xref: /openbsd-src/lib/libcrypto/bn/bn_rand.c (revision 091f637a5964825bc94bebd06624b0aea21eb127)
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 
122 static int
bnrand(int pseudorand,BIGNUM * rnd,int bits,int top,int bottom)123 bnrand(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 
196 err:
197 	freezero(buf, bytes);
198 	return (ret);
199 }
200 
201 int
BN_rand(BIGNUM * rnd,int bits,int top,int bottom)202 BN_rand(BIGNUM *rnd, int bits, int top, int bottom)
203 {
204 	return bnrand(0, rnd, bits, top, bottom);
205 }
206 LCRYPTO_ALIAS(BN_rand);
207 
208 int
BN_pseudo_rand(BIGNUM * rnd,int bits,int top,int bottom)209 BN_pseudo_rand(BIGNUM *rnd, int bits, int top, int bottom)
210 {
211 	return bnrand(1, rnd, bits, top, bottom);
212 }
213 LCRYPTO_ALIAS(BN_pseudo_rand);
214 
215 #if 1
216 int
BN_bntest_rand(BIGNUM * rnd,int bits,int top,int bottom)217 BN_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 */
225 static int
bn_rand_range(int pseudo,BIGNUM * r,const BIGNUM * range)226 bn_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 
284 int
BN_rand_range(BIGNUM * r,const BIGNUM * range)285 BN_rand_range(BIGNUM *r, const BIGNUM *range)
286 {
287 	return bn_rand_range(0, r, range);
288 }
289 LCRYPTO_ALIAS(BN_rand_range);
290 
291 int
bn_rand_in_range(BIGNUM * rnd,const BIGNUM * lower_inc,const BIGNUM * upper_exc)292 bn_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 
314 int
bn_rand_interval(BIGNUM * rnd,BN_ULONG lower_word,const BIGNUM * upper_exc)315 bn_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 
335 int
BN_pseudo_rand_range(BIGNUM * r,const BIGNUM * range)336 BN_pseudo_rand_range(BIGNUM *r, const BIGNUM *range)
337 {
338 	return bn_rand_range(1, r, range);
339 }
340 LCRYPTO_ALIAS(BN_pseudo_rand_range);
341