From 7afe232264e314b9a63888718f2416a4db1f514a Mon Sep 17 00:00:00 2001
From: Reinhard Pointner <reinhard.pointner@gmail.com>
Date: Sat, 1 Oct 2016 01:18:44 +0800
Subject: [PATCH] Access simple bindings directly instead of accessing them via
 the Groovy engine

---
 .../net/filebot/format/ExpressionFormat.java  | 112 ++++++++++++------
 1 file changed, 74 insertions(+), 38 deletions(-)

diff --git a/source/net/filebot/format/ExpressionFormat.java b/source/net/filebot/format/ExpressionFormat.java
index 5b55df50..b81ef1f1 100644
--- a/source/net/filebot/format/ExpressionFormat.java
+++ b/source/net/filebot/format/ExpressionFormat.java
@@ -13,7 +13,9 @@ import java.util.ArrayList;
 import java.util.HashMap;
 import java.util.List;
 import java.util.Map;
+import java.util.concurrent.ExecutionException;
 
+import javax.lang.model.SourceVersion;
 import javax.script.Bindings;
 import javax.script.Compilable;
 import javax.script.CompiledScript;
@@ -33,38 +35,6 @@ import groovy.lang.MissingPropertyException;
 
 public class ExpressionFormat extends Format {
 
-	private static ScriptEngine engine;
-	private static Map<String, CompiledScript> scriptletCache = new HashMap<String, CompiledScript>();
-
-	protected static ScriptEngine createScriptEngine() {
-		CompilerConfiguration config = new CompilerConfiguration();
-
-		// include default functions
-		ImportCustomizer imports = new ImportCustomizer();
-		imports.addStaticStars(ExpressionFormatFunctions.class.getName());
-		config.addCompilationCustomizers(imports);
-
-		GroovyClassLoader classLoader = new GroovyClassLoader(Thread.currentThread().getContextClassLoader(), config);
-		return new GroovyScriptEngineImpl(classLoader);
-	}
-
-	protected static synchronized ScriptEngine getGroovyScriptEngine() throws ScriptException {
-		if (engine == null) {
-			engine = createScriptEngine();
-		}
-		return engine;
-	}
-
-	protected static synchronized CompiledScript compileScriptlet(String expression) throws ScriptException {
-		Compilable engine = (Compilable) getGroovyScriptEngine();
-		CompiledScript scriptlet = scriptletCache.get(expression);
-		if (scriptlet == null) {
-			scriptlet = engine.compile(expression);
-			scriptletCache.put(expression, scriptlet);
-		}
-		return scriptlet;
-	}
-
 	private final String expression;
 
 	private final Object[] compilation;
@@ -230,21 +200,87 @@ public class ExpressionFormat extends Format {
 		return lastException;
 	}
 
+	@Override
+	public Object parseObject(String source, ParsePosition pos) {
+		throw new UnsupportedOperationException();
+	}
+
 	private Object[] secure(Object[] compilation) {
 		for (int i = 0; i < compilation.length; i++) {
-			Object snipped = compilation[i];
+			Object snippet = compilation[i];
 
-			if (snipped instanceof CompiledScript) {
-				compilation[i] = new SecureCompiledScript((CompiledScript) snipped);
+			// simple expressions like {n} can't contain any malicious code
+			if (snippet instanceof Variable) {
+				continue;
+			}
+
+			if (snippet instanceof CompiledScript) {
+				compilation[i] = new SecureCompiledScript((CompiledScript) snippet);
 			}
 		}
 
 		return compilation;
 	}
 
-	@Override
-	public Object parseObject(String source, ParsePosition pos) {
-		throw new UnsupportedOperationException();
+	private static ScriptEngine engine;
+	private static Map<String, CompiledScript> scriptletCache = new HashMap<String, CompiledScript>();
+
+	protected static ScriptEngine createScriptEngine() {
+		CompilerConfiguration config = new CompilerConfiguration();
+
+		// include default functions
+		ImportCustomizer imports = new ImportCustomizer();
+		imports.addStaticStars(ExpressionFormatFunctions.class.getName());
+		config.addCompilationCustomizers(imports);
+
+		GroovyClassLoader classLoader = new GroovyClassLoader(Thread.currentThread().getContextClassLoader(), config);
+		return new GroovyScriptEngineImpl(classLoader);
+	}
+
+	protected static synchronized ScriptEngine getGroovyScriptEngine() throws ScriptException {
+		if (engine == null) {
+			engine = createScriptEngine();
+		}
+		return engine;
+	}
+
+	protected static synchronized CompiledScript compileScriptlet(String expression) throws ScriptException {
+		// simple expressions like {n} don't need to be interpreted by the script engine
+		if (SourceVersion.isIdentifier(expression)) {
+			return new Variable(expression);
+		}
+
+		CompiledScript scriptlet = scriptletCache.get(expression);
+		if (scriptlet == null) {
+			Compilable engine = (Compilable) getGroovyScriptEngine();
+			scriptlet = engine.compile(expression);
+			scriptletCache.put(expression, scriptlet);
+		}
+		return scriptlet;
+	}
+
+	private static class Variable extends CompiledScript {
+
+		private String name;
+
+		public Variable(String name) {
+			this.name = name;
+		}
+
+		@Override
+		public Object eval(ScriptContext context) throws ScriptException {
+			try {
+				return context.getAttribute(name);
+			} catch (Throwable t) {
+				throw new ScriptException(new ExecutionException(t));
+			}
+		}
+
+		@Override
+		public ScriptEngine getEngine() {
+			return null;
+		}
+
 	}
 
 }