text: /****************************************************************************
   *
   * Copyright 2016 Samsung Electronics 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.
   * You may obtain a copy of the License at
   *
   * http://www.apache.org/licenses/LICENSE-2.0
   *
   * Unless required by applicable law or agreed to in writing,
   * software distributed under the License 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.
   *
   ****************************************************************************/
  /**
   * \file entropy.h
   *
   * \brief Entropy accumulator implementation
   */
  /*
   *  Copyright (C) 2006-2016, ARM Limited, All Rights Reserved
   *  SPDX-License-Identifier: Apache-2.0
   *
   *  Licensed under the Apache License, Version 2.0 (the "License"); you may
   *  not use this file except in compliance with the License.
   *  You may obtain a copy of the License at
   *
   *  http://www.apache.org/licenses/LICENSE-2.0
   *
   *  Unless required by applicable law or agreed to in writing, software
   *  distributed under the License 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.
   *
   *  This file is part of mbed TLS (https://tls.mbed.org)
   */
  #ifndef MBEDTLS_ENTROPY_H
  #define MBEDTLS_ENTROPY_H
  
  #if !defined(MBEDTLS_CONFIG_FILE)
  #include "config.h"
  #else
  #include MBEDTLS_CONFIG_FILE
  #endif
  
  #include <stddef.h>
  
  #if defined(MBEDTLS_SHA512_C) && !defined(MBEDTLS_ENTROPY_FORCE_SHA256)
  #include "sha512.h"
  #define MBEDTLS_ENTROPY_SHA512_ACCUMULATOR
  #else
  #if defined(MBEDTLS_SHA256_C)
  #define MBEDTLS_ENTROPY_SHA256_ACCUMULATOR
  #include "sha256.h"
  #endif
  #endif
  
  #if defined(MBEDTLS_THREADING_C)
  #include "threading.h"
  #endif
  
  #if defined(MBEDTLS_HAVEGE_C)
  #include "havege.h"
  #endif
  
  #define MBEDTLS_ERR_ENTROPY_SOURCE_FAILED                 -0x003C  /**< Critical entropy source failure. */
  #define MBEDTLS_ERR_ENTROPY_MAX_SOURCES                   -0x003E  /**< No more sources can be added. */
  #define MBEDTLS_ERR_ENTROPY_NO_SOURCES_DEFINED            -0x0040  /**< No sources have been added to poll. */
  #define MBEDTLS_ERR_ENTROPY_NO_STRONG_SOURCE              -0x003D  /**< No strong sources have been added to poll. */
  #define MBEDTLS_ERR_ENTROPY_FILE_IO_ERROR                 -0x003F  /**< Read/write error in file. */
  
  /**
   * \name SECTION: Module settings
   *
   * The configuration options you can set for this module are in this section.
   * Either change them in config.h or define them on the compiler command line.
   * \{
   */
  
  #if !defined(MBEDTLS_ENTROPY_MAX_SOURCES)
  #define MBEDTLS_ENTROPY_MAX_SOURCES     20      /**< Maximum number of sources supported */
  #endif
  
  #if !defined(MBEDTLS_ENTROPY_MAX_GATHER)
  #define MBEDTLS_ENTROPY_MAX_GATHER      128     /**< Maximum amount requested from entropy sources */
  #endif
  
  /* \} name SECTION: Module settings */
  
  #if defined(MBEDTLS_ENTROPY_SHA512_ACCUMULATOR)
  #define MBEDTLS_ENTROPY_BLOCK_SIZE      64      /**< Block size of entropy accumulator (SHA-512) */
  #else
  #define MBEDTLS_ENTROPY_BLOCK_SIZE      32      /**< Block size of entropy accumulator (SHA-256) */
  #endif
  
  #define MBEDTLS_ENTROPY_MAX_SEED_SIZE   1024    /**< Maximum size of seed we read from seed file */
  #define MBEDTLS_ENTROPY_SOURCE_MANUAL   MBEDTLS_ENTROPY_MAX_SOURCES
  
  #define MBEDTLS_ENTROPY_SOURCE_STRONG   1       /**< Entropy source is strong   */
  #define MBEDTLS_ENTROPY_SOURCE_WEAK     0       /**< Entropy source is weak     */
  
  #ifdef __cplusplus
  extern "C" {
  #endif
  
  /**
   * \brief           Entropy poll callback pointer
   *
   * \param data      Callback-specific data pointer
   * \param output    Data to fill
   * \param len       Maximum size to provide
   * \param olen      The actual amount of bytes put into the buffer (Can be 0)
   *
   * \return          0 if no critical failures occurred,
   *                  MBEDTLS_ERR_ENTROPY_SOURCE_FAILED otherwise
   */
  typedef int (*mbedtls_entropy_f_source_ptr)(void *data, unsigned char *output, size_t len,
                              size_t *olen);
  
  /**
   * \brief           Entropy source state
   */
  typedef struct
  {
      mbedtls_entropy_f_source_ptr    f_source;   /**< The entropy source callback */
      void *          p_source;   /**< The callback data pointer */
      size_t          size;       /**< Amount received in bytes */
      size_t          threshold;  /**< Minimum bytes required before release */
      int             strong;     /**< Is the source strong? */
  }
  mbedtls_entropy_source_state;
  
  /**
   * \brief           Entropy context structure
   */
  typedef struct
  {
      int accumulator_started;
  #if defined(MBEDTLS_ENTROPY_SHA512_ACCUMULATOR)
      mbedtls_sha512_context  accumulator;
  #else
      mbedtls_sha256_context  accumulator;
  #endif
      int             source_count;
      mbedtls_entropy_source_state    source[MBEDTLS_ENTROPY_MAX_SOURCES];
  #if defined(MBEDTLS_HAVEGE_C)
      mbedtls_havege_state    havege_data;
  #endif
  #if defined(MBEDTLS_THREADING_C)
      mbedtls_threading_mutex_t mutex;    /*!< mutex                  */
  #endif
  #if defined(MBEDTLS_ENTROPY_NV_SEED)
      int initial_entropy_run;
  #endif
  }
  mbedtls_entropy_context;
  
  /**
   * \brief           Initialize the context
   *
   * \param ctx       Entropy context to initialize
   */
  void mbedtls_entropy_init( mbedtls_entropy_context *ctx );
  
  /**
   * \brief           Free the data in the context
   *
   * \param ctx       Entropy context to free
   */
  void mbedtls_entropy_free( mbedtls_entropy_context *ctx );
  
  /**
   * \brief           Adds an entropy source to poll
   *                  (Thread-safe if MBEDTLS_THREADING_C is enabled)
   *
   * \param ctx       Entropy context
   * \param f_source  Entropy function
   * \param p_source  Function data
   * \param threshold Minimum required from source before entropy is released
   *                  ( with mbedtls_entropy_func() ) (in bytes)
   * \param strong    MBEDTLS_ENTROPY_SOURCE_STRONG or
   *                  MBEDTSL_ENTROPY_SOURCE_WEAK.
   *                  At least one strong source needs to be added.
   *                  Weaker sources (such as the cycle counter) can be used as
   *                  a complement.
   *
   * \return          0 if successful or MBEDTLS_ERR_ENTROPY_MAX_SOURCES
   */
  int mbedtls_entropy_add_source( mbedtls_entropy_context *ctx,
                          mbedtls_entropy_f_source_ptr f_source, void *p_source,
                          size_t threshold, int strong );
  
  /**
   * \brief           Trigger an extra gather poll for the accumulator
   *                  (Thread-safe if MBEDTLS_THREADING_C is enabled)
   *
   * \param ctx       Entropy context
   *
   * \return          0 if successful, or MBEDTLS_ERR_ENTROPY_SOURCE_FAILED
   */
  int mbedtls_entropy_gather( mbedtls_entropy_context *ctx );
  
  /**
   * \brief           Retrieve entropy from the accumulator
   *                  (Maximum length: MBEDTLS_ENTROPY_BLOCK_SIZE)
   *                  (Thread-safe if MBEDTLS_THREADING_C is enabled)
   *
   * \param data      Entropy context
   * \param output    Buffer to fill
   * \param len       Number of bytes desired, must be at most MBEDTLS_ENTROPY_BLOCK_SIZE
   *
   * \return          0 if successful, or MBEDTLS_ERR_ENTROPY_SOURCE_FAILED
   */
  int mbedtls_entropy_func( void *data, unsigned char *output, size_t len );
  
  /**
   * \brief           Add data to the accumulator manually
   *                  (Thread-safe if MBEDTLS_THREADING_C is enabled)
   *
   * \param ctx       Entropy context
   * \param data      Data to add
   * \param len       Length of data
   *
   * \return          0 if successful
   */
  int mbedtls_entropy_update_manual( mbedtls_entropy_context *ctx,
                             const unsigned char *data, size_t len );
  
  #if defined(MBEDTLS_ENTROPY_NV_SEED)
  /**
   * \brief           Trigger an update of the seed file in NV by using the
   *                  current entropy pool.
   *
   * \param ctx       Entropy context
   *
   * \return          0 if successful
   */
  int mbedtls_entropy_update_nv_seed( mbedtls_entropy_context *ctx );
  #endif /* MBEDTLS_ENTROPY_NV_SEED */
  
  #if defined(MBEDTLS_FS_IO)
  /**
   * \brief               Write a seed file
   *
   * \param ctx           Entropy context
   * \param path          Name of the file
   *
   * \return              0 if successful,
   *                      MBEDTLS_ERR_ENTROPY_FILE_IO_ERROR on file error, or
   *                      MBEDTLS_ERR_ENTROPY_SOURCE_FAILED
   */
  int mbedtls_entropy_write_seed_file( mbedtls_entropy_context *ctx, const char *path );
  
  /**
   * \brief               Read and update a seed file. Seed is added to this
   *                      instance. No more than MBEDTLS_ENTROPY_MAX_SEED_SIZE bytes are
   *                      read from the seed file. The rest is ignored.
   *
   * \param ctx           Entropy context
   * \param path          Name of the file
   *
   * \return              0 if successful,
   *                      MBEDTLS_ERR_ENTROPY_FILE_IO_ERROR on file error,
   *                      MBEDTLS_ERR_ENTROPY_SOURCE_FAILED
   */
  int mbedtls_entropy_update_seed_file( mbedtls_entropy_context *ctx, const char *path );
  #endif /* MBEDTLS_FS_IO */
  
  #if defined(MBEDTLS_SELF_TEST)
  /**
   * \brief          Checkup routine
   *
   *                 This module self-test also calls the entropy self-test,
   *                 mbedtls_entropy_source_self_test();
   *
   * \return         0 if successful, or 1 if a test failed
   */
  int mbedtls_entropy_self_test( int verbose );
  
  #if defined(MBEDTLS_ENTROPY_HARDWARE_ALT)
  /**
   * \brief          Checkup routine
   *
   *                 Verifies the integrity of the hardware entropy source
   *                 provided by the function 'mbedtls_hardware_poll()'.
   *
   *                 Note this is the only hardware entropy source that is known
   *                 at link time, and other entropy sources configured
   *                 dynamically at runtime by the function
   *                 mbedtls_entropy_add_source() will not be tested.
   *
   * \return         0 if successful, or 1 if a test failed
   */
  int mbedtls_entropy_source_self_test( int verbose );
  #endif /* MBEDTLS_ENTROPY_HARDWARE_ALT */
  #endif /* MBEDTLS_SELF_TEST */
  
  #ifdef __cplusplus
  }
  #endif
  
  #endif /* entropy.h */
  