Refactor anti speed and tune anti KillAura

gradle.properties

@@ -9,7 +9,7 @@ loader_version=0.15.9
 fabric_kotlin_version=1.10.19+kotlin.1.9.23
 access_widener=puffy-anti-exploit.accesswidener
 # Mod Properties
-mod_version=0.2.5
+mod_version=0.2.6
 maven_group=com.puffy
 archives_base_name=puffy-anti-exploit
 # Dependencies

src/main/kotlin/com/puffy/mitigations/AntiKillAuraMitigation.kt

@@ -12,9 +12,9 @@ import net.minecraft.entity.Entity
 import net.minecraft.network.packet.c2s.play.PlayerInteractEntityC2SPacket
 import net.minecraft.server.network.ServerPlayerEntity
 
-const val MAXIMUM_SUSPICIOUS_HITS_IN_PERIOD = 4
+const val MAXIMUM_SUSPICIOUS_HITS_IN_PERIOD = 6
 const val PERIOD_TIME_IN_TICKS = 150
-const val AIM_DEGREE_TOLERANCE = 35
+const val AIM_DEGREE_TOLERANCE = 45
 
 const val MAXIMUM_DISTANCE_METERS = 6
 private const val MITIGATION_NAME = "KillAura"

src/main/kotlin/com/puffy/mitigations/AntiSpeedMitigation.kt

@@ -3,17 +3,16 @@ package com.puffy.mitigations
 import com.puffy.events.DetectionEventEmitter
 import com.puffy.events.DetectionInfo
 import com.puffy.events.PacketEventEmitter
+import com.puffy.mitigations.antispeed.MagnitudeWeighter
+import com.puffy.util.trimToLength
 import kotlin.math.abs
-import kotlin.math.sqrt
 import net.fabricmc.fabric.api.event.lifecycle.v1.ServerTickEvents
 import net.fabricmc.fabric.api.event.lifecycle.v1.ServerTickEvents.EndTick
 import net.minecraft.network.packet.c2s.play.PlayerMoveC2SPacket
 import net.minecraft.server.network.ServerPlayerEntity
 
 const val SLIDING_WINDOW_LENGTH_TICKS = 20
 const val MAXIMUM_AVERAGE_MAGNITUDE = 0.95
-const val MAX_FALLING_Y_DIFFERENCE = -0.5
-const val MAX_ASCENDING_Y_DIFFERENCE = 0.2
 const val MAXIMUM_SUSPICIOUS_MAGNITUDE_TICKS = 25
 
 // Used if minecraft reports a XYZ before the player loads (usually garbage)
@@ -50,19 +49,18 @@ class AntiSpeedMitigation(val player: ServerPlayerEntity) {
         )
     }
 
-    private fun isSpeedHacking(): Boolean {
-        return suspiciousMagnitudeTicks > MAXIMUM_SUSPICIOUS_MAGNITUDE_TICKS
-    }
+    private fun isSpeedHacking(): Boolean =
+        suspiciousMagnitudeTicks > MAXIMUM_SUSPICIOUS_MAGNITUDE_TICKS
 
     private fun updateSuspiciousTicksCount() {
-        if (calculateAverageMagnitude() >= MAXIMUM_AVERAGE_MAGNITUDE) {
+        if (getAverageMagnitude() >= MAXIMUM_AVERAGE_MAGNITUDE) {
             suspiciousMagnitudeTicks++
         } else {
             suspiciousMagnitudeTicks = 0
         }
     }
 
-    private fun calculateAverageMagnitude(): Double {
+    private fun getAverageMagnitude(): Double {
         if (movementMagnitudes.isEmpty()) {
             return 0.0
         }
@@ -76,9 +74,7 @@ class AntiSpeedMitigation(val player: ServerPlayerEntity) {
             return
         }
 
-        if (movementMagnitudes.count() >= SLIDING_WINDOW_LENGTH_TICKS) {
-            movementMagnitudes.removeAt(0)
-        }
+        movementMagnitudes.trimToLength(SLIDING_WINDOW_LENGTH_TICKS)
         movementMagnitudes.add(magnitude)
     }
 
@@ -87,47 +83,8 @@ class AntiSpeedMitigation(val player: ServerPlayerEntity) {
         val yDiff = player.y - lastY
         val zDiff = player.z - lastZ
 
-        return sqrt(abs(xDiff) * abs(xDiff) + abs(yDiff) * abs(yDiff) + abs(zDiff) * abs(zDiff)) *
-            getPlayerSpecificWeight()
-    }
-
-    /**
-     * Returns a weight to weight the final magnitude. Allows for normal behaviors to be discarded
-     * earlier in the system, such as boat-ice speed and falling
-     */
-    private fun getPlayerSpecificWeight(): Double {
-        var weight = 1.0
-
-        if (player.isFallFlying) {
-            weight *= 0.20
-        }
-
-        if (player.y - lastY < MAX_FALLING_Y_DIFFERENCE) {
-            weight *= 0.55 // Helpful for reducing false positive when falling
-        }
-
-        // However, to combat elytra fly + other antics with fall-flight cheats we can *increase*
-        // sensitivity when someone is oddly levitating in fall flight.
-        if (player.isFallFlying && player.y - lastY > MAX_ASCENDING_Y_DIFFERENCE) {
-            weight *= 6
-        }
-
-        if (player.isCreative) {
-            weight *= 0
-        }
-
-        if (player.abilities.flying || player.abilities.allowFlying) {
-            // Friction is not considered during flight, so players can accidentally trigger this
-            // mitigation.
-            weight *= 0.25
-        }
-
-        if (player.velocity.length() > SERVER_VELOCITY_THRESHOLD) {
-            // Players cannot affect their own velocity, only where they are supposed to move
-            weight *= 0.25
-        }
-
-        return weight
+        val magnitude = abs(xDiff) * abs(xDiff) + abs(yDiff) * abs(yDiff) + abs(zDiff) * abs(zDiff)
+        return MagnitudeWeighter.getWeightedMagnitude(magnitude, player, lastY)
     }
 
     private fun updateLastPositionWithCurrentPosition() {

src/main/kotlin/com/puffy/mitigations/antispeed/MagnitudeWeighter.kt

@@ -0,0 +1,57 @@
+package com.puffy.mitigations.antispeed
+
+import java.util.function.BiPredicate
+import net.minecraft.server.network.ServerPlayerEntity
+import org.slf4j.LoggerFactory
+
+data class Weight(
+    val title: String,
+    val multiplier: Double,
+    val predicate: BiPredicate<ServerPlayerEntity, Double>
+)
+
+const val MAX_FALLING_Y_DIFFERENCE = -0.5
+const val MAX_ASCENDING_Y_DIFFERENCE = 0.2
+const val SERVER_VELOCITY_THRESHOLD = 3
+
+object MagnitudeWeighter {
+    private val logger = LoggerFactory.getLogger("puffy-anti-exploit")
+
+    private val weights =
+        listOf(
+            Weight("Elytra Bias", 0.20) { player, _ -> player.isFallFlying },
+            Weight("Falling Bias", 0.55) { player, lastY ->
+                player.y - lastY < MAX_FALLING_Y_DIFFERENCE
+            },
+            Weight("Elytra Flyhack Bias", 6.0) { player, lastY ->
+                player.isFallFlying && player.y - lastY > MAX_ASCENDING_Y_DIFFERENCE
+            },
+            Weight("Creative Mode Bias", 0.0) { player, _ -> player.isCreative },
+            Weight("Server-permitted Flight Bias", 0.25) { player, _ ->
+                player.abilities.flying || player.abilities.allowFlying
+            },
+            Weight("Server-permitted Velocity Bias", 0.25) { player, _ ->
+                player.velocity.length() > SERVER_VELOCITY_THRESHOLD
+            }
+        )
+
+    private fun getActiveWeightsForPlayer(player: ServerPlayerEntity, lastY: Double) =
+        weights.filter { weight -> weight.predicate.test(player, lastY) }
+
+    private fun getTotalWeightedMultiplier(weights: List<Weight>) =
+        weights.fold(1.0) { acc, weight -> weight.multiplier * acc }
+
+    fun getWeightedMagnitude(
+        initialMagnitude: Double,
+        player: ServerPlayerEntity,
+        lastY: Double
+    ): Double {
+        val activeWeights = getActiveWeightsForPlayer(player, lastY)
+
+        activeWeights.forEach { weight ->
+            logger.debug("Weight '${weight.title}' is active for player ${player.name.string}")
+        }
+
+        return initialMagnitude * getTotalWeightedMultiplier(activeWeights)
+    }
+}

src/main/kotlin/com/puffy/util/TrimToLength.kt

@@ -0,0 +1,7 @@
+package com.puffy.util
+
+fun <T> MutableList<T>.trimToLength(length: Int) {
+    if (this.count() >= length) {
+        this.removeAt(0)
+    }
+}

src/main/resources/fabric.mod.json

@@ -1,7 +1,7 @@
 {
   "schemaVersion": 1,
   "id": "puffy-anti-exploit",
-  "version": "0.2.5",
+  "version": "0.2.6",
   "name": "puffy-anti-exploit",
   "description": "A server-side anti exploit which aims to reduce the possible amount of advantages a player can obtain with a hacked client. This mod does not attempt to ban such players, it only aims to fix certain parts of the server and gently counter these players.",
   "authors": [