One document matched: draft-nottingham-http-new-status-03.xml
<?xml version="1.0" encoding="utf-8"?>
<!DOCTYPE rfc SYSTEM "xml2rfc/rfc2629.dtd" [
<!ENTITY rfc2119 SYSTEM 'http://xml.resource.org/public/rfc/bibxml/reference.RFC.2119.xml'>
<!ENTITY rfc2616 SYSTEM 'http://xml.resource.org/public/rfc/bibxml/reference.RFC.2616.xml'>
<!ENTITY rfc4791 SYSTEM 'http://xml.resource.org/public/rfc/bibxml/reference.RFC.4791.xml'>
<!ENTITY rfc4918 SYSTEM 'http://xml.resource.org/public/rfc/bibxml/reference.RFC.4918.xml'>
]>
<?xml-stylesheet type='text/xsl' href='rfc2629.xslt' ?>
<?rfc toc="yes" ?>
<?rfc tocdepth="1" ?>
<?rfc tocindent="yes" ?>
<?rfc symrefs="yes" ?>
<?rfc sortrefs="yes"?>
<?rfc iprnotified="no" ?>
<?rfc strict="yes" ?>
<?rfc compact="yes" ?>
<?rfc comments="yes" ?>
<?rfc inline="yes" ?>
<rfc ipr="trust200902"
docName="draft-nottingham-http-new-status-03"
category="std"
updates="2616">
<front>
<title>Additional HTTP Status Codes</title>
<author initials="M." surname="Nottingham" fullname="Mark Nottingham">
<organization>Rackspace</organization>
<address>
<email>mnot@mnot.net</email>
<uri>http://www.mnot.net/</uri>
</address>
</author>
<author initials="R." surname="Fielding" fullname="Roy T. Fielding">
<organization abbrev="Adobe">Adobe Systems Incorporated</organization>
<address>
<postal>
<street>345 Park Ave</street>
<city>San Jose</city>
<region>CA</region>
<code>95110</code>
<country>USA</country>
</postal>
<email>fielding@gbiv.com</email>
<uri>http://roy.gbiv.com/</uri>
</address>
</author>
<date year="2011"/>
<abstract>
<t>This document specifies additional HyperText Transfer Protocol (HTTP)
status codes for a variety of common situations.</t>
</abstract>
<note title="Editorial Note (To be removed by RFC Editor before publication)">
<t>
Distribution of this document is unlimited. Although this is not a work
item of the HTTPbis Working Group, comments should be sent to the
Hypertext Transfer Protocol (HTTP) mailing list at <eref
target="mailto:ietf-http-wg@w3.org">ietf-http-wg@w3.org</eref>, which
may be joined by sending a message with subject "subscribe" to <eref target="mailto:ietf-http-wg-request@w3.org?subject=subscribe">ietf-http-wg-request@w3.org</eref>.
</t>
<t>
Discussions of the HTTPbis Working Group are archived at
<eref target="http://lists.w3.org/Archives/Public/ietf-http-wg/"/>.
</t>
</note>
</front>
<middle>
<section title="Introduction">
<t>This document specifies additional HTTP <xref target="RFC2616"/>
status codes for a variety of common situations, to improve
interoperability and avoid confusion when other, less precise status
codes are used.</t>
</section>
<section title="Requirements">
<t>The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL
NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in
this document are to be interpreted as described in <xref
target="RFC2119"/>.</t>
</section>
<section title="428 Precondition Required">
<t>This status code indicates that the origin server requires the
request to be conditional.</t>
<t>Its typical use is to avoid the "lost update" problem, where a client
GETs a resource's state, modifies it, and PUTs it back to the server,
when meanwhile a third party has modified the state on the server,
leading to a conflict. By requiring requests to be conditional, the
server can assure that clients are working with the correct
copies.</t>
<t>Responses using this status code SHOULD explain how to resubmit
the request successfully. For example:</t>
<figure><artwork xml:space="preserve" type="message/http: msgtype="response""><![CDATA[
HTTP/1.1 428 Precondition Required
Content-Type: text/html
<html>
<head>
<title>Precondition Required</title>
</head>
<body>
<h1>Precondition Required</h1>
<p>This request is required to be conditional;
try using "If-Match".</p>
</body>
</html>
]]></artwork></figure>
<t>Responses with the 428 status code MUST NOT be stored by a
cache.</t>
</section>
<section title="429 Too Many Requests">
<t>This status code indicates that the user has sent too many requests
in a given amount of time ("rate limiting").</t>
<t>The response representations SHOULD include details explaining
the condition, and MAY include a Retry-After header indicating how
long to wait before making a new request.</t>
<t>For example:</t>
<figure><artwork xml:space="preserve" type="message/http: msgtype="response""><![CDATA[
HTTP/1.1 429 Too Many Requests
Content-Type: text/html
Retry-After: 3600
<html>
<head>
<title>Too Many Requests</title>
</head>
<body>
<h1>Too many Requests</h1>
<p>I only allow 50 requests per hour to this Web site per
logged in user. Try again soon.</p>
</body>
</html>
]]></artwork></figure>
<t>Note that this specification does not define how the origin server
identifies the user, nor how it counts requests. For example, an
origin server that is limiting request rates can do so based upon
counts of requests on a per-resource basis, across the entire
server, or even among a set of servers. Likewise, it might identify
the user by its authentication credentials, or a stateful cookie.</t>
<t>Responses with the 429 status code MUST NOT be stored by a
cache.</t>
</section>
<section title="431 Request Header Fields Too Large">
<t>This status code indicates that the server is unwilling to process
the request because its header fields are too large. The request MAY
be resubmitted after reducing the size of the request header fields.
</t>
<t>It can be used both when the set of request header fields in total
are too large, and when a single header field is at fault. In the
latter case, the response representation SHOULD specify which header
field was too large.</t>
<t>For example:</t>
<figure><artwork xml:space="preserve" type="message/http: msgtype="response""><![CDATA[
HTTP/1.1 431 Request Header Fields Too Large
Content-Type: text/html
<html>
<head>
<title>Request Header Fields Too Large</title>
</head>
<body>
<h1>Request Header Fields Too Large</h1>
<p>The "Example" header was too large.</p>
</body>
</html>
]]></artwork></figure>
<t>Responses with the 431 status code MUST NOT be stored by a
cache.</t>
</section>
<section title="511 Network Authentication Required" anchor="status-code">
<t>This status code indicates that the client needs to authenticate to
gain network access.</t>
<t>The response representation SHOULD indicate how to do this;
e.g., with an HTML form for submitting credentials.</t>
<t>The 511 status SHOULD NOT be generated by origin servers; it is
intended for use by intercepting proxies that are interposed as a
means of controlling access to the network.</t>
<t>Responses with the 511 status code MUST NOT be stored by a
cache.</t>
<section title="The 511 Status Code and Captive Portals" anchor="use511">
<t>A network operator wishing to require some authentication,
acceptance of terms or other user interaction before granting access
usually does so by identify clients who have not done so ("unknown
clients") using their MAC addresses.</t>
<t>Unknown clients then have all traffic blocked, except for that on
TCP port 80, which is sent to a HTTP server (the "login server")
dedicated to "logging in" unknown clients, and of course traffic to
the login server itself.</t>
<t>For example, a user agent might connect to a network and make the
following HTTP request on TCP port 80:</t>
<figure><artwork xml:space="preserve" type="message/http: msgtype="request""><![CDATA[
GET /index.htm HTTP/1.1
Host: www.example.com
]]></artwork></figure>
<t>Upon receiving such a request, the login server would generate a
511 response:</t>
<figure><artwork xml:space="preserve" type="message/http: msgtype="response""><![CDATA[
HTTP/1.1 511 Network Authentication Required
Content-Type: text/html
<html>
<head>
<title>Network Authentication Required</title>
<meta http-equiv="refresh"
content="0; url=https://login.example.net/">
</head>
<body>
<p>You need to <a href="https://login.example.net/">
authenticate with the local network</a> in order to gain
access.</p>
</body>
</html>
]]></artwork></figure>
<t>Here, the 511 status code assures that non-browser clients will not
interpret the response as being from the origin server, and the
META HTML element redirects the user agent to the login server.</t>
<t>Note that the 511 response can itself contain the login
interface, but it may not be desirable to do so, because browsers
would show the login interface as being associated with the
originally requested URL, which may cause confusion.</t>
</section>
</section>
<section title="Security Considerations">
<section title="428 Precondition Required">
<t>The 428 status code is optional; clients cannot rely upon its
use to prevent "lost update" conflicts.
</t>
</section>
<section title="429 Too Many Requests">
<t>Servers are not required to use the 429 status code; when limiting
resource usage, it may be more appropriate to just drop connections,
or take other steps.</t>
</section>
<section title="431 Request Header Fields Too Large">
<t>Servers are not required to use the 431 status code; when under
attack, it may be more appropriate to just drop connections, or
take other steps.
</t>
</section>
<section title="511 Network Authentication Required">
<t>In common use, a response carrying the 511 status code will not
come from the origin server indicated in the request's URL. This
presents many security issues; e.g., an attacking intermediary may be
inserting cookies into the original domain's name space, may be
observing cookies or HTTP authentication credentials sent from the
user agent, and so on.</t>
<t>However, these risks are not unique to the 511 status code; in
other words, a captive portal that is not using this status code
introduces the same issues.</t>
</section>
</section>
<section title="IANA Considerations">
<t>The HTTP Status Codes Registry should be updated with the
following entries:</t>
<t><list style="symbols">
<t>Code: 428</t>
<t>Description: Precondition Required</t>
<t>Specification: [ this document ]</t>
</list></t>
<t><list style="symbols">
<t>Code: 429</t>
<t>Description: Too Many Requests</t>
<t>Specification: [ this document ]</t>
</list></t>
<t><list style="symbols">
<t>Code: 431</t>
<t>Description: Request Header Fields Too Large</t>
<t>Specification: [ this document ]</t>
</list></t>
<t><list style="symbols">
<t>Code: 511</t>
<t>Description: Network Authentication Required</t>
<t>Specification: [ this document ]</t>
</list></t>
</section>
</middle>
<back>
<references title="Normative References">
&rfc2119; &rfc2616;
</references>
<references title="Informative References">
&rfc4918; &rfc4791;
</references>
<section title="Acknowledgements">
<t>Thanks to
Jan Algermissen and
Julian Reschke
for their suggestions and feedback.
</t>
<t>The authors take all responsibility for errors and
omissions.</t>
</section>
<section title="Issues Raised by Captive Portals" anchor="issues">
<t>Since clients cannot differentiate between a portal's response and
that of the HTTP server that they intended to communicate with, a
number of issues arise.</t>
<t>One example is the "favicon.ico" <eref
target="http://en.wikipedia.org/wiki/Favicon"/> commonly used by
browsers to identify the site being accessed. If the favicon for a
given site is fetched from a captive portal instead of the intended
site (e.g., because the user is unauthenticated), it will often
"stick" in the browser's cache (most implementations cache favicons
aggressively) beyond the portal session, so that it seems as if the
portal's favicon has "taken over" the legitimate site.</t>
<t>Another browser-based issue comes about when P3P <eref
target="http://www.w3.org/TR/P3P/"/> is supported. Depending on how
it is implemented, it's possible a browser might interpret a portal's
response for the p3p.xml file as the server's, resulting in the
privacy policy (or lack thereof) advertised by the portal being
interpreted as applying to the intended site. Other Web-based
protocols such as WebFinger <eref
target="http://code.google.com/p/webfinger/wiki/WebFingerProtocol"/>,
CORS <eref target="http://www.w3.org/TR/cors/"/> and OAuth <eref
target="http://tools.ietf.org/html/draft-ietf-oauth-v2"/> may also be
vulnerable to such issues.</t>
<t>Although HTTP is most widely used with Web browsers, a growing
number of non-browsing applications use it as a substrate protocol. For
example, WebDAV <xref target="RFC4918"/> and CalDAV <xref
target="RFC4791"/> both use HTTP as the basis (for remote authoring and
calendaring, respectively). Using these applications from behind a
captive portal can result in spurious errors being presented to the
user, and might result in content corruption, in extreme cases.</t>
<t>Similarly, other non-browser applications using HTTP can be
affected as well; e.g., widgets <eref
target="http://www.w3.org/TR/widgets/"/>, software updates, and other
specialised software such as Twitter clients and the iTunes Music
Store.</t>
<t>It should be noted that it's sometimes believed that using HTTP
redirection to direct traffic to the portal addresses these issues.
However, since many of these uses "follow" redirects, this is not a
good solution.</t>
</section>
</back>
</rfc>
| PAFTECH AB 2003-2026 | 2026-04-24 15:50:21 |