Container Authenticated by Multiple MACs
draft-ietf-krb-wg-cammac-02

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Document Type Active Internet-Draft (krb-wg WG)
Last updated 2012-05-23
Replaced by draft-ietf-kitten-cammac, rfc7751
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Internet Engineering Task Force                            S. Sorce, Ed.
Internet-Draft                                                   Red Hat
Updates: 4120 (if approved)                                   T. Yu, Ed.
Intended status: Standards Track                        T. Hardjono, Ed.
Expires: November 24, 2012                       MIT Kerberos Consortium
                                                            May 23, 2012

                Container Authenticated by Multiple MACs
                      draft-ietf-krb-wg-cammac-02

Abstract

   Abstract: This document proposes a Kerberos Authorization Data
   container that supersedes AD-KDC-ISSUED.  It allows for multiple MACs
   or signatures on the contained Authorization Data elements.

Status of this Memo

   This Internet-Draft is submitted in full conformance with the
   provisions of BCP 78 and BCP 79.

   Internet-Drafts are working documents of the Internet Engineering
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   This Internet-Draft will expire on November 24, 2012.

Copyright Notice

   Copyright (c) 2012 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

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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 application server
   needs 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 application server can verify autonomusly
   without further contact with the KDC.

   The following information is needed:

   o  The KDC MAC.

   o  The Service MAC.

   o  Optional Trusted Service Key MAC.

   The KDC MAC is required to allow the KDC to validate the data
   withouth requiring to recompute the contents at every TGS request.

   The SVC MAC is required so that the Service can verify that the
   authorization data has been validated by the KDC.

   The Trusted Service MAC is useful to verify the authenticity of the
   contents on the same host, when the data is received by a less
   trusted service and passed to a more trusted service on the same host
   without the need for additional roundtrips to the KDC.

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   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 {
         elements              [0] AuthorizationData,
         kdc-verifier          [1] Verifier-MAC,
         svc-verifier          [2] Verifier-MAC OPTIONAL,
         other-verifiers       [3] SEQUENCE OF Verifier
   }

   Verifier             ::= CHOICE {
         mac            Verifier-MAC
   }

   Verifier-MAC         ::= SEQUENCE {
         identifier     [0] PrincipalName OPTIONAL,
         kvno           [1] UInt32,
         enctype        [2] Int32,
         mac            [3] Checksum
   }

   elements
      A sequence of authorization data elements issued by the KDC.

   kdc-verifier
      A container that includes a cryptographic checksum computed over
      the encoding of the elements field, keyed with the krbtgt key.
      Checksum type TBD.

   svc-verifier
      A container that includes a cryptographic checksum computed over
      the encoding of the elements field, keyed with the service long
      term key.
      This field is marked OPTIONAL and can be omitted when the CAMMAC
      is attached to a local TGT. It MUST be present in all other cases,
      including cross-realm TGTs.
      Checksum type TBD.

   other-verifiers
      A container including 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
      identifier field. The PrincipalNAme MUST be present and a valid
      principal in the REALM for additional verifiers.
      KDCs MAY add one or more 'trusted service' verifiers. Unless
      otherwise explicitly administratively configured, the 'trusted
      service' SHOULD be found by substituting the service identifier
      component of the principal name of the svc-verifier with 'host'.
      Checksum type TBD.

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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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