This is a small write-up of the “Mic check” challenge from DeadSec CTF 2024 (Misc Category). The difficulty was easy and it was a kind of stuff that appears often in CTF challenges.
Description :
mic is it ok?
mic is it ok?
A link is to start a docker container and the command to connect to it are provided.
Solution :
When connecting to the docker with netcat, we receive a letter, we must reply with the same letter, then we receive 2 letters and must reply with the same 2 letters, and so on. We could do that manually but the “difficulty” is that you have to type the increasing amount of letters in less than 1 or 2 seconds.
A very good and easy library to use in Python to solve this challenge is called pwntools. Now we just need to make a small script that reads what we receive, and send the same string.
| from pwn import * | |
| p = remote("35.225.65.217",32456) | |
| output="" | |
| while len(output)<100: | |
| p.recvuntil(b">") | |
| input = p.recvuntil(b" [") | |
| p.recvline() | |
| p.recvuntil(b">") | |
| output = input.decode("utf-8") | |
| output = output[:-1] | |
| output = output.replace(" ", "") | |
| log.info("Sending : "+output) | |
| p.sendline(output.encode('utf-8')) | |
| input = p.recvline() | |
| log.info("Received : "+input.decode("utf-8")) |
by Then run it :
Until you see the flag :
That’s it, the flag was DEAD{mic is working!}