Implement FindFreeKeySlotInRange for PSA key slots

src/crypto/CHIPCryptoPALPSA.cpp

@@ -263,6 +263,28 @@ void Hash_SHA256_stream::Clear()
     psa_hash_abort(toHashOperation(&mContext));
 }
 
+CHIP_ERROR FindFreeKeySlotInRange(psa_key_id_t & keyId, psa_key_id_t start, uint32_t range)
+{
+    psa_key_attributes_t attributes = PSA_KEY_ATTRIBUTES_INIT;
+    psa_key_id_t end                = start + range;
+
+    VerifyOrReturnError(start >= PSA_KEY_ID_USER_MIN && end - 1 <= PSA_KEY_ID_USER_MAX, CHIP_ERROR_INVALID_ARGUMENT);
+
+    for (keyId = start; keyId < end; keyId++)
+    {
+        psa_status_t status = psa_get_key_attributes(keyId, &attributes);
+        if (status == PSA_ERROR_INVALID_HANDLE)
+        {
+            return CHIP_NO_ERROR;
+        }
+        else if (status != PSA_SUCCESS)
+        {
+            return CHIP_ERROR_INTERNAL;
+        }
+    }
+    return CHIP_ERROR_NOT_FOUND;
+}
+
 CHIP_ERROR PsaKdf::Init(const ByteSpan & secret, const ByteSpan & salt, const ByteSpan & info)
 {
     psa_status_t status        = PSA_SUCCESS;

src/crypto/CHIPCryptoPALPSA.h

@@ -68,6 +68,20 @@ enum class KeyIdBase : psa_key_id_t
 static_assert(to_underlying(KeyIdBase::Minimum) >= PSA_KEY_ID_USER_MIN && to_underlying(KeyIdBase::Maximum) <= PSA_KEY_ID_USER_MAX,
               "PSA key ID base out of allowed range");
 
+/**
+ * @brief Finds first free persistent Key slot ID within range.
+ *
+ * @param[out] keyId Key ID handler to which free ID will be set.
+ * @param[in]  start Starting ID in search range.
+ * @param[in]  range Search range.
+ *
+ * @retval CHIP_NO_ERROR               On success.
+ * @retval CHIP_ERROR_INTERNAL         On PSA crypto API error.
+ * @retval CHIP_ERROR_NOT_FOUND        On no free Key ID within range.
+ * @retval CHIP_ERROR_INVALID_ARGUMENT On search arguments out of PSA allowed range.
+ */
+CHIP_ERROR FindFreeKeySlotInRange(psa_key_id_t & keyId, psa_key_id_t start, uint32_t range);
+
 /**
  * @brief Calculates PSA key ID for Node Operational Certificate private key for the given fabric.
  */