1 /* $OpenBSD: bn_word.c,v 1.19 2023/03/11 14:13:11 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_local.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 w &= BN_MASK2; 91 for (i = a->top - 1; i >= 0; i--) { 92 #ifndef BN_LLONG 93 ret = ((ret << BN_BITS4) | ((a->d[i] >> BN_BITS4) & 94 BN_MASK2l)) % w; 95 ret = ((ret << BN_BITS4) | (a->d[i] & BN_MASK2l)) % w; 96 #else 97 ret = (BN_ULLONG)(((ret << (BN_ULLONG)BN_BITS2) | 98 a->d[i]) % (BN_ULLONG)w); 99 #endif 100 } 101 return ((BN_ULONG)ret); 102 } 103 104 BN_ULONG 105 BN_div_word(BIGNUM *a, BN_ULONG w) 106 { 107 BN_ULONG ret = 0; 108 int i, j; 109 110 w &= BN_MASK2; 111 112 if (!w) 113 /* actually this an error (division by zero) */ 114 return (BN_ULONG) - 1; 115 if (a->top == 0) 116 return 0; 117 118 /* normalize input (so bn_div_words doesn't complain) */ 119 j = BN_BITS2 - BN_num_bits_word(w); 120 w <<= j; 121 if (!BN_lshift(a, a, j)) 122 return (BN_ULONG) - 1; 123 124 for (i = a->top - 1; i >= 0; i--) { 125 BN_ULONG l, d; 126 127 l = a->d[i]; 128 bn_div_rem_words(ret, l, w, &d, &ret); 129 a->d[i] = d; 130 } 131 if ((a->top > 0) && (a->d[a->top - 1] == 0)) 132 a->top--; 133 ret >>= j; 134 return (ret); 135 } 136 137 int 138 BN_add_word(BIGNUM *a, BN_ULONG w) 139 { 140 BN_ULONG l; 141 int i; 142 143 w &= BN_MASK2; 144 145 /* degenerate case: w is zero */ 146 if (!w) 147 return 1; 148 /* degenerate case: a is zero */ 149 if (BN_is_zero(a)) 150 return BN_set_word(a, w); 151 /* handle 'a' when negative */ 152 if (a->neg) { 153 a->neg = 0; 154 i = BN_sub_word(a, w); 155 BN_set_negative(a, !a->neg); 156 return (i); 157 } 158 for (i = 0; w != 0 && i < a->top; i++) { 159 a->d[i] = l = (a->d[i] + w) & BN_MASK2; 160 w = (w > l) ? 1 : 0; 161 } 162 if (w && i == a->top) { 163 if (!bn_wexpand(a, a->top + 1)) 164 return 0; 165 a->top++; 166 a->d[i] = w; 167 } 168 return (1); 169 } 170 171 int 172 BN_sub_word(BIGNUM *a, BN_ULONG w) 173 { 174 int i; 175 176 w &= BN_MASK2; 177 178 /* degenerate case: w is zero */ 179 if (!w) 180 return 1; 181 /* degenerate case: a is zero */ 182 if (BN_is_zero(a)) { 183 i = BN_set_word(a, w); 184 if (i != 0) 185 BN_set_negative(a, 1); 186 return i; 187 } 188 /* handle 'a' when negative */ 189 if (a->neg) { 190 a->neg = 0; 191 i = BN_add_word(a, w); 192 BN_set_negative(a, !a->neg); 193 return (i); 194 } 195 196 if ((a->top == 1) && (a->d[0] < w)) { 197 a->d[0] = w - a->d[0]; 198 BN_set_negative(a, 1); 199 return (1); 200 } 201 i = 0; 202 for (;;) { 203 if (a->d[i] >= w) { 204 a->d[i] -= w; 205 break; 206 } else { 207 a->d[i] = (a->d[i] - w) & BN_MASK2; 208 i++; 209 w = 1; 210 } 211 } 212 if ((a->d[i] == 0) && (i == (a->top - 1))) 213 a->top--; 214 return (1); 215 } 216 217 int 218 BN_mul_word(BIGNUM *a, BN_ULONG w) 219 { 220 BN_ULONG ll; 221 222 w &= BN_MASK2; 223 if (a->top) { 224 if (w == 0) 225 BN_zero(a); 226 else { 227 ll = bn_mul_words(a->d, a->d, a->top, w); 228 if (ll) { 229 if (!bn_wexpand(a, a->top + 1)) 230 return (0); 231 a->d[a->top++] = ll; 232 } 233 } 234 } 235 return (1); 236 } 237