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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: Informational J. Korhonen
Expires: April 24, 2014 Broadcom
G. Zorn
Network Zen
K. Pillay
Oracle Communications
October 21, 2013
Diameter AVP Level Security: Scenarios and Requirements
draft-ietf-dime-e2e-sec-req-01.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.
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This Internet-Draft will expire on April 24, 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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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 . . . . . . . . . 4
5. Requirements . . . . . . . . . . . . . . . . . . . . . . . . 6
6. Open Issues . . . . . . . . . . . . . . . . . . . . . . . . . 7
7. Security Considerations . . . . . . . . . . . . . . . . . . . 8
8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 8
9. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 8
10. References . . . . . . . . . . . . . . . . . . . . . . . . . 8
10.1. Normative References . . . . . . . . . . . . . . . . . . 8
10.2. Informative References . . . . . . . . . . . . . . . . . 8
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 9
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) 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].
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 follow description aims to illustrate various security threats
that raise the need for protecting Diameter Attribute Value Pairs
(AVPs). Figure 1 illustrates an example Diameter topology where a
Diameter clients want to interact with the example.com home domain.
To interconnect the two visited networks a AAA interconnection
provider, labeled as AAA Broker, is used.
+oooooooooooooooooo+ +====================+
| Example.net | | |
| | | |
+--------+ +--------+ +--------+ +--------+
|Diameter| |Diameter+--------+Diameter| |Diameter|
|Client 1+------+Proxy A1| +------+Proxy B +--------+Proxy C |----+
+--------+ +--------+ | +--------+ +--------+ |
| | | | | |
| Visited Domain 1 | | | AAA Broker | |
+oooooooooooooooooo+ | +====================+ |
| |
| |
| |
| +\\\\\\\\\\\\\\\\\\\\+ |
| +--------+ Example.com | |
| |Diameter| | |
+oooooooooooooooooo+ | |Server X+--+ +--------+ |
| Example.org | | +--------+ | |Diameter| |
| | | +--------+ +---------+Proxy D |-+
+--------+ +--------+ | |Diameter| | +--------+
|Diameter| |Diameter| | |Server Y+--+ |
|Client 2+------+Proxy A2+-+ +--------+ Home Domain |
+--------+ +--------+ +////////////////////+
| |
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| Visited Domain 2 |
+oooooooooooooooooo+
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 keying material for the protection of
air interface between the end device and the network access server
to be carried from the Diameter server to the Diameter client
(using the EAP-Master-Session-Key AVP). The content of the EAP-
Master-Session-Key AVP would benefit from protection against
eavesdropping by intermediaries. Other AVPs 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.
Injection and Manipulation: The Diameter base 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
Example.net contains information claiming to be from Example.org.
This would either require strict verification at the edge of the
AAA broker network or cryptographic assurance at the Diameter
layer to provent 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.
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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.
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 key
pairs need to be negotiated and provisioned.
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+--------+ +--------+ +--------+ +--------+
|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.
5. 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.
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 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
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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
MUST be possible 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 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.
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.
6. Open Issues
Open Issue #1: 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
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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?
Open Issue #2: 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.
7. Security Considerations
This entire document focused on the discussion of new functionality
for securing Diameter AVPs selectively between non-neighboring nodes.
8. IANA Considerations
This document does not require actions by IANA.
9. Acknowledgments
We would like to thank Guenther Horn, Martin Dolly, for his review
comments.
10. References
10.1. 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.
10.2. 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., Hiller, T., and G. Zorn, "Diameter Extensible
Authentication Protocol (EAP) Application", RFC 4072,
August 2005.
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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
Broadcom
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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