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 size_t 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, 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 size_t field_size = ec_field_size(EC_KEY_get0_group(key));
91 const int md_size = EVP_MD_get_size(digest);
92 size_t sz;
93
94 if (field_size == 0 || md_size <= 0)
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, msg_len, V_ASN1_OCTET_STRING);
101 /* Sequence is structured type; set constructed = 1, means constructed and definite length encoding. */
102 *ct_size = 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 size_t 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 (hash == NULL || C3_size <= 0) {
141 ERR_raise(ERR_LIB_SM2, ERR_R_INTERNAL_ERROR);
142 goto done;
143 }
144
145 field_size = ec_field_size(group);
146 if (field_size == 0) {
147 ERR_raise(ERR_LIB_SM2, ERR_R_INTERNAL_ERROR);
148 goto done;
149 }
150
151 kG = EC_POINT_new(group);
152 kP = EC_POINT_new(group);
153 if (kG == NULL || kP == NULL) {
154 ERR_raise(ERR_LIB_SM2, ERR_R_EC_LIB);
155 goto done;
156 }
157 ctx = BN_CTX_new_ex(libctx);
158 if (ctx == NULL) {
159 ERR_raise(ERR_LIB_SM2, ERR_R_BN_LIB);
160 goto done;
161 }
162
163 BN_CTX_start(ctx);
164 k = BN_CTX_get(ctx);
165 x1 = BN_CTX_get(ctx);
166 x2 = BN_CTX_get(ctx);
167 y1 = BN_CTX_get(ctx);
168 y2 = BN_CTX_get(ctx);
169
170 if (y2 == NULL) {
171 ERR_raise(ERR_LIB_SM2, ERR_R_BN_LIB);
172 goto done;
173 }
174
175 x2y2 = OPENSSL_zalloc(2 * field_size);
176 C3 = OPENSSL_zalloc(C3_size);
177
178 if (x2y2 == NULL || C3 == NULL)
179 goto done;
180
181 memset(ciphertext_buf, 0, *ciphertext_len);
182
183 msg_mask = OPENSSL_zalloc(msg_len);
184 if (msg_mask == NULL)
185 goto done;
186
187 again:
188 if (!BN_priv_rand_range_ex(k, order, 0, ctx)) {
189 ERR_raise(ERR_LIB_SM2, ERR_R_INTERNAL_ERROR);
190 goto done;
191 }
192
193 if (!EC_POINT_mul(group, kG, k, NULL, NULL, ctx)
194 || !EC_POINT_get_affine_coordinates(group, kG, x1, y1, ctx)
195 || !EC_POINT_mul(group, kP, NULL, P, k, ctx)
196 || !EC_POINT_get_affine_coordinates(group, kP, x2, y2, ctx)) {
197 ERR_raise(ERR_LIB_SM2, ERR_R_EC_LIB);
198 goto done;
199 }
200
201 if (BN_bn2binpad(x2, x2y2, field_size) < 0
202 || BN_bn2binpad(y2, x2y2 + field_size, field_size) < 0) {
203 ERR_raise(ERR_LIB_SM2, ERR_R_INTERNAL_ERROR);
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 if (is_all_zeros(msg_mask, msg_len)) {
215 memset(x2y2, 0, 2 * field_size);
216 goto again;
217 }
218
219 for (i = 0; i != msg_len; ++i)
220 msg_mask[i] ^= msg[i];
221
222 fetched_digest = EVP_MD_fetch(libctx, EVP_MD_get0_name(digest), propq);
223 if (fetched_digest == NULL) {
224 ERR_raise(ERR_LIB_SM2, ERR_R_INTERNAL_ERROR);
225 goto done;
226 }
227 if (EVP_DigestInit(hash, fetched_digest) == 0
228 || EVP_DigestUpdate(hash, x2y2, field_size) == 0
229 || EVP_DigestUpdate(hash, msg, msg_len) == 0
230 || EVP_DigestUpdate(hash, x2y2 + field_size, field_size) == 0
231 || EVP_DigestFinal(hash, C3, NULL) == 0) {
232 ERR_raise(ERR_LIB_SM2, ERR_R_EVP_LIB);
233 goto done;
234 }
235
236 ctext_struct.C1x = x1;
237 ctext_struct.C1y = y1;
238 ctext_struct.C3 = ASN1_OCTET_STRING_new();
239 ctext_struct.C2 = ASN1_OCTET_STRING_new();
240
241 if (ctext_struct.C3 == NULL || ctext_struct.C2 == NULL) {
242 ERR_raise(ERR_LIB_SM2, ERR_R_ASN1_LIB);
243 goto done;
244 }
245 if (!ASN1_OCTET_STRING_set(ctext_struct.C3, C3, C3_size)
246 || !ASN1_OCTET_STRING_set(ctext_struct.C2, msg_mask, msg_len)) {
247 ERR_raise(ERR_LIB_SM2, ERR_R_INTERNAL_ERROR);
248 goto done;
249 }
250
251 ciphertext_leni = i2d_SM2_Ciphertext(&ctext_struct, &ciphertext_buf);
252 /* Ensure cast to size_t is safe */
253 if (ciphertext_leni < 0) {
254 ERR_raise(ERR_LIB_SM2, ERR_R_INTERNAL_ERROR);
255 goto done;
256 }
257 *ciphertext_len = (size_t)ciphertext_leni;
258
259 rc = 1;
260
261 done:
262 EVP_MD_free(fetched_digest);
263 ASN1_OCTET_STRING_free(ctext_struct.C2);
264 ASN1_OCTET_STRING_free(ctext_struct.C3);
265 OPENSSL_free(msg_mask);
266 OPENSSL_free(x2y2);
267 OPENSSL_free(C3);
268 EVP_MD_CTX_free(hash);
269 BN_CTX_free(ctx);
270 EC_POINT_free(kG);
271 EC_POINT_free(kP);
272 return rc;
273 }
274
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)275 int ossl_sm2_decrypt(const EC_KEY *key,
276 const EVP_MD *digest,
277 const uint8_t *ciphertext, size_t ciphertext_len,
278 uint8_t *ptext_buf, size_t *ptext_len)
279 {
280 int rc = 0;
281 int i;
282 BN_CTX *ctx = NULL;
283 const EC_GROUP *group = EC_KEY_get0_group(key);
284 EC_POINT *C1 = NULL;
285 struct SM2_Ciphertext_st *sm2_ctext = NULL;
286 BIGNUM *x2 = NULL;
287 BIGNUM *y2 = NULL;
288 uint8_t *x2y2 = NULL;
289 uint8_t *computed_C3 = NULL;
290 const size_t field_size = ec_field_size(group);
291 const int hash_size = EVP_MD_get_size(digest);
292 uint8_t *msg_mask = NULL;
293 const uint8_t *C2 = NULL;
294 const uint8_t *C3 = NULL;
295 int msg_len = 0;
296 EVP_MD_CTX *hash = NULL;
297 OSSL_LIB_CTX *libctx = ossl_ec_key_get_libctx(key);
298 const char *propq = ossl_ec_key_get0_propq(key);
299
300 if (field_size == 0 || hash_size <= 0)
301 goto done;
302
303 memset(ptext_buf, 0xFF, *ptext_len);
304
305 sm2_ctext = d2i_SM2_Ciphertext(NULL, &ciphertext, ciphertext_len);
306
307 if (sm2_ctext == NULL) {
308 ERR_raise(ERR_LIB_SM2, SM2_R_ASN1_ERROR);
309 goto done;
310 }
311
312 if (sm2_ctext->C3->length != hash_size) {
313 ERR_raise(ERR_LIB_SM2, SM2_R_INVALID_ENCODING);
314 goto done;
315 }
316
317 C2 = sm2_ctext->C2->data;
318 C3 = sm2_ctext->C3->data;
319 msg_len = sm2_ctext->C2->length;
320 if (*ptext_len < (size_t)msg_len) {
321 ERR_raise(ERR_LIB_SM2, SM2_R_BUFFER_TOO_SMALL);
322 goto done;
323 }
324
325 ctx = BN_CTX_new_ex(libctx);
326 if (ctx == NULL) {
327 ERR_raise(ERR_LIB_SM2, ERR_R_BN_LIB);
328 goto done;
329 }
330
331 BN_CTX_start(ctx);
332 x2 = BN_CTX_get(ctx);
333 y2 = BN_CTX_get(ctx);
334
335 if (y2 == NULL) {
336 ERR_raise(ERR_LIB_SM2, ERR_R_BN_LIB);
337 goto done;
338 }
339
340 msg_mask = OPENSSL_zalloc(msg_len);
341 x2y2 = OPENSSL_zalloc(2 * field_size);
342 computed_C3 = OPENSSL_zalloc(hash_size);
343
344 if (msg_mask == NULL || x2y2 == NULL || computed_C3 == NULL)
345 goto done;
346
347 C1 = EC_POINT_new(group);
348 if (C1 == NULL) {
349 ERR_raise(ERR_LIB_SM2, ERR_R_EC_LIB);
350 goto done;
351 }
352
353 if (!EC_POINT_set_affine_coordinates(group, C1, sm2_ctext->C1x,
354 sm2_ctext->C1y, ctx)
355 || !EC_POINT_mul(group, C1, NULL, C1, EC_KEY_get0_private_key(key),
356 ctx)
357 || !EC_POINT_get_affine_coordinates(group, C1, x2, y2, ctx)) {
358 ERR_raise(ERR_LIB_SM2, ERR_R_EC_LIB);
359 goto done;
360 }
361
362 if (BN_bn2binpad(x2, x2y2, field_size) < 0
363 || BN_bn2binpad(y2, x2y2 + field_size, field_size) < 0
364 || !ossl_ecdh_kdf_X9_63(msg_mask, msg_len, x2y2, 2 * field_size,
365 NULL, 0, digest, libctx, propq)) {
366 ERR_raise(ERR_LIB_SM2, ERR_R_INTERNAL_ERROR);
367 goto done;
368 }
369
370 if (is_all_zeros(msg_mask, msg_len)) {
371 ERR_raise(ERR_LIB_SM2, SM2_R_INVALID_ENCODING);
372 goto done;
373 }
374
375 for (i = 0; i != msg_len; ++i)
376 ptext_buf[i] = C2[i] ^ msg_mask[i];
377
378 hash = EVP_MD_CTX_new();
379 if (hash == NULL) {
380 ERR_raise(ERR_LIB_SM2, ERR_R_EVP_LIB);
381 goto done;
382 }
383
384 if (!EVP_DigestInit(hash, digest)
385 || !EVP_DigestUpdate(hash, x2y2, field_size)
386 || !EVP_DigestUpdate(hash, ptext_buf, msg_len)
387 || !EVP_DigestUpdate(hash, x2y2 + field_size, field_size)
388 || !EVP_DigestFinal(hash, computed_C3, NULL)) {
389 ERR_raise(ERR_LIB_SM2, ERR_R_EVP_LIB);
390 goto done;
391 }
392
393 if (CRYPTO_memcmp(computed_C3, C3, hash_size) != 0) {
394 ERR_raise(ERR_LIB_SM2, SM2_R_INVALID_DIGEST);
395 goto done;
396 }
397
398 rc = 1;
399 *ptext_len = msg_len;
400
401 done:
402 if (rc == 0)
403 memset(ptext_buf, 0, *ptext_len);
404
405 OPENSSL_free(msg_mask);
406 OPENSSL_free(x2y2);
407 OPENSSL_free(computed_C3);
408 EC_POINT_free(C1);
409 BN_CTX_free(ctx);
410 SM2_Ciphertext_free(sm2_ctext);
411 EVP_MD_CTX_free(hash);
412
413 return rc;
414 }
415
