2 * Copyright 2002-2018 The OpenSSL Project Authors. All Rights Reserved.
4 * Licensed under the OpenSSL license (the "License"). You may not use
5 * this file except in compliance with the License. You can obtain a copy
6 * in the file LICENSE in the source distribution or at
7 * https://www.openssl.org/source/license.html
11 #include <openssl/err.h>
12 #include <openssl/obj_mac.h>
13 #include <openssl/bn.h>
14 #include <openssl/rand.h>
15 #include <openssl/ec.h>
18 int ossl_ecdsa_sign(int type, const unsigned char *dgst, int dlen,
19 unsigned char *sig, unsigned int *siglen,
20 const BIGNUM *kinv, const BIGNUM *r, EC_KEY *eckey)
24 s = ECDSA_do_sign_ex(dgst, dlen, kinv, r, eckey);
29 *siglen = i2d_ECDSA_SIG(s, &sig);
34 static int ecdsa_sign_setup(EC_KEY *eckey, BN_CTX *ctx_in,
35 BIGNUM **kinvp, BIGNUM **rp,
36 const unsigned char *dgst, int dlen)
39 BIGNUM *k = NULL, *r = NULL, *X = NULL;
41 EC_POINT *tmp_point = NULL;
42 const EC_GROUP *group;
46 if (eckey == NULL || (group = EC_KEY_get0_group(eckey)) == NULL) {
47 ECerr(EC_F_ECDSA_SIGN_SETUP, ERR_R_PASSED_NULL_PARAMETER);
51 if (!EC_KEY_can_sign(eckey)) {
52 ECerr(EC_F_ECDSA_SIGN_SETUP, EC_R_CURVE_DOES_NOT_SUPPORT_SIGNING);
57 if ((ctx = BN_CTX_new()) == NULL) {
58 ECerr(EC_F_ECDSA_SIGN_SETUP, ERR_R_MALLOC_FAILURE);
64 k = BN_new(); /* this value is later returned in *kinvp */
65 r = BN_new(); /* this value is later returned in *rp */
67 if (k == NULL || r == NULL || X == NULL) {
68 ECerr(EC_F_ECDSA_SIGN_SETUP, ERR_R_MALLOC_FAILURE);
71 if ((tmp_point = EC_POINT_new(group)) == NULL) {
72 ECerr(EC_F_ECDSA_SIGN_SETUP, ERR_R_EC_LIB);
75 order = EC_GROUP_get0_order(group);
77 ECerr(EC_F_ECDSA_SIGN_SETUP, ERR_R_EC_LIB);
81 /* Preallocate space */
82 order_bits = BN_num_bits(order);
83 if (!BN_set_bit(k, order_bits)
84 || !BN_set_bit(r, order_bits)
85 || !BN_set_bit(X, order_bits))
92 if (!BN_generate_dsa_nonce
93 (k, order, EC_KEY_get0_private_key(eckey), dgst, dlen,
95 ECerr(EC_F_ECDSA_SIGN_SETUP,
96 EC_R_RANDOM_NUMBER_GENERATION_FAILED);
100 if (!BN_priv_rand_range(k, order)) {
101 ECerr(EC_F_ECDSA_SIGN_SETUP,
102 EC_R_RANDOM_NUMBER_GENERATION_FAILED);
106 while (BN_is_zero(k));
108 /* compute r the x-coordinate of generator * k */
109 if (!EC_POINT_mul(group, tmp_point, k, NULL, NULL, ctx)) {
110 ECerr(EC_F_ECDSA_SIGN_SETUP, ERR_R_EC_LIB);
113 if (EC_METHOD_get_field_type(EC_GROUP_method_of(group)) ==
114 NID_X9_62_prime_field) {
115 if (!EC_POINT_get_affine_coordinates_GFp
116 (group, tmp_point, X, NULL, ctx)) {
117 ECerr(EC_F_ECDSA_SIGN_SETUP, ERR_R_EC_LIB);
121 #ifndef OPENSSL_NO_EC2M
122 else { /* NID_X9_62_characteristic_two_field */
124 if (!EC_POINT_get_affine_coordinates_GF2m(group,
127 ECerr(EC_F_ECDSA_SIGN_SETUP, ERR_R_EC_LIB);
132 if (!BN_nnmod(r, X, order, ctx)) {
133 ECerr(EC_F_ECDSA_SIGN_SETUP, ERR_R_BN_LIB);
137 while (BN_is_zero(r));
139 /* Check if optimized inverse is implemented */
140 if (EC_GROUP_do_inverse_ord(group, k, k, ctx) == 0) {
141 /* compute the inverse of k */
142 if (group->mont_data != NULL) {
144 * We want inverse in constant time, therefore we utilize the fact
145 * order must be prime and use Fermats Little Theorem instead.
147 if (!BN_set_word(X, 2)) {
148 ECerr(EC_F_ECDSA_SIGN_SETUP, ERR_R_BN_LIB);
151 if (!BN_mod_sub(X, order, X, order, ctx)) {
152 ECerr(EC_F_ECDSA_SIGN_SETUP, ERR_R_BN_LIB);
155 BN_set_flags(X, BN_FLG_CONSTTIME);
156 if (!BN_mod_exp_mont_consttime(k, k, X, order, ctx,
158 ECerr(EC_F_ECDSA_SIGN_SETUP, ERR_R_BN_LIB);
162 if (!BN_mod_inverse(k, k, order, ctx)) {
163 ECerr(EC_F_ECDSA_SIGN_SETUP, ERR_R_BN_LIB);
169 /* clear old values if necessary */
171 BN_clear_free(*kinvp);
172 /* save the pre-computed values */
183 EC_POINT_free(tmp_point);
188 int ossl_ecdsa_sign_setup(EC_KEY *eckey, BN_CTX *ctx_in, BIGNUM **kinvp,
191 return ecdsa_sign_setup(eckey, ctx_in, kinvp, rp, NULL, 0);
194 ECDSA_SIG *ossl_ecdsa_sign_sig(const unsigned char *dgst, int dgst_len,
195 const BIGNUM *in_kinv, const BIGNUM *in_r,
199 BIGNUM *kinv = NULL, *s, *m = NULL, *tmp = NULL, *blind = NULL;
200 BIGNUM *blindm = NULL;
201 const BIGNUM *order, *ckinv;
203 const EC_GROUP *group;
205 const BIGNUM *priv_key;
207 group = EC_KEY_get0_group(eckey);
208 priv_key = EC_KEY_get0_private_key(eckey);
210 if (group == NULL || priv_key == NULL) {
211 ECerr(EC_F_OSSL_ECDSA_SIGN_SIG, ERR_R_PASSED_NULL_PARAMETER);
215 if (!EC_KEY_can_sign(eckey)) {
216 ECerr(EC_F_OSSL_ECDSA_SIGN_SIG, EC_R_CURVE_DOES_NOT_SUPPORT_SIGNING);
220 ret = ECDSA_SIG_new();
222 ECerr(EC_F_OSSL_ECDSA_SIGN_SIG, ERR_R_MALLOC_FAILURE);
227 if (ret->r == NULL || ret->s == NULL) {
228 ECerr(EC_F_OSSL_ECDSA_SIGN_SIG, ERR_R_MALLOC_FAILURE);
233 ctx = BN_CTX_secure_new();
235 ECerr(EC_F_OSSL_ECDSA_SIGN_SIG, ERR_R_MALLOC_FAILURE);
240 tmp = BN_CTX_get(ctx);
242 blind = BN_CTX_get(ctx);
243 blindm = BN_CTX_get(ctx);
244 if (blindm == NULL) {
245 ECerr(EC_F_OSSL_ECDSA_SIGN_SIG, ERR_R_MALLOC_FAILURE);
249 order = EC_GROUP_get0_order(group);
251 ECerr(EC_F_OSSL_ECDSA_SIGN_SIG, ERR_R_EC_LIB);
254 i = BN_num_bits(order);
256 * Need to truncate digest if it is too long: first truncate whole bytes.
258 if (8 * dgst_len > i)
259 dgst_len = (i + 7) / 8;
260 if (!BN_bin2bn(dgst, dgst_len, m)) {
261 ECerr(EC_F_OSSL_ECDSA_SIGN_SIG, ERR_R_BN_LIB);
264 /* If still too long truncate remaining bits with a shift */
265 if ((8 * dgst_len > i) && !BN_rshift(m, m, 8 - (i & 0x7))) {
266 ECerr(EC_F_OSSL_ECDSA_SIGN_SIG, ERR_R_BN_LIB);
270 if (in_kinv == NULL || in_r == NULL) {
271 if (!ecdsa_sign_setup(eckey, ctx, &kinv, &ret->r, dgst, dgst_len)) {
272 ECerr(EC_F_OSSL_ECDSA_SIGN_SIG, ERR_R_ECDSA_LIB);
278 if (BN_copy(ret->r, in_r) == NULL) {
279 ECerr(EC_F_OSSL_ECDSA_SIGN_SIG, ERR_R_MALLOC_FAILURE);
285 * The normal signature calculation is:
287 * s := k^-1 * (m + r * priv_key) mod order
289 * We will blind this to protect against side channel attacks
291 * s := k^-1 * blind^-1 * (blind * m + blind * r * priv_key) mod order
294 /* Generate a blinding value */
296 if (!BN_priv_rand(blind, BN_num_bits(order) - 1,
297 BN_RAND_TOP_ANY, BN_RAND_BOTTOM_ANY))
299 } while (BN_is_zero(blind));
300 BN_set_flags(blind, BN_FLG_CONSTTIME);
301 BN_set_flags(blindm, BN_FLG_CONSTTIME);
302 BN_set_flags(tmp, BN_FLG_CONSTTIME);
304 /* tmp := blind * priv_key * r mod order */
305 if (!BN_mod_mul(tmp, blind, priv_key, order, ctx)) {
306 ECerr(EC_F_OSSL_ECDSA_SIGN_SIG, ERR_R_BN_LIB);
309 if (!BN_mod_mul(tmp, tmp, ret->r, order, ctx)) {
310 ECerr(EC_F_OSSL_ECDSA_SIGN_SIG, ERR_R_BN_LIB);
314 /* blindm := blind * m mod order */
315 if (!BN_mod_mul(blindm, blind, m, order, ctx)) {
316 ECerr(EC_F_OSSL_ECDSA_SIGN_SIG, ERR_R_BN_LIB);
320 /* s : = (blind * priv_key * r) + (blind * m) mod order */
321 if (!BN_mod_add_quick(s, tmp, blindm, order)) {
322 ECerr(EC_F_OSSL_ECDSA_SIGN_SIG, ERR_R_BN_LIB);
326 /* s:= s * blind^-1 mod order */
327 if (BN_mod_inverse(blind, blind, order, ctx) == NULL) {
328 ECerr(EC_F_OSSL_ECDSA_SIGN_SIG, ERR_R_BN_LIB);
331 if (!BN_mod_mul(s, s, blind, order, ctx)) {
332 ECerr(EC_F_OSSL_ECDSA_SIGN_SIG, ERR_R_BN_LIB);
336 /* s := s * k^-1 mod order */
337 if (!BN_mod_mul(s, s, ckinv, order, ctx)) {
338 ECerr(EC_F_OSSL_ECDSA_SIGN_SIG, ERR_R_BN_LIB);
344 * if kinv and r have been supplied by the caller, don't
345 * generate new kinv and r values
347 if (in_kinv != NULL && in_r != NULL) {
348 ECerr(EC_F_OSSL_ECDSA_SIGN_SIG, EC_R_NEED_NEW_SETUP_VALUES);
352 /* s != 0 => we have a valid signature */
371 * 1: correct signature
372 * 0: incorrect signature
375 int ossl_ecdsa_verify(int type, const unsigned char *dgst, int dgst_len,
376 const unsigned char *sigbuf, int sig_len, EC_KEY *eckey)
379 const unsigned char *p = sigbuf;
380 unsigned char *der = NULL;
387 if (d2i_ECDSA_SIG(&s, &p, sig_len) == NULL)
389 /* Ensure signature uses DER and doesn't have trailing garbage */
390 derlen = i2d_ECDSA_SIG(s, &der);
391 if (derlen != sig_len || memcmp(sigbuf, der, derlen) != 0)
393 ret = ECDSA_do_verify(dgst, dgst_len, s, eckey);
395 OPENSSL_clear_free(der, derlen);
400 int ossl_ecdsa_verify_sig(const unsigned char *dgst, int dgst_len,
401 const ECDSA_SIG *sig, EC_KEY *eckey)
406 BIGNUM *u1, *u2, *m, *X;
407 EC_POINT *point = NULL;
408 const EC_GROUP *group;
409 const EC_POINT *pub_key;
411 /* check input values */
412 if (eckey == NULL || (group = EC_KEY_get0_group(eckey)) == NULL ||
413 (pub_key = EC_KEY_get0_public_key(eckey)) == NULL || sig == NULL) {
414 ECerr(EC_F_OSSL_ECDSA_VERIFY_SIG, EC_R_MISSING_PARAMETERS);
418 if (!EC_KEY_can_sign(eckey)) {
419 ECerr(EC_F_OSSL_ECDSA_VERIFY_SIG, EC_R_CURVE_DOES_NOT_SUPPORT_SIGNING);
425 ECerr(EC_F_OSSL_ECDSA_VERIFY_SIG, ERR_R_MALLOC_FAILURE);
429 u1 = BN_CTX_get(ctx);
430 u2 = BN_CTX_get(ctx);
434 ECerr(EC_F_OSSL_ECDSA_VERIFY_SIG, ERR_R_BN_LIB);
438 order = EC_GROUP_get0_order(group);
440 ECerr(EC_F_OSSL_ECDSA_VERIFY_SIG, ERR_R_EC_LIB);
444 if (BN_is_zero(sig->r) || BN_is_negative(sig->r) ||
445 BN_ucmp(sig->r, order) >= 0 || BN_is_zero(sig->s) ||
446 BN_is_negative(sig->s) || BN_ucmp(sig->s, order) >= 0) {
447 ECerr(EC_F_OSSL_ECDSA_VERIFY_SIG, EC_R_BAD_SIGNATURE);
448 ret = 0; /* signature is invalid */
451 /* calculate tmp1 = inv(S) mod order */
452 /* Check if optimized inverse is implemented */
453 if (EC_GROUP_do_inverse_ord(group, u2, sig->s, ctx) == 0) {
454 if (!BN_mod_inverse(u2, sig->s, order, ctx)) {
455 ECerr(EC_F_OSSL_ECDSA_VERIFY_SIG, ERR_R_BN_LIB);
460 i = BN_num_bits(order);
462 * Need to truncate digest if it is too long: first truncate whole bytes.
464 if (8 * dgst_len > i)
465 dgst_len = (i + 7) / 8;
466 if (!BN_bin2bn(dgst, dgst_len, m)) {
467 ECerr(EC_F_OSSL_ECDSA_VERIFY_SIG, ERR_R_BN_LIB);
470 /* If still too long truncate remaining bits with a shift */
471 if ((8 * dgst_len > i) && !BN_rshift(m, m, 8 - (i & 0x7))) {
472 ECerr(EC_F_OSSL_ECDSA_VERIFY_SIG, ERR_R_BN_LIB);
475 /* u1 = m * tmp mod order */
476 if (!BN_mod_mul(u1, m, u2, order, ctx)) {
477 ECerr(EC_F_OSSL_ECDSA_VERIFY_SIG, ERR_R_BN_LIB);
480 /* u2 = r * w mod q */
481 if (!BN_mod_mul(u2, sig->r, u2, order, ctx)) {
482 ECerr(EC_F_OSSL_ECDSA_VERIFY_SIG, ERR_R_BN_LIB);
486 if ((point = EC_POINT_new(group)) == NULL) {
487 ECerr(EC_F_OSSL_ECDSA_VERIFY_SIG, ERR_R_MALLOC_FAILURE);
490 if (!EC_POINT_mul(group, point, u1, pub_key, u2, ctx)) {
491 ECerr(EC_F_OSSL_ECDSA_VERIFY_SIG, ERR_R_EC_LIB);
494 if (EC_METHOD_get_field_type(EC_GROUP_method_of(group)) ==
495 NID_X9_62_prime_field) {
496 if (!EC_POINT_get_affine_coordinates_GFp(group, point, X, NULL, ctx)) {
497 ECerr(EC_F_OSSL_ECDSA_VERIFY_SIG, ERR_R_EC_LIB);
501 #ifndef OPENSSL_NO_EC2M
502 else { /* NID_X9_62_characteristic_two_field */
504 if (!EC_POINT_get_affine_coordinates_GF2m(group, point, X, NULL, ctx)) {
505 ECerr(EC_F_OSSL_ECDSA_VERIFY_SIG, ERR_R_EC_LIB);
510 if (!BN_nnmod(u1, X, order, ctx)) {
511 ECerr(EC_F_OSSL_ECDSA_VERIFY_SIG, ERR_R_BN_LIB);
514 /* if the signature is correct u1 is equal to sig->r */
515 ret = (BN_ucmp(u1, sig->r) == 0);
519 EC_POINT_free(point);