2 * Copyright 2017-2018 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 "internal/sm2.h"
13 #include <openssl/evp.h>
14 #include <openssl/bn.h>
15 #include <openssl/asn1.h>
16 #include <openssl/asn1t.h>
19 typedef struct SM2_Ciphertext_st SM2_Ciphertext;
20 DECLARE_ASN1_FUNCTIONS(SM2_Ciphertext)
22 struct SM2_Ciphertext_st {
25 ASN1_OCTET_STRING *C3;
26 ASN1_OCTET_STRING *C2;
29 ASN1_SEQUENCE(SM2_Ciphertext) = {
30 ASN1_SIMPLE(SM2_Ciphertext, C1x, BIGNUM),
31 ASN1_SIMPLE(SM2_Ciphertext, C1y, BIGNUM),
32 ASN1_SIMPLE(SM2_Ciphertext, C3, ASN1_OCTET_STRING),
33 ASN1_SIMPLE(SM2_Ciphertext, C2, ASN1_OCTET_STRING),
34 } ASN1_SEQUENCE_END(SM2_Ciphertext)
36 IMPLEMENT_ASN1_FUNCTIONS(SM2_Ciphertext)
38 static size_t EC_field_size(const EC_GROUP *group)
40 /* Is there some simpler way to do this? */
44 size_t field_size = 0;
46 if (p == NULL || a == NULL || b == NULL)
49 EC_GROUP_get_curve_GFp(group, p, a, b, NULL);
50 field_size = (BN_num_bits(p) + 7) / 8;
60 size_t SM2_plaintext_size(const EC_KEY *key, const EVP_MD *digest, size_t msg_len)
62 const size_t field_size = EC_field_size(EC_KEY_get0_group(key));
63 const size_t md_size = EVP_MD_size(digest);
65 const size_t overhead = 10 + 2 * field_size + md_size;
66 if(msg_len <= overhead)
69 return msg_len - overhead;
72 size_t SM2_ciphertext_size(const EC_KEY *key, const EVP_MD *digest, size_t msg_len)
74 const size_t field_size = EC_field_size(EC_KEY_get0_group(key));
75 const size_t md_size = EVP_MD_size(digest);
76 return 10 + 2 * field_size + md_size + msg_len;
79 int SM2_encrypt(const EC_KEY *key,
82 size_t msg_len, uint8_t *ciphertext_buf, size_t *ciphertext_len)
93 EVP_MD_CTX *hash = EVP_MD_CTX_new();
95 struct SM2_Ciphertext_st ctext_struct;
96 const EC_GROUP *group = EC_KEY_get0_group(key);
97 const BIGNUM *order = EC_GROUP_get0_order(group);
98 const EC_POINT *P = EC_KEY_get0_public_key(key);
101 uint8_t *msg_mask = NULL;
103 uint8_t *x2y2 = NULL;
106 const size_t field_size = EC_field_size(group);
107 const size_t C3_size = EVP_MD_size(digest);
109 if (field_size == 0 || C3_size == 0)
112 kG = EC_POINT_new(group);
113 kP = EC_POINT_new(group);
114 if (kG == NULL || kP == NULL)
123 x1 = BN_CTX_get(ctx);
124 x2 = BN_CTX_get(ctx);
125 y1 = BN_CTX_get(ctx);
126 y2 = BN_CTX_get(ctx);
131 x2y2 = OPENSSL_zalloc(2 * field_size);
132 C3 = OPENSSL_zalloc(C3_size);
134 if (x2y2 == NULL || C3 == NULL)
137 memset(ciphertext_buf, 0, *ciphertext_len);
139 BN_priv_rand_range(k, order);
141 if (EC_POINT_mul(group, kG, k, NULL, NULL, ctx) == 0)
144 if (EC_POINT_get_affine_coordinates_GFp(group, kG, x1, y1, ctx) == 0)
147 if (EC_POINT_mul(group, kP, NULL, P, k, ctx) == 0)
150 if (EC_POINT_get_affine_coordinates_GFp(group, kP, x2, y2, ctx) == 0)
153 BN_bn2binpad(x2, x2y2, field_size);
154 BN_bn2binpad(y2, x2y2 + field_size, field_size);
156 msg_mask = OPENSSL_zalloc(msg_len);
157 if (msg_mask == NULL)
160 /* X9.63 with no salt happens to match the KDF used in SM2 */
161 if (ECDH_KDF_X9_62(msg_mask, msg_len, x2y2, 2 * field_size, NULL, 0, digest)
165 for (i = 0; i != msg_len; ++i)
166 msg_mask[i] ^= msg[i];
168 if (EVP_DigestInit(hash, digest) == 0)
171 if (EVP_DigestUpdate(hash, x2y2, field_size) == 0)
174 if (EVP_DigestUpdate(hash, msg, msg_len) == 0)
177 if (EVP_DigestUpdate(hash, x2y2 + field_size, field_size) == 0)
180 if (EVP_DigestFinal(hash, C3, NULL) == 0)
183 ctext_struct.C1x = x1;
184 ctext_struct.C1y = y1;
185 ctext_struct.C3 = ASN1_OCTET_STRING_new();
186 ASN1_OCTET_STRING_set(ctext_struct.C3, C3, C3_size);
187 ctext_struct.C2 = ASN1_OCTET_STRING_new();
188 ASN1_OCTET_STRING_set(ctext_struct.C2, msg_mask, msg_len);
190 *ciphertext_len = i2d_SM2_Ciphertext(&ctext_struct, &ciphertext_buf);
192 ASN1_OCTET_STRING_free(ctext_struct.C2);
193 ASN1_OCTET_STRING_free(ctext_struct.C3);
198 OPENSSL_free(msg_mask);
201 EVP_MD_CTX_free(hash);
208 int SM2_decrypt(const EC_KEY *key,
209 const EVP_MD *digest,
210 const uint8_t *ciphertext,
211 size_t ciphertext_len, uint8_t *ptext_buf, size_t *ptext_len)
217 const EC_GROUP *group = EC_KEY_get0_group(key);
219 struct SM2_Ciphertext_st *sm2_ctext = NULL;
223 uint8_t *x2y2 = NULL;
224 uint8_t *computed_C3 = NULL;
226 const size_t field_size = EC_field_size(group);
227 const int hash_size = EVP_MD_size(digest);
229 uint8_t *msg_mask = NULL;
230 const uint8_t *C2 = NULL;
231 const uint8_t *C3 = NULL;
233 EVP_MD_CTX *hash = NULL;
235 if (field_size == 0 || hash_size == 0)
238 memset(ptext_buf, 0xFF, *ptext_len);
240 sm2_ctext = d2i_SM2_Ciphertext(NULL, &ciphertext, ciphertext_len);
242 if (sm2_ctext == NULL)
245 if (sm2_ctext->C3->length != hash_size)
248 C2 = sm2_ctext->C2->data;
249 C3 = sm2_ctext->C3->data;
250 msg_len = sm2_ctext->C2->length;
257 x2 = BN_CTX_get(ctx);
258 y2 = BN_CTX_get(ctx);
263 msg_mask = OPENSSL_zalloc(msg_len);
264 x2y2 = OPENSSL_zalloc(2 * field_size);
265 computed_C3 = OPENSSL_zalloc(hash_size);
267 if(msg_mask == NULL || x2y2 == NULL || computed_C3 == NULL)
270 C1 = EC_POINT_new(group);
274 if (EC_POINT_set_affine_coordinates_GFp
275 (group, C1, sm2_ctext->C1x, sm2_ctext->C1y, ctx) == 0)
278 if (EC_POINT_mul(group, C1, NULL, C1, EC_KEY_get0_private_key(key), ctx) ==
282 if (EC_POINT_get_affine_coordinates_GFp(group, C1, x2, y2, ctx) == 0)
285 BN_bn2binpad(x2, x2y2, field_size);
286 BN_bn2binpad(y2, x2y2 + field_size, field_size);
288 if (ECDH_KDF_X9_62(msg_mask, msg_len, x2y2, 2 * field_size, NULL, 0, digest)
292 for (i = 0; i != msg_len; ++i)
293 ptext_buf[i] = C2[i] ^ msg_mask[i];
295 hash = EVP_MD_CTX_new();
300 if (EVP_DigestInit(hash, digest) == 0)
303 if (EVP_DigestUpdate(hash, x2y2, field_size) == 0)
306 if (EVP_DigestUpdate(hash, ptext_buf, msg_len) == 0)
309 if (EVP_DigestUpdate(hash, x2y2 + field_size, field_size) == 0)
312 if (EVP_DigestFinal(hash, computed_C3, NULL) == 0)
315 if (memcmp(computed_C3, C3, hash_size) != 0)
319 *ptext_len = msg_len;
324 memset(ptext_buf, 0, *ptext_len);
326 OPENSSL_free(msg_mask);
328 OPENSSL_free(computed_C3);
331 SM2_Ciphertext_free(sm2_ctext);
332 EVP_MD_CTX_free(hash);