/*

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

 * Copyright (C) 2017 Red Hat, 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/>

 *

 */

/* This file contains the code for the Elliptic Curve Point Formats extension.

 */

#include "ext/ec_point_formats.h"

#include "str.h"

#include "state.h"

#include <gnutls/gnutls.h>

static int _gnutls_supported_ec_point_formats_recv_params(

  gnutls_session_t session, const uint8_t *data, size_t data_size);

static int

_gnutls_supported_ec_point_formats_send_params(gnutls_session_t session,

                 gnutls_buffer_st *extdata);

const hello_ext_entry_st ext_mod_supported_ec_point_formats = {

  .name = "Supported EC Point Formats",

  .tls_id = 11,

  .gid = GNUTLS_EXTENSION_SUPPORTED_EC_POINT_FORMATS,

  .client_parse_point = GNUTLS_EXT_TLS,

  .server_parse_point = GNUTLS_EXT_TLS,

  .validity = GNUTLS_EXT_FLAG_TLS | GNUTLS_EXT_FLAG_DTLS |

        GNUTLS_EXT_FLAG_CLIENT_HELLO |

        GNUTLS_EXT_FLAG_TLS12_SERVER_HELLO,

  .recv_func = _gnutls_supported_ec_point_formats_recv_params,

  .send_func = _gnutls_supported_ec_point_formats_send_params,

  .pack_func = NULL,

  .unpack_func = NULL,

  .deinit_func = NULL

};

/* Receive point formats

 */

static int _gnutls_supported_ec_point_formats_recv_params(

  gnutls_session_t session, const uint8_t *data, size_t data_size)

{

  size_t len, i;

  int uncompressed = 0;

  if (session->security_parameters.entity == GNUTLS_CLIENT) {

    if (data_size < 1)

      return gnutls_assert_val(

        GNUTLS_E_RECEIVED_ILLEGAL_EXTENSION);

    len = data[0];

    if (len < 1)

      return gnutls_assert_val(

        GNUTLS_E_RECEIVED_ILLEGAL_EXTENSION);

    DECR_LEN(data_size, len + 1);

    for (i = 1; i <= len; i++)

      if (data[i] == 0) { /* uncompressed */

        uncompressed = 1;

        break;

      }

    if (uncompressed == 0)

      return gnutls_assert_val(GNUTLS_E_UNKNOWN_PK_ALGORITHM);

  } else {

    /* only sanity check here. We only support uncompressed points

     * and a client must support it thus nothing to check.

     */

    if (data_size < 1)

      return gnutls_assert_val(

        GNUTLS_E_RECEIVED_ILLEGAL_EXTENSION);

  }

  return 0;

}

/* returns data_size or a negative number on failure

 */

static int

_gnutls_supported_ec_point_formats_send_params(gnutls_session_t session,

                 gnutls_buffer_st *extdata)

{

  const uint8_t p[2] = {

    0x01, 0x00

  }; /* only support uncompressed point format */

  int ret;

  if (session->security_parameters.entity == GNUTLS_SERVER &&

      !_gnutls_session_is_ecc(session))

    return 0;

  if (session->internals.priorities->groups.size > 0) {

    ret = _gnutls_buffer_append_data(extdata, p, 2);

    if (ret < 0)

      return gnutls_assert_val(ret);

    return 2;

  }

  return 0;

}