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  <body style="display: inherit; "><div class="head"><p><a href="http://www.w3.org/"><img width="72" height="48" src="http://www.w3.org/Icons/w3c_home" alt="W3C"></a></p><h1 class="title" id="title">Content Security Policy</h1><h2 id="w3c-working-draft-29-november-2011">W3C Working Draft 29 November 2011</h2><dl><dt>This version:</dt><dd><a href="http://www.w3.org/TR/2011/WD-CSP-20111129/">http://www.w3.org/TR/2011/WD-CSP-20111129/</a></dd><dt>Latest published version:</dt><dd><a href="http://www.w3.org/TR/CSP/">http://www.w3.org/TR/CSP/</a></dd><dt>Latest editor's draft:</dt><dd><a href="http://dvcs.w3.org/hg/content-security-policy/raw-file/tip/csp-specification.dev.html">http://dvcs.w3.org/hg/content-security-policy/raw-file/tip/csp-specification.dev.html</a></dd><dt>Editors:</dt><dd><a href="mailto:bsterne@mozilla.com">Brandon Sterne</a>, <a href="http://www.mozilla.com/">Mozilla Corporation</a></dd>
<dd><a href="mailto:w3c@adambarth.com">Adam Barth</a>, <a href="http://www.google.com/">Google, Inc.</a></dd>
</dl><p class="copyright"><a href="http://www.w3.org/Consortium/Legal/ipr-notice#Copyright">Copyright</a> © 2010-2011 <a href="http://www.w3.org/"><acronym title="World Wide Web Consortium">W3C</acronym></a><sup>®</sup> (<a href="http://www.csail.mit.edu/"><acronym title="Massachusetts Institute of Technology">MIT</acronym></a>, <a href="http://www.ercim.eu/"><acronym title="European Research Consortium for Informatics and Mathematics">ERCIM</acronym></a>, <a href="http://www.keio.ac.jp/">Keio</a>), All Rights Reserved. W3C <a href="http://www.w3.org/Consortium/Legal/ipr-notice#Legal_Disclaimer">liability</a>, <a href="http://www.w3.org/Consortium/Legal/ipr-notice#W3C_Trademarks">trademark</a> and <a href="http://www.w3.org/Consortium/Legal/copyright-documents">document use</a> rules apply.</p><hr></div>
    <div id="abstract" class="introductory section"><h2>Abstract</h2>
      <p>This document defines a policy language used to declare a set of
      content restrictions for a web resource, and a mechanism for
      transmitting the policy from a server to a client where the policy is
      enforced.</p>
    </div><div id="sotd" class="introductory section"><h2>Status of This Document</h2><p><em>This section describes the status of this document at the time of its publication. Other documents may supersede this document. A list of current W3C publications and the latest revision of this technical report can be found in the <a href="http://www.w3.org/TR/">W3C technical reports index</a> at http://www.w3.org/TR/.</em></p>
      <p>Although a FPWD, this document describes a proposal that has been
      discussed by the broader community for approximately a year.  There are experimental
      implementations in Firefox and Chrome, using the header names
      <code>X-Content-Security-Policy</code> and <code>X-WebKit-CSP</code>
      respectively.  Internet Explorer 10 Platform Preview also contains a
      partial implementation, using the header name
      X-Content-Security-Policy.</p>

      <p>In addition to the documents in the W3C Web Application Security
      working group, the work on this document is also informed by the work of
      the <a href="http://tools.ietf.org/wg/websec/">IETF websec working
      group</a>, particularly that working group's requirements document:
      <a href="http://tools.ietf.org/id/draft-hodges-websec-framework-reqs">draft-hodges-websec-framework-reqs</a></p>
    <p>This document was published by the <a href="http://www.w3.org/2011/webappsec/">Web Application Security Working Group</a> as a First Public Working Draft. This document is intended to become a W3C Recommendation. If you wish to make comments regarding this document, please send them to <a href="mailto:public-webappsec@w3.org">public-webappsec@w3.org</a> (<a href="mailto:public-webappsec-request@w3.org?subject=subscribe">subscribe</a>, <a href="http://lists.w3.org/Archives/Public/public-webappsec/">archives</a>). All feedback is welcome.</p><p>Publication as a Working Draft does not imply endorsement by the W3C Membership. This is a draft document and may be updated, replaced or obsoleted by other documents at any time. It is inappropriate to cite this document as other than work in progress.</p><p>This document was produced by a group operating under the <a href="http://www.w3.org/Consortium/Patent-Policy-20040205/">5 February 2004 W3C Patent Policy</a>. W3C maintains a <a href="http://www.w3.org/2004/01/pp-impl/49309/status" rel="disclosure">public list of any patent disclosures</a> made in connection with the deliverables of the group; that page also includes instructions for disclosing a patent. An individual who has actual knowledge of a patent which the individual believes contains <a href="http://www.w3.org/Consortium/Patent-Policy-20040205/#def-essential">Essential Claim(s)</a> must disclose the information in accordance with <a href="http://www.w3.org/Consortium/Patent-Policy-20040205/#sec-Disclosure">section 6 of the W3C Patent Policy</a>.</p></div><div id="toc" class="section"><h2 class="introductory">Table of Contents</h2><ul class="toc"><li class="tocline"><a href="#introduction" class="tocxref"><span class="secno">1. </span>Introduction</a></li><li class="tocline"><a href="#conformance" class="tocxref"><span class="secno">2. </span>Conformance</a><ul class="toc"><li class="tocline"><a href="#terminology" class="tocxref"><span class="secno">2.1 </span>Terminology</a></li></ul></li><li class="tocline"><a href="#framework" class="tocxref"><span class="secno">3. </span>Framework</a><ul class="toc"><li class="tocline"><a href="#policy-delivery" class="tocxref"><span class="secno">3.1 </span>Policy Delivery</a><ul class="toc"><li class="tocline"><a href="#content-security-policy-header-field" class="tocxref"><span class="secno">3.1.1 </span><code>Content-Security-Policy</code> Header Field</a></li><li class="tocline"><a href="#content-security-policy-report-only-header-field" class="tocxref"><span class="secno">3.1.2 </span><code>Content-Security-Policy-Report-Only</code> Header Field</a></li><li class="tocline"><a href="#html-meta-element" class="tocxref"><span class="secno">3.1.3 </span>HTML <code>meta</code> Element</a></li></ul></li><li class="tocline"><a href="#syntax" class="tocxref"><span class="secno">3.2 </span>Syntax</a><ul class="toc"><li class="tocline"><a href="#policies" class="tocxref"><span class="secno">3.2.1 </span>Policies</a></li><li class="tocline"><a href="#source-list" class="tocxref"><span class="secno">3.2.2 </span>Source List</a></li></ul></li><li class="tocline"><a href="#processing-model" class="tocxref"><span class="secno">3.3 </span>Processing Model</a></li></ul></li><li class="tocline"><a href="#directives" class="tocxref"><span class="secno">4. </span>Directives</a><ul class="toc"><li class="tocline"><a href="#default-src" class="tocxref"><span class="secno">4.1 </span><code>default-src</code></a></li><li class="tocline"><a href="#script-src" class="tocxref"><span class="secno">4.2 </span><code>script-src</code></a></li><li class="tocline"><a href="#object-src" class="tocxref"><span class="secno">4.3 </span><code>object-src</code></a></li><li class="tocline"><a href="#style-src" class="tocxref"><span class="secno">4.4 </span><code>style-src</code></a></li><li class="tocline"><a href="#img-src" class="tocxref"><span class="secno">4.5 </span><code>img-src</code></a></li><li class="tocline"><a href="#media-src" class="tocxref"><span class="secno">4.6 </span><code>media-src</code></a></li><li class="tocline"><a href="#frame-src" class="tocxref"><span class="secno">4.7 </span><code>frame-src</code></a></li><li class="tocline"><a href="#font-src" class="tocxref"><span class="secno">4.8 </span><code>font-src</code></a></li><li class="tocline"><a href="#connect-src" class="tocxref"><span class="secno">4.9 </span><code>connect-src</code></a></li><li class="tocline"><a href="#sandbox" class="tocxref"><span class="secno">4.10 </span><code>sandbox</code></a></li><li class="tocline"><a href="#report-uri" class="tocxref"><span class="secno">4.11 </span><code>report-uri</code></a></li><li class="tocline"><a href="#policy-uri" class="tocxref"><span class="secno">4.12 </span><code>policy-uri</code></a></li></ul></li><li class="tocline"><a href="#examples" class="tocxref"><span class="secno">5. </span>Examples</a><ul class="toc"><li class="tocline"><a href="#sample-policy-definitions" class="tocxref"><span class="secno">5.1 </span>Sample Policy Definitions</a></li><li class="tocline"><a href="#sample-violation-report" class="tocxref"><span class="secno">5.2 </span>Sample Violation Report</a></li></ul></li><li class="tocline"><a href="#references" class="tocxref"><span class="secno">A. </span>References</a><ul class="toc"><li class="tocline"><a href="#normative-references" class="tocxref"><span class="secno">A.1 </span>Normative references</a></li><li class="tocline"><a href="#informative-references" class="tocxref"><span class="secno">A.2 </span>Informative references</a></li></ul></li></ul></div>

    

    <div class="informative section" id="introduction">
      <!--OddPage--><h2><span class="secno">1. </span>Introduction</h2><p><em>This section is non-normative.</em></p>

      <p>This document defines Content Security Policy, a mechanism web
      applications can use to mitigate the broad class of content injection
      vulnerabilities, such as cross-site scripting (XSS). Content Security
      Policy is a declarative policy that lets the authors (or server
      administrators) of a web application restrict from where the application
      can load resources.</p>

      <p>To mitigate XSS, for example, a web application can restrict itself
      to loading scripts only from known, trusted URIs, making it difficult
      for an attacker who can inject content into the web application to
      inject malicious script.</p>

      <p>Content Security Policy (CSP) is not intended as a first line of
      defense against content injection vulnerabilities. Instead, CSP is best
      used as defense-in-depth, to reduce the harm caused by content injection
      attacks.</p>

      <p>There is often a non-trivial amount of work required to apply CSP to
      an existing web application. To reap the greatest benefit, authors will
      need to move all inline script and style out-of-line, for example into
      external scripts, because the user agent cannot determine whether an
      inline script was injected by an attacker.</p>

      <p>To take advantage of CSP, a web application needs to opt into using
      CSP by supplying a Content-Security-Policy HTTP header or an appropriate
      HTML <code>meta</code> element. Such policies apply the current document
      only. To supply a policy for an entire site, the server need to supply a
      policy along with each resource representation.</p>
    </div>

    <div id="conformance" class="section"><!--OddPage--><h2><span class="secno">2. </span>Conformance</h2><p>As well as sections marked as non-normative, all authoring guidelines, diagrams, examples, and notes in this specification are non-normative. Everything else in this specification is normative.</p>
<p>The key words <em class="rfc2119" title="must">must</em>, <em class="rfc2119" title="must not">must not</em>, <em class="rfc2119" title="required">required</em>, <em class="rfc2119" title="should">should</em>, <em class="rfc2119" title="should not">should not</em>, <em class="rfc2119" title="recommended">recommended</em>, <em class="rfc2119" title="may">may</em>, and <em class="rfc2119" title="optional">optional</em> in this specification are to be interpreted as described in [<cite><a class="bibref" rel="biblioentry" href="#bib-RFC2119">RFC2119</a></cite>].</p>

      <p>Requirements phrased in the imperative as part of algorithms (such as
      "strip any leading space characters" or "return false and abort these
      steps") are to be interpreted with the meaning of the key word ("<em class="rfc2119" title="must">must</em>",
      "<em class="rfc2119" title="should">should</em>", "<em class="rfc2119" title="may">may</em>", etc) used in introducing the algorithm.</p>

      <p>A conformant user-agent is one that implements all the requirements
      listed in this specification that are applicable to user-agents.</p>

      <p>A conformant server is one that implements all the requirements
      listed in this specification that are applicable to servers.</p>

      <div id="terminology" class="section">
        <h3><span class="secno">2.1 </span>Terminology</h3>

        <p>This section defines several terms used throughout the document.</p>

        <p>The term <dfn id="dfn-security-policy">security policy</dfn>, or
        simply <dfn id="dfn-policy">policy</dfn>, for the purposes of this
        specification refers to either:
          </p><ol>
            <li>a set of security preferences for restricting the behavior of
            content within a given document, or</li>
            <li>a fragment of text that codifies these preferences.</li>
          </ol>
        <p></p>

        <p>The security policies defined by this document are applied by a
        user-agent on a <em>per-resource representation basis</em>.
        Specifically, when a user agent receives a policy along with the
        representation of a given resource, that policy applies to <em>that
        resource representation only</em>. That resource representation is
        often referred to in this document as the <dfn id="dfn-protected-document">protected
        document</dfn>.

        </p><p>A server transmits its security policy for a particular resource as
        a collection of <dfn id="dfn-directives">directives</dfn>, such as <code>default-src
        'self'</code>, each of which controls a specific set of privileges for
        a document rendered by a user-agent. More details are provided in the
        <a href="#directives">directives</a> section.</p>

        <p>A directive consists of a <dfn id="dfn-directive-name">directive name</dfn>, which
        indicates the privileges controlled by the directive, and a
        <dfn id="dfn-directive-value">directive value</dfn>, which specifies the restrictions the
        policy imposes on those privileges.</p>

        <p>Fetching resources requires <dfn id="resolve">resolving</dfn>
        and <dfn id="parse-url">parsing</dfn> URLs.  The algorithms
        for <a href="http://www.whatwg.org/specs/web-apps/current-work/multipage/urls.html#resolving-urls">resolving
        a URL</a>
        and <a href="http://www.whatwg.org/specs/web-apps/current-work/multipage/urls.html#parse-a-url">parsing
        a URL</a> are defined in the HTML5 standard [<cite><a class="bibref" rel="biblioentry" href="#bib-HTML5">HTML5</a></cite>].</p>

        <p>The term <dfn id="dfn-origin">origin</dfn> is defined in the Origin specification.
        [<em><a href="http://tools.ietf.org/html/draft-ietf-websec-origin">ORIGIN</a></em>]</p>

        <p>The term <dfn id="dfn-uri">URI</dfn> is defined in the URI specification.  [<cite><a class="bibref" rel="biblioentry" href="#bib-URI">URI</a></cite>]</p>

        <p>The <code>&lt;script&gt;</code>, <code>&lt;object&gt;</code>, <code>&lt;embed&gt;</code>,
        <code>&lt;img&gt;</code>, <code>&lt;video&gt;</code>, <code>&lt;audio&gt;</code>,
        <code>&lt;link&gt;</code>, <code>&lt;frame&gt;</code> and <code>&lt;iframe&gt;</code>
        elements are defined in the HTML5 standard. [<cite><a class="bibref" rel="biblioentry" href="#bib-HTML5">HTML5</a></cite>].</p>

        <p>The <code>&lt;applet&gt;</code> element is defined in the HTML 4.01 standard. [<cite><a class="bibref" rel="biblioentry" href="#bib-HTML401">HTML401</a></cite>].</p>

        <p>The <code>@font-face</code> CSS rule is defined in the CSS Fonts Module Level 3 standard.
        [<cite><a class="bibref" rel="biblioentry" href="#bib-CSS3FONT">CSS3FONT</a></cite>]</p>

        <p>The <code>XMLHttpRequest</code> object is defined in the <code>XMLHttpRequest</code>
        standard. [<cite><a class="bibref" rel="biblioentry" href="#bib-XMLHTTPREQUEST">XMLHTTPREQUEST</a></cite>]</p>

        <p>The <code>WebSocket</code> object is defined in the <code>WebSocket</code>
        standard. [<em><a href="http://dev.w3.org/html5/websockets/">WEBSOCKET</a></em>].</p>

        <p>The <code>EventSource</code> object is defined in the <code>EventSource</code>
        standard. [<em><a href="http://dev.w3.org/html5/eventsource/">EVENTSOURCE</a></em>].</p>

        <p>The Augmented Backus-Naur Form (ABNF) notation used in this
        document is specified in RFC 5234. [<cite><a class="bibref" rel="biblioentry" href="#bib-ABNF">ABNF</a></cite>]</p>

        <p>The following core rules are included by reference, as defined in
        [<em><a href="http://tools.ietf.org/html/rfc5234#appendix-B.1">ABNF Appendix B.1</a></em>]:
        <code>ALPHA</code> (letters), <code>DIGIT</code> (decimal
        0-9), <code>WSP</code> (white space) and <code>VCHAR</code> (printing
        characters).</p>
      </div>
    </div>

    <div id="framework" class="section">
      <!--OddPage--><h2><span class="secno">3. </span>Framework</h2>

      <p>This section defines the general framework for content security
      policies, including the delivery mechanisms and general syntax for
      policies. The next section contains the details of the specific
      directives introduced in this specification.</p>

      <div id="policy-delivery" class="section">
        <h3><span class="secno">3.1 </span>Policy Delivery</h3>

        <p>The policy can be delivered from the server to the client via an HTTP response header
        or an HTML <code>meta</code> element.</p>

        <p>Of the two delivery mechanisms, servers <em class="rfc2119" title="should">should</em> use the HTTP
        response header mechanism whenever possible because, when using the
        <code>meta</code> element mechanism, there is a period of time between
        when the user agent begins to process the document and when the user
        agent encounters the <code>meta</code> element when the document is
        not protected by the policy.</p>

        <div id="content-security-policy-header-field" class="section">
          <h4><span class="secno">3.1.1 </span><code>Content-Security-Policy</code> Header Field</h4>

          <p>The <code>Content-Security-Policy</code> header field is the
          preferred mechanism for delivering a CSP policy.</p>

          <p>A server <em class="rfc2119" title="may">may</em> supply one or more CSP policies in HTTP response
          header fields named <code>Content-Security-Policy</code> along with
          the protected document.</p>

          <p>Upon receiving an HTTP response containing at least one
          <code>Content-Security-Policy</code> header field, the user agent
          <em class="rfc2119" title="must">must</em> <a href="#enforce-the-combination">enforce the combination</a>
          of all the policies contained in these header fields.</p>
        </div>

        <div id="content-security-policy-report-only-header-field" class="section">
          <h4><span class="secno">3.1.2 </span><code>Content-Security-Policy-Report-Only</code> Header Field</h4>

          <p>The <code>Content-Security-Policy-Report-Only</code> header field
          lets server experiment with CSP by monitoring (rather than
          enforcing) a policy. This feature lets server operators develop
          their security policy iteratively. They can deploy a report-only
          policy based on their best estimate of how their site behaves. If
          their site violates this policy, instead of breaking the site, the
          user agent will send violation reports to a URI specified in the
          policy. Once a site has confidence that the policy is appropriate,
          they can promote the report-only policy to normal blocking mode.</p>

          <p>A server <em class="rfc2119" title="may">may</em> supply one or more CSP policies in HTTP response
          header fields named <code>Content-Security-Policy-Report-Only</code>
          along with the protected document.</p>

          <p>If a server supplies at least one
          <code>Content-Security-Policy-Report-Only</code> header field in an
          HTTP response, the server <em class="rfc2119" title="must not">must not</em> supply any
          <code>Content-Security-Policy</code> header fields.</p>

          <p>Upon receiving an HTTP response containing at least one
          <code>Content-Security-Policy-Report-Only</code> header field, the
          user agent <em class="rfc2119" title="must">must</em> <a href="#monitor-the-combination">monitor the
          combination</a> of all the policies contained in these header
          fields.</p>
        </div>

        <div id="html-meta-element" class="section">
          <h4><span class="secno">3.1.3 </span>HTML <code>meta</code> Element</h4>

          <p>The server <em class="rfc2119" title="may">may</em> supply a CSP policy in an HTML <code>meta</code>
          element with an <code>http-equiv</code> attribute that is a case
          insensitive match for either <code>Content-Security-Policy</code> or
          <code>Content-Security-Policy-Report-Only</code>.</p>

          <p>Add the following entries to the <a href="http://www.w3.org/TR/html5/semantics.html#pragma-directives">pragma
          directives</a> for the <code>meta</code> element:</p>

          <dl>
            <dt>Content security policy (<code>http-equiv="content-security-policy"</code>)</dt>
            <dd>
              <ol>
                <li>If the document already has a <var>csp-policy</var>, abort
                these steps.</li>

                <li>If the <code>meta</code> element lacks a
                <code>content</code> attribute, abort these steps.</li>

                <li><a href="#enforce">Enforce</a> the CSP policy contained in
                the <code>content</code> attribute of the <code>meta</code>
                element.</li>
              </ol>
            </dd>

            <dt>Content security policy, report only (<code>http-equiv="content-security-policy-report-only"</code>)</dt>
            <dd>
              <ol>
                <li>If the document already has a <var>csp-policy</var>, abort
                these steps.</li>

                <li>If the <code>meta</code> element lacks a
                <code>content</code> attribute, abort these steps.</li>

                <li><a href="#monitor">Monitor</a> the CSP policy contained in
                the <code>content</code> attribute of the <code>meta</code>
                element.</li>
              </ol>
            </dd>
          </dl>
        </div>
      </div>

      <div id="syntax" class="section">
        <h3><span class="secno">3.2 </span>Syntax</h3>

        <div id="policies" class="section">
          <h4><span class="secno">3.2.1 </span>Policies</h4>

          <p>A CSP <dfn id="dfn-policy-1">policy</dfn> consists of a U+003B SEMICOLON
          (<code>;</code>) delimited list of directives:</p>

<pre>policy            = directive-list
directive-list    = [ directive *( ";" [ directive ] ) ]
</pre>

          <p>Each <dfn id="dfn-directive">directive</dfn> consists of a <var>directive-name</var>
          and (optionally) a <var>directive-value</var>:</p>

<pre>directive         = *WSP [ directive-name [ WSP directive-value ] ]
directive-name    = 1*( ALPHA / DIGIT / "-" )
directive-value   = *( WSP / &lt;VCHAR except ";"&gt; )
</pre>

          <p>To <dfn id="parse-a-csp-policy">parse a CSP policy</dfn>
          <var>policy</var>, the user agent <em class="rfc2119" title="must">must</em> use an algorithm equivalent to
          the following:</p>

          <ol>
            <li>Let the <var>set of directives</var> be the empty set.</li>

            <li>For each token returned by <a href="http://dev.w3.org/html5/spec/common-microsyntaxes.html#strictly-split-a-string">strictly
            splitting</a> the string <var>policy</var> on the character U+003B
            SEMICOLON (<code>;</code>):
              <ol>
                <li><a href="http://dev.w3.org/html5/spec/common-microsyntaxes.html#skip-whitespace">Skip whitespace</a>.</li>

                <li><a href="http://dev.w3.org/html5/spec/common-microsyntaxes.html#collect-a-sequence-of-characters">Collect
                a sequence of characters</a> that are not
                <a href="http://dev.w3.org/html5/spec/common-microsyntaxes.html#space-character">space characters</a>. The
                collected characters are the <var>directive name</var>.</li>

                <li>If <var>position</var> doesn't point past the end of the
                token, skip ahead one character (which must be a <a href="http://dev.w3.org/html5/spec/common-microsyntaxes.html#space-character">space
                character</a>).</li>

                <li>The remaining characters in <var>token</var> (if any) are
                the <var>directive value</var>.</li>

                <li>If the <var>set of directives</var> already contains a
                directive with name <var>directive name</var>, ignore this
                instance of the directive and continue to the next token.</li>

                <li>Add a <var>directive</var> to the <var>set of
                directives</var> with name <var>directive name</var> and value
                <var>directive value</var>.</li>
              </ol>
            </li>

            <li>Return the <var>set of directives</var>.
          </li></ol>
        </div>

        <div id="source-list" class="section">
          <h4><span class="secno">3.2.2 </span>Source List</h4>

          <p>Many CSP directives use a value consisting of a <dfn id="dfn-source-list">source
          list</dfn>.</p>

          <p>Each <dfn id="dfn-source-expression">source expression</dfn> in the source list represents a
          location from which content of the specified type can be retrieved.
          For example, the source expression <code>'self'</code> represents
          the set of URIs which are in the same origin as the protected
          document and the source expression <code>'unsafe-inline'</code>
          represents content supplied inline in the document itself.</p>

<pre>source-list       = *WSP [ source-expression *( 1*WSP source-expression ) *WSP ]
                  / *WSP "'none'" *WSP
source-expression = scheme-source / host-source / keyword-source
scheme-source     = scheme ":"
host-source       = ( [ scheme "://" ] host [ port ] )
keyword-source    = "'self'" / "'unsafe-inline'" / "'unsafe-eval'"
scheme            = &lt;scheme&gt; production from RFC 3986
host              = "*" / [ "*." ] 1*host-char *( "." 1*host-char )
host-char         = ALPHA / DIGIT / "-"
port              = ":" ( 1*DIGIT / "*" )
</pre>

          <p>To <dfn id="parse-a-source-list">parse a source list</dfn>
          <var>source list</var>, the user agent <em class="rfc2119" title="must">must</em> use an algorithm
          equivalent to the following:</p>

          <ol>
            <li>If <var>source list</var> (with <a href="http://dev.w3.org/html5/spec/common-microsyntaxes.html#strip-leading-and-trailing-whitespace">leading
            and trailing whitespace stripped</a>) is a case insensitive match
            for the string <code>'none'</code> (including the quotation
            marks), return the empty set.</li>

            <li>Let the <var>set of source expressions</var> be the empty set.</li>

            <li>For each token returned by <a href="http://dev.w3.org/html5/spec/common-microsyntaxes.html#split-a-string-on-spaces">splitting
            <var>source list</var> on spaces</a>, if the token matches the
            grammar for <code>source-expression</code>, add the token to the
            <var>set of source expressions</var>.</li>

            <li>Return the <var>set of source expressions</var>.</li>
          </ol>

          <p>To check whether a URI <dfn id="matches-a-source-expression">matches a source expression</dfn>,
          the user agent <em class="rfc2119" title="must">must</em> use an algorithm equivalent to the
          following:</p>

          <ol>
            <li>If the source expression a single U+002A ASTERISK character
            (<code>*</code>), then return <em>does match</em>.</li>

            <li>If the source expression matches the grammar for
            <code>scheme-source</code>, then the URI matches the source
            expression of the URI's scheme is a case-insensitive match for the
            source expression's <code>scheme</code>.</li>

            <li>Otherwise, if the source expression matches the grammar for
            <code>host-source</code>:
              <ol>
                <li>If the URI does not contain a host, then return <em>does
                not match</em>.</li>

                <li>Let <var>scheme</var>, <var>host</var>, and
                <var>port</var> be the scheme, host, and port of the URI,
                respectively. If the URI does not have a port, then let
                <var>port</var> be the default port for
                <var>scheme</var>.</li>

                <li>If the source expression has a <code>scheme</code> that is
                not a case insensitive match for <var>scheme</var>, then
                return <em>does not match</em>.</li>

                <li>If <var>scheme</var> is not a case insensitive match for
                the scheme of the protected document's URI, then return
                <em>does not match</em>.<br>
                <em>FIXME: Should we allow HTTPS when the document's scheme is
                HTTP?</em></li>

                <li>If the first character of the source expression's
                <code>host</code> is an U+002A ASTERISK character
                (<code>*</code>) and the remaining characters, including the
                leading U+002E FULL STOP character (<code>.</code>), are not a
                case insensitive match for the rightmost characters of
                <var>host</var>, then return <em>does not match</em>.</li>

                <li>If <var>host</var> is not a case insensitive match for the
                source expression's <code>host</code>, then return <em>does
                not match</em>.</li>

                <li>If the source expression does not contain a
                <code>port</code> and <var>port</var> is not the default port
                for <var>scheme</var>, then return <em>does not
                match</em>.</li>

                <li>If the source expression does contain a <code>port</code>
                that (a) does <em>not</em> contain an U+002A ASTERISK
                character (<code>*</code>) and (b) does <em>not</em> represent
                the same number as <var>port</var>, then return <em>does not
                match</em>.</li>

                <li>Return <em>does match</em>.</li>
              </ol>

              </li><li>Otherwise, if the source expression is a case insensitive
              match for <code>'self'</code> (including the quotation marks),
              then return the URI matches the source expression if the URI has
              the same scheme, host, and port as the document's URI.</li>

              <li>Otherwise, the URI does not match the source expression.</li>
            
          </ol>

          <p>A URI <dfn id="matches-a-source-list">matches a source
          list</dfn>, if, and only if, the URI <a href="#matches-a-source-expression">matches at least one source
          expression</a> in the set of source expressions obtained by <a href="#parse-a-source-list">parsing the source list</a>. Notice that
          no URIs match an empty set of source expressions, such as the set
          obtained by parsing the source list <code>'none'</code>.</p>
        </div>
      </div>

      <div id="processing-model" class="section">
        <h3><span class="secno">3.3 </span>Processing Model</h3>

        <p>To <dfn id="enforce">enforce</dfn> a CSP policy, the user agent <em class="rfc2119" title="must">must</em>
        <a href="#parse-a-csp-policy">parse the policy</a> and enforce each of
        the directives contained in the policy, where the specific
        requirements for enforcing each directive are defined separately for
        each directive (See <a href="#sec-directives">Directives</a>,
        below).</p>

        <p>Generally speaking, enforcing a directive prevent the protected
        document from performing certain actions, such as loading scripts from
        URIs other than those indicated in a source list. These restrictions
        make it more difficult for an attacker to abuse an injection
        vulnerability in the document because the attacker will be unable to
        usurp the document's privileges that have been restricted in this
        way.</p>

        <p>Enforcing a CSP policy <em class="rfc2119" title="should not">should not</em> interfere with the operation of
        user-supplied scripts such as third-party user-agent add-ons and
        JavaScript bookmarklets.</p>

        <p>To <dfn id="monitor">monitor</dfn> a CSP policy, the user agent <em class="rfc2119" title="must">must</em>
        <a href="#parse-a-csp-policy">parse the policy</a> and monitor each of
        the directives contained in the policy, where the specific
        requirements for monitoring each directive are defined separately for
        each directive (See <a href="#sec-directives">Directives</a>,
        below).</p>

        <p>Generally speaking, monitoring a directive does not prevent the
        protected document from undertaking any actions. Instead, any actions
        that would have been prevented by the directive are instead reported
        to the developer of the web application. Monitoring a CSP policy is
        most useful for testing whether enforcing the policy will break the
        web application.</p>

        <p>If the user agent monitors or enforces a CSP policy that does not
        contain any directives, the user agent <em class="rfc2119" title="should">should</em> report a warning message
        in the developer console.</p>

        <p>If the user agent monitors or enforces a CSP policy that contains
        an unrecognized directive, the user agent <em class="rfc2119" title="should">should</em> report a warning
        message in the developer console indicating the name of the
        unrecognized directive.</p>

        <p>To <dfn id="enforce-the-combination">enforce the combination</dfn>
        of one or more policies, the user agent <em class="rfc2119" title="must">must</em> enforce each policy. For
        example, if an action is prevented by at least one of the policies,
        then the action will be prevented by the combination of the
        policies.</p>

        <p>To <dfn id="monitor-the-combination">monitor the combination</dfn>
        of one or more policies, the user agent <em class="rfc2119" title="must">must</em> monitor each each
        policy.</p>
      </div>
    </div>

    <div id="directives" class="section">
      <!--OddPage--><h2 id="sec-directives"><span class="secno">4. </span>Directives</h2>

      <p>This section describes the content security policy directives
      introduced in this specification.</p>

      <p>In order to protect against Cross-site Scripting (XSS), authors
      <em class="rfc2119" title="should">should</em> include
      </p><ul>
        <li>both the <code>script-src</code> and <code>object-src</code>
        directives, or</li>

        <li>include a <code>default-src</code> directive, which covers both
        scripts and plug-ins.</li>
      </ul>

      <p>In either case, authors <em class="rfc2119" title="should not">should not</em> include
      <code>'unsafe-inline'</code> in their CSP policies if they wish to
      protect themselves against XSS.</p>

      <div id="default-src" class="section">
        <h3><span class="secno">4.1 </span><code>default-src</code></h3>

        <p>The <code>default-src</code> directive sets a default source list
        for a number of directives. The syntax for the name and value of the
        directive are described by the following ABNF grammar:</p>

<pre>directive-name    = "default-src"
directive-value   = source-list
</pre>

        <p>Let the <var>default sources</var> be the result of <a href="#parse-a-source-list">parsing the directive's value as a
        source list</a>.</p>

        <p>To enforce the <code>default-src</code> directive, the user agent
        <em class="rfc2119" title="must">must</em> enforce the following directives:</p>
        <ul>
          <li>script-src</li>
          <li>object-src</li>
          <li>style-src</li>
          <li>img-src</li>
          <li>media-src</li>
          <li>frame-src</li>
          <li>font-src</li>
          <li>connect-src</li>
        </ul>

        <p>If not specified explicitly in the policy, the directives listed
        above will use the <var>default sources</var>.</p>
      </div>

      <div id="script-src" class="section">
        <h3><span class="secno">4.2 </span><code>script-src</code></h3>

        <p>The <code>script-src</code> directive restricts which scripts the
        protected document can execute. The directive also controls other
        resources, such as XSLT stylesheets, which can cause the user agent to
        execute script. The syntax for the name and value of the directive are
        described by the following ABNF grammar:</p>

<pre>directive-name    = "script-src"
directive-value   = source-list
</pre>

        <p>If the policy contains an explicit <code>script-src</code>, let the
        <var>allowed script sources</var> be the result of <a href="#parse-a-source-list">parsing the directive's value as a source
        list</a>. Otherwise, let the <var>allowed script sources</var> be the
        <var>default sources</var></p>

        <p>If <code>'unsafe-inline'</code> is not in <var>allowed script
        sources</var>:</p>
        <ul>
          <li>Whenever the user agent would execute an inline script (either
          from a <code>script</code> element or from an inline event handler),
          instead the user agent <em class="rfc2119" title="must not">must not</em> execute script.</li>

          <li>Whenever the user agent would execute script contained in a
          <code>javascript</code> URI, instead the user agent <em class="rfc2119" title="must not">must not</em> execute
          the script. (Note: The user agent <em class="rfc2119" title="should">should</em> execute script contained in
          "bookmarklets" even when enforcing this restriction.)</li>
        </ul>

        <p>If <code>'unsafe-eval'</code> is not in <var>allowed script
        sources</var>:</p>
        <ul>
          <li>Instead of evaluating their arguments, both operator
          <code>eval</code> and function <code>eval</code> <em class="rfc2119" title="must">must</em> throw a
          security exception.</li>

          <li>When called as a constructor, the function <code>Function</code>
          <em class="rfc2119" title="must">must</em> throw a security exception.</li>

          <li>When called with a first argument that is non-callable (e.g.,
          not a function), the <code>setTimeout</code> function <em class="rfc2119" title="must">must</em> return
          zero without creating a timer.</li>

          <li>When called with a first argument that is non-callable (e.g.,
          not a function), the <code>setInterval</code> function <em class="rfc2119" title="must">must</em> return
          zero without creating a timer.</li>
        </ul>

        <p>The term <dfn id="dfn-callable">callable</dfn> refers to an object whose interface
        has one or more <dfn id="dfn-callers">callers</dfn> as defined in the <a href="http://www.w3.org/TR/2010/WD-WebIDL-20101021/#idl-callers">Web
        IDL</a> specification [<cite><a class="bibref" rel="biblioentry" href="#bib-WEBIDL">WEBIDL</a></cite>].</p>

        <p>Whenever the user agent <a href="http://www.w3.org/TR/html5/fetching-resources.html#fetch">fetches</a>
        a URI (including when following redirects) in the course of one of the
        following activities, if the URI does not <a href="#matches-a-source-list">match the <var>allowed script
        sources</var></a>, the user agent <em class="rfc2119" title="must">must</em> act as if it had received an empty
        HTTP 400 response:</p>
        <ul>
          <li>Requesting a script, such as when processing the
          <code>src</code> attribute of a <code>script</code> element or when
          processing the <code>Worker</code> or <code>SharedWorker</code>
          constructors.</li>

          <li>Requesting an Extensible Stylesheet Language Transformations
          (XSLT), such as when processing the
          <code>&lt;?xml-stylesheet?&gt;</code> processing directive in an XML
          document, the <code>href</code> attributes on
          <code>&lt;xsl:include&gt;</code> element, or the <code>href</code>
          attributes on <code>&lt;xsl:import&gt;</code> element.</li>
        </ul>
      </div>
      <div id="object-src" class="section">
        <h3><span class="secno">4.3 </span><code>object-src</code></h3>

        <p>The <code>object-src</code> directive restricts from where the
        protected document can load plugins. The syntax for the name and value
        of the directive are described by the following ABNF grammar:</p>

<pre>directive-name    = "object-src"
directive-value   = source-list
</pre>

        <p>If the policy contains an explicit <code>object-src</code>, let the
        <var>allowed object sources</var> be the result of <a href="#parse-a-source-list">parsing the directive's value as a source
        list</a>. Otherwise, let the <var>allowed object sources</var> be the
        <var>default sources</var></p>

        <p>Whenever the user agent <a href="http://www.w3.org/TR/html5/fetching-resources.html#fetch">fetches</a>
        a URI (including when following redirects) in the course of one of the
        following activities, if the URI does not <a href="#matches-a-source-list">match the <var>allowed object
        sources</var></a>, the user agent <em class="rfc2119" title="must">must</em> act as if it had received an empty
        HTTP 400 response:</p>
        <ul>
          <li>Requesting data for a plugin, such as when processing the
          <code>data</code> attribute of an <code>object</code> element, the
          <code>src</code> attribute of an <code>embed</code> elements, or the
          <code>code</code> or <code>archive</code> attributes of an
          <code>applet</code> element.</li>
        </ul>

        <p>Whenever the user agent would load a plug-in without an associated
        URI (e.g., because the <code>object</code> element lacked a
        <code>data</code> attribute), if the protected document's URI does not
        <a href="#matches-a-source-list">match the <var>allowed object
        sources</var></a>, the user agent <em class="rfc2119" title="must not">must not</em> load the plug-in.</p>
      </div>

      <div id="style-src" class="section">
        <h3><span class="secno">4.4 </span><code>style-src</code></h3>

        <p>The <code>style-src</code> directive restricts which styles the
        user applies to the protected document. The syntax for the name and
        value of the directive are described by the following ABNF
        grammar:</p>

<pre>directive-name    = "style-src"
directive-value   = source-list
</pre>


        <p>If the policy contains an explicit <code>style-src</code>, let the
        <var>allowed style sources</var> be the result of <a href="#parse-a-source-list">parsing the directive's value as a source
        list</a>. Otherwise, let the <var>allowed style sources</var> be the
        <var>default sources</var></p>

        <p>If <code>'unsafe-inline'</code> is not in <var>allowed style
        sources</var>:</p>
        <ul>
          <li>Whenever the user agent would apply style from a
          <code>style</code> element, instead the user agent <code><em class="rfc2119" title="must">must</em></code>
          ignore the style.</li>

          <li>Whenever the user agent would apply style from a
          <code>style</code> attribute, instead the user agent
          <code><em class="rfc2119" title="must">must</em></code> ignore the style.</li>
        </ul>

        <p>Note: These restrictions on inline do not prevent the user agent
        from applying style from an external stylesheet (e.g., found via
        <code>&lt;link rel="stylesheet"&gt;</code>). The user agent is also
        not prevented from applying style from CSSOM.</p>

        <p>Whenever the user agent <a href="http://www.w3.org/TR/html5/fetching-resources.html#fetch">fetches</a>
        a URI (including when following redirects) in the course of one of the
        following activities, if the URI does not <a href="#matches-a-source-list">match the <var>allowed style
        sources</var></a>, the user agent <em class="rfc2119" title="must">must</em> act as if it had received an empty
        HTTP 400 response:</p>
        <ul>
          <li>Requesting external stylesheets, such as when processing the
          <code>href</code> attribute of a <code>link</code> element with a
          <code>rel</code> attribute containing the token
          <code>stylesheet</code> or when processing the <code>@import</code>
          directive in a stylesheet.</li>
        </ul>

        <p>Note: The <code>style-src</code> directive does not restrict the
        use of XSLT. XSLT is restricted by the <code>script-src</code>
        directive because the security consequences of including an untrusted
        XSLT stylesheet are similar to those incurred by including an
        untrusted script.</p>
      </div>

      <div id="img-src" class="section">
        <h3><span class="secno">4.5 </span><code>img-src</code></h3>

        <p>The <code>img-src</code> directive restricts from where the
        protected document can load images. The syntax for the name and value
        of the directive are described by the following ABNF grammar:</p>

<pre>directive-name    = "img-src"
directive-value   = source-list
</pre>

        <p>If the policy contains an explicit <code>img-src</code>, let the
        <var>allowed image sources</var> be the result of <a href="#parse-a-source-list">parsing the directive's value as a source
        list</a>. Otherwise, let the <var>allowed image sources</var> be the
        <var>default sources</var></p>

        <p>Whenever the user agent <a href="http://www.w3.org/TR/html5/fetching-resources.html#fetch">fetches</a>
        a URI (including when following redirects) in the course of one of the
        following activities, if the URI does not <a href="#matches-a-source-list">match the <var>allowed image
        sources</var></a>, the user agent <em class="rfc2119" title="must">must</em> act as if it had received an empty
        HTTP 400 response:</p>
        <ul>
          <li>Requesting data for an image, such as when processing the
          <code>src</code> attribute of an <code>img</code> elements,
          the <code>url()</code> or <code>image()</code> values on any CSS
          property that is capable of loading an image [<em><a href="http://www.w3.org/TR/css3-images/">CSS3-Images</a></em>], or
          the <code>href</code> attribute of a <code>link</code> element with
          an image-related <code>rel</code> attribute, such as
          <code>icon</code>.</li>
        </ul>

        <p class="issue">Should the user agent fire the error event when one of these loads fails?</p>
      </div>

      <div id="media-src" class="section">
        <h3><span class="secno">4.6 </span><code>media-src</code></h3>

        <p>The <code>media-src</code> directive restricts from where the
        protected document can load video and audio. The syntax for the name
        and value of the directive are described by the following ABNF
        grammar:</p>

<pre>directive-name    = "media-src"
directive-value   = source-list
</pre>

        <p>If the policy contains an explicit <code>media-src</code>, let the
        <var>allowed media sources</var> be the result of <a href="#parse-a-source-list">parsing the directive's value as a source
        list</a>. Otherwise, let the <var>allowed media sources</var> be the
        <var>default sources</var></p>

        <p>Whenever the user agent <a href="http://www.w3.org/TR/html5/fetching-resources.html#fetch">fetches</a>
        a URI (including when following redirects) in the course of one of the
        following activities, if the URI does not <a href="#matches-a-source-list">match the <var>allowed media
        sources</var></a>, the user agent <em class="rfc2119" title="must">must</em> act as if it had received an empty
        HTTP 400 response:</p>
        <ul>
          <li>Requesting data for a video or audio clip, such as when
          processing the <code>src</code> attribute of a <code>video</code>
          or <code>audio</code> elements.</li>
        </ul>
      </div>

      <div id="frame-src" class="section">
        <h3><span class="secno">4.7 </span><code>frame-src</code></h3>

        <p>The <code>frame-src</code> directive restricts from where the
        protected document can embed frames. The syntax for the name
        and value of the directive are described by the following ABNF
        grammar:</p>

<pre>directive-name    = "frame-src"
directive-value   = source-list
</pre>

        <p>If the policy contains an explicit <code>frame-src</code>, let the
        <var>allowed frame sources</var> be the result of <a href="#parse-a-source-list">parsing the directive's value as a source
        list</a>. Otherwise, let the <var>allowed frame sources</var> be the
        <var>default sources</var></p>

        <p>Whenever the user agent <a href="http://www.w3.org/TR/html5/fetching-resources.html#fetch">fetches</a>
        a URI (including when following redirects) in the course of one of the
        following activities, if the URI does not <a href="#matches-a-source-list">match the <var>allowed frame
        sources</var></a>, the user agent <em class="rfc2119" title="must">must</em> act as if it had received an empty
        HTTP 400 response:</p>
        <ul>
          <li>Requesting data for display in a frame, such as when processing
          the <code>src</code> attribute of an <code>iframe</code> or
          <code>frame</code> element.</li>
          <li>Navigating a nested browsing context within the protected
          document.</li>
        </ul>

        <p class="issue">How does this work for the <code>object</code>
        element? We don't know whether the request is going to lead to a
        plug-in or a frame until we get the response back and can look at the
        MIME type.</p>
      </div>

      <div id="font-src" class="section">
        <h3><span class="secno">4.8 </span><code>font-src</code></h3>

        <p>The <code>font-src</code> directive restricts from where the
        protected document can load fonts. The syntax for the name and value
        of the directive are described by the following ABNF grammar:</p>

<pre>directive-name    = "font-src"
directive-value   = source-list
</pre>

        <p>If the policy contains an explicit <code>font-src</code>, let the
        <var>allowed font sources</var> be the result of <a href="#parse-a-source-list">parsing the directive's value as a source
        list</a>. Otherwise, let the <var>allowed font sources</var> be the
        <var>default sources</var></p>

        <p>Whenever the user agent <a href="http://www.w3.org/TR/html5/fetching-resources.html#fetch">fetches</a>
        a URI (including when following redirects) in the course of one of the
        following activities, if the URI does not <a href="#matches-a-source-list">match the <var>allowed font
        sources</var></a>, the user agent <em class="rfc2119" title="must">must</em> act as if it had received an empty
        HTTP 400 response:</p>
        <ul>
          <li>Requesting data for display in a font, such as when processing
          the <code>@font-face</code> CSS rule. <em>TODO: Citation needed.</em></li>
        </ul>
      </div>

      <div id="connect-src" class="section">
        <h3><span class="secno">4.9 </span><code>connect-src</code></h3>

        <p>The <code>connect-src</code> directive restricts which URIs the
        protected document can load using DOM APIs. The syntax for the name
        and value of the directive are described by the following ABNF
        grammar:</p>

<pre>directive-name    = "connect-src"
directive-value   = source-list
</pre>

        <p>If the policy contains an explicit <code>connect-src</code>, let
        the <var>allowed connection targets</var> be the result of <a href="#parse-a-source-list">parsing the directive's value as a source
        list</a>. Otherwise, let the <var>allowed connection targets</var> be
        the <var>default sources</var></p>

        <p>Whenever the user agent <a href="http://www.w3.org/TR/html5/fetching-resources.html#fetch">fetches</a>
        a URI (including when following redirects) in the course of one of the
        following activities, if the URI does not <a href="#matches-a-source-list">match the <var>allowed font
        sources</var></a>, the user agent <em class="rfc2119" title="must">must</em> act as if it had received an empty
        HTTP 400 response:</p>
        <ul>
          <li>Processing the <a href="http://www.w3.org/TR/XMLHttpRequest/#the-open-method"><code>open()</code>
          method</a> of an <code>XMLHttpRequest</code> object.</li>

          <li>Processing the <a href="http://dev.w3.org/html5/websockets/#websocket"><code>WebSocket</code>
          constructor</a>.</li>

          <li>Processing the <a href="http://dev.w3.org/html5/eventsource/#eventsource"><code>EventSource</code>
          constructor</a>.</li>
        </ul>
      </div>

      <div id="sandbox" class="section">
        <h3><span class="secno">4.10 </span><code>sandbox</code></h3>

        <p class="issue">A future version of this document might include a
        <code>sandbox</code> directive for controlling the HTML5 sandbox
        flags.</p>
      </div>

      <div id="report-uri" class="section">
        <h3><span class="secno">4.11 </span><code>report-uri</code></h3>

        <p>The <code>report-uri</code> directive specifies a URI to which the
        user agent sends reports about policy violation. The syntax for the
        name and value of the directive are described by the following ABNF
        grammar:</p>

<pre>directive-name    = "report-uri"
directive-value   = uri-reference *( 1*WSP uri-reference )
uri-reference     = &lt;URI-reference from RFC 3986&gt;
</pre>

        <p>Let the <var>set of report URIs</var> be the value of the
        <code>report-uri</code> directive, each resolved relative to the
        protected document's URI.</p>

        <p>To <dfn id="send-a-violation-report">send a violation report</dfn>,
        the user agent <em class="rfc2119" title="must">must</em> use an algorithm equivalent to the following:</p>
        <ol>
          <li>Prepare a dictionary <var>violation dictionary</var> with the
          following keys and values:
            <dl>
              <dt>request</dt>
              <dd>HTTP request line of the protected resource whose policy was
              violated including method, URI and HTTP version</dd>

              <dt>request-headers</dt>
              <dd>HTTP request headers sent with the request for the protected
              resource whose policy was violated</dd>

              <dt>blocked-uri</dt>
              <dd>URI of the resource that was prevented from loading due to
              the policy violation</dd>

              <dt>violated-directive</dt>
              <dd>The policy directive that was violated</dd>

              <dt>original-policy</dt>
              <dd>The original policy as received by the user-agent. If the
              policy was received via more than one Content Security Policy
              response header, this field <em class="rfc2119" title="must">must</em> contain a comma separated list
              of original policies</dd>
            </dl>

            <p class="issue">We might need to change some of these keys
            because they can leak sensitive information.</p>
          </li>

          <li>If the origin of the blocked-uri is not the same as the
          document's origin, then replace the blocked-uri with the ASCII
          serialization of the blocked-uri's origin.</li>

          <li>Let the <var>violation report</var> be the JSON stringification
          of the <var>violation dictionary</var>.</li>

          <li>For each <var>report URI</var> in the <var>set of report URIs</var>:
            <ol>
              <li>If the <var>report URI</var> has a different scheme than the
              URI of the protected document, then ignore this <var>report
              URI</var> and continue to the next iteration of the loop.</li>

              <li>If the <var>report URI</var> has a different port than the
              URI of the protected document, then ignore this <var>report
              URI</var> and continue to the next iteration of the loop.</li>

              <li>If the <var>report URI</var>'s host does not share the same
              <em><a href="http://publicsuffix.org/">public suffix</a> +1 DNS
              label</em> as the URI of the protected document, then ignore
              this <var>report URI</var> and continue to the next iteration of
              the loop.

              <p>Examples of public suffixes include <code>.com</code>,
              <code>.net</code> and <code>.co.uk</code>. Examples of
              <em>"public suffix +1 DNS label"</em> include
              <code>example.com</code>, <code>example.net</code> and
              <code>example.co.uk</code>. Therefore a protected document whose
              host is <code>www.example.com</code> could have a
              <code>report-uri</code> hosted on
              <code>reports.example.com</code> but <b>not</b>
              <code>reports.example.net</code>.</p></li>

              <li>Fetch the <var>report URI</var> from origin of the protected
              document, with the synchronous flag <em>not</em> set, using HTTP
              method <code>POST</code>, with a <code>Content-Type</code>
              header field of <code>application/json</code> with an entity
              body consisting of the <var>violation report</var>. The user
              agent <em class="rfc2119" title="must not">must not</em> follow redirects when fetching this resource.
              (Note: The user agent ignores the fetched resource.)</li>
            </ol>
          </li>
        </ol>
      </div>

      <div id="policy-uri" class="section">
        <h3><span class="secno">4.12 </span><code>policy-uri</code></h3>

        <p>The <code>policy-uri</code> directive specifies a URI from which
        the user agent can retrieve the actual policy. The syntax for the name
        and value of the directive are described by the following ABNF
        grammar:</p>

<pre>directive-name    = "policy-uri"
directive-value   = &lt;URI-reference from RFC 3986&gt;
</pre>

        <p class="issue">The <code>policy-uri</code> directive might be
        removed from this document.</p>

        <p>Authors <em class="rfc2119" title="must not">must not</em> specify policies that contain both a
        <code>policy-uri</code> directive and another directive.</p>

        <p>If the user agent would enforce a policy containing both the
        <code>policy-uri</code> directive and another directive, instead the
        user agent <em class="rfc2119" title="must">must</em> enforce the policy <code>default-src
        'none'</code>.</p>

        <p>When processing the <code>policy-uri</code> directive, the user
        agent <em class="rfc2119" title="must">must</em> run an algorithm equivalent to the following:</p>
        <ul>
          <li>Let <var>request URI</var> be the URI that results from
          resolving the value of the <code>policy-uri</code> directive
          relative to the URI of the protected document.</li>

          <li>If <var>request URI</var> is not from the same origin as the
          protected document, abort these steps and enforce the policy
          <code>default-src 'none'</code>.

          </li><li>Fetch the <var>request URI</var> from origin of the protected
          document, with the synchronous flag set, using HTTP method
          <code>GET</code>.</li>

          <li>If the fetch returned a status code other than <code>200</code>
          or if the request encountered an HTTP redirect, abort these steps
          and enforce the policy <code>default-src 'none'</code>.</li>

          <li>If the fetched resource lacks a <code>Content-Type</code> header
          field or if the <code>Content-Type</code> header field is not a case
          insensitive match for <code>text/x-content-security-policy</code>,
          abort these steps and enforce the policy <code>default-src
          'none'</code>.</li>

          <li>Let the <var>fetched policy</var> be the result of <a href="#parse-a-csp-policy">parsing the fetched resource as a CSP
          policy</a>.</li>

          <li>If the <var>fetched policy</var> contains a
          <code>policy-uri</code> directive, abort these steps and enforce the
          policy <code>default-src 'none'</code>.</li>

          <li><a href="#enforce">Enforce</a> the <var>fetched
          policy</var>.</li>
        </ul>
      </div>
    </div>

    <div id="examples" class="section">
      <!--OddPage--><h2><span class="secno">5. </span>Examples</h2>

      <div class="informative section" id="sample-policy-definitions">
        <h3><span class="secno">5.1 </span>Sample Policy Definitions</h3><p><em>This section is non-normative.</em></p>

        <p>This section provides some sample use cases and accompanying security policies.</p>

        <p><strong>Example 1:</strong> A server wishes to load resources only
        form its own origin:</p>

        <pre>Content-Security-Policy: default-src 'self'</pre>

        <p><strong>Example 2:</strong> An auction site wishes to load images
        from any URI, plug-in content from a list of trusted media providers
        (including a content distribution network), and scripts only from a
        server under its control hosting sanitized ECMAScript:</p>

        <pre>Content-Security-Policy: default-src 'self'; img-src *;
                         object-src media1.example.com media2.example.com *.cdn.example.com;
                         script-src trustedscripts.example.com</pre>

        <p><strong>Example 3:</strong> A site operations group wishes to globally deny all
        third-party scripts in the site, and a particular project team wishes to also disallow
        third-party media in their section of the site.  Site operations sends the first header
        while the project team sends the second header, and the user-agent takes the combination of
        the two headers to form the complete interpreted policy:</p>

        <pre>Content-Security-Policy: default-src *; script-src 'self'
Content-Security-Policy: default-src *; script-src 'self'; media-src 'self'</pre>

        <p><strong>Example 4:</strong> Online banking site wishes to ensure that all of the content
        in its pages is loaded over TLS to prevent attackers from eavesdropping on insecure content
        requests:</p>

        <pre>Content-Security-Policy: default-src https:</pre>
      </div>

      <div class="informative section" id="sample-violation-report">
        <h3><span class="secno">5.2 </span>Sample Violation Report</h3><p><em>This section is non-normative.</em></p>

        <p>This section contains an example violation report the user agent
        might sent to a server when the protected document violations a sample
        policy.</p>

        <p>In the following example, a document from
        <code>http://example.org/page.html</code> was rendered with the
        following CSP policy:</p>

<pre>default-src 'self'; report-uri http://example.org/csp-report.cgi</pre>

        <p>The document loaded an image from
        <code>http://evil.example.com/image.png</code>, violating the
        policy.</p>

        <pre>{
  "csp-report": {
    "request": "GET http://example.org/page.html HTTP/1.1",
    "request-headers": "Host: example.org
                        User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.6; rv:2.0b12pre) Gecko/20110222 Firefox/4.0b12pre
                        Accept: text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8
                        Accept-Language: en-us,en;q=0.5
                        Accept-Encoding: gzip, deflate
                        Accept-Charset: ISO-8859-1,utf-8;q=0.7,*;q=0.7
                        Keep-Alive: 115
                        Proxy-Connection: keep-alive
                        Cache-Control: max-age=0",
    "blocked-uri": "http://evil.example.com/image.png",
    "violated-directive": "default-src http://example.org"
  }
}</pre>

        <p>In the above sample report the <code>violated-directive</code>
        field was sent in the way it was interpreted by the user-agent. The
        directive was made explicit by replacing the keyword
        <code>'self'</code> with the explicit host name of the protected
        resource. This is recommended behavior for user-agents as it reduces
        ambiguity, making policy violations easier to trace by server
        admins.</p>

        <p class="issue">Should we add this as a requirement when preparing
        reports?</p>
      </div>
    </div>
  

<div id="references" class="appendix section"><!--OddPage--><h2><span class="secno">A. </span>References</h2><div id="normative-references" class="section"><h3><span class="secno">A.1 </span>Normative references</h3><dl class="bibliography"><dt id="bib-ABNF">[ABNF]</dt><dd>D. Crocker and P. Overell. <a href="http://www.ietf.org/rfc/rfc5234.txt"><cite>Augmented BNF for Syntax Specifications: ABNF.</cite></a> January 2008. Internet RFC 5234. URL: <a href="http://www.ietf.org/rfc/rfc5234.txt">http://www.ietf.org/rfc/rfc5234.txt</a>
</dd><dt id="bib-CSS3FONT">[CSS3FONT]</dt><dd>Michel Suignard; Chris Lilley. <a href="http://www.w3.org/TR/2002/WD-css3-fonts-20020802"><cite>CSS3 module: Fonts.</cite></a> 2 August 2002. W3C Working Draft. (Work in progress.) URL: <a href="http://www.w3.org/TR/2002/WD-css3-fonts-20020802">http://www.w3.org/TR/2002/WD-css3-fonts-20020802</a> 
</dd><dt id="bib-HTML401">[HTML401]</dt><dd>David Raggett; Ian Jacobs; Arnaud Le Hors. <a href="http://www.w3.org/TR/1999/REC-html401-19991224"><cite>HTML 4.01 Specification.</cite></a> 24 December 1999. W3C Recommendation. URL: <a href="http://www.w3.org/TR/1999/REC-html401-19991224">http://www.w3.org/TR/1999/REC-html401-19991224</a> 
</dd>

<dt id="bib-HTML5">[HTML5]</dt><dd>Ian Hickson; David Hyatt. <a
   href="http://www.w3.org/TR/html5"><cite>HTML5.</cite></a> 25 May
  2011. W3C Last Call Working Draft. (Work in progress.) URL: <a
   href="http://www.w3.org/TR/html5">http://www.w3.org/TR/html5</a><br>
  This draft refers to an updated version of section <a
   href="http://dev.w3.org/html5/spec/common-microsyntaxes.html">2.5
  Common microsyntaxes</a> that is, at time of this publication, only
  contained in the <a
   href="http://dev.w3.org/html5/spec/Overview.html">HTML5 Editor's
  Draft</a>.  </dd>

<dt id="bib-RFC2119">[RFC2119]</dt><dd>S. Bradner. <a href="http://www.ietf.org/rfc/rfc2119.txt"><cite>Key words for use in RFCs to Indicate Requirement Levels.</cite></a> March 1997. Internet RFC 2119.  URL: <a href="http://www.ietf.org/rfc/rfc2119.txt">http://www.ietf.org/rfc/rfc2119.txt</a> 
</dd><dt id="bib-URI">[URI]</dt><dd>T. Berners-Lee; R. Fielding; L. Masinter. <a href="http://www.ietf.org/rfc/rfc3986.txt"><cite>Uniform Resource Identifiers (URI): generic syntax.</cite></a> January 2005. Internet RFC 3986. URL: <a href="http://www.ietf.org/rfc/rfc3986.txt">http://www.ietf.org/rfc/rfc3986.txt</a> 
</dd><dt id="bib-WEBIDL">[WEBIDL]</dt><dd>Cameron McCormack. <a href="http://www.w3.org/TR/2008/WD-WebIDL-20081219"><cite>Web IDL.</cite></a> 19 December 2008. W3C Working Draft. (Work in progress.) URL: <a href="http://www.w3.org/TR/2008/WD-WebIDL-20081219">http://www.w3.org/TR/2008/WD-WebIDL-20081219</a> 
</dd><dt id="bib-XMLHTTPREQUEST">[XMLHTTPREQUEST]</dt><dd>Anne van Kesteren. <a href="http://www.w3.org/TR/2008/WD-XMLHttpRequest-20080415"><cite>The XMLHttpRequest Object.</cite></a> 15 April 2008. W3C Working Draft. (Work in progress.) URL: <a href="http://www.w3.org/TR/2008/WD-XMLHttpRequest-20080415">http://www.w3.org/TR/2008/WD-XMLHttpRequest-20080415</a> 
</dd></dl></div><div id="informative-references" class="section"><h3><span class="secno">A.2 </span>Informative references</h3><p>No informative references.</p></div></div></body></html>