JSObject * WrapperFactory::PrepareForWrapping(JSContext *cx, HandleObject scope, HandleObject objArg, unsigned flags) { RootedObject obj(cx, objArg); // Outerize any raw inner objects at the entry point here, so that we don't // have to worry about them for the rest of the wrapping code. if (js::IsInnerObject(obj)) { JSAutoCompartment ac(cx, obj); obj = JS_ObjectToOuterObject(cx, obj); NS_ENSURE_TRUE(obj, nullptr); // The outerization hook wraps, which means that we can end up with a // CCW here if |obj| was a navigated-away-from inner. Strip any CCWs. obj = js::UncheckedUnwrap(obj); MOZ_ASSERT(js::IsOuterObject(obj)); } // If we've got an outer window, there's nothing special that needs to be // done here, and we can move on to the next phase of wrapping. We handle // this case first to allow us to assert against wrappers below. if (js::IsOuterObject(obj)) return DoubleWrap(cx, obj, flags); // Here are the rules for wrapping: // We should never get a proxy here (the JS engine unwraps those for us). MOZ_ASSERT(!IsWrapper(obj)); // If the object being wrapped is a prototype for a standard class and the // wrapper does not subsumes the wrappee, use the one from the content // compartment. This is generally safer all-around, and in the COW case this // lets us safely take advantage of things like .forEach() via the // ChromeObjectWrapper machinery. // // If the prototype chain of chrome object |obj| looks like this: // // obj => foo => bar => chromeWin.StandardClass.prototype // // The prototype chain of COW(obj) looks lke this: // // COW(obj) => COW(foo) => COW(bar) => contentWin.StandardClass.prototype // // NB: We now remap all non-subsuming access of standard prototypes. // // NB: We need to ignore domain here so that the security relationship we // compute here can't change over time. See the comment above the other // subsumes call below. bool subsumes = AccessCheck::subsumes(js::GetContextCompartment(cx), js::GetObjectCompartment(obj)); XrayType xrayType = GetXrayType(obj); if (!subsumes && xrayType == NotXray) { JSProtoKey key = JSProto_Null; { JSAutoCompartment ac(cx, obj); key = IdentifyStandardPrototype(obj); } if (key != JSProto_Null) { RootedObject homeProto(cx); if (!JS_GetClassPrototype(cx, key, &homeProto)) return nullptr; MOZ_ASSERT(homeProto); // No need to double-wrap here. We should never have waivers to // COWs. return homeProto; } } // Now, our object is ready to be wrapped, but several objects (notably // nsJSIIDs) have a wrapper per scope. If we are about to wrap one of // those objects in a security wrapper, then we need to hand back the // wrapper for the new scope instead. Also, global objects don't move // between scopes so for those we also want to return the wrapper. So... if (!IS_WN_REFLECTOR(obj) || !js::GetObjectParent(obj)) return DoubleWrap(cx, obj, flags); XPCWrappedNative *wn = XPCWrappedNative::Get(obj); JSAutoCompartment ac(cx, obj); XPCCallContext ccx(JS_CALLER, cx, obj); RootedObject wrapScope(cx, scope); { if (NATIVE_HAS_FLAG(&ccx, WantPreCreate)) { // We have a precreate hook. This object might enforce that we only // ever create JS object for it. // Note: this penalizes objects that only have one wrapper, but are // being accessed across compartments. We would really prefer to // replace the above code with a test that says "do you only have one // wrapper?" nsresult rv = wn->GetScriptableInfo()->GetCallback()-> PreCreate(wn->Native(), cx, scope, wrapScope.address()); NS_ENSURE_SUCCESS(rv, DoubleWrap(cx, obj, flags)); // If the handed back scope differs from the passed-in scope and is in // a separate compartment, then this object is explicitly requesting // that we don't create a second JS object for it: create a security // wrapper. if (js::GetObjectCompartment(scope) != js::GetObjectCompartment(wrapScope)) return DoubleWrap(cx, obj, flags); RootedObject currentScope(cx, JS_GetGlobalForObject(cx, obj)); if (MOZ_UNLIKELY(wrapScope != currentScope)) { // The wrapper claims it wants to be in the new scope, but // currently has a reflection that lives in the old scope. This // can mean one of two things, both of which are rare: // // 1 - The object has a PreCreate hook (we checked for it above), // but is deciding to request one-wrapper-per-scope (rather than // one-wrapper-per-native) for some reason. Usually, a PreCreate // hook indicates one-wrapper-per-native. In this case we want to // make a new wrapper in the new scope. // // 2 - We're midway through wrapper reparenting. The document has // moved to a new scope, but |wn| hasn't been moved yet, and // we ended up calling JS_WrapObject() on its JS object. In this // case, we want to return the existing wrapper. // // So we do a trick: call PreCreate _again_, but say that we're // wrapping for the old scope, rather than the new one. If (1) is // the case, then PreCreate will return the scope we pass to it // (the old scope). If (2) is the case, PreCreate will return the // scope of the document (the new scope). RootedObject probe(cx); rv = wn->GetScriptableInfo()->GetCallback()-> PreCreate(wn->Native(), cx, currentScope, probe.address()); // Check for case (2). if (probe != currentScope) { MOZ_ASSERT(probe == wrapScope); return DoubleWrap(cx, obj, flags); } // Ok, must be case (1). Fall through and create a new wrapper. } // Nasty hack for late-breaking bug 781476. This will confuse identity checks, // but it's probably better than any of our alternatives. // // Note: We have to ignore domain here. The JS engine assumes that, given a // compartment c, if c->wrap(x) returns a cross-compartment wrapper at time t0, // it will also return a cross-compartment wrapper for any time t1 > t0 unless // an explicit transplant is performed. In particular, wrapper recomputation // assumes that recomputing a wrapper will always result in a wrapper. // // This doesn't actually pose a security issue, because we'll still compute // the correct (opaque) wrapper for the object below given the security // characteristics of the two compartments. if (!AccessCheck::isChrome(js::GetObjectCompartment(wrapScope)) && AccessCheck::subsumes(js::GetObjectCompartment(wrapScope), js::GetObjectCompartment(obj))) { return DoubleWrap(cx, obj, flags); } } } // This public WrapNativeToJSVal API enters the compartment of 'wrapScope' // so we don't have to. RootedValue v(cx); nsresult rv = nsXPConnect::XPConnect()->WrapNativeToJSVal(cx, wrapScope, wn->Native(), nullptr, &NS_GET_IID(nsISupports), false, &v); NS_ENSURE_SUCCESS(rv, nullptr); obj.set(&v.toObject()); MOZ_ASSERT(IS_WN_REFLECTOR(obj), "bad object"); // Because the underlying native didn't have a PreCreate hook, we had // to a new (or possibly pre-existing) XPCWN in our compartment. // This could be a problem for chrome code that passes XPCOM objects // across compartments, because the effects of QI would disappear across // compartments. // // So whenever we pull an XPCWN across compartments in this manner, we // give the destination object the union of the two native sets. We try // to do this cleverly in the common case to avoid too much overhead. XPCWrappedNative *newwn = XPCWrappedNative::Get(obj); XPCNativeSet *unionSet = XPCNativeSet::GetNewOrUsed(newwn->GetSet(), wn->GetSet(), false); if (!unionSet) return nullptr; newwn->SetSet(unionSet); return DoubleWrap(cx, obj, flags); }
JSObject * WrapperFactory::Rewrap(JSContext *cx, HandleObject existing, HandleObject obj, HandleObject wrappedProto, HandleObject parent, unsigned flags) { MOZ_ASSERT(!IsWrapper(obj) || GetProxyHandler(obj) == &XrayWaiver || js::GetObjectClass(obj)->ext.innerObject, "wrapped object passed to rewrap"); MOZ_ASSERT(JS_GetClass(obj) != &XrayUtils::HolderClass, "trying to wrap a holder"); MOZ_ASSERT(!js::IsInnerObject(obj)); // We sometimes end up here after nsContentUtils has been shut down but before // XPConnect has been shut down, so check the context stack the roundabout way. MOZ_ASSERT(XPCJSRuntime::Get()->GetJSContextStack()->Peek() == cx); // Compute the information we need to select the right wrapper. JSCompartment *origin = js::GetObjectCompartment(obj); JSCompartment *target = js::GetContextCompartment(cx); bool originIsChrome = AccessCheck::isChrome(origin); bool targetIsChrome = AccessCheck::isChrome(target); bool originSubsumesTarget = AccessCheck::subsumes(origin, target); bool targetSubsumesOrigin = AccessCheck::subsumes(target, origin); bool sameOrigin = targetSubsumesOrigin && originSubsumesTarget; XrayType xrayType = GetXrayType(obj); bool waiveXrayFlag = flags & WAIVE_XRAY_WRAPPER_FLAG; // By default we use the wrapped proto of the underlying object as the // prototype for our wrapper, but we may select something different below. RootedObject proxyProto(cx, wrappedProto); Wrapper *wrapper; CompartmentPrivate *targetdata = EnsureCompartmentPrivate(target); // // First, handle the special cases. // // If UniversalXPConnect is enabled, this is just some dumb mochitest. Use // a vanilla CCW. if (xpc::IsUniversalXPConnectEnabled(target)) { wrapper = &CrossCompartmentWrapper::singleton; // If this is a chrome object being exposed to content without Xrays, use // a COW. } else if (originIsChrome && !targetIsChrome && xrayType == NotXray) { wrapper = &ChromeObjectWrapper::singleton; // If content is accessing a Components object or NAC, we need a special filter, // even if the object is same origin. } else if (IsComponentsObject(obj) && !AccessCheck::isChrome(target)) { wrapper = &FilteringWrapper<CrossCompartmentSecurityWrapper, ComponentsObjectPolicy>::singleton; } else if (AccessCheck::needsSystemOnlyWrapper(obj) && !(targetIsChrome || (targetSubsumesOrigin && nsContentUtils::IsCallerXBL()))) { wrapper = &FilteringWrapper<CrossCompartmentSecurityWrapper, OnlyIfSubjectIsSystem>::singleton; } // Normally, a non-xrayable non-waived content object that finds itself in // a privileged scope is wrapped with a CrossCompartmentWrapper, even though // the lack of a waiver _really_ should give it an opaque wrapper. This is // a bit too entrenched to change for content-chrome, but we can at least fix // it for XBL scopes. // // See bug 843829. else if (targetSubsumesOrigin && !originSubsumesTarget && !waiveXrayFlag && xrayType == NotXray && IsXBLScope(target)) { wrapper = &FilteringWrapper<CrossCompartmentSecurityWrapper, GentlyOpaque>::singleton; } // // Now, handle the regular cases. // // These are wrappers we can compute using a rule-based approach. In order // to do so, we need to compute some parameters. // else { // The wrapper is a security wrapper (protecting the wrappee) if and // only if the target does not subsume the origin. bool securityWrapper = !targetSubsumesOrigin; // Xrays are warranted if either the target or the origin don't trust // each other. This is generally the case, unless the two are same-origin // and the caller has not requested same-origin Xrays. // // Xrays are a bidirectional protection, since it affords clarity to the // caller and privacy to the callee. bool wantXrays = !(sameOrigin && !targetdata->wantXrays); // If Xrays are warranted, the caller may waive them for non-security // wrappers. bool waiveXrays = wantXrays && !securityWrapper && waiveXrayFlag; wrapper = SelectWrapper(securityWrapper, wantXrays, xrayType, waiveXrays); } // If the prototype of a chrome object being wrapped in content is a prototype // for a standard class, use the one from the content compartment so // that we can safely take advantage of things like .forEach(). // // If the prototype chain of chrome object |obj| looks like this: // // obj => foo => bar => chromeWin.StandardClass.prototype // // The prototype chain of COW(obj) looks lke this: // // COW(obj) => COW(foo) => COW(bar) => contentWin.StandardClass.prototype if (wrapper == &ChromeObjectWrapper::singleton) { JSProtoKey key = JSProto_Null; { JSAutoCompartment ac(cx, obj); RootedObject unwrappedProto(cx); if (!js::GetObjectProto(cx, obj, unwrappedProto.address())) return NULL; if (unwrappedProto && IsCrossCompartmentWrapper(unwrappedProto)) unwrappedProto = Wrapper::wrappedObject(unwrappedProto); if (unwrappedProto) { JSAutoCompartment ac2(cx, unwrappedProto); key = JS_IdentifyClassPrototype(cx, unwrappedProto); } } if (key != JSProto_Null) { RootedObject homeProto(cx); if (!JS_GetClassPrototype(cx, key, homeProto.address())) return NULL; MOZ_ASSERT(homeProto); proxyProto = homeProto; } // This shouldn't happen, but do a quick check to make some dumb addon // doesn't expose chrome eval or Function(). JSFunction *fun = JS_GetObjectFunction(obj); if (fun) { if (JS_IsBuiltinEvalFunction(fun) || JS_IsBuiltinFunctionConstructor(fun)) { JS_ReportError(cx, "Not allowed to access chrome eval or Function from content"); return nullptr; } } } DEBUG_CheckUnwrapSafety(obj, wrapper, origin, target); if (existing && proxyProto == wrappedProto) return Wrapper::Renew(cx, existing, obj, wrapper); return Wrapper::New(cx, obj, proxyProto, parent, wrapper); }