Protect document.execCommand() from recursive call and DOM mutation events

Source/core/dom/Document.cpp

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  *           (C) 1999 Antti Koivisto (koivisto@kde.org)
  *           (C) 2001 Dirk Mueller (mueller@kde.org)
  *           (C) 2006 Alexey Proskuryakov (ap@webkit.org)
  * Copyright (C) 2004, 2005, 2006, 2007, 2008, 2009, 2011, 2012 Apple Inc. All rights reserved.
  * Copyright (C) 2008, 2009 Torch Mobile Inc. All rights reserved. (http://www.torchmobile.com/)
  * Copyright (C) 2008, 2009, 2011, 2012 Google Inc. All rights reserved.
  * Copyright (C) 2010 Nokia Corporation and/or its subsidiary(-ies)
  * Copyright (C) Research In Motion Limited 2010-2011. All rights reserved.
@@ skipping 4133 matching lines @@
     Frame* frame = document->frame();
     if (!frame || frame->document() != document)
         return Editor::Command();
 
     document->updateStyleIfNeeded();
     return frame->editor().command(commandName, userInterface ? CommandFromDOMWithUserInterface : CommandFromDOM);
 }
 
 bool Document::execCommand(const String& commandName, bool userInterface, const String& value)
 {
+    // We don't allow recusrive |execCommand()| to protect against attack code.
+    // Recursive call of |execCommand()| could be happened by moving iframe
+    // with script triggered by insertion, e.g. <iframe src="javascript:...">
+    // <iframe onload="...">. This usage is valid as of the specification
+    // although, it isn't common use case, rather it is used as attack code.
+    static bool inExecCommand = false;
+    if (inExecCommand) {
+        String message = "document.execCommand() is called recursively. Please revise event handler to avoid calling document.execCommand() recursively.";

[tkent, 2014/01/29 07:56:06]

Please say that we won't execute document.execCommand this time. This message
doesn't mention whether the command will be executed or not.

[yosin_UTC9, 2014/01/29 08:06:42]

Done.

+        addConsoleMessage(JSMessageSource, WarningMessageLevel, message);
+        return false;
+    }
+    TemporaryChange<bool> executeScope(inExecCommand, true);
+
+    // Postpone DOM mutation events, which can execute scripts and change
+    // DOM tree against implementation assumption.
+    EventQueueScope eventQueueScope;
     return command(this, commandName, userInterface).execute(value);
 }
 
 bool Document::queryCommandEnabled(const String& commandName)
 {
     return command(this, commandName).isEnabled();
 }
 
 bool Document::queryCommandIndeterm(const String& commandName)
 {
@@ skipping 1202 matching lines @@
     if (!page->focusController().isActive() || !page->focusController().isFocused())
         return false;
     if (Frame* focusedFrame = page->focusController().focusedFrame()) {
         if (focusedFrame->tree().isDescendantOf(frame()))
             return true;
     }
     return false;
 }
 
 } // namespace WebCore