1/* $OpenBSD: bn_rand.c,v 1.30 2024/03/16 20:42:33 tb Exp $ */
2/* Copyright (C) 1995-1998 Eric Young (eay@cryptsoft.com)
3 * All rights reserved.
4 *
5 * This package is an SSL implementation written
6 * by Eric Young (eay@cryptsoft.com).
7 * The implementation was written so as to conform with Netscapes SSL.
8 *
9 * This library is free for commercial and non-commercial use as long as
10 * the following conditions are aheared to.  The following conditions
11 * apply to all code found in this distribution, be it the RC4, RSA,
12 * lhash, DES, etc., code; not just the SSL code.  The SSL documentation
13 * included with this distribution is covered by the same copyright terms
14 * except that the holder is Tim Hudson (tjh@cryptsoft.com).
15 *
16 * Copyright remains Eric Young's, and as such any Copyright notices in
17 * the code are not to be removed.
18 * If this package is used in a product, Eric Young should be given attribution
19 * as the author of the parts of the library used.
20 * This can be in the form of a textual message at program startup or
21 * in documentation (online or textual) provided with the package.
22 *
23 * Redistribution and use in source and binary forms, with or without
24 * modification, are permitted provided that the following conditions
25 * are met:
26 * 1. Redistributions of source code must retain the copyright
27 *    notice, this list of conditions and the following disclaimer.
28 * 2. Redistributions in binary form must reproduce the above copyright
29 *    notice, this list of conditions and the following disclaimer in the
30 *    documentation and/or other materials provided with the distribution.
31 * 3. All advertising materials mentioning features or use of this software
32 *    must display the following acknowledgement:
33 *    "This product includes cryptographic software written by
34 *     Eric Young (eay@cryptsoft.com)"
35 *    The word 'cryptographic' can be left out if the rouines from the library
36 *    being used are not cryptographic related :-).
37 * 4. If you include any Windows specific code (or a derivative thereof) from
38 *    the apps directory (application code) you must include an acknowledgement:
39 *    "This product includes software written by Tim Hudson (tjh@cryptsoft.com)"
40 *
41 * THIS SOFTWARE IS PROVIDED BY ERIC YOUNG ``AS IS'' AND
42 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
43 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
44 * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
45 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
46 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
47 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
48 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
49 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
50 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
51 * SUCH DAMAGE.
52 *
53 * The licence and distribution terms for any publically available version or
54 * derivative of this code cannot be changed.  i.e. this code cannot simply be
55 * copied and put under another distribution licence
56 * [including the GNU Public Licence.]
57 */
58/* ====================================================================
59 * Copyright (c) 1998-2001 The OpenSSL Project.  All rights reserved.
60 *
61 * Redistribution and use in source and binary forms, with or without
62 * modification, are permitted provided that the following conditions
63 * are met:
64 *
65 * 1. Redistributions of source code must retain the above copyright
66 *    notice, this list of conditions and the following disclaimer.
67 *
68 * 2. Redistributions in binary form must reproduce the above copyright
69 *    notice, this list of conditions and the following disclaimer in
70 *    the documentation and/or other materials provided with the
71 *    distribution.
72 *
73 * 3. All advertising materials mentioning features or use of this
74 *    software must display the following acknowledgment:
75 *    "This product includes software developed by the OpenSSL Project
76 *    for use in the OpenSSL Toolkit. (http://www.openssl.org/)"
77 *
78 * 4. The names "OpenSSL Toolkit" and "OpenSSL Project" must not be used to
79 *    endorse or promote products derived from this software without
80 *    prior written permission. For written permission, please contact
81 *    openssl-core@openssl.org.
82 *
83 * 5. Products derived from this software may not be called "OpenSSL"
84 *    nor may "OpenSSL" appear in their names without prior written
85 *    permission of the OpenSSL Project.
86 *
87 * 6. Redistributions of any form whatsoever must retain the following
88 *    acknowledgment:
89 *    "This product includes software developed by the OpenSSL Project
90 *    for use in the OpenSSL Toolkit (http://www.openssl.org/)"
91 *
92 * THIS SOFTWARE IS PROVIDED BY THE OpenSSL PROJECT ``AS IS'' AND ANY
93 * EXPRESSED OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
94 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
95 * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE OpenSSL PROJECT OR
96 * ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
97 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
98 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
99 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
100 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
101 * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
102 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
103 * OF THE POSSIBILITY OF SUCH DAMAGE.
104 * ====================================================================
105 *
106 * This product includes cryptographic software written by Eric Young
107 * (eay@cryptsoft.com).  This product includes software written by Tim
108 * Hudson (tjh@cryptsoft.com).
109 *
110 */
111
112#include <limits.h>
113#include <stdio.h>
114#include <stdlib.h>
115#include <string.h>
116#include <time.h>
117
118#include <openssl/err.h>
119
120#include "bn_local.h"
121
122static int
123bnrand(int pseudorand, BIGNUM *rnd, int bits, int top, int bottom)
124{
125	unsigned char *buf = NULL;
126	int ret = 0, bit, bytes, mask;
127
128	if (rnd == NULL) {
129		BNerror(ERR_R_PASSED_NULL_PARAMETER);
130		return (0);
131	}
132
133	if (bits < 0 || (bits == 1 && top > 0)) {
134		BNerror(BN_R_BITS_TOO_SMALL);
135		return (0);
136	}
137	if (bits > INT_MAX - 7) {
138		BNerror(BN_R_BIGNUM_TOO_LONG);
139		return (0);
140	}
141
142	if (bits == 0) {
143		BN_zero(rnd);
144		return (1);
145	}
146
147	bytes = (bits + 7) / 8;
148	bit = (bits - 1) % 8;
149	mask = 0xff << (bit + 1);
150
151	buf = malloc(bytes);
152	if (buf == NULL) {
153		BNerror(ERR_R_MALLOC_FAILURE);
154		goto err;
155	}
156
157	/* make a random number and set the top and bottom bits */
158	arc4random_buf(buf, bytes);
159
160#if 1
161	if (pseudorand == 2) {
162		/* generate patterns that are more likely to trigger BN
163		   library bugs */
164		int i;
165		unsigned char c;
166
167		for (i = 0; i < bytes; i++) {
168			arc4random_buf(&c, 1);
169			if (c >= 128 && i > 0)
170				buf[i] = buf[i - 1];
171			else if (c < 42)
172				buf[i] = 0;
173			else if (c < 84)
174				buf[i] = 255;
175		}
176	}
177#endif
178
179	if (top > 0) {
180		if (bit == 0) {
181			buf[0] = 1;
182			buf[1] |= 0x80;
183		} else {
184			buf[0] |= (3 << (bit - 1));
185		}
186	}
187	if (top == 0)
188		buf[0] |= (1 << bit);
189	buf[0] &= ~mask;
190	if (bottom) /* set bottom bit if requested */
191		buf[bytes - 1] |= 1;
192	if (BN_bin2bn(buf, bytes, rnd) == NULL)
193		goto err;
194	ret = 1;
195
196err:
197	freezero(buf, bytes);
198	return (ret);
199}
200
201int
202BN_rand(BIGNUM *rnd, int bits, int top, int bottom)
203{
204	return bnrand(0, rnd, bits, top, bottom);
205}
206LCRYPTO_ALIAS(BN_rand);
207
208int
209BN_pseudo_rand(BIGNUM *rnd, int bits, int top, int bottom)
210{
211	return bnrand(1, rnd, bits, top, bottom);
212}
213LCRYPTO_ALIAS(BN_pseudo_rand);
214
215#if 1
216int
217BN_bntest_rand(BIGNUM *rnd, int bits, int top, int bottom)
218{
219	return bnrand(2, rnd, bits, top, bottom);
220}
221#endif
222
223
224/* random number r:  0 <= r < range */
225static int
226bn_rand_range(int pseudo, BIGNUM *r, const BIGNUM *range)
227{
228	int (*bn_rand)(BIGNUM *, int, int, int) = pseudo ? BN_pseudo_rand : BN_rand;
229	int n;
230	int count = 100;
231
232	if (range->neg || BN_is_zero(range)) {
233		BNerror(BN_R_INVALID_RANGE);
234		return 0;
235	}
236
237	n = BN_num_bits(range); /* n > 0 */
238
239	/* BN_is_bit_set(range, n - 1) always holds */
240
241	if (n == 1)
242		BN_zero(r);
243	else if (!BN_is_bit_set(range, n - 2) && !BN_is_bit_set(range, n - 3)) {
244		/* range = 100..._2,
245		 * so  3*range (= 11..._2)  is exactly one bit longer than  range */
246		do {
247			if (!bn_rand(r, n + 1, -1, 0))
248				return 0;
249			/* If  r < 3*range,  use  r := r MOD range
250			 * (which is either  r, r - range,  or  r - 2*range).
251			 * Otherwise, iterate once more.
252			 * Since  3*range = 11..._2, each iteration succeeds with
253			 * probability >= .75. */
254			if (BN_cmp(r, range) >= 0) {
255				if (!BN_sub(r, r, range))
256					return 0;
257				if (BN_cmp(r, range) >= 0)
258					if (!BN_sub(r, r, range))
259						return 0;
260			}
261
262			if (!--count) {
263				BNerror(BN_R_TOO_MANY_ITERATIONS);
264				return 0;
265			}
266
267		} while (BN_cmp(r, range) >= 0);
268	} else {
269		do {
270			/* range = 11..._2  or  range = 101..._2 */
271			if (!bn_rand(r, n, -1, 0))
272				return 0;
273
274			if (!--count) {
275				BNerror(BN_R_TOO_MANY_ITERATIONS);
276				return 0;
277			}
278		} while (BN_cmp(r, range) >= 0);
279	}
280
281	return 1;
282}
283
284int
285BN_rand_range(BIGNUM *r, const BIGNUM *range)
286{
287	return bn_rand_range(0, r, range);
288}
289LCRYPTO_ALIAS(BN_rand_range);
290
291int
292bn_rand_in_range(BIGNUM *rnd, const BIGNUM *lower_inc, const BIGNUM *upper_exc)
293{
294	BIGNUM *len;
295	int ret = 0;
296
297	if ((len = BN_new()) == NULL)
298		goto err;
299	if (!BN_sub(len, upper_exc, lower_inc))
300		goto err;
301	if (!BN_rand_range(rnd, len))
302		goto err;
303	if (!BN_add(rnd, rnd, lower_inc))
304		goto err;
305
306	ret = 1;
307
308 err:
309	BN_free(len);
310
311	return ret;
312}
313
314int
315bn_rand_interval(BIGNUM *rnd, BN_ULONG lower_word, const BIGNUM *upper_exc)
316{
317	BIGNUM *lower_inc = NULL;
318	int ret = 0;
319
320	if ((lower_inc = BN_new()) == NULL)
321		goto err;
322	if (!BN_set_word(lower_inc, lower_word))
323		goto err;
324	if (!bn_rand_in_range(rnd, lower_inc, upper_exc))
325		goto err;
326
327	ret = 1;
328
329 err:
330	BN_free(lower_inc);
331
332	return ret;
333}
334
335int
336BN_pseudo_rand_range(BIGNUM *r, const BIGNUM *range)
337{
338	return bn_rand_range(1, r, range);
339}
340LCRYPTO_ALIAS(BN_pseudo_rand_range);
341