Debugging Interface

scenario: We accessed the embedded device's asynchronous serial debugging interface while it was operational and captured some messages that were being transmitted over it. Can you decode them?

After we have downloaded the files through HackTheBox, we need to unzip the zip file

unzip  Debugging\ Interface.zip

we have one file

debugging_interface_signal.sal

lets see the file type

file debugging_interface_signal.sal

we can see it is a zip file so lets unzip the file

unzip debugging_interface_signal.sal

we have two new files

digital-0.bin
meta.json

Looking through the meta.json file, I could not find anything of use (yet), so redirect my focus on the digital-0.bin file

Lets run strings and see if anything pops out

strings digital-0.bin

we find an interesting header

After some googling it looks like SALESE is a logic analyzer. So Lets download the demo and see if we can find anything interesting

https://www.saleae.com/downloads/

give it the approiate permissions

chmod +x Logic-2.4.13-linux-x64.AppImage

we can now load in the Debugging Interface.zip zip file into the analyzer

This white block we can see is the data block, we can zoom in on the block by double clicking

we can see this is the signal we want to analyze, we want to start analyzing from the start of the data block,

we can see the data block start at 0.7ms, if we hover of the gaps in the data block we can see the bit rate

we can see the bit rate where I have highlighted is 32.2 ms, we need to find the bit rate (important), we can

1,000,000 / 32.02 = 31,230.48094940662 (31,230 Bits/s)

Now that we have the bit rate (31,230 Bits/s)

Next we want to go over to the analyzers -> Async Serial

as you can see we specified the channel we are on and the bit rate. click save

Now we have successfully decoded the data, Now we just need to find where we can access it from

on the right pane we should have a terminal button

Now we can view the data that has been captured, which holds the flag for this challenge