crypto/libressl/crypto/bn/bn_mod.c

   1 /* $OpenBSD: bn_mod.c,v 1.8 2014/07/11 08:44:48 jsing 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
 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(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         return (d->neg ? BN_sub : BN_add)(r, r, d);
 130 }
 131
 132 int
 133 BN_mod_add(BIGNUM *r, const BIGNUM *a, const BIGNUM *b, const BIGNUM *m,
 134     BN_CTX *ctx)
 135 {
 136         if (!BN_add(r, a, b))
 137                 return 0;
 138         return BN_nnmod(r, r, m, ctx);
 139 }
 140
 141 /* BN_mod_add variant that may be used if both  a  and  b  are non-negative
 142  * and less than  m */
 143 int
 144 BN_mod_add_quick(BIGNUM *r, const BIGNUM *a, const BIGNUM *b, const BIGNUM *m)
 145 {
 146         if (!BN_uadd(r, a, b))
 147                 return 0;
 148         if (BN_ucmp(r, m) >= 0)
 149                 return BN_usub(r, r, m);
 150         return 1;
 151 }
 152
 153 int
 154 BN_mod_sub(BIGNUM *r, const BIGNUM *a, const BIGNUM *b, const BIGNUM *m,
 155     BN_CTX *ctx)
 156 {
 157         if (!BN_sub(r, a, b))
 158                 return 0;
 159         return BN_nnmod(r, r, m, ctx);
 160 }
 161
 162 /* BN_mod_sub variant that may be used if both  a  and  b  are non-negative
 163  * and less than  m */
 164 int
 165 BN_mod_sub_quick(BIGNUM *r, const BIGNUM *a, const BIGNUM *b, const BIGNUM *m)
 166 {
 167         if (!BN_sub(r, a, b))
 168                 return 0;
 169         if (r->neg)
 170                 return BN_add(r, r, m);
 171         return 1;
 172 }
 173
 174 /* slow but works */
 175 int
 176 BN_mod_mul(BIGNUM *r, const BIGNUM *a, const BIGNUM *b, const BIGNUM *m,
 177     BN_CTX *ctx)
 178 {
 179         BIGNUM *t;
 180         int ret = 0;
 181
 182         bn_check_top(a);
 183         bn_check_top(b);
 184         bn_check_top(m);
 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         bn_check_top(r);
 199         ret = 1;
 200
 201 err:
 202         BN_CTX_end(ctx);
 203         return (ret);
 204 }
 205
 206 int
 207 BN_mod_sqr(BIGNUM *r, const BIGNUM *a, const BIGNUM *m, BN_CTX *ctx)
 208 {
 209         if (!BN_sqr(r, a, ctx))
 210                 return 0;
 211         /* r->neg == 0,  thus we don't need BN_nnmod */
 212         return BN_mod(r, r, m, ctx);
 213 }
 214
 215 int
 216 BN_mod_lshift1(BIGNUM *r, const BIGNUM *a, const BIGNUM *m, BN_CTX *ctx)
 217 {
 218         if (!BN_lshift1(r, a))
 219                 return 0;
 220         bn_check_top(r);
 221         return BN_nnmod(r, r, m, ctx);
 222 }
 223
 224 /* BN_mod_lshift1 variant that may be used if  a  is non-negative
 225  * and less than  m */
 226 int
 227 BN_mod_lshift1_quick(BIGNUM *r, const BIGNUM *a, const BIGNUM *m)
 228 {
 229         if (!BN_lshift1(r, a))
 230                 return 0;
 231         bn_check_top(r);
 232         if (BN_cmp(r, m) >= 0)
 233                 return BN_sub(r, r, m);
 234         return 1;
 235 }
 236
 237 int
 238 BN_mod_lshift(BIGNUM *r, const BIGNUM *a, int n, const BIGNUM *m, BN_CTX *ctx)
 239 {
 240         BIGNUM *abs_m = NULL;
 241         int ret;
 242
 243         if (!BN_nnmod(r, a, m, ctx))
 244                 return 0;
 245
 246         if (m->neg) {
 247                 abs_m = BN_dup(m);
 248                 if (abs_m == NULL)
 249                         return 0;
 250                 abs_m->neg = 0;
 251         }
 252
 253         ret = BN_mod_lshift_quick(r, r, n, (abs_m ? abs_m : m));
 254         bn_check_top(r);
 255
 256         BN_free(abs_m);
 257         return ret;
 258 }
 259
 260 /* BN_mod_lshift variant that may be used if  a  is non-negative
 261  * and less than  m */
 262 int
 263 BN_mod_lshift_quick(BIGNUM *r, const BIGNUM *a, int n, const BIGNUM *m)
 264 {
 265         if (r != a) {
 266                 if (BN_copy(r, a) == NULL)
 267                         return 0;
 268         }
 269
 270         while (n > 0) {
 271                 int max_shift;
 272
 273                 /* 0 < r < m */
 274                 max_shift = BN_num_bits(m) - BN_num_bits(r);
 275                 /* max_shift >= 0 */
 276
 277                 if (max_shift < 0) {
 278                         BNerr(BN_F_BN_MOD_LSHIFT_QUICK, BN_R_INPUT_NOT_REDUCED);
 279                         return 0;
 280                 }
 281
 282                 if (max_shift > n)
 283                         max_shift = n;
 284
 285                 if (max_shift) {
 286                         if (!BN_lshift(r, r, max_shift))
 287                                 return 0;
 288                         n -= max_shift;
 289                 } else {
 290                         if (!BN_lshift1(r, r))
 291                                 return 0;
 292                         --n;
 293                 }
 294
 295                 /* BN_num_bits(r) <= BN_num_bits(m) */
 296
 297                 if (BN_cmp(r, m) >= 0) {
 298                         if (!BN_sub(r, r, m))
 299                                 return 0;
 300                 }
 301         }
 302         bn_check_top(r);
 303
 304         return 1;
 305 }