{
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"/home/derp/keys/derp-mesh.key",
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filepath.Join(os.Getenv("HOME"), "keys", "derp-mesh.key"),
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}
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for _, p := range try {
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if _, err := os.Stat(p); err == nil {
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return p
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}
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}
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return ""
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}
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func rateLimitedListenAndServeTLS(srv *http.Server, lc *net.ListenConfig) error {
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ln, err := lc.Listen(context.Background(), "tcp", cmp.Or(srv.Addr, ":https"))
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if err != nil {
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return err
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}
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rln := newRateLimitedListener(ln, rate.Limit(*acceptConnLimit), *acceptConnBurst)
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expvar.Publish("tls_listener", rln.ExpVar())
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defer rln.Close()
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return srv.ServeTLS(rln, "", "")
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}
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type rateLimitedListener struct {
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// These are at the start of the struct to ensure 64-bit alignment
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// on 32-bit architecture regardless of what other fields may exist
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// in this package.
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numAccepts expvar.Int // does not include number of rejects
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numRejects expvar.Int
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net.Listener
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lim *rate.Limiter
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}
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func newRateLimitedListener(ln net.Listener, limit rate.Limit, burst int) *rateLimitedListener {
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return &rateLimitedListener{Listener: ln, lim: rate.NewLimiter(limit, burst)}
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}
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func (l *rateLimitedListener) ExpVar() expvar.Var {
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m := new(metrics.Set)
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m.Set("counter_accepted_connections", &l.numAccepts)
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m.Set("counter_rejected_connections", &l.numRejects)
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return m
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}
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var errLimitedConn = errors.New("cannot accept connection; rate limited")
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func (l *rateLimitedListener) Accept() (net.Conn, error) {
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// Even under a rate limited situation, we accept the connection immediately
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// and close it, rather than being slow at accepting new connections.
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// This provides two benefits: 1) it signals to the client that something
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// is going on on the server, and 2) it prevents new connections from
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// piling up and occupying resources in the OS kernel.
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// The client will retry as needing (with backoffs in place).
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cn, err := l.Listener.Accept()
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if err != nil {
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return nil, err
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}
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if !l.lim.Allow() {
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l.numRejects.Add(1)
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cn.Close()
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return nil, errLimitedConn
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}
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l.numAccepts.Add(1)
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return cn, nil
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}
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