lib/libcrypto/bn/bn_mod.c

   1 /* $OpenBSD: bn_mod.c,v 1.12 2017/01/29 17:49:22 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_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_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         bn_check_top(a);
 186         bn_check_top(b);
 187         bn_check_top(m);
 188
 189         BN_CTX_start(ctx);
 190         if ((t = BN_CTX_get(ctx)) == NULL)
 191                 goto err;
 192         if (a == b) {
 193                 if (!BN_sqr(t, a, ctx))
 194                         goto err;
 195         } else {
 196                 if (!BN_mul(t, a,b, ctx))
 197                         goto err;
 198         }
 199         if (!BN_nnmod(r, t,m, ctx))
 200                 goto err;
 201         bn_check_top(r);
 202         ret = 1;
 203
 204 err:
 205         BN_CTX_end(ctx);
 206         return (ret);
 207 }
 208
 209 int
 210 BN_mod_sqr(BIGNUM *r, const BIGNUM *a, const BIGNUM *m, BN_CTX *ctx)
 211 {
 212         if (!BN_sqr(r, a, ctx))
 213                 return 0;
 214         /* r->neg == 0,  thus we don't need BN_nnmod */
 215         return BN_mod_ct(r, r, m, ctx);
 216 }
 217
 218 int
 219 BN_mod_lshift1(BIGNUM *r, const BIGNUM *a, const BIGNUM *m, BN_CTX *ctx)
 220 {
 221         if (!BN_lshift1(r, a))
 222                 return 0;
 223         bn_check_top(r);
 224         return BN_nnmod(r, r, m, ctx);
 225 }
 226
 227 /* BN_mod_lshift1 variant that may be used if  a  is non-negative
 228  * and less than  m */
 229 int
 230 BN_mod_lshift1_quick(BIGNUM *r, const BIGNUM *a, const BIGNUM *m)
 231 {
 232         if (!BN_lshift1(r, a))
 233                 return 0;
 234         bn_check_top(r);
 235         if (BN_cmp(r, m) >= 0)
 236                 return BN_sub(r, r, m);
 237         return 1;
 238 }
 239
 240 int
 241 BN_mod_lshift(BIGNUM *r, const BIGNUM *a, int n, const BIGNUM *m, BN_CTX *ctx)
 242 {
 243         BIGNUM *abs_m = NULL;
 244         int ret;
 245
 246         if (!BN_nnmod(r, a, m, ctx))
 247                 return 0;
 248
 249         if (m->neg) {
 250                 abs_m = BN_dup(m);
 251                 if (abs_m == NULL)
 252                         return 0;
 253                 abs_m->neg = 0;
 254         }
 255
 256         ret = BN_mod_lshift_quick(r, r, n, (abs_m ? abs_m : m));
 257         bn_check_top(r);
 258
 259         BN_free(abs_m);
 260         return ret;
 261 }
 262
 263 /* BN_mod_lshift variant that may be used if  a  is non-negative
 264  * and less than  m */
 265 int
 266 BN_mod_lshift_quick(BIGNUM *r, const BIGNUM *a, int n, const BIGNUM *m)
 267 {
 268         if (r != a) {
 269                 if (BN_copy(r, a) == NULL)
 270                         return 0;
 271         }
 272
 273         while (n > 0) {
 274                 int max_shift;
 275
 276                 /* 0 < r < m */
 277                 max_shift = BN_num_bits(m) - BN_num_bits(r);
 278                 /* max_shift >= 0 */
 279
 280                 if (max_shift < 0) {
 281                         BNerror(BN_R_INPUT_NOT_REDUCED);
 282                         return 0;
 283                 }
 284
 285                 if (max_shift > n)
 286                         max_shift = n;
 287
 288                 if (max_shift) {
 289                         if (!BN_lshift(r, r, max_shift))
 290                                 return 0;
 291                         n -= max_shift;
 292                 } else {
 293                         if (!BN_lshift1(r, r))
 294                                 return 0;
 295                         --n;
 296                 }
 297
 298                 /* BN_num_bits(r) <= BN_num_bits(m) */
 299
 300                 if (BN_cmp(r, m) >= 0) {
 301                         if (!BN_sub(r, r, m))
 302                                 return 0;
 303                 }
 304         }
 305         bn_check_top(r);
 306
 307         return 1;
 308 }