/*

 * Copyright (C) 2011-2012 Free Software Foundation, Inc.

 *

 * Author: Nikos Mavrogiannopoulos

 *

 * This file is part of GnuTLS.

 *

 * The GnuTLS is free software; you can redistribute it and/or

 * modify it under the terms of the GNU Lesser General Public License

 * as published by the Free Software Foundation; either version 2.1 of

 * the License, or (at your option) any later version.

 *

 * This library is distributed in the hope that it will be useful, but

 * WITHOUT ANY WARRANTY; without even the implied warranty of

 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU

 * Lesser General Public License for more details.

 *

 * You should have received a copy of the GNU Lesser General Public License

 * along with this program.  If not, see <https://www.gnu.org/licenses/>

 *

 */

/* Helper functions for ECC handling 

 * based on public domain code by Tom St. Dennis.

 */

#include "gnutls_int.h"

#include <mpi.h>

#include <ecc.h>

#include <algorithms.h>

#include "errors.h"

int

_gnutls_ecc_ansi_x962_export(gnutls_ecc_curve_t curve, bigint_t x,

			     bigint_t y, gnutls_datum_t * out)

{

	int numlen = gnutls_ecc_curve_get_size(curve);

	int byte_size, ret;

	size_t size;

	if (numlen == 0)

		return gnutls_assert_val(GNUTLS_E_INVALID_REQUEST);

	out->size = 1 + 2 * numlen;

	out->data = gnutls_malloc(out->size);

	if (out->data == NULL)

		return gnutls_assert_val(GNUTLS_E_MEMORY_ERROR);

	memset(out->data, 0, out->size);

	/* store byte 0x04 */

	out->data[0] = 0x04;

	/* pad and store x */

	byte_size = (_gnutls_mpi_get_nbits(x) + 7) / 8;

	if (numlen < byte_size) {

		ret = gnutls_assert_val(GNUTLS_E_INVALID_REQUEST);

		goto cleanup;

	}

	size = out->size - (1 + (numlen - byte_size));

	ret =

	    _gnutls_mpi_print(x, &out->data[1 + (numlen - byte_size)],

			      &size);

	if (ret < 0) {

		gnutls_assert();

		goto cleanup;

	}

	byte_size = (_gnutls_mpi_get_nbits(y) + 7) / 8;

	if (numlen < byte_size) {

		ret = gnutls_assert_val(GNUTLS_E_INVALID_REQUEST);

		goto cleanup;

	}

	size = out->size - (1 + (numlen + numlen - byte_size));

	ret =

	    _gnutls_mpi_print(y,

			      &out->data[1 + numlen + numlen - byte_size],

			      &size);

	if (ret < 0) {

		gnutls_assert();

		goto cleanup;

	}

	/* pad and store y */

	return 0;

 cleanup:

	_gnutls_free_datum(out);

	return ret;

}

int

_gnutls_ecc_ansi_x962_import(const uint8_t * in,

			     unsigned long inlen, bigint_t * x,

			     bigint_t * y)

{

	int ret;

	/* must be odd */

	if ((inlen & 1) == 0) {

		return GNUTLS_E_INVALID_REQUEST;

	}

	/* check for 4  */

	if (in[0] != 4) {

		return gnutls_assert_val(GNUTLS_E_PARSING_ERROR);

	}

	/* read data */

	ret = _gnutls_mpi_init_scan(x, in + 1, (inlen - 1) >> 1);

	if (ret < 0)

		return gnutls_assert_val(GNUTLS_E_MEMORY_ERROR);

	ret =

	    _gnutls_mpi_init_scan(y, in + 1 + ((inlen - 1) >> 1),

			     (inlen - 1) >> 1);

	if (ret < 0) {

		_gnutls_mpi_release(x);

		return gnutls_assert_val(GNUTLS_E_MEMORY_ERROR);

	}

	return 0;

}