1/*
2 * Copyright 2001-2021 The OpenSSL Project Authors. All Rights Reserved.
3 * Copyright (c) 2002, Oracle and/or its affiliates. All rights reserved
4 *
5 * Licensed under the Apache License 2.0 (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/*
12 * ECDSA low level APIs are deprecated for public use, but still ok for
13 * internal use.
14 */
15#include "internal/deprecated.h"
16
17#include <openssl/err.h>
18
19#include "ec_local.h"
20
21const EC_METHOD *EC_GFp_mont_method(void)
22{
23    static const EC_METHOD ret = {
24        EC_FLAGS_DEFAULT_OCT,
25        NID_X9_62_prime_field,
26        ossl_ec_GFp_mont_group_init,
27        ossl_ec_GFp_mont_group_finish,
28        ossl_ec_GFp_mont_group_clear_finish,
29        ossl_ec_GFp_mont_group_copy,
30        ossl_ec_GFp_mont_group_set_curve,
31        ossl_ec_GFp_simple_group_get_curve,
32        ossl_ec_GFp_simple_group_get_degree,
33        ossl_ec_group_simple_order_bits,
34        ossl_ec_GFp_simple_group_check_discriminant,
35        ossl_ec_GFp_simple_point_init,
36        ossl_ec_GFp_simple_point_finish,
37        ossl_ec_GFp_simple_point_clear_finish,
38        ossl_ec_GFp_simple_point_copy,
39        ossl_ec_GFp_simple_point_set_to_infinity,
40        ossl_ec_GFp_simple_point_set_affine_coordinates,
41        ossl_ec_GFp_simple_point_get_affine_coordinates,
42        0, 0, 0,
43        ossl_ec_GFp_simple_add,
44        ossl_ec_GFp_simple_dbl,
45        ossl_ec_GFp_simple_invert,
46        ossl_ec_GFp_simple_is_at_infinity,
47        ossl_ec_GFp_simple_is_on_curve,
48        ossl_ec_GFp_simple_cmp,
49        ossl_ec_GFp_simple_make_affine,
50        ossl_ec_GFp_simple_points_make_affine,
51        0 /* mul */ ,
52        0 /* precompute_mult */ ,
53        0 /* have_precompute_mult */ ,
54        ossl_ec_GFp_mont_field_mul,
55        ossl_ec_GFp_mont_field_sqr,
56        0 /* field_div */ ,
57        ossl_ec_GFp_mont_field_inv,
58        ossl_ec_GFp_mont_field_encode,
59        ossl_ec_GFp_mont_field_decode,
60        ossl_ec_GFp_mont_field_set_to_one,
61        ossl_ec_key_simple_priv2oct,
62        ossl_ec_key_simple_oct2priv,
63        0, /* set private */
64        ossl_ec_key_simple_generate_key,
65        ossl_ec_key_simple_check_key,
66        ossl_ec_key_simple_generate_public_key,
67        0, /* keycopy */
68        0, /* keyfinish */
69        ossl_ecdh_simple_compute_key,
70        ossl_ecdsa_simple_sign_setup,
71        ossl_ecdsa_simple_sign_sig,
72        ossl_ecdsa_simple_verify_sig,
73        0, /* field_inverse_mod_ord */
74        ossl_ec_GFp_simple_blind_coordinates,
75        ossl_ec_GFp_simple_ladder_pre,
76        ossl_ec_GFp_simple_ladder_step,
77        ossl_ec_GFp_simple_ladder_post
78    };
79
80    return &ret;
81}
82
83int ossl_ec_GFp_mont_group_init(EC_GROUP *group)
84{
85    int ok;
86
87    ok = ossl_ec_GFp_simple_group_init(group);
88    group->field_data1 = NULL;
89    group->field_data2 = NULL;
90    return ok;
91}
92
93void ossl_ec_GFp_mont_group_finish(EC_GROUP *group)
94{
95    BN_MONT_CTX_free(group->field_data1);
96    group->field_data1 = NULL;
97    BN_free(group->field_data2);
98    group->field_data2 = NULL;
99    ossl_ec_GFp_simple_group_finish(group);
100}
101
102void ossl_ec_GFp_mont_group_clear_finish(EC_GROUP *group)
103{
104    BN_MONT_CTX_free(group->field_data1);
105    group->field_data1 = NULL;
106    BN_clear_free(group->field_data2);
107    group->field_data2 = NULL;
108    ossl_ec_GFp_simple_group_clear_finish(group);
109}
110
111int ossl_ec_GFp_mont_group_copy(EC_GROUP *dest, const EC_GROUP *src)
112{
113    BN_MONT_CTX_free(dest->field_data1);
114    dest->field_data1 = NULL;
115    BN_clear_free(dest->field_data2);
116    dest->field_data2 = NULL;
117
118    if (!ossl_ec_GFp_simple_group_copy(dest, src))
119        return 0;
120
121    if (src->field_data1 != NULL) {
122        dest->field_data1 = BN_MONT_CTX_new();
123        if (dest->field_data1 == NULL)
124            return 0;
125        if (!BN_MONT_CTX_copy(dest->field_data1, src->field_data1))
126            goto err;
127    }
128    if (src->field_data2 != NULL) {
129        dest->field_data2 = BN_dup(src->field_data2);
130        if (dest->field_data2 == NULL)
131            goto err;
132    }
133
134    return 1;
135
136 err:
137    BN_MONT_CTX_free(dest->field_data1);
138    dest->field_data1 = NULL;
139    return 0;
140}
141
142int ossl_ec_GFp_mont_group_set_curve(EC_GROUP *group, const BIGNUM *p,
143                                     const BIGNUM *a, const BIGNUM *b,
144                                     BN_CTX *ctx)
145{
146    BN_CTX *new_ctx = NULL;
147    BN_MONT_CTX *mont = NULL;
148    BIGNUM *one = NULL;
149    int ret = 0;
150
151    BN_MONT_CTX_free(group->field_data1);
152    group->field_data1 = NULL;
153    BN_free(group->field_data2);
154    group->field_data2 = NULL;
155
156    if (ctx == NULL) {
157        ctx = new_ctx = BN_CTX_new_ex(group->libctx);
158        if (ctx == NULL)
159            return 0;
160    }
161
162    mont = BN_MONT_CTX_new();
163    if (mont == NULL)
164        goto err;
165    if (!BN_MONT_CTX_set(mont, p, ctx)) {
166        ERR_raise(ERR_LIB_EC, ERR_R_BN_LIB);
167        goto err;
168    }
169    one = BN_new();
170    if (one == NULL)
171        goto err;
172    if (!BN_to_montgomery(one, BN_value_one(), mont, ctx))
173        goto err;
174
175    group->field_data1 = mont;
176    mont = NULL;
177    group->field_data2 = one;
178    one = NULL;
179
180    ret = ossl_ec_GFp_simple_group_set_curve(group, p, a, b, ctx);
181
182    if (!ret) {
183        BN_MONT_CTX_free(group->field_data1);
184        group->field_data1 = NULL;
185        BN_free(group->field_data2);
186        group->field_data2 = NULL;
187    }
188
189 err:
190    BN_free(one);
191    BN_CTX_free(new_ctx);
192    BN_MONT_CTX_free(mont);
193    return ret;
194}
195
196int ossl_ec_GFp_mont_field_mul(const EC_GROUP *group, BIGNUM *r, const BIGNUM *a,
197                               const BIGNUM *b, BN_CTX *ctx)
198{
199    if (group->field_data1 == NULL) {
200        ERR_raise(ERR_LIB_EC, EC_R_NOT_INITIALIZED);
201        return 0;
202    }
203
204    return BN_mod_mul_montgomery(r, a, b, group->field_data1, ctx);
205}
206
207int ossl_ec_GFp_mont_field_sqr(const EC_GROUP *group, BIGNUM *r, const BIGNUM *a,
208                               BN_CTX *ctx)
209{
210    if (group->field_data1 == NULL) {
211        ERR_raise(ERR_LIB_EC, EC_R_NOT_INITIALIZED);
212        return 0;
213    }
214
215    return BN_mod_mul_montgomery(r, a, a, group->field_data1, ctx);
216}
217
218/*-
219 * Computes the multiplicative inverse of a in GF(p), storing the result in r.
220 * If a is zero (or equivalent), you'll get a EC_R_CANNOT_INVERT error.
221 * We have a Mont structure, so SCA hardening is FLT inversion.
222 */
223int ossl_ec_GFp_mont_field_inv(const EC_GROUP *group, BIGNUM *r, const BIGNUM *a,
224                               BN_CTX *ctx)
225{
226    BIGNUM *e = NULL;
227    BN_CTX *new_ctx = NULL;
228    int ret = 0;
229
230    if (group->field_data1 == NULL)
231        return 0;
232
233    if (ctx == NULL
234            && (ctx = new_ctx = BN_CTX_secure_new_ex(group->libctx)) == NULL)
235        return 0;
236
237    BN_CTX_start(ctx);
238    if ((e = BN_CTX_get(ctx)) == NULL)
239        goto err;
240
241    /* Inverse in constant time with Fermats Little Theorem */
242    if (!BN_set_word(e, 2))
243        goto err;
244    if (!BN_sub(e, group->field, e))
245        goto err;
246    /*-
247     * Exponent e is public.
248     * No need for scatter-gather or BN_FLG_CONSTTIME.
249     */
250    if (!BN_mod_exp_mont(r, a, e, group->field, ctx, group->field_data1))
251        goto err;
252
253    /* throw an error on zero */
254    if (BN_is_zero(r)) {
255        ERR_raise(ERR_LIB_EC, EC_R_CANNOT_INVERT);
256        goto err;
257    }
258
259    ret = 1;
260
261  err:
262    BN_CTX_end(ctx);
263    BN_CTX_free(new_ctx);
264    return ret;
265}
266
267int ossl_ec_GFp_mont_field_encode(const EC_GROUP *group, BIGNUM *r,
268                                  const BIGNUM *a, BN_CTX *ctx)
269{
270    if (group->field_data1 == NULL) {
271        ERR_raise(ERR_LIB_EC, EC_R_NOT_INITIALIZED);
272        return 0;
273    }
274
275    return BN_to_montgomery(r, a, (BN_MONT_CTX *)group->field_data1, ctx);
276}
277
278int ossl_ec_GFp_mont_field_decode(const EC_GROUP *group, BIGNUM *r,
279                                  const BIGNUM *a, BN_CTX *ctx)
280{
281    if (group->field_data1 == NULL) {
282        ERR_raise(ERR_LIB_EC, EC_R_NOT_INITIALIZED);
283        return 0;
284    }
285
286    return BN_from_montgomery(r, a, group->field_data1, ctx);
287}
288
289int ossl_ec_GFp_mont_field_set_to_one(const EC_GROUP *group, BIGNUM *r,
290                                      BN_CTX *ctx)
291{
292    if (group->field_data2 == NULL) {
293        ERR_raise(ERR_LIB_EC, EC_R_NOT_INITIALIZED);
294        return 0;
295    }
296
297    if (!BN_copy(r, group->field_data2))
298        return 0;
299    return 1;
300}
301