Negotiation of security protocol for Mobile IPv6 operation
draft-patil-mext-sec-negotiate-02

Abstract

Mobile IPv6 has relied on IPsec and IKE/v2 for securing the signaling and user traffic. A single security mechanism for Mobile IPv6 does not adequately address various deployment scenarios. The one-size-fits-all security approach is ill suited for Mobile IPv6. Multiple alternatives to securing signaling and user traffic have been proposed and are being considered for standardization. When multiple security protocols coexist for providing security for mobile IPv6 nodes, there is a need to negotiate the choice of protocol between a mobile node and home agent apriori. This document proposes a method for negotiation the security protocol to be used between mobile IPv6 nodes.

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 27, 2012.

Copyright Notice

Copyright (c) 2011 IETF Trust and the persons identified as the document authors. All rights reserved.

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Table of Contents

• 1. Introduction
• 2. Requirements Language
• 2.1. Terminology
• 3. Problem Statement
• 4. Using the Home agent controller
• 5. Negotiation of security protocol
• 6. IANA Considerations
• 7. Security Considerations
• 8. Summary and Conclusion
• 9. References
• 9.1. Normative References
• 9.2. Informative References
• Authors' Addresses

1. Introduction

Mobile IPv6 has relied on IPsec and IKE/v2 for securing the signaling and user traffic. A single security mechanism for Mobile IPv6 does not adequately address various deployment scenarios. The one-size-fits-all security approach is ill suited for Mobile IPv6. Multiple alternatives to securing signaling and user traffic have been proposed and are being considered for standardization. When multiple security protocols coexist for providing security for mobile IPv6 nodes, there is a need to negotiate the choice of protocol between a mobile node and home agent apriori. This document proposes a method for negotiation the security protocol to be used betewen mobile IPv6 nodes.

Mobile IPv6 [RFC3775] security using IPsec and IKE is specified in [RFC3776] and [RFC4877]. A number of alternate security protocols for use by mobile IPv6 nodes have been proposed. Authentication protocol for Mobile IPv6 [RFC4285] is an example of one such. The use of such a mechanism is however restricted to networks with certain characterstics that are documented in the RFC.

More recently other security mechanisms for use in Mobile IPv6 deployments have been proposed. Transport Layer Security-based Mobile IPv6 Security Framework for Mobile Node to Home Agent Communication [I-D.ietf-mext-mip6-tls] proposes a security solution that uses TLS between the mobile node (MN) and a home agent controller (HAC) to bootstrap the security protocol between the MN and home agent (HA). Authorizing Mobile IPv6 Binding Update with Cryptographically Generated Addresses [I-D.laganier-mext-cga] proposes the use of CGA for securing the signaling between an MN and HA.

2. Requirements Language

The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in [RFC2119].

2.1. Terminology

The terminology used in this I-D is based on the Mobile IPv6 terminology defined in [RFC3775].

Home Agent Controller (HAC)

The home agent controller is a node responsible for bootstrapping Mobile IPv6 security associations between a mobile node and one or more home agents. The home agent controller also provides key distribution to both mobile nodes and home agents. Optionally, Mobile IPv6 bootstrapping can be done in addition to the security association bootstrapping between the mobile node and home agent controller.

3. Problem Statement

Security for Mobile IPv6 signaling and user traffic can be achieved via the use of different mechanisms. At the present time the use of IPsec and IKEv2 is mandated and choice of any other security protocol does not exist. However the use of IPsec and IKE for providing security does not fit all deployments. Alternate security solutions have been proposed and could be used. The use of a security protocol by mobile IPv6 nodes should be driven by the needs and requirements of a specific deployment. An enterprise deployment of Mobile IPv6 will have a different set of security requirements as compared to a cellular operator offering mobile IPv6 service.

When Mobile IPv6 hosts have the option of choosing from multiple security protocols, there is a need to negotiate the use of a specific protocol between a mobile node and home agent prior to operation. This problem is dealt with in the scope of this draft and solutions proposed.

4. Using the Home agent controller

The home agent controller (HAC) is an entity that is defined in [I-D.ietf-mext-mip6-tls]. The HAC provides the MN with bootstrapping information of Mobile IPv6 such as assigned HA address, Home Network Prefix and MN IPv6 and/or IPv4 HoA. In addition, it assigns security parameters information to constitute the MN-HA security association. The security association information is distributed to the HA assigned to be used by the MN. When negotiating the security protocol to be used by the MN, the home agent controller plays the role of negotiating the security protocol to be used between a mobile node and the home agent. The HAC is aware of the capabilities and security protocols of various home agents that it is associated with. An MN MUST contact the HAC to obtain the home agent and home address to use. The MN can also inform the HAC about the security protocols that it supports and can use for securing signaling and user traffic. The HAC will then assign the MN a valid home agent in addition to informing it of the security protocol to be used. Optionally the HAC may provide the MN and assigned HA the relevant security paremeters such as keys, SPI, ciphers etc. for securing the signaling and traffic. The MN may be configured with the address of HACs or alternatively it may discover a HAC via DNS. This is dealt with in the [I-D.ietf-mext-mip6-tls] document.

5. Negotiation of security protocol

      MN                     HAC                 HA               AAA
      |                       |	       	       	 |     	       	   |
      |<===TLS connection====>|(1)               |                 |
      |	 		      |	  		 |		   |
      |-Indicate capability-->| (2)    	 	 |		   |
      |			      |	   		 |		   |
      |			      |<--Obtain profile, security-------->| (3)
      |<--Security protocol---|(4)     	       	 |	       	   |
      |			      |--MN_ID, Sec----->|(5)  	       	   |
      |	    		      |			 |   		   |
      |<------Establish SA --------------------->|(6)		   |
      |	       	       	      |	       	       	 |		   |
      |<--------BU/BAck------------------------->|		   |
      |	       	       	      |	       	       	 |		   |
      |			      |			 |		   |

        

The mobile node establishes a TLS connection with the home agent controller (HAC) and exchanges a set of messages via this secure TLS tunnel to bootstrap mobile IPv6 as well as negotiate the choice of security protocol. The security protocol information is exchanged using the Request-Response messaging within the TLS secure tunnel. The signaling flow diagram below illustrates this negotiation mechanism:

1. The MN establishes a TLS connection with the HAC and authenticates itself. Authentication details are described in [I-D.ietf-mext-mip6-tls]. All subsequent messaging between the MN and HAC is within the secure TLS connection.
2. The MN signals the security protocols that it supports including ciphersuite and capabilities.
3. The HAC obtains the MNs profile and allowed security methods for the MN from the AAA server. The Home agent to be assigned to the MN is also informed by the AAA. The HAC chooses the security protocol to be used based on the capabilities of the MN as well as policy information from the AAA.
4. The HAC indicates the security protocol to be used by the MN. It also provides the MN with the security parameters such as encryption and integrity keys, SPI, and ciphers to be used for establishing the SA with the allocated HA.
5. The HAC also indicates to the assigned HA information about the MN and selected security protocol. Additionally security parameters required for establishing the SA are delivered to the HA.
6. The MN establishes the security association of the type indicated by the HAC. This could be an IPsec SA, or it could be the use of the SA defined in [I-D.ietf-mext-mip6-tls], the use of CGA or the use of Mobility Security Association as defined in [RFC4285].
7. The MN performs registration with the HA. The BU/BAck are secured using the security protocol that has been chosen.

6. IANA Considerations

This document does not have any IANA requests at the present time.

7. Security Considerations

The signaling between the mobile node and home agent controller is secured by TLS. All the messages between the MN and HAC are tunnelled within the TLS connection and hence secured. The MN and Home agent (HA) are either colocated or have a secure messaging interface between them. There exists the potential to downgrade the choice of the security protocol between an MN and HA. However the HAC chooses the security protocol to be used based on the capabilities of the MN as well as policy information from an entity such as AAA. In case the MN is incapable of more robust secure mechanisms, the HAC may assign such a home agent with limited capabilities and connectivity.

8. Summary and Conclusion

The choice of security protocols to be used in mobile IPv6 deployments increases the flexibility of the protocol and makes it viable for use in different deployment scenarios. This however does result in the need for negotiation of a security protocol to be used between the MN and HA. The capabilities of the MN and home agents available for use to an MN determine the security protocol that can be used. Use of a home agent controller provides Mobile IPv6 with a robust mechanism for bootstrapping as well negotiation the security protocol.

9. References

9.1. Normative References

9.2. Informative References

Authors' Addresses