405 lines
12 KiB
C
405 lines
12 KiB
C
/*
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* Copyright 2017-2021 The OpenSSL Project Authors. All Rights Reserved.
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* Copyright 2017 Ribose Inc. All Rights Reserved.
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* Ported from Ribose contributions from Botan.
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*
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* Licensed under the Apache License 2.0 (the "License"). You may not use
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* this file except in compliance with the License. You can obtain a copy
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* in the file LICENSE in the source distribution or at
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* https://www.openssl.org/source/license.html
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*/
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/*
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* ECDSA low level APIs are deprecated for public use, but still ok for
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* internal use.
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*/
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#include "internal/deprecated.h"
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#include "crypto/sm2.h"
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#include "crypto/sm2err.h"
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#include "crypto/ec.h" /* ossl_ecdh_kdf_X9_63() */
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#include <openssl/err.h>
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#include <openssl/evp.h>
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#include <openssl/bn.h>
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#include <openssl/asn1.h>
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#include <openssl/asn1t.h>
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#include <string.h>
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typedef struct SM2_Ciphertext_st SM2_Ciphertext;
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DECLARE_ASN1_FUNCTIONS(SM2_Ciphertext)
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struct SM2_Ciphertext_st {
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BIGNUM *C1x;
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BIGNUM *C1y;
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ASN1_OCTET_STRING *C3;
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ASN1_OCTET_STRING *C2;
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};
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ASN1_SEQUENCE(SM2_Ciphertext) = {
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ASN1_SIMPLE(SM2_Ciphertext, C1x, BIGNUM),
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ASN1_SIMPLE(SM2_Ciphertext, C1y, BIGNUM),
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ASN1_SIMPLE(SM2_Ciphertext, C3, ASN1_OCTET_STRING),
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ASN1_SIMPLE(SM2_Ciphertext, C2, ASN1_OCTET_STRING),
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} ASN1_SEQUENCE_END(SM2_Ciphertext)
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IMPLEMENT_ASN1_FUNCTIONS(SM2_Ciphertext)
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static size_t ec_field_size(const EC_GROUP *group)
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{
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/* Is there some simpler way to do this? */
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BIGNUM *p = BN_new();
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BIGNUM *a = BN_new();
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BIGNUM *b = BN_new();
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size_t field_size = 0;
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if (p == NULL || a == NULL || b == NULL)
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goto done;
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if (!EC_GROUP_get_curve(group, p, a, b, NULL))
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goto done;
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field_size = (BN_num_bits(p) + 7) / 8;
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done:
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BN_free(p);
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BN_free(a);
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BN_free(b);
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return field_size;
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}
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int ossl_sm2_plaintext_size(const unsigned char *ct, size_t ct_size,
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size_t *pt_size)
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{
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struct SM2_Ciphertext_st *sm2_ctext = NULL;
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sm2_ctext = d2i_SM2_Ciphertext(NULL, &ct, ct_size);
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if (sm2_ctext == NULL) {
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ERR_raise(ERR_LIB_SM2, SM2_R_INVALID_ENCODING);
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return 0;
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}
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*pt_size = sm2_ctext->C2->length;
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SM2_Ciphertext_free(sm2_ctext);
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return 1;
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}
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int ossl_sm2_ciphertext_size(const EC_KEY *key, const EVP_MD *digest,
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size_t msg_len, size_t *ct_size)
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{
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const size_t field_size = ec_field_size(EC_KEY_get0_group(key));
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const int md_size = EVP_MD_get_size(digest);
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size_t sz;
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if (field_size == 0 || md_size < 0)
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return 0;
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/* Integer and string are simple type; set constructed = 0, means primitive and definite length encoding. */
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sz = 2 * ASN1_object_size(0, field_size + 1, V_ASN1_INTEGER)
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+ ASN1_object_size(0, md_size, V_ASN1_OCTET_STRING)
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+ ASN1_object_size(0, msg_len, V_ASN1_OCTET_STRING);
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/* Sequence is structured type; set constructed = 1, means constructed and definite length encoding. */
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*ct_size = ASN1_object_size(1, sz, V_ASN1_SEQUENCE);
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return 1;
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}
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int ossl_sm2_encrypt(const EC_KEY *key,
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const EVP_MD *digest,
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const uint8_t *msg, size_t msg_len,
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uint8_t *ciphertext_buf, size_t *ciphertext_len)
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{
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int rc = 0, ciphertext_leni;
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size_t i;
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BN_CTX *ctx = NULL;
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BIGNUM *k = NULL;
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BIGNUM *x1 = NULL;
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BIGNUM *y1 = NULL;
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BIGNUM *x2 = NULL;
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BIGNUM *y2 = NULL;
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EVP_MD_CTX *hash = EVP_MD_CTX_new();
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struct SM2_Ciphertext_st ctext_struct;
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const EC_GROUP *group = EC_KEY_get0_group(key);
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const BIGNUM *order = EC_GROUP_get0_order(group);
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const EC_POINT *P = EC_KEY_get0_public_key(key);
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EC_POINT *kG = NULL;
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EC_POINT *kP = NULL;
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uint8_t *msg_mask = NULL;
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uint8_t *x2y2 = NULL;
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uint8_t *C3 = NULL;
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size_t field_size;
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const int C3_size = EVP_MD_get_size(digest);
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EVP_MD *fetched_digest = NULL;
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OSSL_LIB_CTX *libctx = ossl_ec_key_get_libctx(key);
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const char *propq = ossl_ec_key_get0_propq(key);
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/* NULL these before any "goto done" */
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ctext_struct.C2 = NULL;
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ctext_struct.C3 = NULL;
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if (hash == NULL || C3_size <= 0) {
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ERR_raise(ERR_LIB_SM2, ERR_R_INTERNAL_ERROR);
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goto done;
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}
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field_size = ec_field_size(group);
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if (field_size == 0) {
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ERR_raise(ERR_LIB_SM2, ERR_R_INTERNAL_ERROR);
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goto done;
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}
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kG = EC_POINT_new(group);
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kP = EC_POINT_new(group);
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if (kG == NULL || kP == NULL) {
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ERR_raise(ERR_LIB_SM2, ERR_R_EC_LIB);
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goto done;
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}
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ctx = BN_CTX_new_ex(libctx);
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if (ctx == NULL) {
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ERR_raise(ERR_LIB_SM2, ERR_R_BN_LIB);
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goto done;
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}
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BN_CTX_start(ctx);
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k = BN_CTX_get(ctx);
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x1 = BN_CTX_get(ctx);
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x2 = BN_CTX_get(ctx);
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y1 = BN_CTX_get(ctx);
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y2 = BN_CTX_get(ctx);
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if (y2 == NULL) {
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ERR_raise(ERR_LIB_SM2, ERR_R_BN_LIB);
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goto done;
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}
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x2y2 = OPENSSL_zalloc(2 * field_size);
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C3 = OPENSSL_zalloc(C3_size);
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if (x2y2 == NULL || C3 == NULL)
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goto done;
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memset(ciphertext_buf, 0, *ciphertext_len);
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if (!BN_priv_rand_range_ex(k, order, 0, ctx)) {
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ERR_raise(ERR_LIB_SM2, ERR_R_INTERNAL_ERROR);
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goto done;
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}
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if (!EC_POINT_mul(group, kG, k, NULL, NULL, ctx)
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|| !EC_POINT_get_affine_coordinates(group, kG, x1, y1, ctx)
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|| !EC_POINT_mul(group, kP, NULL, P, k, ctx)
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|| !EC_POINT_get_affine_coordinates(group, kP, x2, y2, ctx)) {
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ERR_raise(ERR_LIB_SM2, ERR_R_EC_LIB);
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goto done;
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}
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if (BN_bn2binpad(x2, x2y2, field_size) < 0
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|| BN_bn2binpad(y2, x2y2 + field_size, field_size) < 0) {
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ERR_raise(ERR_LIB_SM2, ERR_R_INTERNAL_ERROR);
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goto done;
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}
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msg_mask = OPENSSL_zalloc(msg_len);
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if (msg_mask == NULL)
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goto done;
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/* X9.63 with no salt happens to match the KDF used in SM2 */
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if (!ossl_ecdh_kdf_X9_63(msg_mask, msg_len, x2y2, 2 * field_size, NULL, 0,
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digest, libctx, propq)) {
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ERR_raise(ERR_LIB_SM2, ERR_R_EVP_LIB);
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goto done;
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}
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for (i = 0; i != msg_len; ++i)
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msg_mask[i] ^= msg[i];
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fetched_digest = EVP_MD_fetch(libctx, EVP_MD_get0_name(digest), propq);
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if (fetched_digest == NULL) {
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ERR_raise(ERR_LIB_SM2, ERR_R_INTERNAL_ERROR);
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goto done;
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}
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if (EVP_DigestInit(hash, fetched_digest) == 0
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|| EVP_DigestUpdate(hash, x2y2, field_size) == 0
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|| EVP_DigestUpdate(hash, msg, msg_len) == 0
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|| EVP_DigestUpdate(hash, x2y2 + field_size, field_size) == 0
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|| EVP_DigestFinal(hash, C3, NULL) == 0) {
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ERR_raise(ERR_LIB_SM2, ERR_R_EVP_LIB);
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goto done;
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}
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ctext_struct.C1x = x1;
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ctext_struct.C1y = y1;
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ctext_struct.C3 = ASN1_OCTET_STRING_new();
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ctext_struct.C2 = ASN1_OCTET_STRING_new();
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if (ctext_struct.C3 == NULL || ctext_struct.C2 == NULL) {
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ERR_raise(ERR_LIB_SM2, ERR_R_ASN1_LIB);
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goto done;
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}
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if (!ASN1_OCTET_STRING_set(ctext_struct.C3, C3, C3_size)
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|| !ASN1_OCTET_STRING_set(ctext_struct.C2, msg_mask, msg_len)) {
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ERR_raise(ERR_LIB_SM2, ERR_R_INTERNAL_ERROR);
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goto done;
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}
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ciphertext_leni = i2d_SM2_Ciphertext(&ctext_struct, &ciphertext_buf);
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/* Ensure cast to size_t is safe */
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if (ciphertext_leni < 0) {
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ERR_raise(ERR_LIB_SM2, ERR_R_INTERNAL_ERROR);
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goto done;
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}
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*ciphertext_len = (size_t)ciphertext_leni;
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rc = 1;
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done:
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EVP_MD_free(fetched_digest);
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ASN1_OCTET_STRING_free(ctext_struct.C2);
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ASN1_OCTET_STRING_free(ctext_struct.C3);
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OPENSSL_free(msg_mask);
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OPENSSL_free(x2y2);
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OPENSSL_free(C3);
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EVP_MD_CTX_free(hash);
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BN_CTX_free(ctx);
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EC_POINT_free(kG);
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EC_POINT_free(kP);
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return rc;
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}
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int ossl_sm2_decrypt(const EC_KEY *key,
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const EVP_MD *digest,
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const uint8_t *ciphertext, size_t ciphertext_len,
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uint8_t *ptext_buf, size_t *ptext_len)
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{
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int rc = 0;
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int i;
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BN_CTX *ctx = NULL;
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const EC_GROUP *group = EC_KEY_get0_group(key);
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EC_POINT *C1 = NULL;
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struct SM2_Ciphertext_st *sm2_ctext = NULL;
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BIGNUM *x2 = NULL;
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BIGNUM *y2 = NULL;
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uint8_t *x2y2 = NULL;
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uint8_t *computed_C3 = NULL;
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const size_t field_size = ec_field_size(group);
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const int hash_size = EVP_MD_get_size(digest);
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uint8_t *msg_mask = NULL;
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const uint8_t *C2 = NULL;
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const uint8_t *C3 = NULL;
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int msg_len = 0;
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EVP_MD_CTX *hash = NULL;
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OSSL_LIB_CTX *libctx = ossl_ec_key_get_libctx(key);
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const char *propq = ossl_ec_key_get0_propq(key);
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if (field_size == 0 || hash_size <= 0)
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goto done;
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memset(ptext_buf, 0xFF, *ptext_len);
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sm2_ctext = d2i_SM2_Ciphertext(NULL, &ciphertext, ciphertext_len);
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if (sm2_ctext == NULL) {
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ERR_raise(ERR_LIB_SM2, SM2_R_ASN1_ERROR);
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goto done;
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}
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if (sm2_ctext->C3->length != hash_size) {
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ERR_raise(ERR_LIB_SM2, SM2_R_INVALID_ENCODING);
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goto done;
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}
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C2 = sm2_ctext->C2->data;
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C3 = sm2_ctext->C3->data;
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msg_len = sm2_ctext->C2->length;
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if (*ptext_len < (size_t)msg_len) {
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ERR_raise(ERR_LIB_SM2, SM2_R_BUFFER_TOO_SMALL);
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goto done;
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}
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ctx = BN_CTX_new_ex(libctx);
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if (ctx == NULL) {
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ERR_raise(ERR_LIB_SM2, ERR_R_BN_LIB);
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goto done;
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}
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BN_CTX_start(ctx);
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x2 = BN_CTX_get(ctx);
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y2 = BN_CTX_get(ctx);
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if (y2 == NULL) {
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ERR_raise(ERR_LIB_SM2, ERR_R_BN_LIB);
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goto done;
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}
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msg_mask = OPENSSL_zalloc(msg_len);
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x2y2 = OPENSSL_zalloc(2 * field_size);
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computed_C3 = OPENSSL_zalloc(hash_size);
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if (msg_mask == NULL || x2y2 == NULL || computed_C3 == NULL)
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goto done;
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C1 = EC_POINT_new(group);
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if (C1 == NULL) {
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ERR_raise(ERR_LIB_SM2, ERR_R_EC_LIB);
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goto done;
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}
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if (!EC_POINT_set_affine_coordinates(group, C1, sm2_ctext->C1x,
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sm2_ctext->C1y, ctx)
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|| !EC_POINT_mul(group, C1, NULL, C1, EC_KEY_get0_private_key(key),
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ctx)
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|| !EC_POINT_get_affine_coordinates(group, C1, x2, y2, ctx)) {
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ERR_raise(ERR_LIB_SM2, ERR_R_EC_LIB);
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goto done;
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}
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if (BN_bn2binpad(x2, x2y2, field_size) < 0
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|| BN_bn2binpad(y2, x2y2 + field_size, field_size) < 0
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|| !ossl_ecdh_kdf_X9_63(msg_mask, msg_len, x2y2, 2 * field_size,
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NULL, 0, digest, libctx, propq)) {
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ERR_raise(ERR_LIB_SM2, ERR_R_INTERNAL_ERROR);
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goto done;
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}
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for (i = 0; i != msg_len; ++i)
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ptext_buf[i] = C2[i] ^ msg_mask[i];
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hash = EVP_MD_CTX_new();
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if (hash == NULL) {
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ERR_raise(ERR_LIB_SM2, ERR_R_EVP_LIB);
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goto done;
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}
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if (!EVP_DigestInit(hash, digest)
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|| !EVP_DigestUpdate(hash, x2y2, field_size)
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|| !EVP_DigestUpdate(hash, ptext_buf, msg_len)
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|| !EVP_DigestUpdate(hash, x2y2 + field_size, field_size)
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|| !EVP_DigestFinal(hash, computed_C3, NULL)) {
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ERR_raise(ERR_LIB_SM2, ERR_R_EVP_LIB);
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goto done;
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}
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if (CRYPTO_memcmp(computed_C3, C3, hash_size) != 0) {
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ERR_raise(ERR_LIB_SM2, SM2_R_INVALID_DIGEST);
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goto done;
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}
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rc = 1;
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*ptext_len = msg_len;
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done:
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if (rc == 0)
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memset(ptext_buf, 0, *ptext_len);
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OPENSSL_free(msg_mask);
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OPENSSL_free(x2y2);
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OPENSSL_free(computed_C3);
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EC_POINT_free(C1);
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BN_CTX_free(ctx);
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SM2_Ciphertext_free(sm2_ctext);
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EVP_MD_CTX_free(hash);
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return rc;
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}
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