murkmod

murkmod

murkmod is a utility script that patches fakemurk and mush to include additional useful utilities, with the most prominent being a plugin manager. This tool enables you to easily install and manage various packages and plugins for mush, and, eventually, fakemurk itself. murkmod also includes additional useful tools and features that can aid you in your various Chromebook hacking tasks.

Heads up!

v1.2.0 of fakemurk is mostly working with murkmod, but in some rare edge cases it breaks, and it breaks badly. Use caution!

Installation

Want a complete guide, with steps all the way from choosing an exploit to configuring fakemurk? Check out the Chromebook Exploit Guide.

In order to use all of the features of murkmod, you must create a emergency revert backup during the installation of fakemurk.

To install murkmod, simply spawn a root shell (option 1) from mush, and paste in the following command:

bash <(curl -SLk https://raw.githubusercontent.com/rainestorme/murkmod/main/murkmod.sh)

This command will download and install murkmod and its (almost minimal) dependencies. Once the installation is complete, you can start using murkmod by running mush as usual.

Installing (or updating) fakemurk will set the password for the chronos user to murkmod.

Plugin Management

Once murkmod is installed, refresh your mush tab or open a new one with Ctrl+Alt+T. You'll see a few new options, such as the ability to run neofetch, but the important ones here are Install plugins, Uninstall plugins and Plugins.

To install a plugin, head over to this link. Find the plugin you want and remember its filename. You'll need it in a bit. Select Install plugins and enter the filename. The file should be installed, then you can enter q to quit.

You can go to Plugins to use your installed plugins. Once you select an option, it should execute the plugin's contents.

Plugin Development

It's pretty straightforward to create a pluign. Just create a .sh file with the following content:

#!/bin/bash
# menu_plugin
PLUGIN_NAME="Hello World Plugin"
PLUGIN_FUNCTION="Print a hello world message"
PLUGIN_DESCRIPTION="The friendliest murkmod plugin you'll ever see."
PLUGIN_AUTHOR="rainestorme"
PLUGIN_VERSION=1
echo "Hello, World!"

Of course, you should change this to match your plugin. Every time you update your plugin, you should increment PLUGIN_VERSION. Everything below the initial variables, though, is what is executed when you run the plugin from the mush menu.

To add a plugin to this repository (for easy download from mush), just fork the repo, add the file in /plugins/ and make a PR. I'll review it and merge it if it doesn't do anything malicious.

The second comment at the top defines the type of the plugin. There are four plugin types:

• menu_plugin
• daemon_plugin
• startup_plugin

Menu plugins aren't run as root - all other plugins are. Startup plugins run once, in a late stage of the boot process, and daemon plugins are run infinitely in a loop after startup.

Make sure that your startup plugin runs quickly - or, at least, as quickly as possible. It'll hold up the boot process until it exits.

Careful! If your startup plugin tries to use /mnt/stateful_partition, it will crash! Startup plugins are run before stateful is mounted. If your startup plugin needs to access stateful, see example-plugins/startup/read_file_from_stateful.sh for an example.

Using Hacked Sudo

Murkmod makes a few changes to system permission to allow chronos to use sudo with no password, and setting the password to the chronos account so that root can su into it, meaning that you can properly use sudo in a command line if you run the following at a root bash prompt:

su chronos
sudo <your command here>

Regarding Chromebrew

Chromebrew is almost functional in the current state. I welcome PRs to fix issues you encounter with it.

Are your menu plugins no longer showing up after updating?

Open a root shell and run the following commands:

rm /mnt/stateful_partition/murkmod/plugins/*
exit

Now, reinstall all plugins you want to use.

Notes on USB Boot

In order to boot a traditionally built linux distro (one not designed to be used on Chromebook hardware), you'll need to install MrChromebox's RW_LEGACY firmware. To do so, the mrchromebox-fwscript.sh plugin is provided. However, it is highly reccomended that you use depthboot to build a more compatible linux image that you can then boot from with Ctrl+U at the developer mode warning screen. Keep in mind that the step requiring the enabling of dev_boot_usb can be performed from the mush menu.