text: /*
   * Copyright 2014 Amazon.com, Inc. or its affiliates. All Rights Reserved.
   *
   * Licensed under the Apache License, Version 2.0 (the "License").
   * You may not use this file except in compliance with the License.
   * A copy of the License is located at
   *
   *  http://aws.amazon.com/apache2.0
   *
   * or in the "license" file accompanying this file. This file is distributed
   * on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either
   * express or implied. See the License for the specific language governing
   * permissions and limitations under the License.
   */
  
  #include <stdint.h>
  
  #include "error/s2n_errno.h"
  
  #include "tls/s2n_cipher_suites.h"
  #include "tls/s2n_connection.h"
  #include "tls/s2n_tls.h"
  
  #include "stuffer/s2n_stuffer.h"
  
  #include "utils/s2n_safety.h"
  
  /* From RFC5246 7.1: https://tools.ietf.org/html/rfc5246#section-7.1 */
  #define CHANGE_CIPHER_SPEC_TYPE  1
  
  int s2n_basic_ccs_recv(struct s2n_connection *conn)
  {
      uint8_t type;
  
      GUARD(s2n_stuffer_read_uint8(&conn->handshake.io, &type));
      S2N_ERROR_IF(type != CHANGE_CIPHER_SPEC_TYPE, S2N_ERR_BAD_MESSAGE);
  
      return 0;
  }
  
  int s2n_client_ccs_recv(struct s2n_connection *conn)
  {
      GUARD(s2n_basic_ccs_recv(conn));
  
      /* Zero the sequence number */
      struct s2n_blob seq = {.data = conn->secure.client_sequence_number,.size = sizeof(conn->secure.client_sequence_number) };
      GUARD(s2n_blob_zero(&seq));
  
      /* Compute the finished message */
      GUARD(s2n_prf_client_finished(conn));
  
      /* Update the client to use the cipher-suite */
      conn->client = &conn->secure;
  
      /* Flush any partial alert messages that were pending.
       * If we don't do this, an attacker can inject a 1-byte alert message into the handshake
       * and cause later, valid alerts to be processed incorrectly. */
      GUARD(s2n_stuffer_wipe(&conn->alert_in));
  
      return 0;
  }
  
  int s2n_server_ccs_recv(struct s2n_connection *conn)
  {
      GUARD(s2n_basic_ccs_recv(conn));
  
      /* Zero the sequence number */
      struct s2n_blob seq = {.data = conn->secure.server_sequence_number,.size = sizeof(conn->secure.server_sequence_number) };
      GUARD(s2n_blob_zero(&seq));
  
      /* Compute the finished message */
      GUARD(s2n_prf_server_finished(conn));
  
      /* Update the secure state to active, and point the client at the active state */
      conn->server = &conn->secure;
  
      /* Flush any partial alert messages that were pending.
       * If we don't do this, an attacker can inject a 1-byte alert message into the handshake
       * and cause later, valid alerts to be processed incorrectly. */
      GUARD(s2n_stuffer_wipe(&conn->alert_in));
  
      return 0;
  }
  
  int s2n_ccs_send(struct s2n_connection *conn)
  {
      GUARD(s2n_stuffer_write_uint8(&conn->handshake.io, CHANGE_CIPHER_SPEC_TYPE));
  
      return 0;
  }
  