fix(emqx): validate mqtt malformed variable byte integer

src/emqx.appup.src

@@ -8,16 +8,22 @@
     end,
 {VSN,
   [
+    {<<"4.2.[34567]">>, [
+      {load_module, emqx_frame, brutal_purge, soft_purge, []}
+    ]},
     {"4.2.2", [
+      {load_module, emqx_frame, brutal_purge, soft_purge, []},
       {load_module, emqx_metrics, brutal_purge, soft_purge, []}
     ]},
     {"4.2.1", [
+      {load_module, emqx_frame, brutal_purge, soft_purge, []},
       {load_module, emqx_metrics, brutal_purge, soft_purge, []},
       {load_module, emqx_channel, brutal_purge, soft_purge, []},
       {load_module, emqx_mod_topic_metrics, brutal_purge, soft_purge, []},
       {load_module, emqx_json, brutal_purge, soft_purge, []}
     ]},
     {"4.2.0", [
+      {load_module, emqx_frame, brutal_purge, soft_purge, []},
       {load_module, emqx_metrics, brutal_purge, soft_purge, []},
       {load_module, emqx_channel, brutal_purge, soft_purge, []},
       {load_module, emqx_mod_topic_metrics, brutal_purge, soft_purge, []},
@@ -30,16 +36,22 @@
     {<<".*">>, []}
   ],
   [
+    {<<"4.2.[34567]">>, [
+      {load_module, emqx_frame, brutal_purge, soft_purge, []}
+    ]},
     {"4.2.2", [
+      {load_module, emqx_frame, brutal_purge, soft_purge, []},
       {load_module, emqx_metrics, brutal_purge, soft_purge, []}
     ]},
     {"4.2.1", [
+      {load_module, emqx_frame, brutal_purge, soft_purge, []},
       {load_module, emqx_metrics, brutal_purge, soft_purge, []},
       {load_module, emqx_channel, brutal_purge, soft_purge, []},
       {load_module, emqx_mod_topic_metrics, brutal_purge, soft_purge, []},
       {load_module, emqx_json, brutal_purge, soft_purge, []}
     ]},
     {"4.2.0", [
+      {load_module, emqx_frame, brutal_purge, soft_purge, []},
       {load_module, emqx_metrics, brutal_purge, soft_purge, []},
       {load_module, emqx_channel, brutal_purge, soft_purge, []},
       {load_module, emqx_mod_topic_metrics, brutal_purge, soft_purge, []},

src/emqx_frame.erl

@@ -125,6 +125,9 @@ parse_remaining_len(<<0:8, Rest/binary>>, Header, 1, 0, Options) ->
 %% Match PUBACK, PUBREC, PUBREL, PUBCOMP, UNSUBACK...
 parse_remaining_len(<<0:1, 2:7, Rest/binary>>, Header, 1, 0, Options) ->
     parse_frame(Rest, Header, 2, Options);
+parse_remaining_len(<<1:1, _Len:7, _Rest/binary>>, _Header, Multiplier, _Value, _Options)
+         when Multiplier > 2097152 ->
+    error(malformed_variable_byte_integer);
 parse_remaining_len(<<1:1, Len:7, Rest/binary>>, Header, Multiplier, Value, Options) ->
     parse_remaining_len(Rest, Header, Multiplier * ?HIGHBIT, Value + Len * Multiplier, Options);
 parse_remaining_len(<<0:1, Len:7, Rest/binary>>, Header, Multiplier, Value,

test/emqx_frame_SUITE.erl

@@ -42,7 +42,8 @@ all() ->
 groups() ->
     [{parse, [parallel],
       [t_parse_cont,
-       t_parse_frame_too_large
+       t_parse_frame_too_large,
+       t_parse_frame_malformed_variable_byte_integer
       ]},
      {connect, [parallel],
       [t_serialize_parse_v3_connect,
@@ -129,6 +130,12 @@ t_parse_frame_too_large(_) ->
     ?catch_error(frame_too_large, parse_serialize(Packet, #{max_size => 512})),
     ?assertEqual(Packet, parse_serialize(Packet, #{max_size => 2048, version => ?MQTT_PROTO_V4})).
 
+t_parse_frame_malformed_variable_byte_integer(_) ->
+    MalformedPayload = << <<16#80>> || _ <- lists:seq(1, 4) >>,
+    ParseState = emqx_frame:initial_parse_state(#{}),
+    ?catch_error(malformed_variable_byte_integer,
+        emqx_frame:parse(MalformedPayload, ParseState)).
+
 t_serialize_parse_v3_connect(_) ->
     Bin = <<16,37,0,6,77,81,73,115,100,112,3,2,0,60,0,23,109,111,115,
             113,112,117, 98,47,49,48,52,53,49,45,105,77,97,99,46,108,