/* $OpenBSD: gostr341001.c,v 1.12 2023/07/05 11:37:45 tb Exp $ */
/*
 * Copyright (c) 2014 Dmitry Eremin-Solenikov <dbaryshkov@gmail.com>
 * Copyright (c) 2005-2006 Cryptocom LTD
 *
 * 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 OpenSSL Project
 *    for use in the OpenSSL Toolkit. (http://www.openssl.org/)"
 *
 * 4. The names "OpenSSL Toolkit" and "OpenSSL Project" must not be used to
 *    endorse or promote products derived from this software without
 *    prior written permission. For written permission, please contact
 *    openssl-core@openssl.org.
 *
 * 5. Products derived from this software may not be called "OpenSSL"
 *    nor may "OpenSSL" appear in their names without prior written
 *    permission of the OpenSSL Project.
 *
 * 6. Redistributions of any form whatsoever must retain the following
 *    acknowledgment:
 *    "This product includes software developed by the OpenSSL Project
 *    for use in the OpenSSL Toolkit (http://www.openssl.org/)"
 *
 * THIS SOFTWARE IS PROVIDED BY THE OpenSSL 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 OpenSSL 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 <string.h>

#include <openssl/opensslconf.h>

#ifndef OPENSSL_NO_GOST
#include <openssl/bn.h>
#include <openssl/err.h>
#include <openssl/gost.h>

#include "bn_local.h"
#include "ecdsa_local.h"
#include "gost_local.h"

/* Convert little-endian byte array into bignum */
BIGNUM *
GOST_le2bn(const unsigned char *buf, size_t len, BIGNUM *bn)
{
	unsigned char temp[64];
	int i;

	if (len > 64)
		return NULL;

	for (i = 0; i < len; i++) {
		temp[len - 1 - i] = buf[i];
	}

	return BN_bin2bn(temp, len, bn);
}

int
GOST_bn2le(BIGNUM *bn, unsigned char *buf, int len)
{
	unsigned char temp[64];
	int i, bytes;

	bytes = BN_num_bytes(bn);
	if (len > 64 || bytes > len)
		return 0;

	BN_bn2bin(bn, temp);

	for (i = 0; i < bytes; i++) {
		buf[bytes - 1 - i] = temp[i];
	}

	memset(buf + bytes, 0, len - bytes);

	return 1;
}

int
gost2001_compute_public(GOST_KEY *ec)
{
	const EC_GROUP *group = GOST_KEY_get0_group(ec);
	EC_POINT *pub_key = NULL;
	const BIGNUM *priv_key = NULL;
	BN_CTX *ctx = NULL;
	int ok = 0;

	if (group == NULL) {
		GOSTerror(GOST_R_KEY_IS_NOT_INITIALIZED);
		return 0;
	}
	ctx = BN_CTX_new();
	if (ctx == NULL) {
		GOSTerror(ERR_R_MALLOC_FAILURE);
		return 0;
	}
	BN_CTX_start(ctx);
	if ((priv_key = GOST_KEY_get0_private_key(ec)) == NULL)
		goto err;

	pub_key = EC_POINT_new(group);
	if (pub_key == NULL)
		goto err;
	if (EC_POINT_mul(group, pub_key, priv_key, NULL, NULL, ctx) == 0)
		goto err;
	if (GOST_KEY_set_public_key(ec, pub_key) == 0)
		goto err;
	ok = 1;

	if (ok == 0) {
err:
		GOSTerror(ERR_R_EC_LIB);
	}
	EC_POINT_free(pub_key);
	if (ctx != NULL) {
		BN_CTX_end(ctx);
		BN_CTX_free(ctx);
	}
	return ok;
}

ECDSA_SIG *
gost2001_do_sign(BIGNUM *md, GOST_KEY *eckey)
{
	ECDSA_SIG *newsig = NULL;
	BIGNUM *order = NULL;
	const EC_GROUP *group;
	const BIGNUM *priv_key;
	BIGNUM *r = NULL, *s = NULL, *X = NULL, *tmp = NULL, *tmp2 = NULL, *k =
	    NULL, *e = NULL;
	EC_POINT *C = NULL;
	BN_CTX *ctx = BN_CTX_new();
	int ok = 0;

	if (ctx == NULL) {
		GOSTerror(ERR_R_MALLOC_FAILURE);
		return NULL;
	}
	BN_CTX_start(ctx);
	newsig = ECDSA_SIG_new();
	if (newsig == NULL) {
		GOSTerror(ERR_R_MALLOC_FAILURE);
		goto err;
	}
	s = newsig->s;
	r = newsig->r;
	group = GOST_KEY_get0_group(eckey);
	if ((order = BN_CTX_get(ctx)) == NULL)
		goto err;
	if (EC_GROUP_get_order(group, order, ctx) == 0)
		goto err;
	priv_key = GOST_KEY_get0_private_key(eckey);
	if ((e = BN_CTX_get(ctx)) == NULL)
		goto err;
	if (BN_mod_ct(e, md, order, ctx) == 0)
		goto err;
	if (BN_is_zero(e)) {
		if (!BN_one(e))
			goto err;
	}
	if ((k = BN_CTX_get(ctx)) == NULL)
		goto err;
	if ((X = BN_CTX_get(ctx)) == NULL)
		goto err;
	if ((C = EC_POINT_new(group)) == NULL)
		goto err;
	do {
		do {
			if (!BN_rand_range(k, order)) {
				GOSTerror(GOST_R_RANDOM_NUMBER_GENERATOR_FAILED);
				goto err;
			}
			/*
			 * We do not want timing information to leak the length
			 * of k, so we compute G*k using an equivalent scalar
			 * of fixed bit-length.
			 */
			if (BN_add(k, k, order) == 0)
				goto err;
			if (BN_num_bits(k) <= BN_num_bits(order))
				if (BN_add(k, k, order) == 0)
					goto err;

			if (EC_POINT_mul(group, C, k, NULL, NULL, ctx) == 0) {
				GOSTerror(ERR_R_EC_LIB);
				goto err;
			}
			if (EC_POINT_get_affine_coordinates(group, C, X,
			    NULL, ctx) == 0) {
				GOSTerror(ERR_R_EC_LIB);
				goto err;
			}
			if (BN_nnmod(r, X, order, ctx) == 0)
				goto err;
		} while (BN_is_zero(r));
		/* s = (r*priv_key+k*e) mod order */
		if (tmp == NULL) {
			if ((tmp = BN_CTX_get(ctx)) == NULL)
				goto err;
		}
		if (BN_mod_mul(tmp, priv_key, r, order, ctx) == 0)
			goto err;
		if (tmp2 == NULL) {
			if ((tmp2 = BN_CTX_get(ctx)) == NULL)
				goto err;
		}
		if (BN_mod_mul(tmp2, k, e, order, ctx) == 0)
			goto err;
		if (BN_mod_add(s, tmp, tmp2, order, ctx) == 0)
			goto err;
	} while (BN_is_zero(s));
	ok = 1;

err:
	EC_POINT_free(C);
	if (ctx != NULL) {
		BN_CTX_end(ctx);
		BN_CTX_free(ctx);
	}
	if (ok == 0) {
		ECDSA_SIG_free(newsig);
		newsig = NULL;
	}
	return newsig;
}

int
gost2001_do_verify(BIGNUM *md, ECDSA_SIG *sig, GOST_KEY *ec)
{
	BN_CTX *ctx = BN_CTX_new();
	const EC_GROUP *group = GOST_KEY_get0_group(ec);
	BIGNUM *order;
	BIGNUM *e = NULL, *R = NULL, *v = NULL, *z1 = NULL, *z2 = NULL;
	BIGNUM *X = NULL, *tmp = NULL;
	EC_POINT *C = NULL;
	const EC_POINT *pub_key = NULL;
	int ok = 0;

	if (ctx == NULL)
		goto err;
	BN_CTX_start(ctx);
	if ((order = BN_CTX_get(ctx)) == NULL)
		goto err;
	if ((e = BN_CTX_get(ctx)) == NULL)
		goto err;
	if ((z1 = BN_CTX_get(ctx)) == NULL)
		goto err;
	if ((z2 = BN_CTX_get(ctx)) == NULL)
		goto err;
	if ((tmp = BN_CTX_get(ctx)) == NULL)
		goto err;
	if ((X = BN_CTX_get(ctx)) == NULL)
		goto err;
	if ((R = BN_CTX_get(ctx)) == NULL)
		goto err;
	if ((v = BN_CTX_get(ctx)) == NULL)
		goto err;

	if (EC_GROUP_get_order(group, order, ctx) == 0)
		goto err;
	pub_key = GOST_KEY_get0_public_key(ec);
	if (BN_is_zero(sig->s) || BN_is_zero(sig->r) ||
	    BN_cmp(sig->s, order) >= 1 || BN_cmp(sig->r, order) >= 1) {
		GOSTerror(GOST_R_SIGNATURE_PARTS_GREATER_THAN_Q);
		goto err;
	}

	if (BN_mod_ct(e, md, order, ctx) == 0)
		goto err;
	if (BN_is_zero(e)) {
		if (!BN_one(e))
			goto err;
	}
	if ((v = BN_mod_inverse_ct(v, e, order, ctx)) == NULL)
		goto err;
	if (BN_mod_mul(z1, sig->s, v, order, ctx) == 0)
		goto err;
	if (BN_sub(tmp, order, sig->r) == 0)
		goto err;
	if (BN_mod_mul(z2, tmp, v, order, ctx) == 0)
		goto err;
	if ((C = EC_POINT_new(group)) == NULL)
		goto err;
	if (EC_POINT_mul(group, C, z1, pub_key, z2, ctx) == 0) {
		GOSTerror(ERR_R_EC_LIB);
		goto err;
	}
	if (EC_POINT_get_affine_coordinates(group, C, X, NULL, ctx) == 0) {
		GOSTerror(ERR_R_EC_LIB);
		goto err;
	}
	if (BN_mod_ct(R, X, order, ctx) == 0)
		goto err;
	if (BN_cmp(R, sig->r) != 0) {
		GOSTerror(GOST_R_SIGNATURE_MISMATCH);
	} else {
		ok = 1;
	}
err:
	EC_POINT_free(C);
	if (ctx != NULL) {
		BN_CTX_end(ctx);
		BN_CTX_free(ctx);
	}
	return ok;
}

/* Implementation of CryptoPro VKO 34.10-2001 algorithm */
int
VKO_compute_key(BIGNUM *X, BIGNUM *Y, const GOST_KEY *pkey, GOST_KEY *priv_key,
    const BIGNUM *ukm)
{
	BIGNUM *p = NULL, *order = NULL;
	const BIGNUM *key = GOST_KEY_get0_private_key(priv_key);
	const EC_GROUP *group = GOST_KEY_get0_group(priv_key);
	const EC_POINT *pub_key = GOST_KEY_get0_public_key(pkey);
	EC_POINT *pnt;
	BN_CTX *ctx = NULL;
	int ok = 0;

	pnt = EC_POINT_new(group);
	if (pnt == NULL)
		goto err;
	ctx = BN_CTX_new();
	if (ctx == NULL)
		goto err;
	BN_CTX_start(ctx);
	if ((p = BN_CTX_get(ctx)) == NULL)
		goto err;
	if ((order = BN_CTX_get(ctx)) == NULL)
		goto err;
	if (EC_GROUP_get_order(group, order, ctx) == 0)
		goto err;
	if (BN_mod_mul(p, key, ukm, order, ctx) == 0)
		goto err;
	if (EC_POINT_mul(group, pnt, NULL, pub_key, p, ctx) == 0)
		goto err;
	if (EC_POINT_get_affine_coordinates(group, pnt, X, Y, ctx) == 0)
		goto err;
	ok = 1;

err:
	if (ctx != NULL) {
		BN_CTX_end(ctx);
		BN_CTX_free(ctx);
	}
	EC_POINT_free(pnt);
	return ok;
}

int
gost2001_keygen(GOST_KEY *ec)
{
	BIGNUM *order = BN_new(), *d = BN_new();
	const EC_GROUP *group = GOST_KEY_get0_group(ec);
	int rc = 0;

	if (order == NULL || d == NULL)
		goto err;
	if (EC_GROUP_get_order(group, order, NULL) == 0)
		goto err;

	do {
		if (BN_rand_range(d, order) == 0) {
			GOSTerror(GOST_R_RANDOM_NUMBER_GENERATOR_FAILED);
			goto err;
		}
	} while (BN_is_zero(d));

	if (GOST_KEY_set_private_key(ec, d) == 0)
		goto err;
	rc = gost2001_compute_public(ec);

err:
	BN_free(d);
	BN_free(order);
	return rc;
}
#endif
