Network Working Group Y. Xu Internet-Draft Tsinghua Univ. Intended status: Standards Track P. Yang Expires: January 8, 2009 Y. Ma Hitachi (China) R&D Corporation H. Deng China Mobile K. Xu Tsinghua University July 7, 2008 IKE SA Synchronization draft-xu-ike-sa-sync-00 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 January 8, 2009. Xu, et al. Expires January 8, 2009 [Page 1] Internet-Draft IKE SA SYNC July 2008 Abstract It will take a long time to do security association syncronization among IKE/IPsec gateways possibly maintaining huge numbers of IKEv2/ IPsec SAs. The major reason is that the prcocedure of IKEv2 SA re- establishment will incur a time-consuming computation especially in the Diffie-Hellman exchange. In this draft, a new IKE security associations synchronization solution is proposed to reduce the computation by directly transferring the indexed IKE SA from old gateway to new gateway, wherein the most expensive Diffie-Hellman calculation can be avoided. Without some time-consuming IKEv2 exchanges, the huge amount of IKE/IPsec SA synchronization procedures can be finished in a short time. Table of Contents 1. Background . . . . . . . . . . . . . . . . . . . . . . . . . . 3 2. Application scenarios . . . . . . . . . . . . . . . . . . . . 4 2.1. Scenario of failover . . . . . . . . . . . . . . . . . . . 4 2.2. Scenario of load-balance . . . . . . . . . . . . . . . . . 5 3. Details on Proposed solution . . . . . . . . . . . . . . . . . 6 3.1. Overview of the Proposed solution . . . . . . . . . . . . 6 3.2. Key data structure . . . . . . . . . . . . . . . . . . . . 6 3.3. Consideration on Stub handling . . . . . . . . . . . . . . 7 3.4. Consideration on location of Stub . . . . . . . . . . . . 8 3.5. When should Gateways download/update Stub . . . . . . . . 9 3.6. Related new messages . . . . . . . . . . . . . . . . . . . 9 4. Modification on the base IKEv2 protocol . . . . . . . . . . . 11 5. Security Considerations . . . . . . . . . . . . . . . . . . . 12 6. Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . 13 7. Normative References . . . . . . . . . . . . . . . . . . . . . 14 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 15 Intellectual Property and Copyright Statements . . . . . . . . . . 17 Xu, et al. Expires January 8, 2009 [Page 2] Internet-Draft IKE SA SYNC July 2008 1. Background IKEv2 protocol which has been defined by rfc4306[1] provides us a method to negotiate ipsec's key automatically between ipsec clients and gateway. Before negotiating ipsec's key, they should negotiate IKE's SA first. Usually, ipsec client sends IKE_INIT message to gateway with SAi1, KEi, Ni, then gateway chooses some proposal of SAi1 which come to the algorithm for encryption and decryption, also proposal for Diffie-Hellman, and then calculates the Diffie-Hellman, sends IKE_INIT respond message back to ipsec client. At this time, the most important keyring can be generated. After other IKE_AUTH exchange, each other has verified the identity. IKE SA has completely been established. Initiator Responder ----------- ----------- HDR, SAi1, KEi, Ni --> < -- HDR, SAr1, KEr, Nr, [CERTREQ] HDR, SK {IDi, [CERT,] [CERTREQ,] [IDr,],AUTH, SAi2, TSi, TSr} --> < -- HDR, SK {IDr, [CERT,] AUTH, SAr2, TSi, TSr} Figure 1: IKE_INIT and IKE_AUTH exchanges But it seems too time consuming to establish an IKE SA in these first two exchanges, especially Diffie-Hellman computation, as we know it is too slow to compute, so it is a challenge to the new gateway when thousands of, even more, ipsec clients are transfered from old gateway to new the gateway. Xu, et al. Expires January 8, 2009 [Page 3] Internet-Draft IKE SA SYNC July 2008 2. Application scenarios 2.1. Scenario of failover IPsec old new/old client Gateway gateway | | | | IKE/IPsec SAs | | |< ========================== >| | | | | | | | | O Fail of old GW | | | | O detect the fail | | | of old GW | | | | | | new IKE init procedure | |< =================================================== >| | | | | set up other child IPsec SAs | |< =================================================== >| | | | Figure 2: failover scenarios In this scenario, ipsec clients has established IKE connections with old gateway, then for some reason, old gateway fails, after a short time, ipsec client knows old gateway has failed(how to know gateway fail is out of our scope), and reconnect to the old gateway or another new gateway. It must be a rush hour, so many ipsec clients connect to the gateway in the same time, as we know, re-establish IKE security associations(SAs) is too slow to compute because of Diffie- Huffman(DH). The problem statement and goals for a failover solution are described in [2]. Xu, et al. Expires January 8, 2009 [Page 4] Internet-Draft IKE SA SYNC July 2008 2.2. Scenario of load-balance IPsec old new client Gateway gateway | | | | IKE/IPsec SAs | | |< ========================== >| | | | | | | | | O overload of old GW | | | | O detect the overload | | | of old GW | | | | | | new IKE init procedure | |< =================================================== >| | | | | set up other child IPsec SAs | |< =================================================== >| | | | Figure 3: load-balance scenarios In this scenario, after establishing IKE connections between ipsec clients and old gateway, old gateway may not fail, owing to traffic engineer or old gateway is over-loading, ipsec clients knows they should stop the connection with old gateway and establish the connection with new gateway(how to know new gateway is also out of our scope). If many ipsec clients are transferd from old gateway to new gateway, as same as failover, it is a challenge to new gateway to establish IKE SA in the same time. Xu, et al. Expires January 8, 2009 [Page 5] Internet-Draft IKE SA SYNC July 2008 3. Details on Proposed solution 3.1. Overview of the Proposed solution In this section, we define a new data structure stub which has the most important information of IKE SA, and gateway can use this data structure to fast rebuild IKE SA. We expand the IKE_INIT exchange, and add a payload called IKE_SA_SYN. because old gateway's IP address and SPI can index the unique stub of IKE SA, so we make them in SYN payload to index stub. Initiator Responder ----------- -------------- HDR, SAi1, KEi, Ni, [SYN] ---> < -- HDR, Nr Figure 4: IKE SA synchronization exchange Once ipsec client has to be transfer from old gateway to new gateway, it can send IKE_INIT which is extended a SYN payload as optional, the IKE SYN payload has some index informatin such as old gateway ip address and old gateway's SPI, if old/new gateway finds IKE_SA_SYN payload in the IKE_INIT message, it can fast re-establish IKE SA without DH computation and IKE_AUTH exchange, and IKE_INIT respond with olny Nr to ipsec client to tell it IKE_SA has been re- established. If new gateway does not support IKE_SA_SYN or not find the proper stub, it can establish IKE SA by IKE_INIT and IKE_AUTH exchanges, or just drop the packet. 3.2. Key data structure the stub data structure should conclude all these informations. (We have referenced "ticket" proposal[3].) o IDi, IDr. o SPIi, SPIr. o SAr (the accepted proposal). o SK_d. o shared secret. o old gateway's ip address. We propose using c++ STL map data structure to store this stub message, use old gateway's ip address and SPI as key, and the other properties as value. You also can use other data structure to hash old gateway's ip address and SPI to other properties. SAr have the encrypt and decrypt algorithm, and shared secrect is the DH exchange's result, we can calculate the IKE SA's keyring as rekey Xu, et al. Expires January 8, 2009 [Page 6] Internet-Draft IKE SA SYNC July 2008 process. It will be very quick. 3.3. Consideration on Stub handling 1) generation When IKE SA has been established(after first two exchanges), the gateway extracts the stub from IKE SA and store it. 2) propagation After extrcted from IKE SA, stubs should be updated to infrastructure such as stub bank(we will define next section) or other gateway. 3) look-up As the old gateway's ip address and spi can index the unique stub. Such as map data structure, hash operation is very light-weighted, you can find it very fast. 4) usage In some senarios, the ipsec clients want to synchrinazation IKE SA with a gateway. Then the ipsec clients send IKE_INIT message with SYN payload to old/new gateway, gateway will get old gateway's IP address and SPI from IKE_SA SYN payload, and find the stub in local machine database (maybe download the stub from other gateway or stub bank before), then rebuild the IKE SA. If IKE SA has been established, gateway sends IKE_INIT respond(only conclude HDR and Nr) to ipsec client. then create-child-sa exchanges, and so on. The following signaling shall be supported by IKE/IPsec gateways to communicate with Stub. o Update Stub: Gateway updates its stub to infrastructure once new stub has been established, and the infrastructure store them by gateway's IP address and SPI in a hash data structure. o GET Stub: Gateway receives IKE_SA SYN payload, then it send GET Stub to ask for some stubs, the infrastructure index the stubs. o Download Stub: After infrastructure finds the stubs, it pushs the stubs to gateway. Xu, et al. Expires January 8, 2009 [Page 7] Internet-Draft IKE SA SYNC July 2008 3.4. Consideration on location of Stub 1. Centralized infrastructure ipsec old/new stub client gateway bank || || Update Stub || || HDR,SAi1,KEi,Ni,SYN||------------------->|| ||------------------->|| GET Stub || ||< ------------------||------------------->|| || HDR,Nr || Download Stub || || ||< ------------------|| || || || Figure 5: centralized structure This proposal has a centralized Stub Bank server, gateway doesn't need local stub database. a) After IKE connection has been established, old gateway update the stub to stub bank. b) Once transferring ipsec from old gateway to old/new gateway, ipsec client send IKE_INIT with SYN payload. c) When old/new gateway receives IKE_INIT with SYN payload, it ask Stub Bank for stub via GET Stub signaling. d) stub bank push proper stub to old/new gateway. old/new gateway find the proper stub and rebuild IKE SA, then send HDR, Nr to tell ipsec client that it has accepted the stub. 2. Distributed infrastructure ipsec old/new Old GW client gateway Stub || || || || HDR,SAi1,KEi,Ni,SYN|| Update Stub || ||------------------->||< ------------------|| ||< ------------------|| || || HDR,Nr || || Figure 6: distributed structure This structure doesn't have centralized Stub Bank, and all gateway must have local stub database, if there is stub in local database, it Xu, et al. Expires January 8, 2009 [Page 8] Internet-Draft IKE SA SYNC July 2008 will find the stub in local database, otherwise, it will GET the stub from other gateway. a) After IKE connection has been established, old gateway update the stub to stub bank. b) Once transferring ipsec from old gateway to old/new gateway, ipsec client send IKE_INIT with SYN payload. c) old/new gateway find the proper stub and rebuild IKE SA, then send HDR, Nr to tell ipsec client that it has accepted the stub. Gateway has to store stubs in distributed structure, but it seems more simple than centralized structure. Also, these two proposals can mix together, other gateway also can be Stub Bank. 3.5. When should Gateways download/update Stub Because of the stub is not sensitive with time, we can assemble the stub messages to reduce the message number in update event. The single gateway can get many stubs at a time in download event. The gateway may also update the stubs in bundles whenever it was thought to be necessary 3.6. Related new messages 1)IKE_SA_SYN Payload format 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 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | GateWay's SPI | | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | GateWay's IP Address | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ C bit is the direction of this message. 2) Stub related signaling Header Format Xu, et al. Expires January 8, 2009 [Page 9] Internet-Draft IKE SA SYNC July 2008 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| type | Payload Length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ type number update 01 get 10 download 11 reserved 00 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| RESERVED | Payload Length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | | PAYLOAD CONTENT | ~ ~ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Xu, et al. Expires January 8, 2009 [Page 10] Internet-Draft IKE SA SYNC July 2008 4. Modification on the base IKEv2 protocol As our principle, The base IKEv2 protocol should be changed as little as possible. In the proposal, three aspects require slight modification on IKEv2 protocol 1) new IKE message: IKE_SA_SYN 2) modification on the state machine As ipsec client, it can send IKE_INIT message with SYN payload as usual, and if it receives IKE_INIT respond only have Nr, it will calculate the new ike sa like rekey. And set state to ike sa has been established. As gateway, once receives IKE_SA_SYN payload, will firstly find the proper stub, if find the stub, it will fast re-establish IKE SA, send IKE_INIT respond with Nr only to ipsec client, and set state to ike sa has been established. 3) The gateway should support the Stub related functions like extract_stub, update_stub and get_stub Xu, et al. Expires January 8, 2009 [Page 11] Internet-Draft IKE SA SYNC July 2008 5. Security Considerations the security framework of IKEv2 protocol will not be compromised in this solution. 1) index is a light-weighted operation, and no stub, no response. 2) The Gateway can use SAr1, KEi to verify the identity, such as ID property. But it depends on the configuration of operators. 3) Even if the index is right, ipsec client cannot rebuild IKE_SA, the communication can't last, after a little time, the IKE_SA in gateway will be deleted. Xu, et al. Expires January 8, 2009 [Page 12] Internet-Draft IKE SA SYNC July 2008 6. Conclusion In this draft, a new solution is proposed to do IKE SA synchrinization for fast re-establishment of IKE SA. It will remove the most time-consuming IKEv2 exchanges, which makes it much faster to transfer millions of ipsec clients from old gateway to old/new gateway. And the proposal in this draft will only slightly modify the base IKEv2 protocol with a new logical IKE SA Stub in the network. Xu, et al. Expires January 8, 2009 [Page 13] Internet-Draft IKE SA SYNC July 2008 7. Normative References [Narayanan06] Narayanan, V., "IPsec Gateway Failover and Redundancy Problem Statement and Goals", draft-vidya-ipsec-failover-ps-00.txt (work in progress), December 2006. [RFC4306] Kaufman, C., "Internet Key Exchange (IKEv2) Protocol", RFC 4306, December 2005. [Sheffer07] Xie, Y., "Stateless Session Resumption for the IKE Protocol", draft-sheffer-ike-session-resumption-00.txt (work in progress), January 2007. Xu, et al. Expires January 8, 2009 [Page 14] Internet-Draft IKE SA SYNC July 2008 Authors' Addresses Yan Xu Tsinghua Univ. Department of Computer Science Tsinghua University Haidian District Beijing, 100088 P.R. China Email: xydkl@163.com Peng Yang Hitachi (China) R&D Corporation 301, North Wing, Tower C Raycom Infotech Park 2 kexueyuan Nanlu Haidian District Beijing, 100080 P.R. China Phone: +861082862918(ext.)328 Email: pyang@hitachi.cn Yuanchen Ma Hitachi (China) R&D Corporation 301, North Wing, Tower C Raycom Infotech Park 2 kexueyuan Nanlu Haidian District Beijing, 100080 P.R. China Phone: +861082862918(ext.)327 Email: ycma@hitachi.cn Hui Deng China Mobile Xu, et al. Expires January 8, 2009 [Page 15] Internet-Draft IKE SA SYNC July 2008 Xu Ke Tsinghua University Department of Computer Science Tsinghua University Haidian District Beijing, 100088 P.R. China Email: xuke@mail.tsinghua.edu.cn Xu, et al. Expires January 8, 2009 [Page 16] Internet-Draft IKE SA SYNC July 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. 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