Network Working Group V. Devarapalli Internet-Draft Wichorus Intended status: Standards Track K. Weniger Expires: November 16, 2008 Panasonic P. Eronen Nokia May 15, 2008 Re-direct Mechanism for IKEv2 draft-devarapalli-ipsec-ikev2-redirect-00.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 November 16, 2008. Abstract IKEv2 is a popular protocol for setting up VPN tunnels from a remote location to a gateway so that the VPN client can access services in the network behind the gateway. Currently there is no standard mechanism specified that allows an overloaded VPN gateway to re- direct the VPN client to attach to another gateway. This document proposes a re-direct mechanism for IKEv2. The proposed mechanism can also be used for Mobile IPv6 to enable the home agent to re-direct the mobile node to another home agent. Devarapalli, et al. Expires November 16, 2008 [Page 1] Internet-Draft IKEv2 Re-direct May 2008 Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3 3. IKEv2 Exchange with Redirect . . . . . . . . . . . . . . . . . 4 4. Use of Anycast Addresses with the Re-direct Mechanism . . . . 5 5. Redirect Messages . . . . . . . . . . . . . . . . . . . . . . 6 5.1. REDIRECT_SUPPORTED . . . . . . . . . . . . . . . . . . . . 6 5.2. REDIRECT . . . . . . . . . . . . . . . . . . . . . . . . . 7 5.3. REDIRECTED_FROM . . . . . . . . . . . . . . . . . . . . . 7 6. Security Considerations . . . . . . . . . . . . . . . . . . . 8 7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 8 8. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 9 9. References . . . . . . . . . . . . . . . . . . . . . . . . . . 9 9.1. Normative References . . . . . . . . . . . . . . . . . . . 9 9.2. Informative References . . . . . . . . . . . . . . . . . . 9 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 9 Intellectual Property and Copyright Statements . . . . . . . . . . 11 Devarapalli, et al. Expires November 16, 2008 [Page 2] Internet-Draft IKEv2 Re-direct May 2008 1. Introduction IKEv2 [2] is widely used for setting up IPsec-based VPNs. The IP address of the VPN gateway can be configured on the VPN client. But this does not scale well, when the number of VPN gateways is large. Dynamic discovery of VPN gateways using DNS is quite widely used too. However, using DNS is not flexible when it comes to assigning a VPN gateway to the VPN client based on the load on the VPN gateways. The VPN client typically tries to connect to the IP address of the VPN gateways that appears first in the DNS response. If the VPN tunnel setup fails, then the VPN client tries to attach to the other VPN gateways returned in the DNS response. This document proposes a re-direct mechanism for IKEv2 that enables a VPN gateway to re-direct the VPN client to another VPN gateway, based on load condition. The re-direct is done during the IKE_SA_INIT exchange. The re-direct mechanism can also be used in conjunction with anycast addresses. In this case, anycast address for the cluster of VPN gateways is stored in the DNS instead of a list of unicast IP addresses of the VPN gateways. The re-direct can also happen because of administrative or optimal routing reasons. This document does not attempt to provide an exhaustive list of reasons for re-directing a VPN client to another VPN gateway. Mobile IPv6 [3] uses IKEv2 for mutual authentication between the mobile node and the home agent. IKEv2 is also used for home address configuration and setting up IPsec security associations for protecting Mobile IPv6 signaling messages [4]. The IKEv2 exchange precedes the exchange of Mobile IPv6 signaling messages. Therefore the mechanism described in this document can be also be used by a Mobile IPv6 home agent to re-direct a mobile node to another home agent. There is a Home Agent Switch mechanism available for re-directing a mobile node to another home agent, described in [5]. The Home Agent Switch mechanism can only be used after the binding cache had been created at the home agent for the mobile node. The disadvantage with this is that quite a bit of state is created on the home agent before the mobile node can be re-directed to another home agent. The mechanism described in this document can be used for re-directing a mobile node before any state is created on the home agent. 2. Terminology The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", Devarapalli, et al. Expires November 16, 2008 [Page 3] Internet-Draft IKEv2 Re-direct May 2008 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in [1]. 3. IKEv2 Exchange with Redirect To redirect a IKEv2 session to another VPN gateway, the VPN gateway that initially received the IKE_SA_INIT request selects another VPN gateway and responds to the VPN client with a REDIRECT Notification payload. The mechanism by which the initial VPN gateway selects another VPN gateway is out of scope for this document. The IP address of the selected VPN gateway is sent in the REDIRECT payload. The VPN client indicates support for the IKEv2 redirect mechanism by including a REDIRECT_SUPPORTED notification message in the initial IKE_SA_INIT request. If the IKE_SA_INIT request did not include the REDIRECT_SUPPORTED payload, the responder MUST NOT send the REDIRECT payload to the VPN client. Initiator Responder (initial VPN GW) --------- ------------------------- (IP_I:500 -> Initial_IP_R:500) HDR(A,0), SAi1, KEi, Ni, --> N(REDIRECT_SUPPORTED) (Initial_IP_R:500 -> IP_I:500) <-- HDR(A,0), N(REDIRECT, IP_R) When the VPN client receives the IKE_SA_INIT response with the REDIRECT payload, it initiates a new IKE_SA_INIT exchange with the VPN gateway listed in the REDIRECT payload. The VPN client includes the IP address of the original VPN gateway that re-directed the client. The IKEv2 exchange then proceeds as normal with the selected VPN gateway. Devarapalli, et al. Expires November 16, 2008 [Page 4] Internet-Draft IKEv2 Re-direct May 2008 Initiator Responder (Selected VPN GW) --------- --------------------------- (IP_I:500 -> IP_R:500) HDR(A,0), SAi1, KEi, Ni, --> N(REDIRECTED_FROM, Initial_IP_R) (IP_R:500 -> IP_I:500) <-- HDR(A,B), SAr1, KEr, Nr,[CERTREQ] (IP_I:500 -> IP_R:500) HDR(A,B), SK {IDi, [CERT,] [CERTREQ,] [IDr,]AUTH, SAi2, TSi, TSr} --> (IP_R:500 -> IP_I:500) <-- HDR(A,B), SK {IDr, [CERT,] AUTH, SAr2, TSi, TSr} When this mechanism is used with Mobile IPv6, a mobile node's security associations with its home agent may expire while it still has a valid binding cache entry at the home agent. In this case, the mobile node MUST NOT use an anycast address as the destination address in the IKE_SA_INIT exchange to setup new security associations. It MUST try to setup security associations with its existing home agent. 4. Use of Anycast Addresses with the Re-direct Mechanism The use of anycast addresses will avoid having to configure a particular VPN gateway's IP address in the DNS. Instead, the anycast address that represents the group of VPN gateways is stored in the DNS. When the VPN client performs a DNS lookup for the VPN gateway, it receives the anycast address of the VPN gateway in the DNS response. If an anycast address is returned in response to DNS resolution of an FQDN, the IKEv2 transaction between the VPN client and the VPN gateway is slightly modified. The VPN client sends the IKE_SA_INIT request to the anycast address. The IKE_SA_INIT request is routed to one of the VPN gateways that is part of the anycast group. The VPN gateway that receives the IKE_SA_INIT request responds with an IKE_SA_INIT reply from the anycast address. Devarapalli, et al. Expires November 16, 2008 [Page 5] Internet-Draft IKEv2 Re-direct May 2008 Initiator Responder (any VPN GW) --------- ------------------------- (IP_I:500 -> ANYCAST:500) HDR(A,0), SAi1, KEi, Ni) --> N(REDIRECT_SUPPORTED) (ANYCAST:500 -> IP_I:500) <-- HDR(A,0), N(REDIRECT, IP_R) If the destination address on the IKE_SA_INIT request is an anycast address, the VPN gateway that received the IKE_SA_INIT request MUST include the REDIRECT payload to re-direct the VPN client to a unicast address of one of the VPN gateway. The VPN gateway that received the IKE_SA_INIT request MAY re-direct the client to itself, if it is not overloaded. The rest of the IKEv2 exchange is the same as described in Section 3. 5. Redirect Messages 5.1. REDIRECT_SUPPORTED The REDIRECT_SUPPORTED payload is included in the initial IKE_SA_INIT request by the initiator to indicate support for the IKEv2 re-direct mechanism described in this document. 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Next Payload |C| RESERVED | Payload Length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Protocol ID | SPI Size (=0) | Notify Message Type | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ The 'Next Payload', 'Payload Length', 'Protocol ID', 'SPI Size' and the 'Notify Message Type' fields are the same as described in Section 3.10 of RFC 4306 [2]. The 'SPI Size' field MUST be set to 0 to indicate that the SPI is not present in this message. The 'Payload Length' field MUST be set to '8'. The 'Notify Message Type' field is set to indicate the REDIRECT_SUPPORTED payload . Devarapalli, et al. Expires November 16, 2008 [Page 6] Internet-Draft IKEv2 Re-direct May 2008 5.2. REDIRECT The REDIRECT payload is included in an IKE_SA_INIT response from the responder when the responder wants to re-direct the initiator to another VPN gateway. The message includes the new responder's IP address. 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Next Payload |C| RESERVED | Payload Length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Protocol ID | SPI Size (=0) | Notify Message Type | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | ~ New Responder GW IP Address ~ | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ The 'Next Payload', 'Payload Length', 'Protocol ID', 'SPI Size' and the 'Notify Message Type' fields are the same as described in Section 3.10 of RFC 4306 [2]. The 'SPI Size' field MUST be set to 0 to indicate that the SPI is not present in this message. The 'Payload Length' field MUST be set to either '12' or '24' depending on whether an IPv4 or IPv6 address of the new VPN gateway is sent in the message. The 'Notify Message Type' field is set to indicate the REDIRECT payload . The IP address of the new VPN gateway is carried in the 'New Responder GW IP Address' field. 5.3. REDIRECTED_FROM The REDIRECTED_FROM message type is included in the IKE_SA_INIT request from the initiator to the new VPN gateway to indicate the IP address of the original VPN gateway that re-directed the initiator. The original VPN gateway's IP address is included in the message. 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Next Payload |C| RESERVED | Payload Length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Protocol ID | SPI Size (=0) | Notify Message Type | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | ~ Original Responder GW IP Address ~ | | Devarapalli, et al. Expires November 16, 2008 [Page 7] Internet-Draft IKEv2 Re-direct May 2008 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ The 'Next Payload', 'Payload Length', 'Protocol ID', 'SPI Size' and the 'Notify Message Type' fields are the same as described in Section 3.10 of RFC 4306 [2]. The 'SPI Size' field MUST be set to 0 to indicate that the SPI is not present in this message. The 'Payload Length' field MUST be set to either '12' or '24' depending on whether an IPv4 or IPv6 address of the original VPN gateway is sent in the message. The 'Notify Message Type' field is set to indicate the REDIRECTED_FROM payload . The IP address of the original VPN gateway is carried in the 'Original Responder GW IP Address' field. 6. Security Considerations An eavesdropper on the path between VPN client and server may send a redirect to the client upon receiving an IKE_SA_INIT message from this client. This is no problem regarding DoS attacks for the VPN connection, since an on-path-attacker can as well drop the IKE_SA_INIT requests to prevent VPN access for the client. But an eavesdropper on the path between VPN client and server can redirect a large number of clients to a victim, which is then flooded with IKE_SA_INIT requests. Flooding only happens if many clients initiate IKEv2 exchange at almost the same time, which is considered a rare event. seldom. However, it may happen if a Home Agent/VPN server is shutdown for maintenance and all clients need to be moved to another Home Agent/VPN server or if the on-path attacker forces all IPSec security associations to expire by dropping all received IKEv2 messages. The use of REDIRECTED_FROM payload is intended to discourage a rogue VPN gateway from re-directing a large number of VPN clients to a particular VPN gateway. It does not prevent such a DoS attack. 7. IANA Considerations This document defines three new IKEv2 Notification Message types as described in Section 5. The three Notify Message Types must be assigned values between 16396 and 40959. o REDIRECT_SUPPORTED o REDIRECT o REDIRECTED_FROM Devarapalli, et al. Expires November 16, 2008 [Page 8] Internet-Draft IKEv2 Re-direct May 2008 8. Acknowledgements The use of anycast address with IKEv2 was first described in [6]. It was then added to an early draft version of RFC 5026 and later removed before the RFC was published. Therefore the authors of [6] and RFC 5026 are acknowledged. Thanks to Tero Kivinen for suggesting the use of REDIRECTED_FROM payload. 9. References 9.1. Normative References [1] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. [2] Kaufman, C., "Internet Key Exchange (IKEv2) Protocol", RFC 4306, December 2005. 9.2. Informative References [3] Johnson, D., Perkins, C., and J. Arkko, "Mobility Support in IPv6", RFC 3775, June 2004. [4] Giaretta, G., Kempf, J., and V. Devarapalli, "Mobile IPv6 Bootstrapping in Split Scenario", RFC 5026, October 2007. [5] Haley, B., Devarapalli, V., Deng, H., and J. Kempf, "Mobility Header Home Agent Switch Message", RFC 5142, January 2008. [6] Weniger, K. and F. Dupont, "IKEv2-based Home Agent Assignment in Mobile IPv6/NEMO Bootstrapping", draft-dupont-ikev2-haassign-02 (work in progress), January 2007. Authors' Addresses Vijay Devarapalli Wichorus 3590 North First St San Jose, CA 95134 USA Email: vijay@wichorus.com Devarapalli, et al. Expires November 16, 2008 [Page 9] Internet-Draft IKEv2 Re-direct May 2008 Killian Weniger Panasonic R&D Center Germany Monzastr. 4c Langen 63225 Germany Email: kilian.weniger@eu.panasonic.com Pasi Eronen Nokia P.O. Box 407 FIN-0045 Nokia Group Finland Email: pasi.eronen@nokia.com Devarapalli, et al. Expires November 16, 2008 [Page 10] Internet-Draft IKEv2 Re-direct May 2008 Full Copyright Statement Copyright (C) The IETF Trust (2008). This document is subject to the rights, licenses and restrictions contained in BCP 78, and except as set forth therein, the authors retain all their rights. This document and the information contained herein are provided on an "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY, THE IETF TRUST AND THE INTERNET ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE. Intellectual Property 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. The IETF invites any interested party to bring to its attention any copyrights, patents or patent applications, or other proprietary rights that may cover technology that may be required to implement this standard. Please address the information to the IETF at ietf-ipr@ietf.org. Devarapalli, et al. Expires November 16, 2008 [Page 11]