One document matched: draft-moskowitz-radius-sec-roadmap-00.txt

Radius Extensions                                           R. Moskowitz
Internet-Draft                        ICSAlabs a Division of Cybertrust
Expires: August 18, 2005                                     Corporation
                                                       February 14, 2005


                        RADIUS Security Roadmap
               draft-moskowitz-radius-sec-roadmap-00.txt

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Copyright Notice

   Copyright (C) The Internet Society (2005).

Abstract

   RADIUS has become the defacto protocol between network edge devices
   (e,g, dial NAS or Wireless AP) and a backend Authentication Server.
   In this environment the backend Server is often called a (RADIUS
   Server).  RADIUS is gaining very broad penetration, even into homes,
   because of its use with wireless authentication.  Because of the
   amount of deployed infrastructure already in place, we believe that



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   RADIUS will not be supplanted by another authentication service in
   the foreseeable future.  Because the widespread deployment in
   wireless has different infrastructure requirements than what is
   required for dialup, RADIUS requirements, especially trust between
   Edge devices and RADIUS Servers needs to be addressed.  This document
   sets the requirements for RADIUS security and then sets forth
   technologies that will satisfy those requirements.

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].

Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  3

   2.  RADIUS as a simple Client/Server environment . . . . . . . . .  3

   3.  RADIUS security requirements . . . . . . . . . . . . . . . . .  3

   4.  RADIUS identity credentials  . . . . . . . . . . . . . . . . .  4

   5.  Establishment of Session keys  . . . . . . . . . . . . . . . .  4

   6.  Communication Integrity and Privacy  . . . . . . . . . . . . .  4

   7.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . .  5

   8.  Security Considerations  . . . . . . . . . . . . . . . . . . .  5

   9.  Acknowledgements . . . . . . . . . . . . . . . . . . . . . . .  5

   10.   Normative References . . . . . . . . . . . . . . . . . . . .  5

       Author's Address . . . . . . . . . . . . . . . . . . . . . . .  5

       Intellectual Property and Copyright Statements . . . . . . . .  6












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1.  Introduction

   The RADIUS [RFC2865] protocol carries sensitive user authentication
   information and various keys.  When this protocol traverses networks
   that should be considered hostile such as when carried over a
   wireless link, the confidentiality of generic information in messages
   is not protected.  There is also the risk of malicious RADIUS clients
   and servers that can act as Man-in-the-Middle (MITM) attack points,
   or allow malicious devices onto a network.  The original security
   services in RADIUS are inadequate and incomplete as is evident in the
   wireless infrastructure case.  This document sets forth the security
   requirements that is needed for RADIUS, and defines the services that
   can meet those requirements.  Separate documents will provide full
   specifications for those services.

2.  RADIUS as a simple Client/Server environment

   RADIUS consists of a set of clients and one or more servers.  The
   clients are generically called Network Access Servers (NAS) and
   include most managed infrastructure platforms that provide network
   connectivity.  RADIUS has a fairly straightforward stateless
   request/response protocol.  It uses UDP as its transport.  Although
   the protocol is stateless, a number of security requirements that are
   common to many such Client/Server environments can be defined.

3.  RADIUS security requirements

   There are three principal security requirements for RADIUS that are
   standard for Client/Server Environments:

   o  Creation and maintenance of identity credentials

   o  Establishment of session keys

   o  Communication Integrity and Privacy

   In the RADIUS environment it is desirable that these requirements are
   met:

   o  Within the RADIUS protocol.  That is without requiring services or
      additional infrastructure beyond RADIUS [e.g.  IPsec, or either
      SSL or SNMPv3 for Identity management]

   o  Simplicity in design, use, and user interfaces







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4.  RADIUS identity credentials

   The identity credentials SHALL be a 128-bit secret and the names of
   the RADIUS client and server.  The names MUST NOT be IP addresses.
   The names can be any or no meaning, e.g.  FQDNs, NAIs, randomly
   selected characters.  This credential MAY be set manually on the
   client and server.  There MUST be a mechanism within RADIUS to deploy
   and maintain this credential.  It MUST support credentials for high
   availability RADIUS configurations (i.e.  multiple servers accessible
   by the client with the same information.  There MAY be a mechanism
   outside of RADIUS for the deployment and maintenance of this
   credential (e.g.  SNMP).

5.  Establishment of Session keys

   A session in RADIUS SHALL defined as commencing from the time of
   starting either the client or server service until either the client
   or server service terminates.  The client is responsible for
   maintaining the session key.  That is it will establish the session
   key on start up.  If the server responds with a error of client key
   not known, the client will establish a new session key.  Since this
   is a significant Denial of Service attack, this process MUST take
   steps to mitigate this attack.  The session key is not used directly
   for protecting RADIUS datagrams.  It is used to derive a set of keys
   that will be used.

6.  Communication Integrity and Privacy

   Five 128-bit keys are needed:

   o  Legacy use -- Used for the original RADIUS secret

   o  Client Integrity -- Used by the client in a new message integrity
      attribute

   o  Server Integrity -- Used by the server in a new message integrity
      attribute

   o  Client Privacy -- Used by the client to encrypt attributes that
      require privacy

   o  Server Privacy -- Used by the server to encrypt attributes that
      require privacy

   These keys will be derived from the session key through a key
   expansion function.  A new message integrity attribute and a standard
   encrypt function will also be provided.




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7.  IANA Considerations

   This document makes no request of IANA.

   Note to RFC Editor: this section may be removed on publication as an
   RFC.

8.  Security Considerations

   All in band keying methods that can be used to create the Identity
   credentials are subject to MITM attacks.  This risk must either be
   accepted, or an out of band validation process SHALL be included.
   For example, if a Diffie-Hellman key exchange is used, then either
   party could validate the other party's public key by comparing a
   fingerprint of it to an externally obtained copy.  This could be done
   at the server if the client has a manufacturer key pair and the
   fingerprint is included in the packing literature.

9.  Acknowledgements

   This roadmap was developed with the able assistance of John
   Vollbrecht of Merit Networks and ????.

10.  Normative References

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119, March 1997.

   [RFC2865]  Rigney, C., Willens, S., Rubens, A. and W. Simpson,
              "Remote Authentication Dial In User Service (RADIUS)",
              RFC 2865, June 2000.


Author's Address

   Robert Moskowitz
   ICSAlabs a Division of Cybertrust Corporation
   1000 Bent Creek Blvd, Suite 200
   Mechanicsburg, PA  22222
   USA

   Email: rgm@icsalabs.com









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