Initial import of source code.

262dbdc6 · Philipp Winter · 37254249 · 262dbdc6 · 262dbdc6 · 262dbdc6
Unverified Commit 262dbdc6 authored 5 years ago by Philipp Winter
--- a/handlers.go
+++ b/handlers.go
+package main
+
+import (
+	"fmt"
+	"golang.org/x/time/rate"
+	"net"
+	"net/http"
+	"time"
+)
+
+// limiter implements a rate limiter.  We allow 1 request per second on average
+// with bursts of up to 5 requests per second.
+var limiter = rate.NewLimiter(1, 5)
+
+// Index returns the landing page (which contains the scanning form) to the
+// user.
+func Index(w http.ResponseWriter, r *http.Request) {
+
+	fmt.Fprintln(w, IndexPage)
+}
+
+// SendResponse sends the given response to the user.
+func SendResponse(w http.ResponseWriter, response string) {
+
+	w.Header().Set("Content-Type", "text/html; charset=utf-8")
+	w.WriteHeader(http.StatusOK)
+	fmt.Fprintln(w, response)
+}
+
+// ScanDestination extracts the given IP address and port from the POST
+// parameters, triggers TCP scanning of the tuple, and returns the result.
+func ScanDestination(w http.ResponseWriter, r *http.Request) {
+
+	// We implement rate limiting to prevent someone from abusing this service
+	// as a port scanner.
+	if limiter.Allow() == false {
+		SendResponse(w, "Rate limit exceeded.  Wait for a bit.")
+		return
+	}
+
+	// The number of seconds we're willing to wait until we decide that the
+	// given destination is offline.
+	timeout, _ := time.ParseDuration("3s")
+
+	r.ParseForm()
+	// These variables will be "" if they're not set.
+	address := r.Form.Get("address")
+	port := r.Form.Get("port")
+
+	if address == "" {
+		SendResponse(w, "No address given.")
+		return
+	}
+	if port == "" {
+		SendResponse(w, "No port given.")
+		return
+	}
+
+	portReachable, err := IsTCPPortReachable(address, port, timeout)
+	if portReachable {
+		SendResponse(w, SuccessPage)
+	} else {
+		SendResponse(w, FailurePage(err))
+	}
+}
+
+// IsTCPPortReachable returns `true' if it can establish a TCP connection with
+// the given IP address and port.  If not, it returns `false' and the
+// respective error, as reported by `net.DialTimeout'.
+func IsTCPPortReachable(addr, port string, timeout time.Duration) (bool, error) {
+
+	conn, err := net.DialTimeout("tcp", fmt.Sprintf("%s:%s", addr, port), timeout)
+	if err != nil {
+		return false, err
+	}
+	conn.Close()
+	return true, nil
+}
--- a/html.go
+++ b/html.go
+package main
+
+import (
+	"fmt"
+)
+
+// IndexPage contains the landing page of the service.  It implements a simple
+// form that asks for an IP address and TCP port.
+var IndexPage = `<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01//EN"
+    "http://www.w3.org/TR/html4/strict.dtd">
+<html lang="en">
+
+<head>
+  <meta http-equiv="content-type" content="text/html; charset=utf-8">
+  <title>Test your obfs4 bridge's TCP port</title>
+</head>
+
+<body>
+  <form method="POST" action="scan">
+    <h2>Tor bridge reachability test</h2>
+    <p>This service allows you to test if your obfs4 bridge is reachable to the
+    rest of the world.</p>
+    <p>Enter your bridge's IP address and obfs4 port, and click 'Scan'.  The service
+    will then try to establish a TCP connection with your bridge and tell you
+    if it succeeded.</p>
+    <input type="text" required name="address" placeholder="IP address">
+    <input type="text" required name="port" placeholder="Obfs4 port">
+    <label ></label>
+    <button type="submit">Scan</button>
+  </form>
+</body>
+
+</html>
+`
+
+// SuccessPage is shown when the given address and port are reachable.
+var SuccessPage = `<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01//EN"
+    "http://www.w3.org/TR/html4/strict.dtd">
+<html lang="en">
+
+<head>
+  <meta http-equiv="content-type" content="text/html; charset=utf-8">
+  <title>Success!</title>
+</head>
+
+<body>
+  <div align='center'>
+    <h2 style='color:green'>TCP port is reachable!</h2>
+  </div>
+</body>
+
+</html>
+`
+
+// FailurePage2 is shown when the given address and port are unreachable.
+func FailurePage(reason error) string {
+
+	var failurePage1 = `<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01//EN"
+    "http://www.w3.org/TR/html4/strict.dtd">
+<html lang="en">
+
+<head>
+  <meta http-equiv="content-type" content="text/html; charset=utf-8">
+  <title>Failure!</title>
+</head>
+
+<body>
+  <div align='center'>
+    <h2 style='color:red'>TCP port is <i>not</i> reachable!</h2>
+    <tt>
+`
+
+	var failurePage2 = `</tt>
+  </div>
+</body>
+
+</html>
+`
+
+	return fmt.Sprintf("%s%s%s", failurePage1, reason, failurePage2)
+}
--- a/main.go
+++ b/main.go
+package main
+
+import (
+	"fmt"
+	"log"
+	"net/http"
+	"os"
+	"time"
+
+	"github.com/gorilla/mux"
+)
+
+type Route struct {
+	Name        string
+	Method      string
+	Pattern     string
+	HandlerFunc http.HandlerFunc
+}
+
+type Routes []Route
+
+var routes = Routes{
+	Route{
+		"Index",
+		"GET",
+		"/",
+		Index,
+	},
+	Route{
+		"ScanDestination",
+		"POST",
+		"/scan",
+		ScanDestination,
+	},
+}
+
+// NewRouter creates and returns a new request router.
+func NewRouter() *mux.Router {
+
+	router := mux.NewRouter().StrictSlash(true)
+	for _, route := range routes {
+		var handler http.Handler
+
+		handler = route.HandlerFunc
+		handler = Logger(handler, route.Name)
+
+		router.
+			Methods(route.Method).
+			Path(route.Pattern).
+			Name(route.Name).
+			Handler(handler)
+	}
+
+	return router
+}
+
+// Logger logs when we receive requests, and the execution time of handling
+// these requests.  We don't log client IP addresses or the given obfs4
+// parameters.
+func Logger(inner http.Handler, name string) http.Handler {
+	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		start := time.Now()
+
+		inner.ServeHTTP(w, r)
+
+		log.Printf(
+			"%s\t%s\t%s\t%s",
+			r.Method,
+			r.RequestURI,
+			name,
+			time.Since(start),
+		)
+	})
+}
+
+// main is the entry point of this tool.
+func main() {
+
+	if len(os.Args) != 3 {
+		fmt.Printf("Usage: %s CERT_FILE KEY_FILE\n", os.Args[0])
+		os.Exit(1)
+	}
+	certFile := os.Args[1]
+	keyFile := os.Args[2]
+
+	router := NewRouter()
+	log.Fatal(http.ListenAndServeTLS(":8080", certFile, keyFile, router))
+}