OBSIDIAN

Setup

Download the code to your machine using: $ git clone https://github.com/ash-v3/obsidian.git

Make sure PyCryptodome is running the latest version as some of the cryptographic functionality used in this repo was added in later versions.

$ python -m pip install -U pycryptodome

Steps

[] indicates required arguments, <> indicates optional arguments.

• Provide a firmware to be compiled with (optional) or automatically build the initial firmware with the bootloader. $ cd tools $ python bl_build.py --initial-firmware <firmware>
• Protect a firmware $ python fw_protect.py --infile [infile] --outfile [outfile] --version [version] --message [message]
• Start an update $ python fw_update --firmware [firmware]

Design Implementations

Notable Functions

• init_interfaces() prepares the bootloader for communication. UART interfaces are setup and the initial firmware is loaded at this stage.
• load_metadata() parses the metadata received from the update tool into an internal structure to be used throughout the program. Sanity checks are conducted to ensure the data received is acceptable.
• load_firmware() initalizes communication with the update tool before writing encrypted firmware to a buffer.
• decrypt_and_write_firmware() uses AES-256 to decrypt the firmware downloaded from load_firmware and writes it to memory.

Notable Information

• The bootloader is designed to support an message size up to 1kB (1,000 bytes) and a firmware size up to 30kB (30,000 bytes), along with a maximum version of 65,535.
• Firmware data is sent in chunks of 256 bytes
• Any modification of the firmware file will cancel the installation and reset the device.
• You can ignore caller.py and uart.py. We needed these Python scripts for our .vscode tasks (made our lives 10x easier).

we love bwsi!