Paper/patches/server/0571-Fix-dangerous-end-portal-logic.patch

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/world/entity/Entity.java b/src/main/java/net/minecraft/world/entity/Entity.java
index 04581cd90272775208a0192ef36f9c7458ad3a0c..aac47d2de2825b46e54ad936a48c96ef7f6703e1 100644
--- a/src/main/java/net/minecraft/world/entity/Entity.java
+++ b/src/main/java/net/minecraft/world/entity/Entity.java
@@ -423,6 +423,36 @@ public abstract class Entity implements SyncedDataHolder, Nameable, EntityAccess
         return this.originWorld;
     }
     // Paper end - Entity origin API
+    // Paper start - make end portalling safe
+    public BlockPos portalBlock;
+    public ServerLevel portalWorld;
+    public void tickEndPortal() {
+        BlockPos pos = this.portalBlock;
+        ServerLevel world = this.portalWorld;
+        this.portalBlock = null;
+        this.portalWorld = null;
+
+        if (pos == null || world == null || world != this.level) {
+            return;
+        }
+
+        if (this.isPassenger() || this.isVehicle() || !this.canChangeDimensions() || this.isRemoved() || !this.valid || !this.isAlive()) {
+            return;
+        }
+
+        ResourceKey<Level> resourcekey = world.getTypeKey() == LevelStem.END ? Level.OVERWORLD : Level.END; // CraftBukkit - SPIGOT-6152: send back to main overworld in custom ends
+        ServerLevel worldserver = world.getServer().getLevel(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 ServerPlayer) {
+            ((ServerPlayer) this).changeDimension(worldserver, PlayerTeleportEvent.TeleportCause.END_PORTAL);
+            return;
+        }
+        this.teleportTo(worldserver, null);
+    }
+    // Paper end - make end portalling safe
     public float getBukkitYaw() {
         return this.yRot;
     }
@@ -2828,6 +2858,7 @@ public abstract class Entity implements SyncedDataHolder, Nameable, EntityAccess
             }
 
             this.processPortalCooldown();
+            if (!io.papermc.paper.configuration.GlobalConfiguration.get().unsupportedSettings.allowUnsafeEndPortalTeleportation) this.tickEndPortal(); // Paper - make end portalling safe
         }
     }
 
diff --git a/src/main/java/net/minecraft/world/level/block/EndPortalBlock.java b/src/main/java/net/minecraft/world/level/block/EndPortalBlock.java
index a2de13a366e4a462b746dab035372838127f4994..7272d70c672b54dcf595beafd7a2ed33c96e35cb 100644
--- a/src/main/java/net/minecraft/world/level/block/EndPortalBlock.java
+++ b/src/main/java/net/minecraft/world/level/block/EndPortalBlock.java
@@ -61,16 +61,13 @@ public class EndPortalBlock extends BaseEntityBlock {
                 // 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(), pos.getX(), pos.getY(), pos.getZ()));
-            world.getCraftServer().getPluginManager().callEvent(event);
-
-            if (entity instanceof ServerPlayer) {
-                ((ServerPlayer) entity).changeDimension(worldserver, PlayerTeleportEvent.TeleportCause.END_PORTAL);
-                return;
+            // Paper start - move all of this logic into portal tick
+            entity.portalWorld = ((ServerLevel)world);
+            entity.portalBlock = pos.immutable();
+            if (io.papermc.paper.configuration.GlobalConfiguration.get().unsupportedSettings.allowUnsafeEndPortalTeleportation) {
+                entity.tickEndPortal();
             }
-            // CraftBukkit end
-            entity.changeDimension(worldserver);
+            // Paper end - move all of this logic into portal tick
         }
 
     }