From 4972cb6d5e68c0ad9f7b290e33f49ecf6436361b Mon Sep 17 00:00:00 2001
From: Bohdan Horbeshko <bodqhrohro@gmail.com>
Date: Wed, 4 Oct 2023 05:57:29 -0400
Subject: [PATCH] Reject MUC nickname change attempts

---
 telegram/utils.go | 33 +++++++++++++++++++++
 xmpp/handlers.go  | 73 +++++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 106 insertions(+)

diff --git a/telegram/utils.go b/telegram/utils.go
index addeee8..a730113 100644
--- a/telegram/utils.go
+++ b/telegram/utils.go
@@ -478,6 +478,39 @@ func (c *Client) updateMUCsNickname(memberID int64, newNickname string) {
 	}
 }
 
+// MUCHasResource checks if a MUC was joined from a given resource
+func (c *Client) MUCHasResource(chatID int64, resource string) bool {
+	c.locks.mucCacheLock.Lock()
+	defer c.locks.mucCacheLock.Unlock()
+
+	mucState, ok := c.mucCache[chatID]
+	if !ok || mucState == nil {
+		return false
+	}
+	_, ok = mucState.Resources[resource]
+	return ok
+}
+
+// GetMyMUCNickname obtains this account's nickname in a given MUC
+func (c *Client) GetMyMUCNickname(chatID int64) (string, bool) {
+	if c.me == nil {
+		return "", false
+	}
+
+	c.locks.mucCacheLock.Lock()
+	defer c.locks.mucCacheLock.Unlock()
+
+	mucState, ok := c.mucCache[chatID]
+	if !ok || mucState == nil {
+		return "", false
+	}
+	member, ok := mucState.Members[c.me.Id]
+	if !ok {
+		return "", false
+	}
+	return member.Nickname, true
+}
+
 func (c *Client) formatContact(chatID int64) string {
 	if chatID == 0 {
 		return ""
diff --git a/xmpp/handlers.go b/xmpp/handlers.go
index 3ab79c7..eea14be 100644
--- a/xmpp/handlers.go
+++ b/xmpp/handlers.go
@@ -324,7 +324,9 @@ func HandlePresence(s xmpp.Sender, p stanza.Packet) {
 	prs.Get(&mucExt)
 	if mucExt.XMLName.Space != "" {
 		handleMUCPresence(s, prs, mucExt)
+		return
 	}
+	tryHandleMUCNicknameChange(s, prs)
 }
 
 func handleSubscription(s xmpp.Sender, p stanza.Presence) {
@@ -498,6 +500,77 @@ func handleMUCPresence(s xmpp.Sender, p stanza.Presence, mucExt stanza.MucPresen
 	}
 }
 
+func tryHandleMUCNicknameChange(s xmpp.Sender, p stanza.Presence) {
+	log.WithFields(log.Fields{
+		"type": p.Type,
+		"from": p.From,
+		"to":   p.To,
+	}).Warn("Nickname change presence?")
+	log.Debugf("%#v", p)
+
+	if p.Type != "" {
+		return
+	}
+
+	toBare, nickname, ok := gateway.SplitJID(p.To)
+	if !ok || nickname == "" {
+		return
+	}
+
+	fromBare, fromResource, ok := gateway.SplitJID(p.From)
+	if !ok {
+		return
+	}
+
+	session, ok := sessions[fromBare]
+	if !ok || !session.Session.MUC {
+		return
+	}
+
+	chatId, ok := toToID(toBare)
+	if !ok {
+		return
+	}
+
+	chat, _, err := session.GetContactByID(chatId, nil)
+	if err != nil || !session.IsGroup(chat) {
+		return
+	}
+
+	if !session.MUCHasResource(chatId, fromResource) {
+		return
+	}
+
+	log.Warn("🗿 Yes")
+
+	component, ok := s.(*xmpp.Component)
+	if !ok {
+		log.Error("Not a component")
+		return
+	}
+
+	from := toBare
+	nickname, ok = session.GetMyMUCNickname(chatId)
+	if ok {
+		from = from+"/"+nickname
+	}
+	reply := &stanza.Presence{
+		Attrs: stanza.Attrs{
+			From:  from,
+			To:    p.From,
+			Id:    p.Id,
+			Type:  stanza.PresenceTypeError,
+		},
+		Error: stanza.Err{
+			Code:   406,
+			Type:   stanza.ErrorTypeModify,
+			Reason: "not-acceptable",
+			Text:   "Telegram does not support changing nicknames per-chat. Issue a /setname command to the transport if you wish to change the global name",
+		},
+	}
+	gateway.ResumableSend(component, reply)
+}
+
 func handleGetVcardIq(s xmpp.Sender, iq *stanza.IQ, typ byte) {
 	log.WithFields(log.Fields{
 		"from": iq.From,