draft-ietf-ipsecme-ikev2-redirect-08.txt   draft-ietf-ipsecme-ikev2-redirect-09.txt 
Network Working Group V. Devarapalli Network Working Group V. Devarapalli
Internet-Draft WiChorus Internet-Draft WiChorus
Intended status: Standards Track K. Weniger Intended status: Standards Track K. Weniger
Expires: October 15, 2009 April 13, 2009 Expires: November 12, 2009 May 11, 2009
Redirect Mechanism for IKEv2 Redirect Mechanism for IKEv2
draft-ietf-ipsecme-ikev2-redirect-08.txt draft-ietf-ipsecme-ikev2-redirect-09.txt
Status of this Memo Status of this Memo
This Internet-Draft is submitted to IETF in full conformance with the This Internet-Draft is submitted to IETF in full conformance with the
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than English. than English.
Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
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and may be updated, replaced, or obsoleted by other documents at any and may be updated, replaced, or obsoleted by other documents at any
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This Internet-Draft will expire on October 15, 2009. This Internet-Draft will expire on November 12, 2009.
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 in effect on the date of
publication of this document (http://trustee.ietf.org/license-info). publication of this document (http://trustee.ietf.org/license-info).
Please review these documents carefully, as they describe your rights Please review these documents carefully, as they describe your rights
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attach to another gateway. This document proposes a redirect attach to another gateway. This document proposes a redirect
mechanism for IKEv2. The proposed mechanism can also be used in mechanism for IKEv2. The proposed mechanism can also be used in
Mobile IPv6 to enable the home agent to redirect the mobile node to Mobile IPv6 to enable the home agent to redirect the mobile node to
another home agent. another home agent.
Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 4 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 4
3. IKEv2 Initial Exchange with Redirect . . . . . . . . . . . . . 4 3. IKEv2 Initial Exchange with Redirect . . . . . . . . . . . . . 4
4. Use of Anycast Addresses with the Redirect Mechanism . . . . . 5 4. Use of Anycast Addresses with the Redirect Mechanism . . . . . 6
5. Gateway Initiated Redirect . . . . . . . . . . . . . . . . . . 6 5. Gateway Initiated Redirect . . . . . . . . . . . . . . . . . . 7
6. Redirect During IKE_AUTH Exchange . . . . . . . . . . . . . . 7 6. Redirect During IKE_AUTH Exchange . . . . . . . . . . . . . . 7
7. Redirect Messages . . . . . . . . . . . . . . . . . . . . . . 8 7. Redirect Messages . . . . . . . . . . . . . . . . . . . . . . 8
7.1. REDIRECT_SUPPORTED . . . . . . . . . . . . . . . . . . . . 8 7.1. REDIRECT_SUPPORTED . . . . . . . . . . . . . . . . . . . . 9
7.2. REDIRECT . . . . . . . . . . . . . . . . . . . . . . . . . 8 7.2. REDIRECT . . . . . . . . . . . . . . . . . . . . . . . . . 9
7.3. REDIRECTED_FROM . . . . . . . . . . . . . . . . . . . . . 10 7.3. REDIRECTED_FROM . . . . . . . . . . . . . . . . . . . . . 10
8. Use of the Redirect Mechanism between IKEv2 Peers . . . . . . 10 8. Use of the Redirect Mechanism between IKEv2 Peers . . . . . . 11
9. Security Considerations . . . . . . . . . . . . . . . . . . . 11 9. Security Considerations . . . . . . . . . . . . . . . . . . . 11
10. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 11 10. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 12
11. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 12 11. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 13
12. References . . . . . . . . . . . . . . . . . . . . . . . . . . 12 12. References . . . . . . . . . . . . . . . . . . . . . . . . . . 13
12.1. Normative References . . . . . . . . . . . . . . . . . . . 12 12.1. Normative References . . . . . . . . . . . . . . . . . . . 13
12.2. Informative References . . . . . . . . . . . . . . . . . . 12 12.2. Informative References . . . . . . . . . . . . . . . . . . 13
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 13 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 14
1. Introduction 1. Introduction
IKEv2 [2] is used for setting up IPsec-based VPNs. The IP address of IKEv2 [2] is used for setting up IPsec-based VPNs. The IP address of
the VPN gateway can be configured on the VPN client. But this does the VPN gateway can be configured on the VPN client. But this does
not scale well, when the number of VPN gateways is large. Dynamic not scale well, when the number of VPN gateways is large. Dynamic
discovery of VPN gateways using DNS is quite widely used too. 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
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"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 Redirect mechanism during the
IKE_SA_INIT exchange. Gateway-initiated redirect and the use of IKE_SA_INIT exchange. Gateway-initiated redirect and the use of
redirect during IKE_AUTH exchange are explained in subsequent redirect during IKE_AUTH exchange are explained in subsequent
sections. sections.
To redirect an IKEv2 session to another VPN gateway, the VPN gateway
that initially received the IKE_SA_INIT request selects another VPN
gateway and responds to the VPN client with a REDIRECT Notification
payload. The mechanism by which the initial VPN gateway selects
another VPN gateway is out of scope for this document. The IP
address of the selected VPN gateway is sent in the REDIRECT payload.
The gateway MUST include the nonce data from the Ni payload sent by
the initiator in the REDIRECT payload. This prevents certain Denial-
of-Service attacks on the initiator that could be caused by an
attacker injecting IKE_SA_INIT responses with REDIRECT payloads.
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 the willingness to be redirected by including a REDIRECT_SUPPORTED
notification message in the initial IKE_SA_INIT request. If the notification message in the initial IKE_SA_INIT request. If the
IKE_SA_INIT request did not include the REDIRECT_SUPPORTED payload, IKE_SA_INIT request did not include the REDIRECT_SUPPORTED payload,
the responder MUST NOT send the REDIRECT payload to the VPN client. the responder MUST NOT send the REDIRECT payload to the VPN client.
To redirect an IKEv2 session to another VPN gateway, the VPN gateway
that initially received the IKE_SA_INIT request selects another VPN
gateway (how the selection is made is beyond the scope of this
document), and replies with an IKE_SA_INIT response containing a
REDIRECT notification message. The notification includes information
about the selected VPN gateway, and the nonce data from the Ni
payload in the IKE_SA_INIT request.
Note that when the IKE_SA_INIT response includes the REDIRECT
notification, the exchange does not result in the creation of an
IKE_SA and the responder SPI will be zero.
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, IP_R) <-- HDR(A,0), N(REDIRECT, New_GW_ID, Ni_data)
When the VPN client receives the IKE_SA_INIT response with the When the client receives the IKE_SA_INIT response, it MUST verify
REDIRECT payload, it initiates a new IKE_SA_INIT exchange with the that the nonce data matches the value sent in the IKE_SA_INIT
VPN gateway listed in the REDIRECT payload provided this is allowed request. If the values do not match, the client MUST silently
by its IPsec policy. The VPN client includes the IP address of the discard the response (and keep waiting for another response). This
original VPN gateway that redirected the client. The IKEv2 exchange prevents certain Denial-of-Service attacks on the initiator that
then proceeds as normal with the selected VPN gateway. could be caused by an attacker injecting IKE_SA_INIT responses with
the REDIRECT payloads.
Next, the client initiates a new IKE_SA_INIT exchange with the VPN
gateway listed in the REDIRECT payload provided this is allowed by
its IPsec policy. The VPN client includes the IP address of the
original VPN gateway that redirected the client in the
REDIRECTED_FROM notification. The IKEv2 exchange then proceeds as it
would have 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}
When this mechanism is used with Mobile IPv6, care must be taken to In particular, the client MUST use the same Peer Authorization
ensure that the home agent information is consistent with the IKEv2 Database (PAD) and Security Policy Database (SPD) entries as it would
gateway information. The Mobile IPv6 home agent discovery mechanisms have used with the original gateway. Receiving a redirect
(for instance, RFC 5026 [4]) would have configured the mobile node notification MUST NOT result in the modification of any PAD or SPD
with a particular home agent. When the mobile node initiates an entries. In practice, this means the new gateway either has to
IKEv2 exchange with the home agent and is redirected to another either use the same responder identity (IDr) as the original gateway,
gateway, the home agent information should also be updated, subject or both should be part of a group of responders that are authorized
to the policy on the mobile node. by the same PAD entry. See section 4.4.3.1 of [8] on using DNS names
to represent a group of peers in a PAD entry.
When running IKEv2 between a Mobile IPv6 Mobile Node (MN) and Home
Agent (HA), redirecting the IKEv2 exchange to another HA is not
enough; the Mobile IPv6 signalling also needs to be sent to the new
HA address. The MN MAY treat the information received in the
IKE_SA_INIT response in similar way as it would treat HA discovery
information received from other unauthenticated (and potentially
untrustworthy) sources (such as DNS lookups not protected with
DNSSEC). However, if the MN has authenticated information 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
(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
information from the Home Agent Switch Message [5].
Gateway-initiated REDIRECT notifications exchanged in INFORMATIONAL
exchanges (see Section 5) MUST NOT result in updating any Mobile IPv6
state. In such cases, the Home Agent Switch Message specified in [5]
is used instead.
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 The use of anycast addresses will avoid having to configure 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.
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from the anycast address. from the anycast address.
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, IP_R) <-- 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 gateway. The VPN gateway that received the
IKE_SA_INIT request MAY redirect the client to its own unicast 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.
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initiated message and is protected by the IKEv2 security association. initiated message and is protected by the IKEv2 security association.
When the client receives this message, it MUST send an empty message When the client receives this message, it MUST send an empty message
as an acknowledgement. Until the client responds with an as an acknowledgement. Until the client responds with an
acknowledgement, the gateway SHOULD re-transmit the redirect acknowledgement, the gateway SHOULD re-transmit the redirect
INFORMATIONAL message as described in [2]. The following illustrates INFORMATIONAL message as described in [2]. The following illustrates
the INFORMATIONAL message exchange for gateway-initiated redirect. the INFORMATIONAL message exchange for gateway-initiated redirect.
Initiator (VPN client) Responder (VPN GW) Initiator (VPN client) Responder (VPN GW)
---------------------- ------------------ ---------------------- ------------------
<-- HDR, SK {N[REDIRECT, IP_R/FQDN_R]} <-- HDR, SK {N(REDIRECT, New_GW_ID)}
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
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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. When the client sends the REDIRECT payload in the IKE_AUTH response. When the client
receives the IKE_AUTH response with the REDIRECT payload, it SHOULD receives the IKE_AUTH response with the REDIRECT payload, it SHOULD
delete the existing IKEv2 security association with the gateway. The delete the existing IKEv2 security association with the gateway by
gateway MUST verify the client's AUTH payload before sending the sending an Informational mesage with a DELETE payload. The gateway
Redirect payload, and the client MUST verify the gateway's AUTH MUST verify the client's AUTH payload before sending the Redirect
payload before acting on the Redirect payload. payload, and the client MUST verify the gateway's AUTH payload before
acting on the Redirect 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, IP_R/FQDN_R]} N(REDIRECT, New_GW_ID)}
In case the IKE_AUTH exchange involves EAP authentication as In case the IKE_AUTH exchange involves EAP authentication as
described in Section 2.16 of RFC 4306 [2] or multiple authentication described in Section 2.16 of RFC 4306 [2], or multiple authentication
methods as described in RFC 4739 [6], the IKE_AUTH exchange is more methods as described in RFC 4739 [6], the gateway may decide to
complicated. The identity presented by the client in the first redirect the client based on the interaction with the AAA server or
IKE_AUTH request might be a temporary one. In addition, the gateway the external authentication server. In this case, the gateway MUST
might decide to redirect the client based on the interaction with the send the REDIRECT Notification payload in either the first or the
the AAA server, when EAP authentication is used or the external last IKE_AUTH response. The client and the gateway MUST verify the
authentication server, when multiple authentication methods are used. AUTH payloads as described above.
In such cases, the gateway should send the REDIRECT notification
payload in the final IKE_AUTH response message that carries the AUTH When EAP is used, the gateway MAY also redirect the client based on
payload and the traffic selectors. The gateway MUST NOT send and the the unauthenticated identity presented by the client in the first
client MUST NOT accept a redirect in an earlier IKE_AUTH message. IKE_AUTH exchange itself. presented by the client in the first
IKE_AUTH exchange itself. Since EAP is used as the authentication
mechanism, the client does not include AUTH payload to authenticate
his identity, but the server still MUST include his own AUTH payload,
and client MUST verify it. Note that the IKEv2 SA is not created in
this case and the client does not have to explicitly delete the IKEv2
SA.
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
response. It MUST NOT accept the REDIRECT notification in an
intermediate IKE_AUTH response.
7. Redirect Messages 7. Redirect Messages
7.1. REDIRECT_SUPPORTED 7.1. 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
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| Protocol ID | SPI Size (=0) | Notify Message Type | | Protocol ID | 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 the '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 MUST be set to '8'. The 'Notify Message The 'Payload Length' field is set to the length in octets of the
Type' field is set to indicate the REDIRECT_SUPPORTED payload <value entire payload, including the generic payload header. The 'Notify
to be assigned by IANA>. Message Type' field is set to indicate the REDIRECT_SUPPORTED payload
<value to be assigned by IANA>.
7.2. REDIRECT 7.2. REDIRECT
The REDIRECT payload is included in an IKE_SA_INIT response from the The REDIRECT payload is included in an IKE_SA_INIT response from the
responder or an INFORMATIONAL message from the responder, when the responder or an INFORMATIONAL message from the responder, when the
responder wants to redirect the initiator to another VPN gateway. responder wants to redirect the initiator to another VPN gateway.
The message includes the new responder's IP address. 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 | SPI Size (=0) | Notify Message Type | | Protocol ID | SPI Size (=0) | Notify Message Type |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| GW Ident Type | GW Ident Len | | | GW Ident Type | GW Ident Len | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ~ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ~
skipping to change at page 9, line 34 skipping to change at page 10, line 18
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. 'Notify
Message Type' field is set to indicate the REDIRECT payload <value to Message Type' field is set to indicate the REDIRECT payload <value to
be assigned by IANA>. The 'GW Identity Type' field indicates the be assigned by IANA>. The 'GW Identity Type' field indicates the
type of information that is sent to identify the new VPN gateway. type of information that is sent to identify the new VPN gateway.
The following values are reserved by this document. The following values are 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
All other values for this field are reserved and MUST NOT be used.
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. 'New Responder GW Identity' field. The IPv4 address, the IPv6
address or the FQDN of the new VPN gateway MUST be encoded as
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' field
is present in the REDIRECT payload only when the REDIRECT payload is is present in the REDIRECT payload only when the REDIRECT payload is
sent in the IKE_SA_INIT response message. It MUST NOT be included in sent in the IKE_SA_INIT response message. It MUST NOT be included in
the REDIRECT payload if sent in an IKE_AUTH response or in a gateway- the REDIRECT payload if sent in an IKE_AUTH response or in a gateway-
initiated redirect message. initiated redirect message.
7.3. REDIRECTED_FROM 7.3. REDIRECTED_FROM
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| | | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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 the '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 MUST be set to either '13' or '25' The 'Payload Length' field is set to the length in octets of the
depending on whether an IPv4 or IPv6 address of the original VPN entire payload, including the generic payload header. The 'Notify
gateway is sent in the message. The 'Notify Message Type' field is Message Type' field is set to indicate the REDIRECTED_FROM payload
set to indicate the REDIRECTED_FROM payload <value to be assigned by <value to be assigned by IANA>. The 'GW Identity Type' field
IANA>. The 'GW Identity Type' field indicates the type of indicates the type of information that is sent to identify the new
information that is sent to identify the new VPN gateway. The VPN gateway. The following values are valid in the REDIRECTED_FROM
following values are reserved by this document. 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
All other values for this field are reserved and MUST NOT be used.
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.
8. Use of the Redirect Mechanism between IKEv2 Peers 8. 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
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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 REDIRECTED_FROM payload is intended to discourage a rogue
VPN gateway from redirecting a large number of VPN clients to a 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.
Since the redirect message is not always sent as a secure message, it The redirect mechanism MUST NOT update any state on the client apart
MUST NOT result in the modification of the PAD entries on the client. from the VPN gateway information. When used with Mobile IPv6, care
The new gateway, to which the client is redirected to should be must be taken to ensure that the home agent information that the
subject to the same authentication and authorization requirements as mobile node has configured is not modified wrongly by the redirect
the original gateway. To support a scenario where the FQDN of the message.
gateway is in the client's PAD entry and the client is redirected to
another gateway in the same administrative domain, one can either Redirecting based on the unauthenticated identities might leak out
configure all the possible gateways from the domain or use a wildcard information about the user when active attacker can get information
entry like, for example, GW*.example.com, in the client's to which gateway user was redirected to. If redirection is based on
corresponding PAD entry. some internal information of the user, it might leak information to
attacker about the user which might not available otherwise. To
protect against this kind of attack the redirection based on the ID
should happen only after client has also authenticated himself.
10. IANA Considerations 10. IANA Considerations
This document defines four new IKEv2 Notification Message types as This document defines three new IKEv2 Notification Message types as
described in Section 7. The three Notify Message Types must be described in Section 7. The three Notify Message Types must be
assigned values between 16396 and 40959. assigned values between 16396 and 40959.
o REDIRECT_SUPPORTED o REDIRECT_SUPPORTED
o REDIRECT o REDIRECT
o REDIRECTED_FROM o REDIRECTED_FROM
This document creates a new namespace called the "Gateway Identity
Type". This is used to indicate the type of information regarding
the VPN gateway that is carried in the REDIRECT (Section 7.2) and
REDIRECTED_FROM (Section 7.3) Notification payloads. The following
values are assigned.
1 - IPv4 address of the new VPN gateway
2 - IPv6 address of the new VPN gateway
3 - FQDN of the new VPN gateway
Values '0', and 4-255 are reserved. New values can be allocated by
expert review.
11. Acknowledgements 11. Acknowledgements
The use of anycast address with IKEv2 was first described in [7]. It The use of anycast address with IKEv2 was first described in [7]. It
was then added to an early draft version of RFC 5026 and later was then added to an early draft version of RFC 5026 and later
removed before the RFC was published. Therefore the authors of [7] removed before the RFC was published. Therefore the authors of [7]
and RFC 5026 are acknowledged. and RFC 5026 are acknowledged.
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 REDIRECTED_FROM payload and other comments
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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] Weniger, K. and F. Dupont, "IKEv2-based Home Agent Assignment in
Mobile IPv6/NEMO Bootstrapping", draft-dupont-ikev2-haassign-02 Mobile IPv6/NEMO Bootstrapping", draft-dupont-ikev2-haassign-02
(work in progress), January 2007. (work in progress), January 2007.
[8] Kent, S. and K. Seo, "Security Architecture for the Internet
Protocol", RFC 4301, December 2005.
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
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