1/* $NetBSD: pkcs5_pbkdf2.c,v 1.17 2021/11/22 16:04:03 nia 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 1.17 2021/11/22 16:04:03 nia Exp $");
50#endif
51
52#include <sys/resource.h>
53#include <sys/endian.h>
54
55#include <assert.h>
56#include <stdio.h>
57#include <stdlib.h>
58#include <string.h>
59#include <err.h>
60#include <util.h>
61
62#include "pkcs5_pbkdf2.h"
63#include "utils.h"
64
65static void	prf_iterate(u_int8_t *, const u_int8_t *, size_t,
66			    const u_int8_t *, size_t, size_t, size_t);
67static int	pkcs5_pbkdf2_time(size_t, size_t);
68
69#define PRF_BLOCKLEN	20
70
71static void
72prf_iterate(u_int8_t *r, const u_int8_t *P, size_t Plen,
73	    const u_int8_t *S, size_t Slen, size_t c, size_t ind)
74{
75	int		 first_time = 1;
76	size_t		 i;
77	size_t		 datalen;
78	ssize_t		 tmplen;
79	u_int8_t	*data;
80	u_int8_t	 tmp[128];
81
82	data = emalloc(Slen + 4);
83	(void)memcpy(data, S, Slen);
84	be32enc(data + Slen, ind);
85	datalen = Slen + 4;
86
87	for (i=0; i < c; i++) {
88		tmplen = hmac("sha1", P, Plen, data, datalen, tmp, sizeof(tmp));
89
90		assert(tmplen == PRF_BLOCKLEN);
91
92		if (first_time) {
93			(void)memcpy(r, tmp, PRF_BLOCKLEN);
94			first_time = 0;
95		} else
96			memxor(r, tmp, PRF_BLOCKLEN);
97		(void)memcpy(data, tmp, PRF_BLOCKLEN);
98		datalen = PRF_BLOCKLEN;
99	}
100	free(data);
101}
102
103/*
104 * pkcs5_pbkdf2 takes all of its lengths in bytes.
105 */
106
107int
108pkcs5_pbkdf2(u_int8_t **r, size_t dkLen, const u_int8_t *P, size_t Plen,
109	     const u_int8_t *S, size_t Slen, size_t c, int compat)
110{
111	size_t	i;
112	size_t	l;
113
114	/* sanity */
115	if (!r)
116		return -1;
117	if (dkLen == 0)
118		return -1;
119	if (c < 1)
120		return -1;
121
122	/* Step 2 */
123	l = (dkLen + PRF_BLOCKLEN - 1) / PRF_BLOCKLEN;
124
125	/* allocate the output */
126	*r = emalloc(l * PRF_BLOCKLEN);
127
128	/* Step 3 */
129	for (i = 0; i < l; i++)
130		prf_iterate(*r + (PRF_BLOCKLEN * i), P, Plen, S, Slen, c,
131			(compat?i:i+1));
132
133	/* Step 4 and 5
134	 *  by the structure of the code, we do not need to concatenate
135	 *  the blocks, they're already concatenated.  We do not extract
136	 *  the first dkLen octets, since we [naturally] assume that the
137	 *  calling function will use only the octets that it needs and
138	 *  the free(3) will free all of the allocated memory.
139	 */
140	return 0;
141}
142
143/*
144 * We use predefined lengths for the password and salt to ensure that
145 * no analysis can be done on the output of the calibration based on
146 * those parameters.  We do not do the same for dkLen because:
147 *	1.  dkLen is known to the attacker if they know the iteration
148 *	    count, and
149 *	2.  using the wrong dkLen will skew the calibration by an
150 *	    integral factor n = (dkLen / 160).
151 */
152
153#define CAL_PASSLEN	   64
154#define CAL_SALTLEN	   64
155#define CAL_TIME	30000		/* Minimum number of microseconds that
156					 * are considered significant.
157					 */
158
159/*
160 * We return the user time in microseconds that c iterations
161 * of the algorithm take.
162 */
163
164static int
165pkcs5_pbkdf2_time(size_t dkLen, size_t c)
166{
167	struct rusage	 start;
168	struct rusage	 end;
169	int		 ret;
170	u_int8_t	*r = NULL;
171	u_int8_t	 P[CAL_PASSLEN];
172	u_int8_t	 S[CAL_SALTLEN];
173
174	(void)getrusage(RUSAGE_SELF, &start);
175	/* XXX compat flag at end to be removed when _OLD keygen method is */
176	ret = pkcs5_pbkdf2(&r, dkLen, P, sizeof(P), S, sizeof(S), c, 0);
177	if (ret)
178		return ret;
179	(void)getrusage(RUSAGE_SELF, &end);
180	free(r);
181
182	return (end.ru_utime.tv_sec - start.ru_utime.tv_sec) * 1000000
183	     + (end.ru_utime.tv_usec - start.ru_utime.tv_usec);
184}
185
186int
187pkcs5_pbkdf2_calibrate(size_t dkLen, int microseconds)
188{
189	size_t	c;
190	int	t = 0;
191	size_t	ret, i;
192
193	fprintf(stderr, "pkcs5_pbkdf2: calibrating iterations...");
194
195	for (i = 0; i < 5; i++) {
196		/*
197		 * First we get a meaningfully long time by doubling the
198		 * iteration count until it takes longer than CAL_TIME.  This
199		 * should take approximately 2 * CAL_TIME.
200		 */
201		for (c = 1;; c *= 2) {
202			t = pkcs5_pbkdf2_time(dkLen, c);
203			fprintf(stderr, ".");
204			if (t > CAL_TIME)
205				break;
206		}
207
208		/* Now that we know that, we scale it. */
209		ret = (size_t) ((u_int64_t) c * microseconds / t);
210
211		/*
212		 * Since it is quite important to not get this wrong,
213		 * we test the result.
214		 */
215
216		t = pkcs5_pbkdf2_time(dkLen, ret);
217
218		/* if we are over 5% off, return an error */
219		if (abs(microseconds - t) > (microseconds / 20))
220			continue;
221		fprintf(stderr, " done\n");
222		return ret;
223	}
224	fprintf(stderr, " failed\n");
225	return -1;
226}
227