michael@0: /* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 4 -*- */
michael@0: /* vim: set ts=8 sts=4 et sw=4 tw=99: */
michael@0: /* This Source Code Form is subject to the terms of the Mozilla Public
michael@0:  * License, v. 2.0. If a copy of the MPL was not distributed with this
michael@0:  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
michael@0: 
michael@0: #include "WaiveXrayWrapper.h"
michael@0: #include "FilteringWrapper.h"
michael@0: #include "XrayWrapper.h"
michael@0: #include "AccessCheck.h"
michael@0: #include "XPCWrapper.h"
michael@0: #include "ChromeObjectWrapper.h"
michael@0: #include "WrapperFactory.h"
michael@0: 
michael@0: #include "xpcprivate.h"
michael@0: #include "XPCMaps.h"
michael@0: #include "mozilla/dom/BindingUtils.h"
michael@0: #include "jsfriendapi.h"
michael@0: #include "mozilla/Likely.h"
michael@0: #include "nsContentUtils.h"
michael@0: 
michael@0: using namespace JS;
michael@0: using namespace js;
michael@0: using namespace mozilla;
michael@0: 
michael@0: namespace xpc {
michael@0: 
michael@0: // When chrome pulls a naked property across the membrane using
michael@0: // .wrappedJSObject, we want it to cross the membrane into the
michael@0: // chrome compartment without automatically being wrapped into an
michael@0: // X-ray wrapper. We achieve this by wrapping it into a special
michael@0: // transparent wrapper in the origin (non-chrome) compartment. When
michael@0: // an object with that special wrapper applied crosses into chrome,
michael@0: // we know to not apply an X-ray wrapper.
michael@0: Wrapper XrayWaiver(WrapperFactory::WAIVE_XRAY_WRAPPER_FLAG);
michael@0: 
michael@0: // When objects for which we waived the X-ray wrapper cross into
michael@0: // chrome, we wrap them into a special cross-compartment wrapper
michael@0: // that transitively extends the waiver to all properties we get
michael@0: // off it.
michael@0: WaiveXrayWrapper WaiveXrayWrapper::singleton(0);
michael@0: 
michael@0: bool
michael@0: WrapperFactory::IsCOW(JSObject *obj)
michael@0: {
michael@0:     return IsWrapper(obj) &&
michael@0:            Wrapper::wrapperHandler(obj) == &ChromeObjectWrapper::singleton;
michael@0: }
michael@0: 
michael@0: JSObject *
michael@0: WrapperFactory::GetXrayWaiver(HandleObject obj)
michael@0: {
michael@0:     // Object should come fully unwrapped but outerized.
michael@0:     MOZ_ASSERT(obj == UncheckedUnwrap(obj));
michael@0:     MOZ_ASSERT(!js::GetObjectClass(obj)->ext.outerObject);
michael@0:     XPCWrappedNativeScope *scope = GetObjectScope(obj);
michael@0:     MOZ_ASSERT(scope);
michael@0: 
michael@0:     if (!scope->mWaiverWrapperMap)
michael@0:         return nullptr;
michael@0: 
michael@0:     JSObject* xrayWaiver = scope->mWaiverWrapperMap->Find(obj);
michael@0:     if (xrayWaiver)
michael@0:         JS::ExposeObjectToActiveJS(xrayWaiver);
michael@0: 
michael@0:     return xrayWaiver;
michael@0: }
michael@0: 
michael@0: JSObject *
michael@0: WrapperFactory::CreateXrayWaiver(JSContext *cx, HandleObject obj)
michael@0: {
michael@0:     // The caller is required to have already done a lookup.
michael@0:     // NB: This implictly performs the assertions of GetXrayWaiver.
michael@0:     MOZ_ASSERT(!GetXrayWaiver(obj));
michael@0:     XPCWrappedNativeScope *scope = GetObjectScope(obj);
michael@0: 
michael@0:     JSAutoCompartment ac(cx, obj);
michael@0:     JSObject *waiver = Wrapper::New(cx, obj,
michael@0:                                     JS_GetGlobalForObject(cx, obj),
michael@0:                                     &XrayWaiver);
michael@0:     if (!waiver)
michael@0:         return nullptr;
michael@0: 
michael@0:     // Add the new waiver to the map. It's important that we only ever have
michael@0:     // one waiver for the lifetime of the target object.
michael@0:     if (!scope->mWaiverWrapperMap) {
michael@0:         scope->mWaiverWrapperMap =
michael@0:           JSObject2JSObjectMap::newMap(XPC_WRAPPER_MAP_SIZE);
michael@0:         MOZ_ASSERT(scope->mWaiverWrapperMap);
michael@0:     }
michael@0:     if (!scope->mWaiverWrapperMap->Add(cx, obj, waiver))
michael@0:         return nullptr;
michael@0:     return waiver;
michael@0: }
michael@0: 
michael@0: JSObject *
michael@0: WrapperFactory::WaiveXray(JSContext *cx, JSObject *objArg)
michael@0: {
michael@0:     RootedObject obj(cx, objArg);
michael@0:     obj = UncheckedUnwrap(obj);
michael@0:     MOZ_ASSERT(!js::IsInnerObject(obj));
michael@0: 
michael@0:     JSObject *waiver = GetXrayWaiver(obj);
michael@0:     if (waiver)
michael@0:         return waiver;
michael@0:     return CreateXrayWaiver(cx, obj);
michael@0: }
michael@0: 
michael@0: // DoubleWrap is called from PrepareForWrapping to maintain the state that
michael@0: // we're supposed to waive Xray wrappers for the given on. On entrance, it
michael@0: // expects |cx->compartment != obj->compartment()|. The returned object will
michael@0: // be in the same compartment as |obj|.
michael@0: JSObject *
michael@0: WrapperFactory::DoubleWrap(JSContext *cx, HandleObject obj, unsigned flags)
michael@0: {
michael@0:     if (flags & WrapperFactory::WAIVE_XRAY_WRAPPER_FLAG) {
michael@0:         JSAutoCompartment ac(cx, obj);
michael@0:         return WaiveXray(cx, obj);
michael@0:     }
michael@0:     return obj;
michael@0: }
michael@0: 
michael@0: JSObject *
michael@0: WrapperFactory::PrepareForWrapping(JSContext *cx, HandleObject scope,
michael@0:                                    HandleObject objArg, unsigned flags)
michael@0: {
michael@0:     RootedObject obj(cx, objArg);
michael@0:     // Outerize any raw inner objects at the entry point here, so that we don't
michael@0:     // have to worry about them for the rest of the wrapping code.
michael@0:     if (js::IsInnerObject(obj)) {
michael@0:         JSAutoCompartment ac(cx, obj);
michael@0:         obj = JS_ObjectToOuterObject(cx, obj);
michael@0:         NS_ENSURE_TRUE(obj, nullptr);
michael@0:         // The outerization hook wraps, which means that we can end up with a
michael@0:         // CCW here if |obj| was a navigated-away-from inner. Strip any CCWs.
michael@0:         obj = js::UncheckedUnwrap(obj);
michael@0:         MOZ_ASSERT(js::IsOuterObject(obj));
michael@0:     }
michael@0: 
michael@0:     // If we've got an outer window, there's nothing special that needs to be
michael@0:     // done here, and we can move on to the next phase of wrapping. We handle
michael@0:     // this case first to allow us to assert against wrappers below.
michael@0:     if (js::IsOuterObject(obj))
michael@0:         return DoubleWrap(cx, obj, flags);
michael@0: 
michael@0:     // Here are the rules for wrapping:
michael@0:     // We should never get a proxy here (the JS engine unwraps those for us).
michael@0:     MOZ_ASSERT(!IsWrapper(obj));
michael@0: 
michael@0:     // If the object being wrapped is a prototype for a standard class and the
michael@0:     // wrapper does not subsumes the wrappee, use the one from the content
michael@0:     // compartment. This is generally safer all-around, and in the COW case this
michael@0:     // lets us safely take advantage of things like .forEach() via the
michael@0:     // ChromeObjectWrapper machinery.
michael@0:     //
michael@0:     // If the prototype chain of chrome object |obj| looks like this:
michael@0:     //
michael@0:     // obj => foo => bar => chromeWin.StandardClass.prototype
michael@0:     //
michael@0:     // The prototype chain of COW(obj) looks lke this:
michael@0:     //
michael@0:     // COW(obj) => COW(foo) => COW(bar) => contentWin.StandardClass.prototype
michael@0:     //
michael@0:     // NB: We now remap all non-subsuming access of standard prototypes.
michael@0:     //
michael@0:     // NB: We need to ignore domain here so that the security relationship we
michael@0:     // compute here can't change over time. See the comment above the other
michael@0:     // subsumes call below.
michael@0:     bool subsumes = AccessCheck::subsumes(js::GetContextCompartment(cx),
michael@0:                                           js::GetObjectCompartment(obj));
michael@0:     XrayType xrayType = GetXrayType(obj);
michael@0:     if (!subsumes && xrayType == NotXray) {
michael@0:         JSProtoKey key = JSProto_Null;
michael@0:         {
michael@0:             JSAutoCompartment ac(cx, obj);
michael@0:             key = IdentifyStandardPrototype(obj);
michael@0:         }
michael@0:         if (key != JSProto_Null) {
michael@0:             RootedObject homeProto(cx);
michael@0:             if (!JS_GetClassPrototype(cx, key, &homeProto))
michael@0:                 return nullptr;
michael@0:             MOZ_ASSERT(homeProto);
michael@0:             // No need to double-wrap here. We should never have waivers to
michael@0:             // COWs.
michael@0:             return homeProto;
michael@0:         }
michael@0:     }
michael@0: 
michael@0:     // Now, our object is ready to be wrapped, but several objects (notably
michael@0:     // nsJSIIDs) have a wrapper per scope. If we are about to wrap one of
michael@0:     // those objects in a security wrapper, then we need to hand back the
michael@0:     // wrapper for the new scope instead. Also, global objects don't move
michael@0:     // between scopes so for those we also want to return the wrapper. So...
michael@0:     if (!IS_WN_REFLECTOR(obj) || !js::GetObjectParent(obj))
michael@0:         return DoubleWrap(cx, obj, flags);
michael@0: 
michael@0:     XPCWrappedNative *wn = XPCWrappedNative::Get(obj);
michael@0: 
michael@0:     JSAutoCompartment ac(cx, obj);
michael@0:     XPCCallContext ccx(JS_CALLER, cx, obj);
michael@0:     RootedObject wrapScope(cx, scope);
michael@0: 
michael@0:     {
michael@0:         if (NATIVE_HAS_FLAG(&ccx, WantPreCreate)) {
michael@0:             // We have a precreate hook. This object might enforce that we only
michael@0:             // ever create JS object for it.
michael@0: 
michael@0:             // Note: this penalizes objects that only have one wrapper, but are
michael@0:             // being accessed across compartments. We would really prefer to
michael@0:             // replace the above code with a test that says "do you only have one
michael@0:             // wrapper?"
michael@0:             nsresult rv = wn->GetScriptableInfo()->GetCallback()->
michael@0:                 PreCreate(wn->Native(), cx, scope, wrapScope.address());
michael@0:             NS_ENSURE_SUCCESS(rv, DoubleWrap(cx, obj, flags));
michael@0: 
michael@0:             // If the handed back scope differs from the passed-in scope and is in
michael@0:             // a separate compartment, then this object is explicitly requesting
michael@0:             // that we don't create a second JS object for it: create a security
michael@0:             // wrapper.
michael@0:             if (js::GetObjectCompartment(scope) != js::GetObjectCompartment(wrapScope))
michael@0:                 return DoubleWrap(cx, obj, flags);
michael@0: 
michael@0:             RootedObject currentScope(cx, JS_GetGlobalForObject(cx, obj));
michael@0:             if (MOZ_UNLIKELY(wrapScope != currentScope)) {
michael@0:                 // The wrapper claims it wants to be in the new scope, but
michael@0:                 // currently has a reflection that lives in the old scope. This
michael@0:                 // can mean one of two things, both of which are rare:
michael@0:                 //
michael@0:                 // 1 - The object has a PreCreate hook (we checked for it above),
michael@0:                 // but is deciding to request one-wrapper-per-scope (rather than
michael@0:                 // one-wrapper-per-native) for some reason. Usually, a PreCreate
michael@0:                 // hook indicates one-wrapper-per-native. In this case we want to
michael@0:                 // make a new wrapper in the new scope.
michael@0:                 //
michael@0:                 // 2 - We're midway through wrapper reparenting. The document has
michael@0:                 // moved to a new scope, but |wn| hasn't been moved yet, and
michael@0:                 // we ended up calling JS_WrapObject() on its JS object. In this
michael@0:                 // case, we want to return the existing wrapper.
michael@0:                 //
michael@0:                 // So we do a trick: call PreCreate _again_, but say that we're
michael@0:                 // wrapping for the old scope, rather than the new one. If (1) is
michael@0:                 // the case, then PreCreate will return the scope we pass to it
michael@0:                 // (the old scope). If (2) is the case, PreCreate will return the
michael@0:                 // scope of the document (the new scope).
michael@0:                 RootedObject probe(cx);
michael@0:                 rv = wn->GetScriptableInfo()->GetCallback()->
michael@0:                     PreCreate(wn->Native(), cx, currentScope, probe.address());
michael@0: 
michael@0:                 // Check for case (2).
michael@0:                 if (probe != currentScope) {
michael@0:                     MOZ_ASSERT(probe == wrapScope);
michael@0:                     return DoubleWrap(cx, obj, flags);
michael@0:                 }
michael@0: 
michael@0:                 // Ok, must be case (1). Fall through and create a new wrapper.
michael@0:             }
michael@0: 
michael@0:             // Nasty hack for late-breaking bug 781476. This will confuse identity checks,
michael@0:             // but it's probably better than any of our alternatives.
michael@0:             //
michael@0:             // Note: We have to ignore domain here. The JS engine assumes that, given a
michael@0:             // compartment c, if c->wrap(x) returns a cross-compartment wrapper at time t0,
michael@0:             // it will also return a cross-compartment wrapper for any time t1 > t0 unless
michael@0:             // an explicit transplant is performed. In particular, wrapper recomputation
michael@0:             // assumes that recomputing a wrapper will always result in a wrapper.
michael@0:             //
michael@0:             // This doesn't actually pose a security issue, because we'll still compute
michael@0:             // the correct (opaque) wrapper for the object below given the security
michael@0:             // characteristics of the two compartments.
michael@0:             if (!AccessCheck::isChrome(js::GetObjectCompartment(wrapScope)) &&
michael@0:                  AccessCheck::subsumes(js::GetObjectCompartment(wrapScope),
michael@0:                                        js::GetObjectCompartment(obj)))
michael@0:             {
michael@0:                 return DoubleWrap(cx, obj, flags);
michael@0:             }
michael@0:         }
michael@0:     }
michael@0: 
michael@0:     // This public WrapNativeToJSVal API enters the compartment of 'wrapScope'
michael@0:     // so we don't have to.
michael@0:     RootedValue v(cx);
michael@0:     nsresult rv =
michael@0:         nsXPConnect::XPConnect()->WrapNativeToJSVal(cx, wrapScope, wn->Native(), nullptr,
michael@0:                                                     &NS_GET_IID(nsISupports), false, &v);
michael@0:     NS_ENSURE_SUCCESS(rv, nullptr);
michael@0: 
michael@0:     obj.set(&v.toObject());
michael@0:     MOZ_ASSERT(IS_WN_REFLECTOR(obj), "bad object");
michael@0: 
michael@0:     // Because the underlying native didn't have a PreCreate hook, we had
michael@0:     // to a new (or possibly pre-existing) XPCWN in our compartment.
michael@0:     // This could be a problem for chrome code that passes XPCOM objects
michael@0:     // across compartments, because the effects of QI would disappear across
michael@0:     // compartments.
michael@0:     //
michael@0:     // So whenever we pull an XPCWN across compartments in this manner, we
michael@0:     // give the destination object the union of the two native sets. We try
michael@0:     // to do this cleverly in the common case to avoid too much overhead.
michael@0:     XPCWrappedNative *newwn = XPCWrappedNative::Get(obj);
michael@0:     XPCNativeSet *unionSet = XPCNativeSet::GetNewOrUsed(newwn->GetSet(),
michael@0:                                                         wn->GetSet(), false);
michael@0:     if (!unionSet)
michael@0:         return nullptr;
michael@0:     newwn->SetSet(unionSet);
michael@0: 
michael@0:     return DoubleWrap(cx, obj, flags);
michael@0: }
michael@0: 
michael@0: #ifdef DEBUG
michael@0: static void
michael@0: DEBUG_CheckUnwrapSafety(HandleObject obj, js::Wrapper *handler,
michael@0:                         JSCompartment *origin, JSCompartment *target)
michael@0: {
michael@0:     if (AccessCheck::isChrome(target) || xpc::IsUniversalXPConnectEnabled(target)) {
michael@0:         // If the caller is chrome (or effectively so), unwrap should always be allowed.
michael@0:         MOZ_ASSERT(!handler->hasSecurityPolicy());
michael@0:     } else if (handler == &FilteringWrapper<CrossCompartmentSecurityWrapper, GentlyOpaque>::singleton) {
michael@0:         // We explicitly use a SecurityWrapper to protect privileged callers from
michael@0:         // less-privileged objects that they should never see. Skip the check in
michael@0:         // this case.
michael@0:     } else {
michael@0:         // Otherwise, it should depend on whether the target subsumes the origin.
michael@0:         MOZ_ASSERT(handler->hasSecurityPolicy() == !AccessCheck::subsumesConsideringDomain(target, origin));
michael@0:     }
michael@0: }
michael@0: #else
michael@0: #define DEBUG_CheckUnwrapSafety(obj, handler, origin, target) {}
michael@0: #endif
michael@0: 
michael@0: static Wrapper *
michael@0: SelectWrapper(bool securityWrapper, bool wantXrays, XrayType xrayType,
michael@0:               bool waiveXrays, bool originIsXBLScope)
michael@0: {
michael@0:     // Waived Xray uses a modified CCW that has transparent behavior but
michael@0:     // transitively waives Xrays on arguments.
michael@0:     if (waiveXrays) {
michael@0:         MOZ_ASSERT(!securityWrapper);
michael@0:         return &WaiveXrayWrapper::singleton;
michael@0:     }
michael@0: 
michael@0:     // If we don't want or can't use Xrays, select a wrapper that's either
michael@0:     // entirely transparent or entirely opaque.
michael@0:     if (!wantXrays || xrayType == NotXray) {
michael@0:         if (!securityWrapper)
michael@0:             return &CrossCompartmentWrapper::singleton;
michael@0:         // In general, we don't want opaque function wrappers to be callable.
michael@0:         // But in the case of XBL, we rely on content being able to invoke
michael@0:         // functions exposed from the XBL scope. We could remove this exception,
michael@0:         // if needed, by using ExportFunction to generate the content-side
michael@0:         // representations of XBL methods.
michael@0:         else if (originIsXBLScope)
michael@0:             return &FilteringWrapper<CrossCompartmentSecurityWrapper, OpaqueWithCall>::singleton;
michael@0:         return &FilteringWrapper<CrossCompartmentSecurityWrapper, Opaque>::singleton;
michael@0:     }
michael@0: 
michael@0:     // Ok, we're using Xray. If this isn't a security wrapper, use the permissive
michael@0:     // version and skip the filter.
michael@0:     if (!securityWrapper) {
michael@0:         if (xrayType == XrayForWrappedNative)
michael@0:             return &PermissiveXrayXPCWN::singleton;
michael@0:         else if (xrayType == XrayForDOMObject)
michael@0:             return &PermissiveXrayDOM::singleton;
michael@0:         MOZ_ASSERT(xrayType == XrayForJSObject);
michael@0:         return &PermissiveXrayJS::singleton;
michael@0:     }
michael@0: 
michael@0:     // This is a security wrapper. Use the security versions and filter.
michael@0:     if (xrayType == XrayForWrappedNative)
michael@0:         return &FilteringWrapper<SecurityXrayXPCWN,
michael@0:                                  CrossOriginAccessiblePropertiesOnly>::singleton;
michael@0:     else if (xrayType == XrayForDOMObject)
michael@0:         return &FilteringWrapper<SecurityXrayDOM,
michael@0:                                  CrossOriginAccessiblePropertiesOnly>::singleton;
michael@0:     // There's never any reason to expose pure JS objects to non-subsuming actors.
michael@0:     // Just use an opaque wrapper in this case.
michael@0:     MOZ_ASSERT(xrayType == XrayForJSObject);
michael@0:     return &FilteringWrapper<CrossCompartmentSecurityWrapper, Opaque>::singleton;
michael@0: }
michael@0: 
michael@0: JSObject *
michael@0: WrapperFactory::Rewrap(JSContext *cx, HandleObject existing, HandleObject obj,
michael@0:                        HandleObject wrappedProto, HandleObject parent,
michael@0:                        unsigned flags)
michael@0: {
michael@0:     MOZ_ASSERT(!IsWrapper(obj) ||
michael@0:                GetProxyHandler(obj) == &XrayWaiver ||
michael@0:                js::GetObjectClass(obj)->ext.innerObject,
michael@0:                "wrapped object passed to rewrap");
michael@0:     MOZ_ASSERT(!XrayUtils::IsXPCWNHolderClass(JS_GetClass(obj)), "trying to wrap a holder");
michael@0:     MOZ_ASSERT(!js::IsInnerObject(obj));
michael@0:     // We sometimes end up here after nsContentUtils has been shut down but before
michael@0:     // XPConnect has been shut down, so check the context stack the roundabout way.
michael@0:     MOZ_ASSERT(XPCJSRuntime::Get()->GetJSContextStack()->Peek() == cx);
michael@0: 
michael@0:     // Compute the information we need to select the right wrapper.
michael@0:     JSCompartment *origin = js::GetObjectCompartment(obj);
michael@0:     JSCompartment *target = js::GetContextCompartment(cx);
michael@0:     bool originIsChrome = AccessCheck::isChrome(origin);
michael@0:     bool targetIsChrome = AccessCheck::isChrome(target);
michael@0:     bool originSubsumesTarget = AccessCheck::subsumesConsideringDomain(origin, target);
michael@0:     bool targetSubsumesOrigin = AccessCheck::subsumesConsideringDomain(target, origin);
michael@0:     bool sameOrigin = targetSubsumesOrigin && originSubsumesTarget;
michael@0:     XrayType xrayType = GetXrayType(obj);
michael@0:     bool waiveXrayFlag = flags & WAIVE_XRAY_WRAPPER_FLAG;
michael@0: 
michael@0:     Wrapper *wrapper;
michael@0:     CompartmentPrivate *targetdata = EnsureCompartmentPrivate(target);
michael@0: 
michael@0:     //
michael@0:     // First, handle the special cases.
michael@0:     //
michael@0: 
michael@0:     // If UniversalXPConnect is enabled, this is just some dumb mochitest. Use
michael@0:     // a vanilla CCW.
michael@0:     if (xpc::IsUniversalXPConnectEnabled(target)) {
michael@0:         wrapper = &CrossCompartmentWrapper::singleton;
michael@0:     }
michael@0: 
michael@0:     // If this is a chrome object being exposed to content without Xrays, use
michael@0:     // a COW.
michael@0:     else if (originIsChrome && !targetIsChrome && xrayType == NotXray) {
michael@0:         wrapper = &ChromeObjectWrapper::singleton;
michael@0:     }
michael@0: 
michael@0:     // Normally, a non-xrayable non-waived content object that finds itself in
michael@0:     // a privileged scope is wrapped with a CrossCompartmentWrapper, even though
michael@0:     // the lack of a waiver _really_ should give it an opaque wrapper. This is
michael@0:     // a bit too entrenched to change for content-chrome, but we can at least fix
michael@0:     // it for XBL scopes.
michael@0:     //
michael@0:     // See bug 843829.
michael@0:     else if (targetSubsumesOrigin && !originSubsumesTarget &&
michael@0:              !waiveXrayFlag && xrayType == NotXray &&
michael@0:              IsXBLScope(target))
michael@0:     {
michael@0:         wrapper = &FilteringWrapper<CrossCompartmentSecurityWrapper, GentlyOpaque>::singleton;
michael@0:     }
michael@0: 
michael@0:     //
michael@0:     // Now, handle the regular cases.
michael@0:     //
michael@0:     // These are wrappers we can compute using a rule-based approach. In order
michael@0:     // to do so, we need to compute some parameters.
michael@0:     //
michael@0:     else {
michael@0: 
michael@0:         // The wrapper is a security wrapper (protecting the wrappee) if and
michael@0:         // only if the target does not subsume the origin.
michael@0:         bool securityWrapper = !targetSubsumesOrigin;
michael@0: 
michael@0:         // Xrays are warranted if either the target or the origin don't trust
michael@0:         // each other. This is generally the case, unless the two are same-origin
michael@0:         // and the caller has not requested same-origin Xrays.
michael@0:         //
michael@0:         // Xrays are a bidirectional protection, since it affords clarity to the
michael@0:         // caller and privacy to the callee.
michael@0:         bool wantXrays = !(sameOrigin && !targetdata->wantXrays);
michael@0: 
michael@0:         // If Xrays are warranted, the caller may waive them for non-security
michael@0:         // wrappers.
michael@0:         bool waiveXrays = wantXrays && !securityWrapper && waiveXrayFlag;
michael@0: 
michael@0:         // We have slightly different behavior for the case when the object
michael@0:         // being wrapped is in an XBL scope.
michael@0:         bool originIsXBLScope = IsXBLScope(origin);
michael@0: 
michael@0:         wrapper = SelectWrapper(securityWrapper, wantXrays, xrayType, waiveXrays,
michael@0:                                 originIsXBLScope);
michael@0:     }
michael@0: 
michael@0:     if (!targetSubsumesOrigin) {
michael@0:         // Do a belt-and-suspenders check against exposing eval()/Function() to
michael@0:         // non-subsuming content.
michael@0:         JSFunction *fun = JS_GetObjectFunction(obj);
michael@0:         if (fun) {
michael@0:             if (JS_IsBuiltinEvalFunction(fun) || JS_IsBuiltinFunctionConstructor(fun)) {
michael@0:                 JS_ReportError(cx, "Permission denied to expose eval or Function to non-subsuming content");
michael@0:                 return nullptr;
michael@0:             }
michael@0:         }
michael@0:     }
michael@0: 
michael@0:     DEBUG_CheckUnwrapSafety(obj, wrapper, origin, target);
michael@0: 
michael@0:     if (existing)
michael@0:         return Wrapper::Renew(cx, existing, obj, wrapper);
michael@0: 
michael@0:     return Wrapper::New(cx, obj, parent, wrapper);
michael@0: }
michael@0: 
michael@0: // Call WaiveXrayAndWrap when you have a JS object that you don't want to be
michael@0: // wrapped in an Xray wrapper. cx->compartment is the compartment that will be
michael@0: // using the returned object. If the object to be wrapped is already in the
michael@0: // correct compartment, then this returns the unwrapped object.
michael@0: bool
michael@0: WrapperFactory::WaiveXrayAndWrap(JSContext *cx, MutableHandleValue vp)
michael@0: {
michael@0:     if (vp.isPrimitive())
michael@0:         return JS_WrapValue(cx, vp);
michael@0: 
michael@0:     RootedObject obj(cx, &vp.toObject());
michael@0:     if (!WaiveXrayAndWrap(cx, &obj))
michael@0:         return false;
michael@0: 
michael@0:     vp.setObject(*obj);
michael@0:     return true;
michael@0: }
michael@0: 
michael@0: bool
michael@0: WrapperFactory::WaiveXrayAndWrap(JSContext *cx, MutableHandleObject argObj)
michael@0: {
michael@0:     MOZ_ASSERT(argObj);
michael@0:     RootedObject obj(cx, js::UncheckedUnwrap(argObj));
michael@0:     MOZ_ASSERT(!js::IsInnerObject(obj));
michael@0:     if (js::IsObjectInContextCompartment(obj, cx)) {
michael@0:         argObj.set(obj);
michael@0:         return true;
michael@0:     }
michael@0: 
michael@0:     // Even though waivers have no effect on access by scopes that don't subsume
michael@0:     // the underlying object, good defense-in-depth dictates that we should avoid
michael@0:     // handing out waivers to callers that can't use them. The transitive waiving
michael@0:     // machinery unconditionally calls WaiveXrayAndWrap on return values from
michael@0:     // waived functions, even though the return value might be not be same-origin
michael@0:     // with the function. So if we find ourselves trying to create a waiver for
michael@0:     // |cx|, we should check whether the caller has any business with waivers
michael@0:     // to things in |obj|'s compartment.
michael@0:     JSCompartment *target = js::GetContextCompartment(cx);
michael@0:     JSCompartment *origin = js::GetObjectCompartment(obj);
michael@0:     obj = AccessCheck::subsumes(target, origin) ? WaiveXray(cx, obj) : obj;
michael@0:     if (!obj)
michael@0:         return false;
michael@0: 
michael@0:     if (!JS_WrapObject(cx, &obj))
michael@0:         return false;
michael@0:     argObj.set(obj);
michael@0:     return true;
michael@0: }
michael@0: 
michael@0: bool
michael@0: WrapperFactory::XrayWrapperNotShadowing(JSObject *wrapper, jsid id)
michael@0: {
michael@0:     ResolvingId *rid = ResolvingId::getResolvingIdFromWrapper(wrapper);
michael@0:     return rid->isXrayShadowing(id);
michael@0: }
michael@0: 
michael@0: /*
michael@0:  * Calls to JS_TransplantObject* should go through these helpers here so that
michael@0:  * waivers get fixed up properly.
michael@0:  */
michael@0: 
michael@0: static bool
michael@0: FixWaiverAfterTransplant(JSContext *cx, HandleObject oldWaiver, HandleObject newobj)
michael@0: {
michael@0:     MOZ_ASSERT(Wrapper::wrapperHandler(oldWaiver) == &XrayWaiver);
michael@0:     MOZ_ASSERT(!js::IsCrossCompartmentWrapper(newobj));
michael@0: 
michael@0:     // Create a waiver in the new compartment. We know there's not one already
michael@0:     // because we _just_ transplanted, which means that |newobj| was either
michael@0:     // created from scratch, or was previously cross-compartment wrapper (which
michael@0:     // should have no waiver). CreateXrayWaiver asserts this.
michael@0:     JSObject *newWaiver = WrapperFactory::CreateXrayWaiver(cx, newobj);
michael@0:     if (!newWaiver)
michael@0:         return false;
michael@0: 
michael@0:     // Update all the cross-compartment references to oldWaiver to point to
michael@0:     // newWaiver.
michael@0:     if (!js::RemapAllWrappersForObject(cx, oldWaiver, newWaiver))
michael@0:         return false;
michael@0: 
michael@0:     // There should be no same-compartment references to oldWaiver, and we
michael@0:     // just remapped all cross-compartment references. It's dead, so we can
michael@0:     // remove it from the map.
michael@0:     XPCWrappedNativeScope *scope = GetObjectScope(oldWaiver);
michael@0:     JSObject *key = Wrapper::wrappedObject(oldWaiver);
michael@0:     MOZ_ASSERT(scope->mWaiverWrapperMap->Find(key));
michael@0:     scope->mWaiverWrapperMap->Remove(key);
michael@0:     return true;
michael@0: }
michael@0: 
michael@0: JSObject *
michael@0: TransplantObject(JSContext *cx, JS::HandleObject origobj, JS::HandleObject target)
michael@0: {
michael@0:     RootedObject oldWaiver(cx, WrapperFactory::GetXrayWaiver(origobj));
michael@0:     RootedObject newIdentity(cx, JS_TransplantObject(cx, origobj, target));
michael@0:     if (!newIdentity || !oldWaiver)
michael@0:        return newIdentity;
michael@0: 
michael@0:     if (!FixWaiverAfterTransplant(cx, oldWaiver, newIdentity))
michael@0:         return nullptr;
michael@0:     return newIdentity;
michael@0: }
michael@0: 
michael@0: nsIGlobalObject *
michael@0: GetNativeForGlobal(JSObject *obj)
michael@0: {
michael@0:     MOZ_ASSERT(JS_IsGlobalObject(obj));
michael@0:     if (!MaybeGetObjectScope(obj))
michael@0:         return nullptr;
michael@0: 
michael@0:     // Every global needs to hold a native as its private or be a
michael@0:     // WebIDL object with an nsISupports DOM object.
michael@0:     MOZ_ASSERT((GetObjectClass(obj)->flags & (JSCLASS_PRIVATE_IS_NSISUPPORTS |
michael@0:                                              JSCLASS_HAS_PRIVATE)) ||
michael@0:                dom::UnwrapDOMObjectToISupports(obj));
michael@0: 
michael@0:     nsISupports *native = dom::UnwrapDOMObjectToISupports(obj);
michael@0:     if (!native) {
michael@0:         native = static_cast<nsISupports *>(js::GetObjectPrivate(obj));
michael@0:         MOZ_ASSERT(native);
michael@0: 
michael@0:         // In some cases (like for windows) it is a wrapped native,
michael@0:         // in other cases (sandboxes, backstage passes) it's just
michael@0:         // a direct pointer to the native. If it's a wrapped native
michael@0:         // let's unwrap it first.
michael@0:         if (nsCOMPtr<nsIXPConnectWrappedNative> wn = do_QueryInterface(native)) {
michael@0:             native = wn->Native();
michael@0:         }
michael@0:     }
michael@0: 
michael@0:     nsCOMPtr<nsIGlobalObject> global = do_QueryInterface(native);
michael@0:     MOZ_ASSERT(global, "Native held by global needs to implement nsIGlobalObject!");
michael@0: 
michael@0:     return global;
michael@0: }
michael@0: 
michael@0: }