1 files changed, 491 insertions, 0 deletions
diff --git a/js/xpconnect/src/ExportHelpers.cpp b/js/xpconnect/src/ExportHelpers.cpp
new file mode 100644
index 0000000000..3dbf83e3ba
--- /dev/null
+++ b/js/xpconnect/src/ExportHelpers.cpp
@@ -0,0 +1,491 @@
+/* -*- 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 "xpcprivate.h"
+#include "WrapperFactory.h"
+#include "AccessCheck.h"
+#include "jsfriendapi.h"
+#include "jswrapper.h"
+#include "js/Proxy.h"
+#include "mozilla/dom/BindingUtils.h"
+#include "mozilla/dom/BlobBinding.h"
+#include "mozilla/dom/File.h"
+#include "mozilla/dom/FileListBinding.h"
+#include "mozilla/dom/StructuredCloneHolder.h"
+#include "nsGlobalWindow.h"
+#include "nsJSUtils.h"
+#include "nsIDOMFileList.h"
+
+using namespace mozilla;
+using namespace mozilla::dom;
+using namespace JS;
+
+namespace xpc {
+
+bool
+IsReflector(JSObject* obj)
+{
+    obj = js::CheckedUnwrap(obj, /* 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,
+};
+
+// The HTML5 structured cloning algorithm includes a few DOM objects, notably
+// FileList. That wouldn't in itself be a reason to support them here,
+// but we've historically supported them for Cu.cloneInto (where we didn't support
+// other reflectors), so we need to continue to do so in the wrapReflectors == false
+// case to maintain compatibility.
+//
+// FileList clones are supposed to give brand new objects, rather than
+// cross-compartment wrappers. For this, our current implementation relies on the
+// fact that these objects are implemented with XPConnect and have one reflector
+// per scope.
+bool IsFileList(JSObject* obj)
+{
+    return IS_INSTANCE_OF(FileList, obj);
+}
+
+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,
+                                uint32_t aTag,
+                                uint32_t aData)
+    {
+        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), "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::NativeGlobal(JS::CurrentGlobalOrNull(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 (!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)
+    {
+        {
+            JS::Rooted<JSObject*> obj(aCx, aObj);
+            Blob* blob = nullptr;
+            if (NS_SUCCEEDED(UNWRAP_OBJECT(Blob, &obj, blob))) {
+                BlobImpl* blobImpl = blob->Impl();
+                MOZ_ASSERT(blobImpl);
+
+                if (!mBlobImpls.AppendElement(blobImpl))
+                    return false;
+
+                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)) ||
+            IsFileList(aObj))
+        {
+            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;
+    AutoObjectVector mReflectors;
+    AutoObjectVector 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,
+                 MutableHandleValue val)
+{
+    StackScopedCloneData data(cx, &options);
+    {
+        // For parsing val we have to enter its compartment.
+        // (unless it's a primitive)
+        Maybe<JSAutoCompartment> ac;
+        if (val.isObject()) {
+            ac.emplace(cx, &val.toObject());
+        } else if (val.isString() && !JS_WrapValue(cx, val)) {
+            return false;
+        }
+
+        if (!data.Write(cx, val))
+            return false;
+    }
+
+    // Now recreate the clones in the target compartment.
+    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::GetObjectCompartment(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::GetObjectCompartment(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;
+}
+
+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()));
+
+    RootedObject thisObj(cx, args.isConstructing() ? nullptr : JS_THIS_OBJECT(cx, vp));
+    {
+        // We manually implement the contents of CrossCompartmentWrapper::call
+        // here, because certain function wrappers (notably content->nsEP) are
+        // not callable.
+        JSAutoCompartment ac(cx, unwrappedFun);
+
+        RootedValue thisVal(cx, ObjectOrNullValue(thisObj));
+        if (!CheckSameOriginArg(cx, options, thisVal) || !JS_WrapObject(cx, &thisObj))
+            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);
+            if (!JS::Construct(cx, fval, args, &obj))
+                return false;
+            args.rval().setObject(*obj);
+        } else {
+            if (!JS_CallFunctionValue(cx, thisObj, fval, args, args.rval()))
+                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);
+
+    // 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,
+                                                      0, 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::CheckedUnwrap(targetScope);
+    funObj = js::CheckedUnwrap(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 compartment.
+        JSAutoCompartment ac(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.
+            JSFunction* fun = JS_GetObjectFunction(funObj);
+            RootedString funName(cx, JS_GetFunctionId(fun));
+            if (!funName)
+                funName = JS_AtomizeAndPinString(cx, "");
+
+            if (!JS_StringToId(cx, funName, &id))
+                return false;
+        }
+        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,
+                                       JS_STUBGETTER, JS_STUBSETTER)) {
+                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;
+    }
+
+    RootedObject scope(cx, js::CheckedUnwrap(&vobj.toObject()));
+    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);
+    {
+        JSAutoCompartment ac(cx, scope);
+        obj = JS_NewPlainObject(cx);
+        if (!obj)
+            return false;
+
+        if (define) {
+            if (!JS_DefinePropertyById(cx, scope, options.defineAs, obj,
+                                       JSPROP_ENUMERATE,
+                                       JS_STUBGETTER, JS_STUBSETTER))
+                return false;
+        }
+    }
+
+    rval.setObject(*obj);
+    if (!WrapperFactory::WaiveXrayAndWrap(cx, rval))
+        return false;
+
+    return true;
+}
+
+} /* namespace xpc */