psa: mgmt: Add key slot access counter
Add key slot access counter to be able to
state if a key slot containing the description
of a permanent key can be reset or reset
and re-used.
Signed-off-by: Ronald Cron <ronald.cron@arm.com>
diff --git a/library/psa_crypto.c b/library/psa_crypto.c
index 2c4878d..a510e3c 100644
--- a/library/psa_crypto.c
+++ b/library/psa_crypto.c
@@ -1189,20 +1189,25 @@
/** Retrieve a slot which must contain a key. The key must have allow all the
* usage flags set in \p usage. If \p alg is nonzero, the key must allow
- * operations with this algorithm. */
+ * operations with this algorithm.
+ *
+ * On success, the access counter of the returned key slot is incremented by
+ * one. It is the responsibility of the caller to call
+ * psa_decrement_key_slot_access_count() when it does not access the key slot
+ * anymore.
+ */
static psa_status_t psa_get_key_from_slot( mbedtls_svc_key_id_t key,
psa_key_slot_t **p_slot,
psa_key_usage_t usage,
psa_algorithm_t alg )
{
- psa_status_t status;
- psa_key_slot_t *slot = NULL;
+ psa_status_t status = PSA_ERROR_CORRUPTION_DETECTED;
+ psa_key_slot_t *slot;
- *p_slot = NULL;
-
- status = psa_get_key_slot( key, &slot );
+ status = psa_get_key_slot( key, p_slot );
if( status != PSA_SUCCESS )
return( status );
+ slot = *p_slot;
/* Enforce that usage policy for the key slot contains all the flags
* required by the usage parameter. There is one exception: public
@@ -1210,15 +1215,22 @@
* if they had the export flag. */
if( PSA_KEY_TYPE_IS_PUBLIC_KEY( slot->attr.type ) )
usage &= ~PSA_KEY_USAGE_EXPORT;
+
+ status = PSA_ERROR_NOT_PERMITTED;
if( ( slot->attr.policy.usage & usage ) != usage )
- return( PSA_ERROR_NOT_PERMITTED );
+ goto error;
/* Enforce that the usage policy permits the requested algortihm. */
if( alg != 0 && ! psa_key_policy_permits( &slot->attr.policy, alg ) )
- return( PSA_ERROR_NOT_PERMITTED );
+ goto error;
- *p_slot = slot;
return( PSA_SUCCESS );
+
+error:
+ *p_slot = NULL;
+ psa_decrement_key_slot_access_count( slot );
+
+ return( status );
}
/** Retrieve a slot which must contain a transparent key.
@@ -1228,6 +1240,11 @@
*
* This is a temporary function to use instead of psa_get_key_from_slot()
* until secure element support is fully implemented.
+ *
+ * On success, the access counter of the returned key slot is incremented by
+ * one. It is the responsibility of the caller to call
+ * psa_decrement_key_slot_access_count() when it does not access the key slot
+ * anymore.
*/
#if defined(MBEDTLS_PSA_CRYPTO_SE_C)
static psa_status_t psa_get_transparent_key( mbedtls_svc_key_id_t key,
@@ -1238,11 +1255,14 @@
psa_status_t status = psa_get_key_from_slot( key, p_slot, usage, alg );
if( status != PSA_SUCCESS )
return( status );
+
if( psa_key_slot_is_external( *p_slot ) )
{
+ psa_decrement_key_slot_access_count( *p_slot );
*p_slot = NULL;
return( PSA_ERROR_NOT_SUPPORTED );
}
+
return( PSA_SUCCESS );
}
#else /* MBEDTLS_PSA_CRYPTO_SE_C */
@@ -1473,8 +1493,9 @@
psa_status_t psa_get_key_attributes( mbedtls_svc_key_id_t key,
psa_key_attributes_t *attributes )
{
+ psa_status_t status = PSA_ERROR_CORRUPTION_DETECTED;
+ psa_status_t decrement_status = PSA_ERROR_CORRUPTION_DETECTED;
psa_key_slot_t *slot;
- psa_status_t status;
psa_reset_key_attributes( attributes );
@@ -1528,7 +1549,10 @@
if( status != PSA_SUCCESS )
psa_reset_key_attributes( attributes );
- return( status );
+
+ decrement_status = psa_decrement_key_slot_access_count( slot );
+
+ return( ( status == PSA_SUCCESS ) ? decrement_status : status );
}
#if defined(MBEDTLS_PSA_CRYPTO_SE_C)
@@ -1688,8 +1712,9 @@
size_t data_size,
size_t *data_length )
{
+ psa_status_t status = PSA_ERROR_CORRUPTION_DETECTED;
+ psa_status_t decrement_status = PSA_ERROR_CORRUPTION_DETECTED;
psa_key_slot_t *slot;
- psa_status_t status;
/* Set the key to empty now, so that even when there are errors, we always
* set data_length to a value between 0 and data_size. On error, setting
@@ -1703,8 +1728,11 @@
status = psa_get_key_from_slot( key, &slot, PSA_KEY_USAGE_EXPORT, 0 );
if( status != PSA_SUCCESS )
return( status );
- return( psa_internal_export_key( slot, data, data_size,
- data_length, 0 ) );
+
+ status = psa_internal_export_key( slot, data, data_size, data_length, 0 );
+ decrement_status = psa_decrement_key_slot_access_count( slot );
+
+ return( ( status == PSA_SUCCESS ) ? decrement_status : status );
}
psa_status_t psa_export_public_key( mbedtls_svc_key_id_t key,
@@ -1712,8 +1740,9 @@
size_t data_size,
size_t *data_length )
{
+ psa_status_t status = PSA_ERROR_CORRUPTION_DETECTED;
+ psa_status_t decrement_status = PSA_ERROR_CORRUPTION_DETECTED;
psa_key_slot_t *slot;
- psa_status_t status;
/* Set the key to empty now, so that even when there are errors, we always
* set data_length to a value between 0 and data_size. On error, setting
@@ -1725,8 +1754,11 @@
status = psa_get_key_from_slot( key, &slot, 0, 0 );
if( status != PSA_SUCCESS )
return( status );
- return( psa_internal_export_key( slot, data, data_size,
- data_length, 1 ) );
+
+ status = psa_internal_export_key( slot, data, data_size, data_length, 1 );
+ decrement_status = psa_decrement_key_slot_access_count( slot );
+
+ return( ( status == PSA_SUCCESS ) ? decrement_status : status );
}
#if defined(static_assert)
@@ -1833,6 +1865,11 @@
* In case of failure at any step, stop the sequence and call
* psa_fail_key_creation().
*
+ * On success, the access counter of the returned key slot is incremented by
+ * one. It is the responsibility of the caller to call
+ * psa_decrement_key_slot_access_count() when it does not access the key slot
+ * anymore.
+ *
* \param method An identification of the calling function.
* \param[in] attributes Key attributes for the new key.
* \param[out] key On success, identifier of the key. Note that the
@@ -1943,7 +1980,6 @@
#endif /* MBEDTLS_PSA_CRYPTO_SE_C */
*key = slot->attr.id;
-
return( PSA_SUCCESS );
}
@@ -2203,6 +2239,9 @@
psa_fail_key_creation( slot, driver );
*key = MBEDTLS_SVC_KEY_ID_INIT;
}
+ else
+ status = psa_decrement_key_slot_access_count( slot );
+
return( status );
}
@@ -2233,9 +2272,10 @@
exit:
if( status != PSA_SUCCESS )
- {
psa_fail_key_creation( slot, driver );
- }
+ else
+ status = psa_decrement_key_slot_access_count( slot );
+
/* Registration doesn't keep the key in RAM. */
psa_close_key( key );
return( status );
@@ -2261,7 +2301,8 @@
const psa_key_attributes_t *specified_attributes,
mbedtls_svc_key_id_t *target_key )
{
- psa_status_t status;
+ psa_status_t status = PSA_ERROR_CORRUPTION_DETECTED;
+ psa_status_t decrement_status = PSA_ERROR_CORRUPTION_DETECTED;
psa_key_slot_t *source_slot = NULL;
psa_key_slot_t *target_slot = NULL;
psa_key_attributes_t actual_attributes = *specified_attributes;
@@ -2308,7 +2349,12 @@
psa_fail_key_creation( target_slot, driver );
*target_key = MBEDTLS_SVC_KEY_ID_INIT;
}
- return( status );
+ else
+ status = psa_decrement_key_slot_access_count( target_slot );
+
+ decrement_status = psa_decrement_key_slot_access_count( source_slot );
+
+ return( ( status == PSA_SUCCESS ) ? decrement_status : status );
}
@@ -3094,7 +3140,8 @@
psa_algorithm_t alg,
int is_sign )
{
- psa_status_t status;
+ psa_status_t status = PSA_ERROR_CORRUPTION_DETECTED;
+ psa_status_t decrement_status = PSA_ERROR_CORRUPTION_DETECTED;
psa_key_slot_t *slot;
size_t key_bits;
psa_key_usage_t usage =
@@ -3203,7 +3250,10 @@
{
operation->key_set = 1;
}
- return( status );
+
+ decrement_status = psa_decrement_key_slot_access_count( slot );
+
+ return( ( status == PSA_SUCCESS ) ? decrement_status : status );
}
psa_status_t psa_mac_sign_setup( psa_mac_operation_t *operation,
@@ -3700,8 +3750,9 @@
size_t signature_size,
size_t *signature_length )
{
+ psa_status_t status = PSA_ERROR_CORRUPTION_DETECTED;
+ psa_status_t decrement_status = PSA_ERROR_CORRUPTION_DETECTED;
psa_key_slot_t *slot;
- psa_status_t status;
*signature_length = signature_size;
/* Immediately reject a zero-length signature buffer. This guarantees
@@ -3807,7 +3858,10 @@
memset( signature, '!', signature_size );
/* If signature_size is 0 then we have nothing to do. We must not call
* memset because signature may be NULL in this case. */
- return( status );
+
+ decrement_status = psa_decrement_key_slot_access_count( slot );
+
+ return( ( status == PSA_SUCCESS ) ? decrement_status : status );
}
psa_status_t psa_verify_hash( mbedtls_svc_key_id_t key,
@@ -3817,8 +3871,9 @@
const uint8_t *signature,
size_t signature_length )
{
+ psa_status_t status = PSA_ERROR_CORRUPTION_DETECTED;
+ psa_status_t decrement_status = PSA_ERROR_CORRUPTION_DETECTED;
psa_key_slot_t *slot;
- psa_status_t status;
status = psa_get_key_from_slot( key, &slot,
PSA_KEY_USAGE_VERIFY_HASH, alg );
@@ -3834,7 +3889,7 @@
signature_length );
if( status != PSA_ERROR_NOT_SUPPORTED ||
psa_key_lifetime_is_external( slot->attr.lifetime ) )
- return status;
+ goto exit;
#if defined(MBEDTLS_RSA_C)
if( PSA_KEY_TYPE_IS_RSA( slot->attr.type ) )
@@ -3846,7 +3901,7 @@
slot->data.key.bytes,
&rsa );
if( status != PSA_SUCCESS )
- return( status );
+ goto exit;
status = psa_rsa_verify( rsa,
alg,
@@ -3854,7 +3909,7 @@
signature, signature_length );
mbedtls_rsa_free( rsa );
mbedtls_free( rsa );
- return( status );
+ goto exit;
}
else
#endif /* defined(MBEDTLS_RSA_C) */
@@ -3870,25 +3925,31 @@
slot->data.key.bytes,
&ecp );
if( status != PSA_SUCCESS )
- return( status );
+ goto exit;
status = psa_ecdsa_verify( ecp,
hash, hash_length,
signature, signature_length );
mbedtls_ecp_keypair_free( ecp );
mbedtls_free( ecp );
- return( status );
+ goto exit;
}
else
#endif /* defined(MBEDTLS_PSA_BUILTIN_ALG_ECDSA) || defined(MBEDTLS_PSA_BUILTIN_ALG_DETERMINISTIC_ECDSA) */
{
- return( PSA_ERROR_INVALID_ARGUMENT );
+ status = PSA_ERROR_INVALID_ARGUMENT;
+ goto exit;
}
}
else
#endif /* defined(MBEDTLS_ECP_C) */
{
- return( PSA_ERROR_NOT_SUPPORTED );
+ status = PSA_ERROR_NOT_SUPPORTED;
}
+
+exit:
+ decrement_status = psa_decrement_key_slot_access_count( slot );
+
+ return( ( status == PSA_SUCCESS ) ? decrement_status : status );
}
#if defined(MBEDTLS_RSA_C) && defined(MBEDTLS_PKCS1_V21)
@@ -3912,8 +3973,9 @@
size_t output_size,
size_t *output_length )
{
+ psa_status_t status = PSA_ERROR_CORRUPTION_DETECTED;
+ psa_status_t decrement_status = PSA_ERROR_CORRUPTION_DETECTED;
psa_key_slot_t *slot;
- psa_status_t status;
(void) input;
(void) input_length;
@@ -3931,7 +3993,10 @@
return( status );
if( ! ( PSA_KEY_TYPE_IS_PUBLIC_KEY( slot->attr.type ) ||
PSA_KEY_TYPE_IS_KEY_PAIR( slot->attr.type ) ) )
- return( PSA_ERROR_INVALID_ARGUMENT );
+ {
+ status = PSA_ERROR_INVALID_ARGUMENT;
+ goto exit;
+ }
#if defined(MBEDTLS_RSA_C)
if( PSA_KEY_TYPE_IS_RSA( slot->attr.type ) )
@@ -3989,13 +4054,17 @@
mbedtls_rsa_free( rsa );
mbedtls_free( rsa );
- return( status );
}
else
#endif /* defined(MBEDTLS_RSA_C) */
{
- return( PSA_ERROR_NOT_SUPPORTED );
+ status = PSA_ERROR_NOT_SUPPORTED;
}
+
+exit:
+ decrement_status = psa_decrement_key_slot_access_count( slot );
+
+ return( ( status == PSA_SUCCESS ) ? decrement_status : status );
}
psa_status_t psa_asymmetric_decrypt( mbedtls_svc_key_id_t key,
@@ -4008,8 +4077,9 @@
size_t output_size,
size_t *output_length )
{
+ psa_status_t status = PSA_ERROR_CORRUPTION_DETECTED;
+ psa_status_t decrement_status = PSA_ERROR_CORRUPTION_DETECTED;
psa_key_slot_t *slot;
- psa_status_t status;
(void) input;
(void) input_length;
@@ -4026,7 +4096,10 @@
if( status != PSA_SUCCESS )
return( status );
if( ! PSA_KEY_TYPE_IS_KEY_PAIR( slot->attr.type ) )
- return( PSA_ERROR_INVALID_ARGUMENT );
+ {
+ status = PSA_ERROR_INVALID_ARGUMENT;
+ goto exit;
+ }
#if defined(MBEDTLS_RSA_C)
if( slot->attr.type == PSA_KEY_TYPE_RSA_KEY_PAIR )
@@ -4037,7 +4110,7 @@
slot->data.key.bytes,
&rsa );
if( status != PSA_SUCCESS )
- return( status );
+ goto exit;
if( input_length != mbedtls_rsa_get_len( rsa ) )
{
@@ -4084,13 +4157,17 @@
rsa_exit:
mbedtls_rsa_free( rsa );
mbedtls_free( rsa );
- return( status );
}
else
#endif /* defined(MBEDTLS_RSA_C) */
{
- return( PSA_ERROR_NOT_SUPPORTED );
+ status = PSA_ERROR_NOT_SUPPORTED;
}
+
+exit:
+ decrement_status = psa_decrement_key_slot_access_count( slot );
+
+ return( ( status == PSA_SUCCESS ) ? decrement_status : status );
}
@@ -4104,8 +4181,9 @@
psa_algorithm_t alg,
mbedtls_operation_t cipher_operation )
{
+ psa_status_t status = PSA_ERROR_CORRUPTION_DETECTED;
+ psa_status_t decrement_status = PSA_ERROR_CORRUPTION_DETECTED;
int ret = 0;
- psa_status_t status = PSA_ERROR_GENERIC_ERROR;
psa_key_slot_t *slot;
size_t key_bits;
const mbedtls_cipher_info_t *cipher_info = NULL;
@@ -4249,7 +4327,10 @@
}
else
psa_cipher_abort( operation );
- return( status );
+
+ decrement_status = psa_decrement_key_slot_access_count( slot );
+
+ return( ( status == PSA_SUCCESS ) ? decrement_status : status );
}
psa_status_t psa_cipher_encrypt_setup( psa_cipher_operation_t *operation,
@@ -4615,6 +4696,7 @@
const mbedtls_cipher_info_t *cipher_info;
union
{
+ unsigned dummy; /* Make the union non-empty even with no supported algorithms. */
#if defined(MBEDTLS_CCM_C)
mbedtls_ccm_context ccm;
#endif /* MBEDTLS_CCM_C */
@@ -4630,6 +4712,8 @@
uint8_t tag_length;
} aead_operation_t;
+#define AEAD_OPERATION_INIT {0, 0, {0}, 0, 0, 0}
+
static void psa_aead_abort_internal( aead_operation_t *operation )
{
switch( operation->core_alg )
@@ -4645,6 +4729,8 @@
break;
#endif /* MBEDTLS_GCM_C */
}
+
+ psa_decrement_key_slot_access_count( operation->slot );
}
static psa_status_t psa_aead_setup( aead_operation_t *operation,
@@ -4666,7 +4752,10 @@
mbedtls_cipher_info_from_psa( alg, operation->slot->attr.type, key_bits,
&cipher_id );
if( operation->cipher_info == NULL )
- return( PSA_ERROR_NOT_SUPPORTED );
+ {
+ status = PSA_ERROR_NOT_SUPPORTED;
+ goto cleanup;
+ }
switch( PSA_ALG_AEAD_WITH_TAG_LENGTH( alg, 0 ) )
{
@@ -4678,7 +4767,10 @@
* The call to mbedtls_ccm_encrypt_and_tag or
* mbedtls_ccm_auth_decrypt will validate the tag length. */
if( PSA_BLOCK_CIPHER_BLOCK_SIZE( operation->slot->attr.type ) != 16 )
- return( PSA_ERROR_INVALID_ARGUMENT );
+ {
+ status = PSA_ERROR_INVALID_ARGUMENT;
+ goto cleanup;
+ }
mbedtls_ccm_init( &operation->ctx.ccm );
status = mbedtls_to_psa_error(
mbedtls_ccm_setkey( &operation->ctx.ccm, cipher_id,
@@ -4697,7 +4789,10 @@
* The call to mbedtls_gcm_crypt_and_tag or
* mbedtls_gcm_auth_decrypt will validate the tag length. */
if( PSA_BLOCK_CIPHER_BLOCK_SIZE( operation->slot->attr.type ) != 16 )
- return( PSA_ERROR_INVALID_ARGUMENT );
+ {
+ status = PSA_ERROR_INVALID_ARGUMENT;
+ goto cleanup;
+ }
mbedtls_gcm_init( &operation->ctx.gcm );
status = mbedtls_to_psa_error(
mbedtls_gcm_setkey( &operation->ctx.gcm, cipher_id,
@@ -4714,7 +4809,10 @@
operation->full_tag_length = 16;
/* We only support the default tag length. */
if( alg != PSA_ALG_CHACHA20_POLY1305 )
- return( PSA_ERROR_NOT_SUPPORTED );
+ {
+ status = PSA_ERROR_NOT_SUPPORTED;
+ goto cleanup;
+ }
mbedtls_chachapoly_init( &operation->ctx.chachapoly );
status = mbedtls_to_psa_error(
mbedtls_chachapoly_setkey( &operation->ctx.chachapoly,
@@ -4725,7 +4823,8 @@
#endif /* MBEDTLS_CHACHAPOLY_C */
default:
- return( PSA_ERROR_NOT_SUPPORTED );
+ status = PSA_ERROR_NOT_SUPPORTED;
+ goto cleanup;
}
if( PSA_AEAD_TAG_LENGTH( alg ) > operation->full_tag_length )
@@ -4755,7 +4854,7 @@
size_t *ciphertext_length )
{
psa_status_t status;
- aead_operation_t operation;
+ aead_operation_t operation = AEAD_OPERATION_INIT;
uint8_t *tag;
*ciphertext_length = 0;
@@ -4869,7 +4968,7 @@
size_t *plaintext_length )
{
psa_status_t status;
- aead_operation_t operation;
+ aead_operation_t operation = AEAD_OPERATION_INIT;
const uint8_t *tag = NULL;
*plaintext_length = 0;
@@ -5409,6 +5508,9 @@
psa_fail_key_creation( slot, driver );
*key = MBEDTLS_SVC_KEY_ID_INIT;
}
+ else
+ status = psa_decrement_key_slot_access_count( slot );
+
return( status );
}
@@ -5772,8 +5874,9 @@
psa_key_derivation_step_t step,
mbedtls_svc_key_id_t key )
{
+ psa_status_t status = PSA_ERROR_CORRUPTION_DETECTED;
+ psa_status_t decrement_status = PSA_ERROR_CORRUPTION_DETECTED;
psa_key_slot_t *slot;
- psa_status_t status;
status = psa_get_transparent_key( key, &slot,
PSA_KEY_USAGE_DERIVE, operation->alg );
@@ -5788,10 +5891,14 @@
if( step == PSA_KEY_DERIVATION_INPUT_SECRET )
operation->can_output_key = 1;
- return( psa_key_derivation_input_internal( operation,
- step, slot->attr.type,
- slot->data.key.data,
- slot->data.key.bytes ) );
+ status = psa_key_derivation_input_internal( operation,
+ step, slot->attr.type,
+ slot->data.key.data,
+ slot->data.key.bytes );
+
+ decrement_status = psa_decrement_key_slot_access_count( slot );
+
+ return( ( status == PSA_SUCCESS ) ? decrement_status : status );
}
@@ -5939,8 +6046,10 @@
const uint8_t *peer_key,
size_t peer_key_length )
{
+ psa_status_t status = PSA_ERROR_CORRUPTION_DETECTED;
+ psa_status_t decrement_status = PSA_ERROR_CORRUPTION_DETECTED;
psa_key_slot_t *slot;
- psa_status_t status;
+
if( ! PSA_ALG_IS_KEY_AGREEMENT( operation->alg ) )
return( PSA_ERROR_INVALID_ARGUMENT );
status = psa_get_transparent_key( private_key, &slot,
@@ -5959,7 +6068,10 @@
if( step == PSA_KEY_DERIVATION_INPUT_SECRET )
operation->can_output_key = 1;
}
- return( status );
+
+ decrement_status = psa_decrement_key_slot_access_count( slot );
+
+ return( ( status == PSA_SUCCESS ) ? decrement_status : status );
}
psa_status_t psa_raw_key_agreement( psa_algorithm_t alg,
@@ -5970,8 +6082,9 @@
size_t output_size,
size_t *output_length )
{
- psa_key_slot_t *slot;
- psa_status_t status;
+ psa_status_t status = PSA_ERROR_CORRUPTION_DETECTED;
+ psa_status_t decrement_status = PSA_ERROR_CORRUPTION_DETECTED;
+ psa_key_slot_t *slot = NULL;
if( ! PSA_ALG_IS_KEY_AGREEMENT( alg ) )
{
@@ -6001,7 +6114,10 @@
psa_generate_random( output, output_size );
*output_length = output_size;
}
- return( status );
+
+ decrement_status = psa_decrement_key_slot_access_count( slot );
+
+ return( ( status == PSA_SUCCESS ) ? decrement_status : status );
}
@@ -6250,6 +6366,9 @@
psa_fail_key_creation( slot, driver );
*key = MBEDTLS_SVC_KEY_ID_INIT;
}
+ else
+ status = psa_decrement_key_slot_access_count( slot );
+
return( status );
}
diff --git a/library/psa_crypto_core.h b/library/psa_crypto_core.h
index 86d804b..32d1d60 100644
--- a/library/psa_crypto_core.h
+++ b/library/psa_crypto_core.h
@@ -36,6 +36,33 @@
typedef struct
{
psa_core_key_attributes_t attr;
+
+ /*
+ * Number of on-going accesses, read and/or write, to the key slot by the
+ * library.
+ *
+ * This counter is incremented by one each time a library function
+ * retrieves through one of the dedicated internal API a pointer to the
+ * key slot.
+ *
+ * This counter is decremented by one each time a library function stops
+ * accessing to the key slot and states it by calling the
+ * psa_decrement_key_slot_access_count() API.
+ *
+ * This counter is used to prevent resetting the key slot while the library
+ * may access it. For example, such control is needed in the following
+ * scenarios:
+ * . In case of key slot starvation, all key slots contain the description
+ * of a key, and the library asks for the description of a permanent
+ * key not present in the key slots, the key slots currently accessed by
+ * the library cannot be reclaimed to free a key slot to load the
+ * permanent key.
+ * . In case of a multi-threaded application where one thread asks to close
+ * or purge or destroy a key while it is in used by the library through
+ * another thread.
+ */
+ size_t access_count;
+
union
{
/* Dynamically allocated key data buffer.
@@ -74,6 +101,20 @@
return( slot->attr.type != 0 );
}
+/** Test whether a key slot is accessed.
+ *
+ * A key slot is accessed iff its access counter is strickly greater than
+ * 0.
+ *
+ * \param[in] slot The key slot to test.
+ *
+ * \return 1 if the slot is accessed, 0 otherwise.
+ */
+static inline int psa_is_key_slot_accessed( const psa_key_slot_t *slot )
+{
+ return( slot->access_count > 0 );
+}
+
/** Retrieve flags from psa_key_slot_t::attr::core::flags.
*
* \param[in] slot The key slot to query.
diff --git a/library/psa_crypto_slot_management.c b/library/psa_crypto_slot_management.c
index 7308f6f..e207477 100644
--- a/library/psa_crypto_slot_management.c
+++ b/library/psa_crypto_slot_management.c
@@ -88,6 +88,11 @@
* key with identifier key_id can only be stored in slot of index
* ( key_id - #PSA_KEY_ID_VOLATILE_MIN ).
*
+ * On success, the access counter of the returned key slot is incremented by
+ * one. It is the responsibility of the caller to call
+ * psa_decrement_key_slot_access_count() when it does not access the key slot
+ * anymore.
+ *
* \param key Key identifier to query.
* \param[out] p_slot On success, `*p_slot` contains a pointer to the
* key slot containing the description of the key
@@ -135,7 +140,10 @@
}
if( status == PSA_SUCCESS )
+ {
*p_slot = slot;
+ psa_increment_key_slot_access_count( slot );
+ }
return( status );
}
@@ -177,9 +185,12 @@
*volatile_key_id = PSA_KEY_ID_VOLATILE_MIN +
( (psa_key_id_t)slot_idx ) - 1;
+ psa_increment_key_slot_access_count( *p_slot );
+
return( PSA_SUCCESS );
}
}
+
*p_slot = NULL;
return( PSA_ERROR_INSUFFICIENT_MEMORY );
}
@@ -232,6 +243,10 @@
if( ! global_data.key_slots_initialized )
return( PSA_ERROR_BAD_STATE );
+ /*
+ * On success, the pointer to the slot is passed directly to the caller
+ * thus no need to decrement the key slot access counter here.
+ */
status = psa_search_key_in_slots( key, p_slot );
if( status != PSA_ERROR_DOES_NOT_EXIST )
return( status );
@@ -257,6 +272,36 @@
}
+psa_status_t psa_decrement_key_slot_access_count( psa_key_slot_t *slot )
+{
+ if( slot == NULL )
+ return( PSA_SUCCESS );
+
+ if( slot->access_count > 0 )
+ {
+ slot->access_count--;
+ return( PSA_SUCCESS );
+ }
+
+ /*
+ * As the return error code may not be handled in case of multiple errors,
+ * do our best to report if the access counter is equal to zero: if
+ * available call MBEDTLS_PARAM_FAILED that may terminate execution (if
+ * called as part of the execution of a unit test suite this will stop the
+ * test suite execution) and if MBEDTLS_PARAM_FAILED does not terminate
+ * execution ouput an error message on standard error output.
+ */
+#ifdef MBEDTLS_CHECK_PARAMS
+ MBEDTLS_PARAM_FAILED( slot->access_count > 0 );
+#endif
+#ifdef MBEDTLS_PLATFORM_C
+ mbedtls_fprintf( stderr,
+ "\nFATAL psa_decrement_key_slot_access_count Decrementing a zero access counter.\n" );
+#endif
+
+ return( PSA_ERROR_CORRUPTION_DETECTED );
+}
+
psa_status_t psa_validate_key_location( psa_key_lifetime_t lifetime,
psa_se_drv_table_entry_t **p_drv )
{
@@ -315,7 +360,7 @@
*handle = key;
- return( PSA_SUCCESS );
+ return( psa_decrement_key_slot_access_count( slot ) );
#else /* defined(MBEDTLS_PSA_CRYPTO_STORAGE_C) */
(void) key;
@@ -349,7 +394,7 @@
return( status );
if( PSA_KEY_LIFETIME_IS_VOLATILE( slot->attr.lifetime ) )
- return PSA_SUCCESS;
+ return( psa_decrement_key_slot_access_count( slot ) );
return( psa_wipe_key_slot( slot ) );
}
diff --git a/library/psa_crypto_slot_management.h b/library/psa_crypto_slot_management.h
index 2b90ce8..d22e343 100644
--- a/library/psa_crypto_slot_management.h
+++ b/library/psa_crypto_slot_management.h
@@ -70,6 +70,11 @@
* In case of a persistent key, the function loads the description of the key
* into a key slot if not already done.
*
+ * On success, the access counter of the returned key slot is incremented by
+ * one. It is the responsibility of the caller to call
+ * psa_decrement_key_slot_access_count() when it does not access the slot
+ * anymore.
+ *
* \param key Key identifier to query.
* \param[out] p_slot On success, `*p_slot` contains a pointer to the
* key slot containing the description of the key
@@ -110,7 +115,10 @@
/** Find a free key slot.
*
* This function returns a key slot that is available for use and is in its
- * ground state (all-bits-zero).
+ * ground state (all-bits-zero). On success, the access counter of the
+ * returned key slot is incremented by one. It is the responsibility of the
+ * caller to call psa_decrement_key_slot_access_count() when it does not access
+ * the key slot anymore.
*
* \param[out] volatile_key_id On success, volatile key identifier
* associated to the returned slot.
@@ -123,6 +131,35 @@
psa_status_t psa_get_empty_key_slot( psa_key_id_t *volatile_key_id,
psa_key_slot_t **p_slot );
+/** Increment slot access counter.
+ *
+ * This function increments the slot access counter by one.
+ *
+ * \param[in] slot The key slot.
+ */
+static inline void psa_increment_key_slot_access_count( psa_key_slot_t *slot )
+{
+ slot->access_count++;
+}
+
+/** Decrement slot access counter.
+ *
+ * This function decrements the slot access counter by one.
+ *
+ * \note To ease the handling of errors in retrieving a key slot
+ * a NULL input pointer is valid, and the function returns
+ * successfully without doing anything in that case.
+ *
+ * \param[in] slot The key slot.
+ * \retval #PSA_SUCCESS
+ * \p slot is NULL or the key slot access pointer has been
+ * decremented successfully.
+ * \retval #PSA_ERROR_CORRUPTION_DETECTED
+ * The access counter was equal to 0.
+ *
+ */
+psa_status_t psa_decrement_key_slot_access_count( psa_key_slot_t *slot );
+
/** Test whether a lifetime designates a key in an external cryptoprocessor.
*
* \param lifetime The lifetime to test.