Leaking Secret Data with a Heap Overflow - "Leek" Pwn Challenge [Angstrom CTF 2023]

Video walkthrough for the binary exploitation (pwn) challenge, "Leek" from the Angstrom capture the flag (CTF) competition 2023. The challenge involves performing a heap overflow to overwrite all null bytes between our user input chunk and secret data chunk so that when puts() is called, it prints both chunks (there's no null terminator separating them). After this, we need to repair the header of the chunk we modified so that the program can continue execution. We repeat this process of leaking and submitting the random (secret) bytes 100 times, at which point we receive the flag! Write-ups/tutorials aimed at beginners - Hope you enjoy 🙂 #Angstrom #AngstromCTF #CTF #Pentesting #OffSec #Pwn #BinaryExploitation #Reversing #ReverseEngineering

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↢AngstromCTF↣
https://ctftime.org/event/1859
https://2023.angstromctf.com/challenges
https://discord.gg/Dduuscw
https://twitter.com/angstromctf

↢Resources↣
Ghidra: https://ghidra-sre.org/CheatSheet.html
Volatility: https://github.com/volatilityfoundation/volatility/wiki/Linux
PwnTools: https://github.com/Gallopsled/pwntools-tutorial
CyberChef: https://gchq.github.io/CyberChef
DCode: https://www.dcode.fr/en
HackTricks: https://book.hacktricks.xyz/pentesting-methodology
CTF Tools: https://github.com/apsdehal/awesome-ctf
Forensics: https://cugu.github.io/awesome-forensics
Decompile Code: https://www.decompiler.com
Run Code: https://tio.run

↢Chapters↣
Start: 0:00
Patch lib-c (pwninit): 0:20
Test the program functionality: 1:05
Check the binary protections (checksec): 1:37
Analyse decompiled code (ghidra): 3:53
Recap of analysis: 6:51
PwnTools script: 8:40
Setup breakpoints: 14:38
Debug with GDB (pwndbg): 15:33
Heap recap (chunk structure): 16:20
Reviewing vulnerability / exploit: 18:01
Finish PwnTools script: 20:40
Test against remote server: 24:13
Final recap: 25:07
End: 25:56