The Tor Browser: js/xpconnect/wrappers/WrapperFactory.cpp@6474c204b198 (annotated)

js/xpconnect/wrappers/WrapperFactory.cpp@6474c204b198 (annotated)

js/xpconnect/wrappers/WrapperFactory.cpp

Wed, 31 Dec 2014 06:09:35 +0100

author: Michael Schloh von Bennewitz <michael@schloh.com>
date: Wed, 31 Dec 2014 06:09:35 +0100
changeset 0: 6474c204b198
permissions: -rw-r--r--

Cloned upstream origin tor-browser at tor-browser-31.3.0esr-4.5-1-build1
revision ID fc1c9ff7c1b2defdbc039f12214767608f46423f for hacking purpose.

 /* -*- 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<CrossCompartmentSecurityWrapper, GentlyOpaque>::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<CrossCompartmentSecurityWrapper, OpaqueWithCall>::singleton;
         return &FilteringWrapper<CrossCompartmentSecurityWrapper, Opaque>::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<SecurityXrayXPCWN,
                                  CrossOriginAccessiblePropertiesOnly>::singleton;
     else if (xrayType == XrayForDOMObject)
         return &FilteringWrapper<SecurityXrayDOM,
                                  CrossOriginAccessiblePropertiesOnly>::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<CrossCompartmentSecurityWrapper, Opaque>::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<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;
         // 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<nsISupports *>(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<nsIXPConnectWrappedNative> wn = do_QueryInterface(native)) {
             native = wn->Native();
         }
     }
     nsCOMPtr<nsIGlobalObject> global = do_QueryInterface(native);
     MOZ_ASSERT(global, "Native held by global needs to implement nsIGlobalObject!");
     return global;
 }
 }

The Tor Browser / annotate

js/xpconnect/wrappers/WrapperFactory.cpp@6474c204b198 (annotated)

js/xpconnect/wrappers/WrapperFactory.cpp