Stack One

This level looks at the concept of modifying variables to specific values in the program, and how the variables are laid out in memory.

This level is at /opt/protostar/bin/stack1

Hints

  • If you are unfamiliar with the hexadecimal being displayed, “man ascii” is your friend.
  • Protostar is little endian

Source code

#include <stdlib.h> #include <unistd.h> #include <stdio.h> #include <string.h>  int main(int argc, char **argv) { volatile int modified; char buffer[64]; if(argc == 1) { errx(1, "please specify an argument\n"); } modified = 0; strcpy(buffer, argv[1]); if(modified == 0x61626364) { printf("you have correctly got the variable to the right value\n"); } else { printf("Try again, you got 0x%08x\n", modified); } }