Internet DRAFT - draft-tschofenig-dime-e2e-sec-req
draft-tschofenig-dime-e2e-sec-req
DIME H. Tschofenig, Ed.
Internet-Draft Nokia Siemens Networks
Intended status: Standards Track J. Korhonen
Expires: January 16, 2014 Renesas Mobile
G. Zorn
Network Zen
K. Pillay
Oracle Communications
July 15, 2013
Diameter AVP Level Security: Scenarios and Requirements
draft-tschofenig-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
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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 todays 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 backend network management infastructure.
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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 Siemens 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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