From efb4fd0d1020faa105bf932c06cf4c67fb389952 Mon Sep 17 00:00:00 2001
From: Badlop <badlop@process-one.net>
Date: Mon, 30 Jul 2018 17:26:57 +0200
Subject: [PATCH] New option tombstone_expiry locks recent room creation after
 destroy (#2546)

Setting the new mod_muc option tombstone_expiry to a positive integer
will make that any room destroyed gets replaced with a room tombstone.
That tombstone cannot be joined, so it blocks accessing the old room JID
until the expiry seconds have passed.
The default value is 0 seconds, so tombstones are not created.
---
 src/mod_muc.erl      | 31 ++++++++++++++++++++++++++++-
 src/mod_muc_room.erl | 46 +++++++++++++++++++++++++++++++++++++++++++-
 2 files changed, 75 insertions(+), 2 deletions(-)

diff --git a/src/mod_muc.erl b/src/mod_muc.erl
index f871c0b77..6b53e38d9 100644
--- a/src/mod_muc.erl
+++ b/src/mod_muc.erl
@@ -435,7 +435,7 @@ do_route1(Host, ServerHost, Access, HistorySize, RoomShaper,
     {_AccessRoute, AccessCreate, _AccessAdmin, _AccessPersistent} = Access,
     {Room, _, Nick} = jid:tolower(To),
     RMod = gen_mod:ram_db_mod(ServerHost, ?MODULE),
-    case RMod:find_online_room(ServerHost, Room, Host) of
+    case find_online_available_room(RMod, ServerHost, Room, Host) of
 	error ->
 	    case is_create_request(Packet) of
 		true ->
@@ -463,12 +463,38 @@ do_route1(Host, ServerHost, Access, HistorySize, RoomShaper,
 		    Err = xmpp:err_item_not_found(ErrText, Lang),
 		    ejabberd_router:route_error(Packet, Err)
 	    end;
+	locked_room ->
+	    Lang = xmpp:get_lang(Packet),
+	    ErrText = <<"Conference room was destroyed">>,
+	    Err = xmpp:err_item_not_found(ErrText, Lang),
+	    ejabberd_router:route_error(Packet, Err);
 	{ok, Pid} ->
 	    ?DEBUG("MUC: send to process ~p~n", [Pid]),
 	    mod_muc_room:route(Pid, Packet),
 	    ok
     end.
 
+find_online_available_room(RMod, ServerHost, Room, Host) ->
+    case RMod:find_online_room(ServerHost, Room, Host) of
+	error ->
+	    error;
+	{ok, Pid} ->
+	    check_tombstone(Pid)
+    end.
+
+-define(TOMBSTONE_REASON, <<"Expiring tombstone">>).
+
+check_tombstone(Pid) ->
+    case p1_fsm:sync_send_all_state_event(Pid, check_tombstone) of
+	not_tombstone ->
+	    {ok, Pid};
+	locked ->
+	    locked_room;
+	expired ->
+	    p1_fsm:send_all_state_event(Pid, {destroy, ?TOMBSTONE_REASON}),
+	    error
+    end.
+
 -spec process_vcard(iq()) -> iq().
 process_vcard(#iq{type = get, lang = Lang, sub_els = [#vcard_temp{}]} = IQ) ->
     xmpp:make_iq_result(
@@ -922,6 +948,8 @@ mod_opt_type(min_presence_interval) ->
     fun (I) when is_number(I), I >= 0 -> I end;
 mod_opt_type(room_shaper) ->
     fun (A) when is_atom(A) -> A end;
+mod_opt_type(tombstone_expiry) ->
+    fun (I) when is_integer(I) -> I end;
 mod_opt_type(user_message_shaper) ->
     fun (A) when is_atom(A) -> A end;
 mod_opt_type(user_presence_shaper) ->
@@ -1011,6 +1039,7 @@ mod_options(Host) ->
      {queue_type, ejabberd_config:default_queue_type(Host)},
      {regexp_room_id, <<"">>},
      {room_shaper, none},
+     {tombstone_expiry, 0},
      {user_message_shaper, none},
      {user_presence_shaper, none},
      {default_room_options,
diff --git a/src/mod_muc_room.erl b/src/mod_muc_room.erl
index f1acf3cb0..33c58e416 100644
--- a/src/mod_muc_room.erl
+++ b/src/mod_muc_room.erl
@@ -533,6 +533,9 @@ handle_sync_event({change_config, Config}, _From,
 handle_sync_event({change_state, NewStateData}, _From,
 		  StateName, _StateData) ->
     {reply, {ok, NewStateData}, StateName, NewStateData};
+handle_sync_event(check_tombstone, _From,
+		  StateName, StateData) ->
+    {reply, check_tombstone(StateData), StateName, StateData};
 handle_sync_event({process_item_change, Item, UJID}, _From, StateName, StateData) ->
     case process_item_change(Item, StateData, UJID) of
 	{error, _} = Err ->
@@ -3784,11 +3787,52 @@ destroy_room(DEl, StateData) ->
     case (StateData#state.config)#config.persistent of
       true ->
 	  mod_muc:forget_room(StateData#state.server_host,
-			      StateData#state.host, StateData#state.room);
+			      StateData#state.host, StateData#state.room),
+	  maybe_create_tombstone(DEl, StateData);
       false -> ok
     end,
     {result, undefined, stop}.
 
+-define(TOMBSTONE_NAME, <<"Room tombstone">>).
+-define(TOMBSTONE_REASON, <<"Expiring tombstone">>).
+
+maybe_create_tombstone(DEl, StateData) ->
+    case DEl#muc_destroy.reason of
+	?TOMBSTONE_REASON ->
+	    ok;
+	_ ->
+	    TombstoneExpiry = gen_mod:get_module_opt(StateData#state.server_host,
+					 mod_muc, tombstone_expiry),
+	    create_tombstone(TombstoneExpiry, StateData)
+    end.
+
+create_tombstone(TombstoneExpiry, _) when TombstoneExpiry =< 0 ->
+    ok;
+create_tombstone(TombstoneExpiry, #state{server_host = Server, host = Host, room = Room}) ->
+    ?INFO_MSG("Creating tombstone for room ~s@~s", [Room, Host]),
+    Password = integer_to_binary(misc:now_to_usec(now()) + TombstoneExpiry*1000000),
+    Opts1 = gen_mod:get_module_opt(Server, mod_muc, default_room_options),
+    {_, Opts2} = proplists:split(Opts1, [title, password, persistent, public]),
+    Opts3 = [{title, ?TOMBSTONE_NAME}, {password, Password}, {persistent, true}, {public, false} | Opts2],
+    mod_muc:create_room(
+	    Host,
+	    Room,
+	    jid:make(<<"tombstone">>, <<"">>),
+	    <<"">>,
+	    Opts3).
+
+check_tombstone(#state{config = Config}) ->
+    case Config#config.title of
+        ?TOMBSTONE_NAME ->
+            case binary_to_integer(Config#config.password) < misc:now_to_usec(now()) of
+                true ->
+                    expired;
+                false ->
+                    locked
+            end;
+        _ -> not_tombstone
+    end.
+
 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
 % Disco
 
-- 
2.40.0