draft-ietf-ipsecme-failure-detection-08.txt   rfc6290.txt 
IPsecME Working Group Y. Nir, Ed. Internet Engineering Task Force (IETF) Y. Nir, Ed.
Internet-Draft Check Point Request for Comments: 6290 Check Point
Intended status: Standards Track D. Wierbowski Category: Standards Track D. Wierbowski
Expires: October 3, 2011 IBM ISSN: 2070-1721 IBM
F. Detienne F. Detienne
P. Sethi P. Sethi
Cisco Cisco
April 1, 2011 June 2011
A Quick Crash Detection Method for IKE A Quick Crash Detection Method for the
draft-ietf-ipsecme-failure-detection-08 Internet Key Exchange Protocol (IKE)
Abstract Abstract
This document describes an extension to the IKEv2 protocol that This document describes an extension to the Internet Key Exchange
allows for faster detection of Security Association (SA) Protocol version 2 (IKEv2) that allows for faster detection of
desynchronization using a saved token. Security Association (SA) desynchronization using a saved token.
When an IPsec tunnel between two IKEv2 peers is disconnected due to a When an IPsec tunnel between two IKEv2 peers is disconnected due to a
restart of one peer, it can take as much as several minutes for the restart of one peer, it can take as much as several minutes for the
other peer to discover that the reboot has occurred, thus delaying other peer to discover that the reboot has occurred, thus delaying
recovery. In this text we propose an extension to the protocol, that recovery. In this text, we propose an extension to the protocol that
allows for recovery immediately following the restart. allows for recovery immediately following the restart.
Status of this Memo 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 This is an Internet Standards Track document.
Task Force (IETF). Note that other groups may also distribute
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Internet-Drafts are draft documents valid for a maximum of six months This document is a product of the Internet Engineering Task Force
and may be updated, replaced, or obsoleted by other documents at any (IETF). It represents the consensus of the IETF community. It has
time. It is inappropriate to use Internet-Drafts as reference received public review and has been approved for publication by the
material or to cite them other than as "work in progress." Internet Engineering Steering Group (IESG). Further information on
Internet Standards is available in Section 2 of RFC 5741.
This Internet-Draft will expire on October 3, 2011. Information about the current status of this document, any errata,
and how to provide feedback on it may be obtained at
http://www.rfc-editor.org/info/rfc6290.
Copyright Notice Copyright Notice
Copyright (c) 2011 IETF Trust and the persons identified as the Copyright (c) 2011 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
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described in the Simplified BSD License. described in the Simplified BSD License.
Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1. Conventions Used in This Document . . . . . . . . . . . . 4 1.1. Conventions Used in This Document . . . . . . . . . . . . 3
2. RFC 5996 Crash Recovery . . . . . . . . . . . . . . . . . . . 5 2. RFC 5996 Crash Recovery . . . . . . . . . . . . . . . . . . . 4
3. Protocol Outline . . . . . . . . . . . . . . . . . . . . . . . 6 3. Protocol Outline . . . . . . . . . . . . . . . . . . . . . . . 5
4. Formats and Exchanges . . . . . . . . . . . . . . . . . . . . 7 4. Formats and Exchanges . . . . . . . . . . . . . . . . . . . . 6
4.1. Notification Format . . . . . . . . . . . . . . . . . . . 7 4.1. Notification Format . . . . . . . . . . . . . . . . . . . 6
4.2. Passing a Token in the AUTH Exchange . . . . . . . . . . 8 4.2. Passing a Token in the AUTH Exchange . . . . . . . . . . . 7
4.3. Replacing Tokens After Rekey or Resumption . . . . . . . 9 4.3. Replacing Tokens after Rekey or Resumption . . . . . . . . 8
4.4. Replacing the Token for an Existing SA . . . . . . . . . 10 4.4. Replacing the Token for an Existing SA . . . . . . . . . . 9
4.5. Presenting the Token in an Unprotected Message . . . . . 10 4.5. Presenting the Token in an Unprotected Message . . . . . . 9
5. Token Generation and Verification . . . . . . . . . . . . . . 11 5. Token Generation and Verification . . . . . . . . . . . . . . 10
5.1. A Stateless Method of Token Generation . . . . . . . . . 12 5.1. A Stateless Method of Token Generation . . . . . . . . . . 11
5.2. A Stateless Method with IP addresses . . . . . . . . . . 12 5.2. A Stateless Method with IP Addresses . . . . . . . . . . . 11
5.3. Token Lifetime . . . . . . . . . . . . . . . . . . . . . 13 5.3. Token Lifetime . . . . . . . . . . . . . . . . . . . . . . 12
6. Backup Gateways . . . . . . . . . . . . . . . . . . . . . . . 13 6. Backup Gateways . . . . . . . . . . . . . . . . . . . . . . . 12
7. Interaction with Session Resumption . . . . . . . . . . . . . 13 7. Interaction with Session Resumption . . . . . . . . . . . . . 13
8. Operational Considerations . . . . . . . . . . . . . . . . . . 15 8. Operational Considerations . . . . . . . . . . . . . . . . . . 14
8.1. Who should implement this specification . . . . . . . . . 15 8.1. Who Should Implement This Specification . . . . . . . . . 14
8.2. Response to unknown child SPI . . . . . . . . . . . . . . 16 8.2. Response to Unknown Child SPI . . . . . . . . . . . . . . 15
9. Security Considerations . . . . . . . . . . . . . . . . . . . 17 9. Security Considerations . . . . . . . . . . . . . . . . . . . 16
9.1. QCD Token Generation and Handling . . . . . . . . . . . . 17 9.1. QCD Token Generation and Handling . . . . . . . . . . . . 16
9.2. QCD Token Transmission . . . . . . . . . . . . . . . . . 18 9.2. QCD Token Transmission . . . . . . . . . . . . . . . . . . 17
9.3. QCD Token Enumeration . . . . . . . . . . . . . . . . . . 18 9.3. QCD Token Enumeration . . . . . . . . . . . . . . . . . . 18
10. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 19 10. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 18
11. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 19 11. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 18
12. Change Log . . . . . . . . . . . . . . . . . . . . . . . . . . 19 12. References . . . . . . . . . . . . . . . . . . . . . . . . . . 19
12.1. Changes from draft-ietf-ipsecme-failure-detection-05 . . 19 12.1. Normative References . . . . . . . . . . . . . . . . . . . 19
12.2. Changes from draft-ietf-ipsecme-failure-detection-04 . . 19 12.2. Informative References . . . . . . . . . . . . . . . . . . 19
12.3. Changes from draft-ietf-ipsecme-failure-detection-03 . . 20 Appendix A. The Path Not Taken . . . . . . . . . . . . . . . . . 20
12.4. Changes from draft-ietf-ipsecme-failure-detection-02 . . 20 A.1. Initiating a New IKE SA . . . . . . . . . . . . . . . . . 20
12.5. Changes from draft-ietf-ipsecme-failure-detection-01 . . 20 A.2. SIR . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
12.6. Changes from draft-ietf-ipsecme-failure-detection-00 . . 20 A.3. Birth Certificates . . . . . . . . . . . . . . . . . . . . 20
12.7. Changes from draft-nir-ike-qcd-07 . . . . . . . . . . . . 20 A.4. Reducing Liveness Check Length . . . . . . . . . . . . . . 21
12.8. Changes from draft-nir-ike-qcd-03 and -04 . . . . . . . . 21
12.9. Changes from draft-nir-ike-qcd-02 . . . . . . . . . . . . 21
12.10. Changes from draft-nir-ike-qcd-01 . . . . . . . . . . . . 21
12.11. Changes from draft-nir-ike-qcd-00 . . . . . . . . . . . . 21
12.12. Changes from draft-nir-qcr-00 . . . . . . . . . . . . . . 21
13. References . . . . . . . . . . . . . . . . . . . . . . . . . . 21
13.1. Normative References . . . . . . . . . . . . . . . . . . 21
13.2. Informative References . . . . . . . . . . . . . . . . . 22
Appendix A. The Path Not Taken . . . . . . . . . . . . . . . . . 22
A.1. Initiating a new IKE SA . . . . . . . . . . . . . . . . . 22
A.2. SIR . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
A.3. Birth Certificates . . . . . . . . . . . . . . . . . . . 23
A.4. Reducing Liveness Check Length . . . . . . . . . . . . . 23
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 23
1. Introduction 1. Introduction
IKEv2, as described in [RFC5996] and its predecessor RFC 4306, has a IKEv2, as described in [RFC5996] and its predecessor RFC 4306, has a
method for recovering from a reboot of one peer. As long as traffic method for recovering from a reboot of one peer. As long as traffic
flows in both directions, the rebooted peer should re-establish the flows in both directions, the rebooted peer should re-establish the
tunnels immediately. However, in many cases the rebooted peer is a tunnels immediately. However, in many cases, the rebooted peer is a
VPN gateway that protects only servers, so all traffic is inbound. VPN gateway that protects only servers, so all traffic is inbound.
In other cases, the non-rebooted peer has a dynamic IP address, so In other cases, the non-rebooted peer has a dynamic IP address, so
the rebooted peer cannot initiate IKE because its current IP address the rebooted peer cannot initiate IKE because its current IP address
is unknown. In such cases, the rebooted peer will not be able to re- is unknown. In such cases, the rebooted peer will not be able to
establish the tunnels. Section 2 describes how recovery works under re-establish the tunnels. Section 2 describes how recovery works
RFC 5996, and explains why it may take several minutes. under RFC 5996, and explains why it may take several minutes.
The method proposed here, is to send an octet string, called a "QCD The method proposed here is to send an octet string, called a "QCD
token" in the IKE_AUTH exchange that establishes the tunnel. That token", in the IKE_AUTH exchange that establishes the tunnel. That
token can be stored on the peer as part of the IKE SA. After a token can be stored on the peer as part of the IKE SA. After a
reboot, the rebooted implementation can re-generate the token, and reboot, the rebooted implementation can re-generate the token and
send it to the peer, so as to delete the IKE SA. Deleting the IKE SA send it to the peer, so as to delete the IKE SA. Deleting the IKE SA
results in a quick establishment of new IPsec tunnels. This is results in a quick establishment of new IPsec tunnels. This is
described in Section 3. described in Section 3.
1.1. Conventions Used in This Document 1.1. Conventions Used in This Document
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in [RFC2119]. document are to be interpreted as described in [RFC2119].
The term "token" refers to an octet string that an implementation can The term "token" refers to an octet string that an implementation can
generate using only the properties of a protected IKE message (such generate using only the properties of a protected IKE message (such
as IKE SPIs) as input. A conforming implementation MUST be able to as IKE Security Parameter Indexes (SPIs)) as input. A conforming
generate the same token from the same input even after rebooting. implementation MUST be able to generate the same token from the same
input even after rebooting.
The term "token maker" refers to an implementation that generates a The term "token maker" refers to an implementation that generates a
token and sends it to the peer as specified in this document. token and sends it to the peer as specified in this document.
The term "token taker" refers to an implementation that stores such a The term "token taker" refers to an implementation that stores such a
token or a digest thereof, in order to verify that a new token it token or a digest thereof, in order to verify that a new token it
receives is identical to the old token it has stored. receives is identical to the old token it has stored.
The term "non-volatile storage" in this document refers to a data The term "non-volatile storage" in this document refers to a data
storage module, that persists across restarts of the token maker. storage module that persists across restarts of the token maker.
Examples of such a storage module include an internal disk, an Examples of such a storage module include an internal disk, an
internal flash memory module, an external disk and an external internal flash memory module, an external disk, and an external
database. A small non-volatile storage module is required for a database. A small non-volatile storage module is required for a
token maker, but a larger one can be used to enhance performance, as token maker, but a larger one can be used to enhance performance, as
described in Section 8.2. described in Section 8.2.
2. RFC 5996 Crash Recovery 2. RFC 5996 Crash Recovery
When one peer loses state or reboots, the other peer does not get any When one peer loses state or reboots, the other peer does not get any
notification, so unidirectional IPsec traffic can still flow. The notification, so unidirectional IPsec traffic can still flow. The
rebooted peer will not be able to decrypt it, however, and the only rebooted peer will not be able to decrypt it, however, and the only
remedy is to send an unprotected INVALID_SPI notification as remedy is to send an unprotected INVALID_SPI notification as
described in section 3.10.1 of [RFC5996]. That section also described in Section 3.10.1 of [RFC5996]. That section also
describes the processing of such a notification: describes the processing of such a notification:
"If this Informational Message is sent outside the If this Informational Message is sent outside the context of an
context of an IKE_SA, it should be used by the recipient IKE_SA, it should be used by the recipient only as a "hint" that
only as a "hint" that something might be wrong (because it something might be wrong (because it could easily be forged).
could easily be forged)."
Since the INVALID_SPI can only be used as a hint, the non-rebooted Since the INVALID_SPI can only be used as a hint, the non-rebooted
peer has to determine whether the IPsec SA, and indeed the parent IKE peer has to determine whether the IPsec SA and indeed the parent IKE
SA are still valid. The method of doing this is described in section SA are still valid. The method of doing this is described in Section
2.4 of [RFC5996]. This method, called "liveness check" involves 2.4 of [RFC5996]. This method, called "liveness check", involves
sending a protected empty INFORMATIONAL message, and awaiting a sending a protected empty INFORMATIONAL message, and awaiting a
response. This procedure is sometimes referred to as "Dead Peer response. This procedure is sometimes referred to as "Dead Peer
Detection" or DPD. Detection" or DPD.
Section 2.4 does not mandate how many times the liveness check Section 2.4 does not mandate how many times the liveness check
message should be retransmitted, or for how long, but does recommend message should be retransmitted, or for how long, but does recommend
the following: the following:
"It is It is suggested that messages be retransmitted at least a dozen
suggested that messages be retransmitted at least a dozen times over times over a period of at least several minutes before giving up
a period of at least several minutes before giving up on an SA..." on an SA...
Those "at least several minutes" are a time during part of which both Those "at least several minutes" are a time during part of which both
peers are active, but IPsec cannot be used. peers are active, but IPsec cannot be used.
Especially in the case of a reboot (rather than fail-over or Especially in the case of a reboot (rather than fail-over or
administrative clearing of state), the peer does not recover administrative clearing of state), the peer does not recover
immediately. Reboot, depending on the system, may take from a few immediately. Reboot, depending on the system, may take from a few
seconds to a few minutes. This means that at first the peer just seconds to a few minutes. This means that at first the peer just
goes silent, i.e., does not send or respond to any messages. IKEv2 goes silent, i.e., does not send or respond to any messages. IKEv2
implementations can detect this situation and follow the rules given implementations can detect this situation and follow the rules given
in section 2.4: in Section 2.4:
If there has only been outgoing traffic on all of If there has only been outgoing traffic on all of the SAs
the SAs associated with an IKE SA, it is essential to confirm associated with an IKE SA, it is essential to confirm liveness of
liveness of the other endpoint to avoid black holes. If no the other endpoint to avoid black holes. If no cryptographically
cryptographically protected messages have been received on an IKE protected messages have been received on an IKE SA or any of its
SA or any of its Child SAs recently, the system needs to perform a Child SAs recently, the system needs to perform a liveness check
liveness check in order to prevent sending messages to a dead peer. in order to prevent sending messages to a dead peer.
[RFC5996] does not mandate any time limits, but it is possible that [RFC5996] does not mandate any time limits, but it is possible that
the peer will start liveness checks even before the other end is the peer will start liveness checks even before the other end is
sending INVALID_SPI notification, as it detected that the other end sending INVALID_SPI notification, as it detected that the other end
is not sending any packets anymore while it is still rebooting or is not sending any packets anymore while it is still rebooting or
recovering from the situation. recovering from the situation.
This means that the several minutes recovery period is overlaping the This means that the several minutes recovery period is overlapping
actual recover time of the other peer, i.e., if the security gateway the actual recover time of the other peer; i.e., if the security
requires several minutes to boot up from the crash then the other gateway requires several minutes to boot up from the crash, then the
peers have already finished their liveness checks before the crashing other peers have already finished their liveness checks before the
peer even has a chance to send INVALID_SPI notifications. crashing peer even has a chance to send INVALID_SPI notifications.
There are cases where the peer loses state and is able to recover There are cases where the peer loses state and is able to recover
immediately; in those cases it might take several minutes to recreate immediately; in those cases it might take several minutes to recreate
the IPsec SAs. the IPsec SAs.
Note that the IKEv2 specification specifically gives no guidance for Note that the IKEv2 specification specifically gives no guidance for
the number of retries or the length of timeouts, as these do not the number of retries or the length of timeouts, as these do not
affect interoperability. This means that implementations are allowed affect interoperability. This means that implementations are allowed
to use the hints provided by the INVALID_SPI messages to shorten to use the hints provided by the INVALID_SPI messages to shorten
those timeouts (i.e., different environment and situation requiring those timeouts (i.e., a different environment and situation requiring
different rules). different rules).
Some existing IKEv2 implementations already do that (i.e., both Some existing IKEv2 implementations already do that (i.e., shorten
shorten timeouts or limit number of retries) based on these kind of timeouts or limit number of retries) based on these kinds of hints
hints and also start liveness checks quickly after the other end goes and also start liveness checks quickly after the other end goes
silent. However, see Appendix A.4 for a discussion of why this may silent. However, see Appendix A.4 for a discussion of why this may
not be enough. not be enough.
3. Protocol Outline 3. Protocol Outline
Supporting implementations will send a notification, called a "QCD Supporting implementations will send a notification, called a "QCD
token", as described in Section 4.1 in the first IKE_AUTH exchange token", as described in Section 4.1 in the first IKE_AUTH exchange
messages. These are the first IKE_AUTH request and final IKE_AUTH messages. These are the first IKE_AUTH request and final IKE_AUTH
response that contain the AUTH payloads. The generation of these response that contain the AUTH payloads. The generation of these
tokens is a local matter for implementations, but considerations are tokens is a local matter for implementations, but considerations are
skipping to change at page 7, line 13 skipping to change at page 6, line 15
When a token maker receives a protected IKE request message with When a token maker receives a protected IKE request message with
unknown IKE SPIs, it SHOULD generate a new token that is identical to unknown IKE SPIs, it SHOULD generate a new token that is identical to
the previous token, and send it to the requesting peer in an the previous token, and send it to the requesting peer in an
unprotected IKE message as described in Section 4.5. unprotected IKE message as described in Section 4.5.
When a token taker receives the QCD token in an unprotected When a token taker receives the QCD token in an unprotected
notification, it MUST verify that the TOKEN_SECRET_DATA matches the notification, it MUST verify that the TOKEN_SECRET_DATA matches the
token stored with the matching IKE SA. If the verification fails, or token stored with the matching IKE SA. If the verification fails, or
if the IKE SPIs in the message do not match any existing IKE SA, it if the IKE SPIs in the message do not match any existing IKE SA, it
SHOULD log the event. If it succeeds, it MUST silently delete the SHOULD log the event. If it succeeds, it MUST silently delete the
IKE SA associated with the IKE_SPI fields, and all dependent child IKE SA associated with the IKE_SPI fields and all dependent child
SAs. This event MAY also be logged. The token taker MUST accept SAs. This event MAY also be logged. The token taker MUST accept
such tokens from any IP address and port combination, so as to allow such tokens from any IP address and port combination, so as to allow
different kinds of high-availability configurations of the token different kinds of high-availability configurations of the token
maker. maker.
A supporting token taker MAY immediately create new SAs using an A supporting token taker MAY immediately create new SAs using an
Initial exchange, or it may wait for subsequent traffic to trigger Initial exchange, or it may wait for subsequent traffic to trigger
the creation of new SAs. the creation of new SAs.
See Section 7 for a short discussion about this extensions's See Section 7 for a short discussion about this extension's
interaction with IKEv2 Session Resumption ([RFC5723]). interaction with IKEv2 Session Resumption ([RFC5723]).
4. Formats and Exchanges 4. Formats and Exchanges
4.1. Notification Format 4.1. Notification Format
The notification payload called "QCD token" is formatted as follows: The notification payload called "QCD token" is formatted as follows:
1 2 3 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 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
skipping to change at page 7, line 46 skipping to change at page 6, line 48
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
! Protocol ID ! SPI Size ! QCD Token Notify Message Type ! ! Protocol ID ! SPI Size ! QCD Token Notify Message Type !
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
! ! ! !
~ TOKEN_SECRET_DATA ~ ~ TOKEN_SECRET_DATA ~
! ! ! !
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
o Protocol ID (1 octet) MUST be 1, as this message is related to an o Protocol ID (1 octet) MUST be 1, as this message is related to an
IKE SA. IKE SA.
o SPI Size (1 octet) MUST be zero, in conformance with section 3.10
o SPI Size (1 octet) MUST be zero, in conformance with Section 3.10
of [RFC5996]. of [RFC5996].
o QCD Token Notify Message Type (2 octets) - MUST be xxxxx, the
value assigned for QCD token notifications. TBA by IANA. o QCD Token Notify Message Type (2 octets) - MUST be 16419, the
value assigned for QCD token notifications.
o TOKEN_SECRET_DATA (variable) contains a generated token as o TOKEN_SECRET_DATA (variable) contains a generated token as
described in Section 5. described in Section 5.
4.2. Passing a Token in the AUTH Exchange 4.2. Passing a Token in the AUTH Exchange
For brevity, only the EAP version of an AUTH exchange will be For brevity, only the Extensible Authentication Protocol (EAP)
presented here. The non-EAP version is very similar. The figures version of an AUTH exchange will be presented here. The non-EAP
below are based on appendix C.3 of [RFC5996]. version is very similar. The figures below are based on Appendix C.3
of [RFC5996].
first request --> IDi, first request --> IDi,
[N(INITIAL_CONTACT)], [N(INITIAL_CONTACT)],
[[N(HTTP_CERT_LOOKUP_SUPPORTED)], CERTREQ+], [[N(HTTP_CERT_LOOKUP_SUPPORTED)], CERTREQ+],
[IDr], [IDr],
[N(QCD_TOKEN)] [N(QCD_TOKEN)]
[CP(CFG_REQUEST)], [CP(CFG_REQUEST)],
[N(IPCOMP_SUPPORTED)+], [N(IPCOMP_SUPPORTED)+],
[N(USE_TRANSPORT_MODE)], [N(USE_TRANSPORT_MODE)],
[N(ESP_TFC_PADDING_NOT_SUPPORTED)], [N(ESP_TFC_PADDING_NOT_SUPPORTED)],
skipping to change at page 9, line 9 skipping to change at page 8, line 15
Note that the QCD_TOKEN notification is marked as optional because it Note that the QCD_TOKEN notification is marked as optional because it
is not required by this specification that every implementation be is not required by this specification that every implementation be
both token maker and token taker. If only one peer sends the QCD both token maker and token taker. If only one peer sends the QCD
token, then a reboot of the other peer will not be recoverable by token, then a reboot of the other peer will not be recoverable by
this method. This may be acceptable if traffic typically originates this method. This may be acceptable if traffic typically originates
from the other peer. from the other peer.
In any case, the lack of a QCD_TOKEN notification MUST NOT be taken In any case, the lack of a QCD_TOKEN notification MUST NOT be taken
as an indication that the peer does not support this standard. as an indication that the peer does not support this standard.
Conversely, if a peer does not understand this notification, it will Conversely, if a peer does not understand this notification, it will
simply ignore it. Therefore a peer may send this notification simply ignore it. Therefore, a peer may send this notification
freely, even if it does not know whether the other side supports it. freely, even if it does not know whether the other side supports it.
The QCD_TOKEN notification is related to the IKE SA and should follow The QCD_TOKEN notification is related to the IKE SA and should follow
the AUTH payload and precede the Configuration payload and all the AUTH payload and precede the Configuration payload and all
payloads related to the child SA. payloads related to the child SA.
4.3. Replacing Tokens After Rekey or Resumption 4.3. Replacing Tokens after Rekey or Resumption
After rekeying an IKE SA, the IKE SPIs are replaced, so the new SA After rekeying an IKE SA, the IKE SPIs are replaced, so the new SA
also needs to have a token. If only the responder in the rekey also needs to have a token. If only the responder in the rekey
exchange is the token maker, this can be done within the exchange is the token maker, this can be done within the
CREATE_CHILD_SA exchange. If the initiator is a token maker, then we CREATE_CHILD_SA exchange. If the initiator is a token maker, then we
need an extra informational exchange. need an extra informational exchange.
The following figure shows the CREATE_CHILD_SA exchange for rekeying The following figure shows the CREATE_CHILD_SA exchange for rekeying
the IKE SA. Only the responder sends a QCD token. the IKE SA. Only the responder sends a QCD token.
skipping to change at page 9, line 50 skipping to change at page 9, line 10
similar. The responder, which is necessarily the peer that has similar. The responder, which is necessarily the peer that has
crashed, SHOULD send a new ticket within the protected payload of the crashed, SHOULD send a new ticket within the protected payload of the
IKE_SESSION_RESUME exchange. If the Initiator is also a token maker, IKE_SESSION_RESUME exchange. If the Initiator is also a token maker,
it needs to send a QCD_TOKEN in a separate INFORMATIONAL exchange. it needs to send a QCD_TOKEN in a separate INFORMATIONAL exchange.
The INFORMATIONAL exchange described in this section can also be used The INFORMATIONAL exchange described in this section can also be used
if QCD tokens need to be replaced due to a key rollover. However, if QCD tokens need to be replaced due to a key rollover. However,
since token takers are required to verify at least 4 QCD tokens, this since token takers are required to verify at least 4 QCD tokens, this
is only necessary if secret QCD keys are rolled over more than four is only necessary if secret QCD keys are rolled over more than four
times as often as IKE SAs are rekeyed. See Section 5.1 for an times as often as IKE SAs are rekeyed. See Section 5.1 for an
example method that uses secret keys which may require rollover. example method that uses secret keys that may require rollover.
4.4. Replacing the Token for an Existing SA 4.4. Replacing the Token for an Existing SA
With some token generation methods, such as that described in With some token generation methods, such as that described in
Section 5.2, a QCD token may sometimes become invalid, although the Section 5.2, a QCD token may sometimes become invalid, although the
IKE SA is still perfectly valid. IKE SA is still perfectly valid.
In such a case, the token maker MUST send the new token in a In such a case, the token maker MUST send the new token in a
protected message under that IKE SA. That exchange could be a simple protected message under that IKE SA. That exchange could be a simple
INFORMATIONAL, such as in the last figure in the previous section, or INFORMATIONAL, such as in the last figure in the previous section, or
else it can be part of a MOBIKE INFORMATIONAL exchange such as in the else it can be part of a MOBIKE INFORMATIONAL exchange such as in the
following figure taken from section 2.2 of [RFC4555] and modified by following figure taken from Section 2.2 of [RFC4555] and modified by
adding a QCD_TOKEN notification: adding a QCD_TOKEN notification:
(IP_I2:4500 -> IP_R1:4500) (IP_I2:4500 -> IP_R1:4500)
HDR, SK { N(UPDATE_SA_ADDRESSES), HDR, SK { N(UPDATE_SA_ADDRESSES),
N(NAT_DETECTION_SOURCE_IP), N(NAT_DETECTION_SOURCE_IP),
N(NAT_DETECTION_DESTINATION_IP) } --> N(NAT_DETECTION_DESTINATION_IP) } -->
<-- (IP_R1:4500 -> IP_I2:4500) <-- (IP_R1:4500 -> IP_I2:4500)
HDR, SK { N(NAT_DETECTION_SOURCE_IP), HDR, SK { N(NAT_DETECTION_SOURCE_IP),
N(NAT_DETECTION_DESTINATION_IP) } N(NAT_DETECTION_DESTINATION_IP) }
skipping to change at page 10, line 47 skipping to change at page 10, line 7
4.5. Presenting the Token in an Unprotected Message 4.5. Presenting the Token in an Unprotected Message
This QCD_TOKEN notification is unprotected, and is sent as a response This QCD_TOKEN notification is unprotected, and is sent as a response
to a protected IKE request, which uses an IKE SA that is unknown. to a protected IKE request, which uses an IKE SA that is unknown.
message --> N(INVALID_IKE_SPI), N(QCD_TOKEN)+ message --> N(INVALID_IKE_SPI), N(QCD_TOKEN)+
If child SPIs are persistently mapped to IKE SPIs as described in If child SPIs are persistently mapped to IKE SPIs as described in
Section 8.2, a token taker may get the following unprotected message Section 8.2, a token taker may get the following unprotected message
in response to an ESP or AH packet. in response to an Encapsulating Security Payload (ESP) or
Authentication Header (AH) packet.
message --> N(INVALID_SPI), N(QCD_TOKEN)+ message --> N(INVALID_SPI), N(QCD_TOKEN)+
The QCD_TOKEN and INVALID_IKE_SPI notifications are sent together to The QCD_TOKEN and INVALID_IKE_SPI notifications are sent together to
support both implementations that conform to this specification and support both implementations that conform to this specification and
implementations that don't. Similar to the description in section implementations that don't. Similar to the description in Section
2.21 of [RFC5996], the IKE SPI and message ID fields in the packet 2.21 of [RFC5996], the IKE SPI and message ID fields in the packet
headers are taken from the protected IKE request. headers are taken from the protected IKE request.
To support a periodic rollover of the secret used for token To support a periodic rollover of the secret used for token
generation, the token taker MUST support at least four QCD_TOKEN generation, the token taker MUST support at least four QCD_TOKEN
notifications in a single packet. The token is considered verified notifications in a single packet. The token is considered verified
if any of the QCD_TOKEN notifications matches. The token maker MAY if any of the QCD_TOKEN notifications matches. The token maker MAY
generate up to four QCD_TOKEN notifications, based on several generate up to four QCD_TOKEN notifications, based on several
generations of keys. generations of keys.
skipping to change at page 11, line 28 skipping to change at page 10, line 38
Section 5 defines token verification. Section 5 defines token verification.
5. Token Generation and Verification 5. Token Generation and Verification
No token generation method is mandated by this document. Two methods No token generation method is mandated by this document. Two methods
are documented in the following sub-sections, but they only serve as are documented in the following sub-sections, but they only serve as
examples. examples.
The following lists the requirements for a token generation The following lists the requirements for a token generation
mechanism: mechanism:
o Tokens MUST be at least 16 octets long, and no more than 128 o Tokens MUST be at least 16 octets long, and no more than 128
octets long, to facilitate storage and transmission. Tokens octets long, to facilitate storage and transmission. Tokens
SHOULD be indistinguishable from random data. SHOULD be indistinguishable from random data.
o It should not be possible for an external attacker to guess the o It should not be possible for an external attacker to guess the
QCD token generated by an implementation. Cryptographic QCD token generated by an implementation. Cryptographic
mechanisms such as PRNG and hash functions are RECOMMENDED. mechanisms such as a pseudo-random number generator (PRNG) and
hash functions are RECOMMENDED.
o The token maker MUST be able to re-generate or retrieve the token o The token maker MUST be able to re-generate or retrieve the token
based on the IKE SPIs even after it reboots. based on the IKE SPIs even after it reboots.
o The method of token generation MUST be such that a collision of o The method of token generation MUST be such that a collision of
QCD tokens between different pairs of IKE SPI will be highly QCD tokens between different pairs of IKE SPI will be highly
unlikely. unlikely.
For verification, the token taker makes a bitwise comparison of the For verification, the token taker makes a bitwise comparison of the
token stored along with the IKE SA with the token sent in the token stored along with the IKE SA with the token sent in the
unprotected message. Multihomed takers might flip back-and-forth unprotected message. Multihomed takers might flip back-and-forth
between several addresses, and have their tokens replaced as between several addresses, and have their tokens replaced as
described in Section 4.4. To help avoid the case where the latest described in Section 4.4. To help avoid the case where the latest
stored token does not match the address used after the maker lost stored token does not match the address used after the maker lost
skipping to change at page 12, line 10 skipping to change at page 11, line 23
described in Section 4.4. To help avoid the case where the latest described in Section 4.4. To help avoid the case where the latest
stored token does not match the address used after the maker lost stored token does not match the address used after the maker lost
state, the token taker MAY store several earlier tokens associated state, the token taker MAY store several earlier tokens associated
with the IKE SA, and silently discard the SA if any of them matches. with the IKE SA, and silently discard the SA if any of them matches.
5.1. A Stateless Method of Token Generation 5.1. A Stateless Method of Token Generation
The following describes a stateless method of generating a token. In The following describes a stateless method of generating a token. In
this case, 'stateless' means not maintaining any per-tunnel state, this case, 'stateless' means not maintaining any per-tunnel state,
although there is a small amount of non-volatile storage required. although there is a small amount of non-volatile storage required.
o At installation or immediately after the first boot of the token o At installation or immediately after the first boot of the token
maker, 32 random octets are generated using a secure random number maker, 32 random octets are generated using a secure random number
generator or a PRNG. generator or a PRNG.
o Those 32 bytes, called the "QCD_SECRET", are stored in non- o Those 32 bytes, called the "QCD_SECRET", are stored in non-
volatile storage on the machine, and kept indefinitely. volatile storage on the machine, and kept indefinitely.
o If key rollover is required by policy, the implementation MAY o If key rollover is required by policy, the implementation MAY
periodically generate a new QCD_SECRET and keep up to 3 previous periodically generate a new QCD_SECRET and keep up to 3 previous
generations. When sending an unprotected QCD_TOKEN, as many as 4 generations. When sending an unprotected QCD_TOKEN, as many as 4
notification payloads may be sent, each from a different notification payloads may be sent, each from a different
QCD_SECRET. QCD_SECRET.
o The TOKEN_SECRET_DATA is calculated as follows: o The TOKEN_SECRET_DATA is calculated as follows:
TOKEN_SECRET_DATA = HASH(QCD_SECRET | SPI-I | SPI-R) TOKEN_SECRET_DATA = HASH(QCD_SECRET | SPI-I | SPI-R)
5.2. A Stateless Method with IP addresses 5.2. A Stateless Method with IP Addresses
This method is similar to the one in the previous section, except This method is similar to the one in the previous section, except
that the IP address of the token taker is also added to the block that the IP address of the token taker is also added to the block
being hashed. This has the disadvantage that the token needs to be being hashed. This has the disadvantage that the token needs to be
replaced (as described in Section 4.4) whenever the token taker replaced (as described in Section 4.4) whenever the token taker
changes its address. changes its address.
See Section 9.2 for a discussion of a use-case for this method. When See Section 9.2 for a discussion of a use-case for this method. When
using this method, the TOKEN_SECRET_DATA field is calculated as using this method, the TOKEN_SECRET_DATA field is calculated as
follows: follows:
TOKEN_SECRET_DATA = HASH(QCD_SECRET | SPI-I | SPI-R | IPaddr-T) TOKEN_SECRET_DATA = HASH(QCD_SECRET | SPI-I | SPI-R | IPaddr-T)
The IPaddr-T field specifies the IP address of the token taker. The IPaddr-T field specifies the IP address of the token taker.
Secret rollover considerations are similar to those in the previous Secret rollover considerations are similar to those in the previous
section. section.
Note that with a multi-homed token taker, the QCD token matches just Note that with a multihomed token taker, the QCD token matches just
one of the token taker IP addresses. Usually this is not a problem, one of the token taker IP addresses. Usually this is not a problem,
as packets sent to the token maker come out the same IP address. If as packets sent to the token maker come out the same IP address. If
for some reason this changes, then the token maker can replace the for some reason this changes, then the token maker can replace the
token as described in section 4.4. If MOBIKE is used, replacing the token as described in Section 4.4. If IKEv2 Mobility and Multihoming
tokens SHOULD be piggybacked on the INFORMATIONAL exchange with the (MOBIKE) is used, replacing the tokens SHOULD be piggybacked on the
UPDATE_SA_ADDRESSES notifications. INFORMATIONAL exchange with the UPDATE_SA_ADDRESSES notifications.
There is a corner case where the token taker begins using a new IP There is a corner case where the token taker begins using a new IP
address (because of multi-homing, roaming or normal network address (because of multihoming, roaming, or normal network
operations) and the token maker loses state before replacing the operations) and the token maker loses state before replacing the
token. In that case, it will send a correct QCD token, but the token token. In that case, it will send a correct QCD token, but the token
taker will still have the old token. In that case the extension will taker will still have the old token. In that case, the extension
not work, and the peers will revert to RFC 5996 recovery. will not work, and the peers will revert to RFC 5996 recovery.
5.3. Token Lifetime 5.3. Token Lifetime
The token is associated with a single IKE SA, and SHOULD be deleted The token is associated with a single IKE SA and SHOULD be deleted by
by the token taker when the SA is deleted or expires. More formally, the token taker when the SA is deleted or expires. More formally,
the token is associated with the pair (SPI-I, SPI-R). the token is associated with the pair (SPI-I, SPI-R).
6. Backup Gateways 6. Backup Gateways
Making crash detection and recovery quick is a worthy goal, but since Making crash detection and recovery quick is a worthy goal, but since
rebooting a gateway takes a non-zero amount of time, many rebooting a gateway takes a non-zero amount of time, many
implementations choose to have a stand-by gateway ready to take over implementations choose to have a standby gateway ready to take over
as soon as the primary gateway fails for any reason. [RFC6027] as soon as the primary gateway fails for any reason. [RFC6027]
describes considerations for such clusters of gateways with describes considerations for such clusters of gateways with
synchronized state, but the rest of this section is relevant even synchronized state, but the rest of this section is relevant even
when there is no synchronized state. when there is no synchronized state.
If such a configuration is available, it is RECOMMENDED that the If such a configuration is available, it is RECOMMENDED that the
stand-by gateway be able to generate the same token as the active standby gateway be able to generate the same token as the active
gateway. if the method described in Section 5.1 is used, this means gateway. If the method described in Section 5.1 is used, this means
that the QCD_SECRET field is identical in both gateways. This has that the QCD_SECRET field is identical in both gateways. This has
the effect of having the crash recovery available immediately. the effect of having the crash recovery available immediately.
Note that this refers to "high availability" configurations, where Note that this refers to "high-availability" configurations, where
only one gateway is active at any given moment. This is different only one gateway is active at any given moment. This is different
from "load sharing" configurations where more than one gateway is from "load sharing" configurations where more than one gateway is
active at the same time. For load sharing configurations, please see active at the same time. For load sharing configurations, please see
Section 9.2 for security considerations. Section 9.2 for security considerations.
7. Interaction with Session Resumption 7. Interaction with Session Resumption
Session resumption, specified in [RFC5723], allows the setting up of Session resumption, specified in [RFC5723], allows the setting up of
a new IKE SA to consume less computing resources. This is a new IKE SA to consume less computing resources. This is
particularly useful in the case of a remote access gateway that has particularly useful in the case of a remote access gateway that has
many tunnels. A failure of such a gateway requires all these many many tunnels. A failure of such a gateway requires all these many
remote access clients to establish an IKE SA either with the rebooted remote access clients to establish an IKE SA either with the rebooted
gateway or with a backup. This tunnel re-establishment occurs within gateway or with a backup. This tunnel re-establishment occurs within
a short period of time, creating a burden on the remote access a short period of time, creating a burden on the remote access
gateway. Session resumption addresses this problem by having the gateway. Session resumption addresses this problem by having the
clients store an encrypted derivative of the IKE SA for quick re- clients store an encrypted derivative of the IKE SA for quick
establishment. re-establishment.
What Session Resumption does not help is the problem of detecting What Session Resumption does not help is the problem of detecting
that the peer gateway has failed. A failed gateway may go undetected that the peer gateway has failed. A failed gateway may go undetected
for an arbitrarily long time, because IPsec does not have packet for an arbitrarily long time, because IPsec does not have packet
acknowledgement, and applications cannot signal the IPsec layer that acknowledgement, and applications cannot signal the IPsec layer that
the tunnel "does not work". Section 2.4 of RFC 5996 does not specify the tunnel "does not work". Section 2.4 of RFC 5996 does not specify
how long an implementation needs to wait before beginning a liveness how long an implementation needs to wait before beginning a liveness
check, and only says "not recently" (see full quote in Section 2). check, and only says "not recently" (see full quote in Section 2).
In practice some mobile devices wait a very long time before In practice, some mobile devices wait a very long time before
beginning liveness check, in order to extend battery life by allowing beginning a liveness check, in order to extend battery life by
parts of the device to remain in low-power modes. allowing parts of the device to remain in low-power modes.
QCD tokens provide a way to detect the failure of the peer in the QCD tokens provide a way to detect the failure of the peer in the
case where liveness check has not yet ended (or begun). case where a liveness check has not yet ended (or begun).
A remote access client conforming to both specifications will store A remote access client conforming to both specifications will store
QCD tokens, as well as the Session Resumption ticket, if provided by QCD tokens, as well as the Session Resumption ticket, if provided by
the gateway. A remote access gateway conforming to both the gateway. A remote access gateway conforming to both
specifications will generate a QCD token for the client. When the specifications will generate a QCD token for the client. When the
gateway reboots, the client will discover this in either of two ways: gateway reboots, the client will discover this in either of two ways:
1. The client does regular liveness checks, or else the time for 1. The client does regular liveness checks, or else the time for
some other IKE exchange has come. Since the gateway is still some other IKE exchange has come. Since the gateway is still
down, the IKE exchange times out after several minutes. In this down, the IKE exchange times out after several minutes. In this
case QCD does not help. case, QCD does not help.
2. Either the primary gateway or a backup gateway (see Section 6) is 2. Either the primary gateway or a backup gateway (see Section 6) is
ready and sends a QCD token to the client. In that case the ready and sends a QCD token to the client. In that case, the
client will quickly re-establish the IPsec tunnel, either with client will quickly re-establish the IPsec tunnel, either with
the rebooted primary gateway or the backup gateway as described the rebooted primary gateway or the backup gateway as described
in this document. in this document.
The full combined protocol looks like this: The full combined protocol looks like this:
Initiator Responder Initiator Responder
----------- ----------- ----------- -----------
HDR, SAi1, KEi, Ni --> HDR, SAi1, KEi, Ni -->
skipping to change at page 15, line 32 skipping to change at page 14, line 40
HDR, {} --> HDR, {} -->
<-- HDR, N(QCD_TOKEN) <-- HDR, N(QCD_TOKEN)
HDR, [N(COOKIE),] HDR, [N(COOKIE),]
Ni, N(TICKET_OPAQUE) Ni, N(TICKET_OPAQUE)
[,N+] --> [,N+] -->
<-- HDR, Nr [,N+] <-- HDR, Nr [,N+]
8. Operational Considerations 8. Operational Considerations
8.1. Who should implement this specification 8.1. Who Should Implement This Specification
Throughout this document, we have referred to reboot time Throughout this document, we have referred to reboot time
alternatingly as the time that the implementation crashes and the alternatingly as the time that the implementation crashes and the
time when it is ready to process IPsec packets and IKE exchanges. time when it is ready to process IPsec packets and IKE exchanges.
Depending on the hardware and software platforms and the cause of the Depending on the hardware and software platforms and the cause of the
reboot, rebooting may take anywhere from a few seconds to several reboot, rebooting may take anywhere from a few seconds to several
minutes. If the implementation is down for a long time, the benefit minutes. If the implementation is down for a long time, the benefit
of this protocol extension is reduced. For this reason critical of this protocol extension is reduced. For this reason, critical
systems should implement backup gateways as described in Section 6. systems should implement backup gateways as described in Section 6.
Implementing the "token maker" side of QCD makes sense for IKE Implementing the "token maker" side of QCD makes sense for IKE
implementation where protected connections originate from the peer, implementation where protected connections originate from the peer,
such as inter-domain VPNs and remote access gateways. Implementing such as inter-domain VPNs and remote access gateways. Implementing
the "token taker" side of QCD makes sense for IKE implementations the "token taker" side of QCD makes sense for IKE implementations
where protected connections originate, such as inter-domain VPNs and where protected connections originate, such as inter-domain VPNs and
remote access clients. remote access clients.
To clarify the this discussion: To clarify this discussion:
o For remote-access clients it makes sense to implement the token o For remote-access clients it makes sense to implement the token
taker role. taker role.
o For remote-access gateways it makes sense to implement the token o For remote-access gateways it makes sense to implement the token
maker role. maker role.
o For inter-domain VPN gateways it makes sense to implement both o For inter-domain VPN gateways it makes sense to implement both
roles, because it can't be known in advance where the traffic roles, because it can't be known in advance where the traffic
originates. originates.
o It is perfectly valid to implement both roles in any case, for o It is perfectly valid to implement both roles in any case, for
example when using a single library or a single gateway to perform example, when using a single library or a single gateway to
several roles. perform several roles.
In order to limit the effects of DoS attacks, a token taker SHOULD In order to limit the effects of Denial-of-Service (DoS) attacks, a
limit the rate of QCD_TOKENs verified from a particular source. token taker SHOULD limit the rate of QCD_TOKENs verified from a
particular source.
If excessive amounts of IKE requests protected with unknown IKE SPIs If excessive amounts of IKE requests protected with unknown IKE SPIs
arrive at a token maker, the IKE module SHOULD revert to the behavior arrive at a token maker, the IKE module SHOULD revert to the behavior
described in section 2.21 of [RFC5996] and either send an described in Section 2.21 of [RFC5996] and either send an
INVALID_IKE_SPI notification, or ignore it entirely. INVALID_IKE_SPI notification or ignore it entirely.
Section 9.2 requires that token makers never send a QCD token in the Section 9.2 requires that token makers never send a QCD token in the
clear for a valid IKE SA, and describes some configurations where clear for a valid IKE SA and describes some configurations where this
this could occur. Implementations that may be installed in such could occur. Implementations that may be installed in such
configurations SHOULD automatically detect this and disable this configurations SHOULD automatically detect this and disable this
extension in unsafe configurations, and MUST allow the user to extension in unsafe configurations and MUST allow the user to control
control whether the extension is enabled or disabled. whether the extension is enabled or disabled.
8.2. Response to unknown child SPI 8.2. Response to Unknown Child SPI
After a reboot, it is more likely that an implementation receives After a reboot, it is more likely that an implementation will receive
IPsec packets than IKE packets. In that case, the rebooted IPsec packets than IKE packets. In that case, the rebooted
implementation will send an INVALID_SPI notification, triggering a implementation will send an INVALID_SPI notification, triggering a
liveness check. The token will only be sent in a response to the liveness check. The token will only be sent in a response to the
liveness check, thus requiring an extra round-trip. liveness check, thus requiring an extra round trip.
To avoid this, an implementation that has access to enough non- To avoid this, an implementation that has access to enough non-
volatile storage MAY store a mapping of child SPIs to owning IKE volatile storage MAY store a mapping of child SPIs to owning IKE
SPIs, or to generated tokens. If such a mapping is available and SPIs, or to generated tokens. If such a mapping is available and
persistent across reboots, the rebooted implementation SHOULD respond persistent across reboots, the rebooted implementation SHOULD respond
to the IPsec packet with an INVALID_SPI notification, along with the to the IPsec packet with an INVALID_SPI notification, along with the
appropriate QCD_Token notifications. A token taker SHOULD verify the appropriate QCD_TOKEN notifications. A token taker SHOULD verify the
QCD token that arrives with an INVALID_SPI notification the same as QCD token that arrives with an INVALID_SPI notification the same as
if it arrived with the IKE SPIs of the parent IKE SA. if it arrived with the IKE SPIs of the parent IKE SA.
However, a persistent storage module might not be updated in a timely However, a persistent storage module might not be updated in a timely
manner, and could be populated with tokens relating to IKE SPIs that manner and could be populated with tokens relating to IKE SPIs that
have already been rekeyed. A token taker MUST NOT take an invalid have already been rekeyed. A token taker MUST NOT take an invalid
QCD Token sent along with an INVALID_SPI notification as evidence QCD token sent along with an INVALID_SPI notification as evidence
that the peer is either malfunctioning or attacking, but it SHOULD that the peer is either malfunctioning or attacking, but it SHOULD
limit the rate at which such notifications are processed. limit the rate at which such notifications are processed.
9. Security Considerations 9. Security Considerations
The extension described in this document must not reduce the security The extension described in this document must not reduce the security
of IKEv2 or IPsec. Specifically, an eavesdropper must not learn any of IKEv2 or IPsec. Specifically, an eavesdropper must not learn any
non-public information about the peers. non-public information about the peers.
The proposed mechanism should be secure against attacks by a passive The proposed mechanism should be secure against attacks by a passive
MITM (eavesdropper). Such an attacker must not be able to disrupt an man in the middle (MITM) (eavesdropper). Such an attacker must not
existing IKE session, either by resetting the session or by be able to disrupt an existing IKE session, either by resetting the
introducing significant delays. This requirement is especially session or by introducing significant delays. This requirement is
significant, because this document introduces a new way to reset an especially significant, because this document introduces a new way to
IKE SA. reset an IKE SA.
The mechanism need not be similarly secure against an active MITM, The mechanism need not be similarly secure against an active MITM,
since this type of attacker is already able to disrupt IKE sessions. since this type of attacker is already able to disrupt IKE sessions.
9.1. QCD Token Generation and Handling 9.1. QCD Token Generation and Handling
Tokens MUST be hard to guess. This is critical, because if an Tokens MUST be hard to guess. This is critical, because if an
attacker can guess the token associated with an IKE SA, they can tear attacker can guess the token associated with an IKE SA, they can tear
down the IKE SA and associated tunnels at will. When the token is down the IKE SA and associated tunnels at will. When the token is
delivered in the IKE_AUTH exchange, it is encrypted. When it is sent delivered in the IKE_AUTH exchange, it is encrypted. When it is sent
skipping to change at page 17, line 47 skipping to change at page 17, line 13
sufficiently long. sufficiently long.
The token taker MUST store the token in a secure manner. No attacker The token taker MUST store the token in a secure manner. No attacker
should be able to gain access to a stored token. should be able to gain access to a stored token.
The QCD_SECRET MUST be protected from access by other parties. The QCD_SECRET MUST be protected from access by other parties.
Anyone gaining access to this value will be able to delete all the Anyone gaining access to this value will be able to delete all the
IKE SAs for this token maker. IKE SAs for this token maker.
The QCD token is sent by the rebooted peer in an unprotected message. The QCD token is sent by the rebooted peer in an unprotected message.
A message like that is subject to modification, deletion and replay A message like that is subject to modification, deletion, and replay
by an attacker. However, these attacks will not compromise the by an attacker. However, these attacks will not compromise the
security of either side. Modification is meaningless because a security of either side. Modification is meaningless because a
modified token is simply an invalid token. Deletion will only cause modified token is simply an invalid token. Deletion will only cause
the protocol not to work, resulting in a delay in tunnel re- the protocol not to work, resulting in a delay in tunnel
establishment as described in Section 2. Replay is also meaningless, re-establishment as described in Section 2. Replay is also
because the IKE SA has been deleted after the first transmission. meaningless, because the IKE SA has been deleted after the first
transmission.
9.2. QCD Token Transmission 9.2. QCD Token Transmission
A token maker MUST NOT send a valid QCD token in an unprotected A token maker MUST NOT send a valid QCD token in an unprotected
message for an existing IKE SA. message for an existing IKE SA.
This requirement is obvious and easy in the case of a single gateway. This requirement is obvious and easy in the case of a single gateway.
However, some implementations use a load balancer to divide the load However, some implementations use a load balancer to divide the load
between several physical gateways. It MUST NOT be possible even in between several physical gateways. It MUST NOT be possible even in
such a configuration to trick one gateway into sending a valid QCD such a configuration to trick one gateway into sending a valid QCD
token for an IKE SA which is valid on another gateway. This is true token for an IKE SA that is valid on another gateway. This is true
whether the attempt to trick the gateway uses the token taker's IP whether the attempt to trick the gateway uses the token taker's IP
address or a different IP address. address or a different IP address.
IPsec Failure Detection is not applicable to deployments where the IPsec failure detection is not applicable to deployments where the
QCD secret is shared by multiple gateways and the gateways cannot QCD secret is shared by multiple gateways and the gateways cannot
assess whether the token can be legitimately sent in the clear while assess whether the token can be legitimately sent in the clear while
another gateway may actually still own the SA's. Load balancer another gateway may actually still own the SA's. Load balancing
configurations typically fall in this category. In order for a load configurations typically fall in this category. In order for a load
balancing configuration of IPsec gateways to support this balancing configuration of IPsec gateways to support this
specification, all members MUST be able to tell whether a particular specification, all members MUST be able to tell whether a particular
IKE SA is active anywhere in the cluster. One way to do this is to IKE SA is active anywhere in the cluster. One way to do this is to
synchronize a list of active IKE SPIs among all the cluster members. synchronize a list of active IKE SPIs among all the cluster members.
Because it includes the token taker's IP address in the token Because it includes the token taker's IP address in the token
generation, the method in Section 5.2 can (under certain conditions) generation, the method in Section 5.2 can (under certain conditions)
prevent revealing the QCD token for an existing pair of IKE SPIs to prevent revealing the QCD token for an existing pair of IKE SPIs to
an attacker who is using a different IP address, even in a load- an attacker who is using a different IP address, even in a load-
skipping to change at page 18, line 49 skipping to change at page 18, line 14
the IKE SA in an attempt to trick that gateway into sending a QCD the IKE SA in an attempt to trick that gateway into sending a QCD
token for a valid IKE SA. That method should not be used unless the token for a valid IKE SA. That method should not be used unless the
load balancer guarantees that IKE packets from the same source IP load balancer guarantees that IKE packets from the same source IP
address always go to the same cluster member. address always go to the same cluster member.
9.3. QCD Token Enumeration 9.3. QCD Token Enumeration
An attacker may try to attack QCD if the generation algorithm An attacker may try to attack QCD if the generation algorithm
described in Section 5.1 is used. The attacker will send several described in Section 5.1 is used. The attacker will send several
fake IKE requests to the gateway under attack, receiving and fake IKE requests to the gateway under attack, receiving and
recording the QCD Tokens in the responses. This will allow the recording the QCD tokens in the responses. This will allow the
attacker to create a dictionary of IKE SPIs to QCD Tokens, which can attacker to create a dictionary of IKE SPIs to QCD tokens, which can
later be used to tear down any IKE SA. later be used to tear down any IKE SA.
Three factors mitigate this threat: Three factors mitigate this threat:
o The space of all possible IKE SPI pairs is huge: 2^128, so making o The space of all possible IKE SPI pairs is huge: 2^128, so making
such a dictionary is impractical. Even if we assume that one such a dictionary is impractical. Even if we assume that one
implementation always generates predictable IKE SPIs, the space is implementation always generates predictable IKE SPIs, the space is
still at least 2^64 entries, so making the dictionary is extremely still at least 2^64 entries, so making the dictionary is extremely
hard. To ensure this, token makers MUST generate unpredictable hard. To ensure this, token makers MUST generate unpredictable
IKE SPIs by using a cryptographically strong pseudo-random number IKE SPIs by using a cryptographically strong pseudo-random number
generator. generator.
o Throttling the amount of QCD_TOKEN notifications sent out, as o Throttling the amount of QCD_TOKEN notifications sent out, as
discussed in Section 8.1, especially when not soon after a crash discussed in Section 8.1, especially when not soon after a crash
will limit the attacker's ability to construct a dictionary. will limit the attacker's ability to construct a dictionary.
o The methods in Section 5.1 and Section 5.2 allow for a periodic o The methods in Section 5.1 and Section 5.2 allow for a periodic
change of the QCD_SECRET. Any such change invalidates the entire change of the QCD_SECRET. Any such change invalidates the entire
dictionary. dictionary.
10. IANA Considerations 10. IANA Considerations
IANA is requested to assign a notify message type from the status IANA has assigned a notify message type (16419) from the status types
types range (16406-40959) of the "IKEv2 Notify Message Types" range (16406-40959) of the "IKEv2 Notify Message Types" registry with
registry with name "QUICK_CRASH_DETECTION". the name "QUICK_CRASH_DETECTION".
11. Acknowledgements 11. Acknowledgements
We would like to thank Hannes Tschofenig and Yaron Sheffer for their We would like to thank Hannes Tschofenig and Yaron Sheffer for their
comments about Session Resumption. comments about Session Resumption.
Others who have contributed valuable comments are, in alphabetical Others who have contributed valuable comments are, in alphabetical
order, Lakshminath Dondeti, Paul Hoffman, Tero Kivinen, Scott C order, Lakshminath Dondeti, Paul Hoffman, Tero Kivinen, Scott C
Moonen, Magnus Nystrom, and Keith Welter. Moonen, Magnus Nystrom, and Keith Welter.
12. Change Log 12. References
This section lists all changes in this document
NOTE TO RFC EDITOR : Please remove this section in the final RFC
12.1. Changes from draft-ietf-ipsecme-failure-detection-05
o Some clarifications suggested by Magnus Nystrom.
12.2. Changes from draft-ietf-ipsecme-failure-detection-04
o Some more rephrasing of section 9.2 based on suggestions by Tero
Kivinen and Dave Wierbowski.
12.3. Changes from draft-ietf-ipsecme-failure-detection-03
o Merged section 9.4 into section 9.2.
o Multiple typos discovered by Scott Moonen, Keith Welter and Yaron.
12.4. Changes from draft-ietf-ipsecme-failure-detection-02
o Moved section 7 to Appendix A. Also changed some wording.
o Fixed some language in the "interaction with session resumption"
section to say that although liveness check MUST be done, there
are no time limits to how long an implementation takes before
starting liveness check, or ending it.
12.5. Changes from draft-ietf-ipsecme-failure-detection-01
o Fixed the language requiring random IKE SPIs.
o Some better explanation of the reasons to choose the methods in
Section 5.2 and the method in Section 5.1, to close issue #193.
o Added text to the beginning of Section 9 to accomodate issue #194.
12.6. Changes from draft-ietf-ipsecme-failure-detection-00
o Nits pointed out by Scott and Yaron.
o Pratima and Frederic are back on board.
o Changed IKEv2bis draft reference to RFC 5996.
o Resolved issues #189, #190, #191, and #192:
* Renamed section 4.5 and removed the requirement to send an
acknowledgement for the unprotected message.
* Moved the QCD token from the last to the first IKE_AUTH
request.
* Added a MUST to Section 9.3 to require that IKE SPIs be
randomly generated.
* Changed the language in Section 8.1, to not use RFC 2119
terminology.
* Moved the section describing why one would want the method
dependant on IP addresses (in Section 5.2 from operational
considerations to security considerations.
12.7. Changes from draft-nir-ike-qcd-07
o First WG version.
o Addressed Scott C Moonen's concern about collisions of QCD tokens.
o Updated references to point to IKEv2bis instead of RFC 4306 and
4718. Also converted draft reference for resumption to RFC 5723.
o Added Dave Wiebrowski as author, and removed Pratima and Frederic.
12.8. Changes from draft-nir-ike-qcd-03 and -04
Mostly editorial changes and cleaning up.
12.9. Changes from draft-nir-ike-qcd-02
o Described QCD token enumeration, following a question by
Lakshminath Dondeti.
o Added the ability to replace the QCD token for an existing IKE SA.
o Added tokens dependent on peer IP address and their interaction
with MOBIKE.
12.10. Changes from draft-nir-ike-qcd-01
o Removed stateless method.
o Added discussion of rekeying and resumption.
o Added discussion of non-synchronized load-balanced clusters of
gateways in the security considerations.
o Other wording fixes.
12.11. Changes from draft-nir-ike-qcd-00
o Merged proposal with draft-detienne-ikev2-recovery
o Changed the protocol so that the rebooted peer generates the
token. This has the effect, that the need for persistent storage
is eliminated.
o Added discussion of birth certificates.
12.12. Changes from draft-nir-qcr-00
o Changed name to reflect that this relates to IKE. Also changed
from quick crash recovery to quick crash detection to avoid
confusion with IFARE.
o Added more operational considerations.
o Added interaction with IFARE.
o Added discussion of backup gateways.
13. References
13.1. Normative References 12.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997. Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC4555] Eronen, P., "IKEv2 Mobility and Multihoming Protocol [RFC4555] Eronen, P., "IKEv2 Mobility and Multihoming Protocol
(MOBIKE)", RFC 4555, June 2006. (MOBIKE)", RFC 4555, June 2006.
[RFC5996] Kaufman, C., Hoffman, P., Nir, Y., and P. Eronen, [RFC5996] Kaufman, C., Hoffman, P., Nir, Y., and P. Eronen,
"Internet Key Exchange Protocol: IKEv2", RFC 5996, "Internet Key Exchange Protocol Version 2 (IKEv2)",
September 2010. RFC 5996, September 2010.
13.2. Informative References 12.2. Informative References
[RFC5723] Sheffer, Y. and H. Tschofenig, "IKEv2 Session Resumption", [RFC5723] Sheffer, Y. and H. Tschofenig, "Internet Key Exchange
RFC 5723, January 2010. Protocol Version 2 (IKEv2) Session Resumption", RFC 5723,
January 2010.
[RFC6027] Nir, Y., Ed., "IPsec Cluster Problem Statement", RFC 6027, [RFC6027] Nir, Y., "IPsec Cluster Problem Statement", RFC 6027,
October 2010. October 2010.
[recovery] [recovery] Detienne, F., Sethi, P., and Y. Nir, "Safe IKE Recovery",
Detienne, F., Sethi, P., and Y. Nir, "Safe IKE Recovery", Work in Progress, July 2009.
draft-detienne-ikev2-recovery (work in progress),
July 2009.
Appendix A. The Path Not Taken Appendix A. The Path Not Taken
A.1. Initiating a new IKE SA A.1. Initiating a New IKE SA
Instead of sending a QCD token, we could have the rebooted Instead of sending a QCD token, we could have the rebooted
implementation start an Initial exchange with the peer, including the implementation start an Initial exchange with the peer, including the
INITIAL_CONTACT notification. This would have the same effect, INITIAL_CONTACT notification. This would have the same effect,
instructing the peer to erase the old IKE SA, as well as establishing instructing the peer to erase the old IKE SA, as well as establishing
a new IKE SA with fewer rounds. a new IKE SA with fewer rounds.
The disadvantage here, is that in IKEv2 an authentication exchange The disadvantage here is that in IKEv2, an authentication exchange
MUST have a piggy-backed Child SA set up. Since our use case is such MUST have a piggybacked Child SA set up. Since our use-case is such
that the rebooted implementation does not have traffic flowing to the that the rebooted implementation does not have traffic flowing to the
peer, there are no good selectors for such a Child SA. peer, there are no good selectors for such a Child SA.
Additionally, when authentication is asymmetric, such as when EAP is Additionally, when authentication is asymmetric, such as when EAP is
used, it is not possible for the rebooted implementation to initiate used, it is not possible for the rebooted implementation to initiate
IKE. IKE.
A.2. SIR A.2. SIR
Another proposal that was considered for this work item is the SIR Another proposal that was considered for this work item is the SIR
extension, which is described in [recovery]. Under that proposal, extension, which is described in [recovery]. Under that proposal,
the non-rebooted peer sends a non-protected query to the possibly the non-rebooted peer sends a non-protected query to the possibly
rebooted peer, asking whether the IKE SA exists. The peer replies rebooted peer, asking whether the IKE SA exists. The peer replies
with either a positive or negative response, and the absence of a with either a positive or negative response, and the absence of a
positive response, along with the existence of a negative response is positive response, along with the existence of a negative response,
taken as proof that the IKE SA has really been lost. is taken as proof that the IKE SA has really been lost.
The working group preferred the QCD proposal to this one. The working group preferred the QCD proposal to this one.
A.3. Birth Certificates A.3. Birth Certificates
Birth Certificates is a method of crash detection that has never been Birth Certificates is a method of crash detection that has never been
formally defined. Bill Sommerfeld suggested this idea in a mail to formally defined. Bill Sommerfeld suggested this idea in a mail to
the IPsec mailing list on August 7, 2000, in a thread discussing the IPsec mailing list on August 7, 2000, in a thread discussing
methods of crash detection: methods of crash detection:
If we have the system sign a "birth certificate" when it If we have the system sign a "birth certificate" when it
reboots (including a reboot time or boot sequence number), reboots (including a reboot time or boot sequence number),
we could include that with a "bad spi" ICMP error and in we could include that with a "bad spi" ICMP error and in
the negotiation of the IKE SA. the negotiation of the IKE SA.
We believe that this method would have some problems. First, it We believe that this method would have some problems. First, it
requires Alice to store the certificate, so as to be able to compare requires Alice to store the certificate, so as to be able to compare
the public keys. That requires more storage than does a QCD token. the public keys. That requires more storage than does a QCD token.
Additionally, the public-key operations needed to verify the self- Additionally, the public key operations needed to verify the self-
signed certificates are more expensive for Alice. signed certificates are more expensive for Alice.
We believe that a symmetric-key operation such as proposed here is We believe that a symmetric-key operation such as proposed here is
more light-weight and simple than that implied by the Birth more light-weight and simple than that implied by the Birth
Certificate idea. Certificate idea.
A.4. Reducing Liveness Check Length A.4. Reducing Liveness Check Length
Some implementations require fewer retransmissions over a shorter Some implementations require fewer retransmissions over a shorter
period of time for cases of liveness check started because of an period of time for cases of liveness check started because of an
skipping to change at page 24, line 8 skipping to change at page 22, line 8
one minute, it is still a very noticeable delay from a human one minute, it is still a very noticeable delay from a human
perspective, from the time that the gateway has come up (i.e., is perspective, from the time that the gateway has come up (i.e., is
able to respond with an INVALID_SPI or INVALID_IKE_SPI notification) able to respond with an INVALID_SPI or INVALID_IKE_SPI notification)
and until the tunnels are active, or from the time the backup gateway and until the tunnels are active, or from the time the backup gateway
has taken over until the tunnels are active. The use of QCD tokens has taken over until the tunnels are active. The use of QCD tokens
can reduce this delay. can reduce this delay.
Authors' Addresses Authors' Addresses
Yoav Nir (editor) Yoav Nir (editor)
Check Point Software Technologies Ltd. Check Point Software Technologies, Ltd.
5 Hasolelim st. 5 Hasolelim st.
Tel Aviv 67897 Tel Aviv 67897
Israel Israel
Email: ynir@checkpoint.com EMail: ynir@checkpoint.com
David Wierbowski David Wierbowski
International Business Machines International Business Machines
1701 North Street 1701 North Street
Endicott, New York 13760 Endicott, New York 13760
United States United States
Email: wierbows@us.ibm.com EMail: wierbows@us.ibm.com
Frederic Detienne Frederic Detienne
Cisco Systems, Inc. Cisco Systems, Inc.
De Kleetlaan, 7 De Kleetlaan, 7
Diegem B-1831 Diegem B-1831
Belgium Belgium
Phone: +32 2 704 5681 Phone: +32 2 704 5681
Email: fd@cisco.com EMail: fd@cisco.com
Pratima Sethi Pratima Sethi
Cisco Systems, Inc. Cisco Systems, Inc.
O'Shaugnessy Road, 11 O'Shaugnessy Road, 11
Bangalore, Karnataka 560027 Bangalore, Karnataka 560027
India India
Phone: +91 80 4154 1654 Phone: +91 80 4154 1654
Email: psethi@cisco.com EMail: psethi@cisco.com
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