dom/base/WindowNamedPropertiesHandler.cpp

   1 /* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
   2 /* vim: set ts=8 sts=2 et sw=2 tw=80: */
   3 /* This Source Code Form is subject to the terms of the Mozilla Public
   4  * License, v. 2.0. If a copy of the MPL was not distributed with this
   5  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
   6
   7 #include "WindowNamedPropertiesHandler.h"
   8 #include "mozilla/dom/EventTargetBinding.h"
   9 #include "mozilla/dom/WindowBinding.h"
  10 #include "mozilla/dom/WindowProxyHolder.h"
  11 #include "nsContentUtils.h"
  12 #include "nsGlobalWindow.h"
  13 #include "nsHTMLDocument.h"
  14 #include "nsJSUtils.h"
  15 #include "xpcprivate.h"
  16
  17 namespace mozilla::dom {
  18
  19 static bool ShouldExposeChildWindow(const nsString& aNameBeingResolved,
  20                                     BrowsingContext* aChild) {
  21   Element* e = aChild->GetEmbedderElement();
  22   if (e && e->IsInShadowTree()) {
  23     return false;
  24   }
  25
  26   // If we're same-origin with the child, go ahead and expose it.
  27   nsPIDOMWindowOuter* child = aChild->GetDOMWindow();
  28   nsCOMPtr<nsIScriptObjectPrincipal> sop = do_QueryInterface(child);
  29   if (sop && nsContentUtils::SubjectPrincipal()->Equals(sop->GetPrincipal())) {
  30     return true;
  31   }
  32
  33   // If we're not same-origin, expose it _only_ if the name of the browsing
  34   // context matches the 'name' attribute of the frame element in the parent.
  35   // The motivations behind this heuristic are worth explaining here.
  36   //
  37   // Historically, all UAs supported global named access to any child browsing
  38   // context (that is to say, window.dolske returns a child frame where either
  39   // the "name" attribute on the frame element was set to "dolske", or where
  40   // the child explicitly set window.name = "dolske").
  41   //
  42   // This is problematic because it allows possibly-malicious and unrelated
  43   // cross-origin subframes to pollute the global namespace of their parent in
  44   // unpredictable ways (see bug 860494). This is also problematic for browser
  45   // engines like Servo that want to run cross-origin script on different
  46   // threads.
  47   //
  48   // The naive solution here would be to filter out any cross-origin subframes
  49   // obtained when doing named lookup in global scope. But that is unlikely to
  50   // be web-compatible, since it will break named access for consumers that do
  51   // <iframe name="dolske" src="http://cross-origin.com/sadtrombone.html"> and
  52   // expect to be able to access the cross-origin subframe via named lookup on
  53   // the global.
  54   //
  55   // The optimal behavior would be to do the following:
  56   // (a) Look for any child browsing context with name="dolske".
  57   // (b) If the result is cross-origin, null it out.
  58   // (c) If we have null, look for a frame element whose 'name' attribute is
  59   //     "dolske".
  60   //
  61   // Unfortunately, (c) would require some engineering effort to be performant
  62   // in Gecko, and probably in other UAs as well. So we go with a simpler
  63   // approximation of the above. This approximation will only break sites that
  64   // rely on their cross-origin subframes setting window.name to a known value,
  65   // which is unlikely to be very common. And while it does introduce a
  66   // dependency on cross-origin state when doing global lookups, it doesn't
  67   // allow the child to arbitrarily pollute the parent namespace, and requires
  68   // cross-origin communication only in a limited set of cases that can be
  69   // computed independently by the parent.
  70   return e && e->AttrValueIs(kNameSpaceID_None, nsGkAtoms::name,
  71                              aNameBeingResolved, eCaseMatters);
  72 }
  73
  74 bool WindowNamedPropertiesHandler::getOwnPropDescriptor(
  75     JSContext* aCx, JS::Handle<JSObject*> aProxy, JS::Handle<jsid> aId,
  76     bool /* unused */,
  77     JS::MutableHandle<Maybe<JS::PropertyDescriptor>> aDesc) const {
  78   aDesc.reset();
  79
  80   if (aId.isSymbol()) {
  81     if (aId.isWellKnownSymbol(JS::SymbolCode::toStringTag)) {
  82       JS::Rooted<JSString*> toStringTagStr(
  83           aCx, JS_NewStringCopyZ(aCx, "WindowProperties"));
  84       if (!toStringTagStr) {
  85         return false;
  86       }
  87
  88       aDesc.set(Some(
  89           JS::PropertyDescriptor::Data(JS::StringValue(toStringTagStr),
  90                                        {JS::PropertyAttribute::Configurable})));
  91       return true;
  92     }
  93
  94     // Nothing to do if we're resolving another symbol property.
  95     return true;
  96   }
  97
  98   bool hasOnPrototype;
  99   if (!HasPropertyOnPrototype(aCx, aProxy, aId, &hasOnPrototype)) {
 100     return false;
 101   }
 102   if (hasOnPrototype) {
 103     return true;
 104   }
 105
 106   nsAutoJSString str;
 107   if (!str.init(aCx, aId)) {
 108     return false;
 109   }
 110
 111   if (str.IsEmpty()) {
 112     return true;
 113   }
 114
 115   // Grab the DOM window.
 116   nsGlobalWindowInner* win = xpc::WindowGlobalOrNull(aProxy);
 117   if (win->Length() > 0) {
 118     RefPtr<BrowsingContext> child = win->GetChildWindow(str);
 119     if (child && ShouldExposeChildWindow(str, child)) {
 120       // We found a subframe of the right name. Shadowing via |var foo| in
 121       // global scope is still allowed, since |var| only looks up |own|
 122       // properties. But unqualified shadowing will fail, per-spec.
 123       JS::Rooted<JS::Value> v(aCx);
 124       if (!ToJSValue(aCx, WindowProxyHolder(std::move(child)), &v)) {
 125         return false;
 126       }
 127       aDesc.set(mozilla::Some(
 128           JS::PropertyDescriptor::Data(v, {JS::PropertyAttribute::Configurable,
 129                                            JS::PropertyAttribute::Writable})));
 130       return true;
 131     }
 132   }
 133
 134   // The rest of this function is for HTML documents only.
 135   Document* doc = win->GetExtantDoc();
 136   if (!doc || !doc->IsHTMLOrXHTML()) {
 137     return true;
 138   }
 139   nsHTMLDocument* document = doc->AsHTMLDocument();
 140
 141   JS::Rooted<JS::Value> v(aCx);
 142   Element* element = document->GetElementById(str);
 143   if (element) {
 144     if (!ToJSValue(aCx, element, &v)) {
 145       return false;
 146     }
 147     aDesc.set(mozilla::Some(
 148         JS::PropertyDescriptor::Data(v, {JS::PropertyAttribute::Configurable,
 149                                          JS::PropertyAttribute::Writable})));
 150     return true;
 151   }
 152
 153   ErrorResult rv;
 154   bool found = document->ResolveName(aCx, str, &v, rv);
 155   if (rv.MaybeSetPendingException(aCx)) {
 156     return false;
 157   }
 158
 159   if (found) {
 160     aDesc.set(mozilla::Some(
 161         JS::PropertyDescriptor::Data(v, {JS::PropertyAttribute::Configurable,
 162                                          JS::PropertyAttribute::Writable})));
 163   }
 164   return true;
 165 }
 166
 167 bool WindowNamedPropertiesHandler::defineProperty(
 168     JSContext* aCx, JS::Handle<JSObject*> aProxy, JS::Handle<jsid> aId,
 169     JS::Handle<JS::PropertyDescriptor> aDesc,
 170     JS::ObjectOpResult& result) const {
 171   return result.failCantDefineWindowNamedProperty();
 172 }
 173
 174 bool WindowNamedPropertiesHandler::ownPropNames(
 175     JSContext* aCx, JS::Handle<JSObject*> aProxy, unsigned flags,
 176     JS::MutableHandleVector<jsid> aProps) const {
 177   if (!(flags & JSITER_HIDDEN)) {
 178     // None of our named properties are enumerable.
 179     return true;
 180   }
 181
 182   // Grab the DOM window.
 183   nsGlobalWindowInner* win = xpc::WindowGlobalOrNull(aProxy);
 184   nsTArray<nsString> names;
 185   // The names live on the outer window, which might be null
 186   nsGlobalWindowOuter* outer = win->GetOuterWindowInternal();
 187   if (outer) {
 188     if (BrowsingContext* bc = outer->GetBrowsingContext()) {
 189       for (const auto& child : bc->Children()) {
 190         const nsString& name = child->Name();
 191         if (!name.IsEmpty() && !names.Contains(name)) {
 192           // Make sure we really would expose it from getOwnPropDescriptor.
 193           if (ShouldExposeChildWindow(name, child)) {
 194             names.AppendElement(name);
 195           }
 196         }
 197       }
 198     }
 199   }
 200   if (!AppendNamedPropertyIds(aCx, aProxy, names, false, aProps)) {
 201     return false;
 202   }
 203
 204   names.Clear();
 205   Document* doc = win->GetExtantDoc();
 206   if (!doc || !doc->IsHTMLOrXHTML()) {
 207     // Define to @@toStringTag on this object to keep Object.prototype.toString
 208     // backwards compatible.
 209     JS::Rooted<jsid> toStringTagId(aCx, SYMBOL_TO_JSID(JS::GetWellKnownSymbol(
 210                                             aCx, JS::SymbolCode::toStringTag)));
 211     return aProps.append(toStringTagId);
 212   }
 213
 214   nsHTMLDocument* document = doc->AsHTMLDocument();
 215   // Document names are enumerable, so we want to get them no matter what flags
 216   // is.
 217   document->GetSupportedNames(names);
 218
 219   JS::RootedVector<jsid> docProps(aCx);
 220   if (!AppendNamedPropertyIds(aCx, aProxy, names, false, &docProps)) {
 221     return false;
 222   }
 223
 224   JS::Rooted<jsid> toStringTagId(aCx, SYMBOL_TO_JSID(JS::GetWellKnownSymbol(
 225                                           aCx, JS::SymbolCode::toStringTag)));
 226   if (!docProps.append(toStringTagId)) {
 227     return false;
 228   }
 229
 230   return js::AppendUnique(aCx, aProps, docProps);
 231 }
 232
 233 bool WindowNamedPropertiesHandler::delete_(JSContext* aCx,
 234                                            JS::Handle<JSObject*> aProxy,
 235                                            JS::Handle<jsid> aId,
 236                                            JS::ObjectOpResult& aResult) const {
 237   return aResult.failCantDeleteWindowNamedProperty();
 238 }
 239
 240 // Note that this class doesn't need any reserved slots, but SpiderMonkey
 241 // asserts all proxy classes have at least one reserved slot.
 242 static const DOMIfaceAndProtoJSClass WindowNamedPropertiesClass = {
 243     PROXY_CLASS_DEF("WindowProperties", JSCLASS_IS_DOMIFACEANDPROTOJSCLASS |
 244                                             JSCLASS_HAS_RESERVED_SLOTS(1)),
 245     eNamedPropertiesObject,
 246     false,
 247     prototypes::id::_ID_Count,
 248     0,
 249     &sEmptyNativePropertyHooks,
 250     "[object WindowProperties]",
 251     EventTarget_Binding::GetProtoObject};
 252
 253 // static
 254 JSObject* WindowNamedPropertiesHandler::Create(JSContext* aCx,
 255                                                JS::Handle<JSObject*> aProto) {
 256   js::ProxyOptions options;
 257   options.setClass(&WindowNamedPropertiesClass.mBase);
 258
 259   JS::Rooted<JSObject*> gsp(
 260       aCx, js::NewProxyObject(aCx, WindowNamedPropertiesHandler::getInstance(),
 261                               JS::NullHandleValue, aProto, options));
 262   if (!gsp) {
 263     return nullptr;
 264   }
 265
 266   bool succeeded;
 267   if (!JS_SetImmutablePrototype(aCx, gsp, &succeeded)) {
 268     return nullptr;
 269   }
 270   MOZ_ASSERT(succeeded,
 271              "errors making the [[Prototype]] of the named properties object "
 272              "immutable should have been JSAPI failures, not !succeeded");
 273
 274   return gsp;
 275 }
 276
 277 }  // namespace mozilla::dom