/*

 * Copyright (C) 2014-2017 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 RFC7627 (ext master secret) TLS extension.

 */

#include "gnutls_int.h"

#include "errors.h"

#include "num.h"

#include <hello_ext.h>

#include <ext/ext_master_secret.h>

static int _gnutls_ext_master_secret_recv_params(gnutls_session_t session,

					  const uint8_t * data,

					  size_t data_size);

static int _gnutls_ext_master_secret_send_params(gnutls_session_t session,

					  gnutls_buffer_st * extdata);

const hello_ext_entry_st ext_mod_ext_master_secret = {

	.name = "Extended Master Secret",

	.tls_id = 23,

	.gid = GNUTLS_EXTENSION_EXT_MASTER_SECRET,

	.client_parse_point = GNUTLS_EXT_MANDATORY,

	.server_parse_point = GNUTLS_EXT_MANDATORY,

	.validity = GNUTLS_EXT_FLAG_TLS|GNUTLS_EXT_FLAG_DTLS | GNUTLS_EXT_FLAG_CLIENT_HELLO |

		    GNUTLS_EXT_FLAG_TLS12_SERVER_HELLO,

	.recv_func = _gnutls_ext_master_secret_recv_params,

	.send_func = _gnutls_ext_master_secret_send_params,

	.pack_func = NULL,

	.unpack_func = NULL,

	.deinit_func = NULL,

	.cannot_be_overriden = 1

};

#ifdef ENABLE_SSL3

static inline unsigned have_only_ssl3_enabled(gnutls_session_t session)

{

	if (session->internals.priorities->protocol.num_priorities == 1 &&

	    session->internals.priorities->protocol.priorities[0] == GNUTLS_SSL3)

	    return 1;

	return 0;

}

#endif

/*

 * In case of a server: if an EXT_MASTER_SECRET extension type is received then it

 * sets a flag into the session security parameters.

 *

 */

static int

_gnutls_ext_master_secret_recv_params(gnutls_session_t session,

			       const uint8_t * data, size_t _data_size)

{

	ssize_t data_size = _data_size;

	if ((session->internals.flags & GNUTLS_NO_EXTENSIONS) ||

	    session->internals.priorities->no_extensions ||

	    session->internals.no_ext_master_secret != 0) {

		return 0;

	}

	if (data_size != 0) {

		return gnutls_assert_val(GNUTLS_E_UNEXPECTED_PACKET_LENGTH);

	}

#ifdef ENABLE_SSL3

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

		const version_entry_st *ver = get_version(session);

		if (unlikely(ver == NULL))

			return gnutls_assert_val(GNUTLS_E_INTERNAL_ERROR);

		if (ver->id != GNUTLS_SSL3)

			session->security_parameters.ext_master_secret = 1;

	/* do not enable ext master secret if SSL 3.0 is the only protocol supported by server */

	} else if (!have_only_ssl3_enabled(session))

#endif

		session->security_parameters.ext_master_secret = 1;

	return 0;

}

/* returns data_size or a negative number on failure

 */

static int

_gnutls_ext_master_secret_send_params(gnutls_session_t session,

			       gnutls_buffer_st * extdata)

{

	if ((session->internals.flags & GNUTLS_NO_EXTENSIONS) ||

	    session->internals.priorities->no_extensions != 0 ||

	    session->internals.no_ext_master_secret != 0) {

	    session->security_parameters.ext_master_secret = 0;

	    return 0;

	}

	/* this function sends the client extension data */

#ifdef ENABLE_SSL3

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

		if (have_only_ssl3_enabled(session))

		    return 0; /* this extension isn't available for SSL 3.0 */

		return GNUTLS_E_INT_RET_0;

	} else { /* server side */

		const version_entry_st *ver = get_version(session);

		if (unlikely(ver == NULL))

			return gnutls_assert_val(GNUTLS_E_INTERNAL_ERROR);

		if (ver->id != GNUTLS_SSL3 && session->security_parameters.ext_master_secret != 0)

			return GNUTLS_E_INT_RET_0;

	}

	return 0;

#else

	if (session->security_parameters.entity == GNUTLS_CLIENT ||

	    session->security_parameters.ext_master_secret != 0)

		return GNUTLS_E_INT_RET_0;

	return 0;

#endif

}

/**

 * gnutls_session_ext_master_secret_status:

 * @session: is a #gnutls_session_t type.

 *

 * Get the status of the extended master secret extension negotiation.

 * This is in accordance to RFC7627. That information is also

 * available to the more generic gnutls_session_get_flags().

 *

 * Returns: Non-zero if the negotiation was successful or zero otherwise.

 **/

unsigned gnutls_session_ext_master_secret_status(gnutls_session_t session)

{

	return session->security_parameters.ext_master_secret;

}