forked from minetest-mods/mesecons
Improve LuaController security (#393)
Fixes:
1. Lack of 'safe' on minetest.deserialize usage
2. String sandbox bypass via (""):evil()
3. Loss of upcoming digilines messages on server shutdown
4. LCs failing to show information on some errors
5. Interrupt IDs as infinite data storage
This commit is contained in:
20kdc
Vitaliy
parent
fec82ab246
commit
065e870349
@ -13,8 +13,10 @@
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-- newport = merge_port_states(state1, state2): just does result = state1 or state2 for every port
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-- set_port(pos, rule, state): activates/deactivates the mesecons according to the port states
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-- set_port_states(pos, ports): Applies new port states to a Luacontroller at pos
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-- run(pos): runs the code in the controller at pos
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-- reset_meta(pos, code, errmsg): performs a software-reset, installs new code and prints error messages
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-- run_inner(pos, code, event): runs code on the controller at pos and event
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-- reset_formspec(pos, code, errmsg): installs new code and prints error messages, without resetting LCID
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-- reset_meta(pos, code, errmsg): performs a software-reset, installs new code and prints error message
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-- run(pos, event): a wrapper for run_inner which gets code & handles errors via reset_meta
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-- resetn(pos): performs a hardware reset, turns off all ports
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--
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-- The Sandbox
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@ -141,7 +143,7 @@ local function set_port_states(pos, ports)
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-- Solution / Workaround:
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-- Remember which output was turned off and ignore next "off" event.
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local meta = minetest.get_meta(pos)
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local ign = minetest.deserialize(meta:get_string("ignore_offevents")) or {}
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local ign = minetest.deserialize(meta:get_string("ignore_offevents"), true) or {}
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if ports.a and not vports.a and not mesecon.is_powered(pos, rules.a) then ign.A = true end
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if ports.b and not vports.b and not mesecon.is_powered(pos, rules.b) then ign.B = true end
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if ports.c and not vports.c and not mesecon.is_powered(pos, rules.c) then ign.C = true end
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@ -183,7 +185,7 @@ end
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local function ignore_event(event, meta)
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if event.type ~= "off" then return false end
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local ignore_offevents = minetest.deserialize(meta:get_string("ignore_offevents")) or {}
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local ignore_offevents = minetest.deserialize(meta:get_string("ignore_offevents"), true) or {}
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if ignore_offevents[event.pin.name] then
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ignore_offevents[event.pin.name] = nil
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meta:set_string("ignore_offevents", minetest.serialize(ignore_offevents))
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@ -236,6 +238,7 @@ local function remove_functions(x)
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local seen = {}
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local function rfuncs(x)
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if x == nil then return end
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if seen[x] then return end
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seen[x] = true
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if type(x) ~= "table" then return end
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@ -259,12 +262,27 @@ local function remove_functions(x)
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return x
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end
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local function get_interrupt(pos)
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-- itbl: Flat table of functions to run after sandbox cleanup, used to prevent various security hazards
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local function get_interrupt(pos, itbl, send_warning)
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-- iid = interrupt id
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local function interrupt(time, iid)
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-- NOTE: This runs within string metatable sandbox, so don't *rely* on anything of the form (""):y
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-- Hence the values get moved out. Should take less time than original, so totally compatible
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if type(time) ~= "number" then return end
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table.insert(itbl, function ()
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-- Outside string metatable sandbox, can safely run this now
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local luac_id = minetest.get_meta(pos):get_int("luac_id")
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-- Check if IID is dodgy, so you can't use interrupts to store an infinite amount of data.
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-- Note that this is safe from alter-after-free because this code gets run after the sandbox has ended.
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-- This runs outside of the timer and *shouldn't* harm perf. unless dodgy data is being sent in the first place
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iid = remove_functions(iid)
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local msg_ser = minetest.serialize(iid)
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if #msg_ser <= mesecon.setting("luacontroller_interruptid_maxlen", 256) then
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mesecon.queue:add_action(pos, "lc_interrupt", {luac_id, iid}, time, iid, 1)
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else
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send_warning("An interrupt ID was too large!")
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end
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end)
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end
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return interrupt
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end
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@ -357,32 +375,49 @@ local function clean_and_weigh_digiline_message(msg, back_references)
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end
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local function get_digiline_send(pos)
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-- itbl: Flat table of functions to run after sandbox cleanup, used to prevent various security hazards
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local function get_digiline_send(pos, itbl, send_warning)
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if not minetest.global_exists("digilines") then return end
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local chan_maxlen = mesecon.setting("luacontroller_digiline_channel_maxlen", 256)
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local maxlen = mesecon.setting("luacontroller_digiline_maxlen", 50000)
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return function(channel, msg)
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-- NOTE: This runs within string metatable sandbox, so don't *rely* on anything of the form (""):y
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-- or via anything that could.
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-- Make sure channel is string, number or boolean
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if (type(channel) ~= "string" and type(channel) ~= "number" and type(channel) ~= "boolean") then
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if type(channel) == "string" then
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if #channel > chan_maxlen then
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send_warning("Channel string too long.")
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return false
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end
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elseif (type(channel) ~= "string" and type(channel) ~= "number" and type(channel) ~= "boolean") then
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send_warning("Channel must be string, number or boolean.")
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return false
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end
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local msg_cost
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msg, msg_cost = clean_and_weigh_digiline_message(msg)
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if msg == nil or msg_cost > mesecon.setting("luacontroller_digiline_maxlen", 50000) then
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if msg == nil or msg_cost > maxlen then
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send_warning("Message was too complex, or contained invalid data.")
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return false
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end
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minetest.after(0, digilines.receptor_send, pos, digilines.rules.default, channel, msg)
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table.insert(itbl, function ()
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-- Runs outside of string metatable sandbox
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local luac_id = minetest.get_meta(pos):get_int("luac_id")
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mesecon.queue:add_action(pos, "lc_digiline_relay", {channel, luac_id, msg})
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end)
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return true
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end
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end
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local safe_globals = {
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-- Don't add pcall/xpcall unless willing to deal with the consequences (unless very careful, incredibly likely to allow killing server indirectly)
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"assert", "error", "ipairs", "next", "pairs", "select",
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"tonumber", "tostring", "type", "unpack", "_VERSION"
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}
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local function create_environment(pos, mem, event)
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local function create_environment(pos, mem, event, itbl, send_warning)
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-- Gather variables for the environment
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local vports = minetest.registered_nodes[minetest.get_node(pos).name].virtual_portstates
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local vports_copy = {}
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@ -399,8 +434,8 @@ local function create_environment(pos, mem, event)
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heat = mesecon.get_heat(pos),
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heat_max = mesecon.setting("overheat_max", 20),
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print = safe_print,
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interrupt = get_interrupt(pos),
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digiline_send = get_digiline_send(pos),
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interrupt = get_interrupt(pos, itbl, send_warning),
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digiline_send = get_digiline_send(pos, itbl, send_warning),
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string = {
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byte = string.byte,
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char = string.char,
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@ -488,10 +523,11 @@ local function create_sandbox(code, env)
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jit.off(f, true)
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end
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local maxevents = mesecon.setting("luacontroller_maxevents", 10000)
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return function(...)
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-- NOTE: This runs within string metatable sandbox, so the setting's been moved out for safety
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-- Use instruction counter to stop execution
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-- after luacontroller_maxevents
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local maxevents = mesecon.setting("luacontroller_maxevents", 10000)
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debug.sethook(timeout, "", maxevents)
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local ok, ret = pcall(f, ...)
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debug.sethook() -- Clear hook
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@ -502,7 +538,7 @@ end
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local function load_memory(meta)
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return minetest.deserialize(meta:get_string("lc_memory")) or {}
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return minetest.deserialize(meta:get_string("lc_memory"), true) or {}
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end
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@ -519,26 +555,42 @@ local function save_memory(pos, meta, mem)
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end
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end
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local function run(pos, event)
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-- Returns success (boolean), errmsg (string)
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-- run (as opposed to run_inner) is responsible for setting up meta according to this output
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local function run_inner(pos, code, event)
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local meta = minetest.get_meta(pos)
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if overheat(pos) then return end
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if ignore_event(event, meta) then return end
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-- Note: These return success, presumably to avoid changing LC ID.
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if overheat(pos) then return true, "" end
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if ignore_event(event, meta) then return true, "" end
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-- Load code & mem from meta
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local mem = load_memory(meta)
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local code = meta:get_string("code")
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-- 'Last warning' label.
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local warning = ""
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local function send_warning(str)
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warning = "Warning: " .. str
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end
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-- Create environment
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local env = create_environment(pos, mem, event)
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local itbl = {}
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local env = create_environment(pos, mem, event, itbl, send_warning)
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-- Create the sandbox and execute code
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local f, msg = create_sandbox(code, env)
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if not f then return msg end
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if not f then return false, msg end
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-- Start string true sandboxing
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local onetruestring = getmetatable("")
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-- If a string sandbox is already up yet inconsistent, something is very wrong
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assert(onetruestring.__index == string)
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onetruestring.__index = env.string
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local success, msg = pcall(f)
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if not success then return msg end
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onetruestring.__index = string
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-- End string true sandboxing
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if not success then return false, msg end
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if type(env.port) ~= "table" then
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return "Ports set are invalid."
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return false, "Ports set are invalid."
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end
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-- Actually set the ports
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@ -546,17 +598,18 @@ local function run(pos, event)
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-- Save memory. This may burn the luacontroller if a memory overflow occurs.
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save_memory(pos, meta, env.mem)
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-- Execute deferred tasks
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for _, v in ipairs(itbl) do
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local failure = v()
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if failure then
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return false, failure
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end
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end
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return true, warning
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end
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mesecon.queue:add_function("lc_interrupt", function (pos, luac_id, iid)
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-- There is no luacontroller anymore / it has been reprogrammed / replaced / burnt
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if (minetest.get_meta(pos):get_int("luac_id") ~= luac_id) then return end
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if (minetest.registered_nodes[minetest.get_node(pos).name].is_burnt) then return end
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run(pos, {type="interrupt", iid = iid})
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end)
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local function reset_meta(pos, code, errmsg)
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local meta = minetest.get_meta(pos)
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local function reset_formspec(meta, code, errmsg)
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meta:set_string("code", code)
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code = minetest.formspec_escape(code or "")
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errmsg = minetest.formspec_escape(tostring(errmsg or ""))
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@ -566,13 +619,50 @@ local function reset_meta(pos, code, errmsg)
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"image_button[4.75,8.75;2.5,1;jeija_luac_runbutton.png;program;]"..
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"image_button_exit[11.72,-0.25;0.425,0.4;jeija_close_window.png;exit;]"..
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"label[0.1,9;"..errmsg.."]")
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end
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local function reset_meta(pos, code, errmsg)
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local meta = minetest.get_meta(pos)
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reset_formspec(meta, code, errmsg)
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meta:set_int("luac_id", math.random(1, 65535))
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end
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-- Wraps run_inner with LC-reset-on-error
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local function run(pos, event)
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local meta = minetest.get_meta(pos)
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local code = meta:get_string("code")
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local ok, errmsg = run_inner(pos, code, event)
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if not ok then
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reset_meta(pos, code, errmsg)
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else
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reset_formspec(meta, code, errmsg)
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end
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return ok, errmsg
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end
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local function reset(pos)
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set_port_states(pos, {a=false, b=false, c=false, d=false})
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end
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-----------------------
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-- A.Queue callbacks --
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-----------------------
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mesecon.queue:add_function("lc_interrupt", function (pos, luac_id, iid)
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-- There is no luacontroller anymore / it has been reprogrammed / replaced / burnt
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if (minetest.get_meta(pos):get_int("luac_id") ~= luac_id) then return end
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if (minetest.registered_nodes[minetest.get_node(pos).name].is_burnt) then return end
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run(pos, {type="interrupt", iid = iid})
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end)
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mesecon.queue:add_function("lc_digiline_relay", function (pos, channel, luac_id, msg)
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if not digiline then return end
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-- This check is only really necessary because in case of server crash, old actions can be thrown into the future
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if (minetest.get_meta(pos):get_int("luac_id") ~= luac_id) then return end
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if (minetest.registered_nodes[minetest.get_node(pos).name].is_burnt) then return end
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-- The actual work
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digiline:receptor_send(pos, digiline.rules.default, channel, msg)
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end)
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-----------------------
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-- Node Registration --
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@ -613,12 +703,7 @@ end
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local function set_program(pos, code)
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reset(pos)
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reset_meta(pos, code)
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local err = run(pos, {type="program"})
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if err then
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reset_meta(pos, code, err)
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return false, err
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end
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return true
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return run(pos, {type="program"})
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end
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local function on_receive_fields(pos, form_name, fields, sender)
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