From 77cb30c3cb9a0f0b3ae6200bc930dcd2c3ac9fe4 Mon Sep 17 00:00:00 2001 From: Gavin Acquroff Date: Sun, 1 Mar 2020 17:06:11 -0800 Subject: [PATCH] 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_*_DRBG_RESEED_INTERVAL. Signed-off-by: gacquroff --- include/mbedtls/ctr_drbg.h | 8 +++++++- include/mbedtls/hmac_drbg.h | 7 ++++++- library/ctr_drbg.c | 11 ++++++++++- library/hmac_drbg.c | 11 ++++++++--- tests/suites/test_suite_ctr_drbg.function | 18 +++++++++++------- tests/suites/test_suite_hmac_drbg.function | 18 +++++++++++------- 6 files changed, 53 insertions(+), 20 deletions(-) diff --git a/include/mbedtls/ctr_drbg.h b/include/mbedtls/ctr_drbg.h index 7e5f2e576..278fbbbb7 100644 --- a/include/mbedtls/ctr_drbg.h +++ b/include/mbedtls/ctr_drbg.h @@ -224,6 +224,11 @@ mbedtls_ctr_drbg_context; * 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 ); @@ -305,7 +310,8 @@ int mbedtls_ctr_drbg_seed( mbedtls_ctr_drbg_context *ctx, 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 688367820..970c033c1 100644 --- a/include/mbedtls/hmac_drbg.h +++ b/include/mbedtls/hmac_drbg.h @@ -138,6 +138,10 @@ typedef struct mbedtls_hmac_drbg_context * 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 ); @@ -361,7 +365,8 @@ int mbedtls_hmac_drbg_random_with_add( void *p_rng, 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 b98df29a9..e92008bbe 100644 --- a/library/ctr_drbg.c +++ b/library/ctr_drbg.c @@ -82,11 +82,17 @@ void mbedtls_ctr_drbg_init( mbedtls_ctr_drbg_context *ctx ) { memset( ctx, 0, sizeof( mbedtls_ctr_drbg_context ) ); + 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 ) @@ -97,6 +103,10 @@ void mbedtls_ctr_drbg_free( mbedtls_ctr_drbg_context *ctx ) #endif mbedtls_aes_free( &ctx->aes_ctx ); mbedtls_platform_zeroize( ctx, sizeof( mbedtls_ctr_drbg_context ) ); + ctx->reseed_interval = MBEDTLS_CTR_DRBG_RESEED_INTERVAL; +#if defined(MBEDTLS_THREADING_C) + mbedtls_mutex_init( &ctx->mutex ); +#endif } void mbedtls_ctr_drbg_set_prediction_resistance( mbedtls_ctr_drbg_context *ctx, int resistance ) @@ -419,7 +429,6 @@ int mbedtls_ctr_drbg_seed( mbedtls_ctr_drbg_context *ctx, if( ctx->entropy_len == 0 ) ctx->entropy_len = MBEDTLS_CTR_DRBG_ENTROPY_LEN; - ctx->reseed_interval = MBEDTLS_CTR_DRBG_RESEED_INTERVAL; /* * Initialize with an empty key diff --git a/library/hmac_drbg.c b/library/hmac_drbg.c index 9fbfc3066..10cbd462b 100644 --- a/library/hmac_drbg.c +++ b/library/hmac_drbg.c @@ -83,6 +83,8 @@ void mbedtls_hmac_drbg_init( mbedtls_hmac_drbg_context *ctx ) { 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 @@ -296,8 +298,6 @@ int mbedtls_hmac_drbg_seed( mbedtls_hmac_drbg_context *ctx, ctx->f_entropy = f_entropy; ctx->p_entropy = p_entropy; - ctx->reseed_interval = MBEDTLS_HMAC_DRBG_RESEED_INTERVAL; - if( ctx->entropy_len == 0 ) { /* @@ -442,7 +442,8 @@ int mbedtls_hmac_drbg_random( void *p_rng, unsigned char *output, size_t out_len } /* - * 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 ) { @@ -454,6 +455,10 @@ void mbedtls_hmac_drbg_free( mbedtls_hmac_drbg_context *ctx ) #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 01050d92d..d6cf82865 100644 --- a/tests/suites/test_suite_ctr_drbg.function +++ b/tests/suites/test_suite_ctr_drbg.function @@ -206,13 +206,16 @@ void ctr_drbg_entropy_usage( ) memset( out, 0, sizeof( out ) ); memset( add, 0, sizeof( add ) ); + /* Set reseed interval before seed */ + mbedtls_ctr_drbg_set_reseed_interval( &ctx, 2 * reps ); + /* Init must use entropy */ last_idx = test_offset_idx; TEST_ASSERT( mbedtls_ctr_drbg_seed( &ctx, mbedtls_test_entropy_func, entropy, NULL, 0 ) == 0 ); TEST_ASSERT( last_idx < test_offset_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 */ last_idx = test_offset_idx; for( i = 0; i < reps; i++ ) { @@ -228,15 +231,16 @@ void ctr_drbg_entropy_usage( ) 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 ); TEST_ASSERT( last_idx < test_offset_idx ); - /* The new few calls should not reseed */ + /* Set reseed interval after seed */ + mbedtls_ctr_drbg_set_reseed_interval( &ctx, 4 * reps + 1 ); + + /* The next few calls should not reseed */ last_idx = test_offset_idx; - for( i = 0; i < reps / 2; i++ ) + 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 13bc40062..fbbb1bd21 100644 --- a/tests/suites/test_suite_hmac_drbg.function +++ b/tests/suites/test_suite_hmac_drbg.function @@ -49,14 +49,17 @@ void hmac_drbg_entropy_usage( int md_alg ) md_info = mbedtls_md_info_from_type( md_alg ); TEST_ASSERT( md_info != NULL ); + /* Set reseed interval before seed */ + mbedtls_hmac_drbg_set_reseed_interval( &ctx, 2 * reps ); + /* Init must use entropy */ last_len = entropy.len; TEST_ASSERT( mbedtls_hmac_drbg_seed( &ctx, md_info, mbedtls_test_entropy_func, &entropy, NULL, 0 ) == 0 ); TEST_ASSERT( entropy.len < last_len ); - /* 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 */ last_len = entropy.len; for( i = 0; i < reps; i++ ) { @@ -72,15 +75,16 @@ void hmac_drbg_entropy_usage( int md_alg ) 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 ); TEST_ASSERT( entropy.len < last_len ); + /* Set reseed interval after seed */ + mbedtls_hmac_drbg_set_reseed_interval( &ctx, 4 * reps + 1); + /* The new few calls should not reseed */ last_len = entropy.len; - 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 ) , @@ -189,7 +193,7 @@ void hmac_drbg_no_reseed( int md_alg, data_t * entropy, 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 );