From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
From: Noah van der Aa <ndvdaa@gmail.com>
Date: Tue, 3 Aug 2021 17:28:27 +0200
Subject: [PATCH] Hide unnecessary itemmeta from clients


diff --git a/src/main/java/com/destroystokyo/paper/PaperWorldConfig.java b/src/main/java/com/destroystokyo/paper/PaperWorldConfig.java
index 8150330bc55a010c7d0f96421586226631eb72f7..d71cd626bcbefc576f9c05b8885acc9fb2a33cd5 100644
--- a/src/main/java/com/destroystokyo/paper/PaperWorldConfig.java
+++ b/src/main/java/com/destroystokyo/paper/PaperWorldConfig.java
@@ -916,6 +916,13 @@ public class PaperWorldConfig {
         behaviorTickRates = loadTickRates("behavior");
     }
 
+    public boolean hideItemmetaFromClients = false;
+    public boolean hideDurabilityFromClients = false;
+    private void getHideItemmetaFromClients() {
+        hideItemmetaFromClients = getBoolean("anticheat.obfuscation.items.hide-itemmeta", hideItemmetaFromClients);
+        hideDurabilityFromClients = getBoolean("anticheat.obfuscation.items.hide-durability", hideDurabilityFromClients);
+    }
+
     private com.google.common.collect.Table<String, String, Integer> loadTickRates(String type) {
         log("  " + type + ":");
         com.google.common.collect.Table<String, String, Integer> table = com.google.common.collect.HashBasedTable.create();
diff --git a/src/main/java/net/minecraft/server/level/ServerEntity.java b/src/main/java/net/minecraft/server/level/ServerEntity.java
index d8ef6137133716b9ee519e6e4668d2e1ae5d9ca3..9a6c67b614944f841813ec2892381c3342bc365c 100644
--- a/src/main/java/net/minecraft/server/level/ServerEntity.java
+++ b/src/main/java/net/minecraft/server/level/ServerEntity.java
@@ -321,7 +321,7 @@ public class ServerEntity {
                 if (!itemstack.isEmpty()) {
                     // Paper start - prevent oversized data
                     final ItemStack sanitized = LivingEntity.sanitizeItemStack(itemstack.copy(), false);
-                    list.add(Pair.of(enumitemslot, sanitized));
+                    list.add(Pair.of(enumitemslot, ((LivingEntity) this.entity).stripMeta(sanitized, false))); // Paper - remove unnecessary item meta
                     // Paper end
                 }
             }
diff --git a/src/main/java/net/minecraft/world/entity/LivingEntity.java b/src/main/java/net/minecraft/world/entity/LivingEntity.java
index 430d4e98134dce62d30ddb31fcb125a69571fa5a..fe7e22d9a69d69dfcce63faa28e90945ea45fc49 100644
--- a/src/main/java/net/minecraft/world/entity/LivingEntity.java
+++ b/src/main/java/net/minecraft/world/entity/LivingEntity.java
@@ -3069,7 +3069,7 @@ public abstract class LivingEntity extends Entity {
 
             // Paper start - prevent oversized data
             ItemStack toSend = sanitizeItemStack(itemstack1, true);
-            list.add(Pair.of(enumitemslot, toSend));
+            list.add(Pair.of(enumitemslot, stripMeta(toSend, toSend == itemstack1))); // Paper - hide unnecessary item meta
             // Paper end
             switch (enumitemslot.getType()) {
                 case HAND:
@@ -3083,6 +3083,45 @@ public abstract class LivingEntity extends Entity {
         ((ServerLevel) this.level).getChunkSource().broadcast(this, new ClientboundSetEquipmentPacket(this.getId(), list));
     }
 
+    // Paper start - hide unnecessary item meta
+    public ItemStack stripMeta(final ItemStack itemStack, final boolean copyItemStack) {
+        if (itemStack.isEmpty() || (!itemStack.hasTag() && itemStack.getCount() < 2)) {
+            return itemStack;
+        }
+
+        final ItemStack copy = copyItemStack ? itemStack.copy() : itemStack;
+        if (level.paperConfig.hideDurabilityFromClients) {
+            // Only show damage values for elytra's, since they show a different texture when broken.
+            if (!copy.is(Items.ELYTRA) || copy.getDamageValue() < copy.getMaxDamage() - 1) {
+                copy.setDamageValue(0);
+            }
+        }
+
+        if (level.paperConfig.hideItemmetaFromClients) {
+            // Some resource packs show different textures when there is more than one item. Since this shouldn't provide a big advantage,
+            // we'll tell the client if there's one or (more than) two items.
+            copy.setCount(copy.getCount() > 1 ? 2 : 1);
+            // We can't just strip out display, leather helmets still use the display.color tag.
+            final CompoundTag tag = copy.getTag();
+            if (tag != null) {
+                if (tag.get("display") instanceof CompoundTag displayTag) {
+                    displayTag.remove("Lore");
+                    displayTag.remove("Name");
+                }
+
+                if (tag.get("Enchantments") instanceof ListTag enchantmentsTag && !enchantmentsTag.isEmpty()) {
+                    // The client still renders items with the enchantment glow if the enchantments tag contains at least one (empty) child.
+                    ListTag enchantments = new ListTag();
+                    enchantments.add(new CompoundTag());
+                    tag.put("Enchantments", enchantments);
+                }
+                tag.remove("AttributeModifiers");
+            }
+        }
+        return copy;
+    }
+    // Paper end
+
     // Paper end - prevent oversized data
     public static ItemStack sanitizeItemStack(final ItemStack itemStack, final boolean copyItemStack) {
         if (itemStack.isEmpty() || !itemStack.hasTag()) {