/*

 * Copyright (C) 2014 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 Max Record Size TLS extension.

 */

#include "gnutls_int.h"

#include "errors.h"

#include "num.h"

#include <hello_ext.h>

#include <ext/etm.h>

static int _gnutls_ext_etm_recv_params(gnutls_session_t session,

					  const uint8_t * data,

					  size_t data_size);

static int _gnutls_ext_etm_send_params(gnutls_session_t session,

					  gnutls_buffer_st * extdata);

const hello_ext_entry_st ext_mod_etm = {

	.name = "Encrypt-then-MAC",

	.tls_id = 22,

	.gid = GNUTLS_EXTENSION_ETM,

	.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_etm_recv_params,

	.send_func = _gnutls_ext_etm_send_params,

	.pack_func = NULL,

	.unpack_func = NULL,

	.deinit_func = NULL,

	.cannot_be_overriden = 1

};

/* 

 * 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_etm_recv_params(gnutls_session_t session,

			       const uint8_t * data, size_t _data_size)

{

	ssize_t data_size = _data_size;

	if (data_size != 0) {

		return gnutls_assert_val(GNUTLS_E_RECEIVED_ILLEGAL_PARAMETER);

	}

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

		gnutls_ext_priv_data_t epriv;

		if (session->internals.no_etm != 0)

			return 0;

		epriv = (void*)(intptr_t)1;

		_gnutls_hello_ext_set_priv(session,

						   GNUTLS_EXTENSION_ETM,

						   epriv);

		/* don't decide now, decide on send */

		return 0;

	} else { /* client */

		const gnutls_cipher_suite_entry_st *e = 

			session->security_parameters.cs;

		if (e != NULL) {

			const cipher_entry_st *c;

			c = cipher_to_entry(e->block_algorithm);

			if (c == NULL || (c->type == CIPHER_AEAD || c->type == CIPHER_STREAM))

				return 0;

			session->security_parameters.etm = 1;

		}

	}

	return 0;

}

/* returns data_size or a negative number on failure

 */

static int

_gnutls_ext_etm_send_params(gnutls_session_t session,

			       gnutls_buffer_st * extdata)

{

	if (session->internals.no_etm != 0)

		return 0;

	/* this function sends the client extension data */

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

		if (session->internals.priorities->have_cbc != 0)

			return GNUTLS_E_INT_RET_0;

		else

			return 0;

	} else { /* server side */

		const gnutls_cipher_suite_entry_st *e;

		const cipher_entry_st *c;

		int ret;

		gnutls_ext_priv_data_t epriv;

		e = session->security_parameters.cs;

		if (e != NULL) {

			c = cipher_to_entry(e->block_algorithm);

			if (c == NULL || (c->type == CIPHER_AEAD || c->type == CIPHER_STREAM))

				return 0;

			ret = _gnutls_hello_ext_get_priv(session,

							   GNUTLS_EXTENSION_ETM,

							   &epriv);

			if (ret < 0 || ((intptr_t)epriv) == 0)

				return 0;

			session->security_parameters.etm = 1;

			return GNUTLS_E_INT_RET_0;

		}

	}

	return 0;

}

/**

 * gnutls_session_etm_status:

 * @session: is a #gnutls_session_t type.

 *

 * Get the status of the encrypt-then-mac extension negotiation.

 * This is in accordance to rfc7366

 *

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

 **/

unsigned gnutls_session_etm_status(gnutls_session_t session)

{

	return session->security_parameters.etm;

}