2 * Copyright 2017-2021 The OpenSSL Project Authors. All Rights Reserved.
3 * Copyright 2017 Ribose Inc. All Rights Reserved.
4 * Ported from Ribose contributions from Botan.
6 * Licensed under the OpenSSL license (the "License"). You may not use
7 * this file except in compliance with the License. You can obtain a copy
8 * in the file LICENSE in the source distribution or at
9 * https://www.openssl.org/source/license.html
12 #include "crypto/sm2.h"
13 #include "crypto/sm2err.h"
14 #include "crypto/ec.h" /* ecdh_KDF_X9_63() */
15 #include <openssl/err.h>
16 #include <openssl/evp.h>
17 #include <openssl/bn.h>
18 #include <openssl/asn1.h>
19 #include <openssl/asn1t.h>
22 typedef struct SM2_Ciphertext_st SM2_Ciphertext;
23 DECLARE_ASN1_FUNCTIONS(SM2_Ciphertext)
25 struct SM2_Ciphertext_st {
28 ASN1_OCTET_STRING *C3;
29 ASN1_OCTET_STRING *C2;
32 ASN1_SEQUENCE(SM2_Ciphertext) = {
33 ASN1_SIMPLE(SM2_Ciphertext, C1x, BIGNUM),
34 ASN1_SIMPLE(SM2_Ciphertext, C1y, BIGNUM),
35 ASN1_SIMPLE(SM2_Ciphertext, C3, ASN1_OCTET_STRING),
36 ASN1_SIMPLE(SM2_Ciphertext, C2, ASN1_OCTET_STRING),
37 } ASN1_SEQUENCE_END(SM2_Ciphertext)
39 IMPLEMENT_ASN1_FUNCTIONS(SM2_Ciphertext)
41 static size_t ec_field_size(const EC_GROUP *group)
43 /* Is there some simpler way to do this? */
47 size_t field_size = 0;
49 if (p == NULL || a == NULL || b == NULL)
52 if (!EC_GROUP_get_curve(group, p, a, b, NULL))
54 field_size = (BN_num_bits(p) + 7) / 8;
64 int sm2_plaintext_size(const unsigned char *ct, size_t ct_size, size_t *pt_size)
66 struct SM2_Ciphertext_st *sm2_ctext = NULL;
68 sm2_ctext = d2i_SM2_Ciphertext(NULL, &ct, ct_size);
70 if (sm2_ctext == NULL) {
71 SM2err(SM2_F_SM2_PLAINTEXT_SIZE, SM2_R_INVALID_ENCODING);
75 *pt_size = sm2_ctext->C2->length;
76 SM2_Ciphertext_free(sm2_ctext);
81 int sm2_ciphertext_size(const EC_KEY *key, const EVP_MD *digest, size_t msg_len,
84 const size_t field_size = ec_field_size(EC_KEY_get0_group(key));
85 const int md_size = EVP_MD_size(digest);
88 if (field_size == 0 || md_size < 0)
91 /* Integer and string are simple type; set constructed = 0, means primitive and definite length encoding. */
92 sz = 2 * ASN1_object_size(0, field_size + 1, V_ASN1_INTEGER)
93 + ASN1_object_size(0, md_size, V_ASN1_OCTET_STRING)
94 + ASN1_object_size(0, msg_len, V_ASN1_OCTET_STRING);
95 /* Sequence is structured type; set constructed = 1, means constructed and definite length encoding. */
96 *ct_size = ASN1_object_size(1, sz, V_ASN1_SEQUENCE);
101 int sm2_encrypt(const EC_KEY *key,
102 const EVP_MD *digest,
104 size_t msg_len, uint8_t *ciphertext_buf, size_t *ciphertext_len)
106 int rc = 0, ciphertext_leni;
114 EVP_MD_CTX *hash = EVP_MD_CTX_new();
115 struct SM2_Ciphertext_st ctext_struct;
116 const EC_GROUP *group = EC_KEY_get0_group(key);
117 const BIGNUM *order = EC_GROUP_get0_order(group);
118 const EC_POINT *P = EC_KEY_get0_public_key(key);
121 uint8_t *msg_mask = NULL;
122 uint8_t *x2y2 = NULL;
125 const int C3_size = EVP_MD_size(digest);
127 /* NULL these before any "goto done" */
128 ctext_struct.C2 = NULL;
129 ctext_struct.C3 = NULL;
131 if (hash == NULL || C3_size <= 0) {
132 SM2err(SM2_F_SM2_ENCRYPT, ERR_R_INTERNAL_ERROR);
136 field_size = ec_field_size(group);
137 if (field_size == 0) {
138 SM2err(SM2_F_SM2_ENCRYPT, ERR_R_INTERNAL_ERROR);
142 kG = EC_POINT_new(group);
143 kP = EC_POINT_new(group);
145 if (kG == NULL || kP == NULL || ctx == NULL) {
146 SM2err(SM2_F_SM2_ENCRYPT, ERR_R_MALLOC_FAILURE);
152 x1 = BN_CTX_get(ctx);
153 x2 = BN_CTX_get(ctx);
154 y1 = BN_CTX_get(ctx);
155 y2 = BN_CTX_get(ctx);
158 SM2err(SM2_F_SM2_ENCRYPT, ERR_R_BN_LIB);
162 x2y2 = OPENSSL_zalloc(2 * field_size);
163 C3 = OPENSSL_zalloc(C3_size);
165 if (x2y2 == NULL || C3 == NULL) {
166 SM2err(SM2_F_SM2_ENCRYPT, ERR_R_MALLOC_FAILURE);
170 memset(ciphertext_buf, 0, *ciphertext_len);
172 if (!BN_priv_rand_range(k, order)) {
173 SM2err(SM2_F_SM2_ENCRYPT, ERR_R_INTERNAL_ERROR);
177 if (!EC_POINT_mul(group, kG, k, NULL, NULL, ctx)
178 || !EC_POINT_get_affine_coordinates(group, kG, x1, y1, ctx)
179 || !EC_POINT_mul(group, kP, NULL, P, k, ctx)
180 || !EC_POINT_get_affine_coordinates(group, kP, x2, y2, ctx)) {
181 SM2err(SM2_F_SM2_ENCRYPT, ERR_R_EC_LIB);
185 if (BN_bn2binpad(x2, x2y2, field_size) < 0
186 || BN_bn2binpad(y2, x2y2 + field_size, field_size) < 0) {
187 SM2err(SM2_F_SM2_ENCRYPT, ERR_R_INTERNAL_ERROR);
191 msg_mask = OPENSSL_zalloc(msg_len);
192 if (msg_mask == NULL) {
193 SM2err(SM2_F_SM2_ENCRYPT, ERR_R_MALLOC_FAILURE);
197 /* X9.63 with no salt happens to match the KDF used in SM2 */
198 if (!ecdh_KDF_X9_63(msg_mask, msg_len, x2y2, 2 * field_size, NULL, 0,
200 SM2err(SM2_F_SM2_ENCRYPT, ERR_R_EVP_LIB);
204 for (i = 0; i != msg_len; ++i)
205 msg_mask[i] ^= msg[i];
207 if (EVP_DigestInit(hash, digest) == 0
208 || EVP_DigestUpdate(hash, x2y2, field_size) == 0
209 || EVP_DigestUpdate(hash, msg, msg_len) == 0
210 || EVP_DigestUpdate(hash, x2y2 + field_size, field_size) == 0
211 || EVP_DigestFinal(hash, C3, NULL) == 0) {
212 SM2err(SM2_F_SM2_ENCRYPT, ERR_R_EVP_LIB);
216 ctext_struct.C1x = x1;
217 ctext_struct.C1y = y1;
218 ctext_struct.C3 = ASN1_OCTET_STRING_new();
219 ctext_struct.C2 = ASN1_OCTET_STRING_new();
221 if (ctext_struct.C3 == NULL || ctext_struct.C2 == NULL) {
222 SM2err(SM2_F_SM2_ENCRYPT, ERR_R_MALLOC_FAILURE);
225 if (!ASN1_OCTET_STRING_set(ctext_struct.C3, C3, C3_size)
226 || !ASN1_OCTET_STRING_set(ctext_struct.C2, msg_mask, msg_len)) {
227 SM2err(SM2_F_SM2_ENCRYPT, ERR_R_INTERNAL_ERROR);
231 ciphertext_leni = i2d_SM2_Ciphertext(&ctext_struct, &ciphertext_buf);
232 /* Ensure cast to size_t is safe */
233 if (ciphertext_leni < 0) {
234 SM2err(SM2_F_SM2_ENCRYPT, ERR_R_INTERNAL_ERROR);
237 *ciphertext_len = (size_t)ciphertext_leni;
242 ASN1_OCTET_STRING_free(ctext_struct.C2);
243 ASN1_OCTET_STRING_free(ctext_struct.C3);
244 OPENSSL_free(msg_mask);
247 EVP_MD_CTX_free(hash);
254 int sm2_decrypt(const EC_KEY *key,
255 const EVP_MD *digest,
256 const uint8_t *ciphertext,
257 size_t ciphertext_len, uint8_t *ptext_buf, size_t *ptext_len)
262 const EC_GROUP *group = EC_KEY_get0_group(key);
264 struct SM2_Ciphertext_st *sm2_ctext = NULL;
267 uint8_t *x2y2 = NULL;
268 uint8_t *computed_C3 = NULL;
269 const size_t field_size = ec_field_size(group);
270 const int hash_size = EVP_MD_size(digest);
271 uint8_t *msg_mask = NULL;
272 const uint8_t *C2 = NULL;
273 const uint8_t *C3 = NULL;
275 EVP_MD_CTX *hash = NULL;
277 if (field_size == 0 || hash_size <= 0)
280 memset(ptext_buf, 0xFF, *ptext_len);
282 sm2_ctext = d2i_SM2_Ciphertext(NULL, &ciphertext, ciphertext_len);
284 if (sm2_ctext == NULL) {
285 SM2err(SM2_F_SM2_DECRYPT, SM2_R_ASN1_ERROR);
289 if (sm2_ctext->C3->length != hash_size) {
290 SM2err(SM2_F_SM2_DECRYPT, SM2_R_INVALID_ENCODING);
294 C2 = sm2_ctext->C2->data;
295 C3 = sm2_ctext->C3->data;
296 msg_len = sm2_ctext->C2->length;
297 if (*ptext_len < (size_t)msg_len) {
298 SM2err(SM2_F_SM2_DECRYPT, SM2_R_BUFFER_TOO_SMALL);
304 SM2err(SM2_F_SM2_DECRYPT, ERR_R_MALLOC_FAILURE);
309 x2 = BN_CTX_get(ctx);
310 y2 = BN_CTX_get(ctx);
313 SM2err(SM2_F_SM2_DECRYPT, ERR_R_BN_LIB);
317 msg_mask = OPENSSL_zalloc(msg_len);
318 x2y2 = OPENSSL_zalloc(2 * field_size);
319 computed_C3 = OPENSSL_zalloc(hash_size);
321 if (msg_mask == NULL || x2y2 == NULL || computed_C3 == NULL) {
322 SM2err(SM2_F_SM2_DECRYPT, ERR_R_MALLOC_FAILURE);
326 C1 = EC_POINT_new(group);
328 SM2err(SM2_F_SM2_DECRYPT, ERR_R_MALLOC_FAILURE);
332 if (!EC_POINT_set_affine_coordinates(group, C1, sm2_ctext->C1x,
334 || !EC_POINT_mul(group, C1, NULL, C1, EC_KEY_get0_private_key(key),
336 || !EC_POINT_get_affine_coordinates(group, C1, x2, y2, ctx)) {
337 SM2err(SM2_F_SM2_DECRYPT, ERR_R_EC_LIB);
341 if (BN_bn2binpad(x2, x2y2, field_size) < 0
342 || BN_bn2binpad(y2, x2y2 + field_size, field_size) < 0
343 || !ecdh_KDF_X9_63(msg_mask, msg_len, x2y2, 2 * field_size, NULL, 0,
345 SM2err(SM2_F_SM2_DECRYPT, ERR_R_INTERNAL_ERROR);
349 for (i = 0; i != msg_len; ++i)
350 ptext_buf[i] = C2[i] ^ msg_mask[i];
352 hash = EVP_MD_CTX_new();
354 SM2err(SM2_F_SM2_DECRYPT, ERR_R_MALLOC_FAILURE);
358 if (!EVP_DigestInit(hash, digest)
359 || !EVP_DigestUpdate(hash, x2y2, field_size)
360 || !EVP_DigestUpdate(hash, ptext_buf, msg_len)
361 || !EVP_DigestUpdate(hash, x2y2 + field_size, field_size)
362 || !EVP_DigestFinal(hash, computed_C3, NULL)) {
363 SM2err(SM2_F_SM2_DECRYPT, ERR_R_EVP_LIB);
367 if (CRYPTO_memcmp(computed_C3, C3, hash_size) != 0) {
368 SM2err(SM2_F_SM2_DECRYPT, SM2_R_INVALID_DIGEST);
373 *ptext_len = msg_len;
377 memset(ptext_buf, 0, *ptext_len);
379 OPENSSL_free(msg_mask);
381 OPENSSL_free(computed_C3);
384 SM2_Ciphertext_free(sm2_ctext);
385 EVP_MD_CTX_free(hash);