/*
 *  Copyright 2014-2022 The GmSSL Project. All Rights Reserved.
 *
 *  Licensed under the Apache License, Version 2.0 (the License); you may
 *  not use this file except in compliance with the License.
 *
 *  http://www.apache.org/licenses/LICENSE-2.0
 */


#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <stdint.h>
#include <gmssl/mem.h>
#include <gmssl/sm3.h>
#include <gmssl/sm9.h>
#include <gmssl/asn1.h>
#include <gmssl/error.h>


int sm9_kem_encrypt(const SM9_ENC_MASTER_KEY *mpk, const char *id, size_t idlen,
	size_t klen, uint8_t *kbuf, SM9_Z256_POINT *C)
{
	sm9_z256_t r;
	sm9_z256_fp12_t w;
	uint8_t wbuf[32 * 12];
	uint8_t cbuf[65];
	SM3_KDF_CTX kdf_ctx;

	// A1: Q = H1(ID||hid,N) * P1 + Ppube
	sm9_z256_hash1(r, id, idlen, SM9_HID_ENC);
	sm9_z256_point_mul(C, r, sm9_z256_generator());
	sm9_z256_point_add(C, C, &mpk->Ppube);

	do {
		// A2: rand r in [1, N-1]
		if (sm9_z256_rand_range(r, sm9_z256_order()) != 1) {
			error_print();
			return -1;
		}

		// A3: C1 = r * Q
		sm9_z256_point_mul(C, r, C);
		sm9_z256_point_to_uncompressed_octets(C, cbuf);

		// A4: g = e(Ppube, P2)
		sm9_z256_pairing(w, sm9_z256_twist_generator(), &mpk->Ppube);

		// A5: w = g^r
		sm9_z256_fp12_pow(w, w, r);
		sm9_z256_fp12_to_bytes(w, wbuf);

		// A6: K = KDF(C || w || ID_B, klen), if K == 0, goto A2
		sm3_kdf_init(&kdf_ctx, klen);
		sm3_kdf_update(&kdf_ctx, cbuf + 1, 64);
		sm3_kdf_update(&kdf_ctx, wbuf, sizeof(wbuf));
		sm3_kdf_update(&kdf_ctx, (uint8_t *)id, idlen);
		sm3_kdf_finish(&kdf_ctx, kbuf);

	} while (mem_is_zero(kbuf, klen) == 1);

	gmssl_secure_clear(&r, sizeof(r));
	gmssl_secure_clear(&w, sizeof(w));
	gmssl_secure_clear(wbuf, sizeof(wbuf));
	gmssl_secure_clear(&kdf_ctx, sizeof(kdf_ctx));

	// A7: output (K, C)
	return 1;
}

int sm9_kem_decrypt(const SM9_ENC_KEY *key, const char *id, size_t idlen, const SM9_Z256_POINT *C,
	size_t klen, uint8_t *kbuf)
{
	sm9_z256_fp12_t w;
	uint8_t wbuf[32 * 12];
	uint8_t cbuf[65];
	SM3_KDF_CTX kdf_ctx;

	// B1: check C in G1
	sm9_z256_point_to_uncompressed_octets(C, cbuf);

	// B2: w = e(C, de);
	sm9_z256_pairing(w, &key->de, C);
	sm9_z256_fp12_to_bytes(w, wbuf);

	// B3: K = KDF(C || w || ID, klen)
	sm3_kdf_init(&kdf_ctx, klen);
	sm3_kdf_update(&kdf_ctx, cbuf + 1, 64);
	sm3_kdf_update(&kdf_ctx, wbuf, sizeof(wbuf));
	sm3_kdf_update(&kdf_ctx, (uint8_t *)id, idlen);
	sm3_kdf_finish(&kdf_ctx, kbuf);

	if (mem_is_zero(kbuf, klen)) {
		error_print();
		return -1;
	}

	gmssl_secure_clear(&w, sizeof(w));
	gmssl_secure_clear(wbuf, sizeof(wbuf));
	gmssl_secure_clear(&kdf_ctx, sizeof(kdf_ctx));

	// B4: output K
	return 1;
}

int sm9_do_encrypt(const SM9_ENC_MASTER_KEY *mpk, const char *id, size_t idlen,
	const uint8_t *in, size_t inlen,
	SM9_Z256_POINT *C1, uint8_t *c2, uint8_t c3[SM3_HMAC_SIZE])
{
	SM3_HMAC_CTX hmac_ctx;
	uint8_t K[SM9_MAX_PLAINTEXT_SIZE + 32];

	if (sm9_kem_encrypt(mpk, id, idlen, sizeof(K), K, C1) != 1) {
		error_print();
		return -1;
	}
	gmssl_memxor(c2, K, in, inlen);

	//sm3_hmac(K + inlen, 32, c2, inlen, c3);
	sm3_hmac_init(&hmac_ctx, K + inlen, SM3_HMAC_SIZE);
	sm3_hmac_update(&hmac_ctx, c2, inlen);
	sm3_hmac_finish(&hmac_ctx, c3);
	gmssl_secure_clear(&hmac_ctx, sizeof(hmac_ctx));
	return 1;
}

int sm9_do_decrypt(const SM9_ENC_KEY *key, const char *id, size_t idlen,
	const SM9_Z256_POINT *C1, const uint8_t *c2, size_t c2len, const uint8_t c3[SM3_HMAC_SIZE],
	uint8_t *out)
{
	SM3_HMAC_CTX hmac_ctx;
	uint8_t k[SM9_MAX_PLAINTEXT_SIZE + SM3_HMAC_SIZE];
	uint8_t mac[SM3_HMAC_SIZE];

	if (c2len > SM9_MAX_PLAINTEXT_SIZE) {
		error_print();
		return -1;
	}

	if (sm9_kem_decrypt(key, id, idlen, C1, sizeof(k), k) != 1) {
		error_print();
		return -1;
	}
	//sm3_hmac(k + c2len, SM3_HMAC_SIZE, c2, c2len, mac);
	sm3_hmac_init(&hmac_ctx, k + c2len, SM3_HMAC_SIZE);
	sm3_hmac_update(&hmac_ctx, c2, c2len);
	sm3_hmac_finish(&hmac_ctx, mac);
	gmssl_secure_clear(&hmac_ctx, sizeof(hmac_ctx));

	if (gmssl_secure_memcmp(c3, mac, sizeof(mac)) != 0) {
		error_print();
		return -1;
	}
	gmssl_memxor(out, k, c2, c2len);
	return 1;
}

#define SM9_ENC_TYPE_XOR	0
#define SM9_ENC_TYPE_ECB	1
#define SM9_ENC_TYPE_CBC	2
#define SM9_ENC_TYPE_OFB	4
#define SM9_ENC_TYPE_CFB	8

/*
SM9Cipher ::= SEQUENCE {
	EnType		INTEGER, -- 0 for XOR
	C1		BIT STRING, -- uncompressed octets of ECPoint
	C3		OCTET STRING, -- 32 bytes HMAC-SM3 tag
	CipherText	OCTET STRING,
}
*/
int sm9_ciphertext_to_der(const SM9_Z256_POINT *C1, const uint8_t *c2, size_t c2len,
	const uint8_t c3[SM3_HMAC_SIZE], uint8_t **out, size_t *outlen)
{
	int en_type = SM9_ENC_TYPE_XOR;
	uint8_t c1[65];
	size_t len = 0;

	if (sm9_z256_point_to_uncompressed_octets(C1, c1) != 1) {
		error_print();
		return -1;
	}
	if (asn1_int_to_der(en_type, NULL, &len) != 1
		|| asn1_bit_octets_to_der(c1, sizeof(c1), NULL, &len) != 1
		|| asn1_octet_string_to_der(c3, SM3_HMAC_SIZE, NULL, &len) != 1
		|| asn1_octet_string_to_der(c2, c2len, NULL, &len) != 1
		|| asn1_sequence_header_to_der(len, out, outlen) != 1
		|| asn1_int_to_der(en_type, out, outlen) != 1
		|| asn1_bit_octets_to_der(c1, sizeof(c1), out, outlen) != 1
		|| asn1_octet_string_to_der(c3, SM3_HMAC_SIZE, out, outlen) != 1
		|| asn1_octet_string_to_der(c2, c2len, out, outlen) != 1) {
		error_print();
		return -1;
	}
	return 1;
}

int sm9_ciphertext_from_der(SM9_Z256_POINT *C1, const uint8_t **c2, size_t *c2len,
	const uint8_t **c3, const uint8_t **in, size_t *inlen)
{
	int ret;
	const uint8_t *d;
	size_t dlen;
	int en_type;
	const uint8_t *c1;
	size_t c1len;
	size_t c3len;

	if ((ret = asn1_sequence_from_der(&d, &dlen, in, inlen)) != 1) {
		if (ret < 0) error_print();
		return ret;
	}
	if (asn1_int_from_der(&en_type, &d, &dlen) != 1
		|| asn1_bit_octets_from_der(&c1, &c1len, &d, &dlen) != 1
		|| asn1_octet_string_from_der(c3, &c3len, &d, &dlen) != 1
		|| asn1_octet_string_from_der(c2, c2len, &d, &dlen) != 1
		|| asn1_length_is_zero(dlen) != 1) {
		error_print();
		return -1;
	}
	if (en_type != SM9_ENC_TYPE_XOR) {
		error_print();
		return -1;
	}
	if (c1len != 65) {
		error_print();
		return -1;
	}
	if (c3len != SM3_HMAC_SIZE) {
		error_print();
		return -1;
	}
	if (sm9_z256_point_from_uncompressed_octets(C1, c1) != 1) {
		error_print();
		return -1;
	}
	return 1;
}

int sm9_encrypt(const SM9_ENC_MASTER_KEY *mpk, const char *id, size_t idlen,
	const uint8_t *in, size_t inlen, uint8_t *out, size_t *outlen)
{
	SM9_Z256_POINT C1;
	uint8_t c2[SM9_MAX_PLAINTEXT_SIZE];
	uint8_t c3[SM3_HMAC_SIZE];

	if (inlen > SM9_MAX_PLAINTEXT_SIZE) {
		error_print();
		return -1;
	}

	if (sm9_do_encrypt(mpk, id, idlen, in, inlen, &C1, c2, c3) != 1) {
		error_print();
		return -1;
	}
	*outlen = 0;
	if (sm9_ciphertext_to_der(&C1, c2, inlen, c3, &out, outlen) != 1) { // FIXME: when out == NULL	
		error_print();
		return -1;
	}
	return 1;
}

int sm9_decrypt(const SM9_ENC_KEY *key, const char *id, size_t idlen,
	const uint8_t *in, size_t inlen, uint8_t *out, size_t *outlen)
{
	SM9_Z256_POINT C1;
	const uint8_t *c2;
	size_t c2len;
	const uint8_t *c3;

	if (sm9_ciphertext_from_der(&C1, &c2, &c2len, &c3, &in, &inlen) != 1
		|| asn1_length_is_zero(inlen) != 1) {
		error_print();
		return -1;
	}
	*outlen = c2len;
	if (!out) {
		return 1;
	}
	if (sm9_do_decrypt(key, id, idlen, &C1, c2, c2len, c3, out) != 1) {
		error_print();
		return -1;
	}
	return 1;
}