Linked List Exploit Continued - GOT Overwrite - "Links 2+3" Pwn Challenge [ImaginaryCTF]

"Links 2" (Pwn) challenge from ImaginaryCTF (iCTF) 27/06/22 - "It turns out that there was a bug in how I was handling writing some elements, so I've fixed that. Also, I've stopped putting the flag in a global variable, because that's probably not a good idea. Double check my implementation one more time for me?". In this challenge we'll use Ghidra, GDB-PwnDbg and PwnTools to exploit a vulnerable custom LinkedList implementation by overwriting an global offset table GOT entry to point system(), so we can get a shell.

"Links 3" (Pwn) challenge from ImaginaryCTF (iCTF) 30/06/22 - "And now you guys are exploiting my View Time feature that I put there solely for your convenience? Fine, then - no more time for you!". This challenge has no view_time() function, so we lose the system() call. However, we can leak an arbitrary function from the GOT and use the Lib-C database to find the correct offsets (ret2libc). Hope you enjoy 🙂 #CTF #iCTF #ImaginaryCTF #Pwn #BinaryExploitation

Write-ups: https://github.com/Crypto-Cat/CTF/tree/main/ctf_events/ictf/pwn/links

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↢Video-Specific Resources↣
https://libc.blukat.me
https://libc.rip

↢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
Links 1 Recap: 0:30
Reviewing Heap Layout in GDB-PwnDbg: 3:25
Keeping the Heap intact: 7:45
Links 2 Attack Plan: 11:55
Overwriting the GOT: 16:48
Stack Alignment: 20:08
Solution (leak system): 23:27
Links 3 (leak another lib-c function): 28:08
Recap: 33:27
End: 34:29