source: draft-ietf-httpbis/20/p7-auth.html

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422</style><link rel="Contents" href="#rfc.toc">
423      <link rel="Author" href="#rfc.authors">
424      <link rel="Copyright" href="#rfc.copyrightnotice">
425      <link rel="Index" href="#rfc.index">
426      <link rel="Chapter" title="1 Introduction" href="#rfc.section.1">
427      <link rel="Chapter" title="2 Access Authentication Framework" href="#rfc.section.2">
428      <link rel="Chapter" title="3 Status Code Definitions" href="#rfc.section.3">
429      <link rel="Chapter" title="4 Header Field Definitions" href="#rfc.section.4">
430      <link rel="Chapter" title="5 IANA Considerations" href="#rfc.section.5">
431      <link rel="Chapter" title="6 Security Considerations" href="#rfc.section.6">
432      <link rel="Chapter" title="7 Acknowledgments" href="#rfc.section.7">
433      <link rel="Chapter" href="#rfc.section.8" title="8 References">
434      <link rel="Appendix" title="A Changes from RFCs 2616 and 2617" href="#rfc.section.A">
435      <link rel="Appendix" title="B Imported ABNF" href="#rfc.section.B">
436      <link rel="Appendix" title="C Change Log (to be removed by RFC Editor before publication)" href="#rfc.section.C">
437      <link href="p6-cache.html" rel="prev">
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439      <link rel="schema.dct" href="http://purl.org/dc/terms/">
440      <meta name="dct.creator" content="Fielding, R.">
441      <meta name="dct.creator" content="Lafon, Y.">
442      <meta name="dct.creator" content="Reschke, J. F.">
443      <meta name="dct.identifier" content="urn:ietf:id:draft-ietf-httpbis-p7-auth-20">
444      <meta name="dct.issued" scheme="ISO8601" content="2012-07-16">
445      <meta name="dct.replaces" content="urn:ietf:rfc:2616">
446      <meta name="dct.abstract" content="The Hypertext Transfer Protocol (HTTP) is an application-level protocol for distributed, collaborative, hypermedia information systems. This document defines the HTTP Authentication framework.">
447      <meta name="description" content="The Hypertext Transfer Protocol (HTTP) is an application-level protocol for distributed, collaborative, hypermedia information systems. This document defines the HTTP Authentication framework.">
448   </head>
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450      <table class="header">
451         <tbody>
452            <tr>
453               <td class="left">HTTPbis Working Group</td>
454               <td class="right">R. Fielding, Editor</td>
455            </tr>
456            <tr>
457               <td class="left">Internet-Draft</td>
458               <td class="right">Adobe</td>
459            </tr>
460            <tr>
461               <td class="left">Obsoletes: <a href="https://tools.ietf.org/html/rfc2616">2616</a> (if approved)
462               </td>
463               <td class="right">Y. Lafon, Editor</td>
464            </tr>
465            <tr>
466               <td class="left">Updates: <a href="https://tools.ietf.org/html/rfc2617">2617</a> (if approved)
467               </td>
468               <td class="right">W3C</td>
469            </tr>
470            <tr>
471               <td class="left">Intended status: Standards Track</td>
472               <td class="right">J. Reschke, Editor</td>
473            </tr>
474            <tr>
475               <td class="left">Expires: January 17, 2013</td>
476               <td class="right">greenbytes</td>
477            </tr>
478            <tr>
479               <td class="left"></td>
480               <td class="right">July 16, 2012</td>
481            </tr>
482         </tbody>
483      </table>
484      <p class="title">HTTP/1.1, part 7: Authentication<br><span class="filename">draft-ietf-httpbis-p7-auth-20</span></p>
485      <h1 id="rfc.abstract"><a href="#rfc.abstract">Abstract</a></h1>
486      <p>The Hypertext Transfer Protocol (HTTP) is an application-level protocol for distributed, collaborative, hypermedia information
487         systems. This document defines the HTTP Authentication framework.
488      </p>
489      <h1 id="rfc.note.1"><a href="#rfc.note.1">Editorial Note (To be removed by RFC Editor)</a></h1>
490      <p>Discussion of this draft takes place on the HTTPBIS working group mailing list (ietf-http-wg@w3.org), which is archived at &lt;<a href="http://lists.w3.org/Archives/Public/ietf-http-wg/">http://lists.w3.org/Archives/Public/ietf-http-wg/</a>&gt;.
491      </p>
492      <p>The current issues list is at &lt;<a href="http://tools.ietf.org/wg/httpbis/trac/report/3">http://tools.ietf.org/wg/httpbis/trac/report/3</a>&gt; and related documents (including fancy diffs) can be found at &lt;<a href="http://tools.ietf.org/wg/httpbis/">http://tools.ietf.org/wg/httpbis/</a>&gt;.
493      </p>
494      <p>The changes in this draft are summarized in <a href="#changes.since.19" title="Since draft-ietf-httpbis-p7-auth-19">Appendix&nbsp;C.1</a>.
495      </p>
496      <div id="rfc.status">
497         <h1><a href="#rfc.status">Status of This Memo</a></h1>
498         <p>This Internet-Draft is submitted in full conformance with the provisions of BCP 78 and BCP 79.</p>
499         <p>Internet-Drafts are working documents of the Internet Engineering Task Force (IETF). Note that other groups may also distribute
500            working documents as Internet-Drafts. The list of current Internet-Drafts is at <a href="http://datatracker.ietf.org/drafts/current/">http://datatracker.ietf.org/drafts/current/</a>.
501         </p>
502         <p>Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other
503            documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as “work
504            in progress”.
505         </p>
506         <p>This Internet-Draft will expire on January 17, 2013.</p>
507      </div>
508      <div id="rfc.copyrightnotice">
509         <h1><a href="#rfc.copyrightnotice">Copyright Notice</a></h1>
510         <p>Copyright © 2012 IETF Trust and the persons identified as the document authors. All rights reserved.</p>
511         <p>This document is subject to BCP 78 and the IETF Trust's Legal Provisions Relating to IETF Documents (<a href="http://trustee.ietf.org/license-info">http://trustee.ietf.org/license-info</a>) in effect on the date of publication of this document. Please review these documents carefully, as they describe your rights
512            and restrictions with respect to this document. Code Components extracted from this document must include Simplified BSD License
513            text as described in Section 4.e of the Trust Legal Provisions and are provided without warranty as described in the Simplified
514            BSD License.
515         </p>
516         <p>This document may contain material from IETF Documents or IETF Contributions published or made publicly available before November
517            10, 2008. The person(s) controlling the copyright in some of this material may not have granted the IETF Trust the right to
518            allow modifications of such material outside the IETF Standards Process. Without obtaining an adequate license from the person(s)
519            controlling the copyright in such materials, this document may not be modified outside the IETF Standards Process, and derivative
520            works of it may not be created outside the IETF Standards Process, except to format it for publication as an RFC or to translate
521            it into languages other than English.
522         </p>
523      </div>
524      <hr class="noprint">
525      <h1 class="np" id="rfc.toc"><a href="#rfc.toc">Table of Contents</a></h1>
526      <ul class="toc">
527         <li><a href="#rfc.section.1">1.</a>&nbsp;&nbsp;&nbsp;<a href="#introduction">Introduction</a><ul>
528               <li><a href="#rfc.section.1.1">1.1</a>&nbsp;&nbsp;&nbsp;<a href="#intro.conformance.and.error.handling">Conformance and Error Handling</a></li>
529               <li><a href="#rfc.section.1.2">1.2</a>&nbsp;&nbsp;&nbsp;<a href="#notation">Syntax Notation</a></li>
530            </ul>
531         </li>
532         <li><a href="#rfc.section.2">2.</a>&nbsp;&nbsp;&nbsp;<a href="#access.authentication.framework">Access Authentication Framework</a><ul>
533               <li><a href="#rfc.section.2.1">2.1</a>&nbsp;&nbsp;&nbsp;<a href="#challenge.and.response">Challenge and Response</a></li>
534               <li><a href="#rfc.section.2.2">2.2</a>&nbsp;&nbsp;&nbsp;<a href="#protection.space">Protection Space (Realm)</a></li>
535               <li><a href="#rfc.section.2.3">2.3</a>&nbsp;&nbsp;&nbsp;<a href="#authentication.scheme.registry">Authentication Scheme Registry</a><ul>
536                     <li><a href="#rfc.section.2.3.1">2.3.1</a>&nbsp;&nbsp;&nbsp;<a href="#considerations.for.new.authentication.schemes">Considerations for New Authentication Schemes</a></li>
537                  </ul>
538               </li>
539            </ul>
540         </li>
541         <li><a href="#rfc.section.3">3.</a>&nbsp;&nbsp;&nbsp;<a href="#status.code.definitions">Status Code Definitions</a><ul>
542               <li><a href="#rfc.section.3.1">3.1</a>&nbsp;&nbsp;&nbsp;<a href="#status.401">401 Unauthorized</a></li>
543               <li><a href="#rfc.section.3.2">3.2</a>&nbsp;&nbsp;&nbsp;<a href="#status.407">407 Proxy Authentication Required</a></li>
544            </ul>
545         </li>
546         <li><a href="#rfc.section.4">4.</a>&nbsp;&nbsp;&nbsp;<a href="#header.field.definitions">Header Field Definitions</a><ul>
547               <li><a href="#rfc.section.4.1">4.1</a>&nbsp;&nbsp;&nbsp;<a href="#header.authorization">Authorization</a></li>
548               <li><a href="#rfc.section.4.2">4.2</a>&nbsp;&nbsp;&nbsp;<a href="#header.proxy-authenticate">Proxy-Authenticate</a></li>
549               <li><a href="#rfc.section.4.3">4.3</a>&nbsp;&nbsp;&nbsp;<a href="#header.proxy-authorization">Proxy-Authorization</a></li>
550               <li><a href="#rfc.section.4.4">4.4</a>&nbsp;&nbsp;&nbsp;<a href="#header.www-authenticate">WWW-Authenticate</a></li>
551            </ul>
552         </li>
553         <li><a href="#rfc.section.5">5.</a>&nbsp;&nbsp;&nbsp;<a href="#IANA.considerations">IANA Considerations</a><ul>
554               <li><a href="#rfc.section.5.1">5.1</a>&nbsp;&nbsp;&nbsp;<a href="#authentication.scheme.registration">Authentication Scheme Registry</a></li>
555               <li><a href="#rfc.section.5.2">5.2</a>&nbsp;&nbsp;&nbsp;<a href="#status.code.registration">Status Code Registration</a></li>
556               <li><a href="#rfc.section.5.3">5.3</a>&nbsp;&nbsp;&nbsp;<a href="#header.field.registration">Header Field Registration</a></li>
557            </ul>
558         </li>
559         <li><a href="#rfc.section.6">6.</a>&nbsp;&nbsp;&nbsp;<a href="#security.considerations">Security Considerations</a><ul>
560               <li><a href="#rfc.section.6.1">6.1</a>&nbsp;&nbsp;&nbsp;<a href="#auth.credentials.and.idle.clients">Authentication Credentials and Idle Clients</a></li>
561               <li><a href="#rfc.section.6.2">6.2</a>&nbsp;&nbsp;&nbsp;<a href="#protection.spaces">Protection Spaces</a></li>
562            </ul>
563         </li>
564         <li><a href="#rfc.section.7">7.</a>&nbsp;&nbsp;&nbsp;<a href="#acks">Acknowledgments</a></li>
565         <li><a href="#rfc.section.8">8.</a>&nbsp;&nbsp;&nbsp;<a href="#rfc.references">References</a><ul>
566               <li><a href="#rfc.section.8.1">8.1</a>&nbsp;&nbsp;&nbsp;<a href="#rfc.references.1">Normative References</a></li>
567               <li><a href="#rfc.section.8.2">8.2</a>&nbsp;&nbsp;&nbsp;<a href="#rfc.references.2">Informative References</a></li>
568            </ul>
569         </li>
570         <li><a href="#rfc.section.A">A.</a>&nbsp;&nbsp;&nbsp;<a href="#changes.from.rfc.2616">Changes from RFCs 2616 and 2617</a></li>
571         <li><a href="#rfc.section.B">B.</a>&nbsp;&nbsp;&nbsp;<a href="#imported.abnf">Imported ABNF</a></li>
572         <li><a href="#rfc.section.C">C.</a>&nbsp;&nbsp;&nbsp;<a href="#change.log">Change Log (to be removed by RFC Editor before publication)</a><ul>
573               <li><a href="#rfc.section.C.1">C.1</a>&nbsp;&nbsp;&nbsp;<a href="#changes.since.19">Since draft-ietf-httpbis-p7-auth-19</a></li>
574            </ul>
575         </li>
576         <li><a href="#rfc.index">Index</a></li>
577         <li><a href="#rfc.authors">Authors' Addresses</a></li>
578      </ul>
579      <div id="introduction">
580         <h1 id="rfc.section.1" class="np"><a href="#rfc.section.1">1.</a>&nbsp;<a href="#introduction">Introduction</a></h1>
581         <p id="rfc.section.1.p.1">This document defines HTTP/1.1 access control and authentication. It includes the relevant parts of <cite title="Hypertext Transfer Protocol -- HTTP/1.1" id="rfc.xref.RFC2616.1">RFC 2616</cite> with only minor changes (<a href="#RFC2616" id="rfc.xref.RFC2616.2"><cite title="Hypertext Transfer Protocol -- HTTP/1.1">[RFC2616]</cite></a>), plus the general framework for HTTP authentication, as previously defined in "HTTP Authentication: Basic and Digest Access
582            Authentication" (<a href="#RFC2617" id="rfc.xref.RFC2617.1"><cite title="HTTP Authentication: Basic and Digest Access Authentication">[RFC2617]</cite></a>).
583         </p>
584         <p id="rfc.section.1.p.2">HTTP provides several <em class="bcp14">OPTIONAL</em> challenge-response authentication mechanisms which can be used by a server to challenge a client request and by a client to
585            provide authentication information. The "basic" and "digest" authentication schemes continue to be specified in <cite title="HTTP Authentication: Basic and Digest Access Authentication" id="rfc.xref.RFC2617.2">RFC 2617</cite>.
586         </p>
587         <div id="intro.conformance.and.error.handling">
588            <h2 id="rfc.section.1.1"><a href="#rfc.section.1.1">1.1</a>&nbsp;<a href="#intro.conformance.and.error.handling">Conformance and Error Handling</a></h2>
589            <p id="rfc.section.1.1.p.1">The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL"
590               in this document are to be interpreted as described in <a href="#RFC2119" id="rfc.xref.RFC2119.1"><cite title="Key words for use in RFCs to Indicate Requirement Levels">[RFC2119]</cite></a>.
591            </p>
592            <p id="rfc.section.1.1.p.2">This specification targets conformance criteria according to the role of a participant in HTTP communication. Hence, HTTP
593               requirements are placed on senders, recipients, clients, servers, user agents, intermediaries, origin servers, proxies, gateways,
594               or caches, depending on what behavior is being constrained by the requirement. See <a href="p1-messaging.html#architecture" title="Architecture">Section 2</a> of <a href="#Part1" id="rfc.xref.Part1.1"><cite title="HTTP/1.1, part 1: Message Routing and Syntax&#34;">[Part1]</cite></a> for definitions of these terms.
595            </p>
596            <p id="rfc.section.1.1.p.3">The verb "generate" is used instead of "send" where a requirement differentiates between creating a protocol element and merely
597               forwarding a received element downstream.
598            </p>
599            <p id="rfc.section.1.1.p.4">An implementation is considered conformant if it complies with all of the requirements associated with the roles it partakes
600               in HTTP. Note that SHOULD-level requirements are relevant here, unless one of the documented exceptions is applicable.
601            </p>
602            <p id="rfc.section.1.1.p.5">This document also uses ABNF to define valid protocol elements (<a href="#notation" title="Syntax Notation">Section&nbsp;1.2</a>). In addition to the prose requirements placed upon them, senders <em class="bcp14">MUST NOT</em> generate protocol elements that do not match the grammar defined by the ABNF rules for those protocol elements that are applicable
603               to the sender's role. If a received protocol element is processed, the recipient <em class="bcp14">MUST</em> be able to parse any value that would match the ABNF rules for that protocol element, excluding only those rules not applicable
604               to the recipient's role.
605            </p>
606            <p id="rfc.section.1.1.p.6">Unless noted otherwise, a recipient <em class="bcp14">MAY</em> attempt to recover a usable protocol element from an invalid construct. HTTP does not define specific error handling mechanisms
607               except when they have a direct impact on security, since different applications of the protocol require different error handling
608               strategies. For example, a Web browser might wish to transparently recover from a response where the <a href="p2-semantics.html#header.location" class="smpl">Location</a> header field doesn't parse according to the ABNF, whereas a systems control client might consider any form of error recovery
609               to be dangerous.
610            </p>
611         </div>
612         <div id="notation">
613            <h2 id="rfc.section.1.2"><a href="#rfc.section.1.2">1.2</a>&nbsp;<a href="#notation">Syntax Notation</a></h2>
614            <p id="rfc.section.1.2.p.1">This specification uses the Augmented Backus-Naur Form (ABNF) notation of <a href="#RFC5234" id="rfc.xref.RFC5234.1"><cite title="Augmented BNF for Syntax Specifications: ABNF">[RFC5234]</cite></a> with the list rule extension defined in <a href="p1-messaging.html#notation" title="Syntax Notation">Section 1.2</a> of <a href="#Part1" id="rfc.xref.Part1.2"><cite title="HTTP/1.1, part 1: Message Routing and Syntax&#34;">[Part1]</cite></a>. <a href="#imported.abnf" title="Imported ABNF">Appendix&nbsp;B</a> describes rules imported from other documents.
615               <div class="error">ERROR: Undefined target: collected.abnf (at line 194)</div> shows the collected ABNF with the list rule expanded.
616            </p>
617         </div>
618      </div>
619      <div id="access.authentication.framework">
620         <h1 id="rfc.section.2"><a href="#rfc.section.2">2.</a>&nbsp;<a href="#access.authentication.framework">Access Authentication Framework</a></h1>
621         <div id="challenge.and.response">
622            <h2 id="rfc.section.2.1"><a href="#rfc.section.2.1">2.1</a>&nbsp;<a href="#challenge.and.response">Challenge and Response</a></h2>
623            <p id="rfc.section.2.1.p.1">HTTP provides a simple challenge-response authentication mechanism that can be used by a server to challenge a client request
624               and by a client to provide authentication information. It uses an extensible, case-insensitive token to identify the authentication
625               scheme, followed by additional information necessary for achieving authentication via that scheme. The latter can either be
626               a comma-separated list of parameters or a single sequence of characters capable of holding base64-encoded information.
627            </p>
628            <p id="rfc.section.2.1.p.2">Parameters are name-value pairs where the name is matched case-insensitively, and each parameter name <em class="bcp14">MUST</em> only occur once per challenge.
629            </p>
630            <div id="rfc.figure.u.1"></div><pre class="inline"><span id="rfc.iref.a.1"></span><span id="rfc.iref.a.2"></span><span id="rfc.iref.g.1"></span><span id="rfc.iref.g.2"></span><span id="rfc.iref.b.1"></span><span id="rfc.iref.g.3"></span>  auth-scheme    = <a href="#imported.abnf" class="smpl">token</a>
631 
632  auth-param     = <a href="#imported.abnf" class="smpl">token</a> <a href="#imported.abnf" class="smpl">BWS</a> "=" <a href="#imported.abnf" class="smpl">BWS</a> ( <a href="#imported.abnf" class="smpl">token</a> / <a href="#imported.abnf" class="smpl">quoted-string</a> )
633
634  b64token       = 1*( <a href="#imported.abnf" class="smpl">ALPHA</a> / <a href="#imported.abnf" class="smpl">DIGIT</a> /
635                       "-" / "." / "_" / "~" / "+" / "/" ) *"="
636</pre><p id="rfc.section.2.1.p.4">The "b64token" syntax allows the 66 unreserved URI characters (<a href="#RFC3986" id="rfc.xref.RFC3986.1"><cite title="Uniform Resource Identifier (URI): Generic Syntax">[RFC3986]</cite></a>), plus a few others, so that it can hold a base64, base64url (URL and filename safe alphabet), base32, or base16 (hex) encoding,
637               with or without padding, but excluding whitespace (<a href="#RFC4648" id="rfc.xref.RFC4648.1"><cite title="The Base16, Base32, and Base64 Data Encodings">[RFC4648]</cite></a>).
638            </p>
639            <p id="rfc.section.2.1.p.5">The <a href="#status.401" class="smpl">401 (Unauthorized)</a> response message is used by an origin server to challenge the authorization of a user agent. This response <em class="bcp14">MUST</em> include a <a href="#header.www-authenticate" class="smpl">WWW-Authenticate</a> header field containing at least one challenge applicable to the requested resource.
640            </p>
641            <p id="rfc.section.2.1.p.6">The <a href="#status.407" class="smpl">407 (Proxy Authentication Required)</a> response message is used by a proxy to challenge the authorization of a client and <em class="bcp14">MUST</em> include a <a href="#header.proxy-authenticate" class="smpl">Proxy-Authenticate</a> header field containing at least one challenge applicable to the proxy for the requested resource.
642            </p>
643            <div id="rfc.figure.u.2"></div><pre class="inline"><span id="rfc.iref.c.1"></span><span id="rfc.iref.g.4"></span>  <a href="#challenge.and.response" class="smpl">challenge</a>   = <a href="#challenge.and.response" class="smpl">auth-scheme</a> [ 1*<a href="#imported.abnf" class="smpl">SP</a> ( <a href="#challenge.and.response" class="smpl">b64token</a> / #<a href="#challenge.and.response" class="smpl">auth-param</a> ) ]
644</pre><div class="note" id="rfc.section.2.1.p.8">
645               <p><b>Note:</b> User agents will need to take special care in parsing the <a href="#header.www-authenticate" class="smpl">WWW-Authenticate</a> and <a href="#header.proxy-authenticate" class="smpl">Proxy-Authenticate</a> header field values because they can contain more than one challenge, or if more than one of each is provided, since the contents
646                  of a challenge can itself contain a comma-separated list of authentication parameters.
647               </p>
648            </div>
649            <div class="note" id="rfc.section.2.1.p.9">
650               <p><b>Note:</b> Many clients fail to parse challenges containing unknown schemes. A workaround for this problem is to list well-supported
651                  schemes (such as "basic") first.
652               </p>
653            </div>
654            <p id="rfc.section.2.1.p.10">A user agent that wishes to authenticate itself with an origin server — usually, but not necessarily, after receiving a <a href="#status.401" class="smpl">401 (Unauthorized)</a> — can do so by including an <a href="#header.authorization" class="smpl">Authorization</a> header field with the request.
655            </p>
656            <p id="rfc.section.2.1.p.11">A client that wishes to authenticate itself with a proxy — usually, but not necessarily, after receiving a <a href="#status.407" class="smpl">407 (Proxy Authentication Required)</a> — can do so by including a <a href="#header.proxy-authorization" class="smpl">Proxy-Authorization</a> header field with the request.
657            </p>
658            <p id="rfc.section.2.1.p.12">Both the <a href="#header.authorization" class="smpl">Authorization</a> field value and the <a href="#header.proxy-authorization" class="smpl">Proxy-Authorization</a> field value contain the client's credentials for the realm of the resource being requested, based upon a challenge received
659               from the server (possibly at some point in the past). When creating their values, the user agent ought to do so by selecting
660               the challenge with what it considers to be the most secure auth-scheme that it understands, obtaining credentials from the
661               user as appropriate.
662            </p>
663            <div id="rfc.figure.u.3"></div><pre class="inline"><span id="rfc.iref.c.2"></span><span id="rfc.iref.g.5"></span>  <a href="#challenge.and.response" class="smpl">credentials</a> = <a href="#challenge.and.response" class="smpl">auth-scheme</a> [ 1*<a href="#imported.abnf" class="smpl">SP</a> ( <a href="#challenge.and.response" class="smpl">b64token</a> / #<a href="#challenge.and.response" class="smpl">auth-param</a> ) ]
664</pre><p id="rfc.section.2.1.p.14">Upon a request for a protected resource that omits credentials, contains invalid credentials (e.g., a bad password) or partial
665               credentials (e.g., when the authentication scheme requires more than one round trip), an origin server <em class="bcp14">SHOULD</em> return a <a href="#status.401" class="smpl">401 (Unauthorized)</a> response. Such responses <em class="bcp14">MUST</em> include a <a href="#header.www-authenticate" class="smpl">WWW-Authenticate</a> header field containing at least one (possibly new) challenge applicable to the requested resource.
666            </p>
667            <p id="rfc.section.2.1.p.15">Likewise, upon a request that requires authentication by proxies that omit credentials or contain invalid or partial credentials,
668               a proxy <em class="bcp14">SHOULD</em> return a <a href="#status.407" class="smpl">407 (Proxy Authentication Required)</a> response. Such responses <em class="bcp14">MUST</em> include a <a href="#header.proxy-authenticate" class="smpl">Proxy-Authenticate</a> header field containing a (possibly new) challenge applicable to the proxy.
669            </p>
670            <p id="rfc.section.2.1.p.16">A server receiving credentials that are valid, but not adequate to gain access, ought to respond with the <a href="p2-semantics.html#status.403" class="smpl">403 (Forbidden)</a> status code (<a href="p2-semantics.html#status.403" title="403 Forbidden">Section 4.6.3</a> of <a href="#Part2" id="rfc.xref.Part2.1"><cite title="HTTP/1.1, part 2: Semantics and Payloads">[Part2]</cite></a>).
671            </p>
672            <p id="rfc.section.2.1.p.17">The HTTP protocol does not restrict applications to this simple challenge-response mechanism for access authentication. Additional
673               mechanisms <em class="bcp14">MAY</em> be used, such as encryption at the transport level or via message encapsulation, and with additional header fields specifying
674               authentication information. However, such additional mechanisms are not defined by this specification.
675            </p>
676            <p id="rfc.section.2.1.p.18">Proxies <em class="bcp14">MUST</em> forward the <a href="#header.www-authenticate" class="smpl">WWW-Authenticate</a> and <a href="#header.authorization" class="smpl">Authorization</a> header fields unmodified and follow the rules found in <a href="#header.authorization" id="rfc.xref.header.authorization.1" title="Authorization">Section&nbsp;4.1</a>.
677            </p>
678         </div>
679         <div id="protection.space">
680            <div id="rfc.iref.p.1"></div>
681            <div id="rfc.iref.r.1"></div>
682            <div id="rfc.iref.c.3"></div>
683            <h2 id="rfc.section.2.2"><a href="#rfc.section.2.2">2.2</a>&nbsp;<a href="#protection.space">Protection Space (Realm)</a></h2>
684            <p id="rfc.section.2.2.p.1">The authentication parameter realm is reserved for use by authentication schemes that wish to indicate the scope of protection.</p>
685            <p id="rfc.section.2.2.p.2">A <dfn>protection space</dfn> is defined by the canonical root URI (the scheme and authority components of the effective request URI; see <a href="p1-messaging.html#effective.request.uri" title="Effective Request URI">Section 5.5</a> of <a href="#Part1" id="rfc.xref.Part1.3"><cite title="HTTP/1.1, part 1: Message Routing and Syntax&#34;">[Part1]</cite></a>) of the server being accessed, in combination with the realm value if present. These realms allow the protected resources
686               on a server to be partitioned into a set of protection spaces, each with its own authentication scheme and/or authorization
687               database. The realm value is a string, generally assigned by the origin server, which can have additional semantics specific
688               to the authentication scheme. Note that there can be multiple challenges with the same auth-scheme but different realms.
689            </p>
690            <p id="rfc.section.2.2.p.3">The protection space determines the domain over which credentials can be automatically applied. If a prior request has been
691               authorized, the same credentials <em class="bcp14">MAY</em> be reused for all other requests within that protection space for a period of time determined by the authentication scheme,
692               parameters, and/or user preference. Unless otherwise defined by the authentication scheme, a single protection space cannot
693               extend outside the scope of its server.
694            </p>
695            <p id="rfc.section.2.2.p.4">For historical reasons, senders <em class="bcp14">MUST</em> only use the quoted-string syntax. Recipients might have to support both token and quoted-string syntax for maximum interoperability
696               with existing clients that have been accepting both notations for a long time.
697            </p>
698         </div>
699         <div id="authentication.scheme.registry">
700            <h2 id="rfc.section.2.3"><a href="#rfc.section.2.3">2.3</a>&nbsp;<a href="#authentication.scheme.registry">Authentication Scheme Registry</a></h2>
701            <p id="rfc.section.2.3.p.1">The HTTP Authentication Scheme Registry defines the name space for the authentication schemes in challenges and credentials.</p>
702            <p id="rfc.section.2.3.p.2">Registrations <em class="bcp14">MUST</em> include the following fields:
703            </p>
704            <ul>
705               <li>Authentication Scheme Name</li>
706               <li>Pointer to specification text</li>
707               <li>Notes (optional)</li>
708            </ul>
709            <p id="rfc.section.2.3.p.3">Values to be added to this name space require IETF Review (see <a href="#RFC5226" id="rfc.xref.RFC5226.1"><cite title="Guidelines for Writing an IANA Considerations Section in RFCs">[RFC5226]</cite></a>, <a href="https://tools.ietf.org/html/rfc5226#section-4.1">Section 4.1</a>).
710            </p>
711            <p id="rfc.section.2.3.p.4">The registry itself is maintained at &lt;<a href="http://www.iana.org/assignments/http-authschemes">http://www.iana.org/assignments/http-authschemes</a>&gt;.
712            </p>
713            <div id="considerations.for.new.authentication.schemes">
714               <h3 id="rfc.section.2.3.1"><a href="#rfc.section.2.3.1">2.3.1</a>&nbsp;<a href="#considerations.for.new.authentication.schemes">Considerations for New Authentication Schemes</a></h3>
715               <p id="rfc.section.2.3.1.p.1">There are certain aspects of the HTTP Authentication Framework that put constraints on how new authentication schemes can
716                  work:
717               </p>
718               <p id="rfc.section.2.3.1.p.2"></p>
719               <ul>
720                  <li>
721                     <p>HTTP authentication is presumed to be stateless: all of the information necessary to authenticate a request <em class="bcp14">MUST</em> be provided in the request, rather than be dependent on the server remembering prior requests. Authentication based on, or
722                        bound to, the underlying connection is outside the scope of this specification and inherently flawed unless steps are taken
723                        to ensure that the connection cannot be used by any party other than the authenticated user (see <a href="p1-messaging.html#intermediaries" title="Intermediaries">Section 2.4</a> of <a href="#Part1" id="rfc.xref.Part1.4"><cite title="HTTP/1.1, part 1: Message Routing and Syntax&#34;">[Part1]</cite></a>).
724                     </p>
725                  </li>
726                  <li>
727                     <p>The authentication parameter "realm" is reserved for defining Protection Spaces as defined in <a href="#protection.space" title="Protection Space (Realm)">Section&nbsp;2.2</a>. New schemes <em class="bcp14">MUST NOT</em> use it in a way incompatible with that definition.
728                     </p>
729                  </li>
730                  <li>
731                     <p>The "b64token" notation was introduced for compatibility with existing authentication schemes and can only be used once per
732                        challenge/credentials. New schemes thus ought to use the "auth-param" syntax instead, because otherwise future extensions
733                        will be impossible.
734                     </p>
735                  </li>
736                  <li>
737                     <p>The parsing of challenges and credentials is defined by this specification, and cannot be modified by new authentication schemes.
738                        When the auth-param syntax is used, all parameters ought to support both token and quoted-string syntax, and syntactical constraints
739                        ought to be defined on the field value after parsing (i.e., quoted-string processing). This is necessary so that recipients
740                        can use a generic parser that applies to all authentication schemes.
741                     </p>
742                     <p><b>Note:</b> The fact that the value syntax for the "realm" parameter is restricted to quoted-string was a bad design choice not to be
743                        repeated for new parameters.
744                     </p>
745                  </li>
746                  <li>
747                     <p>Definitions of new schemes ought to define the treatment of unknown extension parameters. In general, a "must-ignore" rule
748                        is preferable over "must-understand", because otherwise it will be hard to introduce new parameters in the presence of legacy
749                        recipients. Furthermore, it's good to describe the policy for defining new parameters (such as "update the specification",
750                        or "use this registry").
751                     </p>
752                  </li>
753                  <li>
754                     <p>Authentication schemes need to document whether they are usable in origin-server authentication (i.e., using <a href="#header.www-authenticate" class="smpl">WWW-Authenticate</a>), and/or proxy authentication (i.e., using <a href="#header.proxy-authenticate" class="smpl">Proxy-Authenticate</a>).
755                     </p>
756                  </li>
757                  <li>
758                     <p>The credentials carried in an <a href="#header.authorization" class="smpl">Authorization</a> header field are specific to the User Agent, and therefore have the same effect on HTTP caches as the "private" Cache-Control
759                        response directive, within the scope of the request they appear in.
760                     </p>
761                     <p>Therefore, new authentication schemes which choose not to carry credentials in the <a href="#header.authorization" class="smpl">Authorization</a> header field (e.g., using a newly defined header field) will need to explicitly disallow caching, by mandating the use of
762                        either Cache-Control request directives (e.g., "no-store") or response directives (e.g., "private").
763                     </p>
764                  </li>
765               </ul>
766            </div>
767         </div>
768      </div>
769      <div id="status.code.definitions">
770         <h1 id="rfc.section.3"><a href="#rfc.section.3">3.</a>&nbsp;<a href="#status.code.definitions">Status Code Definitions</a></h1>
771         <div id="status.401">
772            <div id="rfc.iref.4.1"></div>
773            <div id="rfc.iref.s.1"></div>
774            <h2 id="rfc.section.3.1"><a href="#rfc.section.3.1">3.1</a>&nbsp;<a href="#status.401">401 Unauthorized</a></h2>
775            <p id="rfc.section.3.1.p.1">The request requires user authentication. The response <em class="bcp14">MUST</em> include a <a href="#header.www-authenticate" class="smpl">WWW-Authenticate</a> header field (<a href="#header.www-authenticate" id="rfc.xref.header.www-authenticate.1" title="WWW-Authenticate">Section&nbsp;4.4</a>) containing a challenge applicable to the target resource. The client <em class="bcp14">MAY</em> repeat the request with a suitable <a href="#header.authorization" class="smpl">Authorization</a> header field (<a href="#header.authorization" id="rfc.xref.header.authorization.2" title="Authorization">Section&nbsp;4.1</a>). If the request already included Authorization credentials, then the 401 response indicates that authorization has been
776               refused for those credentials. If the 401 response contains the same challenge as the prior response, and the user agent has
777               already attempted authentication at least once, then the user <em class="bcp14">SHOULD</em> be presented the representation that was given in the response, since that representation might include relevant diagnostic
778               information.
779            </p>
780         </div>
781         <div id="status.407">
782            <div id="rfc.iref.4.2"></div>
783            <div id="rfc.iref.s.2"></div>
784            <h2 id="rfc.section.3.2"><a href="#rfc.section.3.2">3.2</a>&nbsp;<a href="#status.407">407 Proxy Authentication Required</a></h2>
785            <p id="rfc.section.3.2.p.1">This code is similar to <a href="#status.401" class="smpl">401 (Unauthorized)</a>, but indicates that the client ought to first authenticate itself with the proxy. The proxy <em class="bcp14">MUST</em> return a <a href="#header.proxy-authenticate" class="smpl">Proxy-Authenticate</a> header field (<a href="#header.proxy-authenticate" id="rfc.xref.header.proxy-authenticate.1" title="Proxy-Authenticate">Section&nbsp;4.2</a>) containing a challenge applicable to the proxy for the target resource. The client <em class="bcp14">MAY</em> repeat the request with a suitable <a href="#header.proxy-authorization" class="smpl">Proxy-Authorization</a> header field (<a href="#header.proxy-authorization" id="rfc.xref.header.proxy-authorization.1" title="Proxy-Authorization">Section&nbsp;4.3</a>).
786            </p>
787         </div>
788      </div>
789      <div id="header.field.definitions">
790         <h1 id="rfc.section.4"><a href="#rfc.section.4">4.</a>&nbsp;<a href="#header.field.definitions">Header Field Definitions</a></h1>
791         <p id="rfc.section.4.p.1">This section defines the syntax and semantics of HTTP/1.1 header fields related to authentication.</p>
792         <div id="header.authorization">
793            <div id="rfc.iref.a.3"></div>
794            <div id="rfc.iref.h.1"></div>
795            <h2 id="rfc.section.4.1"><a href="#rfc.section.4.1">4.1</a>&nbsp;<a href="#header.authorization">Authorization</a></h2>
796            <p id="rfc.section.4.1.p.1">The "Authorization" header field allows a user agent to authenticate itself with a server — usually, but not necessarily,
797               after receiving a <a href="#status.401" class="smpl">401
798                  (Unauthorized)</a> response. Its value consists of credentials containing information of the user agent for the realm of the resource being requested.
799            </p>
800            <div id="rfc.figure.u.4"></div><pre class="inline"><span id="rfc.iref.g.6"></span>  <a href="#header.authorization" class="smpl">Authorization</a> = <a href="#challenge.and.response" class="smpl">credentials</a>
801</pre><p id="rfc.section.4.1.p.3">If a request is authenticated and a realm specified, the same credentials <em class="bcp14">SHOULD</em> be valid for all other requests within this realm (assuming that the authentication scheme itself does not require otherwise,
802               such as credentials that vary according to a challenge value or using synchronized clocks).
803            </p>
804            <p id="rfc.section.4.1.p.4">When a shared cache (see <a href="p6-cache.html#shared.and.non-shared.caches">Section 1.2</a> of <a href="#Part6" id="rfc.xref.Part6.1"><cite title="HTTP/1.1, part 6: Caching">[Part6]</cite></a>) receives a request containing an Authorization field, it <em class="bcp14">MUST NOT</em> return the corresponding response as a reply to any other request, unless one of the following specific exceptions holds:
805            </p>
806            <p id="rfc.section.4.1.p.5"></p>
807            <ol>
808               <li>If the response includes the "s-maxage" cache-control directive, the cache <em class="bcp14">MAY</em> use that response in replying to a subsequent request. But (if the specified maximum age has passed) a proxy cache <em class="bcp14">MUST</em> first revalidate it with the origin server, using the header fields from the new request to allow the origin server to authenticate
809                  the new request. (This is the defined behavior for s-maxage.) If the response includes "s-maxage=0", the proxy <em class="bcp14">MUST</em> always revalidate it before re-using it.
810               </li>
811               <li>If the response includes the "must-revalidate" cache-control directive, the cache <em class="bcp14">MAY</em> use that response in replying to a subsequent request. But if the response is stale, all caches <em class="bcp14">MUST</em> first revalidate it with the origin server, using the header fields from the new request to allow the origin server to authenticate
812                  the new request.
813               </li>
814               <li>If the response includes the "public" cache-control directive, it <em class="bcp14">MAY</em> be returned in reply to any subsequent request.
815               </li>
816            </ol>
817         </div>
818         <div id="header.proxy-authenticate">
819            <div id="rfc.iref.p.2"></div>
820            <div id="rfc.iref.h.2"></div>
821            <h2 id="rfc.section.4.2"><a href="#rfc.section.4.2">4.2</a>&nbsp;<a href="#header.proxy-authenticate">Proxy-Authenticate</a></h2>
822            <p id="rfc.section.4.2.p.1">The "Proxy-Authenticate" header field consists of at least one challenge that indicates the authentication scheme(s) and parameters
823               applicable to the proxy for this effective request URI (<a href="p1-messaging.html#effective.request.uri" title="Effective Request URI">Section 5.5</a> of <a href="#Part1" id="rfc.xref.Part1.5"><cite title="HTTP/1.1, part 1: Message Routing and Syntax&#34;">[Part1]</cite></a>). It <em class="bcp14">MUST</em> be included as part of a <a href="#status.407" class="smpl">407 (Proxy Authentication Required)</a> response.
824            </p>
825            <div id="rfc.figure.u.5"></div><pre class="inline"><span id="rfc.iref.g.7"></span>  <a href="#header.proxy-authenticate" class="smpl">Proxy-Authenticate</a> = 1#<a href="#challenge.and.response" class="smpl">challenge</a>
826</pre><p id="rfc.section.4.2.p.3">Unlike <a href="#header.www-authenticate" class="smpl">WWW-Authenticate</a>, the Proxy-Authenticate header field applies only to the current connection, and intermediaries <em class="bcp14">SHOULD NOT</em> forward it to downstream clients. However, an intermediate proxy might need to obtain its own credentials by requesting them
827               from the downstream client, which in some circumstances will appear as if the proxy is forwarding the Proxy-Authenticate header
828               field.
829            </p>
830            <p id="rfc.section.4.2.p.4">Note that the parsing considerations for <a href="#header.www-authenticate" class="smpl">WWW-Authenticate</a> apply to this header field as well; see <a href="#header.www-authenticate" id="rfc.xref.header.www-authenticate.2" title="WWW-Authenticate">Section&nbsp;4.4</a> for details.
831            </p>
832         </div>
833         <div id="header.proxy-authorization">
834            <div id="rfc.iref.p.3"></div>
835            <div id="rfc.iref.h.3"></div>
836            <h2 id="rfc.section.4.3"><a href="#rfc.section.4.3">4.3</a>&nbsp;<a href="#header.proxy-authorization">Proxy-Authorization</a></h2>
837            <p id="rfc.section.4.3.p.1">The "Proxy-Authorization" header field allows the client to identify itself (or its user) to a proxy which requires authentication.
838               Its value consists of credentials containing the authentication information of the user agent for the proxy and/or realm of
839               the resource being requested.
840            </p>
841            <div id="rfc.figure.u.6"></div><pre class="inline"><span id="rfc.iref.g.8"></span>  <a href="#header.proxy-authorization" class="smpl">Proxy-Authorization</a> = <a href="#challenge.and.response" class="smpl">credentials</a>
842</pre><p id="rfc.section.4.3.p.3">Unlike <a href="#header.authorization" class="smpl">Authorization</a>, the Proxy-Authorization header field applies only to the next outbound proxy that demanded authentication using the <a href="#header.proxy-authenticate" class="smpl">Proxy-Authenticate</a> field. When multiple proxies are used in a chain, the Proxy-Authorization header field is consumed by the first outbound proxy
843               that was expecting to receive credentials. A proxy <em class="bcp14">MAY</em> relay the credentials from the client request to the next proxy if that is the mechanism by which the proxies cooperatively
844               authenticate a given request.
845            </p>
846         </div>
847         <div id="header.www-authenticate">
848            <div id="rfc.iref.w.1"></div>
849            <div id="rfc.iref.h.4"></div>
850            <h2 id="rfc.section.4.4"><a href="#rfc.section.4.4">4.4</a>&nbsp;<a href="#header.www-authenticate">WWW-Authenticate</a></h2>
851            <p id="rfc.section.4.4.p.1">The "WWW-Authenticate" header field consists of at least one challenge that indicates the authentication scheme(s) and parameters
852               applicable to the effective request URI (<a href="p1-messaging.html#effective.request.uri" title="Effective Request URI">Section 5.5</a> of <a href="#Part1" id="rfc.xref.Part1.6"><cite title="HTTP/1.1, part 1: Message Routing and Syntax&#34;">[Part1]</cite></a>).
853            </p>
854            <p id="rfc.section.4.4.p.2">It <em class="bcp14">MUST</em> be included in <a href="#status.401" class="smpl">401 (Unauthorized)</a> response messages and <em class="bcp14">MAY</em> be included in other response messages to indicate that supplying credentials (or different credentials) might affect the
855               response.
856            </p>
857            <div id="rfc.figure.u.7"></div><pre class="inline"><span id="rfc.iref.g.9"></span>  <a href="#header.www-authenticate" class="smpl">WWW-Authenticate</a> = 1#<a href="#challenge.and.response" class="smpl">challenge</a>
858</pre><p id="rfc.section.4.4.p.4">User agents are advised to take special care in parsing the WWW-Authenticate field value as it might contain more than one
859               challenge, or if more than one WWW-Authenticate header field is provided, the contents of a challenge itself can contain a
860               comma-separated list of authentication parameters.
861            </p>
862            <div id="rfc.figure.u.8"></div>
863            <p>For instance:</p><pre class="text">  WWW-Authenticate: Newauth realm="apps", type=1,
864                    title="Login to \"apps\"", Basic realm="simple"
865</pre><p>This header field contains two challenges; one for the "Newauth" scheme with a realm value of "apps", and two additional parameters
866               "type" and "title", and another one for the "Basic" scheme with a realm value of "simple".
867            </p>
868            <div class="note" id="rfc.section.4.4.p.6">
869               <p><b>Note:</b> The challenge grammar production uses the list syntax as well. Therefore, a sequence of comma, whitespace, and comma can be
870                  considered both as applying to the preceding challenge, or to be an empty entry in the list of challenges. In practice, this
871                  ambiguity does not affect the semantics of the header field value and thus is harmless.
872               </p>
873            </div>
874         </div>
875      </div>
876      <div id="IANA.considerations">
877         <h1 id="rfc.section.5"><a href="#rfc.section.5">5.</a>&nbsp;<a href="#IANA.considerations">IANA Considerations</a></h1>
878         <div id="authentication.scheme.registration">
879            <h2 id="rfc.section.5.1"><a href="#rfc.section.5.1">5.1</a>&nbsp;<a href="#authentication.scheme.registration">Authentication Scheme Registry</a></h2>
880            <p id="rfc.section.5.1.p.1">The registration procedure for HTTP Authentication Schemes is defined by <a href="#authentication.scheme.registry" title="Authentication Scheme Registry">Section&nbsp;2.3</a> of this document.
881            </p>
882            <p id="rfc.section.5.1.p.2">The HTTP Method Authentication Scheme shall be created at &lt;<a href="http://www.iana.org/assignments/http-authschemes">http://www.iana.org/assignments/http-authschemes</a>&gt;.
883            </p>
884         </div>
885         <div id="status.code.registration">
886            <h2 id="rfc.section.5.2"><a href="#rfc.section.5.2">5.2</a>&nbsp;<a href="#status.code.registration">Status Code Registration</a></h2>
887            <p id="rfc.section.5.2.p.1">The HTTP Status Code Registry located at &lt;<a href="http://www.iana.org/assignments/http-status-codes">http://www.iana.org/assignments/http-status-codes</a>&gt; shall be updated with the registrations below:
888            </p>
889         </div>
890         <div id="header.field.registration">
891            <h2 id="rfc.section.5.3"><a href="#rfc.section.5.3">5.3</a>&nbsp;<a href="#header.field.registration">Header Field Registration</a></h2>
892            <p id="rfc.section.5.3.p.1">The Message Header Field Registry located at &lt;<a href="http://www.iana.org/assignments/message-headers/message-header-index.html">http://www.iana.org/assignments/message-headers/message-header-index.html</a>&gt; shall be updated with the permanent registrations below (see <a href="#RFC3864" id="rfc.xref.RFC3864.1"><cite title="Registration Procedures for Message Header Fields">[RFC3864]</cite></a>):
893            </p>
894            <p id="rfc.section.5.3.p.2">The change controller is: "IETF (iesg@ietf.org) - Internet Engineering Task Force".</p>
895         </div>
896      </div>
897      <div id="security.considerations">
898         <h1 id="rfc.section.6"><a href="#rfc.section.6">6.</a>&nbsp;<a href="#security.considerations">Security Considerations</a></h1>
899         <p id="rfc.section.6.p.1">This section is meant to inform application developers, information providers, and users of the security limitations in HTTP/1.1
900            as described by this document. The discussion does not include definitive solutions to the problems revealed, though it does
901            make some suggestions for reducing security risks.
902         </p>
903         <div id="auth.credentials.and.idle.clients">
904            <h2 id="rfc.section.6.1"><a href="#rfc.section.6.1">6.1</a>&nbsp;<a href="#auth.credentials.and.idle.clients">Authentication Credentials and Idle Clients</a></h2>
905            <p id="rfc.section.6.1.p.1">Existing HTTP clients and user agents typically retain authentication information indefinitely. HTTP/1.1 does not provide
906               a method for a server to direct clients to discard these cached credentials. This is a significant defect that requires further
907               extensions to HTTP. Circumstances under which credential caching can interfere with the application's security model include
908               but are not limited to:
909            </p>
910            <ul>
911               <li>Clients which have been idle for an extended period following which the server might wish to cause the client to reprompt
912                  the user for credentials.
913               </li>
914               <li>Applications which include a session termination indication (such as a "logout" or "commit" button on a page) after which
915                  the server side of the application "knows" that there is no further reason for the client to retain the credentials.
916               </li>
917            </ul>
918            <p id="rfc.section.6.1.p.2">This is currently under separate study. There are a number of work-arounds to parts of this problem, and we encourage the
919               use of password protection in screen savers, idle time-outs, and other methods which mitigate the security problems inherent
920               in this problem. In particular, user agents which cache credentials are encouraged to provide a readily accessible mechanism
921               for discarding cached credentials under user control.
922            </p>
923         </div>
924         <div id="protection.spaces">
925            <h2 id="rfc.section.6.2"><a href="#rfc.section.6.2">6.2</a>&nbsp;<a href="#protection.spaces">Protection Spaces</a></h2>
926            <p id="rfc.section.6.2.p.1">Authentication schemes that solely rely on the "realm" mechanism for establishing a protection space will expose credentials
927               to all resources on a server. Clients that have successfully made authenticated requests with a resource can use the same
928               authentication credentials for other resources on the same server. This makes it possible for a different resource to harvest
929               authentication credentials for other resources.
930            </p>
931            <p id="rfc.section.6.2.p.2">This is of particular concern when a server hosts resources for multiple parties under the same canonical root URI (<a href="#protection.space" title="Protection Space (Realm)">Section&nbsp;2.2</a>). Possible mitigation strategies include restricting direct access to authentication credentials (i.e., not making the content
932               of the <a href="#header.authorization" class="smpl">Authorization</a> request header field available), and separating protection spaces by using a different host name for each party.
933            </p>
934         </div>
935      </div>
936      <div id="acks">
937         <h1 id="rfc.section.7"><a href="#rfc.section.7">7.</a>&nbsp;<a href="#acks">Acknowledgments</a></h1>
938         <p id="rfc.section.7.p.1">This specification takes over the definition of the HTTP Authentication Framework, previously defined in <cite title="HTTP Authentication: Basic and Digest Access Authentication" id="rfc.xref.RFC2617.3">RFC 2617</cite>. We thank John Franks, Phillip M. Hallam-Baker, Jeffery L. Hostetler, Scott D. Lawrence, Paul J. Leach, Ari Luotonen, and
939            Lawrence C. Stewart for their work on that specification. See <a href="https://tools.ietf.org/html/rfc2617#section-6">Section 6</a> of <a href="#RFC2617" id="rfc.xref.RFC2617.4"><cite title="HTTP Authentication: Basic and Digest Access Authentication">[RFC2617]</cite></a> for further acknowledgements.
940         </p>
941         <p id="rfc.section.7.p.2">See <a href="p1-messaging.html#acks" title="Acknowledgments">Section 9</a> of <a href="#Part1" id="rfc.xref.Part1.7"><cite title="HTTP/1.1, part 1: Message Routing and Syntax&#34;">[Part1]</cite></a> for the Acknowledgments related to this document revision.
942         </p>
943      </div>
944      <h1 id="rfc.references"><a id="rfc.section.8" href="#rfc.section.8">8.</a> References
945      </h1>
946      <h2 id="rfc.references.1"><a href="#rfc.section.8.1" id="rfc.section.8.1">8.1</a> Normative References
947      </h2>
948      <table>
949         <tr>
950            <td class="reference"><b id="Part1">[Part1]</b></td>
951            <td class="top"><a href="mailto:fielding@gbiv.com" title="Adobe Systems Incorporated">Fielding, R., Ed.</a>, <a href="mailto:ylafon@w3.org" title="World Wide Web Consortium">Lafon, Y., Ed.</a>, and <a href="mailto:julian.reschke@greenbytes.de" title="greenbytes GmbH">J. Reschke, Ed.</a>, “<a href="https://tools.ietf.org/html/draft-ietf-httpbis-p1-messaging-20">HTTP/1.1, part 1: Message Routing and Syntax"</a>”, Internet-Draft&nbsp;draft-ietf-httpbis-p1-messaging-20 (work in progress), July&nbsp;2012.
952            </td>
953         </tr>
954         <tr>
955            <td class="reference"><b id="Part2">[Part2]</b></td>
956            <td class="top"><a href="mailto:fielding@gbiv.com" title="Adobe Systems Incorporated">Fielding, R., Ed.</a>, <a href="mailto:ylafon@w3.org" title="World Wide Web Consortium">Lafon, Y., Ed.</a>, and <a href="mailto:julian.reschke@greenbytes.de" title="greenbytes GmbH">J. Reschke, Ed.</a>, “<a href="https://tools.ietf.org/html/draft-ietf-httpbis-p2-semantics-20">HTTP/1.1, part 2: Semantics and Payloads</a>”, Internet-Draft&nbsp;draft-ietf-httpbis-p2-semantics-20 (work in progress), July&nbsp;2012.
957            </td>
958         </tr>
959         <tr>
960            <td class="reference"><b id="Part6">[Part6]</b></td>
961            <td class="top"><a href="mailto:fielding@gbiv.com" title="Adobe Systems Incorporated">Fielding, R., Ed.</a>, <a href="mailto:ylafon@w3.org" title="World Wide Web Consortium">Lafon, Y., Ed.</a>, <a href="mailto:mnot@mnot.net" title="Rackspace">Nottingham, M., Ed.</a>, and <a href="mailto:julian.reschke@greenbytes.de" title="greenbytes GmbH">J. Reschke, Ed.</a>, “<a href="https://tools.ietf.org/html/draft-ietf-httpbis-p6-cache-20">HTTP/1.1, part 6: Caching</a>”, Internet-Draft&nbsp;draft-ietf-httpbis-p6-cache-20 (work in progress), July&nbsp;2012.
962            </td>
963         </tr>
964         <tr>
965            <td class="reference"><b id="RFC2119">[RFC2119]</b></td>
966            <td class="top"><a href="mailto:sob@harvard.edu" title="Harvard University">Bradner, S.</a>, “<a href="https://tools.ietf.org/html/rfc2119">Key words for use in RFCs to Indicate Requirement Levels</a>”, BCP&nbsp;14, RFC&nbsp;2119, March&nbsp;1997.
967            </td>
968         </tr>
969         <tr>
970            <td class="reference"><b id="RFC5234">[RFC5234]</b></td>
971            <td class="top"><a href="mailto:dcrocker@bbiw.net" title="Brandenburg InternetWorking">Crocker, D., Ed.</a> and <a href="mailto:paul.overell@thus.net" title="THUS plc.">P. Overell</a>, “<a href="https://tools.ietf.org/html/rfc5234">Augmented BNF for Syntax Specifications: ABNF</a>”, STD&nbsp;68, RFC&nbsp;5234, January&nbsp;2008.
972            </td>
973         </tr>
974      </table>
975      <h2 id="rfc.references.2"><a href="#rfc.section.8.2" id="rfc.section.8.2">8.2</a> Informative References
976      </h2>
977      <table>
978         <tr>
979            <td class="reference"><b id="RFC2616">[RFC2616]</b></td>
980            <td class="top"><a href="mailto:fielding@ics.uci.edu" title="University of California, Irvine">Fielding, R.</a>, <a href="mailto:jg@w3.org" title="W3C">Gettys, J.</a>, <a href="mailto:mogul@wrl.dec.com" title="Compaq Computer Corporation">Mogul, J.</a>, <a href="mailto:frystyk@w3.org" title="MIT Laboratory for Computer Science">Frystyk, H.</a>, <a href="mailto:masinter@parc.xerox.com" title="Xerox Corporation">Masinter, L.</a>, <a href="mailto:paulle@microsoft.com" title="Microsoft Corporation">Leach, P.</a>, and <a href="mailto:timbl@w3.org" title="W3C">T. Berners-Lee</a>, “<a href="https://tools.ietf.org/html/rfc2616">Hypertext Transfer Protocol -- HTTP/1.1</a>”, RFC&nbsp;2616, June&nbsp;1999.
981            </td>
982         </tr>
983         <tr>
984            <td class="reference"><b id="RFC2617">[RFC2617]</b></td>
985            <td class="top"><a href="mailto:john@math.nwu.edu" title="Northwestern University, Department of Mathematics">Franks, J.</a>, <a href="mailto:pbaker@verisign.com" title="Verisign Inc.">Hallam-Baker, P.</a>, <a href="mailto:jeff@AbiSource.com" title="AbiSource, Inc.">Hostetler, J.</a>, <a href="mailto:lawrence@agranat.com" title="Agranat Systems, Inc.">Lawrence, S.</a>, <a href="mailto:paulle@microsoft.com" title="Microsoft Corporation">Leach, P.</a>, Luotonen, A., and <a href="mailto:stewart@OpenMarket.com" title="Open Market, Inc.">L. Stewart</a>, “<a href="https://tools.ietf.org/html/rfc2617">HTTP Authentication: Basic and Digest Access Authentication</a>”, RFC&nbsp;2617, June&nbsp;1999.
986            </td>
987         </tr>
988         <tr>
989            <td class="reference"><b id="RFC3864">[RFC3864]</b></td>
990            <td class="top"><a href="mailto:GK-IETF@ninebynine.org" title="Nine by Nine">Klyne, G.</a>, <a href="mailto:mnot@pobox.com" title="BEA Systems">Nottingham, M.</a>, and <a href="mailto:JeffMogul@acm.org" title="HP Labs">J. Mogul</a>, “<a href="https://tools.ietf.org/html/rfc3864">Registration Procedures for Message Header Fields</a>”, BCP&nbsp;90, RFC&nbsp;3864, September&nbsp;2004.
991            </td>
992         </tr>
993         <tr>
994            <td class="reference"><b id="RFC3986">[RFC3986]</b></td>
995            <td class="top"><a href="mailto:timbl@w3.org" title="World Wide Web Consortium">Berners-Lee, T.</a>, <a href="mailto:fielding@gbiv.com" title="Day Software">Fielding, R.</a>, and <a href="mailto:LMM@acm.org" title="Adobe Systems Incorporated">L. Masinter</a>, “<a href="https://tools.ietf.org/html/rfc3986">Uniform Resource Identifier (URI): Generic Syntax</a>”, STD&nbsp;66, RFC&nbsp;3986, January&nbsp;2005.
996            </td>
997         </tr>
998         <tr>
999            <td class="reference"><b id="RFC4648">[RFC4648]</b></td>
1000            <td class="top">Josefsson, S., “<a href="https://tools.ietf.org/html/rfc4648">The Base16, Base32, and Base64 Data Encodings</a>”, RFC&nbsp;4648, October&nbsp;2006.
1001            </td>
1002         </tr>
1003         <tr>
1004            <td class="reference"><b id="RFC5226">[RFC5226]</b></td>
1005            <td class="top"><a href="mailto:narten@us.ibm.com" title="IBM">Narten, T.</a> and <a href="mailto:Harald@Alvestrand.no" title="Google">H. Alvestrand</a>, “<a href="https://tools.ietf.org/html/rfc5226">Guidelines for Writing an IANA Considerations Section in RFCs</a>”, BCP&nbsp;26, RFC&nbsp;5226, May&nbsp;2008.
1006            </td>
1007         </tr>
1008      </table>
1009      <div id="changes.from.rfc.2616">
1010         <h1 id="rfc.section.A" class="np"><a href="#rfc.section.A">A.</a>&nbsp;<a href="#changes.from.rfc.2616">Changes from RFCs 2616 and 2617</a></h1>
1011         <p id="rfc.section.A.p.1">The "realm" parameter isn't required anymore in general; consequently, the ABNF allows challenges without any auth parameters.
1012            (<a href="#access.authentication.framework" title="Access Authentication Framework">Section&nbsp;2</a>)
1013         </p>
1014         <p id="rfc.section.A.p.2">The "b64token" alternative to auth-param lists has been added for consistency with legacy authentication schemes such as "Basic".
1015            (<a href="#access.authentication.framework" title="Access Authentication Framework">Section&nbsp;2</a>)
1016         </p>
1017         <p id="rfc.section.A.p.3">Introduce Authentication Scheme Registry. (<a href="#authentication.scheme.registry" title="Authentication Scheme Registry">Section&nbsp;2.3</a>)
1018         </p>
1019         <p id="rfc.section.A.p.4">Change ABNF productions for header fields to only define the field value. (<a href="#header.field.definitions" title="Header Field Definitions">Section&nbsp;4</a>)
1020         </p>
1021      </div>
1022      <div id="imported.abnf">
1023         <h1 id="rfc.section.B"><a href="#rfc.section.B">B.</a>&nbsp;<a href="#imported.abnf">Imported ABNF</a></h1>
1024         <p id="rfc.section.B.p.1">The following core rules are included by reference, as defined in <a href="https://tools.ietf.org/html/rfc5234#appendix-B.1">Appendix B.1</a> of <a href="#RFC5234" id="rfc.xref.RFC5234.2"><cite title="Augmented BNF for Syntax Specifications: ABNF">[RFC5234]</cite></a>: ALPHA (letters), CR (carriage return), CRLF (CR LF), CTL (controls), DIGIT (decimal 0-9), DQUOTE (double quote), HEXDIG
1025            (hexadecimal 0-9/A-F/a-f), LF (line feed), OCTET (any 8-bit sequence of data), SP (space), and VCHAR (any visible US-ASCII
1026            character).
1027         </p>
1028         <p id="rfc.section.B.p.2">The rules below are defined in <a href="#Part1" id="rfc.xref.Part1.8"><cite title="HTTP/1.1, part 1: Message Routing and Syntax&#34;">[Part1]</cite></a>:
1029         </p>
1030         <div id="rfc.figure.u.9"></div><pre class="inline">  <a href="#imported.abnf" class="smpl">BWS</a>           = &lt;BWS, defined in <a href="#Part1" id="rfc.xref.Part1.9"><cite title="HTTP/1.1, part 1: Message Routing and Syntax&#34;">[Part1]</cite></a>, <a href="p1-messaging.html#whitespace" title="Whitespace">Section 3.2.1</a>&gt;
1031  <a href="#imported.abnf" class="smpl">OWS</a>           = &lt;OWS, defined in <a href="#Part1" id="rfc.xref.Part1.10"><cite title="HTTP/1.1, part 1: Message Routing and Syntax&#34;">[Part1]</cite></a>, <a href="p1-messaging.html#whitespace" title="Whitespace">Section 3.2.1</a>&gt;
1032  <a href="#imported.abnf" class="smpl">quoted-string</a> = &lt;quoted-string, defined in <a href="#Part1" id="rfc.xref.Part1.11"><cite title="HTTP/1.1, part 1: Message Routing and Syntax&#34;">[Part1]</cite></a>, <a href="p1-messaging.html#field.components" title="Field value components">Section 3.2.4</a>&gt;
1033  <a href="#imported.abnf" class="smpl">token</a>         = &lt;token, defined in <a href="#Part1" id="rfc.xref.Part1.12"><cite title="HTTP/1.1, part 1: Message Routing and Syntax&#34;">[Part1]</cite></a>, <a href="p1-messaging.html#field.components" title="Field value components">Section 3.2.4</a>&gt;
1034</pre></div>
1035      <div id="change.log">
1036         <h1 id="rfc.section.C"><a href="#rfc.section.C">C.</a>&nbsp;<a href="#change.log">Change Log (to be removed by RFC Editor before publication)</a></h1>
1037         <p id="rfc.section.C.p.1">Changes up to the first Working Group Last Call draft are summarized in &lt;<a href="http://trac.tools.ietf.org/html/draft-ietf-httpbis-p7-auth-19#appendix-C">http://trac.tools.ietf.org/html/draft-ietf-httpbis-p7-auth-19#appendix-C</a>&gt;.
1038         </p>
1039         <div id="changes.since.19">
1040            <h2 id="rfc.section.C.1"><a href="#rfc.section.C.1">C.1</a>&nbsp;<a href="#changes.since.19">Since draft-ietf-httpbis-p7-auth-19</a></h2>
1041            <p id="rfc.section.C.1.p.1">Closed issues: </p>
1042            <ul>
1043               <li>&lt;<a href="http://tools.ietf.org/wg/httpbis/trac/ticket/348">http://tools.ietf.org/wg/httpbis/trac/ticket/348</a>&gt;: "Realms and scope"
1044               </li>
1045               <li>&lt;<a href="http://tools.ietf.org/wg/httpbis/trac/ticket/349">http://tools.ietf.org/wg/httpbis/trac/ticket/349</a>&gt;: "Strength"
1046               </li>
1047               <li>&lt;<a href="http://tools.ietf.org/wg/httpbis/trac/ticket/357">http://tools.ietf.org/wg/httpbis/trac/ticket/357</a>&gt;: "Authentication exchanges"
1048               </li>
1049               <li>&lt;<a href="http://tools.ietf.org/wg/httpbis/trac/ticket/361">http://tools.ietf.org/wg/httpbis/trac/ticket/361</a>&gt;: "ABNF requirements for recipients"
1050               </li>
1051               <li>&lt;<a href="http://tools.ietf.org/wg/httpbis/trac/ticket/368">http://tools.ietf.org/wg/httpbis/trac/ticket/368</a>&gt;: "note introduction of new IANA registries as normative changes"
1052               </li>
1053            </ul>
1054         </div>
1055      </div>
1056      <h1 id="rfc.index"><a href="#rfc.index">Index</a></h1>
1057      <p class="noprint"><a href="#rfc.index.4">4</a> <a href="#rfc.index.A">A</a> <a href="#rfc.index.B">B</a> <a href="#rfc.index.C">C</a> <a href="#rfc.index.G">G</a> <a href="#rfc.index.H">H</a> <a href="#rfc.index.P">P</a> <a href="#rfc.index.R">R</a> <a href="#rfc.index.S">S</a> <a href="#rfc.index.W">W</a>
1058      </p>
1059      <div class="print2col">
1060         <ul class="ind">
1061            <li><a id="rfc.index.4" href="#rfc.index.4"><b>4</b></a><ul>
1062                  <li>401 Unauthorized (status code)&nbsp;&nbsp;<a href="#rfc.iref.4.1"><b>3.1</b></a></li>
1063                  <li>407 Proxy Authentication Required (status code)&nbsp;&nbsp;<a href="#rfc.iref.4.2"><b>3.2</b></a></li>
1064               </ul>
1065            </li>
1066            <li><a id="rfc.index.A" href="#rfc.index.A"><b>A</b></a><ul>
1067                  <li><tt>auth-param</tt>&nbsp;&nbsp;<a href="#rfc.iref.a.2"><b>2.1</b></a></li>
1068                  <li><tt>auth-scheme</tt>&nbsp;&nbsp;<a href="#rfc.iref.a.1"><b>2.1</b></a></li>
1069                  <li>Authorization header field&nbsp;&nbsp;<a href="#rfc.xref.header.authorization.1">2.1</a>, <a href="#rfc.xref.header.authorization.2">3.1</a>, <a href="#rfc.iref.a.3"><b>4.1</b></a></li>
1070               </ul>
1071            </li>
1072            <li><a id="rfc.index.B" href="#rfc.index.B"><b>B</b></a><ul>
1073                  <li><tt>b64token</tt>&nbsp;&nbsp;<a href="#rfc.iref.b.1"><b>2.1</b></a></li>
1074               </ul>
1075            </li>
1076            <li><a id="rfc.index.C" href="#rfc.index.C"><b>C</b></a><ul>
1077                  <li>Canonical Root URI&nbsp;&nbsp;<a href="#rfc.iref.c.3">2.2</a></li>
1078                  <li><tt>challenge</tt>&nbsp;&nbsp;<a href="#rfc.iref.c.1"><b>2.1</b></a></li>
1079                  <li><tt>credentials</tt>&nbsp;&nbsp;<a href="#rfc.iref.c.2"><b>2.1</b></a></li>
1080               </ul>
1081            </li>
1082            <li><a id="rfc.index.G" href="#rfc.index.G"><b>G</b></a><ul>
1083                  <li><tt>Grammar</tt>&nbsp;&nbsp;
1084                     <ul>
1085                        <li><tt>auth-param</tt>&nbsp;&nbsp;<a href="#rfc.iref.g.2"><b>2.1</b></a></li>
1086                        <li><tt>auth-scheme</tt>&nbsp;&nbsp;<a href="#rfc.iref.g.1"><b>2.1</b></a></li>
1087                        <li><tt>Authorization</tt>&nbsp;&nbsp;<a href="#rfc.iref.g.6"><b>4.1</b></a></li>
1088                        <li><tt>b64token</tt>&nbsp;&nbsp;<a href="#rfc.iref.g.3"><b>2.1</b></a></li>
1089                        <li><tt>challenge</tt>&nbsp;&nbsp;<a href="#rfc.iref.g.4"><b>2.1</b></a></li>
1090                        <li><tt>credentials</tt>&nbsp;&nbsp;<a href="#rfc.iref.g.5"><b>2.1</b></a></li>
1091                        <li><tt>Proxy-Authenticate</tt>&nbsp;&nbsp;<a href="#rfc.iref.g.7"><b>4.2</b></a></li>
1092                        <li><tt>Proxy-Authorization</tt>&nbsp;&nbsp;<a href="#rfc.iref.g.8"><b>4.3</b></a></li>
1093                        <li><tt>WWW-Authenticate</tt>&nbsp;&nbsp;<a href="#rfc.iref.g.9"><b>4.4</b></a></li>
1094                     </ul>
1095                  </li>
1096               </ul>
1097            </li>
1098            <li><a id="rfc.index.H" href="#rfc.index.H"><b>H</b></a><ul>
1099                  <li>Header Fields&nbsp;&nbsp;
1100                     <ul>
1101                        <li>Authorization&nbsp;&nbsp;<a href="#rfc.xref.header.authorization.1">2.1</a>, <a href="#rfc.xref.header.authorization.2">3.1</a>, <a href="#rfc.iref.h.1"><b>4.1</b></a></li>
1102                        <li>Proxy-Authenticate&nbsp;&nbsp;<a href="#rfc.xref.header.proxy-authenticate.1">3.2</a>, <a href="#rfc.iref.h.2"><b>4.2</b></a></li>
1103                        <li>Proxy-Authorization&nbsp;&nbsp;<a href="#rfc.xref.header.proxy-authorization.1">3.2</a>, <a href="#rfc.iref.h.3"><b>4.3</b></a></li>
1104                        <li>WWW-Authenticate&nbsp;&nbsp;<a href="#rfc.xref.header.www-authenticate.1">3.1</a>, <a href="#rfc.xref.header.www-authenticate.2">4.2</a>, <a href="#rfc.iref.h.4"><b>4.4</b></a></li>
1105                     </ul>
1106                  </li>
1107               </ul>
1108            </li>
1109            <li><a id="rfc.index.P" href="#rfc.index.P"><b>P</b></a><ul>
1110                  <li><em>Part1</em>&nbsp;&nbsp;<a href="#rfc.xref.Part1.1">1.1</a>, <a href="#rfc.xref.Part1.2">1.2</a>, <a href="#rfc.xref.Part1.3">2.2</a>, <a href="#rfc.xref.Part1.4">2.3.1</a>, <a href="#rfc.xref.Part1.5">4.2</a>, <a href="#rfc.xref.Part1.6">4.4</a>, <a href="#rfc.xref.Part1.7">7</a>, <a href="#Part1"><b>8.1</b></a>, <a href="#rfc.xref.Part1.8">B</a>, <a href="#rfc.xref.Part1.9">B</a>, <a href="#rfc.xref.Part1.10">B</a>, <a href="#rfc.xref.Part1.11">B</a>, <a href="#rfc.xref.Part1.12">B</a><ul>
1111                        <li><em>Section 1.2</em>&nbsp;&nbsp;<a href="#rfc.xref.Part1.2">1.2</a></li>
1112                        <li><em>Section 2</em>&nbsp;&nbsp;<a href="#rfc.xref.Part1.1">1.1</a></li>
1113                        <li><em>Section 2.4</em>&nbsp;&nbsp;<a href="#rfc.xref.Part1.4">2.3.1</a></li>
1114                        <li><em>Section 3.2.1</em>&nbsp;&nbsp;<a href="#rfc.xref.Part1.9">B</a>, <a href="#rfc.xref.Part1.10">B</a></li>
1115                        <li><em>Section 3.2.4</em>&nbsp;&nbsp;<a href="#rfc.xref.Part1.11">B</a>, <a href="#rfc.xref.Part1.12">B</a></li>
1116                        <li><em>Section 5.5</em>&nbsp;&nbsp;<a href="#rfc.xref.Part1.3">2.2</a>, <a href="#rfc.xref.Part1.5">4.2</a>, <a href="#rfc.xref.Part1.6">4.4</a></li>
1117                        <li><em>Section 9</em>&nbsp;&nbsp;<a href="#rfc.xref.Part1.7">7</a></li>
1118                     </ul>
1119                  </li>
1120                  <li><em>Part2</em>&nbsp;&nbsp;<a href="#rfc.xref.Part2.1">2.1</a>, <a href="#Part2"><b>8.1</b></a><ul>
1121                        <li><em>Section 4.6.3</em>&nbsp;&nbsp;<a href="#rfc.xref.Part2.1">2.1</a></li>
1122                     </ul>
1123                  </li>
1124                  <li><em>Part6</em>&nbsp;&nbsp;<a href="#rfc.xref.Part6.1">4.1</a>, <a href="#Part6"><b>8.1</b></a><ul>
1125                        <li><em>Section 1.2</em>&nbsp;&nbsp;<a href="#rfc.xref.Part6.1">4.1</a></li>
1126                     </ul>
1127                  </li>
1128                  <li>Protection Space&nbsp;&nbsp;<a href="#rfc.iref.p.1">2.2</a></li>
1129                  <li>Proxy-Authenticate header field&nbsp;&nbsp;<a href="#rfc.xref.header.proxy-authenticate.1">3.2</a>, <a href="#rfc.iref.p.2"><b>4.2</b></a></li>
1130                  <li>Proxy-Authorization header field&nbsp;&nbsp;<a href="#rfc.xref.header.proxy-authorization.1">3.2</a>, <a href="#rfc.iref.p.3"><b>4.3</b></a></li>
1131               </ul>
1132            </li>
1133            <li><a id="rfc.index.R" href="#rfc.index.R"><b>R</b></a><ul>
1134                  <li>Realm&nbsp;&nbsp;<a href="#rfc.iref.r.1">2.2</a></li>
1135                  <li><em>RFC2119</em>&nbsp;&nbsp;<a href="#rfc.xref.RFC2119.1">1.1</a>, <a href="#RFC2119"><b>8.1</b></a></li>
1136                  <li><em>RFC2616</em>&nbsp;&nbsp;<a href="#rfc.xref.RFC2616.1">1</a>, <a href="#rfc.xref.RFC2616.2">1</a>, <a href="#RFC2616"><b>8.2</b></a></li>
1137                  <li><em>RFC2617</em>&nbsp;&nbsp;<a href="#rfc.xref.RFC2617.1">1</a>, <a href="#rfc.xref.RFC2617.2">1</a>, <a href="#rfc.xref.RFC2617.3">7</a>, <a href="#rfc.xref.RFC2617.4">7</a>, <a href="#RFC2617"><b>8.2</b></a><ul>
1138                        <li><em>Section 6</em>&nbsp;&nbsp;<a href="#rfc.xref.RFC2617.4">7</a></li>
1139                     </ul>
1140                  </li>
1141                  <li><em>RFC3864</em>&nbsp;&nbsp;<a href="#rfc.xref.RFC3864.1">5.3</a>, <a href="#RFC3864"><b>8.2</b></a></li>
1142                  <li><em>RFC3986</em>&nbsp;&nbsp;<a href="#rfc.xref.RFC3986.1">2.1</a>, <a href="#RFC3986"><b>8.2</b></a></li>
1143                  <li><em>RFC4648</em>&nbsp;&nbsp;<a href="#rfc.xref.RFC4648.1">2.1</a>, <a href="#RFC4648"><b>8.2</b></a></li>
1144                  <li><em>RFC5226</em>&nbsp;&nbsp;<a href="#rfc.xref.RFC5226.1">2.3</a>, <a href="#RFC5226"><b>8.2</b></a><ul>
1145                        <li><em>Section 4.1</em>&nbsp;&nbsp;<a href="#rfc.xref.RFC5226.1">2.3</a></li>
1146                     </ul>
1147                  </li>
1148                  <li><em>RFC5234</em>&nbsp;&nbsp;<a href="#rfc.xref.RFC5234.1">1.2</a>, <a href="#RFC5234"><b>8.1</b></a>, <a href="#rfc.xref.RFC5234.2">B</a><ul>
1149                        <li><em>Appendix B.1</em>&nbsp;&nbsp;<a href="#rfc.xref.RFC5234.2">B</a></li>
1150                     </ul>
1151                  </li>
1152               </ul>
1153            </li>
1154            <li><a id="rfc.index.S" href="#rfc.index.S"><b>S</b></a><ul>
1155                  <li>Status Codes&nbsp;&nbsp;
1156                     <ul>
1157                        <li>401 Unauthorized&nbsp;&nbsp;<a href="#rfc.iref.s.1"><b>3.1</b></a></li>
1158                        <li>407 Proxy Authentication Required&nbsp;&nbsp;<a href="#rfc.iref.s.2"><b>3.2</b></a></li>
1159                     </ul>
1160                  </li>
1161               </ul>
1162            </li>
1163            <li><a id="rfc.index.W" href="#rfc.index.W"><b>W</b></a><ul>
1164                  <li>WWW-Authenticate header field&nbsp;&nbsp;<a href="#rfc.xref.header.www-authenticate.1">3.1</a>, <a href="#rfc.xref.header.www-authenticate.2">4.2</a>, <a href="#rfc.iref.w.1"><b>4.4</b></a></li>
1165               </ul>
1166            </li>
1167         </ul>
1168      </div>
1169      <div class="avoidbreak">
1170         <h1 id="rfc.authors"><a href="#rfc.authors">Authors' Addresses</a></h1>
1171         <p><b>Roy T. Fielding</b>
1172            (editor)
1173            <br>Adobe Systems Incorporated<br>345 Park Ave<br>San Jose, CA&nbsp;95110<br>USA<br>Email: <a href="mailto:fielding@gbiv.com">fielding@gbiv.com</a><br>URI: <a href="http://roy.gbiv.com/">http://roy.gbiv.com/</a></p>
1174         <p><b>Yves Lafon</b>
1175            (editor)
1176            <br>World Wide Web Consortium<br>W3C / ERCIM<br>2004, rte des Lucioles<br>Sophia-Antipolis, AM&nbsp;06902<br>France<br>Email: <a href="mailto:ylafon@w3.org">ylafon@w3.org</a><br>URI: <a href="http://www.raubacapeu.net/people/yves/">http://www.raubacapeu.net/people/yves/</a></p>
1177         <p><b>Julian F. Reschke</b>
1178            (editor)
1179            <br>greenbytes GmbH<br>Hafenweg 16<br>Muenster, NW&nbsp;48155<br>Germany<br>Email: <a href="mailto:julian.reschke@greenbytes.de">julian.reschke@greenbytes.de</a><br>URI: <a href="http://greenbytes.de/tech/webdav/">http://greenbytes.de/tech/webdav/</a></p>
1180      </div>
1181   </body>
1182</html>
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