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-rw-r--r--dom/base/MaybeCrossOriginObject.cpp483
1 files changed, 483 insertions, 0 deletions
diff --git a/dom/base/MaybeCrossOriginObject.cpp b/dom/base/MaybeCrossOriginObject.cpp
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+/* -*- 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/MaybeCrossOriginObject.h"
+
+#include "mozilla/BasePrincipal.h"
+#include "mozilla/dom/BindingUtils.h"
+#include "mozilla/dom/DOMJSProxyHandler.h"
+#include "mozilla/dom/RemoteObjectProxy.h"
+#include "js/CallAndConstruct.h" // JS::Call
+#include "js/friend/WindowProxy.h" // js::IsWindowProxy
+#include "js/Object.h" // JS::GetClass
+#include "js/PropertyAndElement.h" // JS_DefineFunctions, JS_DefineProperties
+#include "js/PropertyDescriptor.h" // JS::PropertyDescriptor, JS_GetOwnPropertyDescriptorById
+#include "js/Proxy.h"
+#include "js/RootingAPI.h"
+#include "js/WeakMap.h"
+#include "js/Wrapper.h"
+#include "jsfriendapi.h"
+#include "AccessCheck.h"
+#include "nsContentUtils.h"
+
+#ifdef DEBUG
+static bool IsLocation(JSObject* obj) {
+ return strcmp(JS::GetClass(obj)->name, "Location") == 0;
+}
+#endif // DEBUG
+
+namespace mozilla::dom {
+
+/* static */
+bool MaybeCrossOriginObjectMixins::IsPlatformObjectSameOrigin(JSContext* cx,
+ JSObject* obj) {
+ MOZ_ASSERT(!js::IsCrossCompartmentWrapper(obj));
+ // WindowProxy and Window must always be same-Realm, so we can do
+ // our IsPlatformObjectSameOrigin check against either one. But verify that
+ // in case we have a WindowProxy the right things happen.
+ MOZ_ASSERT(js::GetNonCCWObjectRealm(obj) ==
+ // "true" for second arg means to unwrap WindowProxy to
+ // get at the Window.
+ js::GetNonCCWObjectRealm(js::UncheckedUnwrap(obj, true)),
+ "WindowProxy not same-Realm as Window?");
+
+ BasePrincipal* subjectPrincipal =
+ BasePrincipal::Cast(nsContentUtils::SubjectPrincipal(cx));
+ BasePrincipal* objectPrincipal =
+ BasePrincipal::Cast(nsContentUtils::ObjectPrincipal(obj));
+
+ // The spec effectively has an EqualsConsideringDomain check here,
+ // because the spec has no concept of asymmetric security
+ // relationships. But we shouldn't ever end up here in the
+ // asymmetric case anyway: That case should end up with Xrays, which
+ // don't call into this code.
+ //
+ // Let's assert that EqualsConsideringDomain and
+ // SubsumesConsideringDomain give the same results and use
+ // EqualsConsideringDomain for the check we actually do, since it's
+ // stricter and more closely matches the spec.
+ //
+ // That said, if the (not very well named)
+ // OriginAttributes::IsRestrictOpenerAccessForFPI() method returns
+ // false, we want to use FastSubsumesConsideringDomainIgnoringFPD
+ // instead of FastEqualsConsideringDomain, because in that case we
+ // still want to treat things which are in different first-party
+ // contexts as same-origin.
+ MOZ_ASSERT(
+ subjectPrincipal->FastEqualsConsideringDomain(objectPrincipal) ==
+ subjectPrincipal->FastSubsumesConsideringDomain(objectPrincipal),
+ "Why are we in an asymmetric case here?");
+ if (OriginAttributes::IsRestrictOpenerAccessForFPI()) {
+ return subjectPrincipal->FastEqualsConsideringDomain(objectPrincipal);
+ }
+
+ return subjectPrincipal->FastSubsumesConsideringDomainIgnoringFPD(
+ objectPrincipal) &&
+ objectPrincipal->FastSubsumesConsideringDomainIgnoringFPD(
+ subjectPrincipal);
+}
+
+bool MaybeCrossOriginObjectMixins::CrossOriginGetOwnPropertyHelper(
+ JSContext* cx, JS::Handle<JSObject*> obj, JS::Handle<jsid> id,
+ JS::MutableHandle<Maybe<JS::PropertyDescriptor>> desc) const {
+ MOZ_ASSERT(!IsPlatformObjectSameOrigin(cx, obj) || IsRemoteObjectProxy(obj),
+ "Why did we get called?");
+ // First check for an IDL-defined cross-origin property with the given name.
+ // This corresponds to
+ // https://html.spec.whatwg.org/multipage/browsers.html#crossorigingetownpropertyhelper-(-o,-p-)
+ // step 2.
+ JS::Rooted<JSObject*> holder(cx);
+ if (!EnsureHolder(cx, obj, &holder)) {
+ return false;
+ }
+
+ return JS_GetOwnPropertyDescriptorById(cx, holder, id, desc);
+}
+
+/* static */
+bool MaybeCrossOriginObjectMixins::CrossOriginPropertyFallback(
+ JSContext* cx, JS::Handle<JSObject*> obj, JS::Handle<jsid> id,
+ JS::MutableHandle<Maybe<JS::PropertyDescriptor>> desc) {
+ MOZ_ASSERT(desc.isNothing(), "Why are we being called?");
+
+ // Step 1.
+ if (xpc::IsCrossOriginWhitelistedProp(cx, id)) {
+ // Spec says to return PropertyDescriptor {
+ // [[Value]]: undefined, [[Writable]]: false, [[Enumerable]]: false,
+ // [[Configurable]]: true
+ // }.
+ desc.set(Some(JS::PropertyDescriptor::Data(
+ JS::UndefinedValue(), {JS::PropertyAttribute::Configurable})));
+ return true;
+ }
+
+ // Step 2.
+ return ReportCrossOriginDenial(cx, id, "access"_ns);
+}
+
+/* static */
+bool MaybeCrossOriginObjectMixins::CrossOriginGet(
+ JSContext* cx, JS::Handle<JSObject*> obj, JS::Handle<JS::Value> receiver,
+ JS::Handle<jsid> id, JS::MutableHandle<JS::Value> vp) {
+ // This is fairly similar to BaseProxyHandler::get, but there are some
+ // differences. Most importantly, we want to throw if we have a descriptor
+ // with no getter, while BaseProxyHandler::get returns undefined. The other
+ // big difference is that we don't have to worry about prototypes (ours is
+ // always null).
+
+ // We want to invoke [[GetOwnProperty]] on "obj", but _without_ entering its
+ // compartment, because for the proxies we have here [[GetOwnProperty]] will
+ // do security checks based on the current Realm. Unfortunately,
+ // JS_GetPropertyDescriptorById asserts that compartments match. Luckily, we
+ // know that "obj" is a proxy here, so we can directly call its
+ // getOwnPropertyDescriptor() hook.
+ //
+ // It looks like Proxy::getOwnPropertyDescriptor is not public, so just grab
+ // the handler and call its getOwnPropertyDescriptor hook directly.
+ MOZ_ASSERT(js::IsProxy(obj), "How did we get a bogus object here?");
+ MOZ_ASSERT(
+ js::IsWindowProxy(obj) || IsLocation(obj) || IsRemoteObjectProxy(obj),
+ "Unexpected proxy");
+ MOZ_ASSERT(!IsPlatformObjectSameOrigin(cx, obj) || IsRemoteObjectProxy(obj),
+ "Why did we get called?");
+ js::AssertSameCompartment(cx, receiver);
+
+ // Step 1.
+ JS::Rooted<Maybe<JS::PropertyDescriptor>> desc(cx);
+ if (!js::GetProxyHandler(obj)->getOwnPropertyDescriptor(cx, obj, id, &desc)) {
+ return false;
+ }
+
+ // Step 2.
+ MOZ_ASSERT(desc.isSome(),
+ "Callees should throw in all cases when they are not finding a "
+ "property decriptor");
+ desc->assertComplete();
+
+ // Step 3.
+ if (desc->isDataDescriptor()) {
+ vp.set(desc->value());
+ return true;
+ }
+
+ // Step 4.
+ MOZ_ASSERT(desc->isAccessorDescriptor());
+
+ // Step 5.
+ JS::Rooted<JSObject*> getter(cx);
+ if (!desc->hasGetter() || !(getter = desc->getter())) {
+ // Step 6.
+ return ReportCrossOriginDenial(cx, id, "get"_ns);
+ }
+
+ // Step 7.
+ return JS::Call(cx, receiver, getter, JS::HandleValueArray::empty(), vp);
+}
+
+/* static */
+bool MaybeCrossOriginObjectMixins::CrossOriginSet(
+ JSContext* cx, JS::Handle<JSObject*> obj, JS::Handle<jsid> id,
+ JS::Handle<JS::Value> v, JS::Handle<JS::Value> receiver,
+ JS::ObjectOpResult& result) {
+ // We want to invoke [[GetOwnProperty]] on "obj", but _without_ entering its
+ // compartment, because for the proxies we have here [[GetOwnProperty]] will
+ // do security checks based on the current Realm. Unfortunately,
+ // JS_GetPropertyDescriptorById asserts that compartments match. Luckily, we
+ // know that "obj" is a proxy here, so we can directly call its
+ // getOwnPropertyDescriptor() hook.
+ //
+ // It looks like Proxy::getOwnPropertyDescriptor is not public, so just grab
+ // the handler and call its getOwnPropertyDescriptor hook directly.
+ MOZ_ASSERT(js::IsProxy(obj), "How did we get a bogus object here?");
+ MOZ_ASSERT(
+ js::IsWindowProxy(obj) || IsLocation(obj) || IsRemoteObjectProxy(obj),
+ "Unexpected proxy");
+ MOZ_ASSERT(!IsPlatformObjectSameOrigin(cx, obj) || IsRemoteObjectProxy(obj),
+ "Why did we get called?");
+ js::AssertSameCompartment(cx, receiver);
+ js::AssertSameCompartment(cx, v);
+
+ // Step 1.
+ JS::Rooted<Maybe<JS::PropertyDescriptor>> desc(cx);
+ if (!js::GetProxyHandler(obj)->getOwnPropertyDescriptor(cx, obj, id, &desc)) {
+ return false;
+ }
+
+ // Step 2.
+ MOZ_ASSERT(desc.isSome(),
+ "Callees should throw in all cases when they are not finding a "
+ "property decriptor");
+ desc->assertComplete();
+
+ // Step 3.
+ JS::Rooted<JSObject*> setter(cx);
+ if (desc->hasSetter() && (setter = desc->setter())) {
+ JS::Rooted<JS::Value> ignored(cx);
+ // Step 3.1.
+ if (!JS::Call(cx, receiver, setter, JS::HandleValueArray(v), &ignored)) {
+ return false;
+ }
+
+ // Step 3.2.
+ return result.succeed();
+ }
+
+ // Step 4.
+ return ReportCrossOriginDenial(cx, id, "set"_ns);
+}
+
+/* static */
+bool MaybeCrossOriginObjectMixins::EnsureHolder(
+ JSContext* cx, JS::Handle<JSObject*> obj, size_t slot,
+ const CrossOriginProperties& properties,
+ JS::MutableHandle<JSObject*> holder) {
+ MOZ_ASSERT(!IsPlatformObjectSameOrigin(cx, obj) || IsRemoteObjectProxy(obj),
+ "Why are we calling this at all in same-origin cases?");
+ // We store the holders in a weakmap stored in obj's slot. Our object is
+ // always a proxy, so we can just go ahead and use GetProxyReservedSlot here.
+ JS::Rooted<JS::Value> weakMapVal(cx, js::GetProxyReservedSlot(obj, slot));
+ if (weakMapVal.isUndefined()) {
+ // Enter the Realm of "obj" when we allocate the WeakMap, since we are going
+ // to store it in a slot on "obj" and in general we may not be
+ // same-compartment with "obj" here.
+ JSAutoRealm ar(cx, obj);
+ JSObject* newMap = JS::NewWeakMapObject(cx);
+ if (!newMap) {
+ return false;
+ }
+ weakMapVal.setObject(*newMap);
+ js::SetProxyReservedSlot(obj, slot, weakMapVal);
+ }
+ MOZ_ASSERT(weakMapVal.isObject(),
+ "How did a non-object else end up in this slot?");
+
+ JS::Rooted<JSObject*> map(cx, &weakMapVal.toObject());
+ MOZ_ASSERT(JS::IsWeakMapObject(map),
+ "How did something else end up in this slot?");
+
+ // We need to be in "map"'s compartment to work with it. Per spec, the key
+ // for this map is supposed to be the pair (current settings, relevant
+ // settings). The current settings corresponds to the current Realm of cx.
+ // The relevant settings corresponds to the Realm of "obj", but since all of
+ // our objects are per-Realm singletons, we are basically using "obj" itself
+ // as part of the key.
+ //
+ // To represent the current settings, we use a dedicated key object of the
+ // current-Realm.
+ //
+ // We can't use the current global, because we can't get a useful
+ // cross-compartment wrapper for it; such wrappers would always go
+ // through a WindowProxy and would not be guarantee to keep pointing to a
+ // single Realm when unwrapped. We want to grab this key before we start
+ // changing Realms.
+ //
+ // Also we can't use arbitrary object (e.g.: Object.prototype), because at
+ // this point those compartments are not same-origin, and don't have access to
+ // each other, and the object retrieved here will be wrapped by a security
+ // wrapper below, and the wrapper will be stored into the cache
+ // (see Compartment::wrap). Those compartments can get access later by
+ // modifying `document.domain`, and wrapping objects after that point
+ // shouldn't result in a security wrapper. Wrap operation looks up the
+ // existing wrapper in the cache, that contains the security wrapper created
+ // here. We should use unique/private object here, so that this doesn't
+ // affect later wrap operation.
+ JS::Rooted<JSObject*> key(cx, JS::GetRealmKeyObject(cx));
+ if (!key) {
+ return false;
+ }
+
+ JS::Rooted<JS::Value> holderVal(cx);
+ { // Scope for working with the map
+ JSAutoRealm ar(cx, map);
+ if (!MaybeWrapObject(cx, &key)) {
+ return false;
+ }
+
+ JS::Rooted<JS::Value> keyVal(cx, JS::ObjectValue(*key));
+ if (!JS::GetWeakMapEntry(cx, map, keyVal, &holderVal)) {
+ return false;
+ }
+ }
+
+ if (holderVal.isObject()) {
+ // We want to do an unchecked unwrap, because the holder (and the current
+ // caller) may actually be more privileged than our map.
+ holder.set(js::UncheckedUnwrap(&holderVal.toObject()));
+
+ // holder might be a dead object proxy if things got nuked.
+ if (!JS_IsDeadWrapper(holder)) {
+ MOZ_ASSERT(js::GetContextRealm(cx) == js::GetNonCCWObjectRealm(holder),
+ "How did we end up with a key/value mismatch?");
+ return true;
+ }
+ }
+
+ // We didn't find a usable holder. Go ahead and allocate one. At this point
+ // we have two options: we could allocate the holder in the current Realm and
+ // store a cross-compartment wrapper for it in the map as needed, or we could
+ // allocate the holder in the Realm of the map and have it hold
+ // cross-compartment references to all the methods it holds, since those
+ // methods need to be in our current Realm. It seems better to allocate the
+ // holder in our current Realm.
+ bool isChrome = xpc::AccessCheck::isChrome(js::GetContextRealm(cx));
+ holder.set(JS_NewObjectWithGivenProto(cx, nullptr, nullptr));
+ if (!holder || !JS_DefineProperties(cx, holder, properties.mAttributes) ||
+ !JS_DefineFunctions(cx, holder, properties.mMethods) ||
+ (isChrome && properties.mChromeOnlyAttributes &&
+ !JS_DefineProperties(cx, holder, properties.mChromeOnlyAttributes)) ||
+ (isChrome && properties.mChromeOnlyMethods &&
+ !JS_DefineFunctions(cx, holder, properties.mChromeOnlyMethods))) {
+ return false;
+ }
+
+ holderVal.setObject(*holder);
+ { // Scope for working with the map
+ JSAutoRealm ar(cx, map);
+
+ // Key is already in the right Realm, but we need to wrap the value.
+ if (!MaybeWrapValue(cx, &holderVal)) {
+ return false;
+ }
+
+ JS::Rooted<JS::Value> keyVal(cx, JS::ObjectValue(*key));
+ if (!JS::SetWeakMapEntry(cx, map, keyVal, holderVal)) {
+ return false;
+ }
+ }
+
+ return true;
+}
+
+/* static */
+bool MaybeCrossOriginObjectMixins::ReportCrossOriginDenial(
+ JSContext* aCx, JS::Handle<jsid> aId, const nsACString& aAccessType) {
+ xpc::AccessCheck::reportCrossOriginDenial(aCx, aId, aAccessType);
+ return false;
+}
+
+template <typename Base>
+bool MaybeCrossOriginObject<Base>::getPrototype(
+ JSContext* cx, JS::Handle<JSObject*> proxy,
+ JS::MutableHandle<JSObject*> protop) const {
+ if (!IsPlatformObjectSameOrigin(cx, proxy)) {
+ protop.set(nullptr);
+ return true;
+ }
+
+ { // Scope for JSAutoRealm
+ JSAutoRealm ar(cx, proxy);
+ protop.set(getSameOriginPrototype(cx));
+ if (!protop) {
+ return false;
+ }
+ }
+
+ return MaybeWrapObject(cx, protop);
+}
+
+template <typename Base>
+bool MaybeCrossOriginObject<Base>::setPrototype(
+ JSContext* cx, JS::Handle<JSObject*> proxy, JS::Handle<JSObject*> proto,
+ JS::ObjectOpResult& result) const {
+ // Inlined version of
+ // https://tc39.github.io/ecma262/#sec-set-immutable-prototype
+ js::AssertSameCompartment(cx, proto);
+
+ // We have to be careful how we get the prototype. In particular, we do _NOT_
+ // want to enter the Realm of "proxy" to do that, in case we're not
+ // same-origin with it here.
+ JS::Rooted<JSObject*> wrappedProxy(cx, proxy);
+ if (!MaybeWrapObject(cx, &wrappedProxy)) {
+ return false;
+ }
+
+ JS::Rooted<JSObject*> currentProto(cx);
+ if (!js::GetObjectProto(cx, wrappedProxy, &currentProto)) {
+ return false;
+ }
+
+ if (currentProto != proto) {
+ return result.failCantSetProto();
+ }
+
+ return result.succeed();
+}
+
+template <typename Base>
+bool MaybeCrossOriginObject<Base>::getPrototypeIfOrdinary(
+ JSContext* cx, JS::Handle<JSObject*> proxy, bool* isOrdinary,
+ JS::MutableHandle<JSObject*> protop) const {
+ // We have a custom [[GetPrototypeOf]]
+ *isOrdinary = false;
+ return true;
+}
+
+template <typename Base>
+bool MaybeCrossOriginObject<Base>::setImmutablePrototype(
+ JSContext* cx, JS::Handle<JSObject*> proxy, bool* succeeded) const {
+ // We just want to disallow this.
+ *succeeded = false;
+ return true;
+}
+
+template <typename Base>
+bool MaybeCrossOriginObject<Base>::isExtensible(JSContext* cx,
+ JS::Handle<JSObject*> proxy,
+ bool* extensible) const {
+ // We never allow [[PreventExtensions]] to succeed.
+ *extensible = true;
+ return true;
+}
+
+template <typename Base>
+bool MaybeCrossOriginObject<Base>::preventExtensions(
+ JSContext* cx, JS::Handle<JSObject*> proxy,
+ JS::ObjectOpResult& result) const {
+ return result.failCantPreventExtensions();
+}
+
+template <typename Base>
+bool MaybeCrossOriginObject<Base>::defineProperty(
+ JSContext* cx, JS::Handle<JSObject*> proxy, JS::Handle<jsid> id,
+ JS::Handle<JS::PropertyDescriptor> desc, JS::ObjectOpResult& result) const {
+ if (!IsPlatformObjectSameOrigin(cx, proxy)) {
+ return ReportCrossOriginDenial(cx, id, "define"_ns);
+ }
+
+ // Enter the Realm of proxy and do the remaining work in there.
+ JSAutoRealm ar(cx, proxy);
+ JS::Rooted<JS::PropertyDescriptor> descCopy(cx, desc);
+ if (!JS_WrapPropertyDescriptor(cx, &descCopy)) {
+ return false;
+ }
+
+ JS_MarkCrossZoneId(cx, id);
+
+ return definePropertySameOrigin(cx, proxy, id, descCopy, result);
+}
+
+template <typename Base>
+bool MaybeCrossOriginObject<Base>::enumerate(
+ JSContext* cx, JS::Handle<JSObject*> proxy,
+ JS::MutableHandleVector<jsid> props) const {
+ // Just get the property keys from ourselves, in whatever Realm we happen to
+ // be in. It's important to not enter the Realm of "proxy" here, because that
+ // would affect the list of keys we claim to have. We wrap the proxy in the
+ // current compartment just to be safe; it doesn't affect behavior as far as
+ // CrossOriginObjectWrapper and MaybeCrossOriginObject are concerned.
+ JS::Rooted<JSObject*> self(cx, proxy);
+ if (!MaybeWrapObject(cx, &self)) {
+ return false;
+ }
+
+ return js::GetPropertyKeys(cx, self, 0, props);
+}
+
+// Force instantiations of the out-of-line template methods we need.
+template class MaybeCrossOriginObject<js::Wrapper>;
+template class MaybeCrossOriginObject<DOMProxyHandler>;
+
+} // namespace mozilla::dom
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