1 /* $OpenBSD: bn_mod.c,v 1.22 2023/07/08 12:21:58 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_local.h"
117
118 int
BN_mod_ct(BIGNUM * r,const BIGNUM * a,const BIGNUM * m,BN_CTX * ctx)119 BN_mod_ct(BIGNUM *r, const BIGNUM *a, const BIGNUM *m, BN_CTX *ctx)
120 {
121 return BN_div_ct(NULL, r, a, m, ctx);
122 }
123
124 int
BN_mod_nonct(BIGNUM * r,const BIGNUM * a,const BIGNUM * m,BN_CTX * ctx)125 BN_mod_nonct(BIGNUM *r, const BIGNUM *a, const BIGNUM *m, BN_CTX *ctx)
126 {
127 return BN_div_nonct(NULL, r, a, m, ctx);
128 }
129
130 /*
131 * BN_nnmod() is like BN_mod(), but always returns a non-negative remainder
132 * (that is 0 <= r < |m| always holds). If both a and m have the same sign then
133 * the result is already non-negative. Otherwise, -|m| < r < 0, which needs to
134 * be adjusted as r := r + |m|. This equates to r := |m| - |r|.
135 */
136 int
BN_nnmod(BIGNUM * r,const BIGNUM * a,const BIGNUM * m,BN_CTX * ctx)137 BN_nnmod(BIGNUM *r, const BIGNUM *a, const BIGNUM *m, BN_CTX *ctx)
138 {
139 if (r == m) {
140 BNerror(BN_R_INVALID_ARGUMENT);
141 return 0;
142 }
143 if (!BN_mod_ct(r, a, m, ctx))
144 return 0;
145 if (BN_is_negative(r))
146 return BN_usub(r, m, r);
147 return 1;
148 }
149 LCRYPTO_ALIAS(BN_nnmod);
150
151 int
BN_mod_add(BIGNUM * r,const BIGNUM * a,const BIGNUM * b,const BIGNUM * m,BN_CTX * ctx)152 BN_mod_add(BIGNUM *r, const BIGNUM *a, const BIGNUM *b, const BIGNUM *m,
153 BN_CTX *ctx)
154 {
155 if (r == m) {
156 BNerror(BN_R_INVALID_ARGUMENT);
157 return 0;
158 }
159 if (!BN_add(r, a, b))
160 return 0;
161 return BN_nnmod(r, r, m, ctx);
162 }
163 LCRYPTO_ALIAS(BN_mod_add);
164
165 /*
166 * BN_mod_add() variant that may only be used if both a and b are non-negative
167 * and have already been reduced (less than m).
168 */
169 int
BN_mod_add_quick(BIGNUM * r,const BIGNUM * a,const BIGNUM * b,const BIGNUM * m)170 BN_mod_add_quick(BIGNUM *r, const BIGNUM *a, const BIGNUM *b, const BIGNUM *m)
171 {
172 if (r == m) {
173 BNerror(BN_R_INVALID_ARGUMENT);
174 return 0;
175 }
176 if (!BN_uadd(r, a, b))
177 return 0;
178 if (BN_ucmp(r, m) >= 0)
179 return BN_usub(r, r, m);
180 return 1;
181 }
182 LCRYPTO_ALIAS(BN_mod_add_quick);
183
184 int
BN_mod_sub(BIGNUM * r,const BIGNUM * a,const BIGNUM * b,const BIGNUM * m,BN_CTX * ctx)185 BN_mod_sub(BIGNUM *r, const BIGNUM *a, const BIGNUM *b, const BIGNUM *m,
186 BN_CTX *ctx)
187 {
188 if (r == m) {
189 BNerror(BN_R_INVALID_ARGUMENT);
190 return 0;
191 }
192 if (!BN_sub(r, a, b))
193 return 0;
194 return BN_nnmod(r, r, m, ctx);
195 }
196 LCRYPTO_ALIAS(BN_mod_sub);
197
198 /*
199 * BN_mod_sub() variant that may only be used if both a and b are non-negative
200 * and have already been reduced (less than m).
201 */
202 int
BN_mod_sub_quick(BIGNUM * r,const BIGNUM * a,const BIGNUM * b,const BIGNUM * m)203 BN_mod_sub_quick(BIGNUM *r, const BIGNUM *a, const BIGNUM *b, const BIGNUM *m)
204 {
205 if (r == m) {
206 BNerror(BN_R_INVALID_ARGUMENT);
207 return 0;
208 }
209 if (BN_ucmp(a, b) >= 0)
210 return BN_usub(r, a, b);
211 if (!BN_usub(r, b, a))
212 return 0;
213 return BN_usub(r, m, r);
214 }
215 LCRYPTO_ALIAS(BN_mod_sub_quick);
216
217 int
BN_mod_mul(BIGNUM * r,const BIGNUM * a,const BIGNUM * b,const BIGNUM * m,BN_CTX * ctx)218 BN_mod_mul(BIGNUM *r, const BIGNUM *a, const BIGNUM *b, const BIGNUM *m,
219 BN_CTX *ctx)
220 {
221 BIGNUM *rr;
222 int ret = 0;
223
224 BN_CTX_start(ctx);
225
226 if (r == m) {
227 BNerror(BN_R_INVALID_ARGUMENT);
228 goto err;
229 }
230
231 rr = r;
232 if (rr == a || rr == b)
233 rr = BN_CTX_get(ctx);
234 if (rr == NULL)
235 goto err;
236
237 if (a == b) {
238 if (!BN_sqr(rr, a, ctx))
239 goto err;
240 } else {
241 if (!BN_mul(rr, a, b, ctx))
242 goto err;
243 }
244 if (!BN_nnmod(r, rr, m, ctx))
245 goto err;
246
247 ret = 1;
248
249 err:
250 BN_CTX_end(ctx);
251
252 return ret;
253 }
254 LCRYPTO_ALIAS(BN_mod_mul);
255
256 int
BN_mod_sqr(BIGNUM * r,const BIGNUM * a,const BIGNUM * m,BN_CTX * ctx)257 BN_mod_sqr(BIGNUM *r, const BIGNUM *a, const BIGNUM *m, BN_CTX *ctx)
258 {
259 return BN_mod_mul(r, a, a, m, ctx);
260 }
261 LCRYPTO_ALIAS(BN_mod_sqr);
262
263 int
BN_mod_lshift1(BIGNUM * r,const BIGNUM * a,const BIGNUM * m,BN_CTX * ctx)264 BN_mod_lshift1(BIGNUM *r, const BIGNUM *a, const BIGNUM *m, BN_CTX *ctx)
265 {
266 if (r == m) {
267 BNerror(BN_R_INVALID_ARGUMENT);
268 return 0;
269 }
270 if (!BN_lshift1(r, a))
271 return 0;
272 return BN_nnmod(r, r, m, ctx);
273 }
274 LCRYPTO_ALIAS(BN_mod_lshift1);
275
276 /*
277 * BN_mod_lshift1() variant that may be used if a is non-negative
278 * and has already been reduced (less than m).
279 */
280 int
BN_mod_lshift1_quick(BIGNUM * r,const BIGNUM * a,const BIGNUM * m)281 BN_mod_lshift1_quick(BIGNUM *r, const BIGNUM *a, const BIGNUM *m)
282 {
283 if (r == m) {
284 BNerror(BN_R_INVALID_ARGUMENT);
285 return 0;
286 }
287 if (!BN_lshift1(r, a))
288 return 0;
289 if (BN_ucmp(r, m) >= 0)
290 return BN_usub(r, r, m);
291 return 1;
292 }
293 LCRYPTO_ALIAS(BN_mod_lshift1_quick);
294
295 int
BN_mod_lshift(BIGNUM * r,const BIGNUM * a,int n,const BIGNUM * m,BN_CTX * ctx)296 BN_mod_lshift(BIGNUM *r, const BIGNUM *a, int n, const BIGNUM *m, BN_CTX *ctx)
297 {
298 BIGNUM *abs_m;
299 int ret = 0;
300
301 BN_CTX_start(ctx);
302
303 if (r == m) {
304 BNerror(BN_R_INVALID_ARGUMENT);
305 goto err;
306 }
307
308 if (!BN_nnmod(r, a, m, ctx))
309 goto err;
310
311 if (BN_is_negative(m)) {
312 if ((abs_m = BN_CTX_get(ctx)) == NULL)
313 goto err;
314 if (!bn_copy(abs_m, m))
315 goto err;
316 BN_set_negative(abs_m, 0);
317 m = abs_m;
318 }
319 if (!BN_mod_lshift_quick(r, r, n, m))
320 goto err;
321
322 ret = 1;
323 err:
324 BN_CTX_end(ctx);
325
326 return ret;
327 }
328 LCRYPTO_ALIAS(BN_mod_lshift);
329
330 /*
331 * BN_mod_lshift() variant that may be used if a is non-negative
332 * and has already been reduced (less than m).
333 */
334 int
BN_mod_lshift_quick(BIGNUM * r,const BIGNUM * a,int n,const BIGNUM * m)335 BN_mod_lshift_quick(BIGNUM *r, const BIGNUM *a, int n, const BIGNUM *m)
336 {
337 int max_shift;
338
339 if (r == m) {
340 BNerror(BN_R_INVALID_ARGUMENT);
341 return 0;
342 }
343
344 if (!bn_copy(r, a))
345 return 0;
346
347 while (n > 0) {
348 if ((max_shift = BN_num_bits(m) - BN_num_bits(r)) < 0) {
349 BNerror(BN_R_INPUT_NOT_REDUCED);
350 return 0;
351 }
352 if (max_shift == 0)
353 max_shift = 1;
354 if (max_shift > n)
355 max_shift = n;
356
357 if (!BN_lshift(r, r, max_shift))
358 return 0;
359 n -= max_shift;
360
361 if (BN_ucmp(r, m) >= 0) {
362 if (!BN_usub(r, r, m))
363 return 0;
364 }
365 }
366
367 return 1;
368 }
369 LCRYPTO_ALIAS(BN_mod_lshift_quick);
370