Bug 1548349 - Make sure the image cache for third-party tracking subresources is keyed to the top-level document's eTLD+1; r=baku,aosmond

Differential Revision: https://phabricator.services.mozilla.com/D29546

--HG--
extra : moz-landing-system : lando

image/ImageCacheKey.cpp

@@ -13,10 +13,12 @@
 #include "nsLayoutUtils.h"
 #include "nsString.h"
 #include "mozilla/AntiTrackingCommon.h"
+#include "mozilla/HashFunctions.h"
 #include "mozilla/dom/BlobURLProtocolHandler.h"
 #include "mozilla/dom/File.h"
 #include "mozilla/dom/ServiceWorkerManager.h"
 #include "mozilla/dom/Document.h"
+#include "nsHashKeys.h"
 #include "nsPrintfCString.h"
 
 namespace mozilla {
@@ -43,6 +45,7 @@ ImageCacheKey::ImageCacheKey(nsIURI* aURI, const OriginAttributes& aAttrs,
     : mURI(aURI),
       mOriginAttributes(aAttrs),
       mControlledDocument(GetSpecialCaseDocumentToken(aDocument, aURI)),
+      mTopLevelBaseDomain(GetTopLevelBaseDomain(aDocument, aURI)),
       mIsChrome(false) {
   if (SchemeIs("blob")) {
     mBlobSerial = BlobSerial(mURI);
@@ -57,6 +60,7 @@ ImageCacheKey::ImageCacheKey(const ImageCacheKey& aOther)
       mBlobRef(aOther.mBlobRef),
       mOriginAttributes(aOther.mOriginAttributes),
       mControlledDocument(aOther.mControlledDocument),
+      mTopLevelBaseDomain(aOther.mTopLevelBaseDomain),
       mHash(aOther.mHash),
       mIsChrome(aOther.mIsChrome) {}
 
@@ -66,6 +70,7 @@ ImageCacheKey::ImageCacheKey(ImageCacheKey&& aOther)
       mBlobRef(std::move(aOther.mBlobRef)),
       mOriginAttributes(aOther.mOriginAttributes),
       mControlledDocument(aOther.mControlledDocument),
+      mTopLevelBaseDomain(aOther.mTopLevelBaseDomain),
       mHash(aOther.mHash),
       mIsChrome(aOther.mIsChrome) {}
 
@@ -75,6 +80,12 @@ bool ImageCacheKey::operator==(const ImageCacheKey& aOther) const {
   if (mControlledDocument != aOther.mControlledDocument) {
     return false;
   }
+  // Don't share the image cache between two top-level documents of different
+  // base domains.
+  if (!mTopLevelBaseDomain.Equals(aOther.mTopLevelBaseDomain,
+                                  nsCaseInsensitiveCStringComparator())) {
+    return false;
+  }
   // The origin attributes always have to match.
   if (mOriginAttributes != aOther.mOriginAttributes) {
     return false;
@@ -127,7 +138,8 @@ void ImageCacheKey::EnsureHash() const {
     hash = HashString(spec);
   }
 
-  hash = AddToHash(hash, HashString(suffix), HashString(ptr));
+  hash = AddToHash(hash, HashString(suffix), HashString(mTopLevelBaseDomain),
+                   HashString(ptr));
   mHash.emplace(hash);
 }
 
@@ -153,27 +165,44 @@ void* ImageCacheKey::GetSpecialCaseDocumentToken(Document* aDocument,
     return aDocument;
   }
 
+  return nullptr;
+}
+
+/* static */
+nsCString ImageCacheKey::GetTopLevelBaseDomain(Document* aDocument,
+                                               nsIURI* aURI) {
+  if (!aDocument || !aDocument->GetInnerWindow()) {
+    return EmptyCString();
+  }
+
   // If the window is 3rd party resource, let's see if first-party storage
   // access is granted for this image.
   if (nsContentUtils::IsThirdPartyTrackingResourceWindow(
           aDocument->GetInnerWindow())) {
     return nsContentUtils::StorageDisabledByAntiTracking(aDocument, aURI)
-               ? aDocument
-               : nullptr;
+               ? aDocument->GetBaseDomain()
+               : EmptyCString();
   }
 
   // Another scenario is if this image is a 3rd party resource loaded by a
   // first party context. In this case, we should check if the nsIChannel has
   // been marked as tracking resource, but we don't have the channel yet at
   // this point.  The best approach here is to be conservative: if we are sure
-  // that the permission is granted, let's return a nullptr. Otherwise, let's
-  // make a unique image cache.
+  // that the permission is granted, let's return 0. Otherwise, let's make a
+  // unique image cache per the top-level document eTLD+1.
   if (!AntiTrackingCommon::MaybeIsFirstPartyStorageAccessGrantedFor(
           aDocument->GetInnerWindow(), aURI)) {
-    return aDocument;
+    nsPIDOMWindowOuter* top = aDocument->GetInnerWindow()->GetScriptableTop();
+    nsPIDOMWindowInner* topInner = top->GetCurrentInnerWindow();
+    if (!topInner) {
+      return aDocument
+          ->GetBaseDomain();  // because we don't have anything better!
+    }
+    return topInner->GetExtantDoc() ? topInner->GetExtantDoc()->GetBaseDomain()
+                                    : EmptyCString();
   }
 
-  return nullptr;
+  return EmptyCString();
 }
 
 }  // namespace image

image/ImageCacheKey.h

@@ -61,11 +61,16 @@ class ImageCacheKey final {
  private:
   bool SchemeIs(const char* aScheme);
 
-  // For ServiceWorker and for anti-tracking we need to use the document as
+  // For ServiceWorker we need to use the document as
   // token for the key. All those exceptions are handled by this method.
   static void* GetSpecialCaseDocumentToken(dom::Document* aDocument,
                                            nsIURI* aURI);
 
+  // For anti-tracking we need to use the top-level document's base domain for
+  // the key. This is handled by this method.
+  static nsCString GetTopLevelBaseDomain(dom::Document* aDocument,
+                                         nsIURI* aURI);
+
   void EnsureHash() const;
   void EnsureBlobRef() const;
 
@@ -74,6 +79,7 @@ class ImageCacheKey final {
   mutable nsCString mBlobRef;
   OriginAttributes mOriginAttributes;
   void* mControlledDocument;
+  nsCString mTopLevelBaseDomain;
   mutable Maybe<PLDHashNumber> mHash;
   bool mIsChrome;
 };