How-it-works.md

How it works

A lot of the behavior is similar to the client patcher.

1. Open the Electron Asar archive This file is similar to a zip archive. It contains all the scripts for the client.

   You can find this by opening the folder where the Electron executable can be found. There will be a folder named "resources". Inside of it, you'll find the app.asar.

   Tools that can be used to open the Asar archive are:

   • 7-Zip - Asar7z
   • @electron/asar

2. Open package.json and locate the entry point Electron apps are structured like NodeJS libraries. The package file contains a field named "main". This allows NodeJS and Electron to determine the location of the main entry point.

   In the case of Electron, this entry point is executed in the main process.

   The main process is responsible for creating the BrowserWindow which has an API for running a script everytime a page loads.

3. Hook BrowserWindow and run our own preload.

   We can use require.cache to overwrite the exports on the electron module. By default, Electron freezes the module exports and makes all the descriptors unconfigurable. This can be bypased by overriding the exports on the module itself.

   (() => {
     "use strict";
     const { BrowserWindow } = require("electron");
     const electronModule = require.cache.electron;
     const electronExports = electronModule.exports;
   
     const descs = Object.getOwnPropertyDescriptors(electronExports);
   
     function hooked(options) {
       const bw = new BrowserWindow(options);
   
       console.log("Stole the BrowserWindow:", bw, options);
   
       return bw;
     }
   
     descs.BrowserWindow.get = () => {
       return hooked;
     };
   
     const newExports = Object.defineProperties({}, descs);
   
     Object.defineProperty(electronModule, "exports", {
       get: () => newExports,
       configurable: true,
       enumerable: true,
     });
   })();

   All we have to do is modify the entry point and add this code before everything else.

4. Change the preload to a custom one and make sure the original is executed The original preload can be accessed via options.webPreferences.preload. For the purpose of this, explanation, this part will be omitted.