Diameter Messages in Kerberos5 AuthorizationData
draft-vanrein-krb5-authzdata-diameter-01

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Network Working Group                                        R. Van Rein
Internet-Draft                                                 ARPA2.net
Intended status: Experimental                          February 28, 2019
Expires: September 1, 2019

            Diameter Messages in Kerberos5 AuthorizationData
                draft-vanrein-krb5-authzdata-diameter-01

Abstract

   The Kerberos5 infrastructure is concerned with authentication, but it
   can also carry AuthorizationData in a variety of formats.  Diameter
   is an extensible standard for the expression of authorisation
   information.  This specification defines an embedding of Diameter
   data in the AuthorizationData fields of Kerberos5.

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 September 1, 2019.

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Internet-Draft             Kerberos5 Diameter              February 2019

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Embedding Diameter in Kerberos5 . . . . . . . . . . . . . . .   3
   3.  Use with Realm Crossover  . . . . . . . . . . . . . . . . . .   5
   4.  Security Considerations . . . . . . . . . . . . . . . . . . .   5
   5.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   6
   6.  Normative References  . . . . . . . . . . . . . . . . . . . .   6
   Appendix A.  Acknowledgements . . . . . . . . . . . . . . . . . .   6
   Author's Address  . . . . . . . . . . . . . . . . . . . . . . . .   7

1.  Introduction

   Kerberos5 [RFC4120] is a single-signon system that provides the users
   of its realms with authentication tickets to individual services.
   Such tickets tend to be valid for the remaining user session,
   typically up to a day.  Service tickets are provided by a central
   realm service known as the Key Distribution Center or KDC.

   The KDC may not be able to supply tickets for all services.  When it
   knows that a service belongs to another realm, and when it can locate
   a crossover key to the service's KDC, it will forward the user to a
   remote realm through a realm-crossing ticket.  The user follows such
   tickets under current Kerberos semantics [RFC6806].

   Though designed for authentication and not authorisation, the realm-
   centric position of a KDC makes it a suitable place to control both
   aspects of access control.  The message formats can indeed carry
   AuthorizationData, consisting of a numerical tag and data to be
   interpreted according to that tag.  This specification adds a tag
   value to describe AuthorizationData holding Diameter protocol
   messages.

   AuthorizationData can be included in requests to the KDC, and the KDC
   can include AuthorizationData in a ticket.  When requesting a service
   ticket from the KDC, a single-signon ticket with possible
   AuthorizationData is attached to that request by the Kerberos client.
   All this data is protected in transit; requests to the KDC are
   encrypted with the TGT secret or a sub-key; tickets carry it to a
   service using a key shared between the server and KDC.  The KDC can
   prove to a ticket-receiving service that it originated certain parts
   of AuthorizationData by wrapping it in CAMMAC [RFC7751] structures.

   Diameter frames [RFC6733] hold a list of Attribute-Value Pairs (AVP),
   with optional nesting into group AVPs.  The format is easily parsed
   and applications exist (or can be defined) to capture a class of
   usage scenarios.  Among the existing applications is an extensible
   network access application that lends itself for authorisation

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