psa_crypto: create random and drbg abstraction
Create wrapper functions around calls to CTR_DRBG and around calls to
entropy+DRBG. This is in preparation for allowing alternative DRBG
implementations that use the Mbed TLS entropy module, or complete RNG
implementations that bypass the entropy module as well.
This is purely a refactoring commit. No behavior change.
Signed-off-by: Gilles Peskine <Gilles.Peskine@arm.com>
diff --git a/library/psa_crypto.c b/library/psa_crypto.c
index c041e8e..a8d2621 100644
--- a/library/psa_crypto.c
+++ b/library/psa_crypto.c
@@ -62,7 +62,6 @@
#include "mbedtls/cipher.h"
#include "mbedtls/ccm.h"
#include "mbedtls/cmac.h"
-#include "mbedtls/ctr_drbg.h"
#include "mbedtls/des.h"
#include "mbedtls/ecdh.h"
#include "mbedtls/ecp.h"
@@ -117,10 +116,7 @@
typedef struct
{
- void (* entropy_init )( mbedtls_entropy_context *ctx );
- void (* entropy_free )( mbedtls_entropy_context *ctx );
- mbedtls_entropy_context entropy;
- mbedtls_ctr_drbg_context ctr_drbg;
+ mbedtls_psa_random_context_t rng;
unsigned initialized : 1;
unsigned rng_state : 2;
} psa_global_data_t;
@@ -869,7 +865,7 @@
/* Calculate the public key */
status = mbedtls_to_psa_error(
mbedtls_ecp_mul( &ecp->grp, &ecp->Q, &ecp->d, &ecp->grp.G,
- mbedtls_ctr_drbg_random, &global_data.ctr_drbg ) );
+ mbedtls_psa_get_random, mbedtls_psa_random_state( &global_data.rng ) ) );
if( status != PSA_SUCCESS )
return( status );
}
@@ -3651,8 +3647,8 @@
mbedtls_rsa_set_padding( rsa, MBEDTLS_RSA_PKCS_V15,
MBEDTLS_MD_NONE );
ret = mbedtls_rsa_pkcs1_sign( rsa,
- mbedtls_ctr_drbg_random,
- &global_data.ctr_drbg,
+ mbedtls_psa_get_random,
+ mbedtls_psa_random_state( &global_data.rng ),
MBEDTLS_RSA_PRIVATE,
md_alg,
(unsigned int) hash_length,
@@ -3666,8 +3662,8 @@
{
mbedtls_rsa_set_padding( rsa, MBEDTLS_RSA_PKCS_V21, md_alg );
ret = mbedtls_rsa_rsassa_pss_sign( rsa,
- mbedtls_ctr_drbg_random,
- &global_data.ctr_drbg,
+ mbedtls_psa_get_random,
+ mbedtls_psa_random_state( &global_data.rng ),
MBEDTLS_RSA_PRIVATE,
MBEDTLS_MD_NONE,
(unsigned int) hash_length,
@@ -3709,8 +3705,8 @@
mbedtls_rsa_set_padding( rsa, MBEDTLS_RSA_PKCS_V15,
MBEDTLS_MD_NONE );
ret = mbedtls_rsa_pkcs1_verify( rsa,
- mbedtls_ctr_drbg_random,
- &global_data.ctr_drbg,
+ mbedtls_psa_get_random,
+ mbedtls_psa_random_state( &global_data.rng ),
MBEDTLS_RSA_PUBLIC,
md_alg,
(unsigned int) hash_length,
@@ -3724,8 +3720,8 @@
{
mbedtls_rsa_set_padding( rsa, MBEDTLS_RSA_PKCS_V21, md_alg );
ret = mbedtls_rsa_rsassa_pss_verify( rsa,
- mbedtls_ctr_drbg_random,
- &global_data.ctr_drbg,
+ mbedtls_psa_get_random,
+ mbedtls_psa_random_state( &global_data.rng ),
MBEDTLS_RSA_PUBLIC,
MBEDTLS_MD_NONE,
(unsigned int) hash_length,
@@ -3782,8 +3778,8 @@
MBEDTLS_MPI_CHK( mbedtls_ecdsa_sign_det_ext( &ecp->grp, &r, &s,
&ecp->d, hash,
hash_length, md_alg,
- mbedtls_ctr_drbg_random,
- &global_data.ctr_drbg ) );
+ mbedtls_psa_get_random,
+ mbedtls_psa_random_state( &global_data.rng ) ) );
}
else
#endif /* defined(MBEDTLS_PSA_BUILTIN_ALG_DETERMINISTIC_ECDSA) */
@@ -3791,8 +3787,8 @@
(void) alg;
MBEDTLS_MPI_CHK( mbedtls_ecdsa_sign( &ecp->grp, &r, &s, &ecp->d,
hash, hash_length,
- mbedtls_ctr_drbg_random,
- &global_data.ctr_drbg ) );
+ mbedtls_psa_get_random,
+ mbedtls_psa_random_state( &global_data.rng ) ) );
}
MBEDTLS_MPI_CHK( mbedtls_mpi_write_binary( &r,
@@ -3837,7 +3833,7 @@
{
MBEDTLS_MPI_CHK(
mbedtls_ecp_mul( &ecp->grp, &ecp->Q, &ecp->d, &ecp->grp.G,
- mbedtls_ctr_drbg_random, &global_data.ctr_drbg ) );
+ mbedtls_psa_get_random, mbedtls_psa_random_state( &global_data.rng ) ) );
}
ret = mbedtls_ecdsa_verify( &ecp->grp, hash, hash_length,
@@ -4137,8 +4133,8 @@
{
status = mbedtls_to_psa_error(
mbedtls_rsa_pkcs1_encrypt( rsa,
- mbedtls_ctr_drbg_random,
- &global_data.ctr_drbg,
+ mbedtls_psa_get_random,
+ mbedtls_psa_random_state( &global_data.rng ),
MBEDTLS_RSA_PUBLIC,
input_length,
input,
@@ -4152,8 +4148,8 @@
psa_rsa_oaep_set_padding_mode( alg, rsa );
status = mbedtls_to_psa_error(
mbedtls_rsa_rsaes_oaep_encrypt( rsa,
- mbedtls_ctr_drbg_random,
- &global_data.ctr_drbg,
+ mbedtls_psa_get_random,
+ mbedtls_psa_random_state( &global_data.rng ),
MBEDTLS_RSA_PUBLIC,
salt, salt_length,
input_length,
@@ -4244,8 +4240,8 @@
{
status = mbedtls_to_psa_error(
mbedtls_rsa_pkcs1_decrypt( rsa,
- mbedtls_ctr_drbg_random,
- &global_data.ctr_drbg,
+ mbedtls_psa_get_random,
+ mbedtls_psa_random_state( &global_data.rng ),
MBEDTLS_RSA_PRIVATE,
output_length,
input,
@@ -4260,8 +4256,8 @@
psa_rsa_oaep_set_padding_mode( alg, rsa );
status = mbedtls_to_psa_error(
mbedtls_rsa_rsaes_oaep_decrypt( rsa,
- mbedtls_ctr_drbg_random,
- &global_data.ctr_drbg,
+ mbedtls_psa_get_random,
+ mbedtls_psa_random_state( &global_data.rng ),
MBEDTLS_RSA_PRIVATE,
salt, salt_length,
output_length,
@@ -4495,8 +4491,8 @@
status = PSA_ERROR_BUFFER_TOO_SMALL;
goto exit;
}
- ret = mbedtls_ctr_drbg_random( &global_data.ctr_drbg,
- iv, operation->iv_size );
+ ret = mbedtls_psa_get_random( mbedtls_psa_random_state( &global_data.rng ),
+ iv, operation->iv_size );
if( ret != 0 )
{
status = mbedtls_to_psa_error( ret );
@@ -6111,8 +6107,8 @@
mbedtls_ecdh_calc_secret( &ecdh,
shared_secret_length,
shared_secret, shared_secret_size,
- mbedtls_ctr_drbg_random,
- &global_data.ctr_drbg ) );
+ mbedtls_psa_get_random,
+ mbedtls_psa_random_state( &global_data.rng ) ) );
if( status != PSA_SUCCESS )
goto exit;
if( PSA_BITS_TO_BYTES( bits ) != *shared_secret_length )
@@ -6290,28 +6286,72 @@
}
+
/****************************************************************/
/* Random generation */
/****************************************************************/
+/** Initialize the PSA random generator.
+ */
+static void mbedtls_psa_random_init( mbedtls_psa_random_context_t *rng )
+{
+ /* Set default configuration if
+ * mbedtls_psa_crypto_configure_entropy_sources() hasn't been called. */
+ if( rng->entropy_init == NULL )
+ rng->entropy_init = mbedtls_entropy_init;
+ if( rng->entropy_free == NULL )
+ rng->entropy_free = mbedtls_entropy_free;
+
+ rng->entropy_init( &rng->entropy );
+#if defined(MBEDTLS_PSA_INJECT_ENTROPY) && \
+ defined(MBEDTLS_NO_DEFAULT_ENTROPY_SOURCES)
+ /* The PSA entropy injection feature depends on using NV seed as an entropy
+ * source. Add NV seed as an entropy source for PSA entropy injection. */
+ mbedtls_entropy_add_source( &rng->entropy,
+ mbedtls_nv_seed_poll, NULL,
+ MBEDTLS_ENTROPY_BLOCK_SIZE,
+ MBEDTLS_ENTROPY_SOURCE_STRONG );
+#endif
+
+ mbedtls_psa_drbg_init( mbedtls_psa_random_state( rng ) );
+}
+
+/** Deinitialize the PSA random generator.
+ */
+static void mbedtls_psa_random_free( mbedtls_psa_random_context_t *rng )
+{
+ mbedtls_psa_drbg_free( mbedtls_psa_random_state( rng ) );
+ rng->entropy_free( &rng->entropy );
+}
+
+/** Seed the PSA random generator.
+ */
+static psa_status_t mbedtls_psa_random_seed( mbedtls_psa_random_context_t *rng )
+{
+ const unsigned char drbg_seed[] = "PSA";
+ int ret = mbedtls_psa_drbg_seed( rng, drbg_seed, sizeof( drbg_seed ) - 1 );
+ return mbedtls_to_psa_error( ret );
+}
+
psa_status_t psa_generate_random( uint8_t *output,
size_t output_size )
{
int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;
GUARD_MODULE_INITIALIZED;
- while( output_size > MBEDTLS_CTR_DRBG_MAX_REQUEST )
+ while( output_size > MBEDTLS_PSA_RANDOM_MAX_REQUEST )
{
- ret = mbedtls_ctr_drbg_random( &global_data.ctr_drbg,
- output,
- MBEDTLS_CTR_DRBG_MAX_REQUEST );
+ ret = mbedtls_psa_get_random(
+ mbedtls_psa_random_state( &global_data.rng ),
+ output, MBEDTLS_PSA_RANDOM_MAX_REQUEST );
if( ret != 0 )
return( mbedtls_to_psa_error( ret ) );
- output += MBEDTLS_CTR_DRBG_MAX_REQUEST;
- output_size -= MBEDTLS_CTR_DRBG_MAX_REQUEST;
+ output += MBEDTLS_PSA_RANDOM_MAX_REQUEST;
+ output_size -= MBEDTLS_PSA_RANDOM_MAX_REQUEST;
}
- ret = mbedtls_ctr_drbg_random( &global_data.ctr_drbg, output, output_size );
+ ret = mbedtls_psa_get_random( mbedtls_psa_random_state( &global_data.rng ),
+ output, output_size );
return( mbedtls_to_psa_error( ret ) );
}
@@ -6417,8 +6457,8 @@
return( status );
mbedtls_rsa_init( &rsa, MBEDTLS_RSA_PKCS_V15, MBEDTLS_MD_NONE );
ret = mbedtls_rsa_gen_key( &rsa,
- mbedtls_ctr_drbg_random,
- &global_data.ctr_drbg,
+ mbedtls_psa_get_random,
+ mbedtls_psa_random_state( &global_data.rng ),
(unsigned int) bits,
exponent );
if( ret != 0 )
@@ -6463,8 +6503,8 @@
return( PSA_ERROR_NOT_SUPPORTED );
mbedtls_ecp_keypair_init( &ecp );
ret = mbedtls_ecp_gen_key( grp_id, &ecp,
- mbedtls_ctr_drbg_random,
- &global_data.ctr_drbg );
+ mbedtls_psa_get_random,
+ mbedtls_psa_random_state( &global_data.rng ) );
if( ret != 0 )
{
mbedtls_ecp_keypair_free( &ecp );
@@ -6550,8 +6590,8 @@
{
if( global_data.rng_state != RNG_NOT_INITIALIZED )
return( PSA_ERROR_BAD_STATE );
- global_data.entropy_init = entropy_init;
- global_data.entropy_free = entropy_free;
+ global_data.rng.entropy_init = entropy_init;
+ global_data.rng.entropy_free = entropy_free;
return( PSA_SUCCESS );
}
@@ -6560,8 +6600,7 @@
psa_wipe_all_key_slots( );
if( global_data.rng_state != RNG_NOT_INITIALIZED )
{
- mbedtls_ctr_drbg_free( &global_data.ctr_drbg );
- global_data.entropy_free( &global_data.entropy );
+ mbedtls_psa_random_free( &global_data.rng );
}
/* Wipe all remaining data, including configuration.
* In particular, this sets all state indicator to the value
@@ -6603,37 +6642,15 @@
psa_status_t psa_crypto_init( void )
{
psa_status_t status;
- const unsigned char drbg_seed[] = "PSA";
/* Double initialization is explicitly allowed. */
if( global_data.initialized != 0 )
return( PSA_SUCCESS );
- /* Set default configuration if
- * mbedtls_psa_crypto_configure_entropy_sources() hasn't been called. */
- if( global_data.entropy_init == NULL )
- global_data.entropy_init = mbedtls_entropy_init;
- if( global_data.entropy_free == NULL )
- global_data.entropy_free = mbedtls_entropy_free;
-
- /* Initialize the random generator. */
- global_data.entropy_init( &global_data.entropy );
-#if defined(MBEDTLS_PSA_INJECT_ENTROPY) && \
- defined(MBEDTLS_NO_DEFAULT_ENTROPY_SOURCES)
- /* The PSA entropy injection feature depends on using NV seed as an entropy
- * source. Add NV seed as an entropy source for PSA entropy injection. */
- mbedtls_entropy_add_source( &global_data.entropy,
- mbedtls_nv_seed_poll, NULL,
- MBEDTLS_ENTROPY_BLOCK_SIZE,
- MBEDTLS_ENTROPY_SOURCE_STRONG );
-#endif
- mbedtls_ctr_drbg_init( &global_data.ctr_drbg );
+ /* Initialize and seed the random generator. */
+ mbedtls_psa_random_init( &global_data.rng );
global_data.rng_state = RNG_INITIALIZED;
- status = mbedtls_to_psa_error(
- mbedtls_ctr_drbg_seed( &global_data.ctr_drbg,
- mbedtls_entropy_func,
- &global_data.entropy,
- drbg_seed, sizeof( drbg_seed ) - 1 ) );
+ status = mbedtls_psa_random_seed( &global_data.rng );
if( status != PSA_SUCCESS )
goto exit;
global_data.rng_state = RNG_SEEDED;
diff --git a/library/psa_crypto_random.h b/library/psa_crypto_random.h
index c90891d..95974d9 100644
--- a/library/psa_crypto_random.h
+++ b/library/psa_crypto_random.h
@@ -22,5 +22,109 @@
#ifndef PSA_CRYPTO_RANDOM_H
#define PSA_CRYPTO_RANDOM_H
+/* Currently, the only supported RNG is Mbed TLS's CTR_DRBG seeded with
+ * mbedtls_entropy_func(). */
+
+#include "mbedtls/ctr_drbg.h"
+#include "mbedtls/entropy.h"
+
+/** The type of the PSA DRBG context.
+ */
+typedef mbedtls_ctr_drbg_context mbedtls_psa_drbg_context_t;
+
+/** Initialize the PSA DRBG.
+ *
+ * \param p_rng Pointer to the Mbed TLS DRBG state.
+ */
+static inline void mbedtls_psa_drbg_init( mbedtls_psa_drbg_context_t *p_rng )
+{
+ mbedtls_ctr_drbg_init( p_rng );
+}
+
+/** Deinitialize the PSA DRBG.
+ *
+ * \param p_rng Pointer to the Mbed TLS DRBG state.
+ */
+static inline void mbedtls_psa_drbg_free( mbedtls_psa_drbg_context_t *p_rng )
+{
+ mbedtls_ctr_drbg_free( p_rng );
+}
+
+/** The type of the PSA random generator context.
+ *
+ * The random generator context is composed of an entropy context and
+ * a DRBG context.
+ */
+typedef struct
+{
+ void (* entropy_init )( mbedtls_entropy_context *ctx );
+ void (* entropy_free )( mbedtls_entropy_context *ctx );
+ mbedtls_entropy_context entropy;
+ mbedtls_psa_drbg_context_t drbg;
+} mbedtls_psa_random_context_t;
+
+/** 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
+ * obtain the \p p_rng parameter.
+ *
+ * \param p_rng The CTR_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.
+ * \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.
+ *
+ * \return \c 0 on success.
+ * \return #MBEDTLS_ERR_CTR_DRBG_ENTROPY_SOURCE_FAILED or
+ * #MBEDTLS_ERR_CTR_DRBG_REQUEST_TOO_BIG on failure.
+ */
+static inline int mbedtls_psa_get_random( void *p_rng,
+ unsigned char *output,
+ size_t output_len )
+{
+ return( mbedtls_ctr_drbg_random( p_rng, output, output_len ) );
+}
+
+/** The maximum number of bytes that mbedtls_psa_get_random() is expected to
+ * return.
+ */
+#define MBEDTLS_PSA_RANDOM_MAX_REQUEST MBEDTLS_CTR_DRBG_MAX_REQUEST
+
+/** Retrieve the DRBG state from the PSA RNG state.
+ *
+ * \param rng Pointer to the PSA random generator state.
+ *
+ * \return The DRBG state (\c p_rng argument ).
+ */
+static inline mbedtls_psa_drbg_context_t *mbedtls_psa_random_state(
+ mbedtls_psa_random_context_t *rng )
+{
+ return( &rng->drbg );
+}
+
+
+/** Seed the PSA DRBG.
+ *
+ * \param rng DRBG context to be seeded.
+ * \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.
+ * \param len The length of the personalization string.
+ *
+ * \return \c 0 on success.
+ * \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,
+ const unsigned char *custom, size_t len )
+{
+ return( mbedtls_ctr_drbg_seed( mbedtls_psa_random_state( rng ),
+ mbedtls_entropy_func,
+ &rng->entropy,
+ custom, len ) );
+}
#endif /* PSA_CRYPTO_RANDOM_H */