filter chat TLVs for cross-client compatibility

foodgroup/chat.go

@@ -85,7 +85,7 @@ func (s ChatService) ChannelMsgToHost(ctx context.Context, sess *state.Session,
 			Body:  bodyOut,
 		})
 	} else {
-		// forward  message all participants, except sender
+		// forward message all participants, except sender
 		s.chatMessageRelayer.RelayToAllExcept(ctx, sess.ChatRoomCookie(), sess.IdentScreenName(), wire.SNACMessage{
 			Frame: frameOut,
 			Body:  bodyOut,
@@ -116,32 +116,53 @@ func (s ChatService) transformChatMessage(inBody wire.SNAC_0x0E_0x05_ChatChannel
 	if !hasMessage {
 		return wire.TLVRestBlock{}, errors.New("SNAC(0x0E,0x05) does not contain a message TLV")
 	}
-	messageText, err := textFromChatMsgBlob(messageBlob)
-	if err != nil {
+
+	restBlock := wire.TLVRestBlock{}
+	if err := wire.UnmarshalBE(&restBlock, bytes.NewBuffer(messageBlob)); err != nil {
 		return wire.TLVRestBlock{}, err
 	}
 
-	newMessageBlock := func(sess *state.Session, msg any) wire.TLVRestBlock {
-		block := wire.TLVRestBlock{}
-		// the order of these TLVs matters for AIM 2.x. if out of order, screen
-		// names do not appear with each chat message.
-		block.Append(wire.NewTLVBE(wire.ChatTLVSenderInformation, sess.TLVUserInfo()))
-		if inBody.HasTag(wire.ChatTLVPublicWhisperFlag) {
-			// send message to all chat room participants
-			block.Append(wire.NewTLVBE(wire.ChatTLVPublicWhisperFlag, []byte{}))
-		}
-		block.Append(wire.NewTLVBE(wire.ChatTLVMessageInfo, msg))
-		return block
+	txt, err := extractChatMessage(restBlock)
+	if err != nil {
+		return wire.TLVRestBlock{}, err
 	}
 
-	if doRoll, dice, sides := parseDiceCommand(messageText); doRoll {
+	if doRoll, dice, sides := parseDiceCommand(txt); doRoll {
 		payload := s.rollDice(sender, dice, sides)
 		// send die roll results from OnlineHost user
-		return newMessageBlock(sessOnlineHost, payload), nil
+		return newChatTLVBlock(inBody, sessOnlineHost, payload), nil
+	}
+
+	newRestBlock := wire.TLVRestBlock{}
+
+	// Strip down to the essential TLVs for cross-client compatibility.
+	// Some newer clients include extra metadata that cause older clients
+	// to crash when they encounter unfamiliar TLVs. For example, chat messages
+	// sent by Windows AIM 5.9 will cause macOS AIM 2.x to crash. Rather than
+	// implement complex per-client filtering, we simply preserve only the three
+	// TLVs that every client expects.
+	for _, tlv := range restBlock.TLVList {
+		if tlv.Tag == wire.ChatTLVMessageInfoText ||
+			tlv.Tag == wire.ChatTLVMessageInfoEncoding ||
+			tlv.Tag == wire.ChatTLVMessageInfoLang {
+			newRestBlock.TLVList = append(newRestBlock.TLVList, tlv)
+		}
 	}
 
-	// return the incoming payload without modification
-	return newMessageBlock(sender, messageBlob), nil
+	return newChatTLVBlock(inBody, sender, newRestBlock), nil
+}
+
+func newChatTLVBlock(body wire.SNAC_0x0E_0x05_ChatChannelMsgToHost, sess *state.Session, msg any) wire.TLVRestBlock {
+	block := wire.TLVRestBlock{}
+	// the order of these TLVs matters for AIM 2.x. if out of order, screen
+	// names do not appear with each chat message.
+	block.Append(wire.NewTLVBE(wire.ChatTLVSenderInformation, sess.TLVUserInfo()))
+	if body.HasTag(wire.ChatTLVPublicWhisperFlag) {
+		// send message to all chat room participants
+		block.Append(wire.NewTLVBE(wire.ChatTLVPublicWhisperFlag, []byte{}))
+	}
+	block.Append(wire.NewTLVBE(wire.ChatTLVMessageInfo, msg))
+	return block
 }
 
 // rollDice generates a chat response for the results of a die roll.
@@ -161,15 +182,11 @@ func (s ChatService) rollDice(sess *state.Session, dice int, sides int) wire.TLV
 	return block
 }
 
-// textFromChatMsgBlob extracts plaintext message text from HTML located in
+// extractChatMessage extracts plaintext message text from HTML located in
 // chat message info TLV(0x05).
-func textFromChatMsgBlob(msg []byte) ([]byte, error) {
-	block := wire.TLVRestBlock{}
-	if err := wire.UnmarshalBE(&block, bytes.NewBuffer(msg)); err != nil {
-		return nil, err
-	}
+func extractChatMessage(msg wire.TLVRestBlock) ([]byte, error) {
 
-	b, hasMsg := block.Bytes(wire.ChatTLVMessageInfoText)
+	b, hasMsg := msg.Bytes(wire.ChatTLVMessageInfoText)
 	if !hasMsg {
 		return nil, errors.New("SNAC(0x0E,0x05) has no chat msg text TLV")
 	}

foodgroup/chat_test.go

@@ -402,6 +402,69 @@ func TestChatService_ChannelMsgToHost(t *testing.T) {
 				},
 			},
 		},
+		{
+			name: "send chat room message, expect that TLVs that crash macos client",
+			userSession: newTestSession("user_sending_chat_msg", sessOptCannedSignonTime,
+				sessOptChatRoomCookie("the-chat-cookie")),
+			inputSNAC: wire.SNACMessage{
+				Frame: wire.SNACFrame{
+					RequestID: 1234,
+				},
+				Body: wire.SNAC_0x0E_0x05_ChatChannelMsgToHost{
+					Cookie:  1234,
+					Channel: 14,
+					TLVRestBlock: wire.TLVRestBlock{
+						TLVList: wire.TLVList{
+							{
+								Tag:   wire.ChatTLVPublicWhisperFlag,
+								Value: []byte{},
+							},
+							wire.NewTLVBE(wire.ChatTLVMessageInfo, wire.TLVRestBlock{
+								TLVList: wire.TLVList{
+									wire.NewTLVBE(wire.ChatTLVMessageInfoText,
+										"<HTML><BODY BGCOLOR=\"#ffffff\"><FONT LANG=\"0\">Hello</FONT></BODY></HTML>"),
+									wire.NewTLVBE(0x04, "remove me"),
+									wire.NewTLVBE(0x05, "remove me"),
+								},
+							}),
+						},
+					},
+				},
+			},
+			mockParams: mockParams{
+				chatMessageRelayerParams: chatMessageRelayerParams{
+					chatRelayToAllExceptParams: chatRelayToAllExceptParams{
+						{
+							screenName: state.NewIdentScreenName("user_sending_chat_msg"),
+							cookie:     "the-chat-cookie",
+							message: wire.SNACMessage{
+								Frame: wire.SNACFrame{
+									FoodGroup: wire.Chat,
+									SubGroup:  wire.ChatChannelMsgToClient,
+								},
+								Body: wire.SNAC_0x0E_0x06_ChatChannelMsgToClient{
+									Cookie:  1234,
+									Channel: 14,
+									TLVRestBlock: wire.TLVRestBlock{
+										TLVList: wire.TLVList{
+											wire.NewTLVBE(wire.ChatTLVSenderInformation,
+												newTestSession("user_sending_chat_msg", sessOptCannedSignonTime).TLVUserInfo()),
+											wire.NewTLVBE(wire.ChatTLVPublicWhisperFlag, []byte{}),
+											wire.NewTLVBE(wire.ChatTLVMessageInfo, wire.TLVRestBlock{
+												TLVList: wire.TLVList{
+													wire.NewTLVBE(wire.ChatTLVMessageInfoText,
+														"<HTML><BODY BGCOLOR=\"#ffffff\"><FONT LANG=\"0\">Hello</FONT></BODY></HTML>"),
+												},
+											}),
+										},
+									},
+								},
+							},
+						},
+					},
+				},
+			},
+		},
 	}
 
 	for _, tc := range cases {