From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
From: Spottedleaf <spottedleaf@users.noreply.github.com>
Date: Fri, 4 Jun 2021 17:06:52 -0400
Subject: [PATCH] Fix dangerous end portal logic

End portals could teleport entities during move calls. Stupid
logic given the caller will never expect that kind of thing,
and will result in all kinds of dupes.

Move the tick logic into the post tick, where portaling was
designed to happen in the first place.

diff --git a/src/main/java/net/minecraft/server/level/EntityPlayer.java b/src/main/java/net/minecraft/server/level/EntityPlayer.java
index 558af73ac16550ee6964c4dce681a404633b2552..75bcfb3a2b4a104aeebb2fe3298714b2e5b569d2 100644
--- a/src/main/java/net/minecraft/server/level/EntityPlayer.java
+++ b/src/main/java/net/minecraft/server/level/EntityPlayer.java
@@ -1023,6 +1023,7 @@ public class EntityPlayer extends EntityHuman implements ICrafting {
         return b(worldserver, TeleportCause.UNKNOWN);
     }
 
+    @Nullable public final Entity changeDimension(WorldServer worldserver, PlayerTeleportEvent.TeleportCause cause) { return this.b(worldserver, cause); } // Paper - OBFHELPER
     @Nullable
     public Entity b(WorldServer worldserver, PlayerTeleportEvent.TeleportCause cause) {
         // CraftBukkit end
diff --git a/src/main/java/net/minecraft/world/entity/Entity.java b/src/main/java/net/minecraft/world/entity/Entity.java
index 89b2be0e9e42d65b7d2d2833de4e6cd1c6e17e8e..6e1304f7169c11f67c573b2c8dc11825bcc7da0d 100644
--- a/src/main/java/net/minecraft/world/entity/Entity.java
+++ b/src/main/java/net/minecraft/world/entity/Entity.java
@@ -314,6 +314,37 @@ public abstract class Entity implements INamableTileEntity, ICommandListener, ne
     }
     // Paper end - optimise entity tracking
 
+    // Paper start - make end portalling safe
+    public BlockPosition portalBlock;
+    public WorldServer portalWorld;
+    public void tickEndPortal() {
+        BlockPosition pos = this.portalBlock;
+        WorldServer world = this.portalWorld;
+        this.portalBlock = null;
+        this.portalWorld = null;
+
+        if (pos == null || world == null || world != this.world) {
+            return;
+        }
+
+        if (this.isPassenger() || this.isVehicle() || !this.canPortal() || this.dead || !this.valid || !this.isAlive()) {
+            return;
+        }
+
+        ResourceKey<World> resourcekey = world.getTypeKey() == DimensionManager.THE_END ? World.OVERWORLD : World.THE_END; // CraftBukkit - SPIGOT-6152: send back to main overworld in custom ends
+        WorldServer worldserver = world.getMinecraftServer().getWorldServer(resourcekey);
+
+        org.bukkit.event.entity.EntityPortalEnterEvent event = new org.bukkit.event.entity.EntityPortalEnterEvent(this.getBukkitEntity(), new org.bukkit.Location(world.getWorld(), pos.getX(), pos.getY(), pos.getZ()));
+        event.callEvent();
+
+        if (this instanceof EntityPlayer) {
+            ((EntityPlayer)this).changeDimension(worldserver, PlayerTeleportEvent.TeleportCause.END_PORTAL);
+            return;
+        }
+        this.teleportTo(worldserver, null);
+    }
+    // Paper end - make end portalling safe
+
     public Entity(EntityTypes<?> entitytypes, World world) {
         this.id = Entity.entityCount.incrementAndGet();
         this.passengers = Lists.newArrayList();
@@ -2299,6 +2330,7 @@ public abstract class Entity implements INamableTileEntity, ICommandListener, ne
             }
 
             this.E();
+            this.tickEndPortal(); // Paper - make end portalling safe
         }
     }
 
diff --git a/src/main/java/net/minecraft/world/level/block/BlockEnderPortal.java b/src/main/java/net/minecraft/world/level/block/BlockEnderPortal.java
index ed916f69747b44b75eb06db4cf27adaf5e47fd1e..9483d75fbe2a8c8f7cce00355e93ff1f943f3444 100644
--- a/src/main/java/net/minecraft/world/level/block/BlockEnderPortal.java
+++ b/src/main/java/net/minecraft/world/level/block/BlockEnderPortal.java
@@ -52,16 +52,10 @@ public class BlockEnderPortal extends BlockTileEntity {
                 // return; // CraftBukkit - always fire event in case plugins wish to change it
             }
 
-            // CraftBukkit start - Entity in portal
-            EntityPortalEnterEvent event = new EntityPortalEnterEvent(entity.getBukkitEntity(), new org.bukkit.Location(world.getWorld(), blockposition.getX(), blockposition.getY(), blockposition.getZ()));
-            world.getServer().getPluginManager().callEvent(event);
-
-            if (entity instanceof EntityPlayer) {
-                ((EntityPlayer) entity).b(worldserver, PlayerTeleportEvent.TeleportCause.END_PORTAL);
-                return;
-            }
-            // CraftBukkit end
-            entity.b(worldserver);
+            // Paper start - move all of this logic into portal tick
+            entity.portalWorld = ((WorldServer)world);
+            entity.portalBlock = blockposition.immutableCopy();
+            // Paper end - move all of this logic into portal tick
         }
 
     }