Replace mbedtls_psa_random_state( ... ) by MBEDTLS_PSA_RANDOM_STATE
Hide the obtention of the pointer to the RNG state behind a macro.
To make it possible to use this macro in a module other than
psa_crypto.c, which will happen in the future, make sure that the
definition of the macro does not reference internal variables of
psa_crypto.c. For this purpose, in the internal-DRBG case, export a
symbol containing the address of the DRBG state.
When the RNG state is a pointer a DRBG state, just keep this pointer
in a variable: there's no need to store a pointer to a larger structure.
Signed-off-by: Gilles Peskine <Gilles.Peskine@arm.com>
diff --git a/library/psa_crypto_random.h b/library/psa_crypto_random.h
index 0f13c13..cc1222a 100644
--- a/library/psa_crypto_random.h
+++ b/library/psa_crypto_random.h
@@ -42,11 +42,7 @@
return( MBEDTLS_ERR_ENTROPY_SOURCE_FAILED );
}
-static inline void *mbedtls_psa_random_state( mbedtls_psa_random_context_t *rng )
-{
- (void) rng;
- return( NULL );
-}
+#define MBEDTLS_PSA_RANDOM_STATE NULL
#else /* MBEDTLS_PSA_CRYPTO_EXTERNAL_RNG */
@@ -135,13 +131,11 @@
/** Return random data.
*
* This function is suitable as the \p f_rng parameter to Mbed TLS functions
- * that require a random generator. Use mbedtls_psa_random_state() to
+ * that require a random generator. Use #MBEDTLS_PSA_RANDOM_STATE to
* obtain the \p p_rng parameter.
*
* \param p_rng The DRBG context. This must be
- * mbedtls_psa_random_state( \c rng )
- * where \c rng is a pointer to a
- * ::mbedtls_psa_random_context_t structure.
+ * #MBEDTLS_PSA_RANDOM_STATE.
* \param output The buffer to fill.
* \param output_len The length of the buffer in bytes.
* It must be at most #MBEDTLS_PSA_RANDOM_MAX_REQUEST.
@@ -170,21 +164,26 @@
#define MBEDTLS_PSA_RANDOM_MAX_REQUEST MBEDTLS_HMAC_DRBG_MAX_REQUEST
#endif
-/** Retrieve the DRBG state from the PSA RNG state.
+/** A pointer to the PSA DRBG state.
*
- * \param rng Pointer to the PSA random generator state.
- *
- * \return The DRBG state (\c p_rng argument ).
+ * This variable is only intended to be used through the macro
+ * #MBEDTLS_PSA_RANDOM_STATE.
*/
-static inline mbedtls_psa_drbg_context_t *mbedtls_psa_random_state(
- mbedtls_psa_random_context_t *rng )
-{
- return( &rng->drbg );
-}
+extern mbedtls_psa_drbg_context_t *const mbedtls_psa_random_state;
+
+/** A pointer to the PSA DRBG state.
+ *
+ * This macro expnds to an expression that is suitable as the \c p_rng
+ * parameter to pass to mbedtls_psa_get_random().
+ *
+ * This macro exists in all configurations where the psa_crypto module is
+ * enabled. Its expansion depends on the configuration.
+ */
+#define MBEDTLS_PSA_RANDOM_STATE mbedtls_psa_random_state
/** Seed the PSA DRBG.
*
- * \param rng DRBG context to be seeded.
+ * \param entropy An entropy context to read the seed from.
* \param custom The personalization string.
* This can be \c NULL, in which case the personalization
* string is empty regardless of the value of \p len.
@@ -194,21 +193,21 @@
* \return An Mbed TLS error code (\c MBEDTLS_ERR_xxx) on failure.
*/
static inline int mbedtls_psa_drbg_seed(
- mbedtls_psa_random_context_t *rng,
+ mbedtls_entropy_context *entropy,
const unsigned char *custom, size_t len )
{
#if defined(MBEDTLS_CTR_DRBG_C)
- return( mbedtls_ctr_drbg_seed( mbedtls_psa_random_state( rng ),
+ return( mbedtls_ctr_drbg_seed( MBEDTLS_PSA_RANDOM_STATE,
mbedtls_entropy_func,
- &rng->entropy,
+ entropy,
custom, len ) );
#elif defined(MBEDTLS_HMAC_DRBG_C)
const mbedtls_md_info_t *md_info =
mbedtls_md_info_from_type( MBEDTLS_PSA_HMAC_DRBG_MD_TYPE );
- return( mbedtls_hmac_drbg_seed( mbedtls_psa_random_state( rng ),
+ return( mbedtls_hmac_drbg_seed( MBEDTLS_PSA_RANDOM_STATE,
md_info,
mbedtls_entropy_func,
- &rng->entropy,
+ entropy,
custom, len ) );
#endif
}