Expose a way to make a same-origin realm

Some tests, e.g. in test262, want to create a new same-origin
realm. This patch exposes a new function,
Realm.createAllowCrossRealmAccess(), which vends a new realm with
the same security token as the currently executing one.

Review-Url: https://codereview.chromium.org/1973363004
Cr-Commit-Position: refs/heads/master@{#36561}

src/d8.cc

@@ -523,9 +523,8 @@ void Shell::RealmGlobal(const v8::FunctionCallbackInfo<v8::Value>& args) {
       Local<Context>::New(args.GetIsolate(), data->realms_[index])->Global());
 }
 
-
-// Realm.create() creates a new realm and returns its index.
-void Shell::RealmCreate(const v8::FunctionCallbackInfo<v8::Value>& args) {
+MaybeLocal<Context> Shell::CreateRealm(
+    const v8::FunctionCallbackInfo<v8::Value>& args) {
   Isolate* isolate = args.GetIsolate();
   TryCatch try_catch(isolate);
   PerIsolateData* data = PerIsolateData::Get(isolate);
@@ -542,12 +541,29 @@ void Shell::RealmCreate(const v8::FunctionCallbackInfo<v8::Value>& args) {
   if (context.IsEmpty()) {
     DCHECK(try_catch.HasCaught());
     try_catch.ReThrow();
-    return;
+    return MaybeLocal<Context>();
   }
   data->realms_[index].Reset(isolate, context);
   args.GetReturnValue().Set(index);
+  return context;
+}
+
+// Realm.create() creates a new realm with a distinct security token
+// and returns its index.
+void Shell::RealmCreate(const v8::FunctionCallbackInfo<v8::Value>& args) {
+  CreateRealm(args);
 }
 
+// Realm.createAllowCrossRealmAccess() creates a new realm with the same
+// security token as the current realm.
+void Shell::RealmCreateAllowCrossRealmAccess(
+    const v8::FunctionCallbackInfo<v8::Value>& args) {
+  Local<Context> context;
+  if (CreateRealm(args).ToLocal(&context)) {
+    context->SetSecurityToken(
+        args.GetIsolate()->GetEnteredContext()->GetSecurityToken());
+  }
+}
 
 // Realm.dispose(i) disposes the reference to the realm i.
 void Shell::RealmDispose(const v8::FunctionCallbackInfo<v8::Value>& args) {
@@ -1135,6 +1151,11 @@ Local<ObjectTemplate> Shell::CreateGlobalTemplate(Isolate* isolate) {
       String::NewFromUtf8(isolate, "create", NewStringType::kNormal)
           .ToLocalChecked(),
       FunctionTemplate::New(isolate, RealmCreate));
+  realm_template->Set(
+      String::NewFromUtf8(isolate, "createAllowCrossRealmAccess",
+                          NewStringType::kNormal)
+          .ToLocalChecked(),
+      FunctionTemplate::New(isolate, RealmCreateAllowCrossRealmAccess));
   realm_template->Set(
       String::NewFromUtf8(isolate, "dispose", NewStringType::kNormal)
           .ToLocalChecked(),

src/d8.h

@@ -375,6 +375,8 @@ class Shell : public i::AllStatic {
   static void RealmOwner(const v8::FunctionCallbackInfo<v8::Value>& args);
   static void RealmGlobal(const v8::FunctionCallbackInfo<v8::Value>& args);
   static void RealmCreate(const v8::FunctionCallbackInfo<v8::Value>& args);
+  static void RealmCreateAllowCrossRealmAccess(
+      const v8::FunctionCallbackInfo<v8::Value>& args);
   static void RealmDispose(const v8::FunctionCallbackInfo<v8::Value>& args);
   static void RealmSwitch(const v8::FunctionCallbackInfo<v8::Value>& args);
   static void RealmEval(const v8::FunctionCallbackInfo<v8::Value>& args);
@@ -469,6 +471,8 @@ class Shell : public i::AllStatic {
   static void RunShell(Isolate* isolate);
   static bool SetOptions(int argc, char* argv[]);
   static Local<ObjectTemplate> CreateGlobalTemplate(Isolate* isolate);
+  static MaybeLocal<Context> CreateRealm(
+      const v8::FunctionCallbackInfo<v8::Value>& args);
 };
 
 

test/mjsunit/realm-property-access.js

+// Copyright 2016 the V8 project authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+var r = Realm.create();
+var f = Realm.eval(r, "function f() { return this }; f()");
+assertEquals(f, Realm.global(r));
+
+// Cross-origin property access throws
+assertThrows(() => f.a, TypeError);
+assertThrows(() => { 'use strict'; f.a = 1 }, TypeError);
+
+var r2 = Realm.createAllowCrossRealmAccess();
+var f2 = Realm.eval(r2, "function f() { return this }; f()");
+assertEquals(f2, Realm.global(r2));
+
+// Same-origin property access doesn't throw
+assertEquals(undefined, f2.a);
+f2.a = 1;
+assertEquals(1, f2.a);