Internet Engineering Task Force S. Sorce, Ed.
Internet-Draft Red Hat
Intended status: Standards Track T. Yu, Ed.
Expires: August 11, 2012 T. Hardjono, Ed.
MIT Kerberos Consortium
Feb 8, 2012
Container Authenticated by Multiple MACs
draft-ietf-krb-wg-cammac-00
Abstract
This draft proposes a new Authorization Data container for the
Kerberos V5 protocol. This container allows to Authenticate the
contents using multiple MACs
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 August 11, 2012.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Requirements Language . . . . . . . . . . . . . . . . . . . . . 3
3. Validation . . . . . . . . . . . . . . . . . . . . . . . . . . 3
4. Encoding . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
4.1. AD-CAMMAC . . . . . . . . . . . . . . . . . . . . . . . . . 4
5. Assigned numbers . . . . . . . . . . . . . . . . . . . . . . . 6
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 6
7. Security Considerations . . . . . . . . . . . . . . . . . . . . 6
8. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 6
9. References . . . . . . . . . . . . . . . . . . . . . . . . . . 6
9.1. Normative References . . . . . . . . . . . . . . . . . . . 6
9.2. Informative References . . . . . . . . . . . . . . . . . . 6
Appendix A. Additional Stuff . . . . . . . . . . . . . . . . . . . 7
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 7
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1. Introduction
This draft proposes a Authorization Data container for Kerberos that
identifies a base set of MAC and other elements necessary to
authenticate the authorization data being carried in such a way that
not only the KDC but also services can independently verify that the
data has been authenticated by the KDC and has not been tampered
with.
2. Requirements Language
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. Validation
Authorization data is highly sensitive and must be validated to
insure no tampering has occured.
In order to validate any information the receiving client need to be
able to cryptographically verify the data. This is done by
introducing a new AuthorizationData element called AD-CAMMAC that
contains enough information to bind the contents to a principal in a
way that a receiving client can verify autonomusly without further
contact with the KDC.
The following information is needed:
o The KDC signature.
o The Service Signature.
o Optional Trusted Service Key Signature.
o Optional PUBKEY KDC Signature.
The KDC signature is required to allow the KDC to validate the data
withouth requiring to recompute the contents at every TGS request.
The SVC signature is required so that the Service can verify that the
authorization data has been validated by the KDC.
Both the Trusted Service Checksum and the asymmetric KDC Signature
are useful to verify the authenticity of the contents on the same
host, when the data is received by a less trusted service and passed
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to a more trusted service on the same host without the need for
additional roundtrips to the KDC.
The ad-type for AD-CAMMAC is (TBD).
4. Encoding
The Kerberos protocol is defined in [RFC4120] using Abstract Syntax
Notation One (ASN.1) [X680]. As such, this specification also uses
the ASN.1 syntax for specifying both the abstract layout of the AD-
CAMMAC attributes, as well as its encoding.
4.1. AD-CAMMAC
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AD-CAMMAC ::= SEQUENCE {
kdc-signature [0] Checksum,
svc-signature [1] Checksum,
trusted-svc-signature [2] OPT-Checksum OPTIONAL,
pubkey-signature [3] TBD OPTIONAL,
elements [4] AuthorizationData
}
OPT-Checksum ::= SEQUENCE {
identifier [0] PrincipalName,
signature [1] Checksum
}
kdc-signature
A cryptographic checksum computed over the encoding of the
elements field, keyed with the krbtgt key.
Checksum type TBD.
svc-signature
A cryptographic checksum computed over the encoding of the
elements field, keyed with the service long term key.
Checksum type TBD.
trusted-svc-signature
A principal name and a cryptographic checksum computed over the
encoding of the elements field, keyed with the long term key of
the principal name specified in the Name field. Unless otherwise
explicitly administratively configured, the key SHOULD be found
by substituting the service name component of the principal name
of the service with 'host'.
If the service is 'host' this checksum is redundant and can be
omitted.
If the resulting host/<name>@REALM or the administratively
configured service is not found in the KDC database this
cheksum can be omitted.
Checksum type TBD.
pubkey-signature
A name identifying the asymmetric key-pair used.
A checksum computed over the encoding of the elements field using
the Private Key identified in the Name field.
If an asymmetric key is not available this checksum MUST be
omitted.
Signature type TBD.
elements
A sequence of authorization data elements issued by the KDC.
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5. Assigned numbers
TBD
6. IANA Considerations
TBD.
7. Security Considerations
Although generally authorization data are conveyed within a ticket
and are thereby protected using the existing encryption methods on
the ticket, some authorization data requires the additional
protection provided by the CAMMAC.
8. Acknowledgements
TBD.
9. References
9.1. Normative References
[RFC3961] Raeburn, K., "Encryption and Checksum Specifications for
Kerberos 5", RFC 3961, February 2005.
[RFC3962] Raeburn, K., "Advanced Encryption Standard (AES)
Encryption for Kerberos 5", RFC 3962, February 2005.
[RFC4120] Neuman, C., Yu, T., Hartman, S., and K. Raeburn, "The
Kerberos Network Authentication Service (V5)", RFC 4120,
July 2005.
9.2. Informative References
[MIT-Athena]
Steiner, J., Neuman, B., and J. Schiller, "Kerberos: An
Authentication Service for Open Network Systems. In
Proceedings of the Winter 1988 Usenix Conference.
February.", 1988.
[RFC1510] Kohl, J. and B. Neuman, "The Kerberos Network
Authentication Service (V5)", RFC 1510, September 1993.
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[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC3552] Rescorla, E. and B. Korver, "Guidelines for Writing RFC
Text on Security Considerations", BCP 72, RFC 3552,
July 2003.
[X.690] ISO, "ASN.1 encoding rules: Specification of Basic
Encoding Rules (BER), Canonical Encoding Rules (CER) and
Distinguished Encoding Rules (DER) - ITU-T Recommendation
X.690 (ISO/IEC International Standard 8825-1:1998)", 1997.
Appendix A. Additional Stuff
This becomes an Appendix.
Authors' Addresses
Simo Sorce (editor)
Red Hat
Email: ssorce@redhat.com
Tom Yu (editor)
MIT Kerberos Consortium
Email: tlyu@mit.edu
Thomas Hardjono (editor)
MIT Kerberos Consortium
Email: hardjono@mit.edu
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