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.

diff --git a/src/main/java/com/destroystokyo/paper/PaperWorldConfig.java b/src/main/java/com/destroystokyo/paper/PaperWorldConfig.java
index 4e0f61179e3b2ae91811746d32b24998173a922c..a0937dd52e4a2aa1bfadcbd1ac0dc2cb26d59cf0 100644
--- a/src/main/java/com/destroystokyo/paper/PaperWorldConfig.java
+++ b/src/main/java/com/destroystokyo/paper/PaperWorldConfig.java
@@ -398,4 +398,10 @@ public class PaperWorldConfig {
     private void disableSprintInterruptionOnAttack() {
         disableSprintInterruptionOnAttack = getBoolean("game-mechanics.disable-sprint-interruption-on-attack", false);
     }
+
+    public boolean disableEnderpearlExploit = true;
+    private void disableEnderpearlExploit() {
+        disableEnderpearlExploit = getBoolean("game-mechanics.disable-unloaded-chunk-enderpearl-exploit", disableEnderpearlExploit);
+        log("Disable Unloaded Chunk Enderpearl Exploit: " + (disableEnderpearlExploit ? "enabled" : "disabled"));
+    }
 }
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 4306db7db2c5b4eb1529dc3e9f0659ead2688fa5..8af1571c614a39c9673e0dc90e3aa9a89a367e34 100644
--- a/src/main/java/net/minecraft/world/entity/projectile/Projectile.java
+++ b/src/main/java/net/minecraft/world/entity/projectile/Projectile.java
@@ -88,6 +88,7 @@ public abstract class Projectile extends Entity {
     protected void readAdditionalSaveData(CompoundTag nbt) {
         if (nbt.hasUUID("Owner")) {
             this.ownerUUID = nbt.getUUID("Owner");
+            if (this instanceof ThrownEnderpearl && this.level != null && this.level.paperConfig.disableEnderpearlExploit) { this.ownerUUID = null; } // Paper - Don't store shooter name for pearls to block enderpearl travel exploit
         }
 
         this.leftOwner = nbt.getBoolean("LeftOwner");
diff --git a/src/main/java/net/minecraft/world/entity/projectile/ThrownEnderpearl.java b/src/main/java/net/minecraft/world/entity/projectile/ThrownEnderpearl.java
index 541ca82405d0b4d1457dcd63b58dc61eb67482d6..1b2ada3663cc0739782ac591f2ee1f6d0fb94841 100644
--- a/src/main/java/net/minecraft/world/entity/projectile/ThrownEnderpearl.java
+++ b/src/main/java/net/minecraft/world/entity/projectile/ThrownEnderpearl.java
@@ -108,6 +108,16 @@ public class ThrownEnderpearl extends ThrowableItemProjectile {
             super.tick();
         }
 
+        // Paper start
+        if (this.level.paperConfig.disableEnderpearlExploit) {
+            final net.minecraft.server.level.ChunkHolder chunkHolder = ((net.minecraft.server.level.ServerChunkCache) this.level.getChunkSource()).chunkMap.getVisibleChunkIfPresent(net.minecraft.world.level.ChunkPos.asLong(this.blockPosition()));
+            if (chunkHolder == null || !net.minecraft.server.level.ChunkHolder.getFullChunkStatus(chunkHolder.getTicketLevel()).isOrAfter(net.minecraft.server.level.ChunkHolder.FullChunkStatus.ENTITY_TICKING)) {
+                this.cachedOwner = null;
+                this.ownerUUID = null;
+            }
+        }
+        // Paper end
+
     }
 
     @Nullable