/*

 * 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;

}