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/**
* \file entropy.h
*
* \brief Entropy accumulator implementation
*
* Copyright (C) 2006-2011, Brainspark B.V.
*
* This file is part of PolarSSL (http://www.polarssl.org)
* Lead Maintainer: Paul Bakker <polarssl_maintainer at polarssl.org>
*
* All rights reserved.
*
* 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.
*/
#ifndef POLARSSL_ENTROPY_H
#define POLARSSL_ENTROPY_H
#include <string.h>
#include "config.h"
#include "sha4.h"
#if defined(POLARSSL_HAVEGE_C)
#include "havege.h"
#endif
#define POLARSSL_ERR_ENTROPY_SOURCE_FAILED -0x003C /**< Critical entropy source failure. */
#define POLARSSL_ERR_ENTROPY_MAX_SOURCES -0x003E /**< No more sources can be added. */
#define POLARSSL_ERR_ENTROPY_NO_SOURCES_DEFINED -0x0040 /**< No sources have been added to poll. */
#define ENTROPY_MAX_SOURCES 20 /**< Maximum number of sources supported */
#define ENTROPY_MAX_GATHER 128 /**< Maximum amount requested from entropy sources */
#define ENTROPY_BLOCK_SIZE 64 /**< Block size of entropy accumulator (SHA-512) */
#define ENTROPY_SOURCE_MANUAL ENTROPY_MAX_SOURCES
#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,
* POLARSSL_ERR_ENTROPY_SOURCE_FAILED otherwise
*/
typedef int (*f_source_ptr)(void *, unsigned char *, size_t, size_t *);
/**
* \brief Entropy source state
*/
typedef struct
{
f_source_ptr f_source; /**< The entropy source callback */
void * p_source; /**< The callback data pointer */
size_t size; /**< Amount received */
size_t threshold; /**< Minimum level required before release */
}
source_state;
/**
* \brief Entropy context structure
*/
typedef struct
{
sha4_context accumulator;
int source_count;
source_state source[ENTROPY_MAX_SOURCES];
#if defined(POLARSSL_HAVEGE_C)
havege_state havege_data;
#endif
}
entropy_context;
/**
* \brief Initialize the context
*
* \param ctx Entropy context to initialize
*/
void entropy_init( entropy_context *ctx );
/**
* \brief Adds an entropy source to poll
*
* \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 entropy_func() )
*
* \return 0 if successful or POLARSSL_ERR_ENTROPY_MAX_SOURCES
*/
int entropy_add_source( entropy_context *ctx,
f_source_ptr f_source, void *p_source,
size_t threshold );
/**
* \brief Trigger an extra gather poll for the accumulator
*
* \param ctx Entropy context
*
* \return 0 if successful, or POLARSSL_ERR_ENTROPY_SOURCE_FAILED
*/
int entropy_gather( entropy_context *ctx );
/**
* \brief Retrieve entropy from the accumulator (Max ENTROPY_BLOCK_SIZE)
*
* \param data Entropy context
* \param output Buffer to fill
* \param len Length of buffer
*
* \return 0 if successful, or POLARSSL_ERR_ENTROPY_SOURCE_FAILED
*/
int entropy_func( void *data, unsigned char *output, size_t len );
/**
* \brief Add data to the accumulator manually
*
* \param ctx Entropy context
* \param data Data to add
* \param len Length of data
*
* \return 0 if successful
*/
int entropy_update_manual( entropy_context *ctx,
const unsigned char *data, size_t len );
#ifdef __cplusplus
}
#endif
#endif /* entropy.h */
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