Bad Grades @ HackTheBox Challenge

Binary Exploitation - Bad Grades

Difficulty: Easy

Overview: This challenge presents a classic binary exploitation scenario centered on a buffer overflow vulnerability due to an out-of-bounds write. By leveraging this flaw, we can manipulate the program’s control flow and craft a Return-Oriented Programming (ROP) chain to bypass security mechanisms and spawn a shell on the target system.

Basic file checks

First all we do some basic file checks to see the security protections enabled on the binary.

mcsam@0x32:~/Desktop/ctf/hackthebox/challenges/pwn/bad_grades$ checksec --file bad_grades
[*] '/home/mcsam/Desktop/ctf/hackthebox/challenges/pwn/bad_grades/bad_grades'
    Arch:       amd64-64-little
    RELRO:      Full RELRO
    Stack:      Canary found
    NX:         NX enabled
    PIE:        No PIE (0x400000)

From checksec we can see that only PIE is disabled.

Decompiling and identifying vulnerabilties