Writing Toolbox Analyzers

The Toolbox Commons project defines an Analyzer interface that encapsulates the logic for traversing a program graph to extract an "envelope" (a subgraph that is either empty if a property is satisfied or non-empty containing the necessary information to locate the violation of the property). Analyzers encapsulate their descriptions, assumptions, analysis context, and analysis logic. Of course you can define your own "Analyzer" simply by writing a program with your analysis logic, but we find this abstraction helps keep code organized when contributing to a toolbox project.

Let's update our Starter Toolbox to define a few new Analyzer objects. Specifically let's write analyzers that detect uses of native code (JNI), Java class loaders, reflection, and native processes. We want to be able to detect the usage of these language features because these exotic features tend to break naive program analysis implementations. Depending on our implementation, without the ability to detect these features we may not be able to tell if our analysis is sound or complete.

Analyzing Native Code Usage

public class NativeCodeUsage extends Analyzer {

	@Override
	public String getName() {
		return "Native Code Usage";
	}
	
	@Override
	public String getDescription() {
		return "Discovers uses of the Java Native Interface (JNI).";
	}
	
	@Override
	public String[] getAssumptions() {
		return new String[]{"Uses of native code are limited to method calls to app methods with the \"native\" keyword.",
							"Uses of native code are only made through direct method calls."};
	}
	
	@Override
	protected Q evaluateEnvelope() {
		Q nativeMethods = appContext.nodesTaggedWithAll(Node.METHOD, Node.IS_NATIVE);
		return CommonQueries.interactions(context, appContext, nativeMethods, Edge.CALL);
	}

}

Analyzing Class Loader Usage

public class ClassLoaderUsage extends Analyzer {

	@Override
	public String getName() {
		return "Class Loader Usage";
	}

	@Override
	public String getDescription() {
		return "Discovers uses of Java class loaders.";
	}

	@Override
	public String[] getAssumptions() {
		return new String[] { "Uses of class loader APIs are only made through direct method calls." };
	}

	@Override
	protected Q evaluateEnvelope() {
		// get all ClassLoader implementations (getting type hierarchy here
		// instead of just base types and overrides because the custom 
		// ClassLoader methods may contain valuable contextual information)
		Q classLoaderAPIs = CommonQueries.typeHierarchy(context,
				Common.typeSelect("java.lang", "ClassLoader"),
				TraversalDirection.REVERSE);

		// get the class loader API methods
		Q classLoaderMethods = CommonQueries.declarations(context,
				classLoaderAPIs, TraversalDirection.FORWARD)
				.nodesTaggedWithAny(Node.METHOD);

		// remove the boring class loader methods inherited from Object
		classLoaderMethods = classLoaderMethods.difference(SetDefinitions
				.objectMethodOverrides());

		// get the calls to the class loader API methods by the application
		return CommonQueries.interactions(context, appContext,
				classLoaderMethods, Edge.CALL);
	}

}

Analyzing Reflection Usage

TODO

Analyzing Native Process Usage

TODO

Running Analyzers

TODO

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