draft-ietf-kitten-krb-auth-indicator-01.txt   draft-ietf-kitten-krb-auth-indicator-02.txt 
Internet Engineering Task Force A. Jain Internet Engineering Task Force A. Jain
Internet-Draft Georgia Tech Internet-Draft Georgia Tech
Updates: 4120 (if approved) N. Kinder Updates: 4120 (if approved) N. Kinder
Intended status: Standards Track N. McCallum Intended status: Standards Track N. McCallum
Expires: November 17, 2016 Red Hat, Inc. Expires: November 17, 2016 Red Hat, Inc.
May 16, 2016 May 16, 2016
Authentication Indicator in Kerberos Tickets Authentication Indicator in Kerberos Tickets
draft-ietf-kitten-krb-auth-indicator-01 draft-ietf-kitten-krb-auth-indicator-02
Abstract Abstract
This document proposes an extension in the Kerberos protocol This document specifies an extension in the Kerberos protocol
[RFC4120]. It defines a new Authorization Data Type AD- [RFC4120]. It defines a new authorization data type AD-
AUTHENTICATION-INDICATOR. The purpose of introducing this data type AUTHENTICATION-INDICATOR. The purpose of introducing this data type
is to include an indicator of the strength of a client's is to include an indicator of the strength of a client's
authentication in the service tickets so that the application authentication in the service tickets so that application services
services can use it as an input into policy decisions. can use it as an input into policy decisions.
Status of This Memo Status of This Memo
This Internet-Draft is submitted in full conformance with the This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79. provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet- working documents as Internet-Drafts. The list of current Internet-
Drafts is at http://datatracker.ietf.org/drafts/current/. Drafts is at http://datatracker.ietf.org/drafts/current/.
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carefully, as they describe your rights and restrictions with respect carefully, as they describe your rights and restrictions with respect
to this document. Code Components extracted from this document must to this document. Code Components extracted from this document must
include Simplified BSD License text as described in Section 4.e of include Simplified BSD License text as described in Section 4.e of
the Trust Legal Provisions and are provided without warranty as the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License. described in the Simplified BSD License.
Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Document Conventions . . . . . . . . . . . . . . . . . . . . 2 2. Document Conventions . . . . . . . . . . . . . . . . . . . . 2
3. AD Type Specification . . . . . . . . . . . . . . . . . . . . 3 3. AD Type Specification . . . . . . . . . . . . . . . . . . . . 2
4. Security Considerations . . . . . . . . . . . . . . . . . . . 3 4. Security Considerations . . . . . . . . . . . . . . . . . . . 3
5. References . . . . . . . . . . . . . . . . . . . . . . . . . 4 5. References . . . . . . . . . . . . . . . . . . . . . . . . . 3
5.1. Normative References . . . . . . . . . . . . . . . . . . 4 5.1. Normative References . . . . . . . . . . . . . . . . . . 3
5.2. Informative References . . . . . . . . . . . . . . . . . 4 5.2. Informative References . . . . . . . . . . . . . . . . . 4
Appendix A. ASN.1 Module . . . . . . . . . . . . . . . . . . . . 4 Appendix A. ASN.1 Module . . . . . . . . . . . . . . . . . . . . 4
Appendix B. Acknowledgements . . . . . . . . . . . . . . . . . . 5 Appendix B. Acknowledgements . . . . . . . . . . . . . . . . . . 4
1. Introduction 1. Introduction
Kerberos [RFC4120] allows secure interaction among users and services Kerberos [RFC4120] allows secure interaction among users and services
over a network. It supports a variety of authentication mechanisms over a network. It supports a variety of authentication mechanisms
using its Pre-Authentication framework [RFC6113]. The Kerberos using its pre-authentication framework [RFC6113]. The Kerberos
Authentication Service has been architected to support password based authentication service has been architected to support password based
authentication as well as multi-factor authentication using One Time authentication as well as multi-factor authentication using one-time
Password devices or Public Key Cryptography. Implementations that password devices or public key cryptography. Implementations that
have Pre-Authentication mechanisms offering significantly different have pre-authentication mechanisms offering significantly different
strengths of client authentication may choose to keep track of the strengths of client authentication may choose to keep track of the
strength of the authentication used as an input into policy strength of the authentication used as an input into policy
decisions. decisions.
This document proposes a new Authorization Data Type to be used to This document specifies a new authorization data type to convey
convey the authentication strength to the application services. The authentication strength to application services. Elements of this
KDC can provide the DER encoding of the ASN.1 type defined in this type appear within an AD-CAMMAC [RFC7751] container.
document into the ad-data field of the AD-CAMMAC [RFC7751] container.
This ASN.1 type contains information about the type of authentication
mechanism used by the Kerberos client to authenticate itself to the
KDC.
2. Document Conventions 2. Document Conventions
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in RFC 2119 [RFC2119]. document are to be interpreted as described in RFC 2119 [RFC2119].
3. AD Type Specification 3. AD Type Specification
The KDC MAY include the following Authorization Data element, wrapped The KDC MAY include the following authorization data element, wrapped
in AD-CAMMAC, in the initial credentials and copy it from a ticket- in AD-CAMMAC, in initial credentials, and copy it from a ticket-
granting ticket into service tickets: granting ticket into service tickets:
AD-AUTHENTICATION-INDICATOR 97 AD-AUTHENTICATION-INDICATOR 97
The corresponding ad-data field contains the DER encoding of the The corresponding ad-data field contains the DER encoding of the
ASN.1 type which is defined as following ASN.1 type:
AD-AUTHENTICATION-INDICATOR ::= SEQUENCE OF UTF8String AD-AUTHENTICATION-INDICATOR ::= SEQUENCE OF UTF8String
Each UTF8String value is a short string that indicates that a Each UTF8String value is a short string that indicates that a
particular set of requirements was met during the initial particular set of requirements was met during the initial
authentication. These strings are intended to be compared against authentication. These strings are intended to be compared against
known values. They are not intended to store structured data. These known values. They are not intended to store structured data. These
strings MAY be site-defined strings that do not contain a colon such strings MAY be site-defined strings that do not contain a colon such
as the name of the Pre-Authentication mechanism used, or as the name of the Pre-Authentication mechanism used, or
alternatively URIs that reference a Level of Assurance Profile alternatively URIs that reference a Level of Assurance Profile
[RFC6711]. [RFC6711].
The AD-AUTHENTICATION-INDICATOR MUST be included in the AD-CAMMAC Authorization data elements of type AD-AUTHENTICATION-INDICATOR MUST
container so that its contents can be protected. The AD- be included in an AD-CAMMAC container so that their contents can be
AUTHENTICATION-INDICATOR MAY safely be ignored by the applications verified as originating from the KDC. Elements of type AD-
and KDCs that do not implement this element. AUTHENTICATION-INDICATOR MAY safely be ignored by applications and
KDCs that do not implement this element.
4. Security Considerations 4. Security Considerations
AD-AUTHENTICATION-INDICATOR is wrapped in AD-CAMMAC which supersedes Elements of type AD-AUTHENTICATION-INDICATOR are wrapped in AD-CAMMAC
AD-KDC-ISSUED container. AD-CAMMAC allows both the application containers. AD-CAMMAC supersedes AD-KDC-ISSUED, and allows both
service and the KDC to verify the authenticity of the contained application services and the KDC to verify the authenticity of the
Authorization Data. contained authorization data.
A malicious service can replace AD-CAMMAC in a service ticket with a KDC implementations MUST use AD-CAMMAC verifiers as described in the
legitimate AD-CAMMAC present in some other ticket that the service the security considerations of RFC 7751 [RFC7751] to ensure that AD-
has received. The KDC MUST ensure that the service does not tamper AUTHENTICATION-INDICATOR elements are not modified by an attacker.
with the contents of AD-CAMMAC or the ticket by including a kdc- Application servers MUST validate the AD-CAMMAC container before
verifier in the containing CAMMAC. This binding protects AD- making authorization decisions based on AD-AUTHENTICATION-INDICATOR
AUTHENTICATION-INDICATOR in case of constrained delegation such as elements. Application servers MUST NOT make authorization decisions
S4U2Proxy [MS-SFU] extension. based on AD-AUTHENTICATION-INDICATOR elements which appear outside of
AD-CAMMAC containers.
Using multiple strings in AD-AUTHENTICATION-INDICATOR MAY lead to Using multiple strings in AD-AUTHENTICATION-INDICATOR MAY lead to
ambiguity when a service tries to make a decision based on the AD- ambiguity when a service tries to make a decision based on the AD-
AUTHENTICATION-INDICATOR values. This ambiguity can be avoided if AUTHENTICATION-INDICATOR values. This ambiguity can be avoided if
indicator values are always used as a positive indication of certain indicator values are always used as a positive indication of certain
requirements being met during the initial authentication. requirements being met during the initial authentication.
5. References 5. References
5.1. Normative References 5.1. Normative References
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} DEFINITIONS EXPLICIT TAGS ::= BEGIN } DEFINITIONS EXPLICIT TAGS ::= BEGIN
AD-AUTHENTICATION-INDICATOR ::= SEQUENCE OF UTF8String AD-AUTHENTICATION-INDICATOR ::= SEQUENCE OF UTF8String
END END
Appendix B. Acknowledgements Appendix B. Acknowledgements
Dmitri Pal (Red Hat) Dmitri Pal (Red Hat)
Simo Sorce (Red Hat) Simo Sorce (Red Hat)
Greg Hudson (MIT)
Authors' Addresses Authors' Addresses
Anupam Jain Anupam Jain
Georgia Tech Georgia Tech
225 North Ave NW 225 North Ave NW
Atlanta, GA 30332 Atlanta, GA 30332
USA USA
EMail: ajain323@gatech.edu EMail: ajain323@gatech.edu
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