1 /* $OpenBSD: bn_mod.c,v 1.20 2023/03/27 10:21:23 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 (!BN_mod_ct(r, a, m, ctx)) 140 return 0; 141 if (BN_is_negative(r)) 142 return BN_usub(r, m, r); 143 return 1; 144 } 145 146 int 147 BN_mod_add(BIGNUM *r, const BIGNUM *a, const BIGNUM *b, const BIGNUM *m, 148 BN_CTX *ctx) 149 { 150 if (!BN_add(r, a, b)) 151 return 0; 152 return BN_nnmod(r, r, m, ctx); 153 } 154 155 /* 156 * BN_mod_add() variant that may only be used if both a and b are non-negative 157 * and have already been reduced (less than m). 158 */ 159 int 160 BN_mod_add_quick(BIGNUM *r, const BIGNUM *a, const BIGNUM *b, const BIGNUM *m) 161 { 162 if (!BN_uadd(r, a, b)) 163 return 0; 164 if (BN_ucmp(r, m) >= 0) 165 return BN_usub(r, r, m); 166 return 1; 167 } 168 169 int 170 BN_mod_sub(BIGNUM *r, const BIGNUM *a, const BIGNUM *b, const BIGNUM *m, 171 BN_CTX *ctx) 172 { 173 if (!BN_sub(r, a, b)) 174 return 0; 175 return BN_nnmod(r, r, m, ctx); 176 } 177 178 /* 179 * BN_mod_sub() variant that may only be used if both a and b are non-negative 180 * and have already been reduced (less than m). 181 */ 182 int 183 BN_mod_sub_quick(BIGNUM *r, const BIGNUM *a, const BIGNUM *b, const BIGNUM *m) 184 { 185 if (BN_ucmp(a, b) >= 0) 186 return BN_usub(r, a, b); 187 if (!BN_usub(r, b, a)) 188 return 0; 189 return BN_usub(r, m, r); 190 } 191 192 int 193 BN_mod_mul(BIGNUM *r, const BIGNUM *a, const BIGNUM *b, const BIGNUM *m, 194 BN_CTX *ctx) 195 { 196 BIGNUM *rr; 197 int ret = 0; 198 199 BN_CTX_start(ctx); 200 201 rr = r; 202 if (rr == a || rr == b) 203 rr = BN_CTX_get(ctx); 204 if (rr == NULL) 205 goto err; 206 207 if (a == b) { 208 if (!BN_sqr(rr, a, ctx)) 209 goto err; 210 } else { 211 if (!BN_mul(rr, a, b, ctx)) 212 goto err; 213 } 214 if (!BN_nnmod(r, rr, m, ctx)) 215 goto err; 216 217 ret = 1; 218 219 err: 220 BN_CTX_end(ctx); 221 222 return ret; 223 } 224 225 int 226 BN_mod_sqr(BIGNUM *r, const BIGNUM *a, const BIGNUM *m, BN_CTX *ctx) 227 { 228 return BN_mod_mul(r, a, a, m, ctx); 229 } 230 231 int 232 BN_mod_lshift1(BIGNUM *r, const BIGNUM *a, const BIGNUM *m, BN_CTX *ctx) 233 { 234 if (!BN_lshift1(r, a)) 235 return 0; 236 return BN_nnmod(r, r, m, ctx); 237 } 238 239 /* 240 * BN_mod_lshift1() variant that may be used if a is non-negative 241 * and has already been reduced (less than m). 242 */ 243 int 244 BN_mod_lshift1_quick(BIGNUM *r, const BIGNUM *a, const BIGNUM *m) 245 { 246 if (!BN_lshift1(r, a)) 247 return 0; 248 if (BN_ucmp(r, m) >= 0) 249 return BN_usub(r, r, m); 250 return 1; 251 } 252 253 int 254 BN_mod_lshift(BIGNUM *r, const BIGNUM *a, int n, const BIGNUM *m, BN_CTX *ctx) 255 { 256 BIGNUM *abs_m; 257 int ret = 0; 258 259 BN_CTX_start(ctx); 260 261 if (!BN_nnmod(r, a, m, ctx)) 262 goto err; 263 264 if (BN_is_negative(m)) { 265 if ((abs_m = BN_CTX_get(ctx)) == NULL) 266 goto err; 267 if (!bn_copy(abs_m, m)) 268 goto err; 269 BN_set_negative(abs_m, 0); 270 m = abs_m; 271 } 272 if (!BN_mod_lshift_quick(r, r, n, m)) 273 goto err; 274 275 ret = 1; 276 err: 277 BN_CTX_end(ctx); 278 279 return ret; 280 } 281 282 /* 283 * BN_mod_lshift() variant that may be used if a is non-negative 284 * and has already been reduced (less than m). 285 */ 286 int 287 BN_mod_lshift_quick(BIGNUM *r, const BIGNUM *a, int n, const BIGNUM *m) 288 { 289 int max_shift; 290 291 if (!bn_copy(r, a)) 292 return 0; 293 294 while (n > 0) { 295 if ((max_shift = BN_num_bits(m) - BN_num_bits(r)) < 0) { 296 BNerror(BN_R_INPUT_NOT_REDUCED); 297 return 0; 298 } 299 if (max_shift == 0) 300 max_shift = 1; 301 if (max_shift > n) 302 max_shift = n; 303 304 if (!BN_lshift(r, r, max_shift)) 305 return 0; 306 n -= max_shift; 307 308 if (BN_ucmp(r, m) >= 0) { 309 if (!BN_usub(r, r, m)) 310 return 0; 311 } 312 } 313 314 return 1; 315 } 316