crypto/bn/bn_mod.c

   1 /* crypto/bn/bn_mod.c */
   2 /*
   3  * Includes code written by Lenka Fibikova <fibikova@exp-math.uni-essen.de>
   4  * for the OpenSSL project.
   5  */
   6 /* ====================================================================
   7  * Copyright (c) 1998-2000 The OpenSSL Project.  All rights reserved.
   8  *
   9  * Redistribution and use in source and binary forms, with or without
  10  * modification, are permitted provided that the following conditions
  11  * are met:
  12  *
  13  * 1. Redistributions of source code must retain the above copyright
  14  *    notice, this list of conditions and the following disclaimer.
  15  *
  16  * 2. Redistributions in binary form must reproduce the above copyright
  17  *    notice, this list of conditions and the following disclaimer in
  18  *    the documentation and/or other materials provided with the
  19  *    distribution.
  20  *
  21  * 3. All advertising materials mentioning features or use of this
  22  *    software must display the following acknowledgment:
  23  *    "This product includes software developed by the OpenSSL Project
  24  *    for use in the OpenSSL Toolkit. (http://www.openssl.org/)"
  25  *
  26  * 4. The names "OpenSSL Toolkit" and "OpenSSL Project" must not be used to
  27  *    endorse or promote products derived from this software without
  28  *    prior written permission. For written permission, please contact
  29  *    openssl-core@openssl.org.
  30  *
  31  * 5. Products derived from this software may not be called "OpenSSL"
  32  *    nor may "OpenSSL" appear in their names without prior written
  33  *    permission of the OpenSSL Project.
  34  *
  35  * 6. Redistributions of any form whatsoever must retain the following
  36  *    acknowledgment:
  37  *    "This product includes software developed by the OpenSSL Project
  38  *    for use in the OpenSSL Toolkit (http://www.openssl.org/)"
  39  *
  40  * THIS SOFTWARE IS PROVIDED BY THE OpenSSL PROJECT ``AS IS'' AND ANY
  41  * EXPRESSED OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  42  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
  43  * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE OpenSSL PROJECT OR
  44  * ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
  45  * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
  46  * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
  47  * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  48  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
  49  * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
  50  * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
  51  * OF THE POSSIBILITY OF SUCH DAMAGE.
  52  * ====================================================================
  53  *
  54  * This product includes cryptographic software written by Eric Young
  55  * (eay@cryptsoft.com).  This product includes software written by Tim
  56  * Hudson (tjh@cryptsoft.com).
  57  *
  58  */
  59 /* Copyright (C) 1995-1998 Eric Young (eay@cryptsoft.com)
  60  * All rights reserved.
  61  *
  62  * This package is an SSL implementation written
  63  * by Eric Young (eay@cryptsoft.com).
  64  * The implementation was written so as to conform with Netscapes SSL.
  65  *
  66  * This library is free for commercial and non-commercial use as long as
  67  * the following conditions are aheared to.  The following conditions
  68  * apply to all code found in this distribution, be it the RC4, RSA,
  69  * lhash, DES, etc., code; not just the SSL code.  The SSL documentation
  70  * included with this distribution is covered by the same copyright terms
  71  * except that the holder is Tim Hudson (tjh@cryptsoft.com).
  72  *
  73  * Copyright remains Eric Young's, and as such any Copyright notices in
  74  * the code are not to be removed.
  75  * If this package is used in a product, Eric Young should be given attribution
  76  * as the author of the parts of the library used.
  77  * This can be in the form of a textual message at program startup or
  78  * in documentation (online or textual) provided with the package.
  79  *
  80  * Redistribution and use in source and binary forms, with or without
  81  * modification, are permitted provided that the following conditions
  82  * are met:
  83  * 1. Redistributions of source code must retain the copyright
  84  *    notice, this list of conditions and the following disclaimer.
  85  * 2. Redistributions in binary form must reproduce the above copyright
  86  *    notice, this list of conditions and the following disclaimer in the
  87  *    documentation and/or other materials provided with the distribution.
  88  * 3. All advertising materials mentioning features or use of this software
  89  *    must display the following acknowledgement:
  90  *    "This product includes cryptographic software written by
  91  *     Eric Young (eay@cryptsoft.com)"
  92  *    The word 'cryptographic' can be left out if the rouines from the library
  93  *    being used are not cryptographic related :-).
  94  * 4. If you include any Windows specific code (or a derivative thereof) from
  95  *    the apps directory (application code) you must include an acknowledgement:
  96  *    "This product includes software written by Tim Hudson (tjh@cryptsoft.com)"
  97  *
  98  * THIS SOFTWARE IS PROVIDED BY ERIC YOUNG ``AS IS'' AND
  99  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 100  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 101  * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
 102  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 103  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 104  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 105  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 106  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 107  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 108  * SUCH DAMAGE.
 109  *
 110  * The licence and distribution terms for any publically available version or
 111  * derivative of this code cannot be changed.  i.e. this code cannot simply be
 112  * copied and put under another distribution licence
 113  * [including the GNU Public Licence.]
 114  */
 115
 116 #include "cryptlib.h"
 117 #include "bn_lcl.h"
 118
 119 int BN_nnmod(BIGNUM *r, const BIGNUM *m, const BIGNUM *d, BN_CTX *ctx)
 120 {
 121     /*
 122      * like BN_mod, but returns non-negative remainder (i.e., 0 <= r < |d|
 123      * always holds)
 124      */
 125
 126     if (!(BN_mod(r, m, d, ctx)))
 127         return 0;
 128     if (!r->neg)
 129         return 1;
 130     /* now   -|d| < r < 0,  so we have to set  r := r + |d| */
 131     return (d->neg ? BN_sub : BN_add) (r, r, d);
 132 }
 133
 134 int BN_mod_add(BIGNUM *r, const BIGNUM *a, const BIGNUM *b, const BIGNUM *m,
 135                BN_CTX *ctx)
 136 {
 137     if (!BN_add(r, a, b))
 138         return 0;
 139     return BN_nnmod(r, r, m, ctx);
 140 }
 141
 142 /*
 143  * BN_mod_add variant that may be used if both a and b are non-negative and
 144  * less than m
 145  */
 146 int BN_mod_add_quick(BIGNUM *r, const BIGNUM *a, const BIGNUM *b,
 147                      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 BN_mod_sub(BIGNUM *r, const BIGNUM *a, const BIGNUM *b, const BIGNUM *m,
 157                BN_CTX *ctx)
 158 {
 159     if (!BN_sub(r, a, b))
 160         return 0;
 161     return BN_nnmod(r, r, m, ctx);
 162 }
 163
 164 /*
 165  * BN_mod_sub variant that may be used if both a and b are non-negative and
 166  * less than m
 167  */
 168 int BN_mod_sub_quick(BIGNUM *r, const BIGNUM *a, const BIGNUM *b,
 169                      const BIGNUM *m)
 170 {
 171     if (!BN_sub(r, a, b))
 172         return 0;
 173     if (r->neg)
 174         return BN_add(r, r, m);
 175     return 1;
 176 }
 177
 178 /* slow but works */
 179 int 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  err:
 204     BN_CTX_end(ctx);
 205     return (ret);
 206 }
 207
 208 int BN_mod_sqr(BIGNUM *r, const BIGNUM *a, const BIGNUM *m, BN_CTX *ctx)
 209 {
 210     if (!BN_sqr(r, a, ctx))
 211         return 0;
 212     /* r->neg == 0,  thus we don't need BN_nnmod */
 213     return BN_mod(r, r, m, ctx);
 214 }
 215
 216 int 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 /*
 225  * BN_mod_lshift1 variant that may be used if a is non-negative and less than
 226  * m
 227  */
 228 int BN_mod_lshift1_quick(BIGNUM *r, const BIGNUM *a, const BIGNUM *m)
 229 {
 230     if (!BN_lshift1(r, a))
 231         return 0;
 232     bn_check_top(r);
 233     if (BN_cmp(r, m) >= 0)
 234         return BN_sub(r, r, m);
 235     return 1;
 236 }
 237
 238 int BN_mod_lshift(BIGNUM *r, const BIGNUM *a, int n, const BIGNUM *m,
 239                   BN_CTX *ctx)
 240 {
 241     BIGNUM *abs_m = NULL;
 242     int ret;
 243
 244     if (!BN_nnmod(r, a, m, ctx))
 245         return 0;
 246
 247     if (m->neg) {
 248         abs_m = BN_dup(m);
 249         if (abs_m == NULL)
 250             return 0;
 251         abs_m->neg = 0;
 252     }
 253
 254     ret = BN_mod_lshift_quick(r, r, n, (abs_m ? abs_m : m));
 255     bn_check_top(r);
 256
 257     BN_free(abs_m);
 258     return ret;
 259 }
 260
 261 /*
 262  * BN_mod_lshift variant that may be used if a is non-negative and less than
 263  * m
 264  */
 265 int BN_mod_lshift_quick(BIGNUM *r, const BIGNUM *a, int n, const BIGNUM *m)
 266 {
 267     if (r != a) {
 268         if (BN_copy(r, a) == NULL)
 269             return 0;
 270     }
 271
 272     while (n > 0) {
 273         int max_shift;
 274
 275         /* 0 < r < m */
 276         max_shift = BN_num_bits(m) - BN_num_bits(r);
 277         /* max_shift >= 0 */
 278
 279         if (max_shift < 0) {
 280             BNerr(BN_F_BN_MOD_LSHIFT_QUICK, BN_R_INPUT_NOT_REDUCED);
 281             return 0;
 282         }
 283
 284         if (max_shift > n)
 285             max_shift = n;
 286
 287         if (max_shift) {
 288             if (!BN_lshift(r, r, max_shift))
 289                 return 0;
 290             n -= max_shift;
 291         } else {
 292             if (!BN_lshift1(r, r))
 293                 return 0;
 294             --n;
 295         }
 296
 297         /* BN_num_bits(r) <= BN_num_bits(m) */
 298
 299         if (BN_cmp(r, m) >= 0) {
 300             if (!BN_sub(r, r, m))
 301                 return 0;
 302         }
 303     }
 304     bn_check_top(r);
 305
 306     return 1;
 307 }