1 files changed, 591 insertions, 0 deletions
diff --git a/js/xpconnect/src/ExportHelpers.cpp b/js/xpconnect/src/ExportHelpers.cpp
new file mode 100644
index 0000000000..2f291583f8
--- /dev/null
+++ b/js/xpconnect/src/ExportHelpers.cpp
@@ -0,0 +1,591 @@
+/* -*- 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
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "xpcprivate.h"
+#include "WrapperFactory.h"
+#include "AccessCheck.h"
+#include "jsfriendapi.h"
+#include "js/Exception.h"
+#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 "nsGlobalWindow.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 IS_WN_REFLECTOR(obj) || dom::IsDOMObject(obj);
+}
+
+enum StackScopedCloneTags {
+  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, JSID_VOIDHANDLE, 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);
+
+        // XXX(Bug 1631371) Check if this should use a fallible operation as it
+        // 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);
+
+  // 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, this was an uncatchable
+    // exception, or we somehow failed to wrap the exception into our
+    // compartment.  In either case, treating this as uncatchable exception,
+    // by returning without setting any exception on the JSContext,
+    // seems fine.
+    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 == JSID_VOIDHANDLE) {
+    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 (JSID_IS_VOID(id)) {
+      // 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);
+      JSFunction* fun = JS_GetObjectFunction(funObj);
+      if (fun) {
+        funName = JS_GetFunctionId(fun);
+      }
+      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(JSID_IS_STRING(id));
+
+    // 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 (!JSID_IS_VOID(options.defineAs)) {
+      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 = !JSID_IS_VOID(options.defineAs);
+
+  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 */