| HTTPbis Working Group | J. Reschke |
| Internet-Draft | greenbytes |
| Intended status: Standards Track | January 30, 2015 |
| Expires: August 3, 2015 |
The Hypertext Transfer Protocol (HTTP) Authentication-Info and Proxy-Authentication-Info Response Header Fields
draft-ietf-httpbis-auth-info-00
This specification defines the "Authentication-Info" and "Proxy-Authentication-Info" response header fields for use in HTTP authentication schemes which need to return additional information during or after authentication.
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.
This Internet-Draft is submitted in full conformance with the provisions of BCP 78 and BCP 79.
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This Internet-Draft will expire on August 3, 2015.
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This specification defines the "Authentication-Info" and "Proxy-Authentication-Info" response header fields for use in HTTP authentication schemes ([RFC7235]) which need to return additional information during or after authentication.
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 other future schemes that might have the same requirements for carrying additional information during authentication.
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].
HTTP authentication schemes can use the Authentication-Info response header field to return additional information applicable to the authentication currently in use.
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 3.5.1 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 applicable authentication scheme. Intermediaries are not allowed to modify the field value in any way. Authentication-Info can be used inside trailers ([RFC7230], Section 4.1.2).
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.
The Proxy-Authentication-Info response header field is equivalent to Authentication-Info, except that it applies to proxy authentication ([RFC7235]):
Proxy-Authentication-Info = #auth-param
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.
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 |
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, Yutaka Oiwa, Rifaat Shekh-Yusef, and Martin Thomson.
| [RFC5234] | Crocker, D. and P. Overell, "Augmented BNF for Syntax Specifications: ABNF", STD 68, RFC 5234, January 2008. |
| [RFC7230] | Fielding, R. and J. Reschke, "Hypertext Transfer Protocol (HTTP/1.1): Message Syntax and Routing", RFC 7230, June 2014. |
| [RFC7235] | Fielding, R. and J. Reschke, "Hypertext Transfer Protocol (HTTP/1.1): Authentication", RFC 7235, June 2014. |
| [BCP90] | Klyne, G., Nottingham, M. and J. Mogul, "Registration Procedures for Message Header Fields", BCP 90, RFC 3864, September 2004. |
| [DIGEST] | Shekh-Yusef, R., Ahrens, D. and S. Bremer, "HTTP Digest Access Authentication", Internet-Draft draft-ietf-httpauth-digest-12, January 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. |
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.