Internet DRAFT - draft-ietf-httpbis-auth-info
draft-ietf-httpbis-auth-info
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
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This Internet-Draft will expire on October 9, 2015.
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Copyright Notice
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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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