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2 WEBSEC D. Ross
3 Internet-Draft Microsoft
4 Intended status: Informational T. Gondrom
5 Expires: September 6, 2012 March 5, 2012
7 HTTP Header X-Frame-Options
8 draft-gondrom-x-frame-options-00
10 Abstract
12 To improve the protection of web applications against Cross Site
13 Request Forgery (CSRF) and Clickjacking this standards defines a http
14 response header that declares a policy communicated from a host to
15 the client browser whether the transmitted content MUST NOT be
16 displayed in frames of other pages from different origins or a list
17 of trusted origins which are allowed to frame the content. This
18 drafts serves to document the existing use and specification of
19 X-Frame-Options.
21 Status of this Memo
23 This Internet-Draft is submitted in full conformance with the
24 provisions of BCP 78 and BCP 79.
26 Internet-Drafts are working documents of the Internet Engineering
27 Task Force (IETF). Note that other groups may also distribute
28 working documents as Internet-Drafts. The list of current Internet-
29 Drafts is at http://datatracker.ietf.org/drafts/current/.
31 Internet-Drafts are draft documents valid for a maximum of six months
32 and may be updated, replaced, or obsoleted by other documents at any
33 time. It is inappropriate to use Internet-Drafts as reference
34 material or to cite them other than as "work in progress."
36 This Internet-Draft will expire on September 6, 2012.
38 Copyright Notice
40 Copyright (c) 2012 IETF Trust and the persons identified as the
41 document authors. All rights reserved.
43 This document is subject to BCP 78 and the IETF Trust's Legal
44 Provisions Relating to IETF Documents
45 (http://trustee.ietf.org/license-info) in effect on the date of
46 publication of this document. Please review these documents
47 carefully, as they describe your rights and restrictions with respect
48 to this document. Code Components extracted from this document must
49 include Simplified BSD License text as described in Section 4.e of
50 the Trust Legal Provisions and are provided without warranty as
51 described in the Simplified BSD License.
53 Table of Contents
55 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
56 1.1. Requirements Language . . . . . . . . . . . . . . . . . . . 3
57 2. Frame-Options Header . . . . . . . . . . . . . . . . . . . . . 3
58 2.1. Syntax . . . . . . . . . . . . . . . . . . . . . . . . . . 4
59 2.2. Backus-Naur Form (BNF) . . . . . . . . . . . . . . . . . . 5
60 2.3. Design Issues . . . . . . . . . . . . . . . . . . . . . . . 5
61 2.3.1. Enable HTML content from other domains . . . . . . . . 5
62 2.3.2. Browser Behaviour and Processing . . . . . . . . . . . 5
63 2.4. Examples of Frame-Options Headers . . . . . . . . . . . . . 6
64 2.4.1. Example scenario for the ALLOW-FROM parameter . . . . . 6
65 3. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 6
66 4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 6
67 4.1. Registration Template . . . . . . . . . . . . . . . . . . . 7
68 5. Security Considerations . . . . . . . . . . . . . . . . . . . . 7
69 6. References . . . . . . . . . . . . . . . . . . . . . . . . . . 7
70 6.1. Normative References . . . . . . . . . . . . . . . . . . . 7
71 6.2. Informative References . . . . . . . . . . . . . . . . . . 7
72 Appendix A. Description of a Clickjacking attack . . . . . . . . . 8
73 A.1. Shop . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
74 A.2. Confirm Purchase Page . . . . . . . . . . . . . . . . . . . 9
75 A.3. Flash Configuration . . . . . . . . . . . . . . . . . . . . 9
76 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 9
78 1. Introduction
80 In 2009 and 2010 many browser vendors introduced the use of a non-
81 standard http header RFC 2616 [RFC2616] "X-Frame-Options" to protect
82 against Clickjacking [Clickjacking] and Cross Site Request Forgery
83 (CSRF) [CSRF]. This draft is to document the current use of X-Frame-
84 Options header and shall in the future be replaced by the Frame-
85 Options (CSRF) [FRAME-OPTIONS] standard.
87 In some forms of Clickjacking and CSRF an attacker tricks a user into
88 clicking on a button or link to another page and by thus executing an
89 unintended command in the context of a different web application.
90 For example with Clickjacking the attacker might use transparent or
91 opaque layers to integrate and obscure a button to another page so
92 that the user may click on it in the expectation of a different
93 action. So, in this way the attacker is "hijacking" the "Click" on a
94 button meant by the user to be sent to host A, while clicking the
95 button in effect sends a message to host B. If the user does for
96 example also have an open session with host B this can lead to a CSRF
97 attack and executing a command in the session context of the user
98 (using the user's authentication and authorization) on host B without
99 his intention or knowledge.
101 Existing anti-ClickJacking measures, e.g. Frame-breaking Javascript,
102 have weaknesses so that their protection can be circumvented as a
103 study [FRAME-BUSTING] demonstrated.
105 Short of configuring the browser to disable frames and script
106 entirely, which massively impairs browser utility, browser users are
107 vulnerable to this type of attack.
109 The by "Frame-Options" provided defense mechanism against
110 Clickjacking is to allow a secure web page from host B to declare
111 that its content (for example a button, links, text, etc.) must not
112 be displayed in a frame of another page (e.g. from host A). In
113 principle this is done by a policy declared in the HTTP header and
114 obeyed by conform browser implementations.
116 1.1. Requirements Language
118 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
119 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
120 document are to be interpreted as described in RFC 2119 [RFC2119].
122 2. Frame-Options Header
124 The Frame-Options HTTP response header indicates a policy whether a
125 browser MUST NOT allow to render a page in a or