Purpur/patches/server/0124-PaperPR-Fix-more-exploits-carpet-dupe-rail-dupe-bedr.patch

From b2c766502d6a3d85a6d8743a9ff235bd10acacf6 Mon Sep 17 00:00:00 2001
From: Spottedleaf <Spottedleaf@users.noreply.github.com>
Date: Thu, 11 Jun 2020 17:29:42 -0700
Subject: [PATCH] PaperPR - Fix more exploits (carpet dupe, rail dupe, bedrock
 destroying, falling block (sand/dragon egg/etc) duping)

---
 src/main/java/net/minecraft/server/BlockPiston.java | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/src/main/java/net/minecraft/server/BlockPiston.java b/src/main/java/net/minecraft/server/BlockPiston.java
index 9cca30a94f..80a4cf1641 100644
--- a/src/main/java/net/minecraft/server/BlockPiston.java
+++ b/src/main/java/net/minecraft/server/BlockPiston.java
@@ -373,12 +373,14 @@ public class BlockPiston extends BlockDirectional {
             }
 
             for (k = list.size() - 1; k >= 0; --k) {
-                blockposition3 = (BlockPosition) list.get(k);
-                iblockdata1 = world.getType(blockposition3); map.replace(blockposition3, iblockdata1); // Paper - fix piston physics inconsistency
+                BlockPosition oldPos = blockposition3 = (BlockPosition) list.get(k); // Purpur
+                iblockdata1 = null; // Purpur - explode if usage changes
                 blockposition3 = blockposition3.shift(enumdirection1);
                 map.remove(blockposition3);
                 world.setTypeAndData(blockposition3, (IBlockData) Blocks.MOVING_PISTON.getBlockData().set(BlockPiston.FACING, enumdirection), 68);
+                iblockdata1 = world.getType(oldPos); map.replace(oldPos, iblockdata1); // Purpur - fix piston physics inconsistency - move after the physics update
                 world.setTileEntity(blockposition3, BlockPistonMoving.a(iblockdata1, enumdirection, flag, false)); // Paper - fix piston physics inconsistency
+                world.setTypeAndData(oldPos, Blocks.AIR.getBlockData(), 68); // Purpur - set air to prevent later physics updates from seeing this block
                 --j;
                 aiblockdata[j] = iblockdata1;
             }
-- 
2.26.2