draft-ietf-kitten-pkinit-freshness-02.txt   draft-ietf-kitten-pkinit-freshness-03.txt 
Kitten Working Group M. Short, Ed. Kitten Working Group M. Short, Ed.
Internet-Draft S. Moore Internet-Draft S. Moore
Intended status: Standards Track P. Miller Intended status: Standards Track P. Miller
Expires: June 13, 2016 Microsoft Corporation Expires: August 27, 2016 Microsoft Corporation
December 11, 2015 February 24, 2016
Public Key Cryptography for Initial Authentication in Kerberos (PKINIT) Public Key Cryptography for Initial Authentication in Kerberos (PKINIT)
Freshness Extension Freshness Extension
draft-ietf-kitten-pkinit-freshness-02 draft-ietf-kitten-pkinit-freshness-03
Abstract Abstract
This document describes how to further extend the Public Key This document describes how to further extend the Public Key
Cryptography for Initial Authentication in Kerberos (PKINIT) Cryptography for Initial Authentication in Kerberos (PKINIT)
extension [RFC4556] to exchange an opaque data blob that a KDC can extension [RFC4556] to exchange an opaque data blob that a KDC can
validate to ensure that the client is currently in possession of the validate to ensure that the client is currently in possession of the
private key during a PKINIT AS exchange. private key during a PKINIT AS exchange.
Status of This Memo Status of This Memo
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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/.
Internet-Drafts are draft documents valid for a maximum of six months Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress." material or to cite them other than as "work in progress."
This Internet-Draft will expire on June 13, 2016. This Internet-Draft will expire on August 27, 2016.
Copyright Notice Copyright Notice
Copyright (c) 2015 IETF Trust and the persons identified as the Copyright (c) 2016 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents Provisions Relating to IETF Documents
(http://trustee.ietf.org/license-info) in effect on the date of (http://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents publication of this document. Please review these documents
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
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authentication . . . . . . . . . . . . . . . . . . . . . 3 authentication . . . . . . . . . . . . . . . . . . . . . 3
1.2. Requirements Language . . . . . . . . . . . . . . . . . . 3 1.2. Requirements Language . . . . . . . . . . . . . . . . . . 3
2. Message Exchanges . . . . . . . . . . . . . . . . . . . . . . 3 2. Message Exchanges . . . . . . . . . . . . . . . . . . . . . . 3
2.1. Generation of KRB_AS_REQ Message . . . . . . . . . . . . 4 2.1. Generation of KRB_AS_REQ Message . . . . . . . . . . . . 4
2.2. Generation of KRB_ERROR Message . . . . . . . . . . . . . 4 2.2. Generation of KRB_ERROR Message . . . . . . . . . . . . . 4
2.3. Generation of KRB_AS_REQ Message . . . . . . . . . . . . 4 2.3. Generation of KRB_AS_REQ Message . . . . . . . . . . . . 4
2.4. Receipt of KRB_AS_REQ Message . . . . . . . . . . . . . . 4 2.4. Receipt of KRB_AS_REQ Message . . . . . . . . . . . . . . 4
2.5. Receipt of second KRB_ERROR Message . . . . . . . . . . . 5 2.5. Receipt of second KRB_ERROR Message . . . . . . . . . . . 5
3. PreAuthentication Data Types . . . . . . . . . . . . . . . . 5 3. PreAuthentication Data Types . . . . . . . . . . . . . . . . 5
4. Extended PKAuthenticator . . . . . . . . . . . . . . . . . . 5 4. Extended PKAuthenticator . . . . . . . . . . . . . . . . . . 5
5. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 5 5. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 6
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 6 6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 6
7. Security Considerations . . . . . . . . . . . . . . . . . . . 6 7. Security Considerations . . . . . . . . . . . . . . . . . . . 7
8. Interoperability Considerations . . . . . . . . . . . . . . . 6 8. Interoperability Considerations . . . . . . . . . . . . . . . 7
9. Normative References . . . . . . . . . . . . . . . . . . . . 7 9. Normative References . . . . . . . . . . . . . . . . . . . . 7
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 7 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 8
1. Introduction 1. Introduction
The Kerberos PKINIT extension [RFC4556] defines two schemes for using The Kerberos PKINIT extension [RFC4556] defines two schemes for using
asymmetric cryptography in a Kerberos preauthenticator. One uses asymmetric cryptography in a Kerberos preauthenticator. One uses
Diffie-Hellman key exchange and the other depends on public key Diffie-Hellman key exchange and the other depends on public key
encryption. The public key encryption scheme is less commonly used encryption. The public key encryption scheme is less commonly used
for two reasons: for two reasons:
o Elliptic Curve Cryptography (ECC) Support for PKINIT [RFC5349] o Elliptic Curve Cryptography (ECC) Support for PKINIT [RFC5349]
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[RFC4556]. [RFC4556].
2.1. Generation of KRB_AS_REQ Message 2.1. Generation of KRB_AS_REQ Message
The client indicates support of freshness tokens by adding a padata The client indicates support of freshness tokens by adding a padata
element with padata-type PA_AS_FRESHNESS and padata-value of an empty element with padata-type PA_AS_FRESHNESS and padata-value of an empty
octet string. octet string.
2.2. Generation of KRB_ERROR Message 2.2. Generation of KRB_ERROR Message
The KDC will respond by adding a padata element with padata-type The KDC will respond with a KRB_ERROR [RFC4120] message with the
PA_AS_FRESHNESS and padata-value of the freshness token to the error-code KDC_ERR_PREAUTH_REQUIRED [RFC4120] and adding a padata
METHOD-DATA object. element with padata-type PA_AS_FRESHNESS and padata-value of the
freshness token to the METHOD-DATA object.
2.3. Generation of KRB_AS_REQ Message 2.3. Generation of KRB_AS_REQ Message
After the client receives the KRB-ERROR message containing a After the client receives the KRB-ERROR message containing a
freshness token, it extracts the PA_AS_FRESHNESS padata-value field freshness token, it extracts the PA_AS_FRESHNESS padata-value field
of the PA-DATA structure as an opaque data blob. The PA_AS_FRESHNESS of the PA-DATA structure as an opaque data blob. The PA_AS_FRESHNESS
padata-value field of the PA-DATA structure SHALL then be added as an padata-value field of the PA-DATA structure SHALL then be added as an
opaque blob in the freshnessToken field when the client generates the opaque blob in the freshnessToken field when the client generates the
PKAuthenticator for the PA_PK_AS_REQ message. This ensures that the PKAuthenticator for the PA_PK_AS_REQ message. This ensures that the
freshness token value will be included in the signed data portion of freshness token value will be included in the signed data portion of
the KRB_AS_REQ value. the KRB_AS_REQ value.
2.4. Receipt of KRB_AS_REQ Message 2.4. Receipt of KRB_AS_REQ Message
After validating the PA_PK_AS_REQ message normally, the KDC will If the realm requires freshness and the PA_PK_AS_REQ message does not
validate the freshnessToken value in the PKAuthenticator in an contain the freshness token, the KDC MUST return a KRB_ERROR
implementation-specific way. If the freshness token is not valid, [RFC4120] message with the error-code KDC_ERR_PREAUTH_REQUIRED
the KDC MUST return KDC_ERR_PREAUTH_EXPIRED [RFC6113] with [RFC4120] with a padata element with padata-type PA_AS_FRESHNESS and
PA_AS_FRESHNESS. Since the freshness tokens are validated by KDCs in padata-value of the freshness token to the METHOD-DATA object.
the same realm, standardizing the contents of the freshness token is
not a concern for interoperability. When the PA_PK_AS_REQ message contains a freshness token, after
validating the PA_PK_AS_REQ message normally, the KDC will validate
the freshnessToken value in the PKAuthenticator in an implementation-
specific way. If the freshness token is not valid, the KDC MUST
return a KRB_ERROR [RFC4120] message with the error-code
KDC_ERR_PREAUTH_EXPIRED [RFC6113]. The e-data field of the error
contains a METHOD-DATA object [RFC4120] which specifies a valid
PA_AS_FRESHNESS padata-value. Since the freshness tokens are
validated by KDCs in the same realm, standardizing the contents of
the freshness token is not a concern for interoperability.
2.5. Receipt of second KRB_ERROR Message 2.5. Receipt of second KRB_ERROR Message
If a client receives a KDC_ERR_PREAUTH_EXPIRED KRB_ERROR message that If a client receives a KDC_ERR_PREAUTH_EXPIRED KRB_ERROR message that
includes a freshness token, it MUST retry using the new freshness includes a freshness token, it MUST retry using the new freshness
token. token.
3. PreAuthentication Data Types 3. PreAuthentication Data Types
The following are the new PreAuthentication data types: The following are the new PreAuthentication data types:
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-- KDC. MUST be present if sent by KDC -- KDC. MUST be present if sent by KDC
... ...
} }
5. Acknowledgements 5. Acknowledgements
Douglas E. Engert, Sam Hartman, Henry B. Hotz, Nikos Douglas E. Engert, Sam Hartman, Henry B. Hotz, Nikos
Mavrogiannopoulos, Martin Rex, Nico Williams, and Tom Yu were key Mavrogiannopoulos, Martin Rex, Nico Williams, and Tom Yu were key
contributors to the discovery of the freshness issue in PKINIT. contributors to the discovery of the freshness issue in PKINIT.
Sam Hartman,Greg Hudson, Jeffrey Hutzelman, Nathan Ide, Benjamin Sam Hartman, Greg Hudson, Jeffrey Hutzelman, Nathan Ide, Benjamin
Kaduk, Bryce Nordgren, Magnus Nystrom, Nico Williams and Tom Yu Kaduk, Bryce Nordgren, Magnus Nystrom, Nico Williams and Tom Yu
reviewed the document and provided suggestions for improvements. reviewed the document and provided suggestions for improvements.
6. IANA Considerations 6. IANA Considerations
IANA is requested to assign numbers for PA_AS_FRESHNESS listed in the IANA is requested to assign numbers for PA_AS_FRESHNESS listed in the
Kerberos Parameters registry Pre-authentication and Typed Data as Kerberos Parameters registry Pre-authentication and Typed Data as
follows: follows:
+------+-----------------+------------+ +------+-----------------+------------+
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