Internet Engineering Task Force A. Jain
Internet-Draft Georgia Tech
Updates: 4120 (if approved) N. Kinder
Intended status: Standards Track N. McCallum
Expires: November 17, 2016 Red Hat, Inc.
May 16, 2016
Authentication Indicator in Kerberos Tickets
draft-ietf-kitten-krb-auth-indicator-02
Abstract
This document specifies an extension in the Kerberos protocol
[RFC4120]. It defines a new authorization data type AD-
AUTHENTICATION-INDICATOR. The purpose of introducing this data type
is to include an indicator of the strength of a client's
authentication in the service tickets so that 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 November 17, 2016.
Copyright Notice
Copyright (c) 2016 IETF Trust and the persons identified as the
document authors. All rights reserved.
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include Simplified BSD License text as described in Section 4.e of
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described in the Simplified BSD License.
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. ASN.1 Module . . . . . . . . . . . . . . . . . . . . 4
Appendix B. Acknowledgements . . . . . . . . . . . . . . . . . . 4
1. Introduction
Kerberos [RFC4120] allows secure interaction among users and services
over a network. It supports a variety of authentication mechanisms
using its pre-authentication framework [RFC6113]. The 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 specifies a new authorization data type to convey
authentication strength to application services. Elements of this
type appear within an AD-CAMMAC [RFC7751] container.
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 initial credentials, and copy it from a ticket-
granting ticket into service tickets:
AD-AUTHENTICATION-INDICATOR 97
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The corresponding ad-data field contains the DER encoding of the
following ASN.1 type:
AD-AUTHENTICATION-INDICATOR ::= SEQUENCE OF UTF8String
Each UTF8String value is a short string that indicates 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].
Authorization data elements of type AD-AUTHENTICATION-INDICATOR MUST
be included in an AD-CAMMAC container so that their contents can be
verified as originating from the KDC. Elements of type AD-
AUTHENTICATION-INDICATOR MAY safely be ignored by applications and
KDCs that do not implement this element.
4. Security Considerations
Elements of type AD-AUTHENTICATION-INDICATOR are wrapped in AD-CAMMAC
containers. AD-CAMMAC supersedes AD-KDC-ISSUED, and allows both
application services and the KDC to verify the authenticity of the
contained authorization data.
KDC implementations MUST use AD-CAMMAC verifiers as described in the
the security considerations of RFC 7751 [RFC7751] to ensure that AD-
AUTHENTICATION-INDICATOR elements are not modified by an attacker.
Application servers MUST validate the AD-CAMMAC container before
making authorization decisions based on AD-AUTHENTICATION-INDICATOR
elements. Application servers MUST NOT make authorization decisions
based on AD-AUTHENTICATION-INDICATOR elements which appear outside of
AD-CAMMAC containers.
Using multiple strings in AD-AUTHENTICATION-INDICATOR MAY lead to
ambiguity when a service tries to make a decision based on the AD-
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
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/
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RFC2119, March 1997,
<http://www.rfc-editor.org/info/rfc2119>.
[RFC4120] Neuman, C., Yu, T., Hartman, S., and K. Raeburn, "The
Kerberos Network Authentication Service (V5)", RFC 4120,
DOI 10.17487/RFC4120, July 2005,
<http://www.rfc-editor.org/info/rfc4120>.
[RFC6113] Hartman, S. and L. Zhu, "A Generalized Framework for
Kerberos Pre-Authentication", RFC 6113, DOI 10.17487/
RFC6113, April 2011,
<http://www.rfc-editor.org/info/rfc6113>.
[RFC7751] Sorce, S. and T. Yu, "Kerberos Authorization Data
Container Authenticated by Multiple Message Authentication
Codes (MACs)", RFC 7751, DOI 10.17487/RFC7751, March 2016,
<http://www.rfc-editor.org/info/rfc7751>.
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>.
[RFC6711] Johansson, L., "An IANA Registry for Level of Assurance
(LoA) Profiles", RFC 6711, DOI 10.17487/RFC6711, August
2012, <http://www.rfc-editor.org/info/rfc6711>.
Appendix A. ASN.1 Module
KerberosV5AuthenticationIndicators {
iso(1) identified-organization(3) dod(6) internet(1)
security(5) kerberosV5(2) modules(4)
authentication-indicators(9)
} DEFINITIONS EXPLICIT TAGS ::= BEGIN
AD-AUTHENTICATION-INDICATOR ::= SEQUENCE OF UTF8String
END
Appendix B. Acknowledgements
Dmitri Pal (Red Hat)
Simo Sorce (Red Hat)
Greg Hudson (MIT)
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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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