1/* $NetBSD: pkcs5_pbkdf2.c,v 1.14 2008/04/28 20:23:08 martin Exp $ */
2
3/*-
4 * Copyright (c) 2002, 2003 The NetBSD Foundation, Inc.
5 * All rights reserved.
6 *
7 * This code is derived from software contributed to The NetBSD Foundation
8 * by Roland C. Dowdeswell.
9 *
10 * Redistribution and use in source and binary forms, with or without
11 * modification, are permitted provided that the following conditions
12 * are met:
13 * 1. Redistributions of source code must retain the above copyright
14 *    notice, this list of conditions and the following disclaimer.
15 * 2. Redistributions in binary form must reproduce the above copyright
16 *    notice, this list of conditions and the following disclaimer in the
17 *    documentation and/or other materials provided with the distribution.
18 *
19 * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
20 * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
21 * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
22 * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
23 * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
24 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
25 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
26 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
27 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
28 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
29 * POSSIBILITY OF SUCH DAMAGE.
30 */
31
32/*
33 * This code is an implementation of PKCS #5 PBKDF2 which is described
34 * in:
35 *
36 * ``PKCS #5 v2.0: Password-Based Cryptography Standard'', RSA Laboratories,
37 * March 25, 1999.
38 *
39 * and can be found at the following URL:
40 *
41 *	http://www.rsasecurity.com/rsalabs/pkcs/pkcs-5/
42 *
43 * It was also republished as RFC 2898.
44 */
45
46
47#include <sys/cdefs.h>
48#ifndef lint
49__RCSID("$NetBSD: pkcs5_pbkdf2.c,v 1.14 2008/04/28 20:23:08 martin Exp $");
50#endif
51
52#include <sys/resource.h>
53#include <sys/endian.h>
54
55#include <assert.h>
56#include <stdlib.h>
57#include <string.h>
58#include <err.h>
59#include <util.h>
60
61#include <openssl/hmac.h>
62
63#include "pkcs5_pbkdf2.h"
64#include "utils.h"
65
66static void	prf_iterate(u_int8_t *, const u_int8_t *, size_t,
67			    const u_int8_t *, size_t, size_t, size_t);
68static int	pkcs5_pbkdf2_time(size_t, size_t);
69
70#define PRF_BLOCKLEN	20
71
72static void
73prf_iterate(u_int8_t *r, const u_int8_t *P, size_t Plen,
74	    const u_int8_t *S, size_t Slen, size_t c, size_t ind)
75{
76	int		 first_time = 1;
77	size_t		 i;
78	size_t		 datalen;
79	unsigned int	 tmplen;
80	u_int8_t	*data;
81	u_int8_t	 tmp[EVP_MAX_MD_SIZE];
82
83	data = emalloc(Slen + 4);
84	(void)memcpy(data, S, Slen);
85	be32enc(data + Slen, ind);
86	datalen = Slen + 4;
87
88	for (i=0; i < c; i++) {
89		(void)HMAC(EVP_sha1(), P, Plen, data, datalen, tmp, &tmplen);
90
91		assert(tmplen == PRF_BLOCKLEN);
92
93		if (first_time) {
94			(void)memcpy(r, tmp, PRF_BLOCKLEN);
95			first_time = 0;
96		} else
97			memxor(r, tmp, PRF_BLOCKLEN);
98		(void)memcpy(data, tmp, PRF_BLOCKLEN);
99		datalen = PRF_BLOCKLEN;
100	}
101	free(data);
102}
103
104/*
105 * pkcs5_pbkdf2 takes all of its lengths in bytes.
106 */
107
108int
109pkcs5_pbkdf2(u_int8_t **r, size_t dkLen, const u_int8_t *P, size_t Plen,
110	     const u_int8_t *S, size_t Slen, size_t c, int compat)
111{
112	size_t	i;
113	size_t	l;
114
115	/* sanity */
116	if (!r)
117		return -1;
118	if (dkLen == 0)
119		return -1;
120	if (c < 1)
121		return -1;
122
123	/* Step 2 */
124	l = (dkLen + PRF_BLOCKLEN - 1) / PRF_BLOCKLEN;
125
126	/* allocate the output */
127	*r = emalloc(l * PRF_BLOCKLEN);
128
129	/* Step 3 */
130	for (i = 0; i < l; i++)
131		prf_iterate(*r + (PRF_BLOCKLEN * i), P, Plen, S, Slen, c,
132			(compat?i:i+1));
133
134	/* Step 4 and 5
135	 *  by the structure of the code, we do not need to concatenate
136	 *  the blocks, they're already concatenated.  We do not extract
137	 *  the first dkLen octets, since we [naturally] assume that the
138	 *  calling function will use only the octets that it needs and
139	 *  the free(3) will free all of the allocated memory.
140	 */
141	return 0;
142}
143
144/*
145 * We use predefined lengths for the password and salt to ensure that
146 * no analysis can be done on the output of the calibration based on
147 * those parameters.  We do not do the same for dkLen because:
148 *	1.  dkLen is known to the attacker if they know the iteration
149 *	    count, and
150 *	2.  using the wrong dkLen will skew the calibration by an
151 *	    integral factor n = (dkLen / 160).
152 */
153
154#define CAL_PASSLEN	   64
155#define CAL_SALTLEN	   64
156#define CAL_TIME	30000		/* Minimum number of microseconds that
157					 * are considered significant.
158					 */
159
160/*
161 * We return the user time in microseconds that c iterations
162 * of the algorithm take.
163 */
164
165static int
166pkcs5_pbkdf2_time(size_t dkLen, size_t c)
167{
168	struct rusage	 start;
169	struct rusage	 end;
170	int		 ret;
171	u_int8_t	*r = NULL;
172	u_int8_t	 P[CAL_PASSLEN];
173	u_int8_t	 S[CAL_SALTLEN];
174
175	(void)getrusage(RUSAGE_SELF, &start);
176	/* XXX compat flag at end to be removed when _OLD keygen method is */
177	ret = pkcs5_pbkdf2(&r, dkLen, P, sizeof(P), S, sizeof(S), c, 0);
178	if (ret)
179		return ret;
180	(void)getrusage(RUSAGE_SELF, &end);
181	free(r);
182
183	return (end.ru_utime.tv_sec - start.ru_utime.tv_sec) * 1000000
184	     + (end.ru_utime.tv_usec - start.ru_utime.tv_usec);
185}
186
187int
188pkcs5_pbkdf2_calibrate(size_t dkLen, int microseconds)
189{
190	size_t	c;
191	int	t = 0;
192	size_t	ret, i;
193
194	for (i = 0; i < 5; i++) {
195		/*
196		 * First we get a meaningfully long time by doubling the
197		 * iteration count until it takes longer than CAL_TIME.  This
198		 * should take approximately 2 * CAL_TIME.
199		 */
200		for (c = 1;; c *= 2) {
201			t = pkcs5_pbkdf2_time(dkLen, c);
202			if (t > CAL_TIME)
203				break;
204		}
205
206		/* Now that we know that, we scale it. */
207		ret = (size_t) ((u_int64_t) c * microseconds / t);
208
209		/*
210		 * Since it is quite important to not get this wrong,
211		 * we test the result.
212		 */
213
214		t = pkcs5_pbkdf2_time(dkLen, ret);
215
216		/* if we are over 5% off, return an error */
217		if (abs(microseconds - t) > (microseconds / 20))
218			continue;
219		return ret;
220	}
221	return -1;
222}
223