1 /* $OpenBSD: bn_add.c,v 1.13 2018/07/23 18:07:21 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 61 #include <openssl/err.h> 62 63 #include "bn_lcl.h" 64 65 int 66 BN_add(BIGNUM *r, const BIGNUM *a, const BIGNUM *b) 67 { 68 int ret, r_neg; 69 70 bn_check_top(a); 71 bn_check_top(b); 72 73 if (a->neg == b->neg) { 74 r_neg = a->neg; 75 ret = BN_uadd(r, a, b); 76 } else { 77 int cmp = BN_ucmp(a, b); 78 79 if (cmp > 0) { 80 r_neg = a->neg; 81 ret = BN_usub(r, a, b); 82 } else if (cmp < 0) { 83 r_neg = b->neg; 84 ret = BN_usub(r, b, a); 85 } else { 86 r_neg = 0; 87 BN_zero(r); 88 ret = 1; 89 } 90 } 91 92 r->neg = r_neg; 93 bn_check_top(r); 94 return ret; 95 } 96 97 int 98 BN_uadd(BIGNUM *r, const BIGNUM *a, const BIGNUM *b) 99 { 100 int max, min, dif; 101 const BN_ULONG *ap, *bp; 102 BN_ULONG *rp, carry, t1, t2; 103 104 bn_check_top(a); 105 bn_check_top(b); 106 107 if (a->top < b->top) { 108 const BIGNUM *tmp; 109 110 tmp = a; 111 a = b; 112 b = tmp; 113 } 114 max = a->top; 115 min = b->top; 116 dif = max - min; 117 118 if (bn_wexpand(r, max + 1) == NULL) 119 return 0; 120 121 r->top = max; 122 123 ap = a->d; 124 bp = b->d; 125 rp = r->d; 126 127 carry = bn_add_words(rp, ap, bp, min); 128 rp += min; 129 ap += min; 130 131 while (dif) { 132 dif--; 133 t1 = *(ap++); 134 t2 = (t1 + carry) & BN_MASK2; 135 *(rp++) = t2; 136 carry &= (t2 == 0); 137 } 138 *rp = carry; 139 r->top += carry; 140 141 r->neg = 0; 142 bn_check_top(r); 143 return 1; 144 } 145 146 int 147 BN_usub(BIGNUM *r, const BIGNUM *a, const BIGNUM *b) 148 { 149 int max, min, dif; 150 const BN_ULONG *ap, *bp; 151 BN_ULONG t1, t2, borrow, *rp; 152 153 bn_check_top(a); 154 bn_check_top(b); 155 156 max = a->top; 157 min = b->top; 158 dif = max - min; 159 160 if (dif < 0) { 161 BNerror(BN_R_ARG2_LT_ARG3); 162 return 0; 163 } 164 165 if (bn_wexpand(r, max) == NULL) 166 return 0; 167 168 ap = a->d; 169 bp = b->d; 170 rp = r->d; 171 172 borrow = bn_sub_words(rp, ap, bp, min); 173 ap += min; 174 rp += min; 175 176 while (dif) { 177 dif--; 178 t1 = *(ap++); 179 t2 = (t1 - borrow) & BN_MASK2; 180 *(rp++) = t2; 181 borrow &= (t1 == 0); 182 } 183 184 while (max > 0 && *--rp == 0) 185 max--; 186 187 r->top = max; 188 r->neg = 0; 189 bn_correct_top(r); 190 return 1; 191 } 192 193 int 194 BN_sub(BIGNUM *r, const BIGNUM *a, const BIGNUM *b) 195 { 196 int ret, r_neg; 197 198 bn_check_top(a); 199 bn_check_top(b); 200 201 if (a->neg != b->neg) { 202 r_neg = a->neg; 203 ret = BN_uadd(r, a, b); 204 } else { 205 int cmp = BN_ucmp(a, b); 206 207 if (cmp > 0) { 208 r_neg = a->neg; 209 ret = BN_usub(r, a, b); 210 } else if (cmp < 0) { 211 r_neg = !b->neg; 212 ret = BN_usub(r, b, a); 213 } else { 214 r_neg = 0; 215 BN_zero(r); 216 ret = 1; 217 } 218 } 219 220 r->neg = r_neg; 221 bn_check_top(r); 222 return ret; 223 } 224