void entropy_init( entropy_context *ctx )
{
memset( ctx, 0, sizeof(entropy_context) );
#if defined(POLARSSL_THREADING_C)
polarssl_mutex_init( &ctx->mutex );
#endif
#if defined(POLARSSL_ENTROPY_SHA512_ACCUMULATOR)
sha512_starts( &ctx->accumulator, 0 );
#else
sha256_starts( &ctx->accumulator, 0 );
#endif
#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 */
}
static void sha512_starts_wrap( void *ctx )
{
sha512_starts( (sha512_context *) ctx, 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 );
#if defined(POLARSSL_THREADING_C)
if( ( ret = polarssl_mutex_lock( &ctx->mutex ) ) != 0 )
return( ret );
#endif
/*
* Always gather extra entropy before a call
*/
do
{
if( count++ > ENTROPY_MAX_LOOP )
{
ret = POLARSSL_ERR_ENTROPY_SOURCE_FAILED;
goto exit;
}
if( ( ret = entropy_gather_internal( ctx ) ) != 0 )
goto exit;
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 );
#if defined(POLARSSL_ENTROPY_SHA512_ACCUMULATOR)
sha512_finish( &ctx->accumulator, buf );
/*
* Reset accumulator and counters and recycle existing entropy
*/
memset( &ctx->accumulator, 0, sizeof( sha512_context ) );
sha512_starts( &ctx->accumulator, 0 );
sha512_update( &ctx->accumulator, buf, ENTROPY_BLOCK_SIZE );
/*
* Perform second SHA-512 on entropy
*/
sha512( buf, ENTROPY_BLOCK_SIZE, buf, 0 );
#else /* POLARSSL_ENTROPY_SHA512_ACCUMULATOR */
sha256_finish( &ctx->accumulator, buf );
/*
* Reset accumulator and counters and recycle existing entropy
*/
memset( &ctx->accumulator, 0, sizeof( sha256_context ) );
sha256_starts( &ctx->accumulator, 0 );
sha256_update( &ctx->accumulator, buf, ENTROPY_BLOCK_SIZE );
/*
* Perform second SHA-256 on entropy
*/
sha256( buf, ENTROPY_BLOCK_SIZE, buf, 0 );
#endif /* POLARSSL_ENTROPY_SHA512_ACCUMULATOR */
for( i = 0; i < ctx->source_count; i++ )
ctx->source[i].size = 0;
memcpy( output, buf, len );
ret = 0;
exit:
#if defined(POLARSSL_THREADING_C)
if( polarssl_mutex_unlock( &ctx->mutex ) != 0 )
return( POLARSSL_ERR_THREADING_MUTEX_ERROR );
#endif
return( ret );
}
