/* 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/. */ #ifndef mozilla_dom_DOMJSClass_h #define mozilla_dom_DOMJSClass_h #include "js/Object.h" // JS::GetClass, JS::GetReservedSlot #include "js/Wrapper.h" #include "jsapi.h" #include "jsfriendapi.h" #include "mozilla/Assertions.h" #include "mozilla/Attributes.h" #include "mozilla/OriginTrials.h" #include "mozilla/dom/PrototypeList.h" // auto-generated #include "mozilla/dom/WebIDLPrefs.h" // auto-generated class nsCycleCollectionParticipant; class nsWrapperCache; struct JSFunctionSpec; struct JSPropertySpec; struct JSStructuredCloneReader; struct JSStructuredCloneWriter; class nsIGlobalObject; // All DOM globals must have a slot at DOM_PROTOTYPE_SLOT. #define DOM_PROTOTYPE_SLOT JSCLASS_GLOBAL_SLOT_COUNT // Keep this count up to date with any extra global slots added above. #define DOM_GLOBAL_SLOTS 1 // We use these flag bits for the new bindings. #define JSCLASS_DOM_GLOBAL JSCLASS_USERBIT1 #define JSCLASS_IS_DOMIFACEANDPROTOJSCLASS JSCLASS_USERBIT2 namespace mozilla::dom { /** * Returns true if code running in the given JSContext is allowed to access * [SecureContext] API on the given JSObject. * * [SecureContext] API exposure is restricted to use by code in a Secure * Contexts: * * https://w3c.github.io/webappsec-secure-contexts/ * * Since we want [SecureContext] exposure to depend on the privileges of the * running code (rather than the privileges of an object's creator), this * function checks to see whether the given JSContext's Realm is flagged * as a Secure Context. That allows us to make sure that system principal code * (which is marked as a Secure Context) can access Secure Context API on an * object in a different realm, regardless of whether the other realm is a * Secure Context or not. * * Checking the JSContext's Realm doesn't work for expanded principal * globals accessing a Secure Context web page though (e.g. those used by frame * scripts). To handle that we fall back to checking whether the JSObject came * from a Secure Context. * * Note: We'd prefer this function to live in BindingUtils.h, but we need to * call it in this header, and BindingUtils.h includes us (i.e. we'd have a * circular dependency between headers if it lived there). */ inline bool IsSecureContextOrObjectIsFromSecureContext(JSContext* aCx, JSObject* aObj) { MOZ_ASSERT(!js::IsWrapper(aObj)); return JS::GetIsSecureContext(js::GetContextRealm(aCx)) || JS::GetIsSecureContext(js::GetNonCCWObjectRealm(aObj)); } typedef bool (*ResolveOwnProperty)( JSContext* cx, JS::Handle wrapper, JS::Handle obj, JS::Handle id, JS::MutableHandle> desc); typedef bool (*EnumerateOwnProperties)(JSContext* cx, JS::Handle wrapper, JS::Handle obj, JS::MutableHandleVector props); typedef bool (*DeleteNamedProperty)(JSContext* cx, JS::Handle wrapper, JS::Handle obj, JS::Handle id, JS::ObjectOpResult& opresult); // Returns true if the given global is of a type whose bit is set in // aGlobalSet. bool IsGlobalInExposureSet(JSContext* aCx, JSObject* aGlobal, uint32_t aGlobalSet); struct ConstantSpec { const char* name; JS::Value value; }; typedef bool (*PropertyEnabled)(JSContext* cx, JSObject* global); namespace GlobalNames { // The names of our possible globals. These are the names of the actual // interfaces, not of the global names used to refer to them in IDL [Exposed] // annotations. static const uint32_t Window = 1u << 0; static const uint32_t DedicatedWorkerGlobalScope = 1u << 1; static const uint32_t SharedWorkerGlobalScope = 1u << 2; static const uint32_t ServiceWorkerGlobalScope = 1u << 3; static const uint32_t WorkerDebuggerGlobalScope = 1u << 4; static const uint32_t AudioWorkletGlobalScope = 1u << 5; static const uint32_t PaintWorkletGlobalScope = 1u << 6; static constexpr uint32_t kCount = 7; } // namespace GlobalNames struct PrefableDisablers { inline bool isEnabled(JSContext* cx, JS::Handle obj) const { if (nonExposedGlobals && IsGlobalInExposureSet(cx, JS::GetNonCCWObjectGlobal(obj), nonExposedGlobals)) { return false; } if (prefIndex != WebIDLPrefIndex::NoPref && !sWebIDLPrefs[uint16_t(prefIndex)]()) { return false; } if (secureContext && !IsSecureContextOrObjectIsFromSecureContext(cx, obj)) { return false; } if (trial != OriginTrial(0) && !OriginTrials::IsEnabled(cx, JS::GetNonCCWObjectGlobal(obj), trial)) { // TODO(emilio): Perhaps reconsider the interaction between [Trial=""] and // [Pref=""]. // // In particular, it might be desirable to only check the trial if there // is no pref or the pref is disabled. return false; } if (enabledFunc && !enabledFunc(cx, JS::GetNonCCWObjectGlobal(obj))) { return false; } return true; } // Index into the array of StaticPrefs const WebIDLPrefIndex prefIndex; // Bitmask of global names that we should not be exposed in. const uint16_t nonExposedGlobals : GlobalNames::kCount; // A boolean indicating whether a Secure Context is required. const uint16_t secureContext : 1; // An origin trial controlling the feature. This can be made a bitfield too if // needed. const OriginTrial trial; // A function pointer to a function that can say the property is disabled // even if "enabled" is set to true. If the pointer is null the value of // "enabled" is used as-is. const PropertyEnabled enabledFunc; }; template struct Prefable { inline bool isEnabled(JSContext* cx, JS::Handle obj) const { MOZ_ASSERT(!js::IsWrapper(obj)); if (!disablers) [[likely]] { return true; } return disablers->isEnabled(cx, obj); } // Things that can disable this set of specs. |nullptr| means "cannot be // disabled". const PrefableDisablers* const disablers; // Array of specs, terminated in whatever way is customary for T. // Null to indicate a end-of-array for Prefable, when such an // indicator is needed. const T* const specs; }; enum PropertyType { eStaticMethod, eStaticAttribute, eMethod, eAttribute, eUnforgeableMethod, eUnforgeableAttribute, eConstant, ePropertyTypeCount }; #define NUM_BITS_PROPERTY_INFO_TYPE 3 #define NUM_BITS_PROPERTY_INFO_PREF_INDEX 13 #define NUM_BITS_PROPERTY_INFO_SPEC_INDEX 16 struct PropertyInfo { private: // MSVC generates static initializers if we store a jsid here, even if // PropertyInfo has a constexpr constructor. See bug 1460341 and bug 1464036. uintptr_t mIdBits; public: // One of PropertyType, will be used for accessing the corresponding Duo in // NativePropertiesN.duos[]. uint32_t type : NUM_BITS_PROPERTY_INFO_TYPE; // The index to the corresponding Preable in Duo.mPrefables[]. uint32_t prefIndex : NUM_BITS_PROPERTY_INFO_PREF_INDEX; // The index to the corresponding spec in Duo.mPrefables[prefIndex].specs[]. uint32_t specIndex : NUM_BITS_PROPERTY_INFO_SPEC_INDEX; void SetId(jsid aId) { static_assert(sizeof(jsid) == sizeof(mIdBits), "jsid should fit in mIdBits"); mIdBits = aId.asRawBits(); } MOZ_ALWAYS_INLINE jsid Id() const { return jsid::fromRawBits(mIdBits); } bool IsStaticMethod() const { return type == eStaticMethod; } static int Compare(const PropertyInfo& aInfo1, const PropertyInfo& aInfo2) { // IdToIndexComparator needs to be updated if the order here is changed! if (aInfo1.mIdBits == aInfo2.mIdBits) [[unlikely]] { MOZ_ASSERT((aInfo1.type == eMethod || aInfo1.type == eStaticMethod) && (aInfo2.type == eMethod || aInfo2.type == eStaticMethod)); bool isStatic1 = aInfo1.IsStaticMethod(); MOZ_ASSERT(isStatic1 != aInfo2.IsStaticMethod(), "We shouldn't have 2 static methods with the same name!"); return isStatic1 ? -1 : 1; } return aInfo1.mIdBits < aInfo2.mIdBits ? -1 : 1; } }; static_assert( ePropertyTypeCount <= 1ull << NUM_BITS_PROPERTY_INFO_TYPE, "We have property type count that is > (1 << NUM_BITS_PROPERTY_INFO_TYPE)"); // Conceptually, NativeProperties has seven (Prefable*, PropertyInfo*) duos // (where T is one of JSFunctionSpec, JSPropertySpec, or ConstantSpec), one for // each of: static methods and attributes, methods and attributes, unforgeable // methods and attributes, and constants. // // That's 14 pointers, but in most instances most of the duos are all null, and // there are many instances. To save space we use a variable-length type, // NativePropertiesN, to hold the data and getters to access it. It has N // actual duos (stored in duos[]), plus four bits for each of the 7 possible // duos: 1 bit that states if that duo is present, and 3 that state that duo's // offset (if present) in duos[]. // // All duo accesses should be done via the getters, which contain assertions // that check we don't overrun the end of the struct. (The duo data members are // public only so they can be statically initialized.) These assertions should // never fail so long as (a) accesses to the variable-length part are guarded by // appropriate Has*() calls, and (b) all instances are well-formed, i.e. the // value of N matches the number of mHas* members that are true. // // We store all the property ids a NativePropertiesN owns in a single array of // PropertyInfo structs. Each struct contains an id and the information needed // to find the corresponding Prefable for the enabled check, as well as the // information needed to find the correct property descriptor in the // Prefable. We also store an array of indices into the PropertyInfo array, // sorted by bits of the corresponding jsid. Given a jsid, this allows us to // binary search for the index of the corresponding PropertyInfo, if any. // // Finally, we define a typedef of NativePropertiesN<7>, NativeProperties, which // we use as a "base" type used to refer to all instances of NativePropertiesN. // (7 is used because that's the maximum valid parameter, though any other // value 1..6 could also be used.) This is reasonable because of the // aforementioned assertions in the getters. Upcast() is used to convert // specific instances to this "base" type. // // An example // ---------- // NativeProperties points to various things, and it can be hard to keep track. // The following example shows the layout. // // Imagine an example interface, with: // - 10 properties // - 6 methods, 3 with no disablers struct, 2 sharing the same disablers // struct, 1 using a different disablers struct // - 4 attributes, all with no disablers // - The property order is such that those using the same disablers structs are // together. (This is not guaranteed, but it makes the example simpler.) // // Each PropertyInfo also contain indices into sMethods/sMethods_specs (for // method infos) and sAttributes/sAttributes_specs (for attributes), which let // them find their spec, but these are not shown. // // sNativeProperties sNativeProperties_ sNativeProperties_ // ---- sortedPropertyIndices[10] propertyInfos[10] // - ---- ---- // - sortedPropertyIndices ----> <10 indices> +--> 0 info (method) // - duos[2] ---- | 1 info (method) // ----(methods) | 2 info (method) // 0 - mPrefables -------> points to sMethods below | 3 info (method) // - mPropertyInfos ------------------------------+ 4 info (method) // 1 - mPrefables -------> points to sAttributes below 5 info (method) // - mPropertyInfos ---------------------------------> 6 info (attr) // ---- 7 info (attr) // ---- 8 info (attr) // 9 info (attr) // ---- // // sMethods has three entries (excluding the terminator) because there are // three disablers structs. The {nullptr,nullptr} serves as the terminator. // There are also END terminators within sMethod_specs; the need for these // terminators (as opposed to a length) is deeply embedded in SpiderMonkey. // Disablers structs are suffixed with the index of the first spec they cover. // // sMethods sMethods_specs // ---- ---- // 0 - nullptr +----> 0 spec // - specs ----------------------+ 1 spec // 1 - disablers ---> disablers4 2 spec // - specs ------------------------+ 3 END // 2 - disablers ---> disablers7 +--> 4 spec // - specs ----------------------+ 5 spec // 3 - nullptr | 6 END // - nullptr +----> 7 spec // ---- 8 END // // sAttributes has a single entry (excluding the terminator) because all of the // specs lack disablers. // // sAttributes sAttributes_specs // ---- ---- // 0 - nullptr +----> 0 spec // - specs ----------------------+ 1 spec // 1 - nullptr 2 spec // - nullptr 3 spec // ---- 4 END // ---- template struct NativePropertiesN { // Duo structs are stored in the duos[] array, and each element in the array // could require a different T. Therefore, we can't use the correct type for // mPrefables. Instead we use void* and cast to the correct type in the // getters. struct Duo { const /*Prefable*/ void* const mPrefables; PropertyInfo* const mPropertyInfos; }; constexpr const NativePropertiesN<7>* Upcast() const { return reinterpret_cast*>(this); } const PropertyInfo* PropertyInfos() const { return duos[0].mPropertyInfos; } #define DO(SpecT, FieldName) \ public: \ /* The bitfields indicating the duo's presence and (if present) offset. */ \ const uint32_t mHas##FieldName##s : 1; \ const uint32_t m##FieldName##sOffset : 3; \ \ private: \ const Duo* FieldName##sDuo() const { \ MOZ_ASSERT(Has##FieldName##s()); \ return &duos[m##FieldName##sOffset]; \ } \ \ public: \ bool Has##FieldName##s() const { return mHas##FieldName##s; } \ const Prefable* FieldName##s() const { \ return static_cast*>( \ FieldName##sDuo()->mPrefables); \ } \ PropertyInfo* FieldName##PropertyInfos() const { \ return FieldName##sDuo()->mPropertyInfos; \ } DO(JSFunctionSpec, StaticMethod) DO(JSPropertySpec, StaticAttribute) DO(JSFunctionSpec, Method) DO(JSPropertySpec, Attribute) DO(JSFunctionSpec, UnforgeableMethod) DO(JSPropertySpec, UnforgeableAttribute) DO(ConstantSpec, Constant) #undef DO // The index to the iterator method in MethodPropertyInfos() array. const int16_t iteratorAliasMethodIndex; // The number of PropertyInfo structs that the duos manage. This is the total // count across all duos. const uint16_t propertyInfoCount; // The sorted indices array from sorting property ids, which will be used when // we binary search for a property. uint16_t* sortedPropertyIndices; const Duo duos[N]; }; // Ensure the struct has the expected size. The 8 is for the bitfields plus // iteratorAliasMethodIndex and idsLength; the rest is for the idsSortedIndex, // and duos[]. static_assert(sizeof(NativePropertiesN<1>) == 8 + 3 * sizeof(void*), "1 size"); static_assert(sizeof(NativePropertiesN<2>) == 8 + 5 * sizeof(void*), "2 size"); static_assert(sizeof(NativePropertiesN<3>) == 8 + 7 * sizeof(void*), "3 size"); static_assert(sizeof(NativePropertiesN<4>) == 8 + 9 * sizeof(void*), "4 size"); static_assert(sizeof(NativePropertiesN<5>) == 8 + 11 * sizeof(void*), "5 size"); static_assert(sizeof(NativePropertiesN<6>) == 8 + 13 * sizeof(void*), "6 size"); static_assert(sizeof(NativePropertiesN<7>) == 8 + 15 * sizeof(void*), "7 size"); // The "base" type. typedef NativePropertiesN<7> NativeProperties; struct NativePropertiesHolder { const NativeProperties* regular; const NativeProperties* chromeOnly; // Points to a static bool that's set to true once the regular and chromeOnly // NativeProperties have been inited. This is a pointer to a bool instead of // a bool value because NativePropertiesHolder is stored by value in // a static const NativePropertyHooks. bool* inited; }; struct NativeNamedOrIndexedPropertyHooks { // The hook to call for resolving indexed or named properties. ResolveOwnProperty mResolveOwnProperty; // The hook to call for enumerating indexed or named properties. EnumerateOwnProperties mEnumerateOwnProperties; // The hook to call to delete a named property. May be null if there are no // named properties or no named property deleter. On success (true return) // the "found" argument will be set to true if there was in fact such a named // property and false otherwise. If it's set to false, the caller is expected // to proceed with whatever deletion behavior it would have if there were no // named properties involved at all (i.e. if the hook were null). If it's set // to true, it will indicate via opresult whether the delete actually // succeeded. DeleteNamedProperty mDeleteNamedProperty; }; // Helper structure for Xrays for DOM binding objects. The same instance is used // for instances, interface objects and interface prototype objects of a // specific interface. struct NativePropertyHooks { const NativeNamedOrIndexedPropertyHooks* mIndexedOrNamedNativeProperties; // The property arrays for this interface. NativePropertiesHolder mNativeProperties; // This will be set to the ID of the interface prototype object for the // interface, if it has one. If it doesn't have one it will be set to // prototypes::id::_ID_Count. prototypes::ID mPrototypeID; // This will be set to the ID of the interface object for the interface, if it // has one. If it doesn't have one it will be set to // constructors::id::_ID_Count. constructors::ID mConstructorID; // The JSClass to use for expandos on our Xrays. Can be null, in which case // Xrays will use a default class of their choice. const JSClass* mXrayExpandoClass; }; enum DOMObjectType : uint8_t { eInstance, eGlobalInstance, eInterface, eInterfacePrototype, eGlobalInterfacePrototype, eNamespace, eNamedPropertiesObject }; inline bool IsInstance(DOMObjectType type) { return type == eInstance || type == eGlobalInstance; } inline bool IsInterfacePrototype(DOMObjectType type) { return type == eInterfacePrototype || type == eGlobalInterfacePrototype; } typedef JSObject* (*ProtoGetter)(JSContext* aCx); /** * Returns a handle to the relevant WebIDL prototype object for the current * compartment global (which may be a handle to null on out of memory). Once * allocated, the prototype object is guaranteed to exist as long as the global * does, since the global traces its array of WebIDL prototypes and * constructors. */ typedef JS::Handle (*ProtoHandleGetter)(JSContext* aCx); /** * Serializes a WebIDL object for structured cloning. aObj may not be in the * compartment of aCx in cases when we were working with a cross-compartment * wrapper. aObj is expected to be an object of the DOMJSClass that we got the * serializer from. */ typedef bool (*WebIDLSerializer)(JSContext* aCx, JSStructuredCloneWriter* aWriter, JS::Handle aObj); /** * Deserializes a WebIDL object from a structured clone serialization. */ typedef JSObject* (*WebIDLDeserializer)(JSContext* aCx, nsIGlobalObject* aGlobal, JSStructuredCloneReader* aReader); using WrapperCacheGetter = nsWrapperCache* (*)(JSObject*); // Special JSClass for reflected DOM objects. struct DOMJSClass { // It would be nice to just inherit from JSClass, but that precludes pure // compile-time initialization of the form |DOMJSClass = {...};|, since C++ // only allows brace initialization for aggregate/POD types. const JSClass mBase; // A list of interfaces that this object implements, in order of decreasing // derivedness. const prototypes::ID mInterfaceChain[MAX_PROTOTYPE_CHAIN_LENGTH]; // We store the DOM object in reserved slot with index DOM_OBJECT_SLOT or in // the proxy private if we use a proxy object. // Sometimes it's an nsISupports and sometimes it's not; this class tells // us which it is. const bool mDOMObjectIsISupports; const NativePropertyHooks* mNativeHooks; ProtoHandleGetter mGetProto; // This stores the CC participant for the native, null if this class does not // implement cycle collection or if it inherits from nsISupports (we can get // the CC participant by QI'ing in that case). nsCycleCollectionParticipant* mParticipant; // The serializer for this class if the relevant object is [Serializable]. // Null otherwise. WebIDLSerializer mSerializer; // A callback to get the wrapper cache for C++ objects that don't inherit from // nsISupports, or null. WrapperCacheGetter mWrapperCacheGetter; static const DOMJSClass* FromJSClass(const JSClass* base) { MOZ_ASSERT(base->flags & JSCLASS_IS_DOMJSCLASS); return reinterpret_cast(base); } const JSClass* ToJSClass() const { return &mBase; } }; // Special JSClass for DOM interface and interface prototype objects. struct DOMIfaceAndProtoJSClass { // It would be nice to just inherit from JSClass, but that precludes pure // compile-time initialization of the form // |DOMJSInterfaceAndPrototypeClass = {...};|, since C++ only allows brace // initialization for aggregate/POD types. const JSClass mBase; // Either eNamespace, eInterfacePrototype, // eGlobalInterfacePrototype or eNamedPropertiesObject. DOMObjectType mType; // uint8_t const prototypes::ID mPrototypeID; // uint16_t const uint32_t mDepth; const NativePropertyHooks* mNativeHooks; ProtoGetter mGetParentProto; static const DOMIfaceAndProtoJSClass* FromJSClass(const JSClass* base) { MOZ_ASSERT(base->flags & JSCLASS_IS_DOMIFACEANDPROTOJSCLASS); return reinterpret_cast(base); } const JSClass* ToJSClass() const { return &mBase; } }; class ProtoAndIfaceCache; inline bool DOMGlobalHasProtoAndIFaceCache(const JSObject* global) { MOZ_DIAGNOSTIC_ASSERT(JS::GetClass(global)->flags & JSCLASS_DOM_GLOBAL); // This can be undefined if we GC while creating the global return !JS::GetReservedSlot(global, DOM_PROTOTYPE_SLOT).isUndefined(); } inline bool HasProtoAndIfaceCache(const JSObject* global) { if (!(JS::GetClass(global)->flags & JSCLASS_DOM_GLOBAL)) { return false; } return DOMGlobalHasProtoAndIFaceCache(global); } inline ProtoAndIfaceCache* GetProtoAndIfaceCache(JSObject* global) { MOZ_DIAGNOSTIC_ASSERT(JS::GetClass(global)->flags & JSCLASS_DOM_GLOBAL); return static_cast( JS::GetReservedSlot(global, DOM_PROTOTYPE_SLOT).toPrivate()); } } // namespace mozilla::dom #endif /* mozilla_dom_DOMJSClass_h */