lib/libcrypto/bn/bn_add.c

   1 /* $OpenBSD: bn_add.c,v 1.13 2018/07/23 18:07:21 tb Exp $ */
   2 /* Copyright (C) 1995-1998 Eric Young (eay@cryptsoft.com)
   3  * All rights reserved.
   4  *
   5  * This package is an SSL implementation written
   6  * by Eric Young (eay@cryptsoft.com).
   7  * The implementation was written so as to conform with Netscapes SSL.
   8  *
   9  * This library is free for commercial and non-commercial use as long as
  10  * the following conditions are aheared to.  The following conditions
  11  * apply to all code found in this distribution, be it the RC4, RSA,
  12  * lhash, DES, etc., code; not just the SSL code.  The SSL documentation
  13  * included with this distribution is covered by the same copyright terms
  14  * except that the holder is Tim Hudson (tjh@cryptsoft.com).
  15  *
  16  * Copyright remains Eric Young's, and as such any Copyright notices in
  17  * the code are not to be removed.
  18  * If this package is used in a product, Eric Young should be given attribution
  19  * as the author of the parts of the library used.
  20  * This can be in the form of a textual message at program startup or
  21  * in documentation (online or textual) provided with the package.
  22  *
  23  * Redistribution and use in source and binary forms, with or without
  24  * modification, are permitted provided that the following conditions
  25  * are met:
  26  * 1. Redistributions of source code must retain the copyright
  27  *    notice, this list of conditions and the following disclaimer.
  28  * 2. Redistributions in binary form must reproduce the above copyright
  29  *    notice, this list of conditions and the following disclaimer in the
  30  *    documentation and/or other materials provided with the distribution.
  31  * 3. All advertising materials mentioning features or use of this software
  32  *    must display the following acknowledgement:
  33  *    "This product includes cryptographic software written by
  34  *     Eric Young (eay@cryptsoft.com)"
  35  *    The word 'cryptographic' can be left out if the rouines from the library
  36  *    being used are not cryptographic related :-).
  37  * 4. If you include any Windows specific code (or a derivative thereof) from
  38  *    the apps directory (application code) you must include an acknowledgement:
  39  *    "This product includes software written by Tim Hudson (tjh@cryptsoft.com)"
  40  *
  41  * THIS SOFTWARE IS PROVIDED BY ERIC YOUNG ``AS IS'' AND
  42  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  43  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  44  * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
  45  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  46  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  47  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  48  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  49  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  50  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  51  * SUCH DAMAGE.
  52  *
  53  * The licence and distribution terms for any publically available version or
  54  * derivative of this code cannot be changed.  i.e. this code cannot simply be
  55  * copied and put under another distribution licence
  56  * [including the GNU Public Licence.]
  57  */
  58
  59 #include <stdio.h>
  60
  61 #include <openssl/err.h>
  62
  63 #include "bn_lcl.h"
  64
  65 int
  66 BN_add(BIGNUM *r, const BIGNUM *a, const BIGNUM *b)
  67 {
  68         int ret, r_neg;
  69
  70         bn_check_top(a);
  71         bn_check_top(b);
  72
  73         if (a->neg == b->neg) {
  74                 r_neg = a->neg;
  75                 ret = BN_uadd(r, a, b);
  76         } else {
  77                 int cmp = BN_ucmp(a, b);
  78
  79                 if (cmp > 0) {
  80                         r_neg = a->neg;
  81                         ret = BN_usub(r, a, b);
  82                 } else if (cmp < 0) {
  83                         r_neg = b->neg;
  84                         ret = BN_usub(r, b, a);
  85                 } else {
  86                         r_neg = 0;
  87                         BN_zero(r);
  88                         ret = 1;
  89                 }
  90         }
  91
  92         r->neg = r_neg;
  93         bn_check_top(r);
  94         return ret;
  95 }
  96
  97 int
  98 BN_uadd(BIGNUM *r, const BIGNUM *a, const BIGNUM *b)
  99 {
 100         int max, min, dif;
 101         const BN_ULONG *ap, *bp;
 102         BN_ULONG *rp, carry, t1, t2;
 103
 104         bn_check_top(a);
 105         bn_check_top(b);
 106
 107         if (a->top < b->top) {
 108                 const BIGNUM *tmp;
 109
 110                 tmp = a;
 111                 a = b;
 112                 b = tmp;
 113         }
 114         max = a->top;
 115         min = b->top;
 116         dif = max - min;
 117
 118         if (bn_wexpand(r, max + 1) == NULL)
 119                 return 0;
 120
 121         r->top = max;
 122
 123         ap = a->d;
 124         bp = b->d;
 125         rp = r->d;
 126
 127         carry = bn_add_words(rp, ap, bp, min);
 128         rp += min;
 129         ap += min;
 130
 131         while (dif) {
 132                 dif--;
 133                 t1 = *(ap++);
 134                 t2 = (t1 + carry) & BN_MASK2;
 135                 *(rp++) = t2;
 136                 carry &= (t2 == 0);
 137         }
 138         *rp = carry;
 139         r->top += carry;
 140
 141         r->neg = 0;
 142         bn_check_top(r);
 143         return 1;
 144 }
 145
 146 int
 147 BN_usub(BIGNUM *r, const BIGNUM *a, const BIGNUM *b)
 148 {
 149         int max, min, dif;
 150         const BN_ULONG *ap, *bp;
 151         BN_ULONG t1, t2, borrow, *rp;
 152
 153         bn_check_top(a);
 154         bn_check_top(b);
 155
 156         max = a->top;
 157         min = b->top;
 158         dif = max - min;
 159
 160         if (dif < 0) {
 161                 BNerror(BN_R_ARG2_LT_ARG3);
 162                 return 0;
 163         }
 164
 165         if (bn_wexpand(r, max) == NULL)
 166                 return 0;
 167
 168         ap = a->d;
 169         bp = b->d;
 170         rp = r->d;
 171
 172         borrow = bn_sub_words(rp, ap, bp, min);
 173         ap += min;
 174         rp += min;
 175
 176         while (dif) {
 177                 dif--;
 178                 t1 = *(ap++);
 179                 t2 = (t1 - borrow) & BN_MASK2;
 180                 *(rp++) = t2;
 181                 borrow &= (t1 == 0);
 182         }
 183
 184         while (max > 0 && *--rp == 0)
 185                 max--;
 186
 187         r->top = max;
 188         r->neg = 0;
 189         bn_correct_top(r);
 190         return 1;
 191 }
 192
 193 int
 194 BN_sub(BIGNUM *r, const BIGNUM *a, const BIGNUM *b)
 195 {
 196         int ret, r_neg;
 197
 198         bn_check_top(a);
 199         bn_check_top(b);
 200
 201         if (a->neg != b->neg) {
 202                 r_neg = a->neg;
 203                 ret = BN_uadd(r, a, b);
 204         } else {
 205                 int cmp = BN_ucmp(a, b);
 206
 207                 if (cmp > 0) {
 208                         r_neg = a->neg;
 209                         ret = BN_usub(r, a, b);
 210                 } else if (cmp < 0) {
 211                         r_neg = !b->neg;
 212                         ret = BN_usub(r, b, a);
 213                 } else {
 214                         r_neg = 0;
 215                         BN_zero(r);
 216                         ret = 1;
 217                 }
 218         }
 219
 220         r->neg = r_neg;
 221         bn_check_top(r);
 222         return ret;
 223 }