GENWiki

Premier IT Outsourcing and Support Services within the UK

User Tools

Site Tools


rfc:rfc4559

Network Working Group K. Jaganathan Request for Comments: 4559 L. Zhu Category: Informational J. Brezak

                                                 Microsoft Corporation
                                                             June 2006
         SPNEGO-based Kerberos and NTLM HTTP Authentication
                        in Microsoft Windows

Status of This Memo

 This memo provides information for the Internet community.  It does
 not specify an Internet standard of any kind.  Distribution of this
 memo is unlimited.

Copyright Notice

 Copyright (C) The Internet Society (2006).

Abstract

 This document describes how the Microsoft Internet Explorer (MSIE)
 and Internet Information Services (IIS) incorporated in Microsoft
 Windows 2000 use Kerberos for security enhancements of web
 transactions.  The Hypertext Transport Protocol (HTTP) auth-scheme of
 "negotiate" is defined here; when the negotiation results in the
 selection of Kerberos, the security services of authentication and,
 optionally, impersonation (the IIS server assumes the windows
 identity of the principal that has been authenticated) are performed.
 This document explains how HTTP authentication utilizes the Simple
 and Protected GSS-API Negotiation mechanism.  Details of Simple And
 Protected Negotiate (SPNEGO) implementation are not provided in this
 document.

Table of Contents

 1. Introduction ....................................................2
 2. Conventions Used in This Document ...............................2
 3. Access Authentication ...........................................2
    3.1. Reliance on the HTTP/1.1 Specification .....................2
 4. HTTP Negotiate Authentication Scheme ............................2
    4.1. The WWW-Authenticate Response Header .......................2
 5. Negotiate Operation Example .....................................4
 6. Security Considerations .........................................5
 7. Normative References ............................................6

Jaganathan, et al. Informational [Page 1] RFC 4559 HTTP Authentication in Microsoft Windows June 2006

1. Introduction

 Microsoft has provided support for Kerberos authentication in
 Microsoft Internet Explorer (MSIE) and Internet Information Services
 (IIS), in addition to other mechanisms.  This provides the benefits
 of the Kerberos v5 protocol for Web applications.
 Support for Kerberos authentication is based on other previously
 defined mechanisms, such as SPNEGO Simple And Protected Negotiate
 (SPNEGO) [RFC4178] and the Generic Security Services Application
 Program Interface(GSSAPI).

2. Conventions Used in This Document

 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" are to
 be interpreted as described in [RFC2119].

3. Access Authentication

3.1. Reliance on the HTTP/1.1 Specification

 This specification is a companion to the HTTP/1.1 specification
 [RFC2616], and it builds on the authentication mechanisms defined in
 [RFC2617].  It uses the augmented BNF section of that document (2.1),
 and it relies on both the non-terminals defined in that document and
 other aspects of the HTTP/1.1 specification.

4. HTTP Negotiate Authentication Scheme

 Use of Kerberos is wrapped in an HTTP auth-scheme of "Negotiate".
 The auth-params exchanged use data formats defined for use with the
 GSS-API [RFC2743].  In particular, they follow the formats set for
 the SPNEGO [RFC4178] and Kerberos [RFC4121] mechanisms for GSSAPI.
 The "Negotiate" auth-scheme calls for the use of SPNEGO GSSAPI tokens
 that the specific mechanism type specifies.
 The current implementation of this protocol is limited to the use of
 SPNEGO with the Kerberos and Microsoft(NT Lan Manager) NTLM
 protocols.

4.1. The WWW-Authenticate Response Header

 If the server receives a request for an access-protected object, and
 if an acceptable Authorization header has not been sent, the server
 responds with a "401 Unauthorized" status code, and a "WWW-
 Authenticate:" header as per the framework described in [RFC2616].
 The initial WWW-Authenticate header will not carry any gssapi-data.

Jaganathan, et al. Informational [Page 2] RFC 4559 HTTP Authentication in Microsoft Windows June 2006

 The negotiate scheme will operate as follows:
         challenge       = "Negotiate" auth-data
         auth-data       = 1#( [gssapi-data] )
 The meanings of the values of the directives used above are as
 follows:
 gssapi-data
 If the gss_accept_security_context returns a token for the client,
 this directive contains the base64 encoding of an
 initialContextToken, as defined in [RFC2743].  This is not present in
 the initial response from the server.
 A status code 200 status response can also carry a "WWW-Authenticate"
 response header containing the final leg of an authentication.  In
 this case, the gssapi-data will be present.  Before using the
 contents of the response, the gssapi-data should be processed by
 gss_init_security_context to determine the state of the security
 context.  If this function indicates success, the response can be
 used by the application.  Otherwise, an appropriate action, based on
 the authentication status, should be taken.
 For example, the authentication could have failed on the final leg if
 mutual authentication was requested and the server was not able to
 prove its identity.  In this case, the returned results are suspect.
 It is not always possible to mutually authenticate the server before
 the HTTP operation.  POST methods are in this category.
 When the Kerberos Version 5 GSSAPI mechanism [RFC4121] is being used,
 the HTTP server will be using a principal name of the form of
 "HTTP/hostname".

4.2. The Authorization Request Header

 Upon receipt of the response containing a "WWW-Authenticate" header
 from the server, the client is expected to retry the HTTP request,
 passing a HTTP "Authorization" header line.  This is defined
 according to the framework described in [RFC2616] and is utilized as
 follows:
         credentials             = "Negotiate" auth-data2
         auth-data2              = 1#( gssapi-data )
 gssapi-data

Jaganathan, et al. Informational [Page 3] RFC 4559 HTTP Authentication in Microsoft Windows June 2006

 This directive contains the base64 encoding of an
 InitialContextToken, as defined in [RFC2743].
 Any returned code other than a success 2xx code represents an
 authentication error.  If a 401 containing a "WWW-Authenticate"
 header with "Negotiate" and gssapi-data is returned from the server,
 it is a continuation of the authentication request.
 A client may initiate a connection to the server with an
 "Authorization" header containing the initial token for the server.
 This form will bypass the initial 401 error from the server when the
 client knows that the server will accept the Negotiate HTTP
 authentication type.

5. Negotiate Operation Example

 The client requests an access-protected document from server via a
 GET method request.  The URI of the document is
 "http://www.nowhere.org/dir/index.html".
         C: GET dir/index.html
 The first time the client requests the document, no Authorization
 header is sent, so the server responds with
         S: HTTP/1.1 401 Unauthorized
         S: WWW-Authenticate: Negotiate
 The client will obtain the user credentials using the SPNEGO GSSAPI
 mechanism type to identify generate a GSSAPI message to be sent to
 the server with a new request, including the following Authorization
 header:
         C: GET dir/index.html
         C: Authorization: Negotiate a87421000492aa874209af8bc028
 The server will decode the gssapi-data and pass this to the SPNEGO
 GSSAPI mechanism in the gss_accept_security_context function.  If the
 context is not complete, the server will respond with a 401 status
 code with a WWW-Authenticate header containing the gssapi-data.
         S: HTTP/1.1 401 Unauthorized
         S: WWW-Authenticate: Negotiate 749efa7b23409c20b92356
 The client will decode the gssapi-data, pass this into
 Gss_Init_security_context, and return the new gssapi-data to the
 server.

Jaganathan, et al. Informational [Page 4] RFC 4559 HTTP Authentication in Microsoft Windows June 2006

         C: GET dir/index.html
         C: Authorization: Negotiate 89a8742aa8729a8b028
 This cycle can continue until the security context is complete.  When
 the return value from the gss_accept_security_context function
 indicates that the security context is complete, it may supply final
 authentication data to be returned to the client.  If the server has
 more gssapi data to send to the client to complete the context, it is
 to be carried in a WWW-Authenticate header with the final response
 containing the HTTP body.
         S: HTTP/1.1 200 Success
         S: WWW-Authenticate: Negotiate ade0234568a4209af8bc0280289eca
 The client will decode the gssapi-data and supply it to
 gss_init_security_context using the context for this server.  If the
 status is successful from the final gss_init_security_context, the
 response can be used by the application.

6. Security Considerations

 The SPNEGO HTTP authentication facility is only used to provide
 authentication of a user to a server.  It provides no facilities for
 protecting the HTTP headers or data including the Authorization and
 WWW-Authenticate headers that are used to implement this mechanism.
 Alternate mechanisms such as TLS can be used to provide
 confidentiality.  Hashes of the TLS certificates can be used as
 channel bindings to secure the channel.  In this case clients would
 need to enforce that the channel binding information is valid.  Note
 that Kerb-TLS [RFC2712] could be used to provide both authentication
 and confidentiality, but this requires a change to the TLS provider.
 This mechanism is not used for HTTP authentication to HTTP proxies.
 If an HTTP proxy is used between the client and server, it must take
 care to not share authenticated connections between different
 authenticated clients to the same server.  If this is not honored,
 then the server can easily lose track of security context
 associations.  A proxy that correctly honors client to server
 authentication integrity will supply the "Proxy-support:  Session-
 Based-Authentication" HTTP header to the client in HTTP responses
 from the proxy.  The client MUST NOT utilize the SPNEGO HTTP
 authentication mechanism through a proxy unless the proxy supplies
 this header with the "401 Unauthorized" response from the server.

Jaganathan, et al. Informational [Page 5] RFC 4559 HTTP Authentication in Microsoft Windows June 2006

 When using the SPNEGO HTTP authentication facility with client-
 supplied data such as PUT and POST, the authentication should be
 complete between the client and server before sending the user data.
 The return status from the gss_init_security_context will indicate
 that the security context is complete.  At this point, the data can
 be sent to the server.

7. Normative References

 [RFC2743]  Linn, J., "Generic Security Service Application Program
            Interface Version 2", 2, Update 1", 2743, January 2000.
 [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
            Requirement Levels", BCP 14, RFC 2119, March 1997.
 [RFC4178] Zhu, L., Leach, P., Jaganathan, K., and W. Ingersoll, "The
            Simple and Protected GSS-API Generic Security Service
            Application Program Interface (GSS-API) Negotiation
            Mechanism", 4178, October 2005.
 [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.
 [RFC2712]  Medvinsky, A. and M. Hur, "Addition of Kerberos Cipher
            Suites to Transport Layer Security (TLS)", RFC 2712,
            October 1999.
 [RFC4121]  Zhu, L., Jaganathan, K., and S. Hartman, "The Kerberos
            Version 5 Generic Security Service Application Program
            Interface (GSS-API) Mechanism: Version 2", RFC 4121, July
            2005.

Jaganathan, et al. Informational [Page 6] RFC 4559 HTTP Authentication in Microsoft Windows June 2006

Authors' Addresses

 Karthik Jaganathan
 Microsoft Corporation
 One Microsoft Way
 Redmond, WA  98052
 US
 EMail: karthikj@microsoft.com
 Larry Zhu
 Microsoft Corporation
 One Microsoft Way
 Redmond, WA  98052
 US
 EMail: lzhu@microsoft.com
 John Brezak
 Microsoft Corporation
 One Microsoft Way
 Redmond, WA  98052
 US
 EMail: jbrezak@microsoft.com

Jaganathan, et al. Informational [Page 7] RFC 4559 HTTP Authentication in Microsoft Windows June 2006

Full Copyright Statement

 Copyright (C) The Internet Society (2006).
 This document is subject to the rights, licenses and restrictions
 contained in BCP 78 and at www.rfc-editor.org/copyright.html, and
 except as set forth therein, the authors retain all their rights.
 This document and the information contained herein are provided on an
 "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS
 OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY AND THE INTERNET
 ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS OR IMPLIED,
 INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE
 INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED
 WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.

Intellectual Property

 The IETF takes no position regarding the validity or scope of any
 Intellectual Property Rights or other rights that might be claimed to
 pertain to the implementation or use of the technology described in
 this document or the extent to which any license under such rights
 might or might not be available; nor does it represent that it has
 made any independent effort to identify any such rights.  Information
 on the procedures with respect to rights in RFC documents can be
 found in BCP 78 and BCP 79.
 Copies of IPR disclosures made to the IETF Secretariat and any
 assurances of licenses to be made available, or the result of an
 attempt made to obtain a general license or permission for the use of
 such proprietary rights by implementers or users of this
 specification can be obtained from the IETF on-line IPR repository at
 http://www.ietf.org/ipr.
 The IETF invites any interested party to bring to its attention any
 copyrights, patents or patent applications, or other proprietary
 rights that may cover technology that may be required to implement
 this standard.  Please address the information to the IETF at
 ietf-ipr@ietf.org.

Acknowledgement

 Funding for the RFC Editor function is provided by the IETF
 Administrative Support Activity (IASA).

Jaganathan, et al. Informational [Page 8]

/data/webs/external/dokuwiki/data/pages/rfc/rfc4559.txt · Last modified: 2006/06/27 23:28 by 127.0.0.1

Donate Powered by PHP Valid HTML5 Valid CSS Driven by DokuWiki