picoCTF 2022 | Bbbbloat Write-up

Challenge description

Can you get the flag? Reverse engineer this binary.

Category: Reverse Engineering

Solution

To solve this challenge, I used ghidra, a popular tool for reverse-engineering.

I opened up a new project, imported the provided executable, and started looking for the main function.

This seems to be it

Of particular interest is this:

The program asks you for a number, and if you input the correct number, it will return the flag. The number in question is “0x86187”, which is hexadecimal for “549255”, you can either convert the hex value to decimal in your converter of choice or more conveniently, hover over the value in ghidra, which will convert it for you!

Run the program and input “549255” for the flag

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