1 /* 2 * Copyright 1995-2016 The OpenSSL Project Authors. All Rights Reserved. 3 * 4 * Licensed under the OpenSSL license (the "License"). You may not use 5 * this file except in compliance with the License. You can obtain a copy 6 * in the file LICENSE in the source distribution or at 7 * https://www.openssl.org/source/license.html 8 */ 9 10 #include "internal/cryptlib.h" 11 #include "bn_lcl.h" 12 13 int BN_lshift1(BIGNUM *r, const BIGNUM *a) 14 { 15 register BN_ULONG *ap, *rp, t, c; 16 int i; 17 18 bn_check_top(r); 19 bn_check_top(a); 20 21 if (r != a) { 22 r->neg = a->neg; 23 if (bn_wexpand(r, a->top + 1) == NULL) 24 return 0; 25 r->top = a->top; 26 } else { 27 if (bn_wexpand(r, a->top + 1) == NULL) 28 return 0; 29 } 30 ap = a->d; 31 rp = r->d; 32 c = 0; 33 for (i = 0; i < a->top; i++) { 34 t = *(ap++); 35 *(rp++) = ((t << 1) | c) & BN_MASK2; 36 c = (t & BN_TBIT) ? 1 : 0; 37 } 38 if (c) { 39 *rp = 1; 40 r->top++; 41 } 42 bn_check_top(r); 43 return 1; 44 } 45 46 int BN_rshift1(BIGNUM *r, const BIGNUM *a) 47 { 48 BN_ULONG *ap, *rp, t, c; 49 int i, j; 50 51 bn_check_top(r); 52 bn_check_top(a); 53 54 if (BN_is_zero(a)) { 55 BN_zero(r); 56 return 1; 57 } 58 i = a->top; 59 ap = a->d; 60 j = i - (ap[i - 1] == 1); 61 if (a != r) { 62 if (bn_wexpand(r, j) == NULL) 63 return 0; 64 r->neg = a->neg; 65 } 66 rp = r->d; 67 t = ap[--i]; 68 c = (t & 1) ? BN_TBIT : 0; 69 if (t >>= 1) 70 rp[i] = t; 71 while (i > 0) { 72 t = ap[--i]; 73 rp[i] = ((t >> 1) & BN_MASK2) | c; 74 c = (t & 1) ? BN_TBIT : 0; 75 } 76 r->top = j; 77 if (!r->top) 78 r->neg = 0; /* don't allow negative zero */ 79 bn_check_top(r); 80 return 1; 81 } 82 83 int BN_lshift(BIGNUM *r, const BIGNUM *a, int n) 84 { 85 int i, nw, lb, rb; 86 BN_ULONG *t, *f; 87 BN_ULONG l; 88 89 bn_check_top(r); 90 bn_check_top(a); 91 92 if (n < 0) { 93 BNerr(BN_F_BN_LSHIFT, BN_R_INVALID_SHIFT); 94 return 0; 95 } 96 97 nw = n / BN_BITS2; 98 if (bn_wexpand(r, a->top + nw + 1) == NULL) 99 return 0; 100 r->neg = a->neg; 101 lb = n % BN_BITS2; 102 rb = BN_BITS2 - lb; 103 f = a->d; 104 t = r->d; 105 t[a->top + nw] = 0; 106 if (lb == 0) 107 for (i = a->top - 1; i >= 0; i--) 108 t[nw + i] = f[i]; 109 else 110 for (i = a->top - 1; i >= 0; i--) { 111 l = f[i]; 112 t[nw + i + 1] |= (l >> rb) & BN_MASK2; 113 t[nw + i] = (l << lb) & BN_MASK2; 114 } 115 memset(t, 0, sizeof(*t) * nw); 116 r->top = a->top + nw + 1; 117 bn_correct_top(r); 118 bn_check_top(r); 119 return 1; 120 } 121 122 int BN_rshift(BIGNUM *r, const BIGNUM *a, int n) 123 { 124 int i, j, nw, lb, rb; 125 BN_ULONG *t, *f; 126 BN_ULONG l, tmp; 127 128 bn_check_top(r); 129 bn_check_top(a); 130 131 if (n < 0) { 132 BNerr(BN_F_BN_RSHIFT, BN_R_INVALID_SHIFT); 133 return 0; 134 } 135 136 nw = n / BN_BITS2; 137 rb = n % BN_BITS2; 138 lb = BN_BITS2 - rb; 139 if (nw >= a->top || a->top == 0) { 140 BN_zero(r); 141 return 1; 142 } 143 i = (BN_num_bits(a) - n + (BN_BITS2 - 1)) / BN_BITS2; 144 if (r != a) { 145 if (bn_wexpand(r, i) == NULL) 146 return 0; 147 r->neg = a->neg; 148 } else { 149 if (n == 0) 150 return 1; /* or the copying loop will go berserk */ 151 } 152 153 f = &(a->d[nw]); 154 t = r->d; 155 j = a->top - nw; 156 r->top = i; 157 158 if (rb == 0) { 159 for (i = j; i != 0; i--) 160 *(t++) = *(f++); 161 } else { 162 l = *(f++); 163 for (i = j - 1; i != 0; i--) { 164 tmp = (l >> rb) & BN_MASK2; 165 l = *(f++); 166 *(t++) = (tmp | (l << lb)) & BN_MASK2; 167 } 168 if ((l = (l >> rb) & BN_MASK2)) 169 *(t) = l; 170 } 171 if (!r->top) 172 r->neg = 0; /* don't allow negative zero */ 173 bn_check_top(r); 174 return 1; 175 } 176