draft-ietf-ipsecme-ikev2-redirect-13.txt   rfc5685.txt 
Network Working Group V. Devarapalli Network Working Group V. Devarapalli
Internet-Draft WiChorus Request for Comments: 5685 WiChorus
Intended status: Standards Track K. Weniger Category: Standards Track K. Weniger
Expires: February 5, 2010 August 4, 2009 Unaffiliated
November 2009
Redirect Mechanism for IKEv2
draft-ietf-ipsecme-ikev2-redirect-13.txt
Status of this Memo
This Internet-Draft is submitted to IETF in full conformance with the
provisions of BCP 78 and BCP 79. This document may contain material
from IETF Documents or IETF Contributions published or made publicly
available before November 10, 2008. The person(s) controlling the
copyright in some of this material may not have granted the IETF
Trust the right to allow modifications of such material outside the
IETF Standards Process. Without obtaining an adequate license from
the person(s) controlling the copyright in such materials, this
document may not be modified outside the IETF Standards Process, and
derivative works of it may not be created outside the IETF Standards
Process, except to format it for publication as an RFC or to
translate it into languages other than English.
Internet-Drafts are working documents of the Internet Engineering Redirect Mechanism for
Task Force (IETF), its areas, and its working groups. Note that the Internet Key Exchange Protocol Version 2 (IKEv2)
other groups may also distribute working documents as Internet-
Drafts.
Internet-Drafts are draft documents valid for a maximum of six months Abstract
and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."
The list of current Internet-Drafts can be accessed at The Internet Key Exchange Protocol version 2 (IKEv2) is a protocol
http://www.ietf.org/ietf/1id-abstracts.txt. for setting up Virtual Private Network (VPN) tunnels from a remote
location to a gateway so that the VPN client can access services in
the network behind the gateway. This document defines an IKEv2
extension that allows an overloaded VPN gateway or a VPN gateway that
is being shut down for maintenance to redirect the VPN client to
attach to another gateway. The proposed mechanism can also be used
in Mobile IPv6 to enable the home agent to redirect the mobile node
to another home agent.
The list of Internet-Draft Shadow Directories can be accessed at Status of This Memo
http://www.ietf.org/shadow.html.
This Internet-Draft will expire on February 5, 2010. This document specifies an Internet standards track protocol for the
Internet community, and requests discussion and suggestions for
improvements. Please refer to the current edition of the "Internet
Official Protocol Standards" (STD 1) for the standardization state
and status of this protocol. Distribution of this memo is unlimited.
Copyright Notice Copyright Notice
Copyright (c) 2009 IETF Trust and the persons identified as the Copyright (c) 2009 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents in effect on the date of Provisions Relating to IETF Documents
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Please review these documents carefully, as they describe your rights publication of this document. Please review these documents
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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 BSD License.
Abstract This document may contain material from IETF Documents or IETF
Contributions published or made publicly available before November
10, 2008. The person(s) controlling the copyright in some of this
IKEv2 is a protocol for setting up Virtual Private Network (VPN) RFC 5685 IKEv2 Redirect November 2009
tunnels from a remote location to a gateway so that the VPN client
can access services in the network behind the gateway. This document material may not have granted the IETF Trust the right to allow
defines an IKEv2 extension that allows an overloaded VPN gateway or a modifications of such material outside the IETF Standards Process.
VPN gateway that is being shut down for maintenance to redirect the Without obtaining an adequate license from the person(s) controlling
VPN client to attach to another gateway. The proposed mechanism can the copyright in such materials, this document may not be modified
also be used in Mobile IPv6 to enable the home agent to redirect the outside the IETF Standards Process, and derivative works of it may
mobile node to another home agent. not be created outside the IETF Standards Process, except to format
it for publication as an RFC or to translate it into languages other
than English.
Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 1. Introduction ....................................................2
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3 2. Terminology .....................................................3
3. IKEv2 Initial Exchange with Redirect . . . . . . . . . . . . . 3 3. IKEv2 Initial Exchange with Redirect ............................3
4. Use of Anycast Addresses with the Redirect Mechanism . . . . . 5 4. Use of Anycast Addresses with the Redirect Mechanism ............5
5. Redirect During an Active Session . . . . . . . . . . . . . . 6 5. Redirect during an Active Session ...............................6
6. Redirect During IKE_AUTH Exchange . . . . . . . . . . . . . . 7 6. Redirect during IKE_AUTH Exchange ...............................7
7. Handling Redirect Loops . . . . . . . . . . . . . . . . . . . 8 7. Handling Redirect Loops .........................................8
8. Using the Redirect Mechanism with Mobile IPv6 . . . . . . . . 8 8. Using the Redirect Mechanism with Mobile IPv6 ...................8
9. Redirect Messages . . . . . . . . . . . . . . . . . . . . . . 9 9. Redirect Messages ...............................................9
9.1. REDIRECT_SUPPORTED . . . . . . . . . . . . . . . . . . . . 9 9.1. REDIRECT_SUPPORTED .........................................9
9.2. REDIRECT . . . . . . . . . . . . . . . . . . . . . . . . . 10 9.2. REDIRECT ..................................................10
9.3. REDIRECTED_FROM . . . . . . . . . . . . . . . . . . . . . 11 9.3. REDIRECTED_FROM ...........................................11
10. Use of the Redirect Mechanism between IKEv2 Peers . . . . . . 12 10. Use of the Redirect Mechanism between IKEv2 Peers .............12
11. Security Considerations . . . . . . . . . . . . . . . . . . . 12 11. Security Considerations .......................................12
12. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 13 12. IANA Considerations ...........................................13
13. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 13 13. Acknowledgements ..............................................13
14. References . . . . . . . . . . . . . . . . . . . . . . . . . . 14 14. References ....................................................14
14.1. Normative References . . . . . . . . . . . . . . . . . . . 14 14.1. Normative References .....................................14
14.2. Informative References . . . . . . . . . . . . . . . . . . 14 14.2. Informative References ...................................14
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 14
1. Introduction 1. Introduction
IKEv2 [2] is used for setting up IPsec [8] based VPNs. The IP IKEv2 [2] is used for setting up IPsec-based [7] VPNs. The IP
address of the VPN gateway can be configured on the VPN client. But address of the VPN gateway can be configured on the VPN client. But
this does not scale well, when the number of VPN gateways is large. this does not scale well when the number of VPN gateways is large.
Dynamic discovery of VPN gateways using DNS is quite widely used too. Dynamic discovery of VPN gateways using DNS is quite widely used too.
However, using DNS is not flexible when it comes to assigning a VPN However, using DNS is not flexible when it comes to assigning a VPN
gateway to the VPN client based on the load on the VPN gateways. The gateway to the VPN client based on the load on the VPN gateways. The
VPN client typically tries to connect to the IP address of the VPN VPN client typically tries to connect to the IP address of the VPN
gateway that appears first in the DNS response. If the VPN tunnel gateway that appears first in the DNS response. If the VPN tunnel
setup fails, then the VPN client tries to attach to the other VPN setup fails, then the VPN client tries to attach to the other VPN
gateways returned in the DNS response. gateways returned in the DNS response.
This document proposes a redirect mechanism for IKEv2 that enables a This document proposes a redirect mechanism for IKEv2 that enables a
VPN gateway to redirect the VPN client to another VPN gateway, for VPN gateway to redirect the VPN client to another VPN gateway, for
example, based on the load condition. The redirect can be done example, based on the load condition. The redirect can be done
during the IKE_SA_INIT or the IKE_AUTH exchange. Gateway-initiated during the IKE_SA_INIT or the IKE_AUTH exchange. Gateway-initiated
RFC 5685 IKEv2 Redirect November 2009
redirect in the middle of a session is also supported. The redirect redirect in the middle of a session is also supported. The redirect
mechanism can also be used in conjunction with anycast addresses. In mechanism can also be used in conjunction with anycast addresses. In
this case, anycast address for the cluster of VPN gateways is stored this case, an anycast address for the cluster of VPN gateways is
in the DNS instead of a list of unicast IP addresses of the VPN stored in the DNS instead of a list of unicast IP addresses of the
gateways. VPN gateways.
The redirect can also happen because of administrative or optimal The redirect can also happen because of administrative or optimal-
routing reasons. This document does not attempt to provide an routing reasons. This document does not attempt to provide an
exhaustive list of reasons for redirecting a VPN client to another exhaustive list of reasons for redirecting a VPN client to another
VPN gateway. VPN gateway.
2. Terminology 2. Terminology
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 [1]. document are to be interpreted as described in [1].
3. IKEv2 Initial Exchange with Redirect 3. IKEv2 Initial Exchange with Redirect
This section describes the use of Redirect mechanism during the This section describes the use of the redirect mechanism during the
IKE_SA_INIT exchange. Gateway-initiated redirect during an active IKE_SA_INIT exchange. Gateway-initiated redirect during an active
session and the use of redirect during IKE_AUTH exchange are session and the use of redirect during IKE_AUTH exchange are
explained in subsequent sections. explained in subsequent sections.
The VPN client indicates support for the IKEv2 redirect mechanism and The VPN client indicates support for the IKEv2 redirect mechanism and
the willingness to be redirected by including a REDIRECT_SUPPORTED its willingness to be redirected by including a REDIRECT_SUPPORTED
notification message in the initial IKE_SA_INIT request. (See notification message in the initial IKE_SA_INIT request (see
Section 9.1). The gateway MUST keep track of those clients that Section 9.1). The gateway MUST keep track of those clients that
indicated support for the redirect mechanism and those that didn't. indicated support for the redirect mechanism and those that didn't.
To redirect an IKEv2 session to another VPN gateway, the VPN gateway To redirect an IKEv2 session to another VPN gateway, the VPN gateway
that initially received the IKE_SA_INIT request selects another VPN that initially received the IKE_SA_INIT request selects another VPN
gateway (how the selection is made is beyond the scope of this gateway (how the selection is made is beyond the scope of this
document), and replies with an IKE_SA_INIT response containing a document) and replies with an IKE_SA_INIT response containing a
REDIRECT notification message. (See Section 9.2). The notification REDIRECT notification message (see Section 9.2). The notification
includes information about the selected VPN gateway, and the nonce includes information about the selected VPN gateway and the nonce
data from the Ni payload in the IKE_SA_INIT request. If the data from the Ni payload in the IKE_SA_INIT request. If the
IKE_SA_INIT request did not indicate support for the redirect IKE_SA_INIT request did not indicate support for the redirect
mechanism, the responder MUST NOT send the REDIRECT payload to the mechanism, the responder MUST NOT send the REDIRECT payload to the
VPN client. This is applicable to all REDIRECT scenarios described VPN client. This is applicable to all REDIRECT scenarios described
in this document. in this document.
Note that when the IKE_SA_INIT response includes the REDIRECT Note that when the IKE_SA_INIT response includes the REDIRECT
notification, the exchange does not result in the creation of an notification, the exchange does not result in the creation of an
IKE_SA and the responder SPI will be zero. IKE_SA and the responder Security Parameter Index (SPI) will be zero.
RFC 5685 IKEv2 Redirect November 2009
Initiator Responder (initial VPN GW) Initiator Responder (initial VPN GW)
--------- ------------------------- --------- -------------------------
(IP_I:500 -> Initial_IP_R:500) (IP_I:500 -> Initial_IP_R:500)
HDR(A,0), SAi1, KEi, Ni, --> HDR(A,0), SAi1, KEi, Ni, -->
N(REDIRECT_SUPPORTED) N(REDIRECT_SUPPORTED)
(Initial_IP_R:500 -> IP_I:500) (Initial_IP_R:500 -> IP_I:500)
<-- HDR(A,0), N(REDIRECT, New_GW_ID, Ni_data) <-- HDR(A,0), N(REDIRECT, New_GW_ID, Ni_data)
When the client receives the IKE_SA_INIT response, it MUST verify When the client receives the IKE_SA_INIT response, it MUST verify
that the nonce data matches the value sent in the IKE_SA_INIT that the nonce data matches the value sent in the IKE_SA_INIT
request. If the values do not match, the client MUST silently request. If the values do not match, the client MUST silently
discard the response (and keep waiting for another response). This discard the response (and keep waiting for another response). This
prevents certain Denial-of-Service attacks on the initiator that prevents certain denial-of-service (DoS) attacks on the initiator
could be caused by an attacker injecting IKE_SA_INIT responses with that could be caused by an attacker injecting IKE_SA_INIT responses
the REDIRECT payloads. with REDIRECT payloads.
After verifying the nonce data, the client initiates a new After verifying the nonce data, the client initiates a new
IKE_SA_INIT exchange with the VPN gateway listed in the REDIRECT IKE_SA_INIT exchange with the VPN gateway listed in the REDIRECT
payload provided this is allowed by its PAD entries. In the payload, provided this is allowed by its Peer Authorization Database
IKE_SA_INIT exchange with the new VPN gateway, the client MUST (PAD) entries. In the IKE_SA_INIT exchange with the new VPN gateway,
include the REDIRECTED_FROM payload. (See Section 9.3). The VPN the client MUST include the REDIRECTED_FROM payload (see
client includes the IP address of the original VPN gateway that Section 9.3). The VPN client includes the IP address of the original
redirected the client in the REDIRECTED_FROM notification. The IKEv2 VPN gateway that redirected the client in the REDIRECTED_FROM
exchange then proceeds as it would have proceeded with the original notification. The IKEv2 exchange then proceeds as it would have
VPN gateway. proceeded with the original VPN gateway.
Initiator Responder (Selected VPN GW) Initiator Responder (Selected VPN GW)
--------- --------------------------- --------- ---------------------------
(IP_I:500 -> IP_R:500) (IP_I:500 -> IP_R:500)
HDR(A,0), SAi1, KEi, Ni, --> HDR(A,0), SAi1, KEi, Ni, -->
N(REDIRECTED_FROM, Initial_IP_R) N(REDIRECTED_FROM, Initial_IP_R)
(IP_R:500 -> IP_I:500) (IP_R:500 -> IP_I:500)
<-- HDR(A,B), SAr1, KEr, Nr,[CERTREQ] <-- HDR(A,B), SAr1, KEr, Nr,[CERTREQ]
(IP_I:500 -> IP_R:500) (IP_I:500 -> IP_R:500)
HDR(A,B), SK {IDi, [CERT,] [CERTREQ,] HDR(A,B), SK {IDi, [CERT,] [CERTREQ,]
[IDr,]AUTH, SAi2, TSi, TSr} --> [IDr,]AUTH, SAi2, TSi, TSr} -->
(IP_R:500 -> IP_I:500) (IP_R:500 -> IP_I:500)
<-- HDR(A,B), SK {IDr, [CERT,] AUTH, <-- HDR(A,B), SK {IDr, [CERT,] AUTH,
SAr2, TSi, TSr} SAr2, TSi, TSr}
RFC 5685 IKEv2 Redirect November 2009
The client MAY get redirected again by the new VPN gateway if the new The client MAY get redirected again by the new VPN gateway if the new
VPN gateway cannot also serve the client. The client does not have VPN gateway also cannot serve the client. The client does not have
to include the REDIRECT_SUPPORTED payload again in the IKE_SA_INIT to include the REDIRECT_SUPPORTED payload again in the IKE_SA_INIT
exchange with the new gateway after a redirect. The presence of the exchange with the new gateway after a redirect. The presence of the
REDIRECT_FROM payload in the IKE_SA_INIT exchange with the new REDIRECT_FROM payload in the IKE_SA_INIT exchange with the new
gateway indicates to the new gateway that the client supports the gateway indicates to the new gateway that the client supports the
redirect mechanism. redirect mechanism.
When the client gets redirected, it MUST use the same Peer When the client gets redirected, it MUST use the same Peer
Authorization Database (PAD) and Security Policy Database (SPD) Authorization Database (PAD) and Security Policy Database (SPD)
entries as it would have used with the original gateway. Receiving a entries as it would have used with the original gateway. Receiving a
redirect notification MUST NOT result in the modification of any PAD redirect notification MUST NOT result in the modification of any PAD
or SPD entries. In practice, this means the new gateway either has or SPD entries. In practice, this means the new gateway either has
to use the same responder identity (IDr) as the original gateway, or to use the same responder identity (IDr) as the original gateway, or
both should be part of a group of responders that are authorized by both should be part of a group of responders that are authorized by
the same PAD entry. See section 4.4.3.1 of [8] on using DNS names to the same PAD entry. See Section 4.4.3.1 of [7] on using DNS names to
represent a group of peers in a PAD entry. represent a group of peers in a PAD entry.
This document allows the client to be redirected in several protocol
states. In some of them, the gateway is already authenticated at the
point of redirect; in others, it is not. We emphasize that the above
rules regarding the identity of the new gateway and the PAD and SPD
entries apply equally to all these scenarios.
4. Use of Anycast Addresses with the Redirect Mechanism 4. Use of Anycast Addresses with the Redirect Mechanism
The use of anycast addresses will avoid having to configure a Using anycast addresses will avoid the necessity of configuring a
particular VPN gateway's IP address in the DNS. Instead, the anycast particular VPN gateway's IP address in the DNS. Instead, the anycast
address that represents the group of VPN gateways is stored in the address that represents the group of VPN gateways is stored in the
DNS. When the VPN client performs a DNS lookup for the VPN gateway, DNS. When the VPN client performs a DNS lookup for the VPN gateway,
it receives the anycast address of the VPN gateway in the DNS it receives the anycast address of the VPN gateway in the DNS
response. response.
If an anycast address is returned in response to DNS resolution of an If an anycast address is returned in response to the DNS resolution
FQDN, the VPN client sends the IKE_SA_INIT request to the anycast of a Fully Qualified Domain Name (FQDN), the VPN client sends the
address. The REDIRECT_SUPPORTED payload is included in the IKE_SA_INIT request to the anycast address. The REDIRECT_SUPPORTED
IKE_SA_INIT request sent to the anycast address. The IKE_SA_INIT payload is included in the IKE_SA_INIT request sent to the anycast
request is routed to one of the VPN gateways that is part of the address. The IKE_SA_INIT request is routed to one of the VPN
anycast group. The VPN gateway that receives the IKE_SA_INIT request gateways that is part of the anycast group. The VPN gateway that
responds with an IKE_SA_INIT reply from the anycast address. receives the IKE_SA_INIT request responds with an IKE_SA_INIT reply
from the anycast address.
RFC 5685 IKEv2 Redirect November 2009
Initiator Responder (any VPN GW) Initiator Responder (any VPN GW)
--------- ------------------------- --------- -------------------------
(IP_I:500 -> ANYCAST:500) (IP_I:500 -> ANYCAST:500)
HDR(A,0), SAi1, KEi, Ni) --> HDR(A,0), SAi1, KEi, Ni) -->
N(REDIRECT_SUPPORTED) N(REDIRECT_SUPPORTED)
(ANYCAST:500 -> IP_I:500) (ANYCAST:500 -> IP_I:500)
<-- HDR(A,0), N(REDIRECT, New_GW_ID, Ni_data) <-- HDR(A,0), N(REDIRECT, New_GW_ID, Ni_data)
If the destination address on the IKE_SA_INIT request is an anycast If the destination address on the IKE_SA_INIT request is an anycast
address, the VPN gateway that received the IKE_SA_INIT request MUST address, the VPN gateway that received the IKE_SA_INIT request MUST
include the REDIRECT payload to redirect the VPN client to a unicast include the REDIRECT payload to redirect the VPN client to a unicast
address of one of the VPN gateway. The VPN gateway that received the address of one of the VPN gateways. The VPN gateway that received
IKE_SA_INIT request MAY redirect the client to its own unicast the IKE_SA_INIT request MAY redirect the client to its own unicast
address, if it is not overloaded. address if it is not overloaded.
The rest of the IKEv2 exchange is the same as described in Section 3. The rest of the IKEv2 exchange is the same as described in Section 3.
5. Redirect During an Active Session 5. Redirect during an Active Session
The redirect mechanism may also be used by a VPN gateway to redirect The redirect mechanism may also be used by a VPN gateway to redirect
the client to another VPN gateway in middle of a session. To the client to another VPN gateway in the middle of a session. To
redirect a client, the gateway should send an INFORMATIONAL message redirect a client, the gateway should send an INFORMATIONAL message
with the REDIRECT Notify payload. The REDIRECT payload MUST carry with the REDIRECT Notify payload. The REDIRECT payload MUST carry
information about the new VPN gateway. The gateway MUST NOT include information about the new VPN gateway. The gateway MUST NOT include
any nonce data in the REDIRECT payload, since it is a gateway- any nonce data in the REDIRECT payload, since it is a gateway-
initiated redirect and is protected by the IKEv2 security initiated redirect and is protected by the IKEv2 security
association. When the client receives this message, it sends a association. When the client receives this message, it sends a
response (usually empty) to the gateway. The gateway retransmits the response (usually empty) to the gateway. The gateway retransmits the
redirect INFORMATIONAL message as described in [2], until it gets a redirect INFORMATIONAL message as described in [2], until it gets a
response. The following illustrates the INFORMATIONAL message response. The following illustrates the INFORMATIONAL message
exchange for gateway-initiated redirect. exchange for gateway-initiated redirect.
skipping to change at page 7, line 12 skipping to change at page 7, line 4
HDR, SK {} --> HDR, SK {} -->
The INFORMATIONAL message exchange described above is protected by The INFORMATIONAL message exchange described above is protected by
the existing IKEv2 SA between the client and the gateway. the existing IKEv2 SA between the client and the gateway.
Once the client sends an acknowledgement to the gateway, it SHOULD Once the client sends an acknowledgement to the gateway, it SHOULD
delete the existing security associations with the old gateway by delete the existing security associations with the old gateway by
sending an INFORMATIONAL message with a DELETE payload. The gateway sending an INFORMATIONAL message with a DELETE payload. The gateway
MAY also decide to delete the security associations without any MAY also decide to delete the security associations without any
RFC 5685 IKEv2 Redirect November 2009
signaling from the client, again by sending an INFORMATIONAL message signaling from the client, again by sending an INFORMATIONAL message
with a DELETE payload. However, it should allow sufficient time for with a DELETE payload; however, it should allow sufficient time for
the client to setup the required security associations with the new the client to set up the required security associations with the new
security gateway. This time period should be configurable on the security gateway. This time period should be configurable on the
gateway. gateway.
6. Redirect During IKE_AUTH Exchange 6. Redirect during IKE_AUTH Exchange
If the gateway decides to redirect the client during the IKE_AUTH If the gateway decides to redirect the client during the IKE_AUTH
exchange, based on the identity presented by the client in the exchange, based on the identity presented by the client in the
IKE_AUTH request message, it prevents the creation of a CHILD SA and IKE_AUTH request message, it prevents the creation of a CHILD SA and
sends the REDIRECT payload in the IKE_AUTH response. The gateway sends the REDIRECT payload in the IKE_AUTH response. The gateway
MUST verify the client's AUTH payload before sending the Redirect MUST verify the client's AUTH payload before sending the REDIRECT
payload, and the client MUST verify the gateway's AUTH payload before payload, and the client MUST verify the gateway's AUTH payload before
acting on the Redirect payload. Since the AUTH payloads were acting on the REDIRECT payload. Since the AUTH payloads were
exchanged and successfully verified, the IKEv2 security association exchanged and successfully verified, the IKEv2 security association
is valid. When the client receives the IKE_AUTH response with the is valid. When the client receives the IKE_AUTH response with the
REDIRECT payload, it SHOULD delete the IKEv2 security association REDIRECT payload, it SHOULD delete the IKEv2 security association
with the gateway by sending an INFORMATIONAL message with a DELETE with the gateway by sending an INFORMATIONAL message with a DELETE
payload. payload.
Initiator Responder ( VPN GW) Initiator Responder (VPN GW)
--------- ------------------- --------- ------------------
(IP_I:500 -> IP_R:500) (IP_I:500 -> IP_R:500)
HDR(A,0), SAi1, KEi, Ni, --> HDR(A,0), SAi1, KEi, Ni, -->
N(REDIRECTED_SUPPORTED) N(REDIRECTED_SUPPORTED)
(IP_R:500 -> IP_I:500) (IP_R:500 -> IP_I:500)
<-- HDR(A,B), SAr1, KEr, Nr,[CERTREQ] <-- HDR(A,B), SAr1, KEr, Nr,[CERTREQ]
(IP_I:500 -> IP_R:500) (IP_I:500 -> IP_R:500)
HDR(A,B), SK {IDi, [CERT,] [CERTREQ,] HDR(A,B), SK {IDi, [CERT,] [CERTREQ,]
[IDr,]AUTH, SAi2, TSi, TSr} --> [IDr,]AUTH, SAi2, TSi, TSr} -->
(IP_R:500 -> IP_I:500) (IP_R:500 -> IP_I:500)
<-- HDR(A,B), SK {IDr, [CERT,] AUTH, <-- HDR(A,B), SK {IDr, [CERT,] AUTH,
N(REDIRECT, New_GW_ID)} N(REDIRECT, New_GW_ID)}
In case the IKE_AUTH exchange involves EAP authentication as In case the IKE_AUTH exchange involves Extensible Authentication
described in Section 2.16 of RFC 4306 [2], or multiple authentication Protocol (EAP) authentication (as described in Section 2.16 of RFC
methods as described in RFC 4739 [6], the gateway may decide to 4306 [2]) or multiple authentication methods (as described in RFC
redirect the client based on the interaction with the AAA server or 4739 [6]), the gateway may decide to redirect the client based on the
the external authentication server. In this case, the gateway MUST interaction with the Authentication, Authorization, and Accounting
send the REDIRECT Notification payload in either the first or the (AAA) server or the external authentication server. In this case,
last IKE_AUTH response. The client and the gateway MUST verify the the gateway MUST send the REDIRECT Notify payload in either the first
AUTH payloads as described above. or the last IKE_AUTH response. The client and the gateway MUST
verify the AUTH payloads as described above.
RFC 5685 IKEv2 Redirect November 2009
When EAP is used, the gateway MAY also redirect the client based on When EAP is used, the gateway MAY also redirect the client based on
the unauthenticated identity presented by the client in the first the unauthenticated identity presented by the client in the first
IKE_AUTH exchange itself. Since EAP is used as the authentication IKE_AUTH exchange, itself. Since EAP is used as the authentication
mechanism, the client does not include AUTH payload to authenticate mechanism, the client does not include AUTH payload to authenticate
his identity, but the server still MUST include his own AUTH payload, its identity, but the server MUST still include its own AUTH payload,
and client MUST verify it. Note that the IKEv2 SA is not created in and the client MUST verify it. Note that the IKEv2 SA is not created
this case and the client does not have to explicitly delete the IKEv2 in this case and the client does not have to explicitly delete the
SA. IKEv2 SA.
In all of the cases above, the client MUST accept the REDIRECT In all of the cases above, the client MUST accept the REDIRECT
notification only in the first IKE_AUTH response or the last IKE_AUTH notification only in the first IKE_AUTH response or the last IKE_AUTH
response. It MUST NOT accept the REDIRECT notification in an response. It MUST NOT accept the REDIRECT notification in an
intermediate IKE_AUTH response. intermediate IKE_AUTH response.
7. Handling Redirect Loops 7. Handling Redirect Loops
The client could end up getting redirected multiple times in a The client could end up getting redirected multiple times in a
sequence, either because of wrong configuration or a DoS attack. The sequence, either because of a wrong configuration or a DoS attack.
client could even end up in a loop with two or more gateways The client could even end up in a loop with two or more gateways
redirecting the client to each other. This could deny service to the redirecting the client to each other. This could deny service to the
client. To prevent this, the client SHOULD be configured not to client. To prevent this, the client SHOULD be configured to not
accept more than a certain number of redirects (MAX_REDIRECTS) within accept more than a certain number of redirects (MAX_REDIRECTS) within
a short time period (REDIRECT_LOOP_DETECT_PERIOD) for a particular a short time period (REDIRECT_LOOP_DETECT_PERIOD) for a particular
IKEv2 SA setup. The default value for MAX_REDIRECTS configuration IKEv2 SA setup. The default value for the MAX_REDIRECTS
variable is 5. The default value for REDIRECT_LOOP_DETECT_PERIOD configuration variable is 5. The default value for the
configuration variable is 300 seconds. Client implementations may REDIRECT_LOOP_DETECT_PERIOD configuration variable is 300 seconds.
allow these variables to be configured depending on a specific Client implementations may allow these variables to be configured,
deployment or system configuration. depending on a specific deployment or system configuration.
8. Using the Redirect Mechanism with Mobile IPv6 8. Using the Redirect Mechanism with Mobile IPv6
Mobile IPv6 [3] may use IKEv2 for mutual authentication between the Mobile IPv6 [3] may use IKEv2 for mutual authentication between the
mobile node and the home agent, for home address configuration and mobile node and the home agent, for home address configuration, and
for setting up security associations for protecting Mobile IPv6 for setting up security associations for protecting Mobile IPv6
signaling messages [4]. The IKEv2 exchange, if IKEv2 is used, signaling messages [4]. The IKEv2 exchange, if IKEv2 is used,
precedes the exchange of Mobile IPv6 signaling messages. Therefore, precedes the exchange of Mobile IPv6 signaling messages. Therefore,
the mechanism described in this document can also be used by a Mobile the mechanism described in this document can also be used by a Mobile
IPv6 home agent to redirect a mobile node to another home agent. IPv6 home agent to redirect a mobile node to another home agent.
There is a Home Agent Switch mechanism available for redirecting a There is a Home Agent Switch mechanism available for redirecting a
mobile node to another home agent, described in [5]. The Home Agent mobile node to another home agent, described in [5]. The Home Agent
Switch mechanism can only be used after the binding cache had been Switch mechanism can only be used after the binding cache has been
created at the home agent for the mobile node. The disadvantage with created at the home agent for the mobile node. The disadvantage with
this is that quite a bit of state is created on the home agent before this is that quite a bit of state is created on the home agent before
the mobile node can be redirected to another home agent. The the mobile node can be redirected to another home agent. The
mechanism described in this document can be used for redirecting a mechanism described in this document can be used for redirecting a
mobile node before any state related to the Mobile IPv6 binding is mobile node before any state related to the Mobile IPv6 binding is
created on the home agent. created on the home agent.
When running IKEv2 between a Mobile IPv6 Mobile Node (MN) and Home RFC 5685 IKEv2 Redirect November 2009
Agent (HA), redirecting the IKEv2 exchange to another HA is not
enough; the Mobile IPv6 signalling also needs to be sent to the new When running IKEv2 between a Mobile IPv6 mobile node (MN) and home
HA address. The MN MAY treat the information received in the agent (HA), redirecting the IKEv2 exchange to another HA is not
IKE_SA_INIT response in similar way as it would treat HA discovery enough; the Mobile IPv6 signaling also needs to be sent to the new HA
address. The MN MAY treat the information received in the
IKE_SA_INIT response in a similar way as it would treat HA discovery
information received from other unauthenticated (and potentially information received from other unauthenticated (and potentially
untrustworthy) sources (such as DNS lookups not protected with untrustworthy) sources (such as DNS lookups not protected with DNS
DNSSEC). However, if the MN has authenticated information about its Security (DNSSEC)). However, if the MN has authenticated information
Home Agent, it MUST NOT be updated based on the IKE_SA_INIT response. about its home agent, it MUST NOT be updated based on the IKE_SA_INIT
response.
If the REDIRECT notification is received during the IKE_AUTH exchange If the REDIRECT notification is received during the IKE_AUTH exchange
(after the HA has been authenticated; see Section 6), the MN MAY pass (after the HA has been authenticated; see Section 6), the MN MAY pass
the new address to Mobile IPv6 and treat it in similar fashion as the new address to Mobile IPv6 and treat it in a similar fashion as
information from the Home Agent Switch Message [5]. information from the Home Agent Switch message [5].
Gateway-initiated REDIRECT notifications exchanged in INFORMATIONAL Gateway-initiated REDIRECT notifications exchanged in INFORMATIONAL
exchanges (see Section 5) MUST NOT result in updating any Mobile IPv6 exchanges (see Section 5) MUST NOT result in updating any Mobile IPv6
state. In such cases, the Home Agent Switch Message specified in [5] state. In such cases, the Home Agent Switch message specified in [5]
is used instead. is used instead.
9. Redirect Messages 9. Redirect Messages
9.1. REDIRECT_SUPPORTED 9.1. REDIRECT_SUPPORTED
The REDIRECT_SUPPORTED payload is included in the initial IKE_SA_INIT The REDIRECT_SUPPORTED payload is included in the initial IKE_SA_INIT
request by the initiator to indicate support for the IKEv2 redirect request by the initiator to indicate support for the IKEv2 redirect
mechanism described in this document. mechanism described in this document.
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Next Payload |C| RESERVED | Payload Length | | Next Payload |C| RESERVED | Payload Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|Protocol ID(=0)| SPI Size (=0) | Notify Message Type | |Protocol ID(=0)| SPI Size (=0) | Notify Message Type |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
The 'Next Payload', 'Payload Length', 'Protocol ID', 'SPI Size' and The 'Next Payload', 'Payload Length', 'Protocol ID', 'SPI Size', and
the 'Notify Message Type' fields are the same as described in Section 'Notify Message Type' fields are the same as described in Section
3.10 of [2]. The 'SPI Size' field MUST be set to 0 to indicate that 3.10 of [2]. 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 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 set to 0, since the notification is not specific to a particular
security association. security association.
The 'Payload Length' field is set to the length in octets of the The 'Payload Length' field is set to the length in octets of the
entire payload, including the generic payload header. The 'Notify entire payload, including the generic payload header. The 'Notify
Message Type' field is set to indicate the REDIRECT_SUPPORTED payload Message Type' field is set to indicate the REDIRECT_SUPPORTED payload
<value to be assigned by IANA>. (16406).
RFC 5685 IKEv2 Redirect November 2009
9.2. REDIRECT 9.2. REDIRECT
The REDIRECT payload is included in an IKE_SA_INIT response from the When the responder wants to redirect the initiator to another VPN
responder or an INFORMATIONAL message from the responder, when the gateway, the REDIRECT payload is included in either an IKE_SA_INIT
responder wants to redirect the initiator to another VPN gateway. response from the responder or an INFORMATIONAL message from the
The message includes the new responder's IP address or DNS name. responder. The message includes the new responder's IP address or
DNS name.
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Next Payload |C| RESERVED | Payload Length | | Next Payload |C| RESERVED | Payload Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|Protocol ID(=0)| SPI Size (=0) | Notify Message Type | |Protocol ID(=0)| SPI Size (=0) | Notify Message Type |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| GW Ident Type | GW Ident Len | | | GW Ident Type | GW Ident Len | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ~ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ~
~ New Responder GW Identity ~ ~ New Responder GW Identity ~
| | | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| | | |
~ Nonce Data ~ ~ Nonce Data ~
| | | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
The 'Next Payload', 'Payload Length', 'Protocol ID', 'SPI Size' and The 'Next Payload', 'Payload Length', 'Protocol ID', 'SPI Size', and
the 'Notify Message Type' fields are the same as described in Section 'Notify Message Type' fields are the same as described in Section
3.10 of [2]. The 'SPI Size' field MUST be set to 0 to indicate that 3.10 of [2]. 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 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 set to 0, since the notification is not specific to a particular
security association. security association.
The 'Payload Length' field is set to the length in octets of the The 'Payload Length' field is set to the length in octets of the
entire payload, including the generic payload header. 'Notify entire payload, including the generic payload header. The 'Notify
Message Type' field is set to indicate the REDIRECT payload <value to Message Type' field is set to indicate the REDIRECT payload (16407).
be assigned by IANA>. The 'GW Identity Type' field indicates the The 'GW Identity Type' field indicates the type of information that
type of information that is sent to identify the new VPN gateway. is sent to identify the new VPN gateway. The following values are
The following values are valid in the REDIRECT payload. valid in the REDIRECT payload.
1 - IPv4 address of the new VPN gateway 1 - IPv4 address of the new VPN gateway
2 - IPv6 address of the new VPN gateway 2 - IPv6 address of the new VPN gateway
3 - FQDN of the new VPN gateway 3 - FQDN of the new VPN gateway
RFC 5685 IKEv2 Redirect November 2009
The 'GW Ident Len' field is set to the length of the gateway identity The 'GW Ident Len' field is set to the length of the gateway identity
information. The identity of the new VPN gateway is carried in the information. The identity of the new VPN gateway is carried in the
'New Responder GW Identity' field. The IPv4 address, the IPv6 'New Responder GW Identity' field. The IPv4 address, the IPv6
address or the FQDN of the new VPN gateway MUST be encoded as address, or the FQDN of the new VPN gateway MUST be encoded as
described in section 3.5 of [2]. described in Section 3.5 of [2].
The 'Nonce Data' field carries the nonce data from the Ni payload The 'Nonce Data' field carries the nonce data from the Ni payload
sent by the initiator. The size of the nonce MUST be between 16 and sent by the initiator. The size of the nonce MUST be between 16 and
256 bytes as described in Section 3.9 of [2]. The 'Nonce Data' field 256 bytes, as described in Section 3.9 of [2]. The 'Nonce Data'
is present in the REDIRECT payload only when the REDIRECT payload is field is present in the REDIRECT payload only when the REDIRECT
sent in the IKE_SA_INIT response message. It MUST NOT be included in payload is sent in the IKE_SA_INIT response message. It MUST NOT be
the REDIRECT payload if sent in an IKE_AUTH response or in a gateway- included in the REDIRECT payload if sent in an IKE_AUTH response or
initiated redirect message. in a gateway-initiated redirect message.
9.3. REDIRECTED_FROM 9.3. REDIRECTED_FROM
The REDIRECTED_FROM notification payload is included in the The REDIRECTED_FROM Notify payload is included in the IKE_SA_INIT
IKE_SA_INIT request from the initiator to the new VPN gateway to request from the initiator to the new VPN gateway to indicate the IP
indicate the IP address of the original VPN gateway that redirected address of the original VPN gateway that redirected the initiator.
the initiator. The original VPN gateway's IP address is included in The original VPN gateway's IP address is included in the message. If
the message. If the IKE_SA_INIT request was sent to any anycast the IKE_SA_INIT request was sent to any anycast address (see
address (see Section 4), then the anycast address is included in the Section 4), then the anycast address is included in the message.
message. This payload also serves the purpose of indicating support This payload also serves the purpose of indicating support for the
for the redirect mechanism to the new VPN gateway after a redirect. redirect mechanism to the new VPN gateway after a redirect.
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Next Payload |C| RESERVED | Payload Length | | Next Payload |C| RESERVED | Payload Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|Protocol ID(=0)| SPI Size (=0) | Notify Message Type | |Protocol ID(=0)| SPI Size (=0) | Notify Message Type |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| GW Ident Type | GW Ident Len | | | GW Ident Type | GW Ident Len | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ~ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ~
~ Original Responder GW Identity ~ ~ Original Responder GW Identity ~
| | | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
The 'Next Payload', 'Payload Length', 'Protocol ID', 'SPI Size' and The 'Next Payload', 'Payload Length', 'Protocol ID', 'SPI Size', and
the 'Notify Message Type' fields are the same as described in Section 'Notify Message Type' fields are the same as described in Section
3.10 of [2] The 'SPI Size' field MUST be set to 0 to indicate that 3.10 of [2]. 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 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 set to 0, since the notification is not specific to a particular
security association. security association.
The 'Payload Length' field is set to the length in octets of the The 'Payload Length' field is set to the length in octets of the
entire payload, including the generic payload header. The 'Notify entire payload, including the generic payload header. The 'Notify
Message Type' field is set to indicate the REDIRECTED_FROM payload Message Type' field is set to indicate the REDIRECTED_FROM payload
<value to be assigned by IANA>. The 'GW Identity Type' field
indicates the type of information that is sent to identify the new RFC 5685 IKEv2 Redirect November 2009
VPN gateway. The following values are valid in the REDIRECTED_FROM
payload. (16408). The 'GW Identity Type' field indicates the type of
information that is sent to identify the new VPN gateway. The
following values are valid in the REDIRECTED_FROM payload.
1 - IPv4 address of the original VPN gateway 1 - IPv4 address of the original VPN gateway
2 - IPv6 address of the original VPN gateway 2 - IPv6 address of the original VPN gateway
The 'GW Ident Len' field is set to the length of the gateway identity The 'GW Ident Len' field is set to the length of the gateway identity
information. The identity of the original VPN gateway is carried in information. The identity of the original VPN gateway is carried in
the 'Original Responder GW Identity' field. the 'Original Responder GW Identity' field.
10. Use of the Redirect Mechanism between IKEv2 Peers 10. Use of the Redirect Mechanism between IKEv2 Peers
The Redirect mechanism described in this document is mainly intended The redirect mechanism described in this document is mainly intended
for use in client-gateway scenarios. However, the mechanism can also for use in client-gateway scenarios. However, the mechanism can also
be used between any two IKEv2 peers. But this protocol is be used between any two IKEv2 peers. But this protocol is
asymmetric, meaning that only the original responder can redirect the asymmetric, meaning that only the original responder can redirect the
original initiator to another server. original initiator to another server.
11. Security Considerations 11. Security Considerations
An eavesdropper on the path between VPN client and server may send a An eavesdropper on the path between a VPN client and server may send
redirect to the client upon receiving an IKE_SA_INIT message from a redirect to the client upon receiving an IKE_SA_INIT message from
this client. This is no problem regarding DoS attacks for the VPN this client. This is no problem regarding DoS attacks for the VPN
connection, since an on-path-attacker can as well drop the connection, since an on-path-attacker can as well drop the
IKE_SA_INIT requests to prevent VPN access for the client. But an IKE_SA_INIT requests to prevent VPN access for the client. But an
eavesdropper on the path between VPN client and server can redirect a eavesdropper on the path between VPN client and server can redirect a
large number of clients to a victim, which is then flooded with large number of clients to a victim, which is then flooded with
IKE_SA_INIT requests. Flooding only happens if many clients initiate IKE_SA_INIT requests. Flooding only happens if many clients initiate
IKEv2 exchange at almost the same time, which is considered a rare IKEv2 exchange at almost the same time, which is considered a rare
event. However, this may happen if a Home Agent/VPN server is event. However, this may happen if a home agent / VPN server is
shutdown for maintenance and all clients need to re-establish VPN shutdown for maintenance and all clients need to re-establish VPN
connections with another Home Agent/VPN server or if the on-path connections with another home agent / VPN server, or if the on-path
attacker forces all IPsec security associations to expire by dropping attacker forces all IPsec security associations to expire by dropping
all received IKEv2 messages. all received IKEv2 messages.
The use of REDIRECTED_FROM payload is intended to discourage a rogue The use of the REDIRECTED_FROM payload is intended to discourage a
VPN gateway from redirecting a large number of VPN clients to a rogue VPN gateway from redirecting a large number of VPN clients to a
particular VPN gateway. It does not prevent such a DoS attack. particular VPN gateway. It does not prevent such a DoS attack.
The redirect mechanism MUST NOT update any state on the client apart The redirect mechanism MUST NOT update any state on the client apart
from the VPN gateway information. When used with Mobile IPv6, care from the VPN gateway information. When used with Mobile IPv6, care
must be taken to ensure that the home agent information that the must be taken to ensure that the home agent information that the
mobile node has configured is not modified wrongly by the redirect mobile node has configured is not modified wrongly by the redirect
message. message.
RFC 5685 IKEv2 Redirect November 2009
Redirecting based on the unauthenticated identities from the client Redirecting based on the unauthenticated identities from the client
might leak out information about the user when an active attacker, might leak out information about the user when an active attacker,
pretending to be a VPN client can get information to which gateway pretending to be a VPN client, can get information on the gateway to
the real user was redirected to. If redirection is based on some which the real user was redirected. If redirection is based on some
internal information of the user, it might leak information to internal information of the user, it might leak information (that
attacker about the user which might not be available otherwise. To might not be available otherwise) about the user to the attacker. To
prevent these kind of attacks, redirection based on unauthenticated prevent these kinds of attacks, redirection based on unauthenticated
ID should be avoided and should be done only after the client has IDs should be avoided and should be done only after the client has
also authenticated itself. also authenticated itself.
12. IANA Considerations 12. IANA Considerations
This document defines three new IKEv2 Notification Message types as This document defines three new IKEv2 Notify Message Types, as
described in Section 9. The three Notify Message Types must be described in Section 9. The three Notify Message Types have been
assigned values between 16396 and 40959. assigned the following values:
o REDIRECT_SUPPORTED 16406 - REDIRECT_SUPPORTED
o REDIRECT
o REDIRECTED_FROM 16407 - REDIRECT
16408 - REDIRECTED_FROM
This document creates a new namespace called the "Gateway Identity This document creates a new namespace called the "Gateway Identity
Type". This is used to indicate the type of information regarding Type". This is used to indicate the type of information regarding
the VPN gateway that is carried in the REDIRECT (Section 9.2) and the VPN gateway that is carried in the REDIRECT (Section 9.2) and
REDIRECTED_FROM (Section 9.3) Notification payloads. The following REDIRECTED_FROM (Section 9.3) Notify payloads. The following values
values are assigned. have been assigned.
1 - IPv4 address of the new VPN gateway 1 - IPv4 address of the VPN gateway
2 - IPv6 address of the new VPN gateway
3 - FQDN of the new VPN gateway
Values '0', and 4-240 are reserved. New values can be allocated by 2 - IPv6 address of the VPN gateway
Expert Review [9]. Values 241-255 are set aside for private use. A
specification that extends this registry MUST also mention which of 3 - FQDN of the VPN gateway
the new values are valid in which Notification payload.
Value '0' is reserved. Values 4-240 are unassigned. New values can
be allocated by Expert Review [8]. Values 241-255 are set aside for
private use. A specification that extends this registry MUST also
mention which of the new values are valid in which Notify payload.
13. Acknowledgements 13. Acknowledgements
The use of anycast address with IKEv2 was first described in [7]. It The use of anycast addresses with IKEv2 was first proposed by K.
was then added to an early draft version of RFC 5026 and later Weniger and F. Dupont in the context of home agent assignment in
removed before the RFC was published. Therefore the authors of [7] Mobile IPv6 / Network Mobility (NEMO) bootstrapping. It was then
and RFC 5026 are acknowledged. added to an early version of [4] and later removed before the RFC was
published. The authors of RFC 5026 are acknowledged.
RFC 5685 IKEv2 Redirect November 2009
Thanks to Pasi Eronen, with whom the solution described in this Thanks to Pasi Eronen, with whom the solution described in this
document was extensively discussed. Thanks to Tero Kivinen for document was extensively discussed. Thanks to Tero Kivinen for
suggesting the use of REDIRECTED_FROM payload and other comments suggesting the use of the REDIRECTED_FROM payload and other comments
which helped improve the document. The authors would also like to that helped improve the document. The authors would also like to
thank Yaron Sheffer, Sunil Kumar, Fan Zhao, Yoav Nir, Richard thank Yaron Sheffer, Sunil Kumar, Fan Zhao, Yoav Nir, Richard
Graveman, Kanagavel Rajan, Srini Addepalli, Raj Singh, and Arnaud Graveman, Kanagavel Rajan, Srini Addepalli, Raj Singh, and Arnaud
Ebalard for their reviews and comments. Ebalard for their reviews and comments.
14. References 14. References
14.1. Normative References 14.1. Normative References
[1] Bradner, S., "Key words for use in RFCs to Indicate Requirement [1] Bradner, S., "Key words for use in RFCs to Indicate Requirement
Levels", BCP 14, RFC 2119, March 1997. Levels", BCP 14, RFC 2119, March 1997.
skipping to change at page 14, line 38 skipping to change at page 14, line 40
[4] Giaretta, G., Kempf, J., and V. Devarapalli, "Mobile IPv6 [4] Giaretta, G., Kempf, J., and V. Devarapalli, "Mobile IPv6
Bootstrapping in Split Scenario", RFC 5026, October 2007. Bootstrapping in Split Scenario", RFC 5026, October 2007.
[5] Haley, B., Devarapalli, V., Deng, H., and J. Kempf, "Mobility [5] Haley, B., Devarapalli, V., Deng, H., and J. Kempf, "Mobility
Header Home Agent Switch Message", RFC 5142, January 2008. Header Home Agent Switch Message", RFC 5142, January 2008.
[6] Eronen, P. and J. Korhonen, "Multiple Authentication Exchanges [6] Eronen, P. and J. Korhonen, "Multiple Authentication Exchanges
in the Internet Key Exchange (IKEv2) Protocol", RFC 4739, in the Internet Key Exchange (IKEv2) Protocol", RFC 4739,
November 2006. November 2006.
[7] Weniger, K. and F. Dupont, "IKEv2-based Home Agent Assignment in [7] Kent, S. and K. Seo, "Security Architecture for the Internet
Mobile IPv6/NEMO Bootstrapping", draft-dupont-ikev2-haassign-02
(work in progress), January 2007.
[8] Kent, S. and K. Seo, "Security Architecture for the Internet
Protocol", RFC 4301, December 2005. Protocol", RFC 4301, December 2005.
[9] Narten, T. and H. Alvestrand, "Guidelines for Writing an IANA [8] Narten, T. and H. Alvestrand, "Guidelines for Writing an IANA
Considerations Section in RFCs", BCP 26, RFC 5226, May 2008. Considerations Section in RFCs", BCP 26, RFC 5226, May 2008.
RFC 5685 IKEv2 Redirect November 2009
Authors' Addresses Authors' Addresses
Vijay Devarapalli Vijay Devarapalli
WiChorus WiChorus
3590 North First St 3590 North First St
San Jose, CA 95134 San Jose, CA 95134
USA USA
Email: vijay@wichorus.com EMail: vijay@wichorus.com
Kilian Weniger Kilian Weniger
Unaffiliated
Email: kilian.weniger@googlemail.com EMail: kilian.weniger@googlemail.com
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