--- 1/draft-ietf-ipsecme-ipsecha-protocol-01.txt 2010-10-25 15:16:38.000000000 +0200 +++ 2/draft-ietf-ipsecme-ipsecha-protocol-02.txt 2010-10-25 15:16:38.000000000 +0200 @@ -1,758 +1,822 @@ Network Working Group R. Singh, Ed. Internet-Draft G. Kalyani Intended status: Standards Track Cisco -Expires: April 14, 2011 Y. Nir +Expires: April 28, 2011 Y. Nir Check Point D. Zhang Huawei - October 11, 2010 + October 25, 2010 - Protocol Support for High Availability IKEv2/IPsec - draft-ietf-ipsecme-ipsecha-protocol-01 + Protocol Support for High Availability of IKEv2/IPsec + draft-ietf-ipsecme-ipsecha-protocol-02 Abstract - IKEv2 and IPsec protocols are widely used for deploying VPN. In - order to make such VPN highly available, more scalable and failure- - prone, these VPNs are implemented as IKEv2/IPsec Highly Available - (HA) cluster. But there are many issues in IKEv2/IPsec HA cluster. - The draft "IPsec Cluster Problem Statement" enumerates all the issues - encountered in IKEv2/IPsec HA cluster environment. + The IPsec protocol suite is widely used for the deployment of virtual + private networks (VPNs). In order to make such VPNs highly + available, more scalable and failure-resistant, these VPNs are + implemented as IPsec High Availability (HA) clusters. However there + are many issues in IPsec HA clustering, and in particular in IKEv2 + clustering. An earlier document, "IPsec Cluster Problem Statement", + enumerates the issues encountered in the IKEv2/IPsec HA cluster + environment. This document attempts to resolve these issues with the + least possible change to the protocol. - This document proposes an extension to IKEv2 protocol to solve main - issues of "IPsec Cluster Problem Statement" in Hot Standby cluster - and gives implementation advice for other issues. The main issues to - be solved are: - o IKEv2 Message Id synchronization : This is done by syncing up - expected send and receive message Id values with the peer and - updating the values at the newly active cluster member after the - failover. - o IPsec Replay Counter synchronization : This is done by syncing up - bumped up outgoing SA replay counters values with peer and - updating the values at the newly active cluster member after the - failover. + This document proposes an extension to the IKEv2 protocol to solve + the main issues of "IPsec Cluster Problem Statement" in the commonly + deployed hot-standby cluster, and provides implementation advice for + other issues. The main issues to be solved are the synchronization + of IKEv2 Message ID counters, and of IPsec Replay Counters. Status of this Memo This Internet-Draft is submitted in full conformance with the provisions of BCP 78 and BCP 79. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF). Note that other groups may also distribute working documents as Internet-Drafts. The list of current Internet- Drafts is at http://datatracker.ietf.org/drafts/current/. 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." - This Internet-Draft will expire on April 14, 2011. + This Internet-Draft will expire on April 28, 2011. Copyright Notice Copyright (c) 2010 IETF Trust and the persons identified as the document authors. All rights reserved. This document is subject to BCP 78 and the IETF Trust's Legal Provisions Relating to IETF Documents (http://trustee.ietf.org/license-info) in effect on the date of publication of this document. Please review these documents carefully, as they describe your rights and restrictions with respect to this document. Code Components extracted from this document must include Simplified BSD License text as described in Section 4.e of the Trust Legal Provisions and are provided without warranty as described in the Simplified BSD License. Table of Contents - 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4 - 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 5 - 3. Issues solved from IPsec Cluster Problem Statement . . . . . . 6 - 4. IKEv2/IPsec SA Counter Synchronization Problem . . . . . . . . 6 - 5. IKEv2/IPsec SA Counter Synchronization Solution . . . . . . . 8 - 6. IKEv2/IPsec synchronization notification payloads . . . . . . 9 - 6.1. IKEV2_MESSAGE_ID_SYNC_SUPPORTED . . . . . . . . . . . . . 10 + 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 + 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 4 + 3. Issues Resolved from IPsec Cluster Problem Statement . . . . . 5 + 4. The IKEv2/IPsec SA Counter Synchronization Problem . . . . . . 5 + 5. Counter Synchronization Solution . . . . . . . . . . . . . . . 7 + 6. IKEv2/IPsec Synchronization Notification Payloads . . . . . . 9 + 6.1. IKEV2_MESSAGE_ID_SYNC_SUPPORTED . . . . . . . . . . . . . 9 6.2. IPSEC_REPLAY_COUNTER_SYNC_SUPPORTED . . . . . . . . . . . 10 - 6.3. IKEV2_MESSAGE_ID_SYNC . . . . . . . . . . . . . . . . . . 11 + 6.3. IKEV2_MESSAGE_ID_SYNC . . . . . . . . . . . . . . . . . . 10 6.4. IPSEC_REPLAY_COUNTER_SYNC . . . . . . . . . . . . . . . . 11 - 7. Details of implementation . . . . . . . . . . . . . . . . . . 12 - 8. Step-by-Step details . . . . . . . . . . . . . . . . . . . . . 13 + 7. Implementation Details . . . . . . . . . . . . . . . . . . . . 12 + 8. Step by Step Details . . . . . . . . . . . . . . . . . . . . . 13 9. Security Considerations . . . . . . . . . . . . . . . . . . . 14 10. Interaction with other drafts . . . . . . . . . . . . . . . . 14 11. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 15 - 12. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 16 - 13. Change Log . . . . . . . . . . . . . . . . . . . . . . . . . . 16 - 13.1. Draft -01 . . . . . . . . . . . . . . . . . . . . . . . . 16 - 13.2. Draft -00 . . . . . . . . . . . . . . . . . . . . . . . . 16 - 14. References . . . . . . . . . . . . . . . . . . . . . . . . . . 17 - 14.1. Normative References . . . . . . . . . . . . . . . . . . . 17 + 12. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 15 + 13. Change Log . . . . . . . . . . . . . . . . . . . . . . . . . . 15 + 13.1. Draft -02 . . . . . . . . . . . . . . . . . . . . . . . . 16 + 13.2. Draft -01 . . . . . . . . . . . . . . . . . . . . . . . . 16 + 13.3. Draft -00 . . . . . . . . . . . . . . . . . . . . . . . . 16 + 14. References . . . . . . . . . . . . . . . . . . . . . . . . . . 16 + 14.1. Normative References . . . . . . . . . . . . . . . . . . . 16 14.2. Informative References . . . . . . . . . . . . . . . . . . 17 - Appendix A. IKEv2 Message Id examples . . . . . . . . . . . . . . 17 + Appendix A. IKEv2 Message ID Sync Examples . . . . . . . . . . . 17 + A.1. Normal Failover - Example 1 . . . . . . . . . . . . . . . 17 + A.2. Normal Failover - Example 2 . . . . . . . . . . . . . . . 18 + A.3. Simultaneous Failover . . . . . . . . . . . . . . . . . . 18 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 18 1. Introduction - IKEv2 is used for deploying IPsec-based VPNs. In order to make such - VPN highly available, more scalable and failure-prone, these VPNs are - implemented as IKEv2/IPsec Highly Available (HA) cluster. But there - are many issues in IKEv2/IPsec HA cluster. The draft "IPsec Cluster - Problem Statement" enumerates all the issues encountered in IKEv2/ - IPsec HA cluster. - - In case of Hot Standby cluster implementation of IKEv2/IPsec based - VPNs, the IKEv2/IPsec session gets established with the peer and the - active member of cluster. After that, the active member syncs/ - updates the IKE/IPsec SA state to the standby member of the cluster. - This primary SA state sync-up is done on SA bring up and/or rekey. - Doing SA state synchronization/updation between active and peer - member for each IKE and IPsec message standby cluster is very costly, - so normally its done periodically. So, when "failover" event happens - in the cluster, first "failover' is detected by the standby member - and then it becomes active member and it takes considerable time. - During the time of failover and standby member becoming newly active - member, the peer is unaware of failover and keeps sending IKE request - and IPsec packets to the cluster which is allowed as per IKEv2 and - IPsec windowing feature. Now, newly active member after coming up - finds the mismtach in IKE message Id's and IPsec replay counters. - Please see Section 4 for more details. + The IPsec protocol suite, including IKEv2, is a major building block + of virtual private networks (VPNs). In order to make such VPNs + highly available, more scalable and failure-resistant, these VPNs are + implemented as IKEv2/IPsec Highly Available (HA) cluster. However + there are many issues with the IKEv2/IPsec HA cluster. The problem + statement draft Section 4 enumerates the issues around the IKEv2/ + IPsec HA cluster solution. - This document proposes an extension to IKEv2 protocol to solve main - issues of IKE message id sync and IPsec SA replay counter sync and - gives implementation advice for others. Here is summary of solutions - provided in this document: + In the case of a hot-standby cluster implementation of IKEv2/IPsec + based VPNs, the IKEv2/IPsec session is first established between the + peer and the active member of the cluster. Later, the active member + continuously syncs/updates the IKE/IPsec SA state to the standby + member of the cluster. This primary SA state sync-up takes place + upon each SA bring-up and/or rekey. Performing the SA state + synchronization/update for every single IKE and IPsec message is very + costly, so normally it is done periodically. As a result, when the + failover event happens, this is first detected by the standby member + and, possibly after a considerable amount of time, it becomes the + active member. During this failover process the peer is unaware of + the failover event, and keeps sending IKE requests and IPsec packets + to the cluster, as in fact it is allowed to do because of the IKEv2 + windowing feature. After the newly-active member starts, it detects + the mismatch in IKE Message ID values and IPsec replay counters and + needs to resolve this situation. Please see Section 4 for more + details of the problem. - IKEv2 Message Id synchronization :This is done by syncing up expected - send and receive message Id values with the peer and updating the - values at the newly active cluster member after the failover. + This document proposes an extension to the IKEv2 protocol to solve + main issues of IKE Message ID synchronization and IPsec SA replay + counter synchronization and gives implementation advice for others. + Following is a summary of the solutions provided in this document: - IPsec Replay Counter synchronization : This is done by syncing up - bumped up outgoing SA replay counters values with peer and updating - the values at the newly active cluster member after the failover + o IKEv2 Message ID synchronization: this is done by syncing up the + expected send and receive Message ID values with the peer, and + updating the values at the newly active cluster member. + o IPsec Replay Counter synchronization: this is done by incrementing + the cluster's outgoing SA replay counter values by a "large" + number, and synchronizing these values with the peer. The peer + send its outgoing SA reply counter in the response. - Though this document describes the IKEv2 message Id sync and IPsec - replay counter synchronization in context of IPsec HA cluster, the - solution provided is genetic and can be used in other scenarios where - IKEv2 message Id sync or IPsec SA replay counters sync is required. + Although this document describes the IKEv2 Message ID and IPsec + replay counter synchronization in the context of an IPsec HA cluster, + the solution provided is generic and can be used in other scenarios + where IKEv2 Message ID or IPsec SA replay counter synchronization may + be required. - While some IPsec HA implementation suffers from IKEv2 message Id - synchronization problem, some other implementation suffers from IPsec - replay counter synchronization. Both of these problem are handled - separately, using separate notify for each problem. This provides - the flexibility of implementing IKEv2 message Id synchronization or - IPsec replay counter synchronization or both. + Implementations differ on the need to synchronize the IKEv2 Message + ID and/or IPsec replay counters. Both of these problem are handled + separately, using a separate notification for each capability. This + provides the flexibility of implementing either or both of these + solutions. 2. Terminology 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 RFC 2119 [RFC2119]. - - "SA Counter SYNC Request" is the information exchange request defined - in this document to synchronize the IKEv2/IPsec SA counter - information between member of the cluster and the peer. - - "SA Counter SYNC Response" is the information exchange response - defined in this document to synchronize the IKEv2/IPsec SA counter - information between member of the cluster and the peer. - - Below are the terms taken from [IPsec Cluster Problem Statement] with - added information in context of this document. - - "Hot Standby Cluster", or "HS Cluster" is a cluster where only one of - the members is active at any one time. This member is also referred - to as the "active", whereas the other(s) are referred to as - "standbys". VRRP ([RFC5798]) is one method of building such a - cluster. The goal of Hot Standby Cluster is that it creates illusion - of single virtual gateway to the peer(s). - - "Active Member" is the primary member in the Hot Standby cluster. It - is responsible for forwarding packets for the virtual gateway. - - "Standby Member" is the primary backup router. The member takes - control i.e. becomes active member after the "failover" event. + document are to be interpreted as described in [RFC2119]. - "Peer" is the IKEv2/IPsec endpoint which establishes VPN connection - with Hot Standby cluster. The Peer knows Hot Standby Cluster by - single cluster's IP address. In case of "failover", the standby - member of the cluster becomes active, so the peer normally doesn't - notice that "failover" has occurred in the cluster. + "SA Counter Synchronization Request/Response" are the request viz. + response of the information exchange defined in this document to + synchronize the IKEv2/IPsec SA counter information between one member + of the cluster and the peer. - "Multiple failover" is the situation when in a cluster with three or - more nodes failover happens in rapid succession. The protocol and - implementation must be able to handle multiple failover i.e. able to - handle new failover even if they are still processing the old - failover. + Some of the terms listed below are reused from [RFC6027] with further + clarification in the context of the current document. - "Simultaneous failover" is the situation when in a cluster the - failover happens at the both ends at the same time. The protocol and - implementation must be able to handle simultaneous failover. + o "Hot Standby Cluster", or "HS Cluster" is a cluster where only one + of the members is active at any one time. This member is also + referred to as the "active" member, whereas the other(s) are + referred to as "standby" members. VRRP [RFC5798] is one method of + building such a cluster. The goal of Hot Standby Cluster is that + it creates illusion of single virtual gateway to the peer(s). + o "Active Member" is the primary member in the Hot-Standby cluster. + It is responsible for forwarding packets on behalf of the virtual + gateway. + o "Standby Member" is the primary backup member. This member takes + control, i.e. becomes the active member, after the failover event. + o "Peer" is an IKEv2/IPsec endpoint that maintains a VPN connection + with the Hot-Standby cluster. The Peer identifies the cluster by + the cluster's (single) IP address. If a failover event occurs, + the standby member of the cluster becomes active, and the peer + normally doesn't notice that failover has taken place. + o "Failover Count" is a global failover event counter maintained by + the HA cluster and incremented by 1 upon each failover event in + the HA cluster. All members of the HA cluster share the failover + count. + o "Multiple failover" is the situation where, in a cluster with + three or more members, failover happens in rapid succession. It + is our goal that the implementation should be able to handle this + situation, i.e. to handle the new failover event even if it is + still processing the old failover. + o "Simultaneous failover" is the situation where two clusters have a + VPN connection between them, and failover happens at the both ends + at the same time. It is our goal that implementation should be + able to handle simultaneous failover. - The generic term IKEv2/IPsec SA counters is used throughout. By - IKEv2 SA counter stands for IKEv2 message ids and IPsec SA counter - stands for IPsec SA replay counters which are used to provide - optional anti-replay feature. + The generic term "IKEv2/IPsec SA Counters" is used throughout this + document. This term refers to both IKEv2 Message ID counters + (mandatory, and used to ensure reliable delivery as well as to + protect against message replay in IKEv2) and IPsec SA replay counters + (optional, and used to provide the IPsec anti-replay feature). -3. Issues solved from IPsec Cluster Problem Statement +3. Issues Resolved from IPsec Cluster Problem Statement - IPsec Cluster Problem Statement defines the problems encountered in - IPsec Clusters. . The problems along with their section names as - given in the statement are as follows. + The IPsec Cluster Problem Statement [RFC6027] enumerates the problems + raised by IPsec clusters. The following table lists the problem + statement's sections that are resolved by this document. o 3.2. Lots of Long Lived State o 3.3. IKE Counters o 3.4. Outbound SA Counters o 3.5. Inbound SA Counters - o 3.6. Missing Synch Messages + o 3.6. Missing Synchronization Messages o 3.7. Simultaneous use of IKE and IPsec SAs by Different Members * 3.7.1. Outbound SAs using counter modes o 3.8. Different IP addresses for IKE and IPsec o 3.9. Allocation of SPIs - This document solves the main issues using the protocol extension, - and provides implementation advice for other issues, given as - follows. - o 3.2 This section mentions that there's lots of state that needs to - be synchronized. If state is not synchronized, it's not really an - interesting cluster - failover will be just like a reboot, so the - issue need not be solved with protocol extensions. + The main problem areas are solved using the protocol extension + defined below, and additionally this document provides implementation + advice for other issues, given as follows. + o 3.2 This section mentions that there is a large amount of state + that needs to be synchronized. However if state is not + synchronized, this is not really an interesting cluster: failover + is equivalent to a reboot of the cluster member, and so the issue + need not be solved with protocol extensions. o 3.3, 3.4,3.5, and 3.6 are solved by this document. Please see Section 4, for more details. - o 3.7 is the problem to be solved while building clusters. However, - the peers should be mandated to accept multiple parallel SAs for - 3.7.1 - o 3.8 can be solved by using IKEv2 Redirect Mechanism [RFC-5685]. - o 3.9 is the problem about avoiding collision of same SPI's among - the cluster members. This is outside the scope of the document - since this has to be solved within the context of the cluster and - not with the peer. + o 3.7 is an implementation problem that needs to be solved while + building IPsec clusters. However, the peers should be required to + accept multiple parallel SAs for 3.7.1. + o 3.8 can be solved by using the IKEv2 Redirect mechanism [RFC5685]. + o 3.9 discusses the avoidance of collisions where the same SPI value + is used by multiple cluster members. This is outside the + document's scope since the problem needs to be solved internally + to the cluster and does not involve the peer. -4. IKEv2/IPsec SA Counter Synchronization Problem +4. The IKEv2/IPsec SA Counter Synchronization Problem - IKEv2 RFC states that "An IKE endpoint MUST NOT exceed the peer's - stated window size for transmitted IKE requests". + The IKEv2 protocol [RFC5996] states that "An IKE endpoint MUST NOT + exceed the peer's stated window size for transmitted IKE requests". - As per the protocol, all IKEv2 packets follows request-response + All IKEv2 messages are required to follow a request-response paradigm. The initiator of an IKEv2 request MUST retransmit the request, until it has received a response from the peer. IKEv2 introduces a windowing mechanism that allows multiple requests to be outstanding at a given point of time, but mandates that the sender - window does not move until the oldest message sent from one peer to - another is acknowledged. Loss of even a single packet leads to - repeated re-transmissions followed by an IKEv2 SA teardown if the re- - transmissions are unacknowledged. + window should not move until the oldest message sent from one peer to + another is acknowledged. Loss of even a single message leads to + repeated retransmissions followed by an IKEv2 SA teardown if the + retransmissions are unacknowledged. - IPsec Hot Standby Cluster is required to ensure that in case of - failover of active member, the standby member becomes active - immediately. The standby member is expected to have the exact values - of message id fields of active member before failover. Even with the - best efforts to update the message Id values from active to standby - member, the values at standby member can be stale due to following - reasons: - o Standby member is unaware of the last message that was received - and acknowledged by the older active member as failover could have - happened before the standby could be updated. - o Standby member does not have information about on-going - unacknowledged requests of active member before the failover - event. So after failover event when standby member becomes - active, it can not re-transmit those requests. + An IPsec Hot Standby Cluster is required to ensure that in the case + of failover, the standby member becomes active immediately. The + standby member is expected to have the exact value of the Message ID + counter as the active member had before failover. Even assuming the + best effort to update the Message ID values from active to standby + member, the values at the standby member can still be stale due to + the following reasons: + o The standby member is unaware of the last message that was + received and acknowledged by the previously active member, as the + failover event could have happened before the standby member could + be updated. + o The standby member does not have information about on-going + unacknowledged requests received by the previously active member. + As a result after the failover event, the newly active member + cannot retransmit those requests. - When a standby member takes over as the active member, it would start - the message id ranges from previously updated values. This would - make it reject requests from the peer, since the values would be - stale. As a sender, the standby member may end up reusing a stale - message id which will cause the peer to drop the request. Eventually - there is a high probability of the IKEv2 and corresponding IPsec SAs - getting torn down simply because of a transitory message id mis-match - and re-transmission of requests. This is not a desirable feature of - HA. Even after updating standby member periodically the cluster can - loose IKE and so all IPsec SA due to message id i.e. SA counter - mismatch. + When a standby member takes over as the active member, it can only + initialize the Message ID values from the previously updated values. + This would make it reject requests from the peer when these values + are stale. Conversely, the standby member may end up reusing a stale + Message ID value which would cause the peer to drop the request. + Eventually there is a high probability of the IKEv2 and corresponding + IPsec SAs getting torn down simply because of a transitory Message ID + mismatch and retransmission of requests, negating the benefits of the + high availability cluster despite the periodic update between the + cluster members. - Similar issue is observed in IPsec counters also if anti-replay - protection/ESN is implemented. Even with the best efforts of syncing - the ESP and AH SA counter numbers from active to stand by member , - there is a chance that the stand-by member would have stale counter - values. The standby member would then send the stale counter - numbers. The peer would reject/drop such packets since in case of - anti-replay protection feature, duplicate use of counters are not - allowed. In case of IPsec it is OK to skip some counter values and - start with the higher counter values. + A similar issue is also observed with IPsec anti-replay counters if + anti-replay protection/ESN is implemented, which is commonly the + case. Regardless of how well the ESP and AH SA counters are + synchronized from the active to the standby member, there is a chance + that the standby member would end up with stale counter values. The + standby member would then use those stale counter values when sending + IPsec packets. The peer would reject/drop such packets since when + the anti-replay protection feature is enabled, duplicate use of + counters is not allowed. Note that IPsec allows the sender to skip + some counter values and continue sending with higher counter values. - Hence a mechanism is required in HA to ensure that the standby member - has correct values of message Id values and IPsec counters, so that - sessions are not torn down just because of mismatching counters. + We conclude that a mechanism is required to ensure that the standby + member has correct Message ID and IPsec counter values when it + becomes active, so that sessions are not torn down as a result of + mismatched counters. -5. IKEv2/IPsec SA Counter Synchronization Solution +5. Counter Synchronization Solution - When the standby member becomes the active member after failover - event in the cluster, the standby member would send an authenticated - IKEv2 request to the peer to send its values of SA counters. + In general, when the standby member becomes the active member after + the failover event, the standby member sends an authenticated IKEv2 + request to the peer, asking it to send its SA counter values. - The standby member would then update its values of SA counters and - then start sending/receiving the requests. + The standby member then updates its own SA counter values and can + resume normally sending and receiving protocol messages. - First, the peer MUST negotiate its ability to support IKEv2 message - Id synchronization information with active member of the cluster by - sending the IKEV2_MESSAGE_ID_SYNC_SUPPORTED notification in IKE_AUTH + First, the peer MUST negotiate its ability to support IKEv2 Message + ID synchronization with the active member of the cluster by sending + the IKEV2_MESSAGE_ID_SYNC_SUPPORTED notification in the IKE_AUTH exchange. - Similarly to support IPsec replay counter synchronization, the peer - MUST negotiate its ability to support IPsec replay counter - synchronization with active member of the cluster by sending - IPSEC_REPLAY_COUNTER_SYNC_SUPPORTED notification in IKE_AUTH - exchange. + Similarly, to support IPsec Replay Counter synchronization, the peer + MUST negotiate this capability with the active member of the cluster + by sending the IPSEC_REPLAY_COUNTER_SYNC_SUPPORTED notification in + the IKE_AUTH exchange. Peer Active Member - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - HDR, SK {IDi, [CERT], [CERTREQ], [IDr], AUTH, - N[IKEV2_MESSAGE_ID_SYNC_SUPPORTED], - N[IPSEC_REPLAY_COUNTER_SYNC_SUPPORTED], + [N(IKEV2_MESSAGE_ID_SYNC_SUPPORTED),] + [N(IPSEC_REPLAY_COUNTER_SYNC_SUPPORTED),] SAi2, TSi, TSr} ----------> -<---------- HDR, SK {IDr, [CERT+], [CERTREQ+], AUTH, - N[IKEV2_MESSAGE_ID_SYNC_SUPPORTED], - N[IPSEC_REPLAY_COUNTER_SYNC_SUPPORTED], SAr2, TSi, TSr} +<-------- HDR, SK {IDr, [CERT+], [CERTREQ+], AUTH, + [N(IKEV2_MESSAGE_ID_SYNC_SUPPORTED),] + [N(IPSEC_REPLAY_COUNTER_SYNC_SUPPORTED),] SAr2, TSi, TSr} - When peer and active member both support SA counter synchronization, - the active member MUST sync/update SA counter synchronization - capability to the standby member after the establishment of the IKE - SA . So that standby member is aware of the capability and can use - it when it becomes the active member after failover event. + When the peer and active member both support SA counter + synchronization, the active member MUST inform the standby member of + the SA counter synchronization capability after the establishment of + the IKE SA. The standby member can then use this capability when it + becomes the active member after a failover event. - After failover event, when the standby member becomes the active - member, it has to request the peer for the SA counters. Standby - member would initiate the SYNC Request with an INFORMATIONAL exchange - with message Id zero containing the notify IKEV2_MESSAGE_ID_SYNC or - IPSEC_REPLAY_COUNTER_SYNC or both depending on whether the - synchronization needs to be done for IKEv2 message Ids, IPsec replay - counters, or both. + After the failover event, when the standby member becomes active, it + has to request the SA counters from the peer. The newly-active + member initiates the synchronization request with an Informational + exchange with Message ID zero containing either the notification + IKEV2_MESSAGE_ID_SYNC or the two notifications IKEV2_MESSAGE_ID_SYNC + and IPSEC_REPLAY_COUNTER_SYNC, depending on whether the + synchronization is to be done for IKEv2 Message IDs or for both IKEv2 + Message IDs and IPsec replay counters. If the active member has only + negotiated synchronization of IPsec Replay Counters, the request is + sent as a regular IKEv2 Informational exchange (i.e. with a non-zero + Message ID) containing the notification IPSEC_REPLAY_COUNTER_SYNC. - The initiator of IKEv2 message Id sync request sends its expected - send and receive message Id values and "failover count" in - IKEV2_MESSAGE_ID_SYNC notify. The responder of the request compares - the received values with the available local values. The higher - among both is selected and sent as sync response with notify - IKEV2_MESSAGE_ID_SYNC. The initiator now updates send and receive - IKEv2 message Ids to the values received in sync response and can - start normal IKEv2 message exchange. + The initiator of the IKEv2 Message ID synchronization request sends + its expected send and receive Message ID values and "failover count" + in a IKEV2_MESSAGE_ID_SYNC notification. The responder compares the + received values with its local values. For both send and receive + values, The higher between the cluster member's and the local value + is selected, and sent in the response message with the notification + IKEV2_MESSAGE_ID_SYNC. The initiator now updates its send and + receive IKEv2 Message IDs to the values received in the response and + can now start a normal IKEv2 message exchange. - The initiator of IPsec replay counter sync sends bumped outgoing - IPsec SA reply counter value and "failover count" in - IPSEC_REPLAY_COUNTER_SYNC notify. The responder of the request - updates its incoming IPsec SA counter values and sends its bumped - outgoing IPsec SA replay counter value in sync response with - IPSEC_REPLAY_COUNTER_SYNC. The initiator now updates its incoming - IPsec SA counter to values received in sync response and can start - normal IPsec data traffic. + The initiator of an IPsec Replay Counter synchronization sends the + incremented outgoing IPsec SA reply counter value and a "failover + count" in a IPSEC_REPLAY_COUNTER_SYNC notification in IKEv2 + INFORMATIONAL exchange. The responder updates its incoming IPsec SA + counter values according to the received value. The responder now + sends its own incremented outgoing IPsec SA Replay Counter value in a + synchronization response message, with the same + IPSEC_REPLAY_COUNTER_SYNC notification. The initiator can now update + its incoming IPsec SA counter to values received in the response + message and can start normal IPsec data traffic. - Both the notify types IKEV2_MESSAGE_ID_SYNC and - IPSEC_REPLAY_COUNTER_SYNC contain Nonce Data in the payload to avoid - DOS attack due to replay of SA counter sync request/response. The - Nonce are defined per notify and MUST be validated. The Nonce data - sent in response MUST match with nonce data sent by newly-active - member in request. If nonce data received in response does not match - with nonce data sent in request, the standby i.e. newly-active member - MUST discard this response, and normal IKEv2 behavior of re- - transmitting the request and waiting for genuine reply from the peer - SHOULD follow, before tearing down the SA because of re-transmits. + The IKEV2_MESSAGE_ID_SYNC notification payload contain nonce data to + avoid a denial-of-service (DoS) attack due to replay of SA counter + synchronization response. The nonce values are selected randomly on + each new notification and MUST be validated by the receiver. The + nonce data sent in the response MUST match the nonce data sent by the + newly-active member in its request. If the nonce data received in + the response does not match the request's nonce data, the cluster + member MUST silently discard this response, and SHOULD revert to + normal IKEv2 behavior of retransmitting the request and waiting for a + genuine a reply from the peer. Eventually this might result in the + SA being torn down because of excessive retransmissions. Standby [Newly Active] Member Peer - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - HDR, SK {N[IKEV2_MESSAGE_ID_SYNC ], - N[IPSEC_REPLAY_COUNTER_SYNC]} --------> + HDR, SK {N(IKEV2_MESSAGE_ID_SYNC), + [N(IPSEC_REPLAY_COUNTER_SYNC)]} --------> + <--------- HDR, SK {N(IKEV2_MESSAGE_ID_SYNC), + [N(IPSEC_REPLAY_COUNTER_SYNC)]} - <--------- HDR, SK {N[IKEV2_MESSAGE_ID_SYNC ], - N[IPSEC_REPLAY_COUNTER_SYNC]} + Alternatively, if only IPsec Replay Counter synchronization is + desired, a normal Information exchange is used, where the Message ID + is non-zero: -6. IKEv2/IPsec synchronization notification payloads + Standby [Newly Active] Member Peer + - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - + HDR, SK{N(IPSEC_REPLAY_COUNTER_SYNC)} --------> - Below are the new notify and payload types that are defined + <--------- HDR, SK {N(IPSEC_REPLAY_COUNTER_SYNC)} + +6. IKEv2/IPsec Synchronization Notification Payloads + + This section lists the new notification payloads types defined by + this extension. 6.1. IKEV2_MESSAGE_ID_SYNC_SUPPORTED - IKEV2_MESSAGE_ID_SYNC_SUPPORTED: This notify is included in the - IKE_AUTH request/response to indicate support for IKEv2 message Id - synchronization mechanism described in this document. + IKEV2_MESSAGE_ID_SYNC_SUPPORTED: This notification payload is + included in the IKE_AUTH request/response to indicate support of the + IKEv2 Message ID synchronization 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(=0)| SPI Size (=0) | Notify Message Type | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ The 'Next Payload', 'Payload Length', 'Protocol ID', 'SPI Size', and 'Notify Message Type' fields are the same as described in Section 3 - of [RFC5996]. The 'SPI Size' field MUST be set to 0 to indicate that - the SPI is not present in this message. The 'Protocol ID' MUST be - set to 0, since the notification is not specific to a particular - security association. 'Payload Length' field is set to the length in - octets of the entire payload, including the generic payload header. - The 'Notify Message Type' field is set to indicate the - IKEV2_MESSAGE_ID_SYNC_SUPPORTED payload. + of [RFC5996] . The 'SPI Size' field MUST be set to 0 to indicate + that the SPI is not present in this message. The 'Protocol ID' MUST + be set to 0, since the notification is not specific to a particular + security association. The 'Payload Length' field is set to the + length in octets of the entire payload, including the generic payload + header. The 'Notify Message Type' field is set to indicate + IKEV2_MESSAGE_ID_SYNC_SUPPORTED, value TBD by IANA. There is no data + associated with this notification. 6.2. IPSEC_REPLAY_COUNTER_SYNC_SUPPORTED - IPSEC_REPLAY_COUNTER_SYNC_SUPPORTED: This notify is included in the - IKE_AUTH request/response to indicate support for IPsec SA replay - counter synchronization mechanism described in this document. + IPSEC_REPLAY_COUNTER_SYNC_SUPPORTED: This notification payload is + included in the IKE_AUTH request/response to indicate support for the + IPsec SA Replay Counter synchronization 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(=0)| SPI Size (=0) | Notify Message Type | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ The 'Next Payload', 'Payload Length', 'Protocol ID', 'SPI Size', and 'Notify Message Type' fields are the same as described in Section 3 - of [RFC5996]. The 'SPI Size' field MUST be set to 0 to indicate that - the SPI is not present in this message. The 'Protocol ID' MUST be - set to 0, since the notification is not specific to a particular - security association. 'Payload Length' field is set to the length in - octets of the entire payload, including the generic payload header. - The 'Notify Message Type' field is set to indicate the - IPSEC_REPLAY_COUNTER_SYNC_SUPPORTED payload. + of [RFC5996] . The 'SPI Size' field MUST be set to 0 to indicate + that the SPI is not present in this message. The 'Protocol ID' MUST + be set to 0, since the notification is not specific to a particular + security association. The 'Payload Length' field is set to the + length in octets of the entire payload, including the generic payload + header. The 'Notify Message Type' field is set to indicate + IPSEC_REPLAY_COUNTER_SYNC_SUPPORTED, value TBD by IANA. There is no + data associated with this notification. 6.3. IKEV2_MESSAGE_ID_SYNC - IKEV2_MESSAGE_ID_SYNC : This payload type is defined to sync the - IKEv2 message Ids among newly-active [standby] member and the peer. + IKEV2_MESSAGE_ID_SYNC : This notification payload type (value TBD by + IANA) is defined to synchronize the IKEv2 Message ID values between + the newly-active (formerly standby) cluster member and the peer. 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 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ - | Failover count | + |Protocol ID(=0)| SPI Size (=0) | Notify Message Type | + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + | Failover Count | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Nonce Data | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | EXPECTED_SEND_REQ_MESSAGE_ID | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | EXPECTED_RECV_REQ_MESSAGE_ID | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ - It contains the following data. - o Failover count (4 octets) : The failover count within the cluster, - it increases with each failover event in HA cluster. - o Nonce Data (4 octets) : The random nonce data. It should be sent - same in the SYNC Request and Response. The nonce data is used to - counter the replay of IKEV2_MESSAGE_ID_SYNC response by the - attacker. - o EXPECTED_SEND_REQ_MESSAGE_ID (4 octets) : This MUST be present - only if protocol ID is IKE. This field is used by the sender of - this notify, to indicate the message Id it will use in the next - request, that it will send to the other side peer. - o EXPECTED_RECV_REQ_MESSAGE_ID (4 octets) : This field is used by - the sender of this notify, to indicate the message Id it can - accept in the next request, received from the other side peer. + o Failover Count (4 octets): a running count of failover events + between cluster members, it is initialized to 0 when the cluster + is first set up, and incremented by 1 upon each failover event. + o Nonce Data (4 octets): the random nonce data. The data should be + identical in the synchronization request and response. + o EXPECTED_SEND_REQ_MESSAGE_ID (4 octets): this field is used by the + sender of this notification payload to indicate the Message ID it + will use in the next request that it will send to the other + protocol peer. + o EXPECTED_RECV_REQ_MESSAGE_ID (4 octets): this field is used by the + sender of this notification payload to indicate the Message ID it + is expecting in the next request to be received from the other + protocol peer. 6.4. IPSEC_REPLAY_COUNTER_SYNC - IPSEC_REPLAY_COUNTER_SYNC: This payload type is defined to sync the - IPsec SA replay counters among newly-active [standby] member and the - peer. + IPSEC_REPLAY_COUNTER_SYNC: This notification payload type (value TBD + by IANA) is defined to synchronize the IPsec SA Replay Counters + between the newly-active (formerly standby) cluster member and the + peer. Since there may be numerous IPsec SAs established under a + single IKE SA, we do not directly synchronize the value of each one. + Instead, a delta value is sent and all Replay Counters for child SAs + of this IKE SA are incremented by the same value. Note that this + solution requires that all these Child SAs either use or do not use + Extended Sequence Numbers [RFC4301]. 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 |ESN| RESERVED | Payload Length | + | Next Payload |E| RESERVED | Payload Length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ - | Failover count | + |Protocol ID(=0)| SPI Size (=0) | Notify Message Type | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Outgoing IPsec SA counter | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ - It contains the following data. - o ESN (1 bit) : The ESN bit MUST be ON if IPsec SA were established - with Extended Sequence Numbers. - o Failover count (4 octets) : The failover count within the cluster, - it increases with each failover event in HA cluster. - o Outgoing IPsec SA counter (4 octets or 8 octect) : The outgoing - IPsec SA counter is the bumped-up outgoing IPsec SA replay counter - value considering ALL Child SA under the IKEv2 SA. The size of - outgoing IPsec SA counter depends on ESN bit. If ESN bit is ON, - it is size of 8 octets else it is 4 octets. + The notification payload contains the following data. + o E (1 bit): The ESN bit. This MUST be 1 if the IPsec SAs were + established with Extended Sequence Numbers. + o Outgoing IPsec SA delta value (4 or 8 octects): The sender will + increment the all the Child SA Replay Counters for its outgoing + traffic by this value. The size of this field depends on ESN bit: + if the ESN bit is 1, its size is 8 octets, otherwise it is 4 + octets. -7. Details of implementation +7. Implementation Details - The message Id used IKEV2_MESSAGE_ID_SYNC exchange MUST be zero so - that it is not validated upon receipt as per IKEv2 windowing. - Message Id zero MUST be permitted only for informational exchange - that would have NOTIFY of type IKEV2_MESSAGE_ID_SYNC. If any - INFORMATIONAL exchange uses the message Id Zero, without having this - Notify, then such packets MUST be discarded upon decryption and - INVALID_SYNTAX notify SHOULD be sent. No other payloads are allowed - in this Informational exchange. Whenever IKEV2_MESSAGE_ID_SYNC or - IPSEC_REPLAY_COUNTER_SYNC notify is received with invalid failover - count or nonce data, the event SHOULD be logged. + The Message ID value used in the Informational exchange that contains + the IKEV2_MESSAGE_ID_SYNC notification MUST be zero so that it is not + validated upon receipt as required by normal IKEv2 windowing. The + Message ID zero MUST be accepted only in an Informational exchange + that contains a notification of type IKEV2_MESSAGE_ID_SYNC. If any + Informational exchange has a Message ID zero, but not this + notification type, such messages MUST be discarded upon decryption + and the INVALID_SYNTAX notification SHOULD be sent. Other payloads + MUST NOT be sent in this Informational exchange. Whenever an + IKEV2_MESSAGE_ID_SYNC or IPSEC_REPLAY_COUNTER_SYNC notification + payload is received with an invalid failover count or invalid nonce + data, the event SHOULD be logged. The standby member can initiate the synchronization of IKEv2 Message - Id's - o When it receives the bad IKEv2/IPsec packet. The 'bad" IKEv2/ - IPsec packet means a packet outside receive window. - o When it has to send an IKEv2/IPsec packet after failover event. - o It has just got the control from active member and would require - to update the values before-hand, so that it need not start this - exchange at the time of sending/receiving the request. + ID's under different circumstances. + o When it receives a problematic IKEv2/IPsec packet, i.e. a packet + outside its expected receive window. + o When it has to send the first IKEv2/IPsec packet after a failover + event. + o When it has just received control from active member and wishes to + update the values proactively, so that it need not start this + exchange later, when sending or receiving the request. The standby member can initiate the synchronization of IPsec SA - Counters - o If there is traffic using the IPsec SA in the recent past and - there could be stale replay counter at standby member - - Since there can be many sessions at Standby member, and sending - exchanges from all of the sessions can cause throttling, the standby - member can choose to initiate the exchange when it has to send or - receive the request. Thus the trigger to initiate this exchange - depends on the requirement/discretion of the standby member. + Replay Counters: + o If there has been traffic using the IPsec SA in the recent past + and the standby member suspects that its Replay Counter may be + stale. - The member which has not announced its capability - IKEV2_MESSAGE_ID_SYNC_SUPPORTED MUST NOT send/receive the notify - IKEV2_MESSAGE_ID_SYNC. + Since there can be a large number of sessions at the standby member, + and sending synchronization exchanges for all of them may result in + overload, the standby member can choose to initiate the exchange in a + "lazy" fashion: only when it has to send or receive the request. In + general, the standby member is free to initiate this exchange at its + discretion. - The member which has not announced its capability - IPSEC_REPLAY_COUNTER_SYNC_SUPPORTED MUST NOT send/receive the notify - IPSEC_REPLAY_COUNTER_SYNC. + A cluster member which has not announced its capability by using + IKEV2_MESSAGE_ID_SYNC_SUPPORTED MUST NOT send or accept the + notification IKEV2_MESSAGE_ID_SYNC. - If a peer gets IKEV2_MESSAGE_ID_SYNC or IPSEC_REPLAY_COUNTER_SYNC - request even though it did not announce its capability in IKE_AUTH - exchange, then it MUST ignore this message. + A cluster member which has not announced its capability by using + IPSEC_REPLAY_COUNTER_SYNC_SUPPORTED MUST NOT send or accept the + notification IPSEC_REPLAY_COUNTER_SYNC. - If any of the Notify or the SYNC request/response is malformed, then - it is treated as INVALID_SYNTAX message. + If a peer receives a IKEV2_MESSAGE_ID_SYNC or + IPSEC_REPLAY_COUNTER_SYNC request although it had not announced the + appropriate capability in the IKE_AUTH exchange, then it MUST + silently ignore this message. -8. Step-by-Step details + As usual in IKEv2, if any of the notification payloads defined here + is malformed, the receiver must announce this fact using the + INVALID_SYNTAX notification. - The step by step details of the synchronization of IKE message Id is - as follows. - o Active member and peer device establish the session . They - announce the capability to sync the counter info by sending - IKEV2_MESSAGE_ID_SYNC_SUPPORTED notify in IKE_AUTH Exchange. - o Active member dies and Stand-by member takes over. Standby Member - sends its own idea of the IKE Message ID (its side) to peer in an - INFORMATIONAL message exchange with message Id zero. - o The peer first authenticates the message and then validates that - failover count. The peer will compare the received values with - the values available locally and finally picks the higher value. - It then updates its message Id's with the higher values and also - propose the same in Response. - o The peer should not wait for pending response while responding - with this message Id values. For example if window size is 5 and - peer window is 3-7 and if peer has sent requests 3, 4,5,6,7 and - but got response only for 4,5,6,7 but not 3 then it should send - the EXPECTED_SEND_REQ_MESSAGE_ID as 8 and should not wait for - response of 3 anymore. +8. Step by Step Details - o The peer should not wait for pending request also. For example if - window size is 5 and peer window is 3-7 and if peer has received - requests 4,5,6,7 but not 3 then it should send the - EXPECTED_RECV_REQ_MESSAGE_ID as 8 and should not wait for 3 - anymore. + This section goes through the sequence of steps of a typical failover + event, where the IKEv2 Message ID values are synchronized. + o The active cluster member and the peer device establish the + session. They both announce the capability to synchronize counter + information by sending the IKEV2_MESSAGE_ID_SYNC_SUPPORTED + notification in the IKE_AUTH Exchange. + o The active member dies, and a standby member takes over. The + standby member sends its own idea of the IKE Message IDs (both + incoming and outgoing) to the peer in an Informational message + exchange with Message ID zero. + o The peer first authenticates the message and then validates the + failover count. The peer compares the received values with the + values available locally and picks the higher value. It then + updates its Message IDs with the higher values and also propose + the same values in its response. + o The peer should not wait for any pending responses while + responding with the new Message ID values. For example, if the + window size is 5 and the peer's window is 3-7, and if the peer has + sent requests 3, 4, 5, 6, 7 and received responses only for 4, 5, + 6, 7 but not for 3, then it should include the value 8 in its + EXPECTED_SEND_REQ_MESSAGE_ID payload and should not wait for a + response to message 3 anymore. + o Similarly, the peer should also not wait for pending (incoming) + requests. For example if the window size is 5 and the peer's + window is 3-7 and if the peer has received requests 4, 5, 6, 7 but + not 3, then it should send the value 8 in the + EXPECTED_RECV_REQ_MESSAGE_ID payload, and should not expect to + receive message 3 anymore. - There is corner case with "failover count' and multiple failover. - What if "failover count" is not updated on a member, and next - "failover" happened, then "failover count" is updated on other side - but not on this member. [[ This need to be discussed on mailing list. - ]] + In case multiple successive failover events and sync request getting + lost, the failover count value at peer will not be updated and new + standby member will become active with incremented failover count + value. So, peer can receive valid failover count value which is not + just incremented by 1 in case of multiple failover. Accepting + incremented failover count within a range is allowed and increases + interoperability. 9. Security Considerations - There can be two types of DOS attacks. - o Replay of Message SYNC Request. This is countered by "failover - count", since synchronization starts after failover event and each - member of the cluster is aware of failover event. The receiver of - sync request should verify and maintain failover count. If a peer - again receives a sync request with same "failover count', it can - safely safely discard the request if it has received valid - request/response from other side peer after sync exchange. The - peer can send the cached response for sync request till it has not - received valid request/response from other side peer or failover - count has not increased. - o Replay of Message SYNC Response. This is countered by sending the - NONCE data along with the sync notify. The same NONCE data has to - be returned in response. Thus the standby member can accept the - reply only for the current request. After it receives the valid - response, it MUST NOT process same response again and MUST discard - the response. + Since Message ID synchronization messages need to be sent with + Message ID zero, they are potentially vulnerable to replay attacks. + Because of the semantics of this protocol, these can only be denial- + of-service (DoS) attacks, and we are aware of two variants. + o Replay of Message ID synchronization request: This is countered by + use of the Failover Count, since synchronization starts after the + failover event and each member of the cluster needs to be aware of + the failover event. The receiver of the synchronization request + should verify the received Failover Count and maintain its own + copy of it. If a peer receives a synchronization request with an + already observed Failover Count, it can safely discard the request + if it has already received valid IKEv2 request/response from other + side peer after sync exchange. The peer will be not be aware that + sync response has reached to other side till it receives a valid + IKEv2 request/response from other side. The peer can send the + cached response for sync request till it has not received valid + request/response from other side peer or failover count has not + increased. + o Replay of the Message ID synchronization response: This is + countered by sending the nonce data along with the synchronization + payload. The same nonce data has to be returned in response. + Thus the standby member will accept a reply only for the current + request. After it receives a valid response, it MUST NOT process + the same response again and MUST discard any additional responses. 10. Interaction with other drafts - The primary assumption of IKEv2/IPsec SA Counter Synchronization - proposal is IKEv2 SA has been established between active member of - Hot Standby Cluster and peer, after that the failover event occurred - and now standby member has "become" active. It also assumes the - IKEv2 SA state was synced between active and standby member of the - Hot Standby Cluster before the failover event. - o Session Resumption. Session resumption assumes that peer i.e. - client or initiator detects the need to re-establish the session. - In IKEv2/IPsec SA counter synchronization, standby member which - becomes active i.e. gateway or responder detects the need to - synchronize the SA counter after the failover event. Also in Hot - Standby Cluster, peer establishes the IKEv2/IPsec session with - single cluster's IP address, so peer normally does not detect the - event of failover in the cluster until standby member took very - long to become active and IKEv2 SA times out via liveness check. - So, session resumption and SA counter synchronization after - failover are mutually exclusive. - o This document describes the operation of tightly coupled clusters, - which are the common way of building IPsec clusters. In these - clusters, all members appear to the peer as one gateway, - specifically they share a single IP address. High availability - can also be provided by loosely coupled clusters (for lack of a - better term), which are a group of gateways that do not share an - IP address and do not synchronize state. In this architecture, - the client can use Session Resumption to fail-over from one - cluster member to another. Specifically this requires: - * Support of session resumption on peers and gateways. - * A common session resumption ticket format on all gateways (not - currently standardized). - * Configuration on the peers of the group of gateways that - constitute the cluster. - o Redirect. Redirect mechanism for load-balancing can be used - during init (IKE_SA_INIT) and auth (IKE_AUTH) and after session - establishment. While SA counter sync is used after IKE SA has - been established and failover event has occurred. So it is - mutually exclusive with redirect during init and auth. The - redirect after session established is used for timed or planned - shutdown/maintenance. The failover event can not be detected on - active member beforehand and so using redirect after session - establishment is not possible in case of failover. So, Redirect - and SA counter synchronization after failover are mutually - exclusive. - o Crash detection. Solves the similar problem where peer detect - that cluster member has crashed based on a token. It is mutually - exclusive with HA with SA counter sync. + The usage scenario of the IKEv2/IPsec SA counter synchronization + proposal is that an IKEv2 SA has been established between the active + member of a hot-standby cluster and a peer, then a failover event + occurred with the standby member becoming active. The proposal + further assumes that the IKEv2 SA state was continuously synchronized + between the active and standby members of the cluster before the + failover event. + o Session resumption [RFC5723] assumes that a peer (client or + initiator) detects the need to re-establish the session. In + IKEv2/IPsec SA counter synchronization, it is the newly-active + member (a gateway or responder) that detects the need to + synchronize the SA counter after the failover event. Also in a + hot-standby cluster, the peer establishes the IKEv2/IPsec session + with a single IP address that represents the whole cluster, so the + peer normally does not detect the event of failover in the cluster + unless the standby member takes too long to become active and the + IKEv2 SA times out by use of the IKEv2 liveness check mechanism. + To conclude, session resumption and SA counter synchronization + after failover are mutually exclusive. + o The IKEv2 Redirect mechanism for load-balancing [RFC5685] can be + used either during the initial stages of SA setup (the IKE_SA_INIT + and IKE_AUTH exchanges) or after session establishment. SA + counter synchronization is only useful after the IKE SA has been + established and a failover event has occurred. So, unlike + Redirect, it is irrelevant during the first two exchanges. + Redirect after the session has been established is mostly useful + for timed or planned shutdown/maintenance. A real failover event + cannot be detected by the active member ahead of time, and so + using Redirect after session establishment is not possible in the + case of failover. So, Redirect and SA counter synchronization + after failover are mutually exclusive. + o IKEv2 Failure Detection [I-D.ietf-ipsecme-failure-detection] + solves a similar problem where the peer can rapidly detect that a + cluster member has crashed based on a token. It is unrelated to + the current scenario because the goal in failover is for the peer + not to notice that a failure has occurred. 11. IANA Considerations This document introduces four new IKEv2 Notification Message types as described in Section 6.The new Notify Message Types must be assigned values between 16396 and 40959. o IKEV2_MESSAGE_ID_SYNC_SUPPORTED. o IPSEC_REPLAY_COUNTER_SYNC_SUPPORTED. o IKEV2_MESSAGE_ID_SYNC. o IPSEC_REPLAY_COUNTER_SYNC. 12. Acknowledgements We would like to thank Pratima Sethi and Frederic Detienne for their - reviews comments and valuable suggestions for initial version of the - document. + review comments and valuable suggestions for the initial version of + the document. - We would also like to thank following people (in alphabetical order) - for their review comments and valuable suggestions: Dan Harkins, Paul - Hoffman, Steve Kent, Tero Kivinen, David McGrew, Pekka Riikonen, and - Yaron Sheffar. + We would also like to thank the following people (in alphabetical + order) for their review comments and valuable suggestions: Dan + Harkins, Paul Hoffman, Steve Kent, Tero Kivinen, David McGrew, Pekka + Riikonen, and Yaron Sheffer. 13. Change Log This section lists all the changes in this document. NOTE TO RFC EDITOR: Please remove this section before publication. -13.1. Draft -01 +13.1. Draft -02 - Added "Multiple and Simultaneous failover' scenarios. + Addressed comments by Yaron Sheffer posted on the WG mailing list. + + Numerous editorial changes. + +13.2. Draft -01 + + Added "Multiple and Simultaneous failover' scenarios as pointed out + by Pekka Riikonen. Now document provides a mechanism to sync either IKEv2 message or IPsec replay counter or both to cater different types of implementations. HA cluster's "failover count' is used to encounter replay of sync requests by attacker. The sync of IPsec SA replay counter optimized to to have just one global bumped-up outgoing IPsec SA counter of ALL Child SAs under an IKEv2 SA. - The examples added for IKEv2 message Id sync to provide more clarity. + The examples added for IKEv2 Message ID sync to provide more clarity. Some edits as per comments on mailing list to enhance clarity. -13.2. Draft -00 +13.3. Draft -00 Version 00 is identical to draft-kagarigi-ipsecme-ikev2-windowsync-04, started as WG document. Added IPSECME WG HA design team members as authors. Added comment in Introduction to discuss the window sync process on WG mailing list to solve some concerns. 14. References 14.1. Normative References - [IPsec Cluster Problem Statement] - Nir, Y., "IPsec Cluster Problem Statement", July 2010. - [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. + [RFC4301] Kent, S. and K. Seo, "Security Architecture for the + Internet Protocol", RFC 4301, December 2005. + [RFC5996] Kaufman, C., Hoffman, P., Nir, Y., and P. Eronen, - "Internet Key Exchange Protocol: IKEv2", RFC 5996, - September 2010. + "Internet Key Exchange Protocol Version 2 (IKEv2)", + RFC 5996, September 2010. + + [RFC6027] Nir, Y., "IPsec Cluster Problem Statement", RFC 6027, + October 2010. 14.2. Informative References + [I-D.ietf-ipsecme-failure-detection] + Nir, Y., Wierbowski, D., Detienne, F., and P. Sethi, "A + Quick Crash Detection Method for IKE", + draft-ietf-ipsecme-failure-detection-01 (work in + progress), October 2010. + [RFC5685] Devarapalli, V. and K. Weniger, "Redirect Mechanism for - IKEv2", RFC 5685, November 2009. + the Internet Key Exchange Protocol Version 2 (IKEv2)", + RFC 5685, November 2009. - [RFC5723] Sheffer, Y. and H. Tschofenig, "IKEv2 Session Resumption", - RFC 5723, January 2010. + [RFC5723] Sheffer, Y. and H. Tschofenig, "Internet Key Exchange + Protocol Version 2 (IKEv2) Session Resumption", RFC 5723, + January 2010. -Appendix A. IKEv2 Message Id examples + [RFC5798] Nadas, S., "Virtual Router Redundancy Protocol (VRRP) + Version 3 for IPv4 and IPv6", RFC 5798, March 2010. - Below are the examples to illustrate how the IKEv2 message Id values - are synced. The notation used to denote EXPECTED_SEND_REQ_MESSAGE_ID - and EXPECTED_RECV_REQ_MESSAGE_ID on a member is +Appendix A. IKEv2 Message ID Sync Examples + + This (non-normative) section presents some examples that illustrate + how the IKEv2 Message ID values are synchronized. We use a tuple + notation, denoting the two counters EXPECTED_SEND_REQ_MESSAGE_ID and + EXPECTED_RECV_REQ_MESSAGE_ID on a member as (EXPECTED_SEND_REQ_MESSAGE_ID, EXPECTED_RECV_REQ_MESSAGE_ID). - Normal failover - Example 1 +A.1. Normal Failover - Example 1 - Standby [Newly Active] Member Peer + Standby (Newly Active) Member Peer - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - Request SYNC (2, 3) --------> + Sync Request (2, 3) --------> - Peer has values as (4, 5) so it sends - < -------------( 4, 5) Response SYNC + Peer has the values (4, 5) so it sends + <------------- (4, 5) as the Sync Response - Normal failover - Example 2 +A.2. Normal Failover - Example 2 - Standby [Newly Active] Member Peer + Standby (Newly Active) Member Peer - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - Request SYNC (2, 5) --------> - Peer has values as (2, 4) so it sends - < -------------( 5, 4) Response SYNC + Sync Request (2, 5) --------> - Simultaneous failover + Peer has the values (2, 4) so it sends + <-------------(5, 4) as the Sync Response - In case of simultaneous failover, both the sides send the SYNC - request, but whichever side has the higher value will be eventually - synced. +A.3. Simultaneous Failover - Standby [Newly Active] Member Peer + In the case of simultaneous failover, both sides send the + synchronization request, but whichever side has the higher value will + be eventually synchronized. + + Standby (Newly Active) Member Peer - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - request SYNC (4,4) -----> + Sync Request (4,4) -----> - <-------------- request SYNC (5,5) + <-------------- Sync Request (5,5) - response SYNC (5,5) ----> + Sync Response (5,5) ----> - <-------- response SYNC (5,5) + <-------- Sync Response (5,5) Authors' Addresses Raj Singh (Editor) Cisco Systems, Inc. Divyashree Chambers, B Wing, O'Shaugnessy Road Bangalore, Karnataka 560025 India Phone: +91 80 4301 3320 @@ -750,31 +814,31 @@ Authors' Addresses Raj Singh (Editor) Cisco Systems, Inc. Divyashree Chambers, B Wing, O'Shaugnessy Road Bangalore, Karnataka 560025 India Phone: +91 80 4301 3320 Email: rsj@cisco.com - Kalyani Garigipati Cisco Systems, Inc. Divyashree Chambers, B Wing, O'Shaugnessy Road Bangalore, Karnataka 560025 India Phone: +91 80 4426 4831 Email: kagarigi@cisco.com + Yoav Nir Check Point Software Technologies Ltd. - 5 Hasolelim st. + 5 Hasolelim St. Tel Aviv 67897 Israel Email: ynir@checkpoint.com Dacheng Zhang Huawei Technologies Ltd. Email: zhangdacheng@huawei.com