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 68dc68238adc8d288052132e9f70663e8bba1e80..bfaaa80a5b144bd46ff3ea6a782aa87e5c51e8ea 100644
--- a/src/main/java/com/destroystokyo/paper/PaperConfig.java
+++ b/src/main/java/com/destroystokyo/paper/PaperConfig.java
@@ -434,4 +434,15 @@ public class PaperConfig {
     private static void loggerSettings() {
         deobfuscateStacktraces = getBoolean("settings.loggers.deobfuscate-stacktraces", deobfuscateStacktraces);
     }
+
+    public static boolean allowBlockPermanentBreakingExploits = false;
+    private static void allowBlockPermanentBreakingExploits() {
+        if (config.contains("allow-perm-block-break-exploits")) {
+            allowBlockPermanentBreakingExploits = config.getBoolean("allow-perm-block-break-exploits", false);
+            config.set("allow-perm-block-break-exploits", null);
+        }
+
+        config.set("settings.unsupported-settings.allow-permanent-block-break-exploits-readme", "This setting controls if players should be able to break bedrock, end portals and other intended to be permanent blocks.");
+        allowBlockPermanentBreakingExploits = getBoolean("settings.unsupported-settings.allow-permanent-block-break-exploits", allowBlockPermanentBreakingExploits);
+    }
 }
diff --git a/src/main/java/net/minecraft/world/level/Explosion.java b/src/main/java/net/minecraft/world/level/Explosion.java
index 548f103e648d9670d7434182c6598dc29ae77b57..f0c789d339fe8402c9c2a684d7e0415fa298b20e 100644
--- a/src/main/java/net/minecraft/world/level/Explosion.java
+++ b/src/main/java/net/minecraft/world/level/Explosion.java
@@ -173,6 +173,7 @@ public class Explosion {
                         for (float f1 = 0.3F; f > 0.0F; f -= 0.22500001F) {
                             BlockPos blockposition = new BlockPos(d4, d5, d6);
                             BlockState iblockdata = this.level.getBlockState(blockposition);
+                            if (!iblockdata.isDestroyable()) continue; // Paper
                             FluidState fluid = iblockdata.getFluidState(); // Paper
 
                             if (!this.level.isInWorldBounds(blockposition)) {
@@ -330,7 +331,7 @@ public class Explosion {
                 BlockState iblockdata = this.level.getBlockState(blockposition);
                 Block block = iblockdata.getBlock();
 
-                if (!iblockdata.isAir()) {
+                if (!iblockdata.isAir() && iblockdata.isDestroyable()) { // Paper
                     BlockPos blockposition1 = blockposition.immutable();
 
                     this.level.getProfiler().push("explosion_blocks");
diff --git a/src/main/java/net/minecraft/world/level/Level.java b/src/main/java/net/minecraft/world/level/Level.java
index 5abdb1c0247fde6da03e7689d5e2abab54f116d1..c7a69b84dada3fef89d798bd9c4cb151d61ee2de 100644
--- a/src/main/java/net/minecraft/world/level/Level.java
+++ b/src/main/java/net/minecraft/world/level/Level.java
@@ -416,6 +416,10 @@ public abstract class Level implements LevelAccessor, AutoCloseable {
     public boolean setBlock(BlockPos pos, BlockState state, int flags, int maxUpdateDepth) {
         // CraftBukkit start - tree generation
         if (this.captureTreeGeneration) {
+            // Paper start
+            BlockState type = getBlockState(pos);
+            if (!type.isDestroyable()) return false;
+            // Paper end
             CraftBlockState blockstate = this.capturedBlockStates.get(pos);
             if (blockstate == null) {
                 blockstate = CapturedBlockState.getTreeBlockState(this, pos, flags);
diff --git a/src/main/java/net/minecraft/world/level/block/Block.java b/src/main/java/net/minecraft/world/level/block/Block.java
index b77eda6af8b430311e502465a2590d83555ff6cf..a37213bce34f45898f56a22196b0d5ef1470e812 100644
--- a/src/main/java/net/minecraft/world/level/block/Block.java
+++ b/src/main/java/net/minecraft/world/level/block/Block.java
@@ -89,6 +89,19 @@ public class Block extends BlockBehaviour implements ItemLike {
     protected final StateDefinition<Block, BlockState> stateDefinition;
     private BlockState defaultBlockState;
     // 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.COMMAND_BLOCK &&
+            this != Blocks.REPEATING_COMMAND_BLOCK &&
+            this != Blocks.CHAIN_COMMAND_BLOCK &&
+            this != Blocks.BARRIER &&
+            this != Blocks.STRUCTURE_BLOCK &&
+            this != Blocks.JIGSAW;
+    }
     public co.aikar.timings.Timing timing;
     public co.aikar.timings.Timing getTiming() {
         if (timing == null) {
diff --git a/src/main/java/net/minecraft/world/level/block/piston/PistonBaseBlock.java b/src/main/java/net/minecraft/world/level/block/piston/PistonBaseBlock.java
index 2f1345d3c3671953a806cb243a152e080fbb9108..e9b315fb5a7b466e2ac65ae4ae69e893dd992739 100644
--- a/src/main/java/net/minecraft/world/level/block/piston/PistonBaseBlock.java
+++ b/src/main/java/net/minecraft/world/level/block/piston/PistonBaseBlock.java
@@ -199,6 +199,12 @@ public class PistonBaseBlock extends DirectionalBlock {
     @Override
     public boolean triggerEvent(BlockState state, Level world, BlockPos pos, int type, int data) {
         Direction enumdirection = (Direction) state.getValue(PistonBaseBlock.FACING);
+        // Paper start - prevent retracting when we're facing the wrong way (we were replaced before retraction could occur)
+        Direction directionQueuedAs = Direction.from3DDataValue(data & 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.getNeighborSignal(world, pos, enumdirection);
@@ -231,7 +237,7 @@ public class PistonBaseBlock extends DirectionalBlock {
             BlockState iblockdata1 = (BlockState) ((BlockState) Blocks.MOVING_PISTON.defaultBlockState().setValue(MovingPistonBlock.FACING, enumdirection)).setValue(MovingPistonBlock.TYPE, this.isSticky ? PistonType.STICKY : PistonType.DEFAULT);
 
             world.setBlock(pos, iblockdata1, 20);
-            world.setBlockEntity(MovingPistonBlock.newMovingBlockEntity(pos, iblockdata1, (BlockState) this.defaultBlockState().setValue(PistonBaseBlock.FACING, Direction.from3DDataValue(data & 7)), enumdirection, false, true));
+            world.setBlockEntity(MovingPistonBlock.newMovingBlockEntity(pos, iblockdata1, (BlockState) this.defaultBlockState().setValue(PistonBaseBlock.FACING, Direction.from3DDataValue(data & 7)), enumdirection, false, true)); // Paper - diff on change
             world.blockUpdated(pos, iblockdata1.getBlock());
             iblockdata1.updateNeighbourShapes(world, pos, 2);
             if (this.isSticky) {
@@ -260,7 +266,14 @@ public class PistonBaseBlock extends DirectionalBlock {
                     }
                 }
             } else {
-                world.removeBlock(pos.relative(enumdirection), false);
+                // Paper start - fix headless pistons breaking blocks
+                BlockPos headPos = pos.relative(enumdirection);
+                if (com.destroystokyo.paper.PaperConfig.allowBlockPermanentBreakingExploits || world.getBlockState(headPos) == Blocks.PISTON_HEAD.defaultBlockState().setValue(FACING, enumdirection)) { // double check to make sure we're not a headless piston.
+                    world.removeBlock(headPos, false);
+                } else {
+                    ((ServerLevel)world).getChunkSource().blockChanged(headPos); // ... fix client desync
+                }
+                // Paper end - fix headless pistons breaking blocks
             }
 
             world.playSound((Player) null, pos, SoundEvents.PISTON_CONTRACT, SoundSource.BLOCKS, 0.5F, world.random.nextFloat() * 0.15F + 0.6F);
diff --git a/src/main/java/net/minecraft/world/level/block/state/BlockBehaviour.java b/src/main/java/net/minecraft/world/level/block/state/BlockBehaviour.java
index 3c6b1b92fedf9986ebb835170c070ebd461f5d25..9055a82e9c91ecb8fc2ef5ac58db043ffb759168 100644
--- a/src/main/java/net/minecraft/world/level/block/state/BlockBehaviour.java
+++ b/src/main/java/net/minecraft/world/level/block/state/BlockBehaviour.java
@@ -223,7 +223,7 @@ public abstract class BlockBehaviour {
     /** @deprecated */
     @Deprecated
     public boolean canBeReplaced(BlockState state, BlockPlaceContext context) {
-        return this.material.isReplaceable() && (context.getItemInHand().isEmpty() || !context.getItemInHand().is(this.asItem()));
+        return this.material.isReplaceable() && (context.getItemInHand().isEmpty() || !context.getItemInHand().is(this.asItem())) && (state.isDestroyable() || (context.getPlayer() != null && context.getPlayer().getAbilities().instabuild)); // Paper
     }
 
     /** @deprecated */
@@ -705,7 +705,11 @@ public abstract class BlockBehaviour {
         public Block getBlock() {
             return (Block) this.owner;
         }
-
+        // Paper start
+        public final boolean isDestroyable() {
+            return getBlock().isDestroyable();
+        }
+        // Paper end
         public Material getMaterial() {
             return this.material;
         }
@@ -803,7 +807,7 @@ public abstract class BlockBehaviour {
         }
 
         public PushReaction getPistonPushReaction() {
-            return this.getBlock().getPistonPushReaction(this.asState());
+            return !isDestroyable() ? PushReaction.BLOCK : this.getBlock().getPistonPushReaction(this.asState()); // Paper
         }
 
         public boolean isSolidRender(BlockGetter world, BlockPos pos) {
diff --git a/src/main/java/net/minecraft/world/level/portal/PortalForcer.java b/src/main/java/net/minecraft/world/level/portal/PortalForcer.java
index 05150fbade1d5a9b3b6de8ad1f5e825f34d1037e..ed79058696eb26a89b9d4116821840dbad9ea449 100644
--- a/src/main/java/net/minecraft/world/level/portal/PortalForcer.java
+++ b/src/main/java/net/minecraft/world/level/portal/PortalForcer.java
@@ -210,6 +210,13 @@ public class PortalForcer {
         for (int j = -1; j < 3; ++j) {
             for (int k = -1; k < 4; ++k) {
                 temp.setWithOffset(pos, portalDirection.getStepX() * j + enumdirection1.getStepX() * distanceOrthogonalToPortal, k, portalDirection.getStepZ() * j + enumdirection1.getStepZ() * distanceOrthogonalToPortal);
+                // Paper start - prevent destroying unbreakable blocks
+                if (!com.destroystokyo.paper.PaperConfig.allowBlockPermanentBreakingExploits) {
+                    if (!this.level.getBlockState(temp).isDestroyable()) {
+                        return false;
+                    }
+                }
+                // Paper end - prevent destroying unbreakable blocks
                 if (k < 0 && !this.level.getBlockState(temp).getMaterial().isSolid()) {
                     return false;
                 }
