crypt.c

/*-
 * SPDX-License-Identifier: BSD-2-Clause
 *
 * Copyright (c) 1999 Mark Murray
 * Copyright (c) 2014 Dag-Erling Smørgrav
 * 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 MARK MURRAY 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 MARK MURRAY 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.
 */

#include <sys/types.h>

#include <string.h>
#include <unistd.h>

#include "crypt.h"

/*
 * List of supported crypt(3) formats.
 *
 * The default algorithm is the last entry in the list (second-to-last
 * array element since the last is a sentinel).  The reason for placing
 * the default last rather than first is that DES needs to be at the
 * bottom for the algorithm guessing logic in crypt(3) to work correctly,
 * and it needs to be the default for backward compatibility.
 */
static const struct crypt_format {
	const char *name;
	int (*func)(const char *, const char *, char *);
	const char *magic;
} crypt_formats[] = {
	{ "md5",	crypt_md5,		"$1$"	},
#ifdef HAS_BLOWFISH
	{ "blf",	crypt_blowfish,		"$2"	},
#endif
	{ "nth",	crypt_nthash,		"$3$"	},
	{ "sha256",	crypt_sha256,		"$5$"	},
	{ "sha512",	crypt_sha512,		"$6$"	},
#ifdef HAS_DES
	{ "des",	crypt_des,		"_"	},
#endif

	/* sentinel */
	{ NULL,		NULL,			NULL	}
};

static const struct crypt_format *crypt_format =
    &crypt_formats[(sizeof crypt_formats / sizeof *crypt_formats) - 2];

#define DES_SALT_ALPHABET \
	"./0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz"

/*
 * Returns the name of the currently selected format.
 */
const char *
crypt_get_format(void)
{

	return (crypt_format->name);
}

/*
 * Selects the format to use for subsequent crypt(3) invocations.
 */
int
crypt_set_format(const char *format)
{
	const struct crypt_format *cf;

	for (cf = crypt_formats; cf->name != NULL; ++cf) {
		if (strcasecmp(cf->name, format) == 0) {
			crypt_format = cf;
			return (1);
		}
	}
	return (0);
}

/*
 * Hash the given password with the given salt.  If the salt begins with a
 * magic string (e.g. "$6$" for sha512), the corresponding format is used;
 * otherwise, the currently selected format is used.
 */
char *
crypt_r(const char *passwd, const char *salt, struct crypt_data *data)
{
	const struct crypt_format *cf;
	int (*func)(const char *, const char *, char *);
#ifdef HAS_DES
	int len;
#endif

	for (cf = crypt_formats; cf->name != NULL; ++cf)
		if (cf->magic != NULL && strstr(salt, cf->magic) == salt) {
			func = cf->func;
			goto match;
		}
#ifdef HAS_DES
	len = strlen(salt);
	if ((len == 13 || len == 2) && strspn(salt, DES_SALT_ALPHABET) == len) {
		func = crypt_des;
		goto match;
	}
#endif
	func = crypt_format->func;
match:
	if (func(passwd, salt, data->__buf) != 0)
		return (NULL);
	return (data->__buf);
}

char *
crypt(const char *passwd, const char *salt)
{
	static struct crypt_data data;

	return (crypt_r(passwd, salt, &data));
}