End to bridge encryption implementation

So far this is passing my basic tests, but could use some testing from people
that are much more familiar with how this is supposed to work.

Refs #27

bridge/portal.go

@@ -35,6 +35,7 @@ type Portal struct {
 	log    log.Logger
 
 	roomCreateLock sync.Mutex
+	encryptLock    sync.Mutex
 
 	discordMessages chan portalDiscordMessage
 	matrixMessages  chan portalMatrixMessage
@@ -144,7 +145,7 @@ func (p *Portal) handleMatrixInvite(sender *User, evt *event.Event) {
 		p.log.Infoln("no puppet for %v", sender)
 		// Open a conversation on the discord side?
 	}
-	p.log.Infoln("puppet:", puppet)
+	p.log.Infoln("matrixInvite: puppet:", puppet)
 }
 
 func (p *Portal) messageLoop() {
@@ -212,14 +213,25 @@ func (p *Portal) createMatrixRoom(user *User, channel *discordgo.Channel) error
 
 	var invite []id.UserID
 
-	if p.IsPrivateChat() {
-		invite = append(invite, p.bridge.bot.UserID)
+	if p.bridge.Config.Bridge.Encryption.Default {
+		initialState = append(initialState, &event.Event{
+			Type: event.StateEncryption,
+			Content: event.Content{
+				Parsed: event.EncryptionEventContent{Algorithm: id.AlgorithmMegolmV1},
+			},
+		})
+		p.Encrypted = true
+
+		if p.IsPrivateChat() {
+			invite = append(invite, p.bridge.bot.UserID)
+		}
 	}
 
 	resp, err := intent.CreateRoom(&mautrix.ReqCreateRoom{
 		Visibility:      "private",
 		Name:            p.Name,
 		Topic:           p.Topic,
+		Invite:          invite,
 		Preset:          "private_chat",
 		IsDirect:        p.IsPrivateChat(),
 		InitialState:    initialState,
@@ -325,7 +337,7 @@ func (p *Portal) sendMediaFailedMessage(intent *appservice.IntentAPI, bridgeErr
 		MsgType: event.MsgNotice,
 	}
 
-	_, err := intent.SendMessageEvent(p.MXID, event.EventMessage, content)
+	_, err := p.sendMatrixMessage(intent, event.EventMessage, content, nil, time.Now().UTC().UnixMilli())
 	if err != nil {
 		p.log.Warnfln("failed to send error message to matrix: %v", err)
 	}
@@ -379,7 +391,7 @@ func (p *Portal) handleDiscordAttachment(intent *appservice.IntentAPI, msgID str
 		return
 	}
 
-	resp, err := intent.SendMessageEvent(p.MXID, event.EventMessage, content)
+	resp, err := p.sendMatrixMessage(intent, event.EventMessage, content, nil, time.Now().UTC().UnixMilli())
 	if err != nil {
 		p.log.Warnfln("failed to send media message to matrix: %v", err)
 	}
@@ -426,7 +438,7 @@ func (p *Portal) handleDiscordMessageCreate(user *User, msg *discordgo.Message)
 			}
 		}
 
-		resp, err := intent.SendMessageEvent(p.MXID, event.EventMessage, content)
+		resp, err := p.sendMatrixMessage(intent, event.EventMessage, content, nil, time.Now().UTC().UnixMilli())
 		if err != nil {
 			p.log.Warnfln("failed to send message %q to matrix: %v", msg.ID, err)
 
@@ -498,7 +510,7 @@ func (p *Portal) handleDiscordMessagesUpdate(user *User, msg *discordgo.Message)
 
 	content.SetEdit(existing.MatrixID)
 
-	resp, err := intent.SendMessageEvent(p.MXID, event.EventMessage, content)
+	resp, err := p.sendMatrixMessage(intent, event.EventMessage, content, nil, time.Now().UTC().UnixMilli())
 	if err != nil {
 		p.log.Warnfln("failed to send message %q to matrix: %v", msg.ID, err)
 
@@ -567,6 +579,57 @@ func (p *Portal) syncParticipants(source *User, participants []*discordgo.User)
 	}
 }
 
+func (portal *Portal) encrypt(content *event.Content, eventType event.Type) (event.Type, error) {
+	if portal.Encrypted && portal.bridge.crypto != nil {
+		// TODO maybe the locking should be inside mautrix-go?
+		portal.encryptLock.Lock()
+		encrypted, err := portal.bridge.crypto.Encrypt(portal.MXID, eventType, *content)
+		portal.encryptLock.Unlock()
+		if err != nil {
+			return eventType, fmt.Errorf("failed to encrypt event: %w", err)
+		}
+		eventType = event.EventEncrypted
+		content.Parsed = encrypted
+	}
+	return eventType, nil
+}
+
+const doublePuppetKey = "fi.mau.double_puppet_source"
+const doublePuppetValue = "mautrix-discord"
+
+func (portal *Portal) sendMatrixMessage(intent *appservice.IntentAPI, eventType event.Type, content *event.MessageEventContent, extraContent map[string]interface{}, timestamp int64) (*mautrix.RespSendEvent, error) {
+	wrappedContent := event.Content{Parsed: content, Raw: extraContent}
+	if timestamp != 0 && intent.IsCustomPuppet {
+		if wrappedContent.Raw == nil {
+			wrappedContent.Raw = map[string]interface{}{}
+		}
+		if intent.IsCustomPuppet {
+			wrappedContent.Raw[doublePuppetKey] = doublePuppetValue
+		}
+	}
+	var err error
+	eventType, err = portal.encrypt(&wrappedContent, eventType)
+	if err != nil {
+		return nil, err
+	}
+
+	if eventType == event.EventEncrypted {
+		// Clear other custom keys if the event was encrypted, but keep the double puppet identifier
+		if intent.IsCustomPuppet {
+			wrappedContent.Raw = map[string]interface{}{doublePuppetKey: doublePuppetValue}
+		} else {
+			wrappedContent.Raw = nil
+		}
+	}
+
+	_, _ = intent.UserTyping(portal.MXID, false, 0)
+	if timestamp == 0 {
+		return intent.SendMessageEvent(portal.MXID, eventType, &wrappedContent)
+	} else {
+		return intent.SendMassagedMessageEvent(portal.MXID, eventType, &wrappedContent, timestamp)
+	}
+}
+
 func (p *Portal) handleMatrixMessages(msg portalMatrixMessage) {
 	switch msg.evt.Type {
 	case event.EventMessage: