- Changed entropy accumulator to have per-source thresholds
diff --git a/include/polarssl/entropy.h b/include/polarssl/entropy.h
index 46df929..0c1f13f 100644
--- a/include/polarssl/entropy.h
+++ b/include/polarssl/entropy.h
@@ -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) */
@@ -59,15 +58,25 @@
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 @@
* \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
diff --git a/include/polarssl/entropy_poll.h b/include/polarssl/entropy_poll.h
index d9acbe5..0116598 100644
--- a/include/polarssl/entropy_poll.h
+++ b/include/polarssl/entropy_poll.h
@@ -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
diff --git a/library/entropy.c b/library/entropy.c
index 0ece345..bc0e141 100644
--- a/library/entropy.c
+++ b/library/entropy.c
@@ -39,21 +39,26 @@
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 @@
sha4_update( &ctx->accumulator, header, 2 );
sha4_update( &ctx->accumulator, p, use_len );
- ctx->size += use_len;
-
return( 0 );
}
@@ -111,7 +114,7 @@
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 @@
* 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_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 @@
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 @@
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 );