fix: check system time against remote time server

fixes issue where incorrect time data is sent and causes desyncs
Skytils · Feb 1, 2024 · 17da0ec · 17da0ec
1 parent ebd814f
commit 17da0ec
Show file tree

Hide file tree

Showing 3 changed files with 455 additions and 1 deletion.
diff --git a/src/main/kotlin/gg/skytils/skytilsmod/Skytils.kt b/src/main/kotlin/gg/skytils/skytilsmod/Skytils.kt
@@ -21,7 +21,6 @@ package gg.skytils.skytilsmod
 import gg.essential.api.EssentialAPI
 import gg.essential.universal.UChat
 import gg.essential.universal.UKeyboard
-import gg.skytils.event.Events
 import gg.skytils.skytilsmod.commands.impl.*
 import gg.skytils.skytilsmod.commands.stats.impl.CataCommand
 import gg.skytils.skytilsmod.commands.stats.impl.SlayerCommand
@@ -103,10 +102,14 @@ import net.minecraftforge.fml.common.network.FMLNetworkEvent
 import skytils.hylin.HylinAPI
 import sun.misc.Unsafe
 import java.io.File
+import java.net.DatagramPacket
+import java.net.DatagramSocket
+import java.net.InetAddress
 import java.util.*
 import java.util.concurrent.Executors
 import java.util.concurrent.ThreadPoolExecutor
 import kotlin.coroutines.CoroutineContext
+import kotlin.math.abs
 
 @Mod(
     modid = Skytils.MOD_ID,
@@ -232,6 +235,8 @@ class Skytils {
         const val prefix = "§9§lSkytils §8»"
         const val successPrefix = "§a§lSkytils §8»"
         const val failPrefix = "§c§lSkytils §8»"
+
+        var trustClientTime = false
     }
 
     @Mod.EventHandler
@@ -413,6 +418,8 @@ class Skytils {
                 UChat.chat("$prefix §fYou are on a development version of Skytils. Change your update channel to pre-release to get notified of new updates.")
             }
         }
+
+        checkSystemTime()
     }
 
     @SubscribeEvent(priority = EventPriority.HIGHEST)
@@ -585,4 +592,34 @@ class Skytils {
             }
         }
     }
+
+    private fun checkSystemTime() {
+        IO.launch {
+            DatagramSocket().use { socket ->
+                val address = InetAddress.getByName("time.nist.gov")
+                val buffer = NtpMessage().toByteArray()
+                var packet = DatagramPacket(buffer, buffer.size, address, 123)
+                socket.send(packet)
+                packet = DatagramPacket(buffer, buffer.size)
+
+                val destinationTimestamp = NtpMessage.now()
+                val msg = NtpMessage(packet.data)
+
+                val localClockOffset =
+                    ((msg.receiveTimestamp - msg.originateTimestamp) +
+                            (msg.transmitTimestamp - destinationTimestamp)) / 2
+
+                println("Got local clock offset: $localClockOffset")
+                if (abs(localClockOffset) > 3) {
+                    if (ModChecker.canShowNotifications) {
+                        EssentialAPI.getNotifications().push("Skytils", "Your system time is inaccurate.", 3f)
+                    } else {
+                        UChat.chat("$prefix §fYour system time appears to be inaccurate. Please sync your system time to avoid issues with Skytils.")
+                    }
+                } else {
+                    trustClientTime = true
+                }
+            }
+        }
+    }
 }
diff --git a/src/main/kotlin/gg/skytils/skytilsmod/features/impl/handlers/MayorInfo.kt b/src/main/kotlin/gg/skytils/skytilsmod/features/impl/handlers/MayorInfo.kt
@@ -153,6 +153,10 @@ object MayorInfo {
 
     fun sendJerryData(mayor: Mayor?, nextSwitch: Long) = Skytils.IO.launch {
         if (mayor == null || nextSwitch <= System.currentTimeMillis()) return@launch
+        if (!Skytils.trustClientTime) {
+            println("Client's time isn't trusted, skip sending jerry data.")
+            return@launch
+        }
         try {
             val serverId = UUID.randomUUID().toString().replace("-".toRegex(), "")
             val commentForDecompilers =