1 /*
2 * Copyright 2001-2019 The OpenSSL Project Authors. All Rights Reserved.
3 * Copyright (c) 2002, Oracle and/or its affiliates. All rights reserved
4 *
5 * Licensed under the OpenSSL license (the "License"). You may not use
6 * this file except in compliance with the License. You can obtain a copy
7 * in the file LICENSE in the source distribution or at
8 * https://www.openssl.org/source/license.html
9 */
10
11 #include <openssl/err.h>
12
13 #include "ec_local.h"
14
EC_GFp_mont_method(void)15 const EC_METHOD *EC_GFp_mont_method(void)
16 {
17 static const EC_METHOD ret = {
18 EC_FLAGS_DEFAULT_OCT,
19 NID_X9_62_prime_field,
20 ec_GFp_mont_group_init,
21 ec_GFp_mont_group_finish,
22 ec_GFp_mont_group_clear_finish,
23 ec_GFp_mont_group_copy,
24 ec_GFp_mont_group_set_curve,
25 ec_GFp_simple_group_get_curve,
26 ec_GFp_simple_group_get_degree,
27 ec_group_simple_order_bits,
28 ec_GFp_simple_group_check_discriminant,
29 ec_GFp_simple_point_init,
30 ec_GFp_simple_point_finish,
31 ec_GFp_simple_point_clear_finish,
32 ec_GFp_simple_point_copy,
33 ec_GFp_simple_point_set_to_infinity,
34 ec_GFp_simple_set_Jprojective_coordinates_GFp,
35 ec_GFp_simple_get_Jprojective_coordinates_GFp,
36 ec_GFp_simple_point_set_affine_coordinates,
37 ec_GFp_simple_point_get_affine_coordinates,
38 0, 0, 0,
39 ec_GFp_simple_add,
40 ec_GFp_simple_dbl,
41 ec_GFp_simple_invert,
42 ec_GFp_simple_is_at_infinity,
43 ec_GFp_simple_is_on_curve,
44 ec_GFp_simple_cmp,
45 ec_GFp_simple_make_affine,
46 ec_GFp_simple_points_make_affine,
47 0 /* mul */ ,
48 0 /* precompute_mult */ ,
49 0 /* have_precompute_mult */ ,
50 ec_GFp_mont_field_mul,
51 ec_GFp_mont_field_sqr,
52 0 /* field_div */ ,
53 ec_GFp_mont_field_inv,
54 ec_GFp_mont_field_encode,
55 ec_GFp_mont_field_decode,
56 ec_GFp_mont_field_set_to_one,
57 ec_key_simple_priv2oct,
58 ec_key_simple_oct2priv,
59 0, /* set private */
60 ec_key_simple_generate_key,
61 ec_key_simple_check_key,
62 ec_key_simple_generate_public_key,
63 0, /* keycopy */
64 0, /* keyfinish */
65 ecdh_simple_compute_key,
66 0, /* field_inverse_mod_ord */
67 ec_GFp_simple_blind_coordinates,
68 ec_GFp_simple_ladder_pre,
69 ec_GFp_simple_ladder_step,
70 ec_GFp_simple_ladder_post
71 };
72
73 return &ret;
74 }
75
ec_GFp_mont_group_init(EC_GROUP * group)76 int ec_GFp_mont_group_init(EC_GROUP *group)
77 {
78 int ok;
79
80 ok = ec_GFp_simple_group_init(group);
81 group->field_data1 = NULL;
82 group->field_data2 = NULL;
83 return ok;
84 }
85
ec_GFp_mont_group_finish(EC_GROUP * group)86 void ec_GFp_mont_group_finish(EC_GROUP *group)
87 {
88 BN_MONT_CTX_free(group->field_data1);
89 group->field_data1 = NULL;
90 BN_free(group->field_data2);
91 group->field_data2 = NULL;
92 ec_GFp_simple_group_finish(group);
93 }
94
ec_GFp_mont_group_clear_finish(EC_GROUP * group)95 void ec_GFp_mont_group_clear_finish(EC_GROUP *group)
96 {
97 BN_MONT_CTX_free(group->field_data1);
98 group->field_data1 = NULL;
99 BN_clear_free(group->field_data2);
100 group->field_data2 = NULL;
101 ec_GFp_simple_group_clear_finish(group);
102 }
103
ec_GFp_mont_group_copy(EC_GROUP * dest,const EC_GROUP * src)104 int ec_GFp_mont_group_copy(EC_GROUP *dest, const EC_GROUP *src)
105 {
106 BN_MONT_CTX_free(dest->field_data1);
107 dest->field_data1 = NULL;
108 BN_clear_free(dest->field_data2);
109 dest->field_data2 = NULL;
110
111 if (!ec_GFp_simple_group_copy(dest, src))
112 return 0;
113
114 if (src->field_data1 != NULL) {
115 dest->field_data1 = BN_MONT_CTX_new();
116 if (dest->field_data1 == NULL)
117 return 0;
118 if (!BN_MONT_CTX_copy(dest->field_data1, src->field_data1))
119 goto err;
120 }
121 if (src->field_data2 != NULL) {
122 dest->field_data2 = BN_dup(src->field_data2);
123 if (dest->field_data2 == NULL)
124 goto err;
125 }
126
127 return 1;
128
129 err:
130 BN_MONT_CTX_free(dest->field_data1);
131 dest->field_data1 = NULL;
132 return 0;
133 }
134
ec_GFp_mont_group_set_curve(EC_GROUP * group,const BIGNUM * p,const BIGNUM * a,const BIGNUM * b,BN_CTX * ctx)135 int ec_GFp_mont_group_set_curve(EC_GROUP *group, const BIGNUM *p,
136 const BIGNUM *a, const BIGNUM *b, BN_CTX *ctx)
137 {
138 BN_CTX *new_ctx = NULL;
139 BN_MONT_CTX *mont = NULL;
140 BIGNUM *one = NULL;
141 int ret = 0;
142
143 BN_MONT_CTX_free(group->field_data1);
144 group->field_data1 = NULL;
145 BN_free(group->field_data2);
146 group->field_data2 = NULL;
147
148 if (ctx == NULL) {
149 ctx = new_ctx = BN_CTX_new();
150 if (ctx == NULL)
151 return 0;
152 }
153
154 mont = BN_MONT_CTX_new();
155 if (mont == NULL)
156 goto err;
157 if (!BN_MONT_CTX_set(mont, p, ctx)) {
158 ECerr(EC_F_EC_GFP_MONT_GROUP_SET_CURVE, ERR_R_BN_LIB);
159 goto err;
160 }
161 one = BN_new();
162 if (one == NULL)
163 goto err;
164 if (!BN_to_montgomery(one, BN_value_one(), mont, ctx))
165 goto err;
166
167 group->field_data1 = mont;
168 mont = NULL;
169 group->field_data2 = one;
170 one = NULL;
171
172 ret = ec_GFp_simple_group_set_curve(group, p, a, b, ctx);
173
174 if (!ret) {
175 BN_MONT_CTX_free(group->field_data1);
176 group->field_data1 = NULL;
177 BN_free(group->field_data2);
178 group->field_data2 = NULL;
179 }
180
181 err:
182 BN_free(one);
183 BN_CTX_free(new_ctx);
184 BN_MONT_CTX_free(mont);
185 return ret;
186 }
187
ec_GFp_mont_field_mul(const EC_GROUP * group,BIGNUM * r,const BIGNUM * a,const BIGNUM * b,BN_CTX * ctx)188 int ec_GFp_mont_field_mul(const EC_GROUP *group, BIGNUM *r, const BIGNUM *a,
189 const BIGNUM *b, BN_CTX *ctx)
190 {
191 if (group->field_data1 == NULL) {
192 ECerr(EC_F_EC_GFP_MONT_FIELD_MUL, EC_R_NOT_INITIALIZED);
193 return 0;
194 }
195
196 return BN_mod_mul_montgomery(r, a, b, group->field_data1, ctx);
197 }
198
ec_GFp_mont_field_sqr(const EC_GROUP * group,BIGNUM * r,const BIGNUM * a,BN_CTX * ctx)199 int ec_GFp_mont_field_sqr(const EC_GROUP *group, BIGNUM *r, const BIGNUM *a,
200 BN_CTX *ctx)
201 {
202 if (group->field_data1 == NULL) {
203 ECerr(EC_F_EC_GFP_MONT_FIELD_SQR, EC_R_NOT_INITIALIZED);
204 return 0;
205 }
206
207 return BN_mod_mul_montgomery(r, a, a, group->field_data1, ctx);
208 }
209
210 /*-
211 * Computes the multiplicative inverse of a in GF(p), storing the result in r.
212 * If a is zero (or equivalent), you'll get a EC_R_CANNOT_INVERT error.
213 * We have a Mont structure, so SCA hardening is FLT inversion.
214 */
ec_GFp_mont_field_inv(const EC_GROUP * group,BIGNUM * r,const BIGNUM * a,BN_CTX * ctx)215 int ec_GFp_mont_field_inv(const EC_GROUP *group, BIGNUM *r, const BIGNUM *a,
216 BN_CTX *ctx)
217 {
218 BIGNUM *e = NULL;
219 BN_CTX *new_ctx = NULL;
220 int ret = 0;
221
222 if (group->field_data1 == NULL)
223 return 0;
224
225 if (ctx == NULL && (ctx = new_ctx = BN_CTX_secure_new()) == NULL)
226 return 0;
227
228 BN_CTX_start(ctx);
229 if ((e = BN_CTX_get(ctx)) == NULL)
230 goto err;
231
232 /* Inverse in constant time with Fermats Little Theorem */
233 if (!BN_set_word(e, 2))
234 goto err;
235 if (!BN_sub(e, group->field, e))
236 goto err;
237 /*-
238 * Exponent e is public.
239 * No need for scatter-gather or BN_FLG_CONSTTIME.
240 */
241 if (!BN_mod_exp_mont(r, a, e, group->field, ctx, group->field_data1))
242 goto err;
243
244 /* throw an error on zero */
245 if (BN_is_zero(r)) {
246 ECerr(EC_F_EC_GFP_MONT_FIELD_INV, EC_R_CANNOT_INVERT);
247 goto err;
248 }
249
250 ret = 1;
251
252 err:
253 BN_CTX_end(ctx);
254 BN_CTX_free(new_ctx);
255 return ret;
256 }
257
ec_GFp_mont_field_encode(const EC_GROUP * group,BIGNUM * r,const BIGNUM * a,BN_CTX * ctx)258 int ec_GFp_mont_field_encode(const EC_GROUP *group, BIGNUM *r,
259 const BIGNUM *a, BN_CTX *ctx)
260 {
261 if (group->field_data1 == NULL) {
262 ECerr(EC_F_EC_GFP_MONT_FIELD_ENCODE, EC_R_NOT_INITIALIZED);
263 return 0;
264 }
265
266 return BN_to_montgomery(r, a, (BN_MONT_CTX *)group->field_data1, ctx);
267 }
268
ec_GFp_mont_field_decode(const EC_GROUP * group,BIGNUM * r,const BIGNUM * a,BN_CTX * ctx)269 int ec_GFp_mont_field_decode(const EC_GROUP *group, BIGNUM *r,
270 const BIGNUM *a, BN_CTX *ctx)
271 {
272 if (group->field_data1 == NULL) {
273 ECerr(EC_F_EC_GFP_MONT_FIELD_DECODE, EC_R_NOT_INITIALIZED);
274 return 0;
275 }
276
277 return BN_from_montgomery(r, a, group->field_data1, ctx);
278 }
279
ec_GFp_mont_field_set_to_one(const EC_GROUP * group,BIGNUM * r,BN_CTX * ctx)280 int ec_GFp_mont_field_set_to_one(const EC_GROUP *group, BIGNUM *r,
281 BN_CTX *ctx)
282 {
283 if (group->field_data2 == NULL) {
284 ECerr(EC_F_EC_GFP_MONT_FIELD_SET_TO_ONE, EC_R_NOT_INITIALIZED);
285 return 0;
286 }
287
288 if (!BN_copy(r, group->field_data2))
289 return 0;
290 return 1;
291 }
292