Support set *_drbg reseed interval before seed
mbedtls_ctr_drbg_set_reseed_interval() and
mbedtls_hmac_drbg_set_reseed_interval() can now be called before
their seed functions and the reseed_interval value will persist.
Previously it would be overwritten with the default value.
*_drbg_reseed_interval is now set in init() and free().
mbedtls_ctr_drbg_free() and mbedtls_hmac_drbg_free() now
reset the drbg context to the state immediately after init().
Tests:
- Added test to check that DRBG reseeds when reseed_counter
reaches reseed_interval, if reseed_interval set before seed
and reseed_interval is less than MBEDTLS_CTR_DRBG_RESEED_INTERVAL.
Signed-off-by: gacquroff <gavina352@gmail.com>
diff --git a/include/mbedtls/ctr_drbg.h b/include/mbedtls/ctr_drbg.h
index 6c48ec1..7f1d232 100644
--- a/include/mbedtls/ctr_drbg.h
+++ b/include/mbedtls/ctr_drbg.h
@@ -210,6 +210,11 @@
* and prepares it for mbedtls_ctr_drbg_seed()
* or mbedtls_ctr_drbg_free().
*
+ * \note The reseed interval is
+ * #MBEDTLS_CTR_DRBG_RESEED_INTERVAL by default.
+ * You can override it by calling
+ * mbedtls_ctr_drbg_set_reseed_interval().
+ *
* \param ctx The CTR_DRBG context to initialize.
*/
void mbedtls_ctr_drbg_init( mbedtls_ctr_drbg_context *ctx );
@@ -309,7 +314,8 @@
size_t len );
/**
- * \brief This function clears CTR_CRBG context data.
+ * \brief This function resets CTR_DRBG context to the state immediately
+ * after initial call of mbedtls_ctr_drbg_init().
*
* \param ctx The CTR_DRBG context to clear.
*/
diff --git a/include/mbedtls/hmac_drbg.h b/include/mbedtls/hmac_drbg.h
index 57ce9d9..9116541 100644
--- a/include/mbedtls/hmac_drbg.h
+++ b/include/mbedtls/hmac_drbg.h
@@ -111,6 +111,10 @@
* This function makes the context ready for mbedtls_hmac_drbg_seed(),
* mbedtls_hmac_drbg_seed_buf() or mbedtls_hmac_drbg_free().
*
+ * \note The reseed interval is #MBEDTLS_HMAC_DRBG_RESEED_INTERVAL
+ * by default. Override this value by calling
+ * mbedtls_hmac_drbg_set_reseed_interval().
+ *
* \param ctx HMAC_DRBG context to be initialized.
*/
void mbedtls_hmac_drbg_init( mbedtls_hmac_drbg_context *ctx );
@@ -334,7 +338,8 @@
int mbedtls_hmac_drbg_random( void *p_rng, unsigned char *output, size_t out_len );
/**
- * \brief Free an HMAC_DRBG context
+ * \brief This function resets HMAC_DRBG context to the state immediately
+ * after initial call of mbedtls_hmac_drbg_init().
*
* \param ctx The HMAC_DRBG context to free.
*/
diff --git a/library/ctr_drbg.c b/library/ctr_drbg.c
index 54843a7..023aac5 100644
--- a/library/ctr_drbg.c
+++ b/library/ctr_drbg.c
@@ -55,11 +55,17 @@
* See mbedtls_ctr_drbg_set_nonce_len(). */
ctx->reseed_counter = -1;
+ ctx->reseed_interval = MBEDTLS_CTR_DRBG_RESEED_INTERVAL;
+
#if defined(MBEDTLS_THREADING_C)
mbedtls_mutex_init( &ctx->mutex );
#endif
}
+/*
+ * This function resets CTR_DRBG context to the state immediately
+ * after initial call of mbedtls_ctr_drbg_init().
+ */
void mbedtls_ctr_drbg_free( mbedtls_ctr_drbg_context *ctx )
{
if( ctx == NULL )
@@ -70,6 +76,11 @@
#endif
mbedtls_aes_free( &ctx->aes_ctx );
mbedtls_platform_zeroize( ctx, sizeof( mbedtls_ctr_drbg_context ) );
+ ctx->reseed_interval = MBEDTLS_CTR_DRBG_RESEED_INTERVAL;
+ ctx->reseed_counter = -1;
+#if defined(MBEDTLS_THREADING_C)
+ mbedtls_mutex_init( &ctx->mutex );
+#endif
}
void mbedtls_ctr_drbg_set_prediction_resistance( mbedtls_ctr_drbg_context *ctx,
@@ -468,8 +479,6 @@
(size_t) ctx->reseed_counter :
good_nonce_len( ctx->entropy_len ) );
- ctx->reseed_interval = MBEDTLS_CTR_DRBG_RESEED_INTERVAL;
-
/* Initialize with an empty key. */
if( ( ret = mbedtls_aes_setkey_enc( &ctx->aes_ctx, key,
MBEDTLS_CTR_DRBG_KEYBITS ) ) != 0 )
diff --git a/library/hmac_drbg.c b/library/hmac_drbg.c
index aa3e251..25a0225 100644
--- a/library/hmac_drbg.c
+++ b/library/hmac_drbg.c
@@ -53,6 +53,8 @@
{
memset( ctx, 0, sizeof( mbedtls_hmac_drbg_context ) );
+ ctx->reseed_interval = MBEDTLS_HMAC_DRBG_RESEED_INTERVAL;
+
#if defined(MBEDTLS_THREADING_C)
mbedtls_mutex_init( &ctx->mutex );
#endif
@@ -266,8 +268,6 @@
ctx->f_entropy = f_entropy;
ctx->p_entropy = p_entropy;
- ctx->reseed_interval = MBEDTLS_HMAC_DRBG_RESEED_INTERVAL;
-
if( ctx->entropy_len == 0 )
{
/*
@@ -412,7 +412,8 @@
}
/*
- * Free an HMAC_DRBG context
+ * This function resets HMAC_DRBG context to the state immediately
+ * after initial call of mbedtls_hmac_drbg_init().
*/
void mbedtls_hmac_drbg_free( mbedtls_hmac_drbg_context *ctx )
{
@@ -424,6 +425,10 @@
#endif
mbedtls_md_free( &ctx->md_ctx );
mbedtls_platform_zeroize( ctx, sizeof( mbedtls_hmac_drbg_context ) );
+ ctx->reseed_interval = MBEDTLS_HMAC_DRBG_RESEED_INTERVAL;
+#if defined(MBEDTLS_THREADING_C)
+ mbedtls_mutex_init( &ctx->mutex );
+#endif
}
#if defined(MBEDTLS_FS_IO)
diff --git a/tests/suites/test_suite_ctr_drbg.function b/tests/suites/test_suite_ctr_drbg.function
index 5e4cd26..c3ffe3b 100644
--- a/tests/suites/test_suite_ctr_drbg.function
+++ b/tests/suites/test_suite_ctr_drbg.function
@@ -240,6 +240,9 @@
if( entropy_nonce_len >= 0 )
TEST_ASSERT( mbedtls_ctr_drbg_set_nonce_len( &ctx, entropy_nonce_len ) == 0 );
+ /* Set reseed interval before seed */
+ mbedtls_ctr_drbg_set_reseed_interval( &ctx, 2 * reps );
+
/* Init must use entropy */
TEST_ASSERT( mbedtls_ctr_drbg_seed( &ctx, mbedtls_test_entropy_func, entropy, NULL, 0 ) == 0 );
expected_idx += MBEDTLS_CTR_DRBG_ENTROPY_LEN;
@@ -249,8 +252,8 @@
expected_idx += MBEDTLS_CTR_DRBG_ENTROPY_NONCE_LEN;
TEST_EQUAL( test_offset_idx, expected_idx );
- /* By default, PR is off and reseed_interval is large,
- * so the next few calls should not use entropy */
+ /* By default, PR is off, and reseed interval was set to
+ * 2 * reps so the next few calls should not use entropy */
for( i = 0; i < reps; i++ )
{
TEST_ASSERT( mbedtls_ctr_drbg_random( &ctx, out, sizeof( out ) - 4 ) == 0 );
@@ -265,15 +268,16 @@
TEST_ASSERT( out[sizeof( out ) - 2] == 0 );
TEST_ASSERT( out[sizeof( out ) - 1] == 0 );
- /* Set reseed_interval to the number of calls done,
- * so the next call should reseed */
- mbedtls_ctr_drbg_set_reseed_interval( &ctx, 2 * reps );
+ /* There have been 2 * reps calls to random. The next call should reseed */
TEST_ASSERT( mbedtls_ctr_drbg_random( &ctx, out, sizeof( out ) ) == 0 );
expected_idx += MBEDTLS_CTR_DRBG_ENTROPY_LEN;
TEST_EQUAL( test_offset_idx, expected_idx );
- /* The new few calls should not reseed */
- for( i = 0; i < reps / 2; i++ )
+ /* Set reseed interval after seed */
+ mbedtls_ctr_drbg_set_reseed_interval( &ctx, 4 * reps + 1 );
+
+ /* The next few calls should not reseed */
+ for( i = 0; i < (2 * reps); i++ )
{
TEST_ASSERT( mbedtls_ctr_drbg_random( &ctx, out, sizeof( out ) ) == 0 );
TEST_ASSERT( mbedtls_ctr_drbg_random_with_add( &ctx, out, sizeof( out ) ,
diff --git a/tests/suites/test_suite_hmac_drbg.function b/tests/suites/test_suite_hmac_drbg.function
index 512eeb8..b83d760 100644
--- a/tests/suites/test_suite_hmac_drbg.function
+++ b/tests/suites/test_suite_hmac_drbg.function
@@ -57,6 +57,9 @@
else
default_entropy_len = 32;
+ /* Set reseed interval before seed */
+ mbedtls_hmac_drbg_set_reseed_interval( &ctx, 2 * reps );
+
/* Init must use entropy */
TEST_ASSERT( mbedtls_hmac_drbg_seed( &ctx, md_info, mbedtls_test_entropy_func, &entropy,
NULL, 0 ) == 0 );
@@ -64,8 +67,8 @@
expected_consumed_entropy += default_entropy_len * 3 / 2;
TEST_EQUAL( sizeof( buf ) - entropy.len, expected_consumed_entropy );
- /* By default, PR is off and reseed_interval is large,
- * so the next few calls should not use entropy */
+ /* By default, PR is off, and reseed interval was set to
+ * 2 * reps so the next few calls should not use entropy */
for( i = 0; i < reps; i++ )
{
TEST_ASSERT( mbedtls_hmac_drbg_random( &ctx, out, sizeof( out ) - 4 ) == 0 );
@@ -80,15 +83,16 @@
TEST_ASSERT( out[sizeof( out ) - 2] == 0 );
TEST_ASSERT( out[sizeof( out ) - 1] == 0 );
- /* Set reseed_interval to the number of calls done,
- * so the next call should reseed */
- mbedtls_hmac_drbg_set_reseed_interval( &ctx, 2 * reps );
+ /* There have been 2 * reps calls to random. The next call should reseed */
TEST_ASSERT( mbedtls_hmac_drbg_random( &ctx, out, sizeof( out ) ) == 0 );
expected_consumed_entropy += default_entropy_len;
TEST_EQUAL( sizeof( buf ) - entropy.len, expected_consumed_entropy );
+ /* Set reseed interval after seed */
+ mbedtls_hmac_drbg_set_reseed_interval( &ctx, 4 * reps + 1);
+
/* The new few calls should not reseed */
- for( i = 0; i < reps / 2; i++ )
+ for( i = 0; i < (2 * reps); i++ )
{
TEST_ASSERT( mbedtls_hmac_drbg_random( &ctx, out, sizeof( out ) ) == 0 );
TEST_ASSERT( mbedtls_hmac_drbg_random_with_add( &ctx, out, sizeof( out ) ,
@@ -199,7 +203,7 @@
TEST_ASSERT( mbedtls_hmac_drbg_random_with_add( &ctx, my_output, output->len,
add2->x, add2->len ) == 0 );
- /* clear for second run */
+ /* Reset context for second run */
mbedtls_hmac_drbg_free( &ctx );
TEST_ASSERT( memcmp( my_output, output->x, output->len ) == 0 );