1/* 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. 5 * 6 * Licensed under the Apache License 2.0 (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 10 */ 11 12/* 13 * ECDSA low level APIs are deprecated for public use, but still ok for 14 * internal use. 15 */ 16#include "internal/deprecated.h" 17 18#include "crypto/sm2.h" 19#include "crypto/sm2err.h" 20#include "crypto/ec.h" /* ossl_ecdh_kdf_X9_63() */ 21#include <openssl/err.h> 22#include <openssl/evp.h> 23#include <openssl/bn.h> 24#include <openssl/asn1.h> 25#include <openssl/asn1t.h> 26#include <string.h> 27 28typedef struct SM2_Ciphertext_st SM2_Ciphertext; 29DECLARE_ASN1_FUNCTIONS(SM2_Ciphertext) 30 31struct SM2_Ciphertext_st { 32 BIGNUM *C1x; 33 BIGNUM *C1y; 34 ASN1_OCTET_STRING *C3; 35 ASN1_OCTET_STRING *C2; 36}; 37 38ASN1_SEQUENCE(SM2_Ciphertext) = { 39 ASN1_SIMPLE(SM2_Ciphertext, C1x, BIGNUM), 40 ASN1_SIMPLE(SM2_Ciphertext, C1y, BIGNUM), 41 ASN1_SIMPLE(SM2_Ciphertext, C3, ASN1_OCTET_STRING), 42 ASN1_SIMPLE(SM2_Ciphertext, C2, ASN1_OCTET_STRING), 43} ASN1_SEQUENCE_END(SM2_Ciphertext) 44 45IMPLEMENT_ASN1_FUNCTIONS(SM2_Ciphertext) 46 47static size_t ec_field_size(const EC_GROUP *group) 48{ 49 /* Is there some simpler way to do this? */ 50 BIGNUM *p = BN_new(); 51 BIGNUM *a = BN_new(); 52 BIGNUM *b = BN_new(); 53 size_t field_size = 0; 54 55 if (p == NULL || a == NULL || b == NULL) 56 goto done; 57 58 if (!EC_GROUP_get_curve(group, p, a, b, NULL)) 59 goto done; 60 field_size = (BN_num_bits(p) + 7) / 8; 61 62 done: 63 BN_free(p); 64 BN_free(a); 65 BN_free(b); 66 67 return field_size; 68} 69 70int ossl_sm2_plaintext_size(const unsigned char *ct, size_t ct_size, 71 size_t *pt_size) 72{ 73 struct SM2_Ciphertext_st *sm2_ctext = NULL; 74 75 sm2_ctext = d2i_SM2_Ciphertext(NULL, &ct, ct_size); 76 77 if (sm2_ctext == NULL) { 78 ERR_raise(ERR_LIB_SM2, SM2_R_INVALID_ENCODING); 79 return 0; 80 } 81 82 *pt_size = sm2_ctext->C2->length; 83 SM2_Ciphertext_free(sm2_ctext); 84 85 return 1; 86} 87 88int ossl_sm2_ciphertext_size(const EC_KEY *key, const EVP_MD *digest, 89 size_t msg_len, size_t *ct_size) 90{ 91 const size_t field_size = ec_field_size(EC_KEY_get0_group(key)); 92 const int md_size = EVP_MD_get_size(digest); 93 size_t sz; 94 95 if (field_size == 0 || md_size < 0) 96 return 0; 97 98 /* Integer and string are simple type; set constructed = 0, means primitive and definite length encoding. */ 99 sz = 2 * ASN1_object_size(0, field_size + 1, V_ASN1_INTEGER) 100 + ASN1_object_size(0, md_size, V_ASN1_OCTET_STRING) 101 + ASN1_object_size(0, msg_len, V_ASN1_OCTET_STRING); 102 /* Sequence is structured type; set constructed = 1, means constructed and definite length encoding. */ 103 *ct_size = ASN1_object_size(1, sz, V_ASN1_SEQUENCE); 104 105 return 1; 106} 107 108int ossl_sm2_encrypt(const EC_KEY *key, 109 const EVP_MD *digest, 110 const uint8_t *msg, size_t msg_len, 111 uint8_t *ciphertext_buf, size_t *ciphertext_len) 112{ 113 int rc = 0, ciphertext_leni; 114 size_t i; 115 BN_CTX *ctx = NULL; 116 BIGNUM *k = NULL; 117 BIGNUM *x1 = NULL; 118 BIGNUM *y1 = NULL; 119 BIGNUM *x2 = NULL; 120 BIGNUM *y2 = NULL; 121 EVP_MD_CTX *hash = EVP_MD_CTX_new(); 122 struct SM2_Ciphertext_st ctext_struct; 123 const EC_GROUP *group = EC_KEY_get0_group(key); 124 const BIGNUM *order = EC_GROUP_get0_order(group); 125 const EC_POINT *P = EC_KEY_get0_public_key(key); 126 EC_POINT *kG = NULL; 127 EC_POINT *kP = NULL; 128 uint8_t *msg_mask = NULL; 129 uint8_t *x2y2 = NULL; 130 uint8_t *C3 = NULL; 131 size_t field_size; 132 const int C3_size = EVP_MD_get_size(digest); 133 EVP_MD *fetched_digest = NULL; 134 OSSL_LIB_CTX *libctx = ossl_ec_key_get_libctx(key); 135 const char *propq = ossl_ec_key_get0_propq(key); 136 137 /* NULL these before any "goto done" */ 138 ctext_struct.C2 = NULL; 139 ctext_struct.C3 = NULL; 140 141 if (hash == NULL || C3_size <= 0) { 142 ERR_raise(ERR_LIB_SM2, ERR_R_INTERNAL_ERROR); 143 goto done; 144 } 145 146 field_size = ec_field_size(group); 147 if (field_size == 0) { 148 ERR_raise(ERR_LIB_SM2, ERR_R_INTERNAL_ERROR); 149 goto done; 150 } 151 152 kG = EC_POINT_new(group); 153 kP = EC_POINT_new(group); 154 ctx = BN_CTX_new_ex(libctx); 155 if (kG == NULL || kP == NULL || ctx == NULL) { 156 ERR_raise(ERR_LIB_SM2, ERR_R_MALLOC_FAILURE); 157 goto done; 158 } 159 160 BN_CTX_start(ctx); 161 k = BN_CTX_get(ctx); 162 x1 = BN_CTX_get(ctx); 163 x2 = BN_CTX_get(ctx); 164 y1 = BN_CTX_get(ctx); 165 y2 = BN_CTX_get(ctx); 166 167 if (y2 == NULL) { 168 ERR_raise(ERR_LIB_SM2, ERR_R_BN_LIB); 169 goto done; 170 } 171 172 x2y2 = OPENSSL_zalloc(2 * field_size); 173 C3 = OPENSSL_zalloc(C3_size); 174 175 if (x2y2 == NULL || C3 == NULL) { 176 ERR_raise(ERR_LIB_SM2, ERR_R_MALLOC_FAILURE); 177 goto done; 178 } 179 180 memset(ciphertext_buf, 0, *ciphertext_len); 181 182 if (!BN_priv_rand_range_ex(k, order, 0, ctx)) { 183 ERR_raise(ERR_LIB_SM2, ERR_R_INTERNAL_ERROR); 184 goto done; 185 } 186 187 if (!EC_POINT_mul(group, kG, k, NULL, NULL, ctx) 188 || !EC_POINT_get_affine_coordinates(group, kG, x1, y1, ctx) 189 || !EC_POINT_mul(group, kP, NULL, P, k, ctx) 190 || !EC_POINT_get_affine_coordinates(group, kP, x2, y2, ctx)) { 191 ERR_raise(ERR_LIB_SM2, ERR_R_EC_LIB); 192 goto done; 193 } 194 195 if (BN_bn2binpad(x2, x2y2, field_size) < 0 196 || BN_bn2binpad(y2, x2y2 + field_size, field_size) < 0) { 197 ERR_raise(ERR_LIB_SM2, ERR_R_INTERNAL_ERROR); 198 goto done; 199 } 200 201 msg_mask = OPENSSL_zalloc(msg_len); 202 if (msg_mask == NULL) { 203 ERR_raise(ERR_LIB_SM2, ERR_R_MALLOC_FAILURE); 204 goto done; 205 } 206 207 /* X9.63 with no salt happens to match the KDF used in SM2 */ 208 if (!ossl_ecdh_kdf_X9_63(msg_mask, msg_len, x2y2, 2 * field_size, NULL, 0, 209 digest, libctx, propq)) { 210 ERR_raise(ERR_LIB_SM2, ERR_R_EVP_LIB); 211 goto done; 212 } 213 214 for (i = 0; i != msg_len; ++i) 215 msg_mask[i] ^= msg[i]; 216 217 fetched_digest = EVP_MD_fetch(libctx, EVP_MD_get0_name(digest), propq); 218 if (fetched_digest == NULL) { 219 ERR_raise(ERR_LIB_SM2, ERR_R_INTERNAL_ERROR); 220 goto done; 221 } 222 if (EVP_DigestInit(hash, fetched_digest) == 0 223 || EVP_DigestUpdate(hash, x2y2, field_size) == 0 224 || EVP_DigestUpdate(hash, msg, msg_len) == 0 225 || EVP_DigestUpdate(hash, x2y2 + field_size, field_size) == 0 226 || EVP_DigestFinal(hash, C3, NULL) == 0) { 227 ERR_raise(ERR_LIB_SM2, ERR_R_EVP_LIB); 228 goto done; 229 } 230 231 ctext_struct.C1x = x1; 232 ctext_struct.C1y = y1; 233 ctext_struct.C3 = ASN1_OCTET_STRING_new(); 234 ctext_struct.C2 = ASN1_OCTET_STRING_new(); 235 236 if (ctext_struct.C3 == NULL || ctext_struct.C2 == NULL) { 237 ERR_raise(ERR_LIB_SM2, ERR_R_MALLOC_FAILURE); 238 goto done; 239 } 240 if (!ASN1_OCTET_STRING_set(ctext_struct.C3, C3, C3_size) 241 || !ASN1_OCTET_STRING_set(ctext_struct.C2, msg_mask, msg_len)) { 242 ERR_raise(ERR_LIB_SM2, ERR_R_INTERNAL_ERROR); 243 goto done; 244 } 245 246 ciphertext_leni = i2d_SM2_Ciphertext(&ctext_struct, &ciphertext_buf); 247 /* Ensure cast to size_t is safe */ 248 if (ciphertext_leni < 0) { 249 ERR_raise(ERR_LIB_SM2, ERR_R_INTERNAL_ERROR); 250 goto done; 251 } 252 *ciphertext_len = (size_t)ciphertext_leni; 253 254 rc = 1; 255 256 done: 257 EVP_MD_free(fetched_digest); 258 ASN1_OCTET_STRING_free(ctext_struct.C2); 259 ASN1_OCTET_STRING_free(ctext_struct.C3); 260 OPENSSL_free(msg_mask); 261 OPENSSL_free(x2y2); 262 OPENSSL_free(C3); 263 EVP_MD_CTX_free(hash); 264 BN_CTX_free(ctx); 265 EC_POINT_free(kG); 266 EC_POINT_free(kP); 267 return rc; 268} 269 270int ossl_sm2_decrypt(const EC_KEY *key, 271 const EVP_MD *digest, 272 const uint8_t *ciphertext, size_t ciphertext_len, 273 uint8_t *ptext_buf, size_t *ptext_len) 274{ 275 int rc = 0; 276 int i; 277 BN_CTX *ctx = NULL; 278 const EC_GROUP *group = EC_KEY_get0_group(key); 279 EC_POINT *C1 = NULL; 280 struct SM2_Ciphertext_st *sm2_ctext = NULL; 281 BIGNUM *x2 = NULL; 282 BIGNUM *y2 = NULL; 283 uint8_t *x2y2 = NULL; 284 uint8_t *computed_C3 = NULL; 285 const size_t field_size = ec_field_size(group); 286 const int hash_size = EVP_MD_get_size(digest); 287 uint8_t *msg_mask = NULL; 288 const uint8_t *C2 = NULL; 289 const uint8_t *C3 = NULL; 290 int msg_len = 0; 291 EVP_MD_CTX *hash = NULL; 292 OSSL_LIB_CTX *libctx = ossl_ec_key_get_libctx(key); 293 const char *propq = ossl_ec_key_get0_propq(key); 294 295 if (field_size == 0 || hash_size <= 0) 296 goto done; 297 298 memset(ptext_buf, 0xFF, *ptext_len); 299 300 sm2_ctext = d2i_SM2_Ciphertext(NULL, &ciphertext, ciphertext_len); 301 302 if (sm2_ctext == NULL) { 303 ERR_raise(ERR_LIB_SM2, SM2_R_ASN1_ERROR); 304 goto done; 305 } 306 307 if (sm2_ctext->C3->length != hash_size) { 308 ERR_raise(ERR_LIB_SM2, SM2_R_INVALID_ENCODING); 309 goto done; 310 } 311 312 C2 = sm2_ctext->C2->data; 313 C3 = sm2_ctext->C3->data; 314 msg_len = sm2_ctext->C2->length; 315 if (*ptext_len < (size_t)msg_len) { 316 ERR_raise(ERR_LIB_SM2, SM2_R_BUFFER_TOO_SMALL); 317 goto done; 318 } 319 320 ctx = BN_CTX_new_ex(libctx); 321 if (ctx == NULL) { 322 ERR_raise(ERR_LIB_SM2, ERR_R_MALLOC_FAILURE); 323 goto done; 324 } 325 326 BN_CTX_start(ctx); 327 x2 = BN_CTX_get(ctx); 328 y2 = BN_CTX_get(ctx); 329 330 if (y2 == NULL) { 331 ERR_raise(ERR_LIB_SM2, ERR_R_BN_LIB); 332 goto done; 333 } 334 335 msg_mask = OPENSSL_zalloc(msg_len); 336 x2y2 = OPENSSL_zalloc(2 * field_size); 337 computed_C3 = OPENSSL_zalloc(hash_size); 338 339 if (msg_mask == NULL || x2y2 == NULL || computed_C3 == NULL) { 340 ERR_raise(ERR_LIB_SM2, ERR_R_MALLOC_FAILURE); 341 goto done; 342 } 343 344 C1 = EC_POINT_new(group); 345 if (C1 == NULL) { 346 ERR_raise(ERR_LIB_SM2, ERR_R_MALLOC_FAILURE); 347 goto done; 348 } 349 350 if (!EC_POINT_set_affine_coordinates(group, C1, sm2_ctext->C1x, 351 sm2_ctext->C1y, ctx) 352 || !EC_POINT_mul(group, C1, NULL, C1, EC_KEY_get0_private_key(key), 353 ctx) 354 || !EC_POINT_get_affine_coordinates(group, C1, x2, y2, ctx)) { 355 ERR_raise(ERR_LIB_SM2, ERR_R_EC_LIB); 356 goto done; 357 } 358 359 if (BN_bn2binpad(x2, x2y2, field_size) < 0 360 || BN_bn2binpad(y2, x2y2 + field_size, field_size) < 0 361 || !ossl_ecdh_kdf_X9_63(msg_mask, msg_len, x2y2, 2 * field_size, 362 NULL, 0, digest, libctx, propq)) { 363 ERR_raise(ERR_LIB_SM2, ERR_R_INTERNAL_ERROR); 364 goto done; 365 } 366 367 for (i = 0; i != msg_len; ++i) 368 ptext_buf[i] = C2[i] ^ msg_mask[i]; 369 370 hash = EVP_MD_CTX_new(); 371 if (hash == NULL) { 372 ERR_raise(ERR_LIB_SM2, ERR_R_MALLOC_FAILURE); 373 goto done; 374 } 375 376 if (!EVP_DigestInit(hash, digest) 377 || !EVP_DigestUpdate(hash, x2y2, field_size) 378 || !EVP_DigestUpdate(hash, ptext_buf, msg_len) 379 || !EVP_DigestUpdate(hash, x2y2 + field_size, field_size) 380 || !EVP_DigestFinal(hash, computed_C3, NULL)) { 381 ERR_raise(ERR_LIB_SM2, ERR_R_EVP_LIB); 382 goto done; 383 } 384 385 if (CRYPTO_memcmp(computed_C3, C3, hash_size) != 0) { 386 ERR_raise(ERR_LIB_SM2, SM2_R_INVALID_DIGEST); 387 goto done; 388 } 389 390 rc = 1; 391 *ptext_len = msg_len; 392 393 done: 394 if (rc == 0) 395 memset(ptext_buf, 0, *ptext_len); 396 397 OPENSSL_free(msg_mask); 398 OPENSSL_free(x2y2); 399 OPENSSL_free(computed_C3); 400 EC_POINT_free(C1); 401 BN_CTX_free(ctx); 402 SM2_Ciphertext_free(sm2_ctext); 403 EVP_MD_CTX_free(hash); 404 405 return rc; 406} 407