Internet DRAFT - draft-smyslov-ipsecme-ikev2-r-mobike
draft-smyslov-ipsecme-ikev2-r-mobike
Network Working Group V. Smyslov
Internet-Draft ELVIS-PLUS
Updates: 4555 (if approved) November 15, 2021
Intended status: Standards Track
Expires: May 19, 2022
Responder Initiated IP Addresses Update in MOBIKE
draft-smyslov-ipsecme-ikev2-r-mobike-09
Abstract
IKEv2 Mobility and Multihoming Protocol (MOBIKE), defined in
[RFC4555] allows peers to update their IP addresses without re-
establishing IKE and IPsec Security Associations (SAs). In the
MOBIKE protocol it is the initiator of the IKE SA, who is responsible
for selecting new SA addresses and for initiating the IP addresses
update procedure. This document presents an extension to the MOBIKE
protocol that allows the responder to initiate IP address update.
The document updates [RFC4555].
Status of This Memo
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This Internet-Draft will expire on May 19, 2022.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Terminology and Notation . . . . . . . . . . . . . . . . . . 3
3. Protocol Overview . . . . . . . . . . . . . . . . . . . . . . 3
4. Protocol Description . . . . . . . . . . . . . . . . . . . . 4
4.1. Capability Advertising . . . . . . . . . . . . . . . . . 4
4.2. Responder Initiated IP Address Update . . . . . . . . . . 5
5. Payload Formats . . . . . . . . . . . . . . . . . . . . . . . 7
5.1. MOBIKE_SUPPORTED Notification . . . . . . . . . . . . . . 7
5.2. SWITCH_TO_IP_ADDRESS Notification . . . . . . . . . . . . 7
6. Security Considerations . . . . . . . . . . . . . . . . . . . 7
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 8
8. References . . . . . . . . . . . . . . . . . . . . . . . . . 8
8.1. Normative References . . . . . . . . . . . . . . . . . . 8
8.2. Informative References . . . . . . . . . . . . . . . . . 8
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 8
1. Introduction
The Internet Key Exchange protocol version 2 (IKEv2), specified in
[RFC7296], is a key part of the IP Security (IPsec) architecture. It
allows peers to perform authenticated key exchange, which results in
establishing IKE Security Association (IKE SA) and to create a data
protection channels called IPsec Security Associations (IPsec SAs).
In original IKEv2 the IKE and IPsec SAs are established between the
IP addresses used in IKEv2 negotiation. The IKEv2 Mobility and
Multihoming Protocol (MOBIKE), specified in [RFC4555], extends the
IKEv2 functionality by allowing peers to dynamically change IP
addresses of the established SAs without the need to re-establish
these SAs.
The main use case for the MOBIKE protocol is a remote access user
that travels and moves from one IP address to another without re-
establishing existing SAs with the VPN gateway. However, the MOBIKE
also supports more complex scenarios when VPN gateway is multihomed
and its addresses may change over time.
In the MOBIKE it is the original initiator of the IKE SA (e.g. the
remote access client) who is responsible for detecting the working IP
addresses pairs and for deciding which pair to use. In other words,
the responder (e.g. the VPN gateway) plays a passive role and could
neither initiate the IP address update process nor tell the initiator
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which IP address is preferred to use. This limitation makes use of
complex scenarios less efficient and decreases the value of MOBIKE
protocol.
For example, if the VPN gateway is a load sharing cluster where each
node has its own IP address, then the cluster must be able to move SA
between nodes depending on their current load. Currently Redirect
Mechanism for IKEv2 [RFC5685] can accomplish this task, however it
requires new IKE SA to be established, that is very inefficient.
Another possible solution is to use IKE SA Cloning along with the
MOBIKE (see [RFC7791] for scenario description), but the limitation
of the MOBIKE protocol makes this problematic. Obviously, the client
has insufficient information to choose when and to which of cluster
IP addresses to move an SA to and the VPN gateway has no means to
provide the client with this information.
This specification extends the MOBIKE protocol by adding ability for
the responder to ask the initiator for IP address update and to
provide it with the new IP address to use.
2. Terminology and Notation
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in BCP
14 [RFC2119] [RFC8174] when, and only when, they appear in all
capitals, as shown here.
In this document the term "initiator" means the party who originally
initiated the first IKE SA (in a series of possibly several rekeyed
IKE SAs), and "responder" means the other party. This is consistent
with a way these terms are used in [RFC4555]. Note, that in
[RFC7296] the terms "original initiator" and "original responder"
mean the party, who initiated (or responded to) the latest IKE SA in
a series of possibly several rekeyed IKE SAs.
3. Protocol Overview
The MOBIKE protocol is designed in such a way, that it is the IKE SA
initiator, who is responsible for performing the actions concerned
with the selecting of a working IP addresses pair and for initiating
an IP addresses update exchange. Usually the initiator selects an IP
addresses pair by periodically probing different pairs and choosing
the working one. If several pairs work then the choice between them
is arbitrary. The responder cannot influence the process of
selecting and cannot ask the client to immediately switch to a
particular gateway's address. As a result the process of selection a
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new pair takes substantial time and may ends up with a suboptimal
path.
Obviously, this limitation comes from the fact that there might be
middleboxes on the path like Network Address Translators (NAT) or
firewalls, that might disallow IP packets to come from VPN gateway to
the client unless the client first contacts the VPN gateway. For
example, the client might reside behind a dynamic NAT that creates a
mapping when IP packet first comes from the client to the gateway.
If the gateway tries to send an IP packet to the client from
different IP address, the packet would be dropped since the NAT box
has no corresponding mapping.
This specification provides the following solution to the described
problem. When the responder decides that its end of existing SA
should be switched from its original IP address IP_R1 to a new IP
address IP_R2, it initiates an INFORMATIONAL exchange containing a
new notification SWITCH_TO_IP_ADDRESS, that contains IP_R2. Once the
initiator completes an exchange containing SWITCH_TO_IP_ADDRESS
notification, it immediately initiates standard MOBIKE procedure for
updating SA addresses by starting the INFORMATIONAL exchange
containing UPDATE_SA_ADDRESSES notification.
4. Protocol Description
4.1. Capability Advertising
According to [RFC4555], the peers must exchange MOBIKE_SUPPORTED
notifications in the IKE_AUTH exchange before they can use the MOBIKE
protocol. If the initiator supports this specification and is
willing to use it, then it MUST include a single octet 0x52 ('R') in
the notification data of the MOBIKE_SUPPORTED notification sent to
the responder. There is no need for the initiator to know whether
the responder supports this specification or not, so the
MOBIKE_SUPPORTED notification sent by the responder has an empty
notification data.
Note, that [RFC4555] specifies that MOBIKE_SUPPORTED notification
must contains no data when sending and the content of the
notification data must be ignored while parsing. So, if the
responder doesn't support this specification, it will just ignore the
content of the MOBIKE_SUPPORTED notification and will use MOBIKE
without this extension.
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(IP_I1:500 -> IP_R1:500) -->
HDR, SAi1, KEi, Ni,
N(NAT_DETECTION_SOURCE_IP),
N(NAT_DETECTION_DESTINATION_IP)
<-- (IP_R1:500 -> IP_I1:500)
HDR, SAr1, KEr, Nr,
N(NAT_DETECTION_SOURCE_IP),
N(NAT_DETECTION_DESTINATION_IP)
(IP_I1:4500 -> IP_R1:4500) -->
HDR, SK { IDi, CERT, AUTH,
SAi2, TSi, TSr,
N(MOBIKE_SUPPORTED('R')) }
<-- (IP_R1:4500 -> IP_I1:4500)
HDR, SK { IDr, CERT, AUTH,
SAr2, TSi, TSr,
N(MOBIKE_SUPPORTED),
N(ADDITIONAL_IP4_ADDRESS) }
4.2. Responder Initiated IP Address Update
If the initiator advertised its support for this specification during
the initial exchange as described in Section 4.1, then the responder
is free to initiate IP Address Update request at any time. If the
initiator doesn't indicate its support for this extension, then the
responder MUST NOT initiate IP Address Update request. The IP
Address Update request NUST NOT be initiated by the initiator, the
responder MUST NOT take any action if it receives such a request
(apart from sending an empty response message to complete the
exchange).
It is up to the responder to decide when to initiate an IP Address
Update request and what new address to include into it. Some of the
possible reasons are:
o the responder is multihomed and wishes to switch an SA to a
different IP address
o the responder is a cluster and wishes to move an SA to a different
node having its own IP address
The responder requests the initiator to update SA address by
initiating the INFORMATIONAL exchange containing a new status type
notification SWITCH_TO_IP_ADDRESS. Its notification data contains a
new IP address the responder requests the initiator to use for the
IKE SA and its Child SAs. In the example below the SA was
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established using IP_I1 and IP_R1 addresses for the initiator and
responder respectively, and the responder wishes to change the
address of its end of the SA to IP_R2. So, it initiates the
INFORMATIONAL exchange from IP_R1 address containing the
SWITCH_TO_IP_ADDRESS notification with IP_R2 address.
<-- (IP_R1:4500 -> IP_I1:4500)
HDR, SK { N(SWITCH_TO_IP_ADDRESS(IP_R2)) }
(IP_I1:4500 -> IP_R1:4500) -->
HDR, SK {}
Upon receiving the SWITCH_TO_IP_ADDRESS notification the initiator
extracts its content and makes a decision whether the received IP
address is appropriate for the SA. If the received IP address is
among the addresses previously received from the responder in
ADDITIONAL_IP4_ADDRESS or ADDITIONAL_IP6_ADDRESS notifications, then
it is appropriate for the SA. Otherwise local policy must be
consulted to decide whether the received IP is appropriate. If the
address is considered inappropriate, then the initiator MUST current
address. It is RECOMMENDED that the initiator immediately initiates
Liveness Check exchange to ensure that the responder is able to
operate using its current address.
If the initiator makes a decision that the received address is
appropriate the initiator initiates an IP address update procedure
according to the MOBIKE specification by sending an INFORMATIONAL
exchange request message containing the UPDATE_SA_ADDRESSES
notification. See [RFC4555] for details. As a result, the remote IP
address of the SA is changed from IP_R1 to IP_R2. Note that only the
IP address is changed, the port remains the same.
(IP_I1:4500 -> IP_R2:4500) -->
HDR, SK { N(UPDATE_SA_ADDRESSES),
N(NAT_DETECTION_SOURCE_IP),
N(NAT_DETECTION_DESTINATION_IP),
N(COOKIE2) }
<-- (IP_R2:4500 -> IP_I1:4500)
HDR, SK { N(NAT_DETECTION_SOURCE_IP),
N(NAT_DETECTION_DESTINATION_IP),
N(COOKIE2) }
The responder MUST NOT change IP addresses of the SA until it
receives the UPDATE_SA_ADDRESSES notification from the initiator.
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5. Payload Formats
5.1. MOBIKE_SUPPORTED Notification
The MOBIKE_SUPPORTED Notification is defined in [RFC4555],
Section 4.2.1 with the Notify Message Type 16396. This definition
requires the notification data to be empty while sending and to be
ignored when notification is received.
This document updates the definition from [RFC4555]. Exchange
initiator sets the notification data of the MOBIKE_SUPPORTED
Notification to a single octet 0x52 ('R') to indicate that this
specification is supported.
5.2. SWITCH_TO_IP_ADDRESS Notification
The Notify Message Type for this notification is <TBA by IANA>. The
notification data contains new responder's IP address.
For IPv4, the notification data is 4 octets long and is defined as
follows:
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| New Responder's IPv4 Address |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
For IPv6, the notification data is 16 octets long and is defined as
follows:
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
| New Responder's IPv6 Address |
| |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
The Protocol ID and SPI Size fields are set to zero.
6. Security Considerations
This specification is an extension of the MOBIKE protocol, so the
Security Considerations described in [RFC4555] are applied.
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7. IANA Considerations
This document defines new Notify Message Types in the "IKEv2 Notify
Message Types - Status Types" registry:
<TBA> SWITCH_TO_IP_ADDRESS
8. References
8.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/info/rfc2119>.
[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
May 2017, <https://www.rfc-editor.org/info/rfc8174>.
[RFC4555] Eronen, P., "IKEv2 Mobility and Multihoming Protocol
(MOBIKE)", RFC 4555, DOI 10.17487/RFC4555, June 2006,
<https://www.rfc-editor.org/info/rfc4555>.
[RFC7296] Kaufman, C., Hoffman, P., Nir, Y., Eronen, P., and T.
Kivinen, "Internet Key Exchange Protocol Version 2
(IKEv2)", STD 79, RFC 7296, DOI 10.17487/RFC7296, October
2014, <https://www.rfc-editor.org/info/rfc7296>.
8.2. Informative References
[RFC5685] Devarapalli, V. and K. Weniger, "Redirect Mechanism for
the Internet Key Exchange Protocol Version 2 (IKEv2)",
RFC 5685, DOI 10.17487/RFC5685, November 2009,
<https://www.rfc-editor.org/info/rfc5685>.
[RFC7791] Migault, D., Ed. and V. Smyslov, "Cloning the IKE Security
Association in the Internet Key Exchange Protocol Version
2 (IKEv2)", RFC 7791, DOI 10.17487/RFC7791, March 2016,
<https://www.rfc-editor.org/info/rfc7791>.
Author's Address
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Valery Smyslov
ELVIS-PLUS
PO Box 81
Moscow (Zelenograd) 124460
Russian Federation
Phone: +7 495 276 0211
Email: svan@elvis.ru
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