Dataflow query for detecting paths that disable content access

Since the default value is `true`, we need to determine whether or not
the `setAllowContentAccess` method is ever called using dataflow.

Author: egregius313

java/ql/src/Security/CWE/CWE-200/AndroidWebViewSettingsPermitsContentAccess.ql

@@ -0,0 +1,38 @@
+/**
+ * @id java/android-websettings-permit-contentacces
+ */
+
+import java
+import semmle.code.java.dataflow.DataFlow
+import semmle.code.java.frameworks.android.WebView
+
+private class TypeWebViewOrSubclass extends RefType {
+  TypeWebViewOrSubclass() { this.getASupertype*() instanceof TypeWebView }
+}
+
+// source: WebView
+// sink: settings.setAllowContentAccess(false)
+class WebViewDisallowContentAccessConfiguration extends DataFlow::Configuration {
+  WebViewDisallowContentAccessConfiguration() { this = "WebViewDisallowContentAccessConfiguration" }
+
+  override predicate isSource(DataFlow::Node source) {
+    source.asExpr().getType() instanceof TypeWebViewOrSubclass and
+    (
+      source.asExpr() instanceof ClassInstanceExpr or
+      source.asExpr() instanceof MethodAccess or
+      source.asExpr().(CastExpr).getAChildExpr() instanceof MethodAccess
+    )
+  }
+
+  override predicate isSink(DataFlow::Node sink) {
+    exists(MethodAccess ma |
+      ma = sink.asExpr() and
+      ma.getMethod().hasName("setAllowContentAccess") and
+      ma.getArgument(0).(CompileTimeConstantExpr).getBooleanValue() = false
+    )
+  }
+}
+
+from DataFlow::Node e, WebViewDisallowContentAccessConfiguration cfg
+where cfg.isSource(e) and not cfg.hasFlow(e, _)
+select e