WEBSEC D. Ross
Internet-Draft Microsoft
Intended status: Standards Track T. Gondrom
Expires: September 6, 2012 March 5, 2012
HTTP Header Frame Options
draft-gondrom-frame-options-02
Abstract
To improve the protection of web applications against Cross Site
Request Forgery (CSRF) and Clickjacking this standards defines a http
response header that declares a policy communicated from a host to
the client browser whether the transmitted content MUST NOT be
displayed in frames of other pages from different origins or a list
of trusted origins which are allowed to frame the content.
Status of this Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet-
Drafts is at http://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."
This Internet-Draft will expire on September 6, 2012.
Copyright Notice
Copyright (c) 2012 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents
(http://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents
carefully, as they describe your rights and restrictions with respect
to this document. Code Components extracted from this document must
include Simplified BSD License text as described in Section 4.e of
the Trust Legal Provisions and are provided without warranty as
Ross & Gondrom Expires September 6, 2012 [Page 1]
Internet-Draft Frame-Options March 2012
described in the Simplified BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1. Requirements Language . . . . . . . . . . . . . . . . . . . 3
2. Frame-Options Header . . . . . . . . . . . . . . . . . . . . . 3
2.1. Syntax . . . . . . . . . . . . . . . . . . . . . . . . . . 4
2.2. Backus-Naur Form (BNF) . . . . . . . . . . . . . . . . . . 5
2.3. Design Issues . . . . . . . . . . . . . . . . . . . . . . . 5
2.3.1. Enable HTML content from other domains . . . . . . . . 5
2.3.2. Browser Behaviour and Processing . . . . . . . . . . . 5
2.4. Examples of Frame-Options Headers . . . . . . . . . . . . . 6
2.4.1. Example scenario for the ALLOW-FROM parameter . . . . . 6
3. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 6
4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 6
4.1. Registration Template . . . . . . . . . . . . . . . . . . . 7
5. Security Considerations . . . . . . . . . . . . . . . . . . . . 7
6. References . . . . . . . . . . . . . . . . . . . . . . . . . . 7
6.1. Normative References . . . . . . . . . . . . . . . . . . . 7
6.2. Informative References . . . . . . . . . . . . . . . . . . 7
Appendix A. Description of a Clickjacking attack . . . . . . . . . 8
A.1. Shop . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
A.2. Confirm Purchase Page . . . . . . . . . . . . . . . . . . . 9
A.3. Flash Configuration . . . . . . . . . . . . . . . . . . . . 9
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 9
Ross & Gondrom Expires September 6, 2012 [Page 2]
Internet-Draft Frame-Options March 2012
1. Introduction
In 2009 and 2010 many browser vendors introduced the use of a non-
standard http header RFC 2616 [RFC2616] "X-Frame-Options" to protect
against Clickjacking [Clickjacking] and Cross Site Request Forgery
(CSRF) [CSRF]. This standard is to replace the non-standard header.
In some forms of Clickjacking and CSRF an attacker tricks a user into
clicking on a button or link to another page and by thus executing an
unintended command in the context of a different web application.
For example with Clickjacking the attacker might use transparent or
opaque layers to integrate and obscure a button to another page so
that the user may click on it in the expectation of a different
action. So, in this way the attacker is "hijacking" the "Click" on a
button meant by the user to be sent to host A, while clicking the
button in effect sends a message to host B. If the user does for
example also have an open session with host B this can lead to a CSRF
attack and executing a command in the session context of the user
(using the user's authentication and authorization) on host B without
his intention or knowledge.
Existing anti-ClickJacking measures, e.g. Frame-breaking Javascript,
have weaknesses so that their protection can be circumvented as a
study [FRAME-BUSTING] demonstrated.
Short of configuring the browser to disable frames and script
entirely, which massively impairs browser utility, browser users are
vulnerable to this type of attack.
The by "Frame-Options" provided defense mechanism against
Clickjacking is to allow a secure web page from host B to declare
that its content (for example a button, links, text, etc.) must not
be displayed in a frame of another page (e.g. from host A). In
principle this is done by a policy declared in the HTTP header and
obeyed by conform browser implementations.
1.1. Requirements Language
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in RFC 2119 [RFC2119].
2. Frame-Options Header
The Frame-Options HTTP response header indicates a policy whether a
browser MUST NOT allow to render a page in a or