Authenticator

Login helper for Minecraft. Displays login page using JCEF and outputs the authorization code.

Purpose

This program utilizes JCEF to create a Chromium web viewer. It then opens the official Minecraft login page and prompt the user to login. The authorization code is printed to stdout once login complete.

Some reasons you might want to use this:

• Supports multiple accounts (by changing the cache ID).
• Reliable (the embedded Chromium comes with the latest features).
• Works in China (by utilizing a local mirror).
• Easy to embed (the JAR file is around 7 MiB).

Some reasons you might NOT want to use this:

• If you hate to have multiple Chromiums on your (or your customers') machine.
• If the environment is not capable of downloading files of size around 100 MiB (the browser).
• If you think printing to stdout is dangerous.

Usage

This program is mainly released as fat JARs. To prompt the user to login, run:

java -jar Authenticator.jar [cacheId] [useMirrorCN]

Where Authenticator.jar is the path to the downloaded JAR. For the arguments:

• cacheId: Sets the user data path of this session. Can be used to "forget" cached accounts.
• useMirrorCN: Uses an alternative mirror in China. Set the value to mirror to enable.

On macOS you'll need some extra JVM flags:

--add-opens java.desktop/sun.awt=ALL-UNNAMED
--add-opens java.desktop/sun.lwawt=ALL-UNNAMED
--add-opens java.desktop/sun.lwawt.macosx=ALL-UNNAMED

The output (stdout) looks like:

==== DO NOT SHARE THE CODE BELOW ====
Code=M.XXXX_BAY.1.2.12345678-0000-aaaa-1234-111111111111
==== DO NOT SHARE THE CODE ABOVE ====

There may be some extra stuff printed by the JCEF framework. However, you just need to extract the line that starts with Code=. If there is no such line, then the program has crashed, or the user has closed the window without logging in.

Here is a simple example of retrieving the code using Node.js:

const cp = require("child_process");
cp.exec(`java -jar /path/to/authenticator.jar myCacheId`, (_, stdout) => {
    const code = stdout.split("\n").find(it => it.startsWith("Code="))?.slice(5);
    // Use the code
});

Building

This project is a standard Gradle Java project. Generate a fat JAR using:

./gradlew jar

And the JAR file is placed under build/libs.

License and Disclaimer

Copyright (C) 2024 Ted "skjsjhb" Gao.

Licensed under WTFPL, version 2.

This program is created in the hope that it will be useful, but WITHOUT ANY WARRANTY. Use at your own risk.

The output is not encrypted. It's the caller's responsibility to protect the stdout of this program from malware.

This program by itself does not collect nor send any data. Chromium and Microsoft web services might collect extra informaton when browsing using this program. See their privacy policies for details.

This program is not affiliated with Microsoft or Mojang.