1 /*
2 * Copyright 2017-2024 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 int ec_field_size(const EC_GROUP *group)
48 {
49 const BIGNUM *p = EC_GROUP_get0_field(group);
50
51 if (p == NULL)
52 return 0;
53
54 return BN_num_bytes(p);
55 }
56
is_all_zeros(const unsigned char * msg,size_t msglen)57 static int is_all_zeros(const unsigned char *msg, size_t msglen)
58 {
59 unsigned char re = 0;
60 size_t i;
61
62 for (i = 0; i < msglen; i++) {
63 re |= msg[i];
64 }
65
66 return re == 0 ? 1 : 0;
67 }
68
ossl_sm2_plaintext_size(const unsigned char * ct,size_t ct_size,size_t * pt_size)69 int ossl_sm2_plaintext_size(const unsigned char *ct, size_t ct_size,
70 size_t *pt_size)
71 {
72 struct SM2_Ciphertext_st *sm2_ctext = NULL;
73
74 sm2_ctext = d2i_SM2_Ciphertext(NULL, &ct, (long)ct_size);
75
76 if (sm2_ctext == NULL) {
77 ERR_raise(ERR_LIB_SM2, SM2_R_INVALID_ENCODING);
78 return 0;
79 }
80
81 *pt_size = sm2_ctext->C2->length;
82 SM2_Ciphertext_free(sm2_ctext);
83
84 return 1;
85 }
86
ossl_sm2_ciphertext_size(const EC_KEY * key,const EVP_MD * digest,size_t msg_len,size_t * ct_size)87 int ossl_sm2_ciphertext_size(const EC_KEY *key, const EVP_MD *digest,
88 size_t msg_len, size_t *ct_size)
89 {
90 const int field_size = ec_field_size(EC_KEY_get0_group(key));
91 const int md_size = EVP_MD_get_size(digest);
92 int sz;
93
94 if (field_size == 0 || md_size <= 0 || msg_len > INT_MAX/2)
95 return 0;
96
97 /* Integer and string are simple type; set constructed = 0, means primitive and definite length encoding. */
98 sz = 2 * ASN1_object_size(0, field_size + 1, V_ASN1_INTEGER)
99 + ASN1_object_size(0, md_size, V_ASN1_OCTET_STRING)
100 + ASN1_object_size(0, (int)msg_len, V_ASN1_OCTET_STRING);
101 /* Sequence is structured type; set constructed = 1, means constructed and definite length encoding. */
102 *ct_size = (size_t)ASN1_object_size(1, sz, V_ASN1_SEQUENCE);
103
104 return 1;
105 }
106
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)107 int ossl_sm2_encrypt(const EC_KEY *key,
108 const EVP_MD *digest,
109 const uint8_t *msg, size_t msg_len,
110 uint8_t *ciphertext_buf, size_t *ciphertext_len)
111 {
112 int rc = 0, ciphertext_leni;
113 size_t i;
114 BN_CTX *ctx = NULL;
115 BIGNUM *k = NULL;
116 BIGNUM *x1 = NULL;
117 BIGNUM *y1 = NULL;
118 BIGNUM *x2 = NULL;
119 BIGNUM *y2 = NULL;
120 EVP_MD_CTX *hash = EVP_MD_CTX_new();
121 struct SM2_Ciphertext_st ctext_struct;
122 const EC_GROUP *group = EC_KEY_get0_group(key);
123 const BIGNUM *order = EC_GROUP_get0_order(group);
124 const EC_POINT *P = EC_KEY_get0_public_key(key);
125 EC_POINT *kG = NULL;
126 EC_POINT *kP = NULL;
127 uint8_t *msg_mask = NULL;
128 uint8_t *x2y2 = NULL;
129 uint8_t *C3 = NULL;
130 int field_size;
131 const int C3_size = EVP_MD_get_size(digest);
132 EVP_MD *fetched_digest = NULL;
133 OSSL_LIB_CTX *libctx = ossl_ec_key_get_libctx(key);
134 const char *propq = ossl_ec_key_get0_propq(key);
135
136 /* NULL these before any "goto done" */
137 ctext_struct.C2 = NULL;
138 ctext_struct.C3 = NULL;
139
140 if (msg_len > INT_MAX/2) {
141 ERR_raise(ERR_LIB_SM2, ERR_R_PASSED_INVALID_ARGUMENT);
142 goto done;
143 }
144
145 if (hash == NULL || C3_size <= 0) {
146 ERR_raise(ERR_LIB_SM2, ERR_R_INTERNAL_ERROR);
147 goto done;
148 }
149
150 field_size = ec_field_size(group);
151 if (field_size == 0) {
152 ERR_raise(ERR_LIB_SM2, ERR_R_INTERNAL_ERROR);
153 goto done;
154 }
155
156 kG = EC_POINT_new(group);
157 kP = EC_POINT_new(group);
158 if (kG == NULL || kP == NULL) {
159 ERR_raise(ERR_LIB_SM2, ERR_R_EC_LIB);
160 goto done;
161 }
162 ctx = BN_CTX_new_ex(libctx);
163 if (ctx == NULL) {
164 ERR_raise(ERR_LIB_SM2, ERR_R_BN_LIB);
165 goto done;
166 }
167
168 BN_CTX_start(ctx);
169 k = BN_CTX_get(ctx);
170 x1 = BN_CTX_get(ctx);
171 x2 = BN_CTX_get(ctx);
172 y1 = BN_CTX_get(ctx);
173 y2 = BN_CTX_get(ctx);
174
175 if (y2 == NULL) {
176 ERR_raise(ERR_LIB_SM2, ERR_R_BN_LIB);
177 goto done;
178 }
179
180 x2y2 = OPENSSL_calloc(2, field_size);
181 C3 = OPENSSL_zalloc(C3_size);
182
183 if (x2y2 == NULL || C3 == NULL)
184 goto done;
185
186 memset(ciphertext_buf, 0, *ciphertext_len);
187
188 msg_mask = OPENSSL_zalloc(msg_len);
189 if (msg_mask == NULL)
190 goto done;
191
192 again:
193 if (!BN_priv_rand_range_ex(k, order, 0, ctx)) {
194 ERR_raise(ERR_LIB_SM2, ERR_R_INTERNAL_ERROR);
195 goto done;
196 }
197
198 if (!EC_POINT_mul(group, kG, k, NULL, NULL, ctx)
199 || !EC_POINT_get_affine_coordinates(group, kG, x1, y1, ctx)
200 || !EC_POINT_mul(group, kP, NULL, P, k, ctx)
201 || !EC_POINT_get_affine_coordinates(group, kP, x2, y2, ctx)) {
202 ERR_raise(ERR_LIB_SM2, ERR_R_EC_LIB);
203 goto done;
204 }
205
206 if (BN_bn2binpad(x2, x2y2, field_size) < 0
207 || BN_bn2binpad(y2, x2y2 + field_size, field_size) < 0) {
208 ERR_raise(ERR_LIB_SM2, ERR_R_INTERNAL_ERROR);
209 goto done;
210 }
211
212 /* X9.63 with no salt happens to match the KDF used in SM2 */
213 if (!ossl_ecdh_kdf_X9_63(msg_mask, msg_len, x2y2, 2 * field_size, NULL, 0,
214 digest, libctx, propq)) {
215 ERR_raise(ERR_LIB_SM2, ERR_R_EVP_LIB);
216 goto done;
217 }
218
219 if (is_all_zeros(msg_mask, msg_len)) {
220 memset(x2y2, 0, 2 * field_size);
221 goto again;
222 }
223
224 for (i = 0; i != msg_len; ++i)
225 msg_mask[i] ^= msg[i];
226
227 fetched_digest = EVP_MD_fetch(libctx, EVP_MD_get0_name(digest), propq);
228 if (fetched_digest == NULL) {
229 ERR_raise(ERR_LIB_SM2, ERR_R_INTERNAL_ERROR);
230 goto done;
231 }
232 if (EVP_DigestInit(hash, fetched_digest) == 0
233 || EVP_DigestUpdate(hash, x2y2, field_size) == 0
234 || EVP_DigestUpdate(hash, msg, msg_len) == 0
235 || EVP_DigestUpdate(hash, x2y2 + field_size, field_size) == 0
236 || EVP_DigestFinal(hash, C3, NULL) == 0) {
237 ERR_raise(ERR_LIB_SM2, ERR_R_EVP_LIB);
238 goto done;
239 }
240
241 ctext_struct.C1x = x1;
242 ctext_struct.C1y = y1;
243 ctext_struct.C3 = ASN1_OCTET_STRING_new();
244 ctext_struct.C2 = ASN1_OCTET_STRING_new();
245
246 if (ctext_struct.C3 == NULL || ctext_struct.C2 == NULL) {
247 ERR_raise(ERR_LIB_SM2, ERR_R_ASN1_LIB);
248 goto done;
249 }
250 if (!ASN1_OCTET_STRING_set(ctext_struct.C3, C3, C3_size)
251 || !ASN1_OCTET_STRING_set(ctext_struct.C2, msg_mask, (int)msg_len)) {
252 ERR_raise(ERR_LIB_SM2, ERR_R_INTERNAL_ERROR);
253 goto done;
254 }
255
256 ciphertext_leni = i2d_SM2_Ciphertext(&ctext_struct, &ciphertext_buf);
257 /* Ensure cast to size_t is safe */
258 if (ciphertext_leni < 0) {
259 ERR_raise(ERR_LIB_SM2, ERR_R_INTERNAL_ERROR);
260 goto done;
261 }
262 *ciphertext_len = (size_t)ciphertext_leni;
263
264 rc = 1;
265
266 done:
267 EVP_MD_free(fetched_digest);
268 ASN1_OCTET_STRING_free(ctext_struct.C2);
269 ASN1_OCTET_STRING_free(ctext_struct.C3);
270 OPENSSL_free(msg_mask);
271 OPENSSL_free(x2y2);
272 OPENSSL_free(C3);
273 EVP_MD_CTX_free(hash);
274 BN_CTX_free(ctx);
275 EC_POINT_free(kG);
276 EC_POINT_free(kP);
277 return rc;
278 }
279
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)280 int ossl_sm2_decrypt(const EC_KEY *key,
281 const EVP_MD *digest,
282 const uint8_t *ciphertext, size_t ciphertext_len,
283 uint8_t *ptext_buf, size_t *ptext_len)
284 {
285 int rc = 0;
286 int i;
287 BN_CTX *ctx = NULL;
288 const EC_GROUP *group = EC_KEY_get0_group(key);
289 EC_POINT *C1 = NULL;
290 struct SM2_Ciphertext_st *sm2_ctext = NULL;
291 BIGNUM *x2 = NULL;
292 BIGNUM *y2 = NULL;
293 uint8_t *x2y2 = NULL;
294 uint8_t *computed_C3 = NULL;
295 const int field_size = ec_field_size(group);
296 const int hash_size = EVP_MD_get_size(digest);
297 uint8_t *msg_mask = NULL;
298 const uint8_t *C2 = NULL;
299 const uint8_t *C3 = NULL;
300 int msg_len = 0;
301 EVP_MD_CTX *hash = NULL;
302 OSSL_LIB_CTX *libctx = ossl_ec_key_get_libctx(key);
303 const char *propq = ossl_ec_key_get0_propq(key);
304
305 if (field_size == 0 || hash_size <= 0 || ciphertext_len > LONG_MAX)
306 goto done;
307
308 memset(ptext_buf, 0xFF, *ptext_len);
309
310 sm2_ctext = d2i_SM2_Ciphertext(NULL, &ciphertext, (long)ciphertext_len);
311
312 if (sm2_ctext == NULL) {
313 ERR_raise(ERR_LIB_SM2, SM2_R_ASN1_ERROR);
314 goto done;
315 }
316
317 if (sm2_ctext->C3->length != hash_size) {
318 ERR_raise(ERR_LIB_SM2, SM2_R_INVALID_ENCODING);
319 goto done;
320 }
321
322 C2 = sm2_ctext->C2->data;
323 C3 = sm2_ctext->C3->data;
324 msg_len = sm2_ctext->C2->length;
325 if (*ptext_len < (size_t)msg_len) {
326 ERR_raise(ERR_LIB_SM2, SM2_R_BUFFER_TOO_SMALL);
327 goto done;
328 }
329
330 ctx = BN_CTX_new_ex(libctx);
331 if (ctx == NULL) {
332 ERR_raise(ERR_LIB_SM2, ERR_R_BN_LIB);
333 goto done;
334 }
335
336 BN_CTX_start(ctx);
337 x2 = BN_CTX_get(ctx);
338 y2 = BN_CTX_get(ctx);
339
340 if (y2 == NULL) {
341 ERR_raise(ERR_LIB_SM2, ERR_R_BN_LIB);
342 goto done;
343 }
344
345 msg_mask = OPENSSL_zalloc(msg_len);
346 x2y2 = OPENSSL_calloc(2, field_size);
347 computed_C3 = OPENSSL_zalloc(hash_size);
348
349 if (msg_mask == NULL || x2y2 == NULL || computed_C3 == NULL)
350 goto done;
351
352 C1 = EC_POINT_new(group);
353 if (C1 == NULL) {
354 ERR_raise(ERR_LIB_SM2, ERR_R_EC_LIB);
355 goto done;
356 }
357
358 if (!EC_POINT_set_affine_coordinates(group, C1, sm2_ctext->C1x,
359 sm2_ctext->C1y, ctx)
360 || !EC_POINT_mul(group, C1, NULL, C1, EC_KEY_get0_private_key(key),
361 ctx)
362 || !EC_POINT_get_affine_coordinates(group, C1, x2, y2, ctx)) {
363 ERR_raise(ERR_LIB_SM2, ERR_R_EC_LIB);
364 goto done;
365 }
366
367 if (BN_bn2binpad(x2, x2y2, field_size) < 0
368 || BN_bn2binpad(y2, x2y2 + field_size, field_size) < 0
369 || !ossl_ecdh_kdf_X9_63(msg_mask, msg_len, x2y2, 2 * field_size,
370 NULL, 0, digest, libctx, propq)) {
371 ERR_raise(ERR_LIB_SM2, ERR_R_INTERNAL_ERROR);
372 goto done;
373 }
374
375 if (is_all_zeros(msg_mask, msg_len)) {
376 ERR_raise(ERR_LIB_SM2, SM2_R_INVALID_ENCODING);
377 goto done;
378 }
379
380 for (i = 0; i != msg_len; ++i)
381 ptext_buf[i] = C2[i] ^ msg_mask[i];
382
383 hash = EVP_MD_CTX_new();
384 if (hash == NULL) {
385 ERR_raise(ERR_LIB_SM2, ERR_R_EVP_LIB);
386 goto done;
387 }
388
389 if (!EVP_DigestInit(hash, digest)
390 || !EVP_DigestUpdate(hash, x2y2, field_size)
391 || !EVP_DigestUpdate(hash, ptext_buf, msg_len)
392 || !EVP_DigestUpdate(hash, x2y2 + field_size, field_size)
393 || !EVP_DigestFinal(hash, computed_C3, NULL)) {
394 ERR_raise(ERR_LIB_SM2, ERR_R_EVP_LIB);
395 goto done;
396 }
397
398 if (CRYPTO_memcmp(computed_C3, C3, hash_size) != 0) {
399 ERR_raise(ERR_LIB_SM2, SM2_R_INVALID_DIGEST);
400 goto done;
401 }
402
403 rc = 1;
404 *ptext_len = msg_len;
405
406 done:
407 if (rc == 0)
408 memset(ptext_buf, 0, *ptext_len);
409
410 OPENSSL_free(msg_mask);
411 OPENSSL_free(x2y2);
412 OPENSSL_free(computed_C3);
413 EC_POINT_free(C1);
414 BN_CTX_free(ctx);
415 SM2_Ciphertext_free(sm2_ctext);
416 EVP_MD_CTX_free(hash);
417
418 return rc;
419 }
420