crypto/libressl/crypto/bn/bn_shift.c

   1 /* $OpenBSD: bn_shift.c,v 1.12 2014/07/11 08:44:48 jsing 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 #include <string.h>
  61
  62 #include "bn_lcl.h"
  63
  64 int
  65 BN_lshift1(BIGNUM *r, const BIGNUM *a)
  66 {
  67         BN_ULONG *ap, *rp, t, c;
  68         int i;
  69
  70         bn_check_top(r);
  71         bn_check_top(a);
  72
  73         if (r != a) {
  74                 r->neg = a->neg;
  75                 if (bn_wexpand(r, a->top + 1) == NULL)
  76                         return (0);
  77                 r->top = a->top;
  78         } else {
  79                 if (bn_wexpand(r, a->top + 1) == NULL)
  80                         return (0);
  81         }
  82         ap = a->d;
  83         rp = r->d;
  84         c = 0;
  85         for (i = 0; i < a->top; i++) {
  86                 t= *(ap++);
  87                 *(rp++) = ((t << 1) | c) & BN_MASK2;
  88                 c = (t & BN_TBIT) ? 1 : 0;
  89         }
  90         if (c) {
  91                 *rp = 1;
  92                 r->top++;
  93         }
  94         bn_check_top(r);
  95         return (1);
  96 }
  97
  98 int
  99 BN_rshift1(BIGNUM *r, const BIGNUM *a)
 100 {
 101         BN_ULONG *ap, *rp, t, c;
 102         int i, j;
 103
 104         bn_check_top(r);
 105         bn_check_top(a);
 106
 107         if (BN_is_zero(a)) {
 108                 BN_zero(r);
 109                 return (1);
 110         }
 111         i = a->top;
 112         ap = a->d;
 113         j = i - (ap[i - 1]==1);
 114         if (a != r) {
 115                 if (bn_wexpand(r, j) == NULL)
 116                         return (0);
 117                 r->neg = a->neg;
 118         }
 119         rp = r->d;
 120         t = ap[--i];
 121         c = (t & 1) ? BN_TBIT : 0;
 122         if (t >>= 1)
 123                 rp[i] = t;
 124         while (i > 0) {
 125                 t = ap[--i];
 126                 rp[i] = ((t >> 1) & BN_MASK2) | c;
 127                 c = (t & 1) ? BN_TBIT : 0;
 128         }
 129         r->top = j;
 130         bn_check_top(r);
 131         return (1);
 132 }
 133
 134 int
 135 BN_lshift(BIGNUM *r, const BIGNUM *a, int n)
 136 {
 137         int i, nw, lb, rb;
 138         BN_ULONG *t, *f;
 139         BN_ULONG l;
 140
 141         bn_check_top(r);
 142         bn_check_top(a);
 143
 144         r->neg = a->neg;
 145         nw = n / BN_BITS2;
 146         if (bn_wexpand(r, a->top + nw + 1) == NULL)
 147                 return (0);
 148         lb = n % BN_BITS2;
 149         rb = BN_BITS2 - lb;
 150         f = a->d;
 151         t = r->d;
 152         t[a->top + nw] = 0;
 153         if (lb == 0)
 154                 for (i = a->top - 1; i >= 0; i--)
 155                         t[nw + i] = f[i];
 156         else
 157                 for (i = a->top - 1; i >= 0; i--) {
 158                         l = f[i];
 159                         t[nw + i + 1] |= (l >> rb) & BN_MASK2;
 160                         t[nw + i] = (l << lb) & BN_MASK2;
 161                 }
 162         memset(t, 0, nw * sizeof(t[0]));
 163 /*      for (i=0; i<nw; i++)
 164                 t[i]=0;*/
 165         r->top = a->top + nw + 1;
 166         bn_correct_top(r);
 167         bn_check_top(r);
 168         return (1);
 169 }
 170
 171 int
 172 BN_rshift(BIGNUM *r, const BIGNUM *a, int n)
 173 {
 174         int i, j, nw, lb, rb;
 175         BN_ULONG *t, *f;
 176         BN_ULONG l, tmp;
 177
 178         bn_check_top(r);
 179         bn_check_top(a);
 180
 181         nw = n / BN_BITS2;
 182         rb = n % BN_BITS2;
 183         lb = BN_BITS2 - rb;
 184         if (nw >= a->top || a->top == 0) {
 185                 BN_zero(r);
 186                 return (1);
 187         }
 188         i = (BN_num_bits(a) - n + (BN_BITS2 - 1)) / BN_BITS2;
 189         if (r != a) {
 190                 r->neg = a->neg;
 191                 if (bn_wexpand(r, i) == NULL)
 192                         return (0);
 193         } else {
 194                 if (n == 0)
 195                         return 1; /* or the copying loop will go berserk */
 196         }
 197
 198         f = &(a->d[nw]);
 199         t = r->d;
 200         j = a->top - nw;
 201         r->top = i;
 202
 203         if (rb == 0) {
 204                 for (i = j; i != 0; i--)
 205                         *(t++) = *(f++);
 206         } else {
 207                 l = *(f++);
 208                 for (i = j - 1; i != 0; i--) {
 209                         tmp = (l >> rb) & BN_MASK2;
 210                         l = *(f++);
 211                         *(t++) = (tmp|(l << lb)) & BN_MASK2;
 212                 }
 213                 if ((l = (l >> rb) & BN_MASK2))
 214                         *(t) = l;
 215         }
 216         bn_check_top(r);
 217         return (1);
 218 }