/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 4 -*- */ /* vim: set ts=8 sts=4 et sw=4 tw=99: */ /* 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 "WaiveXrayWrapper.h" #include "FilteringWrapper.h" #include "XrayWrapper.h" #include "AccessCheck.h" #include "XPCWrapper.h" #include "ChromeObjectWrapper.h" #include "WrapperFactory.h" #include "xpcprivate.h" #include "XPCMaps.h" #include "mozilla/dom/BindingUtils.h" #include "jsfriendapi.h" #include "mozilla/Likely.h" #include "nsContentUtils.h" using namespace JS; using namespace js; using namespace mozilla; namespace xpc { // When chrome pulls a naked property across the membrane using // .wrappedJSObject, we want it to cross the membrane into the // chrome compartment without automatically being wrapped into an // X-ray wrapper. We achieve this by wrapping it into a special // transparent wrapper in the origin (non-chrome) compartment. When // an object with that special wrapper applied crosses into chrome, // we know to not apply an X-ray wrapper. Wrapper XrayWaiver(WrapperFactory::WAIVE_XRAY_WRAPPER_FLAG); // When objects for which we waived the X-ray wrapper cross into // chrome, we wrap them into a special cross-compartment wrapper // that transitively extends the waiver to all properties we get // off it. WaiveXrayWrapper WaiveXrayWrapper::singleton(0); bool WrapperFactory::IsCOW(JSObject *obj) { return IsWrapper(obj) && Wrapper::wrapperHandler(obj) == &ChromeObjectWrapper::singleton; } JSObject * WrapperFactory::GetXrayWaiver(HandleObject obj) { // Object should come fully unwrapped but outerized. MOZ_ASSERT(obj == UncheckedUnwrap(obj)); MOZ_ASSERT(!js::GetObjectClass(obj)->ext.outerObject); XPCWrappedNativeScope *scope = GetObjectScope(obj); MOZ_ASSERT(scope); if (!scope->mWaiverWrapperMap) return nullptr; JSObject* xrayWaiver = scope->mWaiverWrapperMap->Find(obj); if (xrayWaiver) JS::ExposeObjectToActiveJS(xrayWaiver); return xrayWaiver; } JSObject * WrapperFactory::CreateXrayWaiver(JSContext *cx, HandleObject obj) { // The caller is required to have already done a lookup. // NB: This implictly performs the assertions of GetXrayWaiver. MOZ_ASSERT(!GetXrayWaiver(obj)); XPCWrappedNativeScope *scope = GetObjectScope(obj); JSAutoCompartment ac(cx, obj); JSObject *waiver = Wrapper::New(cx, obj, JS_GetGlobalForObject(cx, obj), &XrayWaiver); if (!waiver) return nullptr; // Add the new waiver to the map. It's important that we only ever have // one waiver for the lifetime of the target object. if (!scope->mWaiverWrapperMap) { scope->mWaiverWrapperMap = JSObject2JSObjectMap::newMap(XPC_WRAPPER_MAP_SIZE); MOZ_ASSERT(scope->mWaiverWrapperMap); } if (!scope->mWaiverWrapperMap->Add(cx, obj, waiver)) return nullptr; return waiver; } JSObject * WrapperFactory::WaiveXray(JSContext *cx, JSObject *objArg) { RootedObject obj(cx, objArg); obj = UncheckedUnwrap(obj); MOZ_ASSERT(!js::IsInnerObject(obj)); JSObject *waiver = GetXrayWaiver(obj); if (waiver) return waiver; return CreateXrayWaiver(cx, obj); } // DoubleWrap is called from PrepareForWrapping to maintain the state that // we're supposed to waive Xray wrappers for the given on. On entrance, it // expects |cx->compartment != obj->compartment()|. The returned object will // be in the same compartment as |obj|. JSObject * WrapperFactory::DoubleWrap(JSContext *cx, HandleObject obj, unsigned flags) { if (flags & WrapperFactory::WAIVE_XRAY_WRAPPER_FLAG) { JSAutoCompartment ac(cx, obj); return WaiveXray(cx, obj); } return obj; } 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); } #ifdef DEBUG static void DEBUG_CheckUnwrapSafety(HandleObject obj, js::Wrapper *handler, JSCompartment *origin, JSCompartment *target) { if (AccessCheck::isChrome(target) || xpc::IsUniversalXPConnectEnabled(target)) { // If the caller is chrome (or effectively so), unwrap should always be allowed. MOZ_ASSERT(!handler->hasSecurityPolicy()); } else if (handler == &FilteringWrapper::singleton) { // We explicitly use a SecurityWrapper to protect privileged callers from // less-privileged objects that they should never see. Skip the check in // this case. } else { // Otherwise, it should depend on whether the target subsumes the origin. MOZ_ASSERT(handler->hasSecurityPolicy() == !AccessCheck::subsumesConsideringDomain(target, origin)); } } #else #define DEBUG_CheckUnwrapSafety(obj, handler, origin, target) {} #endif static Wrapper * SelectWrapper(bool securityWrapper, bool wantXrays, XrayType xrayType, bool waiveXrays, bool originIsXBLScope) { // Waived Xray uses a modified CCW that has transparent behavior but // transitively waives Xrays on arguments. if (waiveXrays) { MOZ_ASSERT(!securityWrapper); return &WaiveXrayWrapper::singleton; } // If we don't want or can't use Xrays, select a wrapper that's either // entirely transparent or entirely opaque. if (!wantXrays || xrayType == NotXray) { if (!securityWrapper) return &CrossCompartmentWrapper::singleton; // In general, we don't want opaque function wrappers to be callable. // But in the case of XBL, we rely on content being able to invoke // functions exposed from the XBL scope. We could remove this exception, // if needed, by using ExportFunction to generate the content-side // representations of XBL methods. else if (originIsXBLScope) return &FilteringWrapper::singleton; return &FilteringWrapper::singleton; } // Ok, we're using Xray. If this isn't a security wrapper, use the permissive // version and skip the filter. if (!securityWrapper) { if (xrayType == XrayForWrappedNative) return &PermissiveXrayXPCWN::singleton; else if (xrayType == XrayForDOMObject) return &PermissiveXrayDOM::singleton; MOZ_ASSERT(xrayType == XrayForJSObject); return &PermissiveXrayJS::singleton; } // This is a security wrapper. Use the security versions and filter. if (xrayType == XrayForWrappedNative) return &FilteringWrapper::singleton; else if (xrayType == XrayForDOMObject) return &FilteringWrapper::singleton; // There's never any reason to expose pure JS objects to non-subsuming actors. // Just use an opaque wrapper in this case. MOZ_ASSERT(xrayType == XrayForJSObject); return &FilteringWrapper::singleton; } 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(!XrayUtils::IsXPCWNHolderClass(JS_GetClass(obj)), "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::subsumesConsideringDomain(origin, target); bool targetSubsumesOrigin = AccessCheck::subsumesConsideringDomain(target, origin); bool sameOrigin = targetSubsumesOrigin && originSubsumesTarget; XrayType xrayType = GetXrayType(obj); bool waiveXrayFlag = flags & WAIVE_XRAY_WRAPPER_FLAG; 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; } // 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::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; // We have slightly different behavior for the case when the object // being wrapped is in an XBL scope. bool originIsXBLScope = IsXBLScope(origin); wrapper = SelectWrapper(securityWrapper, wantXrays, xrayType, waiveXrays, originIsXBLScope); } if (!targetSubsumesOrigin) { // Do a belt-and-suspenders check against exposing eval()/Function() to // non-subsuming content. JSFunction *fun = JS_GetObjectFunction(obj); if (fun) { if (JS_IsBuiltinEvalFunction(fun) || JS_IsBuiltinFunctionConstructor(fun)) { JS_ReportError(cx, "Permission denied to expose eval or Function to non-subsuming content"); return nullptr; } } } DEBUG_CheckUnwrapSafety(obj, wrapper, origin, target); if (existing) return Wrapper::Renew(cx, existing, obj, wrapper); return Wrapper::New(cx, obj, parent, wrapper); } // Call WaiveXrayAndWrap when you have a JS object that you don't want to be // wrapped in an Xray wrapper. cx->compartment is the compartment that will be // using the returned object. If the object to be wrapped is already in the // correct compartment, then this returns the unwrapped object. bool WrapperFactory::WaiveXrayAndWrap(JSContext *cx, MutableHandleValue vp) { if (vp.isPrimitive()) return JS_WrapValue(cx, vp); RootedObject obj(cx, &vp.toObject()); if (!WaiveXrayAndWrap(cx, &obj)) return false; vp.setObject(*obj); return true; } bool WrapperFactory::WaiveXrayAndWrap(JSContext *cx, MutableHandleObject argObj) { MOZ_ASSERT(argObj); RootedObject obj(cx, js::UncheckedUnwrap(argObj)); MOZ_ASSERT(!js::IsInnerObject(obj)); if (js::IsObjectInContextCompartment(obj, cx)) { argObj.set(obj); return true; } // Even though waivers have no effect on access by scopes that don't subsume // the underlying object, good defense-in-depth dictates that we should avoid // handing out waivers to callers that can't use them. The transitive waiving // machinery unconditionally calls WaiveXrayAndWrap on return values from // waived functions, even though the return value might be not be same-origin // with the function. So if we find ourselves trying to create a waiver for // |cx|, we should check whether the caller has any business with waivers // to things in |obj|'s compartment. JSCompartment *target = js::GetContextCompartment(cx); JSCompartment *origin = js::GetObjectCompartment(obj); obj = AccessCheck::subsumes(target, origin) ? WaiveXray(cx, obj) : obj; if (!obj) return false; if (!JS_WrapObject(cx, &obj)) return false; argObj.set(obj); return true; } bool WrapperFactory::XrayWrapperNotShadowing(JSObject *wrapper, jsid id) { ResolvingId *rid = ResolvingId::getResolvingIdFromWrapper(wrapper); return rid->isXrayShadowing(id); } /* * Calls to JS_TransplantObject* should go through these helpers here so that * waivers get fixed up properly. */ static bool FixWaiverAfterTransplant(JSContext *cx, HandleObject oldWaiver, HandleObject newobj) { MOZ_ASSERT(Wrapper::wrapperHandler(oldWaiver) == &XrayWaiver); MOZ_ASSERT(!js::IsCrossCompartmentWrapper(newobj)); // Create a waiver in the new compartment. We know there's not one already // because we _just_ transplanted, which means that |newobj| was either // created from scratch, or was previously cross-compartment wrapper (which // should have no waiver). CreateXrayWaiver asserts this. JSObject *newWaiver = WrapperFactory::CreateXrayWaiver(cx, newobj); if (!newWaiver) return false; // Update all the cross-compartment references to oldWaiver to point to // newWaiver. if (!js::RemapAllWrappersForObject(cx, oldWaiver, newWaiver)) return false; // There should be no same-compartment references to oldWaiver, and we // just remapped all cross-compartment references. It's dead, so we can // remove it from the map. XPCWrappedNativeScope *scope = GetObjectScope(oldWaiver); JSObject *key = Wrapper::wrappedObject(oldWaiver); MOZ_ASSERT(scope->mWaiverWrapperMap->Find(key)); scope->mWaiverWrapperMap->Remove(key); return true; } JSObject * TransplantObject(JSContext *cx, JS::HandleObject origobj, JS::HandleObject target) { RootedObject oldWaiver(cx, WrapperFactory::GetXrayWaiver(origobj)); RootedObject newIdentity(cx, JS_TransplantObject(cx, origobj, target)); if (!newIdentity || !oldWaiver) return newIdentity; if (!FixWaiverAfterTransplant(cx, oldWaiver, newIdentity)) return nullptr; return newIdentity; } nsIGlobalObject * GetNativeForGlobal(JSObject *obj) { MOZ_ASSERT(JS_IsGlobalObject(obj)); if (!MaybeGetObjectScope(obj)) return nullptr; // Every global needs to hold a native as its private or be a // WebIDL object with an nsISupports DOM object. MOZ_ASSERT((GetObjectClass(obj)->flags & (JSCLASS_PRIVATE_IS_NSISUPPORTS | JSCLASS_HAS_PRIVATE)) || dom::UnwrapDOMObjectToISupports(obj)); nsISupports *native = dom::UnwrapDOMObjectToISupports(obj); if (!native) { native = static_cast(js::GetObjectPrivate(obj)); MOZ_ASSERT(native); // In some cases (like for windows) it is a wrapped native, // in other cases (sandboxes, backstage passes) it's just // a direct pointer to the native. If it's a wrapped native // let's unwrap it first. if (nsCOMPtr wn = do_QueryInterface(native)) { native = wn->Native(); } } nsCOMPtr global = do_QueryInterface(native); MOZ_ASSERT(global, "Native held by global needs to implement nsIGlobalObject!"); return global; } }