[feat] authentication token for webapi

pkg/backend/webapi.go

@@ -4,8 +4,35 @@ import (
 	"fmt"
 	"log"
 	"net/http"
+	"os"
+
+	"0xacab.org/leap/bitmask-vpn/pkg/bitmask"
 )
 
+func Adapt(h http.Handler, adapters ...Adapter) http.Handler {
+	for _, adapter := range adapters {
+		h = adapter(h)
+	}
+	return h
+}
+
+type Adapter func(http.Handler) http.Handler
+
+func CheckAuth(token string) Adapter {
+	return func(h http.Handler) http.Handler {
+		return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+			t := r.Header.Get("X-Auth-Token")
+			if t == token {
+				h.ServeHTTP(w, r)
+			} else {
+				w.WriteHeader(http.StatusUnauthorized)
+				w.Write([]byte("401 - Unauthorized"))
+			}
+
+		})
+	}
+}
+
 func webOn(w http.ResponseWriter, r *http.Request) {
 	log.Println("Web UI: on")
 	SwitchOn()
@@ -24,12 +51,15 @@ func webStatus(w http.ResponseWriter, r *http.Request) {
 func webQuit(w http.ResponseWriter, r *http.Request) {
 	log.Println("Web UI: quit")
 	Quit()
+	os.Exit(0)
 }
 
 func enableWebAPI() {
-	http.HandleFunc("/vpn/start", webOn)
-	http.HandleFunc("/vpn/stop", webOff)
-	http.HandleFunc("/vpn/status", webStatus)
-	http.HandleFunc("/vpn/quit", webQuit)
+	bitmask.GenerateAuthToken()
+	auth := CheckAuth(bitmask.ReadAuthToken())
+	http.Handle("/vpn/start", Adapt(http.HandlerFunc(webOn), auth))
+	http.Handle("/vpn/stop", Adapt(http.HandlerFunc(webOff), auth))
+	http.Handle("/vpn/status", Adapt(http.HandlerFunc(webStatus), auth))
+	http.Handle("/vpn/quit", Adapt(http.HandlerFunc(webQuit), auth))
 	http.ListenAndServe(":8080", nil)
 }

pkg/bitmask/auth.go

+package bitmask
+
+import (
+	"io/ioutil"
+	"log"
+	"math/rand"
+	"os"
+	"runtime"
+	"strings"
+	"time"
+)
+
+/* functions for local authentication of control endpoints */
+
+const tokenPath = "/dev/shm/bitmask-token"
+
+func GenerateAuthToken() {
+	if runtime.GOOS != "linux" {
+		log.Println("Authentication token only implemented in linux at the moment.")
+		return
+	}
+	t := getRandomString()
+	err := ioutil.WriteFile(tokenPath, []byte(t), os.FileMode(int(0600)))
+	if err != nil {
+		log.Println("Could not write authentication token.")
+	}
+}
+
+func ReadAuthToken() string {
+	if runtime.GOOS != "linux" {
+		log.Println("Authentication token only implemented in linux at the moment.")
+		return ""
+	}
+	token, err := ioutil.ReadFile(tokenPath)
+	if err != nil {
+		log.Println("Error reading token:", err)
+	}
+	return string(token)
+}
+
+func getRandomString() string {
+	rand.Seed(time.Now().UnixNano())
+	chars := []rune("ABCDEFGHIJKLMNOPQRSTUVWXYZ" +
+		"abcdefghijklmnopqrstuvwxyz" +
+		"0123456789")
+	length := 40
+	var b strings.Builder
+	for i := 0; i < length; i++ {
+		b.WriteRune(chars[rand.Intn(len(chars))])
+	}
+	return b.String()
+}