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- Changed entropy accumulator to have per-source thresholds

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This commit is contained in:
Paul Bakker 2011-12-10 17:02:19 +00:00
parent 5cb9db4c5b
commit bd4a9d0cda
3 changed files with 52 additions and 18 deletions
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22
include/polarssl/entropy.h
View file

@ -34,7 +34,6 @@
#define POLARSSL_ERR_ENTROPY_SOURCE_FAILED -0x003A /**< Critical entropy source failure. */
#define POLARSSL_ERR_ENTROPY_MAX_SOURCES -0x003C /**< No more sources can be added. */
#define ENTROPY_MIN_POOL 128 /**< Minimum amount of pool entropy needed for release */
#define ENTROPY_MAX_SOURCES 20 /**< Maximum number of sources supported */
#define ENTROPY_MAX_GATHER 128 /**< Maximum amount requested from entropy sources */
#define ENTROPY_BLOCK_SIZE 64 /**< Block size of entropy accumulator (SHA-512) */
@ -58,16 +57,26 @@ extern "C" {
*/
typedef int (*f_source_ptr)(void *, unsigned char *, size_t, size_t *);
/**
* \brief Entropy source state
*/
typedef struct
{
f_source_ptr f_source; /**< The entropy source callback */
void * p_source; /**< The callback data pointer */
size_t size; /**< Amount received */
size_t threshold; /**< Minimum level required before release */
}
source_state;
/**
* \brief Entropy context structure
*/
typedef struct
{
sha4_context accumulator;
size_t size;
int source_count;
f_source_ptr f_source[ENTROPY_MAX_SOURCES];
void * p_source[ENTROPY_MAX_SOURCES];
source_state source[ENTROPY_MAX_SOURCES];
}
entropy_context;
@ -84,11 +93,14 @@ void entropy_init( entropy_context *ctx );
* \param ctx Entropy context
* \param f_source Entropy function
* \param p_source Function data
* \param threshold Minimum required from source before entropy is released
* ( with entropy_func() )
*
* \return 0 is successful or POLARSSL_ERR_ENTROPY_MAX_SOURCES
*/
int entropy_add_source( entropy_context *ctx,
f_source_ptr f_source, void *p_source );
f_source_ptr f_source, void *p_source,
size_t threshold );
/**
* \brief Trigger an extra gather poll for the accumulator

7
include/polarssl/entropy_poll.h
View file

@ -35,6 +35,13 @@
extern "C" {
#endif
/*
* Default thresholds for built-in sources
*/
#define ENTROPY_MIN_PLATFORM 128 /**< Minimum for platform source */
#define ENTROPY_MIN_HAVEGE 128 /**< Minimum for HAVEGE */
#define ENTROPY_MIN_HARDCLOCK 32 /**< Minimum for hardclock() */
#if !defined(POLARSSL_NO_PLATFORM_ENTROPY)
/**
* \brief Platform-specific entropy poll callback

41
library/entropy.c
View file

@ -39,21 +39,26 @@ void entropy_init( entropy_context *ctx )
sha4_starts( &ctx->accumulator, 0 );
#if !defined(POLARSSL_NO_PLATFORM_ENTROPY)
entropy_add_source( ctx, platform_entropy_poll, NULL );
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_add_source( ctx, hardclock_poll, NULL, ENTROPY_MIN_HARDCLOCK );
#endif
}
int entropy_add_source( entropy_context *ctx,
f_source_ptr f_source, void *p_source )
f_source_ptr f_source, void *p_source,
size_t threshold )
{
if( ctx->source_count >= ENTROPY_MAX_SOURCES )
int index = ctx->source_count;
if( index >= ENTROPY_MAX_SOURCES )
return( POLARSSL_ERR_ENTROPY_MAX_SOURCES );
ctx->f_source[ctx->source_count] = f_source;
ctx->p_source[ctx->source_count] = p_source;
ctx->source[index].f_source = f_source;
ctx->source[index].p_source = p_source;
ctx->source[index].threshold = threshold;
ctx->source_count++;
@ -85,8 +90,6 @@ int entropy_update( entropy_context *ctx, unsigned char source_id,
sha4_update( &ctx->accumulator, header, 2 );
sha4_update( &ctx->accumulator, p, use_len );
ctx->size += use_len;
return( 0 );
}
@ -111,7 +114,7 @@ int entropy_gather( entropy_context *ctx )
for( i = 0; i < ctx->source_count; i++ )
{
olen = 0;
if ( ( ret = ctx->f_source[i]( ctx->p_source[i],
if ( ( ret = ctx->source[i].f_source( ctx->source[i].p_source,
buf, ENTROPY_MAX_GATHER, &olen ) ) != 0 )
{
return( ret );
@ -121,7 +124,10 @@ int entropy_gather( entropy_context *ctx )
* Add if we actually gathered something
*/
if( olen > 0 )
{
entropy_update( ctx, (unsigned char) i, buf, olen );
ctx->source[i].size += olen;
}
}
return( 0 );
@ -129,7 +135,7 @@ int entropy_gather( entropy_context *ctx )
int entropy_func( void *data, unsigned char *output, size_t len )
{
int ret, count = 0;
int ret, count = 0, i, reached;
entropy_context *ctx = (entropy_context *) data;
unsigned char buf[ENTROPY_BLOCK_SIZE];
@ -146,8 +152,14 @@ int entropy_func( void *data, unsigned char *output, size_t len )
if( ( ret = entropy_gather( ctx ) ) != 0 )
return( ret );
reached = 0;
for( i = 0; i < ctx->source_count; i++ )
if( ctx->source[i].size >= ctx->source[i].threshold )
reached++;
}
while( ctx->size < ENTROPY_MIN_POOL );
while( reached != ctx->source_count );
memset( buf, 0, ENTROPY_BLOCK_SIZE );
@ -159,11 +171,14 @@ int entropy_func( void *data, unsigned char *output, size_t len )
sha4( buf, ENTROPY_BLOCK_SIZE, buf, 0 );
/*
* Reset accumulator
* Reset accumulator and counters and recycle existing entropy
*/
memset( &ctx->accumulator, 0, sizeof( sha4_context ) );
sha4_starts( &ctx->accumulator, 0 );
ctx->size = 0;
sha4_update( &ctx->accumulator, buf, ENTROPY_BLOCK_SIZE );
for( i = 0; i < ctx->source_count; i++ )
ctx->source[i].size = 0;
memcpy( output, buf, len );