From eb946eb80c170c4eab3b076ae27f76bc8afc9a52 Mon Sep 17 00:00:00 2001
From: Zaiming Shi <zmstone@gmail.com>
Date: Mon, 26 Apr 2021 12:02:49 +0200
Subject: [PATCH] fix(emqx_trie): do not try to match wildcard topics

---
 src/emqx_trie.erl        | 15 +++++++++++++--
 test/emqx_trie_SUITE.erl | 10 ++++++++++
 2 files changed, 23 insertions(+), 2 deletions(-)

diff --git a/src/emqx_trie.erl b/src/emqx_trie.erl
index 30e5bd7b2..1c6e3be58 100644
--- a/src/emqx_trie.erl
+++ b/src/emqx_trie.erl
@@ -105,8 +105,19 @@ delete(Topic) when is_binary(Topic) ->
 -spec(match(emqx_topic:topic()) -> list(emqx_topic:topic())).
 match(Topic) when is_binary(Topic) ->
     Words = emqx_topic:words(Topic),
-    false = emqx_topic:wildcard(Words), % assert
-    do_match(Words).
+    case emqx_topic:wildcard(Words) of
+        true ->
+            %% In MQTT spec, clients are not allowed to
+            %% publish messages to a wildcard topic.
+            %% Here we refuse to match wildcard topic.
+            %%
+            %% NOTE: this does not imply emqx allows clients
+            %% publishing to wildcard topics.
+            %% Such clients will get disconnected.
+            [];
+        false ->
+            do_match(Words)
+    end.
 
 %% @doc Is the trie empty?
 -spec(empty() -> boolean()).
diff --git a/test/emqx_trie_SUITE.erl b/test/emqx_trie_SUITE.erl
index e74b7352e..7516b58a0 100644
--- a/test/emqx_trie_SUITE.erl
+++ b/test/emqx_trie_SUITE.erl
@@ -81,6 +81,16 @@ t_match(_) ->
             end),
     ?assertEqual(Machted, lists:sort(?TRIE:match(<<"sensor/1">>))).
 
+t_match_invalid(_) ->
+    trans(fun() ->
+              ?TRIE:insert(<<"sensor/1/metric/2">>),
+              ?TRIE:insert(<<"sensor/+/#">>),
+              ?TRIE:insert(<<"sensor/#">>)
+            end),
+    ?assertEqual([], lists:sort(?TRIE:match(<<"sensor/+">>))),
+    ?assertEqual([], lists:sort(?TRIE:match(<<"#">>))).
+
+
 t_match2(_) ->
     Matched = [<<"#">>, <<"+/#">>, <<"+/+/#">>],
     trans(fun() ->