XEP-0198: Don't bounce/resend forwarded messages

On connection timeout, drop any messages that were forwarded by some
encapsulating protocol, such as XEP-0280 carbon copies or XEP-0313
archive messages.  Bouncing or resending them could easily lead to
unexpected results.

diff --git a/src/ejabberd_c2s.erl b/src/ejabberd_c2s.erl
index 0051266c7d1c3d14a9e597fce414fdcac3638484..17b54e3c5a0698daba5cd9904eda7ef421674c30 100644 (file)
--- a/src/ejabberd_c2s.erl
+++ b/src/ejabberd_c2s.erl
@@ -2808,19 +2808,63 @@ handle_unacked_stanzas(_StateData, _F) ->
 
 handle_unacked_stanzas(StateData) when StateData#state.sm_state == active;
                                       StateData#state.sm_state == pending ->
-    F = case StateData#state.resend_on_timeout of
-         true ->
-             fun ejabberd_router:route/3;
-         false ->
-             fun(From, To, El) ->
-                     Err = jlib:make_error_reply(El, ?ERR_SERVICE_UNAVAILABLE),
-                     ejabberd_router:route(To, From, Err)
-             end
+    ReRoute = case StateData#state.resend_on_timeout of
+               true ->
+                   fun ejabberd_router:route/3;
+               false ->
+                   fun(From, To, El) ->
+                           Err =
+                               jlib:make_error_reply(El,
+                                                     ?ERR_SERVICE_UNAVAILABLE),
+                           ejabberd_router:route(To, From, Err)
+                   end
+             end,
+    F = fun(From, To, El) ->
+               %% We'll drop the stanza if it was <forwarded/> by some
+               %% encapsulating protocol as per XEP-0297.  One such protocol is
+               %% XEP-0280, which says: "When a receiving server attempts to
+               %% deliver a forked message, and that message bounces with an
+               %% error for any reason, the receiving server MUST NOT forward
+               %% that error back to the original sender."  Resending such a
+               %% stanza could easily lead to unexpected results as well.
+               case is_encapsulated_forward(El) of
+                 true ->
+                     ?DEBUG("Dropping forwarded stanza from ~s",
+                            [xml:get_attr_s(<<"from">>, El#xmlel.attrs)]);
+                 false ->
+                     ReRoute(From, To, El)
+               end
        end,
     handle_unacked_stanzas(StateData, F);
 handle_unacked_stanzas(_StateData) ->
     ok.
 
+is_encapsulated_forward(#xmlel{name = <<"message">>} = El) ->
+    SubTag = case {xml:get_subtag(El, <<"sent">>),
+                  xml:get_subtag(El, <<"received">>),
+                  xml:get_subtag(El, <<"result">>)} of
+              {false, false, false} ->
+                  false;
+              {Tag, false, false} ->
+                  Tag;
+              {false, Tag, false} ->
+                  Tag;
+              {_, _, Tag} ->
+                  Tag
+           end,
+    if SubTag == false ->
+          false;
+       true ->
+          case xml:get_subtag(SubTag, <<"forwarded">>) of
+            false ->
+                false;
+            _ ->
+                true
+          end
+    end;
+is_encapsulated_forward(_El) ->
+    false.
+
 inherit_session_state(#state{user = U, server = S} = StateData, ResumeID) ->
     case jlib:base64_to_term(ResumeID) of
       {term, {U, S, R, Time}} ->