Internet DRAFT - draft-jain-kitten-krb-auth-indicator
draft-jain-kitten-krb-auth-indicator
Internet Engineering Task Force A. Jain
Internet-Draft Georgia Tech
Intended status: Standards Track N. Kinder
Expires: March 1, 2015 N. McCallum
Red Hat, Inc.
August 28, 2014
Authentication Indicator in Kerberos tickets
draft-jain-kitten-krb-auth-indicator-01
Abstract
This document proposes an extension in the Kerberos protocol. It
defines a new Authorization Data Type AUTHENTICATION-INDICATOR. The
purpose of introducing this data type is to include an indicator of
the client's authentication strength in the service tickets so that
the application services can use it as an input into policy
decisions.
Status of This Memo
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 March 1, 2015.
Copyright Notice
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Document Conventions . . . . . . . . . . . . . . . . . . . . 2
3. AD Type Specification . . . . . . . . . . . . . . . . . . . . 2
4. Security Considerations . . . . . . . . . . . . . . . . . . . 3
5. References . . . . . . . . . . . . . . . . . . . . . . . . . 3
5.1. Normative References . . . . . . . . . . . . . . . . . . 3
5.2. Informative References . . . . . . . . . . . . . . . . . 4
Appendix A. Acknowledgements . . . . . . . . . . . . . . . . . . 5
1. Introduction
Kerberos allows secure interaction among users and services over a
network. It supports a variety of authentication mechanisms using
its Pre-Authentication framework [RFC6113]. Kerberos Authentication
Service has been architected to support password based authentication
as well as multi-factor authentication using One Time Password
devices or Public Key Cryptography. Implementations that have Pre-
Authentication mechanisms offering significantly different strengths
of client authentication may choose to keep track of the strength of
the authentication used as an input into policy decisions. This
document proposes a new Authorization Data Type to be used to convey
the authentication strength to the application services. The AD type
is wrapped in the AD-CAMMAC [I-D.ietf-krb-wg-cammac] container and
contains information about the type of authentication mechanism used
by the Kerberos client to authenticate itself to the KDC.
2. Document Conventions
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 RFC 2119 [RFC2119].
3. AD Type Specification
The KDC MAY include the following Authorization Data element, wrapped
in AD-CAMMAC, in the initial credentials and copy it from a ticket-
granting ticket into service tickets:
AUTHENTICATION-INDICATOR TBD
The corresponding ad-data field contains the DER encoding of this AD
type which is defined as
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AUTHENTICATION-INDICATOR ::= SEQUENCE OF UTF8String
These values are short strings that indicate that a particular set of
requirements was met during the initial authentication. These
strings are intended to be compared against known values. They are
not intended to store structured data. These strings MAY be site-
defined strings that do not contain a colon such as the name of the
Pre-Authentication mechanism used, or alternatively URIs that
reference a Level of Assurance Profile [RFC6711].
The AUTHENTICATION-INDICATOR AD type MUST be included in the AD-
CAMMAC container so that its contents can be protected. The AD-
CAMMAC element and the new AD type it encapsulates MAY safely be
ignored by the applications and KDCs that do not implement this
element.
4. Security Considerations
AUTHENTICATION-INDICATOR is wrapped in AD-CAMMAC which supersedes AD-
KDC-ISSUED container. AD-CAMMAC allows both the application service
and the KDC to verify the authenticity of the contained Authorization
Data.
A malicious service can replace AD-CAMMAC in a service ticket with a
legitimate AD-CAMMAC present in some other ticket that the service
has received. KDC MUST ensure that the service does not tamper with
the contents of AD-CAMMAC or the ticket. It SHOULD insert an
Authorization Data element into the AD-CAMMAC container that binds
the contents of the container to the enclosing ticket. This binding
protects AUTHENTICATION-INDICATOR in case of constrained delegation
such as S4U2Proxy [MS-SFU] extension.
Using multiple strings in AUTHENTICATION-INDICATOR MAY lead to
ambiguity when a service tries to make a decision based on the
AUTHENTICATION-INDICATOR values. This ambiguity can be avoided if
indicator values are always used as a positive indication of certain
requirements being met during the initial authentication.
5. References
5.1. Normative References
[I-D.ietf-krb-wg-cammac]
Sorce, S., Yu, T., and T. Hardjono, "Kerberos
Authorization Data Container Authenticated by Multiple
MACs", draft-ietf-krb-wg-cammac-08 (work in progress),
June 2014.
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[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC4120] Neuman, C., Yu, T., Hartman, S., and K. Raeburn, "The
Kerberos Network Authentication Service (V5)", RFC 4120,
July 2005.
[RFC6113] Hartman, S. and L. Zhu, "A Generalized Framework for
Kerberos Pre-Authentication", RFC 6113, April 2011.
5.2. Informative References
[MS-SFU] Microsoft, "Kerberos Protocol Extensions: Service for User
and Constrained Delegation Protocol", January 2013,
<http://msdn.microsoft.com/en-us/library/cc246071.aspx>.
[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.
[RFC6711] Johansson, L., "An IANA Registry for Level of Assurance
(LoA) Profiles", RFC 6711, August 2012.
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Appendix A. Acknowledgements
Dmitri Pal (Red Hat)
Simo Sorce (Red Hat)
Authors' Addresses
Anupam Jain
Georgia Tech
225 North Ave NW
Atlanta, GA 30332
USA
EMail: ajain323@gatech.edu
Nathan Kinder
Red Hat, Inc.
444 Castro St.
Suite 500
Mountain View, CA 94041
USA
EMail: nkinder@redhat.com
Nathaniel McCallum
Red Hat, Inc.
100 East Davie Street
Raleigh, NC 27601
USA
EMail: npmccallum@redhat.com
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