Paper/Spigot-Server-Patches/0519-Protect-Bedrock-and-End-Portal-Frames-from-being-des.patch

From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
From: Aikar <aikar@aikar.co>
Date: Wed, 13 May 2020 23:01:26 -0400
Subject: [PATCH] Protect Bedrock and End Portal/Frames from being destroyed

This fixes exploits that let players destroy bedrock by Pistons, explosions
and Mushrooom/Tree generation.

These blocks are designed to not be broken except by creative players/commands.
So protect them from a multitude of methods of destroying them.

A config is provided if you rather let players use these exploits, and let
them destroy the worlds End Portals and get on top of the nether easy.

diff --git a/src/main/java/com/destroystokyo/paper/PaperConfig.java b/src/main/java/com/destroystokyo/paper/PaperConfig.java
index 3ee7e5671dd2519cec72b81211f1f39176a228ba..cf9b9de8688e3f655631451409096d7ec0471910 100644
--- a/src/main/java/com/destroystokyo/paper/PaperConfig.java
+++ b/src/main/java/com/destroystokyo/paper/PaperConfig.java
@@ -431,4 +431,10 @@ public class PaperConfig {
     private static void midTickChunkTasks() {
         midTickChunkTasks = getInt("settings.chunk-tasks-per-tick", midTickChunkTasks);
     }
+
+    public static boolean allowBlockPermanentBreakingExploits = false;
+    private static void allowBlockPermanentBreakingExploits() {
+        allowBlockPermanentBreakingExploits = getBoolean("allow-perm-block-break-exploits", allowBlockPermanentBreakingExploits);
+    }
+
 }
diff --git a/src/main/java/net/minecraft/server/Block.java b/src/main/java/net/minecraft/server/Block.java
index e40375b67a4a321048c87002a07fde5c5d2395db..d2207a2c95690de586ab2d181b64955a6d2ea70d 100644
--- a/src/main/java/net/minecraft/server/Block.java
+++ b/src/main/java/net/minecraft/server/Block.java
@@ -32,6 +32,14 @@ public class Block implements IMaterial {
     protected final SoundEffectType stepSound;
     protected final Material material;
     // Paper start
+    public final boolean isDestroyable() {
+        return com.destroystokyo.paper.PaperConfig.allowBlockPermanentBreakingExploits ||
+            this != Blocks.BEDROCK &&
+            this != Blocks.END_PORTAL_FRAME &&
+            this != Blocks.END_PORTAL &&
+            this != Blocks.END_GATEWAY &&
+            this != Blocks.MOVING_PISTON; // try to prevent creation of headless pistons
+    }
     public co.aikar.timings.Timing timing;
     public co.aikar.timings.Timing getTiming() {
         if (timing == null) {
@@ -276,7 +284,7 @@ public class Block implements IMaterial {
 
     @Deprecated
     public boolean a(IBlockData iblockdata, BlockActionContext blockactioncontext) {
-        return this.material.isReplaceable() && (blockactioncontext.getItemStack().isEmpty() || blockactioncontext.getItemStack().getItem() != this.getItem());
+        return this.material.isReplaceable() && (blockactioncontext.getItemStack().isEmpty() || blockactioncontext.getItemStack().getItem() != this.getItem()) && (iblockdata.isDestroyable() || (blockactioncontext.getEntity() != null && blockactioncontext.getEntity().abilities.canInstantlyBuild)); // Paper
     }
 
     @Deprecated
@@ -596,7 +604,7 @@ public class Block implements IMaterial {
 
     @Deprecated
     public EnumPistonReaction getPushReaction(IBlockData iblockdata) {
-        return this.material.getPushReaction();
+        return !blockData.isDestroyable() ? EnumPistonReaction.BLOCK : this.material.getPushReaction(); // Paper
     }
 
     public void fallOn(World world, BlockPosition blockposition, Entity entity, float f) {
diff --git a/src/main/java/net/minecraft/server/BlockPiston.java b/src/main/java/net/minecraft/server/BlockPiston.java
index b29525c40dc8e3ae747b8ddf5a3bd79b7cc0b792..39cd8ab5925ceb9494e0ac910c73338c24ecda2c 100644
--- a/src/main/java/net/minecraft/server/BlockPiston.java
+++ b/src/main/java/net/minecraft/server/BlockPiston.java
@@ -175,6 +175,12 @@ public class BlockPiston extends BlockDirectional {
     @Override
     public boolean a(IBlockData iblockdata, World world, BlockPosition blockposition, int i, int j) {
         EnumDirection enumdirection = (EnumDirection) iblockdata.get(BlockPiston.FACING);
+        // Paper start - prevent retracting when we're facing the wrong way (we were replaced before retraction could occur)
+        EnumDirection directionQueuedAs = EnumDirection.fromType1(j & 7); // Paper - copied from below
+        if (!com.destroystokyo.paper.PaperConfig.allowBlockPermanentBreakingExploits && enumdirection != directionQueuedAs) {
+            return false;
+        }
+        // Paper end - prevent retracting when we're facing the wrong way
 
         if (!world.isClientSide) {
             boolean flag = this.a(world, blockposition, enumdirection);
@@ -204,7 +210,7 @@ public class BlockPiston extends BlockDirectional {
             }
 
             world.setTypeAndData(blockposition, (IBlockData) ((IBlockData) Blocks.MOVING_PISTON.getBlockData().set(BlockPistonMoving.a, enumdirection)).set(BlockPistonMoving.b, this.sticky ? BlockPropertyPistonType.STICKY : BlockPropertyPistonType.DEFAULT), 3);
-            world.setTileEntity(blockposition, BlockPistonMoving.a((IBlockData) this.getBlockData().set(BlockPiston.FACING, EnumDirection.fromType1(j & 7)), enumdirection, false, true));
+            world.setTileEntity(blockposition, BlockPistonMoving.a((IBlockData) this.getBlockData().set(BlockPiston.FACING, EnumDirection.fromType1(j & 7)), enumdirection, false, true)); // Paper - diff on change, j is facing direction
             if (this.sticky) {
                 BlockPosition blockposition1 = blockposition.b(enumdirection.getAdjacentX() * 2, enumdirection.getAdjacentY() * 2, enumdirection.getAdjacentZ() * 2);
                 IBlockData iblockdata1 = world.getType(blockposition1);
@@ -232,7 +238,14 @@ public class BlockPiston extends BlockDirectional {
                     }
                 }
             } else {
-                world.a(blockposition.shift(enumdirection), false);
+                // Paper start - fix headless pistons breaking blocks
+                BlockPosition headPos = blockposition.shift(enumdirection);
+                if (com.destroystokyo.paper.PaperConfig.allowBlockPermanentBreakingExploits || world.getType(headPos) == Blocks.PISTON_HEAD.getBlockData().set(FACING, enumdirection)) { // double check to make sure we're not a headless piston.
+                    world.setAir(headPos, false);
+                } else {
+                    ((WorldServer)world).getChunkProvider().flagDirty(headPos); // ... fix client desync
+                }
+                // Paper end - fix headless pistons breaking blocks
             }
 
             world.playSound((EntityHuman) null, blockposition, SoundEffects.BLOCK_PISTON_CONTRACT, SoundCategory.BLOCKS, 0.5F, world.random.nextFloat() * 0.15F + 0.6F);
diff --git a/src/main/java/net/minecraft/server/Explosion.java b/src/main/java/net/minecraft/server/Explosion.java
index a353f3d5fa5a5f54335f73584589de3f5cb20d3e..2552f860ff7a25f74e9a0600e58cefe064fac484 100644
--- a/src/main/java/net/minecraft/server/Explosion.java
+++ b/src/main/java/net/minecraft/server/Explosion.java
@@ -117,6 +117,7 @@ public class Explosion {
                         for (float f1 = 0.3F; f > 0.0F; f -= 0.22500001F) {
                             BlockPosition blockposition = new BlockPosition(d4, d5, d6);
                             IBlockData iblockdata = this.world.getType(blockposition);
+                            if (!iblockdata.isDestroyable()) continue; // Paper
                             Fluid fluid = iblockdata.getFluid(); // Paper
 
                             if (!iblockdata.isAir() || !fluid.isEmpty()) {
@@ -282,7 +283,7 @@ public class Explosion {
                 IBlockData iblockdata = this.world.getType(blockposition);
                 Block block = iblockdata.getBlock();
 
-                if (!iblockdata.isAir()) {
+                if (!iblockdata.isAir() && iblockdata.isDestroyable()) { // Paper
                     BlockPosition blockposition1 = blockposition.immutableCopy();
 
                     this.world.getMethodProfiler().enter("explosion_blocks");
diff --git a/src/main/java/net/minecraft/server/IBlockData.java b/src/main/java/net/minecraft/server/IBlockData.java
index b19bbbbc81376177751396a2de9452ce1f84c06b..296b41bf36ee1ace5bd9db2b810bf926b5f5278f 100644
--- a/src/main/java/net/minecraft/server/IBlockData.java
+++ b/src/main/java/net/minecraft/server/IBlockData.java
@@ -52,6 +52,11 @@ public class IBlockData extends BlockDataAbstract<Block, IBlockData> implements
         return (CraftBlockData) cachedCraftBlockData.clone();
     }
     // Paper end
+    // Paper start
+    public final boolean isDestroyable() {
+        return getBlock().isDestroyable();
+    }
+    // Paper end
 
     public Material getMaterial() {
         return this.getBlock().k(this);
diff --git a/src/main/java/net/minecraft/server/World.java b/src/main/java/net/minecraft/server/World.java
index 7bd3f789b6055d73f3a6c0628652cca241147887..032b7acee8c8af70c0283f5551ce2875607f6c98 100644
--- a/src/main/java/net/minecraft/server/World.java
+++ b/src/main/java/net/minecraft/server/World.java
@@ -342,6 +342,10 @@ public abstract class World implements GeneratorAccess, AutoCloseable {
     public boolean setTypeAndData(BlockPosition blockposition, IBlockData iblockdata, int i) {
         // CraftBukkit start - tree generation
         if (this.captureTreeGeneration) {
+            // Paper start
+            IBlockData type = getType(blockposition);
+            if (!type.isDestroyable()) return false;
+            // Paper end
             CraftBlockState blockstate = capturedBlockStates.get(blockposition);
             if (blockstate == null) {
                 blockstate = CapturedBlockState.getTreeBlockState(this, blockposition, i);