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1 /* Copyright (c) 2018, Google Inc.
2  *
3  * Permission to use, copy, modify, and/or distribute this software for any
4  * purpose with or without fee is hereby granted, provided that the above
5  * copyright notice and this permission notice appear in all copies.
6  *
7  * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
8  * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
9  * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY
10  * SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
11  * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION
12  * OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN
13  * CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE. */
14 
15 #include <openssl/ec.h>
16 #include <openssl/err.h>
17 #include <openssl/mem.h>
18 
19 #include "internal.h"
20 #include "../bn/internal.h"
21 #include "../../internal.h"
22 
23 
ec_bignum_to_scalar(const EC_GROUP * group,EC_SCALAR * out,const BIGNUM * in)24 int ec_bignum_to_scalar(const EC_GROUP *group, EC_SCALAR *out,
25                         const BIGNUM *in) {
26   if (!bn_copy_words(out->words, group->order.width, in) ||
27       !bn_less_than_words(out->words, group->order.d, group->order.width)) {
28     OPENSSL_PUT_ERROR(EC, EC_R_INVALID_SCALAR);
29     return 0;
30   }
31   return 1;
32 }
33 
ec_scalar_equal_vartime(const EC_GROUP * group,const EC_SCALAR * a,const EC_SCALAR * b)34 int ec_scalar_equal_vartime(const EC_GROUP *group, const EC_SCALAR *a,
35                             const EC_SCALAR *b) {
36   return OPENSSL_memcmp(a->words, b->words,
37                         group->order.width * sizeof(BN_ULONG)) == 0;
38 }
39 
ec_scalar_is_zero(const EC_GROUP * group,const EC_SCALAR * a)40 int ec_scalar_is_zero(const EC_GROUP *group, const EC_SCALAR *a) {
41   BN_ULONG mask = 0;
42   for (int i = 0; i < group->order.width; i++) {
43     mask |= a->words[i];
44   }
45   return mask == 0;
46 }
47 
ec_random_nonzero_scalar(const EC_GROUP * group,EC_SCALAR * out,const uint8_t additional_data[32])48 int ec_random_nonzero_scalar(const EC_GROUP *group, EC_SCALAR *out,
49                              const uint8_t additional_data[32]) {
50   return bn_rand_range_words(out->words, 1, group->order.d, group->order.width,
51                              additional_data);
52 }
53 
ec_scalar_add(const EC_GROUP * group,EC_SCALAR * r,const EC_SCALAR * a,const EC_SCALAR * b)54 void ec_scalar_add(const EC_GROUP *group, EC_SCALAR *r, const EC_SCALAR *a,
55                    const EC_SCALAR *b) {
56   const BIGNUM *order = &group->order;
57   BN_ULONG tmp[EC_MAX_WORDS];
58   bn_mod_add_words(r->words, a->words, b->words, order->d, tmp, order->width);
59   OPENSSL_cleanse(tmp, sizeof(tmp));
60 }
61 
ec_scalar_to_montgomery(const EC_GROUP * group,EC_SCALAR * r,const EC_SCALAR * a)62 void ec_scalar_to_montgomery(const EC_GROUP *group, EC_SCALAR *r,
63                              const EC_SCALAR *a) {
64   const BIGNUM *order = &group->order;
65   bn_to_montgomery_small(r->words, a->words, order->width, group->order_mont);
66 }
67 
ec_scalar_from_montgomery(const EC_GROUP * group,EC_SCALAR * r,const EC_SCALAR * a)68 void ec_scalar_from_montgomery(const EC_GROUP *group, EC_SCALAR *r,
69                                const EC_SCALAR *a) {
70   const BIGNUM *order = &group->order;
71   bn_from_montgomery_small(r->words, a->words, order->width, group->order_mont);
72 }
73 
ec_scalar_mul_montgomery(const EC_GROUP * group,EC_SCALAR * r,const EC_SCALAR * a,const EC_SCALAR * b)74 void ec_scalar_mul_montgomery(const EC_GROUP *group, EC_SCALAR *r,
75                               const EC_SCALAR *a, const EC_SCALAR *b) {
76   const BIGNUM *order = &group->order;
77   bn_mod_mul_montgomery_small(r->words, a->words, b->words, order->width,
78                               group->order_mont);
79 }
80 
ec_simple_scalar_inv_montgomery(const EC_GROUP * group,EC_SCALAR * r,const EC_SCALAR * a)81 void ec_simple_scalar_inv_montgomery(const EC_GROUP *group, EC_SCALAR *r,
82                                      const EC_SCALAR *a) {
83   const BIGNUM *order = &group->order;
84   bn_mod_inverse_prime_mont_small(r->words, a->words, order->width,
85                                   group->order_mont);
86 }
87 
ec_scalar_inv_montgomery(const EC_GROUP * group,EC_SCALAR * r,const EC_SCALAR * a)88 void ec_scalar_inv_montgomery(const EC_GROUP *group, EC_SCALAR *r,
89                               const EC_SCALAR *a) {
90   group->meth->scalar_inv_montgomery(group, r, a);
91 }
92 
ec_scalar_inv_montgomery_vartime(const EC_GROUP * group,EC_SCALAR * r,const EC_SCALAR * a)93 int ec_scalar_inv_montgomery_vartime(const EC_GROUP *group, EC_SCALAR *r,
94                                      const EC_SCALAR *a) {
95   return group->meth->scalar_inv_montgomery_vartime(group, r, a);
96 }
97