1/*
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.
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#include "crypto/sm2.h"
13#include "crypto/sm2err.h"
14#include "crypto/ec.h" /* ec_group_do_inverse_ord() */
15#include "internal/numbers.h"
16#include <openssl/err.h>
17#include <openssl/evp.h>
18#include <openssl/err.h>
19#include <openssl/bn.h>
20#include <string.h>
21
22int sm2_compute_z_digest(uint8_t *out,
23 const EVP_MD *digest,
24 const uint8_t *id,
25 const size_t id_len,
26 const EC_KEY *key)
27{
28 int rc = 0;
29 const EC_GROUP *group = EC_KEY_get0_group(key);
30 BN_CTX *ctx = NULL;
31 EVP_MD_CTX *hash = NULL;
32 BIGNUM *p = NULL;
33 BIGNUM *a = NULL;
34 BIGNUM *b = NULL;
35 BIGNUM *xG = NULL;
36 BIGNUM *yG = NULL;
37 BIGNUM *xA = NULL;
38 BIGNUM *yA = NULL;
39 int p_bytes = 0;
40 uint8_t *buf = NULL;
41 uint16_t entl = 0;
42 uint8_t e_byte = 0;
43
44 hash = EVP_MD_CTX_new();
45 ctx = BN_CTX_new();
46 if (hash == NULL || ctx == NULL) {
47 SM2err(SM2_F_SM2_COMPUTE_Z_DIGEST, ERR_R_MALLOC_FAILURE);
48 goto done;
49 }
50
51 p = BN_CTX_get(ctx);
52 a = BN_CTX_get(ctx);
53 b = BN_CTX_get(ctx);
54 xG = BN_CTX_get(ctx);
55 yG = BN_CTX_get(ctx);
56 xA = BN_CTX_get(ctx);
57 yA = BN_CTX_get(ctx);
58
59 if (yA == NULL) {
60 SM2err(SM2_F_SM2_COMPUTE_Z_DIGEST, ERR_R_MALLOC_FAILURE);
61 goto done;
62 }
63
64 if (!EVP_DigestInit(hash, digest)) {
65 SM2err(SM2_F_SM2_COMPUTE_Z_DIGEST, ERR_R_EVP_LIB);
66 goto done;
67 }
68
69 /* Z = h(ENTL || ID || a || b || xG || yG || xA || yA) */
70
71 if (id_len >= (UINT16_MAX / 8)) {
72 /* too large */
73 SM2err(SM2_F_SM2_COMPUTE_Z_DIGEST, SM2_R_ID_TOO_LARGE);
74 goto done;
75 }
76
77 entl = (uint16_t)(8 * id_len);
78
79 e_byte = entl >> 8;
80 if (!EVP_DigestUpdate(hash, &e_byte, 1)) {
81 SM2err(SM2_F_SM2_COMPUTE_Z_DIGEST, ERR_R_EVP_LIB);
82 goto done;
83 }
84 e_byte = entl & 0xFF;
85 if (!EVP_DigestUpdate(hash, &e_byte, 1)) {
86 SM2err(SM2_F_SM2_COMPUTE_Z_DIGEST, ERR_R_EVP_LIB);
87 goto done;
88 }
89
90 if (id_len > 0 && !EVP_DigestUpdate(hash, id, id_len)) {
91 SM2err(SM2_F_SM2_COMPUTE_Z_DIGEST, ERR_R_EVP_LIB);
92 goto done;
93 }
94
95 if (!EC_GROUP_get_curve(group, p, a, b, ctx)) {
96 SM2err(SM2_F_SM2_COMPUTE_Z_DIGEST, ERR_R_EC_LIB);
97 goto done;
98 }
99
100 p_bytes = BN_num_bytes(p);
101 buf = OPENSSL_zalloc(p_bytes);
102 if (buf == NULL) {
103 SM2err(SM2_F_SM2_COMPUTE_Z_DIGEST, ERR_R_MALLOC_FAILURE);
104 goto done;
105 }
106
107 if (BN_bn2binpad(a, buf, p_bytes) < 0
108 || !EVP_DigestUpdate(hash, buf, p_bytes)
109 || BN_bn2binpad(b, buf, p_bytes) < 0
110 || !EVP_DigestUpdate(hash, buf, p_bytes)
111 || !EC_POINT_get_affine_coordinates(group,
112 EC_GROUP_get0_generator(group),
113 xG, yG, ctx)
114 || BN_bn2binpad(xG, buf, p_bytes) < 0
115 || !EVP_DigestUpdate(hash, buf, p_bytes)
116 || BN_bn2binpad(yG, buf, p_bytes) < 0
117 || !EVP_DigestUpdate(hash, buf, p_bytes)
118 || !EC_POINT_get_affine_coordinates(group,
119 EC_KEY_get0_public_key(key),
120 xA, yA, ctx)
121 || BN_bn2binpad(xA, buf, p_bytes) < 0
122 || !EVP_DigestUpdate(hash, buf, p_bytes)
123 || BN_bn2binpad(yA, buf, p_bytes) < 0
124 || !EVP_DigestUpdate(hash, buf, p_bytes)
125 || !EVP_DigestFinal(hash, out, NULL)) {
126 SM2err(SM2_F_SM2_COMPUTE_Z_DIGEST, ERR_R_INTERNAL_ERROR);
127 goto done;
128 }
129
130 rc = 1;
131
132 done:
133 OPENSSL_free(buf);
134 BN_CTX_free(ctx);
135 EVP_MD_CTX_free(hash);
136 return rc;
137}
138
139static BIGNUM *sm2_compute_msg_hash(const EVP_MD *digest,
140 const EC_KEY *key,
141 const uint8_t *id,
142 const size_t id_len,
143 const uint8_t *msg, size_t msg_len)
144{
145 EVP_MD_CTX *hash = EVP_MD_CTX_new();
146 const int md_size = EVP_MD_size(digest);
147 uint8_t *z = NULL;
148 BIGNUM *e = NULL;
149
150 if (md_size < 0) {
151 SM2err(SM2_F_SM2_COMPUTE_MSG_HASH, SM2_R_INVALID_DIGEST);
152 goto done;
153 }
154
155 z = OPENSSL_zalloc(md_size);
156 if (hash == NULL || z == NULL) {
157 SM2err(SM2_F_SM2_COMPUTE_MSG_HASH, ERR_R_MALLOC_FAILURE);
158 goto done;
159 }
160
161 if (!sm2_compute_z_digest(z, digest, id, id_len, key)) {
162 /* SM2err already called */
163 goto done;
164 }
165
166 if (!EVP_DigestInit(hash, digest)
167 || !EVP_DigestUpdate(hash, z, md_size)
168 || !EVP_DigestUpdate(hash, msg, msg_len)
169 /* reuse z buffer to hold H(Z || M) */
170 || !EVP_DigestFinal(hash, z, NULL)) {
171 SM2err(SM2_F_SM2_COMPUTE_MSG_HASH, ERR_R_EVP_LIB);
172 goto done;
173 }
174
175 e = BN_bin2bn(z, md_size, NULL);
176 if (e == NULL)
177 SM2err(SM2_F_SM2_COMPUTE_MSG_HASH, ERR_R_INTERNAL_ERROR);
178
179 done:
180 OPENSSL_free(z);
181 EVP_MD_CTX_free(hash);
182 return e;
183}
184
185static ECDSA_SIG *sm2_sig_gen(const EC_KEY *key, const BIGNUM *e)
186{
187 const BIGNUM *dA = EC_KEY_get0_private_key(key);
188 const EC_GROUP *group = EC_KEY_get0_group(key);
189 const BIGNUM *order = EC_GROUP_get0_order(group);
190 ECDSA_SIG *sig = NULL;
191 EC_POINT *kG = NULL;
192 BN_CTX *ctx = NULL;
193 BIGNUM *k = NULL;
194 BIGNUM *rk = NULL;
195 BIGNUM *r = NULL;
196 BIGNUM *s = NULL;
197 BIGNUM *x1 = NULL;
198 BIGNUM *tmp = NULL;
199
200 kG = EC_POINT_new(group);
201 ctx = BN_CTX_new();
202 if (kG == NULL || ctx == NULL) {
203 SM2err(SM2_F_SM2_SIG_GEN, ERR_R_MALLOC_FAILURE);
204 goto done;
205 }
206
207 BN_CTX_start(ctx);
208 k = BN_CTX_get(ctx);
209 rk = BN_CTX_get(ctx);
210 x1 = BN_CTX_get(ctx);
211 tmp = BN_CTX_get(ctx);
212 if (tmp == NULL) {
213 SM2err(SM2_F_SM2_SIG_GEN, ERR_R_MALLOC_FAILURE);
214 goto done;
215 }
216
217 /*
218 * These values are returned and so should not be allocated out of the
219 * context
220 */
221 r = BN_new();
222 s = BN_new();
223
224 if (r == NULL || s == NULL) {
225 SM2err(SM2_F_SM2_SIG_GEN, ERR_R_MALLOC_FAILURE);
226 goto done;
227 }
228
229 for (;;) {
230 if (!BN_priv_rand_range(k, order)) {
231 SM2err(SM2_F_SM2_SIG_GEN, ERR_R_INTERNAL_ERROR);
232 goto done;
233 }
234
235 if (!EC_POINT_mul(group, kG, k, NULL, NULL, ctx)
236 || !EC_POINT_get_affine_coordinates(group, kG, x1, NULL,
237 ctx)
238 || !BN_mod_add(r, e, x1, order, ctx)) {
239 SM2err(SM2_F_SM2_SIG_GEN, ERR_R_INTERNAL_ERROR);
240 goto done;
241 }
242
243 /* try again if r == 0 or r+k == n */
244 if (BN_is_zero(r))
245 continue;
246
247 if (!BN_add(rk, r, k)) {
248 SM2err(SM2_F_SM2_SIG_GEN, ERR_R_INTERNAL_ERROR);
249 goto done;
250 }
251
252 if (BN_cmp(rk, order) == 0)
253 continue;
254
255 if (!BN_add(s, dA, BN_value_one())
256 || !ec_group_do_inverse_ord(group, s, s, ctx)
257 || !BN_mod_mul(tmp, dA, r, order, ctx)
258 || !BN_sub(tmp, k, tmp)
259 || !BN_mod_mul(s, s, tmp, order, ctx)) {
260 SM2err(SM2_F_SM2_SIG_GEN, ERR_R_BN_LIB);
261 goto done;
262 }
263
264 sig = ECDSA_SIG_new();
265 if (sig == NULL) {
266 SM2err(SM2_F_SM2_SIG_GEN, ERR_R_MALLOC_FAILURE);
267 goto done;
268 }
269
270 /* takes ownership of r and s */
271 ECDSA_SIG_set0(sig, r, s);
272 break;
273 }
274
275 done:
276 if (sig == NULL) {
277 BN_free(r);
278 BN_free(s);
279 }
280
281 BN_CTX_free(ctx);
282 EC_POINT_free(kG);
283 return sig;
284}
285
286static int sm2_sig_verify(const EC_KEY *key, const ECDSA_SIG *sig,
287 const BIGNUM *e)
288{
289 int ret = 0;
290 const EC_GROUP *group = EC_KEY_get0_group(key);
291 const BIGNUM *order = EC_GROUP_get0_order(group);
292 BN_CTX *ctx = NULL;
293 EC_POINT *pt = NULL;
294 BIGNUM *t = NULL;
295 BIGNUM *x1 = NULL;
296 const BIGNUM *r = NULL;
297 const BIGNUM *s = NULL;
298
299 ctx = BN_CTX_new();
300 pt = EC_POINT_new(group);
301 if (ctx == NULL || pt == NULL) {
302 SM2err(SM2_F_SM2_SIG_VERIFY, ERR_R_MALLOC_FAILURE);
303 goto done;
304 }
305
306 BN_CTX_start(ctx);
307 t = BN_CTX_get(ctx);
308 x1 = BN_CTX_get(ctx);
309 if (x1 == NULL) {
310 SM2err(SM2_F_SM2_SIG_VERIFY, ERR_R_MALLOC_FAILURE);
311 goto done;
312 }
313
314 /*
315 * B1: verify whether r' in [1,n-1], verification failed if not
316 * B2: verify whether s' in [1,n-1], verification failed if not
317 * B3: set M'~=ZA || M'
318 * B4: calculate e'=Hv(M'~)
319 * B5: calculate t = (r' + s') modn, verification failed if t=0
320 * B6: calculate the point (x1', y1')=[s']G + [t]PA
321 * B7: calculate R=(e'+x1') modn, verification pass if yes, otherwise failed
322 */
323
324 ECDSA_SIG_get0(sig, &r, &s);
325
326 if (BN_cmp(r, BN_value_one()) < 0
327 || BN_cmp(s, BN_value_one()) < 0
328 || BN_cmp(order, r) <= 0
329 || BN_cmp(order, s) <= 0) {
330 SM2err(SM2_F_SM2_SIG_VERIFY, SM2_R_BAD_SIGNATURE);
331 goto done;
332 }
333
334 if (!BN_mod_add(t, r, s, order, ctx)) {
335 SM2err(SM2_F_SM2_SIG_VERIFY, ERR_R_BN_LIB);
336 goto done;
337 }
338
339 if (BN_is_zero(t)) {
340 SM2err(SM2_F_SM2_SIG_VERIFY, SM2_R_BAD_SIGNATURE);
341 goto done;
342 }
343
344 if (!EC_POINT_mul(group, pt, s, EC_KEY_get0_public_key(key), t, ctx)
345 || !EC_POINT_get_affine_coordinates(group, pt, x1, NULL, ctx)) {
346 SM2err(SM2_F_SM2_SIG_VERIFY, ERR_R_EC_LIB);
347 goto done;
348 }
349
350 if (!BN_mod_add(t, e, x1, order, ctx)) {
351 SM2err(SM2_F_SM2_SIG_VERIFY, ERR_R_BN_LIB);
352 goto done;
353 }
354
355 if (BN_cmp(r, t) == 0)
356 ret = 1;
357
358 done:
359 EC_POINT_free(pt);
360 BN_CTX_free(ctx);
361 return ret;
362}
363
364ECDSA_SIG *sm2_do_sign(const EC_KEY *key,
365 const EVP_MD *digest,
366 const uint8_t *id,
367 const size_t id_len,
368 const uint8_t *msg, size_t msg_len)
369{
370 BIGNUM *e = NULL;
371 ECDSA_SIG *sig = NULL;
372
373 e = sm2_compute_msg_hash(digest, key, id, id_len, msg, msg_len);
374 if (e == NULL) {
375 /* SM2err already called */
376 goto done;
377 }
378
379 sig = sm2_sig_gen(key, e);
380
381 done:
382 BN_free(e);
383 return sig;
384}
385
386int sm2_do_verify(const EC_KEY *key,
387 const EVP_MD *digest,
388 const ECDSA_SIG *sig,
389 const uint8_t *id,
390 const size_t id_len,
391 const uint8_t *msg, size_t msg_len)
392{
393 BIGNUM *e = NULL;
394 int ret = 0;
395
396 e = sm2_compute_msg_hash(digest, key, id, id_len, msg, msg_len);
397 if (e == NULL) {
398 /* SM2err already called */
399 goto done;
400 }
401
402 ret = sm2_sig_verify(key, sig, e);
403
404 done:
405 BN_free(e);
406 return ret;
407}
408
409int sm2_sign(const unsigned char *dgst, int dgstlen,
410 unsigned char *sig, unsigned int *siglen, EC_KEY *eckey)
411{
412 BIGNUM *e = NULL;
413 ECDSA_SIG *s = NULL;
414 int sigleni;
415 int ret = -1;
416
417 e = BN_bin2bn(dgst, dgstlen, NULL);
418 if (e == NULL) {
419 SM2err(SM2_F_SM2_SIGN, ERR_R_BN_LIB);
420 goto done;
421 }
422
423 s = sm2_sig_gen(eckey, e);
424
425 sigleni = i2d_ECDSA_SIG(s, &sig);
426 if (sigleni < 0) {
427 SM2err(SM2_F_SM2_SIGN, ERR_R_INTERNAL_ERROR);
428 goto done;
429 }
430 *siglen = (unsigned int)sigleni;
431
432 ret = 1;
433
434 done:
435 ECDSA_SIG_free(s);
436 BN_free(e);
437 return ret;
438}
439
440int sm2_verify(const unsigned char *dgst, int dgstlen,
441 const unsigned char *sig, int sig_len, EC_KEY *eckey)
442{
443 ECDSA_SIG *s = NULL;
444 BIGNUM *e = NULL;
445 const unsigned char *p = sig;
446 unsigned char *der = NULL;
447 int derlen = -1;
448 int ret = -1;
449
450 s = ECDSA_SIG_new();
451 if (s == NULL) {
452 SM2err(SM2_F_SM2_VERIFY, ERR_R_MALLOC_FAILURE);
453 goto done;
454 }
455 if (d2i_ECDSA_SIG(&s, &p, sig_len) == NULL) {
456 SM2err(SM2_F_SM2_VERIFY, SM2_R_INVALID_ENCODING);
457 goto done;
458 }
459 /* Ensure signature uses DER and doesn't have trailing garbage */
460 derlen = i2d_ECDSA_SIG(s, &der);
461 if (derlen != sig_len || memcmp(sig, der, derlen) != 0) {
462 SM2err(SM2_F_SM2_VERIFY, SM2_R_INVALID_ENCODING);
463 goto done;
464 }
465
466 e = BN_bin2bn(dgst, dgstlen, NULL);
467 if (e == NULL) {
468 SM2err(SM2_F_SM2_VERIFY, ERR_R_BN_LIB);
469 goto done;
470 }
471
472 ret = sm2_sig_verify(eckey, s, e);
473
474 done:
475 OPENSSL_free(der);
476 BN_free(e);
477 ECDSA_SIG_free(s);
478 return ret;
479}
480