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<h1>Content Security Policy Level 3</h1>
<pre class="metadata">
Status: ED
ED: https://w3c.github.io/webappsec-csp/
TR: http://www.w3.org/TR/CSP3/
Shortname: CSP
Level: 3
Editor: Mike West 56384, Google Inc., mkwst@google.com
Group: webappsec
Abstract:
This document defines a mechanism by which web developers can control the
resources which a particular page can fetch or execute, as well as a number
of security-relevant policy decisions.
Indent: 2
Version History: https://github.com/w3c/webappsec-csp/commits/master/index.src.html
Boilerplate: omit conformance, omit feedback-header
!Participate: <a href="https://github.com/w3c/webappsec-csp/issues/new">File an issue</a> (<a href="https://github.com/w3c/webappsec-csp/issues">open issues</a>)
Markup Shorthands: css off, markdown on
</pre>
<pre class="link-defaults">
spec:dom-ls; type:interface; text:Event
</pre>
<pre class="anchors">
spec: RFC6454; urlPrefix: https://tools.ietf.org/html/rfc6454
type: dfn
text: globally unique identifier; url: section-2.3
text: origin; url: section-3.2
text: the same; url: section-5
spec: ES2015; urlPrefix: http://www.ecma-international.org/ecma-262/6.0/index.html
type: method
text: eval(); url: sec-eval-x
text: Function(); url: sec-function-objects
text: JSON.stringify(); url: sec-json.stringify
spec: DOM; urlPrefix: http://www.w3.org/TR/dom/
type: interface
text: Element; url: interface-element
type: attribute
text: textContent; for: Node; url: dom-node-textcontent
spec: HTML5; urlPrefix: http://www.w3.org/TR/html5/
type: dfn
urlPrefix: embedded-content-0.html
text: an iframe srcdoc document
urlPrefix: browsers.html
text: active document
text: ancestor browsing context
text: browsing context
text: create a document object
text: creator document
text: opener browsing context
text: nested browsing context
text: nested through; url: browsing-context-nested-through
text: forced sandboxing flag set
text: parse a sandboxing directive
urlPrefix: dom.html
text: CSP list; for: document; url: concept-document-csp-list
urlPrefix: webappapis.html
text: environment settings object; url: settings-object
text: global object
text: incumbent settings object
text: relevant settings object; url: relevant-settings-object-for-a-global-object
text: responsible browsing context
text: queue a task
urlPrefix: infrastructure.html
text: fire; url: concept-event-fire
text: trusted; url: concept-event-trusted
text: case-sensitive; url: case-sensitive
text: ASCII case-insensitive match; url: ascii-case-insensitive
text: reflect
text: strictly split a string
text: strip leading and trailing whitespace
text: collect a sequence of characters
text: space characters
text: split a string on spaces
text: split a string on commas
urlPrefix: document-metadata.html
text: pragma directives
text: set the frozen base url
urlPrefix: scripting-1.html
text: prepare a script
text: the script block's source; url: the-script-block's-source
type: element
urlPrefix: document-metadata.html
text: base; url: the-base-element
text: head; url: the-head-element
text: link; url: the-link-element
text: meta; url: the-meta-element
text: style; url: the-style-element
urlPrefix: embedded-content-0.html
text: embed; url: the-embed-element
text: object; url: the-object-element
text: iframe; url: the-iframe-element
urlPrefix: scripting-1.html
text: script; url: the-script-element
urlPrefix: text-level-semantics.html
text: a; url: the-a-element
urlPrefix: obsolete.html
text: applet; url: the-applet-element
text: frame
type: element-attr
urlPrefix: document-metadata.html
text: content; for: meta; url: attr-meta-content
text: http-equiv; for: meta; url: attr-meta-http-equiv
urlPrefix: embedded-content-0.html
text: srcdoc; for: iframe; url: attr-iframe-srcdoc
urlPrefix: scripting-1.html
text: src; for: script; url: attr-script-src
type: interface
urlPrefix: dom.html
text: Document
urlPrefix: browsers.html
text: Window; url: dom-window
type: attribute
urlPrefix: browsers.html
text: document; for: Window; url: dom-document-2
urlPrefix: dom.html
text: referrer; for: Document; url: dom-document-referrer
spec: FETCH; urlPrefix: https://fetch.spec.whatwg.org/
type: dfn
text: fetch; url: concept-fetch
text: main fetch
text: http-network fetch
text: http fetch
text: parse a header value; url: concept-header-parse
text: request; url: concept-request
text: response; url: concept-response
text: header; url: concept-header
text: header list; url: concept-header-list
text: network error; url: concept-network-error
for: header
text: name; url: concept-header-name
for: response
text: CSP list; url: concept-response-csp-list
text: header list; url: concept-response-header-list
text: url; url: concept-response-url
for: request
text: body; url:concept-request-body
text: cache mode; url:concept-request-cache-mode
text: client; url: concept-request-client
text: credentials mode; url:concept-request-credentials-mode
text: current url; url: concept-request-current-url
text: destination; url: concept-request-destination
text: global object; url: concept-request-global-object
text: header list; url: concept-request-header-list
text: initiator; url: concept-request-initiator
text: method; url:concept-request-method
text: origin; url:concept-request-origin
text: redirect mode; url:concept-request-redirect-mode
text: target browsing context; url: concept-request-target-browsing-context
text: type; url: concept-request-type
text: url; url: concept-request-url
text: window; url:concept-request-window
type: interface
text: Request
spec: MIX; urlPrefix: http://www.w3.org/TR/mixed-content/
type: dfn; text: block-all-mixed-content
spec: URL; urlPrefix: https://url.spec.whatwg.org/
type: dfn
text: local scheme
text: default port
text: IPv6 address; url: concept-ipv6
text: percent decode
text: URL parser; url: concept-url-parser
text: URL serializer; url: concept-url-serializer
type: attribute
text: host; for: URL; url: concept-url-host
text: port; for: URL; url: concept-url-port
text: path; for: URL; url: concept-url-path
text: origin; for: URL; url: concept-url-origin
text: scheme; for: URL; url: concept-url-scheme
type: interface;
text: URL
spec: SERVICE-WORKERS; urlPrefix: http://www.w3.org/TR/service-workers/
type: interface
text: ServiceWorker; url: service-worker-interface
spec: WORKERS; urlPrefix: http://www.w3.org/TR/workers/
type: interface
text: Worker
spec: CSSOM; urlPrefix: http://www.w3.org/TR/cssom/
type: dfn
text: insert a css rule
text: parse a css declaration block
text: parse a css rule
text: parse a group of selectors
spec: RFC3986; urlPrefix: https://tools.ietf.org/html/rfc3986
type: grammar
text: path; url: section-3.3
text: scheme; url: section-3.1
text: IPv4address; url: section-3.2.2
spec: RFC4648; urlPrefix: https://tools.ietf.org/html/rfc4648
type: dfn
text: base64 encoding; url: section-4
spec: RFC5234; urlPrefix: https://tools.ietf.org/html/rfc5234
type: grammar
text: ALPHA; url: appendix-B.1
text: DIGIT; url: appendix-B.1
text: VCHAR; url: appendix-B.1
text: WSP; url: appendix-B.1
spec: RFC5890; urlPrefix: https://tools.ietf.org/html/rfc5890
type: dfn
text: label; url: section-2.2
spec: RFC7230; urlPrefix: https://tools.ietf.org/html/rfc7230
type: grammar
text: BWS; url: section-3.2.3
text: OWS; url: section-3.2.3
text: RWS; url: section-3.2.3
text: quoted-string; url: section-3.2.6
text: token; url: section-3.2.6
spec: RFC7231; urlPrefix: https://tools.ietf.org/html/rfc7231
type: dfn
url: section-3
text: resource representation
text: representation
spec: OOB-REPORTING; urlPrefix: https://mikewest.github.io/error-reporting/
type: dfn
text: group
text: queue report; url: queue-report
spec: HTML; urlPrefix: https://html.spec.whatwg.org/
type: dfn
text: run a worker
text: initialising a new Document object
text: update a style block
text: the worker's documents
text: Content-Security-Policy http-equiv processing instructions; url: attr-meta-http-equiv-content-security-policy
type: element-attr
text: ping; for: a
text: nonce; for: script; url: attr-script-nonce
spec: SHA2; urlPrefix: http://csrc.nist.gov/publications/fips/fips180-4/fips-180-4.pdf
type: dfn
text: SHA-256; url: #
text: SHA-384; url: #
text: SHA-512; url: #
</pre>
<pre class="biblio">
{
"CSP-DOCUMENT": {
"authors": [ "Mike West" ],
"href": "https://w3c.github.io/webappsec-csp/document/",
"title": "Content Security Policy: Document Features",
"publisher": "W3C"
},
"HTML-DESIGN": {
"authors": [ "Anne Van Kesteren", "Maciej Stachowiak" ],
"href": "http://www.w3.org/TR/html-design-principles/",
"title": "HTML Design Principles",
"publisher": "W3C"
},
"ES2015": {
"authors": [ "Allen Wirfs-Brock" ],
"href": "http://www.ecma-international.org/ecma-262/6.0/index.html",
"title": "ECMAScript® 2015 Language Specification",
"publisher": "ECMA"
},
"SHA2": {
"href": "http://nvlpubs.nist.gov/nistpubs/FIPS/NIST.FIPS.180-4.pdf",
"title": "FIPS PUB 180-4, Secure Hash Standard"
},
"OOB-REPORTING": {
"href": "https://mikewest.github.io/error-reporting/",
"title": "Out-of-band Reporting",
"authors": [ "Ilya Gregorik", "Mike West" ]
}
}
</pre>
<style>
ul.toc ul ul ul {
margin: 0 0 0 2em;
}
ul.toc ul ul ul span.secno {
margin-left: -9em;
}
</style>
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<section>
<h2 id="intro">Introduction</h2>
<em>This section is not normative.</em>
This document defines Content Security Policy (CSP), a tool which developers
can use to lock down their applications in various ways, mitigating the risk
of content injection vulnerabilities such as cross-site scripting, and
reducing the privilege with which their applications execute.
CSP is not intended as a first line of defense against content injection
vulnerabilities. Instead, CSP is best used as defense-in-depth. It reduces
the harm that a malicious injection can cause, but it is not a replacement for
careful input validation and output encoding.
<h3 id="examples">Examples</h3>
<h4 id="example-basic">Control Execution</h4>
<div class="example">
MegaCorp Inc's developers want to protect themselves against cross-site
scripting attacks. They can mitigate the risk of script injection by
ensuring that their trusted CDN is the only origin from which script can
load and execute. Moreover, they wish to ensure that no plugins can
execute in their pages' contexts. The following policy has that effect:
<pre>
Content-Security-Policy: script-src https://cdn.example.com/scripts/; object-src 'none'
</pre>
</div>
<h3 id="goals">Goals</h3>
Content Security Policy aims to do to a few related things:
1. Mitigate the risk of content-injection attacks by giving developers
fairly granular control over
* The resources which can be requested (and subsequently embedded or
executed) on behalf of a specific {{Document}} or {{Worker}}
* The execution of inline script
* Dynamic code execution (via {{eval()}} and similar constructs)
* The application of inline style
2. Mitigate the risk of attacks which require a resource to be embedded
in a malicious context ("Pixel Perfect", etc) by giving developers
granular control over the origins which can embed a given resource.
3. Provide a policy framework which allows developers to reduce the privilege
of their applications.
4. Provide a reporting mechanism which allows developers to detect flaws
being exploited in the wild.
<h3 id="changes-from-level-2">Changes from Level 2</h3>
This document describes an evolution of the Content Security Policy Level 2
specification [[CSP2]]. The following is a high-level overview of the changes:
1. The specification has been rewritten from the ground up in terms of the
[[FETCH]] specification, which should make it simpler to integrate CSP's
requirements and restrictions with other specifications (and with
Service Workers in particular).
2. The `frame-src` directive, which was deprecated in CSP Level
2, has been removed.
3. Insecure schemes in source expressions now match their secure variants.
That is, `http:` is equivalent to `http: https:`, and `http://a.com`
to `http://a.com https://a.com`.
Likewise, `'self'` now matches `https` and `wss` variants of the page's
origin, even on pages whose scheme is `http`.
4. Violation reports generated from inline script or style will now report
"`inline`" as the blocked resource. Likewise, blocked `eval()` execution
will report "`eval`" as the blocked resource.
5. Directives with effects on a {{Document}} or {{Worker}} itself (as opposed
to the resources such a context can load) have moved out into a separate
[[CSP-DOCUMENT]] module. This includes `base-uri`, `form-action`,
`frame-ancestors`, `plugin-types`, `sandbox`.
6. The `manifest-src` directive has been added.
7. The `report-uri` directive is deprecated in favor of the new `report-to`
directive, which relies on [[OOB-REPORTING]] as infrastructure.
<h3 id="open-questions">Open Questions</h3>
1. Do we really want to remove `frame-src`? Though the threat model of
workers and frames is similar, they have distinct capabilities. Perhaps
it makes sense for folks to allow workers while disallowing frames, or
vice-versa?
2. Can we enable `sandbox` inside <{meta}>? It's not clear what threat we're
preventing by dropping support for it (and Chrome and Safari support it
today).
3. Reporting:
1. Do we still need to strip values? I think we've removed much of the
risk by using the original URL of a blocked resource; there shouldn't
be anything in the report JSON that script can't gather on its own by
walking the DOM.
</section>
<!-- Big Text: Framework -->
<section>
<h2 id="framework">Framework</h2>
<h3 id="framework-policy">Policies</h3>
A <dfn local-lt="policies" export>policy</dfn> defines a set of allowed and
restricted behaviors, and may be applied to a {{Window}} or
{{WorkerGlobalScope}} as described in [[#initialize-global-object-csp]].
Each policy has an associated <dfn for="policy">directive set</dfn>, which
is a set of <a>directives</a> that define the policy's implications when
applied.
Each policy has an associated <dfn for="policy">disposition</dfn>, which is
one of `null`, "`enforce`", or "`report`". The value is `null` unless
otherwise specified.
A <dfn export>serialized policy</dfn> is an ASCII string, consisting of a
semicolon-delimited series of <a>serialized directives</a>, adhering to the
following ABNF grammar [[!RFC5234]]:
<pre dfn-type="grammar" link-type="grammar">
<dfn>serialized-policy</dfn> = <a>serialized-directive</a> *( <a>OWS</a> ";" [ <a>OWS</a> <a>serialized-directive</a> ] )
; <a>OWS</a> is defined in section 3.2.3 of RFC 7230
</pre>
<h4 id="parse-serialized-policy" dfn lt="parse a serialized policy" algorithm>
Parse a |serialized policy|
</h4>
Given a <a>serialized policy</a> (|serialized policy|), this
algorithm will return a <a>policy</a> object. If the string cannot be parsed,
the resulting <a>policy</a>'s <a>directive set</a> will be empty.
1. Let |policy| be a new <a>policy</a> with an empty <a>directive
set</a>, and a `null` <a>type</a>.
2. For each |token| returned by
<a lt="strictly split a string">strictly splitting</a> |serialized
policy| on the U+003B SEMICOLON character (`;`):
1. <a>Strip leading and trailing whitespace</a> from |token|.
2. If |token| is an empty string, skip the remaining substeps
and continue to the next item.
3. Let |directive name| be the result of
<a lt="collect a sequence of characters">collecting a sequence of
characters</a> from |token| which are not <a>space
characters</a>.
4. If |policy|'s <a>directive set</a> contains a
<a>directive</a> whose <a for="directive">name</a> is |directive
name|, skip the remaining substeps and continue to the next item.
The user agent SHOULD notify developers that a directive was ignored.
A console warning might be appropriate, for example.
5. Let |directive value| be the result of
<a lt="split a string on spaces">splitting |token| on
spaces</a>.
6. Let |directive| be a new <a>directive</a> whose
<a for="directive">name</a> is |directive name|, and
<a for="directive">value</a> is |directive value|.
7. Add |directive| to |policy|'s <a>directive set</a>.
3. Return |policy|.
<h4 id="parse-serialized-policy-list" algorithm>
Parse a serialized policy list
</h4>
Given a string (|list|) which contains a comma-delimited series of
<a>serialized policies</a>, the following algorithm will return a list of
<a>policies</a>:
1. Let |policies| be an empty list.
2. For each |token| returned by
<a lt="split a string on commas">splitting |list| on commas</a>:
1. Let |policy| be the result of executing
[[#parse-serialized-policy]] on |token|.
2. If |policy|'s <a>directive set</a> is empty, skip the
remaining substeps, and continue to the next item.
3. Add |policy| to |policies|.
3. Return |policies|.
<h3 id="framework-directives">Directives</h3>
<a>Policies</a> contain a set of <dfn>directives</dfn>, each of which controls
a specific behavior. The directives defined in this document are described in
detail in [[#csp-directives]].
Each <a>directive</a> is a <dfn for="directive">name</dfn> /
<dfn for="directive">value</dfn> pair. The <a for="directive">name</a> is a
non-empty string, and the <a>value</a> is a set of non-empty strings. The
<a>value</a> set MAY be empty.
A <dfn>serialized directive</dfn> is an ASCII string, consisting of one or more
whitespace-delimited tokens, and adhering to the following ABNF [[!RFC5234]]:
<pre dfn-type="grammar" link-type="grammar">
<dfn>serialized-directive</dfn> = <a>directive-name</a> [ <a>RWS</a> <a>directive-value</a> ]
<dfn>directive-name</dfn> = 1*( <a>ALPHA</a> / <a>DIGIT</a> / "-" )
<dfn>directive-value</dfn> = *( %x09 / %x20-%x2B / %x2D-%x3A / %x3C-%7E )
; Directive values may contain whitespace and <a>VCHAR</a> characters,
; excluding ";" and ","
; <a>RWS</a> is defined in section 3.2.3 of RFC7230. <a>ALPHA</a>, <a>DIGIT</a>, and
; <a>VCHAR</a> are defined in Appendix B.1 of RFC 5234.
</pre>
<a>Directives</a> have four associated algorithms:
1. A <dfn for="directive">pre-request check</dfn>, which takes a
<a>request</a> and a <a>policy</a> as an argument, and is executed during
[[#should-block-request]]. This algorithm returns "`Allowed`" unless
otherwise specified.
2. A <dfn for="directive">post-request check</dfn>, which takes a
<a>request</a>, a <a>response</a>, and a <a>policy</a> as arguments, and
is executed during [[#should-block-response]]. This algorithm returns
"`Allowed`" unless otherwise specified.
3. A <dfn for="directive">response check</dfn>, which takes a
<a>request</a>, a <a>response</a>, and a <a>policy</a> as arguments, and
is executed during [[#should-block-response]]. This algorithm returns
"`Allowed`" unless otherwise specified.
4. An <dfn for="directive">initialization</dfn>, which takes a {{Document}}
or <a>global object</a>, a <a>response</a>, and a <a>policy</a> as
arguments. This algorithm is executed during [[#initialize-document-csp]],
and has no effect unless otherwise specified.
<h4 id="framework-directive-source-list">Source Lists</h4>
Many <a>directives</a>' <a>values</a> consist of <dfn>source lists</dfn>: sets
of tokens which identify content that can be fetched and potentially embedded
or executed. These tokens represent one of the following types of <dfn>source
expression</dfn>:
1. Keywords such as <a grammar>`'none'`</a> and
<a grammar>`'self'`</a> (which match nothing and the current
URL's origin, respectively)
2. Serialized URLs such as `https://example.com/path/to/file.js`
(which matches a specific file) or `https://example.com/`
(which matches everything on that origin)
3. Schemes such as `https:` (which matches any resource having
the specified scheme)
4. Hosts such as `example.com` (which matches any resource on
the host, regardless of scheme) or `*.example.com` (which
matches any resource on the host or any of its subdomains (and any of
its subdomains' subdomains, and so on))
5. Nonces such as `'nonce-qwertyu12345'` (which can match specific
elements on a page)
6. Digests such as `'sha256-abcd...'` (which can match specific
elements on a page)
A <dfn>serialized source list</dfn> is an ASCII string, consisting of a
space-delimited series of <a>source expressions</a>, adhering to the
following ABNF grammar [[!RFC5234]]:
<pre dfn-type="grammar" link-type="grammar">
<dfn>serialized-source-list</dfn> = ( <a>source-expression</a> *( <a>RWS</a> <a>source-expression</a> ) ) / "<dfn>'none'</dfn>"
<dfn>source-expression</dfn> = <a>scheme-source</a> / <a>host-source</a> / <a>keyword-source</a>
/ <a>nonce-source</a> / <a>hash-source</a>
; Schemes:
<dfn>scheme-source</dfn> = <a>scheme</a> ":"
; <a>scheme</a> is defined in section 3.1 of RFC 3986.
; Hosts: "example.com" / "*.example.com" / "https://*.example.com:12/path/to/file.js"
<dfn>host-source</dfn> = [ <a>scheme-part</a> "://" ] <a>host-part</a> [ <a>port-part</a> ] [ <a>path-part</a> ]
<dfn>scheme-part</dfn> = <a>scheme</a>
<dfn>host-part</dfn> = "*" / [ "*." ] 1*<a>host-char</a> *( "." 1*<a>host-char</a> )
<dfn>host-char</dfn> = <a>ALPHA</a> / <a>DIGIT</a> / "-"
<dfn>port-part</dfn> = ":" ( 1*<a>DIGIT</a> / "*" )
<dfn>path-part</dfn> = <a>path</a>
; <a>path</a> is defined in section 3.3 of RFC 3986.
; Keywords:
<dfn>keyword-source</dfn> = "<dfn>'self'</dfn>" / "<dfn>'unsafe-inline'</dfn>" / "<dfn>'unsafe-eval'</dfn>"
; Nonces: 'nonce-[nonce goes here]'
<dfn>nonce-source</dfn> = "'nonce-" <a>base64-value</a> "'"
<dfn>base64-value</dfn> = 1*( <a>ALPHA</a> / <a>DIGIT</a> / "+" / "/" / "-" / "_" )*2( "=" )
; Digests: 'sha256-[digest goes here]'
<dfn>hash-source</dfn> = "'" <a>hash-algorithm</a> "-" <a>base64-value</a> "'"
<dfn>hash-algorithm</dfn> = "sha256" / "sha384" / "sha512"
</pre>
The <a grammar>host-char</a> production intentionally contains only ASCII
characters; internationalized domain names cannot be entered directly as part
of a <a>serialized policy</a>, but instead MUST be Punycode-encoded
[[!RFC3492]]. For example, the domain `üüüüüü.de` MUST be represented as
`xn--tdaaaaaa.de`.
Note: Though IP address do match the grammar above, only
`127.0.0.1` will actually match a URL when used in a source
expression (see [[#match-url-to-source-list]] for details). The security
properties of IP addresses are suspect, and authors ought to prefer hostnames
whenever possible.
A {{URL}} <dfn>matches a source list</dfn> if the algorithm in
[[#match-url-to-source-list]] returns `Matches`.
<h3 id="framework-violation">Violations</h3>
A <dfn>violation</dfn> represents an action or resource which goes against the
<a>policies</a> associated with a <a>global object</a>.
Each <a>violation</a> has a
<dfn for="violation" id="violation-global-object">global object</dfn>, which
is the <a>global object</a> whose <a>policy</a> has been violated.
Each <a>violation</a> has a <dfn for="violation" id="violation-url">url</dfn>
which is its <a for="violation">global object</a>'s {{URL}}.
Each <a>violation</a> has a
<dfn for="violation" id="violation-status">status</dfn> which is a
non-negative integer representing the HTTP status code of the resource for
which the global object was instantiated.
Each <a>violation</a> has a
<dfn for="violation" id="violation-resource">resource</dfn>, which is
either `null`, "`inline`", "`eval`", or a {{URL}}. It represents the resource
which violated the policy.
Each <a>violation</a> has a
<dfn for="violation" id="violation-referrer">referrer</dfn>, which is either
`null`, or a {{URL}}. It represents the referrer of the resource whose policy
was violated.
Each <a>violation</a> has a
<dfn for="violation" id="violation-policy">policy</dfn>, which is the
<a>policy</a> that has been violated.
Each <a>violation</a> has an
<dfn for="violation" id="violation-effective-directive">effective directive</dfn>
which is a non-empty string representing the <a>directive</a> whose
enforcement caused the violation.
Each <a>violation</a> has a
<dfn for="violation" id="violation-source-file">source file</dfn>, which is
either `null` or a {{URL}}.
Each <a>violation</a> has a
<dfn for="violation" id="violation-line-number">line number</dfn>, which is
a non-negative integer.
Each <a>violation</a> has a
<dfn for="violation" id="violation-column-number">column number</dfn>, which
is a non-negative integer.
<h4 id="create-violation-for-global" algorithm>
Create a violation object for |global|, |policy|, and |directive|
</h4>
Given a <a>global object</a> (|global|), a <a>policy</a> (|policy|), and a
string (|directive|), the following algorithm creates a new <a>violation</a>
object, and populates it with an initial set of data:
1. Let |violation| be a new <a>violation</a> whose <a for="violation">global
object</a> is |global|, <a for="violation">policy</a> is |policy|,
<a for="violation">effective directive</a> is |directive|, and
<a for="violation">resource</a> is `null`.
2. If the user agent is currently executing script, and can extract a source
file's URL, line number, and column number from the |global|, set
|violation|'s <a for="violation">source file</a>, <a for="violation">line
number</a>, and <a for="violation">column number</a> accordingly.
ISSUE: Is this kind of thing specified anywhere? I didn't see anything
that looked useful in [[ES2015]].
3. If |global| is a {{Window}} object, set |violation|'s
<a for="violation">referrer</a> to |global|'s {{Window/document}}'s
{{Document/referrer}}.
4. Set |violation|'s <a for="violation">status</a> to the HTTP status code
for the resource associated with |violation|'s <a for="violation">global
object</a>.
ISSUE: How, exactly, do we get the status code? We don't actually store it
anywhere.
5. Return |violation|.
<h4 id="create-violation-for-request" algorithm>
Create a violation object for |request|, |policy|, and |directive|
</h4>
Given a <a>request</a> (|request|), a <a>policy</a> (|policy|), and a string
(|directive|), the following algorithm creates a new <a>violation</a> object,
and populates it with an initial set of data:
1. Let |violation| be the result of executing
[[#create-violation-for-global]] on |request|'s
<a for="request">client</a>'s <a for="request">global object</a>,
|policy|, and |directive|.
2. Set |violation|'s <a for="violation">resource</a> to |request|'s
<a for="request">url</a>.
Note: We use |request|'s <a for="request">url</a>, and <em>not</em> its
<a for="request">current url</a>, as the latter might contain information
about redirect targets to which the page MUST NOT be given access.
3. Return |violation|.
</section>
<!-- Big Text: Delivery -->
<section>
<h2 id="policy-delivery">
Policy Delivery
</h2>
A server MAY declare a <a>policy</a> for a particular <a>resource
representation</a> via an HTTP response header field whose value is a
<a>serialized policy</a>. This mechanism is defined in detail in
[[#csp-header]] and [[#cspro-header]], and the integration with Fetch
and HTML is described in [[#fetch-integration]] and [[#html-integration]].
A <a>policy</a> may also be declared inline in an HTML document via a
<{meta}> element's <{meta/http-equiv}> attribute, as described in
[[#meta-element]].
<h3 id="csp-header">
The `Content-Security-Policy` HTTP Response Header Field
</h3>
The <dfn>`Content-Security-Policy`</dfn> HTTP response header field
is the preferred mechanism for delivering a policy from a server to a client.
The header's value is represented by the following ABNF [[!RFC5234]]:
<pre>
Content-Security-Policy = 1#<a grammar>serialized-policy</a>
</pre>
<div class="example">
<pre>
<a>Content-Security-Policy</a>: script-src 'self';
reports /csp-reporting-endpoint
</pre>
</div>
A server MAY send different `Content-Security-Policy` header field
values with different <a>representations</a> of the same resource.
A server SHOULD NOT send more than one HTTP response header field named
"`Content-Security-Policy`" with a given <a>resource
representation</a>.
When the user agent receives a `Content-Security-Policy` header field, it
MUST <a lt="parse a serialized policy">parse</a> and <a>enforce</a> each
<a>serialized policy</a> it contains as described in [[#fetch-integration]],
[[#html-integration]].
<h3 id="cspro-header">
The `Content-Security-Policy-Report-Only` HTTP Response Header Field
</h3>
The <dfn>`Content-Security-Policy-Report-Only`</dfn> HTTP response
header field allows web developers to experiment with policies by monitoring
(but not enforcing) their effects. The header's value is represented by the
following ABNF [[!RFC5234]]:
<pre>
Content-Security-Policy-Report-Only = 1#<a grammar>serialized-policy</a>
</pre>
This header field allows developers to piece together their security policy in
an iterative fashion, deploying a report-only policy based on their best
estimate of how their site behaves, watching for violation reports, and then
moving to an enforced policy once they've gained confidence in that behavior.
<div class="example">
<pre>
<a>Content-Security-Policy-Report-Only</a>: script-src 'self';
reports /csp-reporting-endpoint
</pre>
</div>
A server MAY send different `Content-Security-Policy-Report-Only`
header field values with different <a>representations</a> of the same
resource.
A server SHOULD NOT send more than one HTTP response header field named
"`Content-Security-Policy-Report-Only`" with a given <a>resource
representation</a>.
When the user agent receives a `Content-Security-Policy-Report-Only` header
field, it MUST <a lt="parse a serialized policy">parse</a> and <a>monitor</a>
each <a>serialized policy</a> it contains as described in
[[#fetch-integration]] and [[#html-integration]].
Note: The `<a>Content-Security-Policy-Report-Only</a>` header is
<strong>not</strong> supported inside a <{meta}> element.
<h3 id="meta-element">
The `<meta>` element
</h3>
A {{Document}} may deliver a policy via one or more HTML <{meta}> elements
whose <{meta/http-equiv}> attributes are an <a>ASCII case-insensitive
match</a> for the string "`Content-Security-Policy`". For example:
<div class="example">
<pre>
<meta http-equiv="Content-Security-Policy" content="script-src 'self'">
</pre>
</div>
Implementation details can be found in HTML's <a>`Content-Security-Policy`
`http-equiv` processing instructions</a> [[!HTML]].
Note: The `<a>Content-Security-Policy-Report-Only</a>` header is <em>not</em>
supported inside a <{meta}> element. Neither are the `report-uri`,
`frame-ancestors`, and `sandbox` directives.
ISSUE: Why `sandbox`? Can we loosen that?
Authors are <em>strongly encouraged</em> to place <{meta}> elements as early
in the document as possible, because policies in <{meta}> elements are not
applied to content which precedes them. In particular, note that resources
fetched or prefetched using the `Link` HTTP response header
field, and resources fetched or prefetched using <{link}> and <{script}>
elements which precede a <{meta}>-delivered policy will not be blocked.
Note: A policy specified via a <{meta}> element will be enforced along with
any other policies active for the protected resource, regardless
of where they're specified. The general impact of enforcing multiple
policies is described in [[#multiple-policies]].
Note: Modifications to the <{meta/content}> attribute of a <{meta}> element
after the element has been parsed will be ignored.
</section>
<!-- Big Text: Integration -->
<section>
<h2 id="integrations">Integrations</h2>
<em>This section is non-normative.</em>
This document defines a set of algorithms which are used in other
specifications in order to implement the functionality. These
integrations are outlined here for clarity, but those external
documents are the normative references which ought to be consulted for
detailed information.
<h3 id="fetch-integration">
Integration with Fetch
</h3>
A number of <a>directives</a> control resource loading in one way or
another. This specification provides algorithms which allow Fetch to make
decisions about whether or not a particular <a>request</a> should be blocked
or allowed, and about whether a particular <a>response</a> should be replaced
with a <a>network error</a>.
1. [[#should-block-request]] is called as part of step #4 of its <a>Main
Fetch</a> algorithm.
2. [[#should-block-response]] is called as part of step #12 of its <a>Main
Fetch</a> algorithm.
A <a>policy</a> is generally enforced upon a <a>global object</a>, but the
user agent needs to <a lt="parse a serialized policy">parse</a> any policy
delivered via an HTTP response header field before any <a>global object</a>
is created in order to handle directives that require knowledge of a
<a>response</a>'s details. To that end:
1. A <a>response</a> has an associated <a for="response">CSP list</a> which
contains any policy objects delivered in the <a>response</a>'s
<a for="response">header list</a>.
2. [[#set-response-csp-list]] is called in the <a>HTTP fetch</a> and
<a>HTTP-network fetch</a> algorithms.
Note: These two calls should ensure that a <a>response</a>'s
<a for="response">CSP list</a> is set, regardless of how the
<a>response</a> is created. If we hit the network (via <a>HTTP-network
fetch</a>, then we parse the policy before we handle the `Set-Cookie`
header. If we get a response from a Service Worker (via <a>HTTP fetch</a>,
we'll process its <a for="response">CSP list</a> before handing the
response back to our caller.
<h4 id="set-response-csp-list" algorithm>
Set |response|'s `csp list`
</h4>
Given a <a>response</a> (|response|), this algorithm evaluates its
<a for="response">header list</a> for <a>serialized policy</a> values, and
populates its <a for="response">csp list</a> accordingly:
1. Set |response|'s <a for="response">CSP list</a> to the
empty list.
2. Let |policies to enforce| be the result of executing
[[#parse-serialized-policy-list]] on the result of
<a lt="parse a header value">parsing</a> `Content-Security-Policy`
in |response|'s <a for="response">header list</a>.
3. For each |policy| in |policies to enforce|:
1. Set |policy|'s <a for="policy">disposition</a> to
"`enforce`".
2. Insert |policy| into |response|'s
<a for="response">csp list</a>.
4. Let |policies to report| be the result of executing
[[#parse-serialized-policy-list]] on the result of
<a lt="parse a header value">parsing</a>
`Content-Security-Policy-Report-Only` in |response|'s
<a for="response">header list</a>.
5. For each |policy| in |policies to report|:
1. Set |policy|'s <a for="policy">disposition</a> to
"`report`".
2. Insert |policy| into |response|'s
<a for="response">csp list</a>.
<h4 id="report-for-request" algorithm>
Report Content Security Policy violations for |request|
</h4>
Given a <a>request</a> (|request|), this algorithm reports violations based
on <a for="request">client</a>'s "report only" policies.
1. Let |csp list| be |request|'s
<a for="request">client</a>'s <a>global object</a>'s
<a for="global object">csp list</a>.
2. For each |policy| in |csp list|:
1. If |policy|'s <a for="policy">disposition</a> is "`enforce`",
then skip to the next |policy|.
2. Let |violates| be the result of executing
[[#does-request-violate-policy]] on |request| and |policy|.
3. If |violates| is not "`Does Not Violate`", then execute
[[#report-violation]] on the result of executing
[[#create-violation-for-request]] on |request|, |policy|, and
|violates|.
<h4 id="should-block-request" algorithm>
Should |request| be blocked by Content Security Policy?
</h4>
Given a <a>request</a> (|request|), this algorithm returns
`Blocked` or `Allowed` and reports violations based on |request|'s
<a for="request">client</a>'s Content Security Policy.
1. Let |csp list| be |request|'s
<a for="request">client</a>'s <a>global object</a>'s
<a for="global object">csp list</a>.
2. Let |result| be "`Allowed`".
3. For each |policy| in |csp list|:
1. If |policy|'s <a for="policy">disposition</a> is "`report`",
then skip to the next |policy|.
2. Let |violates| be the result of executing
[[#does-request-violate-policy]] on |request| and |policy|.
3. If |violates| is not "`Does Not Violate`", then:
1. Execute [[#report-violation]] on the result of executing
[[#create-violation-for-request]] on |request|, |policy|, and
|violates|.
2. Set |result| to "`Blocked`".
4. Return |result|.
<h4 id="should-block-response" algorithm>
Should |response| to |request| be blocked by Content
Security Policy?
</h4>
Given a <a>response</a> (|response|) and a <a>request</a>
(|request|), this algorithm returns `Blocked` or
`Allowed`, and reports violations based on |request|'s
<a for="request">client</a>'s Content Security Policy.
1. Let |csp list| be |request|'s
<a for="request">client</a>'s <a>global object</a>'s
<a for="global object">csp list</a>.