Skip to main content

Protostar Format1

About

This level shows how format strings can be used to modify arbitrary memory locations.

Hints

  • objdump -t is your friend, and your input string lies far up the stack :)

This level is at /opt/protostar/bin/format1

Source code

(format1.c) download
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20

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

int target;

void vuln(char *string)
{
  printf(string);
  
  if(target) {
      printf("you have modified the target :)\n");
  }
}

int main(int argc, char **argv)
{
  vuln(argv[1]);
}