[331] | 1 | /*
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| 2 | * Copyright 1998-2016 The OpenSSL Project Authors. All Rights Reserved.
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| 3 | *
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| 4 | * Licensed under the OpenSSL license (the "License"). You may not use
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| 5 | * this file except in compliance with the License. You can obtain a copy
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| 6 | * in the file LICENSE in the source distribution or at
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| 7 | * https://www.openssl.org/source/license.html
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| 8 | */
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| 9 |
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| 10 | #include "internal/cryptlib.h"
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| 11 | #include "bn_lcl.h"
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| 12 |
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| 13 | int BN_nnmod(BIGNUM *r, const BIGNUM *m, const BIGNUM *d, BN_CTX *ctx)
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| 14 | {
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| 15 | /*
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| 16 | * like BN_mod, but returns non-negative remainder (i.e., 0 <= r < |d|
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| 17 | * always holds)
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| 18 | */
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| 19 |
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| 20 | if (!(BN_mod(r, m, d, ctx)))
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| 21 | return 0;
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| 22 | if (!r->neg)
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| 23 | return 1;
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| 24 | /* now -|d| < r < 0, so we have to set r := r + |d| */
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| 25 | return (d->neg ? BN_sub : BN_add) (r, r, d);
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| 26 | }
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| 27 |
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| 28 | int BN_mod_add(BIGNUM *r, const BIGNUM *a, const BIGNUM *b, const BIGNUM *m,
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| 29 | BN_CTX *ctx)
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| 30 | {
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| 31 | if (!BN_add(r, a, b))
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| 32 | return 0;
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| 33 | return BN_nnmod(r, r, m, ctx);
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| 34 | }
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| 35 |
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| 36 | /*
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| 37 | * BN_mod_add variant that may be used if both a and b are non-negative and
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| 38 | * less than m
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| 39 | */
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| 40 | int BN_mod_add_quick(BIGNUM *r, const BIGNUM *a, const BIGNUM *b,
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| 41 | const BIGNUM *m)
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| 42 | {
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| 43 | if (!BN_uadd(r, a, b))
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| 44 | return 0;
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| 45 | if (BN_ucmp(r, m) >= 0)
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| 46 | return BN_usub(r, r, m);
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| 47 | return 1;
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| 48 | }
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| 49 |
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| 50 | int BN_mod_sub(BIGNUM *r, const BIGNUM *a, const BIGNUM *b, const BIGNUM *m,
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| 51 | BN_CTX *ctx)
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| 52 | {
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| 53 | if (!BN_sub(r, a, b))
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| 54 | return 0;
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| 55 | return BN_nnmod(r, r, m, ctx);
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| 56 | }
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| 57 |
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| 58 | /*
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| 59 | * BN_mod_sub variant that may be used if both a and b are non-negative and
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| 60 | * less than m
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| 61 | */
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| 62 | int BN_mod_sub_quick(BIGNUM *r, const BIGNUM *a, const BIGNUM *b,
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| 63 | const BIGNUM *m)
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| 64 | {
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| 65 | if (!BN_sub(r, a, b))
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| 66 | return 0;
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| 67 | if (r->neg)
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| 68 | return BN_add(r, r, m);
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| 69 | return 1;
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| 70 | }
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| 71 |
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| 72 | /* slow but works */
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| 73 | int BN_mod_mul(BIGNUM *r, const BIGNUM *a, const BIGNUM *b, const BIGNUM *m,
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| 74 | BN_CTX *ctx)
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| 75 | {
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| 76 | BIGNUM *t;
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| 77 | int ret = 0;
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| 78 |
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| 79 | bn_check_top(a);
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| 80 | bn_check_top(b);
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| 81 | bn_check_top(m);
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| 82 |
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| 83 | BN_CTX_start(ctx);
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| 84 | if ((t = BN_CTX_get(ctx)) == NULL)
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| 85 | goto err;
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| 86 | if (a == b) {
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| 87 | if (!BN_sqr(t, a, ctx))
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| 88 | goto err;
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| 89 | } else {
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| 90 | if (!BN_mul(t, a, b, ctx))
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| 91 | goto err;
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| 92 | }
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| 93 | if (!BN_nnmod(r, t, m, ctx))
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| 94 | goto err;
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| 95 | bn_check_top(r);
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| 96 | ret = 1;
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| 97 | err:
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| 98 | BN_CTX_end(ctx);
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| 99 | return (ret);
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| 100 | }
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| 101 |
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| 102 | int BN_mod_sqr(BIGNUM *r, const BIGNUM *a, const BIGNUM *m, BN_CTX *ctx)
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| 103 | {
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| 104 | if (!BN_sqr(r, a, ctx))
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| 105 | return 0;
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| 106 | /* r->neg == 0, thus we don't need BN_nnmod */
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| 107 | return BN_mod(r, r, m, ctx);
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| 108 | }
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| 109 |
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| 110 | int BN_mod_lshift1(BIGNUM *r, const BIGNUM *a, const BIGNUM *m, BN_CTX *ctx)
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| 111 | {
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| 112 | if (!BN_lshift1(r, a))
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| 113 | return 0;
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| 114 | bn_check_top(r);
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| 115 | return BN_nnmod(r, r, m, ctx);
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| 116 | }
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| 117 |
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| 118 | /*
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| 119 | * BN_mod_lshift1 variant that may be used if a is non-negative and less than
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| 120 | * m
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| 121 | */
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| 122 | int BN_mod_lshift1_quick(BIGNUM *r, const BIGNUM *a, const BIGNUM *m)
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| 123 | {
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| 124 | if (!BN_lshift1(r, a))
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| 125 | return 0;
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| 126 | bn_check_top(r);
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| 127 | if (BN_cmp(r, m) >= 0)
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| 128 | return BN_sub(r, r, m);
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| 129 | return 1;
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| 130 | }
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| 131 |
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| 132 | int BN_mod_lshift(BIGNUM *r, const BIGNUM *a, int n, const BIGNUM *m,
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| 133 | BN_CTX *ctx)
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| 134 | {
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| 135 | BIGNUM *abs_m = NULL;
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| 136 | int ret;
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| 137 |
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| 138 | if (!BN_nnmod(r, a, m, ctx))
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| 139 | return 0;
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| 140 |
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| 141 | if (m->neg) {
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| 142 | abs_m = BN_dup(m);
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| 143 | if (abs_m == NULL)
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| 144 | return 0;
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| 145 | abs_m->neg = 0;
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| 146 | }
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| 147 |
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| 148 | ret = BN_mod_lshift_quick(r, r, n, (abs_m ? abs_m : m));
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| 149 | bn_check_top(r);
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| 150 |
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| 151 | BN_free(abs_m);
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| 152 | return ret;
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| 153 | }
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| 154 |
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| 155 | /*
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| 156 | * BN_mod_lshift variant that may be used if a is non-negative and less than
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| 157 | * m
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| 158 | */
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| 159 | int BN_mod_lshift_quick(BIGNUM *r, const BIGNUM *a, int n, const BIGNUM *m)
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| 160 | {
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| 161 | if (r != a) {
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| 162 | if (BN_copy(r, a) == NULL)
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| 163 | return 0;
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| 164 | }
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| 165 |
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| 166 | while (n > 0) {
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| 167 | int max_shift;
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| 168 |
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| 169 | /* 0 < r < m */
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| 170 | max_shift = BN_num_bits(m) - BN_num_bits(r);
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| 171 | /* max_shift >= 0 */
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| 172 |
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| 173 | if (max_shift < 0) {
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| 174 | BNerr(BN_F_BN_MOD_LSHIFT_QUICK, BN_R_INPUT_NOT_REDUCED);
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| 175 | return 0;
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| 176 | }
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| 177 |
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| 178 | if (max_shift > n)
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| 179 | max_shift = n;
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| 180 |
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| 181 | if (max_shift) {
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| 182 | if (!BN_lshift(r, r, max_shift))
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| 183 | return 0;
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| 184 | n -= max_shift;
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| 185 | } else {
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| 186 | if (!BN_lshift1(r, r))
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| 187 | return 0;
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| 188 | --n;
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| 189 | }
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| 190 |
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| 191 | /* BN_num_bits(r) <= BN_num_bits(m) */
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| 192 |
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| 193 | if (BN_cmp(r, m) >= 0) {
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| 194 | if (!BN_sub(r, r, m))
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| 195 | return 0;
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| 196 | }
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| 197 | }
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| 198 | bn_check_top(r);
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| 199 |
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| 200 | return 1;
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| 201 | }
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