added interface as cli argument, as well as ranking of interfaces if it will be chosen automatically

main.go

@@ -493,7 +493,44 @@ func handler(w http.ResponseWriter, r *http.Request) {
 	tmpl.Execute(w, data)
 }
 
-func startInteractiveServer(cliInteractivePort string) (string, net.Listener) {
+func ipv4Addr(iface *net.Interface) (string, bool) {
+	addrs, _ := iface.Addrs()
+	for _, a := range addrs {
+		if ip, _, _ := net.ParseCIDR(a.String()); ip.To4() != nil {
+			return ip.String(), true
+		}
+	}
+	return "", false
+}
+
+func autoInterface() string {
+	ifaces, _ := net.Interfaces()
+
+	// Interfaces whose IPv4 we want before anything else, in order.
+	var preferredPrefixes = []string{"wg", "tun", "tailscale"}
+
+	for _, prefix := range preferredPrefixes {
+		for _, in := range ifaces {
+			if strings.HasPrefix(in.Name, prefix) && in.Flags&net.FlagUp != 0 {
+				if ip, ok := ipv4Addr(&in); ok {
+					return ip
+				}
+			}
+		}
+	}
+
+	for _, in := range ifaces {
+		if in.Flags&net.FlagLoopback == 0 && in.Flags&net.FlagUp != 0 {
+			if ip, ok := ipv4Addr(&in); ok {
+				return ip
+			}
+		}
+	}
+
+	return ""
+}
+
+func startInteractiveServer(cliInteractivePort, networkInterface string) (string, net.Listener) {
 
 	http.HandleFunc("/", handler)
 	http.HandleFunc("/upload", fileUploadHandler)
@@ -504,28 +541,60 @@ func startInteractiveServer(cliInteractivePort string) (string, net.Listener) {
 	var addPort string
 	var listener net.Listener
 	var err error
-	if len(cliInteractivePort) > 0 {
-		addPort = cliInteractivePort
-		listener, err = net.Listen("tcp", ":" + addPort)
+
+	var host string
+	if networkInterface != "" {
+		iface, err := net.InterfaceByName(networkInterface)
+		if err != nil {
+			log.Fatalf("interface %q not found: %v", networkInterface , err)
+		}
+		if ip, ok  := ipv4Addr(iface); ok {
+			host = ip
+		} else {
+			log.Fatalf("Interface %q has no IPv4 address", networkInterface)
+		}
 	} else {
-		listener, err = net.Listen("tcp", ":0")
-		addPort = strconv.Itoa(listener.Addr().(*net.TCPAddr).Port)
+		host = autoInterface()
 	}
 
-	if err != nil {
-			log.Fatal(err)
+	port := cliInteractivePort
+
+	if port == "" {
+		port = "0"
 	}
 
+	listener, err = net.Listen("tcp4", net.JoinHostPort(host, port))
+	if err != nil {
+		log.Fatal(err)
+	}
+
+	addPort = strconv.Itoa(listener.Addr().(*net.TCPAddr).Port)
+
+
+
+	// if len(cliInteractivePort) > 0 {
+	// 	addPort = cliInteractivePort
+	// 	listener, err = net.Listen("tcp", ":" + addPort)
+	// } else {
+	// 	listener, err = net.Listen("tcp", ":0")
+	// 	addPort = strconv.Itoa(listener.Addr().(*net.TCPAddr).Port)
+	// }
+
+	// if err != nil {
+	// 		log.Fatal(err)
+	// }
+
 	return addPort, listener
 }
 
 // func connectionArgs () (string, string) {
-func connectionArgs () (string, string) {
+func connectionArgs () (string, string, string) {
 	// Get IP address and port of the server through the
  	var serverAddress string
 	// var serverPort    string
 	var serverWebsocketPort string
 	var interactivePort  string
+	var networkInterface string
 
 	flag.StringVar(&serverAddress, "address", "127.0.0.1", "IP Address of the C2 server.")
 	// flag.StringVar(&serverPort, "server-port", "3333", "Port of the C2 server. This is obsolete.")
@@ -533,6 +602,8 @@ func connectionArgs () (string, string) {
 
 	flag.StringVar(&interactivePort, "interactive-port", "", "Port to connect directly to the agent's webapp. Port will be random if not set.")
 
+	flag.StringVar(&networkInterface, "network-interface", "", "Network interface to bind to. Will bind to the first non loopback interface if not set.")
+
 	flag.Parse()
 
 	fmt.Println("Server address is at ", serverAddress)
@@ -544,7 +615,7 @@ func connectionArgs () (string, string) {
 
 	// return webServerAddr, webSocketAddr
 
-	return webSocketAddr, interactivePort
+	return webSocketAddr, interactivePort, networkInterface
 }
 
 
@@ -552,12 +623,15 @@ func connectionArgs () (string, string) {
 
 func main() {
 
-	webSocketAddr, cliInteractivePort := connectionArgs()
+	webSocketAddr, cliInteractivePort, networkInterface := connectionArgs()
 
-	addPort, listener := startInteractiveServer(cliInteractivePort)
+	addPort, listener := startInteractiveServer(cliInteractivePort, networkInterface)
 
-	log.Println("Using interactive port:", addPort)
-	log.Printf("You can connect to port %d through your browser as well", listener.Addr().(*net.TCPAddr).Port)
+	// log.Println("Using network interface:", networkInterface)
+	ipv4Addr := listener.Addr().(*net.TCPAddr).IP.String()
+	log.Printf("You can connect to %s:%d through your browser as well",
+		ipv4Addr,
+		listener.Addr().(*net.TCPAddr).Port)
 
 	var wg sync.WaitGroup
 	wg.Add(2)
@@ -569,7 +643,7 @@ func main() {
 
 	go func() {
 		defer wg.Done()
-		agentconnector.StartServer(addPort, webSocketAddr)
+		agentconnector.StartServer(addPort, webSocketAddr, ipv4Addr)
 	}()
 
 	wg.Wait()

src/agentconnector/agentconnector.go

@@ -211,14 +211,14 @@ func GetLocalIPs() []net.IP {
 }
 
 // func main() {
-func StartServer(addPort, webSocketAddr string){
+func StartServer(addPort, webSocketAddr, agentIp string){
 
 	// webSocketAddr, cliInteractivePort := connectionArgs()
 
 	// agentInteractivePort is only needed for interactive sessions
 	agentName := "Agent-001"
 	agentId := strconv.Itoa(randomInt(8))
-	agentIp := GetLocalIP().String()
+	// agentIp := GetLocalIP().String()
 	agentType := "Interactive"
 	hostname, _ := os.Hostname()