Internet DRAFT - draft-pan-ipsecme-anti-replay-notification
draft-pan-ipsecme-anti-replay-notification
IPSECME Working Group W. Pan
Internet-Draft Q. He
Intended status: Standards Track Huawei
Expires: 4 September 2024 P. Wouters
Aiven
3 March 2024
IKEv2 Support for Anti-Replay Status Notification
draft-pan-ipsecme-anti-replay-notification-00
Abstract
RFC 4302 and RFC 4303 specify that, during Security Association (SA)
establishment, IPsec implementation should notify the peer if it will
not provide anti-replay protection, to avoid having the peer do
unnecessary sequence number monitoring and SA setup.
This document defines the ANTI_REPLAY_STATUS Notify Message Status
Type Payload in the Internet Key Exchange Protocol Version 2 (IKEv2)
to inform the peers of their own anti-replay status when creating the
IPsec SAs, to fulfill the above requirement.
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-pan-ipsecme-anti-replay-
notification/.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
1.1. Problem Statement . . . . . . . . . . . . . . . . . . . . 3
2. Requirements Language . . . . . . . . . . . . . . . . . . . . 4
3. Notifying the Anti-replay Status . . . . . . . . . . . . . . 4
4. ANTI_REPLAY_STATUS Notify Payload Format . . . . . . . . . . 6
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 6
6. Security Considerations . . . . . . . . . . . . . . . . . . . 6
7. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 6
8. References . . . . . . . . . . . . . . . . . . . . . . . . . 6
8.1. Normative References . . . . . . . . . . . . . . . . . . 7
8.2. Informative References . . . . . . . . . . . . . . . . . 7
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 7
1. Introduction
IPsec Authentication Header (AH) [RFC4302] and Encapsulating Security
Payload (ESP) [RFC4303] are used to provide security for IP
communications. Both AH and ESP support the anti-replay function to
prevent an attacker from resending the packets received by the IPsec
peer before. Each IPsec packet is sent with a unique sequence
number, which the IPsec receiver checks to see whether the sequence
number is duplicated.
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RFC 4302 and RFC 4303 specify the details of sequence number
generation and verification. When anti-replay is enabled on the
receiver, the sender must monitor the sequence number counter and
increment the counter with every message sent. The sender must
ensure that the counter does not cycle, and trigger the creation and
use of a new IPsec SA before the counter is about to cycle. When
anti-replay is disabled on the receiver, the sender does not need to
monitor or reset the counter. The sender only increments the counter
and rolls it over back to zero when it reaches the maximum value.
It is specified in both RFC 4302 and RFC 4303 that, during SA
establishment, IPsec implementation should notify the peer if it will
not provide anti-replay protection, to avoid having the peer do
unnecessary sequence number monitoring and SA setup. However,
currently, IKEv2 [RFC7296] does not have the notification of anti-
replay status when negotiating the creation of an IPsec SA. As a
result, IPsec implementations must always assume that the peer has
anti-replay enabled. Even though anti-replay is disabled on both
ends, they still have to monitor the sequence numbers.
This document adds a notification in IKEv2 to inform the peers of
their own anti-replay status when creating the IPsec SAs, which can
finally avoid unnecessary sequence number monitoring.
1.1. Problem Statement
When anti-replay is enabled on the peer, the IPsec implementation
needs to monitor the sequence number of outbound packets, and trigger
a rekey to generate and use a new Child SA when the sequence number
counter is about to cycle. In high-performance scenarios, high-speed
traffic causes the 32-bit sequence number to be consumed quickly,
resulting in frequent rekeying of Child SAs. For this reason, IPsec
defines the Extended Sequence Number (ESN) function, extending the
available space for sequence numbers from 32 to 64 bits. Although
ESN is good to avoid the sequence number running out in a short
period, there is a prerequisite for using ESN - RFC 4302 and RFC 4303
both require ESN to be used in conjunction with the anti-replay
function. That is, ESN can only be used if the anti-replay feature
is enabled.
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In the high-performance scenario, operators may choose to disable the
anti-replay function for the considerations of QoS, performance, and
others. For example, the high-level QoS packets arriving first may
cause a large number of low-level QoS packets being dropped, when the
disordered packets exceed the window size of anti-replay. Disabling
anti-replay brings a new problem: IPsec peers cannot successfully
negotiate using ESN. The final result is that neither peer of IPsec
enables anti-replay, but neither can use ESN, leaving the Child SAs
forced to rekey frequently due to the rapid exhaustion of the 32-bit
sequence number.
The solution to this problem can be approached in two ways. One
option is to support the continued use of the ESN when anti-replay is
disabled. Because IPsec packets carry only the low-order 32 bits of
the sequence number, the ESN has a need for the receiver to manage
the anti-replay window in order to determine the correct value for
the high-order 32 bits. To use ESN when anti-replay is disabled, the
IPsec implementation needs to create and maintain a separate window
for ESN as well.
The other option is to add a notification of anti-replay status in
IKEv2. Section 3.4.3 of both RFC 4302 and RFC 4303 specify that the
IPsec receiver should notify the sender during SA establishment that
the receiver will not provide anti-replay protection. Adding the
anti-replay status notification in IKEv2 can fulfill this
requirement. When anti-replay is disabled on both peers, neither
peer needs to monitor the sequence number counter, thus avoiding
frequent rekey of Child SAs.
Although the first option could support using ESN when anti-replay is
enabled at one peer and disabled at the other, this would require an
update to RFC 4302 and RFC 4303. Therefore, this document considers
the second option, given that it is only an extension of IKEv2 to
fulfill a requirement already defined in RFC 4302 and RFC 4303.
2. 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. Notifying the Anti-replay Status
When creating a Child SA, the ANTI_REPLAY_STATUS notify payload can
be used by the initiator and the responder to inform each other of
their own anti-replay status (enabled or disabled) regarding this SA.
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The initiator includes the ANTI_REPLAY_STATUS notify payload in the
IKE_AUTH exchange request for creating the initial Child SA or the
CREATE_CHILD_SA exchange request for creating the subsequent Child
SAs.
A responder that does not support the anti-replay status notification
processes the request as normal, and does not include the new Notify
in the response. As per regular IKEv2 processing, a responder that
does not recognize this new Notify, MUST ignore the notify. As
required in RFC 4302 and RFC 4303, this responder should assume the
anti-replay is enabled in the initiator. The absence of the Notify
in the response indicates to the initiator that the responder doesn't
support the anti-replay status notification. The initiator continues
the IKEv2 negotiation as usual, and also assumes the anti-replay is
enabled in the responder.
A responder that supports the anti-replay status notification can
understand whether the initiator provides the anti-replay protection
for this Child SA, and includes the ANTI_REPLAY_STATUS notify payload
in the response to inform its anti-replay status about this Child SA.
The IKE_AUTH message exchange in this case is shown below:
Initiator Responder
-------------------------------------------------------------------
HDR, SK {IDi, [CERT,] [CERTREQ,]
[IDr,] AUTH, SAi2,
TSi, TSr,
N(ANTI_REPLAY_STATUS)} -->
<-- HDR, SK {IDr, [CERT,] AUTH,
SAr2, TSi, TSr,
N(ANTI_REPLAY_STATUS)}
The CREATE_CHILD_SA message exchange in this case is shown below:
Initiator Responder
-------------------------------------------------------------------
HDR, SK {SA, Ni, [KEi,]
TSi, TSr,
N(ANTI_REPLAY_STATUS)} -->
<-- HDR, SK {SA, Nr, [KEr,]
TSi, TSr,
N(ANTI_REPLAY_STATUS)}
After the Child SA is successfully established and the initiator and
responder mutually notify each other of their own anti-replay status,
the IPsec implementation can choose not to monitor the sequence
number counter if the peer's anti-replay is disabled.
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4. ANTI_REPLAY_STATUS Notify Payload Format
The ANTI_REPLAY_STATUS Notify Message type notification is used by
the initiator and responder to indicate their own anti-replay status
to each other when creating the Child SAs.
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 |
+---------------+---------------+-------------------------------+
| Status |
+---------------------------------------------------------------+
* Protocol ID (1 octet) - this field MUST contain either (2) to
indicate AH or (3) to indicate ESP.
* SPI Size (1 octet) - MUST be 0.
* Notify Message Type (2 octets) - MUST be set to the value TBD1.
* Status (4 octets) - this field MUST be 0 to indicate the anti-
replay is enabled or 1 to indicate the anti-replay is disabled.
The Critical bit MUST be 0. A non-zero value MUST be ignored.
5. IANA Considerations
This document defines a new Notify Message Type in the "IKEv2 Notify
Message Types - Status Types" registry. IANA is requested to assign
the codepoint in this registry.
NOTIFY messages: status types Value
----------------------------------------------------------
ANTI_REPLAY_STATUS TBD1
6. Security Considerations
TBD
7. Acknowledgments
TBD
8. References
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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/rfc/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/rfc/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/rfc/rfc8174>.
8.2. Informative References
[RFC4302] Kent, S., "IP Authentication Header", RFC 4302,
DOI 10.17487/RFC4302, December 2005,
<https://www.rfc-editor.org/rfc/rfc4302>.
[RFC4303] Kent, S., "IP Encapsulating Security Payload (ESP)",
RFC 4303, DOI 10.17487/RFC4303, December 2005,
<https://www.rfc-editor.org/rfc/rfc4303>.
Authors' Addresses
Wei Pan
Huawei Technologies
Email: william.panwei@huawei.com
Qi He
Huawei Technologies
Email: archibald.heqi@huawei.com
Paul Wouters
Aiven
Email: paul.wouters@aiven.io
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