Attach a configurable timeout to expression evaluation

worldedit-core/src/main/java/com/sk89q/worldedit/LocalConfiguration.java

@@ -127,6 +127,7 @@ public abstract class LocalConfiguration {
     public String navigationWand = ItemTypes.COMPASS.getId();
     public int navigationWandMaxDistance = 50;
     public int scriptTimeout = 3000;
+    public int calculationTimeout = 100;
     public Set<String> allowedDataCycleBlocks = new HashSet<>();
     public String saveDir = "schematics";
     public String scriptsDir = "craftscripts";

worldedit-core/src/main/java/com/sk89q/worldedit/internal/expression/Expression.java

@@ -19,6 +19,8 @@
 
 package com.sk89q.worldedit.internal.expression;
 
+import com.google.common.util.concurrent.ThreadFactoryBuilder;
+import com.sk89q.worldedit.WorldEdit;
 import com.sk89q.worldedit.internal.expression.lexer.Lexer;
 import com.sk89q.worldedit.internal.expression.lexer.tokens.Token;
 import com.sk89q.worldedit.internal.expression.parser.Parser;
@@ -34,6 +36,13 @@ import java.util.HashMap;
 import java.util.List;
 import java.util.Map;
 import java.util.Stack;
+import java.util.concurrent.Callable;
+import java.util.concurrent.ExecutionException;
+import java.util.concurrent.ExecutorService;
+import java.util.concurrent.Executors;
+import java.util.concurrent.Future;
+import java.util.concurrent.TimeUnit;
+import java.util.concurrent.TimeoutException;
 
 /**
  * Compiles and evaluates expressions.
@@ -69,6 +78,11 @@ import java.util.Stack;
 public class Expression {
 
     private static final ThreadLocal<Stack<Expression>> instance = new ThreadLocal<>();
+    private static final ExecutorService evalThread = Executors.newCachedThreadPool(
+            new ThreadFactoryBuilder()
+                    .setDaemon(true)
+                    .setNameFormat("worldedit-expression-eval-%d")
+                    .build());
 
     private final Map<String, RValue> variables = new HashMap<>();
     private final String[] variableNames;
@@ -115,9 +129,30 @@ public class Expression {
 
         pushInstance();
         try {
+            Future<Double> result = evalThread.submit(new Callable<Double>() {
+                @Override
+                public Double call() throws Exception {
                     return root.getValue();
-        } catch (ReturnException e) {
-            return e.getValue();
+                }
+            });
+            try {
+                return result.get(WorldEdit.getInstance().getConfiguration().calculationTimeout, TimeUnit.MILLISECONDS);
+            } catch (InterruptedException e) {
+                Thread.currentThread().interrupt();
+                throw new RuntimeException(e);
+            } catch (ExecutionException e) {
+                Throwable cause = e.getCause();
+                if (cause instanceof ReturnException) {
+                    return ((ReturnException) cause).getValue();
+                }
+                if (cause instanceof RuntimeException) {
+                    throw (RuntimeException) cause;
+                }
+                throw new RuntimeException(cause);
+            } catch (TimeoutException e) {
+                result.cancel(true);
+                throw new EvaluationException(-1, "Calculations exceeded time limit.");
+            }
         } finally {
             popInstance();
         }

worldedit-core/src/main/java/com/sk89q/worldedit/internal/expression/runtime/For.java

@@ -50,6 +50,9 @@ public class For extends Node {
             if (iterations > 256) {
                 throw new EvaluationException(getPosition(), "Loop exceeded 256 iterations.");
             }
+            if (Thread.interrupted()) {
+                throw new EvaluationException(getPosition(), "Calculations exceeded time limit.");
+            }
             ++iterations;
 
             try {

worldedit-core/src/main/java/com/sk89q/worldedit/internal/expression/runtime/SimpleFor.java

@@ -53,6 +53,9 @@ public class SimpleFor extends Node {
             if (iterations > 256) {
                 throw new EvaluationException(getPosition(), "Loop exceeded 256 iterations.");
             }
+            if (Thread.interrupted()) {
+                throw new EvaluationException(getPosition(), "Calculations exceeded time limit.");
+            }
             ++iterations;
 
             try {

worldedit-core/src/main/java/com/sk89q/worldedit/internal/expression/runtime/While.java

@@ -49,6 +49,9 @@ public class While extends Node {
                 if (iterations > 256) {
                     throw new EvaluationException(getPosition(), "Loop exceeded 256 iterations.");
                 }
+                if (Thread.interrupted()) {
+                    throw new EvaluationException(getPosition(), "Calculations exceeded time limit.");
+                }
                 ++iterations;
 
                 try {
@@ -66,6 +69,9 @@ public class While extends Node {
                 if (iterations > 256) {
                     throw new EvaluationException(getPosition(), "Loop exceeded 256 iterations.");
                 }
+                if (Thread.interrupted()) {
+                    throw new EvaluationException(getPosition(), "Calculations exceeded time limit.");
+                }
                 ++iterations;
 
                 try {

worldedit-core/src/main/java/com/sk89q/worldedit/util/PropertiesConfiguration.java

@@ -109,6 +109,7 @@ public class PropertiesConfiguration extends LocalConfiguration {
         navigationWandMaxDistance = getInt("nav-wand-distance", navigationWandMaxDistance);
         navigationUseGlass = getBool("nav-use-glass", navigationUseGlass);
         scriptTimeout = getInt("scripting-timeout", scriptTimeout);
+        calculationTimeout = getInt("calculation-timeout", calculationTimeout);
         saveDir = getString("schematic-save-dir", saveDir);
         scriptsDir = getString("craftscript-dir", scriptsDir);
         butcherDefaultRadius = getInt("butcher-default-radius", butcherDefaultRadius);

worldedit-core/src/main/java/com/sk89q/worldedit/util/YAMLConfiguration.java

@@ -105,6 +105,8 @@ public class YAMLConfiguration extends LocalConfiguration {
         scriptTimeout = config.getInt("scripting.timeout", scriptTimeout);
         scriptsDir = config.getString("scripting.dir", scriptsDir);
 
+        calculationTimeout = config.getInt("calculation.timeout", calculationTimeout);
+
         saveDir = config.getString("saving.dir", saveDir);
 
         allowSymlinks = config.getBoolean("files.allow-symbolic-links", false);

worldedit-core/src/test/java/com/sk89q/worldedit/internal/expression/ExpressionPlatform.java

@@ -0,0 +1,96 @@
+/*
+ * WorldEdit, a Minecraft world manipulation toolkit
+ * Copyright (C) sk89q <http://www.sk89q.com>
+ * Copyright (C) WorldEdit team and contributors
+ *
+ * This program is free software: you can redistribute it and/or modify it
+ * under the terms of the GNU Lesser General Public License as published by the
+ * Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public License
+ * for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public License
+ * along with this program. If not, see <http://www.gnu.org/licenses/>.
+ */
+
+package com.sk89q.worldedit.internal.expression;
+
+import com.google.common.collect.ImmutableMap;
+import com.sk89q.worldedit.LocalConfiguration;
+import com.sk89q.worldedit.entity.Player;
+import com.sk89q.worldedit.extension.platform.AbstractPlatform;
+import com.sk89q.worldedit.extension.platform.Capability;
+import com.sk89q.worldedit.extension.platform.Preference;
+import com.sk89q.worldedit.util.command.Dispatcher;
+import com.sk89q.worldedit.world.World;
+
+import java.util.Map;
+
+final class ExpressionPlatform extends AbstractPlatform {
+
+    @Override
+    public int resolveItem(String name) {
+        return 0;
+    }
+
+    @Override
+    public boolean isValidMobType(String type) {
+        return false;
+    }
+
+    @Override
+    public void reload() {
+    }
+
+    @Override
+    public Player matchPlayer(Player player) {
+        return null;
+    }
+
+    @Override
+    public World matchWorld(World world) {
+        return null;
+    }
+
+    @Override
+    public void registerCommands(Dispatcher dispatcher) {
+    }
+
+    @Override
+    public void registerGameHooks() {
+    }
+
+    @Override
+    public LocalConfiguration getConfiguration() {
+        return new LocalConfiguration() {
+
+            @Override
+            public void load() {
+            }
+        };
+    }
+
+    @Override
+    public String getVersion() {
+        return "INVALID";
+    }
+
+    @Override
+    public String getPlatformName() {
+        return "Expression Test";
+    }
+
+    @Override
+    public String getPlatformVersion() {
+        return "INVALID";
+    }
+
+    @Override
+    public Map<Capability, Preference> getCapabilities() {
+        return ImmutableMap.of(Capability.CONFIGURATION, Preference.PREFER_OTHERS);
+    }
+}