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Diameter AVP Level Security End-to-End Security: Scenarios and Requirements

The information below is for an old version of the document.
Document Type
This is an older version of an Internet-Draft that was ultimately published as RFC 7966.
Authors Hannes Tschofenig , Jouni Korhonen , Glen Zorn , Kervin Pillay
Last updated 2016-06-02 (Latest revision 2016-01-13)
Replaces draft-tschofenig-dime-e2e-sec-req
RFC stream Internet Engineering Task Force (IETF)
Additional resources Mailing list discussion
Stream WG state Submitted to IESG for Publication
Document shepherd Lionel Morand
Shepherd write-up Show Last changed 2016-03-03
IESG IESG state Became RFC 7966 (Informational)
Consensus boilerplate Yes
Telechat date (None)
Responsible AD Stephen Farrell
Send notices to (None)
IANA IANA review state IANA OK - No Actions Needed
DIME                                                       H. Tschofenig
Internet-Draft                                               ARM Limited
Intended status: Informational                          J. Korhonen, Ed.
Expires: July 16, 2016                              Broadcom Corporation
                                                                 G. Zorn
                                                             Network Zen
                                                               K. Pillay
                                                   Oracle Communications
                                                        January 13, 2016

     Diameter AVP Level Security End-to-End Security: Scenarios and


   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
   Task Force (IETF).  Note that other groups may also distribute
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   Drafts is at

   Internet-Drafts are draft documents valid for a maximum of six months
   and may be updated, replaced, or obsoleted by other documents at any
   time.  It is inappropriate to use Internet-Drafts as reference
   material or to cite them other than as "work in progress."

   This Internet-Draft will expire on July 16, 2016.

Copyright Notice

   Copyright (c) 2016 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
   Provisions Relating to IETF Documents
   ( in effect on the date of
   publication of this document.  Please review these documents
   carefully, as they describe your rights and restrictions with respect
   to this document.  Code Components extracted from this document must

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   include Simplified BSD License text as described in Section 4.e of
   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.  Security Threats  . . . . . . . . . . . . . . . . . . . . . .   3
   4.  Scenarios for Diameter AVP-Level Protection . . . . . . . . .   5
   5.  Requirements  . . . . . . . . . . . . . . . . . . . . . . . .   7
   6.  Security Considerations . . . . . . . . . . . . . . . . . . .   8
   7.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   8
   8.  Acknowledgments . . . . . . . . . . . . . . . . . . . . . . .   8
   9.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   8
     9.1.  Normative References  . . . . . . . . . . . . . . . . . .   8
     9.2.  Informative References  . . . . . . . . . . . . . . . . .   9
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   9

1.  Introduction

   The Diameter base protocol specification [2] offers security
   protection between neighboring Diameter peers and mandates that peer
   connections must be protected by TLS (for TCP), DTLS (for SCTP) or
   alternative security mechanisms independent of Diameter (e.g., 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.  It should be understood that TLS/DTLS/IPsec in Diameter
   context does not provide end-to-end security unless the Diameter
   nodes are direct peers i.e., neighboring Diameter nodes.  The current
   Diameter security is realized hop-by-hop.

   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 led 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

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   encryption algorithms) and new security building blocks were

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

2.  Terminology

   The key words 'MUST', 'MUST NOT', 'REQUIRED', 'SHALL', 'SHALL NOT',
   documents are to be interpreted as described in RFC 2119 [1].

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

   In the figures below we use the symbols 'AVP' and '{AVP}k'.  AVP
   refers to an unprotected AVP and {AVP}k refers to an AVP that
   experiences security protection (using key "k") without further
   distinguishing between integrity and confidentiality protection.

3.  Security Threats

   The following description aims to illustrate various security threats
   that raise the need for protecting Diameter Attribute-Value Pairs
   (AVPs).  Figure 1 illustrates an example of Diameter based roaming
   architecture in which Diameter clients within the visited networks
   need to interact with Diameter servers in the home domain.  AAA
   domains are interconnected using a Diameter-based AAA interconnection
   network labeled as AAA Broker.

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      +oooooooooooooooooo+              +====================+
      |    |              |                    |
      |                  |              |                    |
   +--------+      +--------+        +--------+        +--------+
   |Diameter|      |Diameter+--------+Diameter|        |Diameter|
   |Client 1+------+Proxy A1| +------+Proxy B +--------+Proxy C |----+
   +--------+      +--------+ |      +--------+        +--------+    |
      |                  |    |         |                    |       |
      | Visited Domain 1 |    |         |      AAA Broker    |       |
      +oooooooooooooooooo+    |         +====================+       |
                              |                                      |
                              |                                      |
                              |                                      |
                              |            +\\\\\\\\\\\\\\\\\\\\+    |
                              |     +--------+     |    |
                              |     |Diameter|                  |    |
      +oooooooooooooooooo+    |     |Server X+--+         +--------+ |
      |    |    |     +--------+  |         |Diameter| |
      |                  |    |     +--------+  +---------+Proxy D |-+
   +--------+      +--------+ |     |Diameter|  |         +--------+
   |Diameter|      |Diameter| |     |Server Y+--+               |
   |Client 2+------+Proxy A2+-+     +--------+    Home Domain   |
   +--------+      +--------+              +////////////////////+
      |                  |
      | Visited Domain 2 |

                  Figure 1: Example Diameter Deployment.

   Eavesdropping:  Some Diameter applications carry information that is
      only intended for consumption by end points, either by the
      Diameter client or by the Diameter server but not by
      intermediaries.  As an example, consider the Diameter EAP
      application [4] that allows the transport of keying material
      between the Diameter server to the Diameter client (using the EAP-
      Master-Session-Key AVP) for the protection of air interface
      between the end device and the network access server.  The content
      of the EAP-Master-Session-Key AVP should benefit from protection
      against eavesdropping by intermediaries.  Other AVPs, for example
      those listed in Section 13.3 of [2], might also carry sensitive
      personal data that, when collected by intermediaries, allow for
      traffic analysis.

      In context of the deployment shown in Figure 1 the adversary
      could, for example, be in the AAA broker network.

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   Injection and Manipulation:  The Diameter base protocol specification
      mandates security protection between neighboring nodes but
      Diameter agents may be compromised or misconfigured and inject/
      manipulate AVPs.  To detect such actions additional security
      protection needs to be applied at the Diameter layer.

      Nodes that could launch such an attack are any Diameter agents
      along the end-to-end communication path.

   Impersonation:  Imagine a case where a Diameter message from contains information claiming to be from
      This would either require strict verification at the edge of the
      AAA broker network or cryptographic assurance at the Diameter
      layer to prevent a successful impersonation attack.

      Any Diameter realm could launch such an attack aiming for
      financial benefits or to disrupt service availability.

4.  Scenarios for Diameter AVP-Level Protection

   This scenario outlines a number of cases for deploying security
   protection of individual Diameter AVPs.

   In the first scenario, shown in Figure 2, end-to-end security
   protection is provided between the Diameter client and the Diameter
   server with any number of intermediate Diameter agents.  Diameter
   AVPs exchanged between these two Diameter nodes may be protected end-
   to-end (notation '{AVP}k') or unprotected (notation 'AVP').

   +--------+                                                +--------+
   |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.  Typically, the proxy enforcing the security
   protection belongs to the same domain as the Diameter client/server
   without end-to-end security features.

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   +--------+     +--------+                                 +--------+
   |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.

   The fourth and the 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 keys
   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

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   origin authentication and integrity protection of AVPs will provide
   the most benefits for existing deployments with minimal overhead and
   (potentially) operating in a full-backwards compatible manner.

5.  Requirements

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

         Motivation: Solutions MUST be able to evolve 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:  The solution MUST support confidentiality,
      integrity, and data-origin authentication.  Solutions for
      integrity protection MUST work in a backwards-compatible way with
      existing Diameter applications.

   Requirement #3:  The solution MUST support replay protection.  All
      Diameter nodes have access to network time and thus can
      synchronize their clocks.

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

         Motivation: As described in Section 4 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:  The solution 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
         MUST be possible to apply security protection selectively.
         Furthermore, there are AVPs that MUST NOT be confidentiality
         protected but MAY still be integrity protected such as those
         required for Diameter message routing.

   Requirement #6:  The solution MUST define a mandatory-to-implement
      cryptographic algorithm.

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

   Requirement #7:  The solution 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 MUST be
      included in the overall solution framework.

         However, 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.

6.  Security Considerations

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

7.  IANA Considerations

   This document does not require actions by IANA.

8.  Acknowledgments

   We would like to thank Guenther Horn, Martin Dolly, Steve Donovan,
   Lionel Morand and Tom Taylor (rest in peace Tom) for their review

9.  References

9.1.  Normative References

   [1]        Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119,
              DOI 10.17487/RFC2119, March 1997,

   [2]        Fajardo, V., Ed., Arkko, J., Loughney, J., and G. Zorn,
              Ed., "Diameter Base Protocol", RFC 6733,
              DOI 10.17487/RFC6733, October 2012,

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9.2.  Informative References

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

   [4]        Eronen, P., Ed., Hiller, T., and G. Zorn, "Diameter
              Extensible Authentication Protocol (EAP) Application",
              RFC 4072, DOI 10.17487/RFC4072, August 2005,

Authors' Addresses

   Hannes Tschofenig
   ARM Limited


   Jouni Korhonen (editor)
   Broadcom Corporation
   3151 Zanker Rd.
   San Jose,  CA 95134


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


   Kervin Pillay
   Oracle Communications
   100 Crosby Drive
   Bedford, Massachusettes  01730


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