Bug 1515665 - SessionStorage should be allowed when StorageAccess is ePartitionedOrDeny, r=ehsan

dom/storage/SessionStorage.cpp

@@ -12,6 +12,7 @@
 #include "mozilla/Preferences.h"
 #include "nsContentUtils.h"
 #include "nsIPrincipal.h"
+#include "nsIWebProgressListener.h"
 #include "nsPIDOMWindow.h"
 
 #define DATASET                                          \
@@ -163,5 +164,11 @@ bool SessionStorage::IsForkOf(const Storage* aOther) const {
   return mCache == static_cast<const SessionStorage*>(aOther)->mCache;
 }
 
+bool SessionStorage::ShouldThrowWhenStorageAccessDenied(
+    uint32_t aRejectedReason) {
+  return aRejectedReason !=
+         nsIWebProgressListener::STATE_COOKIES_BLOCKED_FOREIGN;
+}
+
 }  // namespace dom
 }  // namespace mozilla

dom/storage/SessionStorage.h

@@ -65,6 +65,8 @@ class SessionStorage final : public Storage {
                                    const nsAString& aOldValue,
                                    const nsAString& aNewValue);
 
+  bool ShouldThrowWhenStorageAccessDenied(uint32_t aRejectedReason) override;
+
   RefPtr<SessionStorageCache> mCache;
   RefPtr<SessionStorageManager> mManager;
 

dom/storage/Storage.cpp

@@ -43,15 +43,23 @@ bool Storage::CanUseStorage(nsIPrincipal& aSubjectPrincipal) {
     return false;
   }
 
-  nsContentUtils::StorageAccess access =
-      nsContentUtils::StorageAllowedForPrincipal(Principal());
+  if (nsContentUtils::IsSystemPrincipal(mPrincipal)) {
+    mIsSessionOnly = false;
+  } else if (mWindow) {
+    uint32_t rejectedReason = 0;
+    nsContentUtils::StorageAccess access =
+        nsContentUtils::StorageAllowedForWindow(mWindow, &rejectedReason);
 
-  if (access <= nsContentUtils::StorageAccess::eDeny) {
-    return false;
+    // Note that we allow StorageAccess::ePartitionedOrDeny because we want
+    // tracker to have access to their sessionStorage.
+    if (access == nsContentUtils::StorageAccess::eDeny &&
+        ShouldThrowWhenStorageAccessDenied(rejectedReason)) {
+      return false;
+    }
+
+    mIsSessionOnly = access <= nsContentUtils::StorageAccess::eSessionScoped;
   }
 
-  mIsSessionOnly = access <= nsContentUtils::StorageAccess::eSessionScoped;
-
   return aSubjectPrincipal.Subsumes(mPrincipal);
 }
 

dom/storage/Storage.h

@@ -144,6 +144,13 @@ class Storage : public nsISupports, public nsWrapperCache {
 
   virtual void LastRelease() {}
 
+  // This method is called when StorageAccess is not granted for the owning
+  // window. aRejectedReason is one of the possible blocking states from
+  // nsIWebProgressListener.
+  virtual bool ShouldThrowWhenStorageAccessDenied(uint32_t aRejectedReason) {
+    return true;
+  }
+
  private:
   nsCOMPtr<nsPIDOMWindowInner> mWindow;
   nsCOMPtr<nsIPrincipal> mPrincipal;