1 /* $OpenBSD: bn_mod.c,v 1.14 2022/11/26 16:08:51 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_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 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 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 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 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 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; 184 185 186 BN_CTX_start(ctx); 187 if ((t = BN_CTX_get(ctx)) == NULL) 188 goto err; 189 if (a == b) { 190 if (!BN_sqr(t, a, ctx)) 191 goto err; 192 } else { 193 if (!BN_mul(t, a,b, ctx)) 194 goto err; 195 } 196 if (!BN_nnmod(r, t,m, ctx)) 197 goto err; 198 ret = 1; 199 200 err: 201 BN_CTX_end(ctx); 202 return (ret); 203 } 204 205 int 206 BN_mod_sqr(BIGNUM *r, const BIGNUM *a, const BIGNUM *m, BN_CTX *ctx) 207 { 208 if (!BN_sqr(r, a, ctx)) 209 return 0; 210 /* r->neg == 0, thus we don't need BN_nnmod */ 211 return BN_mod_ct(r, r, m, ctx); 212 } 213 214 int 215 BN_mod_lshift1(BIGNUM *r, const BIGNUM *a, const BIGNUM *m, BN_CTX *ctx) 216 { 217 if (!BN_lshift1(r, a)) 218 return 0; 219 return BN_nnmod(r, r, m, ctx); 220 } 221 222 /* BN_mod_lshift1 variant that may be used if a is non-negative 223 * and less than m */ 224 int 225 BN_mod_lshift1_quick(BIGNUM *r, const BIGNUM *a, const BIGNUM *m) 226 { 227 if (!BN_lshift1(r, a)) 228 return 0; 229 if (BN_cmp(r, m) >= 0) 230 return BN_sub(r, r, m); 231 return 1; 232 } 233 234 int 235 BN_mod_lshift(BIGNUM *r, const BIGNUM *a, int n, const BIGNUM *m, BN_CTX *ctx) 236 { 237 BIGNUM *abs_m = NULL; 238 int ret; 239 240 if (!BN_nnmod(r, a, m, ctx)) 241 return 0; 242 243 if (m->neg) { 244 abs_m = BN_dup(m); 245 if (abs_m == NULL) 246 return 0; 247 abs_m->neg = 0; 248 } 249 250 ret = BN_mod_lshift_quick(r, r, n, (abs_m ? abs_m : m)); 251 252 BN_free(abs_m); 253 return ret; 254 } 255 256 /* BN_mod_lshift variant that may be used if a is non-negative 257 * and less than m */ 258 int 259 BN_mod_lshift_quick(BIGNUM *r, const BIGNUM *a, int n, const BIGNUM *m) 260 { 261 if (r != a) { 262 if (BN_copy(r, a) == NULL) 263 return 0; 264 } 265 266 while (n > 0) { 267 int max_shift; 268 269 /* 0 < r < m */ 270 max_shift = BN_num_bits(m) - BN_num_bits(r); 271 /* max_shift >= 0 */ 272 273 if (max_shift < 0) { 274 BNerror(BN_R_INPUT_NOT_REDUCED); 275 return 0; 276 } 277 278 if (max_shift > n) 279 max_shift = n; 280 281 if (max_shift) { 282 if (!BN_lshift(r, r, max_shift)) 283 return 0; 284 n -= max_shift; 285 } else { 286 if (!BN_lshift1(r, r)) 287 return 0; 288 --n; 289 } 290 291 /* BN_num_bits(r) <= BN_num_bits(m) */ 292 293 if (BN_cmp(r, m) >= 0) { 294 if (!BN_sub(r, r, m)) 295 return 0; 296 } 297 } 298 299 return 1; 300 } 301