#define _GNU_SOURCE

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

#include <sys/time.h>
#include <unistd.h>

char *random_salt()
{
    // Failure is fine (assume garbage on stack will do at a push).
    struct timeval tv;
    if (gettimeofday(&tv, NULL) != 0) {
        fprintf(stderr, "Warning: Could not gettimeofday: %m.\n");
        fprintf(stderr, "Just using garbage on stack as randomness.\n");
    }
    srand(tv.tv_sec + tv.tv_usec);

    const char *salt_chars =
        "abcdefghijklmnopqrstuvwxyz"
        "ABCDEFGHIJKLMNOPQRSTUVWXYZ"
        "0123456789" "./";

    static char salt[3] = "\0\0\0";

    salt[0] = salt_chars[rand() % strlen(salt_chars)];
    salt[1] = salt_chars[rand() % strlen(salt_chars)];

    return salt;
}

int main(int argc, char *argv[])
{
    if (argc != 2 && argc != 3) {
        fprintf(stderr, "Usage: crypt PASSPHRASE [SALT]\n");
        fprintf(stderr, "(If no SALT is given, a random one is chosen)\n");
        return 1;
    }

    if (argc == 3 && strlen(argv[2]) != 2) {
        fprintf(stderr, "Error: salt must be 2 bytes long\n");
        return 1;
    }

    char *salt = (argc == 3) ? argv[2] : random_salt();

    char *pass = crypt(argv[1], salt);
    if (pass) {
        printf("%s\n", pass);
        return 0;
    } else {
        fprintf(stderr, "Error: %m\n");
        return 1;
    }
}