Illuna-Minetest/basic_robot
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allow potentially malicious instructions like for, goto, while but preprocess script to insert counter, this prevents too long executions

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This commit is contained in:
rnd1 2016-11-11 13:35:38 +01:00
parent 0c3f06a428
commit 56b777a3dc
1 changed files with 92 additions and 11 deletions
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103
init.lua
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@ -1,5 +1,6 @@
-- basic_robot by rnd, 2016
basic_robot = {};
basic_robot.call_limit = 32; -- how many function calls per script execution allowed
basic_robot.data = {};
--[[
@ -15,7 +16,7 @@ dofile(minetest.get_modpath("basic_robot").."/commands.lua")
function getSandboxEnv (name)
local commands = basic_robot.commands;
return
local env =
{
pcall=pcall,
ram = basic_robot.data[name].ram, -- "ram" - used to store variables
@ -131,13 +132,29 @@ function getSandboxEnv (name)
time = os.time,
},
}
error = error,
debug = debug,
_ccounter = basic_robot.data[name].ccounter, -- counts how many function calls per execution of script
increase_ccounter =
function()
local _ccounter = basic_robot.data[name].ccounter;
if _ccounter > basic_robot.call_limit then
error("Execution limit " .. basic_robot.call_limit .. " exceeded");
end
basic_robot.data[name].ccounter = _ccounter + 1;
end,
};
env._G = env;
return env
end
local function check_code(code)
local bad_code = {"while ", "for ", "do ", "repeat ", "until ", "goto "}
--"while ", "for ", "do ","goto ",
local bad_code = {"repeat ", "until ", "_ccounter"}
for _, v in pairs(bad_code) do
if string.find(code, v) then
@ -148,8 +165,64 @@ local function check_code(code)
end
local function CompileCode ( script )
--[[ idea: in each local a = function (args) ... end insert counter like:
local a = function (args) counter() ... end
when counter exceeds limit exit with error
--]]
script="_ccounter = 0; " .. script;
local i1 -- process script to insert call counter in every function
local insert_code = " increase_ccounter(); ";
local i1=0; local i2 = 0;
while (i2) do -- PROCESS SCRIPT AND INSERT COUNTER AT PROBLEMATIC SPOTS
i2 = nil;
i2=string.find (script, "function", i1) -- fix functions
if i2 then
i2=string.find(script, ")", i2);
if i2 then
script = script.sub(script,1, i2) .. insert_code .. script.sub(script, i2+1);
i1=i2+string.len(insert_code);
end
end
i2=string.find (script, "for ", i1) -- fix for OK
if i2 then
i2=string.find(script, "do", i2);
if i2 then
script = script.sub(script,1, i2+1) .. insert_code .. script.sub(script, i2+2);
i1=i2+string.len(insert_code);
end
end
i2=string.find (script, "while ", i1) -- fix while OK
if i2 then
i2=string.find(script, "do", i2);
if i2 then
script = script.sub(script,1, i2+1) .. insert_code .. script.sub(script, i2+2);
i1=i2+string.len(insert_code);
end
end
i2=string.find (script, "goto ", i1) -- fix goto OK
if i2 then
script = script.sub(script,1, i2-1) .. insert_code .. script.sub(script, i2);
i1=i2+string.len(insert_code)+5; -- insert + skip goto
end
end
--minetest.chat_send_all("script " .. script)
--if true then return nil end
local ScriptFunc, CompileError = loadstring( script )
if CompileError then
if CompileError then
return nil, CompileError
end
return ScriptFunc, nil
@ -163,6 +236,7 @@ local function setCode( name, script ) -- to run script: 1. initSandbox 2. setCo
local err;
err = check_code(script);
if err then return err end
local bytecode, err = CompileCode ( script );
if err then return err end
basic_robot.data[name].bytecode = bytecode;
@ -177,13 +251,20 @@ local function runSandbox( name)
return "Bytecode missing."
end
setfenv( ScriptFunc, basic_robot.data[name].sandbox )
local Result, RuntimeError = pcall( ScriptFunc )
if RuntimeError then
return RuntimeError
end
basic_robot.data[name].ccounter = 0;
setfenv( ScriptFunc, basic_robot.data[name].sandbox )
-- pcall(
-- function()
-- debug.sethook(error,"l") -- raises error when next line is called
local Result, RuntimeError = pcall( ScriptFunc )
if RuntimeError then
return RuntimeError
end
-- end)
minetest.chat_send_all("ccounter " .. basic_robot.data[name].ccounter)
return nil
end