Fix signature (#50)

* change order of fields in auth_data to match autoscaler for signature verification

* also ignore __request_id

* Revert "change order of fields in auth_data to match autoscaler for signature verification" so that it's alphabetical again

This reverts commit b8223879c9.

* enforce alphabetical json dumping of message for signature verification

---------

Co-authored-by: Edgar Lin <edgarlin2000@gmail.com>

lib/backend.py

@@ -286,7 +286,7 @@ class Backend:
         message = {
             key: value
             for (key, value) in (dataclasses.asdict(auth_data).items())
-            if key != "signature"
+            if key != "signature" and key != "__request_id"
         }
         if auth_data.reqnum < (self.reqnum - MSG_HISTORY_LEN):
             log.debug(
@@ -296,7 +296,7 @@ class Backend:
         elif message in self.msg_history:
             log.debug(f"message: {message} already in message history")
             return False
-        elif verify_signature(json.dumps(message, indent=4), auth_data.signature):
+        elif verify_signature(json.dumps(message, indent=4, sort_keys=True), auth_data.signature):
             self.reqnum = max(auth_data.reqnum, self.reqnum)
             self.msg_history.append(message)
             self.msg_history = self.msg_history[-MSG_HISTORY_LEN:]