Allow enabling sand duping (#10191)

Because this exploit has been widely known for years and has not been fixed by Mojang, we decided that it was worth allowing people to toggle it on/off due to how easy it is to make it configurable.

It should be noted that this decision does not promise all future exploits will be configurable. 

1 files changed, 39 insertions, 0 deletions

diff --git a/patches/server/0677-Entity-powdered-snow-API.patch b/patches/server/0677-Entity-powdered-snow-API.patch
new file mode 100644
index 0000000000..9976726fc5
--- /dev/null
+++ b/patches/server/0677-Entity-powdered-snow-API.patch
@@ -0,0 +1,39 @@
+From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
+From: Jake Potrebic <[email protected]>
+Date: Sun, 24 Oct 2021 20:58:43 -0700
+Subject: [PATCH] Entity powdered snow API
+
+== AT ==
+public net.minecraft.world.entity.monster.Skeleton inPowderSnowTime
+
+diff --git a/src/main/java/org/bukkit/craftbukkit/entity/CraftEntity.java b/src/main/java/org/bukkit/craftbukkit/entity/CraftEntity.java
+index 411e2eed16d5b774900fc12f5ad782ab229dde97..71f9b7bbbabae9291fdb9f902f3f69c13e715c0e 100644
+--- a/src/main/java/org/bukkit/craftbukkit/entity/CraftEntity.java
++++ b/src/main/java/org/bukkit/craftbukkit/entity/CraftEntity.java
+@@ -1087,5 +1087,10 @@ public abstract class CraftEntity implements org.bukkit.entity.Entity {
+         this.entity.setRot(location.getYaw(), location.getPitch());
+         return !this.entity.valid && this.entity.level().addFreshEntity(this.entity, reason);
+     }
++
++    @Override
++    public boolean isInPowderedSnow() {
++        return getHandle().isInPowderSnow || getHandle().wasInPowderSnow; // depending on the location in the entity "tick" either could be needed.
++    }
+     // Paper end
+ }
+diff --git a/src/main/java/org/bukkit/craftbukkit/entity/CraftSkeleton.java b/src/main/java/org/bukkit/craftbukkit/entity/CraftSkeleton.java
+index a0ea54181de6c6685deef265cbe9f66aabbca42b..6f98da9be6aef35e3b5c940188b872459a383c8e 100644
+--- a/src/main/java/org/bukkit/craftbukkit/entity/CraftSkeleton.java
++++ b/src/main/java/org/bukkit/craftbukkit/entity/CraftSkeleton.java
+@@ -45,4 +45,11 @@ public class CraftSkeleton extends CraftAbstractSkeleton implements Skeleton {
+     public SkeletonType getSkeletonType() {
+        return SkeletonType.NORMAL;
+     }
++
++    // Paper start
++    @Override
++    public int inPowderedSnowTime() {
++        return getHandle().inPowderSnowTime;
++    }
++    // Paper end
+ }