From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
From: Aikar <aikar@aikar.co>
Date: Mon, 30 Apr 2018 17:15:26 -0400
Subject: [PATCH] Block Enderpearl Travel Exploit

Players are able to use alt accounts and enderpearls to travel
long distances utilizing the pearls in unloaded chunks and loading
the chunk later when convenient.

This disables that by not saving the thrower when the chunk is unloaded.

This is mainly useful for survival servers that do not allow freeform teleporting.

Note: Currently removed as enderpearls are ticked as long as their owner is online in 1.21.2.
Might be worth to re-add once an option to disable the above vanilla mechanic is added, to
fully prevent enderpearl travel exploits.

== AT ==
public net.minecraft.world.entity.projectile.Projectile ownerUUID

diff --git a/src/main/java/net/minecraft/server/level/ServerLevel.java b/src/main/java/net/minecraft/server/level/ServerLevel.java
index 5979e8d25eaddf990ded79bcf6485cc0612faa63..0a46bf03f9a55c7453f042cba6f448d4d0bcd1e6 100644
--- a/src/main/java/net/minecraft/server/level/ServerLevel.java
+++ b/src/main/java/net/minecraft/server/level/ServerLevel.java
@@ -2664,6 +2664,12 @@ public class ServerLevel extends Level implements ServerEntityGetter, WorldGenLe
 
         public void onTickingEnd(Entity entity) {
             ServerLevel.this.entityTickList.remove(entity);
+            // Paper start - Reset pearls when they stop being ticked
+            if (ServerLevel.this.paperConfig().fixes.disableUnloadedChunkEnderpearlExploit && ServerLevel.this.paperConfig().misc.legacyEnderPearlBehavior && entity instanceof net.minecraft.world.entity.projectile.ThrownEnderpearl pearl) {
+                pearl.cachedOwner = null;
+                pearl.ownerUUID = null;
+            }
+            // Paper end - Reset pearls when they stop being ticked
         }
 
         public void onTrackingStart(Entity entity) {
diff --git a/src/main/java/net/minecraft/world/entity/projectile/Projectile.java b/src/main/java/net/minecraft/world/entity/projectile/Projectile.java
index bf2e79c50092acd13e97ab6e32471a9c527a524e..6c2d4d6f3a36ab452dfd3c33f66e54f152906639 100644
--- a/src/main/java/net/minecraft/world/entity/projectile/Projectile.java
+++ b/src/main/java/net/minecraft/world/entity/projectile/Projectile.java
@@ -134,6 +134,7 @@ public abstract class Projectile extends Entity implements TraceableEntity {
     protected void readAdditionalSaveData(CompoundTag nbt) {
         if (nbt.hasUUID("Owner")) {
             this.setOwnerThroughUUID(nbt.getUUID("Owner"));
+            if (this instanceof ThrownEnderpearl && this.level() != null && this.level().paperConfig().fixes.disableUnloadedChunkEnderpearlExploit && this.level().paperConfig().misc.legacyEnderPearlBehavior) { this.ownerUUID = null; } // Paper - Reset pearls when they stop being ticked; Don't store shooter name for pearls to block enderpearl travel exploit
         }
 
         this.leftOwner = nbt.getBoolean("LeftOwner");