crypto/sm2/sm2_crypt.c

   1 /*
   2  * Copyright 2017-2020 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
  70 int ossl_sm2_plaintext_size(const EC_KEY *key, const EVP_MD *digest,
  71                             size_t msg_len, size_t *pt_size)
  72 {
  73     const size_t field_size = ec_field_size(EC_KEY_get0_group(key));
  74     const int md_size = EVP_MD_size(digest);
  75     size_t overhead;
  76
  77     if (md_size < 0) {
  78         ERR_raise(ERR_LIB_SM2, SM2_R_INVALID_DIGEST);
  79         return 0;
  80     }
  81     if (field_size == 0) {
  82         ERR_raise(ERR_LIB_SM2, SM2_R_INVALID_FIELD);
  83         return 0;
  84     }
  85
  86     overhead = 10 + 2 * field_size + (size_t)md_size;
  87     if (msg_len <= overhead) {
  88         ERR_raise(ERR_LIB_SM2, SM2_R_INVALID_ENCODING);
  89         return 0;
  90     }
  91
  92     *pt_size = msg_len - overhead;
  93     return 1;
  94 }
  95
  96 int ossl_sm2_ciphertext_size(const EC_KEY *key, const EVP_MD *digest,
  97                              size_t msg_len, size_t *ct_size)
  98 {
  99     const size_t field_size = ec_field_size(EC_KEY_get0_group(key));
 100     const int md_size = EVP_MD_size(digest);
 101     size_t sz;
 102
 103     if (field_size == 0 || md_size < 0)
 104         return 0;
 105
 106     /* Integer and string are simple type; set constructed = 0, means primitive and definite length encoding. */
 107     sz = 2 * ASN1_object_size(0, field_size + 1, V_ASN1_INTEGER)
 108          + ASN1_object_size(0, md_size, V_ASN1_OCTET_STRING)
 109          + ASN1_object_size(0, msg_len, V_ASN1_OCTET_STRING);
 110     /* Sequence is structured type; set constructed = 1, means constructed and definite length encoding. */
 111     *ct_size = ASN1_object_size(1, sz, V_ASN1_SEQUENCE);
 112
 113     return 1;
 114 }
 115
 116 int ossl_sm2_encrypt(const EC_KEY *key,
 117                      const EVP_MD *digest,
 118                      const uint8_t *msg, size_t msg_len,
 119                      uint8_t *ciphertext_buf, size_t *ciphertext_len)
 120 {
 121     int rc = 0, ciphertext_leni;
 122     size_t i;
 123     BN_CTX *ctx = NULL;
 124     BIGNUM *k = NULL;
 125     BIGNUM *x1 = NULL;
 126     BIGNUM *y1 = NULL;
 127     BIGNUM *x2 = NULL;
 128     BIGNUM *y2 = NULL;
 129     EVP_MD_CTX *hash = EVP_MD_CTX_new();
 130     struct SM2_Ciphertext_st ctext_struct;
 131     const EC_GROUP *group = EC_KEY_get0_group(key);
 132     const BIGNUM *order = EC_GROUP_get0_order(group);
 133     const EC_POINT *P = EC_KEY_get0_public_key(key);
 134     EC_POINT *kG = NULL;
 135     EC_POINT *kP = NULL;
 136     uint8_t *msg_mask = NULL;
 137     uint8_t *x2y2 = NULL;
 138     uint8_t *C3 = NULL;
 139     size_t field_size;
 140     const int C3_size = EVP_MD_size(digest);
 141     EVP_MD *fetched_digest = NULL;
 142     OSSL_LIB_CTX *libctx = ossl_ec_key_get_libctx(key);
 143     const char *propq = ossl_ec_key_get0_propq(key);
 144
 145     /* NULL these before any "goto done" */
 146     ctext_struct.C2 = NULL;
 147     ctext_struct.C3 = NULL;
 148
 149     if (hash == NULL || C3_size <= 0) {
 150         ERR_raise(ERR_LIB_SM2, ERR_R_INTERNAL_ERROR);
 151         goto done;
 152     }
 153
 154     field_size = ec_field_size(group);
 155     if (field_size == 0) {
 156         ERR_raise(ERR_LIB_SM2, ERR_R_INTERNAL_ERROR);
 157         goto done;
 158     }
 159
 160     kG = EC_POINT_new(group);
 161     kP = EC_POINT_new(group);
 162     ctx = BN_CTX_new_ex(libctx);
 163     if (kG == NULL || kP == NULL || ctx == NULL) {
 164         ERR_raise(ERR_LIB_SM2, ERR_R_MALLOC_FAILURE);
 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_zalloc(2 * field_size);
 181     C3 = OPENSSL_zalloc(C3_size);
 182
 183     if (x2y2 == NULL || C3 == NULL) {
 184         ERR_raise(ERR_LIB_SM2, ERR_R_MALLOC_FAILURE);
 185         goto done;
 186     }
 187
 188     memset(ciphertext_buf, 0, *ciphertext_len);
 189
 190     if (!BN_priv_rand_range(k, order)) {
 191         ERR_raise(ERR_LIB_SM2, ERR_R_INTERNAL_ERROR);
 192         goto done;
 193     }
 194
 195     if (!EC_POINT_mul(group, kG, k, NULL, NULL, ctx)
 196             || !EC_POINT_get_affine_coordinates(group, kG, x1, y1, ctx)
 197             || !EC_POINT_mul(group, kP, NULL, P, k, ctx)
 198             || !EC_POINT_get_affine_coordinates(group, kP, x2, y2, ctx)) {
 199         ERR_raise(ERR_LIB_SM2, ERR_R_EC_LIB);
 200         goto done;
 201     }
 202
 203     if (BN_bn2binpad(x2, x2y2, field_size) < 0
 204             || BN_bn2binpad(y2, x2y2 + field_size, field_size) < 0) {
 205         ERR_raise(ERR_LIB_SM2, ERR_R_INTERNAL_ERROR);
 206         goto done;
 207     }
 208
 209     msg_mask = OPENSSL_zalloc(msg_len);
 210     if (msg_mask == NULL) {
 211        ERR_raise(ERR_LIB_SM2, ERR_R_MALLOC_FAILURE);
 212        goto done;
 213    }
 214
 215     /* X9.63 with no salt happens to match the KDF used in SM2 */
 216     if (!ossl_ecdh_kdf_X9_63(msg_mask, msg_len, x2y2, 2 * field_size, NULL, 0,
 217                              digest, libctx, propq)) {
 218         ERR_raise(ERR_LIB_SM2, ERR_R_EVP_LIB);
 219         goto done;
 220     }
 221
 222     for (i = 0; i != msg_len; ++i)
 223         msg_mask[i] ^= msg[i];
 224
 225     fetched_digest = EVP_MD_fetch(libctx, EVP_MD_name(digest), propq);
 226     if (fetched_digest == NULL) {
 227         ERR_raise(ERR_LIB_SM2, ERR_R_INTERNAL_ERROR);
 228         goto done;
 229     }
 230     if (EVP_DigestInit(hash, fetched_digest) == 0
 231             || EVP_DigestUpdate(hash, x2y2, field_size) == 0
 232             || EVP_DigestUpdate(hash, msg, msg_len) == 0
 233             || EVP_DigestUpdate(hash, x2y2 + field_size, field_size) == 0
 234             || EVP_DigestFinal(hash, C3, NULL) == 0) {
 235         ERR_raise(ERR_LIB_SM2, ERR_R_EVP_LIB);
 236         goto done;
 237     }
 238
 239     ctext_struct.C1x = x1;
 240     ctext_struct.C1y = y1;
 241     ctext_struct.C3 = ASN1_OCTET_STRING_new();
 242     ctext_struct.C2 = ASN1_OCTET_STRING_new();
 243
 244     if (ctext_struct.C3 == NULL || ctext_struct.C2 == NULL) {
 245        ERR_raise(ERR_LIB_SM2, ERR_R_MALLOC_FAILURE);
 246        goto done;
 247     }
 248     if (!ASN1_OCTET_STRING_set(ctext_struct.C3, C3, C3_size)
 249             || !ASN1_OCTET_STRING_set(ctext_struct.C2, msg_mask, msg_len)) {
 250         ERR_raise(ERR_LIB_SM2, ERR_R_INTERNAL_ERROR);
 251         goto done;
 252     }
 253
 254     ciphertext_leni = i2d_SM2_Ciphertext(&ctext_struct, &ciphertext_buf);
 255     /* Ensure cast to size_t is safe */
 256     if (ciphertext_leni < 0) {
 257         ERR_raise(ERR_LIB_SM2, ERR_R_INTERNAL_ERROR);
 258         goto done;
 259     }
 260     *ciphertext_len = (size_t)ciphertext_leni;
 261
 262     rc = 1;
 263
 264  done:
 265     EVP_MD_free(fetched_digest);
 266     ASN1_OCTET_STRING_free(ctext_struct.C2);
 267     ASN1_OCTET_STRING_free(ctext_struct.C3);
 268     OPENSSL_free(msg_mask);
 269     OPENSSL_free(x2y2);
 270     OPENSSL_free(C3);
 271     EVP_MD_CTX_free(hash);
 272     BN_CTX_free(ctx);
 273     EC_POINT_free(kG);
 274     EC_POINT_free(kP);
 275     return rc;
 276 }
 277
 278 int ossl_sm2_decrypt(const EC_KEY *key,
 279                      const EVP_MD *digest,
 280                      const uint8_t *ciphertext, size_t ciphertext_len,
 281                      uint8_t *ptext_buf, size_t *ptext_len)
 282 {
 283     int rc = 0;
 284     int i;
 285     BN_CTX *ctx = NULL;
 286     const EC_GROUP *group = EC_KEY_get0_group(key);
 287     EC_POINT *C1 = NULL;
 288     struct SM2_Ciphertext_st *sm2_ctext = NULL;
 289     BIGNUM *x2 = NULL;
 290     BIGNUM *y2 = NULL;
 291     uint8_t *x2y2 = NULL;
 292     uint8_t *computed_C3 = NULL;
 293     const size_t field_size = ec_field_size(group);
 294     const int hash_size = EVP_MD_size(digest);
 295     uint8_t *msg_mask = NULL;
 296     const uint8_t *C2 = NULL;
 297     const uint8_t *C3 = NULL;
 298     int msg_len = 0;
 299     EVP_MD_CTX *hash = NULL;
 300     OSSL_LIB_CTX *libctx = ossl_ec_key_get_libctx(key);
 301     const char *propq = ossl_ec_key_get0_propq(key);
 302
 303     if (field_size == 0 || hash_size <= 0)
 304        goto done;
 305
 306     memset(ptext_buf, 0xFF, *ptext_len);
 307
 308     sm2_ctext = d2i_SM2_Ciphertext(NULL, &ciphertext, ciphertext_len);
 309
 310     if (sm2_ctext == NULL) {
 311         ERR_raise(ERR_LIB_SM2, SM2_R_ASN1_ERROR);
 312         goto done;
 313     }
 314
 315     if (sm2_ctext->C3->length != hash_size) {
 316         ERR_raise(ERR_LIB_SM2, SM2_R_INVALID_ENCODING);
 317         goto done;
 318     }
 319
 320     C2 = sm2_ctext->C2->data;
 321     C3 = sm2_ctext->C3->data;
 322     msg_len = sm2_ctext->C2->length;
 323
 324     ctx = BN_CTX_new_ex(libctx);
 325     if (ctx == NULL) {
 326         ERR_raise(ERR_LIB_SM2, ERR_R_MALLOC_FAILURE);
 327         goto done;
 328     }
 329
 330     BN_CTX_start(ctx);
 331     x2 = BN_CTX_get(ctx);
 332     y2 = BN_CTX_get(ctx);
 333
 334     if (y2 == NULL) {
 335         ERR_raise(ERR_LIB_SM2, ERR_R_BN_LIB);
 336         goto done;
 337     }
 338
 339     msg_mask = OPENSSL_zalloc(msg_len);
 340     x2y2 = OPENSSL_zalloc(2 * field_size);
 341     computed_C3 = OPENSSL_zalloc(hash_size);
 342
 343     if (msg_mask == NULL || x2y2 == NULL || computed_C3 == NULL) {
 344         ERR_raise(ERR_LIB_SM2, ERR_R_MALLOC_FAILURE);
 345         goto done;
 346     }
 347
 348     C1 = EC_POINT_new(group);
 349     if (C1 == NULL) {
 350         ERR_raise(ERR_LIB_SM2, ERR_R_MALLOC_FAILURE);
 351         goto done;
 352     }
 353
 354     if (!EC_POINT_set_affine_coordinates(group, C1, sm2_ctext->C1x,
 355                                          sm2_ctext->C1y, ctx)
 356             || !EC_POINT_mul(group, C1, NULL, C1, EC_KEY_get0_private_key(key),
 357                              ctx)
 358             || !EC_POINT_get_affine_coordinates(group, C1, x2, y2, ctx)) {
 359         ERR_raise(ERR_LIB_SM2, ERR_R_EC_LIB);
 360         goto done;
 361     }
 362
 363     if (BN_bn2binpad(x2, x2y2, field_size) < 0
 364             || BN_bn2binpad(y2, x2y2 + field_size, field_size) < 0
 365             || !ossl_ecdh_kdf_X9_63(msg_mask, msg_len, x2y2, 2 * field_size,
 366                                     NULL, 0, digest, libctx, propq)) {
 367         ERR_raise(ERR_LIB_SM2, ERR_R_INTERNAL_ERROR);
 368         goto done;
 369     }
 370
 371     for (i = 0; i != msg_len; ++i)
 372         ptext_buf[i] = C2[i] ^ msg_mask[i];
 373
 374     hash = EVP_MD_CTX_new();
 375     if (hash == NULL) {
 376         ERR_raise(ERR_LIB_SM2, ERR_R_MALLOC_FAILURE);
 377         goto done;
 378     }
 379
 380     if (!EVP_DigestInit(hash, digest)
 381             || !EVP_DigestUpdate(hash, x2y2, field_size)
 382             || !EVP_DigestUpdate(hash, ptext_buf, msg_len)
 383             || !EVP_DigestUpdate(hash, x2y2 + field_size, field_size)
 384             || !EVP_DigestFinal(hash, computed_C3, NULL)) {
 385         ERR_raise(ERR_LIB_SM2, ERR_R_EVP_LIB);
 386         goto done;
 387     }
 388
 389     if (CRYPTO_memcmp(computed_C3, C3, hash_size) != 0) {
 390         ERR_raise(ERR_LIB_SM2, SM2_R_INVALID_DIGEST);
 391         goto done;
 392     }
 393
 394     rc = 1;
 395     *ptext_len = msg_len;
 396
 397  done:
 398     if (rc == 0)
 399         memset(ptext_buf, 0, *ptext_len);
 400
 401     OPENSSL_free(msg_mask);
 402     OPENSSL_free(x2y2);
 403     OPENSSL_free(computed_C3);
 404     EC_POINT_free(C1);
 405     BN_CTX_free(ctx);
 406     SM2_Ciphertext_free(sm2_ctext);
 407     EVP_MD_CTX_free(hash);
 408
 409     return rc;
 410 }