avoid an NPE

Author: StevenArzt

soot-infoflow-android/src/soot/jimple/infoflow/android/callbacks/filters/ApplicationCallbackFilter.java

@@ -8,6 +8,7 @@
 import soot.SootClass;
 import soot.SootMethod;
 import soot.jimple.infoflow.android.entryPointCreators.AndroidEntryPointConstants;
+import soot.jimple.infoflow.typing.TypeUtils;
 
 /**
  * A callback filter that restricts application callbacks to ComponentCallbacks
@@ -70,9 +71,9 @@ public boolean accepts(SootClass component, SootClass callbackHandler) {
 				&& !callbackHandler.getName().equals(applicationClass)) {
 			final FastHierarchy fh = Scene.v().getOrMakeFastHierarchy();
 			final RefType callbackType = callbackHandler.getType();
-			if (!fh.canStoreType(callbackType, this.activityLifecycleCallbacks)
-					&& !fh.canStoreType(callbackType, this.provideAssistDataListener)
-					&& !fh.canStoreType(callbackType, this.componentCallbacks))
+			if (!TypeUtils.canStoreType(fh, callbackType, this.activityLifecycleCallbacks)
+					&& !TypeUtils.canStoreType(fh, callbackType, this.provideAssistDataListener)
+					&& !TypeUtils.canStoreType(fh, callbackType, this.componentCallbacks))
 				return false;
 		}
 
@@ -81,10 +82,24 @@ public boolean accepts(SootClass component, SootClass callbackHandler) {
 
 	@Override
 	public void reset() {
-		this.activityLifecycleCallbacks = RefType.v(AndroidEntryPointConstants.ACTIVITYLIFECYCLECALLBACKSINTERFACE);
-		this.provideAssistDataListener = RefType.v("android.app.Application$OnProvideAssistDataListener");
-		this.componentCallbacks = RefType.v(AndroidEntryPointConstants.COMPONENTCALLBACKSINTERFACE);
-		this.componentCallbacks2 = RefType.v(AndroidEntryPointConstants.COMPONENTCALLBACKS2INTERFACE);
+		this.activityLifecycleCallbacks = getRefTypeUnsafe(
+				AndroidEntryPointConstants.ACTIVITYLIFECYCLECALLBACKSINTERFACE);
+		this.provideAssistDataListener = getRefTypeUnsafe("android.app.Application$OnProvideAssistDataListener");
+		this.componentCallbacks = getRefTypeUnsafe(AndroidEntryPointConstants.COMPONENTCALLBACKSINTERFACE);
+		this.componentCallbacks2 = getRefTypeUnsafe(AndroidEntryPointConstants.COMPONENTCALLBACKS2INTERFACE);
+	}
+
+	/**
+	 * Gets the {@link RefType} that corresponds to the given class name, or
+	 * <code>null</code> if the class is unknown
+	 * 
+	 * @param className The class name for which to get the reference type
+	 * @return The reference type for the given class name, or <code>null</code> if
+	 *         the class is unknown
+	 */
+	private RefType getRefTypeUnsafe(String className) {
+		SootClass sc = Scene.v().getSootClassUnsafe(className);
+		return sc == null ? null : sc.getType();
 	}
 
 	@Override

soot-infoflow/src/soot/jimple/infoflow/typing/TypeUtils.java

@@ -315,4 +315,21 @@ public static List<SootClass> getAllDerivedClasses(SootClass classOrInterface) {
 			return h.getSubclassesOfIncluding(classOrInterface);
 	}
 
+	/**
+	 * Checks whether a value of type "child" can be stored in a variable of type
+	 * "parent". If one of the types is <code>null</code>, we assume that the value
+	 * cannot be stored.
+	 * 
+	 * @param fh     The {@link FastHierarchy}
+	 * @param child  The actual type of the value
+	 * @param parent The declared type of the variable
+	 * @return True if a value of type "child" can be stored in a variable of type
+	 *         "parent", false otherwise
+	 */
+	public static boolean canStoreType(FastHierarchy fh, Type child, Type parent) {
+		if (child == null || parent == null)
+			return false;
+		return fh.canStoreType(child, parent);
+	}
+
 }