[331] | 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 | /* r can == a or b */
|
---|
| 14 | int BN_add(BIGNUM *r, const BIGNUM *a, const BIGNUM *b)
|
---|
| 15 | {
|
---|
| 16 | int a_neg = a->neg, ret;
|
---|
| 17 |
|
---|
| 18 | bn_check_top(a);
|
---|
| 19 | bn_check_top(b);
|
---|
| 20 |
|
---|
| 21 | /*-
|
---|
| 22 | * a + b a+b
|
---|
| 23 | * a + -b a-b
|
---|
| 24 | * -a + b b-a
|
---|
| 25 | * -a + -b -(a+b)
|
---|
| 26 | */
|
---|
| 27 | if (a_neg ^ b->neg) {
|
---|
| 28 | /* only one is negative */
|
---|
| 29 | if (a_neg) {
|
---|
| 30 | const BIGNUM *tmp;
|
---|
| 31 |
|
---|
| 32 | tmp = a;
|
---|
| 33 | a = b;
|
---|
| 34 | b = tmp;
|
---|
| 35 | }
|
---|
| 36 |
|
---|
| 37 | /* we are now a - b */
|
---|
| 38 |
|
---|
| 39 | if (BN_ucmp(a, b) < 0) {
|
---|
| 40 | if (!BN_usub(r, b, a))
|
---|
| 41 | return 0;
|
---|
| 42 | r->neg = 1;
|
---|
| 43 | } else {
|
---|
| 44 | if (!BN_usub(r, a, b))
|
---|
| 45 | return 0;
|
---|
| 46 | r->neg = 0;
|
---|
| 47 | }
|
---|
| 48 | return 1;
|
---|
| 49 | }
|
---|
| 50 |
|
---|
| 51 | ret = BN_uadd(r, a, b);
|
---|
| 52 | r->neg = a_neg;
|
---|
| 53 | bn_check_top(r);
|
---|
| 54 | return ret;
|
---|
| 55 | }
|
---|
| 56 |
|
---|
| 57 | /* unsigned add of b to a */
|
---|
| 58 | int BN_uadd(BIGNUM *r, const BIGNUM *a, const BIGNUM *b)
|
---|
| 59 | {
|
---|
| 60 | int max, min, dif;
|
---|
| 61 | const BN_ULONG *ap, *bp;
|
---|
| 62 | BN_ULONG *rp, carry, t1, t2;
|
---|
| 63 |
|
---|
| 64 | bn_check_top(a);
|
---|
| 65 | bn_check_top(b);
|
---|
| 66 |
|
---|
| 67 | if (a->top < b->top) {
|
---|
| 68 | const BIGNUM *tmp;
|
---|
| 69 |
|
---|
| 70 | tmp = a;
|
---|
| 71 | a = b;
|
---|
| 72 | b = tmp;
|
---|
| 73 | }
|
---|
| 74 | max = a->top;
|
---|
| 75 | min = b->top;
|
---|
| 76 | dif = max - min;
|
---|
| 77 |
|
---|
| 78 | if (bn_wexpand(r, max + 1) == NULL)
|
---|
| 79 | return 0;
|
---|
| 80 |
|
---|
| 81 | r->top = max;
|
---|
| 82 |
|
---|
| 83 | ap = a->d;
|
---|
| 84 | bp = b->d;
|
---|
| 85 | rp = r->d;
|
---|
| 86 |
|
---|
| 87 | carry = bn_add_words(rp, ap, bp, min);
|
---|
| 88 | rp += min;
|
---|
| 89 | ap += min;
|
---|
| 90 |
|
---|
| 91 | while (dif) {
|
---|
| 92 | dif--;
|
---|
| 93 | t1 = *(ap++);
|
---|
| 94 | t2 = (t1 + carry) & BN_MASK2;
|
---|
| 95 | *(rp++) = t2;
|
---|
| 96 | carry &= (t2 == 0);
|
---|
| 97 | }
|
---|
| 98 | *rp = carry;
|
---|
| 99 | r->top += carry;
|
---|
| 100 |
|
---|
| 101 | r->neg = 0;
|
---|
| 102 | bn_check_top(r);
|
---|
| 103 | return 1;
|
---|
| 104 | }
|
---|
| 105 |
|
---|
| 106 | /* unsigned subtraction of b from a, a must be larger than b. */
|
---|
| 107 | int BN_usub(BIGNUM *r, const BIGNUM *a, const BIGNUM *b)
|
---|
| 108 | {
|
---|
| 109 | int max, min, dif;
|
---|
| 110 | BN_ULONG t1, t2, borrow, *rp;
|
---|
| 111 | const BN_ULONG *ap, *bp;
|
---|
| 112 |
|
---|
| 113 | bn_check_top(a);
|
---|
| 114 | bn_check_top(b);
|
---|
| 115 |
|
---|
| 116 | max = a->top;
|
---|
| 117 | min = b->top;
|
---|
| 118 | dif = max - min;
|
---|
| 119 |
|
---|
| 120 | if (dif < 0) { /* hmm... should not be happening */
|
---|
| 121 | BNerr(BN_F_BN_USUB, BN_R_ARG2_LT_ARG3);
|
---|
| 122 | return 0;
|
---|
| 123 | }
|
---|
| 124 |
|
---|
| 125 | if (bn_wexpand(r, max) == NULL)
|
---|
| 126 | return 0;
|
---|
| 127 |
|
---|
| 128 | ap = a->d;
|
---|
| 129 | bp = b->d;
|
---|
| 130 | rp = r->d;
|
---|
| 131 |
|
---|
| 132 | borrow = bn_sub_words(rp, ap, bp, min);
|
---|
| 133 | ap += min;
|
---|
| 134 | rp += min;
|
---|
| 135 |
|
---|
| 136 | while (dif) {
|
---|
| 137 | dif--;
|
---|
| 138 | t1 = *(ap++);
|
---|
| 139 | t2 = (t1 - borrow) & BN_MASK2;
|
---|
| 140 | *(rp++) = t2;
|
---|
| 141 | borrow &= (t1 == 0);
|
---|
| 142 | }
|
---|
| 143 |
|
---|
| 144 | r->top = max;
|
---|
| 145 | r->neg = 0;
|
---|
| 146 | bn_correct_top(r);
|
---|
| 147 | return 1;
|
---|
| 148 | }
|
---|
| 149 |
|
---|
| 150 | int BN_sub(BIGNUM *r, const BIGNUM *a, const BIGNUM *b)
|
---|
| 151 | {
|
---|
| 152 | int max;
|
---|
| 153 | int add = 0, neg = 0;
|
---|
| 154 |
|
---|
| 155 | bn_check_top(a);
|
---|
| 156 | bn_check_top(b);
|
---|
| 157 |
|
---|
| 158 | /*-
|
---|
| 159 | * a - b a-b
|
---|
| 160 | * a - -b a+b
|
---|
| 161 | * -a - b -(a+b)
|
---|
| 162 | * -a - -b b-a
|
---|
| 163 | */
|
---|
| 164 | if (a->neg) {
|
---|
| 165 | if (b->neg) {
|
---|
| 166 | const BIGNUM *tmp;
|
---|
| 167 |
|
---|
| 168 | tmp = a;
|
---|
| 169 | a = b;
|
---|
| 170 | b = tmp;
|
---|
| 171 | } else {
|
---|
| 172 | add = 1;
|
---|
| 173 | neg = 1;
|
---|
| 174 | }
|
---|
| 175 | } else {
|
---|
| 176 | if (b->neg) {
|
---|
| 177 | add = 1;
|
---|
| 178 | neg = 0;
|
---|
| 179 | }
|
---|
| 180 | }
|
---|
| 181 |
|
---|
| 182 | if (add) {
|
---|
| 183 | if (!BN_uadd(r, a, b))
|
---|
| 184 | return 0;
|
---|
| 185 | r->neg = neg;
|
---|
| 186 | return 1;
|
---|
| 187 | }
|
---|
| 188 |
|
---|
| 189 | /* We are actually doing a - b :-) */
|
---|
| 190 |
|
---|
| 191 | max = (a->top > b->top) ? a->top : b->top;
|
---|
| 192 | if (bn_wexpand(r, max) == NULL)
|
---|
| 193 | return 0;
|
---|
| 194 | if (BN_ucmp(a, b) < 0) {
|
---|
| 195 | if (!BN_usub(r, b, a))
|
---|
| 196 | return 0;
|
---|
| 197 | r->neg = 1;
|
---|
| 198 | } else {
|
---|
| 199 | if (!BN_usub(r, a, b))
|
---|
| 200 | return 0;
|
---|
| 201 | r->neg = 0;
|
---|
| 202 | }
|
---|
| 203 | bn_check_top(r);
|
---|
| 204 | return 1;
|
---|
| 205 | }
|
---|