draft-ietf-ipsecme-ikev2-redirect-11.txt   draft-ietf-ipsecme-ikev2-redirect-12.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: December 18, 2009 June 16, 2009 Expires: January 31, 2010 July 30, 2009
Redirect Mechanism for IKEv2 Redirect Mechanism for IKEv2
draft-ietf-ipsecme-ikev2-redirect-11.txt draft-ietf-ipsecme-ikev2-redirect-12.txt
Status of this Memo Status of this Memo
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Copyright Notice Copyright Notice
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Abstract Abstract
IKEv2 is a protocol for setting up VPN tunnels from a remote location IKEv2 is a protocol for setting up Virtual Private Network (VPN)
to a gateway so that the VPN client can access services in the tunnels from a remote location to a gateway so that the VPN client
network behind the gateway. Currently there is no standard mechanism can access services in the network behind the gateway. This document
specified that allows an overloaded VPN gateway or a VPN gateway that defines an IKEv2 extension that allows an overloaded VPN gateway or a
is being shut down for maintenance to redirect the VPN client to VPN gateway that is being shot down for maintenance to redirect the
attach to another gateway. This document proposes a redirect VPN client to attach to another gateway. The proposed mechanism can
mechanism for IKEv2. The proposed mechanism can also be used in also be used in Mobile IPv6 to enable the home agent to redirect the
Mobile IPv6 to enable the home agent to redirect the mobile node to mobile node to another home agent.
another home agent.
Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 4 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3
3. IKEv2 Initial Exchange with Redirect . . . . . . . . . . . . . 4 3. IKEv2 Initial Exchange with Redirect . . . . . . . . . . . . . 3
4. Use of Anycast Addresses with the Redirect Mechanism . . . . . 6 4. Use of Anycast Addresses with the Redirect Mechanism . . . . . 5
5. Gateway Initiated Redirect . . . . . . . . . . . . . . . . . . 7 5. Redirect During an Active Session . . . . . . . . . . . . . . 6
6. Redirect During IKE_AUTH Exchange . . . . . . . . . . . . . . 8 6. Redirect During IKE_AUTH Exchange . . . . . . . . . . . . . . 7
7. Using the Redirect Mechanism with Mobile IPv6 . . . . . . . . 9 7. Handling Redirect Loops . . . . . . . . . . . . . . . . . . . 8
8. Redirect Messages . . . . . . . . . . . . . . . . . . . . . . 10 8. Using the Redirect Mechanism with Mobile IPv6 . . . . . . . . 8
8.1. REDIRECT_SUPPORTED . . . . . . . . . . . . . . . . . . . . 10 9. Redirect Messages . . . . . . . . . . . . . . . . . . . . . . 9
8.2. REDIRECT . . . . . . . . . . . . . . . . . . . . . . . . . 10 9.1. REDIRECT_SUPPORTED . . . . . . . . . . . . . . . . . . . . 9
8.3. REDIRECTED_FROM . . . . . . . . . . . . . . . . . . . . . 12 9.2. REDIRECT . . . . . . . . . . . . . . . . . . . . . . . . . 10
9. Use of the Redirect Mechanism between IKEv2 Peers . . . . . . 13 9.3. REDIRECTED_FROM . . . . . . . . . . . . . . . . . . . . . 11
10. Security Considerations . . . . . . . . . . . . . . . . . . . 13 10. Use of the Redirect Mechanism between IKEv2 Peers . . . . . . 12
11. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 14 11. Security Considerations . . . . . . . . . . . . . . . . . . . 12
12. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 14 12. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 13
13. References . . . . . . . . . . . . . . . . . . . . . . . . . . 15 13. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 13
13.1. Normative References . . . . . . . . . . . . . . . . . . . 15 14. References . . . . . . . . . . . . . . . . . . . . . . . . . . 14
13.2. Informative References . . . . . . . . . . . . . . . . . . 15 14.1. Normative References . . . . . . . . . . . . . . . . . . . 14
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 15 14.2. Informative References . . . . . . . . . . . . . . . . . . 14
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 [8] based VPNs. The IP
the VPN gateway can be configured on the VPN client. But this does address of the VPN gateway can be configured on the VPN client. But
not scale well, when the number of VPN gateways is large. Dynamic this does not scale well, when the number of VPN gateways is large.
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
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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 Redirect mechanism during the
IKE_SA_INIT exchange. Gateway-initiated redirect and the use of IKE_SA_INIT exchange. Gateway-initiated redirect during an active
redirect during IKE_AUTH exchange are explained in subsequent session and the use of redirect during IKE_AUTH exchange are
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 the 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 8.1). 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 8.2). 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 SPI will be zero.
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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 attacks on the initiator that
could be caused by an attacker injecting IKE_SA_INIT responses with could be caused by an attacker injecting IKE_SA_INIT responses with
the REDIRECT payloads. the 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 PAD entries. In the
IKE_SA_INIT exchange with the new VPN gateway, the client MUST IKE_SA_INIT exchange with the new VPN gateway, the client MUST
include the REDIRECTED_FROM payload. (See Section 8.3). The VPN include the REDIRECTED_FROM payload. (See Section 9.3). The VPN
client includes the IP address of the original VPN gateway that client includes the IP address of the original VPN gateway that
redirected the client in the REDIRECTED_FROM notification. The IKEv2 redirected the client in the REDIRECTED_FROM notification. The IKEv2
exchange then proceeds as it would have proceeded with the original exchange then proceeds as it would have proceeded with the original
VPN gateway. 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, -->
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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.
5. Gateway Initiated Redirect 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 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 message and is protected by the IKEv2 security association. initiated redirect and is protected by the IKEv2 security
When the client receives this message, it sends a response (usually association. When the client receives this message, it sends a
empty) to the gateway. The gateway retransmits the redirect response (usually empty) to the gateway. The gateway retransmits the
INFORMATIONAL message as described in [2], until it gets a response. redirect INFORMATIONAL message as described in [2], until it gets a
The following illustrates the INFORMATIONAL message exchange for response. The following illustrates the INFORMATIONAL message
gateway-initiated redirect. exchange for gateway-initiated redirect.
Initiator (VPN client) Responder (VPN GW) Initiator (VPN client) Responder (VPN GW)
---------------------- ------------------ ---------------------- ------------------
<-- HDR, SK {N(REDIRECT, New_GW_ID)} <-- 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
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 setup 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)
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his identity, but the server still MUST include his own AUTH payload, 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 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 this case and the client does not have to explicitly delete the IKEv2
SA. 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. Using the Redirect Mechanism with Mobile IPv6 7. Handling Redirect Loops
The client could end up getting redirected multiple times in a
sequence, either because of wrong configuration or a DoS attack. 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
client. To prevent this, the client SHOULD be configured not to
accept more than a certain number of redirects (MAX_REDIRECTS) within
a short time period (REDIRECT_LOOP_DETECT_PERIOD) for a particular
IKEv2 SA setup. The default value for MAX_REDIRECTS configuration
variable is 5. The default value for REDIRECT_LOOP_DETECT_PERIOD
configuration variable is 300 seconds. Client implementations may
allow these variables to be configured depending on a specific
deployment or system configuration.
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
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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 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.
8. Redirect Messages 9. Redirect Messages
8.1. 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 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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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>. <value to be assigned by IANA>.
8.2. REDIRECT 9.2. 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 or DNS name. 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 |
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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' 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.
8.3. REDIRECTED_FROM 9.3. REDIRECTED_FROM
The REDIRECTED_FROM notification payload is included in the The REDIRECTED_FROM notification payload is included in the
IKE_SA_INIT request from the initiator to the new VPN gateway to IKE_SA_INIT request from the initiator to the new VPN gateway to
indicate the IP address of the original VPN gateway that redirected indicate the IP address of the original VPN gateway that redirected
the initiator. The original VPN gateway's IP address is included in the initiator. The original VPN gateway's IP address is included in
the message. This payload also serves the purpose of indicating the message. If the IKE_SA_INIT request was sent to any anycast
support for the redirect mechanism to the new VPN gateway after a address (see Section 4), then the anycast address is included in the
redirect. message. This payload also serves the purpose of indicating support
for the 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 | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ~ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ~
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VPN gateway. The following values are valid in the REDIRECTED_FROM VPN gateway. The following values are valid in the REDIRECTED_FROM
payload. 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.
9. 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.
10. Security Considerations 11. Security Considerations
An eavesdropper on the path between VPN client and server may send a An eavesdropper on the path between VPN client and server may send a
redirect to the client upon receiving an IKE_SA_INIT message from 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
skipping to change at page 13, line 40 skipping to change at page 13, line 8
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.
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.
The client could end up getting redirected multiple times in a
sequence, either because of wrong configuration or a DoS attack. 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
client. To prevent this, the client should be configured not to
accept more a certain number of redirects within a short time period.
This should be configurable on the client.
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 to which gateway
the real user was redirected to. If redirection is based on some the real user was redirected to. 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 to
attacker about the user which might not available otherwise. To attacker about the user which might not be available otherwise. To
prevent these kind of attacks, redirection based on unauthenticated prevent these kind of attacks, redirection based on unauthenticated
ID should be avoided and should be done only after the client has ID should be avoided and should be done only after the client has
also authenticated itself. also authenticated itself.
11. IANA Considerations 12. IANA Considerations
This document defines three new IKEv2 Notification Message types as This document defines three new IKEv2 Notification Message types as
described in Section 8. The three Notify Message Types must be described in Section 9. 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 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 8.2) and the VPN gateway that is carried in the REDIRECT (Section 9.2) and
REDIRECTED_FROM (Section 8.3) Notification payloads. The following REDIRECTED_FROM (Section 9.3) Notification payloads. The following
values are assigned. values are assigned.
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
Values '0', and 4-240 are reserved. New values can be allocated by Values '0', and 4-240 are reserved. New values can be allocated by
Expert Review [9]. Values 241-255 are set aside for private use. A Expert Review [9]. Values 241-255 are set aside for private use. A
specification that extends this registry MUST also mention which of specification that extends this registry MUST also mention which of
the new values are valid in which Notification payload. the new values are valid in which Notification payload.
12. Acknowledgements 13. 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
which helped improve the document. The authors would also like to which 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.
13. References 14. References
13.1. 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.
[2] Kaufman, C., "Internet Key Exchange (IKEv2) Protocol", RFC 4306, [2] Kaufman, C., "Internet Key Exchange (IKEv2) Protocol", RFC 4306,
December 2005. December 2005.
13.2. Informative References 14.2. Informative References
[3] Johnson, D., Perkins, C., and J. Arkko, "Mobility Support in [3] Johnson, D., Perkins, C., and J. Arkko, "Mobility Support in
IPv6", RFC 3775, June 2004. IPv6", RFC 3775, June 2004.
[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.
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