Internet DRAFT - draft-kampati-ipsecme-ikev2-sa-ts-payloads-opt
draft-kampati-ipsecme-ikev2-sa-ts-payloads-opt
IPSECME Working Group S. Kampati
Internet-Draft Microsoft
Intended status: Standards Track W. Pan
Expires: 24 April 2023 Huawei
P. Wouters
Aiven
M. Bharath
Mavenir
M. Chen
CMCC
21 October 2022
IKEv2 Optional SA&TS Payloads in Child Exchange
draft-kampati-ipsecme-ikev2-sa-ts-payloads-opt-10
Abstract
This document describes a method for reducing the size of the
Internet Key Exchange version 2 (IKEv2) CREATE_CHILD_SA exchanges
used for rekeying of the IKE or Child SA by replacing the SA and TS
payloads with a Notify Message payload. Reducing size and complexity
of IKEv2 exchanges is especially useful for low power consumption
battery powered devices.
About This Document
This note is to be removed before publishing as an RFC.
Status information for this document may be found at
https://datatracker.ietf.org/doc/draft-kampati-ipsecme-ikev2-sa-ts-
payloads-opt/.
Discussion of this document takes place on the ipsec Working Group
mailing list (mailto:ipsec@ietf.org), which is archived at
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Source for this draft and an issue tracker can be found at
https://github.com/mcr/ipsecme-ikev2-sa-ts-payloads.git.
Status of This Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Conventions Used in This Document . . . . . . . . . . . . . . 4
2.1. Requirements Language . . . . . . . . . . . . . . . . . . 4
3. Negotiation of Support for OPTIMIZED REKEY . . . . . . . . . 4
4. Optimized Rekey of the IKE SA . . . . . . . . . . . . . . . . 5
5. Optimized Rekey of Child SAs . . . . . . . . . . . . . . . . 5
6. Payload Formats . . . . . . . . . . . . . . . . . . . . . . . 6
6.1. OPTIMIZED_REKEY_SUPPORTED Notify . . . . . . . . . . . . 6
6.2. OPTIMIZED_REKEY Notify . . . . . . . . . . . . . . . . . 7
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 7
8. Operational Considerations . . . . . . . . . . . . . . . . . 8
9. Security Considerations . . . . . . . . . . . . . . . . . . . 8
10. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 8
11. Normative References . . . . . . . . . . . . . . . . . . . . 8
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 8
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1. Introduction
The Internet Key Exchange protocol version 2 (IKEv2) [RFC7296] is
used to negotiate Security Association (SA) parameters for the IKE SA
and the Child SAs. Cryptographic key material for these SAs have a
limited lifetime before it needs to be refreshed, a process referred
to as "rekeying". IKEv2 uses the CREATE_CHILD_SA exchange to rekey
either the IKE SA or the Child SAs.
When rekeying, a full set of negotiation parameters are exchanged.
However, most of these parameters will be the same as before, and
some of these parameters MUST NOT change.
For example, the Traffic Selector (TS) negotiated for the new Child
SA MUST cover the Traffic Selectors negotiated for the old Child SA.
And in practically all cases, a new Child SA does not need to cover a
wider set of Traffic. In the rare case where this would be needed,
either a standard rekey could be used or a new Child SA could be
negotiated followed by a deletion of the replaced Child SA.
Similarly, IKEv2 states that the cryptographic parameters negotiated
for rekeying SHOULD NOT be different. This means that the security
properties of the IKE or Child SA in practise do not change during a
typical rekey.
This document specifies a method to omit these parameters and replace
them with a single Notify Message declaring that all these parameters
are identical to the originally negotiated parameters.
Large scale IKEv2 gateways such as Evolved Packet Data Gateway (ePDG)
in 4G networks or Centralized Radio Access Network (cRAN/Cloud)
gateways in 5G networks typically support more than 100,000 IKE/IPsec
connections. At any point in time, there will be hundreds or
thousands of IKE SAs and Child SAs that are being rekeyed. This
takes a large amount of bandwidth and CPU power and any protocol
simplification or bandwidth reducing would result in a significant
resource saving.
For Internet of Things (IoT) devices which utilize low power
consumption technology, reducing the size of the CREATE_CHILD_SA
exchange for rekeying reduces its power consumption, as sending bytes
over the air is usually the most power consuming operation of such a
device. Reducing the CPU operations required to verify the rekey
exchanges parameters will also save power and extend the lifetime for
these devices.
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When using identical parameters for the IKE SA or Child SA rekey, the
SA and TS payloads can be omitted thanks to the optimization defined
in this document. For an IKE SA rekey, instead of the (large) SA
payload, only a Key Exchange (KE) payload and a new Notify Type
payload with the new SPI are required. For a Child SA payload,
instead of the SA or TS payloads, only an optional nonce payload
(when using PFS) and a new Notify Type payload with the new SPI are
needed. This makes the rekey exchange packets much smaller and the
peers do not need to verify that the SA or TS parameters are
compatible with the old SA parameters.
2. Conventions Used in This Document
2.1. Requirements Language
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.
3. Negotiation of Support for OPTIMIZED REKEY
To indicate support for the optimized rekey negotiation, the
initiator includes the OPTIMIZED_REKEY_SUPPORTED notify payload in
the IKE_AUTH exchange request. During this initial key request, the
entire SA and TS payloads are included as normal. A responder that
supports the optimized rekey exchange includes the
OPTIMIZED_REKEY_SUPPORTED notify payload in its response. Note that
the notify indicates support for optimized rekey for both IKE and
Child SAs.
A responder that does not support the optimized rekey exchange
processes the SA and TS payloads as normal, and does not include the
new Notify. As per regular IKEv2 processing, a responder that does
not recognize this new Notify, MUST ignore the notify. Responders
may have been administratively configured with the optimization
turned off for local reasons. The absense of the Notify indicates to
the initiator that the optimization is not available, and normal,
full rekey should be done.
When a peer wishes to rekey an IKE SA or Child SA, it MAY use the
optimized rekey method during the CREATE_CHILD_SA exchange. If both
peers have exchanged OPTIMIZED_REKEY_SUPPORTED notifies, peers SHOULD
use the optimized rekey method for rekeys. Non-optimized, regular
rekey requests MUST always be accepted.
The IKE_AUTH message exchange in this case is shown below:
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Initiator Responder
--------------------------------------------------------------------
HDR, SK {IDi, [CERT,] [CERTREQ,]
[IDr,] AUTH, SAi2, TSi, TSr,
N(OPTIMIZED_REKEY_SUPPORTED)} -->
<-- HDR, SK {IDr, [CERT,] AUTH,
SAr2, TSi, TSr,
N(OPTIMIZED_REKEY_SUPPORTED)}
4. Optimized Rekey of the IKE SA
The initiator of an optimized rekey request sends a CREATE_CHILD_SA
payload with the OPTIMIZED_REKEY notify payload containing the new
Security Parameter Index (SPI) for the new IKE SA. It omits the SA
payload.
The responder of an optimized rekey request replies with an included
OPTIMIZED_REKEY notify with its new IKE SPI and also omits the SA
payload.
Both parties send their nonce and KE payloads just as they would do
for a regular IKE SA rekey.
Using the old SPI from the IKE header and the two new SPIs
respectively from the initiator and responder's OPTIMIZED_REKEY
payloads, both parties can perform the IKE SA rekey operation.
The CREATE_CHILD_SA message exchange in this case is shown below:
Initiator Responder
--------------------------------------------------------------------
HDR, SK {N(OPTIMIZED_REKEY,newSPIi),
Ni, KEi} -->
<-- HDR, SK {N(OPTIMIZED_REKEY,newSPIr),
Nr, KEr}
5. Optimized Rekey of Child SAs
The initiator of an optimized rekey request sends a CREATE_CHILD_SA
payload with the OPTIMIZED_REKEY notify payload containing the new
Security Parameter Index (SPI) for the new Child SA. It omits the SA
and TS payloads. If the current Child SA was negotiated with Perfect
Forward Secrecy (PFS), a KEi payload MUST be included as well. If no
PFS was negotiated for the current Child SA, a KEi payload MUST NOT
be included.
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The responder of an optimized rekey request performs the same
process. It includes the OPTIMIZED_REKEY notify with its new IKE SPI
and omits the SA and TS payloads. Depending on the PFS negotiation
of the current Child SA, the responder includes a KEr payload.
Both parties send their nonce payloads just as they would do for a
regular Child SA rekey.
Using the old SPI from the REKEY_SA payload and the two new SPIs
respectively from the initiator and responder's OPTIMIZED_REKEY
payloads, both parties can perform the Child SA rekey operation.
The CREATE_CHILD_SA message exchange in this case is shown below:
Initiator Responder
--------------------------------------------------------------------
HDR, SK {N(REKEY_SA,oldSPI), N(OPTIMIZED_REKEY,newSPIi),
Ni, [KEi,]} -->
<-- HDR, SK {N(OPTIMIZED_REKEY,newSPIr),
Nr, [KEr,]}
6. Payload Formats
6.1. OPTIMIZED_REKEY_SUPPORTED Notify
The OPTIMIZED_REKEY_SUPPORTED Notify Message type notification is
used by the initiator and responder to indicate their support for the
optimized rekey negotiation.
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
+---------------+-+-------------+-------------------------------+
| Next Payload |C| RESERVED | Payload Length |
+---------------+-+-------------+-------------------------------+
|Protocol ID(=0)| SPI Size (=0) | Notify Message Type |
+---------------+---------------+-------------------------------+
* Protocol ID (1 octet) - MUST be 0.
* SPI Size (1 octet) - MUST be 0, meaning no SPI is present.
* Notify Message Type (2 octets) - MUST be set to the value TBD1.
This Notify Message type contains no data.
The Critical bit MUST be 0. A non-zero value MUST be ignored.
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6.2. OPTIMIZED_REKEY Notify
The OPTIMIZED_REKEY Notify Message type is used to perform an
optimized IKE SA or Child SA rekey.
0 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
+---------------+-+-------------+-------------------------------+
| Next Payload |C| RESERVED | Payload Length |
+---------------+-+-------------+-------------------------------+
|Protocol ID | SPI Size (=8) | Notify Message Type |
+---------------+---------------+-------------------------------+
| Security Parameter Index (SPI) |
| |
+---------------------------------------------------------------+
* Protocol ID (1 octet) - For an IKE SA rekey, this field MUST
contain (1). For Child SAs, this field MUST contain either (2) to
indicate AH or (3) to indicate ESP.
* SPI Size (1 octet) - MUST be 8 when rekeying an IKE SA. MUST be 4
when rekeying a Child SA.
* Notify Message Type (2 octets) - MUST be set to the value TBD2.
* SPI (4 octets or 8 octets) - Security Parameter Index. The new
SPI.
The Critical bit MUST be 1. A value of 0 MUST be ignored.
7. IANA Considerations
This document defines two new Notify Message Types in the "IKEv2
Notify Message Types - Status Types" registry. IANA is requested to
assign codepoints in this registry.
NOTIFY messages: status types Value
----------------------------------------------------------
OPTIMIZED_REKEY_SUPPORTED TBD1
OPTIMIZED_REKEY TBD2
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8. Operational Considerations
Some implementations allow sending rekey messages with a different
set of Traffic Selectors or cryptographic parameters in response to a
configuration update. IKEv2 [RFC7296] states this SHOULD NOT be
done. Whether or not optimized rekeying is used, a configuration
change that changes the Traffic Selectors or cryptographic parameters
MUST NOT use the optimized rekey method. It SHOULD also not use a
regular rekey method but instead start an entire new IKE and Child SA
negotiation with the new parameters.
9. Security Considerations
The optimized rekey removes sending unnecessary new parameters that
originally would have to be validated against the original
parameters. In that sense, this optimization enhances the security
of the rekey process by reducing the complexity and code required.
10. Acknowledgments
Special thanks go to Valery Smyslov and Antony Antony.
11. 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>.
[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>.
[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>.
Authors' Addresses
Sandeep Kampati
Microsoft
India
Email: skampati@microsoft.com
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Wei Pan
Huawei Technologies
101 Software Avenue, Yuhuatai District
Nanjing
Jiangsu,
China
Email: william.panwei@huawei.com
Paul Wouters
Aiven
Email: paul.wouters@aiven.io
Meduri S S Bharath
Mavenir Systems Pvt Ltd
Manyata Tech Park
Bangalore
Karnataka
India
Email: bharath.meduri@mavenir.com
Meiling Chen
China Mobile
32 Xuanwumen West Street, West District
Beijing
100053
China
Email: chenmeiling@chinamobile.com
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