[Docs] [txt|pdf|xml|html] [Tracker] [Email] [Diff1] [Diff2] [Nits]

Versions: 00 01 02 03 04 05

Network Working Group                                          Johansson
Internet-Draft                                                        SU
Intended status: Standards Track                           March 8, 2009
Expires: September 9, 2009


                     GSSAPI authentication for HTTP
                      draft-johansson-http-gss-05

Status of this Memo

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

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF), its areas, and its working groups.  Note that
   other groups may also distribute working documents as Internet-
   Drafts.

   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."

   The list of current Internet-Drafts can be accessed at
   http://www.ietf.org/ietf/1id-abstracts.txt.

   The list of Internet-Draft Shadow Directories can be accessed at
   http://www.ietf.org/shadow.html.

   This Internet-Draft will expire on September 9, 2009.

Copyright Notice

   Copyright (c) 2009 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 in effect on the date of
   publication of this document (http://trustee.ietf.org/license-info).
   Please review these documents carefully, as they describe your rights
   and restrictions with respect to this document.









Johansson               Expires September 9, 2009               [Page 1]


Internet-Draft                  http-gss                      March 2009


Abstract

   This document specifies a template extension to the HTTP Negotiate
   authentication mechanism defined in RFC4559 which supports mutual
   authentication, fast session-based re-authentication and channel
   bindings.  An IANA registry for such GSS-API HTTP authentication
   mechanisms is defined.


Table of Contents

   1.  Terminology  . . . . . . . . . . . . . . . . . . . . . . . . .  3
   2.  Introduction and motivation  . . . . . . . . . . . . . . . . .  4
   3.  HTTP GSS Authentication Mechanism  . . . . . . . . . . . . . .  5
     3.1.  GSS Token Header Syntax  . . . . . . . . . . . . . . . . .  5
     3.2.  Naming and Transport . . . . . . . . . . . . . . . . . . .  5
     3.3.  Protocol Flow  . . . . . . . . . . . . . . . . . . . . . .  6
       3.3.1.  Intiating authentication . . . . . . . . . . . . . . .  6
       3.3.2.  The authentication phase . . . . . . . . . . . . . . .  7
       3.3.3.  The authorization phase  . . . . . . . . . . . . . . .  8
       3.3.4.  Fast Renegotiation . . . . . . . . . . . . . . . . . .  8
   4.  Examples . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
   5.  Implementation Notes . . . . . . . . . . . . . . . . . . . . . 11
   6.  Security Considerations  . . . . . . . . . . . . . . . . . . . 12
   7.  Notes & TODO . . . . . . . . . . . . . . . . . . . . . . . . . 13
   8.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . . 14
     8.1.  Registration Procedure . . . . . . . . . . . . . . . . . . 14
     8.2.  Change Control . . . . . . . . . . . . . . . . . . . . . . 15
   9.  Changes  . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
     9.1.  00 to 01 . . . . . . . . . . . . . . . . . . . . . . . . . 16
     9.2.  02 to 03 . . . . . . . . . . . . . . . . . . . . . . . . . 16
     9.3.  03 to 04 . . . . . . . . . . . . . . . . . . . . . . . . . 16
   10. References . . . . . . . . . . . . . . . . . . . . . . . . . . 17
     10.1. Normative References . . . . . . . . . . . . . . . . . . . 17
     10.2. Informative References . . . . . . . . . . . . . . . . . . 17
   Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 18















Johansson               Expires September 9, 2009               [Page 2]


Internet-Draft                  http-gss                      March 2009


1.  Terminology

   The keywords "MUST", "MUST NOT", "REQUIRED", "SHOULD", "SHOULD NOT"
   and "MAY" that appear in this document are to be interpreted as
   described in [RFC2119]














































Johansson               Expires September 9, 2009               [Page 3]


Internet-Draft                  http-gss                      March 2009


2.  Introduction and motivation

   [RFC4559] describes an authentication mechanism based on SPNEGO for
   HTTP.  This mechanism suffers from a couple of drawbacks, notably:

      Only supports single-round-trip GSS-API mechanisms due to lack of
      support for proxies.

      Lack of channel bindings to the underlying HTTPS connection which
      makes in unsuitable for deployment in situations where proxies
      exists.

      Lack of session-based re-authentication (compare with TLS).

   This document is intended to solve these problems by introducing a
   new authentication mechanism called 'GSS'.  This mechanism is a
   proper extension of Negotiate but since Negotiate is already widely
   deployed this mechanism was given a separate name.

































Johansson               Expires September 9, 2009               [Page 4]


Internet-Draft                  http-gss                      March 2009


3.  HTTP GSS Authentication Mechanism

   The GSS mechanism is an authentication mechanism for [RFC2616] based
   on a multi-roundrip handshake using base64-encoded GSS-API [RFC2743]
   tokens encoded in the WWW-Authenticate Response Header and the
   Authorization Request Header.  An important difference from [RFC4559]
   is that multiple round trips are supported which means that the
   server can be authenticated to the client (aka mutual
   authentication).  This document specifies a template authentication
   mechanism with an associated IANA registry which provides input
   parameters to the HTTP authentication mechanism describe below.

3.1.  GSS Token Header Syntax

   Both the Authorization and the WWW-Authenticate headers use the same
   syntax throughout the handshake (cf below for details on the protocol
   flow) specified by this Augmented BNF following [RFC2617] and
   [RFC2616]:

     challenge                = auth-scheme-name 1*SP 1#auth-param
     auth-scheme-name         = token
     auth-param               = ( auth-data-value |
                                  auth-param-type "=" auth-param-value )
     auth-param-value         = ( token | quoted-string )
     auth-param-type          = ( "auth-data" | "context-identifier" )
     auth-data-value          = 1*(UPALPHA|DIGIT)  ;base64-encoded
     context-identifier-value = 1*(UPALPHA|DIGIT)  ;base64-encoded

   The auth-param types defined by this specification (auth-data and
   context-identifier) both have auth-param-value which contain base64
   encoded data.  Note that both the auth-data and context-identifier
   auth-param may be absent.  The semantics of these parameters will be
   explained below.  Each auth-param-type MUST NOT occur more than once
   in a single challenge.

   The auth-scheme-name token is the name of the mechanism and is
   supplied in the IANA registry template described below.

   For reasons of backwards compatibility with [RFC4559] two forms of
   the auth-param are allowed - one version based on attribute-parameter
   pairs and one where only GSS-API data is sent.

3.2.  Naming and Transport

   The GSS name of the server is "HTTP@<hostname>[:port]" where the
   :port part is absent if the port == 80 or if the port == 443.

   This mechanism SHOULD be used together with an HTTP transport



Johansson               Expires September 9, 2009               [Page 5]


Internet-Draft                  http-gss                      March 2009


   providing session protection and encryption such as [RFC2817] or
   [RFC2818] .  Session protection is a requirement for fast re-
   authentication described below.

   Like [RFC4559] the mechanism described in this specification is based
   on mapping the GSS-API protocol to HTTP requests and responses where
   the GSS-API tokens are sent in the Authorization and WWW-
   Authentication headers.  Unlike [RFC4559] the entire handshake need
   not take place using a single TCP connection or a single HTTP/1.1
   session.  Instead opaque identifiers in the GSS challenge option
   field are optionally used together with channel bindings to provide a
   way to share a security context over several HTTP connections.  This
   mechanism also serves as a way to let the client do a fast re-
   authentication to the server.

3.3.  Protocol Flow

3.3.1.  Intiating authentication

   Normally the server initiates an authentication handshake when the
   client attempts to access a protected resource.  The exception is
   when the client knows that it is accessing a protected resource and
   that the server supports the GSS mechanism, for instance when fast
   re-authentication is attempted by the client (cf below).  In both
   cases the GSS-API negotiation is initiated by the client - i.e if the
   server initiates the authentication it is only to inform the client
   that authentication is required.  The client SHOULD request mutual
   authentication from the GSS-API layer.

   Note that the first request by the client to a protected resource
   will also serve to let the client and server establish channel
   bindings in the sense of [RFC5056] using the 'tls-server-end-point'
   CB type which means that this first request is not in general
   "wasted" even in the case when the client has no prior knowledge
   about the server or is attempting fast re-authentication.

   If the client tries to access a protected resource the server may
   return a code 401 response with an WWW-Authenticate header containing
   a list of authentication challenges allowing the client to choose
   among different authentication mechanisms supported by the server.
   If the server supports the mechanism specified by the auth-scheme-
   name the server returns a challenge with only the auth-scheme-name
   part and no parameters along with any other challenges for mechanisms
   supported by the server.  This first request also allows the client
   and server to establish channel-bindings.






Johansson               Expires September 9, 2009               [Page 6]


Internet-Draft                  http-gss                      March 2009


3.3.2.  The authentication phase

   In each case below when GSS-API tokens resulting from calls into the
   GSS-API layer are sent from the server to the client or vice-versa,
   the token is encoded using base64 and sent as the "auth-data"
   parameter value of the Authorization and WWW-Authenticate headers
   respectively.

   A client initiates the authentication phase by sending the token
   resulting from the first call to gss_init_security_context to the
   server.

   Upon receipt of token (i.e a request with an accompanying
   Authenticate header with non-empty "auth-data" parameter value), the
   server MUST return the token resulting from a call to
   gss_accept_security_context in a code 401 response, unless the call
   to gss_accept_security_context fails in which case a code 403
   response is returned.

   If the underlying transport provides session protection (eg HTTPS)
   and if channel-bindings are in place (cf below) then the server MAY
   include a unique identifier of the security context beeing negotiated
   (or having been negotiated in the case of the last transaction) in
   the "context-identifier" parameter value.  The server MUST uniquely
   associate this identifier with the client and the security context.

   Upon receipt of a code 401 response from the server when the WWW-
   Authenticate header contains a non-empty "auth-data" parameter value,
   the client MUST return the token resulting from a call to
   gss_initiate_security_context to the server in a new request to the
   same resource.  If the call fails the client MUST close the
   connection.  If a "context-identifier" parameter value is present in
   the response from the server the client MUST include this in the
   ensuing request as the "context-identifier" parameter value.  If the
   "context-identifier" parameter value is not present in the response
   from the server the client MUST use the same HTTP/1.1 connection for
   the entier handshake.  If the client breaks the HTTP/1.1 connection
   the server MUST invalidate the security context unless a context
   identifier was sent to the client and returned to the server.

   A client may close the connection both as the result of using the
   context-identifier to spread the authentication over several
   underlying connections or as the result of a failed call to
   gss_initiate_security_context.  This might at first seem like a
   problem but the GSS-API layer combined with proper handling of the
   context identifier will ensure that handling of these cases are
   disambiguated at the server.




Johansson               Expires September 9, 2009               [Page 7]


Internet-Draft                  http-gss                      March 2009


   The client and server continues the handshake until either an error
   occurs (in which case a 403 is returned to the client or the client
   closes the connection depending on where the error happens) or the
   GSS-API layer has successfully completed the negotiation in which
   case the server sends a normal response to the client.  If the last
   call to gss_accept_sec_context on the server resulted in a non-empty
   token the server MUST include this in a WWW-Authenticate header in
   the response to the client regardless of the return code which is
   beeing sent to the client.  If the underlying transport provides
   session protection (eg HTTPS) and if channel-bindings are in place
   (cf below) then the server MAY include a "context-identifier"
   parameter value uniquely identifying the established security
   context.  The server MAY decide to limit the validity of the
   established context and MAY choose not to consider references to the
   context after a certain amount of time (cf below).

   If the client receives a normal response with an non-empty "auth-
   data" parameter value the client MUST call gss_initiate_sec_context
   with this token as input to complete the authentication handshake.
   If the final response contains a "context-identifier" parameter value
   the client may cache it and use it to provide fast re-authentication
   by including it in a Authorization header with auth-scheme-name and
   empty "auth-data" parameter value.

3.3.3.  The authorization phase

   Authorization failures can occur even if the client is successfully
   authenticated to the server.  In this case the server will send a 403
   response to the client even though the GSS-API handshake has
   succeeded.  It is important to let the client and server finish the
   authentication handshake even if the client is not authorized to
   access the resource.  Therefore the client MUST call
   gss_initiate_sec_context with any GSS-API token returned to the
   client, even if the token was sent along with a 403 response.

   During authorization the server MAY use the GSS-API name associated
   with the established security context for authorization decisions and
   should provide a string representation of the GSS-API name as the
   REMOTE_USER meta-variable and the auth-scheme-name as the AUTH_TYPE
   meta-variable if the Common Gateway Interface (CGI) is provided by
   the server.

3.3.4.  Fast Renegotiation

   Upon receipt of a request containing an Authorization header with the
   auth-scheme-name, an empty auth-data and the context-identifier
   parameter value, the server MUST verify that the identifier
   references a valid security context.  If the security context is



Johansson               Expires September 9, 2009               [Page 8]


Internet-Draft                  http-gss                      March 2009


   missing or invalid the server MUST return a 401 response prompting
   the client to re-negotiate the security context.  If the identifier
   references a valid security context the server MUST process the
   request as if the client had just completed the full authentication
   handshake.

   When this process is completed the client is authenticated to the
   server and possibly (depending on the way the GSS-API layer was
   called and which GSS-mechanism was used) the server is authenticated
   to the client.

   The use of fast regegotiation is optional and clients and servers
   MUST NOT assume that this feature is supported.






































Johansson               Expires September 9, 2009               [Page 9]


Internet-Draft                  http-gss                      March 2009


4.  Examples

   TODO
















































Johansson               Expires September 9, 2009              [Page 10]


Internet-Draft                  http-gss                      March 2009


5.  Implementation Notes

   The context-identifier could be produced by exporting the security
   context through gss_export_sec_context which requires that the GSS-
   API implementation supports exporting unfinished contexts.














































Johansson               Expires September 9, 2009              [Page 11]


Internet-Draft                  http-gss                      March 2009


6.  Security Considerations

   Should channel-bindings be absent, the protocol is subject to a MITM
   attack unless the authentication is between a client and a server
   with no proxies in between and each request is sent over the same
   HTTP/1.1 connection.

   If fast re-authentication is used together with GSS-API credentials
   delegation the server will need to associate forwarded credentials
   with the negotiated security context.  This presents a challenge for
   server implementors since it must be guarateed that security states
   and their associated credentials must be separated from each other.







































Johansson               Expires September 9, 2009              [Page 12]


Internet-Draft                  http-gss                      March 2009


7.  Notes & TODO

   Examples
















































Johansson               Expires September 9, 2009              [Page 13]


Internet-Draft                  http-gss                      March 2009


8.  IANA Considerations

   IANA will create a new registry for HTTP authentication mechanisms
   based on this document.  The purpose of the registry is to bind the
   HTTP authentication mechanism name (auth-scheme-name in the syntax
   above) to the GSS-API mechanism OID.  Such HTTP authentication
   mechanisms will be called GSS-API HTTP authentication mechanisms.

   Names for GSS-API HTTP authentication mechanisms must follow the
   token syntax of section 2.2 of [RFC2616].

   The procedure detailed in the section below is to be used for
   registration of a value naming a specific GSS-API HTTP authentication
   mechanism.

8.1.  Registration Procedure

   Registration of a new GSS-API HTTP authentication mechanism requires
   expert review as defined in BCP 26 [RFC2434].  Registration of a GSS-
   API HTTP authentication mechanism is requested by filling in the
   following template:

      Subject: Registration of GSS-API HTTP authentication mechanism X

      GSS-API HTTP authentication mechanism name:

      GSS-API mechanism OID:

      Description or Published Specification:

      State management: (one of INTERNAL or EXTERNAL)

      Intended usage: (one of COMMON, LIMITED USE, OBSOLETE)

      Person and email address to contact for further information:

      Change manager name and email address:

      Expert reviewer name and contact information: (leave blank)

      Note: (Any other information deemed relevant)

   and sending it via electronic mail to <gss-http@ietf.org> (a public
   mailing list) and carbon copying (cc:) IANA at <iana@iana.org>.
   After allowing new fewer than 2 weeks for community input on the
   mailing list to be determined, an expert will determine the
   appropriateness of the registration request and either approve or
   disapprove the request with notice to the requester, the mailing list



Johansson               Expires September 9, 2009              [Page 14]


Internet-Draft                  http-gss                      March 2009


   and IANA.

   If the registration was approved the expert adds her name to the
   submitted registration.

   The expert is responsible for making sure that GSS-API authentication
   scheme names are unique among all HTTP authentication mechanism names
   and represent an appropriate name for the underlying GSS-API
   mechanism.

   Authors are encouraged to pursue community review by posting the
   technical specification as an Internet-Draft and soliciting comment
   by posting to appropriate IETF mailing lists.

8.2.  Change Control

   Once a GSS-API HTTP authentication mechanism has been published by
   IANA, the author may request a change to its definition.  The change
   request follows the same procedure as the registration request.  The
   change manager is part of the registration template and controls who
   may request changes to the registration.  Passing control of a
   registration is also accomplished by submitting a change request.

   The IESG may also reassign control and responsibility for GSS-API
   HTTP authentication mechanism registrations.  This is expected to
   happen when the author of a registration has died, has moved out of
   contact, or is otherwise unable to make changes to the registered
   mechanism(s)s.  Furthermore the IESG is the owner of all GSS-API HTTP
   authentication mechanisms that correspond to specifications on the
   IETF standards track.





















Johansson               Expires September 9, 2009              [Page 15]


Internet-Draft                  http-gss                      March 2009


9.  Changes

9.1.  00 to 01

   Changed from ABNF to Augmented BNF to align with [RFC2616].

9.2.  02 to 03

   Added reference to rfc 5056.

   Reference to tls-server-end-point channel binding mechanism.

9.3.  03 to 04

   Generalized to IANA-controlled registry of authentication mechanisms.
   Wrote IANA considerations section.  Generalized the ABNF to cover old
   Negotiate case which can now be turned into an IANA registration
   covered by this specification.

































Johansson               Expires September 9, 2009              [Page 16]


Internet-Draft                  http-gss                      March 2009


10.  References

10.1.  Normative References

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119, March 1997.

   [RFC2434]  Narten, T. and H. Alvestrand, "Guidelines for Writing an
              IANA Considerations Section in RFCs", BCP 26, RFC 2434,
              October 1998.

   [RFC2616]  Fielding, R., Gettys, J., Mogul, J., Frystyk, H.,
              Masinter, L., Leach, P., and T. Berners-Lee, "Hypertext
              Transfer Protocol -- HTTP/1.1", RFC 2616, June 1999.

   [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.

   [RFC2743]  Linn, J., "Generic Security Service Application Program
              Interface Version 2, Update 1", RFC 2743, January 2000.

   [RFC2817]  Khare, R. and S. Lawrence, "Upgrading to TLS Within
              HTTP/1.1", RFC 2817, May 2000.

   [RFC2818]  Rescorla, E., "HTTP Over TLS", RFC 2818, May 2000.

   [RFC5056]  Williams, N., "On the Use of Channel Bindings to Secure
              Channels", RFC 5056, November 2007.

10.2.  Informative References

   [RFC4559]  Jaganathan, K., Zhu, L., and J. Brezak, "SPNEGO-based
              Kerberos and NTLM HTTP Authentication in Microsoft
              Windows", RFC 4559, June 2006.















Johansson               Expires September 9, 2009              [Page 17]


Internet-Draft                  http-gss                      March 2009


Author's Address

   Leif Johansson
   Stockholm university

   Email: leifj@it.su.se
   URI:   http://www.su.se/












































Johansson               Expires September 9, 2009              [Page 18]


Html markup produced by rfcmarkup 1.129b, available from https://tools.ietf.org/tools/rfcmarkup/