Script security
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Awareness of client memory
Starting from very basics:
- You should be aware that everything you store on client-side is at risk, this includes .lua files as well. Any confidential (and/or) important data which is stored, or travels through client-side (player PC) could be accessed by malicious clients.
- To keep sensitive data (and/or) Lua logic safe - use server-side.
- Do note that scripts marked as shared act also as client code, which means that everything above applies to them. For example defining:
<script src="script.lua" type="shared"/> <!-- this script will run separately both on client and server -->
Is same as doing:
<script src="script.lua" type="client"/> <!-- define it separately on client --> <script src="script.lua" type="server"/> <!-- do the same, but on server -->
Additional protection layer
In order to make things slightly harder* for those having bad intentions towards your server, you can make use of cache attribute (and/or Lua compile (also known as Luac) with extra obfuscation set to level 3 - API) available in meta.xml, along with configuring MTA's built-in AC by toggling SD (Special detections), see: Anti-cheat guide.
<script src="shared.lua" type="shared" cache="false"/> <!-- cache="false" indicates that this Lua file won't be saved on player's PC --> <script src="client.lua" type="client" cache="false"/> <!-- cache="false" indicates that this Lua file won't be saved on player's PC -->
- Slightly harder but not impossible for some to obtain client code, yet does good job at keeping most people away from inspecting your .lua files - those looking for possible logic flaws (bugs) or missing/incorrect security based checks.
- Can be used on both client and shared script type (has no effect on server-sided Lua).
- It doesn't remove Lua files which were previously downloaded.
Detecting and dealing with backdoors and cheats
To ensure minimum (or no) damage resulting from Lua scripts:
- Keep your server up-to-date, you can download latest server builds from MTA:SA nightly site. Information on specific builds can be found here.
- Keep your resources up-to-date, you can download latest (default) resources from GitHub repository. Those often contain latest security fixes, which could mean difference between having your server resist from attack or not.
- Make sure to properly configure ACL (Access Control List) - which will block resources from using certain, potentially dangerous functions.
- Zero-trust with giving away admin rights for resources (including maps) coming from unknown sources.
- Before running any resource you don't trust, analyze:
- meta.xml of it, for possible hidden scripts lurking beneath other file extensions.
- It's source code, for malicious logic.
- Do not run/keep using compiled resources (scripts) of which legitimacy you aren't sure.
To ensure minimum damage when a cheater connects to your server:
- When making scripts, remember to never trust data coming from a client.
- While reviewing scripts for possible security holes. Look at any data coming from the client that is being trusted.
- Any kind of data could be sent, hence server scripts which communicate with client by receiving data sent by players should validate it, before further use in latter parts of code. Mostly, it will be done either by setElementData or triggerServerEvent.
- You shouldn't rely only on player serial, when it comes to processing crucial operations (auto-login/admin actions). Serials aren't guaranted to be unique or non-fakable. This is why you should put it behind account system, as important authentication factor (e.g: login & password).
- Server-side logic can not be bypassed or tampered with (unless server is breached or when there is a bug in code, but that's whole different scenario) - use it to your advantage. In majority of cases, you will be able to perform security validations with no participation of client-side.
- Using concept of “All parameters including source can be faked and should not be trusted. Global variable client can be trusted.” - gives you reliable assurance that player to which you refer (via client) is in fact, the one which really called event. This approach will protect you from situations where cheater can call (and process) admin events (e.g kick/ban player) by passing the actual admin (2nd argument in triggerServerEvent) - as a consequence of using wrong variable. To make sure you fully understood it, take a look at examples below:
--[[
DON'T EVER DO THAT - THAT IS COMPLETELY WRONG AND INSECURE
THE ISSUE: BY USING 'source' IN hasObjectPermissionTo YOU ARE LEAVING DOOR STRAIGHT OPEN FOR CHEATERS
]]
function onServerWrongAdminEvent(playerToBan)
if (not client) then -- 'client' points to the player who triggered the event, and should be used as security measure (in order to prevent player faking)
return false -- if this variable doesn't exists at the moment (for unknown reason, or it was the server who triggered this event), stop code execution
end
local defaultPermission = false -- do not allow action by default, see (defaultPermission): https://wiki.multitheftauto.com/wiki/HasObjectPermissionTo
local canAdminBanPlayer = hasObjectPermissionTo(source, "function.banPlayer", defaultPermission) -- the vulnerability lies here...
if (not canAdminBanPlayer) then -- if player doesn't have permissions
return false -- don't do it
end
local validElement = isElement(playerToBan) -- check whether argument passed from client is an element
if (not validElement) then -- it is not
return false -- stop code processing
end
local elementType = getElementType(playerToBan) -- it's an element, so get it's type
local playerType = (elementType == "player") -- make sure that it's a player
if (not playerType) then -- it's not a player
return false -- stop here
end
-- banPlayer(...) -- do what needs to be done
end
addEvent("onServerWrongAdminEvent", true)
addEventHandler("onServerWrongAdminEvent", root, onServerWrongAdminEvent)
--[[
onServerCorrectAdminEvent IS PERFECTLY SECURED, AS IT SHOULD BE
NO ISSUE HERE: WE'VE USED 'client' IN hasObjectPermissionTo WHICH MAKES IT SAFE FROM FAKING PLAYER WHO CALLED EVENT
]]
function onServerCorrectAdminEvent(playerToBan)
if (not client) then -- 'client' points to the player who triggered the event, and should be used as security measure (in order to prevent player faking)
return false -- if this variable doesn't exists at the moment (for unknown reason, or it was the server who triggered this event), stop code execution
end
local defaultPermission = false -- do not allow action by default, see (defaultPermission): https://wiki.multitheftauto.com/wiki/HasObjectPermissionTo
local canAdminBanPlayer = hasObjectPermissionTo(client, "function.banPlayer", defaultPermission) -- is player allowed to do that?
if (not canAdminBanPlayer) then -- if player doesn't have permissions
return false -- don't do it
end
local validElement = isElement(playerToBan) -- check whether argument passed from client is an element
if (not validElement) then -- it is not
return false -- stop code processing
end
local elementType = getElementType(playerToBan) -- it's an element, so get it's type
local playerType = (elementType == "player") -- make sure that it's a player
if (not playerType) then -- it's not a player
return false -- stop here
end
-- banPlayer(...) -- do what needs to be done
end
addEvent("onServerCorrectAdminEvent", true)
addEventHandler("onServerCorrectAdminEvent", root, onServerCorrectAdminEvent)
Securing setElementData
- You should refrain from using element data everywhere, it should be only used when really necessary. It is advised to replace it with triggerClientEvent instead.
- If you still insist on using it, it is recommended to set 4th argument in setElementData to false (disabling sync for this, certain data) and use subscriber mode - addElementDataSubscriber, for both security & performance reasons described in event section.
- All parameters including source can be faked and should not be trusted.
- Global variable client can be trusted.
Click to collapse [-]
ServerExample of basic element data anti-cheat.
local function reportAndRevertDataChange(clientElement, sourceElement, dataKey, oldValue, newValue) -- helper function to log and revert changes
local logClient = inspect(clientElement) -- in-depth view of player which forced element data sync
local logSerial = getPlayerSerial(clientElement) or "N/A" -- client serial, or "N/A" if not possible, for some reason
local logSource = tostring(sourceElement) -- element which received data
local logOldValue = tostring(oldValue) -- old value
local logNewValue = tostring(newValue) -- new value
local logText = -- fill our report with data
"=======================================\n"..
"Detected element data abnormality:\n"..
"Client: "..logClient.."\n"..
"Client serial: "..logSerial.."\n"..
"Source: "..logSource.."\n"..
"Data key: "..dataKey.."\n"..
"Old data value: "..logOldValue.."\n"..
"New data value: "..logNewValue.."\n"..
"======================================="
local logVisibleTo = root -- specify who will see this log in console, in this case each player connected to server
local hadData = (oldValue ~= nil) -- check if element had such data before
if (hadData) then -- if element had such data before
setElementData(sourceElement, dataKey, oldValue, true) -- revert changes, it will call onElementDataChange event, but will fail (stop) on first condition - because server (not client) forced change
else
removeElementData(sourceElement, dataKey) -- remove it completely
end
outputConsole(logText, logVisibleTo) -- print it to console
return true -- all success
end
function onElementDataChangeBasicAC(dataKey, oldValue, newValue) -- the heart of our anti-cheat, which does all the magic security measurements
if (not client) then -- check if data is coming from client
return false -- if it's not, do not go further
end
local checkSpecialThing = (dataKey == "special_thing") -- compare whether dataKey matches "special_thing"
local checkFlagWaving = (dataKey == "flag_waving") -- compare whether dataKey matches "flag_waving"
if (checkSpecialThing) then -- if it does, do our security checks
local invalidElement = (client ~= source) -- verify whether source element is different from player which changed data
if (invalidElement) then -- if it's so
reportAndRevertDataChange(client, source, dataKey, oldValue, newValue) -- revert data change, because "special_thing" can only be set for player himself
end
end
if (checkFlagWaving) then -- if it does, do our security checks
local playerVehicle = getPedOccupiedVehicle(client) -- get player's current vehicle
local invalidVehicle = (playerVehicle ~= source) -- verify whether source element is different from player's vehicle
if (invalidVehicle) then -- if it's so
reportAndRevertDataChange(client, source, dataKey, oldValue, newValue) -- revert data change, because "flag_waving" can only be set for player's own vehicle
end
end
end
addEventHandler("onElementDataChange", root, onElementDataChangeBasicAC)
Click to collapse [-]
ServerExample of comfortable advanced element data anti-cheat.
--[[
For maximum security set punishPlayerOnDetect, punishmentBan, allowOnlyProtectedKeys to true (as per default configuration)
If allowOnlyProtectedKeys is enabled, do not forget to add every client-side element data key to protectedKeys table - otherwise you will face false-positives
Anti-cheat (handleDataChange) table structure and it's options:
["keyName"] = { -- name of key which would be protected
onlyForPlayerHimself = true, -- enabling this (true) will make sure that this element data key can only be set on player who synced it (ignores onlyForOwnPlayerVeh and allowForElements), use false/nil to disable this
onlyForOwnPlayerVeh = false, -- enabling this (true) will make sure that this element data key can only be set on player's current vehicle who synced it (ignores allowForElements), use false/nil to disable this
allowForElements = { -- restrict this key for certain element type(s), set to false/nil or leave it empty to not check this (full list of element types: https://wiki.multitheftauto.com/wiki/GetElementsByType)
["player"] = true,
["ped"] = true,
["vehicle"] = true,
["object"] = true,
},
allowedDataTypes = { -- restrict this key for certain value type(s), set to false/nil or leave it empty to not check this
["string"] = true,
["number"] = true,
["table"] = true,
["boolean"] = true,
["nil"] = true,
},
allowedStringLength = {1, 32}, -- if value is a string, then it's length must be in between (min-max), set it to false/nil to not check string length - do note that allowedDataTypes must contain ["string"] = true
allowedTableLength = {1, 64}, -- if value is a table, then it's length must be in between (min-max), set it to false/nil to not check table length - do note that allowedDataTypes must contain ["table"] = true
allowedNumberRange = {1, 128}, -- if value is a number, then it must be in between (min-max), set it to false/nil to not check number range - do note that allowedDataTypes must contain ["number"] = true
}
]]
local punishPlayerOnDetect = true -- should player be punished upon detection (make sure that resource which runs this code has admin rights)
local punishmentBan = true -- only relevant if punishPlayerOnDetect is set to true; use true for ban or false for kick
local punishmentReason = "Altering element data" -- only relevant if punishPlayerOnDetect is set to true; reason which would be shown to punished player
local punishedBy = "Console" -- only relevant if punishPlayerOnDetect is set to true; who was responsible for punishing, as well shown to punished player
local banByIP = false -- only relevant if punishPlayerOnDetect and punishmentBan is set to true; banning by IP nowadays is not recommended (...)
local banByUsername = false -- community username - legacy thing, hence is set to false and should stay like that
local banBySerial = true -- only relevant if punishPlayerOnDetect and punishmentBan is set to true; (...) if there is a player serial to use instead
local banTime = 0 -- only relevant if punishPlayerOnDetect and punishmentBan is set to true; time in seconds, 0 for permanent
local allowOnlyProtectedKeys = true -- disallow (remove by using removeElementData, if it didn't existed before) every element data besides those given in protectedKeys table; in case someone wanted to flood server with garbage keys, which would be kept in memory until server restart or manual remove - setElementData(source, key, nil) won't remove it; it has to be removeElementData
local debugLevel = 4 -- this debug level allows to hide INFO: prefix, and use custom colors
local debugR = 255 -- debug message - red color
local debugG = 127 -- debug message - green color
local debugB = 0 -- debug message - blue color
local protectedKeys = {
["vehicleNumber"] = { -- we want vehicleNumber to be set only on vehicles, with stricte numbers in range of 1-100
allowForElements = {
["vehicle"] = true,
},
allowedDataTypes = {
["number"] = true,
},
allowedNumberRange = {1, 100},
},
["personalVehData"] = { -- we want be able to set personalVehData only on current vehicle, also it should be a string with length between 1-24
onlyForOwnPlayerVeh = true,
allowedDataTypes = {
["string"] = true,
},
allowedStringLength = {1, 24},
},
-- perform security checks on keys stored in this table, in a convenient way
}
local function reportAndRevertDataChange(clientElement, sourceElement, dataKey, oldValue, newValue, failReason, forceRemove) -- helper function to log and revert changes
local logClient = inspect(clientElement) -- in-depth view of player which forced element data sync
local logSerial = getPlayerSerial(clientElement) or "N/A" -- client serial, or "N/A" if not possible, for some reason
local logSource = inspect(sourceElement) -- in-depth view of element which received data
local logOldValue = inspect(oldValue) -- in-depth view of old value
local logNewValue = inspect(newValue) -- in-depth view of new value
local logText = -- fill our report with data
"*\n"..
"Detected element data abnormality:\n"..
"Client: "..logClient.."\n"..
"Client serial: "..logSerial.."\n"..
"Source: "..logSource.."\n"..
"Data key: "..dataKey.."\n"..
"Old data value: "..logOldValue.."\n"..
"New data value: "..logNewValue.."\n"..
"Fail reason: "..failReason.."\n"..
"*"
outputDebugString(logText, debugLevel, debugR, debugG, debugB) -- print it to debug
if (forceRemove) then -- we don't want this element data key to exist at all
removeElementData(sourceElement, dataKey) -- remove it
return true -- return success and stop here, we don't need further checks
end
setElementData(sourceElement, dataKey, oldValue, true) -- revert changes, it will call onElementDataChange event, but will fail (stop) on first condition - because server (not client) forced change
return true -- return success
end
local function handleDataChange(clientElement, sourceElement, dataKey, oldValue, newValue) -- the heart of our anti-cheat, which does all the magic security measurements, returns true if there was no altering from client (based on data from protectedKeys), false otherwise
local protectedKey = protectedKeys[dataKey] -- look up whether key changed is stored in protectedKeys table
if (not protectedKey) then -- if it's not
if (allowOnlyProtectedKeys) then -- if we don't want garbage keys
local failReason = "Key isn't present in protectedKeys" -- reason shown in report
local forceRemove = true -- should key be completely removed
reportAndRevertDataChange(clientElement, sourceElement, dataKey, oldValue, newValue, failReason, forceRemove) -- report accident, and handle (or not) this player
return false -- return failure
end
return true -- this key isn't protected, let it through
end
local onlyForPlayerHimself = protectedKey.onlyForPlayerHimself -- if key has "self-set" lock
local onlyForOwnPlayerVeh = protectedKey.onlyForOwnPlayerVeh -- if key has "self-vehicle" lock
local allowForElements = protectedKey.allowForElements -- if key has element type check
local allowedDataTypes = protectedKey.allowedDataTypes -- if key has allowed data type check
if (onlyForPlayerHimself) then -- if "self-set" lock is active
local matchingElement = (clientElement == sourceElement) -- verify whether player who set data is equal to element which received data
if (not matchingElement) then -- if it's not matching
local failReason = "Can only set on player himself" -- reason shown in report
local forceRemove = false -- should key be completely removed
reportAndRevertDataChange(clientElement, sourceElement, dataKey, oldValue, newValue, failReason, forceRemove) -- report accident, and handle (or not) this player
return false -- return failure
end
end
if (onlyForOwnPlayerVeh) then -- if "self-vehicle" lock is active
local playerVehicle = getPedOccupiedVehicle(clientElement) -- get current vehicle of player which set data
local matchingVehicle = (playerVehicle == sourceElement) -- check whether it matches the one which received data
if (not matchingVehicle) then -- if it doesn't match
local failReason = "Can only set on player's own vehicle" -- reason shown in report
local forceRemove = false -- should key be completely removed
reportAndRevertDataChange(clientElement, sourceElement, dataKey, oldValue, newValue, failReason, forceRemove) -- report accident, and handle (or not) this player
return false -- return failure
end
end
if (allowForElements) then -- check if it's one of them
local elementType = getElementType(sourceElement) -- get type of element whose data changed
local matchingElementType = allowForElements[elementType] -- verify whether it's allowed
if (not matchingElementType) then -- this isn't matching
local failReason = "Invalid element type" -- reason shown in report
local forceRemove = false -- should key be completely removed
reportAndRevertDataChange(clientElement, sourceElement, dataKey, oldValue, newValue, failReason, forceRemove) -- report accident, and handle (or not) this player
return false -- return failure
end
end
if (allowedDataTypes) then -- if there's allowed data types
local valueType = type(newValue) -- get data type of value
local matchingType = allowedDataTypes[valueType] -- check if it's one of allowed
if (not matchingType) then -- if it's not then
local failReason = "Invalid data type" -- reason shown in report
local forceRemove = false -- should key be completely removed
reportAndRevertDataChange(clientElement, sourceElement, dataKey, oldValue, newValue, failReason, forceRemove) -- report accident, and handle (or not) this player
return false -- return failure
end
local allowedStringLength = protectedKey.allowedStringLength -- if key has specified string length check
local dataString = (valueType == "string") -- make sure it's a string
if (allowedStringLength and dataString) then -- if we should check string length
local minLength = allowedStringLength[1] -- retrieve min length
local maxLength = allowedStringLength[2] -- retrieve max length
local stringLength = utf8.len(newValue) -- get length of data string
local matchingLength = (stringLength >= minLength) and (stringLength <= maxLength) -- compare whether value fits in between
if (not matchingLength) then -- if it doesn't
local failReason = "Invalid string length (must be between "..minLength.."-"..maxLength..")" -- reason shown in report
local forceRemove = false -- should key be completely removed
reportAndRevertDataChange(clientElement, sourceElement, dataKey, oldValue, newValue, failReason, forceRemove) -- report accident, and handle (or not) this player
return false -- return failure
end
end
local allowedTableLength = protectedKey.allowedTableLength -- if key has table length check
local dataTable = (valueType == "table") -- make sure it's a table
if (allowedTableLength and dataTable) then -- if we should check table length
local minLength = allowedTableLength[1] -- retrieve min length
local maxLength = allowedTableLength[2] -- retrieve max length
local minLengthAchieved = false -- variable which checks 'does minimum length was achieved'
local maxLengthExceeded = false -- variable which checks 'does length has exceeds more than allowed maximum'
local tableLength = 0 -- store initial table length
for _, _ in pairs(newValue) do -- loop through whole table
tableLength = (tableLength + 1) -- add + 1 on each table entry
minLengthAchieved = (tableLength >= minLength) -- is length bigger or at very minimum we require
maxLengthExceeded = (tableLength > maxLength) -- does table exceeded more than max length?
if (maxLengthExceeded) then -- it is bigger than it should be
break -- break the loop (due of condition above being worthy, it makes no point to count further and waste CPU, on a table which potentially could have huge amount of entries)
end
end
local matchingLength = (minLengthAchieved and not maxLengthExceeded) -- check if min length has been achieved, and make sure that it doesn't go beyond max length
if (not matchingLength) then -- this table doesn't match requirements
local failReason = "Invalid table length (must be between "..minLength.."-"..maxLength..")" -- reason shown in report
local forceRemove = false -- should key be completely removed
reportAndRevertDataChange(clientElement, sourceElement, dataKey, oldValue, newValue, failReason, forceRemove) -- report accident, and handle (or not) this player
return false -- return failure
end
end
local allowedNumberRange = protectedKey.allowedNumberRange -- if key has allowed number range check
local dataNumber = (valueType == "number") -- make sure it's a number
if (allowedNumberRange and dataNumber) then -- if we should check number range
local minRange = allowedNumberRange[1] -- retrieve min number range
local maxRange = allowedNumberRange[2] -- retrieve max number range
local matchingRange = (newValue >= minRange) and (newValue <= maxRange) -- compare whether value fits in between
if (not matchingRange) then -- if it doesn't
local failReason = "Invalid number range (must be between "..minRange.."-"..maxRange..")" -- reason shown in report
local forceRemove = false -- should key be completely removed
reportAndRevertDataChange(clientElement, sourceElement, dataKey, oldValue, newValue, failReason, forceRemove) -- report accident, and handle (or not) this player
return false -- return failure
end
end
end
return true -- security checks passed, we are all clear with this data key
end
function onElementDataChangeAdvancedAC(dataKey, oldValue, newValue) -- this event makes use of handleDataChange, the code was split for better readability
if (not client) then -- check if data is coming from client
return false -- if it's not, do not continue
end
local approvedChange = handleDataChange(client, source, dataKey, oldValue, newValue) -- run our security checks
if (approvedChange) then -- it's all cool and good
return false -- we don't need further action
end
if (not punishPlayerOnDetect) then -- we don't want to punish player for some reason
return false -- so stop here
end
if (punishmentBan) then -- if it's ban
banPlayer(client, banByIP, banByUsername, banBySerial, punishedBy, punishmentReason, banTime) -- remove his presence from server
else -- otherwise
kickPlayer(client, punishedBy, punishmentReason) -- simply kick player out of server
end
end
addEventHandler("onElementDataChange", root, onElementDataChangeAdvancedAC)
Securing triggerServerEvent
- All parameters including source can be faked and should not be trusted.
- Global variable client can be trusted.
- Admin styled events should be verifying player (client) ACL rights, either by isObjectInACLGroup or hasObjectPermissionTo.
- Be aware to which players event is sent via triggerClientEvent. For both security & performance reasons, admin like events should be received by admins only (to prevent confidential data being accessed), in the same time you shouldn't send each event to everyone on server (e.g: login success event which hides login panel for certain player). triggerClientEvent allows you to specify the event receiver as first (optional) argument. It defaults to root, meaning if you don't specify it, it will be sent to everyone connected to server - even those who are still downloading server cache (which results in Server triggered clientside event eventName, but event is not added clientside.). You can either pass player element or table with receivers:
local playersToReceiveEvent = {player1, player2, player3} -- each playerX is player element
triggerClientEvent(playersToReceiveEvent, ...) -- do not forget to fill the latter part of arguments
Click to collapse [-]
ServerExample of comfortable anti-cheat function designed for events, used for data validation for both normal, and admin events which are called from client-side.
--[[
For maximum security set punishPlayerOnDetect, punishmentBan to true (as per default configuration)
Anti-cheat (processServerEventData) table structure and it's options:
checkACLGroup = { -- check whether player who called event belongs to at least one group below, set to false/nil to not check this
"Admin",
},
checkPermissions = { -- check whether player who called event has permission to at least one thing below, set to false/nil to not check this
"function.kickPlayer",
},
checkEventData = {
{
debugData = "source", -- optional details for report shown in debug message
eventData = source, -- data we want to verify
equalTo = client, -- compare whether eventData == equalTo
allowedElements = { -- restrict eventData to be certain element type(s), set to false/nil or leave it empty to not check this (full list of element types: https://wiki.multitheftauto.com/wiki/GetElementsByType)
["player"] = true,
["ped"] = true,
["vehicle"] = true,
["object"] = true,
},
allowedDataTypes = { -- restrict eventData to be certain value type(s), set to false/nil or leave it empty to not check this
["string"] = true,
["number"] = true,
["table"] = true,
["boolean"] = true,
["nil"] = true,
},
allowedStringLength = {1, 32}, -- if eventData is a string, then it's length must be in between (min-max), set it to false/nil to not check string length - do note that allowedDataTypes must contain ["string"] = true
allowedTableLength = {1, 64}, -- if eventData is a table, then it's length must be in between (min-max), set it to false/nil to not check table length - do note that allowedDataTypes must contain ["table"] = true
allowedNumberRange = {1, 128}, -- if eventData is a number, then it must be in between (min-max), set it to false/nil to not check number range - do note that allowedDataTypes must contain ["number"] = true
},
},
]]
local punishPlayerOnDetect = true -- should player be punished upon detection (make sure that resource which runs this code has admin rights)
local punishmentBan = true -- only relevant if punishPlayerOnDetect is set to true; use true for ban or false for kick
local punishmentReason = "Altering server event data" -- only relevant if punishPlayerOnDetect is set to true; reason which would be shown to punished player
local punishedBy = "Console" -- only relevant if punishPlayerOnDetect is set to true; who was responsible for punishing, as well shown to punished player
local banByIP = false -- only relevant if punishPlayerOnDetect and punishmentBan is set to true; banning by IP nowadays is not recommended (...)
local banByUsername = false -- community username - legacy thing, hence is set to false and should stay like that
local banBySerial = true -- only relevant if punishPlayerOnDetect and punishmentBan is set to true; (...) if there is a player serial to use instead
local banTime = 0 -- only relevant if punishPlayerOnDetect and punishmentBan is set to true; time in seconds, 0 for permanent
local debugLevel = 4 -- this debug level allows to hide INFO: prefix, and use custom colors
local debugR = 255 -- debug message - red color
local debugG = 127 -- debug message - green color
local debugB = 0 -- debug message - blue color
function processServerEventData(clientElement, sourceElement, serverEvent, securityChecks) -- the heart of our anti-cheat, which does all the magic security measurements, returns true if there was no altering from client (based on data from securityChecks), false otherwise
if (not securityChecks) then -- if we haven't passed any security checks
return true -- nothing to check, let code go further
end
if (not clientElement) then -- if client variable isn't available for some reason (although it should never happen)
local failReason = "Client variable not present" -- reason shown in report
local skipPunishment = true -- should server skip punishment
reportAndHandleEventAbnormality(clientElement, sourceElement, serverEvent, failReason, skipPunishment) -- report accident, and handle (or not) this player
return false -- return failure
end
local checkACLGroup = securityChecks.checkACLGroup -- if there's any ACL groups to check
local checkPermissions = securityChecks.checkPermissions -- if there's any permissions to check
local checkEventData = securityChecks.checkEventData -- if there's any data checks
if (checkACLGroup) then -- let's check player ACL groups
local playerAccount = getPlayerAccount(clientElement) -- get current account of player
local guestAccount = isGuestAccount(playerAccount) -- if account is guest (meaning player is not logged in)
if (guestAccount) then -- it's the case
local failReason = "Can't retrieve player login - guest account" -- reason shown in report
local skipPunishment = true -- should server skip punishment
reportAndHandleEventAbnormality(clientElement, sourceElement, serverEvent, failReason, skipPunishment) -- report accident, and handle (or not) this player
return false -- return failure
end
local accountName = getAccountName(playerAccount) -- get name of player's current account
local aclString = "user."..accountName -- format it for further use in isObjectInACLGroup function
for groupID = 1, #checkACLGroup do -- iterate over table of given groups
local groupName = checkACLGroup[groupID] -- get each group name
local aclGroup = aclGetGroup(groupName) -- check if such group exists
if (not aclGroup) then -- it doesn't
local failReason = "ACL group '"..groupName.."' is missing" -- reason shown in report
local skipPunishment = true -- should server skip punishment
reportAndHandleEventAbnormality(clientElement, sourceElement, serverEvent, failReason, skipPunishment) -- report accident, and handle (or not) this player
return false -- return failure
end
local playerInACLGroup = isObjectInACLGroup(aclString, aclGroup) -- check if player belong to the group
if (playerInACLGroup) then -- yep, it's the case
return true -- so it's a success
end
end
local failReason = "Player doesn't belong to any given ACL group" -- reason shown in report
local skipPunishment = true -- should server skip punishment
reportAndHandleEventAbnormality(clientElement, sourceElement, serverEvent, failReason, skipPunishment) -- report accident, and handle (or not) this player
return false -- return failure
end
if (checkPermissions) then -- check if player has at least one desired permission
local allowedByDefault = false -- does he have access by default
for permissionID = 1, #checkPermissions do -- iterate over all permissions
local permissionName = checkPermissions[permissionID] -- get permission name
local hasPermission = hasObjectPermissionTo(clientElement, permissionName, allowedByDefault) -- check whether player is allowed to perform certain action
if (hasPermission) then -- if player has access
return true -- one is available (and enough), server won't bother to check others (as return keywords also breaks loop)
end
end
local failReason = "Not enough permissions" -- reason shown in report
local skipPunishment = true -- should server skip punishment
reportAndHandleEventAbnormality(clientElement, sourceElement, serverEvent, failReason, skipPunishment) -- report accident, and handle (or not) this player
return false -- return failure
end
if (checkEventData) then -- if there is some data to verify
for dataID = 1, #checkEventData do -- iterate over each of data
local dataToCheck = checkEventData[dataID] -- get each data set
local eventData = dataToCheck.eventData -- this is the one we'll be verifying
local equalTo = dataToCheck.equalTo -- we want to compare whether eventData == equalTo
local allowedElements = dataToCheck.allowedElements -- check whether is element, and whether belongs to certain element types
local allowedDataTypes = dataToCheck.allowedDataTypes -- do we restrict data to be certain type?
local debugData = dataToCheck.debugData -- additional helper data
local debugText = debugData and " ("..debugData..")" or "" -- if it's present, format it nicely
if (equalTo) then -- equal check exists
local matchingData = (eventData == equalTo) -- compare whether those two values are equal
if (not matchingData) then -- they aren't
local failReason = "Data isn't equal @ argument "..dataID..debugText -- reason shown in report
local skipPunishment = false -- should server skip punishment
reportAndHandleEventAbnormality(clientElement, sourceElement, serverEvent, failReason, skipPunishment) -- report accident, and handle (or not) this player
return false -- return failure
end
end
if (allowedElements) then -- we do check whether is an element, and belongs to at least one given in the list
local validElement = isElement(eventData) -- check if it's actual element
if (not validElement) then -- it's not
local failReason = "Data isn't element @ argument "..dataID..debugText -- reason shown in report
local skipPunishment = false -- should server skip punishment
reportAndHandleEventAbnormality(clientElement, sourceElement, serverEvent, failReason, skipPunishment) -- report accident, and handle (or not) this player
return false -- return failure
end
local elementType = getElementType(eventData) -- it's element, so we want to know it's type
local matchingElementType = allowedElements[elementType] -- verify whether it's allowed
if (not matchingElementType) then -- it's not allowed
local failReason = "Invalid element type @ argument "..dataID..debugText -- reason shown in report
local skipPunishment = false -- should server skip punishment
reportAndHandleEventAbnormality(clientElement, sourceElement, serverEvent, failReason, skipPunishment) -- report accident, and handle (or not) this player
return false -- return failure
end
end
if (allowedDataTypes) then -- let's check allowed data types
local dataType = type(eventData) -- get data type
local matchingType = allowedDataTypes[dataType] -- verify whether it's allowed
if (not matchingType) then -- it isn't
local failReason = "Invalid data type @ argument "..dataID..debugText -- reason shown in report
local skipPunishment = false -- should server skip punishment
reportAndHandleEventAbnormality(clientElement, sourceElement, serverEvent, failReason, skipPunishment) -- report accident, and handle (or not) this player
return false -- return failure
end
local allowedStringLength = dataToCheck.allowedStringLength -- if data has string length check
local dataString = (dataType == "string") -- make sure it's a string
if (allowedStringLength and dataString) then -- if we should check string length
local minLength = allowedStringLength[1] -- retrieve min length
local maxLength = allowedStringLength[2] -- retrieve max length
local stringLength = utf8.len(eventData) -- get length of data string
local matchingLength = (stringLength >= minLength) and (stringLength <= maxLength) -- compare whether value fits in between
if (not matchingLength) then -- if it doesn't
local failReason = "Invalid string length (must be between "..minLength.."-"..maxLength..") @ argument "..dataID..debugText -- reason shown in report
local skipPunishment = false -- should server skip punishment
reportAndHandleEventAbnormality(clientElement, sourceElement, serverEvent, failReason, skipPunishment) -- report accident, and handle (or not) this player
return false -- return failure
end
end
local allowedTableLength = dataToCheck.allowedTableLength -- if data has table length check
local dataTable = (dataType == "table") -- make sure it's a table
if (allowedTableLength and dataTable) then -- if we should check table length
local minLength = allowedTableLength[1] -- retrieve min length
local maxLength = allowedTableLength[2] -- retrieve max length
local minLengthAchieved = false -- variable which checks 'does minimum length was achieved'
local maxLengthExceeded = false -- variable which checks 'does length has exceeds more than allowed maximum'
local tableLength = 0 -- store initial table length
for _, _ in pairs(eventData) do -- loop through whole table
tableLength = (tableLength + 1) -- add + 1 on each table entry
minLengthAchieved = (tableLength >= minLength) -- is length bigger or at very minimum we require
maxLengthExceeded = (tableLength > maxLength) -- does table exceeded more than max length?
if (maxLengthExceeded) then -- it is bigger than it should be
break -- break the loop (due of condition above being worthy, it makes no point to count further and waste CPU, on a table which potentially could have huge amount of entries)
end
end
local matchingLength = (minLengthAchieved and not maxLengthExceeded) -- check if min length has been achieved, and make sure that it doesn't go beyond max length
if (not matchingLength) then -- this table doesn't match requirements
local failReason = "Invalid table length (must be between "..minLength.."-"..maxLength..") @ argument "..dataID..debugText -- reason shown in report
local skipPunishment = false -- should server skip punishment
reportAndHandleEventAbnormality(clientElement, sourceElement, serverEvent, failReason, skipPunishment) -- report accident, and handle (or not) this player
return false -- return failure
end
end
local allowedNumberRange = dataToCheck.allowedNumberRange -- if data has number range check
local dataNumber = (dataType == "number") -- make sure it's a number
if (allowedNumberRange and dataNumber) then -- if we should check number range
local minRange = allowedNumberRange[1] -- retrieve min number range
local maxRange = allowedNumberRange[2] -- retrieve max number range
local matchingRange = (eventData >= minRange) and (eventData <= maxRange) -- compare whether value fits in between
if (not matchingRange) then -- if it doesn't
local failReason = "Invalid number range (must be between "..minRange.."-"..maxRange..") @ argument "..dataID..debugText -- reason shown in report
local skipPunishment = false -- should server skip punishment
reportAndHandleEventAbnormality(clientElement, sourceElement, serverEvent, failReason, skipPunishment) -- report accident, and handle (or not) this player
return false -- return failure
end
end
end
end
end
return true -- security checks passed, we are all clear with this event call
end
function reportAndHandleEventAbnormality(clientElement, sourceElement, serverEvent, failReason, skipPunishment) -- helper function to log and handle accidents
local logClient = inspect(clientElement) -- in-depth view player which called event
local logSerial = getPlayerSerial(clientElement) or "N/A" -- client serial, or "N/A" if not possible, for some reason
local logSource = inspect(sourceElement) -- in-depth view of source element
local logText = -- fill our report with data
"*\n"..
"Detected event abnormality:\n"..
"Client: "..logClient.."\n"..
"Client serial: "..logSerial.."\n"..
"Source: "..logSource.."\n"..
"Event: "..serverEvent.."\n"..
"Reason: "..failReason.."\n"..
"*"
outputDebugString(logText, debugLevel, debugR, debugG, debugB) -- print it to debug
if (not punishPlayerOnDetect or skipPunishment) then -- we don't want to punish player for some reason
return true -- stop here
end
if (punishmentBan) then -- if it's ban
banPlayer(clientElement, banByIP, banByUsername, banBySerial, punishedBy, punishmentReason, banTime) -- remove his presence from server
else -- otherwise
kickPlayer(clientElement, punishedBy, punishmentReason) -- simply kick player out of server
end
return true -- all done, report success
end
function onServerEvent(clientData)
--[[
Assume this server event (function) is called in such way:
local dataToPass = 10
triggerServerEvent("onServerEvent", localPlayer, dataToPass)
]]
local shouldProcessServerCode = processServerEventData(
client, -- client element - responsible for calling event
source, -- source element - passed in triggerServerEvent (as 2nd argument)
eventName, -- name of event - in this case 'onServerEvent'
{
checkEventData = { -- we want to verify everything what comes from client
{
eventData = source, -- first to check, source variable
equalTo = client, -- we want to check whether it matches player who called event
debugData = "source", -- helper details which would be shown in report
},
{
eventData = clientData, -- let's check the data which client sent to us
allowedDataTypes = {
["number"] = true, -- we want it to be only number
},
allowedNumberRange = {1, 100}, -- in range of 1 to 100
debugData = "clientData", -- if something goes wrong, let server know where (it will appear in debug report)
},
},
}
)
if (not shouldProcessServerCode) then -- something isn't right, no green light for processing code behind this scope
return false -- stop code execution
end
-- do code as usual
end
addEvent("onServerEvent", true)
addEventHandler("onServerEvent", root, onServerEvent)
function onServerAdminEvent(playerToBan)
--[[
Assume this server admin event (function) is called in such way:
local playerToBan = getPlayerFromName("playerToBan")
triggerServerEvent("onServerAdminEvent", localPlayer, playerToBan)
]]
local shouldProcessServerCode = processServerEventData(
client, -- client element - responsible for calling event
source, -- source element - passed in triggerServerEvent (as 2nd argument)
eventName, -- name of event - in this case 'onServerAdminEvent'
{
checkACLGroup = { -- we need to check whether player who called event belongs to ACL groups
"Admin", -- in this case admin group
},
checkEventData = { -- we want to verify everything what comes from client
{
eventData = source, -- first to check, source variable
equalTo = client, -- we want to check whether it matches player who called event
debugData = "source", -- helper details which would be shown in report
},
{
eventData = playerToBan, -- let's check the data which client sent to us
allowedDataTypes = {
["player"] = true, -- we want it to be player
},
debugData = "playerToBan", -- if something goes wrong, let server know where (it will appear in debug report)
},
},
}
)
if (not shouldProcessServerCode) then -- something isn't right, no green light for processing code behind this scope
return false -- stop code execution
end
-- do code as usual
end
addEvent("onServerAdminEvent", true)
addEventHandler("onServerAdminEvent", root, onServerAdminEvent)
Securing server-only events
- It is very important to disable remote triggering ability in addEvent, to prevent calling server-side only events from client-side.
- Admin styled events should be verifying player ACL rights, either by isObjectInACLGroup or hasObjectPermissionTo.
Click to collapse [-]
ServerThis example shows how you should make event server-side only.
function onServerSideOnlyEvent()
-- do some server-side stuff
end
addEvent("onServerSideOnlyEvent", false) -- set second argument (allowRemoteTriger) to false, so it can't be called from client
addEventHandler("onServerSideOnlyEvent", root, onServerSideOnlyEvent) -- associate our event with function onServerSideOnlyEvent
Securing projectiles & explosions
This section (and code is work in progress) - use at your own risk.
Click to expand [+]
ServerClick to expand [+]
ServerClick to expand [+]
ServerHandling non-registered events
See: onPlayerTriggerInvalidEvent