draft-ietf-websec-x-frame-options-01

draft-ietf-websec-x-frame-options-01
WEBSEC D. Ross
Internet-Draft Microsoft
Intended status: Informational T. Gondrom
Expires: April 26, 2013 October 23, 2012
HTTP Header X-Frame-Options
draft-ietf-websec-x-frame-options-01
Abstract

To improve the protection of web applications against Clickjacking
this standard defines an http response header that declares a policy
communicated from a host to the client browser on whether the browser
must not display the transmitted content in frames of other web
pages. This drafts serves to document the existing use and
specification of X-Frame-Options.

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
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Drafts is at

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
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This Internet-Draft will expire on April 26, 2013.

This document is subject to
BCP 78
and the IETF Trust's Legal
Provisions Relating to IETF Documents
) in effect on the date of
publication of this document. Please review these documents
carefully, as they describe your rights and restrictions with respect
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include Simplified BSD License text as described in Section 4.e of
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Ross & Gondrom Expires April 26, 2013 [Page 1]
Internet-Draft X-Frame-Options October 2012
described in the Simplified BSD License.

Table of Contents
. Introduction . . . . . . . . . . . . . . . . . . . . . . . . .
1.1
. Requirements Language . . . . . . . . . . . . . . . . . . .
. X-Frame-Options Header . . . . . . . . . . . . . . . . . . . .
2.1
. Syntax . . . . . . . . . . . . . . . . . . . . . . . . . .
2.2
. Backus-Naur Form (BNF) . . . . . . . . . . . . . . . . . .
2.3
. Design Issues . . . . . . . . . . . . . . . . . . . . . . .
2.3.1
. Enable HTML content from other domains . . . . . . . .
2.3.2
. Browser Behaviour and Processing . . . . . . . . . . .
2.4
. Examples of X-Frame-Options Headers . . . . . . . . . . . .
2.4.1
. Example scenario for the ALLOW-FROM parameter . . . . .
. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . .
. IANA Considerations . . . . . . . . . . . . . . . . . . . . . .
4.1
. Registration Template . . . . . . . . . . . . . . . . . . .
. Security Considerations . . . . . . . . . . . . . . . . . . . .
. References . . . . . . . . . . . . . . . . . . . . . . . . . .
6.1
. Normative References . . . . . . . . . . . . . . . . . . .
6.2
. Informative References . . . . . . . . . . . . . . . . . .
Appendix A
. Description of a Clickjacking attack . . . . . . . . .
A.1
. Shop . . . . . . . . . . . . . . . . . . . . . . . . . . .
A.2
. Confirm Purchase Page . . . . . . . . . . . . . . . . . . .
A.3
. Flash Configuration . . . . . . . . . . . . . . . . . . . .
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . .
Ross & Gondrom Expires April 26, 2013 [Page 2]
Internet-Draft X-Frame-Options October 2012
. Introduction
In 2009 and 2010 many browser vendors ([
Microsoft-X-Frame-Options
],
CLICK-DEFENSE-BLOG
], [
Mozilla-X-Frame-Options
]) introduced the use
of a non-standard http header
RFC 2616
RFC2616
] "X-Frame-Options" to
protect against Clickjacking [
Clickjacking
]. This draft is to
document the current use of X-Frame-Options header and shall in the
future be replaced by the Frame-Options [
FRAME-OPTIONS
] standard.

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 "X-Frame-Options" allows 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 ( or ) 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 ]. . X-Frame-Options Header The X-Frame-Options HTTP response header indicates a policy whether a browser MUST NOT allow to render a page in a <frame> or <iframe> . Hosts can declare this policy in the header of their HTTP responses to prevent clickjacking attacks, by ensuring that their content is not embedded into other pages or frames. 2.1 . Syntax The header field name is: X-Frame-Options There are three different values for the header field. These values are exclusive, that is NOT more than one of the three values MUST be set. Ross & Gondrom Expires April 26, 2013 [Page 3] Internet-Draft X-Frame-Options October 2012 DENY A browser receiving content with this header MUST NOT display this content in any frame. SAMEORIGIN A browser receiving content with this header MUST NOT display this content in any frame from a page of different origin than the content itself. If a browser or plugin can not reliably determine whether the origin of the content and the frame have the same origin, this MUST be treated as "DENY". (Please note that current implementations may vary on the interpretation of this criteria: In some it only allows to be framed if the origin of the top-level browsing-context is identical, in other it compares with to the origin of the framing page.) ALLOW-FROM (followed by a URI [ RFC3986 ] of a trusted origin) A browser receiving content with this header MUST NOT display this content in a frame from any page with a top-level browsing contex of different origin than the specified origin. While this can expose the page to risks by the trusted origin, in some cases it may be necessary to allow the framing by content from other domains. For example: X-FRAME-OPTIONS: ALLOW-FROM: The ALLOW-FROM URI MUST be valid. Any data beyond the domain address (i.e. any data after the "/" separator) is to be ignored. And the algorithm to compare origins from [ RFC6454 ] SHOULD be used to verify a referring page is of the same origin as the content or that the referring page's origin is identical with the ALLOW-FROM URI. Wildcards or lists to declare multiple domains in one ALLOW-FROM statement are not permitted. Please note that in conflict with [ RFC6454 ], current implementations do not consider the port as a defining component of the origin. 2.2 . Backus-Naur Form (BNF) The RFC 822 RFC0822 ] EBNF of the X-Frame-Options header is: X-Frame-Options = "Frame-Options" ":" "DENY"/ "SAMEORIGIN" / ("ALLOW-FROM" ":" URI) Ross & Gondrom Expires April 26, 2013 [Page 4] Internet-Draft X-Frame-Options October 2012 With URI as defined in [ RFC3986 [TBD] Or should we use the ABNF ( RFC 2234 ) alternatively to EBNF or in addition? 2.3 . Design Issues 2.3.1 . Enable HTML content from other domains There are three main direct vectors that enable HTML content from other domains: o IFRAME Tag o Frame tag o The Object tag (requires a redirect) Besides these, other ways to host HTML content can be possible. For example some plugins may host HTML views directly. If these plugins appear essentially as frames (as opposed to top-level windows), the plugins MUST conform to the X-FRAME-OPTIONS directive as specified in this draft as well. 2.3.2 . Browser Behaviour and Processing To allow secure implementations, browsers MUST behave in a consistent and reliable way. If an HTTP Header prohibits framing, the user-agent of the browser MAY immediately abort downloading or parsing of the document. When a browser discovers loaded content with the X-FRAME-OPTIONS header would be displayed in a frame against the specified origin orders of the header, the browser SHOULD redirect as soon as possible to a "No-Frame" page. "No-Frame" Page If the display of content is denied by the X-FRAME-OPTIONS header an error page SHOULD be displayed. For example this can be a noframe.html page also stating the full URL of the protected page and the hostname of the protected page. The NoFrame page MAY provide the user with an option to open the target URL in a new window. Variation in current browser behaviour There are currently variations in the implementation of the X-FRAME- OPTIONS header. For example not all browsers may support the "ALLOW- Ross & Gondrom Expires April 26, 2013 [Page 5] Internet-Draft X-Frame-Options October 2012 FROM" option. And the criteria for SAMEORIGIN option is not evaluated unanimously: one implementation may evaluate the SAMEORIGIN option based on the origin of the framed page and the framing page, while another may evaluate based on the framed page and the top-level browsing-context These variations in the evaluation of the header by different implementations impair the useage and reliability of this http header. A revised version of frame-options [ FRAME-OPTIONS ] shall unify the behaviour and replace this document in the future. 2.4 . Examples of X-Frame-Options Headers 2.4.1 . Example scenario for the ALLOW-FROM parameter 1. Inner IFRAME suggests via a querystring parameter what site it wants to be hosted by. This can obviously be specified by an attacker, but that's OK. 2. Server verifies the hostname meets whatever criteria. For example, for a Facebook "Like" button, the server can check to see that the supplied hostname matches the hostname expected for that Like button. 3. Server serves up the hostname in X-FRAME-OPTIONS: ALLOW-FROM if the proper criteria was met in step #2. 4. Browser enforces the X-FRAME-OPTIONS: ALLOW-FROM domain.com header. . Acknowledgements This document was derived from input from specifications published by various browser vendors like Microsoft (Eric Lawrence, David Ross), Mozilla, Google, Opera and Apple. . IANA Considerations This memo a request to IANA to include the specified HTTP header in registry as outlined in Registration Procedures for Message Header Fields [ RFC3864 Ross & Gondrom Expires April 26, 2013 [Page 6] Internet-Draft X-Frame-Options October 2012 4.1 . Registration Template PERMANENT MESSAGE HEADER FIELD REGISTRATION TEMPLATE: Header field name: X-Frame-Option Applicable protocol: http [ RFC2616 Status: Standard Author/Change controller: IETF Specification document(s): draft-ietf-websec-x-frame-options Related information: Figure 1 . Security Considerations The introduction of the http header X-FRAME-OPTIONS does improve the protection against Clickjacking, however it is not self-sufficient on its own but MUST be used in conjunction with other security measures like secure coding and Content Security Policy (CSP) The parameter ALLOW-FROM allows a page to guess who is framing it. This is by design, but may lead to data leakage or data protection concerns. . References 6.1 . Normative References RFC2119 ] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14 RFC 2119 , March 1997. 6.2 . Informative References CLICK-DEFENSE-BLOG Microsoft, "Clickjacking Defense", 2009, < blogs.msdn.com/b/ie/archive/2009/01/27/ ie8-security-part-vii-clickjacking-defenses.aspx >. Clickjacking OWASP (Open Web Application Security Project), Ross & Gondrom Expires April 26, 2013 [Page 7] Internet-Draft X-Frame-Options October 2012 "Clickjacking", 2010, >. FRAME-BUSTING Stanford Web Security Research, "Busting frame busting: a study of clickjacking vulnerabilities at popular sites", 2010, < >. FRAME-OPTIONS IETF, "The Web Origin Concept", July 2012, < tools.ietf.org/id/draft-ietf-websec-frame-options-00.txt >. Microsoft-X-Frame-Options Microsoft, "Combating ClickJacking With X-Frame-Options", 2010, < 03/30/combating-clickjacking-with-x-frame-options.aspx >. Mozilla-X-Frame-Options Mozilla, "The X-Frame-Options response header", 2010, <htt ps://developer.mozilla.org/en-US/docs/ The_X-FRAME-OPTIONS_response_header>. RFC0822 ] Crocker, D., "Standard for the format of ARPA Internet text messages", STD 11, RFC 822 , August 1982. RFC2616 ] Fielding, R., Gettys, J., Mogul, J., Frystyk, H., Masinter, L., Leach, P., and T. Berners-Lee, "Hypertext Transfer Protocol -- HTTP/1.1", RFC 2616 , June 1999. RFC3864 ] Klyne, G., Nottingham, M., and J. Mogul, "Registration Procedures for Message Header Fields", BCP 90 RFC 3864 September 2004. RFC3986 ] Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform Resource Identifier (URI): Generic Syntax", STD 66, RFC 3986 , January 2005. RFC6454 ] Barth, A., "The Web Origin Concept", RFC 6454 December 2011. Appendix A . Description of a Clickjacking attack More detailed explanation of Clickjacking scenarios Ross & Gondrom Expires April 26, 2013 [Page 8] Internet-Draft X-Frame-Options October 2012 A.1 . Shop An Internet Marketplace/Shop offering a feature with a link/button to "Buy this" Gadget The marketplace wants their affiliates (who could be bad guys) to be able to stick the "Buy such-and-such from XYZ" IFRAMES into their pages. There is a ClickJack possibility here, which is why the marketplace/onlineshop needs to then immediately navigate the main browsing context (or a new window) to a confirmation page which is protected by anti-CJ protections. A.2 . Confirm Purchase Page Onlineshop "Confirm purchase" anti-CSRF page The Confirm Purchase page must be shown to the end user without possibility of overlay or misuse by an attacker. For that reason, the confirmation page uses anti-CSRF tokens and contains the X-FRAME- OPTIONS directive, mitigating ClickJack attacks. A.3 . Flash Configuration Macromedia Flash configuration page Macromedia Flash configuration settings are set by a Flash object which can run only from a specific configuration page on Macromedia's site. The object runs inside the page and thus can be subject to a ClickJacking attack. In order to prevent ClickJacking attacks against the security settings, the configuration page uses the X-FRAME-OPTIONS directive. Authors' Addresses David Ross Microsoft U.S. Phone: Email: Tobias Gondrom Kruegerstr. 5A Unterschleissheim, Germany Phone: +44 7521003005 Email: tobias.gondrom@gondrom.org Ross & Gondrom Expires April 26, 2013 [Page 9] Datatracker draft-ietf-websec-x-frame-options-01 This is an older version of an Internet-Draft that was ultimately published as RFC 7034 Document Document type This is an older version of an Internet-Draft that was ultimately published as RFC 7034 Select version 00 01 02 03 04 05 06 07 08 09 10 11 12 RFC 7034 Compare versions Authors David Ross Tobias Gondrom Replaces draft-gondrom-x-frame-options RFC stream Other formats txt bibtex bibxml Additional resources Mailing list discussion Report a datatracker bug Show sidebar by default Yes No Tab to show by default Info Contents HTMLization configuration HTMLize the plaintext Plaintextify the HTML Maximum font size Page dependencies Inline Reference Citation links Go to reference section Go to linked document</div> </div> <div class="detail-actions"> <a href="/search?q=tools.ietf.org" class="btn">Same domain →</a> <a href="/search?q=draft-ietf-websec-x-frame-opti" class="btn btn-secondary">Similar titles →</a> </div> </article> </main> <footer class="site-footer"> <div class="container"> C U Cyber History — Public Interest Web Archive Preserving fading web memories. 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