text: /**
   * \file ssl_ticket.h
   *
   * \brief TLS server ticket callbacks implementation
   */
  /*
   *  Copyright (C) 2006-2015, ARM Limited, All Rights Reserved
   *  SPDX-License-Identifier: GPL-2.0
   *
   *  This program is free software; you can redistribute it and/or modify
   *  it under the terms of the GNU General Public License as published by
   *  the Free Software Foundation; either version 2 of the License, or
   *  (at your option) any later version.
   *
   *  This program 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 General Public License for more details.
   *
   *  You should have received a copy of the GNU General Public License along
   *  with this program; if not, write to the Free Software Foundation, Inc.,
   *  51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
   *
   *  This file is part of mbed TLS (https://tls.mbed.org)
   */
  #ifndef MBEDTLS_SSL_TICKET_H
  #define MBEDTLS_SSL_TICKET_H
  
  #if !defined(MBEDTLS_CONFIG_FILE)
  #include "config.h"
  #else
  #include MBEDTLS_CONFIG_FILE
  #endif
  
  /*
   * This implementation of the session ticket callbacks includes key
   * management, rotating the keys periodically in order to preserve forward
   * secrecy, when MBEDTLS_HAVE_TIME is defined.
   */
  
  #include "ssl.h"
  #include "cipher.h"
  
  #if defined(MBEDTLS_THREADING_C)
  #include "threading.h"
  #endif
  
  #ifdef __cplusplus
  extern "C" {
  #endif
  
  /**
   * \brief   Information for session ticket protection
   */
  typedef struct mbedtls_ssl_ticket_key
  {
      unsigned char name[4];          /*!< random key identifier              */
      uint32_t generation_time;       /*!< key generation timestamp (seconds) */
      mbedtls_cipher_context_t ctx;   /*!< context for auth enc/decryption    */
  }
  mbedtls_ssl_ticket_key;
  
  /**
   * \brief   Context for session ticket handling functions
   */
  typedef struct mbedtls_ssl_ticket_context
  {
      mbedtls_ssl_ticket_key keys[2]; /*!< ticket protection keys             */
      unsigned char active;           /*!< index of the currently active key  */
  
      uint32_t ticket_lifetime;       /*!< lifetime of tickets in seconds     */
  
      /** Callback for getting (pseudo-)random numbers                        */
      int  (*f_rng)(void *, unsigned char *, size_t);
      void *p_rng;                    /*!< context for the RNG function       */
  
  #if defined(MBEDTLS_THREADING_C)
      mbedtls_threading_mutex_t mutex;
  #endif
  }
  mbedtls_ssl_ticket_context;
  
  /**
   * \brief           Initialize a ticket context.
   *                  (Just make it ready for mbedtls_ssl_ticket_setup()
   *                  or mbedtls_ssl_ticket_free().)
   *
   * \param ctx       Context to be initialized
   */
  void mbedtls_ssl_ticket_init( mbedtls_ssl_ticket_context *ctx );
  
  /**
   * \brief           Prepare context to be actually used
   *
   * \param ctx       Context to be set up
   * \param f_rng     RNG callback function
   * \param p_rng     RNG callback context
   * \param cipher    AEAD cipher to use for ticket protection.
   *                  Recommended value: MBEDTLS_CIPHER_AES_256_GCM.
   * \param lifetime  Tickets lifetime in seconds
   *                  Recommended value: 86400 (one day).
   *
   * \note            It is highly recommended to select a cipher that is at
   *                  least as strong as the the strongest ciphersuite
   *                  supported. Usually that means a 256-bit key.
   *
   * \note            The lifetime of the keys is twice the lifetime of tickets.
   *                  It is recommended to pick a reasonnable lifetime so as not
   *                  to negate the benefits of forward secrecy.
   *
   * \return          0 if successful,
   *                  or a specific MBEDTLS_ERR_XXX error code
   */
  int mbedtls_ssl_ticket_setup( mbedtls_ssl_ticket_context *ctx,
      int (*f_rng)(void *, unsigned char *, size_t), void *p_rng,
      mbedtls_cipher_type_t cipher,
      uint32_t lifetime );
  
  /**
   * \brief           Implementation of the ticket write callback
   *
   * \note            See \c mbedtls_ssl_ticket_write_t for description
   */
  mbedtls_ssl_ticket_write_t mbedtls_ssl_ticket_write;
  
  /**
   * \brief           Implementation of the ticket parse callback
   *
   * \note            See \c mbedtls_ssl_ticket_parse_t for description
   */
  mbedtls_ssl_ticket_parse_t mbedtls_ssl_ticket_parse;
  
  /**
   * \brief           Free a context's content and zeroize it.
   *
   * \param ctx       Context to be cleaned up
   */
  void mbedtls_ssl_ticket_free( mbedtls_ssl_ticket_context *ctx );
  
  #ifdef __cplusplus
  }
  #endif
  
  #endif /* ssl_ticket.h */
  