entropy.h

00001 /**
00002  * \file entropy.h
00003  *
00004  * \brief Entropy accumulator implementation
00005  *
00006  *  Copyright (C) 2006-2014, Brainspark B.V.
00007  *
00008  *  This file is part of PolarSSL (http://www.polarssl.org)
00009  *  Lead Maintainer: Paul Bakker <polarssl_maintainer at polarssl.org>
00010  *
00011  *  All rights reserved.
00012  *
00013  *  This program is free software; you can redistribute it and/or modify
00014  *  it under the terms of the GNU General Public License as published by
00015  *  the Free Software Foundation; either version 2 of the License, or
00016  *  (at your option) any later version.
00017  *
00018  *  This program is distributed in the hope that it will be useful,
00019  *  but WITHOUT ANY WARRANTY; without even the implied warranty of
00020  *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
00021  *  GNU General Public License for more details.
00022  *
00023  *  You should have received a copy of the GNU General Public License along
00024  *  with this program; if not, write to the Free Software Foundation, Inc.,
00025  *  51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
00026  */
00027 #ifndef POLARSSL_ENTROPY_H
00028 #define POLARSSL_ENTROPY_H
00029 
00030 #include <string.h>
00031 
00032 #if !defined(POLARSSL_CONFIG_FILE)
00033 #include "config.h"
00034 #else
00035 #include POLARSSL_CONFIG_FILE
00036 #endif
00037 
00038 #if defined(POLARSSL_SHA512_C) && !defined(POLARSSL_ENTROPY_FORCE_SHA256)
00039 #include "sha512.h"
00040 #define POLARSSL_ENTROPY_SHA512_ACCUMULATOR
00041 #else
00042 #if defined(POLARSSL_SHA256_C)
00043 #define POLARSSL_ENTROPY_SHA256_ACCUMULATOR
00044 #include "sha256.h"
00045 #endif
00046 #endif
00047 
00048 #if defined(POLARSSL_THREADING_C)
00049 #include "threading.h"
00050 #endif
00051 
00052 #if defined(POLARSSL_HAVEGE_C)
00053 #include "havege.h"
00054 #endif
00055 
00056 #define POLARSSL_ERR_ENTROPY_SOURCE_FAILED                 -0x003C  /**< Critical entropy source failure. */
00057 #define POLARSSL_ERR_ENTROPY_MAX_SOURCES                   -0x003E  /**< No more sources can be added. */
00058 #define POLARSSL_ERR_ENTROPY_NO_SOURCES_DEFINED            -0x0040  /**< No sources have been added to poll. */
00059 #define POLARSSL_ERR_ENTROPY_FILE_IO_ERROR                 -0x0058  /**< Read/write error in file. */
00060 
00061 /**
00062  * \name SECTION: Module settings
00063  *
00064  * The configuration options you can set for this module are in this section.
00065  * Either change them in config.h or define them on the compiler command line.
00066  * \{
00067  */
00068 
00069 #if !defined(ENTROPY_MAX_SOURCES)
00070 #define ENTROPY_MAX_SOURCES     20      /**< Maximum number of sources supported */
00071 #endif
00072 
00073 #if !defined(ENTROPY_MAX_GATHER)
00074 #define ENTROPY_MAX_GATHER      128     /**< Maximum amount requested from entropy sources */
00075 #endif
00076 
00077 /* \} name SECTION: Module settings */
00078 
00079 #if defined(POLARSSL_ENTROPY_SHA512_ACCUMULATOR)
00080 #define ENTROPY_BLOCK_SIZE      64      /**< Block size of entropy accumulator (SHA-512) */
00081 #else
00082 #define ENTROPY_BLOCK_SIZE      32      /**< Block size of entropy accumulator (SHA-256) */
00083 #endif
00084 
00085 #define ENTROPY_MAX_SEED_SIZE   1024    /**< Maximum size of seed we read from seed file */
00086 #define ENTROPY_SOURCE_MANUAL   ENTROPY_MAX_SOURCES
00087 
00088 #ifdef __cplusplus
00089 extern "C" {
00090 #endif
00091 
00092 /**
00093  * \brief           Entropy poll callback pointer
00094  *
00095  * \param data      Callback-specific data pointer
00096  * \param output    Data to fill
00097  * \param len       Maximum size to provide
00098  * \param olen      The actual amount of bytes put into the buffer (Can be 0)
00099  *
00100  * \return          0 if no critical failures occurred,
00101  *                  POLARSSL_ERR_ENTROPY_SOURCE_FAILED otherwise
00102  */
00103 typedef int (*f_source_ptr)(void *data, unsigned char *output, size_t len,
00104                             size_t *olen);
00105 
00106 /**
00107  * \brief           Entropy source state
00108  */
00109 typedef struct
00110 {
00111     f_source_ptr    f_source;   /**< The entropy source callback */
00112     void *          p_source;   /**< The callback data pointer */
00113     size_t          size;       /**< Amount received */
00114     size_t          threshold;  /**< Minimum level required before release */
00115 }
00116 source_state;
00117 
00118 /**
00119  * \brief           Entropy context structure
00120  */
00121 typedef struct
00122 {
00123 #if defined(POLARSSL_ENTROPY_SHA512_ACCUMULATOR)
00124     sha512_context  accumulator;
00125 #else
00126     sha256_context  accumulator;
00127 #endif
00128     int             source_count;
00129     source_state    source[ENTROPY_MAX_SOURCES];
00130 #if defined(POLARSSL_HAVEGE_C)
00131     havege_state    havege_data;
00132 #endif
00133 #if defined(POLARSSL_THREADING_C)
00134     threading_mutex_t mutex ;    /*!< mutex                  */
00135 #endif
00136 }
00137 entropy_context;
00138 
00139 /**
00140  * \brief           Initialize the context
00141  *
00142  * \param ctx       Entropy context to initialize
00143  */
00144 void entropy_init( entropy_context *ctx );
00145 
00146 /**
00147  * \brief           Free the data in the context
00148  *
00149  * \param ctx       Entropy context to free
00150  */
00151 void entropy_free( entropy_context *ctx );
00152 
00153 /**
00154  * \brief           Adds an entropy source to poll
00155  *                  (Thread-safe if POLARSSL_THREADING_C is enabled)
00156  *
00157  * \param ctx       Entropy context
00158  * \param f_source  Entropy function
00159  * \param p_source  Function data
00160  * \param threshold Minimum required from source before entropy is released
00161  *                  ( with entropy_func() )
00162  *
00163  * \return          0 if successful or POLARSSL_ERR_ENTROPY_MAX_SOURCES
00164  */
00165 int entropy_add_source( entropy_context *ctx,
00166                         f_source_ptr f_source, void *p_source,
00167                         size_t threshold );
00168 
00169 /**
00170  * \brief           Trigger an extra gather poll for the accumulator
00171  *                  (Thread-safe if POLARSSL_THREADING_C is enabled)
00172  *
00173  * \param ctx       Entropy context
00174  *
00175  * \return          0 if successful, or POLARSSL_ERR_ENTROPY_SOURCE_FAILED
00176  */
00177 int entropy_gather( entropy_context *ctx );
00178 
00179 /**
00180  * \brief           Retrieve entropy from the accumulator
00181  *                  (Maximum length: ENTROPY_BLOCK_SIZE)
00182  *                  (Thread-safe if POLARSSL_THREADING_C is enabled)
00183  *
00184  * \param data      Entropy context
00185  * \param output    Buffer to fill
00186  * \param len       Length of buffer
00187  *
00188  * \return          0 if successful, or POLARSSL_ERR_ENTROPY_SOURCE_FAILED
00189  */
00190 int entropy_func( void *data, unsigned char *output, size_t len );
00191 
00192 /**
00193  * \brief           Add data to the accumulator manually
00194  *                  (Thread-safe if POLARSSL_THREADING_C is enabled)
00195  *
00196  * \param ctx       Entropy context
00197  * \param data      Data to add
00198  * \param len       Length of data
00199  *
00200  * \return          0 if successful
00201  */
00202 int entropy_update_manual( entropy_context *ctx,
00203                            const unsigned char *data, size_t len );
00204 
00205 #if defined(POLARSSL_FS_IO)
00206 /**
00207  * \brief               Write a seed file
00208  *
00209  * \param ctx           Entropy context
00210  * \param path          Name of the file
00211  *
00212  * \return              0 if successful,
00213  *                      POLARSSL_ERR_ENTROPY_FILE_IO_ERROR on file error, or
00214  *                      POLARSSL_ERR_ENTROPY_SOURCE_FAILED
00215  */
00216 int entropy_write_seed_file( entropy_context *ctx, const char *path );
00217 
00218 /**
00219  * \brief               Read and update a seed file. Seed is added to this
00220  *                      instance. No more than ENTROPY_MAX_SEED_SIZE bytes are
00221  *                      read from the seed file. The rest is ignored.
00222  *
00223  * \param ctx           Entropy context
00224  * \param path          Name of the file
00225  *
00226  * \return              0 if successful,
00227  *                      POLARSSL_ERR_ENTROPY_FILE_IO_ERROR on file error,
00228  *                      POLARSSL_ERR_ENTROPY_SOURCE_FAILED
00229  */
00230 int entropy_update_seed_file( entropy_context *ctx, const char *path );
00231 #endif /* POLARSSL_FS_IO */
00232 
00233 #ifdef __cplusplus
00234 }
00235 #endif
00236 
00237 #endif /* entropy.h */
00238 
00239