Quick Crack demo

crack.c

#define _XOPEN_SOURCE
#include <stdio.h>
#include <unistd.h>
#include <string.h>

int main(int argc, char **argv)
{
    if (argc != 2)
    {
        printf("Please enter exactly one hashed password as a command line argument.");
        return 1;
    }

    char salt[2] = { argv[1][0], argv[1][1] };
    char guess[5] = { 'a', '\0', '\0', '\0', '\0' };

    while (strcmp(crypt(guess, salt), argv[1]))
    {
        //printf("Tried %s and failed.\n", guess);

        for (int i = 0; i < 4; i++) {
            // Hasn't been used yet, default to a and stop looping
            if (guess[i] < 'a') {
                guess[i] = 'a';
                break;
            }
            // Greater than the upper boundary, reset and continue loop
            else if (++guess[i] > 'z') {
                if (i == 3) {
                    printf("Your password doesn't exist\n");
                    return 1;
                }
                guess[i] = 'a';
            }
            // Less than the upper boundary, break loop
            else {
                break;
            }
        }
    }


    printf("Your password was %s.\n", guess);
    return 0;
}