webrtc_http_tunnel/client/frontend/app/app.ts

/*
 * HTTP tunnel over WebRTC - Client UI implementation
 * Author: Konstantinos Drakontidis
 * Email: gedra100sh@gmail.com
 */
import { app, BrowserWindow, Menu, ipcMain } from "electron";
import { ChildProcessWithoutNullStreams, spawn } from "node:child_process";
import { glob } from "glob";
import * as net from "net";
import * as path from "path";

var backend: ChildProcessWithoutNullStreams;
var shutting_down = false;

// Graceful shutdown
function shutdown() {
    // Check if shutdown has already been called
    if (!shutting_down) {
        shutting_down = true;

        if (backend) {
            // Kill backend child by sending SIGINT
            backend.stdout.removeAllListeners();
            backend.stderr.removeAllListeners();
            backend.once("exit", () => {
                process.exit(0);
            });

            backend.stdin.write("exit\n");
            setTimeout(() => { process.exit(-1) }, 5000);
        } else {
            process.exit(0);
        }
    }
}

// Returns an available port number
function getAvailablePort(): Promise<number> {
    return new Promise((resolve, reject) => {
        const server = net.createServer();
        server.listen(0, () => {
            const address = server.address();
            if (typeof address === "object" && address !== null) {
                const port = address.port;
                server.close(() => resolve(port));
            } else {
                reject(new Error("Could not get port"));
            }
        });
        server.on("error", reject);
    });
}

app.whenReady().then(async () => {
    const main_window = new BrowserWindow({
        webPreferences: {
            nodeIntegration: true,
            contextIsolation: false
        },
        resizable: false,
        width: 800,
        height: 600
    });

    // Load main window and disable menu
    await main_window.loadFile(path.join(__dirname, "..", "views", "main.html"));
    Menu.setApplicationMenu(null);

    var line_buffer = "";
    var connected = false;

    // Generate a port number and search for the peer binary
    const http_port = await getAvailablePort();
    const peer_exec = await glob(path.join(process.resourcesPath, "extra", "peer*").replaceAll("\\", "/"));
    if (peer_exec.length) {
        // Create child
        backend = spawn(peer_exec[0], [http_port.toString()], {
            cwd: path.join(process.resourcesPath, "extra")
        });

        backend.on("spawn", () => {
            main_window.webContents.send("backend_spawn");
        });
        backend.stdout.on("data", (data: Buffer) => {
            main_window.webContents.send("backend_info", data.toString());
            line_buffer += data.toString();

            // Scan each line from stdout to check if datachannel opened
            var lines = line_buffer.split("\n");
            line_buffer = lines.pop() || "";

            for (const line of lines) {
                if (line.trim() === "Opened data channel.") {
                    connected = true;
                    main_window.webContents.send("backend_dc", http_port.toString());
                    main_window.setResizable(true);
                    main_window.maximize();
                }
            }
        });
        backend.stderr.on("data", (data: Buffer) => {
            main_window.webContents.send("backend_error", data.toString());
        });
        backend.on("close", async () => {
            // Check if main window is currently showing and if not redirect
            if (connected) {
                await main_window.loadFile(path.join(__dirname, "..", "views", "main.html"));
                main_window.unmaximize();
                main_window.setSize(800, 600, true)
                main_window.setResizable(false);
            }
            main_window.webContents.send("backend_quit");
        });
    } else {
        process.exit(-1);
    }
});

// Handling basic HTTP authentication
let authCallback: ((user: string, pass: string) => void) | null = null;
app.on("login", (event, webContents, request, authInfo, callback) => {
    event.preventDefault();
    authCallback = callback;

    const loginWin = new BrowserWindow({
        parent: BrowserWindow.getFocusedWindow() ?? undefined,
        width: 300,
        height: 180,
        resizable: false,
        modal: true,
        frame: false,
        webPreferences: {
            nodeIntegration: true,
            contextIsolation: false,
        },
    });

    loginWin.loadFile(path.join(__dirname, "..", "views", "login.html"));
});

app.on("window-all-closed", () => {
    shutdown();
});

app.on("quit", () => {
    shutdown();
});

ipcMain.on("login-submit", (_event, { username, password }) => {
    if (authCallback) {
        authCallback(username, password);
        authCallback = null;
    }
    BrowserWindow.getFocusedWindow()?.close();
});

ipcMain.on("login-cancel", () => {
    shutdown();
});