From 4bac9a4c4b059e887de297de8b3ec7713eaf7420 Mon Sep 17 00:00:00 2001
From: Gilles Peskine <Gilles.Peskine@arm.com>
Date: Thu, 23 May 2019 20:32:30 +0200
Subject: [PATCH] New function to get key slot statistics

New function mbedtls_psa_get_stats to obtain some data about how many
key slots are in use. This is intended for debugging and testing
purposes.
---
 include/psa/crypto_extra.h           | 37 ++++++++++++++++++++++++++++
 library/psa_crypto_slot_management.c | 32 ++++++++++++++++++++++++
 2 files changed, 69 insertions(+)

diff --git a/include/psa/crypto_extra.h b/include/psa/crypto_extra.h
index 56e053604..b08f46d09 100644
--- a/include/psa/crypto_extra.h
+++ b/include/psa/crypto_extra.h
@@ -116,6 +116,43 @@ static inline psa_algorithm_t psa_get_key_enrollment_algorithm(
  */
 void mbedtls_psa_crypto_free( void );
 
+/** \brief Statistics about
+ * resource consumption related to the PSA keystore.
+ *
+ * \note The content of this structure is not part of the stable API and ABI
+ *       of Mbed Crypto and may change arbitrarily from version to version.
+ */
+typedef struct mbedtls_psa_stats_s
+{
+    /** Number of slots containing key material for a volatile key. */
+    size_t volatile_slots;
+    /** Number of slots containing key material for a key which is in
+     * internal persistent storage. */
+    size_t persistent_slots;
+    /** Number of slots containing a reference to a key in a
+     * secure element. */
+    size_t external_slots;
+    /** Number of slots which are occupied, but do not contain
+     * key material yet. */
+    size_t half_filled_slots;
+    /** Number of slots that contain cache data. */
+    size_t cache_slots;
+    /** Number of slots that are not used for anything. */
+    size_t empty_slots;
+    /** Largest key id value among open keys in internal persistent storage. */
+    psa_key_id_t max_open_internal_key_id;
+    /** Largest key id value among open keys in secure elements. */
+    psa_key_id_t max_open_external_key_id;
+} mbedtls_psa_stats_t;
+
+/** \brief Get statistics about
+ * resource consumption related to the PSA keystore.
+ *
+ * \note When Mbed Crypto is built as part of a service, with isolation
+ *       between the application and the keystore, the service may or
+ *       may not expose this function.
+ */
+void mbedtls_psa_get_stats( mbedtls_psa_stats_t *stats );
 
 /**
  * \brief Inject an initial entropy seed for the random generator into
diff --git a/library/psa_crypto_slot_management.c b/library/psa_crypto_slot_management.c
index 0ffc2aae7..900aa41a5 100644
--- a/library/psa_crypto_slot_management.c
+++ b/library/psa_crypto_slot_management.c
@@ -232,4 +232,36 @@ psa_status_t psa_close_key( psa_key_handle_t handle )
     return( psa_wipe_key_slot( slot ) );
 }
 
+void mbedtls_psa_get_stats( mbedtls_psa_stats_t *stats )
+{
+    psa_key_handle_t key;
+    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->type == PSA_KEY_TYPE_NONE )
+        {
+            if( slot->allocated )
+                ++stats->half_filled_slots;
+            else
+                ++stats->empty_slots;
+            continue;
+        }
+        if( slot->lifetime == PSA_KEY_LIFETIME_VOLATILE )
+            ++stats->volatile_slots;
+        else if( slot->lifetime == PSA_KEY_LIFETIME_PERSISTENT )
+        {
+            ++stats->persistent_slots;
+            if( slot->persistent_storage_id > stats->max_open_internal_key_id )
+                stats->max_open_internal_key_id = slot->persistent_storage_id;
+        }
+        else
+        {
+            ++stats->external_slots;
+            if( slot->persistent_storage_id > stats->max_open_external_key_id )
+                stats->max_open_external_key_id = slot->persistent_storage_id;
+        }
+    }
+}
+
 #endif /* MBEDTLS_PSA_CRYPTO_C */