# How to audit source code of proprietary Electron app [](https://www.youtube.com/watch?v=s4S7qgCkVCc "How to audit source code of proprietary Electron app") ## Requirements - Computer running macOS Big Sur or Monterey or disposable [Tails USB flash drive or SD card](../how-to-install-tails-on-usb-flash-drive-or-sd-card-on-macos) ## Caveats - When copy/pasting commands that start with `$`, strip out `$` as this character is not part of the command ## macOS guide ### Step 1: install [Homebrew](https://brew.sh/) ```console $ /bin/bash -c "$(curl -fsSL https://raw.githubusercontent.com/Homebrew/install/master/install.sh)" $ uname -m | grep arm64 && echo 'export PATH=$PATH:/opt/homebrew/bin' >> ~/.zshrc && source ~/.zshrc ``` ### Step 2: disable Homebrew analytics ```shell brew analytics off ``` ### Step 3: install dependencies ```shell brew install node tree ``` ### Step 4: extract source code > Heads-up: replace `QR\ Bridge.app` with Electron app one wishes to audit. ```console $ npx asar extract /Applications/QR\ Bridge.app/Contents/Resources/app.asar ~/Desktop/source npx: installed 17 in 6.041s ``` ### Step 5 (optional): list files ```console $ tree ~/Desktop/source -I node_modules /Users/sunknudsen/Desktop/source ├── LICENSE ├── README.md ├── app │   ├── confirmation.wav │   ├── index.html │   ├── preload.js │   ├── renderer.js │   └── style.css ├── icon.ai ├── main.js ├── package.json └── qr-bridge.code-workspace 1 directory, 11 files ``` ### Step 6: audit app > Heads-up: `code` is a command line utility that opens file or folder in [Visual Studio Code](https://code.visualstudio.com/). > Heads-up: **please respect license**… being able to audit app does not mean app (including its source code) should be considered public domain. ```shell code ~/Desktop/source ``` ### Step 7: check if app calls home Use application-layer firewall such as [Little Snitch](https://www.obdev.at/products/littlesnitch/index.html) or [Lulu](https://objective-see.com/products/lulu.html). 👍 ## Linux guide ### Step 1: boot to Tails and set admin password (required to run commands using `sudo`) > Heads-up: if keyboard layout of computer isn’t “English (US)”, set “Keyboard Layout”. Click “+” under ”Additional Settings”, then “Administration Password”, set password, click “Add” and finally “Start Tails”. ### Step 2: import [Node.js](https://nodejs.org/en/)’s PGP public key ```shell torsocks curl -fsSL https://deb.nodesource.com/gpgkey/nodesource.gpg.key | gpg --dearmor | sudo tee /usr/share/keyrings/nodesource.gpg > /dev/null ``` ### Step 3: enable Node.js’s repository > Heads-up: run `cat /etc/issue` to find Debian version. #### Debian 10 (buster) ```console $ echo -e "deb [signed-by=/usr/share/keyrings/nodesource.gpg] tor+https://deb.nodesource.com/node_16.x buster main\ndeb-src [signed-by=/usr/share/keyrings/nodesource.gpg] tor+https://deb.nodesource.com/node_16.x buster main" | sudo tee /etc/apt/sources.list.d/nodesource.list > /dev/null $ sudo apt update ``` #### Debian 11 (bullseye) ```console $ echo -e "deb [signed-by=/usr/share/keyrings/nodesource.gpg] tor+https://deb.nodesource.com/node_16.x bullseye main\ndeb-src [signed-by=/usr/share/keyrings/nodesource.gpg] tor+https://deb.nodesource.com/node_16.x bullseye main" | sudo tee /etc/apt/sources.list.d/nodesource.list > /dev/null $ sudo apt update ``` ### Step 4: find Node.js version ```console $ sudo apt-cache madison nodejs nodejs | 16.13.1-deb-1nodesource1 | tor+https://deb.nodesource.com/node_16.x buster/main amd64 Packages nodejs | 12.22.7~dfsg-2 | tor+https://cdn-fastly.deb.debian.org/debian sid/main amd64 Packages nodejs | 12.22.5~dfsg-2~11u1 | tor+https://cdn-fastly.deb.debian.org/debian bullseye/main amd64 Packages nodejs | 10.24.0~dfsg-1~deb10u1 | tor+https://cdn-fastly.deb.debian.org/debian buster/main amd64 Packages nodejs | 10.24.0~dfsg-1~deb10u1 | tor+https://cdn-fastly.deb.debian.org/debian-security buster/updates/main amd64 Packages ``` ### Step 5: install dependencies > Heads-up: replace `nodejs=16.13.1-deb-1nodesource1` with version found at [step 4](#step-4-find-nodejs-version). ```shell sudo apt install -y nodejs=16.13.1-deb-1nodesource1 tree ``` ### Step 6: extract “resources” directory from AppImage > Heads-up: replace `qr-bridge.AppImage` with Electron app one wishes to audit. ```console $ ./qr-bridge.AppImage --appimage-extract resources squashfs-root/resources squashfs-root/resources/app-update.yml squashfs-root/resources/app.asar ``` ### Step 7: extract source code > Heads-up: ignore torsocks warnings (if present). ```console $ torsocks npx asar extract squashfs-root/resources/app.asar ~/Desktop/source Need to install the following packages: asar Ok to proceed? (y) y ``` ### Step 8 (optional): list files ```console $ tree ~/Desktop/source -I node_modules /home/amnesia/Desktop/source ├── app │   ├── confirmation.wav │   ├── index.html │   ├── preload.js │   ├── renderer.js │   └── style.css ├── icon.ai ├── LICENSE ├── main.js ├── package.json ├── qr-bridge.code-workspace └── README.md 1 directory, 11 files ``` ### Step 9: audit app > Heads-up: **please respect license**… being able to audit app does not mean app (including its source code) should be considered public domain. Audit source code using “Text Editor”. 👍