Implement signed event handler

tfw/components/fsm/fsm_handler.py

@@ -24,11 +24,10 @@ class FSMHandler:
     An 'fsm_update' message is broadcasted after every successful
     command.
     """
-    def __init__(self, *, fsm_type, require_signature=False):
+    def __init__(self, *, fsm_type):
         self.fsm = fsm_type()
         self._fsm_updater = FSMUpdater(self.fsm)
         self.auth_key = KeyManager().auth_key
-        self._require_signature = require_signature
 
         self.command_handlers = {
             'trigger': self.handle_trigger,
@@ -54,10 +53,6 @@ class FSMHandler:
                         the action to try triggering in data['value']
         """
         trigger = message['data']['value']
-        if self._require_signature:
-            if not verify_message(self.auth_key, message):
-                LOG.error('Ignoring unsigned trigger command: %s', message)
-                return None
         if self.fsm.step(trigger):
             return message
         return None

tfw/event_handlers.py

@@ -1,2 +1,2 @@
 # pylint: disable=unused-import
-from tfw.internals.event_handling import EventHandler, FSMAwareEventHandler
+from tfw.internals.event_handling import EventHandler, FSMAwareEventHandler, SignedEventHandler

tfw/internals/event_handling/__init__.py

@@ -1,3 +1,4 @@
-from .event_handler_factory_base import EventHandlerFactoryBase
 from .event_handler import EventHandler
+from .event_handler_factory_base import EventHandlerFactoryBase
 from .fsm_aware_event_handler import FSMAwareEventHandler
+from .signed_event_handler import SignedEventHandler

tfw/internals/event_handling/signed_event_handler.py

@@ -0,0 +1,20 @@
+import logging
+
+from tfw.internals.crypto import KeyManager, verify_message
+
+from .event_handler import EventHandler
+
+LOG = logging.getLogger(__name__)
+
+
+# pylint: disable=abstract-method
+class SignedEventHandler(EventHandler):
+    def __init__(self, connector):
+        self._auth_key = KeyManager().auth_key
+        super().__init__(connector)
+
+    def _event_callback(self, message):
+        if verify_message(self._auth_key, message):
+            self.handle_event(message, self.connector)
+        else:
+            LOG.error('Message does not have valid signature: %s', message)