HTB Cyber Apocalypse 2023 - (Hardware) Critical Flight

‘Critical Flight’ was one of the challenges in the ‘Hardware’ category at HTB’s Cyber Apocalypse 2023.
Its difficulty was ‘Very easy’ so it was a very simple challenge. This makes it a very good challenge to try for people who tried their first CTF.

For this challenge, we got an archive containing two folders: a __MACOSX folder and a folder containing .gbr files.
The __MACOSX is specific to archives on MacOS so we can ignore that (especially since I’m not using MacOS).

Let’s focus on the .grb files. After a bit of googling, I found out that .gbr is a format used to store designs for Printed Circuit Boards (PCBs).
I also found out that there’s an online viewer available for those files: https://www.pcbway.com/project/OnlineGerberViewer.html.

I dragged all the .gbr files into that viewer and it looks like every file is another layer on the PCB.

I can select “layers” and I can select which layers I want to be visible.
So, I started browsing through the layers to see what they contain.

The first interesting thing can be seen on the Copper layer on the bottom of the board.

This is the first part of our flag.
We just have to rotate the image and copy the first half of the flag: HTB{533_7h3_1nn32_w02k1n95
Maybe the second part is also hidden in one of those layers.

And after a very short time … here it is, on the copper layer in the “inner” part of the board.

The second part is: _0f_313c720n1c5#$@}

We put them together and we get our full flag: HTB{533_7h3_1nn32_w02k1n95_0f_313c720n1c5#$@}
And this was it: very easy indeed.

More hardware challenges

These are the other hardware challenges from this CTF

• Hardware 1/5 - Very Easy - Critical Flight (you are here)
• Hardware 2/5 - Very Easy - Timed Transmission
• Hardware 3/5 - Easy - Debug
• Hardware 4/5 - Easy - Secret Code
• Hardware 5/5 - Medium - HM74