From bf68735664acafec3420d81e8486984f1f6f85bd Mon Sep 17 00:00:00 2001
From: firest <blankalupo@163.com>
Date: Wed, 30 Mar 2022 10:42:56 +0800
Subject: [PATCH 1/3] fix(frame): forbidden empty topic in strict mode

---
 src/emqx_frame.erl        | 12 ++++++++++--
 test/emqx_frame_SUITE.erl |  8 ++++++++
 2 files changed, 18 insertions(+), 2 deletions(-)

diff --git a/src/emqx_frame.erl b/src/emqx_frame.erl
index 48e8b71fb..aa71b16ae 100644
--- a/src/emqx_frame.erl
+++ b/src/emqx_frame.erl
@@ -265,7 +265,7 @@ parse_packet(#mqtt_packet_header{type = ?CONNACK}, <<AckFlags:8, ReasonCode:8, R
 
 parse_packet(#mqtt_packet_header{type = ?PUBLISH, qos = QoS}, Bin,
              #{strict_mode := StrictMode, version := Ver}) ->
-    {TopicName, Rest} = parse_utf8_string(Bin, StrictMode),
+    {TopicName, Rest} = parse_topic_name(Bin, StrictMode),
     {PacketId, Rest1} = case QoS of
                             ?QOS_0 -> {undefined, Rest};
                             _ -> parse_packet_id(Rest)
@@ -357,7 +357,7 @@ parse_will_message(Packet = #mqtt_packet_connect{will_flag = true,
                                                  proto_ver = Ver},
                    Bin, StrictMode) ->
     {Props, Rest} = parse_properties(Bin, Ver, StrictMode),
-    {Topic, Rest1} = parse_utf8_string(Rest, StrictMode),
+    {Topic, Rest1} = parse_topic_name(Rest, StrictMode),
     {Payload, Rest2} = parse_binary_data(Rest1),
     {Packet#mqtt_packet_connect{will_props   = Props,
                                 will_topic   = Topic,
@@ -524,6 +524,14 @@ parse_binary_data(Bin)
   when 2 > byte_size(Bin) ->
     error(malformed_binary_data_length).
 
+parse_topic_name(Bin, false) ->
+    parse_utf8_string(Bin, false);
+parse_topic_name(Bin, true) ->
+    case parse_utf8_string(Bin, true) of
+        {<<>>, _Rest} -> error(empty_topic_name);
+        Result -> Result
+    end.
+
 %%--------------------------------------------------------------------
 %% Serialize MQTT Packet
 %%--------------------------------------------------------------------
diff --git a/test/emqx_frame_SUITE.erl b/test/emqx_frame_SUITE.erl
index d98786e99..81c861bdb 100644
--- a/test/emqx_frame_SUITE.erl
+++ b/test/emqx_frame_SUITE.erl
@@ -162,6 +162,14 @@ t_parse_malformed_utf8_string(_) ->
     ParseState = emqx_frame:initial_parse_state(#{strict_mode => true}),
     ?catch_error(utf8_string_invalid, emqx_frame:parse(MalformedPacket, ParseState)).
 
+t_parse_empty_topic_name(_) ->
+    Packet = <<48, 4, 0, 0, 0, 1>>,
+    NormalState = emqx_frame:initial_parse_state(#{strict_mode => false}),
+    ?assertMatch({_, _}, emqx_frame:parse(Packet, NormalState)),
+
+    StrictState = emqx_frame:initial_parse_state(#{strict_mode => true}),
+    ?catch_error(empty_topic_name, emqx_frame:parse(Packet, StrictState)).
+
 t_parse_frame_proxy_protocol(_) ->
     BinList = [ <<"PROXY TCP4 ">>, <<"PROXY TCP6 ">>, <<"PROXY UNKNOWN">>
               , <<"\r\n\r\n\0\r\nQUIT\n">>],

From 22beba8ebdeca73a947304ffd1c9bbfc141fade1 Mon Sep 17 00:00:00 2001
From: firest <blankalupo@163.com>
Date: Wed, 30 Mar 2022 11:12:33 +0800
Subject: [PATCH 2/3] chore: update changes-4.3.md

---
 CHANGES-4.3.md | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/CHANGES-4.3.md b/CHANGES-4.3.md
index 501ea34c4..ac7061057 100644
--- a/CHANGES-4.3.md
+++ b/CHANGES-4.3.md
@@ -17,6 +17,10 @@ File format:
 * In order to fix the execution order of exhook, e.g. before/after other plugins/modules,
   ExHook now supports user customizing emqx_hook execute priority.
 
+### Bug fixes
+
+* Forbidden empty topics in strict mode
+
 ## v4.3.13
 
 ### Important changes

From ea8ddcef60f71712164467ec9d8dddcef5f18d9c Mon Sep 17 00:00:00 2001
From: firest <blankalupo@163.com>
Date: Thu, 31 Mar 2022 10:19:10 +0800
Subject: [PATCH 3/3] fix: fix spell error in CHANGES-4.3.md

---
 CHANGES-4.3.md | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/CHANGES-4.3.md b/CHANGES-4.3.md
index ac7061057..a27122e59 100644
--- a/CHANGES-4.3.md
+++ b/CHANGES-4.3.md
@@ -19,7 +19,7 @@ File format:
 
 ### Bug fixes
 
-* Forbidden empty topics in strict mode
+* Prohibit empty topics in strict mode
 
 ## v4.3.13