/* ====================================================================
 * Copyright (c) 2015 - 2016 The GmSSL Project.  All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 *
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in
 *    the documentation and/or other materials provided with the
 *    distribution.
 *
 * 3. All advertising materials mentioning features or use of this
 *    software must display the following acknowledgment:
 *    "This product includes software developed by the GmSSL Project.
 *    (http://gmssl.org/)"
 *
 * 4. The name "GmSSL Project" must not be used to endorse or promote
 *    products derived from this software without prior written
 *    permission. For written permission, please contact
 *    guanzhi1980@gmail.com.
 *
 * 5. Products derived from this software may not be called "GmSSL"
 *    nor may "GmSSL" appear in their names without prior written
 *    permission of the GmSSL Project.
 *
 * 6. Redistributions of any form whatsoever must retain the following
 *    acknowledgment:
 *    "This product includes software developed by the GmSSL Project
 *    (http://gmssl.org/)"
 *
 * THIS SOFTWARE IS PROVIDED BY THE GmSSL PROJECT ``AS IS'' AND ANY
 * EXPRESSED OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
 * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE GmSSL PROJECT OR
 * ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
 * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
 * OF THE POSSIBILITY OF SUCH DAMAGE.
 * ====================================================================
 *
 */

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <openssl/err.h>
#include <openssl/crypto.h>
#include <openssl/paillier.h>
#include "pai_lcl.h"

PAILLIER *PAILLIER_new(void)
{
	PAILLIER *ret = NULL;

	if (!(ret = OPENSSL_zalloc(sizeof(*ret)))) {
		PAILLIERerr(PAILLIER_F_PAILLIER_NEW, PAILLIER_R_MALLOC_FAILED);
		return NULL;
	}

	return ret;
}

void PAILLIER_free(PAILLIER *key)
{

	if (key) {
		BN_free(key->n);
		BN_free(key->lambda);
		BN_free(key->n_squared);
		BN_free(key->n_plusone);
		BN_free(key->x);
	}
	OPENSSL_clear_free(key, sizeof(*key));
}

int PAILLIER_generate_key(PAILLIER *key, int bits)
{
	int ret = 0;
	BIGNUM *p = NULL;
	BIGNUM *q = NULL;
	BN_CTX *bn_ctx = NULL;

	p = BN_new();
	q = BN_new();
	bn_ctx = BN_CTX_new();

	if (!key->n) key->n = BN_new();
	if (!key->lambda) key->lambda = BN_new();
	if (!key->n_squared) key->n_squared = BN_new();
	if (!key->n_plusone) key->n_plusone = BN_new();
	if (!key->x) key->x = BN_new();
	if (!p || !q || !bn_ctx || !key->n || !key->lambda ||
		!key->n_squared || !key->n_plusone || !key->x) {
		goto end;
	}

	key->bits = bits;

	do {
		if (!BN_generate_prime_ex(p, bits, 0, NULL, NULL, NULL)) {
			PAILLIERerr(PAILLIER_F_PAILLIER_GENERATE_KEY,
				PAILLIER_R_GENERATE_PRIME_FAILED);
			goto end;
		}

		if (!BN_generate_prime_ex(q, bits, 0, NULL, NULL, NULL)) {
			PAILLIERerr(PAILLIER_F_PAILLIER_GENERATE_KEY,
				PAILLIER_R_GENERATE_PRIME_FAILED);
			goto end;
		}

		if (!BN_mul(key->n, p, q, bn_ctx)) {
			PAILLIERerr(PAILLIER_F_PAILLIER_GENERATE_KEY, ERR_R_BN_LIB);
			goto end;
		}

		if (!BN_sub_word(p, 1)) {
			goto end;
		}
		if (!BN_sub_word(q, 1)) {
			goto end;
		}
		if (!BN_mul(key->lambda, p, q, bn_ctx)) {
			goto end;
		}

		BN_sqr(key->n_squared, key->n, bn_ctx);
		BN_copy(key->n_plusone, key->n);
		BN_add_word(key->n_plusone, 1);

		/*
		BN_mod_exp(key->x, key->n_plusone, key->lambda, key->n_squared, bn_ctx);
		BN_sub_word(key->x, 1);
		BN_div(key->x, key->x, key->n);
		BN_mod_inverse(key->x, key->x, key->n, bn_ctx);
		*/

	} while (0);

	ret = 1;

end:
	BN_clear_free(p);
	BN_clear_free(q);
	return ret;
}

int PAILLIER_check_key(PAILLIER *key)
{
	PAILLIERerr(PAILLIER_F_PAILLIER_CHECK_KEY, PAILLIER_R_NOT_IMPLEMENTED);
	return 0;
}

int PAILLIER_encrypt(BIGNUM *c, const BIGNUM *m, PAILLIER *pub_key)
{
	int ret = 0;
	BIGNUM *r = NULL;
	BN_CTX *bn_ctx = NULL;

	if (BN_cmp(m, pub_key->n) >= 0) {
		PAILLIERerr(PAILLIER_F_PAILLIER_ENCRYPT, PAILLIER_R_INVALID_PLAINTEXT);
		goto end;
	}

	r = BN_new();
	bn_ctx = BN_CTX_new();
	if (!r || !bn_ctx) {
		PAILLIERerr(PAILLIER_F_PAILLIER_ENCRYPT, ERR_R_BN_LIB);
		goto end;
	}

	do {
		if (!BN_rand_range(r, pub_key->n)) {
			PAILLIERerr(PAILLIER_F_PAILLIER_ENCRYPT, ERR_R_BN_LIB);
			goto end;
		}
	} while (BN_is_zero(r));

	if (!pub_key->n_plusone) {
		if (!(pub_key->n_plusone = BN_dup(pub_key->n))) {
			PAILLIERerr(PAILLIER_F_PAILLIER_ENCRYPT, ERR_R_BN_LIB);
			goto end;
		}
		if (!BN_add_word(pub_key->n_plusone, 1)) {
			PAILLIERerr(PAILLIER_F_PAILLIER_ENCRYPT, ERR_R_BN_LIB);
			BN_free(pub_key->n_plusone);
			pub_key->n_plusone = NULL;
			goto end;
		}
	}

	if (!pub_key->n_squared) {
		if (!(pub_key->n_squared = BN_new())) {
			PAILLIERerr(PAILLIER_F_PAILLIER_ENCRYPT, ERR_R_BN_LIB);
			goto end;
		}
		if (!BN_sqr(pub_key->n_squared, pub_key->n, bn_ctx)) {
			PAILLIERerr(PAILLIER_F_PAILLIER_ENCRYPT, ERR_R_BN_LIB);
			BN_free(pub_key->n_squared);
			pub_key->n_squared = NULL;
			goto end;
		}
	}

	if (!BN_mod_exp(c, pub_key->n_plusone, m, pub_key->n_squared, bn_ctx)) {
		PAILLIERerr(PAILLIER_F_PAILLIER_ENCRYPT, ERR_R_BN_LIB);
		goto end;
	}

	if (!BN_mod_exp(r, r, pub_key->n, pub_key->n_squared, bn_ctx)) {
		PAILLIERerr(PAILLIER_F_PAILLIER_ENCRYPT, ERR_R_BN_LIB);
		goto end;
	}

	if (!BN_mod_mul(c, c, r, pub_key->n_squared, bn_ctx)) {
		PAILLIERerr(PAILLIER_F_PAILLIER_ENCRYPT, ERR_R_BN_LIB);
		goto end;
	}

	ret = 1;
end:
	BN_clear_free(r);
	BN_CTX_free(bn_ctx);
	return ret;
}

int PAILLIER_decrypt(BIGNUM *m, const BIGNUM *c, PAILLIER *key)
{
	int ret = 0;
	BN_CTX *bn_ctx = NULL;

	if (!(bn_ctx = BN_CTX_new())) {
		PAILLIERerr(PAILLIER_F_PAILLIER_DECRYPT, ERR_R_BN_LIB);
		goto end;
	}
	if (!BN_mod_exp(m, c, key->lambda, key->n_squared, bn_ctx)) {
		PAILLIERerr(PAILLIER_F_PAILLIER_DECRYPT, ERR_R_BN_LIB);
		goto end;
	}
	if (!BN_sub_word(m, 1)) {
		PAILLIERerr(PAILLIER_F_PAILLIER_DECRYPT, ERR_R_BN_LIB);
		goto end;
	}
	if (!BN_div(m, NULL, m, key->n, bn_ctx)) {
		PAILLIERerr(PAILLIER_F_PAILLIER_DECRYPT, ERR_R_BN_LIB);
		goto end;
	}
	if (!BN_mod_mul(m, m, key->x, key->n, bn_ctx)) {
		PAILLIERerr(PAILLIER_F_PAILLIER_DECRYPT, ERR_R_BN_LIB);
		goto end;
	}
	ret = 1;
end:
	BN_CTX_free(bn_ctx);
	return ret;
}

int PAILLIER_ciphertext_add(BIGNUM *r, const BIGNUM *a, const BIGNUM *b, PAILLIER *key)
{
	int ret = 0;
	BIGNUM *k = NULL;
	BN_CTX *bn_ctx = NULL;

	k = BN_new();
	bn_ctx = BN_CTX_new();
	if (!k || !bn_ctx) {
		PAILLIERerr(PAILLIER_F_PAILLIER_CIPHERTEXT_ADD, ERR_R_BN_LIB);
		goto end;
	}

	do {
		if (!BN_rand_range(k, key->n)) {
			PAILLIERerr(PAILLIER_F_PAILLIER_CIPHERTEXT_ADD, ERR_R_BN_LIB);
			goto end;
		}
	} while (BN_is_zero(k));

	if (!BN_mod_exp(k, k, key->n, key->n_squared, bn_ctx)) {
		PAILLIERerr(PAILLIER_F_PAILLIER_CIPHERTEXT_ADD, ERR_R_BN_LIB);
		goto end;
	}

	if (!BN_mod_mul(r, a, b, key->n_squared, bn_ctx)) {
		PAILLIERerr(PAILLIER_F_PAILLIER_CIPHERTEXT_ADD, ERR_R_BN_LIB);
		goto end;
	}

	if (!BN_mod_mul(r, r, k, key->n_squared, bn_ctx)) {
		PAILLIERerr(PAILLIER_F_PAILLIER_CIPHERTEXT_ADD, ERR_R_BN_LIB);
		goto end;
	}

	ret = 1;
end:
	BN_clear_free(k);
	BN_CTX_free(bn_ctx);
	return ret;
}

int PAILLIER_ciphertext_scalar_mul(BIGNUM *r, const BIGNUM *scalar, const BIGNUM *a, PAILLIER *key)
{
	int ret = 0;
	BIGNUM *k = NULL;
	BN_CTX *bn_ctx = NULL;

	k = BN_new();
	bn_ctx = BN_CTX_new();
	if (!k || !bn_ctx) {
		PAILLIERerr(PAILLIER_F_PAILLIER_CIPHERTEXT_SCALAR_MUL, ERR_R_BN_LIB);
		goto end;
	}

	do {
		if (!BN_rand_range(k, key->n)) {
			PAILLIERerr(PAILLIER_F_PAILLIER_CIPHERTEXT_SCALAR_MUL, ERR_R_BN_LIB);
			goto end;
		}
	} while (BN_is_zero(k));

	if (!BN_mod_exp(k, k, key->n, key->n_squared, bn_ctx)) {
		PAILLIERerr(PAILLIER_F_PAILLIER_CIPHERTEXT_SCALAR_MUL, ERR_R_BN_LIB);
		goto end;
	}

	if (!BN_mod_exp(r, a, scalar, key->n_squared, bn_ctx)) {
		PAILLIERerr(PAILLIER_F_PAILLIER_CIPHERTEXT_SCALAR_MUL, ERR_R_BN_LIB);
		goto end;
	}

	if (!BN_mod_mul(r, r, k, key->n_squared, bn_ctx)) {
		PAILLIERerr(PAILLIER_F_PAILLIER_CIPHERTEXT_SCALAR_MUL, ERR_R_BN_LIB);
		goto end;
	}

	ret = 1;
end:
	BN_clear_free(k);
	BN_CTX_free(bn_ctx);
	return 0;
}

int PAILLIER_up_ref(PAILLIER *r)
{
	int i;

	if (CRYPTO_atomic_add(&r->references, 1, &i, r->lock) <= 0)
		return 0;

	REF_PRINT_COUNT("PAILLIER", r);
	REF_ASSERT_ISNT(i < 2);
	return ((i > 1) ? 1 : 0);
}