1 /* $OpenBSD: bn_word.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 61 #include "bn_lcl.h" 62 63 BN_ULONG 64 BN_mod_word(const BIGNUM *a, BN_ULONG w) 65 { 66 #ifndef BN_LLONG 67 BN_ULONG ret = 0; 68 #else 69 BN_ULLONG ret = 0; 70 #endif 71 int i; 72 73 if (w == 0) 74 return (BN_ULONG) - 1; 75 76 #ifndef BN_ULLONG 77 /* If |w| is too long and we don't have |BN_ULLONG| then we need to fall back 78 * to using |BN_div_word|. */ 79 if (w > ((BN_ULONG)1 << BN_BITS4)) { 80 BIGNUM *tmp = BN_dup(a); 81 if (tmp == NULL) { 82 return (BN_ULONG)-1; 83 } 84 ret = BN_div_word(tmp, w); 85 BN_free(tmp); 86 return ret; 87 } 88 #endif 89 90 bn_check_top(a); 91 w &= BN_MASK2; 92 for (i = a->top - 1; i >= 0; i--) { 93 #ifndef BN_LLONG 94 ret = ((ret << BN_BITS4) | ((a->d[i] >> BN_BITS4) & 95 BN_MASK2l)) % w; 96 ret = ((ret << BN_BITS4) | (a->d[i] & BN_MASK2l)) % w; 97 #else 98 ret = (BN_ULLONG)(((ret << (BN_ULLONG)BN_BITS2) | 99 a->d[i]) % (BN_ULLONG)w); 100 #endif 101 } 102 return ((BN_ULONG)ret); 103 } 104 105 BN_ULONG 106 BN_div_word(BIGNUM *a, BN_ULONG w) 107 { 108 BN_ULONG ret = 0; 109 int i, j; 110 111 bn_check_top(a); 112 w &= BN_MASK2; 113 114 if (!w) 115 /* actually this an error (division by zero) */ 116 return (BN_ULONG) - 1; 117 if (a->top == 0) 118 return 0; 119 120 /* normalize input (so bn_div_words doesn't complain) */ 121 j = BN_BITS2 - BN_num_bits_word(w); 122 w <<= j; 123 if (!BN_lshift(a, a, j)) 124 return (BN_ULONG) - 1; 125 126 for (i = a->top - 1; i >= 0; i--) { 127 BN_ULONG l, d; 128 129 l = a->d[i]; 130 d = bn_div_words(ret, l, w); 131 ret = (l - ((d*w)&BN_MASK2))&BN_MASK2; 132 a->d[i] = d; 133 } 134 if ((a->top > 0) && (a->d[a->top - 1] == 0)) 135 a->top--; 136 ret >>= j; 137 bn_check_top(a); 138 return (ret); 139 } 140 141 int 142 BN_add_word(BIGNUM *a, BN_ULONG w) 143 { 144 BN_ULONG l; 145 int i; 146 147 bn_check_top(a); 148 w &= BN_MASK2; 149 150 /* degenerate case: w is zero */ 151 if (!w) 152 return 1; 153 /* degenerate case: a is zero */ 154 if (BN_is_zero(a)) 155 return BN_set_word(a, w); 156 /* handle 'a' when negative */ 157 if (a->neg) { 158 a->neg = 0; 159 i = BN_sub_word(a, w); 160 if (!BN_is_zero(a)) 161 a->neg=!(a->neg); 162 return (i); 163 } 164 for (i = 0; w != 0 && i < a->top; i++) { 165 a->d[i] = l = (a->d[i] + w) & BN_MASK2; 166 w = (w > l) ? 1 : 0; 167 } 168 if (w && i == a->top) { 169 if (bn_wexpand(a, a->top + 1) == NULL) 170 return 0; 171 a->top++; 172 a->d[i] = w; 173 } 174 bn_check_top(a); 175 return (1); 176 } 177 178 int 179 BN_sub_word(BIGNUM *a, BN_ULONG w) 180 { 181 int i; 182 183 bn_check_top(a); 184 w &= BN_MASK2; 185 186 /* degenerate case: w is zero */ 187 if (!w) 188 return 1; 189 /* degenerate case: a is zero */ 190 if (BN_is_zero(a)) { 191 i = BN_set_word(a, w); 192 if (i != 0) 193 BN_set_negative(a, 1); 194 return i; 195 } 196 /* handle 'a' when negative */ 197 if (a->neg) { 198 a->neg = 0; 199 i = BN_add_word(a, w); 200 a->neg = 1; 201 return (i); 202 } 203 204 if ((a->top == 1) && (a->d[0] < w)) { 205 a->d[0] = w - a->d[0]; 206 a->neg = 1; 207 return (1); 208 } 209 i = 0; 210 for (;;) { 211 if (a->d[i] >= w) { 212 a->d[i] -= w; 213 break; 214 } else { 215 a->d[i] = (a->d[i] - w) & BN_MASK2; 216 i++; 217 w = 1; 218 } 219 } 220 if ((a->d[i] == 0) && (i == (a->top - 1))) 221 a->top--; 222 bn_check_top(a); 223 return (1); 224 } 225 226 int 227 BN_mul_word(BIGNUM *a, BN_ULONG w) 228 { 229 BN_ULONG ll; 230 231 bn_check_top(a); 232 w &= BN_MASK2; 233 if (a->top) { 234 if (w == 0) 235 BN_zero(a); 236 else { 237 ll = bn_mul_words(a->d, a->d, a->top, w); 238 if (ll) { 239 if (bn_wexpand(a, a->top + 1) == NULL) 240 return (0); 241 a->d[a->top++] = ll; 242 } 243 } 244 } 245 bn_check_top(a); 246 return (1); 247 } 248