1 /* $OpenBSD: bn_shift.c,v 1.14 2022/06/22 09:03:06 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 #include <string.h> 61 62 #include <openssl/err.h> 63 64 #include "bn_lcl.h" 65 66 int 67 BN_lshift1(BIGNUM *r, const BIGNUM *a) 68 { 69 BN_ULONG *ap, *rp, t, c; 70 int i; 71 72 bn_check_top(r); 73 bn_check_top(a); 74 75 if (r != a) { 76 r->neg = a->neg; 77 if (bn_wexpand(r, a->top + 1) == NULL) 78 return (0); 79 r->top = a->top; 80 } else { 81 if (bn_wexpand(r, a->top + 1) == NULL) 82 return (0); 83 } 84 ap = a->d; 85 rp = r->d; 86 c = 0; 87 for (i = 0; i < a->top; i++) { 88 t= *(ap++); 89 *(rp++) = ((t << 1) | c) & BN_MASK2; 90 c = (t & BN_TBIT) ? 1 : 0; 91 } 92 if (c) { 93 *rp = 1; 94 r->top++; 95 } 96 bn_check_top(r); 97 return (1); 98 } 99 100 int 101 BN_rshift1(BIGNUM *r, const BIGNUM *a) 102 { 103 BN_ULONG *ap, *rp, t, c; 104 int i, j; 105 106 bn_check_top(r); 107 bn_check_top(a); 108 109 if (BN_is_zero(a)) { 110 BN_zero(r); 111 return (1); 112 } 113 i = a->top; 114 ap = a->d; 115 j = i - (ap[i - 1]==1); 116 if (a != r) { 117 if (bn_wexpand(r, j) == NULL) 118 return (0); 119 r->neg = a->neg; 120 } 121 rp = r->d; 122 t = ap[--i]; 123 c = (t & 1) ? BN_TBIT : 0; 124 if (t >>= 1) 125 rp[i] = t; 126 while (i > 0) { 127 t = ap[--i]; 128 rp[i] = ((t >> 1) & BN_MASK2) | c; 129 c = (t & 1) ? BN_TBIT : 0; 130 } 131 r->top = j; 132 bn_check_top(r); 133 return (1); 134 } 135 136 int 137 BN_lshift(BIGNUM *r, const BIGNUM *a, int n) 138 { 139 int i, nw, lb, rb; 140 BN_ULONG *t, *f; 141 BN_ULONG l; 142 143 if (n < 0) { 144 BNerror(BN_R_INVALID_LENGTH); 145 return 0; 146 } 147 148 bn_check_top(r); 149 bn_check_top(a); 150 151 r->neg = a->neg; 152 nw = n / BN_BITS2; 153 if (bn_wexpand(r, a->top + nw + 1) == NULL) 154 return (0); 155 lb = n % BN_BITS2; 156 rb = BN_BITS2 - lb; 157 f = a->d; 158 t = r->d; 159 t[a->top + nw] = 0; 160 if (lb == 0) 161 for (i = a->top - 1; i >= 0; i--) 162 t[nw + i] = f[i]; 163 else 164 for (i = a->top - 1; i >= 0; i--) { 165 l = f[i]; 166 t[nw + i + 1] |= (l >> rb) & BN_MASK2; 167 t[nw + i] = (l << lb) & BN_MASK2; 168 } 169 memset(t, 0, nw * sizeof(t[0])); 170 /* for (i=0; i<nw; i++) 171 t[i]=0;*/ 172 r->top = a->top + nw + 1; 173 bn_correct_top(r); 174 bn_check_top(r); 175 return (1); 176 } 177 178 int 179 BN_rshift(BIGNUM *r, const BIGNUM *a, int n) 180 { 181 int i, j, nw, lb, rb; 182 BN_ULONG *t, *f; 183 BN_ULONG l, tmp; 184 185 if (n < 0) { 186 BNerror(BN_R_INVALID_LENGTH); 187 return 0; 188 } 189 190 bn_check_top(r); 191 bn_check_top(a); 192 193 nw = n / BN_BITS2; 194 rb = n % BN_BITS2; 195 lb = BN_BITS2 - rb; 196 if (nw >= a->top || a->top == 0) { 197 BN_zero(r); 198 return (1); 199 } 200 i = (BN_num_bits(a) - n + (BN_BITS2 - 1)) / BN_BITS2; 201 if (r != a) { 202 r->neg = a->neg; 203 if (bn_wexpand(r, i) == NULL) 204 return (0); 205 } else { 206 if (n == 0) 207 return 1; /* or the copying loop will go berserk */ 208 } 209 210 f = &(a->d[nw]); 211 t = r->d; 212 j = a->top - nw; 213 r->top = i; 214 215 if (rb == 0) { 216 for (i = j; i != 0; i--) 217 *(t++) = *(f++); 218 } else { 219 l = *(f++); 220 for (i = j - 1; i != 0; i--) { 221 tmp = (l >> rb) & BN_MASK2; 222 l = *(f++); 223 *(t++) = (tmp|(l << lb)) & BN_MASK2; 224 } 225 if ((l = (l >> rb) & BN_MASK2)) 226 *(t) = l; 227 } 228 bn_check_top(r); 229 return (1); 230 } 231