261 lines
6.8 KiB
C
261 lines
6.8 KiB
C
/*
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* Entropy accumulator implementation
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*
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* Copyright (C) 2006-2013, Brainspark B.V.
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*
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* This file is part of PolarSSL (http://www.polarssl.org)
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* Lead Maintainer: Paul Bakker <polarssl_maintainer at polarssl.org>
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*
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* All rights reserved.
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 2 of the License, or
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* (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License along
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* with this program; if not, write to the Free Software Foundation, Inc.,
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* 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
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*/
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#include "polarssl/config.h"
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#if defined(POLARSSL_ENTROPY_C)
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#include "polarssl/entropy.h"
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#include "polarssl/entropy_poll.h"
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#if defined(POLARSSL_HAVEGE_C)
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#include "polarssl/havege.h"
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#endif
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#define ENTROPY_MAX_LOOP 256 /**< Maximum amount to loop before error */
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void entropy_init( entropy_context *ctx )
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{
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memset( ctx, 0, sizeof(entropy_context) );
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#if defined(POLARSSL_THREADING_C)
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polarssl_mutex_init( &ctx->mutex );
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#endif
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#if defined(POLARSSL_ENTROPY_SHA512_ACCUMULATOR)
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sha512_starts( &ctx->accumulator, 0 );
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#else
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sha256_starts( &ctx->accumulator, 0 );
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#endif
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#if defined(POLARSSL_HAVEGE_C)
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havege_init( &ctx->havege_data );
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#endif
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#if !defined(POLARSSL_NO_DEFAULT_ENTROPY_SOURCES)
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#if !defined(POLARSSL_NO_PLATFORM_ENTROPY)
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entropy_add_source( ctx, platform_entropy_poll, NULL,
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ENTROPY_MIN_PLATFORM );
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#endif
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#if defined(POLARSSL_TIMING_C)
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entropy_add_source( ctx, hardclock_poll, NULL, ENTROPY_MIN_HARDCLOCK );
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#endif
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#if defined(POLARSSL_HAVEGE_C)
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entropy_add_source( ctx, havege_poll, &ctx->havege_data,
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ENTROPY_MIN_HAVEGE );
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#endif
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#endif /* POLARSSL_NO_DEFAULT_ENTROPY_SOURCES */
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}
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void entropy_free( entropy_context *ctx )
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{
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((void) ctx);
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#if defined(POLARSSL_THREADING_C)
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polarssl_mutex_free( &ctx->mutex );
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#endif
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}
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int entropy_add_source( entropy_context *ctx,
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f_source_ptr f_source, void *p_source,
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size_t threshold )
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{
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int index = ctx->source_count;
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if( index >= ENTROPY_MAX_SOURCES )
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return( POLARSSL_ERR_ENTROPY_MAX_SOURCES );
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ctx->source[index].f_source = f_source;
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ctx->source[index].p_source = p_source;
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ctx->source[index].threshold = threshold;
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ctx->source_count++;
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return( 0 );
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}
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/*
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* Entropy accumulator update
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*/
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static int entropy_update( entropy_context *ctx, unsigned char source_id,
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const unsigned char *data, size_t len )
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{
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unsigned char header[2];
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unsigned char tmp[ENTROPY_BLOCK_SIZE];
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size_t use_len = len;
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const unsigned char *p = data;
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if( use_len > ENTROPY_BLOCK_SIZE )
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{
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#if defined(POLARSSL_ENTROPY_SHA512_ACCUMULATOR)
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sha512( data, len, tmp, 0 );
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#else
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sha256( data, len, tmp, 0 );
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#endif
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p = tmp;
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use_len = ENTROPY_BLOCK_SIZE;
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}
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header[0] = source_id;
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header[1] = use_len & 0xFF;
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#if defined(POLARSSL_ENTROPY_SHA512_ACCUMULATOR)
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sha512_update( &ctx->accumulator, header, 2 );
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sha512_update( &ctx->accumulator, p, use_len );
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#else
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sha256_update( &ctx->accumulator, header, 2 );
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sha256_update( &ctx->accumulator, p, use_len );
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#endif
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return( 0 );
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}
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int entropy_update_manual( entropy_context *ctx,
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const unsigned char *data, size_t len )
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{
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return entropy_update( ctx, ENTROPY_SOURCE_MANUAL, data, len );
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}
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/*
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* Run through the different sources to add entropy to our accumulator
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*/
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int entropy_gather( entropy_context *ctx )
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{
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int ret, i;
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unsigned char buf[ENTROPY_MAX_GATHER];
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size_t olen;
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if( ctx->source_count == 0 )
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return( POLARSSL_ERR_ENTROPY_NO_SOURCES_DEFINED );
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/*
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* Run through our entropy sources
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*/
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for( i = 0; i < ctx->source_count; i++ )
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{
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olen = 0;
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if ( ( ret = ctx->source[i].f_source( ctx->source[i].p_source,
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buf, ENTROPY_MAX_GATHER, &olen ) ) != 0 )
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{
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return( ret );
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}
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/*
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* Add if we actually gathered something
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*/
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if( olen > 0 )
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{
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entropy_update( ctx, (unsigned char) i, buf, olen );
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ctx->source[i].size += olen;
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}
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}
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return( 0 );
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}
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int entropy_func( void *data, unsigned char *output, size_t len )
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{
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int ret, count = 0, i, reached;
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entropy_context *ctx = (entropy_context *) data;
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unsigned char buf[ENTROPY_BLOCK_SIZE];
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if( len > ENTROPY_BLOCK_SIZE )
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return( POLARSSL_ERR_ENTROPY_SOURCE_FAILED );
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#if defined(POLARSSL_THREADING_C)
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if( ( ret = polarssl_mutex_lock( &ctx->mutex ) ) != 0 )
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return( ret );
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#endif
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/*
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* Always gather extra entropy before a call
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*/
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do
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{
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if( count++ > ENTROPY_MAX_LOOP )
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{
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ret = POLARSSL_ERR_ENTROPY_SOURCE_FAILED;
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goto exit;
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}
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if( ( ret = entropy_gather( ctx ) ) != 0 )
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goto exit;
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reached = 0;
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for( i = 0; i < ctx->source_count; i++ )
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if( ctx->source[i].size >= ctx->source[i].threshold )
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reached++;
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}
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while( reached != ctx->source_count );
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memset( buf, 0, ENTROPY_BLOCK_SIZE );
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#if defined(POLARSSL_ENTROPY_SHA512_ACCUMULATOR)
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sha512_finish( &ctx->accumulator, buf );
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/*
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* Perform second SHA-512 on entropy
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*/
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sha512( buf, ENTROPY_BLOCK_SIZE, buf, 0 );
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/*
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* Reset accumulator and counters and recycle existing entropy
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*/
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memset( &ctx->accumulator, 0, sizeof( sha512_context ) );
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sha512_starts( &ctx->accumulator, 0 );
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sha512_update( &ctx->accumulator, buf, ENTROPY_BLOCK_SIZE );
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#else /* POLARSSL_ENTROPY_SHA512_ACCUMULATOR */
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sha256_finish( &ctx->accumulator, buf );
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/*
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* Perform second SHA-256 on entropy
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*/
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sha256( buf, ENTROPY_BLOCK_SIZE, buf, 0 );
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/*
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* Reset accumulator and counters and recycle existing entropy
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*/
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memset( &ctx->accumulator, 0, sizeof( sha256_context ) );
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sha256_starts( &ctx->accumulator, 0 );
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sha256_update( &ctx->accumulator, buf, ENTROPY_BLOCK_SIZE );
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#endif /* POLARSSL_ENTROPY_SHA512_ACCUMULATOR */
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for( i = 0; i < ctx->source_count; i++ )
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ctx->source[i].size = 0;
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memcpy( output, buf, len );
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ret = 0;
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exit:
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#if defined(POLARSSL_THREADING_C)
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if( polarssl_mutex_unlock( &ctx->mutex ) != 0 )
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return( POLARSSL_ERR_THREADING_MUTEX_ERROR );
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#endif
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return( ret );
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}
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#endif
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