src/libpolarssl/entropy.h

   1 /**
   2  * \file entropy.h
   3  *
   4  * \brief Entropy accumulator implementation
   5  *
   6  *  Copyright (C) 2006-2014, Brainspark B.V.
   7  *
   8  *  This file is part of PolarSSL (http://www.polarssl.org)
   9  *  Lead Maintainer: Paul Bakker <polarssl_maintainer at polarssl.org>
  10  *
  11  *  All rights reserved.
  12  *
  13  *  This program is free software; you can redistribute it and/or modify
  14  *  it under the terms of the GNU General Public License as published by
  15  *  the Free Software Foundation; either version 2 of the License, or
  16  *  (at your option) any later version.
  17  *
  18  *  This program is distributed in the hope that it will be useful,
  19  *  but WITHOUT ANY WARRANTY; without even the implied warranty of
  20  *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  21  *  GNU General Public License for more details.
  22  *
  23  *  You should have received a copy of the GNU General Public License along
  24  *  with this program; if not, write to the Free Software Foundation, Inc.,
  25  *  51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  26  */
  27 #ifndef POLARSSL_ENTROPY_H
  28 #define POLARSSL_ENTROPY_H
  29
  30 #include <string.h>
  31
  32 #if !defined(POLARSSL_CONFIG_FILE)
  33 #include "config.h"
  34 #else
  35 #include POLARSSL_CONFIG_FILE
  36 #endif
  37
  38 #if defined(POLARSSL_SHA512_C) && !defined(POLARSSL_ENTROPY_FORCE_SHA256)
  39 #include "sha512.h"
  40 #define POLARSSL_ENTROPY_SHA512_ACCUMULATOR
  41 #else
  42 #if defined(POLARSSL_SHA256_C)
  43 #define POLARSSL_ENTROPY_SHA256_ACCUMULATOR
  44 #include "sha256.h"
  45 #endif
  46 #endif
  47
  48 #if defined(POLARSSL_THREADING_C)
  49 #include "threading.h"
  50 #endif
  51
  52 #if defined(POLARSSL_HAVEGE_C)
  53 #include "havege.h"
  54 #endif
  55
  56 #define POLARSSL_ERR_ENTROPY_SOURCE_FAILED                 -0x003C  /**< Critical entropy source failure. */
  57 #define POLARSSL_ERR_ENTROPY_MAX_SOURCES                   -0x003E  /**< No more sources can be added. */
  58 #define POLARSSL_ERR_ENTROPY_NO_SOURCES_DEFINED            -0x0040  /**< No sources have been added to poll. */
  59 #define POLARSSL_ERR_ENTROPY_FILE_IO_ERROR                 -0x0058  /**< Read/write error in file. */
  60
  61 /**
  62  * \name SECTION: Module settings
  63  *
  64  * The configuration options you can set for this module are in this section.
  65  * Either change them in config.h or define them on the compiler command line.
  66  * \{
  67  */
  68
  69 #if !defined(ENTROPY_MAX_SOURCES)
  70 #define ENTROPY_MAX_SOURCES     20      /**< Maximum number of sources supported */
  71 #endif
  72
  73 #if !defined(ENTROPY_MAX_GATHER)
  74 #define ENTROPY_MAX_GATHER      128     /**< Maximum amount requested from entropy sources */
  75 #endif
  76
  77 /* \} name SECTION: Module settings */
  78
  79 #if defined(POLARSSL_ENTROPY_SHA512_ACCUMULATOR)
  80 #define ENTROPY_BLOCK_SIZE      64      /**< Block size of entropy accumulator (SHA-512) */
  81 #else
  82 #define ENTROPY_BLOCK_SIZE      32      /**< Block size of entropy accumulator (SHA-256) */
  83 #endif
  84
  85 #define ENTROPY_MAX_SEED_SIZE   1024    /**< Maximum size of seed we read from seed file */
  86 #define ENTROPY_SOURCE_MANUAL   ENTROPY_MAX_SOURCES
  87
  88 #ifdef __cplusplus
  89 extern "C" {
  90 #endif
  91
  92 /**
  93  * \brief           Entropy poll callback pointer
  94  *
  95  * \param data      Callback-specific data pointer
  96  * \param output    Data to fill
  97  * \param len       Maximum size to provide
  98  * \param olen      The actual amount of bytes put into the buffer (Can be 0)
  99  *
 100  * \return          0 if no critical failures occurred,
 101  *                  POLARSSL_ERR_ENTROPY_SOURCE_FAILED otherwise
 102  */
 103 typedef int (*f_source_ptr)(void *data, unsigned char *output, size_t len,
 104                             size_t *olen);
 105
 106 /**
 107  * \brief           Entropy source state
 108  */
 109 typedef struct
 110 {
 111     f_source_ptr    f_source;   /**< The entropy source callback */
 112     void *          p_source;   /**< The callback data pointer */
 113     size_t          size;       /**< Amount received */
 114     size_t          threshold;  /**< Minimum level required before release */
 115 }
 116 source_state;
 117
 118 /**
 119  * \brief           Entropy context structure
 120  */
 121 typedef struct
 122 {
 123 #if defined(POLARSSL_ENTROPY_SHA512_ACCUMULATOR)
 124     sha512_context  accumulator;
 125 #else
 126     sha256_context  accumulator;
 127 #endif
 128     int             source_count;
 129     source_state    source[ENTROPY_MAX_SOURCES];
 130 #if defined(POLARSSL_HAVEGE_C)
 131     havege_state    havege_data;
 132 #endif
 133 #if defined(POLARSSL_THREADING_C)
 134     threading_mutex_t mutex;    /*!< mutex                  */
 135 #endif
 136 }
 137 entropy_context;
 138
 139 /**
 140  * \brief           Initialize the context
 141  *
 142  * \param ctx       Entropy context to initialize
 143  */
 144 void entropy_init( entropy_context *ctx );
 145
 146 /**
 147  * \brief           Free the data in the context
 148  *
 149  * \param ctx       Entropy context to free
 150  */
 151 void entropy_free( entropy_context *ctx );
 152
 153 /**
 154  * \brief           Adds an entropy source to poll
 155  *                  (Thread-safe if POLARSSL_THREADING_C is enabled)
 156  *
 157  * \param ctx       Entropy context
 158  * \param f_source  Entropy function
 159  * \param p_source  Function data
 160  * \param threshold Minimum required from source before entropy is released
 161  *                  ( with entropy_func() )
 162  *
 163  * \return          0 if successful or POLARSSL_ERR_ENTROPY_MAX_SOURCES
 164  */
 165 int entropy_add_source( entropy_context *ctx,
 166                         f_source_ptr f_source, void *p_source,
 167                         size_t threshold );
 168
 169 /**
 170  * \brief           Trigger an extra gather poll for the accumulator
 171  *                  (Thread-safe if POLARSSL_THREADING_C is enabled)
 172  *
 173  * \param ctx       Entropy context
 174  *
 175  * \return          0 if successful, or POLARSSL_ERR_ENTROPY_SOURCE_FAILED
 176  */
 177 int entropy_gather( entropy_context *ctx );
 178
 179 /**
 180  * \brief           Retrieve entropy from the accumulator
 181  *                  (Maximum length: ENTROPY_BLOCK_SIZE)
 182  *                  (Thread-safe if POLARSSL_THREADING_C is enabled)
 183  *
 184  * \param data      Entropy context
 185  * \param output    Buffer to fill
 186  * \param len       Length of buffer
 187  *
 188  * \return          0 if successful, or POLARSSL_ERR_ENTROPY_SOURCE_FAILED
 189  */
 190 int entropy_func( void *data, unsigned char *output, size_t len );
 191
 192 /**
 193  * \brief           Add data to the accumulator manually
 194  *                  (Thread-safe if POLARSSL_THREADING_C is enabled)
 195  *
 196  * \param ctx       Entropy context
 197  * \param data      Data to add
 198  * \param len       Length of data
 199  *
 200  * \return          0 if successful
 201  */
 202 int entropy_update_manual( entropy_context *ctx,
 203                            const unsigned char *data, size_t len );
 204
 205 #if defined(POLARSSL_FS_IO)
 206 /**
 207  * \brief               Write a seed file
 208  *
 209  * \param ctx           Entropy context
 210  * \param path          Name of the file
 211  *
 212  * \return              0 if successful,
 213  *                      POLARSSL_ERR_ENTROPY_FILE_IO_ERROR on file error, or
 214  *                      POLARSSL_ERR_ENTROPY_SOURCE_FAILED
 215  */
 216 int entropy_write_seed_file( entropy_context *ctx, const char *path );
 217
 218 /**
 219  * \brief               Read and update a seed file. Seed is added to this
 220  *                      instance. No more than ENTROPY_MAX_SEED_SIZE bytes are
 221  *                      read from the seed file. The rest is ignored.
 222  *
 223  * \param ctx           Entropy context
 224  * \param path          Name of the file
 225  *
 226  * \return              0 if successful,
 227  *                      POLARSSL_ERR_ENTROPY_FILE_IO_ERROR on file error,
 228  *                      POLARSSL_ERR_ENTROPY_SOURCE_FAILED
 229  */
 230 int entropy_update_seed_file( entropy_context *ctx, const char *path );
 231 #endif /* POLARSSL_FS_IO */
 232
 233 #ifdef __cplusplus
 234 }
 235 #endif
 236
 237 #endif /* entropy.h */