CTFs | 404CTF2023 | Reverse | Le Divin Crackme

Context

We are given the executable “divin-crackme”.

We have to find the compiler used, the function used to compare the user input to the password and the password.

Let’s analyze the executable using Ghidra.

Ghidra indicates us that the gcc compiler was used.

Here is the main function:

The function asks the user to enter the password.

Then it compares the first part of the input to “L4pH1l0so”, the second part to “Ph13_d4N5” and the 3rd part of the input to “l3_Cr4cKm3”.

So, the password is “L4_pH1l0soPh13_d4N5_l3_Cr4cKm3”.

The function used to compare the user input to the password is “strncmp”

Flag format: 404CTF{compilateur:fonction:mot_de_passe}

So, the flag is: 404CTF{gcc:strncmp:L4_pH1l0soPh13_d4N5_l3_Cr4cKm3}

I hope you enjoyed this writeup 😄 !