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 7aedeb487a80ab6dbc67bac60a2cef29177c27d4..c52ed5fe9f67c62c16cb4a0f6dc33c0050f487c6 100644
--- a/src/main/java/net/minecraft/server/level/ServerLevel.java
+++ b/src/main/java/net/minecraft/server/level/ServerLevel.java
@@ -2292,6 +2292,12 @@ 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 4c71642474d97d1943db302947a4566a326b9ac3..9a7b56b653848974e1194eb4f6d40cb99a96ff57 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");