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Add a concept of entropy source strength.

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The main goal is, we want and error if cycle counter is the only source.
This commit is contained in:
Manuel Pégourié-Gonnard
2015-06-19 10:26:32 +02:00
parent 3f77dfbd52
commit 7580ba475d
5 changed files with 47 additions and 19 deletions
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33
library/entropy.c
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@ -77,18 +77,23 @@ void mbedtls_entropy_init( mbedtls_entropy_context *ctx )
#if !defined(MBEDTLS_NO_DEFAULT_ENTROPY_SOURCES)
#if !defined(MBEDTLS_NO_PLATFORM_ENTROPY)
mbedtls_entropy_add_source( ctx, mbedtls_platform_entropy_poll, NULL,
MBEDTLS_ENTROPY_MIN_PLATFORM );
MBEDTLS_ENTROPY_MIN_PLATFORM,
MBEDTLS_ENTROPY_SOURCE_STRONG );
#endif
#if defined(MBEDTLS_TIMING_C)
mbedtls_entropy_add_source( ctx, mbedtls_hardclock_poll, NULL, MBEDTLS_ENTROPY_MIN_HARDCLOCK );
mbedtls_entropy_add_source( ctx, mbedtls_hardclock_poll, NULL,
MBEDTLS_ENTROPY_MIN_HARDCLOCK,
MBEDTLS_ENTROPY_SOURCE_WEAK );
#endif
#if defined(MBEDTLS_HAVEGE_C)
mbedtls_entropy_add_source( ctx, mbedtls_havege_poll, &ctx->havege_data,
MBEDTLS_ENTROPY_MIN_HAVEGE );
MBEDTLS_ENTROPY_MIN_HAVEGE,
MBEDTLS_ENTROPY_SOURCE_STRONG );
#endif
#if defined(MBEDTLS_ENTROPY_HARDWARE_ALT)
mbedtls_entropy_add_source( ctx, mbedtls_hardware_poll, NULL
MBEDTLS_ENTROPY_MIN_HARDWARE );
MBEDTLS_ENTROPY_MIN_HARDWARE,
MBEDTLS_ENTROPY_SOURCE_STRONG );
#endif
#endif /* MBEDTLS_NO_DEFAULT_ENTROPY_SOURCES */
}
@ -106,7 +111,7 @@ void mbedtls_entropy_free( mbedtls_entropy_context *ctx )
int mbedtls_entropy_add_source( mbedtls_entropy_context *ctx,
mbedtls_entropy_f_source_ptr f_source, void *p_source,
size_t threshold )
size_t threshold, int strong )
{
int index, ret = 0;
@ -122,9 +127,10 @@ int mbedtls_entropy_add_source( mbedtls_entropy_context *ctx,
goto exit;
}
ctx->source[index].f_source = f_source;
ctx->source[index].p_source = p_source;
ctx->source[index].f_source = f_source;
ctx->source[index].p_source = p_source;
ctx->source[index].threshold = threshold;
ctx->source[index].strong = strong;
ctx->source_count++;
@ -198,7 +204,7 @@ int mbedtls_entropy_update_manual( mbedtls_entropy_context *ctx,
*/
static int entropy_gather_internal( mbedtls_entropy_context *ctx )
{
int ret, i;
int ret, i, have_one_strong = 0;
unsigned char buf[MBEDTLS_ENTROPY_MAX_GATHER];
size_t olen;
@ -210,6 +216,9 @@ static int entropy_gather_internal( mbedtls_entropy_context *ctx )
*/
for( i = 0; i < ctx->source_count; i++ )
{
if( ctx->source[i].strong == MBEDTLS_ENTROPY_SOURCE_STRONG )
have_one_strong = 1;
olen = 0;
if( ( ret = ctx->source[i].f_source( ctx->source[i].p_source,
buf, MBEDTLS_ENTROPY_MAX_GATHER, &olen ) ) != 0 )
@ -227,6 +236,9 @@ static int entropy_gather_internal( mbedtls_entropy_context *ctx )
}
}
if( have_one_strong == 0 )
return( MBEDTLS_ERR_ENTROPY_NO_STRONG_SOURCE );
return( 0 );
}
@ -424,11 +436,12 @@ int mbedtls_entropy_self_test( int verbose )
mbedtls_entropy_init( &ctx );
/* First do a gather to mek sure we have default sources */
/* First do a gather to make sure we have default sources */
if( ( ret = mbedtls_entropy_gather( &ctx ) ) != 0 )
goto cleanup;
ret = mbedtls_entropy_add_source( &ctx, entropy_dummy_source, NULL, 16 );
ret = mbedtls_entropy_add_source( &ctx, entropy_dummy_source, NULL, 16,
MBEDTLS_ENTROPY_SOURCE_WEAK );
if( ret != 0 )
goto cleanup;