int mbedtls_entropy_func( void *data, unsigned char *output, size_t len )
{
int ret, count = 0, i, done;
mbedtls_entropy_context *ctx = (mbedtls_entropy_context *) data;
unsigned char buf[MBEDTLS_ENTROPY_BLOCK_SIZE];
if( len > MBEDTLS_ENTROPY_BLOCK_SIZE )
return( MBEDTLS_ERR_ENTROPY_SOURCE_FAILED );
#if defined(MBEDTLS_ENTROPY_NV_SEED)
/* Update the NV entropy seed before generating any entropy for outside
* use.
*/
if( ctx->initial_entropy_run == 0 )
{
ctx->initial_entropy_run = 1;
if( ( ret = mbedtls_entropy_update_nv_seed( ctx ) ) != 0 )
return( ret );
}
#endif
#if defined(MBEDTLS_THREADING_C)
if( ( ret = mbedtls_mutex_lock( &ctx->mutex ) ) != 0 )
return( ret );
#endif
/*
* Always gather extra entropy before a call
*/
do
{
if( count++ > ENTROPY_MAX_LOOP )
{
ret = MBEDTLS_ERR_ENTROPY_SOURCE_FAILED;
goto exit;
}
if( ( ret = entropy_gather_internal( ctx ) ) != 0 )
goto exit;
done = 1;
for( i = 0; i < ctx->source_count; i++ )
if( ctx->source[i].size < ctx->source[i].threshold )
done = 0;
}
while( ! done );
memset( buf, 0, MBEDTLS_ENTROPY_BLOCK_SIZE );
#if defined(MBEDTLS_ENTROPY_SHA512_ACCUMULATOR)
/*
* Note that at this stage it is assumed that the accumulator was started
* in a previous call to entropy_update(). If this is not guaranteed, the
* code below will fail.
*/
if( ( ret = mbedtls_sha512_finish_ret( &ctx->accumulator, buf ) ) != 0 )
goto exit;
/*
* Reset accumulator and counters and recycle existing entropy
*/
mbedtls_sha512_free( &ctx->accumulator );
mbedtls_sha512_init( &ctx->accumulator );
if( ( ret = mbedtls_sha512_starts_ret( &ctx->accumulator, 0 ) ) != 0 )
goto exit;
if( ( ret = mbedtls_sha512_update_ret( &ctx->accumulator, buf,
MBEDTLS_ENTROPY_BLOCK_SIZE ) ) != 0 )
goto exit;
/*
* Perform second SHA-512 on entropy
*/
if( ( ret = mbedtls_sha512_ret( buf, MBEDTLS_ENTROPY_BLOCK_SIZE,
buf, 0 ) ) != 0 )
goto exit;
#else /* MBEDTLS_ENTROPY_SHA512_ACCUMULATOR */
if( ( ret = mbedtls_sha256_finish_ret( &ctx->accumulator, buf ) ) != 0 )
goto exit;
/*
* Reset accumulator and counters and recycle existing entropy
*/
mbedtls_sha256_free( &ctx->accumulator );
mbedtls_sha256_init( &ctx->accumulator );
if( ( ret = mbedtls_sha256_starts_ret( &ctx->accumulator, 0 ) ) != 0 )
goto exit;
if( ( ret = mbedtls_sha256_update_ret( &ctx->accumulator, buf,
MBEDTLS_ENTROPY_BLOCK_SIZE ) ) != 0 )
goto exit;
/*
* Perform second SHA-256 on entropy
*/
if( ( ret = mbedtls_sha256_ret( buf, MBEDTLS_ENTROPY_BLOCK_SIZE,
buf, 0 ) ) != 0 )
goto exit;
#endif /* MBEDTLS_ENTROPY_SHA512_ACCUMULATOR */
for( i = 0; i < ctx->source_count; i++ )
ctx->source[i].size = 0;
memcpy( output, buf, len );
ret = 0;
exit:
mbedtls_zeroize( buf, sizeof( buf ) );
#if defined(MBEDTLS_THREADING_C)
if( mbedtls_mutex_unlock( &ctx->mutex ) != 0 )
return( MBEDTLS_ERR_THREADING_MUTEX_ERROR );
#endif
return( ret );
}
static int32_t sha256_finish_wrap( void *ctx, uint8_t *output )
{
return( mbedtls_sha256_finish_ret( (mbedtls_sha256_context *) ctx,
output ) );
}
