1 /* $OpenBSD: bn_mod.c,v 1.12 2017/01/29 17:49:22 beck Exp $ */
2 /* Includes code written by Lenka Fibikova <fibikova@exp-math.uni-essen.de>
3 * for the OpenSSL project. */
4 /* ====================================================================
5 * Copyright (c) 1998-2000 The OpenSSL Project. All rights reserved.
6 *
7 * Redistribution and use in source and binary forms, with or without
8 * modification, are permitted provided that the following conditions
9 * are met:
10 *
11 * 1. Redistributions of source code must retain the above copyright
12 * notice, this list of conditions and the following disclaimer.
13 *
14 * 2. Redistributions in binary form must reproduce the above copyright
15 * notice, this list of conditions and the following disclaimer in
16 * the documentation and/or other materials provided with the
17 * distribution.
18 *
19 * 3. All advertising materials mentioning features or use of this
20 * software must display the following acknowledgment:
21 * "This product includes software developed by the OpenSSL Project
22 * for use in the OpenSSL Toolkit. (http://www.openssl.org/)"
23 *
24 * 4. The names "OpenSSL Toolkit" and "OpenSSL Project" must not be used to
25 * endorse or promote products derived from this software without
26 * prior written permission. For written permission, please contact
27 * openssl-core@openssl.org.
28 *
29 * 5. Products derived from this software may not be called "OpenSSL"
30 * nor may "OpenSSL" appear in their names without prior written
31 * permission of the OpenSSL Project.
32 *
33 * 6. Redistributions of any form whatsoever must retain the following
34 * acknowledgment:
35 * "This product includes software developed by the OpenSSL Project
36 * for use in the OpenSSL Toolkit (http://www.openssl.org/)"
37 *
38 * THIS SOFTWARE IS PROVIDED BY THE OpenSSL PROJECT ``AS IS'' AND ANY
39 * EXPRESSED OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
40 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
41 * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE OpenSSL PROJECT OR
42 * ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
43 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
44 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
45 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
46 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
47 * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
48 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
49 * OF THE POSSIBILITY OF SUCH DAMAGE.
50 * ====================================================================
51 *
52 * This product includes cryptographic software written by Eric Young
53 * (eay@cryptsoft.com). This product includes software written by Tim
54 * Hudson (tjh@cryptsoft.com).
55 *
56 */
57 /* Copyright (C) 1995-1998 Eric Young (eay@cryptsoft.com)
58 * All rights reserved.
59 *
60 * This package is an SSL implementation written
61 * by Eric Young (eay@cryptsoft.com).
62 * The implementation was written so as to conform with Netscapes SSL.
63 *
64 * This library is free for commercial and non-commercial use as long as
65 * the following conditions are aheared to. The following conditions
66 * apply to all code found in this distribution, be it the RC4, RSA,
67 * lhash, DES, etc., code; not just the SSL code. The SSL documentation
68 * included with this distribution is covered by the same copyright terms
69 * except that the holder is Tim Hudson (tjh@cryptsoft.com).
70 *
71 * Copyright remains Eric Young's, and as such any Copyright notices in
72 * the code are not to be removed.
73 * If this package is used in a product, Eric Young should be given attribution
74 * as the author of the parts of the library used.
75 * This can be in the form of a textual message at program startup or
76 * in documentation (online or textual) provided with the package.
77 *
78 * Redistribution and use in source and binary forms, with or without
79 * modification, are permitted provided that the following conditions
80 * are met:
81 * 1. Redistributions of source code must retain the copyright
82 * notice, this list of conditions and the following disclaimer.
83 * 2. Redistributions in binary form must reproduce the above copyright
84 * notice, this list of conditions and the following disclaimer in the
85 * documentation and/or other materials provided with the distribution.
86 * 3. All advertising materials mentioning features or use of this software
87 * must display the following acknowledgement:
88 * "This product includes cryptographic software written by
89 * Eric Young (eay@cryptsoft.com)"
90 * The word 'cryptographic' can be left out if the rouines from the library
91 * being used are not cryptographic related :-).
92 * 4. If you include any Windows specific code (or a derivative thereof) from
93 * the apps directory (application code) you must include an acknowledgement:
94 * "This product includes software written by Tim Hudson (tjh@cryptsoft.com)"
95 *
96 * THIS SOFTWARE IS PROVIDED BY ERIC YOUNG ``AS IS'' AND
97 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
98 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
99 * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
100 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
101 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
102 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
103 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
104 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
105 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
106 * SUCH DAMAGE.
107 *
108 * The licence and distribution terms for any publically available version or
109 * derivative of this code cannot be changed. i.e. this code cannot simply be
110 * copied and put under another distribution licence
111 * [including the GNU Public Licence.]
112 */
113
114 #include <openssl/err.h>
115
116 #include "bn_lcl.h"
117
118 int
BN_nnmod(BIGNUM * r,const BIGNUM * m,const BIGNUM * d,BN_CTX * ctx)119 BN_nnmod(BIGNUM *r, const BIGNUM *m, const BIGNUM *d, BN_CTX *ctx)
120 {
121 /* like BN_mod, but returns non-negative remainder
122 * (i.e., 0 <= r < |d| always holds) */
123
124 if (!(BN_mod_ct(r, m,d, ctx)))
125 return 0;
126 if (!r->neg)
127 return 1;
128 /* now -|d| < r < 0, so we have to set r := r + |d| */
129 if (d->neg)
130 return BN_sub(r, r, d);
131 else
132 return BN_add(r, r, d);
133 }
134
135 int
BN_mod_add(BIGNUM * r,const BIGNUM * a,const BIGNUM * b,const BIGNUM * m,BN_CTX * ctx)136 BN_mod_add(BIGNUM *r, const BIGNUM *a, const BIGNUM *b, const BIGNUM *m,
137 BN_CTX *ctx)
138 {
139 if (!BN_add(r, a, b))
140 return 0;
141 return BN_nnmod(r, r, m, ctx);
142 }
143
144 /* BN_mod_add variant that may be used if both a and b are non-negative
145 * and less than m */
146 int
BN_mod_add_quick(BIGNUM * r,const BIGNUM * a,const BIGNUM * b,const BIGNUM * m)147 BN_mod_add_quick(BIGNUM *r, const BIGNUM *a, const BIGNUM *b, const BIGNUM *m)
148 {
149 if (!BN_uadd(r, a, b))
150 return 0;
151 if (BN_ucmp(r, m) >= 0)
152 return BN_usub(r, r, m);
153 return 1;
154 }
155
156 int
BN_mod_sub(BIGNUM * r,const BIGNUM * a,const BIGNUM * b,const BIGNUM * m,BN_CTX * ctx)157 BN_mod_sub(BIGNUM *r, const BIGNUM *a, const BIGNUM *b, const BIGNUM *m,
158 BN_CTX *ctx)
159 {
160 if (!BN_sub(r, a, b))
161 return 0;
162 return BN_nnmod(r, r, m, ctx);
163 }
164
165 /* BN_mod_sub variant that may be used if both a and b are non-negative
166 * and less than m */
167 int
BN_mod_sub_quick(BIGNUM * r,const BIGNUM * a,const BIGNUM * b,const BIGNUM * m)168 BN_mod_sub_quick(BIGNUM *r, const BIGNUM *a, const BIGNUM *b, const BIGNUM *m)
169 {
170 if (!BN_sub(r, a, b))
171 return 0;
172 if (r->neg)
173 return BN_add(r, r, m);
174 return 1;
175 }
176
177 /* slow but works */
178 int
BN_mod_mul(BIGNUM * r,const BIGNUM * a,const BIGNUM * b,const BIGNUM * m,BN_CTX * ctx)179 BN_mod_mul(BIGNUM *r, const BIGNUM *a, const BIGNUM *b, const BIGNUM *m,
180 BN_CTX *ctx)
181 {
182 BIGNUM *t;
183 int ret = 0;
184
185 bn_check_top(a);
186 bn_check_top(b);
187 bn_check_top(m);
188
189 BN_CTX_start(ctx);
190 if ((t = BN_CTX_get(ctx)) == NULL)
191 goto err;
192 if (a == b) {
193 if (!BN_sqr(t, a, ctx))
194 goto err;
195 } else {
196 if (!BN_mul(t, a,b, ctx))
197 goto err;
198 }
199 if (!BN_nnmod(r, t,m, ctx))
200 goto err;
201 bn_check_top(r);
202 ret = 1;
203
204 err:
205 BN_CTX_end(ctx);
206 return (ret);
207 }
208
209 int
BN_mod_sqr(BIGNUM * r,const BIGNUM * a,const BIGNUM * m,BN_CTX * ctx)210 BN_mod_sqr(BIGNUM *r, const BIGNUM *a, const BIGNUM *m, BN_CTX *ctx)
211 {
212 if (!BN_sqr(r, a, ctx))
213 return 0;
214 /* r->neg == 0, thus we don't need BN_nnmod */
215 return BN_mod_ct(r, r, m, ctx);
216 }
217
218 int
BN_mod_lshift1(BIGNUM * r,const BIGNUM * a,const BIGNUM * m,BN_CTX * ctx)219 BN_mod_lshift1(BIGNUM *r, const BIGNUM *a, const BIGNUM *m, BN_CTX *ctx)
220 {
221 if (!BN_lshift1(r, a))
222 return 0;
223 bn_check_top(r);
224 return BN_nnmod(r, r, m, ctx);
225 }
226
227 /* BN_mod_lshift1 variant that may be used if a is non-negative
228 * and less than m */
229 int
BN_mod_lshift1_quick(BIGNUM * r,const BIGNUM * a,const BIGNUM * m)230 BN_mod_lshift1_quick(BIGNUM *r, const BIGNUM *a, const BIGNUM *m)
231 {
232 if (!BN_lshift1(r, a))
233 return 0;
234 bn_check_top(r);
235 if (BN_cmp(r, m) >= 0)
236 return BN_sub(r, r, m);
237 return 1;
238 }
239
240 int
BN_mod_lshift(BIGNUM * r,const BIGNUM * a,int n,const BIGNUM * m,BN_CTX * ctx)241 BN_mod_lshift(BIGNUM *r, const BIGNUM *a, int n, const BIGNUM *m, BN_CTX *ctx)
242 {
243 BIGNUM *abs_m = NULL;
244 int ret;
245
246 if (!BN_nnmod(r, a, m, ctx))
247 return 0;
248
249 if (m->neg) {
250 abs_m = BN_dup(m);
251 if (abs_m == NULL)
252 return 0;
253 abs_m->neg = 0;
254 }
255
256 ret = BN_mod_lshift_quick(r, r, n, (abs_m ? abs_m : m));
257 bn_check_top(r);
258
259 BN_free(abs_m);
260 return ret;
261 }
262
263 /* BN_mod_lshift variant that may be used if a is non-negative
264 * and less than m */
265 int
BN_mod_lshift_quick(BIGNUM * r,const BIGNUM * a,int n,const BIGNUM * m)266 BN_mod_lshift_quick(BIGNUM *r, const BIGNUM *a, int n, const BIGNUM *m)
267 {
268 if (r != a) {
269 if (BN_copy(r, a) == NULL)
270 return 0;
271 }
272
273 while (n > 0) {
274 int max_shift;
275
276 /* 0 < r < m */
277 max_shift = BN_num_bits(m) - BN_num_bits(r);
278 /* max_shift >= 0 */
279
280 if (max_shift < 0) {
281 BNerror(BN_R_INPUT_NOT_REDUCED);
282 return 0;
283 }
284
285 if (max_shift > n)
286 max_shift = n;
287
288 if (max_shift) {
289 if (!BN_lshift(r, r, max_shift))
290 return 0;
291 n -= max_shift;
292 } else {
293 if (!BN_lshift1(r, r))
294 return 0;
295 --n;
296 }
297
298 /* BN_num_bits(r) <= BN_num_bits(m) */
299
300 if (BN_cmp(r, m) >= 0) {
301 if (!BN_sub(r, r, m))
302 return 0;
303 }
304 }
305 bn_check_top(r);
306
307 return 1;
308 }
309