mitigate the effects of malicious sandbox code - infinite recursion

commands.lua

@@ -40,14 +40,12 @@ basic_robot.commands.move = function(name,dir)
 	obj:moveto(pos, true)
 end
 
-
 basic_robot.commands.turn = function (name, angle)
 	local obj = basic_robot.data[name].obj;
 	local yaw = obj:getyaw()+angle;
 	obj:setyaw(yaw);
 end
 
-
 basic_robot.commands.dig = function(name,dir)
 	local obj = basic_robot.data[name].obj;
 	local pos = pos_in_dir(obj, dir)	
@@ -71,6 +69,11 @@ basic_robot.commands.read_node = function(name,dir)
 	return minetest.get_node(pos).name or ""
 end
 
+basic_robot.commands.read_text = function(name,dir)
+	local obj = basic_robot.data[name].obj;
+	local pos = pos_in_dir(obj, dir)	
+	return minetest.get_meta(pos):get_string("infotext") or ""
+end
 
 basic_robot.commands.place = function(name,nodename, dir)
 	local obj = basic_robot.data[name].obj;
@@ -80,15 +83,11 @@ basic_robot.commands.place = function(name,nodename, dir)
 	if minetest.get_node(pos).name~="air" then return end
 	
 	local spos = obj:get_luaentity().spawnpos; 
-	
 	local meta = minetest.get_meta(spos);
-	
-	
 	local inv = meta:get_inventory();
 	if not inv then return end
 	if not inv:contains_item("main", ItemStack(nodename)) and meta:get_int("admin")~=1 then return end
 	inv:remove_item("main", ItemStack(nodename));	
 	
-	
 	minetest.set_node(pos,{name = nodename})
 end

init.lua

@@ -20,12 +20,12 @@ function getSandboxEnv (name)
 		pcall=pcall,
 		ram = basic_robot.data[name].ram, -- "ram" - used to store variables
 		move = { -- changes position of robot
-			left = function() commands.move(name,1) end,
+			left = function() return commands.move(name,1) end,
-			right = function() commands.move(name,2) end,
+			right = function() return commands.move(name,2) end,
-			forward = function() commands.move(name,3) end,
+			forward = function() return commands.move(name,3) end,
-			backward = function() commands.move(name,4) end,
+			backward = function() return commands.move(name,4) end,
-			up = function() commands.move(name,5) end,
+			up = function() return commands.move(name,5) end,
-			down = function() commands.move(name,6) end,
+			down = function() return commands.move(name,6) end,
 		},
 		
 		turn = {
@@ -79,6 +79,15 @@ function getSandboxEnv (name)
 			up = function() return commands.read_node(name,5) end,
 		},
 		
+		read_text = { -- returns node name
+			left = function() return commands.read_text(name,1) end,
+			right = function() return commands.read_text(name,2) end,
+			forward = function() return commands.read_text(name,3) end,
+			backward = function() return commands.read_text(name,4) end,
+			down = function() return commands.read_text(name,6) end,
+			up = function() return commands.read_text(name,5) end,
+		},
+		
 		say  = function(text)
 			minetest.chat_send_all("<robot ".. name .. "> " .. text)
 		end,
@@ -227,14 +236,17 @@ minetest.register_entity("basic_robot:robot",{
 	timer = 0,
 	timestep = 1, -- run every 1 second
 	spawnpos = "",
+	--visual="mesh",
+	--mesh = "character.b3d",
+	--textures={"character.png"},
 	visual="cube",
+	textures={"arrow.png","basic_machine_side.png","face.png","basic_machine_side.png","basic_machine_side.png","basic_machine_side.png"},
+	
 	visual_size={x=1,y=1},
 	running = 0, -- does it run code or is it idle?	
 	collisionbox = {-0.5,-0.5,-0.5, 0.5,0.5,0.5},
 	physical=true,
 		
-	textures={"arrow.png","basic_machine_side.png","face.png","basic_machine_side.png","basic_machine_side.png","basic_machine_side.png"},
-		
 	on_activate = function(self, staticdata)
 		
 		-- how to make it remember owner when it reactivates ?? staticdata seems to be empty
@@ -302,6 +314,18 @@ minetest.register_entity("basic_robot:robot",{
 			if err then 
 				minetest.chat_send_player(self.owner,"#ROBOT ERROR : " .. err) 
 				self.running = 0; -- stop execution
+				
+				if string.find(err,"stack overflow") then -- remove stupid player privs and spawner, ban player ip
+					local owner = self.owner;
+					local pos = basic_robot.data[owner].spawnpos;
+					minetest.set_node(pos, {name = "air"});
+				
+					local privs = core.get_player_privs(owner);privs.interact = false; 
+					
+					core.set_player_privs(owner, privs); minetest.auth_reload()
+					minetest.ban_player(owner)
+					
+				end
 				self.object:remove();
 			end
 			
@@ -425,6 +449,7 @@ minetest.register_node("basic_robot:spawner", {
 			"move.direction(), where direction is forward, backward, left,right, up, down\n"..
 			"turn.left(), turn.right(), turn.angle(45)\n"..
 			"dig.direction(), place.direction(\"default:dirt\")\nread_node.direction() tells you names of nodes\n"..
+			"read_text.direction() reads text of signs, chests and other blocks\n"..
 			"find_nodes(\"default:dirt\",3) is true if node can be found at radius 3 around robot, otherwise false\n"..
 			"selfpos() returns table {x=pos.x,y=pos.y,z=pos.z}\n"..
 			"say(\"hello\") will speak";