exploitme.c

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

#define BUFSIZE 128
#define A_CONSTANT 0x42424242

void read_input() {
    char buffer[BUFSIZE];
    const int i_dont_change = A_CONSTANT;

    printf("Tell me a message and I will say it back to you.\n");

    // Read a line of input into 'buffer'
    gets(buffer);

    printf("You said: %s, which is located at address %p and has length %lu.\n", buffer, &buffer, strlen(buffer));
    printf("The size of buffer is %i bytes.\n", BUFSIZE);
    // Check for overflow
    if (strlen(buffer) > BUFSIZE) {
        printf("You have overflowed the buffer.  Oh no!\n");
    }
    // Make sure that i_dont_change didn't change!
    if (i_dont_change != A_CONSTANT) {
        printf("i_dont_change has value %#x instead of %#x\n", i_dont_change, A_CONSTANT);
    }
}

void goal_function() {
    printf("If you caused the program to call this function, you win!\n");
}

int main() {
    read_input();
}