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Disable the insecure PSA test RNG by default

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To reduce the risk of people accidentally using the test
implementation of mbedtls_psa_external_get_random(), which is
insecure, require the user to explicitly call
mbedtls_test_enable_insecure_external_rng() first.

Disabling the test implementation of mbedtls_psa_external_get_random()
will also allow negative testing for MBEDTLS_PSA_CRYPTO_EXTERNAL_RNG,
which will be added in a subsequent commit.

Signed-off-by: Gilles Peskine <Gilles.Peskine@arm.com>
This commit is contained in:
Gilles Peskine 2020-11-24 18:39:12 +01:00
parent f6be590bf6
commit 76175ba785
3 changed files with 47 additions and 1 deletions
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26
tests/include/test/psa_crypto_helpers.h
View file

@ -53,6 +53,32 @@ const char *mbedtls_test_helper_is_psa_leaking( void );
#if defined(MBEDTLS_PSA_CRYPTO_EXTERNAL_RNG)
/** Enable the insecure implementation of mbedtls_psa_external_get_random().
*
* The insecure implementation of mbedtls_psa_external_get_random() is
* disabled by default.
*
* When MBEDTLS_PSA_CRYPTO_EXTERNAL_RNG is enabled and the test
* helpers are linked into a program, you must enable this before any code
* that uses the PSA subsystem to generate random data (including internal
* random generation for purposes such as blinding when the random generation
* is routed through PSA).
*
* You can enable and disable it at any time, regardless of the state
* of the PSA subsystem. You may disable it temporarily to simulate a
* depleted entropy source.
*/
void mbedtls_test_enable_insecure_external_rng( void );
/** Disable the insecure implementation of mbedtls_psa_external_get_random().
*
* See mbedtls_test_enable_insecure_external_rng().
*/
void mbedtls_test_disable_insecure_external_rng( void );
#endif /* MBEDTLS_PSA_CRYPTO_EXTERNAL_RNG */
#if defined(RECORD_PSA_STATUS_COVERAGE_LOG)
psa_status_t mbedtls_test_record_status( psa_status_t status,
const char *func,

18
tests/src/psa_crypto_helpers.c
View file

@ -72,13 +72,29 @@ psa_status_t mbedtls_test_record_status( psa_status_t status,
#if defined(MBEDTLS_PSA_CRYPTO_EXTERNAL_RNG)
#include <test/random.h>
static int test_insecure_external_rng_enabled = 0;
void mbedtls_test_enable_insecure_external_rng( void )
{
test_insecure_external_rng_enabled = 1;
}
void mbedtls_test_disable_insecure_external_rng( void )
{
test_insecure_external_rng_enabled = 0;
}
psa_status_t mbedtls_psa_external_get_random(
mbedtls_psa_external_random_context_t *context,
uint8_t *output, size_t output_size, size_t *output_length )
{
(void) context;
if( !test_insecure_external_rng_enabled )
return( PSA_ERROR_INSUFFICIENT_ENTROPY );
/* This implementation is for test purposes only!
* Use the libc non-cryptographic random generator. */
(void) context;
mbedtls_test_rnd_std_rand( NULL, output, output_size );
*output_length = output_size;
return( PSA_SUCCESS );

4
tests/suites/main_test.function
View file

@ -164,6 +164,10 @@ $dispatch_code
*/
void execute_function_ptr(TestWrapper_t fp, void **params)
{
#if defined(MBEDTLS_PSA_CRYPTO_EXTERNAL_RNG)
mbedtls_test_enable_insecure_external_rng( );
#endif
#if defined(MBEDTLS_CHECK_PARAMS)
mbedtls_test_param_failed_location_record_t location_record;