fork/exec <cmd>: Setctty set but Ctty not valid in child

[zamoosh]

Hello, good time!

I have this project (name it goterm) which opens your local terminal in web via websocket connection... used xtermjs to simulate terminal in web.
Things are simple, I just open a PTY and use the websocket to read and write data to it, and every thing works just fine.

Here is how I open a PTY:

cmd := exec.Command("/bin/bash", "-l")
cmd.Env = append(os.Environ(), "TERM=xterm")

tty, err := pty.Start(cmd)
if err != nil {
	l.WithError(err).Error("Unable to start pty/cmd")
	conn.WriteMessage(websocket.TextMessage, []byte(err.Error()))
	return
}
defer func() {
	cmd.Process.Kill()
	cmd.Process.Wait()
	tty.Close()
	conn.Close()
}()

Here is the final result:

BUT my problem comes, when I want to combine this with my other project. My other project is almost the same with above one, but with some differences, let me tell scenario:
I have a Go client (located in my computer) which sends data to my server in a specific period of time via websocket, and I want to use the goterm with it to open a terminal in web, which runs command in go client, and have result back in website. To make the story short, think of how SSH works, I want something like that...

Here is my code:

func main() {
	// load environment
	err := godotenv.Load("/etc/htopNovin/config")
	if err != nil {
		//log.Fatal("Error loading .env file")
	}

	if len(os.Args) > 1 {
		args := os.Args[1]
		if args == "version" && len(os.Args) == 2 {
			fmt.Println(version)
		} else if args == "setup" && len(os.Args) == 2 {
			// service permission
			check_permission()
			setup()
		} else if args == "update" && len(os.Args) == 2 {
			// service permission
			check_permission()
			update()
		} else {
			fmt.Println("you paramts is invalid")
		}
	} else {
		// service permission
		check_permission()
		go servTerm() // <- where I wish to open a PTY
		serversocket() // <- where I start my websocket connection to my server, for sending data in periodic time
	}
}

The serversocket() simply connects to the django channels to send and receive data.
The servTerm() is JUST my go term I mentioned above.

But when I run my project and request to my URL, I'll get this error:
fork/exec /bin/bash: Setctty set but Ctty not valid in child

Here is my code:

func handleWebsocket(w http.ResponseWriter, r *http.Request) {
	// l := log.WithField("remoteaddr", r.RemoteAddr)
	conn, err := upgrader.Upgrade(w, r, nil)
	if err != nil {
		log.Println("Unable to upgrade connection")
		return
	}
	
	cmd := exec.Command("/bin/bash", "-l")
	cmd.Env = append(os.Environ(), "TERM=xterm")
	
	tty, err := pty.Start(cmd)
	if err != nil {
		log.Printf("Unable to start pty/cmd. error: %v \n", err)
		conn.WriteMessage(websocket.TextMessage, []byte(err.Error()))
		return
	}
	defer func() {
		cmd.Process.Kill()
		cmd.Process.Wait()
		tty.Close()
		conn.Close()
	}()
	
	// WRITE MESSAGE
	go func() {
		for {
			buf := make([]byte, 1024)
			read, err := tty.Read(buf)
			if err != nil {
				conn.WriteMessage(websocket.TextMessage, []byte(err.Error()))
				log.Printf("Unable to read from pty/cmd %d \n", err)
				return
			}
			conn.WriteMessage(websocket.BinaryMessage, buf[:read])
		}
	}()
	// END WRITE MESSAGE
	
	// READ MESSAGE
	for {
		messageType, reader, err := conn.NextReader()
		if err != nil {
			log.Println("Unable to grab next reader")
			return
		}
		
		if messageType == websocket.TextMessage {
			log.Println("Unexpected text message")
			conn.WriteMessage(websocket.TextMessage, []byte("Unexpected text message"))
			continue
		}
		
		dataTypeBuf := make([]byte, 1)
		read, err := reader.Read(dataTypeBuf)
		if err != nil {
			conn.WriteMessage(websocket.TextMessage, []byte("Unable to read message type from reader"))
			return
		}
		
		if read != 1 {
			log.Println("Unexpected number of bytes read")
			conn.WriteMessage(websocket.TextMessage, []byte("Unexpected text message"))
			return
		}
		
		switch dataTypeBuf[0] {
		case 0:
			copied, err := io.Copy(tty, reader)
			if err != nil {
				// l.WithError(err).Errorf("Error after copying %d bytes", copied)
				log.Printf("Error after copying %d bytes", copied)
			}
		case 1:
			decoder := json.NewDecoder(reader)
			resizeMessage := windowSize{}
			err := decoder.Decode(&resizeMessage)
			if err != nil {
				conn.WriteMessage(websocket.TextMessage, []byte("Error decoding resize message: "+err.Error()))
				continue
			}
			// log.WithField("resizeMessage", resizeMessage).Info("Resizing terminal")
			log.Println("Resizing terminal")
			_, _, errno := syscall.Syscall(
				syscall.SYS_IOCTL,
				tty.Fd(),
				syscall.TIOCSWINSZ,
				uintptr(unsafe.Pointer(&resizeMessage)),
			)
			if errno != 0 {
				// l.WithError(syscall.Errno(errno)).Error("Unable to resize terminal")
			}
		default:
			log.Println("Unknown data type")
		}
	}
	// END READ MESSAGE
}

func servTerm() {
	var listen = flag.String("listen", "127.0.0.1:3000", "Host:port to listen on")
	var assetsPath = flag.String("assets", "./assets", "Path to assets")

	flag.Parse()

	r := mux.NewRouter()

	r.HandleFunc("/term", handleWebsocket)

	r.PathPrefix("/").Handler(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		// Get the requested file path from the URL.
		requestedFile := r.URL.Path

		// Use the filepath.Ext function to extract the file extension.
		// This will be used to determine the appropriate Content-Type.
		fileExt := filepath.Ext(requestedFile)

		// Set the appropriate Content-Type header based on the file extension.
		if contentType, ok := mimeTypes[fileExt]; ok {
			w.Header().Set("Content-Type", contentType)
		}

		// Serve the file using the file server.
		http.FileServer(http.Dir(*assetsPath)).ServeHTTP(w, r)
	}))


	if !(strings.HasPrefix(*listen, "127.0.0.1") || strings.HasPrefix(*listen, "localhost")) {
		// log.Warn("Danger Will Robinson - This program has no security built in and should not be exposed beyond localhost, you've been warned")
		log.Println("Danger Will Robinson - This program has no security built in and should not be exposed beyond localhost, you've been warned")
	}

	if err := http.ListenAndServe(*listen, r); err != nil {
		// log.WithError(err).Fatal("Something went wrong with the webserver")
		log.Println("Something went wrong with the webserver")
	}
}

Can someone please help me with my problem?
I read this issue (#96), but I didn't understand it.

Anyhow, thanks a lot!

[zamoosh]

I found the solution! the version I was using was old! use the latest version and also remember to change it in go.mod and go.sum files.

Have nice time...