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 itself. Any confidential (and/or) important data 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:
- 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.
- 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 them with no participation of client-side.
Securing setElementData
- 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
outputConsole(logText, logVisibleTo) -- print it to console
setElementData(sourceElement, dataKey, oldValue) -- revert changes, it will call onElementDataChange event, but will fail (stop) on first condition - because server (not client) forced change
return true -- all success
end
function onElementDataChangeBasicAC(dataKey, oldValue, newValue)
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 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
allowedNumberRange = {1, 100}, -- 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) 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 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"..
"*"
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
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) -- disintegrate it
return true -- data was removed, we don't need to bring it back
end
setElementData(sourceElement, dataKey, oldValue) -- 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, dataValue) -- this function 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
return false, "Key isn't present in protectedKeys", true -- let reportAndRevertDataChange know that this key should be removed
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
return false, "Can only set on player himself" -- 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
return false, "Can only set on player's own vehicle" -- 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
return false, "Invalid element type" -- consider it failure
end
end
if allowedDataTypes then -- if there's allowed data types
local valueType = type(dataValue) -- 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
return false, "Invalid data type" -- report 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(dataValue) -- 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
return false, "Invalid string length (must be between "..minLength.."-"..maxLength..")" -- mark it as incorrect
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 = (dataValue >= minRange) and (dataValue <= maxRange) -- compare whether value fits in between
if not matchingRange then -- if it doesn't
return false, "Invalid number range (must be between "..minRange.."-"..maxRange..")" -- mark it as incorrect
end
end
end
return true -- security checks passed, we are all clear with this data key
end
function onElementDataChangeAdvancedAC(dataKey, oldValue, newValue)
if not client then -- check if data is coming from client
return false -- if it's not, do not continue
end
local approvedChange, failReason, forceRemove = handleDataChange(client, source, dataKey, newValue) -- run our security checks
if approvedChange then -- it's all cool and good
return false -- we don't need further action
end
reportAndRevertDataChange(client, source, dataKey, oldValue, newValue, failReason, forceRemove) -- do it!
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 (and server events)
- All parameters including source can be faked and should not be trusted.
- Global variable client can be trusted.
Click to collapse [-]
ServerExample validation for both normal, and admin events.
--[[
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
function processServerEventData(clientElement, sourceElement, securityChecks)
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)
return false, "Client variable not present", true -- stop code execution, skip punishment
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
return false, "Can't retrieve player login - guest account", true -- stop code execution, skip punishment
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
return false, "ACL group '"..groupName.."' is missing", true -- stop code execution, skip punishment
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
return false, "Player doesn't belong to any given ACL group", true -- stop code execution, skip punishment
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
return false, "Not enough permissions", true -- stop code execution, skip punishment
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
return false, "Data isn't equal @ argument "..dataID..debugText -- report 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
return false, "Data isn't element @ argument "..dataID..debugText -- failure here
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
return false, "Invalid element type @ argument "..dataID..debugText -- 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
return false, "Invalid data type @ argument "..dataID..debugText -- it's 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
return false, "Invalid string length (must be between "..minLength.."-"..maxLength..") @ argument "..dataID..debugText -- it doesn't, 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
return false, "Invalid number range (must be between "..minRange.."-"..maxRange..") @ argument "..dataID..debugText -- -- it doesn't, 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 tableLength = 0 -- store initial table length
for _, _ in pairs(eventData) do -- loop through whole table
tableLength = (tableLength + 1) -- add + 1 on each table entry
end
local minLength = allowedTableLength[1] -- retrieve min length
local maxLength = allowedTableLength[2] -- retrieve max length
local matchingLength = (tableLength >= minLength) and (tableLength <= maxLength) -- compare whether value fits in between
if not matchingLength then
return false, "Invalid table length (must be between "..minLength.."-"..maxLength..") @ argument "..dataID..debugText -- it doesn't, 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)
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"..
"*"
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
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, failReason, skipPunishment = processServerEventData(
client, -- client element - responsible for calling event
source, -- source element - passed in triggerServerEvent (as 2nd argument)
{
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
reportAndHandleEventAbnormality(client, source, eventName, failReason, skipPunishment) -- report accident, and handle this player
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, failReason, skipPunishment = processServerEventData(
client, -- client element - responsible for calling event
source, -- source element - passed in triggerServerEvent (as 2nd argument)
{
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
reportAndHandleEventAbnormality(client, source, eventName, failReason, skipPunishment) -- report accident, and handle this player
return false -- stop code execution
end
-- do code as usual
end
addEvent("onServerAdminEvent", true)
addEventHandler("onServerAdminEvent", root, onServerAdminEvent)
Validating client ACL rights
In server side event handlers, always check that client global variable (which refers to player which truthfully called event) has permission before doing anything. This will stop hackers and script bugs from destroying your server.
Firstly, and example of BAD, INSECURE script:
Click to collapse [-]
ServerBAD, INSECURE script:
-- NO PROBLEM HERE: Command 'showgui' will only show the gui for admins
function showGui(player)
if isObjectInGroup( player, "admin" ) then
-- Only trigger client GUI for admins
triggerEvent( player, "onShowGui", resourceRoot )
end
end
addCommandHandler("showgui", showGui)
-- MISTAKE HERE: Incorrectly assume onMyGuiCommand can only be called by admins
-- Script bugs and hackers mean this function can be called by anyone
function onMyGuiCommand(name)
aclGroupAddObject(aclGetGroup("admin"), "user."..name)
outputServerLog( "DO NOT USE THIS IS WRONG " )
end
addEventHandler("onMyGuiCommand", resourceRoot, onMyGuiCommand)
onMyGuiCommand does not check if the sending player has permission, and is depending on code having no bugs, and no hackers in the world. Simple to fix by adding a client global variable check at the start. (Note: checking source will not fix the problem - It has to be client)
Click to collapse [-]
ServerFixed onMyGuiCommand:
function onMyGuiCommand(name)
-- Check 'client' really does have permission
local clientAccountName = getAccountName( getPlayerAccount( client ) )
if not isObjectInACLGroup ( "user." .. clientAccountName, aclGetGroup ( "Admin" ) ) ) then
outputServerLog( "ACCESS VIOLATION by " .. getPlayerName( client ) )
return
end
-- Client has permission now
aclGroupAddObject(aclGetGroup("admin"), "user."..name)
end
addEventHandler("onMyGuiCommand", resourceRoot, onMyGuiCommand)