[AdTracking] Include the top of the stack in AdTracker detection

Includes the script of the top stack frame in ads detection processing.

Bug: 807640
Change-Id: I8f4d0364ea088bf00abcc7310e4dccce7fec78f3
Reviewed-on: https://chromium-review.googlesource.com/986337
Commit-Queue: Josh Karlin <jkarlin@chromium.org>
Reviewed-by: Nate Chapin <japhet@chromium.org>
Cr-Commit-Position: refs/heads/master@{#549509}

third_party/blink/renderer/core/frame/AdTracker.cpp

@@ -4,6 +4,7 @@
 
 #include "third_party/blink/renderer/core/frame/AdTracker.h"
 
+#include "third_party/blink/renderer/bindings/core/v8/source_location.h"
 #include "third_party/blink/renderer/core/CoreProbeSink.h"
 #include "third_party/blink/renderer/core/frame/local_frame.h"
 #include "third_party/blink/renderer/core/probe/core_probes.h"
@@ -27,6 +28,13 @@ void AdTracker::Shutdown() {
   local_root_ = nullptr;
 }
 
+String AdTracker::ScriptAtTopOfStack(ExecutionContext* execution_context) {
+  std::unique_ptr<blink::SourceLocation> current_stack_trace =
+      SourceLocation::Capture(execution_context);
+  // TODO(jkarlin): Url() sometimes returns String(), why?
+  return current_stack_trace ? current_stack_trace->Url() : "";
+}
+
 void AdTracker::WillExecuteScript(const String& script_url) {
   bool is_ad =
       script_url.IsEmpty() ? false : known_ad_scripts_.Contains(script_url);
@@ -76,22 +84,30 @@ void AdTracker::WillSendRequest(ExecutionContext* execution_context,
                                 Resource::Type resource_type) {
   // If the resource is not already marked as an ad, check if any executing
   // script is an ad. If yes, mark this as an ad.
-  if (!request.IsAdResource() && AnyExecutingScriptsTaggedAsAdResource())
+  if (!request.IsAdResource() &&
+      AnyExecutingScriptsTaggedAsAdResource(execution_context))
     request.SetIsAdResource();
 
   // If it is a script marked as an ad, append it to the known ad scripts set.
-  if (resource_type != Resource::kScript || !request.IsAdResource()) {
-    return;
-  }
-  AppendToKnownAdScripts(request.Url());
+  if (resource_type == Resource::kScript && request.IsAdResource())
+    AppendToKnownAdScripts(request.Url());
 }
 
-// Keeping a separate function to easily access from tests.
+// This is a separate function for testing purposes.
 void AdTracker::AppendToKnownAdScripts(const KURL& url) {
   known_ad_scripts_.insert(url.GetString());
 }
 
-bool AdTracker::AnyExecutingScriptsTaggedAsAdResource() {
+bool AdTracker::AnyExecutingScriptsTaggedAsAdResource(
+    ExecutionContext* execution_context) {
+  // The pseudo-stack contains entry points into the stack (e.g., when v8 is
+  // executed) but not the entire stack. It's cheap to retrieve the top of the
+  // stack so scan that as well.
+  String top_script = ScriptAtTopOfStack(execution_context);
+  if (!top_script.IsEmpty() && known_ad_scripts_.Contains(top_script))
+    return true;
+
+  // Scan the pseudo-stack for ad scripts.
   for (const auto& executing_script : executing_scripts_) {
     if (executing_script.is_ad)
       return true;

third_party/blink/renderer/core/frame/AdTracker.h

@@ -27,8 +27,7 @@ class ExecuteScript;
 
 // Tracker for tagging resources as ads based on the call stack scripts.
 // The tracker is maintained per local root.
-class CORE_EXPORT AdTracker final
-    : public GarbageCollectedFinalized<AdTracker> {
+class CORE_EXPORT AdTracker : public GarbageCollectedFinalized<AdTracker> {
  public:
   // Instrumenting methods.
   // Called when a script module or script gets executed from native code.
@@ -56,7 +55,11 @@ class CORE_EXPORT AdTracker final
 
   void Shutdown();
   explicit AdTracker(LocalFrame*);
-  ~AdTracker();
+  virtual ~AdTracker();
+
+ protected:
+  // Protected for testing.
+  virtual String ScriptAtTopOfStack(ExecutionContext*);
 
  private:
   friend class FrameFetchContextSubresourceFilterTest;
@@ -69,7 +72,7 @@ class CORE_EXPORT AdTracker final
   // Returns true if any script in the pseudo call stack has been identified as
   // an ad earlier. An ad is identified as an ad if AppendToKnownAdScripts has
   // been called on it earlier.
-  bool AnyExecutingScriptsTaggedAsAdResource();
+  bool AnyExecutingScriptsTaggedAsAdResource(ExecutionContext*);
 
   Member<LocalFrame> local_root_;
 

third_party/blink/renderer/core/frame/AdTrackerTest.cpp

@@ -13,6 +13,27 @@
 
 namespace blink {
 
+namespace {
+
+class TestAdTracker : public AdTracker {
+ public:
+  explicit TestAdTracker(LocalFrame* frame) : AdTracker(frame) {}
+  void SetScriptAtTopOfStack(String url) { script_at_top_ = url; }
+  ~TestAdTracker() override {}
+
+ protected:
+  // Returns "" by default unless SetScriptAtTopOfStack is called with
+  // something else.
+  String ScriptAtTopOfStack(ExecutionContext* execution_context) override {
+    return script_at_top_;
+  }
+
+ private:
+  String script_at_top_;
+};
+
+}  // namespace
+
 class AdTrackerTest : public testing::Test {
  protected:
   void SetUp() override;
@@ -26,21 +47,22 @@ class AdTrackerTest : public testing::Test {
   }
 
   bool AnyExecutingScriptsTaggedAsAdResource() {
-    return ad_tracker_->AnyExecutingScriptsTaggedAsAdResource();
+    return ad_tracker_->AnyExecutingScriptsTaggedAsAdResource(
+        &page_holder_->GetDocument());
   }
 
   void AppendToKnownAdScripts(const KURL& url) {
     ad_tracker_->AppendToKnownAdScripts(url);
   }
 
-  Persistent<AdTracker> ad_tracker_;
+  Persistent<TestAdTracker> ad_tracker_;
   std::unique_ptr<DummyPageHolder> page_holder_;
 };
 
 void AdTrackerTest::SetUp() {
   page_holder_ = DummyPageHolder::Create(IntSize(800, 600));
   page_holder_->GetDocument().SetURL(KURL("https://example.com/foo"));
-  ad_tracker_ = new AdTracker(GetFrame());
+  ad_tracker_ = new TestAdTracker(GetFrame());
 }
 
 void AdTrackerTest::TearDown() {
@@ -64,4 +86,31 @@ TEST_F(AdTrackerTest, AnyExecutingScriptsTaggedAsAdResource_False) {
   EXPECT_FALSE(AnyExecutingScriptsTaggedAsAdResource());
 }
 
+TEST_F(AdTrackerTest, TopOfStackIncluded) {
+  KURL ad_script_url("https://example.com/ad.js");
+  AppendToKnownAdScripts(ad_script_url);
+
+  WillExecuteScript("https://example.com/foo.js");
+  WillExecuteScript("https://example.com/bar.js");
+  EXPECT_FALSE(AnyExecutingScriptsTaggedAsAdResource());
+
+  ad_tracker_->SetScriptAtTopOfStack("https://www.example.com/baz.js");
+  EXPECT_FALSE(AnyExecutingScriptsTaggedAsAdResource());
+
+  ad_tracker_->SetScriptAtTopOfStack(ad_script_url);
+  EXPECT_TRUE(AnyExecutingScriptsTaggedAsAdResource());
+
+  ad_tracker_->SetScriptAtTopOfStack("https://www.example.com/baz.js");
+  EXPECT_FALSE(AnyExecutingScriptsTaggedAsAdResource());
+
+  ad_tracker_->SetScriptAtTopOfStack("");
+  EXPECT_FALSE(AnyExecutingScriptsTaggedAsAdResource());
+
+  ad_tracker_->SetScriptAtTopOfStack(WTF::String());
+  EXPECT_FALSE(AnyExecutingScriptsTaggedAsAdResource());
+
+  WillExecuteScript(ad_script_url);
+  EXPECT_TRUE(AnyExecutingScriptsTaggedAsAdResource());
+}
+
 }  // namespace blink