From 0f1786370833ac8ffc51684b9534c5e70e440b6e Mon Sep 17 00:00:00 2001
From: Tulir Asokan <tulir@maunium.net>
Date: Mon, 5 Oct 2020 22:32:15 +0300
Subject: [PATCH] Add command to reset the megolm session in a room

---
 commands.go | 13 +++++++++++++
 crypto.go   |  7 +++++++
 main.go     |  1 +
 3 files changed, 21 insertions(+)

diff --git a/commands.go b/commands.go
index 5d7cb00..5d4b72c 100644
--- a/commands.go
+++ b/commands.go
@@ -123,6 +123,8 @@ func (handler *CommandHandler) CommandMux(ce *CommandEvent) {
 		handler.CommandDeletePortal(ce)
 	case "delete-all-portals":
 		handler.CommandDeleteAllPortals(ce)
+	case "discard-megolm-session", "discard-session":
+		handler.CommandDiscardMegolmSession(ce)
 	case "dev-test":
 		handler.CommandDevTest(ce)
 	case "set-pl":
@@ -163,6 +165,17 @@ func (handler *CommandHandler) CommandMux(ce *CommandEvent) {
 	}
 }
 
+func (handler *CommandHandler) CommandDiscardMegolmSession(ce *CommandEvent) {
+	if handler.bridge.Crypto == nil {
+		ce.Reply("This bridge instance doesn't have end-to-bridge encryption enabled")
+	} else if !ce.User.Admin {
+		ce.Reply("Only the bridge admin can reset Megolm sessions")
+	} else {
+		handler.bridge.Crypto.ResetSession(ce.RoomID)
+		ce.Reply("Successfully reset Megolm session in this room. New decryption keys will be shared the next time a message is sent from WhatsApp.")
+	}
+}
+
 func (handler *CommandHandler) CommandRelaybot(ce *CommandEvent) {
 	if handler.bridge.Relaybot == nil {
 		ce.Reply("The relaybot is disabled")
diff --git a/crypto.go b/crypto.go
index ee05cc2..cae1ee9 100644
--- a/crypto.go
+++ b/crypto.go
@@ -189,6 +189,13 @@ func (helper *CryptoHelper) WaitForSession(roomID id.RoomID, senderKey id.Sender
 	return helper.mach.WaitForSession(roomID, senderKey, sessionID, timeout)
 }
 
+func (helper *CryptoHelper) ResetSession(roomID id.RoomID) {
+	err := helper.mach.CryptoStore.RemoveOutboundGroupSession(roomID)
+	if err != nil {
+		helper.log.Debugfln("Error manually removing outbound group session in %s: %v", roomID, err)
+	}
+}
+
 func (helper *CryptoHelper) HandleMemberEvent(evt *event.Event) {
 	helper.mach.HandleMemberEvent(evt)
 }
diff --git a/main.go b/main.go
index a4582cf..6ea9f7f 100644
--- a/main.go
+++ b/main.go
@@ -154,6 +154,7 @@ type Crypto interface {
 	Decrypt(*event.Event) (*event.Event, error)
 	Encrypt(id.RoomID, event.Type, event.Content) (*event.EncryptedEventContent, error)
 	WaitForSession(id.RoomID, id.SenderKey, id.SessionID, time.Duration) bool
+	ResetSession(id.RoomID)
 	Init() error
 	Start()
 	Stop()