draft-ietf-dime-e2e-sec-req-00.txt   draft-ietf-dime-e2e-sec-req-01.txt 
DIME H. Tschofenig, Ed. DIME H. Tschofenig, Ed.
Internet-Draft Nokia Solutions and Networks Internet-Draft Nokia Solutions and Networks
Intended status: Standards Track J. Korhonen Intended status: Informational J. Korhonen
Expires: March 30, 2014 Renesas Mobile Expires: April 24, 2014 Broadcom
G. Zorn G. Zorn
Network Zen Network Zen
K. Pillay K. Pillay
Oracle Communications Oracle Communications
September 26, 2013 October 21, 2013
Diameter AVP Level Security: Scenarios and Requirements Diameter AVP Level Security: Scenarios and Requirements
draft-ietf-dime-e2e-sec-req-00.txt draft-ietf-dime-e2e-sec-req-01.txt
Abstract Abstract
This specification discusses requirements for providing Diameter This specification discusses requirements for providing Diameter
security at the level of individual Attribute Value Pairs. security at the level of individual Attribute Value Pairs.
Status of This Memo Status of This Memo
This Internet-Draft is submitted in full conformance with the This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79. provisions of BCP 78 and BCP 79.
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Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
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material or to cite them other than as "work in progress." material or to cite them other than as "work in progress."
This Internet-Draft will expire on March 30, 2014. This Internet-Draft will expire on April 24, 2014.
Copyright Notice Copyright Notice
Copyright (c) 2013 IETF Trust and the persons identified as the Copyright (c) 2013 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
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Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3
3. Use Case . . . . . . . . . . . . . . . . . . . . . . . . . . 3 3. Security Threats . . . . . . . . . . . . . . . . . . . . . . 3
4. Requirements . . . . . . . . . . . . . . . . . . . . . . . . 5 4. Scenarios for Diameter AVP-Level Protection . . . . . . . . . 4
5. Security Considerations . . . . . . . . . . . . . . . . . . . 7 5. Requirements . . . . . . . . . . . . . . . . . . . . . . . . 6
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 7 6. Open Issues . . . . . . . . . . . . . . . . . . . . . . . . . 7
7. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 7 7. Security Considerations . . . . . . . . . . . . . . . . . . . 8
8. References . . . . . . . . . . . . . . . . . . . . . . . . . 7 8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 8
8.1. Normative References . . . . . . . . . . . . . . . . . . 7 9. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 8
8.2. Informative References . . . . . . . . . . . . . . . . . 7 10. References . . . . . . . . . . . . . . . . . . . . . . . . . 8
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 8 10.1. Normative References . . . . . . . . . . . . . . . . . . 8
10.2. Informative References . . . . . . . . . . . . . . . . . 8
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 9
1. Introduction 1. Introduction
The Diameter Base specification [2] offers security protection The Diameter Base specification [2] offers security protection
between neighboring Diameter peers and mandates that either TLS (for between neighboring Diameter peers and mandates that either TLS (for
TCP), DTLS (for SCTP), or IPsec is used. These security protocols TCP), DTLS (for SCTP), or IPsec is used. These security protocols
offer a wide range of security properties, including entity offer a wide range of security properties, including entity
authentication, data-origin authentication, integrity, authentication, data-origin authentication, integrity,
confidentiality protection and replay protection. They also support confidentiality protection and replay protection. They also support
a large number of cryptographic algorithms, algorithm negotiation, a large number of cryptographic algorithms, algorithm negotiation,
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Cryptographic Message Syntax (CMS) [3]. Due to lack of deployment Cryptographic Message Syntax (CMS) [3]. Due to lack of deployment
interest at that time (and the complexity of the developed solution) interest at that time (and the complexity of the developed solution)
the specification was, however, never completed. the specification was, however, never completed.
In the meanwhile Diameter had received a lot of deployment interest In the meanwhile Diameter had received a lot of deployment interest
from the cellular operator community and because of the from the cellular operator community and because of the
sophistication of those deployments the need for protecting Diameter sophistication of those deployments the need for protecting Diameter
AVPs between non-neighboring nodes re-surfaced. Since early 2000 AVPs between non-neighboring nodes re-surfaced. Since early 2000
(when the work on [3] was discontinued) the Internet community had (when the work on [3] was discontinued) the Internet community had
seen advances in cryptographic algorithms (for example, authenticated seen advances in cryptographic algorithms (for example, authenticated
encryption algorithms were developed) and new security building encryption algorithms) and new security building blocks were
blocks were developed. developed.
This document collects requirements for developing a solution to This document collects requirements for developing a solution to
protect Diameter AVPs. protect Diameter AVPs.
2. Terminology 2. Terminology
The key words 'MUST', 'MUST NOT', 'REQUIRED', 'SHALL', 'SHALL NOT', The key words 'MUST', 'MUST NOT', 'REQUIRED', 'SHALL', 'SHALL NOT',
'SHOULD', 'SHOULD NOT', 'RECOMMENDED', 'MAY', and 'OPTIONAL' in this 'SHOULD', 'SHOULD NOT', 'RECOMMENDED', 'MAY', and 'OPTIONAL' in this
specification are to be interpreted as described in [1]. specification are to be interpreted as described in [1].
This document re-uses terminology from the Diameter base This document re-uses terminology from the Diameter base
specification [2]. specification [2].
3. Use Case 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.
Consider the following use case shown in Figure 1 where a a Diameter 3. Security Threats
client wants to interact with its home Diameter server in the
example.com realm. The visited domain the Diameter client is The follow description aims to illustrate various security threats
attached to makes use of a AAA interconnection provider, shown as AAA that raise the need for protecting Diameter Attribute Value Pairs
Broker in our example. While both the administrators of the visited (AVPs). Figure 1 illustrates an example Diameter topology where a
as well as the home domain are likely to main a business relationship Diameter clients want to interact with the example.com home domain.
with the intermediate AAA broker network they may want to ensure that To interconnect the two visited networks a AAA interconnection
certain Diameter AVPs are not sent in the clear or are integrity provider, labeled as AAA Broker, is used.
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+ +====================+ +oooooooooooooooooo+ +====================+
| | | | | Example.net | | |
| | | | | | | |
+--------+ +--------+ +--------+ +--------+ +--------+ +--------+ +--------+ +--------+
|Diameter| |Diameter| |Diameter| |Diameter| |Diameter| |Diameter+--------+Diameter| |Diameter|
|Client +------+Proxy A +--------+Proxy B +--------+Proxy C |----+ |Client 1+------+Proxy A1| +------+Proxy B +--------+Proxy C |----+
+--------+ +--------+ +--------+ +--------+ | +--------+ +--------+ | +--------+ +--------+ |
| | | | | | | | | | |
| Visited Domain | | AAA Broker | | | Visited Domain 1 | | | AAA Broker | |
+oooooooooooooooooo+ +====================+ | +oooooooooooooooooo+ | +====================+ |
| | |
| | |
| | |
+\\\\\\\\\\\\\\\\\\\\+ | | +\\\\\\\\\\\\\\\\\\\\+ |
+--------+ Example.com | | | +--------+ Example.com | |
|Diameter| | | | |Diameter| | |
|Server X+--+ +--------+ | +oooooooooooooooooo+ | |Server X+--+ +--------+ |
+--------+ | |Diameter| | | Example.org | | +--------+ | |Diameter| |
+--------+ +---------+Proxy D |----+ | | | +--------+ +---------+Proxy D |-+
|Diameter| | +--------+ +--------+ +--------+ | |Diameter| | +--------+
|Server Y+--+ | |Diameter| |Diameter| | |Server Y+--+ |
+--------+ Home Domain | |Client 2+------+Proxy A2+-+ +--------+ Home Domain |
+////////////////////+ +--------+ +--------+ +////////////////////+
| |
| Visited Domain 2 |
+oooooooooooooooooo+
Figure 1: Example Diameter Deployment Setup. Figure 1: Example Diameter Deployment.
Based on Figure 1 the following use cases can be differentiated. AVP Eavesdropping: Some Diameter applications carry information that is
refers to an unprotected AVP and {AVP}k refers to an AVP that only intended for consumption by end points, either by the
experiences security protection without further distinguishing Diameter client or by the Diameter server but not by
between integrity and confidentiality protection. 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.
In the first scenario, shown in Figure 2, end-to-end security In the first scenario, shown in Figure 2, end-to-end security
protection is provided between the Diameter client and the Diameter protection is provided between the Diameter client and the Diameter
server. Diameter AVPs exchanged between these two Diameter nodes are server. Diameter AVPs exchanged between these two Diameter nodes are
protected. protected.
+--------+ +--------+ +--------+ +--------+
|Diameter| AVP, {AVP}k |Diameter| |Diameter| AVP, {AVP}k |Diameter|
|Client +-----------------........... -------------------+Server | |Client +-----------------........... -------------------+Server |
+--------+ +--------+ +--------+ +--------+
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In the third scenario shown in Figure 4 a Diameter proxy acts on In the third scenario shown in Figure 4 a Diameter proxy acts on
behalf of the Diameter server. behalf of the Diameter server.
+--------+ +--------+ +--------+ +--------+ +--------+ +--------+
|Diameter| AVP, {AVP}k |Diameter| AVP |Diameter| |Diameter| AVP, {AVP}k |Diameter| AVP |Diameter|
|Client +-----------------........... ----+Proxy D +-----+Server | |Client +-----------------........... ----+Proxy D +-----+Server |
+--------+ +--------+ +--------+ +--------+ +--------+ +--------+
Figure 4: End-to-Middle Diameter AVP Security Protection. Figure 4: End-to-Middle Diameter AVP Security Protection.
The forth and final scenario (see Figure 5) is a combination of the The fourth and the final scenario (see Figure 5) is a combination of
end-to-middle and the middle-to-end scenario shown in Figure 4 and in the end-to-middle and the middle-to-end scenario shown in Figure 4
Figure 3. From a deployment point of view this scenario is easier to and in Figure 3. From a deployment point of view this scenario is
accomplish for two reasons: First, Diameter clients and Diameter easier to accomplish for two reasons: First, Diameter clients and
servers remain unmodified. This ensures that no modifications are Diameter servers remain unmodified. This ensures that no
needed to the installed Diameter infrastructure. Second, key modifications are needed to the installed Diameter infrastructure.
management is also simplified since fewer number of key pairs need to Second, key management is also simplified since fewer number of key
be negotiated and provisioned. pairs need to be negotiated and provisioned.
+--------+ +--------+ +--------+ +--------+ +--------+ +--------+ +--------+ +--------+
|Diameter| AVP |Diameter| AVP, {AVP}k |Diameter| AVP |Diameter| |Diameter| AVP |Diameter| AVP, {AVP}k |Diameter| AVP |Diameter|
|Client +-----+Proxy A +-- .......... ----+Proxy D +-----+Server | |Client +-----+Proxy A +-- .......... ----+Proxy D +-----+Server |
+--------+ +--------+ +--------+ +--------+ +--------+ +--------+ +--------+ +--------+
Figure 5: Middle-to-Middle Diameter AVP Security Protection. Figure 5: Middle-to-Middle Diameter AVP Security Protection.
Various security threats are mitigated by selectively applying Various security threats are mitigated by selectively applying
security protection for individual Diameter AVPs. Without protection security protection for individual Diameter AVPs. Without protection
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applying digital signature offers non-repudiation capabilities; a applying digital signature offers non-repudiation capabilities; a
feature not yet available in today's Diameter deployment. feature not yet available in today's Diameter deployment.
Modification of certain Diameter AVPs may not necessarily be the act Modification of certain Diameter AVPs may not necessarily be the act
of malicious behavior but could also be the result of of malicious behavior but could also be the result of
misconfiguration. An over-aggressively configured firewalling misconfiguration. An over-aggressively configured firewalling
Diameter proxy may also remove certain AVPs. In most cases data Diameter proxy may also remove certain AVPs. In most cases data
origin authentication and integrity protection of AVPs will provide origin authentication and integrity protection of AVPs will provide
most benefits for existing deployments with minimal overhead and most benefits for existing deployments with minimal overhead and
(potentially) operating in a full-backwards compatible manner. (potentially) operating in a full-backwards compatible manner.
4. Requirements 5. Requirements
Requirement #1: Solutions MUST support an extensible set of Requirement #1: Solutions MUST support an extensible set of
cryptographic algorithms. cryptographic algorithms.
Motivation: Crypto-agility is the ability of a protocol to Motivation: Crypto-agility is the ability of a protocol to
adapt to evolving cryptographic algorithms and security adapt to evolving cryptographic algorithms and security
requirements. This may include the provision of a modular requirements. This may include the provision of a modular
mechanism to allow cryptographic algorithms to be updated mechanism to allow cryptographic algorithms to be updated
without substantial disruption to deployed implementations. without substantial disruption to deployed implementations.
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protection MUST work in a backwards-compatible way with existing protection MUST work in a backwards-compatible way with existing
Diameter applications. Diameter applications.
Requirement #3: Solutions MUST support replay protection. Any Requirement #3: Solutions MUST support replay protection. Any
Diameter node has an access to network time and thus can Diameter node has an access to network time and thus can
synchronise their clocks. synchronise their clocks.
Requirement #4: Solutions MUST support the ability to delegate Requirement #4: Solutions MUST support the ability to delegate
security functionality to another entity security functionality to another entity
Motivation: As described in Section 3 the ability to let a Motivation: As described in Section 4 the ability to let a
Diameter proxy to perform security services on behalf of all Diameter proxy to perform security services on behalf of all
clients within the same administrative domain is important for clients within the same administrative domain is important for
incremental deployability. The same applies to the other incremental deployability. The same applies to the other
communication side where a load balancer terminates security communication side where a load balancer terminates security
services for the servers it interfaces. services for the servers it interfaces.
Requirement #5: Solutions MUST be able to selectively apply their Requirement #5: Solutions MUST be able to selectively apply their
cryptographic protection to certain Diameter AVPs. cryptographic protection to certain Diameter AVPs.
Motivation: Some Diameter applications assume that certain AVPs Motivation: Some Diameter applications assume that certain AVPs
are added, removed, or modified by intermediaries. As such, it are added, removed, or modified by intermediaries. As such, it
may be necessary to apply security protection selectively. MUST be possible to apply security protection selectively.
Requirement #6: Solutions MUST recommend a mandatory-to-implement Requirement #6: Solutions MUST recommend a mandatory-to-implement
cryptographic algorithm. cryptographic algorithm.
Motivation: For interoperability purposes it is beneficial to Motivation: For interoperability purposes it is beneficial to
have a mandatory-to-implement cryptographic algorithm specified have a mandatory-to-implement cryptographic algorithm specified
(unless profiles for specific usage environments specify (unless profiles for specific usage environments specify
otherwise). otherwise).
Requirement #7: Solutions MUST support symmetric keys and asymmetric Requirement #7: Solutions MUST support symmetric keys and asymmetric
keys. keys.
Motivation: Symmetric and asymmetric cryptographic algorithms Motivation: Symmetric and asymmetric cryptographic algorithms
provide different security services. Asymmetric algorithms, provide different security services. Asymmetric algorithms,
for example, allow non-repudiation services to be offered. for example, allow non-repudiation services to be offered.
Requirement #8: A solution for dynamic key management has to be Requirement #8: A solution for dynamic key management MUST be
provided. It is assumed that no "new" key management protocol included in the overall solution framework. However, it is
needs to be developed; instead existing ones are re-used, if at assumed that no "new" key management protocol needs to be
all possible. Rekeying could be triggered by (a) management developed; instead existing ones are re-used, if at all possible.
actions and (b) expiring keying material. Rekeying could be triggered by (a) management actions and (b)
expiring keying material.
Requirement #9: The ability to statically provisioned keys Requirement #9: The ability to statically provisioned keys
(symmetric as well as asymmetric keys) has to be supported to (symmetric as well as asymmetric keys) has to be supported to
simplify management for small-scale deployments that typically do simplify management for small-scale deployments that typically do
not have a back-end network management infrastructure. not have a back-end network management infrastructure.
Requirement #10: Capability/Policy Discovery: This document talks 6. Open Issues
Open Issue #1: Capability/Policy Discovery: This document talks
about selectively protecting Diameter AVPs between different about selectively protecting Diameter AVPs between different
Diameter nodes. A Diameter node has to be configured such that it Diameter nodes. A Diameter node has to be configured such that it
applies security protection to a certain number of AVPs. A number applies security protection to a certain number of AVPs. A number
of policy related questions arise: What keying material should be of policy related questions arise: What keying material should be
used so that the intended recipient is also able to verify it? 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 What AVPs shall be protected so that the result is not rejected by
the recipient? In case of confidentiality protection the Diameter the recipient? In case of confidentiality protection the Diameter
node encrypting AVPs needs to know ahead of time what other node node encrypting AVPs needs to know ahead of time what other node
is intended to decrypt them. Should the list of integrity is intended to decrypt them. Should the list of integrity
protected AVP be indicated in the protected payload itself (or is protected AVP be indicated in the protected payload itself (or is
it known based on out-of-band information)? Is this policy / it known based on out-of-band information)? Is this policy /
capability information assumed to be established out-of-band capability information assumed to be established out-of-band
(manually) or is there a protocol mechanism to distribute this (manually) or is there a protocol mechanism to distribute this
information? information?
Requirement #11: Command-Line Support: Should solutions allow the Open Issue #2: Command-Line Support: Should solutions allow the
provisioning of long-term shared symmetric credentials via a provisioning of long-term shared symmetric credentials via a
command-line interface / text file? This allows easier management command-line interface / text file? This allows easier management
for small-scale deployments. for small-scale deployments.
5. Security Considerations 7. Security Considerations
This entire document focused on the discussion of new functionality This entire document focused on the discussion of new functionality
for securing Diameter AVPs selectively between non-neighboring nodes. for securing Diameter AVPs selectively between non-neighboring nodes.
6. IANA Considerations 8. IANA Considerations
This document does not require actions by IANA. This document does not require actions by IANA.
7. Acknowledgments 9. Acknowledgments
We would like to thank Guenther Horn for his review comments. We would like to thank Guenther Horn, Martin Dolly, for his review
comments.
8. References 10. References
8.1. Normative References 10.1. Normative References
[1] Bradner, S., "Key words for use in RFCs to Indicate [1] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997. Requirement Levels", BCP 14, RFC 2119, March 1997.
[2] Fajardo, V., Arkko, J., Loughney, J., and G. Zorn, [2] Fajardo, V., Arkko, J., Loughney, J., and G. Zorn,
"Diameter Base Protocol", RFC 6733, October 2012. "Diameter Base Protocol", RFC 6733, October 2012.
8.2. Informative References 10.2. Informative References
[3] Calhoun, P., Farrell, S., and W. Bulley, "Diameter CMS [3] Calhoun, P., Farrell, S., and W. Bulley, "Diameter CMS
Security Application", draft-ietf-aaa-diameter-cms-sec-04 Security Application", draft-ietf-aaa-diameter-cms-sec-04
(work in progress), March 2002. (work in progress), March 2002.
[4] Eronen, P., Hiller, T., and G. Zorn, "Diameter Extensible
Authentication Protocol (EAP) Application", RFC 4072,
August 2005.
Authors' Addresses Authors' Addresses
Hannes Tschofenig (editor) Hannes Tschofenig (editor)
Nokia Solutions and Networks Nokia Solutions and Networks
Linnoitustie 6 Linnoitustie 6
Espoo 02600 Espoo 02600
Finland Finland
Phone: +358 (50) 4871445 Phone: +358 (50) 4871445
Email: Hannes.Tschofenig@gmx.net Email: Hannes.Tschofenig@gmx.net
URI: http://www.tschofenig.priv.at URI: http://www.tschofenig.priv.at
Jouni Korhonen Jouni Korhonen
Renesas Mobile Broadcom
Porkkalankatu 24 Porkkalankatu 24
Helsinki 00180 Helsinki 00180
Finland Finland
Email: jouni.nospam@gmail.com Email: jouni.nospam@gmail.com
Glen Zorn Glen Zorn
Network Zen Network Zen
227/358 Thanon Sanphawut 227/358 Thanon Sanphawut
Bang Na Bangkok 10260 Bang Na Bangkok 10260
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