From 70fa89c1f97fe2472c7a324ff5fed00aa648cdcb Mon Sep 17 00:00:00 2001
From: Valerio Setti <valerio.setti@nordicsemi.no>
Date: Wed, 14 Aug 2024 05:12:45 +0200
Subject: [PATCH] psa-core: remove unnecessary element in psa_key_slot_t

Instead of checking for "in_use" to be true/false or "key.data"
to be not NULL, simply check that "key.bytes" is 0/not-0.
psa_allocate_buffer_to_slot() will update this value whenever
a new slot is allocated (for the fully static case "allocated"
actually mean "taken").

Signed-off-by: Valerio Setti <valerio.setti@nordicsemi.no>
---
 library/psa_crypto.c      | 26 +++-----------------------
 library/psa_crypto_core.h |  1 -
 2 files changed, 3 insertions(+), 24 deletions(-)

diff --git a/library/psa_crypto.c b/library/psa_crypto.c
index 696e830b8e..8c2c543d09 100644
--- a/library/psa_crypto.c
+++ b/library/psa_crypto.c
@@ -706,15 +706,9 @@ psa_status_t psa_allocate_buffer_to_slot(psa_key_slot_t *slot,
                                          size_t buffer_length)
 {
 #if defined(MBEDTLS_PSA_STATIC_KEY_SLOTS)
-    if (slot->key.in_use) {
-        return PSA_ERROR_ALREADY_EXISTS;
-    }
-
     if (buffer_length > ((size_t) MBEDTLS_PSA_STATIC_KEY_SLOT_BUFFER_SIZE)) {
         return PSA_ERROR_NOT_SUPPORTED;
     }
-
-    slot->key.in_use = 1;
 #else
     if (slot->key.data != NULL) {
         return PSA_ERROR_ALREADY_EXISTS;
@@ -1189,9 +1183,7 @@ static psa_status_t psa_get_and_lock_transparent_key_slot_with_policy(
 
 psa_status_t psa_remove_key_data_from_memory(psa_key_slot_t *slot)
 {
-#if defined(MBEDTLS_PSA_STATIC_KEY_SLOTS)
-    slot->key.in_use = 0;
-#else /* MBEDTLS_PSA_STATIC_KEY_SLOTS */
+#if !defined(MBEDTLS_PSA_STATIC_KEY_SLOTS)
     if (slot->key.data != NULL) {
         mbedtls_zeroize_and_free(slot->key.data, slot->key.bytes);
     }
@@ -2113,13 +2105,7 @@ psa_status_t psa_import_key(const psa_key_attributes_t *attributes,
      * storage ( thus not in the case of importing a key in a secure element
      * with storage ( MBEDTLS_PSA_CRYPTO_SE_C ) ),we have to allocate a
      * buffer to hold the imported key material. */
-#if defined(MBEDTLS_PSA_STATIC_KEY_SLOTS)
-    int is_slot_unused = (slot->key.in_use == 0);
-#else
-    int is_slot_unused = (slot->key.data == NULL);
-#endif
-
-    if (is_slot_unused) {
+    if (slot->key.bytes == 0) {
         if (psa_key_lifetime_is_external(attributes->lifetime)) {
             status = psa_driver_wrapper_get_key_buffer_size_from_key_data(
                 attributes, data, data_length, &storage_size);
@@ -8036,13 +8022,7 @@ psa_status_t psa_generate_key_custom(const psa_key_attributes_t *attributes,
      * storage ( thus not in the case of generating a key in a secure element
      * with storage ( MBEDTLS_PSA_CRYPTO_SE_C ) ),we have to allocate a
      * buffer to hold the generated key material. */
-#if defined(MBEDTLS_PSA_STATIC_KEY_SLOTS)
-    int is_slot_unused = (slot->key.in_use == 0);
-#else
-    int is_slot_unused = (slot->key.data == NULL);
-#endif
-
-    if (is_slot_unused) {
+    if (slot->key.bytes == 0) {
         if (PSA_KEY_LIFETIME_GET_LOCATION(attributes->lifetime) ==
             PSA_KEY_LOCATION_LOCAL_STORAGE) {
             status = psa_validate_key_type_and_size_for_key_generation(
diff --git a/library/psa_crypto_core.h b/library/psa_crypto_core.h
index a3c0fd6f19..7832001d8c 100644
--- a/library/psa_crypto_core.h
+++ b/library/psa_crypto_core.h
@@ -165,7 +165,6 @@ typedef struct {
      * Format as specified in psa_export_key(). */
     struct key_data {
 #if defined(MBEDTLS_PSA_STATIC_KEY_SLOTS)
-        int in_use;
         uint8_t data[MBEDTLS_PSA_STATIC_KEY_SLOT_BUFFER_SIZE];
 #else /* MBEDTLS_PSA_STATIC_KEY_SLOTS */
         uint8_t *data;