crypto/sm2/sm2_sign.c

   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 #include "internal/deprecated.h"
  13
  14 #include "crypto/sm2.h"
  15 #include "crypto/sm2err.h"
  16 #include "crypto/ec.h" /* ossl_ec_group_do_inverse_ord() */
  17 #include "internal/numbers.h"
  18 #include <openssl/err.h>
  19 #include <openssl/evp.h>
  20 #include <openssl/err.h>
  21 #include <openssl/bn.h>
  22 #include <string.h>
  23
  24 int ossl_sm2_compute_z_digest(uint8_t *out,
  25                               const EVP_MD *digest,
  26                               const uint8_t *id,
  27                               const size_t id_len,
  28                               const EC_KEY *key)
  29 {
  30     int rc = 0;
  31     const EC_GROUP *group = EC_KEY_get0_group(key);
  32     BN_CTX *ctx = NULL;
  33     EVP_MD_CTX *hash = NULL;
  34     BIGNUM *p = NULL;
  35     BIGNUM *a = NULL;
  36     BIGNUM *b = NULL;
  37     BIGNUM *xG = NULL;
  38     BIGNUM *yG = NULL;
  39     BIGNUM *xA = NULL;
  40     BIGNUM *yA = NULL;
  41     int p_bytes = 0;
  42     uint8_t *buf = NULL;
  43     uint16_t entl = 0;
  44     uint8_t e_byte = 0;
  45
  46     hash = EVP_MD_CTX_new();
  47     ctx = BN_CTX_new_ex(ossl_ec_key_get_libctx(key));
  48     if (hash == NULL || ctx == NULL) {
  49         ERR_raise(ERR_LIB_SM2, ERR_R_MALLOC_FAILURE);
  50         goto done;
  51     }
  52
  53     p = BN_CTX_get(ctx);
  54     a = BN_CTX_get(ctx);
  55     b = BN_CTX_get(ctx);
  56     xG = BN_CTX_get(ctx);
  57     yG = BN_CTX_get(ctx);
  58     xA = BN_CTX_get(ctx);
  59     yA = BN_CTX_get(ctx);
  60
  61     if (yA == NULL) {
  62         ERR_raise(ERR_LIB_SM2, ERR_R_MALLOC_FAILURE);
  63         goto done;
  64     }
  65
  66     if (!EVP_DigestInit(hash, digest)) {
  67         ERR_raise(ERR_LIB_SM2, ERR_R_EVP_LIB);
  68         goto done;
  69     }
  70
  71     /* Z = h(ENTL || ID || a || b || xG || yG || xA || yA) */
  72
  73     if (id_len >= (UINT16_MAX / 8)) {
  74         /* too large */
  75         ERR_raise(ERR_LIB_SM2, SM2_R_ID_TOO_LARGE);
  76         goto done;
  77     }
  78
  79     entl = (uint16_t)(8 * id_len);
  80
  81     e_byte = entl >> 8;
  82     if (!EVP_DigestUpdate(hash, &e_byte, 1)) {
  83         ERR_raise(ERR_LIB_SM2, ERR_R_EVP_LIB);
  84         goto done;
  85     }
  86     e_byte = entl & 0xFF;
  87     if (!EVP_DigestUpdate(hash, &e_byte, 1)) {
  88         ERR_raise(ERR_LIB_SM2, ERR_R_EVP_LIB);
  89         goto done;
  90     }
  91
  92     if (id_len > 0 && !EVP_DigestUpdate(hash, id, id_len)) {
  93         ERR_raise(ERR_LIB_SM2, ERR_R_EVP_LIB);
  94         goto done;
  95     }
  96
  97     if (!EC_GROUP_get_curve(group, p, a, b, ctx)) {
  98         ERR_raise(ERR_LIB_SM2, ERR_R_EC_LIB);
  99         goto done;
 100     }
 101
 102     p_bytes = BN_num_bytes(p);
 103     buf = OPENSSL_zalloc(p_bytes);
 104     if (buf == NULL) {
 105         ERR_raise(ERR_LIB_SM2, ERR_R_MALLOC_FAILURE);
 106         goto done;
 107     }
 108
 109     if (BN_bn2binpad(a, buf, p_bytes) < 0
 110             || !EVP_DigestUpdate(hash, buf, p_bytes)
 111             || BN_bn2binpad(b, buf, p_bytes) < 0
 112             || !EVP_DigestUpdate(hash, buf, p_bytes)
 113             || !EC_POINT_get_affine_coordinates(group,
 114                                                 EC_GROUP_get0_generator(group),
 115                                                 xG, yG, ctx)
 116             || BN_bn2binpad(xG, buf, p_bytes) < 0
 117             || !EVP_DigestUpdate(hash, buf, p_bytes)
 118             || BN_bn2binpad(yG, buf, p_bytes) < 0
 119             || !EVP_DigestUpdate(hash, buf, p_bytes)
 120             || !EC_POINT_get_affine_coordinates(group,
 121                                                 EC_KEY_get0_public_key(key),
 122                                                 xA, yA, ctx)
 123             || BN_bn2binpad(xA, buf, p_bytes) < 0
 124             || !EVP_DigestUpdate(hash, buf, p_bytes)
 125             || BN_bn2binpad(yA, buf, p_bytes) < 0
 126             || !EVP_DigestUpdate(hash, buf, p_bytes)
 127             || !EVP_DigestFinal(hash, out, NULL)) {
 128         ERR_raise(ERR_LIB_SM2, ERR_R_INTERNAL_ERROR);
 129         goto done;
 130     }
 131
 132     rc = 1;
 133
 134  done:
 135     OPENSSL_free(buf);
 136     BN_CTX_free(ctx);
 137     EVP_MD_CTX_free(hash);
 138     return rc;
 139 }
 140
 141 static BIGNUM *sm2_compute_msg_hash(const EVP_MD *digest,
 142                                     const EC_KEY *key,
 143                                     const uint8_t *id,
 144                                     const size_t id_len,
 145                                     const uint8_t *msg, size_t msg_len)
 146 {
 147     EVP_MD_CTX *hash = EVP_MD_CTX_new();
 148     const int md_size = EVP_MD_size(digest);
 149     uint8_t *z = NULL;
 150     BIGNUM *e = NULL;
 151     EVP_MD *fetched_digest = NULL;
 152     OSSL_LIB_CTX *libctx = ossl_ec_key_get_libctx(key);
 153     const char *propq = ossl_ec_key_get0_propq(key);
 154
 155     if (md_size < 0) {
 156         ERR_raise(ERR_LIB_SM2, SM2_R_INVALID_DIGEST);
 157         goto done;
 158     }
 159
 160     z = OPENSSL_zalloc(md_size);
 161     if (hash == NULL || z == NULL) {
 162         ERR_raise(ERR_LIB_SM2, ERR_R_MALLOC_FAILURE);
 163         goto done;
 164     }
 165
 166     fetched_digest = EVP_MD_fetch(libctx, EVP_MD_name(digest), propq);
 167     if (fetched_digest == NULL) {
 168         ERR_raise(ERR_LIB_SM2, ERR_R_INTERNAL_ERROR);
 169         goto done;
 170     }
 171
 172     if (!ossl_sm2_compute_z_digest(z, fetched_digest, id, id_len, key)) {
 173         /* SM2err already called */
 174         goto done;
 175     }
 176
 177     if (!EVP_DigestInit(hash, fetched_digest)
 178             || !EVP_DigestUpdate(hash, z, md_size)
 179             || !EVP_DigestUpdate(hash, msg, msg_len)
 180                /* reuse z buffer to hold H(Z || M) */
 181             || !EVP_DigestFinal(hash, z, NULL)) {
 182         ERR_raise(ERR_LIB_SM2, ERR_R_EVP_LIB);
 183         goto done;
 184     }
 185
 186     e = BN_bin2bn(z, md_size, NULL);
 187     if (e == NULL)
 188         ERR_raise(ERR_LIB_SM2, ERR_R_INTERNAL_ERROR);
 189
 190  done:
 191     EVP_MD_free(fetched_digest);
 192     OPENSSL_free(z);
 193     EVP_MD_CTX_free(hash);
 194     return e;
 195 }
 196
 197 static ECDSA_SIG *sm2_sig_gen(const EC_KEY *key, const BIGNUM *e)
 198 {
 199     const BIGNUM *dA = EC_KEY_get0_private_key(key);
 200     const EC_GROUP *group = EC_KEY_get0_group(key);
 201     const BIGNUM *order = EC_GROUP_get0_order(group);
 202     ECDSA_SIG *sig = NULL;
 203     EC_POINT *kG = NULL;
 204     BN_CTX *ctx = NULL;
 205     BIGNUM *k = NULL;
 206     BIGNUM *rk = NULL;
 207     BIGNUM *r = NULL;
 208     BIGNUM *s = NULL;
 209     BIGNUM *x1 = NULL;
 210     BIGNUM *tmp = NULL;
 211     OSSL_LIB_CTX *libctx = ossl_ec_key_get_libctx(key);
 212
 213     kG = EC_POINT_new(group);
 214     ctx = BN_CTX_new_ex(libctx);
 215     if (kG == NULL || ctx == NULL) {
 216         ERR_raise(ERR_LIB_SM2, ERR_R_MALLOC_FAILURE);
 217         goto done;
 218     }
 219
 220     BN_CTX_start(ctx);
 221     k = BN_CTX_get(ctx);
 222     rk = BN_CTX_get(ctx);
 223     x1 = BN_CTX_get(ctx);
 224     tmp = BN_CTX_get(ctx);
 225     if (tmp == NULL) {
 226         ERR_raise(ERR_LIB_SM2, ERR_R_MALLOC_FAILURE);
 227         goto done;
 228     }
 229
 230     /*
 231      * These values are returned and so should not be allocated out of the
 232      * context
 233      */
 234     r = BN_new();
 235     s = BN_new();
 236
 237     if (r == NULL || s == NULL) {
 238         ERR_raise(ERR_LIB_SM2, ERR_R_MALLOC_FAILURE);
 239         goto done;
 240     }
 241
 242     for (;;) {
 243         if (!BN_priv_rand_range_ex(k, order, 0, ctx)) {
 244             ERR_raise(ERR_LIB_SM2, ERR_R_INTERNAL_ERROR);
 245             goto done;
 246         }
 247
 248         if (!EC_POINT_mul(group, kG, k, NULL, NULL, ctx)
 249                 || !EC_POINT_get_affine_coordinates(group, kG, x1, NULL,
 250                                                     ctx)
 251                 || !BN_mod_add(r, e, x1, order, ctx)) {
 252             ERR_raise(ERR_LIB_SM2, ERR_R_INTERNAL_ERROR);
 253             goto done;
 254         }
 255
 256         /* try again if r == 0 or r+k == n */
 257         if (BN_is_zero(r))
 258             continue;
 259
 260         if (!BN_add(rk, r, k)) {
 261             ERR_raise(ERR_LIB_SM2, ERR_R_INTERNAL_ERROR);
 262             goto done;
 263         }
 264
 265         if (BN_cmp(rk, order) == 0)
 266             continue;
 267
 268         if (!BN_add(s, dA, BN_value_one())
 269                 || !ossl_ec_group_do_inverse_ord(group, s, s, ctx)
 270                 || !BN_mod_mul(tmp, dA, r, order, ctx)
 271                 || !BN_sub(tmp, k, tmp)
 272                 || !BN_mod_mul(s, s, tmp, order, ctx)) {
 273             ERR_raise(ERR_LIB_SM2, ERR_R_BN_LIB);
 274             goto done;
 275         }
 276
 277         sig = ECDSA_SIG_new();
 278         if (sig == NULL) {
 279             ERR_raise(ERR_LIB_SM2, ERR_R_MALLOC_FAILURE);
 280             goto done;
 281         }
 282
 283          /* takes ownership of r and s */
 284         ECDSA_SIG_set0(sig, r, s);
 285         break;
 286     }
 287
 288  done:
 289     if (sig == NULL) {
 290         BN_free(r);
 291         BN_free(s);
 292     }
 293
 294     BN_CTX_free(ctx);
 295     EC_POINT_free(kG);
 296     return sig;
 297 }
 298
 299 static int sm2_sig_verify(const EC_KEY *key, const ECDSA_SIG *sig,
 300                           const BIGNUM *e)
 301 {
 302     int ret = 0;
 303     const EC_GROUP *group = EC_KEY_get0_group(key);
 304     const BIGNUM *order = EC_GROUP_get0_order(group);
 305     BN_CTX *ctx = NULL;
 306     EC_POINT *pt = NULL;
 307     BIGNUM *t = NULL;
 308     BIGNUM *x1 = NULL;
 309     const BIGNUM *r = NULL;
 310     const BIGNUM *s = NULL;
 311     OSSL_LIB_CTX *libctx = ossl_ec_key_get_libctx(key);
 312
 313     ctx = BN_CTX_new_ex(libctx);
 314     pt = EC_POINT_new(group);
 315     if (ctx == NULL || pt == NULL) {
 316         ERR_raise(ERR_LIB_SM2, ERR_R_MALLOC_FAILURE);
 317         goto done;
 318     }
 319
 320     BN_CTX_start(ctx);
 321     t = BN_CTX_get(ctx);
 322     x1 = BN_CTX_get(ctx);
 323     if (x1 == NULL) {
 324         ERR_raise(ERR_LIB_SM2, ERR_R_MALLOC_FAILURE);
 325         goto done;
 326     }
 327
 328     /*
 329      * B1: verify whether r' in [1,n-1], verification failed if not
 330      * B2: verify whether s' in [1,n-1], verification failed if not
 331      * B3: set M'~=ZA || M'
 332      * B4: calculate e'=Hv(M'~)
 333      * B5: calculate t = (r' + s') modn, verification failed if t=0
 334      * B6: calculate the point (x1', y1')=[s']G + [t]PA
 335      * B7: calculate R=(e'+x1') modn, verification pass if yes, otherwise failed
 336      */
 337
 338     ECDSA_SIG_get0(sig, &r, &s);
 339
 340     if (BN_cmp(r, BN_value_one()) < 0
 341             || BN_cmp(s, BN_value_one()) < 0
 342             || BN_cmp(order, r) <= 0
 343             || BN_cmp(order, s) <= 0) {
 344         ERR_raise(ERR_LIB_SM2, SM2_R_BAD_SIGNATURE);
 345         goto done;
 346     }
 347
 348     if (!BN_mod_add(t, r, s, order, ctx)) {
 349         ERR_raise(ERR_LIB_SM2, ERR_R_BN_LIB);
 350         goto done;
 351     }
 352
 353     if (BN_is_zero(t)) {
 354         ERR_raise(ERR_LIB_SM2, SM2_R_BAD_SIGNATURE);
 355         goto done;
 356     }
 357
 358     if (!EC_POINT_mul(group, pt, s, EC_KEY_get0_public_key(key), t, ctx)
 359             || !EC_POINT_get_affine_coordinates(group, pt, x1, NULL, ctx)) {
 360         ERR_raise(ERR_LIB_SM2, ERR_R_EC_LIB);
 361         goto done;
 362     }
 363
 364     if (!BN_mod_add(t, e, x1, order, ctx)) {
 365         ERR_raise(ERR_LIB_SM2, ERR_R_BN_LIB);
 366         goto done;
 367     }
 368
 369     if (BN_cmp(r, t) == 0)
 370         ret = 1;
 371
 372  done:
 373     EC_POINT_free(pt);
 374     BN_CTX_free(ctx);
 375     return ret;
 376 }
 377
 378 ECDSA_SIG *ossl_sm2_do_sign(const EC_KEY *key,
 379                             const EVP_MD *digest,
 380                             const uint8_t *id,
 381                             const size_t id_len,
 382                             const uint8_t *msg, size_t msg_len)
 383 {
 384     BIGNUM *e = NULL;
 385     ECDSA_SIG *sig = NULL;
 386
 387     e = sm2_compute_msg_hash(digest, key, id, id_len, msg, msg_len);
 388     if (e == NULL) {
 389         /* SM2err already called */
 390         goto done;
 391     }
 392
 393     sig = sm2_sig_gen(key, e);
 394
 395  done:
 396     BN_free(e);
 397     return sig;
 398 }
 399
 400 int ossl_sm2_do_verify(const EC_KEY *key,
 401                        const EVP_MD *digest,
 402                        const ECDSA_SIG *sig,
 403                        const uint8_t *id,
 404                        const size_t id_len,
 405                        const uint8_t *msg, size_t msg_len)
 406 {
 407     BIGNUM *e = NULL;
 408     int ret = 0;
 409
 410     e = sm2_compute_msg_hash(digest, key, id, id_len, msg, msg_len);
 411     if (e == NULL) {
 412         /* SM2err already called */
 413         goto done;
 414     }
 415
 416     ret = sm2_sig_verify(key, sig, e);
 417
 418  done:
 419     BN_free(e);
 420     return ret;
 421 }
 422
 423 int ossl_sm2_internal_sign(const unsigned char *dgst, int dgstlen,
 424                            unsigned char *sig, unsigned int *siglen,
 425                            EC_KEY *eckey)
 426 {
 427     BIGNUM *e = NULL;
 428     ECDSA_SIG *s = NULL;
 429     int sigleni;
 430     int ret = -1;
 431
 432     e = BN_bin2bn(dgst, dgstlen, NULL);
 433     if (e == NULL) {
 434        ERR_raise(ERR_LIB_SM2, ERR_R_BN_LIB);
 435        goto done;
 436     }
 437
 438     s = sm2_sig_gen(eckey, e);
 439     if (s == NULL) {
 440         ERR_raise(ERR_LIB_SM2, ERR_R_INTERNAL_ERROR);
 441         goto done;
 442     }
 443
 444     sigleni = i2d_ECDSA_SIG(s, &sig);
 445     if (sigleni < 0) {
 446        ERR_raise(ERR_LIB_SM2, ERR_R_INTERNAL_ERROR);
 447        goto done;
 448     }
 449     *siglen = (unsigned int)sigleni;
 450
 451     ret = 1;
 452
 453  done:
 454     ECDSA_SIG_free(s);
 455     BN_free(e);
 456     return ret;
 457 }
 458
 459 int ossl_sm2_internal_verify(const unsigned char *dgst, int dgstlen,
 460                              const unsigned char *sig, int sig_len,
 461                              EC_KEY *eckey)
 462 {
 463     ECDSA_SIG *s = NULL;
 464     BIGNUM *e = NULL;
 465     const unsigned char *p = sig;
 466     unsigned char *der = NULL;
 467     int derlen = -1;
 468     int ret = -1;
 469
 470     s = ECDSA_SIG_new();
 471     if (s == NULL) {
 472         ERR_raise(ERR_LIB_SM2, ERR_R_MALLOC_FAILURE);
 473         goto done;
 474     }
 475     if (d2i_ECDSA_SIG(&s, &p, sig_len) == NULL) {
 476         ERR_raise(ERR_LIB_SM2, SM2_R_INVALID_ENCODING);
 477         goto done;
 478     }
 479     /* Ensure signature uses DER and doesn't have trailing garbage */
 480     derlen = i2d_ECDSA_SIG(s, &der);
 481     if (derlen != sig_len || memcmp(sig, der, derlen) != 0) {
 482         ERR_raise(ERR_LIB_SM2, SM2_R_INVALID_ENCODING);
 483         goto done;
 484     }
 485
 486     e = BN_bin2bn(dgst, dgstlen, NULL);
 487     if (e == NULL) {
 488         ERR_raise(ERR_LIB_SM2, ERR_R_BN_LIB);
 489         goto done;
 490     }
 491
 492     ret = sm2_sig_verify(eckey, s, e);
 493
 494  done:
 495     OPENSSL_free(der);
 496     BN_free(e);
 497     ECDSA_SIG_free(s);
 498     return ret;
 499 }