Remove "allocated" flag from key slots
The flag to mark key slots as allocated was introduced to mark slots
that are claimed and in use, but do not have key material yet, at a
time when creating a key used several API functions: allocate a slot,
then progressively set its metadata, and finally create the key
material. Now that all of these steps are combined into a single
API function call, the notion of allocated-but-not-filled slot is no
longer relevant. So remove the corresponding flag.
A slot is occupied iff there is a key in it. (For a key in a secure
element, the key material is not present, but the slot contains the
key metadata.) This key must have a type which is nonzero, so use this
as an indicator that a slot is in use.
diff --git a/library/psa_crypto.c b/library/psa_crypto.c
index cb80546..f1ddb14 100644
--- a/library/psa_crypto.c
+++ b/library/psa_crypto.c
@@ -897,8 +897,6 @@
status = psa_get_key_slot( handle, &slot );
if( status != PSA_SUCCESS )
return( status );
- if( slot->attr.type == PSA_KEY_TYPE_NONE )
- return( PSA_ERROR_DOES_NOT_EXIST );
/* Enforce that usage policy for the key slot contains all the flags
* required by the usage parameter. There is one exception: public
@@ -1488,9 +1486,6 @@
* is optional (import, copy). */
slot->attr = attributes->core;
- /* This is awkward... Copying the attributes has overwritten the
- * flag that marks this slot as used. Restore it. */
- psa_key_slot_set_bits_in_flags( slot, PSA_KEY_SLOT_FLAG_ALLOCATED );
#if defined(MBEDTLS_PSA_CRYPTO_SE_C)
/* For a key in a secure element, we need to do three things:
diff --git a/library/psa_crypto_core.h b/library/psa_crypto_core.h
index 1ae298e..fbfb6da 100644
--- a/library/psa_crypto_core.h
+++ b/library/psa_crypto_core.h
@@ -64,9 +64,19 @@
} data;
} psa_key_slot_t;
-/** Flag for psa_key_slot_t::attr::core::flags indicating that the
- * slot is in use. */
-#define PSA_KEY_SLOT_FLAG_ALLOCATED ( (uint16_t) 0x0001 )
+/** Test whether a key slot is occupied.
+ *
+ * A key slot is occupied iff the key type is nonzero. This works because
+ * no valid key can have 0 as its key type.
+ *
+ * \param[in] slot The key slot to test.
+ *
+ * \return 1 if the slot is occupied, 0 otherwise.
+ */
+static inline int psa_is_key_slot_occupied( const psa_key_slot_t *slot )
+{
+ return( slot->attr.type != 0 );
+}
/** Retrieve flags from psa_key_slot_t::attr::core::flags.
*
diff --git a/library/psa_crypto_slot_management.c b/library/psa_crypto_slot_management.c
index 43ba412..0734009 100644
--- a/library/psa_crypto_slot_management.c
+++ b/library/psa_crypto_slot_management.c
@@ -74,8 +74,8 @@
return( PSA_ERROR_INVALID_HANDLE );
slot = &global_data.key_slots[handle - 1];
- /* If the slot hasn't been allocated, the handle is invalid. */
- if( ! psa_key_slot_get_flags( slot, PSA_KEY_SLOT_FLAG_ALLOCATED ) )
+ /* If the slot isn't occupied, the handle is invalid. */
+ if( ! psa_is_key_slot_occupied( slot ) )
return( PSA_ERROR_INVALID_HANDLE );
*p_slot = slot;
@@ -111,12 +111,8 @@
for( *handle = PSA_KEY_SLOT_COUNT; *handle != 0; --( *handle ) )
{
*p_slot = &global_data.key_slots[*handle - 1];
- if( ! psa_key_slot_get_flags( *p_slot, PSA_KEY_SLOT_FLAG_ALLOCATED ) )
- {
- psa_key_slot_set_bits_in_flags( *p_slot,
- PSA_KEY_SLOT_FLAG_ALLOCATED );
+ if( ! psa_is_key_slot_occupied( *p_slot ) )
return( PSA_SUCCESS );
- }
}
*p_slot = NULL;
return( PSA_ERROR_INSUFFICIENT_MEMORY );
@@ -272,13 +268,10 @@
memset( stats, 0, sizeof( *stats ) );
for( key = 1; key <= PSA_KEY_SLOT_COUNT; key++ )
{
- psa_key_slot_t *slot = &global_data.key_slots[key - 1];
- if( slot->attr.type == PSA_KEY_TYPE_NONE )
+ const psa_key_slot_t *slot = &global_data.key_slots[key - 1];
+ if( ! psa_is_key_slot_occupied( slot ) )
{
- if( psa_key_slot_get_flags( slot, PSA_KEY_SLOT_FLAG_ALLOCATED ) )
- ++stats->half_filled_slots;
- else
- ++stats->empty_slots;
+ ++stats->empty_slots;
continue;
}
if( slot->attr.lifetime == PSA_KEY_LIFETIME_VOLATILE )
diff --git a/library/psa_crypto_slot_management.h b/library/psa_crypto_slot_management.h
index 049520d..cde590f 100644
--- a/library/psa_crypto_slot_management.h
+++ b/library/psa_crypto_slot_management.h
@@ -58,13 +58,13 @@
* This does not affect persistent storage. */
void psa_wipe_all_key_slots( void );
-/** Find a free key slot and mark it as in use.
+/** 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).
*
* \param[out] handle On success, a slot number that can be used as a
- * handle to the slot. The selected slot was not
- * in use before. This function marks it as in use
- * and otherwise leaves it in a freshly-initialized
- * state.
+ * handle to the slot.
* \param[out] p_slot On success, a pointer to the slot.
*
* \retval #PSA_SUCCESS