Image source: hak5

Physical hacking of a computer encompasses injection of commands with the target to grab files, install programs, create custom users or gain control. With the programmable Ducky Script USB stick, these exploits can be crafted to target any host system. When inserted, a preprogramed script is executed, written in the Ducky Script language.

This article is a concise introduction to the DuckyScript programming language. Based on the official DuckyScript documentation, it covers the essential commands and overall syntax, from keystrokes to host state management and function definition.

This article is for educational purposes only. Only use computers and devices that you own, and be mindful that they can be damaged.

The technical context for this article is CircuitPython v9.1.4 and Adafruit CircuitPython Bundle v9.x. The examples should work with newer releases too, but might require some code changes.

DuckyScript Program

A DuckyScript program is a line terminated sequence of commands that executes keystrokes on a target computer. The goal of these keystrokes is typically to infiltrate or compromise a system, for example by running commands that start a reverse shell, creating user accounts with root privileges, or downloading and installing malware. Therefore, a DuckyScript program can be thought of the vehicle, and the actual, os-specific exploit, as the transport.

The original DuckyScript programs are compiled into a binary using the Hak5 Payload Studio program. This binary is then uploaded to an USB stick, and executed when the USB stick is connected to a host device

The original hardware is not the only option to run DuckyScripts - several interpreters for different hardware are available in the open source community, including these:

• pico ducky: A library for running DuckyScript on the Raspberry Pico microcontroller, using a CircuitPython interpreter.
• Potato Parser: A library for running DuckyScript on ESP32 Devices. This Arduino project creates a custom binary with all included libraries.
• Flipper BadUSB: A DuckyScript 2.x compatible language that runs on the flipper hacking device.
• DucKey-Logger: A special PowerShell based exploit that completely logs all keystrokes and sends them to an online address.

Ducky Script Commands

The DuckyScript commands can be separated into these categories:

• Keystrokes: Most commands initiate a single or sequence of keystrokes, including control keys.
• Host State Management: Some commands read the systems keyboard state, and can be used as triggers to continue program flow, e.g. waiting for the user to start the screensaver, from which the exploit than resumes
• Device State Management: The original rubber duck USB stick features an LED and a button. Commands for these features can turn the LED on or await the press of a button as a trigger
• Program Structure & Control: DuckyScript allow the definition of variables and functions, lopping, branches and functions. For integer and boolean values, several operators exist. Finally, the global program state can be reflected and modified.

Keystrokes

Please continue reading this article on my blog admantium.com - I could not get it compiled on dev.to.

Conclusion

DuckyScript is a programming language to initiate keystrokes on a target computer. Essentially, these commands serve as a vehicle to transport an exploit onto a target system. This article provided a compact introduction to the DuckyScript language. You learned about all commands structured into four categories: a) keystrokes, a single or sequence of keys that are executed, b) host state management, commands that check the state of control keys, c) device management, to control the rubber ducks USB stick button and LED , d) program structure & control, defining variables, functions, and using various expressions to compare and modify numbers, strings and boolean values. Reflecting the language design, a striking feature is that the linear, continuous execution can be controlled by waiting for a specific condition on the target system. And with this, an exploit can be applied at the best moment to fulfill its goal.