From a58cae16cdecadece41f2d1a9e2ca777116c62fc Mon Sep 17 00:00:00 2001
From: Tulir Asokan <tulir@maunium.net>
Date: Sat, 16 Apr 2022 23:16:05 +0300
Subject: [PATCH] Backport fixing custom fields leaking in history sync

---
 historysync.go | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/historysync.go b/historysync.go
index 5fece97..f92e499 100644
--- a/historysync.go
+++ b/historysync.go
@@ -478,6 +478,13 @@ func (portal *Portal) wrapBatchEvent(info *types.MessageInfo, intent *appservice
 	if err != nil {
 		return nil, err
 	}
+	if newEventType == event.EventEncrypted {
+		// Clear other custom keys if the event was encrypted, but keep the double puppet identifier
+		wrappedContent.Raw = map[string]interface{}{backfillIDField: info.ID}
+		if intent.IsCustomPuppet {
+			wrappedContent.Raw[doublePuppetKey] = doublePuppetValue
+		}
+	}
 	return &event.Event{
 		Sender:    intent.UserID,
 		Type:      newEventType,