bn_add.c revision 1.17
1/* $OpenBSD: bn_add.c,v 1.17 2023/01/20 04:49:48 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 <openssl/err.h> 62 63#include "bn_local.h" 64 65int 66BN_uadd(BIGNUM *r, const BIGNUM *a, const BIGNUM *b) 67{ 68 int max, min, dif; 69 const BN_ULONG *ap, *bp; 70 BN_ULONG *rp, carry, t1, t2; 71 72 73 if (a->top < b->top) { 74 const BIGNUM *tmp; 75 76 tmp = a; 77 a = b; 78 b = tmp; 79 } 80 max = a->top; 81 min = b->top; 82 dif = max - min; 83 84 if (!bn_wexpand(r, max + 1)) 85 return 0; 86 87 r->top = max; 88 89 ap = a->d; 90 bp = b->d; 91 rp = r->d; 92 93 carry = bn_add_words(rp, ap, bp, min); 94 rp += min; 95 ap += min; 96 97 while (dif) { 98 dif--; 99 t1 = *(ap++); 100 t2 = (t1 + carry) & BN_MASK2; 101 *(rp++) = t2; 102 carry &= (t2 == 0); 103 } 104 *rp = carry; 105 r->top += carry; 106 107 r->neg = 0; 108 return 1; 109} 110 111int 112BN_usub(BIGNUM *r, const BIGNUM *a, const BIGNUM *b) 113{ 114 int max, min, dif; 115 const BN_ULONG *ap, *bp; 116 BN_ULONG t1, t2, borrow, *rp; 117 118 119 max = a->top; 120 min = b->top; 121 dif = max - min; 122 123 if (dif < 0) { 124 BNerror(BN_R_ARG2_LT_ARG3); 125 return 0; 126 } 127 128 if (!bn_wexpand(r, max)) 129 return 0; 130 131 ap = a->d; 132 bp = b->d; 133 rp = r->d; 134 135 borrow = bn_sub_words(rp, ap, bp, min); 136 ap += min; 137 rp += min; 138 139 while (dif) { 140 dif--; 141 t1 = *(ap++); 142 t2 = (t1 - borrow) & BN_MASK2; 143 *(rp++) = t2; 144 borrow &= (t1 == 0); 145 } 146 147 while (max > 0 && *--rp == 0) 148 max--; 149 150 r->top = max; 151 r->neg = 0; 152 bn_correct_top(r); 153 return 1; 154} 155 156int 157BN_add(BIGNUM *r, const BIGNUM *a, const BIGNUM *b) 158{ 159 int ret, r_neg; 160 161 162 if (a->neg == b->neg) { 163 r_neg = a->neg; 164 ret = BN_uadd(r, a, b); 165 } else { 166 int cmp = BN_ucmp(a, b); 167 168 if (cmp > 0) { 169 r_neg = a->neg; 170 ret = BN_usub(r, a, b); 171 } else if (cmp < 0) { 172 r_neg = b->neg; 173 ret = BN_usub(r, b, a); 174 } else { 175 r_neg = 0; 176 BN_zero(r); 177 ret = 1; 178 } 179 } 180 181 r->neg = r_neg; 182 return ret; 183} 184 185int 186BN_sub(BIGNUM *r, const BIGNUM *a, const BIGNUM *b) 187{ 188 int ret, r_neg; 189 190 191 if (a->neg != b->neg) { 192 r_neg = a->neg; 193 ret = BN_uadd(r, a, b); 194 } else { 195 int cmp = BN_ucmp(a, b); 196 197 if (cmp > 0) { 198 r_neg = a->neg; 199 ret = BN_usub(r, a, b); 200 } else if (cmp < 0) { 201 r_neg = !b->neg; 202 ret = BN_usub(r, b, a); 203 } else { 204 r_neg = 0; 205 BN_zero(r); 206 ret = 1; 207 } 208 } 209 210 r->neg = r_neg; 211 return ret; 212} 213