From d6e95ccb9e03d8a03cb185e6e7a6846e726c2555 Mon Sep 17 00:00:00 2001
From: David Florness <david@florness.com>
Date: Sun, 23 May 2021 10:28:03 -0400
Subject: [PATCH] Start and join events for keys msgs must belong to the same
 election

---
 election/msg.go | 30 ++++++++++++++++++++----------
 1 file changed, 20 insertions(+), 10 deletions(-)

diff --git a/election/msg.go b/election/msg.go
index fee54e0..ccf800c 100644
--- a/election/msg.go
+++ b/election/msg.go
@@ -415,26 +415,36 @@ func (elections *ElectionsMap) onKeysMessage(evt *event.Event, client *mautrix.C
 		return
 	}
 
+	// this makes JoinIDIndex availabe below
+	startEvt := elections.EventStore.GetStartEvent(evt.RoomID, content.StartID)
+	if startEvt == nil {
+		debugf("we couldn't process the start event, %s", content.StartID)
+		return
+	}
+
+	el := elections.GetElection(startEvt.CreateID)
+	if el == nil {
+		// should never happen because we retrieved the join event above
+		errorf("election %s doesn't exist", startEvt.ID)
+		return
+	}
+
 	joinEvt := elections.EventStore.GetJoinEvent(evt.RoomID, content.JoinID)
 	if joinEvt == nil {
 		debugf("we couldn't get the join event, %s", content.JoinID)
 		return
 	}
+
+	// ensure keys sender also sent join event
 	if evt.Sender != joinEvt.Sender {
 		warnf("they did not send the join event; %s did", joinEvt.Sender)
 		return
 	}
 
-	// process the start event so that JoinIDIndex is availabe below
-	if elections.EventStore.GetStartEvent(evt.RoomID, content.StartID) == nil {
-		debugf("we couldn't process the start event, %s", content.StartID)
-		return
-	}
-
-	el := elections.GetElection(joinEvt.CreateID)
-	if el == nil {
-		// should never happen because we retrieved the join event above
-		errorf("election %s doesn't exist", joinEvt.ID)
+	// ensure join event and start event belong to the same election
+	if _, voterExists := el.Joins[joinEvt.ID]; !voterExists {
+		warnf("the join event %s and start event %s do not belong to the same election",
+			joinEvt.ID, startEvt.ID)
 		return
 	}
 
-- 
2.38.4