1 /* crypto/ecdsa/ecs_ossl.c */
3 * Written by Nils Larsch for the OpenSSL project
5 /* ====================================================================
6 * Copyright (c) 1998-2004 The OpenSSL Project. All rights reserved.
8 * Redistribution and use in source and binary forms, with or without
9 * modification, are permitted provided that the following conditions
12 * 1. Redistributions of source code must retain the above copyright
13 * notice, this list of conditions and the following disclaimer.
15 * 2. Redistributions in binary form must reproduce the above copyright
16 * notice, this list of conditions and the following disclaimer in
17 * the documentation and/or other materials provided with the
20 * 3. All advertising materials mentioning features or use of this
21 * software must display the following acknowledgment:
22 * "This product includes software developed by the OpenSSL Project
23 * for use in the OpenSSL Toolkit. (http://www.OpenSSL.org/)"
25 * 4. The names "OpenSSL Toolkit" and "OpenSSL Project" must not be used to
26 * endorse or promote products derived from this software without
27 * prior written permission. For written permission, please contact
28 * openssl-core@OpenSSL.org.
30 * 5. Products derived from this software may not be called "OpenSSL"
31 * nor may "OpenSSL" appear in their names without prior written
32 * permission of the OpenSSL Project.
34 * 6. Redistributions of any form whatsoever must retain the following
36 * "This product includes software developed by the OpenSSL Project
37 * for use in the OpenSSL Toolkit (http://www.OpenSSL.org/)"
39 * THIS SOFTWARE IS PROVIDED BY THE OpenSSL PROJECT ``AS IS'' AND ANY
40 * EXPRESSED OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
41 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
42 * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE OpenSSL PROJECT OR
43 * ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
44 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
45 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
46 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
47 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
48 * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
49 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
50 * OF THE POSSIBILITY OF SUCH DAMAGE.
51 * ====================================================================
53 * This product includes cryptographic software written by Eric Young
54 * (eay@cryptsoft.com). This product includes software written by Tim
55 * Hudson (tjh@cryptsoft.com).
60 #include <openssl/err.h>
61 #include <openssl/obj_mac.h>
62 #include <openssl/bn.h>
64 static ECDSA_SIG *ecdsa_do_sign(const unsigned char *dgst, int dlen,
65 const BIGNUM *, const BIGNUM *,
67 static int ecdsa_sign_setup(EC_KEY *eckey, BN_CTX *ctx_in, BIGNUM **kinvp,
69 static int ecdsa_do_verify(const unsigned char *dgst, int dgst_len,
70 const ECDSA_SIG *sig, EC_KEY *eckey);
72 static ECDSA_METHOD openssl_ecdsa_meth = {
73 "OpenSSL ECDSA method",
85 const ECDSA_METHOD *ECDSA_OpenSSL(void)
87 return &openssl_ecdsa_meth;
90 static int ecdsa_sign_setup(EC_KEY *eckey, BN_CTX *ctx_in, BIGNUM **kinvp,
94 BIGNUM *k = NULL, *r = NULL, *order = NULL, *X = NULL;
95 EC_POINT *tmp_point = NULL;
96 const EC_GROUP *group;
100 if (eckey == NULL || (group = EC_KEY_get0_group(eckey)) == NULL) {
101 ECDSAerr(ECDSA_F_ECDSA_SIGN_SETUP, ERR_R_PASSED_NULL_PARAMETER);
105 if (ctx_in == NULL) {
106 if ((ctx = BN_CTX_new()) == NULL) {
107 ECDSAerr(ECDSA_F_ECDSA_SIGN_SETUP, ERR_R_MALLOC_FAILURE);
113 k = BN_new(); /* this value is later returned in *kinvp */
114 r = BN_new(); /* this value is later returned in *rp */
117 if (!k || !r || !order || !X) {
118 ECDSAerr(ECDSA_F_ECDSA_SIGN_SETUP, ERR_R_MALLOC_FAILURE);
121 if ((tmp_point = EC_POINT_new(group)) == NULL) {
122 ECDSAerr(ECDSA_F_ECDSA_SIGN_SETUP, ERR_R_EC_LIB);
125 if (!EC_GROUP_get_order(group, order, ctx)) {
126 ECDSAerr(ECDSA_F_ECDSA_SIGN_SETUP, ERR_R_EC_LIB);
130 /* Preallocate space */
131 order_bits = BN_num_bits(order);
132 if (!BN_set_bit(k, order_bits)
133 || !BN_set_bit(r, order_bits)
134 || !BN_set_bit(X, order_bits))
140 if (!BN_rand_range(k, order)) {
141 ECDSAerr(ECDSA_F_ECDSA_SIGN_SETUP,
142 ECDSA_R_RANDOM_NUMBER_GENERATION_FAILED);
145 while (BN_is_zero(k)) ;
148 * We do not want timing information to leak the length of k, so we
149 * compute G*k using an equivalent scalar of fixed bit-length.
151 * We unconditionally perform both of these additions to prevent a
152 * small timing information leakage. We then choose the sum that is
153 * one bit longer than the order. This guarantees the code
154 * path used in the constant time implementations elsewhere.
156 * TODO: revisit the BN_copy aiming for a memory access agnostic
159 if (!BN_add(r, k, order)
160 || !BN_add(X, r, order)
161 || !BN_copy(k, BN_num_bits(r) > order_bits ? r : X))
164 /* compute r the x-coordinate of generator * k */
165 if (!EC_POINT_mul(group, tmp_point, k, NULL, NULL, ctx)) {
166 ECDSAerr(ECDSA_F_ECDSA_SIGN_SETUP, ERR_R_EC_LIB);
169 if (EC_METHOD_get_field_type(EC_GROUP_method_of(group)) ==
170 NID_X9_62_prime_field) {
171 if (!EC_POINT_get_affine_coordinates_GFp
172 (group, tmp_point, X, NULL, ctx)) {
173 ECDSAerr(ECDSA_F_ECDSA_SIGN_SETUP, ERR_R_EC_LIB);
177 #ifndef OPENSSL_NO_EC2M
178 else { /* NID_X9_62_characteristic_two_field */
180 if (!EC_POINT_get_affine_coordinates_GF2m(group,
183 ECDSAerr(ECDSA_F_ECDSA_SIGN_SETUP, ERR_R_EC_LIB);
188 if (!BN_nnmod(r, X, order, ctx)) {
189 ECDSAerr(ECDSA_F_ECDSA_SIGN_SETUP, ERR_R_BN_LIB);
193 while (BN_is_zero(r));
195 /* compute the inverse of k */
196 if (EC_GROUP_get_mont_data(group) != NULL) {
198 * We want inverse in constant time, therefore we utilize the fact
199 * order must be prime and use Fermats Little Theorem instead.
201 if (!BN_set_word(X, 2)) {
202 ECDSAerr(ECDSA_F_ECDSA_SIGN_SETUP, ERR_R_BN_LIB);
205 if (!BN_mod_sub(X, order, X, order, ctx)) {
206 ECDSAerr(ECDSA_F_ECDSA_SIGN_SETUP, ERR_R_BN_LIB);
209 BN_set_flags(X, BN_FLG_CONSTTIME);
210 if (!BN_mod_exp_mont_consttime
211 (k, k, X, order, ctx, EC_GROUP_get_mont_data(group))) {
212 ECDSAerr(ECDSA_F_ECDSA_SIGN_SETUP, ERR_R_BN_LIB);
216 if (!BN_mod_inverse(k, k, order, ctx)) {
217 ECDSAerr(ECDSA_F_ECDSA_SIGN_SETUP, ERR_R_BN_LIB);
222 /* clear old values if necessary */
226 BN_clear_free(*kinvp);
227 /* save the pre-computed values */
242 if (tmp_point != NULL)
243 EC_POINT_free(tmp_point);
249 static ECDSA_SIG *ecdsa_do_sign(const unsigned char *dgst, int dgst_len,
250 const BIGNUM *in_kinv, const BIGNUM *in_r,
254 BIGNUM *kinv = NULL, *s, *m = NULL, *tmp = NULL, *order = NULL;
255 BIGNUM *blind = NULL, *blindm = NULL;
258 const EC_GROUP *group;
261 const BIGNUM *priv_key;
263 ecdsa = ecdsa_check(eckey);
264 group = EC_KEY_get0_group(eckey);
265 priv_key = EC_KEY_get0_private_key(eckey);
267 if (group == NULL || priv_key == NULL || ecdsa == NULL) {
268 ECDSAerr(ECDSA_F_ECDSA_DO_SIGN, ERR_R_PASSED_NULL_PARAMETER);
272 ret = ECDSA_SIG_new();
274 ECDSAerr(ECDSA_F_ECDSA_DO_SIGN, ERR_R_MALLOC_FAILURE);
281 ECDSAerr(ECDSA_F_ECDSA_DO_SIGN, ERR_R_MALLOC_FAILURE);
286 order = BN_CTX_get(ctx);
287 tmp = BN_CTX_get(ctx);
289 blind = BN_CTX_get(ctx);
290 blindm = BN_CTX_get(ctx);
291 if (blindm == NULL) {
292 ECDSAerr(ECDSA_F_ECDSA_DO_SIGN, ERR_R_MALLOC_FAILURE);
296 if (!EC_GROUP_get_order(group, order, ctx)) {
297 ECDSAerr(ECDSA_F_ECDSA_DO_SIGN, ERR_R_EC_LIB);
300 i = BN_num_bits(order);
302 * Need to truncate digest if it is too long: first truncate whole bytes.
304 if (8 * dgst_len > i)
305 dgst_len = (i + 7) / 8;
306 if (!BN_bin2bn(dgst, dgst_len, m)) {
307 ECDSAerr(ECDSA_F_ECDSA_DO_SIGN, ERR_R_BN_LIB);
310 /* If still too long truncate remaining bits with a shift */
311 if ((8 * dgst_len > i) && !BN_rshift(m, m, 8 - (i & 0x7))) {
312 ECDSAerr(ECDSA_F_ECDSA_DO_SIGN, ERR_R_BN_LIB);
316 if (in_kinv == NULL || in_r == NULL) {
317 if (!ECDSA_sign_setup(eckey, ctx, &kinv, &ret->r)) {
318 ECDSAerr(ECDSA_F_ECDSA_DO_SIGN, ERR_R_ECDSA_LIB);
324 if (BN_copy(ret->r, in_r) == NULL) {
325 ECDSAerr(ECDSA_F_ECDSA_DO_SIGN, ERR_R_MALLOC_FAILURE);
331 * The normal signature calculation is:
333 * s := k^-1 * (m + r * priv_key) mod order
335 * We will blind this to protect against side channel attacks
337 * s := blind^-1 * k^-1 * (blind * m + blind * r * priv_key) mod order
340 /* Generate a blinding value */
342 if (!BN_rand(blind, BN_num_bits(order) - 1, -1, 0))
344 } while (BN_is_zero(blind));
345 BN_set_flags(blind, BN_FLG_CONSTTIME);
346 BN_set_flags(blindm, BN_FLG_CONSTTIME);
347 BN_set_flags(tmp, BN_FLG_CONSTTIME);
349 /* tmp := blind * priv_key * r mod order */
350 if (!BN_mod_mul(tmp, blind, priv_key, order, ctx)) {
351 ECDSAerr(ECDSA_F_ECDSA_DO_SIGN, ERR_R_BN_LIB);
354 if (!BN_mod_mul(tmp, tmp, ret->r, order, ctx)) {
355 ECDSAerr(ECDSA_F_ECDSA_DO_SIGN, ERR_R_BN_LIB);
359 /* blindm := blind * m mod order */
360 if (!BN_mod_mul(blindm, blind, m, order, ctx)) {
361 ECDSAerr(ECDSA_F_ECDSA_DO_SIGN, ERR_R_BN_LIB);
365 /* s : = (blind * priv_key * r) + (blind * m) mod order */
366 if (!BN_mod_add_quick(s, tmp, blindm, order)) {
367 ECDSAerr(ECDSA_F_ECDSA_DO_SIGN, ERR_R_BN_LIB);
371 /* s := s * k^-1 mod order */
372 if (!BN_mod_mul(s, s, ckinv, order, ctx)) {
373 ECDSAerr(ECDSA_F_ECDSA_DO_SIGN, ERR_R_BN_LIB);
377 /* s:= s * blind^-1 mod order */
378 if (BN_mod_inverse(blind, blind, order, ctx) == NULL) {
379 ECDSAerr(ECDSA_F_ECDSA_DO_SIGN, ERR_R_BN_LIB);
382 if (!BN_mod_mul(s, s, blind, order, ctx)) {
383 ECDSAerr(ECDSA_F_ECDSA_DO_SIGN, ERR_R_BN_LIB);
389 * if kinv and r have been supplied by the caller don't to
390 * generate new kinv and r values
392 if (in_kinv != NULL && in_r != NULL) {
393 ECDSAerr(ECDSA_F_ECDSA_DO_SIGN, ECDSA_R_NEED_NEW_SETUP_VALUES);
397 /* s != 0 => we have a valid signature */
417 static int ecdsa_do_verify(const unsigned char *dgst, int dgst_len,
418 const ECDSA_SIG *sig, EC_KEY *eckey)
422 BIGNUM *order, *u1, *u2, *m, *X;
423 EC_POINT *point = NULL;
424 const EC_GROUP *group;
425 const EC_POINT *pub_key;
427 /* check input values */
428 if (eckey == NULL || (group = EC_KEY_get0_group(eckey)) == NULL ||
429 (pub_key = EC_KEY_get0_public_key(eckey)) == NULL || sig == NULL) {
430 ECDSAerr(ECDSA_F_ECDSA_DO_VERIFY, ECDSA_R_MISSING_PARAMETERS);
436 ECDSAerr(ECDSA_F_ECDSA_DO_VERIFY, ERR_R_MALLOC_FAILURE);
440 order = BN_CTX_get(ctx);
441 u1 = BN_CTX_get(ctx);
442 u2 = BN_CTX_get(ctx);
446 ECDSAerr(ECDSA_F_ECDSA_DO_VERIFY, ERR_R_BN_LIB);
450 if (!EC_GROUP_get_order(group, order, ctx)) {
451 ECDSAerr(ECDSA_F_ECDSA_DO_VERIFY, ERR_R_EC_LIB);
455 if (BN_is_zero(sig->r) || BN_is_negative(sig->r) ||
456 BN_ucmp(sig->r, order) >= 0 || BN_is_zero(sig->s) ||
457 BN_is_negative(sig->s) || BN_ucmp(sig->s, order) >= 0) {
458 ECDSAerr(ECDSA_F_ECDSA_DO_VERIFY, ECDSA_R_BAD_SIGNATURE);
459 ret = 0; /* signature is invalid */
462 /* calculate tmp1 = inv(S) mod order */
463 if (!BN_mod_inverse(u2, sig->s, order, ctx)) {
464 ECDSAerr(ECDSA_F_ECDSA_DO_VERIFY, ERR_R_BN_LIB);
468 i = BN_num_bits(order);
470 * Need to truncate digest if it is too long: first truncate whole bytes.
472 if (8 * dgst_len > i)
473 dgst_len = (i + 7) / 8;
474 if (!BN_bin2bn(dgst, dgst_len, m)) {
475 ECDSAerr(ECDSA_F_ECDSA_DO_VERIFY, ERR_R_BN_LIB);
478 /* If still too long truncate remaining bits with a shift */
479 if ((8 * dgst_len > i) && !BN_rshift(m, m, 8 - (i & 0x7))) {
480 ECDSAerr(ECDSA_F_ECDSA_DO_VERIFY, ERR_R_BN_LIB);
483 /* u1 = m * tmp mod order */
484 if (!BN_mod_mul(u1, m, u2, order, ctx)) {
485 ECDSAerr(ECDSA_F_ECDSA_DO_VERIFY, ERR_R_BN_LIB);
488 /* u2 = r * w mod q */
489 if (!BN_mod_mul(u2, sig->r, u2, order, ctx)) {
490 ECDSAerr(ECDSA_F_ECDSA_DO_VERIFY, ERR_R_BN_LIB);
494 if ((point = EC_POINT_new(group)) == NULL) {
495 ECDSAerr(ECDSA_F_ECDSA_DO_VERIFY, ERR_R_MALLOC_FAILURE);
498 if (!EC_POINT_mul(group, point, u1, pub_key, u2, ctx)) {
499 ECDSAerr(ECDSA_F_ECDSA_DO_VERIFY, ERR_R_EC_LIB);
502 if (EC_METHOD_get_field_type(EC_GROUP_method_of(group)) ==
503 NID_X9_62_prime_field) {
504 if (!EC_POINT_get_affine_coordinates_GFp(group, point, X, NULL, ctx)) {
505 ECDSAerr(ECDSA_F_ECDSA_DO_VERIFY, ERR_R_EC_LIB);
509 #ifndef OPENSSL_NO_EC2M
510 else { /* NID_X9_62_characteristic_two_field */
512 if (!EC_POINT_get_affine_coordinates_GF2m(group, point, X, NULL, ctx)) {
513 ECDSAerr(ECDSA_F_ECDSA_DO_VERIFY, ERR_R_EC_LIB);
518 if (!BN_nnmod(u1, X, order, ctx)) {
519 ECDSAerr(ECDSA_F_ECDSA_DO_VERIFY, ERR_R_BN_LIB);
522 /* if the signature is correct u1 is equal to sig->r */
523 ret = (BN_ucmp(u1, sig->r) == 0);
528 EC_POINT_free(point);