/*
 * Copyright (C) 2010 Christian Franke <nobody@nowhere.ws>
 *
 * Compile this program with something like:
 * cc -o crypt crypt.c -lcrypt
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor,
 * Boston, MA  02110-1301  USA
 *
 */

#define _XOPEN_SOURCE 500
#include <unistd.h>
#include <stdio.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <stdlib.h>
#include <pwd.h>
#include <errno.h>
#include <string.h>

static const char salt_chars[] = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789./";

int main(int argc, char* argv[])
{
	char salt[4];
	char *passwd;
	char *getpass_ret;
	int i;

	int fd = open("/dev/random", O_RDONLY);

	if (fd < 0) {
		perror("Error getting random source for salt");
		exit(EXIT_FAILURE);
	}

	for (i = 0; i < 4; ++i) {
		ssize_t red;

		do {
			red = read(fd, salt + i, sizeof(salt[0]));
			if (red < 0) {
				perror("Error getting random bytes for salt");
				exit(EXIT_FAILURE);
			}
		} while (red < sizeof(salt[0]));
		salt[i] = salt_chars[salt[i]
				% (sizeof(salt_chars) / sizeof(salt_chars[0]))];
	}

	close(fd);

	getpass_ret = getpass("Enter password: ");
	if (!getpass_ret) {
		perror("Error getting password");
		exit(EXIT_FAILURE);
	}
	passwd = strdup(getpass_ret);

	getpass_ret = getpass("Reenter password: ");
	if (!getpass_ret) {
		perror("Error getting password");
		exit(EXIT_FAILURE);
	}

	if (strcmp(passwd, getpass_ret)) {
		fprintf(stderr, "Error: the passwords don't match.\n");
		exit(EXIT_FAILURE);
	}

	memset(passwd, 0, strlen(passwd));
	free(passwd);

	passwd = crypt(getpass_ret, salt);

	if (!passwd) {
		perror("Error calculating crypt-pw");
		exit(EXIT_FAILURE);
	}

	printf("CRYPT-PW %s\n", passwd);
	memset(passwd, 0, strlen(passwd));
	memset(getpass_ret, 0, strlen(getpass_ret));

	exit(EXIT_SUCCESS);
}