Challenge Description: One of our embedded devices has been compromised. It was flashing a message on the debug matrix that was too fast to read, although we managed to capture one iteration of it. We must find out what was displayed. To help you with your mission, we will also provide you with the fabrication files of the PCB module the matrix was on.

Walkthrough

The zip files contains a Gerber module, as well as a .csv containing what seems to be the outputs of different GPIO pins, as well as the time they were recorded.

Having never really worked with a Gerber module before I had to do research to figure out its importance and usage.

Gerber describes the elements of a printed circuit board (PCB). It is used for both the fabrication of the board, and its assembly. A quick google search tells me that I can open the files using gerbv. For some reason, the window would go black whenever I tried importing the .DRL files, so I excluded those. However, this is the final result:

There is a term Common Anode Matrix that I have never heard of before, as well as the MCU on the board being a Raspberry Pi 3b+ Hat. ChatGPT reveals that a common anode matrix is simply a grid of LED’s, and specific LED’s are supplied voltage to create images, letters, or numbers. Based on this, I can assume that the flag is flashing on the matrix, and I need to map the outputs of the .csv file to its LED on the board. I was able to find the following image online which nicely displays the pinout of the Raspberry Pi: