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Automatically update NV seed on initial entropy run

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Update the NV entropy seed before generating any entropy for outside
use. The reason this is triggered here and not in mbedtls_entropy_init(),
is that not all entropy sources mights have been added at that time.
This commit is contained in:
Paul Bakker 2016-06-01 11:30:54 +01:00
parent 54c43fca36
commit 7da307105c
2 changed files with 50 additions and 1 deletions
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14
include/mbedtls/entropy.h
View file

@ -3,7 +3,7 @@
*
* \brief Entropy accumulator implementation
*
* Copyright (C) 2006-2015, ARM Limited, All Rights Reserved
* Copyright (C) 2006-2016, ARM Limited, All Rights Reserved
* SPDX-License-Identifier: Apache-2.0
*
* Licensed under the Apache License, Version 2.0 (the "License"); you may
@ -208,6 +208,18 @@ int mbedtls_entropy_func( void *data, unsigned char *output, size_t len );
int mbedtls_entropy_update_manual( mbedtls_entropy_context *ctx,
const unsigned char *data, size_t len );
#if defined(MBEDTLS_ENTROPY_NV_SEED)
/**
* \brief Trigger an update of the seed file in NV by using the
* current entropy pool.
*
* \param ctx Entropy context
*
* \return 0 if successful
*/
int mbedtls_entropy_update_nv_seed( mbedtls_entropy_context *ctx );
#endif /* MBEDTLS_ENTROPY_NV_SEED */
#if defined(MBEDTLS_FS_IO)
/**
* \brief Write a seed file

37
library/entropy.c
View file

@ -54,6 +54,10 @@ static void mbedtls_zeroize( void *v, size_t n ) {
volatile unsigned char *p = v; while( n-- ) *p++ = 0;
}
#if defined(MBEDTLS_ENTROPY_NV_SEED)
static int initial_entropy_run = 0;
#endif
#define ENTROPY_MAX_LOOP 256 /**< Maximum amount to loop before error */
void mbedtls_entropy_init( mbedtls_entropy_context *ctx )
@ -277,6 +281,18 @@ int mbedtls_entropy_func( void *data, unsigned char *output, size_t len )
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( initial_entropy_run == 0 )
{
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 );
@ -351,6 +367,27 @@ exit:
return( ret );
}
#if defined(MBEDTLS_ENTROPY_NV_SEED)
int mbedtls_entropy_update_nv_seed( mbedtls_entropy_context *ctx )
{
int ret = MBEDTLS_ERR_ENTROPY_FILE_IO_ERROR;
unsigned char buf[ MBEDTLS_ENTROPY_MAX_SEED_SIZE ];
/* Read new seed and write it to NV */
if( ( ret = mbedtls_entropy_func( ctx, buf, MBEDTLS_ENTROPY_BLOCK_SIZE ) ) != 0 )
return( ret );
if( mbedtls_nv_seed_write( buf, MBEDTLS_ENTROPY_BLOCK_SIZE ) < 0 )
return( MBEDTLS_ERR_ENTROPY_FILE_IO_ERROR );
/* Manually update the remaining stream with a separator value to diverge */
memset( buf, 0, MBEDTLS_ENTROPY_BLOCK_SIZE );
mbedtls_entropy_update_manual( ctx, buf, MBEDTLS_ENTROPY_BLOCK_SIZE );
return( 0 );
}
#endif /* MBEDTLS_ENTROPY_NV_SEED */
#if defined(MBEDTLS_FS_IO)
int mbedtls_entropy_write_seed_file( mbedtls_entropy_context *ctx, const char *path )
{