


HTTP Working Group                                            J. Reschke
Internet-Draft                                                greenbytes
Updates: 2617 (if approved)                                April 7, 2015
Intended status: Standards Track
Expires: October 9, 2015


 The Hypertext Transfer Protocol (HTTP) Authentication-Info and Proxy-
               Authentication-Info Response Header Fields
                    draft-ietf-httpbis-auth-info-05

Abstract

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

Editorial Note (To be removed by RFC Editor)

   Discussion of this draft takes place on the HTTPBIS working group
   mailing list (ietf-http-wg@w3.org), which is archived at
   <https://lists.w3.org/Archives/Public/ietf-http-wg/>.

   Working Group information can be found at
   <https://tools.ietf.org/wg/httpbis/> and <http://httpwg.github.io/>;
   source code and issues list for this draft can be found at
   <https://github.com/httpwg/http-extensions>.

   The changes in this draft are summarized in Appendix A.6.

Status of This Memo

   This Internet-Draft is submitted in full conformance with the
   provisions of BCP 78 and BCP 79.

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF).  Note that other groups may also distribute
   working documents as Internet-Drafts.  The list of current Internet-
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   Internet-Drafts are draft documents valid for a maximum of six months
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   time.  It is inappropriate to use Internet-Drafts as reference
   material or to cite them other than as "work in progress."

   This Internet-Draft will expire on October 9, 2015.




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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
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   This document may contain material from IETF Documents or IETF
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   Without obtaining an adequate license from the person(s) controlling
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   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
   Appendix A.  Change Log (to be removed by RFC Editor before
                publication) . . . . . . . . . . . . . . . . . . . . . 6
     A.1.  draft-reschke-httpauth-auth-info-00 . . . . . . . . . . . . 6
     A.2.  Since draft-ietf-httpbis-auth-info-00 . . . . . . . . . . . 6
     A.3.  Since draft-ietf-httpbis-auth-info-01 . . . . . . . . . . . 6
     A.4.  Since draft-ietf-httpbis-auth-info-02 . . . . . . . . . . . 6
     A.5.  Since draft-ietf-httpbis-auth-info-03 . . . . . . . . . . . 7
     A.6.  Since draft-ietf-httpbis-auth-info-04 . . . . . . . . . . . 7
   Appendix B.  Acknowledgements . . . . . . . . . . . . . . . . . . . 7



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1.  Introduction

   This specification defines the "Authentication-Info" and "Proxy-
   Authentication-Info" response header fields for use in HTTP
   authentication schemes ([RFC7235]) which need to return information
   once the client's authentication credentials have been accepted.

   Both were previously defined in Section 3 of [RFC2617], defining the
   HTTP "Digest" authentication scheme.  This document generalizes the
   description for use not only in "Digest" ([DIGEST]), 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 [RFC5234] with a list extension, defined in Section 7 of
   [RFC7230], 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 [RFC7235].

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 [RFC7235].  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 [DIGEST].

     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 ([RFC7235], Section 4.2) of the
   corresponding request.

   A proxy forwarding a response is not allowed to modify the field
   value in any way.




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   Authentication-Info can be used inside trailers ([RFC7230], 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 [RFC7230]).

   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 its semantics are defined by the
   authentication scheme indicated by the Proxy-Authorization header
   field ([RFC7235], Section 4.4) of the corresponding request, and
   applies to proxy authentication ([RFC7235], Section 2):


     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.



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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 shall be 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

   [RFC5234]  Crocker, D., Ed. and P. Overell, "Augmented BNF for Syntax
              Specifications: ABNF", STD 68, RFC 5234, January 2008,
              <http://www.rfc-editor.org/info/rfc5234>.

   [RFC7230]  Fielding, R., Ed. and J. Reschke, Ed., "Hypertext Transfer
              Protocol (HTTP/1.1): Message Syntax and Routing",
              RFC 7230, June 2014,
              <http://www.rfc-editor.org/info/rfc7230>.

   [RFC7235]  Fielding, R., Ed. and J. Reschke, Ed., "Hypertext Transfer
              Protocol (HTTP/1.1): Authentication", RFC 7235, June 2014,
              <http://www.rfc-editor.org/info/rfc7235>.

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/rfc3864>.

   [DIGEST]   Shekh-Yusef, R., Ed., Ahrens, D., and S. Bremer, "HTTP
              Digest Access Authentication",
              draft-ietf-httpauth-digest-15 (work in progress),
              March 2015.




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   [RFC2617]  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, June 1999,
              <http://www.rfc-editor.org/info/rfc2617>.

Appendix A.  Change Log (to be removed by RFC Editor before publication)

A.1.  draft-reschke-httpauth-auth-info-00

   Changed boilerplate to make this an HTTPbis WG draft.  Added
   Acknowledgements.

   In the Security Considerations, remind people that those apply to
   unencryped channels.

   Make it clearer that these are really just response header fields.

A.2.  Since draft-ietf-httpbis-auth-info-00

   Rephrase introduction of header field to be closer to what RFC 2617
   said ("successful authentication").

   Update DIGEST reference.

A.3.  Since draft-ietf-httpbis-auth-info-01

   State that scheme definitions need to define whether the header field
   can be used in trailers.

   Add "updates: 2617" to boilerplate.

A.4.  Since draft-ietf-httpbis-auth-info-02

   Updated DIGEST reference.

   Clarify purpose of header consistently
   (<https://github.com/httpwg/http-extensions/issues/49>).

   The do-not-modify rule does not include proxies that consume
   Authentication-Info
   (<https://github.com/httpwg/http-extensions/issues/50>).

   Borrow more proxy auth related considerations from RFC 7235 for the
   description of Proxy-Authentication-Info
   (<https://github.com/httpwg/http-extensions/issues/51>).





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A.5.  Since draft-ietf-httpbis-auth-info-03

   Updated DIGEST reference.

   Clarify how the applicable auth scheme is determined (it is present
   in the request's (Proxy-)Authorization header field).

   Adjust the IPR boilerplate because we are using some text from RFC
   2617.

A.6.  Since draft-ietf-httpbis-auth-info-04

   Add another clarification about how the applicable scheme for Proxy-
   Authentication-Info is determined.

Appendix B.  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/














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