Network Working Group S. Daniel Park Internet-Draft SAMSUNG Electronics Expires: December 24, 2006 K. Kim Ajou University E. Seo Samsung AIT S. Chakrabarti June 22, 2006 IPv6 over Low Power WPAN Security Analysis draft-daniel-6lowpan-security-analysis-01.txt Status of this Memo By submitting this Internet-Draft, each author represents that any applicable patent or other IPR claims of which he or she is aware have been or will be disclosed, and any of which he or she becomes aware will be disclosed, in accordance with Section 6 of BCP 79. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF), its areas, and its working groups. Note that other groups may also distribute working documents as Internet- Drafts. 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." The list of current Internet-Drafts can be accessed at http://www.ietf.org/ietf/1id-abstracts.txt. The list of Internet-Draft Shadow Directories can be accessed at http://www.ietf.org/shadow.html. This Internet-Draft will expire on December 24, 2006. Copyright Notice Copyright (C) The Internet Society (2006). Abstract This document discusses possible threats and security options for IPv6-over-IEEE802.15.4 networks. It is an informational document to raise awareness of security issues in IPv6 lowPan networks. Daniel Park, et al. Expires December 24, 2006 [Page 1] Internet-Draft 6LoWPAN Security Analysis June 2006 Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 2. Requirements . . . . . . . . . . . . . . . . . . . . . . . . . 3 3. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3 4. Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 5. Security Threats . . . . . . . . . . . . . . . . . . . . . . . 5 6. Assumptions . . . . . . . . . . . . . . . . . . . . . . . . . 5 7. 6lowpan security analysis . . . . . . . . . . . . . . . . . . 5 7.1. IEEE 802.15.4 Security analysis . . . . . . . . . . . . . 6 7.2. IP Security analysis . . . . . . . . . . . . . . . . . . . 7 8. Key Management in 6lowpan . . . . . . . . . . . . . . . . . . 7 8.1. Existing Key management methods . . . . . . . . . . . . . 8 8.2. Issues with Key management in 6lowpan . . . . . . . . . . 8 9. Security consideration in bootstrapping a 6lowpan node . . . . 8 10. Possible scenarios using different levels of security . . . . 8 11. 6lowpan trust models . . . . . . . . . . . . . . . . . . . . . 8 12. Security Considerations . . . . . . . . . . . . . . . . . . . 8 13. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 8 14. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 9 15. No I-D References . . . . . . . . . . . . . . . . . . . . . . 9 16. References . . . . . . . . . . . . . . . . . . . . . . . . . . 9 16.1. Normative References . . . . . . . . . . . . . . . . . . . 9 16.2. Informative References . . . . . . . . . . . . . . . . . . 9 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 10 Intellectual Property and Copyright Statements . . . . . . . . . . 11 Daniel Park, et al. Expires December 24, 2006 [Page 2] Internet-Draft 6LoWPAN Security Analysis June 2006 1. Introduction The principal object of the 6lowpan working group is to design IPv6 transmission over IEEE 802.15.4 [ieee802.15.4] networks. IEEE 802.15.4 [ieee802.15.4] is designed to support variety of applications in personal area networks; many of applications are security sensitive. Specifically, some of the IEEE 802.15.4 optional features actually reduce security and implementation would be limited for their extensions. The applications range from defense systems to building monitoring, fire-safety, patient monitoring etc. If the network is not secured, an intruder can inject incorrect messages to trigger false situations. Thus link-layer security is quite necessary in IEEE802.15.4 networks. IEEE 802.15.4 is working on improving the link-layer security specification. However, this document will focus on discussing different security threats from the 6lowpan perspective and discuss different options of applying existing security methods to overcome those threats. The goal is to provide a trust model using both link- layer and IP layer security packages, if possible. Designing a new security protocol for 6lowpan network is out of scope of this document. However, it may state desired security requirements which can be fed to the appropriate IETF security working group in order to suggest appropriate security protocols. 2. Requirements 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]. 3. Terminology This document uses terminology specific to IPv6 and DHCPv6 as defined in "Terminology" section of the DHCPv6 specification [RFC3315]. 4. Overview As described in [I-D.ietf-6lowpan-problem], 6lowpan has some of the characteristics against existing IP networks such as small packet size, low bandwidth of IEEE 802.15.4 standard [ieee802.15.4], low Daniel Park, et al. Expires December 24, 2006 [Page 3] Internet-Draft 6LoWPAN Security Analysis June 2006 power, low cost, large number of devices, etc. The security aspect, however, seems a bit tradeoff in the 6lowpan since security is always a costly function. This is particularly true to low rate WPAN. Obviously, adding security makes the issue even more challenging. For instance, when putting IPv6 on top of 6lowpan, it seems one could use IP security and turn off the security of WPAN since the security architecture defined by IEEE 802.15.4. But on the other hand, IP security is relatively mature for services at IP or other upper layers. But of course, it is a question whether those 6lowpan devices can support IP security as it is. for low layer services, for example MAC sublayer association, beaconing, orphanning, etc. WPAN security must be used since IP security is not supposed to take care of lower layers. Security Considerations paper[ 802.15.4-ACM] outlines that IEEE802.15.4 link-layer provides access control, message integrity, message confidentiality and replay-protection services. Yet the document is not clear about key management methods, state of ACL table in the event of power loss and support of group keying. Network shared common key may be an answer for link-layer security in this case, but that is vulnerable with replay attacks and with stolen devices. However, in most common cases, network shared keying may be the simple answer to the security at the link-layer for the power- deprived, reduced function-devices, as it is easily configurable among hundreds of devices. IPSec is mandatory to run IPv6, but considering power constraints and limited processing capability of the IEEE802.15.4 capable devices IPSec may be compute intensive; IKE messaging will not work well in LowPower networks as we want to reduce signaling in this network. Thus 6lowpan may need to define its own keying methods that require minimum overhead in packet-size and ofcourse number of signaling messages. IP-layer security will provide authentication and confidentiality between end-nodes and across multiple lowpan-links. This document later discusses applicability of IP-layer security in the case of 6lowpan network usage and applications. It may be useful only when two nodes want to send/receive all messages securely. However, in most cases, the security may be requested at the application layer as needed, while other messages can flow in the network without security overhead. The possible threats in this type of network are intrusion, sink-hole and replay attacks. A third party entity can inject bad routes in the network, act as a default router attracting all the packets to itself, or it can snoop packets and then launch replay attacks on the 6lowpan nodes. These attacks can cause harm especially when the Daniel Park, et al. Expires December 24, 2006 [Page 4] Internet-Draft 6LoWPAN Security Analysis June 2006 attacker is a high-power device, such as a laptop. It can easily drain batteries of the 6lowpan devices by sending broadcast messages, redirecting routes etc. A possible solution to security issues in the 6lowpan network might be application level security (for example, SSL) on top of link-layer security. Link-layer security protects from intrusion in the link and the application-level security protects from another user peeking at the data and impersonation. Further study in the next version. 5. Security Threats TBD 6. Assumptions The [I-D.ietf-6lowpan-problem] describes two security concerns as follows; In Section 4.6 Security: Although IEEE 802.15.4 provides AES link layer security, a complete end-to-end security is needed. In Section 5 Goals: Security threats at different layers must be clearly understood and documented. Bootstrapping of devices into a secure network could also be considered given the location, limited display, high density and ad hoc deployment of devices. This document will try to meet the above considerations. In addition, existing IP security technologies will be simplified to be implemented on the 6lowpan small devices. 6lowpan security architecture will shed off lots of fat from IP security technologies whenever available. IEEE 802.15.4 AES (Advanced Encryption Standard) will be used for 6lowpan security architecture in conjunction with IP security whenever available. Further study in the next version. 7. 6lowpan security analysis In this section, both IEEE 802.15.4 MAC security and IP security are Daniel Park, et al. Expires December 24, 2006 [Page 5] Internet-Draft 6LoWPAN Security Analysis June 2006 tackled to search for a new 6lowpan trust models and available solution spaces if feasible. The principal object of these analysis is to improve 6lowpan security level as we use IP layer security mechanism as possible regardless of 802.15.4 vulnerable MAC security. 802.15.4 MAC enhancement and amendment are not scope of this document but IEEE 802 standard stuff. 7.1. IEEE 802.15.4 Security analysis The MAC of IEEE 802.15.4 provides security services that are controlled by the MAC PIB (PAN Information Base). For security purpose, the MAC sublayer maintains an access control list (ACL) in its MAC PIB. By specifying a security suite in the ACL for a communication peer, a device can indicate what level security should be used (i.e., none, access control, data encryption, frame integrity, etc.) for communications with that peer. In addition, MAC sublayer offers a secured mode and an unsecured mode. A critical function of IEEE 802.15.4 MAC is frame security. Frame security is actually a set of optional services that may be provided by the MAC to the upper layers (applications). The standard strikes a balance between the need for these services in many applications, and the desire to minimize the burden of their implementation on those applications that do not need them. As described in [802.15.4- ACM], if an application does not set any security parameters, then security is not enabled by default. The [ieee802.15.4] defines four packet types: beacon packets, data packets, acknowledgements packets and control packets for the media access control layer. It does not support security for acknowledgement packets. But on the other hand, other packet types can optionally support integrity protection and confidentiality protection for the packet's data field. Due to the variety of applications targeted by IEEE 802.15.4, the processes of authentication and key exchange are not defined in the standard. Devices without the key cannot decrypt the encryped messages. In addition, unsecured mode is suitable for some applications in which implementation cost is important, and security is either not required or obtained in other ways. In this case, 802.15.4 node is very vulnerable. The security service enables the MAC to select the devices with which it is willing to communicate. The device may decide to communicate with some devices, and not others. To minimize complexity, the access control service is performed on an individual device basis, rather than on groups or collections of devices. Daniel Park, et al. Expires December 24, 2006 [Page 6] Internet-Draft 6LoWPAN Security Analysis June 2006 Unlike file transfer or voice communication applications common with other protocols, IEEE 802.15.4 applications often transmit messages that do not convey secret information. Further study in the next version. 7.2. IP Security analysis IPsec (IP security protocol) provides per-packet authenticity and confidentiality guarantees between peers communicate using IPsec. It is available for both IPv4 and IPv6. Basically, IPsec targets to general IP nodes operated over ethernet. It means each node has some of fluent stack size, bandwidth and non- low cost limitations like 6lowpan. Given the IPsec background, it is at least not suitable for 6lowpan nodes. Especially, 6lowpan node may not be able to operate all IPsec algorithms on its own capability either FFD or RFD. Bandwidth is very sensitive element in the 6lowpan, but IPsec generates some of redundant packets such as AH/ESP header. IPsec needs shared secret key between nodes called IKE (Internet Key Exchange), and it will make the key exchange in secrecy possible. It can, however cause some of redundant packets over the 6lowpan networks. if NDP (Neighbor Discovery Protocol) is applied to 6lowpan, SeND (Secure Neighbor Discovery) should at least considered to provide security in conjunction with neighbor discovery protocol. So far, CGA (Cryptographically Generated Addresses) [RFC3972] and SeND options [RFC3971] are newly designed by IETF and it works well over existing IP networks. However, CGA seems very complex to be applied to 6lowpan networks. Furthermore, SeND options requires huge additional options (i.e., CGA option, RSA Signature option, Timestamp and Nonce option and etc.) which increase the packet size accordingly. Thus it is doubtful if Secure Neighbor Discovery protocol could be directly applicable to 6lowpan networks without any optimization. Further study in the next version. 8. Key Management in 6lowpan TBD Daniel Park, et al. Expires December 24, 2006 [Page 7] Internet-Draft 6LoWPAN Security Analysis June 2006 8.1. Existing Key management methods TBD 8.2. Issues with Key management in 6lowpan TBD 9. Security consideration in bootstrapping a 6lowpan node This section should discuss how does a node configures itself securely with a IPv6 router in the network. It involves assignment of IPv6 prefix and the default IPv6 router in the 6lowpan. 10. Possible scenarios using different levels of security This section may suggest example scenarios with example solutions in different cases (IPSec, SSL, other type of Solutions) although this document does not recommend or specify any security solutions. 11. 6lowpan trust models To meet the security requirement of 6lowpan, a new trust models including new IPsec hashing algorithms, new key exchange schemes, etc. 6lowpan bootstraping should be at least considered as one of 6lowpan trust models. Since this document does not provide any particular solution, further specific mentions should be aligned with WG consensus. 12. Security Considerations This document addresses only security issues around IPv6 over Low Power WPAN. 13. IANA Considerations There is no IANA considerations. Daniel Park, et al. Expires December 24, 2006 [Page 8] Internet-Draft 6LoWPAN Security Analysis June 2006 14. Acknowledgements Thanks to Myungjong Lee of CUNY for his valuable comments on this document. 15. No I-D References All references shown in this section MUST be added into the Informative References before publishing it officially. [ieee802.15.4] IEEE Std., 802.15.4-2003, ISBN 0-7381-3677-5, May 2003. [802.15.4-ACM] Sastry, N. and Wagner, D., Security Considerations for IEEE 802.15.4 Networks, ACM WiSE'04, October 2004. 16. References 16.1. Normative References [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. [RFC3315] Droms, R., Bound, J., Volz, B., Lemon, T., Perkins, C., and M. Carney, "Dynamic Host Configuration Protocol for IPv6 (DHCPv6)", RFC 3315, July 2003. 16.2. Informative References [I-D.ietf-6lowpan-problem] Kushalnagar, N. and G. Montenegro, "6LoWPAN: Overview, Assumptions, Problem Statement and Goals", draft-ietf-6lowpan-problem-02 (work in progress), February 2006. [RFC3971] Arkko, J., Kempf, J., Zill, B., and P. Nikander, "SEcure Neighbor Discovery (SEND)", RFC 3971, March 2005. [RFC3972] Aura, T., "Cryptographically Generated Addresses (CGA)", RFC 3972, March 2005. Daniel Park, et al. Expires December 24, 2006 [Page 9] Internet-Draft 6LoWPAN Security Analysis June 2006 Authors' Addresses Soohong Daniel Park Mobile Convergence Laboratory, SAMSUNG Electronics. Email: soohong.park@samsung.com Ki-Hyung Kim Ajou University Email: kkim86@ajou.ac.kr Eunil Seo Samsung AIT Email: eunil.seo@samsung.com Samita Chakrabarti Email: samitac2@gmail.com Daniel Park, et al. Expires December 24, 2006 [Page 10] Internet-Draft 6LoWPAN Security Analysis June 2006 Intellectual Property Statement The IETF takes no position regarding the validity or scope of any Intellectual Property Rights or other rights that might be claimed to pertain to the implementation or use of the technology described in this document or the extent to which any license under such rights might or might not be available; nor does it represent that it has made any independent effort to identify any such rights. Information on the procedures with respect to rights in RFC documents can be found in BCP 78 and BCP 79. Copies of IPR disclosures made to the IETF Secretariat and any assurances of licenses to be made available, or the result of an attempt made to obtain a general license or permission for the use of such proprietary rights by implementers or users of this specification can be obtained from the IETF on-line IPR repository at http://www.ietf.org/ipr. 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Acknowledgment Funding for the RFC Editor function is currently provided by the Internet Society. Daniel Park, et al. Expires December 24, 2006 [Page 11]