/*-
 * Copyright (c) 2013 Jung-uk Kim <jkim@FreeBSD.org>
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 *
 * $FreeBSD$
 */

#include <err.h>
#include <libgen.h>
#include <limits.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sysexits.h>
#include <unistd.h>

/* Mostly stolen from libpam's pam_unix.c */

#define	SALTSIZE	32

static unsigned char itoa64[] = 	/* 0 ... 63 => ascii - 64 */
	"./0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz";

static void
to64(char *s, long v, int n)
{

	while (--n >= 0) {
		*s++ = itoa64[v&0x3f];
		v >>= 6;
	}
}
                        
/* Salt suitable for traditional DES and MD5 */
static void
makesalt(char salt[SALTSIZE + 1])
{
	int i;

	/* These are not really random numbers, they are just
	 * numbers that change to thwart construction of a
	 * dictionary.
	 */
	for (i = 0; i < SALTSIZE; i += 4)
		to64(&salt[i], arc4random(), 4);
	salt[SALTSIZE] = '\0';
}

/* End of the stolen code */

static void
usage(const char *prog)
{

	printf("Usage: %s [format]\n", basename(prog));
}

static char *
read_password(const char *prompt)
{
	char *passwd;

	passwd = strdup(getpass(prompt));
	if (passwd == NULL)
		errx(EX_OSERR, "out of memory");
	return (passwd);
}

int
main(int argc, char *argv[])
{
	char salt[SALTSIZE + 1];
	char *passwd[2];
	const char *opt, *prog;

	prog = argv[0];
	if (argc < 1 || argc > 2) {
		usage(prog);
		exit(EX_USAGE);
	}
	if (argc == 2) {
		opt = argv[1];
		if (strcmp(opt, "-h") == 0 || strcmp(opt, "help") == 0) {
			usage(prog);
			return (EX_OK);
		}
		if (crypt_set_format(opt) == 0)
			errx(EX_DATAERR, "invalid crypto %s", opt);
	} else
		opt = crypt_get_format();
	printf("Generating password hash in %s format.\n", opt);
	for (;;) {
		passwd[0] = read_password("\nType password: ");
		passwd[1] = read_password("Re-type password: ");
		if (strcmp(passwd[0], passwd[1]) == 0) {
			free(passwd[1]);
			break;
		}
		free(passwd[0]);
		free(passwd[1]);
		printf("\nPasswords do not match.  Please try again.\n");
	}
	makesalt(salt);
	passwd[1] = crypt(passwd[0], salt);
	printf("\n%s\n", passwd[1]);
	free(passwd[0]);
	return (EX_OK);
}