[Docs] [txt|pdf|xml] [Tracker] [Email] [Nits] [IPR]
Versions: 00 01 02 03 04
NETWORK WORKING GROUP L. Zhu
Internet-Draft K. Damour
Updates: 4178 (if approved) D. McPherson
Intended status: Informational Microsoft Corporation
Expires: January 8, 2009 July 7, 2008
The Extended GSS-API Negotiation Mechanism (NEGOEX)
draft-zhu-negoex-00
Status of this Memo
By submitting this Internet-Draft, each author represents that any
applicable patent or other IPR claims of which he or she is aware
have been or will be disclosed, and any of which he or she becomes
aware will be disclosed, in accordance with Section 6 of 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 January 8, 2009.
Abstract
This document defines the Extended Generic Security Service
Application Program Interface (GSS-API) Negotiation Mechanism
(NegoEx). NegoEx is a pseudo-security mechanism that logically
extends the SPNEGO protocol as defined in RFC4178.
The NegoEx protocol itself is a security mechanism negotiated by
SPNEGO. When selected as the common mechanism, NegoEx OPTIONALLY
adds a pair of meta-data messages for each negotiated security
mechanism. The meta-data exchange allows security mechanisms to
exchange auxiliary information such as trust configurations, thus
NegoEx provides additional flexibility beyond the negotiation
Zhu, et al. Expires January 8, 2009 [Page 1]
Internet-Draft NEGOEX July 2008
capabilities based on exchanging object identifiers offered by
SPNEGO.
NegoEx preserves the optimistic token semantics of SPNEGO and applies
that recursively. Consequently a context establishment mechanism
token can be included in the initial NegoEx message, and NegoEx does
not require an extra round-trip when the initiator's optimistic token
is accepted by the target.
Similar to SPNEGO, NegoEx defines a few new GSS-API extensions that a
security mechanism MUST support in order to be negotiated by NegoEx.
This document defines these GSS-API extensions.
Unlike SPNEGO however, NegoEx defines its own way for signing the
protocol messages in order to protect the protocol negotiation. The
NegoEx message signing or verification can occur before the security
context for the negotiated real security mechanism is fully
established.
Zhu, et al. Expires January 8, 2009 [Page 2]
Internet-Draft NEGOEX July 2008
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4
2. Requirements Terminology . . . . . . . . . . . . . . . . . . . 6
3. Presentation Language . . . . . . . . . . . . . . . . . . . . . 6
4. Cryptographic Computations . . . . . . . . . . . . . . . . . . 6
5. The NegoEx Protocol . . . . . . . . . . . . . . . . . . . . . . 7
6. Supporting GSS-API Extensions . . . . . . . . . . . . . . . . . 7
7. Security Considerations . . . . . . . . . . . . . . . . . . . . 7
8. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 7
9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 7
10. Normative References . . . . . . . . . . . . . . . . . . . . . 7
Appendix A. Apendix A. Protocol Data Structures and Constant
Values . . . . . . . . . . . . . . . . . . . . . . . . 8
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 8
Intellectual Property and Copyright Statements . . . . . . . . . . 9
Zhu, et al. Expires January 8, 2009 [Page 3]
Internet-Draft NEGOEX July 2008
1. Introduction
If more than one GSS-API mechanism is shared between the client and
the server, the Simple and Protected (GSS-API) Negotiation Mechanism
(SPNEGO) as defined in [RFC4178] can be deployed to choose a mutually
preferred one. This pseudo mechanism does well in the most basic
scenarios but suffers from a couple of drawbacks, notably:
o First, the SPNEGO negotiation model is inefficient when
negotiating based on mechanism specific configuration information.
SPNEGO negotiation is based on by exchanging object identifiers
only, and it does not allow exchange of auxiliary information in
any other from. This is inefficient and often impractical in that
one object identifier effectively conveys only one bit of
information.
o Secondly, the SPNEGO negotiation model is inadequate when the
choice cannot be made by the acceptor in the initial response. In
SPNEGO, the negotiation information is sent one-way from the
initiator for the acceptor to make a choice, and the acceptor must
choose one when it makes the initial response. This negotiation
model is counter intuitive. The selection of a security mechanism
is typically the result of selecting one type of credentials from
the available set, and the initiator typically does not wish to
reveal credentials information often associated with user
identities. In practice, in order to operate in this model, the
Kerberos GSS-API mechanism [RFC4121] must acquire the context
establishment token in the initial call to GSS_Init_sec_context().
If the initiator fails to acquire the Kerberos token, it must not
offer Kerberos; otherwise the SPNEGO context negotiation will fail
without being able to select the next available mechanism that
could work. Obtaining the initial Kerberos GSS-API context token
may require multiple round-trips of network calls and the cost of
the operation can be substantial. It is evidently suboptimal when
multiple GSS-API mechanisms have to operate this way. The cost of
authentication of any real security mechanism should be avoided or
minimized by SPNEGO when the security mechanism is not negotiated
eventually but such considerations are not facilitated by the
SPNEGO negotiation model.
The Extended Generic Security Service Application Program Interface
(GSS-API) Negotiation Mechanism (NegoEx) is defined to address these
concerns. NegoEx is a pseudo security mechanism that is negotiated
by SPNEGO and when negotiated, it can recursively negotiate real
security mechanisms.
Any security mechanism negotiated by NegoEx MUST support integrity
protection.
Zhu, et al. Expires January 8, 2009 [Page 4]
Internet-Draft NEGOEX July 2008
The basic form of NegoEx works as follows:
1. The initiator proposes a list of mechanisms in decreasing
preference order. For each of these mechanism, NegoEx
OPTIOINALLY includes a mechanism specific meta-data token. GSS-
API extensions are defined later in this document for NegoEx to
query the meta-data token for inclusion in the NegoEx message.
2. The acceptor then passes the meta-data token from the initiator
to the intended security mechanism. A meta-token for a security
mechanism not supported on the acceptor side is ignored. New
GSS-API extensions are defined later in this document for a
security mechanism to consume the meta-data token. When
processing the received meta-data token, a security mechanism
that reports a failure is removed from the set of mutually
supported mechanisms. The acceptor then responds with the list
of mutually supported mechanisms in decreasing preference order.
For each of these mechanism, NegoEx again OPTIOINALLY supplies a
mechanism specific meta-data token in the response. These meta-
data tokens are returned to NegoEx via new GSS-API extensions as
described in the initial step.
3. The initiator then passes the meta-data token to the intended
security mechanism by invoking the new GSS-API extensions. When
processing the received meta-data token, a security mechanism
that reports a failure is removed from the set of mutually
supported mechanisms. The initiator then selects a security
mechanism from the set of mutually-supported ones. If more than
one security mechanism is available, unless otherwise specified,
the preferred one in the server preference order SHOULD be
selected. Once the common security mechanism is identified, the
security mechanism may also negotiate mechanism-specific options
during its context establishments. This will be inside the
mechanism tokens, and invisible to the NegoEx protocol.
4. The selected security mechanism provides keying materials to
NegoEx, and NegoEx then signs and verifies the negotiation NegoEx
messages to protect the negotiation.
5. The initiator and the acceptor proceed to exchange tokens till
the GSS-API context for selected security mechanism is
established, Once the security context is established, the per-
message tokens are generated and verified in accordance with the
selected security mechanism.
NegoEx does not work outside of SPNEGO. When negotiated by SPNEGO,
NegoEx uses the concepts developed in the GSS-API specification [1].
The negotiation data is encapsulated in context-level tokens.
Zhu, et al. Expires January 8, 2009 [Page 5]
Internet-Draft NEGOEX July 2008
Therefore, callers of the GSS-API do not need to be aware of the
existence of the negotiation tokens but only of the SPENGO pseudo-
security mechanism.
In its basic form NegoEx requires at least one extra round-trip.
Network connection setup is a critical performance characteristic of
any network infrastructure and extra round trips over WAN links,
packet radio networks, etc. really make a difference. In order to
avoid such an extra round trip the initial security token of the
preferred mechanism for the initiator may be embedded in the initial
NegoEx token. The optimistic mechanism token may be accompanied by
the meta-data tokens and the optimistic mechanism token MUST be that
of the first mechanism in the list of the mechanisms proposed by the
initiator. The signature of NegoEx messages for protecting the
NegoEx negotiation can also be included along with the mechanism
token. If the target preferred mechanism matches the initiator's
preferred mechanism, and when the NegoEx negotiation protection
messages are included along with the mechanism token, no additional
round trips are incurred by using the negotiation protocol.
2. Requirements Terminology
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in [RFC2119].
3. Presentation Language
This document deals with the formatting of data in an external
representation. The following very basic and somewhat casually
defined presentation syntax will be used. The syntax draws from
several sources in its structure. Although it resembles the
programming language "C" in its syntax, it would be risky to draw too
many parallels. The purpose of this presentation language is to
document NegoEx only; it has no general application beyond that
particular goal.
4. Cryptographic Computations
The message signing and verificaiton in NegoEx is based on[RFC3961].
[RFC3961] is used here as a generic framework and this application is
not Kerberos specifc.
Zhu, et al. Expires January 8, 2009 [Page 6]
Internet-Draft NEGOEX July 2008
5. The NegoEx Protocol
TBD.
6. Supporting GSS-API Extensions
TBD.
7. Security Considerations
TBD
8. Acknowledgements
TBD.
9. IANA Considerations
There is no action required for IANA.
10. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC2743] Linn, J., "Generic Security Service Application Program
Interface Version 2, Update 1", RFC 2743, January 2000.
[RFC3961] Raeburn, K., "Encryption and Checksum Specifications for
Kerberos 5", RFC 3961, February 2005.
[RFC4120] Neuman, C., Yu, T., Hartman, S., and K. Raeburn, "The
Kerberos Network Authentication Service (V5)", RFC 4120,
July 2005.
[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.
[RFC4178] Zhu, L., Leach, P., Jaganathan, K., and W. Ingersoll, "The
Simple and Protected Generic Security Service Application
Program Interface (GSS-API) Negotiation Mechanism",
Zhu, et al. Expires January 8, 2009 [Page 7]
Internet-Draft NEGOEX July 2008
RFC 4178, October 2005.
Appendix A. Apendix A. Protocol Data Structures and Constant Values
TBD
Authors' Addresses
Larry Zhu
Microsoft Corporation
One Microsoft Way
Redmond, WA 98052
US
Email: lzhu@microsoft.com
Kevin Damour
Microsoft Corporation
One Microsoft Way
Redmond, WA 98052
US
Email: kdamour@microsoft.com
Dave McPherson
Microsoft Corporation
One Microsoft Way
Redmond, WA 98052
US
Email: davemm@microsoft.com
Zhu, et al. Expires January 8, 2009 [Page 8]
Internet-Draft NEGOEX July 2008
Full Copyright Statement
Copyright (C) The IETF Trust (2008).
This document is subject to the rights, licenses and restrictions
contained in BCP 78, 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, THE IETF TRUST 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.
Zhu, et al. Expires January 8, 2009 [Page 9]
Html markup produced by rfcmarkup 1.129d, available from
https://tools.ietf.org/tools/rfcmarkup/