One document matched: draft-gondrom-frame-options-01.xml
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<rfc category="std" docName="draft-gondrom-frame-options-01" ipr="trust200902">
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ipr values: full3667, noModification3667, noDerivatives3667
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<!-- ***** FRONT MATTER ***** -->
<front>
<!-- The abbreviated title is used in the page header - it is only necessary if the
full title is longer than 39 characters -->
<title abbrev="Frame-Options">HTTP Header Frame Options</title>
<!-- add 'role="editor"' below for the editors if appropriate -->
<!-- Another author who claims to be an editor -->
<author fullname="David Ross" initials="D."
surname="Ross">
<organization>Microsoft</organization>
<address>
<postal>
<street></street>
<!-- Reorder these if your country does things differently -->
<city></city>
<region></region>
<code></code>
<country>U.S.</country>
</postal>
<phone></phone>
<email></email>
<!-- uri and facsimile elements may also be added -->
</address>
</author>
<author fullname="Tobias Gondrom" initials="T."
surname="Gondrom">
<organization></organization>
<address>
<postal>
<street>Kruegerstr. 5A</street>
<!-- Reorder these if your country does things differently -->
<city>Unterschleissheim</city>
<region></region>
<code></code>
<country>Germany</country>
</postal>
<phone>+44 7521003005</phone>
<email>tobias.gondrom@gondrom.org</email>
<!-- uri and facsimile elements may also be added -->
</address>
</author>
<date month="March" year="2011" />
<area>General</area>
<workgroup>WEBSEC</workgroup>
<keyword>frame-options</keyword>
<keyword>HTTP header</keyword>
<keyword>websec</keyword>
<abstract>
<t>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.
</t>
</abstract>
</front>
<middle>
<section title="Introduction">
<t>In 2009 and 2010 many browser vendors introduced the use of a non-standard http header <xref target="RFC2616">RFC 2616</xref>
"X-Frame-Options" to protect against <xref target="Clickjacking">Clickjacking</xref>
and Cross Site Request Forgery <xref target="CSRF">(CSRF)</xref>. This standard is to replace the non-standard header.</t>
<t>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.</t>
<t>Existing anti-ClickJacking measures, e.g. Frame-breaking Javascript,
have weaknesses so that their protection can be circumvented as a study
<xref target="FRAME-BUSTING"></xref> demonstrated.</t>
<t>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.
</t>
<t>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.</t>
<section title="Requirements Language">
<t>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 <xref
target="RFC2119">RFC 2119</xref>.</t>
</section>
</section>
<section title="Frame-Options Header">
<t>The Frame-Options HTTP response header indicates a policy whether a browser MUST
NOT allow to render a page in a<![CDATA[ <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.</t>
<section title="Syntax">
<t>The header field name is:
<vspace /><vspace />
Frame-Options
</t>
<t>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.
<list style="hanging" hangIndent="6">
<t hangText="DENY"><vspace />
A browser receiving content with this header MUST NOT display this content in any frame.</t>
<t hangText="SAMEORIGIN"><vspace />
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.<vspace />
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". <vspace />
[TBD]current implementations do not display if the origin of the top-level-browsing-context is different than the origin of the page containing the FRAME-OPTIONS header.</t>
<t hangText="ALLOW-FROM"> (followed by a list of URIs of trusted origins)<vspace />
A browser receiving content with this header MUST NOT display this content in any frame from a page of different origin than any of the listed origins.
This allows deployment with multi-domain sites, as the webmaster can define a whitelist of origins that are allowed to frame the page.
While this can expose the page to risks by the trusted origins, in some cases it may be necessary to use content from other domains or more than one origin (hostname).<vspace />
for example: FRAME-OPTIONS: ALLOW-FROM https://www.domain.com/</t>
</list>
</t>
<t>The URIs listed for ALLOW-FROM must be valid. <vspace />
Any data beyond the domain address (i.e. any data after the "/" separator) is to be ignored
and to verify a referring page is of the same origin as the content or that the referring page
is listed in the ALLOW-FROM list of URI, the algorithm to compare origins from <xref target="ORIGIN"></xref> should be used.
<vspace />
Wildcards to declare multiple domains in one statement are not permitted.
<vspace />
</t>
<t>
[TBD] Current Implementations do not consider the port a component of the origin - conflicting with <xref target="ORIGIN"></xref>.</t>
</section>
<section title="Backus-Naur Form (BNF)">
<t>The <xref target="RFC0822">RFC 822</xref> EBNF of the Frame-Options header is:<vspace /><vspace />
<figure>
<artwork align="left">
Frame-Options = "Frame-Options" ":" "DENY"/ "SAMEORIGIN" /
("ALLOW-FROM" ":" Origin-List)
Origin-List = 1*URI
</artwork>
</figure>
[TBD] with URI as defined in the websec-origin draft<vspace />
<vspace /> <vspace />
[TBD] Or should we use the ABNF (RFC 2234) alternatively or in addition?<vspace />
<vspace /> <vspace />
</t>
</section>
<section anchor="design" title="Design Issues">
<section anchor="vectors" title="Enable HTML content from other domains">
<t>There are three main direct vectors that enable HTML content from other domains:
<list style="symbols">
<t>IFRAME Tag</t>
<t>Frame tag</t>
<t>The Object tag (requires a redirect)</t>
</list>
</t>
<t>Besides these other ways to host HTML content can be possible. For example some plugins may host
HTML views directly. To allow a conform security configuration those plugins MUST be conform to the
FRAME-OPTIONS directive as specified in this draft as well.
</t>
</section>
<section anchor="processing" title="Browser Behaviour and Processing">
<t>To allow secure implementations browser implementations MUST behave in a consistent and reliable way conform to thsi specition.
</t>
<t>If a HTTP Header prohibits framing, the user-agent of the browser MAY immediately abort downloading or parsing of the document.</t>
<t>When a browser discovers loaded content with the 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.
</t>
<t>"No-Frame" Page<vspace />
If the display of content is denied by the FRAME-OPTIONS header an accroding 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.
</t>
<t>[TBD] The NoFrame page MAY provide the user with an option to open the target URL in a new window.</t>
</section>
</section>
<section anchor="examples" title="Examples of Frame-Options Headers">
<section anchor="ex-allow-from" title="Example scenario for the ALLOW-FROM parameter">
<t><list style="numbers">
<t>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.</t>
<t>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.</t>
<t>Server serves up the hostname in X-FRAME-OPTIONS: ALLOW-FROM if the proper criteria was
met in step #2.</t>
<t>Browser enforces the X-FRAME-OPTIONS: ALLOW-FROM domain.com header.</t>
</list>
</t></section>
</section>
</section>
<section anchor="Acknowledgements" title="Acknowledgements">
<t>This document was derived from input from specifications published by various browser
vendors like Microsoft (Eric Lawrence, David Ross), Mozilla, Google, Opera and Apple.</t>
</section>
<!-- Possibly a 'Contributors' section ... -->
<section anchor="IANA" title="IANA Considerations">
<t>This memo a request to IANA to include the specified HTTP header in registry as outlined in <xref target="RFC3864">Registration Procedures for Message Header Fields</xref></t>
<section anchor="reg-template" title="Registration Template">
<figure align="left" anchor="template">
<preamble></preamble>
<artwork align="left"><![CDATA[
PERMANENT MESSAGE HEADER FIELD REGISTRATION TEMPLATE:
Header field name: Frame-Option
Applicable protocol: http [RFC2616]
Status: Standard
Author/Change controller: IETF
Specification document(s): draft-gondrom-frame-options
Related information:
]]></artwork>
<postamble></postamble>
</figure>
</section>
</section>
<section anchor="Security" title="Security Considerations">
<t>The introduction of the http header 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)
</t>
<t>The parameter ALLOW-FROM allows a page possibilities to guess who is framing it. This is by design, but may lead to data leakage or data protection concerns.</t>
</section>
</middle>
<!-- *****BACK MATTER ***** -->
<back>
<!-- References split into informative and normative -->
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&RFC2119;
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&RFC822;
&RFC2616;
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<reference anchor='ORIGIN' target="http://tools.ietf.org/id/draft-ietf-websec-origin-00.txt">
<front>
<title>The Web Origin Concept</title>
<author>
<organization>IETF</organization>
</author>
<date year='2010' month='December'/></front>
</reference>
<reference anchor="Clickjacking"
target="http://www.owasp.org/index.php/Clickjacking">
<front>
<title>Clickjacking</title>
<author>
<organization>OWASP (Open Web Application Security Project)</organization>
</author>
<date year="2010" />
</front>
</reference>
<reference anchor="CSRF"
target="http://www.owasp.org/index.php/Top_10_2010-A5">
<front>
<title>OWASP Top-10: Cross-Site Request Forgery (CSRF)</title>
<author>
<organization>OWASP (Open Web Application Security Project)</organization>
</author>
<date year="2010" />
</front>
</reference>
<reference anchor="CLICK-DEFENSE-BLOG"
target="http://blogs.msdn.com/b/ie/archive/2009/01/27/ie8-security-part-vii-clickjacking-defenses.aspx">
<front>
<title>Clickjacking Defense</title>
<author>
<organization>Microsoft</organization>
</author>
<date year="2009" />
</front>
</reference>
<reference anchor="FRAME-BUSTING"
target="http://seclab.stanford.edu/websec/framebusting/">
<front>
<title>Busting frame busting: a study of clickjacking vulnerabilities at popular sites</title>
<author>
<organization>Stanford Web Security Research</organization>
</author>
<date year="2010" />
</front>
</reference>
</references>
<section anchor="app-Clickjacking-description" title="Description of a Clickjacking attack">
<t>More detailed explanation of Clickjacking scenarios</t>
<section anchor="scenario-1" title="Shop">
<t>An Internet Marketplace/Shop offering a feature with a link/button to "Buy this" Gadget<vspace />
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 CSRF-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-CSRF/anti-CJ protections.
</t>
</section>
<section anchor="scenario-2" title="Confirm Purchase Page">
<t>Onlineshop "Confirm purchase" anti-CSRF page<vspace />
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
FRAME-OPTIONS directive, mitigating ClickJack attacks.
</t>
</section>
<section anchor="scenario-3" title="Flash Configuration">
<t>Macromedia Flash configuration page<vspace />
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 FRAME-OPTIONS directive.
</t>
</section>
</section>
<!-- Change Log
v00 2011-03-06 TG Initial version
v01 2011-03-14 TG Wording and Grammar version, changed TRUSTED to ALLOW-FROM
v02 2011-04-05 TG Integrate Discussion of IETF-80 meeting, esp. on parameters
-->
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