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
28 typedef struct SM2_Ciphertext_st SM2_Ciphertext;
29 DECLARE_ASN1_FUNCTIONS(SM2_Ciphertext)
30
31 struct SM2_Ciphertext_st {
32 BIGNUM *C1x;
33 BIGNUM *C1y;
34 ASN1_OCTET_STRING *C3;
35 ASN1_OCTET_STRING *C2;
36 };
37
38 ASN1_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
45 IMPLEMENT_ASN1_FUNCTIONS(SM2_Ciphertext)
46
47 static 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
ossl_sm2_plaintext_size(const unsigned char * ct,size_t ct_size,size_t * pt_size)70 int 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
ossl_sm2_ciphertext_size(const EC_KEY * key,const EVP_MD * digest,size_t msg_len,size_t * ct_size)88 int 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
ossl_sm2_encrypt(const EC_KEY * key,const EVP_MD * digest,const uint8_t * msg,size_t msg_len,uint8_t * ciphertext_buf,size_t * ciphertext_len)108 int 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
ossl_sm2_decrypt(const EC_KEY * key,const EVP_MD * digest,const uint8_t * ciphertext,size_t ciphertext_len,uint8_t * ptext_buf,size_t * ptext_len)270 int 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
