/src/openssl/crypto/sm2/sm2_crypt.c

Source
/*
 * Copyright 2017-2025 The OpenSSL Project Authors. All Rights Reserved.
 * Copyright 2017 Ribose Inc. All Rights Reserved.
 * Ported from Ribose contributions from Botan.
 *
 * Licensed under the Apache License 2.0 (the "License").  You may not use
 * this file except in compliance with the License.  You can obtain a copy
 * in the file LICENSE in the source distribution or at
 * https://www.openssl.org/source/license.html
 */

/*
 * ECDSA low level APIs are deprecated for public use, but still ok for
 * internal use.
 */
#include "internal/deprecated.h"

#include "crypto/sm2.h"
#include "crypto/sm2err.h"
#include "crypto/ec.h" /* ossl_ecdh_kdf_X9_63() */
#include <openssl/err.h>
#include <openssl/evp.h>
#include <openssl/bn.h>
#include <openssl/asn1.h>
#include <openssl/asn1t.h>
#include <string.h>

#include <crypto/asn1.h>

typedef struct SM2_Ciphertext_st SM2_Ciphertext;
DECLARE_ASN1_FUNCTIONS(SM2_Ciphertext)

struct SM2_Ciphertext_st {
    BIGNUM *C1x;
    BIGNUM *C1y;
    ASN1_OCTET_STRING *C3;
    ASN1_OCTET_STRING *C2;
};

ASN1_SEQUENCE(SM2_Ciphertext) = {
    ASN1_SIMPLE(SM2_Ciphertext, C1x, BIGNUM),
    ASN1_SIMPLE(SM2_Ciphertext, C1y, BIGNUM),
    ASN1_SIMPLE(SM2_Ciphertext, C3, ASN1_OCTET_STRING),
    ASN1_SIMPLE(SM2_Ciphertext, C2, ASN1_OCTET_STRING),
} ASN1_SEQUENCE_END(SM2_Ciphertext)

IMPLEMENT_ASN1_FUNCTIONS(SM2_Ciphertext)

static int ec_field_size(const EC_GROUP *group)
{
    const BIGNUM *p = EC_GROUP_get0_field(group);

    if (p == NULL)
        return 0;

    return BN_num_bytes(p);
}

static int is_all_zeros(const unsigned char *msg, size_t msglen)
{
    unsigned char re = 0;
    size_t i;

    for (i = 0; i < msglen; i++) {
        re |= msg[i];
    }

    return re == 0 ? 1 : 0;
}

int ossl_sm2_plaintext_size(const unsigned char *ct, size_t ct_size,
    size_t *pt_size)
{
    struct SM2_Ciphertext_st *sm2_ctext = NULL;

    sm2_ctext = d2i_SM2_Ciphertext(NULL, &ct, (long)ct_size);

    if (sm2_ctext == NULL) {
        ERR_raise(ERR_LIB_SM2, SM2_R_INVALID_ENCODING);
        return 0;
    }

    *pt_size = sm2_ctext->C2->length;
    SM2_Ciphertext_free(sm2_ctext);

    return 1;
}

int ossl_sm2_ciphertext_size(const EC_KEY *key, const EVP_MD *digest,
    size_t msg_len, size_t *ct_size)
{
    const int field_size = ec_field_size(EC_KEY_get0_group(key));
    const int md_size = EVP_MD_get_size(digest);
    int sz;

    if (field_size == 0 || md_size <= 0 || msg_len > INT_MAX / 2)
        return 0;

    /* Integer and string are simple type; set constructed = 0, means primitive and definite length encoding. */
    sz = 2 * ASN1_object_size(0, field_size + 1, V_ASN1_INTEGER)
        + ASN1_object_size(0, md_size, V_ASN1_OCTET_STRING)
        + ASN1_object_size(0, (int)msg_len, V_ASN1_OCTET_STRING);
    /* Sequence is structured type; set constructed = 1, means constructed and definite length encoding. */
    *ct_size = (size_t)ASN1_object_size(1, sz, V_ASN1_SEQUENCE);

    return 1;
}

int 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)
{
    int rc = 0, ciphertext_leni;
    size_t i;
    BN_CTX *ctx = NULL;
    BIGNUM *k = NULL;
    BIGNUM *x1 = NULL;
    BIGNUM *y1 = NULL;
    BIGNUM *x2 = NULL;
    BIGNUM *y2 = NULL;
    EVP_MD_CTX *hash = EVP_MD_CTX_new();
    struct SM2_Ciphertext_st ctext_struct;
    const EC_GROUP *group = EC_KEY_get0_group(key);
    const BIGNUM *order = EC_GROUP_get0_order(group);
    const EC_POINT *P = EC_KEY_get0_public_key(key);
    EC_POINT *kG = NULL;
    EC_POINT *kP = NULL;
    uint8_t *msg_mask = NULL;
    uint8_t *x2y2 = NULL;
    uint8_t *C3 = NULL;
    int field_size;
    const int C3_size = EVP_MD_get_size(digest);
    EVP_MD *fetched_digest = NULL;
    OSSL_LIB_CTX *libctx = ossl_ec_key_get_libctx(key);
    const char *propq = ossl_ec_key_get0_propq(key);

    /* NULL these before any "goto done" */
    ctext_struct.C2 = NULL;
    ctext_struct.C3 = NULL;

    if (msg_len > INT_MAX / 2) {
        ERR_raise(ERR_LIB_SM2, ERR_R_PASSED_INVALID_ARGUMENT);
        goto done;
    }

    if (hash == NULL || C3_size <= 0) {
        ERR_raise(ERR_LIB_SM2, ERR_R_INTERNAL_ERROR);
        goto done;
    }

    field_size = ec_field_size(group);
    if (field_size == 0) {
        ERR_raise(ERR_LIB_SM2, ERR_R_INTERNAL_ERROR);
        goto done;
    }

    kG = EC_POINT_new(group);
    kP = EC_POINT_new(group);
    if (kG == NULL || kP == NULL) {
        ERR_raise(ERR_LIB_SM2, ERR_R_EC_LIB);
        goto done;
    }
    ctx = BN_CTX_new_ex(libctx);
    if (ctx == NULL) {
        ERR_raise(ERR_LIB_SM2, ERR_R_BN_LIB);
        goto done;
    }

    BN_CTX_start(ctx);
    k = BN_CTX_get(ctx);
    x1 = BN_CTX_get(ctx);
    x2 = BN_CTX_get(ctx);
    y1 = BN_CTX_get(ctx);
    y2 = BN_CTX_get(ctx);

    if (y2 == NULL) {
        ERR_raise(ERR_LIB_SM2, ERR_R_BN_LIB);
        goto done;
    }

    x2y2 = OPENSSL_calloc(2, field_size);
    C3 = OPENSSL_zalloc(C3_size);

    if (x2y2 == NULL || C3 == NULL)
        goto done;

    memset(ciphertext_buf, 0, *ciphertext_len);

    msg_mask = OPENSSL_zalloc(msg_len);
    if (msg_mask == NULL)
        goto done;

again:
    if (!BN_priv_rand_range_ex(k, order, 0, ctx)) {
        ERR_raise(ERR_LIB_SM2, ERR_R_INTERNAL_ERROR);
        goto done;
    }

    if (!EC_POINT_mul(group, kG, k, NULL, NULL, ctx)
        || !EC_POINT_get_affine_coordinates(group, kG, x1, y1, ctx)
        || !EC_POINT_mul(group, kP, NULL, P, k, ctx)
        || !EC_POINT_get_affine_coordinates(group, kP, x2, y2, ctx)) {
        ERR_raise(ERR_LIB_SM2, ERR_R_EC_LIB);
        goto done;
    }

    if (BN_bn2binpad(x2, x2y2, field_size) < 0
        || BN_bn2binpad(y2, x2y2 + field_size, field_size) < 0) {
        ERR_raise(ERR_LIB_SM2, ERR_R_INTERNAL_ERROR);
        goto done;
    }

    /* X9.63 with no salt happens to match the KDF used in SM2 */
    if (!ossl_ecdh_kdf_X9_63(msg_mask, msg_len, x2y2, 2 * field_size, NULL, 0,
            digest, libctx, propq)) {
        ERR_raise(ERR_LIB_SM2, ERR_R_EVP_LIB);
        goto done;
    }

    if (is_all_zeros(msg_mask, msg_len)) {
        memset(x2y2, 0, 2 * field_size);
        goto again;
    }

    for (i = 0; i != msg_len; ++i)
        msg_mask[i] ^= msg[i];

    fetched_digest = EVP_MD_fetch(libctx, EVP_MD_get0_name(digest), propq);
    if (fetched_digest == NULL) {
        ERR_raise(ERR_LIB_SM2, ERR_R_INTERNAL_ERROR);
        goto done;
    }
    if (EVP_DigestInit(hash, fetched_digest) == 0
        || EVP_DigestUpdate(hash, x2y2, field_size) == 0
        || EVP_DigestUpdate(hash, msg, msg_len) == 0
        || EVP_DigestUpdate(hash, x2y2 + field_size, field_size) == 0
        || EVP_DigestFinal(hash, C3, NULL) == 0) {
        ERR_raise(ERR_LIB_SM2, ERR_R_EVP_LIB);
        goto done;
    }

    ctext_struct.C1x = x1;
    ctext_struct.C1y = y1;
    ctext_struct.C3 = ASN1_OCTET_STRING_new();
    ctext_struct.C2 = ASN1_OCTET_STRING_new();

    if (ctext_struct.C3 == NULL || ctext_struct.C2 == NULL) {
        ERR_raise(ERR_LIB_SM2, ERR_R_ASN1_LIB);
        goto done;
    }
    if (!ASN1_OCTET_STRING_set(ctext_struct.C3, C3, C3_size)
        || !ASN1_OCTET_STRING_set(ctext_struct.C2, msg_mask, (int)msg_len)) {
        ERR_raise(ERR_LIB_SM2, ERR_R_INTERNAL_ERROR);
        goto done;
    }

    ciphertext_leni = i2d_SM2_Ciphertext(&ctext_struct, &ciphertext_buf);
    /* Ensure cast to size_t is safe */
    if (ciphertext_leni < 0) {
        ERR_raise(ERR_LIB_SM2, ERR_R_INTERNAL_ERROR);
        goto done;
    }
    *ciphertext_len = (size_t)ciphertext_leni;

    rc = 1;

done:
    EVP_MD_free(fetched_digest);
    ASN1_OCTET_STRING_free(ctext_struct.C2);
    ASN1_OCTET_STRING_free(ctext_struct.C3);
    OPENSSL_free(msg_mask);
    OPENSSL_free(x2y2);
    OPENSSL_free(C3);
    EVP_MD_CTX_free(hash);
    BN_CTX_free(ctx);
    EC_POINT_free(kG);
    EC_POINT_free(kP);
    return rc;
}

int 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)
{
    int rc = 0;
    int i;
    BN_CTX *ctx = NULL;
    const EC_GROUP *group = EC_KEY_get0_group(key);
    EC_POINT *C1 = NULL;
    struct SM2_Ciphertext_st *sm2_ctext = NULL;
    BIGNUM *x2 = NULL;
    BIGNUM *y2 = NULL;
    uint8_t *x2y2 = NULL;
    uint8_t *computed_C3 = NULL;
    const int field_size = ec_field_size(group);
    const int hash_size = EVP_MD_get_size(digest);
    uint8_t *msg_mask = NULL;
    const uint8_t *C2 = NULL;
    const uint8_t *C3 = NULL;
    int msg_len = 0;
    EVP_MD_CTX *hash = NULL;
    OSSL_LIB_CTX *libctx = ossl_ec_key_get_libctx(key);
    const char *propq = ossl_ec_key_get0_propq(key);

    if (field_size == 0 || hash_size <= 0 || ciphertext_len > LONG_MAX)
        goto done;

    memset(ptext_buf, 0xFF, *ptext_len);

    sm2_ctext = d2i_SM2_Ciphertext(NULL, &ciphertext, (long)ciphertext_len);

    if (sm2_ctext == NULL) {
        ERR_raise(ERR_LIB_SM2, SM2_R_ASN1_ERROR);
        goto done;
    }

    if (sm2_ctext->C3->length != hash_size) {
        ERR_raise(ERR_LIB_SM2, SM2_R_INVALID_ENCODING);
        goto done;
    }

    C2 = sm2_ctext->C2->data;
    C3 = sm2_ctext->C3->data;
    msg_len = sm2_ctext->C2->length;
    if (*ptext_len < (size_t)msg_len) {
        ERR_raise(ERR_LIB_SM2, SM2_R_BUFFER_TOO_SMALL);
        goto done;
    }

    ctx = BN_CTX_new_ex(libctx);
    if (ctx == NULL) {
        ERR_raise(ERR_LIB_SM2, ERR_R_BN_LIB);
        goto done;
    }

    BN_CTX_start(ctx);
    x2 = BN_CTX_get(ctx);
    y2 = BN_CTX_get(ctx);

    if (y2 == NULL) {
        ERR_raise(ERR_LIB_SM2, ERR_R_BN_LIB);
        goto done;
    }

    msg_mask = OPENSSL_zalloc(msg_len);
    x2y2 = OPENSSL_calloc(2, field_size);
    computed_C3 = OPENSSL_zalloc(hash_size);

    if (msg_mask == NULL || x2y2 == NULL || computed_C3 == NULL)
        goto done;

    C1 = EC_POINT_new(group);
    if (C1 == NULL) {
        ERR_raise(ERR_LIB_SM2, ERR_R_EC_LIB);
        goto done;
    }

    if (!EC_POINT_set_affine_coordinates(group, C1, sm2_ctext->C1x,
            sm2_ctext->C1y, ctx)
        || !EC_POINT_mul(group, C1, NULL, C1, EC_KEY_get0_private_key(key),
            ctx)
        || !EC_POINT_get_affine_coordinates(group, C1, x2, y2, ctx)) {
        ERR_raise(ERR_LIB_SM2, ERR_R_EC_LIB);
        goto done;
    }

    if (BN_bn2binpad(x2, x2y2, field_size) < 0
        || BN_bn2binpad(y2, x2y2 + field_size, field_size) < 0
        || !ossl_ecdh_kdf_X9_63(msg_mask, msg_len, x2y2, 2 * field_size,
            NULL, 0, digest, libctx, propq)) {
        ERR_raise(ERR_LIB_SM2, ERR_R_INTERNAL_ERROR);
        goto done;
    }

    if (is_all_zeros(msg_mask, msg_len)) {
        ERR_raise(ERR_LIB_SM2, SM2_R_INVALID_ENCODING);
        goto done;
    }

    for (i = 0; i != msg_len; ++i)
        ptext_buf[i] = C2[i] ^ msg_mask[i];

    hash = EVP_MD_CTX_new();
    if (hash == NULL) {
        ERR_raise(ERR_LIB_SM2, ERR_R_EVP_LIB);
        goto done;
    }

    if (!EVP_DigestInit(hash, digest)
        || !EVP_DigestUpdate(hash, x2y2, field_size)
        || !EVP_DigestUpdate(hash, ptext_buf, msg_len)
        || !EVP_DigestUpdate(hash, x2y2 + field_size, field_size)
        || !EVP_DigestFinal(hash, computed_C3, NULL)) {
        ERR_raise(ERR_LIB_SM2, ERR_R_EVP_LIB);
        goto done;
    }

    if (CRYPTO_memcmp(computed_C3, C3, hash_size) != 0) {
        ERR_raise(ERR_LIB_SM2, SM2_R_INVALID_DIGEST);
        goto done;
    }

    rc = 1;
    *ptext_len = msg_len;

done:
    if (rc == 0)
        memset(ptext_buf, 0, *ptext_len);

    OPENSSL_free(msg_mask);
    OPENSSL_free(x2y2);
    OPENSSL_free(computed_C3);
    EC_POINT_free(C1);
    BN_CTX_free(ctx);
    SM2_Ciphertext_free(sm2_ctext);
    EVP_MD_CTX_free(hash);

    return rc;
}

Coverage Report

Created: 2026-03-09 06:55

Line	Count	Source
1		/*
2		* Copyright 2017-2025 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		#include <crypto/asn1.h>
29
30		typedef struct SM2_Ciphertext_st SM2_Ciphertext;
31		DECLARE_ASN1_FUNCTIONS(SM2_Ciphertext)
32
33		struct SM2_Ciphertext_st {
34		BIGNUM *C1x;
35		BIGNUM *C1y;
36		ASN1_OCTET_STRING *C3;
37		ASN1_OCTET_STRING *C2;
38		};
39
40		ASN1_SEQUENCE(SM2_Ciphertext) = {
41		ASN1_SIMPLE(SM2_Ciphertext, C1x, BIGNUM),
42		ASN1_SIMPLE(SM2_Ciphertext, C1y, BIGNUM),
43		ASN1_SIMPLE(SM2_Ciphertext, C3, ASN1_OCTET_STRING),
44		ASN1_SIMPLE(SM2_Ciphertext, C2, ASN1_OCTET_STRING),
45	0	} ASN1_SEQUENCE_END(SM2_Ciphertext)
46	0
47	0	IMPLEMENT_ASN1_FUNCTIONS(SM2_Ciphertext)
48	0
49	0	static int ec_field_size(const EC_GROUP *group)
50	0	{
51	0	const BIGNUM *p = EC_GROUP_get0_field(group);
52
53	0	if (p == NULL)
54	0	return 0;
55
56	0	return BN_num_bytes(p);
57	0	}
58
59		static int is_all_zeros(const unsigned char *msg, size_t msglen)
60	0	{
61	0	unsigned char re = 0;
62	0	size_t i;
63
64	0	for (i = 0; i < msglen; i++) {
65	0	re \|= msg[i];
66	0	}
67
68	0	return re == 0 ? 1 : 0;
69	0	}
70
71		int ossl_sm2_plaintext_size(const unsigned char *ct, size_t ct_size,
72		size_t *pt_size)
73	0	{
74	0	struct SM2_Ciphertext_st *sm2_ctext = NULL;
75
76	0	sm2_ctext = d2i_SM2_Ciphertext(NULL, &ct, (long)ct_size);
77
78	0	if (sm2_ctext == NULL) {
79	0	ERR_raise(ERR_LIB_SM2, SM2_R_INVALID_ENCODING);
80	0	return 0;
81	0	}
82
83	0	*pt_size = sm2_ctext->C2->length;
84	0	SM2_Ciphertext_free(sm2_ctext);
85
86	0	return 1;
87	0	}
88
89		int ossl_sm2_ciphertext_size(const EC_KEY key, const EVP_MD digest,
90		size_t msg_len, size_t *ct_size)
91	0	{
92	0	const int field_size = ec_field_size(EC_KEY_get0_group(key));
93	0	const int md_size = EVP_MD_get_size(digest);
94	0	int sz;
95
96	0	if (field_size == 0 \|\| md_size <= 0 \|\| msg_len > INT_MAX / 2)
97	0	return 0;
98
99		/* Integer and string are simple type; set constructed = 0, means primitive and definite length encoding. */
100	0	sz = 2 * ASN1_object_size(0, field_size + 1, V_ASN1_INTEGER)
101	0	+ ASN1_object_size(0, md_size, V_ASN1_OCTET_STRING)
102	0	+ ASN1_object_size(0, (int)msg_len, V_ASN1_OCTET_STRING);
103		/* Sequence is structured type; set constructed = 1, means constructed and definite length encoding. */
104	0	*ct_size = (size_t)ASN1_object_size(1, sz, V_ASN1_SEQUENCE);
105
106	0	return 1;
107	0	}
108
109		int ossl_sm2_encrypt(const EC_KEY *key,
110		const EVP_MD *digest,
111		const uint8_t *msg, size_t msg_len,
112		uint8_t ciphertext_buf, size_t ciphertext_len)
113	0	{
114	0	int rc = 0, ciphertext_leni;
115	0	size_t i;
116	0	BN_CTX *ctx = NULL;
117	0	BIGNUM *k = NULL;
118	0	BIGNUM *x1 = NULL;
119	0	BIGNUM *y1 = NULL;
120	0	BIGNUM *x2 = NULL;
121	0	BIGNUM *y2 = NULL;
122	0	EVP_MD_CTX *hash = EVP_MD_CTX_new();
123	0	struct SM2_Ciphertext_st ctext_struct;
124	0	const EC_GROUP *group = EC_KEY_get0_group(key);
125	0	const BIGNUM *order = EC_GROUP_get0_order(group);
126	0	const EC_POINT *P = EC_KEY_get0_public_key(key);
127	0	EC_POINT *kG = NULL;
128	0	EC_POINT *kP = NULL;
129	0	uint8_t *msg_mask = NULL;
130	0	uint8_t *x2y2 = NULL;
131	0	uint8_t *C3 = NULL;
132	0	int field_size;
133	0	const int C3_size = EVP_MD_get_size(digest);
134	0	EVP_MD *fetched_digest = NULL;
135	0	OSSL_LIB_CTX *libctx = ossl_ec_key_get_libctx(key);
136	0	const char *propq = ossl_ec_key_get0_propq(key);
137
138		/* NULL these before any "goto done" */
139	0	ctext_struct.C2 = NULL;
140	0	ctext_struct.C3 = NULL;
141
142	0	if (msg_len > INT_MAX / 2) {
143	0	ERR_raise(ERR_LIB_SM2, ERR_R_PASSED_INVALID_ARGUMENT);
144	0	goto done;
145	0	}
146
147	0	if (hash == NULL \|\| C3_size <= 0) {
148	0	ERR_raise(ERR_LIB_SM2, ERR_R_INTERNAL_ERROR);
149	0	goto done;
150	0	}
151
152	0	field_size = ec_field_size(group);
153	0	if (field_size == 0) {
154	0	ERR_raise(ERR_LIB_SM2, ERR_R_INTERNAL_ERROR);
155	0	goto done;
156	0	}
157
158	0	kG = EC_POINT_new(group);
159	0	kP = EC_POINT_new(group);
160	0	if (kG == NULL \|\| kP == NULL) {
161	0	ERR_raise(ERR_LIB_SM2, ERR_R_EC_LIB);
162	0	goto done;
163	0	}
164	0	ctx = BN_CTX_new_ex(libctx);
165	0	if (ctx == NULL) {
166	0	ERR_raise(ERR_LIB_SM2, ERR_R_BN_LIB);
167	0	goto done;
168	0	}
169
170	0	BN_CTX_start(ctx);
171	0	k = BN_CTX_get(ctx);
172	0	x1 = BN_CTX_get(ctx);
173	0	x2 = BN_CTX_get(ctx);
174	0	y1 = BN_CTX_get(ctx);
175	0	y2 = BN_CTX_get(ctx);
176
177	0	if (y2 == NULL) {
178	0	ERR_raise(ERR_LIB_SM2, ERR_R_BN_LIB);
179	0	goto done;
180	0	}
181
182	0	x2y2 = OPENSSL_calloc(2, field_size);
183	0	C3 = OPENSSL_zalloc(C3_size);
184
185	0	if (x2y2 == NULL \|\| C3 == NULL)
186	0	goto done;
187
188	0	memset(ciphertext_buf, 0, *ciphertext_len);
189
190	0	msg_mask = OPENSSL_zalloc(msg_len);
191	0	if (msg_mask == NULL)
192	0	goto done;
193
194	0	again:
195	0	if (!BN_priv_rand_range_ex(k, order, 0, ctx)) {
196	0	ERR_raise(ERR_LIB_SM2, ERR_R_INTERNAL_ERROR);
197	0	goto done;
198	0	}
199
200	0	if (!EC_POINT_mul(group, kG, k, NULL, NULL, ctx)
201	0	\|\| !EC_POINT_get_affine_coordinates(group, kG, x1, y1, ctx)
202	0	\|\| !EC_POINT_mul(group, kP, NULL, P, k, ctx)
203	0	\|\| !EC_POINT_get_affine_coordinates(group, kP, x2, y2, ctx)) {
204	0	ERR_raise(ERR_LIB_SM2, ERR_R_EC_LIB);
205	0	goto done;
206	0	}
207
208	0	if (BN_bn2binpad(x2, x2y2, field_size) < 0
209	0	\|\| BN_bn2binpad(y2, x2y2 + field_size, field_size) < 0) {
210	0	ERR_raise(ERR_LIB_SM2, ERR_R_INTERNAL_ERROR);
211	0	goto done;
212	0	}
213
214		/* X9.63 with no salt happens to match the KDF used in SM2 */
215	0	if (!ossl_ecdh_kdf_X9_63(msg_mask, msg_len, x2y2, 2 * field_size, NULL, 0,
216	0	digest, libctx, propq)) {
217	0	ERR_raise(ERR_LIB_SM2, ERR_R_EVP_LIB);
218	0	goto done;
219	0	}
220
221	0	if (is_all_zeros(msg_mask, msg_len)) {
222	0	memset(x2y2, 0, 2 * field_size);
223	0	goto again;
224	0	}
225
226	0	for (i = 0; i != msg_len; ++i)
227	0	msg_mask[i] ^= msg[i];
228
229	0	fetched_digest = EVP_MD_fetch(libctx, EVP_MD_get0_name(digest), propq);
230	0	if (fetched_digest == NULL) {
231	0	ERR_raise(ERR_LIB_SM2, ERR_R_INTERNAL_ERROR);
232	0	goto done;
233	0	}
234	0	if (EVP_DigestInit(hash, fetched_digest) == 0
235	0	\|\| EVP_DigestUpdate(hash, x2y2, field_size) == 0
236	0	\|\| EVP_DigestUpdate(hash, msg, msg_len) == 0
237	0	\|\| EVP_DigestUpdate(hash, x2y2 + field_size, field_size) == 0
238	0	\|\| EVP_DigestFinal(hash, C3, NULL) == 0) {
239	0	ERR_raise(ERR_LIB_SM2, ERR_R_EVP_LIB);
240	0	goto done;
241	0	}
242
243	0	ctext_struct.C1x = x1;
244	0	ctext_struct.C1y = y1;
245	0	ctext_struct.C3 = ASN1_OCTET_STRING_new();
246	0	ctext_struct.C2 = ASN1_OCTET_STRING_new();
247
248	0	if (ctext_struct.C3 == NULL \|\| ctext_struct.C2 == NULL) {
249	0	ERR_raise(ERR_LIB_SM2, ERR_R_ASN1_LIB);
250	0	goto done;
251	0	}
252	0	if (!ASN1_OCTET_STRING_set(ctext_struct.C3, C3, C3_size)
253	0	\|\| !ASN1_OCTET_STRING_set(ctext_struct.C2, msg_mask, (int)msg_len)) {
254	0	ERR_raise(ERR_LIB_SM2, ERR_R_INTERNAL_ERROR);
255	0	goto done;
256	0	}
257
258	0	ciphertext_leni = i2d_SM2_Ciphertext(&ctext_struct, &ciphertext_buf);
259		/* Ensure cast to size_t is safe */
260	0	if (ciphertext_leni < 0) {
261	0	ERR_raise(ERR_LIB_SM2, ERR_R_INTERNAL_ERROR);
262	0	goto done;
263	0	}
264	0	*ciphertext_len = (size_t)ciphertext_leni;
265
266	0	rc = 1;
267
268	0	done:
269	0	EVP_MD_free(fetched_digest);
270	0	ASN1_OCTET_STRING_free(ctext_struct.C2);
271	0	ASN1_OCTET_STRING_free(ctext_struct.C3);
272	0	OPENSSL_free(msg_mask);
273	0	OPENSSL_free(x2y2);
274	0	OPENSSL_free(C3);
275	0	EVP_MD_CTX_free(hash);
276	0	BN_CTX_free(ctx);
277	0	EC_POINT_free(kG);
278	0	EC_POINT_free(kP);
279	0	return rc;
280	0	}
281
282		int ossl_sm2_decrypt(const EC_KEY *key,
283		const EVP_MD *digest,
284		const uint8_t *ciphertext, size_t ciphertext_len,
285		uint8_t ptext_buf, size_t ptext_len)
286	0	{
287	0	int rc = 0;
288	0	int i;
289	0	BN_CTX *ctx = NULL;
290	0	const EC_GROUP *group = EC_KEY_get0_group(key);
291	0	EC_POINT *C1 = NULL;
292	0	struct SM2_Ciphertext_st *sm2_ctext = NULL;
293	0	BIGNUM *x2 = NULL;
294	0	BIGNUM *y2 = NULL;
295	0	uint8_t *x2y2 = NULL;
296	0	uint8_t *computed_C3 = NULL;
297	0	const int field_size = ec_field_size(group);
298	0	const int hash_size = EVP_MD_get_size(digest);
299	0	uint8_t *msg_mask = NULL;
300	0	const uint8_t *C2 = NULL;
301	0	const uint8_t *C3 = NULL;
302	0	int msg_len = 0;
303	0	EVP_MD_CTX *hash = NULL;
304	0	OSSL_LIB_CTX *libctx = ossl_ec_key_get_libctx(key);
305	0	const char *propq = ossl_ec_key_get0_propq(key);
306
307	0	if (field_size == 0 \|\| hash_size <= 0 \|\| ciphertext_len > LONG_MAX)
308	0	goto done;
309
310	0	memset(ptext_buf, 0xFF, *ptext_len);
311
312	0	sm2_ctext = d2i_SM2_Ciphertext(NULL, &ciphertext, (long)ciphertext_len);
313
314	0	if (sm2_ctext == NULL) {
315	0	ERR_raise(ERR_LIB_SM2, SM2_R_ASN1_ERROR);
316	0	goto done;
317	0	}
318
319	0	if (sm2_ctext->C3->length != hash_size) {
320	0	ERR_raise(ERR_LIB_SM2, SM2_R_INVALID_ENCODING);
321	0	goto done;
322	0	}
323
324	0	C2 = sm2_ctext->C2->data;
325	0	C3 = sm2_ctext->C3->data;
326	0	msg_len = sm2_ctext->C2->length;
327	0	if (*ptext_len < (size_t)msg_len) {
328	0	ERR_raise(ERR_LIB_SM2, SM2_R_BUFFER_TOO_SMALL);
329	0	goto done;
330	0	}
331
332	0	ctx = BN_CTX_new_ex(libctx);
333	0	if (ctx == NULL) {
334	0	ERR_raise(ERR_LIB_SM2, ERR_R_BN_LIB);
335	0	goto done;
336	0	}
337
338	0	BN_CTX_start(ctx);
339	0	x2 = BN_CTX_get(ctx);
340	0	y2 = BN_CTX_get(ctx);
341
342	0	if (y2 == NULL) {
343	0	ERR_raise(ERR_LIB_SM2, ERR_R_BN_LIB);
344	0	goto done;
345	0	}
346
347	0	msg_mask = OPENSSL_zalloc(msg_len);
348	0	x2y2 = OPENSSL_calloc(2, field_size);
349	0	computed_C3 = OPENSSL_zalloc(hash_size);
350
351	0	if (msg_mask == NULL \|\| x2y2 == NULL \|\| computed_C3 == NULL)
352	0	goto done;
353
354	0	C1 = EC_POINT_new(group);
355	0	if (C1 == NULL) {
356	0	ERR_raise(ERR_LIB_SM2, ERR_R_EC_LIB);
357	0	goto done;
358	0	}
359
360	0	if (!EC_POINT_set_affine_coordinates(group, C1, sm2_ctext->C1x,
361	0	sm2_ctext->C1y, ctx)
362	0	\|\| !EC_POINT_mul(group, C1, NULL, C1, EC_KEY_get0_private_key(key),
363	0	ctx)
364	0	\|\| !EC_POINT_get_affine_coordinates(group, C1, x2, y2, ctx)) {
365	0	ERR_raise(ERR_LIB_SM2, ERR_R_EC_LIB);
366	0	goto done;
367	0	}
368
369	0	if (BN_bn2binpad(x2, x2y2, field_size) < 0
370	0	\|\| BN_bn2binpad(y2, x2y2 + field_size, field_size) < 0
371	0	\|\| !ossl_ecdh_kdf_X9_63(msg_mask, msg_len, x2y2, 2 * field_size,
372	0	NULL, 0, digest, libctx, propq)) {
373	0	ERR_raise(ERR_LIB_SM2, ERR_R_INTERNAL_ERROR);
374	0	goto done;
375	0	}
376
377	0	if (is_all_zeros(msg_mask, msg_len)) {
378	0	ERR_raise(ERR_LIB_SM2, SM2_R_INVALID_ENCODING);
379	0	goto done;
380	0	}
381
382	0	for (i = 0; i != msg_len; ++i)
383	0	ptext_buf[i] = C2[i] ^ msg_mask[i];
384
385	0	hash = EVP_MD_CTX_new();
386	0	if (hash == NULL) {
387	0	ERR_raise(ERR_LIB_SM2, ERR_R_EVP_LIB);
388	0	goto done;
389	0	}
390
391	0	if (!EVP_DigestInit(hash, digest)
392	0	\|\| !EVP_DigestUpdate(hash, x2y2, field_size)
393	0	\|\| !EVP_DigestUpdate(hash, ptext_buf, msg_len)
394	0	\|\| !EVP_DigestUpdate(hash, x2y2 + field_size, field_size)
395	0	\|\| !EVP_DigestFinal(hash, computed_C3, NULL)) {
396	0	ERR_raise(ERR_LIB_SM2, ERR_R_EVP_LIB);
397	0	goto done;
398	0	}
399
400	0	if (CRYPTO_memcmp(computed_C3, C3, hash_size) != 0) {
401	0	ERR_raise(ERR_LIB_SM2, SM2_R_INVALID_DIGEST);
402	0	goto done;
403	0	}
404
405	0	rc = 1;
406	0	*ptext_len = msg_len;
407
408	0	done:
409	0	if (rc == 0)
410	0	memset(ptext_buf, 0, *ptext_len);
411
412	0	OPENSSL_free(msg_mask);
413	0	OPENSSL_free(x2y2);
414	0	OPENSSL_free(computed_C3);
415	0	EC_POINT_free(C1);
416	0	BN_CTX_free(ctx);
417	0	SM2_Ciphertext_free(sm2_ctext);
418	0	EVP_MD_CTX_free(hash);
419
420	0	return rc;
421	0	}