Break dataflow into two steps in order to capture flow from WebView to settings call

Author: egregius313

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

@@ -17,29 +17,82 @@ private class TypeWebViewOrSubclass extends RefType {
   TypeWebViewOrSubclass() { this.getASupertype*() instanceof TypeWebView }
 }
 
-// source: WebView
-// sink: settings.setAllowContentAccess(false)
-class WebViewDisallowContentAccessConfiguration extends DataFlow::Configuration {
-  WebViewDisallowContentAccessConfiguration() { this = "WebViewDisallowContentAccessConfiguration" }
+/**
+ * A method access to a getter method which is private.
+ *
+ * In Kotlin, member accesses are translated to getter methods.
+ */
+private class PrivateGetterMethodAccess extends MethodAccess {
+  PrivateGetterMethodAccess() {
+    this instanceof MethodAccess and
+    this.getMethod() instanceof GetterMethod and
+    this.getMethod().isPrivate()
+  }
+}
 
-  override predicate isSource(DataFlow::Node source) {
-    source.asExpr().getType() instanceof TypeWebViewOrSubclass and
+/**
+ * A flow configuration for tracking flow from the creation of a `WebView` object to a call of the `getSettings` method.
+ */
+private class WebViewGetSettingsConfiguration extends DataFlow::Configuration {
+  WebViewGetSettingsConfiguration() { this = "WebViewGetSettingsConfiguration" }
+
+  override predicate isSource(DataFlow::Node node) {
+    node.asExpr().getType().(RefType) instanceof TypeWebViewOrSubclass and
+    // To reduce duplicate results, we only consider WebView objects from
+    // constructor and method calls, or method accesses which are cast to WebView.
     (
-      source.asExpr() instanceof ClassInstanceExpr or
-      source.asExpr() instanceof MethodAccess or
-      source.asExpr().(CastExpr).getAChildExpr() instanceof MethodAccess
+      node.asExpr() instanceof ClassInstanceExpr or
+      node.asExpr() instanceof MethodAccess or
+      node.asExpr().(CastExpr).getAChildExpr() instanceof MethodAccess
+    ) and
+    // Avoid duplicate results from Kotlin member accesses.
+    not node.asExpr() instanceof PrivateGetterMethodAccess
+  }
+
+  override predicate isSink(DataFlow::Node node) {
+    exists(MethodAccess ma |
+      ma.getQualifier() = node.asExpr() and
+      ma.getMethod() instanceof WebViewGetSettingsMethod
     )
   }
+}
+
+private class WebSettingsSetAllowContentAccessFalseConfiguration extends DataFlow::Configuration {
+  WebSettingsSetAllowContentAccessFalseConfiguration() {
+    this = "WebSettingsSetAllowContentAccessFalseConfiguration"
+  }
 
-  override predicate isSink(DataFlow::Node sink) {
+  override predicate isSource(DataFlow::Node node) {
+    node.asExpr().getType() instanceof TypeWebSettings
+  }
+
+  override predicate isSink(DataFlow::Node node) {
+    // sink: settings.setAllowContentAccess(false)
+    // or (in Kotlin): settings.allowContentAccess = false
     exists(MethodAccess ma |
-      ma = sink.asExpr() and
+      ma.getQualifier() = node.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
+predicate hasContentAccessDisabled(Expr webview) {
+  exists(
+    DataFlow::Node wvSource, DataFlow::Node wvSink, WebViewGetSettingsConfiguration viewCfg,
+    DataFlow::Node settingsSource, DataFlow::Node settingsSink,
+    WebSettingsSetAllowContentAccessFalseConfiguration settingsCfg, MethodAccess getSettingsAccess
+  |
+    wvSource = DataFlow::exprNode(webview) and
+    viewCfg.hasFlow(wvSource, wvSink) and
+    settingsCfg.hasFlow(settingsSource, settingsSink) and
+    getSettingsAccess.getQualifier() = wvSink.asExpr() and
+    getSettingsAccess.getMethod() instanceof WebViewGetSettingsMethod and
+    getSettingsAccess = settingsSource.asExpr()
+  )
+}
+
+from Expr source, WebViewGetSettingsConfiguration cfg
+where cfg.isSource(DataFlow::exprNode(source)) and not hasContentAccessDisabled(source)
+select source,
+  "Sensitive information may be exposed via a malicious link due to access of content:// links being permitted."