1 /* $OpenBSD: bn_shift.c,v 1.13 2014/10/28 07:35:58 jsg 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 } 219