gecko-dev/dom/base/WindowNamedPropertiesHandler.cpp

/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/* vim: set ts=8 sts=2 et sw=2 tw=80: */
/* This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at http://mozilla.org/MPL/2.0/. */

#include "WindowNamedPropertiesHandler.h"
#include "mozilla/dom/EventTargetBinding.h"
#include "mozilla/dom/WindowBinding.h"
#include "nsContentUtils.h"
#include "nsDOMClassInfo.h"
#include "nsDOMWindowList.h"
#include "nsGlobalWindow.h"
#include "nsHTMLDocument.h"
#include "nsJSUtils.h"
#include "xpcprivate.h"

namespace mozilla {
namespace dom {

static bool
ShouldExposeChildWindow(nsString& aNameBeingResolved, nsPIDOMWindowOuter* aChild)
{
  Element* e = aChild->GetFrameElementInternal();
  if (e && e->IsInShadowTree()) {
    return false;
  }

  // If we're same-origin with the child, go ahead and expose it.
  nsCOMPtr<nsIScriptObjectPrincipal> sop = do_QueryInterface(aChild);
  NS_ENSURE_TRUE(sop, false);
  if (nsContentUtils::SubjectPrincipal()->Equals(sop->GetPrincipal())) {
    return true;
  }

  // If we're not same-origin, expose it _only_ if the name of the browsing
  // context matches the 'name' attribute of the frame element in the parent.
  // The motivations behind this heuristic are worth explaining here.
  //
  // Historically, all UAs supported global named access to any child browsing
  // context (that is to say, window.dolske returns a child frame where either
  // the "name" attribute on the frame element was set to "dolske", or where
  // the child explicitly set window.name = "dolske").
  //
  // This is problematic because it allows possibly-malicious and unrelated
  // cross-origin subframes to pollute the global namespace of their parent in
  // unpredictable ways (see bug 860494). This is also problematic for browser
  // engines like Servo that want to run cross-origin script on different
  // threads.
  //
  // The naive solution here would be to filter out any cross-origin subframes
  // obtained when doing named lookup in global scope. But that is unlikely to
  // be web-compatible, since it will break named access for consumers that do
  // <iframe name="dolske" src="http://cross-origin.com/sadtrombone.html"> and
  // expect to be able to access the cross-origin subframe via named lookup on
  // the global.
  //
  // The optimal behavior would be to do the following:
  // (a) Look for any child browsing context with name="dolske".
  // (b) If the result is cross-origin, null it out.
  // (c) If we have null, look for a frame element whose 'name' attribute is
  //     "dolske".
  //
  // Unfortunately, (c) would require some engineering effort to be performant
  // in Gecko, and probably in other UAs as well. So we go with a simpler
  // approximation of the above. This approximation will only break sites that
  // rely on their cross-origin subframes setting window.name to a known value,
  // which is unlikely to be very common. And while it does introduce a
  // dependency on cross-origin state when doing global lookups, it doesn't
  // allow the child to arbitrarily pollute the parent namespace, and requires
  // cross-origin communication only in a limited set of cases that can be
  // computed independently by the parent.
  return e && e->AttrValueIs(kNameSpaceID_None, nsGkAtoms::name,
                             aNameBeingResolved, eCaseMatters);
}

bool
WindowNamedPropertiesHandler::getOwnPropDescriptor(JSContext* aCx,
                                                   JS::Handle<JSObject*> aProxy,
                                                   JS::Handle<jsid> aId,
                                                   bool /* unused */,
                                                   JS::MutableHandle<JS::PropertyDescriptor> aDesc)
                                                   const
{
  if (!JSID_IS_STRING(aId)) {
    // Nothing to do if we're resolving a non-string property.
    return true;
  }

  bool hasOnPrototype;
  if (!HasPropertyOnPrototype(aCx, aProxy, aId, &hasOnPrototype)) {
    return false;
  }
  if (hasOnPrototype) {
    return true;
  }

  nsAutoJSString str;
  if (!str.init(aCx, JSID_TO_STRING(aId))) {
    return false;
  }

  // Grab the DOM window.
  JS::Rooted<JSObject*> global(aCx, JS_GetGlobalForObject(aCx, aProxy));
  nsGlobalWindow* win = xpc::WindowOrNull(global);
  if (win->Length() > 0) {
    nsCOMPtr<nsPIDOMWindowOuter> childWin = win->GetChildWindow(str);
    if (childWin && ShouldExposeChildWindow(str, childWin)) {
      // We found a subframe of the right name. Shadowing via |var foo| in
      // global scope is still allowed, since |var| only looks up |own|
      // properties. But unqualified shadowing will fail, per-spec.
      JS::Rooted<JS::Value> v(aCx);
      if (!WrapObject(aCx, childWin, &v)) {
        return false;
      }
      FillPropertyDescriptor(aDesc, aProxy, 0, v);
      return true;
    }
  }

  // The rest of this function is for HTML documents only.
  nsCOMPtr<nsIHTMLDocument> htmlDoc = do_QueryInterface(win->GetExtantDoc());
  if (!htmlDoc) {
    return true;
  }
  nsHTMLDocument* document = static_cast<nsHTMLDocument*>(htmlDoc.get());

  Element* element = document->GetElementById(str);
  if (element) {
    JS::Rooted<JS::Value> v(aCx);
    if (!WrapObject(aCx, element, &v)) {
      return false;
    }
    FillPropertyDescriptor(aDesc, aProxy, 0, v);
    return true;
  }

  nsWrapperCache* cache;
  nsISupports* result = document->ResolveName(str, &cache);
  if (!result) {
    return true;
  }

  JS::Rooted<JS::Value> v(aCx);
  if (!WrapObject(aCx, result, cache, nullptr, &v)) {
    return false;
  }
  FillPropertyDescriptor(aDesc, aProxy, 0, v);
  return true;
}

bool
WindowNamedPropertiesHandler::defineProperty(JSContext* aCx,
                                             JS::Handle<JSObject*> aProxy,
                                             JS::Handle<jsid> aId,
                                             JS::Handle<JS::PropertyDescriptor> aDesc,
                                             JS::ObjectOpResult &result) const
{
  ErrorResult rv;
  rv.ThrowTypeError<MSG_DEFINEPROPERTY_ON_GSP>();
  rv.MaybeSetPendingException(aCx);
  return false;
}

bool
WindowNamedPropertiesHandler::ownPropNames(JSContext* aCx,
                                           JS::Handle<JSObject*> aProxy,
                                           unsigned flags,
                                           JS::AutoIdVector& aProps) const
{
  if (!(flags & JSITER_HIDDEN)) {
    // None of our named properties are enumerable.
    return true;
  }

  // Grab the DOM window.
  nsGlobalWindow* win = xpc::WindowOrNull(JS_GetGlobalForObject(aCx, aProxy));
  nsTArray<nsString> names;
  // The names live on the outer window, which might be null
  nsGlobalWindow* outer = win->GetOuterWindowInternal();
  if (outer) {
    nsDOMWindowList* childWindows = outer->GetWindowList();
    if (childWindows) {
      uint32_t length = childWindows->GetLength();
      for (uint32_t i = 0; i < length; ++i) {
        nsCOMPtr<nsIDocShellTreeItem> item =
          childWindows->GetDocShellTreeItemAt(i);
        // This is a bit silly, since we could presumably just do
        // item->GetWindow().  But it's not obvious whether this does the same
        // thing as GetChildWindow() with the item's name (due to the complexity
        // of FindChildWithName).  Since GetChildWindow is what we use in
        // getOwnPropDescriptor, let's try to be consistent.
        nsString name;
        item->GetName(name);
        if (!names.Contains(name)) {
          // Make sure we really would expose it from getOwnPropDescriptor.
          nsCOMPtr<nsPIDOMWindowOuter> childWin = win->GetChildWindow(name);
          if (childWin && ShouldExposeChildWindow(name, childWin)) {
            names.AppendElement(name);
          }
        }
      }
    }
  }
  if (!AppendNamedPropertyIds(aCx, aProxy, names, false, aProps)) {
    return false;
  }

  names.Clear();
  nsCOMPtr<nsIHTMLDocument> htmlDoc = do_QueryInterface(win->GetExtantDoc());
  if (!htmlDoc) {
    return true;
  }
  nsHTMLDocument* document = static_cast<nsHTMLDocument*>(htmlDoc.get());
  document->GetSupportedNames(flags, names);

  JS::AutoIdVector docProps(aCx);
  if (!AppendNamedPropertyIds(aCx, aProxy, names, false, docProps)) {
    return false;
  }

  return js::AppendUnique(aCx, aProps, docProps);
}

bool
WindowNamedPropertiesHandler::delete_(JSContext* aCx,
                                      JS::Handle<JSObject*> aProxy,
                                      JS::Handle<jsid> aId,
                                      JS::ObjectOpResult &aResult) const
{
  return aResult.failCantDeleteWindowNamedProperty();
}

static bool
ResolveWindowNamedProperty(JSContext* aCx, JS::Handle<JSObject*> aWrapper,
                           JS::Handle<JSObject*> aObj, JS::Handle<jsid> aId,
                           JS::MutableHandle<JS::PropertyDescriptor> aDesc)
{
  {
    JSAutoCompartment ac(aCx, aObj);
    if (!js::GetProxyHandler(aObj)->getOwnPropertyDescriptor(aCx, aObj, aId,
                                                             aDesc)) {
      return false;
    }
  }

  if (aDesc.object()) {
    aDesc.object().set(aWrapper);

    return JS_WrapPropertyDescriptor(aCx, aDesc);
  }

  return true;
}

static bool
EnumerateWindowNamedProperties(JSContext* aCx, JS::Handle<JSObject*> aWrapper,
                               JS::Handle<JSObject*> aObj,
                               JS::AutoIdVector& aProps)
{
  JSAutoCompartment ac(aCx, aObj);
  return js::GetProxyHandler(aObj)->ownPropertyKeys(aCx, aObj, aProps);
}

const NativePropertyHooks sWindowNamedPropertiesNativePropertyHooks[] = { {
  ResolveWindowNamedProperty,
  EnumerateWindowNamedProperties,
  { nullptr, nullptr },
  prototypes::id::_ID_Count,
  constructors::id::_ID_Count,
  nullptr
} };

static const DOMIfaceAndProtoJSClass WindowNamedPropertiesClass = {
  PROXY_CLASS_DEF("WindowProperties",
                  JSCLASS_IS_DOMIFACEANDPROTOJSCLASS),
  eNamedPropertiesObject,
  prototypes::id::_ID_Count,
  0,
  sWindowNamedPropertiesNativePropertyHooks,
  "[object WindowProperties]",
  EventTargetBinding::GetProtoObject
};

// static
JSObject*
WindowNamedPropertiesHandler::Create(JSContext* aCx,
                                     JS::Handle<JSObject*> aProto)
{
  // Note: since the scope polluter proxy lives on the window's prototype
  // chain, it needs a singleton type to avoid polluting type information
  // for properties on the window.
  js::ProxyOptions options;
  options.setSingleton(true);
  options.setClass(&WindowNamedPropertiesClass.mBase);

  JS::Rooted<JSObject*> gsp(aCx);
  gsp = js::NewProxyObject(aCx, WindowNamedPropertiesHandler::getInstance(),
                           JS::NullHandleValue, aProto,
                           options);
  if (!gsp) {
    return nullptr;
  }

  bool succeeded;
  if (!JS_SetImmutablePrototype(aCx, gsp, &succeeded)) {
    return nullptr;
  }
  MOZ_ASSERT(succeeded,
             "errors making the [[Prototype]] of the named properties object "
             "immutable should have been JSAPI failures, not !succeeded");

  return gsp;
}

} // namespace dom
} // namespace mozilla