Lua: allow a Dissector object to be passed in for register_heuristic

Bug: 10695
Change-Id: I81181b2d00fcb5f0c25ab89bbe4968897f47a3a6
Reviewed-on: https://code.wireshark.org/review/6131
Petri-Dish: Hadriel Kaplan <hadrielk@yahoo.com>
Tested-by: Petri Dish Buildbot <buildbot-no-reply@wireshark.org>
Reviewed-by: Michael Mann <mmann78@netscape.net>

epan/wslua/init_wslua.c

@@ -283,6 +283,8 @@ gboolean heur_dissect_lua(tvbuff_t* tvb, packet_info* pinfo, proto_tree* tree, v
     } else {
         if (lua_isboolean(L, -1) || lua_isnil(L, -1)) {
             result = lua_toboolean(L, -1);
+        } else if (lua_type(L, -1) == LUA_TNUMBER) {
+            result = lua_tointeger(L,-1) != 0 ? TRUE : FALSE;
         } else {
             proto_tree_add_expert_format(tree, pinfo, &ei_lua_error, tvb, 0, 0,
                     "Lua Error: invalid return value from Lua %s heuristic dissector", pinfo->current_proto);

epan/wslua/wslua_proto.c

@@ -1635,6 +1635,13 @@ WSLUA_METHOD Proto_register_heuristic(lua_State* L) {
        and dissect the packet (including setting TreeItem info and such) only if the payload is for it,
        before returning true or false.
 
+       Since version 1.99.1, this function also accepts a Dissector object as the second argument,
+       to allow re-using the same Lua code as the `function proto.dissector(...)`. In this case,
+       the Dissector must return a Lua number of the number of bytes consumed/parsed: if 0 is returned,
+       it will be treated the same as a `false` return for the heuristic; if a positive or negative
+       number is returned, then the it will be treated the same as a `true` return for the heuristic,
+       meaning the packet is for this protocol and no other heuristic will be tried.
+
        @since 1.11.3
      */
 #define WSLUA_ARG_Proto_register_heuristic_LISTNAME 2 /* The heuristic list name this function
@@ -1659,6 +1666,29 @@ WSLUA_METHOD Proto_register_heuristic(lua_State* L) {
         return 0;
     }
 
+    /* we'll check if the second form of this function was called: when the second arg is
+       a Dissector obejct. The truth is we don't need the Dissector object to do this
+       form of registration, but someday we might... so we're using it as a boolean arg
+       right now and in the future might use it for other things in this registration.
+     */
+    if (isDissector(L, WSLUA_ARG_Proto_register_heuristic_FUNC)) {
+        /* retrieve the Dissector's Lua function... first get the table of all dissector funcs */
+        lua_rawgeti(L, LUA_REGISTRYINDEX, lua_dissectors_table_ref);
+        /* then get the one for this Proto */
+        lua_getfield(L, -1, proto_name);
+
+        if (!lua_isfunction(L,-1)) {
+            /* this shouldn't be possible */
+            luaL_error(L,"Proto_register_heuristic: could not get lua function from lua_dissectors_table");
+            return 0;
+        }
+        /* replace the Dissector with the function */
+        lua_replace(L, WSLUA_ARG_Proto_register_heuristic_FUNC);
+        /* pop the lua_dissectors_table */
+        lua_pop(L, 1);
+        g_assert(top == lua_gettop(L));
+    }
+
     /* heuristic functions are stored in a table in the registry; the registry has a
      * table at reference lua_heur_dissectors_table_ref, and that table has keys for
      * the heuristic listname (e.g., "udp", "tcp", etc.), and that key's value is a

test/lua/dissector.lua

@@ -66,6 +66,7 @@ local default_settings =
     debug_level  = DEBUG,
     port         = 65333,
     heur_enabled = true,
+    heur_regmode = 1,
 }
 
 -- for testing purposes, we want to be able to pass in changes to the defaults
@@ -584,7 +585,16 @@ local function heur_dissect_dns(tvbuf,pktinfo,root)
 end
 
 -- now register that heuristic dissector into the udp heuristic list
-dns:register_heuristic("udp",heur_dissect_dns)
+if default_settings.heur_regmode == 1 then
+    -- this is the "normal" way to register a heuristic: using a lua function
+    dns:register_heuristic("udp",heur_dissect_dns)
+elseif default_settings.heur_regmode == 2 then
+    -- this is to test the fix for bug 10695:
+    dns:register_heuristic("udp",dns.dissector)
+elseif default_settings.heur_regmode == 3 then
+    -- and this too is to test the fix for bug 10695:
+    dns:register_heuristic("udp", function (...) return dns.dissector(...); end )
+end
 
 -- We're done!
 -- our protocol (Proto) gets automatically registered after this script finishes loading

test/lua/verify_dissector.lua

@@ -135,6 +135,19 @@ local lines = {
 -- dissector, then the first one by the heuristic, then the second one by
 -- a conversation match
 local numtests = 1 + #lines[1] + #lines[2] + #lines[3] + #lines[4]
+
+local hasHeuristic = true
+
+-- grab passed-in arguments
+local args = { ... }
+if #args > 0 then
+    for _, arg in ipairs(args) do
+        if arg == "no_heur" then
+            numtests = numtests - 1
+        end
+    end
+end
+
 print("going to run "..numtests.." tests")
 
 -- for an example of what we're reading through to verify, look at end of this file

test/suite-wslua.sh

@@ -48,12 +48,50 @@ wslua_step_dissector_test() {
 	if [ ! $RETURNVALUE -eq $EXIT_OK ]; then
 		echo
 		cat ./testin.txt
-		test_step_failed "exit status of $DUT: $RETURNVALUE"
+		test_step_failed "subtest-1 exit status of $DUT: $RETURNVALUE"
 		return
 	fi
 
 	# then run tshark again with the verification script. (it internally reads in testin.txt)
 	$TSHARK -r $CAPTURE_DIR/empty.pcap -X lua_script:$TESTS_DIR/lua/verify_dissector.lua > testout.txt 2>&1
+	grep -q "All tests passed!" testout.txt
+	if [ $? -ne 0 ]; then
+		cat ./testin.txt
+		cat ./testout.txt
+		test_step_failed "subtest-1 didn't find pass marker"
+	fi
+
+	# run tshark with the dissector script again, but in mode 2.
+	$TSHARK -r $CAPTURE_DIR/dns_port.pcap -V -X lua_script:$TESTS_DIR/lua/dissector.lua -X lua_script1:heur_regmode=2 > testin.txt 2>&1
+	RETURNVALUE=$?
+	if [ ! $RETURNVALUE -eq $EXIT_OK ]; then
+		echo
+		cat ./testin.txt
+		test_step_failed "subtest-1 exit status of $DUT: $RETURNVALUE"
+		return
+	fi
+
+	# then run tshark again with the verification script. (it internally reads in testin.txt)
+	$TSHARK -r $CAPTURE_DIR/empty.pcap -X lua_script:$TESTS_DIR/lua/verify_dissector.lua -X lua_script1:no_heur > testout.txt 2>&1
+	grep -q "All tests passed!" testout.txt
+	if [ $? -ne 0 ]; then
+		cat ./testin.txt
+		cat ./testout.txt
+		test_step_failed "subtest-1 didn't find pass marker"
+	fi
+
+	# run tshark with the dissector script again, but in mode 3.
+	$TSHARK -r $CAPTURE_DIR/dns_port.pcap -V -X lua_script:$TESTS_DIR/lua/dissector.lua -X lua_script1:heur_regmode=3 > testin.txt 2>&1
+	RETURNVALUE=$?
+	if [ ! $RETURNVALUE -eq $EXIT_OK ]; then
+		echo
+		cat ./testin.txt
+		test_step_failed "subtest-1 exit status of $DUT: $RETURNVALUE"
+		return
+	fi
+
+	# then run tshark again with the verification script. (it internally reads in testin.txt)
+	$TSHARK -r $CAPTURE_DIR/empty.pcap -X lua_script:$TESTS_DIR/lua/verify_dissector.lua -X lua_script1:no_heur > testout.txt 2>&1
 	if grep -q "All tests passed!" testout.txt; then
 		test_step_ok
 	else