xref: /openssl/crypto/ec/ecp_mont.c (revision 1567a821)
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 
EC_GFp_mont_method(void)21 const 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 
ossl_ec_GFp_mont_group_init(EC_GROUP * group)83 int 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 
ossl_ec_GFp_mont_group_finish(EC_GROUP * group)93 void 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 
ossl_ec_GFp_mont_group_clear_finish(EC_GROUP * group)102 void 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 
ossl_ec_GFp_mont_group_copy(EC_GROUP * dest,const EC_GROUP * src)111 int 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 
ossl_ec_GFp_mont_group_set_curve(EC_GROUP * group,const BIGNUM * p,const BIGNUM * a,const BIGNUM * b,BN_CTX * ctx)142 int 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 
ossl_ec_GFp_mont_field_mul(const EC_GROUP * group,BIGNUM * r,const BIGNUM * a,const BIGNUM * b,BN_CTX * ctx)196 int 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 
ossl_ec_GFp_mont_field_sqr(const EC_GROUP * group,BIGNUM * r,const BIGNUM * a,BN_CTX * ctx)207 int 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 an EC_R_CANNOT_INVERT error.
221  * We have a Mont structure, so SCA hardening is FLT inversion.
222  */
ossl_ec_GFp_mont_field_inv(const EC_GROUP * group,BIGNUM * r,const BIGNUM * a,BN_CTX * ctx)223 int 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 
ossl_ec_GFp_mont_field_encode(const EC_GROUP * group,BIGNUM * r,const BIGNUM * a,BN_CTX * ctx)267 int 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 
ossl_ec_GFp_mont_field_decode(const EC_GROUP * group,BIGNUM * r,const BIGNUM * a,BN_CTX * ctx)278 int 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 
ossl_ec_GFp_mont_field_set_to_one(const EC_GROUP * group,BIGNUM * r,BN_CTX * ctx)289 int 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