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/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/* vim: set ts=8 sts=2 et sw=2 tw=80: */
/* 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
#include "xpcprivate.h"
#include "WrapperFactory.h"
#include "AccessCheck.h"
#include "jsfriendapi.h"
#include "js/CallAndConstruct.h" // JS::Call, JS::Construct, JS::IsCallable
#include "js/Exception.h"
#include "js/PropertyAndElement.h" // JS_DefineProperty, JS_DefinePropertyById
#include "js/Proxy.h"
#include "js/Wrapper.h"
#include "mozilla/ErrorResult.h"
#include "mozilla/Unused.h"
#include "mozilla/dom/BindingUtils.h"
#include "mozilla/dom/BlobBinding.h"
#include "mozilla/dom/BlobImpl.h"
#include "mozilla/dom/File.h"
#include "mozilla/dom/StructuredCloneHolder.h"
#include "nsContentUtils.h"
#include "nsJSUtils.h"
#include "js/Object.h" // JS::GetCompartment
using namespace mozilla;
using namespace mozilla::dom;
using namespace JS;
namespace xpc {
bool IsReflector(JSObject* obj, JSContext* cx) {
obj = js::CheckedUnwrapDynamic(obj, cx, /* stopAtWindowProxy = */ false);
if (!obj) {
return false;
}
return IsWrappedNativeReflector(obj) || dom::IsDOMObject(obj);
}
enum StackScopedCloneTags : uint32_t {
SCTAG_BASE = JS_SCTAG_USER_MIN,
SCTAG_REFLECTOR,
SCTAG_BLOB,
SCTAG_FUNCTION,
};
class MOZ_STACK_CLASS StackScopedCloneData : public StructuredCloneHolderBase {
public:
StackScopedCloneData(JSContext* aCx, StackScopedCloneOptions* aOptions)
: mOptions(aOptions), mReflectors(aCx), mFunctions(aCx) {}
~StackScopedCloneData() { Clear(); }
JSObject* CustomReadHandler(JSContext* aCx, JSStructuredCloneReader* aReader,
const JS::CloneDataPolicy& aCloneDataPolicy,
uint32_t aTag, uint32_t aData) override {
if (aTag == SCTAG_REFLECTOR) {
MOZ_ASSERT(!aData);
size_t idx;
if (!JS_ReadBytes(aReader, &idx, sizeof(size_t))) {
return nullptr;
}
RootedObject reflector(aCx, mReflectors[idx]);
MOZ_ASSERT(reflector, "No object pointer?");
MOZ_ASSERT(IsReflector(reflector, aCx),
"Object pointer must be a reflector!");
if (!JS_WrapObject(aCx, &reflector)) {
return nullptr;
}
return reflector;
}
if (aTag == SCTAG_FUNCTION) {
MOZ_ASSERT(aData < mFunctions.length());
RootedValue functionValue(aCx);
RootedObject obj(aCx, mFunctions[aData]);
if (!JS_WrapObject(aCx, &obj)) {
return nullptr;
}
FunctionForwarderOptions forwarderOptions;
if (!xpc::NewFunctionForwarder(aCx, JS::VoidHandlePropertyKey, obj,
forwarderOptions, &functionValue)) {
return nullptr;
}
return &functionValue.toObject();
}
if (aTag == SCTAG_BLOB) {
MOZ_ASSERT(!aData);
size_t idx;
if (!JS_ReadBytes(aReader, &idx, sizeof(size_t))) {
return nullptr;
}
nsIGlobalObject* global = xpc::CurrentNativeGlobal(aCx);
MOZ_ASSERT(global);
// RefPtr<File> needs to go out of scope before toObjectOrNull() is called
// because otherwise the static analysis thinks it can gc the JSObject via
// the stack.
JS::Rooted<JS::Value> val(aCx);
{
RefPtr<Blob> blob = Blob::Create(global, mBlobImpls[idx]);
if (NS_WARN_IF(!blob)) {
return nullptr;
}
if (!ToJSValue(aCx, blob, &val)) {
return nullptr;
}
}
return val.toObjectOrNull();
}
MOZ_ASSERT_UNREACHABLE("Encountered garbage in the clone stream!");
return nullptr;
}
bool CustomWriteHandler(JSContext* aCx, JSStructuredCloneWriter* aWriter,
JS::Handle<JSObject*> aObj,
bool* aSameProcessScopeRequired) override {
{
JS::Rooted<JSObject*> obj(aCx, aObj);
Blob* blob = nullptr;
if (NS_SUCCEEDED(UNWRAP_OBJECT(Blob, &obj, blob))) {
BlobImpl* blobImpl = blob->Impl();
MOZ_ASSERT(blobImpl);
// pretended earlier.
mBlobImpls.AppendElement(blobImpl);
size_t idx = mBlobImpls.Length() - 1;
return JS_WriteUint32Pair(aWriter, SCTAG_BLOB, 0) &&
JS_WriteBytes(aWriter, &idx, sizeof(size_t));
}
}
if (mOptions->wrapReflectors && IsReflector(aObj, aCx)) {
if (!mReflectors.append(aObj)) {
return false;
}
size_t idx = mReflectors.length() - 1;
if (!JS_WriteUint32Pair(aWriter, SCTAG_REFLECTOR, 0)) {
return false;
}
if (!JS_WriteBytes(aWriter, &idx, sizeof(size_t))) {
return false;
}
return true;
}
if (JS::IsCallable(aObj)) {
if (mOptions->cloneFunctions) {
if (!mFunctions.append(aObj)) {
return false;
}
return JS_WriteUint32Pair(aWriter, SCTAG_FUNCTION,
mFunctions.length() - 1);
} else {
JS_ReportErrorASCII(
aCx, "Permission denied to pass a Function via structured clone");
return false;
}
}
JS_ReportErrorASCII(aCx,
"Encountered unsupported value type writing "
"stack-scoped structured clone");
return false;
}
StackScopedCloneOptions* mOptions;
RootedObjectVector mReflectors;
RootedObjectVector mFunctions;
nsTArray<RefPtr<BlobImpl>> mBlobImpls;
};
/*
* General-purpose structured-cloning utility for cases where the structured
* clone buffer is only used in stack-scope (that is to say, the buffer does
* not escape from this function). The stack-scoping allows us to pass
* references to various JSObjects directly in certain situations without
* worrying about lifetime issues.
*
* This function assumes that |cx| is already entered the compartment we want
* to clone to, and that |val| may not be same-compartment with cx. When the
* function returns, |val| is set to the result of the clone.
*/
bool StackScopedClone(JSContext* cx, StackScopedCloneOptions& options,
HandleObject sourceScope, MutableHandleValue val) {
StackScopedCloneData data(cx, &options);
{
// For parsing val we have to enter (a realm in) its compartment.
JSAutoRealm ar(cx, sourceScope);
if (!data.Write(cx, val)) {
return false;
}
}
// Now recreate the clones in the target realm.
if (!data.Read(cx, val)) {
return false;
}
// Deep-freeze if requested.
if (options.deepFreeze && val.isObject()) {
RootedObject obj(cx, &val.toObject());
if (!JS_DeepFreezeObject(cx, obj)) {
return false;
}
}
return true;
}
// Note - This function mirrors the logic of CheckPassToChrome in
// ChromeObjectWrapper.cpp.
static bool CheckSameOriginArg(JSContext* cx, FunctionForwarderOptions& options,
HandleValue v) {
// Consumers can explicitly opt out of this security check. This is used in
// the web console to allow the utility functions to accept cross-origin
// Windows.
if (options.allowCrossOriginArguments) {
return true;
}
// Primitives are fine.
if (!v.isObject()) {
return true;
}
RootedObject obj(cx, &v.toObject());
MOZ_ASSERT(JS::GetCompartment(obj) != js::GetContextCompartment(cx),
"This should be invoked after entering the compartment but before "
"wrapping the values");
// Non-wrappers are fine.
if (!js::IsWrapper(obj)) {
return true;
}
// Wrappers leading back to the scope of the exported function are fine.
if (JS::GetCompartment(js::UncheckedUnwrap(obj)) ==
js::GetContextCompartment(cx)) {
return true;
}
// Same-origin wrappers are fine.
if (AccessCheck::wrapperSubsumes(obj)) {
return true;
}
// Badness.
JS_ReportErrorASCII(cx,
"Permission denied to pass object to exported function");
return false;
}
// Sanitize the exception on cx (which comes from calling unwrappedFun), if the
// current Realm of cx shouldn't have access to it. unwrappedFun is generally
// _not_ in the current Realm of cx here.
static void MaybeSanitizeException(JSContext* cx,
JS::Handle<JSObject*> unwrappedFun) {
// Ensure that we are not propagating more-privileged exceptions
// to less-privileged code.
nsIPrincipal* callerPrincipal = nsContentUtils::SubjectPrincipal(cx);
// No need to sanitize uncatchable exceptions, just return.
if (!JS_IsExceptionPending(cx)) {
return;
}
// Re-enter the unwrappedFun Realm to do get the current exception, so we
// don't end up unnecessarily wrapping exceptions.
{ // Scope for JSAutoRealm
JSAutoRealm ar(cx, unwrappedFun);
JS::ExceptionStack exnStack(cx);
// If JS::GetPendingExceptionStack returns false, we somehow failed to wrap
// the exception into our compartment. It seems fine to treat this as an
// uncatchable exception by returning without setting any exception on the
// JS context.
if (!JS::GetPendingExceptionStack(cx, &exnStack)) {
JS_ClearPendingException(cx);
return;
}
// Let through non-objects as-is, because some APIs rely on
// that and accidental exceptions are never non-objects.
if (!exnStack.exception().isObject() ||
callerPrincipal->Subsumes(nsContentUtils::ObjectPrincipal(
js::UncheckedUnwrap(&exnStack.exception().toObject())))) {
// Just leave exn as-is.
return;
}
// Whoever we are throwing the exception to should not have access to
// the exception. Sanitize it. First clear the existing exception.
JS_ClearPendingException(cx);
{ // Scope for AutoJSAPI
AutoJSAPI jsapi;
if (jsapi.Init(unwrappedFun)) {
JS::SetPendingExceptionStack(cx, exnStack);
}
// If Init() fails, we can't report the exception, but oh, well.
// Now just let the AutoJSAPI go out of scope and it will report the
// exception in its destructor.
}
}
// Now back in our original Realm again, throw a sanitized exception.
ErrorResult rv;
rv.ThrowInvalidStateError("An exception was thrown");
// Can we provide a better context here?
Unused << rv.MaybeSetPendingException(cx);
}
static bool FunctionForwarder(JSContext* cx, unsigned argc, Value* vp) {
CallArgs args = CallArgsFromVp(argc, vp);
// Grab the options from the reserved slot.
RootedObject optionsObj(
cx, &js::GetFunctionNativeReserved(&args.callee(), 1).toObject());
FunctionForwarderOptions options(cx, optionsObj);
if (!options.Parse()) {
return false;
}
// Grab and unwrap the underlying callable.
RootedValue v(cx, js::GetFunctionNativeReserved(&args.callee(), 0));
RootedObject unwrappedFun(cx, js::UncheckedUnwrap(&v.toObject()));
RootedValue thisVal(cx, NullValue());
if (!args.isConstructing()) {
RootedObject thisObject(cx);
if (!args.computeThis(cx, &thisObject)) {
return false;
}
thisVal.setObject(*thisObject);
}
bool ok = true;
{
// We manually implement the contents of CrossCompartmentWrapper::call
// here, because certain function wrappers (notably content->nsEP) are
// not callable.
JSAutoRealm ar(cx, unwrappedFun);
bool crossCompartment =
JS::GetCompartment(unwrappedFun) != JS::GetCompartment(&args.callee());
if (crossCompartment) {
if (!CheckSameOriginArg(cx, options, thisVal) ||
!JS_WrapValue(cx, &thisVal)) {
return false;
}
for (size_t n = 0; n < args.length(); ++n) {
if (!CheckSameOriginArg(cx, options, args[n]) ||
!JS_WrapValue(cx, args[n])) {
return false;
}
}
}
RootedValue fval(cx, ObjectValue(*unwrappedFun));
if (args.isConstructing()) {
RootedObject obj(cx);
ok = JS::Construct(cx, fval, args, &obj);
if (ok) {
args.rval().setObject(*obj);
}
} else {
ok = JS::Call(cx, thisVal, fval, args, args.rval());
}
}
// Now that we are back in our original Realm, we can check whether to
// sanitize the exception.
if (!ok) {
MaybeSanitizeException(cx, unwrappedFun);
return false;
}
// Rewrap the return value into our compartment.
return JS_WrapValue(cx, args.rval());
}
bool NewFunctionForwarder(JSContext* cx, HandleId idArg, HandleObject callable,
FunctionForwarderOptions& options,
MutableHandleValue vp) {
RootedId id(cx, idArg);
if (id.isVoid()) {
id = GetJSIDByIndex(cx, XPCJSContext::IDX_EMPTYSTRING);
}
// If our callable is a (possibly wrapped) function, we can give
// the exported thing the right number of args.
unsigned nargs = 0;
RootedObject unwrapped(cx, js::UncheckedUnwrap(callable));
if (unwrapped) {
if (JSFunction* fun = JS_GetObjectFunction(unwrapped)) {
nargs = JS_GetFunctionArity(fun);
}
}
// We have no way of knowing whether the underlying function wants to be a
// constructor or not, so we just mark all forwarders as constructors, and
// let the underlying function throw for construct calls if it wants.
JSFunction* fun = js::NewFunctionByIdWithReserved(
cx, FunctionForwarder, nargs, JSFUN_CONSTRUCTOR, id);
if (!fun) {
return false;
}
// Stash the callable in slot 0.
AssertSameCompartment(cx, callable);
RootedObject funobj(cx, JS_GetFunctionObject(fun));
js::SetFunctionNativeReserved(funobj, 0, ObjectValue(*callable));
// Stash the options in slot 1.
RootedObject optionsObj(cx, options.ToJSObject(cx));
if (!optionsObj) {
return false;
}
js::SetFunctionNativeReserved(funobj, 1, ObjectValue(*optionsObj));
vp.setObject(*funobj);
return true;
}
bool ExportFunction(JSContext* cx, HandleValue vfunction, HandleValue vscope,
HandleValue voptions, MutableHandleValue rval) {
bool hasOptions = !voptions.isUndefined();
if (!vscope.isObject() || !vfunction.isObject() ||
(hasOptions && !voptions.isObject())) {
JS_ReportErrorASCII(cx, "Invalid argument");
return false;
}
RootedObject funObj(cx, &vfunction.toObject());
RootedObject targetScope(cx, &vscope.toObject());
ExportFunctionOptions options(cx,
hasOptions ? &voptions.toObject() : nullptr);
if (hasOptions && !options.Parse()) {
return false;
}
// Restrictions:
// * We must subsume the scope we are exporting to.
// * We must subsume the function being exported, because the function
// forwarder manually circumvents security wrapper CALL restrictions.
targetScope = js::CheckedUnwrapDynamic(targetScope, cx);
// For the function we can just CheckedUnwrapStatic, because if it's
// not callable we're going to fail out anyway.
funObj = js::CheckedUnwrapStatic(funObj);
if (!targetScope || !funObj) {
JS_ReportErrorASCII(cx, "Permission denied to export function into scope");
return false;
}
if (js::IsScriptedProxy(targetScope)) {
JS_ReportErrorASCII(cx, "Defining property on proxy object is not allowed");
return false;
}
{
// We need to operate in the target scope from here on, let's enter
// its realm.
JSAutoRealm ar(cx, targetScope);
// Unwrapping to see if we have a callable.
funObj = UncheckedUnwrap(funObj);
if (!JS::IsCallable(funObj)) {
JS_ReportErrorASCII(cx, "First argument must be a function");
return false;
}
RootedId id(cx, options.defineAs);
if (id.isVoid()) {
// If there wasn't any function name specified, copy the name from the
// function being imported. But be careful in case the callable we have
// is not actually a JSFunction.
RootedString funName(cx);
JS::Rooted<JSFunction*> fun(cx, JS_GetObjectFunction(funObj));
if (fun) {
if (!JS_GetFunctionId(cx, fun, &funName)) {
return false;
}
}
if (!funName) {
funName = JS_AtomizeAndPinString(cx, "");
}
JS_MarkCrossZoneIdValue(cx, StringValue(funName));
if (!JS_StringToId(cx, funName, &id)) {
return false;
}
} else {
JS_MarkCrossZoneId(cx, id);
}
MOZ_ASSERT(id.isString());
// The function forwarder will live in the target compartment. Since
// this function will be referenced from its private slot, to avoid a
// GC hazard, we must wrap it to the same compartment.
if (!JS_WrapObject(cx, &funObj)) {
return false;
}
// And now, let's create the forwarder function in the target compartment
// for the function the be exported.
FunctionForwarderOptions forwarderOptions;
forwarderOptions.allowCrossOriginArguments =
options.allowCrossOriginArguments;
if (!NewFunctionForwarder(cx, id, funObj, forwarderOptions, rval)) {
JS_ReportErrorASCII(cx, "Exporting function failed");
return false;
}
// We have the forwarder function in the target compartment. If
// defineAs was set, we also need to define it as a property on
// the target.
if (!options.defineAs.isVoid()) {
if (!JS_DefinePropertyById(cx, targetScope, id, rval, JSPROP_ENUMERATE)) {
return false;
}
}
}
// Finally we have to re-wrap the exported function back to the caller
// compartment.
if (!JS_WrapValue(cx, rval)) {
return false;
}
return true;
}
bool CreateObjectIn(JSContext* cx, HandleValue vobj,
CreateObjectInOptions& options, MutableHandleValue rval) {
if (!vobj.isObject()) {
JS_ReportErrorASCII(cx, "Expected an object as the target scope");
return false;
}
// cx represents the caller Realm.
RootedObject scope(cx, js::CheckedUnwrapDynamic(&vobj.toObject(), cx));
if (!scope) {
JS_ReportErrorASCII(
cx, "Permission denied to create object in the target scope");
return false;
}
bool define = !options.defineAs.isVoid();
if (define && js::IsScriptedProxy(scope)) {
JS_ReportErrorASCII(cx, "Defining property on proxy object is not allowed");
return false;
}
RootedObject obj(cx);
{
JSAutoRealm ar(cx, scope);
JS_MarkCrossZoneId(cx, options.defineAs);
obj = JS_NewPlainObject(cx);
if (!obj) {
return false;
}
if (define) {
if (!JS_DefinePropertyById(cx, scope, options.defineAs, obj,
JSPROP_ENUMERATE))
return false;
}
}
rval.setObject(*obj);
if (!WrapperFactory::WaiveXrayAndWrap(cx, rval)) {
return false;
}
return true;
}
} /* namespace xpc */