1 files changed, 331 insertions, 0 deletions
diff --git a/dom/bindings/DOMJSProxyHandler.cpp b/dom/bindings/DOMJSProxyHandler.cpp
new file mode 100644
index 0000000000..a0f93afcb9
--- /dev/null
+++ b/dom/bindings/DOMJSProxyHandler.cpp
@@ -0,0 +1,331 @@
+/* -*- 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 "mozilla/dom/DOMJSProxyHandler.h"
+#include "xpcpublic.h"
+#include "xpcprivate.h"
+#include "XPCWrapper.h"
+#include "WrapperFactory.h"
+#include "nsWrapperCacheInlines.h"
+#include "mozilla/dom/BindingUtils.h"
+
+#include "jsapi.h"
+#include "js/friend/DOMProxy.h"  // JS::DOMProxyShadowsResult, JS::ExpandoAndGeneration, JS::SetDOMProxyInformation
+#include "js/PropertyAndElement.h"  // JS_AlreadyHasOwnPropertyById, JS_DefineProperty, JS_DefinePropertyById, JS_DeleteProperty, JS_DeletePropertyById
+#include "js/Object.h"              // JS::GetCompartment
+
+using namespace JS;
+
+namespace mozilla::dom {
+
+jsid s_length_id = JS::PropertyKey::Void();
+
+bool DefineStaticJSVals(JSContext* cx) {
+  return AtomizeAndPinJSString(cx, s_length_id, "length");
+}
+
+const char DOMProxyHandler::family = 0;
+
+JS::DOMProxyShadowsResult DOMProxyShadows(JSContext* cx,
+                                          JS::Handle<JSObject*> proxy,
+                                          JS::Handle<jsid> id) {
+  using DOMProxyShadowsResult = JS::DOMProxyShadowsResult;
+
+  JS::Rooted<JSObject*> expando(cx, DOMProxyHandler::GetExpandoObject(proxy));
+  JS::Value v = js::GetProxyPrivate(proxy);
+  bool isOverrideBuiltins = !v.isObject() && !v.isUndefined();
+  if (expando) {
+    bool hasOwn;
+    if (!JS_AlreadyHasOwnPropertyById(cx, expando, id, &hasOwn))
+      return DOMProxyShadowsResult::ShadowCheckFailed;
+
+    if (hasOwn) {
+      return isOverrideBuiltins
+                 ? DOMProxyShadowsResult::ShadowsViaIndirectExpando
+                 : DOMProxyShadowsResult::ShadowsViaDirectExpando;
+    }
+  }
+
+  if (!isOverrideBuiltins) {
+    // Our expando, if any, didn't shadow, so we're not shadowing at all.
+    return DOMProxyShadowsResult::DoesntShadow;
+  }
+
+  bool hasOwn;
+  if (!GetProxyHandler(proxy)->hasOwn(cx, proxy, id, &hasOwn))
+    return DOMProxyShadowsResult::ShadowCheckFailed;
+
+  return hasOwn ? DOMProxyShadowsResult::Shadows
+                : DOMProxyShadowsResult::DoesntShadowUnique;
+}
+
+// Store the information for the specialized ICs.
+struct SetDOMProxyInformation {
+  SetDOMProxyInformation() {
+    JS::SetDOMProxyInformation((const void*)&DOMProxyHandler::family,
+                               DOMProxyShadows,
+                               &RemoteObjectProxyBase::sCrossOriginProxyFamily);
+  }
+};
+
+SetDOMProxyInformation gSetDOMProxyInformation;
+
+static inline void CheckExpandoObject(JSObject* proxy,
+                                      const JS::Value& expando) {
+#ifdef DEBUG
+  JSObject* obj = &expando.toObject();
+  MOZ_ASSERT(!js::gc::EdgeNeedsSweepUnbarriered(&obj));
+  MOZ_ASSERT(JS::GetCompartment(proxy) == JS::GetCompartment(obj));
+
+  // When we create an expando object in EnsureExpandoObject below, we preserve
+  // the wrapper. The wrapper is released when the object is unlinked, but we
+  // should never call these functions after that point.
+  nsISupports* native = UnwrapDOMObject<nsISupports>(proxy);
+  nsWrapperCache* cache;
+  // QueryInterface to nsWrapperCache will not GC.
+  JS::AutoSuppressGCAnalysis suppress;
+  CallQueryInterface(native, &cache);
+  MOZ_ASSERT(cache->PreservingWrapper());
+#endif
+}
+
+static inline void CheckExpandoAndGeneration(
+    JSObject* proxy, JS::ExpandoAndGeneration* expandoAndGeneration) {
+#ifdef DEBUG
+  JS::Value value = expandoAndGeneration->expando;
+  if (!value.isUndefined()) CheckExpandoObject(proxy, value);
+#endif
+}
+
+static inline void CheckDOMProxy(JSObject* proxy) {
+#ifdef DEBUG
+  MOZ_ASSERT(IsDOMProxy(proxy), "expected a DOM proxy object");
+  MOZ_ASSERT(!js::gc::EdgeNeedsSweepUnbarriered(&proxy));
+  nsISupports* native = UnwrapDOMObject<nsISupports>(proxy);
+  nsWrapperCache* cache;
+  // QI to nsWrapperCache cannot GC for very non-obvious reasons; see
+  // https://searchfox.org/mozilla-central/rev/55da592d85c2baf8d8818010c41d9738c97013d2/js/xpconnect/src/XPCWrappedJSClass.cpp#521,545-548
+  JS::AutoSuppressGCAnalysis nogc;
+  CallQueryInterface(native, &cache);
+  MOZ_ASSERT(cache->GetWrapperPreserveColor() == proxy);
+#endif
+}
+
+// static
+JSObject* DOMProxyHandler::GetAndClearExpandoObject(JSObject* obj) {
+  CheckDOMProxy(obj);
+
+  JS::Value v = js::GetProxyPrivate(obj);
+  if (v.isUndefined()) {
+    return nullptr;
+  }
+
+  if (v.isObject()) {
+    js::SetProxyPrivate(obj, UndefinedValue());
+  } else {
+    auto* expandoAndGeneration =
+        static_cast<JS::ExpandoAndGeneration*>(v.toPrivate());
+    v = expandoAndGeneration->expando;
+    if (v.isUndefined()) {
+      return nullptr;
+    }
+    expandoAndGeneration->expando = UndefinedValue();
+  }
+
+  CheckExpandoObject(obj, v);
+
+  return &v.toObject();
+}
+
+// static
+JSObject* DOMProxyHandler::EnsureExpandoObject(JSContext* cx,
+                                               JS::Handle<JSObject*> obj) {
+  CheckDOMProxy(obj);
+
+  JS::Value v = js::GetProxyPrivate(obj);
+  if (v.isObject()) {
+    CheckExpandoObject(obj, v);
+    return &v.toObject();
+  }
+
+  JS::ExpandoAndGeneration* expandoAndGeneration = nullptr;
+  if (!v.isUndefined()) {
+    expandoAndGeneration =
+        static_cast<JS::ExpandoAndGeneration*>(v.toPrivate());
+    CheckExpandoAndGeneration(obj, expandoAndGeneration);
+    if (expandoAndGeneration->expando.isObject()) {
+      return &expandoAndGeneration->expando.toObject();
+    }
+  }
+
+  JS::Rooted<JSObject*> expando(
+      cx, JS_NewObjectWithGivenProto(cx, nullptr, nullptr));
+  if (!expando) {
+    return nullptr;
+  }
+
+  nsISupports* native = UnwrapDOMObject<nsISupports>(obj);
+  nsWrapperCache* cache;
+  CallQueryInterface(native, &cache);
+  cache->PreserveWrapper(native);
+
+  if (expandoAndGeneration) {
+    expandoAndGeneration->expando.setObject(*expando);
+    return expando;
+  }
+
+  js::SetProxyPrivate(obj, ObjectValue(*expando));
+
+  return expando;
+}
+
+bool DOMProxyHandler::preventExtensions(JSContext* cx,
+                                        JS::Handle<JSObject*> proxy,
+                                        JS::ObjectOpResult& result) const {
+  // always extensible per WebIDL
+  return result.failCantPreventExtensions();
+}
+
+bool DOMProxyHandler::isExtensible(JSContext* cx, JS::Handle<JSObject*> proxy,
+                                   bool* extensible) const {
+  *extensible = true;
+  return true;
+}
+
+bool BaseDOMProxyHandler::getOwnPropertyDescriptor(
+    JSContext* cx, Handle<JSObject*> proxy, Handle<jsid> id,
+    MutableHandle<Maybe<PropertyDescriptor>> desc) const {
+  return getOwnPropDescriptor(cx, proxy, id, /* ignoreNamedProps = */ false,
+                              desc);
+}
+
+bool DOMProxyHandler::defineProperty(JSContext* cx, JS::Handle<JSObject*> proxy,
+                                     JS::Handle<jsid> id,
+                                     Handle<PropertyDescriptor> desc,
+                                     JS::ObjectOpResult& result,
+                                     bool* done) const {
+  if (xpc::WrapperFactory::IsXrayWrapper(proxy)) {
+    return result.succeed();
+  }
+
+  JS::Rooted<JSObject*> expando(cx, EnsureExpandoObject(cx, proxy));
+  if (!expando) {
+    return false;
+  }
+
+  if (!JS_DefinePropertyById(cx, expando, id, desc, result)) {
+    return false;
+  }
+  *done = true;
+  return true;
+}
+
+bool DOMProxyHandler::set(JSContext* cx, Handle<JSObject*> proxy,
+                          Handle<jsid> id, Handle<JS::Value> v,
+                          Handle<JS::Value> receiver,
+                          ObjectOpResult& result) const {
+  MOZ_ASSERT(!xpc::WrapperFactory::IsXrayWrapper(proxy),
+             "Should not have a XrayWrapper here");
+  bool done;
+  if (!setCustom(cx, proxy, id, v, &done)) {
+    return false;
+  }
+  if (done) {
+    return result.succeed();
+  }
+
+  // Make sure to ignore our named properties when checking for own
+  // property descriptors for a set.
+  Rooted<Maybe<PropertyDescriptor>> ownDesc(cx);
+  if (!getOwnPropDescriptor(cx, proxy, id, /* ignoreNamedProps = */ true,
+                            &ownDesc)) {
+    return false;
+  }
+
+  return js::SetPropertyIgnoringNamedGetter(cx, proxy, id, v, receiver, ownDesc,
+                                            result);
+}
+
+bool DOMProxyHandler::delete_(JSContext* cx, JS::Handle<JSObject*> proxy,
+                              JS::Handle<jsid> id,
+                              JS::ObjectOpResult& result) const {
+  JS::Rooted<JSObject*> expando(cx);
+  if (!xpc::WrapperFactory::IsXrayWrapper(proxy) &&
+      (expando = GetExpandoObject(proxy))) {
+    return JS_DeletePropertyById(cx, expando, id, result);
+  }
+
+  return result.succeed();
+}
+
+bool BaseDOMProxyHandler::ownPropertyKeys(
+    JSContext* cx, JS::Handle<JSObject*> proxy,
+    JS::MutableHandleVector<jsid> props) const {
+  return ownPropNames(cx, proxy,
+                      JSITER_OWNONLY | JSITER_HIDDEN | JSITER_SYMBOLS, props);
+}
+
+bool BaseDOMProxyHandler::getPrototypeIfOrdinary(
+    JSContext* cx, JS::Handle<JSObject*> proxy, bool* isOrdinary,
+    JS::MutableHandle<JSObject*> proto) const {
+  *isOrdinary = true;
+  proto.set(GetStaticPrototype(proxy));
+  return true;
+}
+
+bool BaseDOMProxyHandler::getOwnEnumerablePropertyKeys(
+    JSContext* cx, JS::Handle<JSObject*> proxy,
+    JS::MutableHandleVector<jsid> props) const {
+  return ownPropNames(cx, proxy, JSITER_OWNONLY, props);
+}
+
+bool DOMProxyHandler::setCustom(JSContext* cx, JS::Handle<JSObject*> proxy,
+                                JS::Handle<jsid> id, JS::Handle<JS::Value> v,
+                                bool* done) const {
+  *done = false;
+  return true;
+}
+
+// static
+JSObject* DOMProxyHandler::GetExpandoObject(JSObject* obj) {
+  CheckDOMProxy(obj);
+
+  JS::Value v = js::GetProxyPrivate(obj);
+  if (v.isObject()) {
+    CheckExpandoObject(obj, v);
+    return &v.toObject();
+  }
+
+  if (v.isUndefined()) {
+    return nullptr;
+  }
+
+  auto* expandoAndGeneration =
+      static_cast<JS::ExpandoAndGeneration*>(v.toPrivate());
+  CheckExpandoAndGeneration(obj, expandoAndGeneration);
+
+  v = expandoAndGeneration->expando;
+  return v.isUndefined() ? nullptr : &v.toObject();
+}
+
+void ShadowingDOMProxyHandler::trace(JSTracer* trc, JSObject* proxy) const {
+  DOMProxyHandler::trace(trc, proxy);
+
+  MOZ_ASSERT(IsDOMProxy(proxy), "expected a DOM proxy object");
+  JS::Value v = js::GetProxyPrivate(proxy);
+  MOZ_ASSERT(!v.isObject(), "Should not have expando object directly!");
+
+  // The proxy's private slot is set when we allocate the proxy,
+  // so it cannot be |undefined|.
+  MOZ_ASSERT(!v.isUndefined());
+
+  auto* expandoAndGeneration =
+      static_cast<JS::ExpandoAndGeneration*>(v.toPrivate());
+  JS::TraceEdge(trc, &expandoAndGeneration->expando,
+                "Shadowing DOM proxy expando");
+}
+
+}  // namespace mozilla::dom