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/*
* 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.
*/
#include "polarssl/config.h"
#if defined(POLARSSL_ENTROPY_C)
#include "polarssl/entropy.h"
#include "polarssl/entropy_poll.h"
#if defined(POLARSSL_HAVEGE_C)
#include "polarssl/havege.h"
#endif
#define ENTROPY_MAX_LOOP 256 /**< Maximum amount to loop before error */
void entropy_init( entropy_context *ctx )
{
memset( ctx, 0, sizeof(entropy_context) );
sha4_starts( &ctx->accumulator, 0 );
#if defined(POLARSSL_HAVEGE_C)
havege_init( &ctx->havege_data );
#endif
#if !defined(POLARSSL_NO_DEFAULT_ENTROPY_SOURCES)
#if !defined(POLARSSL_NO_PLATFORM_ENTROPY)
entropy_add_source( ctx, platform_entropy_poll, NULL,
ENTROPY_MIN_PLATFORM );
#endif
#if defined(POLARSSL_TIMING_C)
entropy_add_source( ctx, hardclock_poll, NULL, ENTROPY_MIN_HARDCLOCK );
#endif
#if defined(POLARSSL_HAVEGE_C)
entropy_add_source( ctx, havege_poll, &ctx->havege_data,
ENTROPY_MIN_HAVEGE );
#endif
#endif /* POLARSSL_NO_DEFAULT_ENTROPY_SOURCES */
}
int entropy_add_source( entropy_context *ctx,
f_source_ptr f_source, void *p_source,
size_t threshold )
{
int index = ctx->source_count;
if( index >= ENTROPY_MAX_SOURCES )
return( POLARSSL_ERR_ENTROPY_MAX_SOURCES );
ctx->source[index].f_source = f_source;
ctx->source[index].p_source = p_source;
ctx->source[index].threshold = threshold;
ctx->source_count++;
return( 0 );
}
/*
* Entropy accumulator update
*/
int entropy_update( entropy_context *ctx, unsigned char source_id,
const unsigned char *data, size_t len )
{
unsigned char header[2];
unsigned char tmp[ENTROPY_BLOCK_SIZE];
size_t use_len = len;
const unsigned char *p = data;
if( use_len > ENTROPY_BLOCK_SIZE )
{
sha4( data, len, tmp, 0 );
p = tmp;
use_len = ENTROPY_BLOCK_SIZE;
}
header[0] = source_id;
header[1] = use_len & 0xFF;
sha4_update( &ctx->accumulator, header, 2 );
sha4_update( &ctx->accumulator, p, use_len );
return( 0 );
}
int entropy_update_manual( entropy_context *ctx,
const unsigned char *data, size_t len )
{
return entropy_update( ctx, ENTROPY_SOURCE_MANUAL, data, len );
}
/*
* Run through the different sources to add entropy to our accumulator
*/
int entropy_gather( entropy_context *ctx )
{
int ret, i;
unsigned char buf[ENTROPY_MAX_GATHER];
size_t olen;
if( ctx->source_count == 0 )
return( POLARSSL_ERR_ENTROPY_NO_SOURCES_DEFINED );
/*
* Run through our entropy sources
*/
for( i = 0; i < ctx->source_count; i++ )
{
olen = 0;
if ( ( ret = ctx->source[i].f_source( ctx->source[i].p_source,
buf, ENTROPY_MAX_GATHER, &olen ) ) != 0 )
{
return( ret );
}
/*
* Add if we actually gathered something
*/
if( olen > 0 )
{
entropy_update( ctx, (unsigned char) i, buf, olen );
ctx->source[i].size += olen;
}
}
return( 0 );
}
int entropy_func( void *data, unsigned char *output, size_t len )
{
int ret, count = 0, i, reached;
entropy_context *ctx = (entropy_context *) data;
unsigned char buf[ENTROPY_BLOCK_SIZE];
if( len > ENTROPY_BLOCK_SIZE )
return( POLARSSL_ERR_ENTROPY_SOURCE_FAILED );
/*
* Always gather extra entropy before a call
*/
do
{
if( count++ > ENTROPY_MAX_LOOP )
return( POLARSSL_ERR_ENTROPY_SOURCE_FAILED );
if( ( ret = entropy_gather( ctx ) ) != 0 )
return( ret );
reached = 0;
for( i = 0; i < ctx->source_count; i++ )
if( ctx->source[i].size >= ctx->source[i].threshold )
reached++;
}
while( reached != ctx->source_count );
memset( buf, 0, ENTROPY_BLOCK_SIZE );
sha4_finish( &ctx->accumulator, buf );
/*
* Perform second SHA-512 on entropy
*/
sha4( buf, ENTROPY_BLOCK_SIZE, buf, 0 );
/*
* Reset accumulator and counters and recycle existing entropy
*/
memset( &ctx->accumulator, 0, sizeof( sha4_context ) );
sha4_starts( &ctx->accumulator, 0 );
sha4_update( &ctx->accumulator, buf, ENTROPY_BLOCK_SIZE );
for( i = 0; i < ctx->source_count; i++ )
ctx->source[i].size = 0;
memcpy( output, buf, len );
return( 0 );
}
#endif
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