Fix creative ArrayIndexOutOfBoundsException. Fixes BUKKIT-4305

When a Player drops an ItemStack while in creative mode by placing it outside
of their inventory window, the slot number in the packet is -1. The check
that was added to avoid throwing InventoryCreativeEvent excessively didn't
take this into account, and would cause an ArrayIndexOutOfBoundsException to
be thrown when attempting to get the slot specified by the packet.

This change shorts the invocation of player.defaultContainer.getSlot(
packet107setcreativeslot.b) to only occur if the slot id is within the range
of the Inventory.  This prevents attempting to get the slot from a location
that is actually outside of the Inventory.

1 files changed, 31 insertions, 35 deletions

diff --git a/src/main/java/net/minecraft/server/PlayerConnection.java b/src/main/java/net/minecraft/server/PlayerConnection.java
index 42dbc56f..cc99ff5f 100644
--- a/src/main/java/net/minecraft/server/PlayerConnection.java
+++ b/src/main/java/net/minecraft/server/PlayerConnection.java
@@ -1459,45 +1459,41 @@ public class PlayerConnection extends Connection {
             boolean flag3 = itemstack == null || itemstack.getData() >= 0 && itemstack.getData() >= 0 && itemstack.count <= 64 && itemstack.count > 0;
 
             // CraftBukkit start - Call click event
-            if (flag1 || flag) { // Insist on valid slot
-                ItemStack existingItem = this.player.defaultContainer.getSlot(packet107setcreativeslot.slot).getItem();
-                // Client assumes that the server forgets the contents of the inventory.  It doesn't.
-                if (!ItemStack.matches(existingItem, packet107setcreativeslot.b)) {
-
-                    org.bukkit.entity.HumanEntity player = this.player.getBukkitEntity();
-                    InventoryView inventory = new CraftInventoryView(player, player.getInventory(), this.player.defaultContainer);
-                    org.bukkit.inventory.ItemStack item = CraftItemStack.asBukkitCopy(packet107setcreativeslot.b); // Should be packet107setcreativeslot.newitem
-
-                    SlotType type = SlotType.QUICKBAR;
-                    if (flag) {
-                        type = SlotType.OUTSIDE;
-                    } else if (packet107setcreativeslot.slot < 36) {
-                        if (packet107setcreativeslot.slot >= 5 && packet107setcreativeslot.slot < 9) {
-                            type = SlotType.ARMOR;
-                        } else {
-                            type = SlotType.CONTAINER;
-                        }
+            if (flag || (flag1 && !ItemStack.matches(this.player.defaultContainer.getSlot(packet107setcreativeslot.slot).getItem(), packet107setcreativeslot.b))) { // Insist on valid slot
+
+                org.bukkit.entity.HumanEntity player = this.player.getBukkitEntity();
+                InventoryView inventory = new CraftInventoryView(player, player.getInventory(), this.player.defaultContainer);
+                org.bukkit.inventory.ItemStack item = CraftItemStack.asBukkitCopy(packet107setcreativeslot.b); // Should be packet107setcreativeslot.newitem
+
+                SlotType type = SlotType.QUICKBAR;
+                if (flag) {
+                    type = SlotType.OUTSIDE;
+                } else if (packet107setcreativeslot.slot < 36) {
+                    if (packet107setcreativeslot.slot >= 5 && packet107setcreativeslot.slot < 9) {
+                        type = SlotType.ARMOR;
+                    } else {
+                        type = SlotType.CONTAINER;
                     }
-                    InventoryCreativeEvent event = new InventoryCreativeEvent(inventory, type, flag ? -999 : packet107setcreativeslot.slot, item);
-                    server.getPluginManager().callEvent(event);
+                }
+                InventoryCreativeEvent event = new InventoryCreativeEvent(inventory, type, flag ? -999 : packet107setcreativeslot.slot, item);
+                server.getPluginManager().callEvent(event);
 
-                    itemstack = CraftItemStack.asNMSCopy(event.getCursor());
+                itemstack = CraftItemStack.asNMSCopy(event.getCursor());
 
-                    switch (event.getResult()) {
-                    case ALLOW:
-                        // Plugin cleared the id / stacksize checks
-                        flag2 = flag3 = true;
-                        break;
-                    case DEFAULT:
-                        break;
-                    case DENY:
-                        // Reset the slot
-                        if (packet107setcreativeslot.slot >= 0) {
-                            this.player.playerConnection.sendPacket(new Packet103SetSlot(this.player.defaultContainer.windowId, packet107setcreativeslot.slot, this.player.defaultContainer.getSlot(packet107setcreativeslot.slot).getItem()));
-                            this.player.playerConnection.sendPacket(new Packet103SetSlot(-1, -1, null));
-                        }
-                        return;
+                switch (event.getResult()) {
+                case ALLOW:
+                    // Plugin cleared the id / stacksize checks
+                    flag2 = flag3 = true;
+                    break;
+                case DEFAULT:
+                    break;
+                case DENY:
+                    // Reset the slot
+                    if (packet107setcreativeslot.slot >= 0) {
+                        this.player.playerConnection.sendPacket(new Packet103SetSlot(this.player.defaultContainer.windowId, packet107setcreativeslot.slot, this.player.defaultContainer.getSlot(packet107setcreativeslot.slot).getItem()));
+                        this.player.playerConnection.sendPacket(new Packet103SetSlot(-1, -1, null));
                     }
+                    return;
                 }
             }
             // CraftBukkit end