Make command computer permission checks stricter

- Placing a command computer requires the player to be in creative and
   opped.
 - Breaking a command computer now requires the player to be opped, as
   well as in creative.

As we've now got a dedicated item class for command comptuers, we move
the command-specific IMedia override to that class.

Fixes #1582.

projects/common/src/main/java/dan200/computercraft/shared/ModRegistry.java

@@ -24,12 +24,14 @@ import dan200.computercraft.shared.common.ClearColourRecipe;
 import dan200.computercraft.shared.common.ColourableRecipe;
 import dan200.computercraft.shared.common.DefaultBundledRedstoneProvider;
 import dan200.computercraft.shared.common.HeldItemMenu;
+import dan200.computercraft.shared.computer.blocks.CommandComputerBlock;
 import dan200.computercraft.shared.computer.blocks.CommandComputerBlockEntity;
 import dan200.computercraft.shared.computer.blocks.ComputerBlock;
 import dan200.computercraft.shared.computer.blocks.ComputerBlockEntity;
 import dan200.computercraft.shared.computer.core.ComputerFamily;
 import dan200.computercraft.shared.computer.inventory.ComputerMenuWithoutInventory;
 import dan200.computercraft.shared.computer.inventory.ViewComputerMenu;
+import dan200.computercraft.shared.computer.items.CommandComputerItem;
 import dan200.computercraft.shared.computer.items.ComputerItem;
 import dan200.computercraft.shared.computer.recipe.ComputerUpgradeRecipe;
 import dan200.computercraft.shared.data.BlockNamedEntityLootCondition;
@@ -139,7 +141,7 @@ public final class ModRegistry {
         public static final RegistryEntry<ComputerBlock<ComputerBlockEntity>> COMPUTER_ADVANCED = REGISTRY.register("computer_advanced",
             () -> new ComputerBlock<>(computerProperties().mapColor(MapColor.GOLD), ComputerFamily.ADVANCED, BlockEntities.COMPUTER_ADVANCED));
 
-        public static final RegistryEntry<ComputerBlock<CommandComputerBlockEntity>> COMPUTER_COMMAND = REGISTRY.register("computer_command", () -> new ComputerBlock<>(
+        public static final RegistryEntry<ComputerBlock<CommandComputerBlockEntity>> COMPUTER_COMMAND = REGISTRY.register("computer_command", () -> new CommandComputerBlock<>(
             computerProperties().strength(-1, 6000000.0F),
             ComputerFamily.COMMAND, BlockEntities.COMPUTER_COMMAND
         ));
@@ -222,7 +224,7 @@ public final class ModRegistry {
 
         public static final RegistryEntry<ComputerItem> COMPUTER_NORMAL = ofBlock(Blocks.COMPUTER_NORMAL, ComputerItem::new);
         public static final RegistryEntry<ComputerItem> COMPUTER_ADVANCED = ofBlock(Blocks.COMPUTER_ADVANCED, ComputerItem::new);
-        public static final RegistryEntry<ComputerItem> COMPUTER_COMMAND = ofBlock(Blocks.COMPUTER_COMMAND, ComputerItem::new);
+        public static final RegistryEntry<ComputerItem> COMPUTER_COMMAND = ofBlock(Blocks.COMPUTER_COMMAND, CommandComputerItem::new);
 
         public static final RegistryEntry<PocketComputerItem> POCKET_COMPUTER_NORMAL = REGISTRY.register("pocket_computer_normal",
             () -> new PocketComputerItem(properties().stacksTo(1), ComputerFamily.NORMAL));

projects/common/src/main/java/dan200/computercraft/shared/computer/blocks/CommandComputerBlock.java

@@ -0,0 +1,23 @@
+// SPDX-FileCopyrightText: 2023 The CC: Tweaked Developers
+//
+// SPDX-License-Identifier: MPL-2.0
+
+package dan200.computercraft.shared.computer.blocks;
+
+import dan200.computercraft.shared.computer.core.ComputerFamily;
+import dan200.computercraft.shared.platform.RegistryEntry;
+import net.minecraft.world.level.block.GameMasterBlock;
+import net.minecraft.world.level.block.entity.BlockEntityType;
+
+/**
+ * A subclass of {@link ComputerBlock} which implements {@link GameMasterBlock}, to prevent players breaking it without
+ * permission.
+ *
+ * @param <T> The type of the computer block entity.
+ * @see dan200.computercraft.shared.computer.items.CommandComputerItem
+ */
+public class CommandComputerBlock<T extends CommandComputerBlockEntity> extends ComputerBlock<T> implements GameMasterBlock {
+    public CommandComputerBlock(Properties settings, ComputerFamily family, RegistryEntry<BlockEntityType<T>> type) {
+        super(settings, family, type);
+    }
+}

projects/common/src/main/java/dan200/computercraft/shared/computer/blocks/CommandComputerBlockEntity.java

@@ -104,11 +104,15 @@ public class CommandComputerBlockEntity extends ComputerBlockEntity {
         if (server == null || !server.isCommandBlockEnabled()) {
             player.displayClientMessage(Component.translatable("advMode.notEnabled"), true);
             return false;
-        } else if (Config.commandRequireCreative ? !player.canUseGameMasterBlocks() : !server.getPlayerList().isOp(player.getGameProfile())) {
+        } else if (!canUseCommandBlock(player)) {
             player.displayClientMessage(Component.translatable("advMode.notAllowed"), true);
             return false;
         }
 
         return true;
     }
+
+    private static boolean canUseCommandBlock(Player player) {
+        return Config.commandRequireCreative ? player.canUseGameMasterBlocks() : player.hasPermissions(2);
+    }
 }

projects/common/src/main/java/dan200/computercraft/shared/computer/items/AbstractComputerItem.java

@@ -64,13 +64,7 @@ public abstract class AbstractComputerItem extends BlockItem implements ICompute
 
     @Override
     public @Nullable Mount createDataMount(ItemStack stack, ServerLevel level) {
-        var family = getFamily();
+        var id = getComputerID(stack);
-        if (family != ComputerFamily.COMMAND) {
+        return id >= 0 ? ComputerCraftAPI.createSaveDirMount(level.getServer(), "computer/" + id, Config.computerSpaceLimit) : null;
-            var id = getComputerID(stack);
-            if (id >= 0) {
-                return ComputerCraftAPI.createSaveDirMount(level.getServer(), "computer/" + id, Config.computerSpaceLimit);
-            }
-        }
-        return null;
     }
 }

projects/common/src/main/java/dan200/computercraft/shared/computer/items/CommandComputerItem.java

@@ -0,0 +1,38 @@
+// SPDX-FileCopyrightText: 2023 The CC: Tweaked Developers
+//
+// SPDX-License-Identifier: MPL-2.0
+
+package dan200.computercraft.shared.computer.items;
+
+import dan200.computercraft.api.filesystem.Mount;
+import dan200.computercraft.shared.computer.blocks.ComputerBlock;
+import net.minecraft.server.level.ServerLevel;
+import net.minecraft.world.item.ItemStack;
+import net.minecraft.world.item.context.BlockPlaceContext;
+import net.minecraft.world.level.block.state.BlockState;
+import org.jetbrains.annotations.Nullable;
+
+/**
+ * A {@link ComputerItem} which prevents players placing it without permission.
+ *
+ * @see net.minecraft.world.item.GameMasterBlockItem
+ * @see dan200.computercraft.shared.computer.blocks.CommandComputerBlock
+ */
+public class CommandComputerItem extends ComputerItem {
+    public CommandComputerItem(ComputerBlock<?> block, Properties settings) {
+        super(block, settings);
+    }
+
+    @Override
+    protected @Nullable BlockState getPlacementState(BlockPlaceContext context) {
+        // Prohibit players placing this block in survival or when not opped.
+        var player = context.getPlayer();
+        return player != null && !player.canUseGameMasterBlocks() ? null : super.getPlacementState(context);
+    }
+
+    @Override
+    public @Nullable Mount createDataMount(ItemStack stack, ServerLevel level) {
+        // Don't allow command computers to be mounted in disk drives.
+        return null;
+    }
+}