v8/test/mjsunit/es6/proxies-global-reference.js

// Copyright 2015 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 failing_proxy = new Proxy({}, new Proxy({}, {
  get() { throw "No trap should fire" }}));

assertThrows(() => Object.setPrototypeOf(Object.prototype, failing_proxy), TypeError);
assertThrows(()=>a, ReferenceError);
Throw TypeError when reading global references through a JSProxy Allowing global references to be read through a proxy results in cross-origin information leaks. The ES6 spec currently does not mitigate this in any way. This CL adds a workaround that's easy for V8: throw whenever an unresolved reference would result in a proxy trap to be fired. I'm landing this so we can move forwards with staging proxies without putting users of --harmony at risk. BUG=chromium:399951 LOG=n Review URL: https://codereview.chromium.org/1529303003 Cr-Commit-Position: refs/heads/master@{#32949} 2015-12-17 14:37:16 +00:00			`// Copyright 2015 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 failing_proxy = new Proxy({}, new Proxy({}, {`
			`get() { throw "No trap should fire" }}));`

Implement immutable prototype chains This patch implements "immutable prototype exotic objects" from the ECMAScript spec, which are objects whose __proto__ cannot be changed, but are not otherwise frozen. They are introduced in order to prevent a Proxy from being introduced to the prototype chain of the global object. The API is extended by a SetImmutablePrototype() call in ObjectTemplate, which can be used to vend new immutable prototype objects. Additionally, Object.prototype is an immutable prototype object. In the implementation, a new bit is added to Maps to say whether the prototype is immutable, which is read by SetPrototype. Map transitions to the immutable prototype state are not saved in the transition tree because the main use case is just for the prototype chain of the global object, which there will be only one of per Context, so no need to take up the extra word for a pointer in each full transition tree. BUG=v8:5149 Review-Url: https://codereview.chromium.org/2108203002 Cr-Commit-Position: refs/heads/master@{#37482} 2016-07-01 19:16:53 +00:00			`assertThrows(() => Object.setPrototypeOf(Object.prototype, failing_proxy), TypeError);`
			`assertThrows(()=>a, ReferenceError);`