Public Key Cryptography for Initial Authentication in Kerberos (PKINIT) Freshness Extension
RFC 8070
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RFC - Proposed Standard
(February 2017; No errata)
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Last updated |
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2017-02-16
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IETF
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Document shepherd |
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Matt Rogers
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Show
(last changed 2016-10-18)
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RFC 8070 (Proposed Standard)
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Stephen Farrell
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RFC-Ed-Ack
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Internet Engineering Task Force (IETF) M. Short, Ed.
Request for Comments: 8070 S. Moore
Category: Standards Track P. Miller
ISSN: 2070-1721 Microsoft Corporation
February 2017
Public Key Cryptography for Initial Authentication in Kerberos (PKINIT)
Freshness Extension
Abstract
This document describes how to further extend the Public Key
Cryptography for Initial Authentication in Kerberos (PKINIT)
extension (defined in RFC 4556) to exchange an opaque data blob that
a Key Distribution Center (KDC) can validate to ensure that the
client is currently in possession of the private key during a PKINIT
Authentication Service (AS) exchange.
Status of This Memo
This is an Internet Standards Track document.
This document is a product of the Internet Engineering Task Force
(IETF). It represents the consensus of the IETF community. It has
received public review and has been approved for publication by the
Internet Engineering Steering Group (IESG). Further information on
Internet Standards is available in Section 2 of RFC 7841.
Information about the current status of this document, any errata,
and how to provide feedback on it may be obtained at
http://www.rfc-editor.org/info/rfc8070.
Copyright Notice
Copyright (c) 2017 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents
(http://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents
carefully, as they describe your rights and restrictions with respect
to this document. Code Components extracted from this document must
include Simplified BSD License text as described in Section 4.e of
the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.
Short, et al. Standards Track [Page 1]
RFC 8070 PKINIT Freshness February 2017
Table of Contents
1. Introduction ....................................................2
1.1. Kerberos Message Flow Using KRB_AS_REQ without
Pre-authentication .........................................3
1.2. Requirements Language ......................................3
2. Message Exchanges ...............................................4
2.1. Generation of KRB_AS_REQ Message ...........................4
2.2. Generation of KRB_ERROR Message ............................4
2.3. Generation of KRB_AS_REQ Message ...........................4
2.4. Receipt of KRB_AS_REQ Message ..............................5
2.5. Receipt of Second KRB_ERROR Message ........................5
3. PreAuthentication Data Types ....................................5
4. Extended PKAuthenticator ........................................6
5. IANA Considerations .............................................6
6. Security Considerations .........................................7
7. Interoperability Considerations .................................7
8. Normative References ............................................8
Acknowledgements ...................................................8
Authors' Addresses .................................................9
1. Introduction
The Kerberos PKINIT extension [RFC4556] defines two schemes for using
asymmetric cryptography in a Kerberos pre-authenticator. One uses
Diffie-Hellman key exchange and the other depends on public key
encryption. The public key encryption scheme is less commonly used
for two reasons:
o Elliptic Curve Cryptography (ECC) Support for PKINIT [RFC5349]
only specified Elliptic Curve Diffie-Hellman (ECDH) key agreement,
so it cannot be used for public key encryption.
o Public key encryption requires certificates with an encryption
key, which is not deployed on many existing smart cards.
In the Diffie-Hellman exchange, the client uses its private key only
to sign the AuthPack structure (specified in Section 3.2.1 of
[RFC4556]), which is performed before any traffic is sent to the KDC.
Thus, a client can generate requests with future times in the
PKAuthenticator, and then send those requests at those future times.
Unless the time is outside the validity period of the client's
certificate, the KDC will validate the PKAuthenticator and return a
Ticket-Granting Ticket (TGT) the client can use without possessing
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