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 . Working Group information can be found at and ; source code and issues list for this draft can be found at . 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- Drafts is at http://datatracker.ietf.org/drafts/current/. Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any 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. Reschke Expires October 9, 2015 [Page 1] Internet-Draft HTTP Authentication-Info April 2015 Copyright Notice Copyright (c) 2015 IETF Trust and the persons identified as the document authors. All rights reserved. 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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 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 Reschke Expires October 9, 2015 [Page 2] Internet-Draft HTTP Authentication-Info April 2015 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. Reschke Expires October 9, 2015 [Page 3] Internet-Draft HTTP Authentication-Info April 2015 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. Reschke Expires October 9, 2015 [Page 4] Internet-Draft HTTP Authentication-Info April 2015 6. IANA Considerations HTTP header fields are registered within the "Message Headers" registry located at , 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, . [RFC7230] Fielding, R., Ed. and J. Reschke, Ed., "Hypertext Transfer Protocol (HTTP/1.1): Message Syntax and Routing", RFC 7230, June 2014, . [RFC7235] Fielding, R., Ed. and J. Reschke, Ed., "Hypertext Transfer Protocol (HTTP/1.1): Authentication", RFC 7235, June 2014, . 7.2. Informative References [BCP90] Klyne, G., Nottingham, M., and J. Mogul, "Registration Procedures for Message Header Fields", BCP 90, RFC 3864, September 2004, . [DIGEST] Shekh-Yusef, R., Ed., Ahrens, D., and S. Bremer, "HTTP Digest Access Authentication", draft-ietf-httpauth-digest-15 (work in progress), March 2015. Reschke Expires October 9, 2015 [Page 5] Internet-Draft HTTP Authentication-Info April 2015 [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, . 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 (). The do-not-modify rule does not include proxies that consume Authentication-Info (). Borrow more proxy auth related considerations from RFC 7235 for the description of Proxy-Authentication-Info (). Reschke Expires October 9, 2015 [Page 6] Internet-Draft HTTP Authentication-Info April 2015 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/ Reschke Expires October 9, 2015 [Page 7]