Network Working Group
Internet Engineering Task Force (IETF) V. Smyslov
Internet-Draft
Request for Comments: 9838 ELVIS-PLUS
Obsoletes: 6407 (if approved) B. Weis
Intended status:
Category: Standards Track Independent
Expires: 1 February 2026 31 July
ISSN: 2070-1721 September 2025
Group Key Management using IKEv2
draft-ietf-ipsecme-g-ikev2-23 Using the Internet Key Exchange Protocol Version 2
(IKEv2)
Abstract
This document presents an extension to the Internet Key Exchange
version
Protocol Version 2 (IKEv2) protocol for the purpose of a group key management.
The protocol is in conformance with the Multicast Security (MSEC) key
management architecture, which contains two components: member
registration and group rekeying. Both components are required for a
GCKS (Group
Group Controller/Key Server) Server (GCKS) to provide authorized Group
Members (GMs) with IPsec group security associations. Group Security Associations (GSAs). The
group members then exchange IP multicast or other group traffic as
IPsec packets.
This document obsoletes RFC 6407.
Status of This Memo
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provisions of BCP 78 and BCP 79.
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This Internet-Draft will expire on 1 February 2026.
https://www.rfc-editor.org/info/rfc9838.
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Table of Contents
1. Introduction and Overview . . . . . . . . . . . . . . . . . . 4
1.1. Requirements Notation . . . . . . . . . . . . . . . . . . 6
1.2. Terminology . . . . . . . . . . . . . . . . . . . . . . . 6
2. G-IKEv2 Protocol . . . . . . . . . . . . . . . . . . . . . . 8
2.1. G-IKEv2 Integration into the IKEv2 Protocol . . . . . . . . . 9
2.1.1. G-IKEv2 Transport and Port . . . . . . . . . . . . . 9
2.2. G-IKEv2 Payloads . . . . . . . . . . . . . . . . . . . . 9
2.3. G-IKEv2 Member Registration and Secure Channel
Establishment . . . . . . . . . . . . . . . . . . . . . . 11
2.3.1. GSA_AUTH Exchange . . . . . . . . . . . . . . . . . . 12
2.3.2. GSA_REGISTRATION Exchange . . . . . . . . . . . . . . 13
2.3.3. GM Registration Operations . . . . . . . . . . . . . 14
2.3.4. GCKS Registration Operations . . . . . . . . . . . . 17
2.4. Group Maintenance Channel . . . . . . . . . . . . . . . . 19
2.4.1. GSA_REKEY . . . . . . . . . . . . . . . . . . . . . . 20
2.4.2. GSA_INBAND_REKEY Exchange . . . . . . . . . . . . . . 26
2.4.3. Deletion of SAs . . . . . . . . . . . . . . . . . . . 27
2.5. Counter-based modes Counter-Based Modes of operation . . . . . . . . . . . . 28 Operation
2.5.1. Allocation of Sender-ID . . . . . . . . . . . . . . . 28
2.5.2. GM Usage of Sender-ID . . . . . . . . . . . . . . . . 30
2.6. Replay Protection for Multicast Data-Security SAs . . . . 30
2.7. Encryption Transforms with Implicit IV . . . . . . . . . 31
3. Group Key Management and Access Control . . . . . . . . . . . 31
3.1. Key Wrap Keys . . . . . . . . . . . . . . . . . . . . . . 31
3.1.1. Default Key Wrap Key . . . . . . . . . . . . . . . . 32
3.2. GCKS Key Management Semantics . . . . . . . . . . . . . . 32
3.2.1. Forward Access Control Requirements . . . . . . . . . 33
3.3. GM Key Management Semantics . . . . . . . . . . . . . . . 33
3.4. SA Keys . . . . . . . . . . . . . . . . . . . . . . . . . 35
4. Header and Payload Formats . . . . . . . . . . . . . . . . . 36
4.1. G-IKEv2 Header . . . . . . . . . . . . . . . . . . . . . 36
4.2. Group Identification Payload . . . . . . . . . . . . . . 36
4.3. Security Association - GM Supported Transforms Payload . 36
4.4. Group Security Association Payload . . . . . . . . . . . 36
4.4.1. Group Policies . . . . . . . . . . . . . . . . . . . 37
4.4.2. Group Security Association Policy Substructure . . . 38
4.4.3. Group-wide Group-Wide Policy Substructure . . . . . . . . . . . 45
4.5. Key Download Payload . . . . . . . . . . . . . . . . . . 48
4.5.1. Key Bags . . . . . . . . . . . . . . . . . . . . . . 48
4.5.2. Group Key Bag Substructure . . . . . . . . . . . . . 49
4.5.3. Member Key Bag Substructure . . . . . . . . . . . . . 51
4.5.4. Key Wrapping . . . . . . . . . . . . . . . . . . . . 53
4.6. Delete Payload . . . . . . . . . . . . . . . . . . . . . 55
4.7. Notify Payload . . . . . . . . . . . . . . . . . . . . . 55
4.7.1. INVALID_GROUP_ID Notification . . . . . . . . . . . . 55
4.7.2. AUTHORIZATION_FAILED Notification . . . . . . . . . . 55
4.7.3. REGISTRATION_FAILED Notification . . . . . . . . . . 55
4.7.4. GROUP_SENDER Notification . . . . . . . . . . . . . . 56
4.8. Authentication Payload . . . . . . . . . . . . . . . . . 56
5. Using G-IKEv2 Attributes . . . . . . . . . . . . . . . . . . 56
6. Interaction with IKEv2 and ESP Extensions . . . . . . . . . . 60
6.1. Implicit IV for Counter-Based Ciphers in ESP . . . . . . 60
6.2. Mixing Preshared Keys in IKEv2 for Post-quantum Post-Quantum Security . . . . . . . . . . . . . . . . . . . . . . . . 60
6.3. Aggregation and Fragmentation Mode for ESP . . . . . . . 61
7. GDOI Protocol Extensions . . . . . . . . . . . . . . . . . . 61
8. Security Considerations . . . . . . . . . . . . . . . . . . . 61
8.1. GSA Registration and Secure Channel . . . . . . . . . . . 61
8.2. GSA Maintenance Channel . . . . . . . . . . . . . . . . . 62
8.2.1. Authentication/Authorization . . . . . . . . . . . . 62
8.2.2. Confidentiality . . . . . . . . . . . . . . . . . . . 62
8.2.3. Man-in-the-Middle Attack Protection . . . . . . . . . 62
8.2.4. Replay/Reflection Attack Protection . . . . . . . . . 62
9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 62
9.1. Note for Reviewers . . . . . . . . . . . . . . . . . . . 63
9.2. New Registries . . . . . . . . . . . . . . . . . . . . . 63
9.2.1.
9.1.1. Guidance for Designated Experts . . . . . . . . . . . 65
9.3.
9.2. Changes in the Existing IKEv2 Registries . . . . . . . . 65
10. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 67
11. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 68
12. References . . . . . . . . . . . . . . . . . . . . . . . . . 68
12.1.
10.1. Normative References . . . . . . . . . . . . . . . . . . 68
12.2.
10.2. Informative References . . . . . . . . . . . . . . . . . 69
Appendix A. Use of LKH in G-IKEv2 . . . . . . . . . . . . . . . 73
A.1. Notation . . . . . . . . . . . . . . . . . . . . . . . . 73
A.2. Group Creation . . . . . . . . . . . . . . . . . . . . . 74
A.3. Simple Group SA Rekey . . . . . . . . . . . . . . . . . . 75
A.4. Group Member Exclusion . . . . . . . . . . . . . . . . . 75
Acknowledgements
Contributors
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 76
1. Introduction and Overview
This document presents an extension to IKEv2 [RFC7296] called
G-IKEv2, which allows performing a group key management. A group key
management protocol provides IPsec keys and policy to a set of IPsec
devices which that are authorized to communicate using a Group Security
Association (GSA) defined in Multicast Group Security Architecture
[RFC3740]. The data communications within the group (e.g., IP
multicast packets) are protected by a key pushed to the group members Group Members
(GMs) by the Group Controller/Key Server (GCKS).
G-IKEv2 conforms to the "The Multicast Group Security Architecture Architecture"
[RFC3740], Multicast "Multicast Extensions to the Security Architecture for the
Internet Protocol [RFC5374] Protocol" [RFC5374], and the Multicast "Multicast Security (MSEC) Group
Key Management Architecture Architecture" [RFC4046]. G-IKEv2 replaces GDOI "The Group
Domain of Interpretation" [RFC6407], which defines a similar group
key management protocol using IKEv1 [RFC2409] (since deprecated by
IKEv2). When G-IKEv2 is used, group key management use cases can
benefit from the simplicity, increased robustness robustness, and cryptographic
improvements of IKEv2 (see Appendix A of [RFC7296]).
G-IKEv2 is composed of two phases: registration and rekeying. In the
registration phase phase, a GM contacts a GCKS to register to a group and
to receive the necessary policy and the keying material to be able
communicate with the other GMs in the group as well as with the GCKS.
The rekeying phase allows the GCKS to periodically renew the keying
material for both GM-to-GM communications as well as for
communication between the GM and the GCKS.
G-IKEv2 defines two ways to perform registration. When a GM first
contacts a GCKS GCKS, it uses the GSA_AUTH exchange (Section 2.3.1) to
register to a group. This exchange happens after the IKE_SA_INIT
exchange (similarly to the IKE_AUTH exchange in IKEv2) and results in
establishing an IKE SA Security Association (SA) between the GM and the
GCKS. During this
exchange exchange, the GCKS authenticates and authorizes
the GM, GM and then pushes policy and keys used by the group to the GM.
The second new exchange type is the GSA_REGISTRATION exchange
(Section 2.3.2), which a GM can
use be used by the GM within the already already-
established IKE SA with the GCKS (e.g. (e.g., for registering to another
group).
Refreshing the group keys can be performed either in an a unicast mode
via the GSA_INBAND_REKEY exchange (Section 2.4.2) performed over a
specific IKE SA between a GM and a GCKS or in a multicast mode with
the GSA_REKEY pseudo exchange (Section 2.4.1), 2.4.1) when new keys are being
distributed to all GMs.
Large and small groups may use different sets of these mechanisms.
When a large group of devices are communicating, the GCKS is likely
to use the GSA_REKEY message for efficiency. This is shown in
Figure 1, where multicast communications are indicated with a double
line. (Note: For clarity, IKE_SA_INIT is omitted from Figure Figures 1 and
Figure 2).
2.)
+--------+
+----IKEv2---->| GCKS |<----IKEv2----+
| +--------+ |
| || ^ |
| || | |
| || GSA_AUTH |
| || or |
| || GSA_REGISTRATION |
| || | |
GSA_AUTH || IKEv2 GSA_AUTH
or || | or
GSA_REGISTRATION GSA_REKEY | GSA_REGISTRATION
| || | |
| *==========**================* |
| || || | || |
v \/ \/ v \/ v
+-------+ +--------+ +-------+
| GM | ... | GM | ... | GM |
+-------+ +--------+ +-------+
|| || ||
*=====ESP/AH=====**=====ESP/AH====*
Figure 1: G-IKEv2 used Used in large groups Large Groups
Alternatively, a small group may simply use the GSA_AUTH or
GSA_REGISTRATION as registration protocols, where the GCKS issues
rekeys using the GSA_INBAND_REKEY within the same IKE SA.
GSA_AUTH or GSA_REGISTRATION, GSA_INBAND_REKEY
+--------------------IKEv2----------------------+
| |
| GSA_AUTH or GSA_REGISTRATION, |
| GSA_INBAND_REKEY |
| +-----------IKEv2-------------+ |
| | | |
| |GSA_AUTH or GSA_REGISTRATION,| |
| | GSA_INBAND_REKEY | |
| | +--IKEv2-+ | |
v v v v v v
+---------+ +----+ +----+ +----+
| GCKS/GM | | GM | | GM | | GM |
+---------+ +----+ +----+ +----+
|| || || ||
*==ESP/AH==**=====ESP/AH====**===ESP/AH===*
Figure 2: G-IKEv2 used Used in small groups Small Groups
A combination of these approaches is also possible. For example, the
GCKS may use more robust GSA_INBAND_REKEY to provide keys for some
GMs (for example, those acting as senders in the group) and GSA_REKEY
for the rest. Note also, Also note that GCKS may also be a GM (as shown in
Figure 2).
IKEv2 message semantics are preserved in that all communications
consists
consist of message request-response pairs. The exception to this
rule is the GSA_REKEY pseudo-exchange, which is a single message
delivering group updates to the GMs.
1.1. Requirements 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.
1.2. Terminology
It is assumed that readers are familiar with the IPsec architecture
[RFC4301],
[RFC4301] and its extension for multicast [RFC5374]. This document
defines an extension to the IKEv2 protocol [RFC7296] and skips many
of its details. The notation and conventions from [RFC7296] are used
for describing G-IKEv2 payloads and exchanges.
The following key terms are used throughout this document (mostly
borrowed from Multicast Group Security Architecture [RFC3740],
Multicast Extensions to the Security Architecture [RFC5374] [RFC5374], and GDOI [RFC6407]).
Group
Group:
A set of IPsec devices that communicate to each other using
multicast.
Group Member (GM) (GM):
An IPsec device that belongs to a group. A Group Member is
authorized to be a Group Sender and/or a Group Receiver.
Group Receiver Receiver:
A Group Member that is authorized to receive packets sent to a
group by a Group Sender.
Group Sender Sender:
A Group Member that is authorized to send packets to a group.
Group Key Management (GKM) Protocol Protocol:
A key management protocol used by a GCKS to distribute IPsec
Security Association policy and keying material. A GKM protocol
is needed because a group of IPsec devices require the same SAs.
For example, when an IPsec SA describes an IP multicast
destination, the sender and all receivers need to have the group
SA.
Group Controller/Key Server (GCKS) (GCKS):
A Group Key Management (GKM) protocol server that manages IPsec
state for a group. A GCKS authenticates and provides the IPsec SA
policy and keying material to GMs.
Data-Security SA SA:
A multicast SA between each multicast sender and the group's
receivers. The Data-Security SA protects data between member
senders and member receivers. One or more SAs are required for
the multicast transmission of data-messages data messages from the Group Sender
to other group members. This specification relies on ESP
Encapsulating Security Payload (ESP) and AH Authentication Header
(AH) as protocols for Data-Security SAs.
Rekey SA SA:
A single multicast SA between the GCKS and all of the group
members. This SA is used for multicast transmission of key
management messages from the GCKS to all GMs.
Group Security Association (GSA) (GSA):
A collection of Data-Security SAs and Rekey SA SAs necessary for a
Group Member to receive key updates. A GSA describes the working
policy for a group. Refer to the MSEC Group Key Management
Architecture [RFC4046] for additional information.
Traffic Encryption Key (TEK) (TEK):
The symmetric cipher key used in a Data-Security SA (e.g., IPsec
ESP) to protect traffic.
Key Encryption Key (KEK) (KEK):
The symmetric key (or a set of keys) used in a Rekey SA to protect
its messages. The set of keys may include keys for encryption and
authentication, as well as keys for key wrapping.
Key Wrap Key (KWK) (KWK):
The symmetric cipher key used to protect another key.
Group-wide (GW) policy policy:
Group policy not related to a particular SA.
Activation Time Delay (ATD) (ATD):
Defines how long Group Senders should wait after receiving new SAs
before starting sending traffic over them.
Deactivation Time Delay (DTD) (DTD):
Defines how long Group Members should wait after receiving a
request to delete Data-Security SAs before actually deleting them.
Sender-ID
Sender-ID:
A unique identifier of a Group Sender in the context of an active
GSA,
GSA used to form the Initialization Vector (IV) in counter-based
cipher modes.
Logical Key Hierarchy (LKH) (LKH):
A group management method defined in Section 5.4 of Key Management
for Multicast [RFC2627].
2. G-IKEv2 Protocol
G-IKEv2 is an extension to the IKEv2 protocol [RFC7296] that provides
group authorization, secure policy policy, and keys download from the GCKS
to GMs.
2.1. G-IKEv2 Integration into the IKEv2 Protocol
G-IKEv2 is compatible with most IKEv2 extensions defined so far (see
Section 6 for details). In particular, it is assumed that, if
necessary, the IKE_INTERMEDIATE exchanges [RFC9242] may be utilized
while establishing the registration SA. It is also believed that
future IKEv2 extensions will be possible to use with G-IKEv2,
however, G-IKEv2.
However, some IKEv2 extensions may require special handling when used
with G-IKEv2.
2.1.1. G-IKEv2 Transport and Port
As an IKEv2 extension, G-IKEv2 SHOULD use the IKEv2 ports (500,
4500). G-IKEv2 MAY also use TCP transport for registration (unicast)
IKE SA, as defined in TCP Encapsulation of IKEv2 and IPsec [RFC9329].
G-IKEv2 MAY also use UDP port 848, the same as GDOI Group Domain of
Interpretation (GDOI) [RFC6407], because they serve a similar
function. The version number in the IKE header distinguishes the
G-IKEv2 protocol from the GDOI protocol [RFC6407].
Section 2.23 of IKEv2 [RFC7296] describes how IKEv2 supports paths with
NATs. The G-IKEv2 registration SA doesn't create any unicast IPsec
SAs, thus
SAs; thus, if a NAT is present between the GM and the GCKS, there is
no unicast ESP traffic to encapsulate in UDP. However, the actions
described in this section regarding the IKE SA MUST be honored. The
behavior of GMs and GCKS MUST NOT depend on the port used to create
the initial IKE SA. For example, if the GM and the GCKS used UDP
port 848 for the IKE_SA_INIT exchange, they will operate the same as
if they had used UDP port 500.
2.2. G-IKEv2 Payloads
In the following descriptions, the payloads contained in the G-IKEv2
messages are indicated by names as listed below.
+==========+============================+=============+
| Notation | Payload | Defined in |
+==========+============================+=============+
| AUTH | Authentication | [RFC7296] |
+----------+----------------------------+-------------+
| CERT | Certificate | [RFC7296] |
+----------+----------------------------+-------------+
| CERTREQ | Certificate Request | [RFC7296] |
+----------+----------------------------+-------------+
| D | Delete | [RFC7296] |
+----------+----------------------------+-------------+
| GSA | Group Security Association | Section 4.4 |
+----------+----------------------------+-------------+
| HDR | IKEv2 Header | [RFC7296] |
+----------+----------------------------+-------------+
| IDg | Identification - Group | Section 4.2 |
+----------+----------------------------+-------------+
| IDi | Identification - Initiator | [RFC7296] |
+----------+----------------------------+-------------+
| IDr | Identification - Responder | [RFC7296] |
+----------+----------------------------+-------------+
| KD | Key Download | Section 4.5 |
+----------+----------------------------+-------------+
| KE | Key Exchange | [RFC7296] |
+----------+----------------------------+-------------+
| Ni, Nr | Nonce | [RFC7296] |
+----------+----------------------------+-------------+
| N | Notify | [RFC7296] |
+----------+----------------------------+-------------+
| SA | Security Association | [RFC7296] |
+----------+----------------------------+-------------+
| SAg | Security Association - GM | Section 4.3 |
| | Supported Transforms | |
+----------+----------------------------+-------------+
| SK | Encrypted | [RFC7296] |
+----------+----------------------------+-------------+
Table 1: Payloads used Used in G-IKEv2
Payloads defined as part of other IKEv2 extensions MAY also be
included in these messages. Payloads that may optionally appear in
G-IKEv2 messages will be shown in brackets, such as [CERTREQ].
G-IKEv2 defines several new payloads not used in IKEv2:
* IDg (Group ID) --
Group ID (IDg):
The GM requests the GCKS for membership into the group by sending
its IDg payload.
* SAg (Security
Security Association -- - GM Supported Transforms) -- the Transforms (SAg):
The GM optionally sends supported transforms, transforms so that GCKS may
select a policy appropriate for all members of the group (which is
not negotiated, unlike SA parameters in IKEv2).
* GSA (Group
Group Security Association) -- Association (GSA):
The GCKS sends the group policy to the GM using this payload.
* KD (Key Download) --
Key Download (KD):
The GCKS sends the keys and the security parameters to the GMs
using this payload.
The details of the contents of each payload are described in
Section 4.
2.3. G-IKEv2 Member Registration and Secure Channel Establishment
Initial registration is combined with establishing a secure
connection between the entity seeking registration and the GCKS.
This process consists of a minimum of two exchanges, IKE_SA_INIT and
GSA_AUTH; member registration may have a few more messages exchanged
if the EAP Extensible Authentication Protocol (EAP) method, cookie
challenge (for DoS protection), negotiation of key exchange method method,
or IKEv2 extensions based on the IKEv2 Intermediate exchange Exchange
[RFC9242] are used. Each exchange consists of request/response
pairs. The first exchange IKE_SA_INIT exchange, called IKE_SA_INIT, is defined in IKEv2
[RFC7296]. This exchange negotiates cryptographic algorithms,
exchanges nonces nonces, and computes a shared key between the GM and the
GCKS. In addition to the cryptographic algorithms negotiated for use
in IKEv2 SA, a key wrap algorithm is also negotiated in this exchange
by means of a new "Key Wrap Algorithm" transform. See Section 4.5.4
for details.
The second exchange exchange, called GSA_AUTH GSA_AUTH, is similar to the IKEv2
IKE_AUTH exchange [RFC7296]. It authenticates the previously
exchanged
messages, messages and exchanges identities and certificates. The
GSA_AUTH messages are encrypted and integrity protected with keys
established through the previous exchanges, so the identities are
hidden from eavesdroppers and all fields in all the messages are
authenticated. The GCKS authorizes group members to be allowed into
the group as part of the GSA_AUTH exchange. Once the GCKS accepts a
GM to join a
group group, it will provide the GM with the data-security
keys (TEKs) and/
or and/or a group key encrypting key (KEK) as part of the
GSA_AUTH response message.
The established secure channel between the GM and the GCKS is in fact
IKE SA (as defined in [RFC7296]) and is referred to as such
throughout this document. However, it is NOT RECOMMENDED to use this
IKE SA for the purpose of creating unicast Child SAs between the GM
and the GCKS, GCKS since authentication requirements for group admission
and for unicast communication may differ. In addition, the lifecycle life
cycle of this IKE SA is determined by the GCKS and this SA can be
deleted at any time.
2.3.1. GSA_AUTH Exchange
The GSA_AUTH exchange is used to authenticate the previous exchanges, exchanges
and exchange identities and certificates. G-IKEv2 also uses this
exchange for group member registration and authorization.
The GSA_AUTH exchange is similar to the IKE_AUTH exchange with the
difference that its goal is to establish a multicast Data-Security
SA(s) and optionally provide GM with the keys for a Rekey SA. The
set of payloads in the GSA_AUTH exchange is slightly different, different
because policy is not negotiated between the group member and the GCKS, but
instead
GCKS; instead, it is provided by the GCKS for the GM. Note also, Also note that
GSA_AUTH has its own exchange type, which is different from the
IKE_AUTH exchange type.
Note,
Note that due to the similarities between IKE_AUTH and GSA_AUTH, most
IKEv2 extensions to the IKE_AUTH exchange (like Secure Password secure password
authentication [RFC6467]) can also be used with the GSA_AUTH
exchange.
Initiator (GM) Responder (GCKS)
-------------------- ------------------
HDR, SK{IDi, [CERT,] [CERTREQ,] [IDr,]
AUTH, IDg, [SAg,] [N(GROUP_SENDER),] [N]} -->
Figure 3: GSA_AUTH Request
A group member initiates a GSA_AUTH request to join a group indicated
by the IDg payload. The GM may include an SAg payload declaring
which Transforms it is willing to accept. A GM that intends to act
as Group Sender MUST include a Notify payload status type of
GROUP_SENDER, which enables the GCKS to provide any additional policy
necessary by group senders.
Initiator (GM) Responder (GCKS)
-------------------- ------------------
<-- HDR, SK{IDr, [CERT,]
AUTH, GSA, KD, [N]}
Figure 4: GSA_AUTH Normal Response
The GCKS responds with IDr, optional CERT, and AUTH payloads with the
same meaning as in IKE_AUTH. It also informs the group member of the
cryptographic policies of the group in the GSA payload and the key
material in the KD payload.
Possible erors errors should be handled in accordance with Section 2.21.2
of [RFC7296]. In addition to the IKEv2 error handling, the GCKS can
reject the registration request when the IDg is invalid or
authorization fails, etc. In these cases, see cases (see Section 4.7, 4.7), the
GSA_AUTH response will not include the GSA and KD, KD but will include a
Notify payload indicating errors. If a GM included an SAg payload, payload
and the GCKS chooses to evaluate it, it and the GCKS detects that the group member
cannot support the security policy defined for the group, then the
GCKS returns the NO_PROPOSAL_CHOSEN notification. Other types of
error notifications can be INVALID_GROUP_ID,
AUTHORIZATION_FAILED AUTHORIZATION_FAILED, or
REGISTRATION_FAILED.
Initiator (GM) Responder (GCKS)
-------------------- ------------------
<-- HDR, SK{IDr, [CERT,] AUTH, N}
Figure 5: GSA_AUTH Error Response for Group-Related Errors
If the GSA_AUTH exchange is completed successfully, successfully but the group
member finds that the policy sent by the GCKS is unacceptable, the
member SHOULD inform the GCKS about this by initiating the
GSA_REGISTRATION exchange with the IDg payload and the
NO_PROPOSAL_CHOSEN notification (see Figure 8).
2.3.2. GSA_REGISTRATION Exchange
Once the IKE SA between the GM and the GCKS is established, the GM
can use it for other registration requests, requests if this is needed. In this scenario
scenario, the GM will use the GSA_REGISTRATION exchange. Payloads in
the exchange are generated and processed as defined in Section 2.3.1.
Initiator (GM) Responder (GCKS)
-------------------- ------------------
HDR, SK{IDg, [SAg,]
[N(GROUP_SENDER),] [N]} -->
<-- HDR, SK{GSA, KD, [N]}
Figure 6: GSA_REGISTRATION Normal Exchange
As with GSA_AUTH exchange, the GCKS can reject the registration
request when the IDg is invalid or authorization fails, or GM cannot
support the security policy defined for the group (which can be
concluded by the GCKS by evaluation of the SAg payload). In this case
case, the GCKS returns an appropriate error notification as described
in Section 2.3.1.
Initiator (GM) Responder (GCKS)
-------------------- ------------------
HDR, SK{IDg, [SAg,]
[N(GROUP_SENDER),] [N]} -->
<-- HDR, SK{N}
Figure 7: GSA_REGISTRATION Error Exchange
This exchange can also be used if the group member finds that the
policy sent by the GCKS is unacceptable or for some reason wants to leave the group. group
for some reason. The group member SHOULD notify the GCKS by sending
IDg and the Notify type NO_PROPOSAL_CHOSEN or REGISTRATION_FAILED, REGISTRATION_FAILED as
shown below. The GCKS in In this case case, the GCKS MUST remove the GM from the
group IDg.
Initiator (GM) Responder (GCKS)
-------------------- ------------------
HDR, SK{IDg, N} -->
<-- HDR, SK{}
Figure 8: GM Reporting Errors in GSA_REGISTRATION Exchange
2.3.3. GM Registration Operations
A GM requesting registration contacts the GCKS using the IKE_SA_INIT
exchange. This exchange is unchanged from IKE_SA_INIT in the IKEv2
protocol. The IKE_SA_INIT exchange may optionally be followed by one
or more of the IKE_INTERMEDIATE exchanges if the GM and the GCKS
negotiated use of IKEv2 extensions based on this exchange.
Next
Next, the GM sends the GSA_AUTH request message with the IKEv2
payloads from IKE_AUTH (without the SAi2, TSi TSi, and TSr payloads)
along with the Group ID informing the GCKS of the group the GM wishes
to join. An A GM intending to emit data traffic MUST send a
GROUP_SENDER Notify message type. The GROUP_SENDER notification not
only signifies that it is a sender, sender but provides the GM the ability to
request Sender-ID values, values in case the Data-Security SA supports a
counter mode
counter-mode cipher. Section 2.5.1 includes guidance on requesting
Sender-ID values.
A GM may be limited in the Transforms IDs that it is able or willing
to use, use and may find it useful to inform the GCKS which Transform IDs
it is willing to accept for different security protocols by including
the SAg payload into the request message. Proposals for Rekey SA and
for Data-Security (AH [RFC4302] and/or ESP [RFC4303]) SAs may be
included into SAg. Proposals for Rekey SA are identified by a new
Protocol ID GIKE_UPDATE with the value <TBA by IANA>. 6. Each Proposal contains a
list of Transforms that the GM is able and willing to support for
that protocol. Valid transform types depend on the protocol (AH,
ESP, GIKE_UPDATE) and are defined in Figure 16. Table 2. Other transform types
SHOULD NOT be included as they will be ignored by the GCKS. The SPI
Security Parameter Index (SPI) length of each Proposal in an SAg is
set to zero, and thus the SPI field is empty. The GCKS MUST NOT use
SPI length and SPI fields in the SAg payload.
Generally, a single Proposal for each protocol (GIKE_UPDATE, AH/ESP)
will suffice, because suffice. Because the transforms are not negotiated, the GM
simply alerts the GCKS to restrictions it may have. In particular,
the restriction from Section 3.3 of IKEv2 [RFC7296] that AEAD Authenticated
Encryption with Associated Data (AEAD) and non-AEAD transforms not be
combined in a single proposal doesn't hold when the SAg payload is
being formed. However However, if the GM has restrictions on the combination
of algorithms, this can be expressed by sending several proposals.
The Proposal Num field in the Proposal substructure is treated
specially in the SAg payload: it allows a GM to indicate that
algorithms used in Rekey SA and in Data-Security (AH and/or ESP) SAs
are dependent. In particular, Proposals for different protocols
having the same value in the Proposal Num field are treated as a set, set
so that if GCKS uses transforms from one of such Proposal for one
protocol, then it MUST only use transforms from one of the Proposals
with the same value in the Proposal Num field for other protocols.
For example, a GM may support algorithms X and Y for both Rekey and
Data-Security SAs, but with a restriction that if X is used in Rekey SA,
SAs, then only X can be used in Data-Security SAs, and the same for
Y. Use of the same value in the Proposal Num field of different
proposals indicates that the GM expects these proposals to be used in
conjunction with each other. In the simplest case when no dependency
between transforms exists, all Proposals in the SAg payload will have
the same value in the Proposal Num field.
Although the SAg payload is optional, it is RECOMMENDED for that the GM to
include this payload into the GSA_AUTH request to allow the GCKS to
select an appropriate policy.
A GM MAY also indicate the support for IPcomp by including one or
more the IPCOMP_SUPPORTED notifications along with the SAg payload in
the request. The Compression Parameter Index (CPI) in these
notifications is set to zero and MUST be ignored by the GCKS.
Upon receiving the GSA_AUTH response, the GM parses the response from
the GCKS authenticating the exchange using the IKEv2 method, then
processes the GSA and KD payloads.
The GSA payload contains the security policy and cryptographic
protocols used by the group. This policy describes the optional
Rekey SA (KEK), Data-Security SAs (TEK), and optional Group-wide (GW)
policy. If the policy in the GSA payload is not acceptable to the
GM, it SHOULD notify the GCKS by initiating a GSA_REGISTRATION
exchange with a NO_PROPOSAL_CHOSEN Notify payload (see
Section 2.3.2). Note, Note that this should normally not happen if the GM
includes the SAg payload in the GSA_AUTH request and the GCKS takes
it into account. Finally Finally, the KD payload is parsed parsed, providing the
keying material for the TEK and/or KEK. The KD payload contains a
list of key bags, where each key bag includes the keying material for
SAs distributed in the GSA payload. Keying material is matched by
comparing the SPIs in the key bags to SPIs previously included in the
GSA payloads. Once TEK keys and policy are matched, the GM provides
them to the data-security subsystem, and it is ready to send or
receive packets matching the TEK policy.
If the group member is not a sender for a received Data-Security SA,
then it MUST install this SA only in the inbound direction. If the
group member is a sender for a received Data-Security SA, and it is
not going to receive back the data it sends, then it MUST install
this SA only in the outgoing direction.
If the first Message ID the GM should expect to receive is non-zero,
the GSA KEK policy includes the attribute GSA_INITIAL_MESSAGE_ID with
the expected non-zero value. The value of the attribute MUST be
checked by a GM against any previously received Message ID for this
group. If it is less than the previously received number, it should
be considered stale and MUST be ignored. This could happen if two
GSA_AUTH exchanges happened in parallel, parallel and the Message ID changed.
This attribute is used by the GM to prevent GSA_REKEY message replay
attacks. The first GSA_REKEY message that the GM receives from the
GCKS will have a Message ID greater than or equal to the Message ID
received in the GSA_INITIAL_MESSAGE_ID attribute.
Group members MUST install the Rekey SA only in the inbound
direction.
Once a GM successfully registers to the group group, it MUST replace any
information related to this group (policy, keys) that it might have
as a result of a previous registration with a new one.
Once a GM has received GIKE_UPDATE policy during a registration, the
IKE SA MAY be closed. By convention, the GCKS closes the IKE SA, SA; the
GM SHOULD NOT close it. The GKCS GCKS MAY choose to keep the IKE SA open
for inband rekey, especially for small groups. If inband rekey is
used, then the initial IKE SA can be rekeyed by any side with the
standard IKEv2 mechanism described in Section 1.3.2 of IKEv2 [RFC7296]. If
for some reason the IKE SA is closed and no GIKE_UPDATE policy is
received during the registration process, the GM MUST consider itself
excluded from the group. To continue participating in the group, the
GM needs to re-register.
2.3.4. GCKS Registration Operations
A G-IKEv2 GCKS listens for incoming requests from group members.
When the GCKS receives an IKE_SA_INIT request, it selects an IKE
proposal and generates a nonce and DH Diffie-Hellman (DH) to include them in
the IKE_SA_INIT response.
Upon receiving the GSA_AUTH request, the GCKS authenticates the group
member via the GSA_AUTH exchange. The GCKS then authorizes the group
member according to group policy before preparing to send the
GSA_AUTH response. If the GCKS fails to authorize the GM, it
responds with an AUTHORIZATION_FAILED notify message type. The GCKS
may also respond with an INVALID_GROUP_ID notify message if the
requested group is unknown to the GCKS or with an REGISTRATION_FAILED
notify message if there is a problem with the requested group (for
example (e.g.,
if the capacity of the group is exceeded).
The GSA_AUTH response will include the group policy in the GSA
payload and keys in the KD payload. If the GCKS policy includes a
group rekey option and the initial Message ID value the GCKS will use
when sending the GSA_REKEY messages to the group members is non-zero,
then this value is specified in the GSA_INITIAL_MESSAGE_ID attribute.
This Message ID is used to prevent GSA_REKEY message replay attacks
and will be increased each time a GSA_REKEY message is sent to the
group. The GCKS data traffic policy is included in the GSA TEK and
keys are included in the KD TEK. The GW policy MAY also be included
to provide the ATD Activation Time Delay (ATD) and/or DTD Deactivation Time
Delay (DTD) (Section 4.4.3.1.1) specifying to specify activation and
deactivation delays for SAs generated from the TEKs. If the group
member has indicated that it is a sender of data traffic and one or
more Data Security Data-Security SAs distributed in the GSA payload included a
counter mode of operation, the GCKS responds with one or more Sender-ID Sender-
ID values (see Section 2.5).
Multicast Extensions to the Security Architecture [RFC5374] defines
two modes of operation for multicast Data-Security SAs: transport
mode and tunnel mode with address preservation. In the latter case case,
outer source and destination addresses are taken from the inner IP
packet. The mode of operation for the Data-Security SAs is
determined by the presence of the USE_TRANSPORT_MODE notification in
the GCKS's response message of the registration exchange: if exchange. If it is
present, then SAs are created in transport mode; otherwise, SAs are
created in tunnel mode. If multiple Data-Security SAs are being
created in a single registration exchange, then all of them will have
the same mode of operation.
If the GCKS receives a GSA_REGISTRATION exchange with a request to
register a GM to a group, the GCKS will need to authorize the GM with
the new group (IDg) and respond with the corresponding group policy
and keys. If the GCKS fails to authorize the GM, it will respond
with the AUTHORIZATION_FAILED notification. The GCKS may also
respond with an INVALID_GROUP_ID or REGISTRATION_FAILED notify
messages for the reasons described above.
If a group member includes an SAg in its GSA_AUTH or GSA_REGISTRATION
request, the GCKS may evaluate it according to an implementation implementation-
specific policy.
* The GCKS could evaluate the list of Transforms and compare it to
its current policy for the group. If the group member did not
include all of the ESP, AH AH, or GIKE_UPDATE Transforms that match
the current group policy or the capabilities of all other
currently active GMs, then the GCKS SHOULD return a
NO_PROPOSAL_CHOSEN Notification. notification. Alternatively, the GCKS can
change the group policy as defined below.
* The GCKS could store the list of Transforms, Transforms with the goal of
migrating the group policy to a different Transforms when all of
the group members indicate that they can support that Transforms.
* The GCKS could store the list of Transforms and adjust the current
group policy based on the capabilities of the devices as long as
they fall within the acceptable security policy of the GCKS.
Depending on its policy, the GCKS may have no further need for the
IKE SA (e.g., it does not plan to initiate an a GSA_INBAND_REKEY
exchange). If the GM does not initiate another registration exchange
or Notify (e.g., NO_PROPOSAL_CHOSEN), NO_PROPOSAL_CHOSEN) and the GCKS is not intended to
use the SA, then after a short period of time the GCKS SHOULD close the IKE SA to save resources. resources
after a short period of time.
2.4. Group Maintenance Channel
The GCKS is responsible for rekeying the secure group per the group
policy. Rekeying is an operation whereby the GCKS provides
replacement TEKs and KEK, KEKs, deleting TEKs, and/or excluding group
members. The GCKS may initiate a rekey message if group membership
and/or policy has changed, changed or if the keys are about to expire. Two
forms of group maintenance channels are provided in G-IKEv2 to push
new policy to group members.
GSA_REKEY
GSA_REKEY:
The GSA_REKEY is a pseudo-exchange, consisting of a one-way IKEv2
message sent by the GCKS, GCKS where the rekey policy is delivered to
group members using IP multicast as a transport. This method is
valuable for large and dynamic groups, groups and where policy may change
frequently and a scalable rekey method is required. When the
GSA_REKEY is used, the IKE SA protecting the member registration
exchanges is usually terminated, terminated and group members await policy
changes from the GCKS via the GSA_REKEY messages.
GSA_INBAND_REKEY
GSA_INBAND_REKEY:
The GSA_INBAND_REKEY is a normal IKEv2 exchange using the IKE SA
that was setup set up to protecting protect the member registration exchange. This
exchange allows the GCKS to rekey without using an independent
GSA_REKEY pseudo-exchange. The GSA_INBAND_REKEY exchange provides
a reliable policy delivery and is useful when G-IKEv2 is used with
a small group of cooperating devices.
Depending on its policy policy, the GCKS MAY combine these two methods. For
example, it the GCKS may use the GSA_INBAND_REKEY to deliver a key to
the GMs in the group acting as senders (as this would provide
reliable keys
delivery), delivery) and the GSA_REKEY for the rest of the GMs.
2.4.1. GSA_REKEY
The GCKS initiates the G-IKEv2 Rekey rekey by sending a protected message
to the GMs, usually using IP multicast. Since the Rekey messages do
not require responses and they are sent to multiple GMs, the windowing
mechanism described in Section 2.3 of IKEv2 [RFC7296] MUST NOT be used for
the Rekey messages. The GCKS rekey message replaces the current
rekey GSA KEK or KEK array (e.g. (e.g., in the case of LKH), LKH) and/or creates
new Data-Security GSA TEKs. The GM_SENDER_ID attribute in the Key
Download payload (defined in Section 4.5.3.3) MUST NOT be part of the
Rekey Exchange Exchange, as this is sender specific sender-specific information and the Rekey
Exchange is group specific. The GCKS initiates the GSA_REKEY pseudo-exchange pseudo-
exchange as following:
GMs (Receivers) GCKS (Sender)
----------------- ---------------
<-- HDR, SK{GSA, KD, [N,] [AUTH]}
Figure 9: GSA_REKEY Pseudo-Exchange
HDR is defined in Section 4.1. While GSA_REKEY re-uses reuses the IKEv2
header, the "IKE SA Initiator's SPI" and the "IKE SA Responder's SPI"
fields are treated as a single field with a length of 16 octets
containing the SPI of a Rekey SA. The value for this field is
provided by the GCKS in the GSA payload (see Section 4.4.2). The
Message ID in this message will start with the value the GCKS sent to
the group members in the attribute GSA_INITIAL_MESSAGE_ID or from
zero if this attribute wasn't sent. The Message ID will be
incremented each time a new GSA_REKEY message is sent to the group
members.
The GSA payload contains the current policy for rekey and Data-
Security SAs. The GSA may contain a new Rekey SA and/or a new Data-
Security SAs Section 4.4. (Section 4.4).
The KD payload contains the keys for the policy included in the GSA.
If one or more Data-Security SAs are being refreshed in this rekey
message, the IPsec keys are updated in the KD, and/or if the rekey Rekey SA
is being refreshed in this rekey message, the rekey Key or the LKH
KEK array (e.g. (e.g., in case of LKH) is updated in the KD payload.
A Delete payload MAY be included to instruct the GM to delete
existing SAs. See Section 4.6 for more detail.
The AUTH payload MUST be included to authenticate the GSA_REKEY
message if the authentication method is based on public key
signatures and MUST NOT be included if authentication is implicit.
In the latter case, the fact that a GM can decrypt the GSA_REKEY
message and verify its ICV Integrity Check Value (ICV) proves that the
sender of this message knows the current KEK, thus authenticating the
sender as a member of the group. Note, Note that implicit authentication
doesn't provide source origin authentication. For this reason reason, using
implicit authentication for GSA_REKEY is NOT RECOMMENDED unless
source origin authentication is not required (for example, in a small
group of highly trusted GMs). See more about authentication methods
in Section 4.4.2.1.1.
During group member registration, the GCKS sends the authentication
key in the KD payload, the AUTH_KEY attribute, which the group member
uses to authenticate the key server. Before the current
authentication key expires, the GCKS will send a new AUTH_KEY to the
group members in a GSA_REKEY message. The authentication key that is
sent in the rekey message may be not be the same as the authentication
key sent during the GM registration. If implicit authentication is
used, then AUTH_KEY MUST NOT be sent to GMs.
2.4.1.1. GSA_REKEY Message Authentication
The content of the AUTH payload generally depends on the
authentication method from the Group Controller Authentication Method
(GCAUTH) transform (Section 4.4.2.1.1). This specification defines
the use of only one authentication method - method, Digital Signature, and the
AUTH payload contains a digital signature calculated over the content
of the
not yet encrypted not-yet-encrypted GSA_REKEY message.
The digital signing is applied to the concatenation of two chunks: A
and P. The chunk Chunk A starts with the first octet of the G-IKEv2 header
(not including prepended four octets of zeros, if port 4500 is used)
and continues to the last octet of the Encrypted Payload header. The
chunk
Chunk P consists of the not yet encrypted not-yet-encrypted content of the Encrypted
payload, excluding the Initialization Vector, the Padding, the Pad
Length
Length, and the Integrity Checksum Data fields (see Section 3.14 of IKEv2
[RFC7296] for the description of the Encrypted payload). In other
words,
the P chunk P is the inner payloads of the Encrypted payload in
plaintext form. Figure 10 11 illustrates the layout of the chunks P and A
chunks
in the GSA_REKEY message.
Before the calculation of the AUTH payload payload, the inner payloads of the
Encrypted payload must be fully formed and ready for encryption, encryption
except for the content of the AUTH payload. The AUTH payload must
have correct values in the Payload Header, the Auth Method Method, and the
RESERVED fields. The Authentication Data field is zeroed, but the
ASN.1 Length and the AlgorithmIdentifier fields must be properly
filled in, in; see Signature Authentication in IKEv2 [RFC7427].
For the purpose of the AUTH payload calculation calculation, the Length field in
the IKE header and the Payload Length field in the Encrypted Payload
header are adjusted so that they don't count the lengths of
Initialization Vector, Integrity Checksum Data Data, and Padding (along
with Pad Length field). In other words, the Length field in the IKE
header (denoted as AdjustedLen in Figure 10) 11) is set to the sum of the
lengths of A and P, and the Payload Length field in the Encrypted
Payload header (denoted as AdjustedPldLen in Figure 10) 11) is set to the
length of P plus the size of the Payload header (four octets).
The input to the digital signature algorithm that computes the
content of the AUTH payload can be described as:
DataToAuthenticate = A | P
GsaRekeyMessage = GenIKEHDR | EncPayload
GenIKEHDR = [ four octets 0 if using port 4500 ] | AdjustedIKEHDR
AdjustedIKEHDR = SPIi | SPIr | . . . | AdjustedLen
EncPayload = AdjustedEncPldHdr | IV | InnerPlds | Pad | PadLen | ICV
AdjustedEncPldHdr = NextPld | C | RESERVED | AdjustedPldLen
A = AdjustedIKEHDR | AdjustedEncPldHdr
P = InnerPlds
Figure 10
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ^ ^
| IKE SA Initiator's SPI | | |
| | | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ I |
| IKE SA Responder's SPI | K |
| | E |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |
| Next Payload | MjVer | MnVer | Exchange Type | Flags | H A
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ d |
| Message ID | r |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | |
| AdjustedLen | | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ x |
| Next Payload |C| RESERVED | AdjustedPldLen | | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | v
| | |
~ Initialization Vector ~ E
| | n
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ c ^
| | r |
~ Inner payloads Payloads (not yet encrypted) ~ P
| | P |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ l v
~ Padding (0-255 octets) | Pad Length | d
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |
| | |
~ Integrity Checksum Data ~ |
| | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ v
Figure 10: 11: Data to Authenticate in the GSA_REKEY Messages
The authentication data is calculated using the authentication
algorithm from the Group Controller Authentication Method transform
(Section 4.4.2.1.1) and the current authentication key provided in
the AUTH_KEY attribute (Section 4.5.3.2). The calculated
authentication data is placed into the AUTH payload, the Length
fields in the IKE Header and the Encryption Payload header are
restored, the content of the Encrypted payload is encrypted and the
ICV is computed using the current KEK.
2.4.1.2. IKE Fragmentation
IKEv2 fragmentation [RFC7383] can be used to perform fragmentation of
large GSA_REKEY messages; however, when the GSA_REKEY message is
emitted as an IP multicast packet packet, there is a lack of response from
the GMs. This has the following implications.
* Policy regarding the use of IKE fragmentation is implicit. If a
GCKS detects that all GMs have negotiated support of IKE
fragmentation in IKE_SA_INIT, then it MAY use IKE fragmentation on
large GSA_REKEY messages.
* The GCKS must always use IKE fragmentation based on a pre-
configured
preconfigured fragmentation threshold, as there is no way to check
if fragmentation is needed by first sending unfragmented messages
and waiting for response. Section 2.5.1 of IKEv2 Fragmentation [RFC7383] contains recommendation
recommendations on selecting the fragmentation threshold.
* PMTU The Path MTU (PMTU) mechanism, defined in Section 2.5.2 of IKEv2 Fragmentation
[RFC7383], cannot be used due to lack of GSA_REKEY response
messages.
The calculation of authentication data MUST be applied to whole
messages only, only before possible IKE Fragmentation. If the message was
received in fragmented form, it should be reconstructed before
verifying its authenticity as if it were received unfragmented. The
RESERVED field in the reconstructed Encrypted Payload header MUST be
set to the value of the RESERVED field in the Encrypted Fragment
payload header from the first fragment (that with (with the Fragment Number
equal to 1).
2.4.1.3. GSA_REKEY GCKS Operations
The GCKS builds the rekey message with a Message ID value that is one
greater than the value included in the previous rekey message. The
first message sent over a new Rekey SA MUST use a Message ID of 0.
The GSA, KD KD, and N payloads follow with the same characteristics as
in the GSA Registration exchange. The AUTH payload (if present) is
created as defined in Section 2.4.1.1.
Because GSA_REKEY messages are not acknowledged and could be
discarded by the network, one or more GMs may not receive the new
policy. To mitigate such lost messages, during a rekey event event, the
GCKS may transmit several copies of an encrypted GSA_REKEY message
with the new policy. The (encrypted) retransmitted messages MUST be
bitwise identical and should be sent within a short time interval (a
few seconds) to ensure that the SA lifetime calculations would not be
substantially skewed for the GMs that would receive different copies
of the messages.
GCKS may also include one or several GSA_NEXT_SPI attributes
specifying SPIs for the prospected rekeys, rekeys so that listening GMs are
able to detect lost rekey messages and recover from this situation.
See Sections Section 4.4.2.2.3 for more detail.
2.4.1.4. GSA_REKEY GM Operations
When a group member receives the Rekey rekey message from the GCKS GCKS, it
decrypts the message and verifies its integrity using the current
KEK. If the AUTH payload is present in the decrypted message, then
the GM validates authenticity of the message using the key retrieved
in a previous G-IKEv2 exchange. Then the GM verifies the Message ID, ID
and processes the GSA and KD payloads. The group member then
installs the new Data-Security SA(s) and/or a new Rekey SA. The
parsing of the payloads is identical to the parsing done in the
registration exchange.
Replay protection is achieved by a group member rejecting a GSA_REKEY
message which that has a Message ID smaller than the current Message ID
that the GM is expecting. The GM expects the Message ID in the first
GSA_REKEY message it receives to be equal to or greater than the
Message ID it receives in the GSA_INITIAL_MESSAGE_ID attribute. Note, Note
that if the GSA_INITIAL_MESSAGE_ID attribute is not received for the
Rekey SA, the GM MUST assume zero as the first expected Message ID.
The GM expects the Message ID in subsequent GSA_REKEY messages to be
greater than the last valid GSA_REKEY message ID it received.
This specification assumes that the GSA_REKEY messages are sent with
intervals,
intervals that are significantly greater than typical network packet
reordering intervals.
If the GSA payload includes a Data-Security SA using cipher in a
counter-mode of operation and the receiving group member is a sender
for that SA, the group member uses its current Sender-ID value with
the Data-Security SAs to create counter-mode nonces. If it is a
sender and does not hold a current Sender-ID value (for example, when
no counter-mode is employed for other Data-Security SAs), it MUST NOT
install the Data-Security SAs. It MUST initiate a re-registration to
the GCKS in order to obtain an a Sender-ID value (along with the current
group policy).
Once a new Rekey SA is installed as a result of a GSA_REKEY message,
the current Rekey SA (over which the message was received) MUST be
silently deleted after waiting the DEACTIVATION_TIME_DELAY interval
regardless of its expiration time. If the message includes a Delete
payload for an existing Data-Security SA, then after installing a new
Data-Security SA SA, the old one, identified one (identified by the Protocol and SPI
fields in the Delete payload, payload) MUST be silently deleted after waiting
the DEACTIVATION_TIME_DELAY interval regardless of its expiration
time.
If a Data-Security SA is not rekeyed yet and is about to expire (a
"soft lifetime" expiration is described in Section 4.4.2.1 of
[RFC4301]), the GM SHOULD initiate a registration to the GCKS. This
registration serves as a request for current SAs, SAs and will result in
the download of replacement SAs, assuming the GCKS policy has created
them. A GM SHOULD also initiate a registration request if a Rekey SA
is about to expire and not yet replaced with a new one.
2.4.2. GSA_INBAND_REKEY Exchange
When the IKE SA protecting the member registration exchange is
maintained while a group member participates in the group, the GCKS
can use the GSA_INBAND_REKEY exchange to individually provide policy
updates to the group member.
GM (Responder) GCKS (Initiator)
---------------- ------------------
<-- HDR, SK{GSA, KD, [N]}
HDR, SK{} -->
Figure 11: 12: GSA_INBAND_REKEY Exchange
Because this is a normal IKEv2 exchange, the HDR is treated as
defined in IKEv2 [RFC7296].
2.4.2.1. GSA_INBAND_REKEY GCKS Operations
The GSA, KD KD, and N payloads are built in the same manner as in a
registration exchange.
2.4.2.2. GSA_INBAND_REKEY GM Operations
The GM processes the GSA, KD KD, and N payloads in the same manner as if
they were received in a registration exchange.
2.4.3. Deletion of SAs
There are occasions when the GCKS may want to signal to group members
to delete policy when the application sending data traffic has ended, ended
or if group policy has changed. Deletion of SAs is accomplished by
sending the Delete Payload described in Section 3.11 of IKEv2 [RFC7296] as
part of the GSA_REKEY pseudo-exchange as shown below.
GMs (Receivers) GCKS (Sender)
---------------- ---------------
<-- HDR, SK{D, [N,] [AUTH]}
Figure 12: 13: SA Deletion in GSA_REKEY
If GCKS has a unicast SA with a group member member, then it can use the
GSA_INBAND_REKEY exchange to delete SAs.
GM (Responder) GCKS (Initiator)
--------------- ------------------
<-- HDR, SK{D, [N]}
HDR, SK{} -->
Figure 13: 14: SA Deletion in GSA_INBAND_REKEY
There may be circumstances where the GCKS may want to start over with
a clean state, for example e.g., in case it runs out of available Sender-
IDs. Sender-IDs.
The GCKS can signal deletion of all the Data-Security SAs by sending
a Delete payload with an SPI value equal to zero. For example, if
the GCKS wishes to remove the Rekey SA and all the Data-
Security Data-Security SAs,
the GCKS sends a Delete payload with an SPI of zero and a Protocol ID
of AH or ESP, followed by another Delete payload with a an SPI of zero
and a Protocol ID of GIKE_UPDATE.
If a group member receives a Delete payload with zero SPI and
protocol a
Protocol ID of GIKE_UPDATE, it means that the group member is
excluded from the group. Such Delete payload may be received either
in the GSA_REKEY pseudo-exchange or in the GSA_INBAND_REKEY exchange.
In this situation situation, the group member MUST re-register if it wants to
continue participating in this group. The registration is performed
as described in Section 2.3. It is RECOMMENDED that a GM waits some
randomly chosen time before initiating a registration request in this
situation to avoid overloading the GCKS. This document doesn't
specify the maximum delay, which is implementation-dependent, but it
is believed, believed that the order of seconds suits most situations. Note, Note
that if the unicast SA between the group member and the GCKS exists,
then the group member may use the GSA_REGISTRATION exchange to re-
register. However, after excluding an a GM from the group group, the GCKS MAY
immediately delete the unicast SA with this GM (if any) if the
credentials of this GM are revoked.
2.5. Counter-based modes Counter-Based Modes of operation Operation
Several counter-based modes of operation have been specified for ESP
(e.g., AES-CTR [RFC3686], AES-GCM [RFC4106], AES-CCM AES CCM [RFC4309],
ChaCha20-Poly1305 [RFC7634], and AES-GMAC [RFC4543]) and AH (e.g., AES-
GMAC
AES-GMAC [RFC4543]). These counter-based modes require that no two
senders in the group ever send a packet with the same Initialization
Vector (IV) IV using the
same cipher key and mode. This requirement is met in G-IKEv2 when
the following measures are taken:
* The GCKS distributes a unique key for each Data-Security SA.
* The GCKS uses the method described in Using Counter Modes with ESP
and AH to Protect Group Traffic [RFC6054], which assigns
each sender a portion of the IV space by provisioning each sender
with one or more unique Sender-ID values.
2.5.1. Allocation of Sender-ID
When at least one Data-Security SA included in the group policy
includes a counter-based mode of operation, the GCKS automatically
allocates and distributes one Sender-ID to each group member acting
in the role of sender on the Data-Security SA. The Sender-ID value
is used exclusively by the group sender to which it was allocated.
The group sender uses the same Sender-ID for each Data-Security SA
specifying the use of a counter-based mode of operation. A GCKS MUST
distribute unique keys for each Data-Security SA SA, including a counter-
based
counter-based mode of operation in order to maintain unique key and
nonce usage.
During registration, the group sender can choose to request one or
more Sender-ID values. Requesting a value of 1 is not necessary
since the GCKS will automatically allocate exactly one to the group
sender. A group sender MUST request as many Sender-ID values
matching the number of encryption modules in which it will be
installing the TEKs in the outbound direction. Alternatively, a
group sender MAY request more than one Sender-ID and use them
serially. This could be useful when it is anticipated that the group
sender will exhaust their range of Data- Security Data-Security SA nonces using a
single Sender-ID too quickly (e.g., before the time-based policy in
the TEK expires).
When the group policy includes a counter-based mode of operation, a
GCKS should use the following method to allocate Sender-ID values,
which ensures that each Sender-ID will be allocated to just one group
sender.
1. A GCKS maintains an a Sender-ID counter, which records the Sender-
IDs that have been allocated. Sender-IDs are allocated
sequentially,
sequentially with zero as the first allocated value.
2. Each time an a Sender-ID is allocated, the current value of the
counter is saved and allocated to the group sender. The Sender-
ID counter is then incremented in preparation for the next
allocation.
3. When the GCKS specifies a counter-based mode of operation in the
Data-Security SA SA, a group sender may request a count of Sender-IDs Sender-
IDs during registration in a Notify payload information of type
SENDER. When the GCKS receives this request, it increments the
Sender-ID counter once for each requested Sender-ID, Sender-ID and
distributes each Sender-ID value to the group sender. The GCKS
should have a policy-defined upper bound for the number of
Sender-ID values that it will return irrespective of the number
requested by the GM.
4. A GCKS allocates new Sender-ID values for each registration
operation by a group sender, regardless of whether the group
sender had previously contacted the GCKS. In this way, the GCKS
is not required to maintaining maintain a record of which Sender-ID values it
had previously allocated to each group sender. More importantly,
since the GCKS cannot reliably detect whether the group sender
had sent data on the current group Data-Security SAs SAs, it does not
know what Data-Security counter-mode nonce values that a group
sender has used. By distributing new Sender-ID values, the key
server ensures that each time a conforming group sender installs
a Data-Security SA SA, it will use a unique set of counter-based
mode nonces.
5. When the Sender-ID counter maintained by the GCKS reaches its
final Sender-ID value, no more Sender-ID values can be
distributed. Before distributing any new Sender-ID values, the
GCKS MUST exclude all group members from the group as described
in Section 2.4.3. This will result in the group members
performing re-registration, during which they will receive new
Data-Security SAs and group senders will additionally receive new
Sender-ID values. The new Sender-ID values can safely be used
because they are only used with the new Data-Security SAs.
2.5.2. GM Usage of Sender-ID
A GM applies the Sender-ID to Data-Security SAs as follows. follows:
* The most significant bits of the IV indicated in the
GWP_SENDER_ID_BITS attribute (Section 4.4.3.1.2) are taken to be
the Sender-ID field of the IV.
* The Sender-ID is placed in the least significant bits of the
Sender-ID field, where any unused most significant bits are set to
zero. If the Sender-ID value doesn't fit into the number of bits
from the GWP_SENDER_ID_BITS attributes, then the GM MUST treat
this as a fatal error and re-register to the group.
2.6. Replay Protection for Multicast Data-Security SAs
IPsec provides anti-replay service as part of its security services.
With multicast extension extensions for IPsec IPsec, replay protection is not always
possible to achieve (see Section 6.1 of Multicast Group Security
Architecture [RFC3740]). In particular,
if there are many group senders for a Data-Security SA, then each of
them will independently increment the Sequence Number field in the
ESP header (see Section 2.2 of ESP [RFC4303] and Section 2.5 of AH [RFC4302])
[RFC4302]), thus making it impossible for the group receivers to
filter out replayed packets. However, if there is only one group
sender for a Data-
Security Data-Security SA, then it is possible to achieve replay
protection with some restrictions (see Section 4.4.2.1.3). The GCKS
MAY create several Data-Security SAs with the same traffic selectors
allowing only a single group sender in each SA if it is desirable to
get replay protection with multiple (but still a limited number) of
group senders.
IPsec architecture assumes that it whether anti-replay service is
enabled or not is a local matter for an IPsec
receiver whether anti-replay service is enabled or not. receiver. In other
words, an IPsec sender always increments the Sequence Number field in
the ESP/AH header and a receiver decides whether to check for
replayed packets or not. Since in some cases it is known in some cases that the
replay protection is not possible (like in an SA with many group
senders), a new transform ID "32-bit Unspecified Numbers" is defined
for the Sequence Numbers (SN) (SNs) transform type. Using this transform
ID the
ID, the GCKS can inform group members that the uniqueness of sequence
numbers for a given SA is not guaranteed. The decision of whether to
enable anti-replay service is still a local matter of a GM (in
accordance with IPsec architecture).
The GCKS MUST include the Sequence Numbers transform in the GSA
payload for every Data-Security SA. See Section 4.4.2.1.3 for more
details.
When a Data-Security SA has a single sender, the GCKS MUST be
configured to rekey the SA frequently enough so that the 32-bit
sequence numbers do not wrap.
2.7. Encryption Transforms with Implicit IV
IKEv2 IANA registry for
The "Transform Type 1 - Encryption Algorithm Transform IDs IDs" IANA
registry [IKEV2-IANA] defines several transforms with implicit IV.
These transforms rely on ESP Sequence Number Numbers for constructing IV
(see
Implicit IV for Counter-Based Ciphers in ESP [RFC8750] for details). It requires anti-replay service to be
enabled for an ESP SA using these encryption transforms. Unless the
properties of sequence numbers for a multicast ESP SA include their
uniqueness (see Section 2.6), encryption transforms that rely on
Sequence Number Numbers for IV construction MUST NOT be used. In any case,
such transforms MUST NOT be used for any G-IKEv2 SA (both unicast and
multicast).
3. Group Key Management and Access Control
Through the G-IKEv2 rekey, G-IKEv2 supports algorithms such as
Logical Key Hierarchy (LKH) that have the property of denying access
to a new group key by a member removed from the group (forward access
control) and to an old group key by a member added to the group
(backward access control). This is unrelated to PFS (Perfect the Perfect Forward
Secrecy)
Secrecy (PFS) property as defined in Section 2.12 of IKEv2 [RFC7296].
Group management algorithms providing forward and backward access
control other than LKH have been proposed in the literature,
including OFT [OFT] and Subset Difference [NNL]. These algorithms
could be used with G-IKEv2, G-IKEv2 but are not specified as a part of this
document.
This specification assumes that all group keys, that are sent to the
GMs by the GCKS, are encrypted with some other keys, called Key Wrap
Keys (KWK). (KWKs). The Key Wrap Algorithm transform defines the algorithm
used for key wrapping in the context of an SA.
3.1. Key Wrap Keys
Every GM always knows at least one KWK -- the KWK that is associated
with the IKE SA or multicast Rekey SA over which wrapped keys are
sent. In this document document, it is called default KWK and is denoted as
GSK_w.
"GSK_w".
For the purpose of forward access control control, the GCKS may provide each
GM with its personal KWK at the time of registration. Additionally,
several intermediate KWKs that form a key hierarchy and are shared
among several GMs may be provided by the GCKS.
Each KWK is associated with a key wrap algorithm, algorithm specified in the Key
Wrap Algorithm transform. The size of these KWKs is determined by
the used key wrap algorithm, algorithm used, but it SHOULD NOT be less than the size
of the key for the Encryption Algorithm transform for the Rekey SA
and for all Data-Security SAs in the group (taking into
consideration the Key Length
attribute into consideration if it is present).
3.1.1. Default Key Wrap Key
The default KWK (GSK_w) is only used in the context of a single IKE
SA. Every IKE SA (unicast IKE SA or multicast Rekey SA) will have
its own GSK_w.
For the unicast IKE SA (used for the GM registration and for the
GSA_INBAND_REKEY exchanges, if they are take place) place), the GSK_w is
computed as follows:
GSK_w = prf+(SK_d, "Key Wrap for G-IKEv2")
where the string "Key Wrap for G-IKEv2" is 20 ASCII characters
without null termination.
For the multicast Rekey SA SA, the GSK_w is provided along with other SA
keys as defined in Section 3.4.
3.2. GCKS Key Management Semantics
The Wrapped Key Download method allows the GCKS to employ various key
management methods
* methods.
A simple key management methods -- when the method: The GCKS always sends group SA keys
encrypted with the GSK_w.
*
An LKH key management method -- when the method: The GCKS provides each GM with an
individual key at the time of the GM registration (encrypted with
GSK_w). Then Then, the GCKS forms an a hierarchy of keys so that the
group SA keys are encrypted with other keys which that are encrypted
with other keys and so on, tracing back to the keys for each GM.
Other key policies may also be employed by the GCKS.
3.2.1. Forward Access Control Requirements
When a group membership is altered using a group management algorithm
algorithm, new Data-Security SAs and their associated keys are
usually also needed. New Data-Security SAs and keys ensure that
members who were denied access can no longer participate in the
group.
If forward access control is a desired property of the group, a new
TEK policy and the associated keys MUST NOT be included in a G-IKEv2
rekey message message, which changes group membership. This is required
because the GSA TEK policy and the associated keys are not protected
with the new KEK. A second G-IKEv2 rekey message can deliver the new
GSA TEK policies and their associated keys because it will be
protected with the new KEK, KEK and thus will not be visible to the
members who were denied access.
If forward access control policy for the group includes keeping group
policy changes from members that are denied access to the group, then
two sequential G-IKEv2 rekey messages changing the group KEK MUST be
sent by the GCKS. The first G-IKEv2 rekey message creates a new KEK
for the group. Group members, which are denied access, will not be
able to access the new KEK, but they will see the group policy since
the G-IKEv2 rekey message is protected under the current KEK. A
subsequent G-IKEv2 rekey message containing the changed group policy
and again changing the KEK allows complete forward access control. A
G-IKEv2 rekey message MUST NOT change the policy without creating a
new KEK.
If other methods of using LKH or other group management algorithms
are added to G-IKEv2, those methods MAY remove the above restrictions
requiring multiple G-IKEv2 rekey messages, providing those methods
specify how the forward access control policy is maintained within a
single G-IKEv2 rekey message.
3.3. GM Key Management Semantics
This specification defines a GM Key Management semantics in such a
way, way
that it doesn't depend on the key management method employed by the
GCKS. This allows having all the complexity of key management in the
GCKS, which is free to implement various key management methods, methods such
as direct transmitting of group SA keys or using some kind of key
hierarchy (e.g. (e.g., LKH). For all these policies the The GM behavior is the same. same for all of these
policies.
All keys in G-IKEv2 are transmitted in encrypted form, form as specified in
Section 4.5.4. This format includes a 32-bit Key ID (ID of a key
that is encrypted) and a 32-bit KWK ID (ID of a key that was used to
encrypt this key). Keys may be encrypted either with a default KWK
(GSK_w) or with other keys, which the GM has received in the WRAP_KEY
attributes. If a key was encrypted with GSK_w, then the KWK ID field
is set to zero, otherwise zero. Otherwise, the KWK ID field identifies the key used
for encryption. Zero A zero Key ID always identifies the key from which
the keys for protecting Data-Security SAs and Rekey SA are taken.
When a GM receives a message from the GCKS installing the new Data-
Security or Rekey SA, it will contain a KD payload with an SA_KEY
attribute containing keying material for this SA. For a Data-
Security SA SA, exactly one SA_KEY attribute will be present with both
Key ID and KWK ID fields set to zero. This means that the default
KWK (GSK_w) should be used to extract this keying material.
For a multicast Rekey SA SA, multiple SA_KEY attributes may be present
depending on the key management method employed by the GCKS. If
multiple SA_KEY attributes are present present, then all of them MUST contain
the same keying material encrypted using different KWKs. The GM in
general is unaware of the key management method used by the GCKS and
can always use the same procedure to get the keys. The GM tries to
decrypt at least one of the SA_KEY attributes using either the GSK_w
or the keys from the WRAP_KEY attributes that are present in the same
message or were receives received in previous messages.
We will use the term "Key Path" to describe an ordered sequence of
keys where each subsequent key was used to encrypt the previous one.
The GM keeps its own Key Path (called Working Key Path) in the memory
associated with each group it is registered to and updates it when
needed. When the GSA_REKEY message is received received, the GM processes the
received SA_KEY attributes one by one trying and tries to construct a new
key path that starts from one of these attributes and ends with any
key in the Working Key Path or with the default KWK (GSK_w).
In the simplest case case, the SA_KEY attribute is encrypted with GSK_w so
that the new Key Path is empty. If more complex key management
methods are used used, then a Key Path will contain intermediate keys from
the WRAP_KEY attributes received by a GM so far far, starting from its
registration to the group. If the GM is able to construct a new Key
Path using intermediate keys it has, then it is able to decrypt the
SA_KEY attribute and use its content to form new SA keys. If it is
unable to build a new Key Path, then in it means that the GM is excluded
from the group.
Depending on the new Key Path Path, the GM should do the following actions
to be prepared for future key updates:
* If the new Key Path is empty empty, then no actions are needed. This
may happen if no WRAP_KEY attributes from the received message
were used.
* If the new Key Path is non-empty and it ends with the default KWK
(GSK_w), then the whole new Key Path is stored by the GM as the
GM's Working Key Path. This situation may only happen at the time
the GM is registering to the group, when the GCKS is providing it the
GM with its personal key and the other keys from the key tree that
are needed for this GM. needed. These keys form an initial Working Key Path for this
GM.
* In all other cases cases, the new Key Path will end at some intermediate
key from the GM's current Working Key Path. In this case case, the new
Key Path is constructed by replacing a part of the GM's current
Working Key Path from the beginning and up to (but not including)
the key that the GM has used to decrypt the last key in the new
Key Path.
Appendix A contains an example of how this algorithm works in case of
LKH key management method.
3.4. SA Keys
The keys that are used for Data-Security SAs or a Rekey SA (called here SA keys)
keys here) are downloaded to GMs in the form of keying material from
which, according to policy, a set of keys are deterministically
extracted.
For a Data-Security SA SA, the keys are taken in accordance to the third
bullet from Section 2.17 of [RFC7296]. In particular, for the ESP
and AH SAs SAs, the encryption key (if any) MUST be taken from the
leftmost bits of the keying material and the integrity key (if any)
MUST be taken from the remaining bits.
For a Rekey SA SA, the following keys are taken from the keying
material:
GSK_e | GSK_a | GSK_w = KEYMAT
Figure 15
where GSK_e and GSK_a are the keys used for the Encryption Algorithm
and the Integrity Algorithm transforms for the corresponding SA and
GSK_w is a default KWK for this SA. Note, Note that GSK_w is used with the
key wrap algorithm specified in the Key Wrap Algorithm transform. If
an AEAD algorithm is used for encryption, then the GSK_a key will not
be used (GM can use the formula above assuming the length of GSK_a is
zero).
4. Header and Payload Formats
The G-IKEv2 is an IKEv2 extension and thus inherits its wire format
for data structures. However, the processing of some payloads are
different. Several new payloads are defined: Group Identification
(IDg, Section
(IDg) (Section 4.2), Security Association - GM Supported Transforms
(SAg, Section
(SAg) (Section 4.3), Group Security Association (GSA, Section (GSA) (Section 4.4),
and Key Download (KD, Section (KD) (Section 4.5). The G-IKEv2 header
(Section 4.1), IDg payload payload, and SAg payload reuse the IKEv2 format
for the IKEv2 header, IDi/IDr payloads payloads, and SA payload payload, respectively.
New exchange types GSA_AUTH, GSA_REGISTRATION, GSA_REKEY GSA_REKEY, and
GSA_INBAND_REKEY are also added.
This section describes new payloads and the differences in the
processing of existing IKEv2 payloads.
4.1. G-IKEv2 Header
G-IKEv2 uses the same IKE header format as specified in [RFC7296]
section 3.1. Section 3.1
of [RFC7296]. The Major Version is 2 and the Minor Version is 0 0, as
in IKEv2. IKE SA Initiator's SPI, IKE SA Responder's SPI, Flags,
Message ID, and Length are as specified in [RFC7296].
4.2. Group Identification Payload
The Group Identification (IDg) payload allows the group member to
indicate which group it wants to join. The payload is constructed by
using the IKEv2 Identification Payload (section (Section 3.5 of [RFC7296]).
ID type ID_KEY_ID MUST be supported. ID types ID_IPV4_ADDR, ID_FQDN,
ID_RFC822_ADDR, and ID_IPV6_ADDR SHOULD be supported. ID types
ID_DER_ASN1_DN and ID_DER_ASN1_GN are not expected to be used. The
Payload Type for the Group Identification IDg payload is fifty (50).
4.3. Security Association - GM Supported Transforms Payload
The Security Association - GM Supported Transforms Payload (SAg) payload
declares which Transforms a GM is willing to accept. The payload is
constructed using the format of the IKEv2 Security Association
payload (section (Section 3.3 of [RFC7296]). The Payload Type for SAg
payloads is thirty-three (33), which is identical to the SA Payload
Type.
4.4. Group Security Association Payload
The Group Security Association (GSA) GSA payload is used by the GCKS to assert security attributes for
both Rekey SA and Data-Security SAs. The Payload Type for the Group Security Association GSA
payload is fifty-
one fifty-one (51).
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 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
~ <Group Policies> ~
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 14: 16: GSA Payload Format
The Security Association Payload payload fields are defined as follows:
*
Next Payload, C, RESERVED, and Payload Length fields comprise fields:
Comprise the IKEv2 Generic Payload Header and are defined in
Section 3.2. 3.2 of [RFC7296].
*
Group Policies (variable) -- (variable):
A set of group policies for the group.
4.4.1. Group Policies
Group policies are comprised of two types of policy -- types: Group SA (GSA) policy and
Group-wide (GW) policy. GSA policy defines parameters for the
Security Association for of the group. Depending on the employed
security protocol protocol, GSA policies may further be classified as Rekey SA
policy (GSA KEK) and Data-Security SA policy (GSA TEK). GSA payload
may contain zero or one GSA KEK policy, zero or more GSA TEK
policies, and zero or one GW policy, where either one GSA KEK or one
GSA TEK policy MUST be present.
This latitude allows various group policies to be accommodated. For
example
example, if the group policy does not require the use of a Rekey SA,
the GCKS would not need to send a GSA KEK policy to the group member
since all SA updates would be performed using the GSA_INBAND_REKEY
exchange via the unicast IKE SA. Alternatively, group policy might
use a Rekey SA but choose to download a KEK to the group member only
as part of the unicast IKE SA. Therefore, the GSA KEK policy would
not be necessary as part of the GSA_REKEY message.
Specifying multiple GSA TEKs allows multiple related data streams
(e.g., video, audio, and text) to be associated with a session, but
each are protected with an individual security association policy.
A GW policy allows for the distribution of group-wide policy, such as
instructions for when to activate and de-activate deactivate SAs.
Policies are distributed in substructures to the GSA payload. The
format of the substructures is defined below in Section 4.4.2 (for GSA
policy) and in Section 4.4.3 (for GW policy). The first octet of the
substructure unambiguously determines its type -- type; it is zero for GW
policy and non-zero (actually, it is a security protocol Protocol ID) for GSA
policies.
4.4.2. Group Security Association Policy Substructure
The GSA policy substructure contains parameters for the SA that are
used with this group. Depending on the security protocol protocol, the SA is
either a Rekey SA or a Data-Security SA (ESP and AH). The GCKS MUST
NOT distribute both ESP and AH policies for the same set of Traffic
Selectors.
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Protocol | SPI Size | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
~ SPI ~
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
~ Source Traffic Selector ~
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
~ Destination Traffic Selector ~
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
~ <GSA Transforms> ~
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
~ <GSA Attributes> ~
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 15: 17: GSA Policy Substructure Format
The GSA policy fields are defined as follows:
*
Protocol (1 octet) -- octet):
Identifies the security protocol for this group SA. The values
are defined in the IKEv2 "IKEv2 Security Protocol
Identifiers Identifiers" registry
in [IKEV2-IANA]. The valid values for this field are:
<TBA> are 6
(GIKE_UPDATE) for Rekey SA and 2 (AH) or 3 (ESP) for Data-
Security Data-Security
SAs.
*
SPI Size (1 octet) -- octet):
Size of Security Parameter Index (SPI) the SPI for the SA. SPI size depends on the SA protocol. For GIKE_UPDATE it
It is 16 octets, while octets for AH GIKE_UPDATE and ESP it is 4 octets.
* octets for AH and ESP.
Length (2 octets, unsigned integer) -- integer):
Length of this substructure including the header.
*
SPI (variable) -- (variable):
Security Parameter Index for the group SA. The size of this field
is determined by the SPI Size field. As described above, these
SPIs are assigned by the GCKS. In the case of
GIKE_UPDATE GIKE_UPDATE, the
SPI is the IKEv2 Header SPI pair where the first 8 octets become
the "IKE SA Initiator's SPI" field in the G-IKEv2 rekey message
IKEv2 HDR, and the second 8 octets become the "IKE SA Responder's
SPI" in the same HDR.
*
Source & Destination Traffic Selectors (variable) -- (variable):
Substructures describing the source and destination of the network
identities. The format for these substructures is defined in
IKEv2 [RFC7296],
Section 3.13.1. (Section 3.13.1 of [RFC7296]).
For the Rekey SA (with the GIKE_UPDATE protocol) protocol), the destination
traffic selectors MUST define a single multicast IP address, an IP
protocol (assumed to be UDP) UDP), and a single port the GSA_REKEY
messages will be destined to. The In this case, the source traffic
selector in this
case SHOULD define a single IP address, an IP protocol
(assumed to be UDP) UDP), and a single port the GSA_REKEY messages will
be originated from. The source traffic selector MAY define a
wildcard IP address and/or wildcard port. For the Data-Security
(AH and ESP) SAs SAs, the destination traffic selectors will usually
define a single multicast IP address. The source traffic selector
in this case will usually define a single IP address or be a
wildcard selector. An IP protocol and ports define the
characteristics of traffic protected by this Data-Security SA.
If the Data-Security SAs are created in tunnel mode, then it MUST
be tunnel mode with address preservation (see Multicast Extensions
to the Security Architecture [RFC5374]. UDP encapsulation of ESP
packets [RFC3948] cannot be specified in G-IKEv2 and thus it is not
used for the multicast Data-Security SAs.
*
GSA Transforms (variable) -- (variable):
A list of Transform Substructures specifies the policy information
for the SA. The format is defined in IKEv2 [RFC7296], section 3.3.2. (Section 3.3.2 of
[RFC7296]). The "Last Substruc" field in each Transform
Substructure is set to 3 except for the last Transform
Substructure, where it is set to 0. Section 4.4.2.1 describes
using IKEv2 transforms in GSA policy substructure.
*
GSA Attributes (variable) -- (variable):
Contains policy attributes associated with the group SA. The
following sections describe the possible attributes. Any or all
attributes may be optional, depending on the protocol and the
group policy. Section 4.4.2.2 defines attributes used in GSA
policy substructure.
4.4.2.1. GSA Transforms
GSA policy is defined by the means of transforms in the GSA policy
substructure. For this purpose purpose, the transforms defined in [RFC7296]
are used. In addition, new transform types are defined for using use in
G-IKEv2: Group Controller Authentication Method (GCAUTH) and Key Wrap
Algorithm (KWA), (KWA); see Section 9.
Valid transform types depend on the SA protocol and are summarized in
the table below. Exactly one instance of each mandatory transform
type and at most one instance of each optional transform type MUST be
present in the GSA policy substructure.
+=============+=============================+================+
| Protocol | Mandatory Types | Optional Types
---------------------------------------------------------------- |
+=============+=============================+================+
| GIKE_UPDATE | ENCR, INTEG*, GCAUTH**, KWA | |
+-------------+-----------------------------+----------------+
| ESP | ENCR, SN | INTEG |
+-------------+-----------------------------+----------------+
| AH | INTEG, SN
Figure 16: | |
+-------------+-----------------------------+----------------+
Table 2: Valid Transform Types
(*)
Notes:
(*): If the AEAD encryption algorithm is used, then INTEG transform
either MUST NOT be specified or MUST contain value NONE; otherwise
otherwise, it MUST be specified and MUST contain a value other
than NONE.
(**)
(**): May only appear at the time of a GM registration, registration (in the
GSA_AUTH and GSA_REGISTRATION exchanges).
4.4.2.1.1. Group Controller Authentication Method Transform
The Group Controller Authentication Method (GCAUTH) transform is used
to convey information of on how the GCKS will authenticate the GSA_REKEY
messages.
This document creates a new IKEv2 IANA registry for transform IDs for of
this transform type, which is has been initially filled populated as described
in Section 9. In particular, the following entries are initially added. have been added:
+========================================+=======+
| Group Controller Authentication Method | Value
------------------------------------------------- |
+========================================+=======+
| Reserved | 0 |
+----------------------------------------+-------+
| Implicit | 1 |
+----------------------------------------+-------+
| Digital Signature | 2 |
+----------------------------------------+-------+
Table 3
These transform IDs are defined as follows.
* Implicit -- means that no follows:
Implicit:
No authentication of the GSA_REKEY messages will be provided by
the GCKS besides the ability for the GMs to correctly decrypt them
and verify their ICV. In this case case, the GCKS MUST NOT include the
AUTH_KEY attribute into the KD payload. Additionally, the AUTH
payload MUST NOT be included in the GIKE_UPDATE messages.
*
Digital Signature -- means that digital
Digital signatures will be used by the GCKS to authenticate the
GSA_REKEY messages. In this case case, the GCKS MUST include the
AUTH_KEY attribute containing the public key into the KD payload
at the time the GM is registered to the group. To specify the
details of the signature algorithm algorithm, a new attribute Signature
Algorithm Identifier (<TBA by IANA>) (value 18) is defined. This attribute
contains DER-encoded ASN.1 object AlgorithmIdentifier, which
specifies the signature algorithm and the hash function that the
GCKS will use for authentication. The AlgorithmIdentifier object
is defined in Section 4.1.1.2 of Internet X.509 Public Key
Infrastructure Certificate and CRL Profile [RFC5280], [RFC5280]. Also, see also
Signature Authentication in IKEv2 [RFC7427]
for the list of common AlgorithmIdentifier values used in IKEv2.
In the case of the Digital Signature transform ID, the GCKS MUST
include the Signature Algorithm Identifier attribute in the Group
Controller Authentication Method transform. In this case case, the
AUTH payload in the GIKE_UPDATE messages MUST contain the Digital
Signature authentication method (value 14) and is be formatted as
defined in Section 3 of [RFC7427]. The AlgorithmIdentifier ASN.1
object in the AUTH payload MUST match the content of the Signature
Algorithm Identifier attribute in the Group Controller
Authentication Method transform. The Signature Algorithm
Identifier attribute is only meaningful for the Digital Signature
transform ID and MUST NOT be used with other transform IDs.
More authentication methods may be defined in the future.
The authentication method MUST NOT change as a result of rekey
operations. This means that the Group Controller Authentication
Method transform MUST NOT appear in the rekey messages, messages; it may only
appear in the registration exchange (either GSA_AUTH or
GSA_REGISTRATION).
The type of the Group Controller Authentication Method Transform transform is
<TBA by IANA>.
14.
4.4.2.1.2. Key Wrap Algorithm Transform
The Key Wrap Algorithm (KWA) transform is used to convey information
about an algorithm, algorithm that is used for key wrapping in G-IKEv2. See
Section 4.5.4 for details.
This document creates a new IKEv2 IANA registry for the key wrap
algorithms
algorithms, which is has been initially filled populated as described in
Section 9. In particular, the following entries are initially added. have been added:
+====================+=======+
| Key Wrap Algorithm | Value
------------------------------------- |
+====================+=======+
| Reserved | 0 |
+--------------------+-------+
| KW_5649_128 | 1 |
+--------------------+-------+
| KW_5649_192 | 2 |
+--------------------+-------+
| KW_5649_256 | 3 |
+--------------------+-------+
| KW_ARX | 4 |
+--------------------+-------+
Table 4
These algorithms are defined as follows.
* follows:
KW_5649_128, KW_5649_192, KW_5649_256 -- Key KW_5649_256:
The key wrap algorithm defined in [RFC5649] with a 128-bit, 192-bit
192-bit, and 256-bit key key, respectively. This key wrap algorithm
is designed for use with AES block cipher.
* KW_ARX --
KW_ARX:
The ARX-KW-8-2-4-GX key wrap algorithm defined in [ARX-KW]. This
key wrap algorithm is designed for use with Chacha20 stream
cipher.
More key wrap algorithms may be defined in the future. The
requirement is that these algorithms MUST be able to wrap key
material of size up to 256 bytes.
The type of the Key Wrap Algorithm transform is <TBA by IANA>. 13.
4.4.2.1.3. Sequence Numbers Transform
The "Sequence Sequence Numbers (SN)" (SNs) transform type is defined in
[I-D.ietf-ipsecme-ikev2-rename-esn]. [RFC9827].
This transform describes the properties of sequence numbers of IPsec
packets. There are currently two transform IDs defined for this
transform type: "32-bit Sequential Numbers" and "Partially
Transmitted 64-bit Sequential Numbers" that correspond to non-ESN and
ESN cases from AH [RFC4302] and ESP [RFC4303] specifications.
Transform ID "32-bit Sequential Numbers" SHOULD be used by the GCKS
for single-sender multicast Data-Security SAs utilizing protocols ESP
or AH.
Since both AH [RFC4302] and ESP [RFC4303] are defined in such a way, way
that high-order 32 bits of extended sequence numbers are never
transmitted, it makes using ESN in multicast Data-Security SAs
problematic,
problematic because GMs that join the group long after it is created
will have to somehow learn the current high order high-order 32 bits of ESN for
each sender in the group. The algorithm for doing this described in
AH [RFC4302] and ESP [RFC4303] is resource-consuming and is only
suitable when a receiver is able to guess the high-order 32 bits
close enough to its real value, which is not the case for multicast
SAs. For this reason reason, the "Partially Transmitted 64-bit Sequential
Numbers" transform ID MUST NOT be used for multicast Data-Security
SAs utilizing protocols ESP or AH.
This document defines a new transform ID "32-bit Unspecified Numbers"
(<TBA by IANA>) for this transform type. type:
32-bit Unspecified Numbers (2). This transform ID defines the
following properties. Sequence numbers are 32-bit 32 bits in size and are
transmitted in the Sequence Number field of AH and ESP packets. The
value of sequence numbers is not guaranteed to be unique for the
duration of an SA, thus they are not suitable for replay protection.
This transform ID MUST be used by the GCKS in case of multi-sender
multicast Data-Security SAs utilizing protocols ESP or AH to inform
the GMs that the replay protection is not expected to be possible.
The GCKS MAY also use this transform ID for single-sender multicast
Data-Security SAs if replay protection is not needed (e.g. (e.g., it is
done on the application level).
4.4.2.2. GSA Attributes
GSA attributes are generally used to provide GMs with additional
parameters for the GSA policy. Unlike security parameters
distributed via transforms, which are expected not to change over
time (unless the policy changes), the parameters distributed via GSA
attributes may depend on the time the provision takes place, on the
existence of others group SAs SAs, or on other conditions.
This document creates a new IKEv2 IANA registry for the types of the GSA attributes
attributes, which is has been initially filled populated as described in
Section 9. In particular, the following attributes are initially added. have been added:
+========================+=====+======+============+==============+
| GSA Attributes Value Format Multi-Valued |Value|Format|Multi-Valued| Used in |
| | | | | Protocol
--------------------------------------------------------------------- |
+========================+=====+======+============+==============+
| Reserved 0 |0 |
+------------------------+-----+------+------------+--------------+
| GSA_KEY_LIFETIME 1 TLV NO |1 |TLV |NO | GIKE_UPDATE, |
| | | | | AH, ESP |
+------------------------+-----+------+------------+--------------+
| GSA_INITIAL_MESSAGE_ID 2 TLV NO |2 |TLV |NO | GIKE_UPDATE |
+------------------------+-----+------+------------+--------------+
| GSA_NEXT_SPI 3 TLV YES |3 |TLV |YES | GIKE_UPDATE, |
| | | | | AH, ESP |
+------------------------+-----+------+------------+--------------+
Table 5
The attributes follow the format defined in the IKEv2 [RFC7296]
section 3.3.5. (Section 3.3.5 of
[RFC7296]). The "Format" column defines what attribute format is
allowed: Type/Length/Value (TLV) or Type/Value (TV). The "Multi-
Valued" column defines whether multiple instances of the attribute
can appear. The "Used in Protocol" column lists the security
protocols, for which the attribute can be used.
4.4.2.2.1. GSA_KEY_LIFETIME Attribute
The GSA_KEY_LIFETIME attribute (1) specifies the maximum time for
which the SA is valid. The value is a 4 octet 4-octet unsigned integer in a
network byte order, specifying a valid time period in seconds. When
the lifetime expires, the group security association GSA and all associated keys MUST be
deleted. The GCKS may delete the SA at any time before the end of
the validity period.
A single attribute of this type MUST be included into any GSA policy
substructure if multicast rekey is employed by the GCKS. This
attribute SHOULD NOT be used if inband rekey (via the
GSA_INBAND_REKEY exchange) is employed by the GCKS for the GM.
4.4.2.2.2. GSA_INITIAL_MESSAGE_ID Attribute
The GSA_INITIAL_MESSAGE_ID attribute (2) defines the initial Message
ID to be used by the GCKS in the GSA_REKEY messages. The Message ID
is a 4 octet 4-octet unsigned integer in network byte order.
A single attribute of this type is included into the GSA KEK policy
substructure if the initial Message ID of the Rekey SA is non-zero.
Note,
Note that it is always the case if GMs join the group after some
multicast rekey operations have already taken place, so in these
cases
cases, this attribute will be included into the GSA policy when the
GM is registered.
This attribute MUST NOT be used if inband rekey (via the
GSA_INBAND_REKEY exchange) is employed by the GCKS for the GM.
4.4.2.2.3. GSA_NEXT_SPI Attribute
The optional GSA_NEXT_SPI attribute (3) contains the SPI that the
GCKS reserved for the next Rekey SA or Data-Security SAs replacing
the current ones. The length of the attribute data is determined by
the SPI Size field in the GSA Policy policy substructure the attribute
resides in (see Section 4.4.2), and the attribute data contains the
SPI as it would appear on the network. Multiple attributes of this
type MAY be included, meaning that any of the supplied SPIs can be
used in the replacement group SA.
The GM MAY store these values and values. Later on, if later the GM starts receiving
messages with one of these SPIs without seeing a rekey message over
the current Rekey SA, this then it may be used as an indication, indication that the
rekey message got lost on its way to this GM. In this case case, the GM
SHOULD re-register to the group.
Note,
Note that this method of detecting lost rekey messages can only be
used by group receivers. Additionally Additionally, there is no point to include
this attribute in the GSA_INBAND_REKEY messages, messages since they use
reliable transport. Note also, Also note that the GCKS is free to forget its
promises and not to use the SPIs it sent in the GSA_NEXT_SPI
attributes before (e.g. (e.g., in case of cases where the GCKS is rebooted), so the
GM must only treat these this information as a "best effort" made by the
GCKS to prepare for future rekeys.
This attribute MUST NOT be used if inband rekey (via the
GSA_INBAND_REKEY exchange) is employed by the GCKS for the GM.
4.4.3. Group-wide Group-Wide Policy Substructure
Group specific
Group-specific policy that does not belong to any SA policy can be
distributed to all group member members using the Group-wide (GW) policy
substructure.
The GW policy substructure 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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Protocol | RESERVED | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
~ <GW Policy Attributes> ~
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 17: 18: GW Policy Substructure Format
The GW policy substructure fields are defined as follows:
*
Protocol (1 octet) -- octet): MUST be zero. This value is reserved in (see
Section 9 9) and is never used for any security protocol, so it is
used here to indicate that this substructure contains policy not
related to any specific protocol.
*
RESERVED ( octet) -- octet): MUST be zero on transmission, transmission and MUST be ignored
on receipt.
*
Length (2 octets, unsigned integer) -- integer): Length of this substructure
including the header.
*
GW Policy Attributes (variable) -- (variable): Contains policy attributes
associated with no specific SA. The following sections describe
possible attributes. Any or all attributes may be optional, optional
depending on the group policy.
4.4.3.1. GW Policy Attributes
This document creates a new IKEv2 IANA registry for the types of the
group-wide policy attributes attributes, which is has been initially filled populated as
described in Section 9. In particular, the following attributes are initially
added. have
been added:
+======================+=======+========+==============+
| GW Policy Attributes | Value | Format | Multi-Valued
-------------------------------------------------------- |
+======================+=======+========+==============+
| Reserved | 0 |
+----------------------+-------+--------+--------------+
| GWP_ATD | 1 | TV | NO |
+----------------------+-------+--------+--------------+
| GWP_DTD | 2 | TV | NO |
+----------------------+-------+--------+--------------+
| GWP_SENDER_ID_BITS | 3 | TV | NO |
+----------------------+-------+--------+--------------+
Table 6
The attributes follow the format defined in the IKEv2 [RFC7296]
section 3.3.5. (Section 3.3.5
of [RFC7296]). The "Format" column defines what attribute format is
allowed: Type/Length/Value (TLV) or Type/Value (TV). The "Multi-
Valued" column defines whether multiple instances of the attribute
can appear.
4.4.3.1.1. GWP_ATD And and GWP_DTD Attributes
Section 4.2.1 of Multicast Extensions to the Security Architecture [RFC5374] specifies a key rollover method that
requires two values be provided to group members -- members: Activation Time
Delay (ATD) and Deactivation Time Delay (DTD).
The GWP_ATD attribute (1) allows a GCKS to set the Activation Time
Delay for Data-Security SAs of the group. The ATD defines how long
active members of the group (those who sends traffic) should wait
after receiving new SAs before staring sending traffic over them.
Note, Note that
to achieve smooth rollover rollover, passive members of the group should
activate the SAs immediately once they receive them.
The GWP_DTD attribute (2) allows the GCKS to set the Deactivation
Time Delay DTD for
previously distributed SAs. The DTD defines how long after receiving
a request to delete Data-Security SAs passive group members should
wait before actually deleting them. Note that active members of the
group should stop sending traffic over these old SAs once new
replacement SAs are activated (after time specified in the GWP_ATD
attribute).
The GWP_ATD and GWP_DTD attributes contain 16 bit a 16-bit unsigned integer
in
a network byte order, specifying the delay in seconds. These
attributes are OPTIONAL. If one of them or both are not sent by the
GCKS, then no corresponding delay should be employed.
4.4.3.1.2. GWP_SENDER_ID_BITS Attribute
The GWP_SENDER_ID_BITS attribute (3) declares how many bits of the
cipher nonce are taken to represent a Sender-ID value. The bits are
applied as the most significant bits of the IV, as shown in Figure 1
of Using Counter Modes with ESP and AH to Protect Group Traffic
[RFC6054] and as specified in Section 2.5.2. Guidance for a GCKS
choosing the value is provided in Section 3 of Using Counter Modes
with ESP and AH to Protect Group Traffic [RFC6054]. This value
is applied to each Sender-ID value distributed in the KD payload.
The GCKS MUST include this attribute if there are more than one
sender
senders in the group and any of the Data-Security SAs use counter-
based cipher mode. The number of Sender-ID bits is represented as 16
bit a
16-bit unsigned integer in network byte order.
4.5. Key Download Payload
The Key Download (KD) payload contains the group keys for the SAs
specified in the GSA Payload. payload. The Payload Type for the Key Download
payload is fifty-two (52).
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 | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
~ <Key Bags> ~
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 18: 19: Key Download Payload Format
The Key Download payload fields are defined as follows:
*
Next Payload, C, RESERVED, Payload and Length fields comprise fields:
Comprise the IKEv2 Generic Payload Header and are defined in
Section 3.2. 3.2 of [RFC7296].
*
Key Bags (variable) -- (variable):
A set of Key Bag substructures.
4.5.1. Key Bags
Keys are distributed in a substructures called key bags. Each key bag
contains one or more keys that are logically related -- either these are
keys for either a single SA (Data-Security SA or Rekey SA) or
these are keys for a
single group member (in the latter case case, besides
keys keys, the key bag
may also contain security parameters for this group member).
For this reason reason, two types of key bags are defined -- defined: Group Key Bag and
Member Key Bag. The type is unambiguously determined by the first
byte of the key bag substructure -- for member key bag substructure. For a Member Key Bag, it is zero zero,
and for group key bag Group Key Bag, it represents the protocol number, which along
with the following SPI, identify the SA associated with the keys in
the bag.
4.5.2. Group Key Bag Substructure
The Group Key Bag substructure contains SA key information. This key
information is associated with some group SAs: either with Data-
Security SAs or with a group Rekey SA.
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Protocol | SPI Size | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
~ SPI ~
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
~ <Group Key Bag Attributes> ~
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 19: 20: Group Key Bag Substructure Format
*
Protocol (1 octet) -- octet):
Identifies the security protocol for this key bag. The values are
defined in the IKEv2 "IKEv2 Security Protocol
Identifiers Identifiers" registry in
[IKEV2-IANA]. The valid values for this field are:
<TBA> 6
(GIKE_UPDATE) for KEK Key packet and 2 (AH) or 3 (ESP) for TEK key
bag.
*
SPI Size (1 octet) -- octet):
Size of Security Parameter Index (SPI) the SPI for the corresponding SA. SPI size depends on the
security protocol.
For GIKE_UPDATE it It is 16 octets, while octets for AH GIKE_UPDATE and ESP it is 4
octets.
* octets
for AH and ESP.
Length (2 octets, unsigned integer) -- integer):
Length of this substructure including the header.
*
SPI (variable) -- (variable):
Security Parameter Index for the corresponding SA. The size of
this field is determined by the SPI Size field. In the case of GIKE_UPDATE
GIKE_UPDATE, the SPI is the IKEv2 Header SPI pair where the first
8 octets become the "IKE SA Initiator's SPI" field in the G-IKEv2
rekey message IKEv2 HDR, and the second 8 octets become the "IKE
SA Responder's SPI" in the same HDR.
*
Group Key Bag Attributes (variable) -- (variable):
Contains Key information for the corresponding SA.
This document creates a new IKEv2 IANA registry for the types of the
Group Key Bag attributes attributes, which is has been initially filled populated as
described in Section 9. In particular, the following attributes are initially
added. have
been added:
+===============+=======+========+==============+=============+
| Group Key Bag
Attributes | Value | Format | Multi-Valued | Used in |
| Attributes | | | | Protocol
-------------------------------------------------------------------- |
+===============+=======+========+==============+=============+
| Reserved | 0 |
+---------------+-------+--------+--------------+-------------+
| SA_KEY | 1 | TLV | YES* | GIKE_UPDATE |
| | | | NO | AH, ESP
(*) |
+---------------+-------+--------+--------------+-------------+
Table 7
Notes:
(*): Multiple SA_KEY attributes may only appear for the GIKE_UPDATE
protocol in the GSA_REKEY exchange if the GCKS uses the group key
management method that allows excluding GMs from the group (like
LKH).
The attributes follow the format defined in the IKEv2 [RFC7296]
section 3.3.5. (Section 3.3.5 of
[RFC7296]). The "Format" column defines what attribute format is
allowed: Type/Length/Value (TLV) or Type/Value (TV). The "Multi-
Valued" column defines whether multiple instances of the attribute
can appear. The "Used in Protocol" column lists the security
protocols, for which the attribute can be used.
4.5.2.1. SA_KEY Attribute
The SA_KEY attribute (1) contains a keying material for the
corresponding SA. The content of the attribute is formatted
according to Section 4.5.4 with a precondition that the Key ID field
MUST always be zero. The size of the keying material MUST be equal
to the total size of the keys needed to be taken from this keying
material (see Section 3.4) for the corresponding SA.
If the key bag is for a Data-Security SA (AH or ESP protocols), then
exactly one SA_KEY attribute MUST be present with both Key ID and KWK
ID fields set to zero.
If the key bag is for a Rekey SA (GIKE_UPDATE protocol), then in the
GSA_AUTH, GSA_REGISTRATION and GSA_INBAND_REKEY exchanges exactly
one SA_KEY attribute MUST be present. present in the GSA_AUTH,
GSA_REGISTRATION, and GSA_INBAND_REKEY exchanges. In the GSA_REKEY exchange
exchange, at least one SA_KEY attribute MUST be present, and more
attributes MAY be present (depending on the key management method
employed by the GCKS).
4.5.3. Member Key Bag Substructure
The Member Key Bag substructure contains keys and other parameters
that are specific for a member of the group and are not associated
with any particular group SA.
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Protocol | RESERVED | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
~ <Member Key Bag Attributes> ~
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 20: 21: Member Key Bag Substructure Format
The Member Key Bag substructure fields are defined as follows:
*
Protocol (1 octet) -- octet):
MUST be zero. This value is reserved in (see Section 9 9) and is never
used for any security protocol, so it is used here to indicate
that this key bag is not associated with any particular SA.
*
RESERVED ( octet) -- octet):
MUST be zero on transmission, transmission and MUST be ignored on receipt.
*
Length (2 octets, unsigned integer) -- integer):
Length of this substructure including the header.
*
Member Key Bag Attributes (variable) -- (variable):
Contains Key information and other parameters exclusively for a
particular member of the group.
The member Member Key Bag substructure contains sensitive information for a
single GM, for GM. For this reason reason, it MUST NOT be sent in GSA_REKEY
messages and MUST only be sent via unicast SA at the time the GM
registers to the group (in either GSA_AUTH or GSA_REGISTRATION
exchanges).
This document creates a new IKEv2 IANA registry for the types of the
Member Key Bag attributes attributes, which is has been initially filled populated as
described in Section 9. In particular, the following attributes are initially
added. have
been added:
+===========================+=======+========+==============+
| Member Key Bag Attributes | Value | Format | Multi-Valued
---------------------------------------------------- |
+===========================+=======+========+==============+
| Reserved | 0 |
+---------------------------+-------+--------+--------------+
| WRAP_KEY | 1 | TLV | YES |
+---------------------------+-------+--------+--------------+
| AUTH_KEY | 2 | TLV | NO |
+---------------------------+-------+--------+--------------+
| GM_SENDER_ID | 3 | TLV | YES |
+---------------------------+-------+--------+--------------+
Table 8
The attributes follow the format defined in the IKEv2 [RFC7296]
section 3.3.5. (Section 3.3.5
of [RFC7296]). The "Format" column defines what attribute format is
allowed: Type/Length/Value (TLV) or Type/Value (TV). The "Multi-
Valued" column defines whether multiple instances of the attribute
can appear.
4.5.3.1. WRAP_KEY Attribute
The WRAP_KEY attribute (1) contains a key that is used to encrypt
other keys. One or more of these attributes are sent to GMs if the
GCKS key management method relies on some key hierarchy (e.g. (e.g., LKH).
This attribute MUST NOT be used if inband rekey (via the
GSA_INBAND_REKEY exchange) is employed by the GCKS for the GM.
The content of the attribute has a format defined in Section 4.5.4
with a precondition that the Key ID field MUST NOT be zero. The
algorithm associated with the key is defined by the Key Wrap
Algorithm transform for the SA the WRAP_KEY attributes was sent in.
The size of the attribute data MUST be equal to the key size for this
key wrap algorithm.
Multiple instances of the WRAP_KEY attributes MAY be present in the
key bag.
4.5.3.2. AUTH_KEY Attribute
The AUTH_KEY attribute (2) contains the key that is used to
authenticate the GSA_REKEY messages. The content of the attribute
depends on the authentication method the GCKS specified in the Group
Controller Authentication Method transform in the GSA payload.
* If digital signatures are used for the GSA_REKEY message
authentication
authentication, then the content of the AUTH_KEY attribute is a
public key used for digital signature authentication. The public
key MUST be represented as DER-encoded ASN.1 object
SubjectPublicKeyInfo, defined in Section 4.1.2.7 of Internet X.509
Public Key Infrastructure Certificate and CRL Profile [RFC5280].
The algorithm field inside the SubjectPublicKeyInfo object MUST
match the content of the Signature Algorithm Identifier attribute
in the Group Controller Authentication Method transform. When the
id-RSASSA-PSS object identifier appears in the algorithm field of
the SubjectPublicKeyInfo object, then the parameters field MUST
include the RSASSA-PSS-params structure.
Multiple instances of the AUTH_KEY attributes MUST NOT be sent.
4.5.3.3. GM_SENDER_ID Attribute
The GM_SENDER_ID attribute (3) is used to download one or more
Sender-ID values for the exclusive use of a group member. One or
more of this these attributes MUST be sent by the GCKS if the GM informed
the GCKS that it would be a sender (by including the GROUP_SENDER
notification to the request) and if at least one of the Data-Security
SAs included in the GSA payload uses a counter-based mode of
encryption.
If the GMs has have requested multiple Sender-ID values in the
GROUP_SENDER notification, then the GCKS SHOULD provide it with the
requested number of Sender-IDs by sending multiple instances of the
GM_SENDER_ID attribute. The GCKS MAY send fewer values than
requested by the GM (e.g. (e.g., if it is running out of Sender-IDs), but
it MUST NOT send more than requested.
This attribute MUST NOT appear in the rekey operations (in the
GSA_REKEY or GSA_INBAND_REKEY exchanges).
4.5.4. Key Wrapping
Symmetric keys in G-IKEv2 are never sent in clear inside G-IKEv2
messages. They are always protected with other symmetric keys. This
protection is called key wrapping. Algorithms used for key wrapping
are usually based on generic encryption algorithms, but their mode of
operation is optimized for protecting short high-entropy data with
minimal additional overhead. While in general key wrap algorithms can be generic,
generic in practice general, they are often tied to the underlying encryption algorithms.
algorithms in practice. For example, AES Key Wrap with Padding
Algorithm [RFC5649] defines key wrapping using AES, and Key Wrapping
Constructions using SipHash and ChaCha [ARX-KW] defines define key wrapping
using Chacha20.
In G-IKEv2 G-IKEv2, the key wrap algorithm MUST be negotiated in the
IKE_SA_INIT exchange, exchange so that the GCKS be is able to send encrypted keys
to the GM in the GSA_AUTH exchange. In addition, if the GCKS plans
to use the multicast Rekey SA for group rekey, then it MUST specify
the key wrap algorithm in the GSA payload. Note that key wrap
algorithms for these cases MAY be different - for different. For the unicast SA SA, the
key wrap algorithms algorithm is negotiated between the GM and the GCKS, while
for the multicast Rekey SA SA, the key wrap algorithm is provided by the
GCKS to the group members as part of the group policy. If an SAg
payload is included in the GSA_AUTH request, then it MUST indicate
which key wrap algorithms are supported by the GM. In all these
cases
cases, the key wrap algorithm is specified in a Key Wrap Algorithm
transform (see Section 4.4.2.1.2. 4.4.2.1.2).
The format of the wrapped key is shown in Figure 21. 22.
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Key ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| KWK ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
~ Encrypted Key ~
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 21: 22: Wrapped Key Format
The Wrapped Key fields are defined as follows:
*
Key ID (4 octets) -- octets):
ID of the encrypted key. The value zero means that the encrypted
key contains SA keys (in the form of keying material, material; see
Section 3.4)), otherwise 3.4). Otherwise, it contains some intermediate key.
*
KWK ID (4 octets) -- octets):
ID of the key that was used to encrypt the key with a specified
Key ID. The value zero means that the default KWK was used to
encrypt the key, otherwise key. Otherwise, some intermediate key was used.
*
Encrypted Key (variable) -- (variable):
The encrypted key bits. These bits comprise either a single
encrypted key or a result of encryption of a concatenation of keys
(key material) for several algorithms. The format of this fields field
is determined by the key wrap algorithm for the SA the wrapped key
is sent over.
4.6. Delete Payload
Delete payload is used in G-IKEv2 when the GCKS wants to delete Data-
Security and Rekey SAs. The interpretation of the Protocol field in
the Delete payload is extended, extended so that zero protocol indicates
deletion of whole Group SA (i.e. (i.e., all Data-Security SAs and the Rekey
SA). See Section 2.4.3 for detail.
4.7. Notify Payload
G-IKEv2 uses the same Notify payload as specified in [RFC7296],
section 3.10. Section 3.10 of
[RFC7296].
There are additional Notify Message types introduced by G-IKEv2 to
communicate error conditions and status (see Section 9).
4.7.1. INVALID_GROUP_ID Notification
INVALID_GROUP_ID (45) is a new error type notification that indicates
that the group ID sent during the registration process is invalid.
The Protocol ID and SPI Size fields in the Notify payload MUST be
zero. There is no data associated with this notification and the
content of the Notification Data field MUST be ignored on receipt.
4.7.2. AUTHORIZATION_FAILED Notification
AUTHORIZATION_FAILED (46) is a new error type notification that is
sent in the response to a GSA_AUTH or GSA_REGISTRATION message when
authorization failed. The Protocol ID and SPI Size fields in the
Notify payload MUST be zero. There is no data associated with this
notification and the content of the Notification Data field MUST be
ignored on receipt.
4.7.3. REGISTRATION_FAILED Notification
REGISTRATION_FAILED (<TBA>) (49) is a new error type notification that is
sent by the GCKS when the GM registration request cannot be satisfied
for the reasons not related to this particular GM, for example e.g., if the capacity
of the group is exceeded. The Protocol ID and SPI Size fields in the
Notify payload MUST be zero. There is no data associated with this
notification and the content of the Notification Data field MUST be
ignored on receipt.
4.7.4. GROUP_SENDER Notification
GROUP_SENDER (16429) is a new status type notification that is sent
in the GSA_AUTH or the GSA_REGISTRATION exchanges to indicate that
the GM intends to be sender of data traffic. The data includes a
count of how many Sender-ID values the GM desires. The count MUST be
4 octets long and contain the big endian big-endian representation of the number
of requested Sender-IDs. The Protocol ID and SPI Size fields in the
Notify payload MUST be zero.
4.8. Authentication Payload
G-IKEv2 uses the same Authentication payload as specified in
[RFC7296], section 3.8,
Section 3.8 of [RFC7296] to authenticate the rekey message. However,
if it is used in the GSA_REKEY messages messages, the content of the payload
is computed differently, differently as described in Section 2.4.1.1.
5. Using G-IKEv2 Attributes
G-IKEv2 defines a number of attributes, attributes that are used to convey
information from the GCKS to GMs. There are some restrictions on
where and when these attributes can appear in G-IKEv2 messages, which
are defined when the attributes are introduced. For convenience convenience,
these restrictions are summarized in Table 2 9 (for multicast rekey
operations) and Table 3 10 (for inband rekey operations) below.
The following notation is notations are used:
S A single attribute of this type MUST be present present.
M Multiple attributes of this type MAY be present present.
[] Attribute is OPTIONAL OPTIONAL.
- Attribute MUST NOT be present
Note, present.
Note that the restrictions are defined per a substructure
corresponding attributes are defined for and not per whole G-IKEv2
message.
+========================+==================+===========+=======+
| Attributes | GSA_AUTH | GSA_REKEY | Notes |
| | GSA_REGISTRATION | | |
+========================+==================+===========+=======+
| GSA Attributes (Section 4.4.2.2) |
+========================+==================+===========+=======+
| GSA_KEY_LIFETIME | S | S | |
+------------------------+------------------+-----------+-------+
| GSA_INITIAL_MESSAGE_ID | [S] | [S] | |
+------------------------+------------------+-----------+-------+
| GSA_NEXT_SPI | [M] | [M] | |
+========================+==================+===========+=======+
| GW Policy Attributes (Section 4.4.3.1) |
+========================+==================+===========+=======+
| GWP_ATD | [S] | [S] | |
+------------------------+------------------+-----------+-------+
| GWP_DTD | [S] | [S] | |
+------------------------+------------------+-----------+-------+
| GWP_SENDER_ID_BITS | S | - | 1 |
+========================+==================+===========+=======+
| Key Bag Attributes (Section 4.5.1) |
+========================+==================+===========+=======+
| SA_KEY | S | S[M] | 2 |
+------------------------+------------------+-----------+-------+
| WRAP_KEY | [M] | [M] | 3 |
+------------------------+------------------+-----------+-------+
| AUTH_KEY | S | [S] | 4 |
+------------------------+------------------+-----------+-------+
| GM_SENDER_ID | S[M] | - | 1 |
+------------------------+------------------+-----------+-------+
|
Table 9: Attributes in G-IKEv2 Exchanges with Multicast Rekey
Operations
Notes: |
| |
| (1)
(1): The GWP_SENDER_ID_BITS attribute MUST be present if the |
| GCKS
policy includes at least one cipher in counter |
| mode of
operation and if the GM included the GROUP_SENDER |
| notify into
the registration request. Otherwise Otherwise, it |
| MUST NOT be present.
At least one GM_SENDER_ID |
| attribute MUST be present in the
former case (and more |
| MAY be present if the GM requested more Sender-IDs)
Sender-IDs), and |
| it MUST NOT be present in the latter case. |
| |
| (2)
(2): For a Data-Security SA SA, exactly one SA_KEY attribute |
| MUST be
present. For a Rekey SA SA, one SA_KEY attribute |
| MUST be present
in all cases and more these attributes |
| MAY be present in a
GSA_REKEY exchange. |
| |
| (3)
(3): The WRAP_KEY attributes attribute MUST be present if the GCKS |
| employs a
key management method that relies on a key tree |
| (like LKH). |
| |
| (4)
(4): The AUTH_KEY attribute MUST be present in the GSA_AUTH |
| / and
GSA_REGISTRATION exchanges if the GCKS employs |
| an
authentication method of rekey operations based on |
| digital
signatures and MUST NOT be present if implicit |
| authentication
is employed. The AUTH_KEY attribute |
| MUST be present in the
GSA_REKEY exchange if the GCKS |
| employs an authentication method
based on digital |
| signatures and wants to change the public key
for the |
| following multicast rekey operations. |
+---------------------------------------------------------------+
Table 2: Attributes in G-IKEv2 exchanges with multicast rekey
operations
+========================+================+==================+=====+
| Attributes | GSA_AUTH |GSA_AUTH | GSA_INBAND_REKEY |Notes|
| |GSA_REGISTRATION| | |
+========================+================+==================+=====+
| GSA Attributes (Section 4.4.2.2) |
+========================+================+==================+=====+
| GSA_KEY_LIFETIME | [S] |[S] | [S] | |
+------------------------+----------------+------------------+-----+
| GSA_INITIAL_MESSAGE_ID | - |- | - | |
+------------------------+----------------+------------------+-----+
| GSA_NEXT_SPI | - |- | - | |
+========================+================+==================+=====+
| GW Policy Attributes (Section 4.4.3.1) |
+========================+================+==================+=====+
| GWP_ATD | [S] |[S] | [S] | |
+------------------------+----------------+------------------+-----+
| GWP_DTD | [S] |[S] | [S] | |
+------------------------+----------------+------------------+-----+
| GWP_SENDER_ID_BITS | S |S | - | 1 |1 |
+========================+================+==================+=====+
| Key Bag Attributes (Section 4.5.1) |
+========================+================+==================+=====+
| SA_KEY | S |S | S | |
+------------------------+----------------+------------------+-----+
| WRAP_KEY | - |- | - | |
+------------------------+----------------+------------------+-----+
| AUTH_KEY | - |- | - | |
+------------------------+----------------+------------------+-----+
| GM_SENDER_ID | S[M] |S[M] | - | 1 |1 |
+------------------------+----------------+------------------+-----+
|
Table 10: Attributes in G-IKEv2 Exchanges with Inband Rekey
Operations
Notes: |
| |
| (1)
(1): The GWP_SENDER_ID_BITS attribute MUST be present if the |
| GCKS
policy includes at least one cipher in counter mode |
| of
operation and the GM included the GROUP_SENDER notify |
| into the
registration request. Otherwise Otherwise, it MUST NOT be |
| present. At
least one GM_SENDER_ID attribute MUST be |
| present in the former
case (and more MAY be present if the |
| GM requested more Sender-IDs) Sender-
IDs), and it MUST NOT be present |
| in the latter case. |
+------------------------------------------------------------------+
Table 3: Attributes in G-IKEv2 exchanges with inband rekey
operations
6. Interaction with IKEv2 and ESP Extensions
A number of IKEv2 and ESP extensions is are defined that can be used to
extend protocol functionality. G-IKEv2 is compatible with most of
them. In particular, EAP authentication defined in [RFC7296] can be
used to establish registration IKE SA, as well as EAP-only
authentication [RFC5998] and Secure Password secure password authentication
[RFC6467]. G-IKEv2 is compatible with and can use IKEv2 Redirect
Mechanism [RFC5685] and IKEv2 Session Resumption [RFC5723]. G-IKEv2
is also compatible with Multiple Key Exchanges in the IKEv2
framework, as defined in [RFC9370].
The above list of compatible IKEv2 extensions is not exhaustive,
however exhaustive.
However, some IKEv2 extensions require special handling if used in
G-IKEv2.
6.1. Implicit IV for Counter-Based Ciphers in ESP
Using implicit IV for counter-based encryption modes in ESP is
defined in [RFC8750]. This extension relies on the uniqueness of ESP
sequence numbers. Thus, it cannot be used for multi-sender multicast
SAs. However, it is possible to use implicit IV extension for a
single-sender multicast ESP SA. Note, Note that while implicit IVs can be
used with ESN, using ESN is prohibited in multicast SAs (see
Section 4.4.2.1.3).
6.2. Mixing Preshared Keys in IKEv2 for Post-quantum Post-Quantum Security
G-IKEv2 can take advantage of the protection provided by Postquantum Post-quantum
Preshared Keys (PPK) (PPKs) for IKEv2 [RFC8784]. However, the use of PPK PPKs
leaves the initial IKE SA susceptible to quantum computer (QC)
attacks. Group SA keys are protected with the default KWK (GSK_w),
which is derived from SK_d and thus cannot be broken even by an
attacker equipped with a QC. However, other data sent over the
initial IKE SA may be susceptible to an attacker equipped with a QC
of a sufficient size. Such an attacker can store all the traffic
until it obtains such a QC and then decrypt it (Store (i.e., Store Now
Decrypt Later attack). See Section 6 of [RFC8784] for details.
While the group keys are protected with PPK and thus are immune to
QC, GCKS implementations that care about other data sent over initial
IKE SA MUST rely on IKEv2 extensions that protect even initial IKE SA
against QC (like [I-D.ietf-ipsecme-ikev2-qr-alt]). [IPSEC-IKEV2-QR-ALT]).
6.3. Aggregation and Fragmentation Mode for ESP
Aggregation and fragmentation mode for ESP is defined in [RFC9347].
This mode allows IP packets to be split over several ESP packets, packets or
several IP packets to be aggregated in a single ESP packet. This
mode can only be used with ESP tunnel mode and relies on
monotonically increasing sequence numbers in the incoming packets.
Thus, it is impossible to use this mode for multi-sender multicast
SAs. Since multicast Data-Security SAs are unidirectional, the
congestion control feature of aggregation and fragmentation mode
cannot be used.
It is possible to use the aggregation and fragmentation mode without
congestion control for a single-sender multicast ESP SA created in
tunnel mode. GMs supporting this mode can send the USE_AGGFRAG
notification in the registration request along with the SAg payload.
If the Data-Security SA(s) to be installed on GMs use uses the
aggregation and fragmentation mode, the GCKS would indicate it by
including the USE_AGGFRAG notification along with the GSA payload in
its response.
7. GDOI Protocol Extensions
Few extensions were defined for the GDOI protocol [RFC6407], like
GDOI Support for IEC 62351 Security Services [RFC8052] or the GDOI GROUPKEY-
PUSH
GROUPKEY-PUSH Acknowledgement Message [RFC8263]. It is expected that
these extensions will be redefined for G-IKEv2 in separate documents,
if needed.
8. Security Considerations
When an entity joins the group and becomes a group member, it has to
trust that the GCKS that only authorized entities that are admitted to the
group and has to trust that other group members that they will not leak the
information shared within the group.
8.1. GSA Registration and Secure Channel
G-IKEv2 registration exchange uses IKEv2 IKE_SA_INIT protocols,
inheriting all the security considerations documented in the Section 5 of
[RFC7296], including authentication, confidentiality, protection
against man-in-the-middle, man-in-the-middle attacks, protection against replay/
reflection attacks, and denial of service denial-of-service protection. The GSA_AUTH
and GSA_REGISTRATION exchanges also take advantage of those
protections. In addition, G-IKEv2 brings in the capability to
authorize a particular group member regardless of whether they have
the IKEv2 credentials.
8.2. GSA Maintenance Channel
The GSA maintenance channel is cryptographically and integrity
protected using the cryptographic algorithm and key negotiated in the
GSA member registration exchange.
8.2.1. Authentication/Authorization
The authentication key is distributed during the GM registration, registration and
the receiver of the rekey message uses that key to verify the message
came from the authorized GCKS. An implicit authentication can also
be used, in which case case, the ability of the GM to decrypt and to
verify ICV of the received message proved that a sender of the
message is a member of the group. However, implicit authentication
doesn't provide source origin authentication, so the GM cannot be
sure that the message came from the GCKS. For this reason reason, using
implicit authentication is NOT RECOMMENDED unless used with a small
group of trusted parties.
8.2.2. Confidentiality
Confidentiality is provided by distributing a confidentiality key as
part of the GSA member registration exchange.
8.2.3. Man-in-the-Middle Attack Protection
The GSA maintenance channel is integrity protected by using a digital
signature.
8.2.4. Replay/Reflection Attack Protection
The GSA_REKEY message includes a monotonically increasing sequence
number to protect against replay and reflection attacks. A group
member will recognize a replayed message by comparing the Message ID
number to that of the last received rekey message, any message. Any rekey message
containing a Message ID number less than or equal to the last
received value MUST be discarded. Implementations should keep a
record of recently received GSA rekey messages for this comparison.
The strict role separation between the GCKS and the GMs and, as a
consequence, the limitation for a Rekey SA to be outbound/inbound
only, helps to prevent reflection attack.
9. IANA Considerations
9.1. Note for Reviewers
**** RFC Editor, please DELETE this Section prior to publication!
****
While reviewing the document please note, that some of the
codepoints, that this draft claims to have allocated, in fact have
been allocated by its predecessor, draft-yeung-g-ikev2-07 in 2013, as
part of the early codepoint assignment. This documents makes use of
these already allocated codepoints, renames one of them and allocates
additional codepoints. Note also, that the semantics of the
codepoints allocated by draft-yeung-g-ikev2-07 is preserved,
including for the renamed one.
9.2. New Registries
A
Per this document, new set of registries is have been created for G-IKEv2 on IKEv2 parameters
page under
the "Internet Key Exchange Version 2 (IKEv2) Parameters" registry
group [IKEV2-IANA]. The terms Reserved, Expert Review Review, and Private
Use are to be applied as defined in [RFC8126].
1. This document creates a new IANA registry has created the "Transform Type <TBA>
-- 13 - Key Wrap Algorithm
Transform IDs". IDs" registry. Changes and additions to the unassigned
range of this registry are to be made through Expert Review
[RFC8126]. The initial values of the
new registry are: are as follows:
+==========================+============+
| Key Wrap Algorithm | Value
----------------------------- |
+==========================+============+
| Reserved | 0 |
+--------------------------+------------+
| KW_5649_128 | 1 |
+--------------------------+------------+
| KW_5649_192 | 2 |
+--------------------------+------------+
| KW_5649_256 | 3 |
+--------------------------+------------+
| KW_ARX | 4 |
+--------------------------+------------+
| Unassigned | 5-1023 |
+--------------------------+------------+
| Reserved for Private Use | 1024-65535 |
+--------------------------+------------+
Table 11
2. IANA has created the "Transform Type 14 - Group Controller
Authentication Method Transform IDs" registry. Changes and
additions to the unassigned range of this registry are by the to be made
through Expert Review Policy [RFC8126].
2. This document creates a new IANA registry "Transform Type <TBA>
-- Group Controller Authentication Method Transform IDs". The initial values of the new
registry are: are as follows:
+========================================+============+
| Group Controller Authentication Method | Value
------------------------------------------------- |
+========================================+============+
| Reserved | 0 |
+----------------------------------------+------------+
| Implicit | 1 |
+----------------------------------------+------------+
| Digital Signature | 2 |
+----------------------------------------+------------+
| Unassigned | 3-1023 |
+----------------------------------------+------------+
| Reserved for Private Use | 1024-65535 |
+----------------------------------------+------------+
Table 12
3. IANA has created the "GSA Attributes" registry. Changes and
additions to the unassigned range of this registry are by the to be made
through Expert Review Policy [RFC8126].
3. This document creates a new IANA registry "GSA Attributes". The initial values of the new
registry are:
GSA are as follows:
+======================+===========+======+======+============+
|GSA Attributes Value Format Multi-Valued Used |Value |Format|Multi-|Used in Protocol
---------------------------------------------------------------------
Reserved 0
GSA_KEY_LIFETIME 1 TLV NO GIKE_UPDATE, AH, |
| | | |Valued|Protocol |
+======================+===========+======+======+============+
|Reserved |0 | |
+----------------------+-----------+------+------+------------+
|GSA_KEY_LIFETIME |1 |TLV |NO |GIKE_UPDATE,|
| | | | |AH, ESP
GSA_INITIAL_MESSAGE_ID 2 TLV NO GIKE_UPDATE
GSA_NEXT_SPI 3 TLV YES GIKE_UPDATE, AH, |
+----------------------+-----------+------+------+------------+
|GSA_INITIAL_MESSAGE_ID|2 |TLV |NO |GIKE_UPDATE |
+----------------------+-----------+------+------+------------+
|GSA_NEXT_SPI |3 |TLV |YES |GIKE_UPDATE,|
| | | | |AH, ESP
Unassigned 5-16383 |
+----------------------+-----------+------+------+------------+
|Unassigned |5-16383 | |
+----------------------+-----------+--------------------------+
|Reserved for Private Use 16384-32767 |16384-32767| |
|Use | | |
+----------------------+-----------+--------------------------+
Table 13
4. IANA has created the "Group-wide Policy Attributes" registry.
Changes and additions to the unassigned range of this registry
are by the to be made through Expert Review Policy [RFC8126].
4. This document creates a new IANA registry "Group-wide Policy
Attributes". The initial
values of the new registry are: are as follows:
+======================+=============+========+==============+
| GW Policy Attributes | Value | Format | Multi-Valued
-------------------------------------------------------- |
+======================+=============+========+==============+
| Reserved | 0 | |
+----------------------+-------------+--------+--------------+
| GWP_ATD | 1 | TV | NO |
+----------------------+-------------+--------+--------------+
| GWP_DTD | 2 | TV | NO |
+----------------------+-------------+--------+--------------+
| GWP_SENDER_ID_BITS | 3 | TV | NO |
+----------------------+-------------+--------+--------------+
| Unassigned | 4-16383 | |
+----------------------+-------------+-----------------------+
| Reserved for Private Use | 16384-32767 | |
| Use | | |
+----------------------+-------------+-----------------------+
Table 14
5. IANA has created the "Group Key Bag Attributes" registry.
Changes and additions to the unassigned range of this registry
are by the to be made through Expert Review Policy [RFC8126].
5. This document creates a new IANA registry "Group Key Bag
Attributes". The initial
values of the new registry are: are as follows:
+=============+=============+======+==============+=============+
| Group Key Bag
Attributes | Value Format |Format| Multi-Valued | Used in |
| Bag | | | | Protocol
-------------------------------------------------------------------- |
| Attributes | | | | |
+=============+=============+======+==============+=============+
| Reserved | 0 | |
+-------------+-------------+------+--------------+-------------+
| SA_KEY | 1 TLV |TLV | YES | GIKE_UPDATE |
| | | | NO | AH, ESP |
+-------------+-------------+------+--------------+-------------+
| Unassigned | 2-16383 | |
+-------------+-------------+-----------------------------------+
| Reserved | 16384-32767 | |
| for | | |
| Private | | |
| Use 16384-32767 | | |
+-------------+-------------+-----------------------------------+
Table 15
6. IANA has created the "Member Key Bag Attributes" registry.
Changes and additions to the unassigned range of this registry
are by the to be made through Expert Review Policy [RFC8126].
6. This document creates a new IANA registry "Member Key Bag
Attributes". The initial
values of the new registry are: are as follows:
+================+=============+========+==============+
| Member Key Bag
Attributes | Value | Format | Multi-Valued
---------------------------------------------------- |
| Attributes | | | |
+================+=============+========+==============+
| Reserved | 0 | |
+----------------+-------------+--------+--------------+
| WRAP_KEY | 1 | TLV | YES |
+----------------+-------------+--------+--------------+
| AUTH_KEY | 2 | TLV | NO |
+----------------+-------------+--------+--------------+
| GM_SENDER_ID | 3 | TLV | YES |
+----------------+-------------+--------+--------------+
| Unassigned | 4-16383 | |
+----------------+-------------+-----------------------+
| Reserved for | 16384-32767 | |
| Private Use 16384-32767
Changes and additions to the unassigned range of this registry
are by the Expert Review Policy [RFC8126].
9.2.1. | | |
+----------------+-------------+-----------------------+
Table 16
9.1.1. Guidance for Designated Experts
In all cases of Expert Review Policy described here, in this section, the Designated
Expert
designated expert (DE) is expected to ascertain the existence of
suitable documentation (a specification) as described in [RFC8126]
and to verify that the document is permanently and publicly available.
The DE is also expected to check the clarity of purpose and use of
the requested code points. Last, Lastly, the DE must verify that any
specification produced outside the IETF does not conflict with work
that is active or already published within the IETF.
9.3.
9.2. Changes in the Existing IKEv2 Registries
1. This document defines new Exchange Types in In the "IKEv2 Exchange Types" registry: registry, IANA has updated the
references for the following entries to point to this document
and has registered "GSA_INBAND_REKEY":
+=======+==================+
| Value | Exchange Type
---------------------------- |
+=======+==================+
| 39 | GSA_AUTH |
+-------+------------------+
| 40 | GSA_REGISTRATION |
+-------+------------------+
| 41 | GSA_REKEY
<TBA> |
+-------+------------------+
| 42 | GSA_INBAND_REKEY |
+-------+------------------+
Table 17
2. This document defines new Payload Types in In the "IKEv2 Payload Types" registry: registry, IANA has listed this
document as a reference for the following entries:
+=======+============================+==========+
| Value | Next Payload Type | Notation
---------------------------------------------------- |
+=======+============================+==========+
| 50 | Group Identification | IDg |
+-------+----------------------------+----------+
| 51 | Group Security Association | GSA |
+-------+----------------------------+----------+
| 52 | Key Download | KD |
+-------+----------------------------+----------+
Table 18
3. This document also updates In the "IKEv2 Payload Types" registry, IANA has updated the
definition of Payload Type 33 in the
"IKEv2 Payload Types" registry by adding an alternative name and
notation for it referencing added a reference to this document:
document as follows:
+=======+=========================+==========+===========+
| Value | Next Payload Type | Notation
-------------------------------------------------------------------- | Reference |
+=======+=========================+==========+===========+
| 33 | Security Association | SA | [RFC7296] |
| +-------------------------+----------+-----------+
| | Security Association - | SAg | RFC 9838 |
| | GM Supported Transforms SAg | | |
+-------+-------------------------+----------+-----------+
Table 19
4. This document makes the following changes in In the "Transform Type Values" registry: registry, IANA has made the
following changes:
* Defines two new transform types -- Registered "Key Wrap Algorithm (KWA)" and "Group Controller
Authentication Method (GCAUTH)"; (GCAUTH)".
* Changes Updated the "Used In" column for the values 1 and 3 as
follows;
* Appends reference to and listed
this document to the values 1 and 3; as an additional reference.
+======+================================+======================+
| Type | Description | Used In
-------------------------------------------------------------------- |
+======+================================+======================+
| 1 | Encryption Algorithm (ENCR) | (IKE, GIKE_UPDATE and GIKE_UPDATE, |
| | | ESP) |
+------+--------------------------------+----------------------+
| 3 | Integrity Algorithm (INTEG) | (IKE, GIKE_UPDATE, |
| | | AH, optional in ESP)
<TBA> |
+------+--------------------------------+----------------------+
| 13 | Key Wrap Algorithm (KWA) | (IKE, GIKE_UPDATE)
<TBA> |
+------+--------------------------------+----------------------+
| 14 | Group Controller | (GIKE_UPDATE) |
| | Authentication Method (GCAUTH) (GIKE_UPDATE) | |
+------+--------------------------------+----------------------+
Table 20
5. This document defines a new Attribute Type in In the "IKEv2 Transform Attribute Types" registry: registry, IANA has added
the following entry:
+=======+================================+========+
| Value | Attribute Type | Format
------------------------------------------------------
<TBA> |
+=======+================================+========+
| 18 | Signature Algorithm Identifier | TLV |
+-------+--------------------------------+--------+
Table 21
6. This document defines a new value in In the "Transform Type 5 - Sequence Numbers Transform IDs" registry:
registry, IANA has added the following entry:
+========+============================+
| Number | Name
---------------------
<TBA> |
+========+============================+
| 2 | 32-bit Unspecified Numbers |
+--------+----------------------------+
Table 22
7. This document defines new Notify Message types in In the "IKEv2 Notify Message Error Types" registry: registry, IANA has made
the following changes:
* Registered "REGISTRATION_FAILED".
* Updated the references for "INVALID_GROUP_ID" and
"AUTHORIZATION_FAILED" to point to this document.
+=======+===========================+
| Value | Notify Message Error Type
----------------------------------------- |
+=======+===========================+
| 45 | INVALID_GROUP_ID |
+-------+---------------------------+
| 46 | AUTHORIZATION_FAILED
<TBA> |
+-------+---------------------------+
| 49 | REGISTRATION_FAILED |
+-------+---------------------------+
Table 23
8. The Notify type with the value 16429 was allocated earlier in the
development of G-IKEv2 document in the "IKEv2 Notify Message
Status Types" registry with the name SENDER_REQUEST_ID. This
document renames it as follows:
+=======+============================+
| Value | Notify Message Status Type
------------------------------------------ |
+=======+============================+
| 16429 | GROUP_SENDER |
+-------+----------------------------+
Table 24
9. This document defines a new Security Protocol Identifier in In the "IKEv2 Security Protocol Identifiers" registry: registry, IANA has
added the following entry:
+=============+=============+
| Protocol ID | Protocol
--------------------------
<TBA> |
+=============+=============+
| 6 | GIKE_UPDATE |
+-------------+-------------+
Table 25
10. Acknowledgements
The authors thank Lakshminath Dondeti and Jing Xiang for first
exploring the use of IKEv2 for group key management and providing the
basis behind the protocol. Mike Sullenberger and Amjad Inamdar were
instrumental in helping resolve many issues in several versions of
the document.
The authors are grateful to Tero Kivinen, Daniel Migault, Gorry
Fairhurst, Robert Sparks, Russ Housley and Paul Wouters for their
careful reviews and valuable proposals for improving the document
quality.
11. Contributors
The following individuals made substantial contributions to early
versions of this memo.
Sheela Rowles
Cisco Systems
Aldous Yeung
Cisco Systems
Email: cyyeung@cisco.com
Paulina Tran
Cisco Systems
Yoav Nir
Dell EMC
Email: ynir.ietf@gmail.com
12. References
12.1.
10.1. Normative References
[I-D.ietf-ipsecme-ikev2-rename-esn]
Smyslov, V., "Renaming Extended Sequence Number (ESN)
Transform Type in the Internet Key Exchange Protocol
Version 2 (IKEv2)", Work in Progress, Internet-Draft,
draft-ietf-ipsecme-ikev2-rename-esn-05, 16 March 2025,
<https://datatracker.ietf.org/doc/html/draft-ietf-ipsecme-
ikev2-rename-esn-05>.
[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>.
[RFC4301] Kent, S. and K. Seo, "Security Architecture for the
Internet Protocol", RFC 4301, DOI 10.17487/RFC4301,
December 2005, <https://www.rfc-editor.org/info/rfc4301>.
[RFC4302] Kent, S., "IP Authentication Header", RFC 4302,
DOI 10.17487/RFC4302, December 2005,
<https://www.rfc-editor.org/info/rfc4302>.
[RFC4303] Kent, S., "IP Encapsulating Security Payload (ESP)",
RFC 4303, DOI 10.17487/RFC4303, December 2005,
<https://www.rfc-editor.org/info/rfc4303>.
[RFC5280] Cooper, D., Santesson, S., Farrell, S., Boeyen, S.,
Housley, R., and W. Polk, "Internet X.509 Public Key
Infrastructure Certificate and Certificate Revocation List
(CRL) Profile", RFC 5280, DOI 10.17487/RFC5280, May 2008,
<https://www.rfc-editor.org/info/rfc5280>.
[RFC6054] McGrew, D. and B. Weis, "Using Counter Modes with
Encapsulating Security Payload (ESP) and Authentication
Header (AH) to Protect Group Traffic", RFC 6054,
DOI 10.17487/RFC6054, November 2010,
<https://www.rfc-editor.org/info/rfc6054>.
[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>.
[RFC7427] Kivinen, T. and J. Snyder, "Signature Authentication in
the Internet Key Exchange Version 2 (IKEv2)", RFC 7427,
DOI 10.17487/RFC7427, January 2015,
<https://www.rfc-editor.org/info/rfc7427>.
[RFC8126] Cotton, M., Leiba, B., and T. Narten, "Guidelines for
Writing an IANA Considerations Section in RFCs", BCP 26,
RFC 8126, DOI 10.17487/RFC8126, June 2017,
<https://www.rfc-editor.org/info/rfc8126>.
[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>.
12.2.
[RFC9827] Smyslov, V., "Renaming the Extended Sequence Numbers (ESN)
Transform Type in the Internet Key Exchange Protocol
Version 2 (IKEv2)", RFC 9827, DOI 10.17487/RFC9827,
September 2025, <https://www.rfc-editor.org/info/rfc9827>.
10.2. Informative References
[ARX-KW] Shinichi, S., "ARX-KW, a family of key wrapping
constructions using SipHash and ChaCha", Cryptology ePrint
Archive, Paper 2020/059, January 2020,
<https://eprint.iacr.org/2020/059.pdf>.
[I-D.ietf-ipsecme-ikev2-qr-alt]
[IKEV2-IANA]
IANA, "Internet Key Exchange Version 2 (IKEv2)
Parameters",
<http://www.iana.org/assignments/ikev2-parameters>.
[IPSEC-IKEV2-QR-ALT]
Smyslov, V., "Mixing Preshared Keys in the
IKE_INTERMEDIATE and in the CREATE_CHILD_SA Exchanges of
IKEv2 for Post-quantum Security", Work in Progress,
Internet-Draft, draft-ietf-ipsecme-ikev2-qr-alt-10, 23 May
2025, <https://datatracker.ietf.org/doc/html/draft-ietf-
ipsecme-ikev2-qr-alt-10>.
[IKEV2-IANA]
IANA, "Internet Key Exchange Version 2 (IKEv2)
Parameters", <http://www.iana.org/assignments/ikev2-
parameters/ikev2-parameters.xhtml>.
[NNL] Naor, D., Noal, Naor, M., and J. Lotspiech, "Revocation and
Tracing Schemes for Stateless Receivers", Advances in
Cryptology, Crypto '01, Springer-Verlag LNCS 2139,
Cryptology - CRYPTO 2001, Lecture Notes in Computer
Science, vol. 2139, pp. 41-62,
DOI 10.1007/3-540-44647-8_3, 2001,
<http://www.wisdom.weizmann.ac.il/~naor/PAPERS/2nl.pdf>.
[OFT] McGrew, D. and A. Sherman, "Key Establishment in Large
Dynamic Groups Using One-Way Function Trees",
Manuscript, submitted to IEEE
Transactions on Software Engineering, vol. 29, no. 5, pp.
444-458, DOI 10.1109/TSE.2003.1199073, May 1998,
<https://pdfs.semanticscholar.org/
d24c/7b41f7bcc2b6690e1b4d80eaf8c3e1cc5ee5.pdf>.
[RFC2409] Harkins, D. and D. Carrel, "The Internet Key Exchange
(IKE)", RFC 2409, DOI 10.17487/RFC2409, November 1998,
<https://www.rfc-editor.org/info/rfc2409>.
[RFC2627] Wallner, D., Harder, E., and R. Agee, "Key Management for
Multicast: Issues and Architectures", RFC 2627,
DOI 10.17487/RFC2627, June 1999,
<https://www.rfc-editor.org/info/rfc2627>.
[RFC3686] Housley, R., "Using Advanced Encryption Standard (AES)
Counter Mode With IPsec Encapsulating Security Payload
(ESP)", RFC 3686, DOI 10.17487/RFC3686, January 2004,
<https://www.rfc-editor.org/info/rfc3686>.
[RFC3740] Hardjono, T. and B. Weis, "The Multicast Group Security
Architecture", RFC 3740, DOI 10.17487/RFC3740, March 2004,
<https://www.rfc-editor.org/info/rfc3740>.
[RFC3948] Huttunen, A., Swander, B., Volpe, V., DiBurro, L., and M.
Stenberg, "UDP Encapsulation of IPsec ESP Packets",
RFC 3948, DOI 10.17487/RFC3948, January 2005,
<https://www.rfc-editor.org/info/rfc3948>.
[RFC4046] Baugher, M., Canetti, R., Dondeti, L., and F. Lindholm,
"Multicast Security (MSEC) Group Key Management
Architecture", RFC 4046, DOI 10.17487/RFC4046, April 2005,
<https://www.rfc-editor.org/info/rfc4046>.
[RFC4106] Viega, J. and D. McGrew, "The Use of Galois/Counter Mode
(GCM) in IPsec Encapsulating Security Payload (ESP)",
RFC 4106, DOI 10.17487/RFC4106, June 2005,
<https://www.rfc-editor.org/info/rfc4106>.
[RFC4309] Housley, R., "Using Advanced Encryption Standard (AES) CCM
Mode with IPsec Encapsulating Security Payload (ESP)",
RFC 4309, DOI 10.17487/RFC4309, December 2005,
<https://www.rfc-editor.org/info/rfc4309>.
[RFC4543] McGrew, D. and J. Viega, "The Use of Galois Message
Authentication Code (GMAC) in IPsec ESP and AH", RFC 4543,
DOI 10.17487/RFC4543, May 2006,
<https://www.rfc-editor.org/info/rfc4543>.
[RFC5374] Weis, B., Gross, G., and D. Ignjatic, "Multicast
Extensions to the Security Architecture for the Internet
Protocol", RFC 5374, DOI 10.17487/RFC5374, November 2008,
<https://www.rfc-editor.org/info/rfc5374>.
[RFC5649] Housley, R. and M. Dworkin, "Advanced Encryption Standard
(AES) Key Wrap with Padding Algorithm", RFC 5649,
DOI 10.17487/RFC5649, September 2009,
<https://www.rfc-editor.org/info/rfc5649>.
[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>.
[RFC5723] Sheffer, Y. and H. Tschofenig, "Internet Key Exchange
Protocol Version 2 (IKEv2) Session Resumption", RFC 5723,
DOI 10.17487/RFC5723, January 2010,
<https://www.rfc-editor.org/info/rfc5723>.
[RFC5998] Eronen, P., Tschofenig, H., and Y. Sheffer, "An Extension
for EAP-Only Authentication in IKEv2", RFC 5998,
DOI 10.17487/RFC5998, September 2010,
<https://www.rfc-editor.org/info/rfc5998>.
[RFC6407] Weis, B., Rowles, S., and T. Hardjono, "The Group Domain
of Interpretation", RFC 6407, DOI 10.17487/RFC6407,
October 2011, <https://www.rfc-editor.org/info/rfc6407>.
[RFC6467] Kivinen, T., "Secure Password Framework for Internet Key
Exchange Version 2 (IKEv2)", RFC 6467,
DOI 10.17487/RFC6467, December 2011,
<https://www.rfc-editor.org/info/rfc6467>.
[RFC7383] Smyslov, V., "Internet Key Exchange Protocol Version 2
(IKEv2) Message Fragmentation", RFC 7383,
DOI 10.17487/RFC7383, November 2014,
<https://www.rfc-editor.org/info/rfc7383>.
[RFC7634] Nir, Y., "ChaCha20, Poly1305, and Their Use in the
Internet Key Exchange Protocol (IKE) and IPsec", RFC 7634,
DOI 10.17487/RFC7634, August 2015,
<https://www.rfc-editor.org/info/rfc7634>.
[RFC8052] Weis, B., Seewald, M., and H. Falk, "Group Domain of
Interpretation (GDOI) Protocol Support for IEC 62351
Security Services", RFC 8052, DOI 10.17487/RFC8052, June
2017, <https://www.rfc-editor.org/info/rfc8052>.
[RFC8263] Weis, B., Mangla, U., Karl, T., and N. Maheshwari, "Group
Domain of Interpretation (GDOI) GROUPKEY-PUSH
Acknowledgement Message", RFC 8263, DOI 10.17487/RFC8263,
November 2017, <https://www.rfc-editor.org/info/rfc8263>.
[RFC8750] Migault, D., Guggemos, T., and Y. Nir, "Implicit
Initialization Vector (IV) for Counter-Based Ciphers in
Encapsulating Security Payload (ESP)", RFC 8750,
DOI 10.17487/RFC8750, March 2020,
<https://www.rfc-editor.org/info/rfc8750>.
[RFC8784] Fluhrer, S., Kampanakis, P., McGrew, D., and V. Smyslov,
"Mixing Preshared Keys in the Internet Key Exchange
Protocol Version 2 (IKEv2) for Post-quantum Security",
RFC 8784, DOI 10.17487/RFC8784, June 2020,
<https://www.rfc-editor.org/info/rfc8784>.
[RFC9242] Smyslov, V., "Intermediate Exchange in the Internet Key
Exchange Protocol Version 2 (IKEv2)", RFC 9242,
DOI 10.17487/RFC9242, May 2022,
<https://www.rfc-editor.org/info/rfc9242>.
[RFC9329] Pauly, T. and V. Smyslov, "TCP Encapsulation of Internet
Key Exchange Protocol (IKE) and IPsec Packets", RFC 9329,
DOI 10.17487/RFC9329, November 2022,
<https://www.rfc-editor.org/info/rfc9329>.
[RFC9347] Hopps, C., "Aggregation and Fragmentation Mode for
Encapsulating Security Payload (ESP) and Its Use for IP
Traffic Flow Security (IP-TFS)", RFC 9347,
DOI 10.17487/RFC9347, January 2023,
<https://www.rfc-editor.org/info/rfc9347>.
[RFC9370] Tjhai, CJ., Tomlinson, M., Bartlett, G., Fluhrer, S., Van
Geest, D., Garcia-Morchon, O., and V. Smyslov, "Multiple
Key Exchanges in the Internet Key Exchange Protocol
Version 2 (IKEv2)", RFC 9370, DOI 10.17487/RFC9370, May
2023, <https://www.rfc-editor.org/info/rfc9370>.
Appendix A. Use of LKH in G-IKEv2
Section 5.4 of [RFC2627] describes the LKH architecture, architecture and how a
GCKS uses LKH to exclude group members. This section clarifies how
the LKH architecture is used with G-IKEv2.
A.1. Notation
In this section section, we will use the notation X{Y} X{Y}, where a key with ID Y
is encrypted with the key with ID X. The notation GSK_w{Y} means
that the default wrap key GSK_w (with zero KWK ID)is used to encrypt
key Y, and the notation X{K_sa} means key X is used to encrypt the SA
key K_sa (wich (which always has zero a Key ID). Note, ID of zero). Note that GSK_w{K_sa}
means that the SA key is encrypted with the default wrap key, in
which case case, both KWK ID and Key ID are zero.
The content of the KD payload will be shown as a sequence of key
bags. The Group Key Bag substructure will be denoted as GP(SAn)(), GP(SAn)()
when n is an SPI for the SA, SA and the Member Key Bag substructure will
be denoted as MP(). The content of the key bags is shown as SA_KEY
and WRAP_KEY attributes with the notation described above. For
simplicity
simplicity, the type of the attribute will not be shown, shown because it is
implicitly defined by the type of key bag.
Here
Below is the example of a KD payload. payload:
KD(GP(SA1)(X{K_sa}),MP(Y{X},Z{Y},GSK_w{Z})
Figure 23
For simplicity simplicity, any other attributes in the KD payload are omitted.
We will also use the notation X->Y->Z to describe the Key Path. In
this case case, key Y is needed to decrypt key X and key Z is needed to
decrypt key Y. In the example above above, the keys had the following
relation: K_sa->X->Y->Z->GSK_w.
A.2. Group Creation
When a GCKS forms a group, it creates a key tree as shown in the
figure below.
Figure 24. The key tree contains logical keys (which are represented
as the values of their Key IDs in the figure) and a private key
shared with only a single GM (the GMs are represented as letters
followed by the corresponding key ID in parentheses in the figure).
The root of the tree contains the multicast Rekey SA key (which is
represented as SAn(K_san). The figure below assumes that the Key IDs
are assigned sequentially; this is not a requirement and only used
for illustrative purposes. The GCKS may create a complete tree as shown,
shown or a partial tree tree, which is created on demand as members join
the group.
SA1(K_sa1)
+------------------------------+
1 2
+---------------+ +---------------+
3 4 5 6
+-------+ +-------+ +--------+ +--------+
A(7) B(8) C(9) D(10) E(11) F(12) G(13) H(14)
Figure 22: 24: Initial LKH tree Tree
When GM A joins the group, the GCKS provides it with the keys in the
KD payload of the GSA_AUTH or GSA_REGISTRATION exchange. Given the
tree shown in figure above, the KD payload will be:
KD(GP(SA1)(1{K_sa1}),MP(3{1},7{3},GSK_w{7})
Figure 23: 25: KD Payload for the Group Member A
From these attributes attributes, the GM A will construct the Key Path
K_sa1->1->3->7->GSK_w and since
K_sa1->1->3->7->GSK_w. Since it ends up with GSK_w, it will use all
the WRAP_KEY attributes present in the path as its Working Key Path:
1->3->7.
Similarly, when other GMs will be joining the group group, they will be
provided with the corresponding keys, so after all all, the GMs will have
the following Working Key Paths:
A: 1->3->7 B: 1->3->8 C: 1->4->9, D: 1->4->10
E: 2->5->11 F: 2->5->12 G: 2->6->13 H: 2->6->14
Figure 26
A.3. Simple Group SA Rekey
If the GCKS performs a simple SA rekey without changing group
membership, it will only send group key bag a Group Key Gag in the KD payload with
a new SA key encrypted with the default KWK.
KD(GP(SA2)(GSK_w{K_sa2}))
Figure 24: 27: KD Payload for the Simple Group SA Rekey
All the GMs will be able to decrypt it and no changes in their
Working Key Paths will happen.
A.4. Group Member Exclusion
If the GKCS GCKS has reason to believe that a GM should be excluded, then
it can do so by sending a GSA_REKEY message that includes a set of
GM_KEY attributes attributes, which would allow all GMs GMs, except for the excluded
one
one, to get a new SA key.
In the example below below, the GCKS excludes GM F. For this purpose purpose, it
changes the key tree as follows, replacing the key 2 with the key 15 and the key
5 with the key 16. It also generates a new SA key for a new SA3.
SA3(K_sa3)
+------------------------------+
1 15
+---------------+ +---------------+
3 4 16 6
+-------+ +-------+ +---- +--------+
A(7) B(8) C(9) D(10) E(11) F(12) G(13) H(14)
Figure 25: 28: LKH tree Tree after F has been excluded Has Been Excluded
Then it sends the following KD payload for the new Rekey SA3:
KD(GP(SA3)(1{K_sa3},15{K_sa3}),MP(6{15},16{15},11{16})
Figure 26: 29: KD Payload for the Group Member F
While processing this KD payload:
* GMs A, B, C C, and D will be able to decrypt the SA_KEY attribute
1{K_sa3} by using the "1" key from their key path. Since no new
GM_KEY attributes are in the new Key Path, they won't update their
Working Key Paths.
* GMs G and H will construct new Key Path 15->6 and will be able to
decrypt the intermediate key 15 using the key 6 from their Working Key
Paths. So, they will update their Working Key Paths replacing
their beginnings up to the key 6 with the new Key Path (thus replacing
the key 2 with the key 15).
* GM E will construct a new Key Path 16->15->11 and will be able to
decrypt the intermediate key 16 using the key 11 from its Working Key
Path. So, it will update its Working Key Path replacing its
beginnings up to the key 11 with the new Key Path (thus replacing
the key
2 with the key 15 and the key 5 with the key 16).
* GM F won't be able to construct any Key Path leading to any key he it
possesses, so it will be unable to decrypt the new SA key for the
SA3 and thus
SA3. Thus, it will be excluded from the group once the SA3 is
used.
Finally, the GMs will have the following Working Key Paths:
A: 1->3->7 B: 1->3->8 C: 1->4->9, D: 1->4->10
E: 15->16->11 F: excluded G: 15->6->13 H: 15->6->14
Figure 30
Acknowledgements
The authors thank Lakshminath Dondeti and Jing Xiang for first
exploring the use of IKEv2 for group key management and providing the
basis behind the protocol. Mike Sullenberger and Amjad Inamdar were
instrumental in helping resolve many issues in several draft versions
of the document.
The authors are grateful to Tero Kivinen, Daniel Migault, Gorry
Fairhurst, Robert Sparks, Russ Housley, and Paul Wouters for their
careful reviews and valuable proposals for improving the document
quality.
Contributors
The following individuals made substantial contributions to earlier
draft versions of this document.
Sheela Rowles
Cisco Systems
Aldous Yeung
Cisco Systems
Email: cyyeung@cisco.com
Paulina Tran
Cisco Systems
Yoav Nir
Dell EMC
Email: ynir.ietf@gmail.com
Authors' Addresses
Valery Smyslov
ELVIS-PLUS
Russian Federation
Email: svan@elvis.ru
Brian Weis
Independent
United States of America
Email: bew.stds@gmail.com