1 /* $OpenBSD: bn_mod.c,v 1.21 2023/06/13 09:28:13 tb 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 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 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 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 } 149 150 int 151 BN_mod_add(BIGNUM *r, const BIGNUM *a, const BIGNUM *b, const BIGNUM *m, 152 BN_CTX *ctx) 153 { 154 if (r == m) { 155 BNerror(BN_R_INVALID_ARGUMENT); 156 return 0; 157 } 158 if (!BN_add(r, a, b)) 159 return 0; 160 return BN_nnmod(r, r, m, ctx); 161 } 162 163 /* 164 * BN_mod_add() variant that may only be used if both a and b are non-negative 165 * and have already been reduced (less than m). 166 */ 167 int 168 BN_mod_add_quick(BIGNUM *r, const BIGNUM *a, const BIGNUM *b, const BIGNUM *m) 169 { 170 if (r == m) { 171 BNerror(BN_R_INVALID_ARGUMENT); 172 return 0; 173 } 174 if (!BN_uadd(r, a, b)) 175 return 0; 176 if (BN_ucmp(r, m) >= 0) 177 return BN_usub(r, r, m); 178 return 1; 179 } 180 181 int 182 BN_mod_sub(BIGNUM *r, const BIGNUM *a, const BIGNUM *b, const BIGNUM *m, 183 BN_CTX *ctx) 184 { 185 if (r == m) { 186 BNerror(BN_R_INVALID_ARGUMENT); 187 return 0; 188 } 189 if (!BN_sub(r, a, b)) 190 return 0; 191 return BN_nnmod(r, r, m, ctx); 192 } 193 194 /* 195 * BN_mod_sub() variant that may only be used if both a and b are non-negative 196 * and have already been reduced (less than m). 197 */ 198 int 199 BN_mod_sub_quick(BIGNUM *r, const BIGNUM *a, const BIGNUM *b, const BIGNUM *m) 200 { 201 if (r == m) { 202 BNerror(BN_R_INVALID_ARGUMENT); 203 return 0; 204 } 205 if (BN_ucmp(a, b) >= 0) 206 return BN_usub(r, a, b); 207 if (!BN_usub(r, b, a)) 208 return 0; 209 return BN_usub(r, m, r); 210 } 211 212 int 213 BN_mod_mul(BIGNUM *r, const BIGNUM *a, const BIGNUM *b, const BIGNUM *m, 214 BN_CTX *ctx) 215 { 216 BIGNUM *rr; 217 int ret = 0; 218 219 BN_CTX_start(ctx); 220 221 if (r == m) { 222 BNerror(BN_R_INVALID_ARGUMENT); 223 goto err; 224 } 225 226 rr = r; 227 if (rr == a || rr == b) 228 rr = BN_CTX_get(ctx); 229 if (rr == NULL) 230 goto err; 231 232 if (a == b) { 233 if (!BN_sqr(rr, a, ctx)) 234 goto err; 235 } else { 236 if (!BN_mul(rr, a, b, ctx)) 237 goto err; 238 } 239 if (!BN_nnmod(r, rr, m, ctx)) 240 goto err; 241 242 ret = 1; 243 244 err: 245 BN_CTX_end(ctx); 246 247 return ret; 248 } 249 250 int 251 BN_mod_sqr(BIGNUM *r, const BIGNUM *a, const BIGNUM *m, BN_CTX *ctx) 252 { 253 return BN_mod_mul(r, a, a, m, ctx); 254 } 255 256 int 257 BN_mod_lshift1(BIGNUM *r, const BIGNUM *a, const BIGNUM *m, BN_CTX *ctx) 258 { 259 if (r == m) { 260 BNerror(BN_R_INVALID_ARGUMENT); 261 return 0; 262 } 263 if (!BN_lshift1(r, a)) 264 return 0; 265 return BN_nnmod(r, r, m, ctx); 266 } 267 268 /* 269 * BN_mod_lshift1() variant that may be used if a is non-negative 270 * and has already been reduced (less than m). 271 */ 272 int 273 BN_mod_lshift1_quick(BIGNUM *r, const BIGNUM *a, const BIGNUM *m) 274 { 275 if (r == m) { 276 BNerror(BN_R_INVALID_ARGUMENT); 277 return 0; 278 } 279 if (!BN_lshift1(r, a)) 280 return 0; 281 if (BN_ucmp(r, m) >= 0) 282 return BN_usub(r, r, m); 283 return 1; 284 } 285 286 int 287 BN_mod_lshift(BIGNUM *r, const BIGNUM *a, int n, const BIGNUM *m, BN_CTX *ctx) 288 { 289 BIGNUM *abs_m; 290 int ret = 0; 291 292 BN_CTX_start(ctx); 293 294 if (r == m) { 295 BNerror(BN_R_INVALID_ARGUMENT); 296 goto err; 297 } 298 299 if (!BN_nnmod(r, a, m, ctx)) 300 goto err; 301 302 if (BN_is_negative(m)) { 303 if ((abs_m = BN_CTX_get(ctx)) == NULL) 304 goto err; 305 if (!bn_copy(abs_m, m)) 306 goto err; 307 BN_set_negative(abs_m, 0); 308 m = abs_m; 309 } 310 if (!BN_mod_lshift_quick(r, r, n, m)) 311 goto err; 312 313 ret = 1; 314 err: 315 BN_CTX_end(ctx); 316 317 return ret; 318 } 319 320 /* 321 * BN_mod_lshift() variant that may be used if a is non-negative 322 * and has already been reduced (less than m). 323 */ 324 int 325 BN_mod_lshift_quick(BIGNUM *r, const BIGNUM *a, int n, const BIGNUM *m) 326 { 327 int max_shift; 328 329 if (r == m) { 330 BNerror(BN_R_INVALID_ARGUMENT); 331 return 0; 332 } 333 334 if (!bn_copy(r, a)) 335 return 0; 336 337 while (n > 0) { 338 if ((max_shift = BN_num_bits(m) - BN_num_bits(r)) < 0) { 339 BNerror(BN_R_INPUT_NOT_REDUCED); 340 return 0; 341 } 342 if (max_shift == 0) 343 max_shift = 1; 344 if (max_shift > n) 345 max_shift = n; 346 347 if (!BN_lshift(r, r, max_shift)) 348 return 0; 349 n -= max_shift; 350 351 if (BN_ucmp(r, m) >= 0) { 352 if (!BN_usub(r, r, m)) 353 return 0; 354 } 355 } 356 357 return 1; 358 } 359