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Versions: (draft-tschofenig-dime-e2e-sec-req) 00 01 02 03 04 05 RFC 7966

DIME                                                  H. Tschofenig, Ed.
Internet-Draft                              Nokia Solutions and Networks
Intended status: Standards Track                             J. Korhonen
Expires: March 30, 2014                                   Renesas Mobile
                                                                 G. Zorn
                                                             Network Zen
                                                               K. Pillay
                                                   Oracle Communications
                                                      September 26, 2013


        Diameter AVP Level Security: Scenarios and Requirements
                   draft-ietf-dime-e2e-sec-req-00.txt

Abstract

   This specification discusses requirements for providing Diameter
   security at the level of individual Attribute Value Pairs.

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 March 30, 2014.

Copyright Notice

   Copyright (c) 2013 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
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   include Simplified BSD License text as described in Section 4.e of



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   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Terminology . . . . . . . . . . . . . . . . . . . . . . . . .   3
   3.  Use Case  . . . . . . . . . . . . . . . . . . . . . . . . . .   3
   4.  Requirements  . . . . . . . . . . . . . . . . . . . . . . . .   5
   5.  Security Considerations . . . . . . . . . . . . . . . . . . .   7
   6.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   7
   7.  Acknowledgments . . . . . . . . . . . . . . . . . . . . . . .   7
   8.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   7
     8.1.  Normative References  . . . . . . . . . . . . . . . . . .   7
     8.2.  Informative References  . . . . . . . . . . . . . . . . .   7
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   8

1.  Introduction

   The Diameter Base specification [2] offers security protection
   between neighboring Diameter peers and mandates that either TLS (for
   TCP), DTLS (for SCTP), or IPsec is used.  These security protocols
   offer a wide range of security properties, including entity
   authentication, data-origin authentication, integrity,
   confidentiality protection and replay protection.  They also support
   a large number of cryptographic algorithms, algorithm negotiation,
   and different types of credentials.

   The need to also offer additional security protection of AVPs between
   non-neighboring Diameter nodes was recognized very early in the work
   on Diameter.  This lead to work on Diameter security using the
   Cryptographic Message Syntax (CMS) [3].  Due to lack of deployment
   interest at that time (and the complexity of the developed solution)
   the specification was, however, never completed.

   In the meanwhile Diameter had received a lot of deployment interest
   from the cellular operator community and because of the
   sophistication of those deployments the need for protecting Diameter
   AVPs between non-neighboring nodes re-surfaced.  Since early 2000
   (when the work on [3] was discontinued) the Internet community had
   seen advances in cryptographic algorithms (for example, authenticated
   encryption algorithms were developed) and new security building
   blocks were developed.

   This document collects requirements for developing a solution to
   protect Diameter AVPs.





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2.  Terminology

   The key words 'MUST', 'MUST NOT', 'REQUIRED', 'SHALL', 'SHALL NOT',
   'SHOULD', 'SHOULD NOT', 'RECOMMENDED', 'MAY', and 'OPTIONAL' in this
   specification are to be interpreted as described in [1].

   This document re-uses terminology from the Diameter base
   specification [2].

3.  Use Case

   Consider the following use case shown in Figure 1 where a a Diameter
   client wants to interact with its home Diameter server in the
   example.com realm.  The visited domain the Diameter client is
   attached to makes use of a AAA interconnection provider, shown as AAA
   Broker in our example.  While both the administrators of the visited
   as well as the home domain are likely to main a business relationship
   with the intermediate AAA broker network they may want to ensure that
   certain Diameter AVPs are not sent in the clear or are integrity
   protected.  Note that the security services are likely offered
   between Diameter Proxy A and Diameter Proxy D for ease of deployment.
   Proxy A may act on behalf of the Diameter client and Diameter Proxy D
   acts on behalf of Diameter Server X and Y it serves.


      +oooooooooooooooooo+              +====================+
      |                  |              |                    |
      |                  |              |                    |
   +--------+      +--------+        +--------+        +--------+
   |Diameter|      |Diameter|        |Diameter|        |Diameter|
   |Client  +------+Proxy A +--------+Proxy B +--------+Proxy C |----+
   +--------+      +--------+        +--------+        +--------+    |
      |                  |              |                    |       |
      |  Visited Domain  |              |      AAA Broker    |       |
      +oooooooooooooooooo+              +====================+       |
                                                                     |
                                                                     |
                                                                     |
                                        +\\\\\\\\\\\\\\\\\\\\+       |
                                 +--------+  Example.com     |       |
                                 |Diameter|                  |       |
                                 |Server X+--+         +--------+    |
                                 +--------+  |         |Diameter|    |
                                 +--------+  +---------+Proxy D |----+
                                 |Diameter|  |         +--------+
                                 |Server Y+--+               |
                                 +--------+    Home Domain   |
                                        +////////////////////+



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               Figure 1: Example Diameter Deployment Setup.

   Based on Figure 1 the following use cases can be differentiated.  AVP
   refers to an unprotected AVP and {AVP}k refers to an AVP that
   experiences security protection without further distinguishing
   between integrity and confidentiality protection.

   In the first scenario, shown in Figure 2, end-to-end security
   protection is provided between the Diameter client and the Diameter
   server.  Diameter AVPs exchanged between these two Diameter nodes are
   protected.


   +--------+                                                +--------+
   |Diameter| AVP, {AVP}k                                    |Diameter|
   |Client  +-----------------........... -------------------+Server  |
   +--------+                                                +--------+


          Figure 2: End-to-End Diameter AVP Security Protection.

   In the second scenario, shown in Figure 3, a Diameter proxy acts on
   behalf of the Diameter client with regard to security protection.  It
   applies security protection to outgoing Diameter AVPs and verifies
   incoming AVPs.


   +--------+     +--------+                                 +--------+
   |Diameter| AVP |Diameter|   AVP, {AVP}k                   |Diameter|
   |Client  +-----+Proxy A +---------- .......... -----------+Server  |
   +--------+     +--------+                                 +--------+


         Figure 3: Middle-to-End Diameter AVP Security Protection.

   In the third scenario shown in Figure 4 a Diameter proxy acts on
   behalf of the Diameter server.


   +--------+                                 +--------+     +--------+
   |Diameter| AVP, {AVP}k                     |Diameter| AVP |Diameter|
   |Client  +-----------------........... ----+Proxy D +-----+Server  |
   +--------+                                 +--------+     +--------+


         Figure 4: End-to-Middle Diameter AVP Security Protection.





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   The forth and final scenario (see Figure 5) is a combination of the
   end-to-middle and the middle-to-end scenario shown in Figure 4 and in
   Figure 3.  From a deployment point of view this scenario is easier to
   accomplish for two reasons: First, Diameter clients and Diameter
   servers remain unmodified.  This ensures that no modifications are
   needed to the installed Diameter infrastructure.  Second, key
   management is also simplified since fewer number of key pairs need to
   be negotiated and provisioned.


   +--------+     +--------+                  +--------+     +--------+
   |Diameter| AVP |Diameter|   AVP, {AVP}k    |Diameter| AVP |Diameter|
   |Client  +-----+Proxy A +-- .......... ----+Proxy D +-----+Server  |
   +--------+     +--------+                  +--------+     +--------+


       Figure 5: Middle-to-Middle Diameter AVP Security Protection.

   Various security threats are mitigated by selectively applying
   security protection for individual Diameter AVPs.  Without protection
   there is the possibility for password sniffing, confidentiality
   violation, AVP insertion, deletion or modification.  Additionally,
   applying digital signature offers non-repudiation capabilities; a
   feature not yet available in today's Diameter deployment.
   Modification of certain Diameter AVPs may not necessarily be the act
   of malicious behavior but could also be the result of
   misconfiguration.  An over-aggressively configured firewalling
   Diameter proxy may also remove certain AVPs.  In most cases data
   origin authentication and integrity protection of AVPs will provide
   most benefits for existing deployments with minimal overhead and
   (potentially) operating in a full-backwards compatible manner.

4.  Requirements

   Requirement #1:  Solutions MUST support an extensible set of
      cryptographic algorithms.

         Motivation: Crypto-agility is the ability of a protocol to
         adapt to evolving cryptographic algorithms and security
         requirements.  This may include the provision of a modular
         mechanism to allow cryptographic algorithms to be updated
         without substantial disruption to deployed implementations.

   Requirement #2:  Solutions MUST support confidentiality, integrity,
      and data-origin authentication.  Solutions for integrity
      protection MUST work in a backwards-compatible way with existing
      Diameter applications.




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   Requirement #3:  Solutions MUST support replay protection.  Any
      Diameter node has an access to network time and thus can
      synchronise their clocks.

   Requirement #4:  Solutions MUST support the ability to delegate
      security functionality to another entity

         Motivation: As described in Section 3 the ability to let a
         Diameter proxy to perform security services on behalf of all
         clients within the same administrative domain is important for
         incremental deployability.  The same applies to the other
         communication side where a load balancer terminates security
         services for the servers it interfaces.

   Requirement #5:  Solutions MUST be able to selectively apply their
      cryptographic protection to certain Diameter AVPs.

         Motivation: Some Diameter applications assume that certain AVPs
         are added, removed, or modified by intermediaries.  As such, it
         may be necessary to apply security protection selectively.

   Requirement #6:  Solutions MUST recommend a mandatory-to-implement
      cryptographic algorithm.

         Motivation: For interoperability purposes it is beneficial to
         have a mandatory-to-implement cryptographic algorithm specified
         (unless profiles for specific usage environments specify
         otherwise).

   Requirement #7:  Solutions MUST support symmetric keys and asymmetric
      keys.

         Motivation: Symmetric and asymmetric cryptographic algorithms
         provide different security services.  Asymmetric algorithms,
         for example, allow non-repudiation services to be offered.

   Requirement #8:  A solution for dynamic key management has to be
      provided.  It is assumed that no "new" key management protocol
      needs to be developed; instead existing ones are re-used, if at
      all possible.  Rekeying could be triggered by (a) management
      actions and (b) expiring keying material.

   Requirement #9:  The ability to statically provisioned keys
      (symmetric as well as asymmetric keys) has to be supported to
      simplify management for small-scale deployments that typically do
      not have a back-end network management infrastructure.





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   Requirement #10:  Capability/Policy Discovery: This document talks
      about selectively protecting Diameter AVPs between different
      Diameter nodes.  A Diameter node has to be configured such that it
      applies security protection to a certain number of AVPs.  A number
      of policy related questions arise: What keying material should be
      used so that the intended recipient is also able to verify it?
      What AVPs shall be protected so that the result is not rejected by
      the recipient?  In case of confidentiality protection the Diameter
      node encrypting AVPs needs to know ahead of time what other node
      is intended to decrypt them.  Should the list of integrity
      protected AVP be indicated in the protected payload itself (or is
      it known based on out-of-band information)?  Is this policy /
      capability information assumed to be established out-of-band
      (manually) or is there a protocol mechanism to distribute this
      information?

   Requirement #11:  Command-Line Support: Should solutions allow the
      provisioning of long-term shared symmetric credentials via a
      command-line interface / text file?  This allows easier management
      for small-scale deployments.

5.  Security Considerations

   This entire document focused on the discussion of new functionality
   for securing Diameter AVPs selectively between non-neighboring nodes.

6.  IANA Considerations

   This document does not require actions by IANA.

7.  Acknowledgments

   We would like to thank Guenther Horn for his review comments.

8.  References

8.1.  Normative References

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

   [2]        Fajardo, V., Arkko, J., Loughney, J., and G. Zorn,
              "Diameter Base Protocol", RFC 6733, October 2012.

8.2.  Informative References






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   [3]        Calhoun, P., Farrell, S., and W. Bulley, "Diameter CMS
              Security Application", draft-ietf-aaa-diameter-cms-sec-04
              (work in progress), March 2002.

Authors' Addresses

   Hannes Tschofenig (editor)
   Nokia Solutions and Networks
   Linnoitustie 6
   Espoo  02600
   Finland

   Phone: +358 (50) 4871445
   Email: Hannes.Tschofenig@gmx.net
   URI:   http://www.tschofenig.priv.at


   Jouni Korhonen
   Renesas Mobile
   Porkkalankatu 24
   Helsinki  00180
   Finland

   Email: jouni.nospam@gmail.com


   Glen Zorn
   Network Zen
   227/358 Thanon Sanphawut
   Bang Na  Bangkok 10260
   Thailand

   Email: glenzorn@gmail.com


   Kervin Pillay
   Oracle Communications
   100 Crosby Drive
   Bedford, Massachusettes  01730
   USA

   Email: kervin.pillay@oracle.com









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