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, 22 insertions, 0 deletions

diff --git a/patches/server/0492-Remove-stale-POIs.patch b/patches/server/0492-Remove-stale-POIs.patch
new file mode 100644
index 0000000000..ca376b9ba7
--- /dev/null
+++ b/patches/server/0492-Remove-stale-POIs.patch
@@ -0,0 +1,22 @@
+From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
+From: Shane Freeder <[email protected]>
+Date: Sat, 9 Jan 2021 14:17:07 +0100
+Subject: [PATCH] Remove stale POIs
+
+
+diff --git a/src/main/java/net/minecraft/server/level/ServerLevel.java b/src/main/java/net/minecraft/server/level/ServerLevel.java
+index 283f686364691f54d9e9e925b33238526de74219..a2113c01d8ea3da13efbf4f0b23460e7fa4e8c68 100644
+--- a/src/main/java/net/minecraft/server/level/ServerLevel.java
++++ b/src/main/java/net/minecraft/server/level/ServerLevel.java
+@@ -1795,6 +1795,11 @@ public class ServerLevel extends Level implements WorldGenLevel {
+             });
+             optional1.ifPresent((holder) -> {
+                 this.getServer().execute(() -> {
++                    // Paper start - Remove stale POIs
++                    if (optional.isEmpty() && this.getPoiManager().exists(blockposition1, poiType -> true)) {
++                        this.getPoiManager().remove(blockposition1);
++                    }
++                    // Paper end - Remove stale POIs
+                     this.getPoiManager().add(blockposition1, holder);
+                     DebugPackets.sendPoiAddedPacket(this, blockposition1);
+                 });