[WIP] Split broker into components

Exploring #26092

broker/http-frontend/http.go

@@ -0,0 +1,344 @@
+package main
+
+import (
+	"crypto/tls"
+	"errors"
+	"flag"
+	"io"
+	"io/ioutil"
+	"log"
+	"net/http"
+	"net/rpc"
+	"os"
+	"strings"
+
+	// "github.com/prometheus/client_golang/prometheus"
+	// "github.com/prometheus/client_golang/prometheus/promhttp"
+	"git.torproject.org/pluggable-transports/snowflake.git/common/messages"
+	"git.torproject.org/pluggable-transports/snowflake.git/common/safelog"
+	"golang.org/x/crypto/acme/autocert"
+)
+
+const (
+	readLimit = 100000 // Maximum number of bytes to be read from an HTTP request
+)
+
+// Implements the http.Handler interface
+type SnowflakeHandler struct {
+	c      *rpc.Client
+	handle func(*rpc.Client, http.ResponseWriter, *http.Request)
+}
+
+func (sh SnowflakeHandler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
+	w.Header().Set("Access-Control-Allow-Origin", "*")
+	w.Header().Set("Access-Control-Allow-Headers", "Origin, X-Session-ID")
+	// Return early if it's CORS preflight.
+	if "OPTIONS" == r.Method {
+		return
+	}
+	sh.handle(sh.c, w, r)
+}
+
+// Implements the http.Handler interface
+type MetricsHandler struct {
+	logFilename string
+	handle      func(string, http.ResponseWriter, *http.Request)
+}
+
+func (mh MetricsHandler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
+	w.Header().Set("Access-Control-Allow-Origin", "*")
+	w.Header().Set("Access-Control-Allow-Headers", "Origin, X-Session-ID")
+	// Return early if it's CORS preflight.
+	if "OPTIONS" == r.Method {
+		return
+	}
+	mh.handle(mh.logFilename, w, r)
+}
+
+func robotsTxtHandler(w http.ResponseWriter, r *http.Request) {
+	w.Header().Set("Content-Type", "text/plain; charset=utf-8")
+	if _, err := w.Write([]byte("User-agent: *\nDisallow: /\n")); err != nil {
+		log.Printf("robotsTxtHandler unable to write, with this error: %v", err)
+	}
+}
+
+func metricsHandler(metricsFilename string, w http.ResponseWriter, r *http.Request) {
+	w.Header().Set("Content-Type", "text/plain; charset=utf-8")
+
+	if metricsFilename == "" {
+		http.NotFound(w, r)
+		return
+	}
+	metricsFile, err := os.OpenFile(metricsFilename, os.O_RDONLY, 0644)
+	if err != nil {
+		log.Println("Error opening metrics file for reading")
+		http.NotFound(w, r)
+		return
+	}
+
+	if _, err := io.Copy(w, metricsFile); err != nil {
+		log.Printf("copying metricsFile returned error: %v", err)
+	}
+}
+
+func debugHandler(c *rpc.Client, w http.ResponseWriter, r *http.Request) {
+	var response string
+
+	err := c.Call("IPC.Debug", new(interface{}), &response)
+	if err != nil {
+		log.Println(err)
+		w.WriteHeader(http.StatusInternalServerError)
+		return
+	}
+
+	if _, err := w.Write([]byte(response)); err != nil {
+		log.Printf("writing proxy information returned error: %v ", err)
+	}
+}
+
+/*
+For snowflake proxies to request a client from the Broker.
+*/
+func proxyPolls(c *rpc.Client, w http.ResponseWriter, r *http.Request) {
+	body, err := ioutil.ReadAll(http.MaxBytesReader(w, r.Body, readLimit))
+	if err != nil {
+		log.Println("Invalid data.")
+		w.WriteHeader(http.StatusBadRequest)
+		return
+	}
+
+	arg := messages.Arg{
+		Body:       body,
+		RemoteAddr: r.RemoteAddr,
+	}
+
+	var response []byte
+	err = c.Call("IPC.ProxyPolls", arg, &response)
+	switch {
+	case err == nil:
+	case errors.Is(err, messages.ErrBadRequest):
+		w.WriteHeader(http.StatusBadRequest)
+		return
+	case errors.Is(err, messages.ErrInternal):
+		fallthrough
+	default:
+		log.Println(err)
+		w.WriteHeader(http.StatusInternalServerError)
+		return
+	}
+
+	if _, err := w.Write(response); err != nil {
+		log.Printf("proxyPolls unable to write offer with error: %v", err)
+	}
+}
+
+/*
+Expects a WebRTC SDP offer in the Request to give to an assigned
+snowflake proxy, which responds with the SDP answer to be sent in
+the HTTP response back to the client.
+*/
+func clientOffers(c *rpc.Client, w http.ResponseWriter, r *http.Request) {
+	body, err := ioutil.ReadAll(http.MaxBytesReader(w, r.Body, readLimit))
+	if err != nil {
+		log.Printf("Error reading client request: %s", err.Error())
+		w.WriteHeader(http.StatusBadRequest)
+		return
+	}
+
+	// Handle the legacy version
+	isLegacy := false
+	if len(body) > 0 && body[0] == '{' {
+		isLegacy = true
+		req := messages.ClientPollRequest{
+			Offer: string(body),
+			NAT:   r.Header.Get("Snowflake-NAT-Type"),
+		}
+		body, err = req.EncodePollRequest()
+		if err != nil {
+			log.Printf("Error shimming the legacy request: %s", err.Error())
+			w.WriteHeader(http.StatusInternalServerError)
+			return
+		}
+	}
+
+	arg := messages.Arg{
+		Body:       body,
+		RemoteAddr: "",
+	}
+
+	var response []byte
+	err = c.Call("IPC.ClientOffers", arg, &response)
+	if err != nil {
+		// Assert err == messages.ErrInternal
+		log.Println(err)
+		w.WriteHeader(http.StatusInternalServerError)
+		return
+	}
+
+	if isLegacy {
+		resp, err := messages.DecodeClientPollResponse(response)
+		if err != nil {
+			log.Println(err)
+			w.WriteHeader(http.StatusInternalServerError)
+			return
+		}
+		switch resp.Error {
+		case "":
+			response = []byte(resp.Answer)
+		case "no snowflake proxies currently available":
+			w.WriteHeader(http.StatusServiceUnavailable)
+			return
+		case "timed out waiting for answer!":
+			w.WriteHeader(http.StatusGatewayTimeout)
+			return
+		default:
+			panic("unknown error")
+		}
+	}
+
+	if _, err := w.Write(response); err != nil {
+		log.Printf("clientOffers unable to write answer with error: %v", err)
+	}
+}
+
+/*
+Expects snowflake proxies which have previously successfully received
+an offer from proxyHandler to respond with an answer in an HTTP POST,
+which the broker will pass back to the original client.
+*/
+func proxyAnswers(c *rpc.Client, w http.ResponseWriter, r *http.Request) {
+	body, err := ioutil.ReadAll(http.MaxBytesReader(w, r.Body, readLimit))
+	if err != nil {
+		log.Println("Invalid data.")
+		w.WriteHeader(http.StatusBadRequest)
+		return
+	}
+
+	arg := messages.Arg{
+		Body:       body,
+		RemoteAddr: "",
+	}
+
+	var response []byte
+	err = c.Call("IPC.ProxyAnswers", arg, &response)
+	switch {
+	case err == nil:
+	case errors.Is(err, messages.ErrBadRequest):
+		w.WriteHeader(http.StatusBadRequest)
+		return
+	case errors.Is(err, messages.ErrInternal):
+		fallthrough
+	default:
+		log.Println(err)
+		w.WriteHeader(http.StatusInternalServerError)
+		return
+	}
+
+	if _, err := w.Write(response); err != nil {
+		log.Printf("proxyAnswers unable to write answer response with error: %v", err)
+	}
+}
+
+func main() {
+	var acmeEmail string
+	var acmeHostnamesCommas string
+	var acmeCertCacheDir string
+	var addr string
+	var disableTLS bool
+	var certFilename, keyFilename string
+
+	var metricsFilename string
+	var unsafeLogging bool
+
+	var socket string
+
+	flag.StringVar(&acmeEmail, "acme-email", "", "optional contact email for Let's Encrypt notifications")
+	flag.StringVar(&acmeHostnamesCommas, "acme-hostnames", "", "comma-separated hostnames for TLS certificate")
+	flag.StringVar(&certFilename, "cert", "", "TLS certificate file")
+	flag.StringVar(&keyFilename, "key", "", "TLS private key file")
+	flag.StringVar(&acmeCertCacheDir, "acme-cert-cache", "acme-cert-cache", "directory in which certificates should be cached")
+	flag.StringVar(&addr, "addr", ":443", "address to listen on")
+	flag.BoolVar(&disableTLS, "disable-tls", false, "don't use HTTPS")
+
+	flag.StringVar(&metricsFilename, "metrics-log", "", "path to metrics logging output")
+	flag.BoolVar(&unsafeLogging, "unsafe-logging", false, "prevent logs from being scrubbed")
+
+	flag.StringVar(&socket, "socket", "/tmp/broker.sock", "path to ipc socket")
+
+	flag.Parse()
+
+	var logOutput io.Writer = os.Stderr
+	if unsafeLogging {
+		log.SetOutput(logOutput)
+	} else {
+		// We want to send the log output through our scrubber first
+		log.SetOutput(&safelog.LogScrubber{Output: logOutput})
+	}
+	log.SetFlags(log.LstdFlags | log.LUTC)
+
+	var c, err = rpc.Dial("unix", socket)
+	if err != nil {
+		log.Fatal(err)
+	}
+	defer c.Close()
+
+	http.HandleFunc("/robots.txt", robotsTxtHandler)
+
+	http.Handle("/proxy", SnowflakeHandler{c, proxyPolls})
+	http.Handle("/client", SnowflakeHandler{c, clientOffers})
+	http.Handle("/answer", SnowflakeHandler{c, proxyAnswers})
+	http.Handle("/debug", SnowflakeHandler{c, debugHandler})
+
+	http.Handle("/metrics", MetricsHandler{metricsFilename, metricsHandler})
+	// http.Handle("/prometheus", promhttp.HandlerFor(ctx.metrics.promMetrics.registry, promhttp.HandlerOpts{}))
+
+	server := http.Server{
+		Addr: addr,
+	}
+
+	// Handle the various ways of setting up TLS. The legal configurations
+	// are:
+	//   --acme-hostnames (with optional --acme-email and/or --acme-cert-cache)
+	//   --cert and --key together
+	//   --disable-tls
+	// The outputs of this block of code are the disableTLS,
+	// needHTTP01Listener, certManager, and getCertificate variables.
+	if acmeHostnamesCommas != "" {
+		acmeHostnames := strings.Split(acmeHostnamesCommas, ",")
+		log.Printf("ACME hostnames: %q", acmeHostnames)
+
+		var cache autocert.Cache
+		if err = os.MkdirAll(acmeCertCacheDir, 0700); err != nil {
+			log.Printf("Warning: Couldn't create cache directory %q (reason: %s) so we're *not* using our certificate cache.", acmeCertCacheDir, err)
+		} else {
+			cache = autocert.DirCache(acmeCertCacheDir)
+		}
+
+		certManager := autocert.Manager{
+			Cache:      cache,
+			Prompt:     autocert.AcceptTOS,
+			HostPolicy: autocert.HostWhitelist(acmeHostnames...),
+			Email:      acmeEmail,
+		}
+		go func() {
+			log.Printf("Starting HTTP-01 listener")
+			log.Fatal(http.ListenAndServe(":80", certManager.HTTPHandler(nil)))
+		}()
+
+		server.TLSConfig = &tls.Config{GetCertificate: certManager.GetCertificate}
+		err = server.ListenAndServeTLS("", "")
+	} else if certFilename != "" && keyFilename != "" {
+		if acmeEmail != "" || acmeHostnamesCommas != "" {
+			log.Fatalf("The --cert and --key options are not allowed with --acme-email or --acme-hostnames.")
+		}
+		err = server.ListenAndServeTLS(certFilename, keyFilename)
+	} else if disableTLS {
+		err = server.ListenAndServe()
+	} else {
+		log.Fatal("the --acme-hostnames, --cert and --key, or --disable-tls option is required")
+	}
+
+	if err != nil {
+		log.Fatal(err)
+	}
+}