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USB Keystroke Injector

An Arduino-based keyboard emulator which injects (i.e. types) a sequence of letters received via Bluetooth protocol or read from predefined SD card payloads.

SD card mode

When it's on SD-card mode, it reads content of a payload (which is selectable using three switches; means 8 possible payloads) from inserted SD card and starts typing them as soon as being recognized as a keyboard to the host. Payloads must be written in a simple syntax explained below.

When the payload injection is done, it automatically switches to Bluetooth mode to give more control to the operator.

Here is how it looks like (GIF size: 11 MB):

Bluetooth mode

When it's explicitly set to Bluetooth mode, it has nothing to do with the SD card. As soon as it gets plugged into the host, it'll wait for the operator to connect via Bluetooth protocol.
Bluetooth Terminal HC-05 can be used as a simple (yet powerful) client for Android based devices. Install it, connect to the device and let it recognize itself as a keyboard to the host. When it's ready, type whatever you need using the a simple syntax explained below.

Here is how it looks like (GIF size: 5 MB):

... and a bonus!

A photoresistor is implemented in the circuit which can be used as an activator. It can be used by {LDR} action (see Payload Syntax section). Basically, it'll keep the initial brightness and will wait for the room to become darker (like when lights go off). Then, it'll continue its operation.

Requirements and Installation

Required components

• Arduino Pro Micro or other compatible arduinos which must have:
  • A built-in USB transceiver (like ATmega3U4; note the letter U in the model)
  • An extra hardware serial port

If you're not using Arduino Pro Micro, you must follow your device pinout instead of the following schematic.

• HC-05 Bluetooth module
• MicroSD Card Adapter
• A 6-position DIP switch
• (Optionally) a photoresistor
• (Optionally) an LED
• Several resistors

Assemble the circuit

First, you need to assemble the following circuit (the schematic is also available as a fritzing project in schematic directory):

Program the software

Codes are available in sources directory as an Arduino IDE project. Connect your device and simply program it.

Configuration

Main functionality can be configured with the switches (so you don't need to re-program again and again for simple changes).
State of switches are explained below:

For example, if you want to operate on SD card with payload on index 3 (PAYLOAD3.txt in the SD card), you'll need to configurate switches like this:

Pin:              #0                  #1                  #2                     #3         #4          #5
State:            1                   0                   1                      0          1           1
Means:      Emulation ON          Debug OFF          SD card mode     Payload#: (+0         +2          +1)

Payload Syntax

Payloads in either SD card files or Bluetooth communication data should follow these rules:

• Lines must be terminated with \n instead of \r\n or \r;
• Lines can be either a single predefined action (see below) or a sequence of characters.

That was all! cool, isn't it?
There are few predefined actions which can make your script lighter and easier to read. Each of them must be typed in a separate line. They are:

You can see example payloads in payload-examples directory. Feel free to extend your predefined actions in m_keyboardAndMouse.ino file.

Note: Due to limited memory size of Arduino and one-time SD card initialization, you need to keep the overall payload size below MAX_SDCARD_LEN (default: 1400 bytes) and each line below MAX_PAYLOAD_LEN (default: 300 bytes) or else, you may face some weird functionalities!

These constraints can be changed in a_globals.h file or you can write your own method to read payloads line by line from the SD card itself, instead of loading them into the memory on initialization.

Contribution

Feel free to extend the functionality of the device and submit some Pull Requests. They'll be reviewed and merged as soon as possible. Just please consider limitations of Arduino especially its memory size.

Disclaimer

Neither the author nor any contributers of this projects are responsible for any kind of misuses that can be happen using this project. This is an educational project and is not developed to be a stable, operation-ready device.

There are pretty good uses for this project including:

• Using Bluetooth mode to controle your computer remotely;
• Extending the security of the device and using it as a simple security key;
• Using photoresistor to put the computer in sleep mode whenever the lights are turned off;
• Using it for penetration testing;
• And plenty of other uses ...

License

This project is licensed under Apache License 2.0.

See Also

• ByteGate (our blog)
• تبدیل PDF به ورد (our sponsored service)