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IETF RFC 7615



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Internet Engineering Task Force (IETF)                        J. Reschke
Request for Comments: 7615                                    greenbytes
Obsoletes: 2617                                           September 2015
Category: Standards Track 
ISSN: 2070-1721


         HTTP Authentication-Info and Proxy-Authentication-Info
                         Response Header Fields

 Abstract

   This specification defines the "Authentication-Info" and "Proxy-
   Authentication-Info" response header fields for use in Hypertext
   Transfer Protocol (HTTP) authentication schemes that need to return
   information once the client's authentication credentials have been
   accepted.

 Status of This Memo

   This is an Internet Standards Track document.

   This document is a product of the Internet Engineering Task Force
   (IETF).  It represents the consensus of the IETF community.  It has
   received public review and has been approved for publication by the
   Internet Engineering Steering Group (IESG).  Further information on
   Internet Standards is available in Section 2 of RFC 5741.

   Information about the current status of this document, any errata,
   and how to provide feedback on it may be obtained at
   http://www.rfc-editor.org/info/RFC 7615.




















Reschke                      Standards Track                 PAGE 1 top


RFC 7615 HTTP Authentication-Info September 2015 Copyright Notice Copyright (c) 2015 IETF Trust and the persons identified as the document authors. All rights reserved. This document is subject to BCP 78 and the IETF Trust's Legal Provisions Relating to IETF Documents (http://trustee.ietf.org/license-info) in effect on the date of publication of this document. Please review these documents carefully, as they describe your rights and restrictions with respect to this document. Code Components extracted from this document must include Simplified BSD License text as described in Section 4.e of the Trust Legal Provisions and are provided without warranty as described in the Simplified BSD License. This document may contain material from IETF Documents or IETF Contributions published or made publicly available before November 10, 2008. The person(s) controlling the copyright in some of this material may not have granted the IETF Trust the right to allow modifications of such material outside the IETF Standards Process. Without obtaining an adequate license from the person(s) controlling the copyright in such materials, this document may not be modified outside the IETF Standards Process, and derivative works of it may not be created outside the IETF Standards Process, except to format it for publication as an RFC or to translate it into languages other than English. Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 2. Notational Conventions . . . . . . . . . . . . . . . . . . . 3 3. The Authentication-Info Response Header Field . . . . . . . . 3 3.1. Parameter Value Format . . . . . . . . . . . . . . . . . 4 4. The Proxy-Authentication-Info Response Header Field . . . . . 4 5. Security Considerations . . . . . . . . . . . . . . . . . . . 4 6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 5 7. References . . . . . . . . . . . . . . . . . . . . . . . . . 5 7.1. Normative References . . . . . . . . . . . . . . . . . . 5 7.2. Informative References . . . . . . . . . . . . . . . . . 5 Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . . 6 Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 6 Reschke Standards Track PAGE 2 top

RFC 7615 HTTP Authentication-Info September 2015 1. Introduction This specification defines the "Authentication-Info" and "Proxy- Authentication-Info" response header fields for use in HTTP authentication schemes ([RFC 7235]) that need to return information once the client's authentication credentials have been accepted. Both were previously defined in Section 3 of [RFC 2617], defining the HTTP "Digest" authentication scheme. This document generalizes the description for use not only in "Digest" ([RFC 7616]), but also in other future schemes that might have the same requirements for carrying additional information during authentication. 2. Notational Conventions This specification uses the Augmented Backus-Naur Form (ABNF) notation of [RFC 5234] with a list extension, defined in Section 7 of [RFC 7230], that allows for compact definition of comma-separated lists using a '#' operator (similar to how the '*' operator indicates repetition). The ABNF production for "auth-param" is defined in Section 2.1 of [RFC 7235]. 3. The Authentication-Info Response Header Field HTTP authentication schemes can use the Authentication-Info response header field to communicate information after the client's authentication credentials have been accepted. This information can include a finalization message from the server (e.g., it can contain the server authentication). The field value is a list of parameters (name/value pairs), using the "auth-param" syntax defined in Section 2.1 of [RFC 7235]. This specification only describes the generic format; authentication schemes using Authentication-Info will define the individual parameters. The "Digest" Authentication Scheme, for instance, defines multiple parameters in Section 3.5 of [RFC 7616]. Authentication-Info = #auth-param The Authentication-Info header field can be used in any HTTP response, independently of request method and status code. Its semantics are defined by the authentication scheme indicated by the Authorization header field ([RFC 7235], Section 4.2) of the corresponding request. A proxy forwarding a response is not allowed to modify the field value in any way. Reschke Standards Track PAGE 3 top

RFC 7615 HTTP Authentication-Info September 2015 Authentication-Info can be used inside trailers ([RFC 7230], Section 4.1.2) when the authentication scheme explicitly allows this. 3.1. Parameter Value Format Parameter values can be expressed either as "token" or as "quoted- string" (Section 3.2.6 of [RFC 7230]). Authentication scheme definitions need to allow both notations, both for senders and recipients. This allows recipients to use generic parsing components, independent of the authentication scheme in use. For backwards compatibility, authentication scheme definitions can restrict the format for senders to one of the two variants. This can be important when it is known that deployed implementations will fail when encountering one of the two formats. 4. The Proxy-Authentication-Info Response Header Field The Proxy-Authentication-Info response header field is equivalent to Authentication-Info, except that it applies to proxy authentication ([RFC 7235], Section 2) and its semantics are defined by the authentication scheme indicated by the Proxy-Authorization header field ([RFC 7235], Section 4.4) of the corresponding request: Proxy-Authentication-Info = #auth-param However, unlike Authentication-Info, the Proxy-Authentication-Info header field applies only to the next outbound client on the response chain. This is because only the client that chose a given proxy is likely to have the credentials necessary for authentication. However, when multiple proxies are used within the same administrative domain, such as office and regional caching proxies within a large corporate network, it is common for credentials to be generated by the user agent and passed through the hierarchy until consumed. Hence, in such a configuration, it will appear as if Proxy-Authentication-Info is being forwarded because each proxy will send the same field value. 5. Security Considerations Adding information to HTTP responses that are sent over an unencrypted channel can affect security and privacy. The presence of the header fields alone indicates that HTTP authentication is in use. Additional information could be exposed by the contents of the authentication-scheme specific parameters; this will have to be considered in the definitions of these schemes. Reschke Standards Track PAGE 4 top

RFC 7615 HTTP Authentication-Info September 2015 6. IANA Considerations HTTP header fields are registered within the "Message Headers" registry located at <http://www.iana.org/assignments/ message-headers>, as defined by [BCP90]. This document updates the definitions of the "Authentication-Info" and "Proxy-Authentication-Info" header fields, so the "Permanent Message Header Field Names" registry has been updated accordingly: +---------------------------+----------+----------+-----------------+ | Header Field Name | Protocol | Status | Reference | +---------------------------+----------+----------+-----------------+ | Authentication-Info | http | standard | Section 3 of | | | | | this document | | Proxy-Authentication-Info | http | standard | Section 4 of | | | | | this document | +---------------------------+----------+----------+-----------------+ 7. References 7.1. Normative References [RFC 5234] Crocker, D., Ed. and P. Overell, "Augmented BNF for Syntax Specifications: ABNF", STD 68, RFC 5234, DOI 10.17487/RFC 5234, January 2008, <http://www.rfc-editor.org/info/RFC 5234>. [RFC 7230] Fielding, R., Ed. and J. Reschke, Ed., "Hypertext Transfer Protocol (HTTP/1.1): Message Syntax and Routing", RFC 7230, DOI 10.17487/RFC 7230, June 2014, <http://www.rfc-editor.org/info/RFC 7230>. [RFC 7235] Fielding, R., Ed. and J. Reschke, Ed., "Hypertext Transfer Protocol (HTTP/1.1): Authentication", RFC 7235, DOI 10.17487/RFC 7235, June 2014, <http://www.rfc-editor.org/info/RFC 7235>. 7.2. Informative References [BCP90] Klyne, G., Nottingham, M., and J. Mogul, "Registration Procedures for Message Header Fields", BCP 90, RFC 3864, September 2004, <http://www.rfc-editor.org/info/bcp90>. Reschke Standards Track PAGE 5 top

RFC 7615 HTTP Authentication-Info September 2015 [RFC 2617] Franks, J., Hallam-Baker, P., Hostetler, J., Lawrence, S., Leach, P., Luotonen, A., and L. Stewart, "HTTP Authentication: Basic and Digest Access Authentication", RFC 2617, DOI 10.17487/RFC 2617, June 1999, <http://www.rfc-editor.org/info/RFC 2617>. [RFC 7616] Shekh-Yusef, R., Ed., Ahrens, D., and S. Bremer, "HTTP Digest Access Authentication", RFC 7616, DOI 10.17487/RFC 7616, September 2015, <http://www.rfc-editor.org/info/RFC 7616>. Acknowledgements This document is based on the header field definitions in RFCs 2069 and 2617, whose authors are: John Franks, Phillip M. Hallam-Baker, Jeffery L. Hostetler, Scott D. Lawrence, Paul J. Leach, Ari Luotonen, Eric W. Sink, and Lawrence C. Stewart. Additional thanks go to the members of the HTTPAUTH and HTTPBIS Working Groups, namely, Amos Jeffries, Benjamin Kaduk, Alexey Melnikov, Mark Nottingham, Yutaka Oiwa, Rifaat Shekh-Yusef, and Martin Thomson. Author's Address Julian F. Reschke greenbytes GmbH Hafenweg 16 Muenster, NW 48155 Germany Email: julian.reschke@greenbytes.de URI: http://greenbytes.de/tech/webdav/ Reschke Standards Track PAGE 6 top

RFC TOTAL SIZE: 12239 bytes PUBLICATION DATE: Thursday, October 1st, 2015 LEGAL RIGHTS: The IETF Trust (see BCP 78)


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