< draft-ietf-ipsecme-g-ikev2-00.txt   draft-ietf-ipsecme-g-ikev2-01.txt >
Network Working Group B. Weis Network Working Group V. Smyslov
Internet-Draft Independent Internet-Draft ELVIS-PLUS
Obsoletes: 6407 (if approved) V. Smyslov Obsoletes: 6407 (if approved) B. Weis
Intended status: Standards Track ELVIS-PLUS Intended status: Standards Track Independent
Expires: July 12, 2020 January 9, 2020 Expires: January 14, 2021 July 13, 2020
Group Key Management using IKEv2 Group Key Management using IKEv2
draft-ietf-ipsecme-g-ikev2-00 draft-ietf-ipsecme-g-ikev2-01
Abstract Abstract
This document presents a set of IKEv2 exchanges that comprise a group This document presents an extension to the Internet Key Exchange
key management protocol. The protocol is in conformance with the version 2 (IKEv2) protocol for the purpose of a group key management.
Multicast Security (MSEC) key management architecture, which contains The protocol is in conformance with the Multicast Security (MSEC) key
two components: member registration and group rekeying. Both management architecture, which contains two components: member
components require a Group Controller/Key Server to download IPsec registration and group rekeying. Both components require a Group
group security associations to authorized members of a group. The Controller/Key Server to download IPsec group security associations
group members then exchange IP multicast or other group traffic as to authorized members of a group. The group members then exchange IP
IPsec packets. This document obsoletes RFC 6407. multicast or other group traffic as IPsec packets. This document
obsoletes RFC 6407.
Status of This Memo Status of This Memo
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This Internet-Draft will expire on July 12, 2020. This Internet-Draft will expire on January 14, 2021.
Copyright Notice Copyright Notice
Copyright (c) 2020 IETF Trust and the persons identified as the Copyright (c) 2020 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
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Table of Contents Table of Contents
1. Introduction and Overview . . . . . . . . . . . . . . . . . . 3 1. Introduction and Overview . . . . . . . . . . . . . . . . . . 3
1.1. Requirements Language . . . . . . . . . . . . . . . . . . 5 1.1. Requirements Language . . . . . . . . . . . . . . . . . . 5
1.2. G-IKEv2 Integration into IKEv2 Protocol . . . . . . . . . 5 1.2. G-IKEv2 Integration into IKEv2 Protocol . . . . . . . . . 5
1.2.1. G-IKEv2 Transport and Port . . . . . . . . . . . . . 5 1.2.1. G-IKEv2 Transport and Port . . . . . . . . . . . . . 6
1.2.2. IKEv2 Header Initialization . . . . . . . . . . . . . 6 1.2.2. IKEv2 Header Initialization . . . . . . . . . . . . . 6
1.3. G-IKEv2 Protocol . . . . . . . . . . . . . . . . . . . . 6 1.3. G-IKEv2 Protocol . . . . . . . . . . . . . . . . . . . . 6
1.3.1. G-IKEv2 Payloads . . . . . . . . . . . . . . . . . . 6 1.3.1. G-IKEv2 Payloads . . . . . . . . . . . . . . . . . . 6
1.4. G-IKEv2 Member Registration and Secure Channel 1.4. G-IKEv2 Member Registration and Secure Channel
Establishment . . . . . . . . . . . . . . . . . . . . . . 7 Establishment . . . . . . . . . . . . . . . . . . . . . . 7
1.4.1. GSA_AUTH exchange . . . . . . . . . . . . . . . . . . 7 1.4.1. GSA_AUTH exchange . . . . . . . . . . . . . . . . . . 7
1.4.2. GSA_REGISTRATION Exchange . . . . . . . . . . . . . . 9 1.4.2. GSA_REGISTRATION Exchange . . . . . . . . . . . . . . 9
1.4.3. GM Registration Operations . . . . . . . . . . . . . 10 1.4.3. GM Registration Operations . . . . . . . . . . . . . 10
1.4.4. GCKS Registration Operations . . . . . . . . . . . . 11 1.4.4. GCKS Registration Operations . . . . . . . . . . . . 12
1.4.5. Group Maintenance Channel . . . . . . . . . . . . . . 12 1.4.5. Group Maintenance Channel . . . . . . . . . . . . . . 13
1.4.6. Counter-based modes of operation . . . . . . . . . . 19 1.4.6. Counter-based modes of operation . . . . . . . . . . 20
1.5. Interaction with IKEv2 Protocol Extensions . . . . . . . 21 2. Group Key Management and Access Control . . . . . . . . . . . 22
1.5.1. Postquantum Preshared Keys for IKEv2 . . . . . . . . 21 2.1. Key Wrap Keys . . . . . . . . . . . . . . . . . . . . . . 23
2. Header and Payload Formats . . . . . . . . . . . . . . . . . 23 2.1.1. Default Key Wrap Key . . . . . . . . . . . . . . . . 23
2.1. The G-IKEv2 Header . . . . . . . . . . . . . . . . . . . 23 2.2. GCKS Key Management Semantics . . . . . . . . . . . . . . 23
2.2. Group Identification (IDg) Payload . . . . . . . . . . . 24 2.2.1. Forward Access Control Requirements . . . . . . . . . 24
2.3. Security Association - GM Supported Transforms (SAg) . . 24 2.3. GM Key Management Semantics . . . . . . . . . . . . . . . 25
2.4. Group Security Association Payload . . . . . . . . . . . 24 2.4. Group SA Keys . . . . . . . . . . . . . . . . . . . . . . 26
2.4.1. GSA Policy . . . . . . . . . . . . . . . . . . . . . 25 3. Header and Payload Formats . . . . . . . . . . . . . . . . . 27
2.4.2. KEK Policy . . . . . . . . . . . . . . . . . . . . . 26 3.1. G-IKEv2 Header . . . . . . . . . . . . . . . . . . . . . 27
2.4.3. GSA TEK Policy . . . . . . . . . . . . . . . . . . . 30 3.2. Group Identification Payload . . . . . . . . . . . . . . 27
2.4.4. GSA Group Associated Policy . . . . . . . . . . . . . 33 3.3. Security Association - GM Supported Transforms Payload . 27
2.5. Key Download Payload . . . . . . . . . . . . . . . . . . 34 3.4. Group Security Association Payload . . . . . . . . . . . 28
2.5.1. TEK Download Type . . . . . . . . . . . . . . . . . . 36 3.4.1. Group Policies . . . . . . . . . . . . . . . . . . . 28
2.5.2. KEK Download Type . . . . . . . . . . . . . . . . . . 37 3.4.2. Group Security Association Policy Substructure . . . 29
2.5.3. LKH Download Type . . . . . . . . . . . . . . . . . . 38 3.4.3. Group Associated Policy Substructure . . . . . . . . 35
2.5.4. SID Download Type . . . . . . . . . . . . . . . . . . 40 3.5. Key Download Payload . . . . . . . . . . . . . . . . . . 37
2.6. Delete Payload . . . . . . . . . . . . . . . . . . . . . 42 3.5.1. Wrapped Key Format . . . . . . . . . . . . . . . . . 37
2.7. Notify Payload . . . . . . . . . . . . . . . . . . . . . 42 3.5.2. Group Key Packet Substructure . . . . . . . . . . . . 39
2.8. Authentication Payload . . . . . . . . . . . . . . . . . 43 3.5.3. Member Key Packet Substructure . . . . . . . . . . . 40
3. Security Considerations . . . . . . . . . . . . . . . . . . . 43 3.6. Delete Payload . . . . . . . . . . . . . . . . . . . . . 43
3.1. GSA Registration and Secure Channel . . . . . . . . . . . 43 3.7. Notify Payload . . . . . . . . . . . . . . . . . . . . . 43
3.2. GSA Maintenance Channel . . . . . . . . . . . . . . . . . 44 3.7.1. USE_TRANSPORT_MODE Notification . . . . . . . . . . . 44
3.2.1. Authentication/Authorization . . . . . . . . . . . . 44 3.8. Authentication Payload . . . . . . . . . . . . . . . . . 45
3.2.2. Confidentiality . . . . . . . . . . . . . . . . . . . 44 4. Interaction with other IKEv2 Protocol Extensions . . . . . . 45
3.2.3. Man-in-the-Middle Attack Protection . . . . . . . . . 44 4.1. Mixing Preshared Keys in IKEv2 for Post-quantum Security 45
3.2.4. Replay/Reflection Attack Protection . . . . . . . . . 44
4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 44 5. Security Considerations . . . . . . . . . . . . . . . . . . . 47
4.1. New Registries . . . . . . . . . . . . . . . . . . . . . 44 5.1. GSA Registration and Secure Channel . . . . . . . . . . . 47
4.2. New Payload and Exchange Types Added to the Existing 5.2. GSA Maintenance Channel . . . . . . . . . . . . . . . . . 47
IKEv2 Registry . . . . . . . . . . . . . . . . . . . . . 45 5.2.1. Authentication/Authorization . . . . . . . . . . . . 47
4.3. Changes to Previous Allocations . . . . . . . . . . . . . 45 5.2.2. Confidentiality . . . . . . . . . . . . . . . . . . . 47
5. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 45 5.2.3. Man-in-the-Middle Attack Protection . . . . . . . . . 48
6. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 46 5.2.4. Replay/Reflection Attack Protection . . . . . . . . . 48
7. References . . . . . . . . . . . . . . . . . . . . . . . . . 46 6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 48
7.1. Normative References . . . . . . . . . . . . . . . . . . 47 6.1. New Registries . . . . . . . . . . . . . . . . . . . . . 48
7.2. Informative References . . . . . . . . . . . . . . . . . 48 6.2. Changes in the Existing IKEv2 Registries . . . . . . . . 50
Appendix A. Use of LKH in G-IKEv2 . . . . . . . . . . . . . . . 50 7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 51
A.1. Group Creation . . . . . . . . . . . . . . . . . . . . . 50 8. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 51
A.2. Group Member Exclusion . . . . . . . . . . . . . . . . . 51 9. References . . . . . . . . . . . . . . . . . . . . . . . . . 52
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 52 9.1. Normative References . . . . . . . . . . . . . . . . . . 52
9.2. Informative References . . . . . . . . . . . . . . . . . 53
Appendix A. Use of LKH in G-IKEv2 . . . . . . . . . . . . . . . 56
A.1. Notation . . . . . . . . . . . . . . . . . . . . . . . . 56
A.2. Group Creation . . . . . . . . . . . . . . . . . . . . . 56
A.3. Simple Group SA Rekey . . . . . . . . . . . . . . . . . . 57
A.4. Group Member Exclusion . . . . . . . . . . . . . . . . . 58
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 59
1. Introduction and Overview 1. Introduction and Overview
A group key management protocol provides IPsec keys and policy to a A group key management protocol provides IPsec keys and policy to a
set of IPsec devices which are authorized to communicate using a set of IPsec devices which are authorized to communicate using a
Group Security Association (GSA) defined in [RFC3740]. The data Group Security Association (GSA) defined in [RFC3740]. The data
communications within the group (e.g., IP multicast packets) are communications within the group (e.g., IP multicast packets) are
protected by a key pushed to the group members (GMs) by the Group protected by a key pushed to the group members (GMs) by the Group
Controller/Key Server (GCKS). This document presents a set of IKEv2 Controller/Key Server (GCKS). This document presents an extension to
[RFC7296] exchanges that comprise a group key management protocol. IKEv2 [RFC7296] called G-IKEv2, that allows to perform a group key
management.
G-IKEv2 conforms to the Multicast Group Security Architecture
[RFC3740], Multicast Extensions to the Security Architecture for the
Internet Protocol [RFC5374] and the Multicast Security (MSEC) Group
Key Management Architecture [RFC4046]. G-IKEv2 replaces GDOI
[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 and cryptographic improvements of IKEv2 (see
Appendix A of [RFC7296].
A GM begins a "registration" exchange when it first joins the group. A GM begins a "registration" exchange when it first joins the group.
With G-IKEv2, the GCKS authenticates and authorizes GMs, then pushes With G-IKEv2, the GCKS authenticates and authorizes GMs, then pushes
policy and keys used by the group to the GM. G-IKEv2 includes two policy and keys used by the group to the GM. G-IKEv2 includes two
"registration" exchanges. The first is the GSA_AUTH exchange ( "registration" exchanges. The first is the GSA_AUTH exchange (
Section 1.4.1), which follows an IKE_SA_INIT exchange. The second is Section 1.4.1), which follows an IKE_SA_INIT exchange. The second is
the GSA_REGISTRATION exchange ( Section 1.4.2), which a GM can use the GSA_REGISTRATION exchange (Section 1.4.2), which a GM can use
within an established IKE SA. Group rekeys are accomplished using within an established IKE SA. Group rekeys are accomplished using
either the GSA_REKEY exchange (a single message distributed to all either the GSA_REKEY pseudo-exchange (a single message distributed to
GMs, usually as a multicast message), or as a GSA_INBAND_REKEY all GMs, usually as a multicast message), or as a GSA_INBAND_REKEY
exchange delivered individually to group members using existing IKE exchange delivered individually to group members using existing IKE
SAs). SAs).
Large and small groups may use different sets of these protocols. Large and small groups may use different sets of these protocols.
When a large group of devices are communicating, the GCKS is likely When a large group of devices are communicating, the GCKS is likely
to use the GSA_REKEY message for efficiency. This is shown in to use the GSA_REKEY message for efficiency. This is shown in
Figure 1. (Note: For clarity, IKE_SA_INIT is omitted from the Figure 1. (Note: For clarity, IKE_SA_INIT is omitted from the
figure.) figure.)
+--------+ +--------+
+------------->| GCKS |<-------------+ +------------->| GCKS |<-------------+
| +--------+ | | +--------+ |
| | ^ | | | ^ |
| | | | | | | |
| | GSA_AUTH | | | GSA_AUTH |
| | or | | | or |
| | GSA_REGISTRATION | | | GSA_REGISTRATION |
| | | | | | | |
GSA_AUTH | | GSA_AUTH GSA_AUTH | | GSA_AUTH
skipping to change at page 4, line 33 skipping to change at page 5, line 4
^ ^ ^ ^ ^ ^
| | | | | |
+-------ESP-------+-------ESP------+ +-------ESP-------+-------ESP------+
Figure 1: G-IKEv2 used in large groups Figure 1: G-IKEv2 used in large groups
Alternatively, a small group may simply use the GSA_AUTH as a Alternatively, a small group may simply use the GSA_AUTH as a
registration protocol, where the GCKS issues rekeys using the registration protocol, where the GCKS issues rekeys using the
GSA_INBAND_REKEY within the same IKEv2 SA. The GCKS is also likely GSA_INBAND_REKEY within the same IKEv2 SA. The GCKS is also likely
to be a GM in a small group (as shown in Figure 2.) to be a GM in a small group (as shown in Figure 2.)
GSA_AUTH, GSA_INBAND_REKEY GSA_AUTH, GSA_INBAND_REKEY
+-----------------------------------------------+ +-----------------------------------------------+
| | | |
| GSA_AUTH, GSA_INBAND_REKEY | | GSA_AUTH, GSA_INBAND_REKEY |
| +-----------------------------+ | | +-----------------------------+ |
| | | | | | | |
| | GSA_AUTH, GSA_INBAND_REKEY | | | | GSA_AUTH, GSA_INBAND_REKEY | |
| | +--------+ | | | | +--------+ | |
v v v v v v v v v v v v
+---------+ +----+ +----+ +----+ +---------+ +----+ +----+ +----+
| GCKS/GM | | GM | | GM | | GM | | GCKS/GM | | GM | | GM | | GM |
+---------+ +----+ +----+ +----+ +---------+ +----+ +----+ +----+
^ ^ ^ ^ ^ ^ ^ ^
| | | | | | | |
+----ESP-----+------ESP-------+-----ESP-----+ +----ESP-----+------ESP-------+-----ESP-----+
Figure 2: G-IKEv2 used in small groups Figure 2: G-IKEv2 used in small groups
IKEv2 message semantics are preserved in that all communications IKEv2 message semantics are preserved in that all communications
consists of message request-response pairs. The exception to this consists of message request-response pairs. The exception to this
rule is the GSA_REKEY exchange, which is a single message delivering rule is the GSA_REKEY pseudo-exchange, which is a single message
group updates to the GMs. delivering group updates to the GMs.
G-IKEv2 conforms with the Multicast Group Security Architecture
[RFC3740], and the Multicast Security (MSEC) Group Key Management
Architecture [RFC4046]. G-IKEv2 replaces GDOI [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 and cryptographic improvements of IKEv2 (see Appendix A of
[RFC7296].
1.1. Requirements Language 1.1. Requirements Language
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in BCP "OPTIONAL" in this document are to be interpreted as described in BCP
14 [RFC2119] [RFC8174] when, and only when, they appear in all 14 [RFC2119] [RFC8174] when, and only when, they appear in all
capitals, as shown here. capitals, as shown here.
1.2. G-IKEv2 Integration into IKEv2 Protocol 1.2. G-IKEv2 Integration into IKEv2 Protocol
G-IKEv2 uses the security mechanisms of IKEv2 (peer authentication, G-IKEv2 uses the security mechanisms of IKEv2 (peer authentication,
confidentiality, message integrity) to ensure that only authenticated confidentiality, message integrity) to ensure that only authenticated
devices have access to the group policy and keys. The G-IKEv2 devices have access to the group policy and keys. The G-IKEv2
exchange further provides group authorization, and secure policy and exchange further provides group authorization, and secure policy and
key download from the GCKS to GMs. Some IKEv2 extensions require key download from the GCKS to GMs. Some IKEv2 extensions require
special handling if used with G-IKEv2. See Section 1.5 for more special handling if used with G-IKEv2. See Section 4 for more
details. details.
It is assumed that readers are familiar with the IKEv2 protocol, so It is assumed that readers are familiar with the IKEv2 protocol, so
this document skips many details that are described in [RFC7296]. this document skips many details that are described in [RFC7296].
1.2.1. G-IKEv2 Transport and Port 1.2.1. G-IKEv2 Transport and Port
G-IKEv2 SHOULD use UDP port 848, the same as GDOI [RFC6407], because G-IKEv2 SHOULD use UDP port 848, the same as GDOI [RFC6407], because
they serve a similar function. They can use the same ports, just as they serve a similar function. They can use the same ports, just as
IKEv1 and IKEv2 can share port 500. The version number in the IKE IKEv1 and IKEv2 can share port 500. The version number in the IKE
skipping to change at page 6, line 24 skipping to change at page 6, line 35
1.3.1. G-IKEv2 Payloads 1.3.1. G-IKEv2 Payloads
In the following descriptions, the payloads contained in the G-IKEv2 In the following descriptions, the payloads contained in the G-IKEv2
messages are indicated by names as listed below. messages are indicated by names as listed below.
Notation Payload Notation Payload
------------------------------------------------------------ ------------------------------------------------------------
AUTH Authentication AUTH Authentication
CERT Certificate CERT Certificate
CERTREQ Certificate Request CERTREQ Certificate Request
D Delete
GSA Group Security Association GSA Group Security Association
HDR IKEv2 Header HDR IKEv2 Header
IDg Identification - Group IDg Identification - Group
IDi Identification - Initiator IDi Identification - Initiator
IDr Identification - Responder IDr Identification - Responder
KD Key Download KD Key Download
KE Key Exchange KE Key Exchange
Ni, Nr Nonce Ni, Nr Nonce
N Notify
SA Security Association SA Security Association
SAg Security Association - GM Supported Transforms SAg Security Association - GM Supported Transforms
Payloads defined as part of other IKEv2 extensions MAY also be Payloads defined as part of other IKEv2 extensions MAY also be
included in these messages. Payloads that may optionally appear will included in these messages. Payloads that may optionally appear in
be shown in brackets, such as [ CERTREQ ], to indicate that a G-IKEv2 messages will be shown in brackets, such as [CERTREQ].
certificate request payload can optionally be included.
G-IKEv2 defines several new payloads not used in IKEv2: G-IKEv2 defines several new payloads not used in IKEv2:
o IDg (Group ID) - The GM requests the GCKS for membership into the o IDg (Group ID) - The GM requests the GCKS for membership into the
group by sending its IDg payload. group by sending its IDg payload.
o GSA (Group Security Association) - The GCKS sends the group policy o GSA (Group Security Association) - The GCKS sends the group policy
to the GM using this payload. to the GM using this payload.
o KD (Key Download) - The GCKS sends the control and data keys to o KD (Key Download) - The GCKS sends the keys and the security
the GM using the KD payload. parameters to the GMs using the KD payload.
o SAg (Security Association - GM Supported Transforms) - the GM o SAg (Security Association - GM Supported Transforms) - the GM
sends supported transforms, so that GCKS may select a policy sends supported transforms, so that GCKS may select a policy
appropriate for all members of the group. appropriate for all members of the group.
The details of the contents of each payload are described in The details of the contents of each payload are described in
Section 2. Section 3.
1.4. G-IKEv2 Member Registration and Secure Channel Establishment 1.4. G-IKEv2 Member Registration and Secure Channel Establishment
The registration protocol consists of a minimum of two messages The registration protocol consists of a minimum of two messages
exchanges, IKE_SA_INIT and GSA_AUTH; member registration may have a exchanges, IKE_SA_INIT and GSA_AUTH; member registration may have a
few more messages exchanged if the EAP method, cookie challenge (for few more messages exchanged if the EAP method, cookie challenge (for
DoS protection) or negotiation of Diffie-Hellman group is included. DoS protection) or negotiation of Diffie-Hellman group is included.
Each exchange consists of request/response pairs. The first exchange Each exchange consists of request/response pairs. The first exchange
IKE_SA_INIT is defined in IKEv2 [RFC7296]. This exchange negotiates IKE_SA_INIT is defined in IKEv2 [RFC7296]. This exchange negotiates
cryptographic algorithms, exchanges nonces and does a Diffie-Hellman cryptographic algorithms, exchanges nonces and does a Diffie-Hellman
skipping to change at page 8, line 5 skipping to change at page 8, line 10
exchange MUST complete before any other exchanges can be done. The exchange MUST complete before any other exchanges can be done. The
security properties of the GSA_AUTH exchange are the same as the security properties of the GSA_AUTH exchange are the same as the
properties of the IKE_AUTH exchange. It is used to authenticate the properties of the IKE_AUTH exchange. It is used to authenticate the
IKE_SA_INIT messages, exchange identities and certificates. G-IKEv2 IKE_SA_INIT messages, exchange identities and certificates. G-IKEv2
also uses this exchange for group member registration and also uses this exchange for group member registration and
authorization. Even though the IKE_AUTH does contain the SA2, TSi, authorization. Even though the IKE_AUTH does contain the SA2, TSi,
and TSr payload the GSA_AUTH does not. They are not needed because and TSr payload the GSA_AUTH does not. They are not needed because
policy is not negotiated between the group member and the GCKS, but policy is not negotiated between the group member and the GCKS, but
instead downloaded from the GCKS to the group member. instead downloaded from the GCKS to the group member.
Initiator (Member) Responder (GCKS) Initiator (Member) Responder (GCKS)
-------------------- ------------------ -------------------- ------------------
HDR, SK { IDi, [CERT,] [CERTREQ, ] [IDr, ] HDR, SK{IDi, [CERT,] [CERTREQ,] [IDr,]
AUTH, IDg, [SAg, ] [N ] } --> AUTH, IDg, [SAg,] [N]} -->
Figure 3: GSA_AUTH Request Figure 3: GSA_AUTH Request
After the IKE_SA_INIT exchange completes, the group member initiates After the IKE_SA_INIT exchange completes, the group member initiates
a GSA_AUTH request to join a group indicated by the IDg payload. The a GSA_AUTH request to join a group indicated by the IDg payload. The
GM MAY include an SAg payload declaring which Transforms that it is GM MAY include an SAg payload declaring which Transforms it is
willing to accept. A GM that intends to emit data packets SHOULD willing to accept. A GM that intends to emit data packets SHOULD
include a Notify payload status type of SENDER, which enables the include a Notify payload status type of SENDER, which enables the
GCKS to provide any additional policy necessary by group senders. GCKS to provide any additional policy necessary by group senders.
Initiator (Member) Responder (GCKS) Initiator (Member) Responder (GCKS)
-------------------- ------------------ -------------------- ------------------
<-- HDR, SK { IDr, [CERT, ] <-- HDR, SK{IDr, [CERT,]
AUTH, [ GSA, KD, ] [D, ] } AUTH, [GSA, KD,] [N,] [D]}
Figure 4: GSA_AUTH Normal Response Figure 4: GSA_AUTH Normal Response
The GCKS responds with IDr, optional CERT, and AUTH material as if it The GCKS responds with IDr, optional CERT, and AUTH material as if it
were an IKE_AUTH. It also informs the group member of the were an IKE_AUTH. It also informs the group member of the
cryptographic policies of the group in the GSA payload and the key cryptographic policies of the group in the GSA payload and the key
material in the KD payload. The GCKS can also include a Delete (D) material in the KD payload. The GCKS can also include a Delete (D)
payload instructing the group member to delete existing SAs it might payload instructing the group member to delete existing SAs it might
have as the result of a previous group member registration. Note, have as the result of a previous group member registration. Note,
that since the GCKS generally doesn't know which SAs the GM has, the that since the GCKS generally doesn't know which SAs the GM has, the
SPI field in the Delete payload(s) SHOULD be set to zero in this SPI field in the Delete payload(s) SHOULD be set to zero in this
case. (See more discussion on the Delete payload in Section 2.6.) case. (See more discussion on the Delete payload in Section 3.6.)
In addition to the IKEv2 error handling, the GCKS can reject the In addition to the IKEv2 error handling, the GCKS can reject the
registration request when the IDg is invalid or authorization fails, registration request when the IDg is invalid or authorization fails,
etc. In these cases, see Section 2.7, the GSA_AUTH response will not etc. In these cases, see Section 3.7, the GSA_AUTH response will not
include the GSA and KD, but will include a Notify payload indicating include the GSA and KD, but will include a Notify payload indicating
errors. If the group member included an SAg payload, and the GCKS errors. If the group member included an SAg payload, and the GCKS
chooses to evaluate it, and it detects that that group member cannot chooses to evaluate it, and it detects that that group member cannot
support the security policy defined for the group, then the GCKS support the security policy defined for the group, then the GCKS
SHOULD return a NO_PROPOSAL_CHOSEN. Other types of notifications can SHOULD return a NO_PROPOSAL_CHOSEN. Other types of notifications can
be AUTHORIZATION_FAILED or REGISTRATION_FAILED. be AUTHORIZATION_FAILED or REGISTRATION_FAILED.
Initiator (Member) Responder (GCKS) Initiator (Member) Responder (GCKS)
-------------------- ------------------ -------------------- ------------------
<-- HDR, SK { IDr, [CERT, ] AUTH, N } <-- HDR, SK{IDr, [CERT,] AUTH, N}
Figure 5: GSA_AUTH Error Response Figure 5: GSA_AUTH Error Response
If the group member finds the policy sent by the GCKS is If the group member finds the policy sent by the GCKS is
unacceptable, the member SHOULD initiate GSA_REGISTRATION exchange unacceptable, the member SHOULD initiate GSA_REGISTRATION exchange
sending IDg and the Notify NO_PROPOSAL_CHOSEN (see Section 1.4.2)). sending IDg and the Notify NO_PROPOSAL_CHOSEN (see Section 1.4.2)).
1.4.2. GSA_REGISTRATION Exchange 1.4.2. GSA_REGISTRATION Exchange
When a secure channel is already established between a GM and the When a secure channel is already established between a GM and the
GCKS, the GM registration for a group can reuse the established GCKS, the GM registration for a group can reuse the established
secure channel. In this scenario the GM will use the secure channel. In this scenario the GM will use the
GSA_REGISTRATION exchange. Payloads in the exchange are generated GSA_REGISTRATION exchange. Payloads in the exchange are generated
and processed as defined in Section 1.4.1. and processed as defined in Section 1.4.1.
Initiator (Member) Responder (GCKS) Initiator (Member) Responder (GCKS)
-------------------- ------------------ -------------------- ------------------
HDR, SK {IDg, [SAg, ][N ] } --> HDR, SK{IDg, [SAg,][N ]} -->
<-- HDR, SK { GSA, KD, [D ] } <-- HDR, SK{GSA,] [N,] [D]}
Figure 6: GSA_REGISTRATION Normal Exchange Figure 6: GSA_REGISTRATION Normal Exchange
As with GSA_AUTH exchange, the GCKS can reject the registration As with GSA_AUTH exchange, the GCKS can reject the registration
request when the IDg is invalid or authorization fails, or GM cannot request when the IDg is invalid or authorization fails, or GM cannot
support the security policy defined for the group (which can be support the security policy defined for the group (which can be
concluded by GCKS by evaluation of SAg payload). In this case the concluded by GCKS by evaluation of SAg payload). In this case the
GCKS returns an appropriate error notification as described in GCKS returns an appropriate error notification as described in
Section 1.4.1. Section 1.4.1.
Initiator (Member) Responder (GCKS) Initiator (Member) Responder (GCKS)
-------------------- ------------------ -------------------- ------------------
HDR, SK {IDg, [SAg, ][N ] } --> HDR, SK{IDg, [SAg,] [N]} -->
<-- HDR, SK { N } <-- HDR, SK{N}
Figure 7: GSA_REGISTRATION Error Exchange Figure 7: GSA_REGISTRATION Error Exchange
This exchange can also be used if the group member finds the policy This exchange can also be used if the group member finds the policy
sent by the GCKS is unacceptable or for some reason wants to sent by the GCKS is unacceptable or for some reason wants to
unregister itself from the group. The group member SHOULD notify the unregister itself from the group. The group member SHOULD notify the
GCKS by sending IDg and the Notify type NO_PROPOSAL_CHOSEN or GCKS by sending IDg and the Notify type NO_PROPOSAL_CHOSEN or
REGISTRATION_FAILED, as shown below. The GCKS MUST unregister the REGISTRATION_FAILED, as shown below. The GCKS MUST unregister the
group member. group member.
Initiator (Member) Responder (GCKS) Initiator (Member) Responder (GCKS)
-------------------- ------------------ -------------------- ------------------
HDR, SK {IDg, N } --> HDR, SK{IDg, N} -->
<-- HDR, SK {} <-- HDR, SK{}
Figure 8: GM Reporting Errors in GSA_REGISTRATION Exchange Figure 8: GM Reporting Errors in GSA_REGISTRATION Exchange
1.4.3. GM Registration Operations 1.4.3. GM Registration Operations
A G-IKEv2 Initiator (GM) requesting registration contacts the GCKS A G-IKEv2 Initiator (GM) requesting registration contacts the GCKS
using the IKE_SA_INIT exchange and receives the response from the using the IKE_SA_INIT exchange and receives the response from the
GCKS. This exchange is unchanged from the IKE_SA_INIT in IKEv2 GCKS. This exchange is unchanged from the IKE_SA_INIT in IKEv2
protocol. protocol.
Upon completion of parsing and verifying the IKE_SA_INIT response, Upon completion of parsing and verifying the IKE_SA_INIT response,
the GM sends the GSA_AUTH message with the IKEv2 payloads from the GM sends the GSA_AUTH message with the IKEv2 payloads from
IKE_AUTH (without the SAi2, TSi and TSr payloads) along with the IKE_AUTH (without the SAi2, TSi and TSr payloads) along with the
Group ID informing the GCKS of the group the initiator wishes to Group ID informing the GCKS of the group the initiator wishes to
join. An initiator intending to emit data traffic SHOULD send a join. An initiator intending to emit data traffic SHOULD send a
SENDER Notify payload status. The SENDER not only signifies that it SENDER Notify payload status. The SENDER not only signifies that it
is a sender, but provides the initiator the ability to request is a sender, but provides the initiator the ability to request
Sender-ID values, in case the Data Security SA supports a counter Sender-ID values, in case the data security SA supports a counter
mode cipher. Section 1.4.6) includes guidance on requesting Sender- mode cipher. Section 1.4.6) includes guidance on requesting Sender-
ID values. ID values.
An initiator may be limited in the types of Transforms that it is A GM may be limited in the types of Transforms that it is able or
able or willing to use, and may find it useful to inform the GCKS willing to use, and may find it useful to inform the GCKS which
which Transforms that it is willing to accept. It can OPTIONALLY Transforms it is willing to accept for different security protocols.
include an SAg payload, which can include ESP and/or AH Proposals. Proposals for Rekey SA (with protocol GIKE_REKEY) and for data
Each Proposal contains a list of Transforms that it is willing to security (AH and/or ESP) SAs may be included into SAg. Each Proposal
support for that protocol. A Proposal of type ESP can include ENCR, contains a list of Transforms that the GM is able to support for that
INTEG, and ESN Transforms. A Proposal of type AH can include INTEG, protocol. Valid transform types depend on the protocol and are
and ESN Transforms. The SPI length of each Proposal in an SAg is set defined in Figure 15. Other transform types SHOULD NOT be included.
to zero, and thus the SPI field is null. The GCKS MUST ignore SPI The SPI length of each Proposal in an SAg is set to zero, and thus
field in the SAg payload. Generally, a single Proposal of each type the SPI field is empty. The GCKS MUST ignore SPI field in the SAg
will suffice, because the group member is not negotiating Transform payload.
sets, simply alerting the GCKS to restrictions it may have, however
if the GM has restrictions on combination of algorithms, this can be Generally, a single Proposal of each type will suffice, because the
expressed by sending several proposals. group member is not negotiating Transform sets, simply alerting the
GCKS to restrictions it may have. In particular, the restriction
from Section 3.3 of [RFC7296] that AEAD and non-AEAD transforms must
not be combined in a single proposal doesn't hold when the SAg
payload is being formed. However if the GM has restrictions on
combination of algorithms, this can be expressed by sending several
proposals.
Although the SAg payload is optional, it is RECOMMENDED for 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 inclusion one or
more the IPCOMP_SUPPORTED notifications along with the SAg payload.
The CPI in these notifications is set to zero and MUST be ignored by
the GCKS.
Upon receiving the GSA_AUTH response, the initiator parses the Upon receiving the GSA_AUTH response, the initiator parses the
response from the GCKS authenticating the exchange using the IKEv2 response from the GCKS authenticating the exchange using the IKEv2
method, then processes the GSA and KD. method, then processes the GSA and KD.
The GSA payload contains the security policy and cryptographic The GSA payload contains the security policy and cryptographic
protocols used by the group. This policy describes the Rekey SA protocols used by the group. This policy describes the Rekey SA
(KEK), if present, Data-security SAs (TEK), and other group policy (KEK), Data-security SAs (TEK), and other group policy (GAP). If the
(GAP). If the policy in the GSA payload is not acceptable to the GM, policy in the GSA payload is not acceptable to the GM, it SHOULD
it SHOULD notify the GCKS by initiating a GSA_REGISTRATION exchange notify the GCKS by initiating a GSA_REGISTRATION exchange with a
with a NO_PROPOSAL_CHOSEN Notify payload (see Section 1.4.2). Note, NO_PROPOSAL_CHOSEN Notify payload (see Section 1.4.2). Note, that
that this should normally not happen if the GM includes SAg payload this should normally not happen if the GM includes SAg payload in the
in the GSA_AUTH request and the GCKS takes it into account. Finally GSA_AUTH request and the GCKS takes it into account. Finally the KD
the KD is parsed providing the keying material for the TEK and/or are parsed providing the keying material for the TEK and/or KEK. The
KEK. The GM interprets the KD key packets, where each key packet GM interprets the KD key packets, where each key packet includes the
includes the keying material for SAs distributed in the GSA payload. keying material for SAs distributed in the GSA payload. Keying
material is matched by comparing the SPIs in the key packets to SPIs
Keying material is matched by comparing the SPIs in the key packets previously included in the GSA payloads. Once TEK keys and policy
to SPIs previously included in the GSA payloads. Once TEK keys and are matched, the GM provides them to the data security subsystem, and
policy are matched, the GM provides them to the data security it is ready to send or receive packets matching the TEK policy.
subsystem, and it is ready to send or receive packets matching the
TEK policy.
The GSA KEK policy MUST include KEK attribute KEK_MESSAGE_ID with a The GSA KEK policy MUST include the attribute GSA_INITIAL_MESSAGE_ID
Message ID. The Message ID in the KEK_MESSAGE_ID attribute MUST be with a first Message ID the GM should expect to receive if it is non-
checked against any previously received Message ID for this group. zero. The value of the attribute MUST be checked by a GM against any
If it is less than the previously received number, it should be previously received Message ID for this group. If it is less than
considered stale and ignored. This could happen if two GSA_AUTH the previously received number, it should be considered stale and
exchanges happened in parallel, and the Message ID changed. This ignored. This could happen if two GSA_AUTH exchanges happened in
KEK_MESSAGE_ID is used by the GM to prevent GSA_REKEY message replay parallel, and the Message ID changed. This attribute is used by the
attacks. The first GSA_REKEY message that the GM receives from the GM to prevent GSA_REKEY message replay attacks. The first GSA_REKEY
GCKS must have a Message ID greater or equal to the Message ID message that the GM receives from the GCKS must have a Message ID
received in the KEK_MESSAGE_ID attribute. greater or equal to the Message ID received in the
GSA_INITIAL_MESSAGE_ID attribute.
Once a GM has received GSA_REKEY policy during a registration the IKE Once a GM has received GSA_REKEY policy during a registration the IKE
SA may be closed. However, the GM SHOULD NOT close IKE SA, it is the SA may be closed. However, the GM SHOULD NOT close IKE SA, it is the
GCKS who makes the decision whether to close or keep it, because GCKS who makes the decision whether to close or keep it, because
depending on the policy the IKE SA may be used for inband rekeying depending on the policy the IKE SA may be used for inband rekeying
for small groups. for small groups.
1.4.4. GCKS Registration Operations 1.4.4. GCKS Registration Operations
A G-IKEv2 GCKS passively listens for incoming requests from group A G-IKEv2 GCKS passively listens for incoming requests from group
skipping to change at page 11, line 46 skipping to change at page 12, line 23
member using the same procedures as in the IKEv2 IKE_AUTH. The GCKS member using the same procedures as in the IKEv2 IKE_AUTH. The GCKS
then authorizes the group member according to group policy before then authorizes the group member according to group policy before
preparing to send the GSA_AUTH response. If the GCKS fails to preparing to send the GSA_AUTH response. If the GCKS fails to
authorize the GM, it will respond with an AUTHORIZATION_FAILED notify authorize the GM, it will respond with an AUTHORIZATION_FAILED notify
message. message.
The GSA_AUTH response will include the group policy in the GSA 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 payload and keys in the KD payload. If the GCKS policy includes a
group rekey option, this policy is constructed in the GSA KEK and the group rekey option, this policy is constructed in the GSA KEK and the
key is constructed in the KD KEK. The GSA KEK MUST include the key is constructed in the KD KEK. The GSA KEK MUST include the
KEK_MESSAGE_ID attribute, specifying the starting Message ID the GCKS GSA_INITIAL_MESSAGE_ID attribute, specifying the starting Message ID
will use when sending the GSA_REKEY message to the group member. the GCKS will use when sending the GSA_REKEY message to the group
This Message ID is used to prevent GSA_REKEY message replay attacks member if this Message ID is non-zero. This Message ID is used to
and will be increased each time a GSA_REKEY message is sent to the prevent GSA_REKEY message replay attacks and will be increased each
group. The GCKS data traffic policy is included in the GSA TEK and time a GSA_REKEY message is sent to the group. The GCKS data traffic
keys are included in the KD TEK. The GSA GAP MAY also be included to policy is included in the GSA TEK and keys are included in the KD
provide the ATD and/or DTD (Section 2.4.4.1) specifying activation TEK. The GAP MAY also be included to provide the ATD and/or DTD
and deactivation delays for SAs generated from the TEKs. If the (Section 3.4.3.1) specifying activation and deactivation delays for
group member has indicated that it is a sender of data traffic and SAs generated from the TEKs. If the group member has indicated that
one or more Data Security SAs distributed in the GSA payload included it is a sender of data traffic and one or more Data Security SAs
a counter mode of operation, the GCKS responds with one or more SIDs distributed in the GSA payload included a counter mode of operation,
(see Section 1.4.6). the GCKS responds with one or more SIDs (see Section 1.4.6).
If the GCKS receives a GSA_REGISTRATION exchange with a request to 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 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 the new group (IDg) and respond with the corresponding group policy
and keys. If the GCKS fails to authorize the GM, it will respond and keys. If the GCKS fails to authorize the GM, it will respond
with the AUTHORIZATION_FAILED notification. with the AUTHORIZATION_FAILED notification.
If a group member includes an SAg in its GSA_AUTH or GSA_REGISTRATION If a group member includes an SAg in its GSA_AUTH or GSA_REGISTRATION
request, the GCKS MAY evaluate it according to an implementation request, the GCKS MAY evaluate it according to an implementation
specific policy. specific policy.
skipping to change at page 13, line 5 skipping to change at page 13, line 32
1.4.5. Group Maintenance Channel 1.4.5. Group Maintenance Channel
The GCKS is responsible for rekeying the secure group per the group The GCKS is responsible for rekeying the secure group per the group
policy. Rekeying is an operation whereby the GCKS provides policy. Rekeying is an operation whereby the GCKS provides
replacement TEKs and KEK, deleting TEKs, and/or excluding group replacement TEKs and KEK, deleting TEKs, and/or excluding group
members. The GCKS may initiate a rekey message if group membership members. The GCKS may initiate a rekey message if group membership
and/or policy has changed, or if the keys are about to expire. Two and/or policy has changed, or if the keys are about to expire. Two
forms of group maintenance channels are provided in G-IKEv2 to push forms of group maintenance channels are provided in G-IKEv2 to push
new policy to group members. new policy to group members.
GSA_REKEY The GSA_REKEY exchange is an exchange initiated by the GSA_REKEY The GSA_REKEY is a pseudo-exchange initiated by the GCKS,
GCKS, where the rekey policy is usually delivered to group members where the rekey policy is usually delivered to group members using
using IP multicast as a transport. This is valuable for large and IP multicast as a transport. This is not a real IKEv2 exchange,
dynamic groups, and where policy may change frequently and an since no response messages are sent. This method is valuable for
scalable rekeying method is required. When the GSA_REKEY exchange large and dynamic groups, and where policy may change frequently
is used, the IKEv2 SA protecting the member registration exchanges and a scalable rekeying method is required. When the GSA_REKEY is
is terminated, and group members await policy changes from the used, the IKEv2 SA protecting the member registration exchanges is
GCKS via the GSA_REKEY exchange. usually terminated, and group members await policy changes from
the GCKS via the GSA_REKEY messages.
GSA_INBAND_REKEY The GSA_INBAND_REKEY exchange is a rekey method GSA_INBAND_REKEY The GSA_INBAND_REKEY is a normal IKEv2 exchange
using the IKEv2 SA that was setup to protecting the member using the IKEv2 SA that was setup to protecting the member
registration exchange. This exchange allows the GCKS to rekey registration exchange. This exchange allows the GCKS to rekey
without using an independent GSA_REKEY exchange. The without using an independent GSA_REKEY pseudo-exchange. The
GSA_INBAND_REKEY exchange is useful when G-IKEv2 is used with a GSA_INBAND_REKEY exchange provides a reliable policy delivery and
small group of cooperating devices. is useful when G-IKEv2 is used with a small group of cooperating
devices.
1.4.5.1. GSA_REKEY Exchange Depending on the policy the GCKS may combine these two methods. For
example, it may use the GSA_INBAND_REKEY to deliver key to the GMs in
the group acting as senders (as this would provide reliable keys
delivery), and the GSA_REKEY for the rest GMs.
1.4.5.1. GSA_REKEY
The GCKS initiates the G-IKEv2 Rekey securely, usually using IP The GCKS initiates the G-IKEv2 Rekey securely, usually using IP
multicast. Since this rekey does not require a response and it sends multicast. Since this rekey does not require a response and it sends
to multiple GMs, G-IKEv2 rekeying MUST NOT support IKE SA windowing. to multiple GMs, G-IKEv2 rekeying MUST NOT support IKE SA windowing.
The GCKS rekey message replaces the rekey GSA KEK or KEK array, and/ The GCKS rekey message replaces the rekey GSA KEK or KEK array, and/
or creates a new Data-Security GSA TEK. The SID Download attribute or creates a new Data-Security GSA TEK. The SID Download attribute
in the Key Download payload (defined in Section 2.5.4) MUST NOT be in the Key Download payload (defined in Section 3.5.3.2) MUST NOT be
part of the Rekey Exchange as this is sender specific information and part of the Rekey Exchange as this is sender specific information and
the Rekey Exchange is group specific. The GCKS initiates the the Rekey Exchange is group specific. The GCKS initiates the
GSA_REKEY exchange as following: GSA_REKEY pseudo-exchange as following:
Members (Responder) GCKS (Initiator) Members (Responder) GCKS (Initiator)
-------------------- ------------------ -------------------- ------------------
<-- HDR, SK { GSA, KD, [D,] [AUTH] } <-- HDR, SK{GSA, KD, [N,] [D,] [AUTH]}
Figure 9: GSA_REKEY Exchange Figure 9: GSA_REKEY Pseudo-Exchange
HDR is defined in Section 2.1. The Message ID in this message will HDR is defined in Section 3.1. The Message ID in this message will
start with the same value the GCKS sent to the group members in the start with the value the GCKS sent to the group members in the KEK
KEK attribute KEK_MESSAGE_ID during registration; this Message ID attribute GSA_INITIAL_MESSAGE_ID or from zero if this attribute
will be increased each time a new GSA_REKEY message is sent to the wasn't sent. The Message ID will be incremented each time a new
group members. GSA_REKEY message is sent to the group members.
The GSA payload contains the current rekey and data security SAs. The GSA payload contains the current rekey and data security SAs.
The GSA may contain a new rekey SA and/or a new data security SA, The GSA may contain a new rekey SA and/or a new data security SA
which, optionally contains an LKH rekey SA, Section 2.4. Section 3.4.
The KD payload contains the keys for the policy included in the GSA. The KD payload contains the keys for the policy included in the GSA.
If the data security SA is being refreshed in this rekey message, the If the data security SA is being refreshed in this rekey message, the
IPsec keys are updated in the KD, and/or if the rekey SA is being IPsec keys are updated in the KD, and/or if the rekey SA is being
refreshed in this rekey message, the rekey Key or the LKH KEK array refreshed in this rekey message, the rekey Key or the LKH KEK array
is updated in the KD payload. is updated in the KD payload.
A Delete payload MAY be included to instruct the GM to delete A Delete payload MAY be included to instruct the GM to delete
existing SAs. existing SAs.
The AUTH payload MUST be included to authenticate the GSA_REKEY The AUTH payload MUST be included to authenticate the GSA_REKEY
message if the authentication method is based on public key message if the authentication method is based on public key
signatures and MUST NOT be included if it is based on shared secret. signatures or a dedicated shared secret and MUST NOT be included if
In a latter case, the fact that a GM can decrypt the GSA_REKEY authentication is implicit. In a latter case, the fact that a GM can
message and verify its ICV proves that the sender of this message decrypt the GSA_REKEY message and verify its ICV proves that the
knows the current KEK, thus authenticating that the sender is a sender of this message knows the current KEK, thus authenticating
member of the group. Shared secret authentication doesen't provide that the sender is a member of the group. Shared secret and implicit
source origin authentication. For this reason using it as authentication don't provide source origin authentication. For this
authentication method for multicast Rekey is NOT RECOMMENDED unless reason using them as authentication methods for GSA_REKEY is NOT
source origin authentication is not required (for example, in a small RECOMMENDED unless source origin authentication is not required (for
group of highly trusted GMs). If AUTH payload is included then the example, in a small group of highly trusted GMs). If AUTH payload is
Auth Method field MUST be one specifying using digital signatures. included then the Auth Method field MUST NOT be NULL Authentication.
During group member registration, the GCKS sends the authentication During group member registration, the GCKS sends the authentication
key in the GSA KEK payload, KEK_AUTH_KEY attribute, which the group key in the GSA KEK payload, AUTH_KEY attribute, which the group
member uses to authenticate the key server. Before the current member uses to authenticate the key server. Before the current
Authentication Key expires, the GCKS will send a new KEK_AUTH_KEY to Authentication Key expires, the GCKS will send a new AUTH_KEY to the
the group members in a GSA_REKEY message. The AUTH key that is used group members in a GSA_REKEY message. The AUTH key that is used in
in the rekey message may be not the same as the authentication key the rekey message may be not the same as the authentication key used
used in GSA_AUTH. in GSA_AUTH. If implicit authentication is used, then AUTH_KEY MUST
NOT be sent to GMs.
1.4.5.1.1. GSA_REKEY GCKS Operations 1.4.5.1.1. GSA_REKEY Messages Authentication
The content of the AUTH payload depends on the authentication method
and is either a digital signature or a result of prf applied to the
content of the not yet encrypted GSA_REKEY message.
The authentication algorithm (prf or digital signing) is applied to
the concatenation of two chunks: A and P. The chunk A lasts from the
first octet of the G-IKEv2 Header (not including prepended four
octets of zeros, if port 4500 is used) to the last octet of the
Encrypted Payload header. The chunk P consists of the not yet
encrypted content of the Encrypted payload, excluding the
Initialization Vector, the Padding, the Pad Length and the Integrity
Checksum Data fields (see 3.14 of [RFC7296] for description of the
Encrypted payload). In other words, the P chunk is the inner
payloads of the Encrypted payload in plaintext form. These inner
payloads must be fully formed and ready for encryption except for the
AUTH payload. Figure 10 illustrates the layout of the P and A chunks
in the GSA_REKEY message.
The AUTH payload must have correct values in the Payload Header, the
Auth Method and the RESERVED fields. The Authentication Data field
is zeroed, but if Digital Signature authentication method is in use,
then the ASN.1 Length and the AlgorithmIdentifier fields must be
properly filled in, see [RFC7427].
For the purpose of the AUTH payload 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 and Padding (along
with Pad Length field). In other words, the Length field in the IKE
header (denoted as AdjustedLen in Figure 10 ) 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) is set to the
length of P plus the size of the Payload header (four octets).
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
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ^ ^
| G-IKEv2 SA Initiator's SPI | | |
| | | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ I |
| G-IKEv2 SA Responder's SPI | K |
| | E |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |
| Next Payload | MjVer | MnVer | Exchange Type | Flags | H A
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ d |
| Message ID | r |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | |
| AdjustedLeng | | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ v |
| Next Payload |C| RESERVED | AdjustedPldLen | | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ E v
| Initialization Vector | n
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ c ^
| | r |
~ Inner payloads (not yet encrypted) ~ P
| | P |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ l v
| Padding (0-255 octets) | Pad Length | d
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |
~ Integrity Checksum Data ~ |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ v
Figure 10: Data to Authenticate in the GSA_REKEY Messages
The authentication data is calculated using the authentication
algorithm from the Authentication Method transform and the key
provided before in the AUTH_KEY attribute. Depending on the
authentication method the authentication data is either a digital
signature or a result of applying prf from the Pseudorandom Function
transform. 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 SKe/SKa keys.
The calculation of authentication data MUST be applied to whole
messages 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 Fragment Number
equal to 1).
1.4.5.1.2. GSA_REKEY GCKS Operations
The GCKS builds the rekey message with a Message ID value that is one The GCKS builds the rekey message with a Message ID value that is one
greater than the value included in the previous rekey. If the greater than the value included in the previous rekey. If the
message is using a new KEK attribute, the Message ID is reset to 1 in message is using a new KEK attribute, the Message ID is reset to 0 in
this message. The GSA, KD, and D payloads follow with the same this message. The GSA, KD, N and D payloads follow with the same
characteristics as in the GSA Registration exchange. characteristics as in the GSA Registration exchange.
If present the AUTH payload is created as follows. First the message The AUTH payload (if present) is created as defined in
is prepared, all payloads are formed and included in the message, but Section 1.4.5.1.1.
the content of the Encrypted payload is not yet encrypted. However,
the Encrypted payload must be fully formed, including correct values
in IV, Padding and Pad Length and fields. The AUTH payload is
included in the message with the correct values in the Payload Header
(including Next Payload, Payload Length and Auth Method fields). The
Authentication Data field is zeroed for the purposes of signature
calculation, but if Digiatal Signature authentication method is in
use, then the ASN.1 Length and the AlgorithmIdentifier fields must be
properly filled in, see [RFC7427]. The signature is computed using
the signature algorithm from the KEK_AUTH_METHOD attribute (along
with the KEK_AUTH_HASH if KEK_AUTH_METHOD is not Digital Signature)
and the private key corresponding to the public key from the
KEK_AUTH_KEY attribute. It is computed over the block of data
starting from the first octet of IKE Header (but non including non-
ESP marker if it is present) to the last octet of the (not yet
encrypted) Encrypted Payload (i.e. up to and including Pad Length
field). Then the signature is placed into the Signature Value of the
AUTH payload, the content of the Encrypted payload is encrypted and
the ICV is computed using current KEK keys.
Because GSA_REKEY messages are not acknowledged and could be Because GSA_REKEY messages are not acknowledged and could be
discarded by the network, one or more GMs may not receive the discarded by the network, one or more GMs may not receive the
message. To mitigate such lost messages, during a rekey event the message. To mitigate such lost messages, during a rekey event the
GCKS may transmit several GSA_REKEY messages with the new policy. GCKS may transmit several GSA_REKEY messages with the new policy.
The retransmitted messages MUST be bitwise identical and SHOULD be The retransmitted messages MUST be bitwise identical and SHOULD be
sent within a short time interval (a few seconds) to ensure that sent within a short time interval (a few seconds) to ensure that
time-to-live would not not substantially skewed for the GMs that time-to-live would not be substantially skewed for the GMs that would
would receive different copies of the messages. receive different copies of the messages.
GCKS may also include one or several KEK_NEXT_SPI/TEK_NEXT_SPI GCKS may also include one or several GSA_NEXT_SPI attributes
attributes specifying SPIs for the prospected rekeys, so that specifying SPIs for the prospected rekeys, so that listening GMs are
listening GMs are able to detect lost rekey messages and recover from able to detect lost rekey messages and recover from this situation.
this situation. See Sections Section 2.4.2.1.6 and Section 2.4.3.1.4 See Sections Section 3.4.2.2.3 for more detail.
for more detail.
1.4.5.1.2. GSA_REKEY GM Operations 1.4.5.1.3. GSA_REKEY GM Operations
When a group member receives the Rekey Message from the GCKS it When a group member receives the Rekey Message from the GCKS it
decrypts the message using the current KEK, validates the signature decrypts the message using the current KEK, validates its
using the public key retrieved in a previous G-IKEv2 exchange if AUTH authenticity using the key retrieved in a previous G-IKEv2 exchange
payload is present, verifies the Message ID, and processes the GSA if AUTH payload is present, verifies the Message ID, and processes
and KD payloads. The group member then downloads the new data the GSA and KD payloads. The group member then downloads the new
security SA and/or new Rekey SA. The parsing of the payloads is data security SA and/or new rekey SA. The parsing of the payloads is
identical to the parsing done in the registration exchange. identical to the parsing done in the registration exchange.
Replay protection is achieved by a group member rejecting a GSA_REKEY Replay protection is achieved by a group member rejecting a GSA_REKEY
message which has a Message ID smaller than the current Message ID message which has a Message ID smaller than the current Message ID
that the GM is expecting. The GM expects the Message ID in the first that the GM is expecting. The GM expects the Message ID in the first
GSA_REKEY message it receives to be equal or greater than the message GSA_REKEY message it receives to be equal or greater than the Message
id it receives in the KEK_MESSAGE_ID attribute. The GM expects the ID it receives in the GSA_INITIAL_MESSAGE_ID attribute. Note, that
message ID in subsequent GSA_REKEY messages to be greater than the if no this attribute was 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. last valid GSA_REKEY message ID it received.
If the GSA payload includes a Data-Security SA including a counter- If the GSA payload includes a Data-Security SA including a counter-
modes of operation and the receiving group member is a sender for modes of operation and the receiving group member is a sender for
that SA, the group member uses its current SID value with the Data- that SA, the group member uses its current SID value with the Data-
Security SAs to create counter-mode nonces. If it is a sender and Security SAs to create counter-mode nonces. If it is a sender and
does not hold a current SID value, it MUST NOT install the Data- does not hold a current SID value, it MUST NOT install the Data-
Security SAs. It MAY initiate a GSA_REGISTRATION exchange to the Security SAs. It MAY initiate a GSA_REGISTRATION exchange to the
GCKS in order to obtain an SID value (along with current group GCKS in order to obtain an SID value (along with current group
policy). policy).
Once a new Rekey SA is installed as a result of GSA_REKEY message, Once a new Rekey SA is installed as a result of GSA_REKEY message,
the current Rekey SA (over which the message was received) MUST be the current Rekey SA (over which the message was received) MUST be
silently deleted after waiting DEACTIVATION_TIME_DELAY interval silently deleted after waiting DEACTIVATION_TIME_DELAY interval
regardless of its expiration time. If the GSA TEK payload includes regardless of its expiration time. If the GSA TEK payload includes
TEK_REKEY_SPI attribute then after installing a new Data-Security SA GSA_REKEY_SPI attribute then after installing a new Data-Security SA
the old one, identified by the SPI in this attribute, MUST be the old one, identified by the SPI in this attribute, MUST be
silently deleted after waiting DEACTIVATION_TIME_DELAY interval silently deleted after waiting DEACTIVATION_TIME_DELAY interval
regardless of its expiration time. regardless of its expiration time.
If a Data-Security SA is not rekeyed yet and is about to expire (a 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 "soft lifetime" expiration is described in Section 4.4.2.1 of
[RFC4301]), the GM SHOULD initiate a registration to the GCKS. This [RFC4301]), the GM SHOULD initiate a registration to the GCKS. This
registration serves as a request for current SAs, and will result in registration serves as a request for current SAs, and will result in
the download of replacement SAs, assuming the GCKS policy has created the download of replacement SAs, assuming the GCKS policy has created
them. A GM SHOULD also initiate a registration request if a Rekey SA 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. is about to expire and not yet replaced with a new one.
1.4.5.1.3. Forward and Backward Access Control 1.4.5.1.4. IKE Fragmentation
Through the G-IKEv2 rekey, G-IKEv2 supports algorithms such as 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).
An unrelated notion to PFS, "forward access control" and "backward
access control" have been called "perfect forward security" and
"perfect backward security" in the literature [RFC2627].
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, but are not specified as a part of this
document.
Support for group management algorithms are supported via the
KEY_MANAGEMENT_ALGORITHM attribute which is sent in the GSA KEK
policy. G-IKEv2 specifies one method by which LKH can be used for
forward and backward access control. Other methods of using LKH, as
well as other group management algorithms such as OFT or Subset
Difference may be added to G-IKEv2 as part of a later document.
1.4.5.1.3.1. Forward Access Control Requirements
When group membership is altered using a group management algorithm
new GSA TEKs (and their associated keys) are usually also needed.
New GSAs 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, new GSA
TEKs and the associated key packets in the KD payload MUST NOT be
included in a G-IKEv2 rekey message which changes group membership.
This is required because the GSA TEK policy and the associated key
packets in the KD payload are not protected with the new KEK. A
second G-IKEv2 rekey message can deliver the new GSA TEKS and their
associated key packets because it will be protected with the new 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 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.
1.4.5.1.4. Fragmentation
IKE fragmentation [RFC7383] can be used to perform fragmentation of IKE fragmentation [RFC7383] can be used to perform fragmentation of
large GSA_REKEY messages, however when the GSA_REKEY message is large GSA_REKEY messages, however when the GSA_REKEY message is
emitted as an IP multicast packet there is a lack of response from emitted as an IP multicast packet there is a lack of response from
the GMs. This has the following implications. the GMs. This has the following implications.
o Policy regarding the use of IKE fragmentation is implicit. If a o Policy regarding the use of IKE fragmentation is implicit. If a
GCKS detects that all GMs have negotiated support of IKE GCKS detects that all GMs have negotiated support of IKE
fragmentation in IKE_SA_INIT, then it MAY use IKE fragmentation on fragmentation in IKE_SA_INIT, then it MAY use IKE fragmentation on
large GSA_REKEY exchange messages. large GSA_REKEY messages.
o The GCKS must always use IKE fragmentation based on a known o The GCKS must always use IKE fragmentation based on a known
fragmentation threshold (unspecified in this memo), as there is no fragmentation threshold (unspecified in this memo), as there is no
way to check if fragmentation is needed by first sending way to check if fragmentation is needed by first sending
unfragmented messages and waiting for response. unfragmented messages and waiting for response.
o PMTU probing cannot be performed due to lack of GSA_REKEY response o PMTU probing cannot be performed due to lack of GSA_REKEY response
message. message.
1.4.5.2. GSA_INBAND_REKEY Exchange 1.4.5.2. GSA_INBAND_REKEY Exchange
When the IKEv2 SA protecting the member registration exchange is When the IKEv2 SA protecting the member registration exchange is
maintained while group member participates in the group, the GCKS can maintained while group member participates in the group, the GCKS can
use the GSA_INBAND_REKEY exchange to individually provide policy use the GSA_INBAND_REKEY exchange to individually provide policy
updates to the group member. updates to the group member.
Member (Responder) GCKS (Initiator) Member (Responder) GCKS (Initiator)
-------------------- ------------------ -------------------- ------------------
<-- HDR, SK { GSA, KD, [D,] } <-- HDR, SK{GSA, KD, [N,] [D]}
HDR, SK {} --> HDR, SK{} -->
Figure 10: GSA_INBAND_REKEY Exchange Figure 11: GSA_INBAND_REKEY Exchange
Because this is an IKEv2 exchange, the HDR is treated as defined in Because this is a normal IKEv2 exchange, the HDR is treated as
[RFC7296]. defined in [RFC7296].
1.4.5.2.1. GSA_INBAND_REKEY GCKS Operations 1.4.5.2.1. GSA_INBAND_REKEY GCKS Operations
The GSA, KD, and D payloads are built in the same manner as in a The GSA, KD, N and D payloads are built in the same manner as in a
registration exchange. registration exchange.
1.4.5.2.2. GSA_INBAND_REKEY GM Operations 1.4.5.2.2. GSA_INBAND_REKEY GM Operations
The GM processes the GSA, KD, and D payloads in the same manner as if The GM processes the GSA, KD, N and D payloads in the same manner as
they were received in a registration exchange. if they were received in a registration exchange.
1.4.5.3. Deletion of SAs 1.4.5.3. Deletion of SAs
There are occasions when the GCKS may want to signal to group members There are occasions when the GCKS may want to signal to group members
to delete policy at the end of a broadcast, or if group policy has to delete policy at the end of a broadcast, or if group policy has
changed. Deletion of keys MAY be accomplished by sending the G-IKEv2 changed. Deletion of keys MAY be accomplished by sending the G-IKEv2
Delete Payload [RFC7296], section 3.11 as part of the GSA_REKEY Delete Payload [RFC7296], section 3.11 as part of the GSA_REKEY
Exchange as shown below. pseudo-exchange as shown below.
Members (Responder) GCKS (Initiator) Members (Responder) GCKS (Initiator)
-------------------- ------------------ -------------------- ------------------
<-- HDR, SK { [GSA ], [KD ], [D, ] [AUTH ] } <-- HDR, SK{[GSA,] [KD,], [N] [D,] [AUTH]}
Figure 11: SA Deletion in GSA_REKEY Figure 12: SA Deletion in GSA_REKEY
The GSA MAY specify the remaining active time of the remaining policy The GSA MAY specify the remaining active time of the remaining policy
by using the DTD attribute in the GSA GAP. If a GCKS has no further by using the DTD attribute in the GSA GAP. If a GCKS has no further
SAs to send to group members, the GSA and KD payloads MUST be omitted SAs to send to group members, the GSA and KD payloads MUST be omitted
from the message. There may be circumstances where the GCKS may want from the message. There may be circumstances where the GCKS may want
to start over with a clean slate. If the administrator is no longer to start over with a clean state. If the administrator is no longer
confident in the integrity of the group, the GCKS can signal deletion confident in the integrity of the group, the GCKS can signal deletion
of all the policies of a particular TEK protocol by sending a TEK of all the policies of a particular TEK protocol by sending a TEK
with a SPI value equal to zero in the delete payload. For example, with a SPI value equal to zero in the delete payload. For example,
if the GCKS wishes to remove all the KEKs and all the TEKs in the if the GCKS wishes to remove all the KEKs and all the TEKs in the
group, the GCKS SHOULD send a Delete payload with a SPI of zero and a group, the GCKS SHOULD send a Delete payload with a SPI of zero and
protocol_id of a TEK protocol_id value defined in Section 2.4.3, Protocol ID of AH or ESP, followed by another Delete payload with a
followed by another Delete payload with a SPI of zero and protocol_id SPI of zero and Protocol ID of GIKE_REKEY, indicating that the KEK SA
of zero, indicating that the KEK SA should be deleted. should be deleted.
1.4.6. Counter-based modes of operation 1.4.6. Counter-based modes of operation
Several new counter-based modes of operation have been specified for Several new counter-based modes of operation have been specified for
ESP (e.g., AES-CTR [RFC3686], AES-GCM [RFC4106], AES-CCM [RFC4309], ESP (e.g., AES-CTR [RFC3686], AES-GCM [RFC4106], AES-CCM [RFC4309],
AES-GMAC [RFC4543]) and AH (e.g., AES-GMAC [RFC4543]). These ChaCha20-Poly1305 [RFC7634], AES-GMAC [RFC4543]) and AH (e.g., AES-
counter-based modes require that no two senders in the group ever GMAC [RFC4543]). These counter-based modes require that no two
send a packet with the same Initialization Vector (IV) using the same senders in the group ever send a packet with the same Initialization
cipher key and mode. This requirement is met in G-IKEv2 when the Vector (IV) using the same cipher key and mode. This requirement is
following requirements are met: met in G-IKEv2 when the following requirements are met:
o The GCKS distributes a unique key for each Data-Security SA. o The GCKS distributes a unique key for each Data-Security SA.
o The GCKS uses the method described in [RFC6054], which assigns each o The GCKS uses the method described in [RFC6054], which assigns
sender a portion of the IV space by provisioning each sender with one each sender a portion of the IV space by provisioning each sender
or more unique SID values. with one or more unique SID values.
1.4.6.1. Allocation of SIDs 1.4.6.1. Allocation of SIDs
When at least one Data-Security SA included in the group policy When at least one Data-Security SA included in the group policy
includes a counter-based mode of operation, the GCKS automatically includes a counter-based mode of operation, the GCKS automatically
allocates and distributes one SID to each group member acting in the allocates and distributes one SID to each group member acting in the
role of sender on the Data-Security SA. The SID value is used role of sender on the Data-Security SA. The SID value is used
exclusively by the group member to which it was allocated. The group exclusively by the group member to which it was allocated. The group
member uses the same SID for each Data-Security SA specifying the use member uses the same SID for each Data-Security SA specifying the use
of a counter-based mode of operation. A GCKS MUST distribute unique of a counter-based mode of operation. A GCKS MUST distribute unique
skipping to change at page 20, line 10 skipping to change at page 21, line 14
than one SID and use them serially. This could be useful when it is than one SID and use them serially. This could be useful when it is
anticipated that the group member will exhaust their range of Data- anticipated that the group member will exhaust their range of Data-
Security SA nonces using a single SID too quickly (e.g., before the Security SA nonces using a single SID too quickly (e.g., before the
time-based policy in the TEK expires). time-based policy in the TEK expires).
When the group policy includes a counter-based mode of operation, a When the group policy includes a counter-based mode of operation, a
GCKS SHOULD use the following method to allocate SID values, which GCKS SHOULD use the following method to allocate SID values, which
ensures that each SID will be allocated to just one group member. ensures that each SID will be allocated to just one group member.
1. A GCKS maintains an SID-counter, which records the SIDs that have 1. A GCKS maintains an SID-counter, which records the SIDs that have
been allocated. SIDs are allocated sequentially, with zero as the been allocated. SIDs are allocated sequentially, with zero as
first allocated SID. the first allocated SID.
2. Each time an SID is allocated, the current value of the counter 2. Each time an SID is allocated, the current value of the counter
is saved and allocated to the group member. The SID-counter is then is saved and allocated to the group member. The SID-counter is
incremented in preparation for the next allocation. then incremented in preparation for the next allocation.
3. When the GCKS specifies a counter-based mode of operation in the 3. When the GCKS specifies a counter-based mode of operation in the
Data Security SA a group member may request a count of SIDs during data security SA a group member may request a count of SIDs
registration in a Notify payload information of type SENDER. When during registration in a Notify payload information of type
the GCKS receives this request, it increments the SID-counter once SENDER. When the GCKS receives this request, it increments the
for each requested SID, and distributes each SID value to the group SID-counter once for each requested SID, and distributes each SID
member. The GCKS SHOULD have a policy-defined upper bound for the value to the group member. The GCKS SHOULD have a policy-defined
number of SIDs that it will return irrespective of the number upper bound for the number of SIDs that it will return
requested by the GM. irrespective of the number requested by the GM.
4. A GCKS allocates new SID values for each GSA_REGISTRATION 4. A GCKS allocates new SID values for each GSA_REGISTRATION
exchange originated by a sender, regardless of whether a group member exchange originated by a sender, regardless of whether a group
had previously contacted the GCKS. In this way, the GCKS is not member had previously contacted the GCKS. In this way, the GCKS
required to maintaining a record of which SID values it had is not required to maintaining a record of which SID values it
previously allocated to each group member. More importantly, since had previously allocated to each group member. More importantly,
the GCKS cannot reliably detect whether the group member had sent since the GCKS cannot reliably detect whether the group member
data on the current group Data-Security SAs it does not know what had sent data on the current group Data-Security SAs it does not
Data-Security counter-mode nonce values that a group member has used. know what Data-Security counter-mode nonce values that a group
By distributing new SID values, the key server ensures that each time member has used. By distributing new SID values, the key server
a conforming group member installs a Data-Security SA it will use a ensures that each time a conforming group member installs a Data-
unique set of counter-based mode nonces. Security SA it will use a unique set of counter-based mode
nonces.
5. When the SID-counter maintained by the GCKS reaches its final SID 5. When the SID-counter maintained by the GCKS reaches its final SID
value, no more SID values can be distributed. Before distributing value, no more SID values can be distributed. Before
any new SID values, the GCKS MUST delete the Data-Security SAs for distributing any new SID values, the GCKS MUST delete the Data-
the group, followed by creation of new Data-Security SAs, and Security SAs for the group, followed by creation of new Data-
resetting the SID-counter to its initial value. Security SAs, and resetting the SID-counter to its initial value.
6. The GCKS SHOULD send a GSA_REKEY message deleting all Data- 6. The GCKS SHOULD send a GSA_REKEY message deleting all Data-
Security SAs and the Rekey SA for the group. This will result in the Security SAs and the Rekey SA for the group. This will result in
group members initiating a new GSA_REGISTRATION exchange, in which the group members initiating a new GSA_REGISTRATION exchange, in
they will receive both new SID values and new Data-Security SAs. The which they will receive both new SID values and new Data-Security
new SID values can safely be used because they are only used with the SAs. The new SID values can safely be used because they are only
new Data-Security SAs. Note that deletion of the Rekey SA is used with the new Data-Security SAs. Note that deletion of the
necessary to ensure that group members receiving a GSA_REKEY exchange Rekey SA is necessary to ensure that group members receiving a
before the re-register do not inadvertently use their old SIDs with GSA_REKEY message before the re-register do not inadvertently use
the new Data-Security SAs. Using the method above, at no time can their old SIDs with the new Data-Security SAs. Using the method
two group members use the same IV values with the same Data-Security above, at no time can two group members use the same IV values
SA key. with the same Data-Security SA key.
1.4.6.2. GM Usage of SIDs 1.4.6.2. GM Usage of SIDs
A GM applies the SID to Data Security SA as follows. A GM applies the SID to data security SA as follows.
1. The most significant bits NUMBER_OF_SID_BITS of the IV are taken
to be the SID field of the IV.
2. The SID is placed in the least significant bits of the SID field,
where any unused most significant bits are set to zero. If the SID
value doesn't fit into the NUMBER_OF_SID_BITS bits, then the GM MUST
treat this as a fatal error and re-register to the group.
1.5. Interaction with IKEv2 Protocol Extensions
IKEv2 defines a number of extensions that can be used to extend
protocol functionality. G-IKEv2 is compatible with most of such
extensions. In particular, EAP authentication defined in [RFC7296]
can be used to establish registration IKE SA, as well as Secure
Password authentication ([RFC6467]). G-IKEv2 is compatible with and
can use IKEv2 Session Resumption [RFC5723] except that a GM would
include the initial ticket request in a GSA_AUTH exchange instead of
an IKE_AUTH exchange. G-IKEv2 is also compatible with Quantum Safe
Key Exchange framework, defined in
[I-D.tjhai-ipsecme-hybrid-qske-ikev2].
Some IKEv2 extensions however require special handling if used in o The most significant bits NUMBER_OF_SID_BITS of the IV are taken
G-IKEv2. to be the SID field of the IV.
1.5.1. Postquantum Preshared Keys for IKEv2 o The SID is placed in the least significant bits of the SID field,
where any unused most significant bits are set to zero. If the
SID value doesn't fit into the NUMBER_OF_SID_BITS bits, then the
GM MUST treat this as a fatal error and re-register to the group.
G-IKEv2 can take advantage of the protection provided by Postquantum 2. Group Key Management and Access Control
Preshared Keys (PPK) for IKEv2 [I-D.ietf-ipsecme-qr-ikev2]. However,
the use of PPK leaves the initial IKE SA susceptible to quantum
computer (QC) attacks. For this reason an alternative approach for
using PPK in IKEv2 defined in [I-D.smyslov-ipsecme-ikev2-qr-alt]
SHOULD be used.
If the alternative approach is not supported by the peers, then the Through the G-IKEv2 rekey, G-IKEv2 supports algorithms such as
GCKS MUST NOT send GSA and KD payloads in the GSA_AUTH response Logical Key Hierarchy (LKH) that have the property of denying access
message. Instead, the GCKS MUST return a new notification to a new group key by a member removed from the group (forward access
REKEY_IS_NEEDED. Upon receiving this notification in the GSA_AUTH control) and to an old group key by a member added to the group
response the GM MUST perform an IKE SA rekey and then initiate a new (backward access control). An unrelated notion to PFS, "forward
GSA_REGISTRATION request for the same group. Below are possible access control" and "backward access control" have been called
scenarios involving using PPK. "perfect forward security" and "perfect backward security" in the
literature [RFC2627].
GM begins IKE_SA_INIT requesting PPK, and GCKS responds with Group management algorithms providing forward and backward access
willingness to do it, or aborts according to its "mandatory_or_not" control other than LKH have been proposed in the literature,
flag: including OFT [OFT] and Subset Difference [NNL]. These algorithms
could be used with G-IKEv2, but are not specified as a part of this
document.
Initiator (Member) Responder (GCKS) The Group Key Management Method transform from the GSA policy
-------------------- ------------------ specifies how members of the group obtain group keys. This document
HDR, SAi1, KEi, Ni, N(USE_PPK) ---> specifies a single method for the group key management - Wrapped Key
<--- HDR, SAr1, KEr, Nr, [CERTREQ], Download. This method assumes that all group keys are sent to the
N(USE_PPK) GMs by the GCKS encrypted with other keys, called Key Wrap Keys
(KWK).
Figure 12: IKE_SA_INIT Exchange requesting using PPK 2.1. Key Wrap Keys
GM begins GSA_AUTH with PPK_ID; if using PPK is not mandatory for the Every GM always knows at least one KWK - the KWK that is associated
GM, N(NO_PPK_AUTH) is included too: with the IKE SA or multicast rekey SA the wrapped keys are sent over.
In this document it is called default KWK and is denoted as SK_w.
Initiator (Member) Responder (GCKS) The GCKS may also send other keys to GMs that will be used as Key
-------------------- ------------------ Wrap Keys for the purpose of building key hierarchy. Each such key
HDR, SK {IDi, AUTH, IDg, is associated with an encryption algorithm from the Encryption
N(PPK_IDENTITY), N(NO_PPK_AUTH) } ---> Algorithm transform used for the SA the key is sent in. The size of
such key MUST be of the size of the key size of this Encryption
Algorithm transform (taking into consideration the Key Length
attribute for this transform if present). This association persists
even if the key is used later in the context of another SA with
possibly different Encryption Algorithm transform.
Figure 13: GSA_AUTH Request using PPK To have an ability to provide forward access control the GCKS
provides each GM with a personal key at the time of registration.
Besides several intermediate keys that form a key hierarchy and are
shared among several GMs are provided by the GCKS.
If GCKS has no such PPK and using PPK is not mandatory for it and 2.1.1. Default Key Wrap Key
N(NO_PPK_AUTH) is included, then the GCKS continues w/o PPK; in this
case no rekey is needed:
Initiator (Member) Responder (GCKS) The default KWK (SK_w) is only used in the context of a single IKE
-------------------- ------------------ SA. Every IKE SA (unicast or group rekey) will have its own SK_w.
<--- HDR, SK { IDr, AUTH, GSA, KD } The SK_w is used with the algorithm from the Encryption Algorithm
transform used for the SA the SK_w is used in. The size of SK_w MUST
be of the key size of this Encryption Algorithm transform (taking
into consideration the Key Length attribute for this transform if
present).
Figure 14: GSA_AUTH Response using no PPK For the unicast IKE SA (used for the GM registration and optionally
for GSA_INBAND_REKEY exchanges) the SK_w is computed as follows:
If GCKS has no such PPK and either N(NO_PPK_AUTH) is missing or using SK_w = prf+(SK_d, "Key Wrap for G-IKEv2")
PPK is mandatory for GCKS, the GCKS aborts the exchange:
Initiator (Member) Responder (GCKS) where the string "Key Wrap for G-IKEv2" is 20 ASCII characters
-------------------- ------------------ without null termination.
<--- HDR, SK { N(AUTHENTICATION_FAILED) }
Figure 15: GSA_AUTH Error Response For the multicast rekey SA the SK_w is provided along with other SA
keys as defined in Section 2.4.
Assuming GCKS has a proper PPK the GCKS continues with request to GM 2.2. GCKS Key Management Semantics
to immediately perform a rekey:
Initiator (Member) Responder (GCKS) Wrapped Key Download method allows the GCKS to employ various key
-------------------- ------------------ management policies.
<--- HDR, SK{IDr, AUTH, N(PPK_IDENTITY),
N(REKEY_IS_NEEDED) }
Figure 16: GSA_AUTH Response using PPK o A simple key management policy - when the GCKS always sends group
SA keys encrypted with the SK_w.
GM initiates CREATE_CHILD_SA to rekey IKE SA and then makes a new o An LKH key management policy - when the GCKS provides each GM with
registration request for the same group over the new IKE SA: an individual key at the time of GM registration (encrypted with
SK_w). Then the GCKS forms an hierarchy of keys so that the group
SA keys are encrypted with other keys which are encrypted with
other keys and so on, tracing back to the individual GMs' keys.
Initiator (Member) Responder (GCKS) Other key policies may also be employed by the GCKS.
-------------------- ------------------
HDR, SK {SA, Ni, KEi } --->
<--- HDR, SK {SA, Nr, KEr }
HDR, SK {IDg } --->
<--- HDR, SK { GSA, KD }
Figure 17: Rekeying IKE SA followed by GSA_REGISTRATION Exchange 2.2.1. Forward Access Control Requirements
2. Header and Payload Formats When group membership is altered using a group management algorithm
new GSA TEKs (and their associated keys) are usually also needed.
New GSAs and keys ensure that members who were denied access can no
longer participate in the group.
Refer to IKEv2 [RFC7296] for existing payloads. Some payloads used If forward access control is a desired property of the group, new GSA
in G-IKEv2 exchanges are not aligned to 4-octet boundaries, which is TEKs and the associated key packets in the KD payload MUST NOT be
also the case for some IKEv2 payloads (see Section 3.2 of [RFC7296]). included in a G-IKEv2 rekey message which changes group membership.
This is required because the GSA TEK policy and the associated key
packets in the KD payload are not protected with the new KEK. A
second G-IKEv2 rekey message can deliver the new GSA TEKS and their
associated key packets because it will be protected with the new KEK,
and thus will not be visible to the members who were denied access.
2.1. The G-IKEv2 Header 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 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.
G-IKEv2 uses the same IKE header format as specified in [RFC7296] If other methods of using LKH or other group management algorithms
section 3.1. 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.
Several new payload formats are required in the group security 2.3. GM Key Management Semantics
exchanges.
Next Payload Type Value This specification defines a GM Key Management semantics in such a
----------------- ----- way, that it doesn't depend on the key management policy employed by
Group Identification (IDg) 50 the GCKS. This allows having all the complexity of key management in
Group Security Association (GSA) 51 the GCKS, which is free to implement various key management policies,
Key Download (KD) 52 such as direct transmitting of group SA keys or using some kind of
key hierarchy (e.g. LKH). For all these policies the GMs' behavior
is the same.
New exchange types GSA_AUTH, GSA_REGISTRATION and GSA_REKEY are added Each key is identified by a 32-bit number called Key ID. Zero Key ID
to the IKEv2 [RFC7296] protocol. has a special meaning - it always contains keying material from which
the group SA keys are taken.
Exchange Type Value All keys in G-IKEv2 are transmitted in encrypted form, which format
-------------- ----- is defined in Section 3.5.1. This format specifies a Key ID (ID of a
GSA_AUTH 39 key that is encrypted in this attribute) and a KWK ID (ID of a key
GSA_REGISTRATION 40 that was used to encrypt this attribute). Keys may be encrypted
GSA_REKEY 41 either with default KWK (SK_w) or with other keys, which the GM has
GSA_INBAND_REKEY TBD received in the KEY_WRAP_KEY attributes. If a key was encrypted with
SK_w, then the KWK ID field is set to zero, otherwise the KWK ID
field identifies the key used for encryption.
Major Version is 2 and Minor Version is 0 as in IKEv2 [RFC7296]. IKE When a GM receives a message from the GCKS installing new data
SA Initiator's SPI, IKE SA Responder's SPI, Flags, Message ID, and security or rekey SA, it will contain a KD payload with a SA_KEY
Length are as specified in [RFC7296]. attribute containing keying material for this SA. For a data
security 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 (SK_w) should be used to extract this keying material.
2.2. Group Identification (IDg) Payload For a multicast rekey SA multiple SA_KEY attributes may be present
depending on the key management policy employed by the GCKS. If
multiple SA_KEY attributes are present then all of them MUST contain
the same keying material encrypted using different keys. The GM in
general is unaware of the GCKS's key management policy and can always
use the same procedure to get the keys. In particular, the GM's task
is to find a way to decrypt at least one of the SA_KEY attributes
using either the SK_w or the keys from the KEY_WRAP_KEY attributes
that are present in the same message or were receives in previous
messages.
The IDg Payload allows the group member to indicate which group it We will use the term "Key Path" to describe an ordered sequence of
wants to join. The payload is constructed by using the IKEv2 keys where each subsequent key was used to encrypt the previous one.
Identification Payload (section 3.5 of [RFC7296]). ID type ID_KEY_ID The GM keeps its own Key Path (called working Key Path) in the memory
MUST be supported. ID types ID_IPV4_ADDR, ID_FQDN, ID_RFC822_ADDR, associated with each group it is registered to and update it when
ID_IPV6_ADDR SHOULD be supported. ID types ID_DER_ASN1_DN and needed. When the GSA_REKEY message is received the GM processes the
ID_DER_ASN1_GN are not expected to be used. received SA_KEY attributes one by one trying to construct a new key
path that starts from this attributes and ends with any key in the
working Key Path or with the default KWK (SK_w).
2.3. Security Association - GM Supported Transforms (SAg) In the simplest case the SA_KEY attribute is encrypted with SK_w so
that the new Key Path is empty. If more complex key management
policies are used then the Key Path will contain intermediate keys,
which will be from the KEY_WRAP_KEY attributes received in the same
messages. If the GM is able to construct a new Key Path, then it is
able to decrypt the SA_KEY attribute and use its content to form the
SA keys. If it is unable to build a new Key Path, then in means that
the GM is excluded from the group.
The SAg payload declares which Transforms a GM is willing to accept. Depending on the new Key Path the GM should do the following actions
The payload is constructed using the format of the IKEv2 Security to be prepared for future key updates:
Association payload (section 3.3 of [RFC7296]). The Payload Type for
SAg is identical to the SA Payload Type (33).
2.4. Group Security Association Payload o If the new Key Path is empty then no actions are needed. This may
happen if no KEY_WRAP_KEY attributes from the received message
were used.
The Group Security Association payload is used by the GCKS to assert o If the new Key Path is non-empty and it ends up with the default
security attributes for both Rekey and Data-security SAs. KWK (SK_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
with its personal key and the other keys from the key tree that
are needed for this GM. These keys form an initial working Key
Path.
1 2 3 o In all other cases the new Key Path will end up where some key
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 from the GM's working Key Path was used. In this case the new Key
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Path replaces the part of the GM's working Key Path from the
| Next Payload |C| RESERVED | Payload Length | beginning and up to (but not including) the key that the GM has
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ used to decrypt the last key in the new Key Path.
Figure 18: GSA Payload Format Appendix A contains an example of how this algorithm works in case of
LKH key management policy.
The Security Association Payload fields are defined as follows: 2.4. Group SA Keys
o Next Payload (1 octet) -- Identifies the next payload type for the Group SA keys are downloaded to GMs in the form of keying material.
G-IKEv2 registration or the G-IKEv2 rekey message. The keys are taken from this keying material as if they were
concatenated to form it.
o Critical (1 bit) -- Set according to [RFC7296]. For a data security 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 the encryption key (if any) MUST be taken from the first
bits of the keying material and the integrity key (if any) MUST be
taken from the remaining bits.
o RESERVED (7 bits) -- Must be zero. For a group rekey SA the following keys are taken from the keying
material:
o Payload Length (2 octets) -- Is the octet length of the current SK_e | SK_a | SK_w = KEYMAT
payload including the generic header and all TEK and KEK policies.
2.4.1. GSA Policy where SK_e and SK_a are the keys used for the Encryption Algorithm
and the Integrity Algorithm transforms for the corresponding SA and
SK_w is a default KWK for this SA. Note, that SK_w is also used with
the Encryption Algorithm transform as well as SK_e. Note also, that
if AEAD algorithm is used for encryption, then SK_a key will not be
used (GM can use the formula above assuming the length of SK_a is
zero).
Following the GSA generic payload header are GSA policies for group 3. Header and Payload Formats
rekeying (KEK), data traffic SAs (TEK) and/or Group Associated Policy
(GAP). There may be zero or one GSA KEK policy, zero or one GAP
policies, and zero or more GSA TEK policies, where either one GSA KEK
or GSA TEK payload MUST be present.
This latitude allows various group policies to be accommodated. For The G-IKEv2 is an IKEv2 extension and thus inherits its wire format
example if the group policy does not require the use of a Rekey SA, for data structures. However, the processing of some payloads are
the GCKS would not need to send a GSA KEK attribute to the group different and several new payloads are defined: Group Identification
member since all SA updates would be performed using the Registration (IDg), Group Security Association (GSA) Key Download (KD). New
SA. Alternatively, group policy might use a Rekey SA but choose to exchange types GSA_AUTH, GSA_REGISTRATION, GSA_REKEY and
download a KEK to the group member only as part of the Registration GSA_INBAND_REKEY are also added.
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 This section describes new payloads and the differences in processing
(e.g., video, audio, and text) to be associated with a session, but of existing IKEv2 payloads.
each protected with an individual security association policy.
A GAP payload allows for the distribution of group-wise policy, such 3.1. G-IKEv2 Header
as instructions for when to activate and de-activate SAs.
Policies are distributed in substructures to the GSA payload, and G-IKEv2 uses the same IKE header format as specified in [RFC7296]
include the following header. section 3.1. Major Version is 2 and Minor Version is 0 as in IKEv2.
IKE SA Initiator's SPI, IKE SA Responder's SPI, Flags, Message ID,
and Length are as specified in [RFC7296].
1 2 3 3.2. Group Identification Payload
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | RESERVED | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 19: GSA Policy Generic Header Format 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 3.5 of [RFC7296]).
ID type ID_KEY_ID MUST be supported. ID types ID_IPV4_ADDR, ID_FQDN,
ID_RFC822_ADDR, 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 payload is fifty (50).
The payload fields are defined as follows: 3.3. Security Association - GM Supported Transforms Payload
o Type (1 octet) -- Identifies the substructure type. In the The Security Association - GM Supported Transforms Payload (SAg)
following table the terms Reserved, Unassigned, and Private Use payload declares which Transforms a GM is willing to accept. The
are to be applied as defined in [RFC8126]. The registration payload is constructed using the format of the IKEv2 Security
procedure is Expert Review. Association payload (section 3.3 of [RFC7296]). The Payload Type for
SAg is identical to the SA Payload Type - thirty-three (33).
Type Value 3.4. Group Security Association Payload
-------- -----
Reserved 0
KEK 1
GAP 2
TEK 3
Unassigned 4-127
Private Use 128-255
o RESERVED (1 octet) -- Unused, set to zero. The Group Security Association (GSA) payload is used by the GCKS to
assert security attributes for both Rekey and Data-security SAs. The
Payload Type for the Group Security Association payload is fifty-one
(51).
o Length (2 octets) -- Length in octets of the substructure, 1 2 3
including its header. 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> ~
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
2.4.2. KEK Policy Figure 13: GSA Payload Format
The GSA KEK policy contains security attributes for the KEK method The Security Association Payload fields are defined as follows:
for a group and parameters specific to the G-IKEv2 registration
operation. The source and destination traffic selectors describe the
network identities used for the rekey messages.
1 2 3 o Next Payload, C, RESERVED, Payload Length fields comprise the
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 IKEv2 Generic Payload Header and are defined in Section 3.2. of
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ [RFC7296].
| Type = 1 | RESERVED | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
~ SPI ~
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
~ <Source Traffic Selector> ~
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
~ <Destination Traffic Selector> ~
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
~ <Transform Substructure List> ~
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
~ KEK Attributes ~
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 20: KEK Policy Format o Group Policies (variable) - A set of group policies for the group.
The GSA KEK Payload fields are defined as follows: 3.4.1. Group Policies
o Type = 1 (1 octet) -- Identifies the GSA payload type as KEK in Croup policies are comprised of two types of policy - Group SA (GSA)
the G-IKEv2 registration or the G-IKEv2 rekey message. policy and Group Associated (GA) policy. GSA policy defines
parameters for the Security Association for the group. Depending on
the employed security protocol GSA policies may further be classified
as rekeying SA policy (GSA KEK) and data traffic SA policy (GSA TEK).
GSA payload may contain zero or one GSA KEK policy, zero or more GSA
TEK policies, and zero or one GA policy, where either one GSA KEK or
GSA TEK policy MUST be present.
o RESERVED (1 octet) -- Must be zero. This latitude allows various group policies to be accommodated. For
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 Registration SA.
Alternatively, group policy might use a Rekey SA but choose to
download a KEK to the group member only as part of the Registration
SA. Therefore, the GSA KEK policy would not be necessary as part of
the GSA_REKEY message.
o Length (2 octets) -- Length of this structure including KEK Specifying multiple GSA TEKs allows multiple related data streams
attributes. (e.g., video, audio, and text) to be associated with a session, but
each protected with an individual security association policy.
o SPI (16 octets) -- Security Parameter Index for the rekey message. A GAP allows for the distribution of group-wise policy, such as
The SPI must be the IKEv2 Header SPI pair where the first 8 octets instructions for when to activate and de-activate SAs.
become the "Initiator's SPI" field in the G-IKEv2 rekey message
IKEv2 HDR, and the second 8 octets become the "Responder's SPI" in
the same HDR. As described above, these SPIs are assigned by the
GCKS. When selecting SPI the GCKS MUST make sure that the sole
first 8 octets (corresponding to "Initiator's SPI" field in the
IKEv2 header) uniquely identify the Rekey SA.
o Source & Destination Traffic Selectors - Substructures describing Policies are distributed in substructures to the GSA payload. The
the source and destination of the network identities. These format of the substructures is defined below in Section 3.4.2 (for
identities refer to the source and destination of the next KEK GSA policy) and in Section 3.4.3 (for GA policy). The first octet of
rekey SA. Defined format and values are specified by IKEv2 the substructure unambiguously determines its type - it is zero for
[RFC7296], section 3.13.1. GAP and non-zero (actually, it is the security protocol ID) for GSA
policies.
o Transform Substructure List -- A list of Transform Substructures 3.4.2. Group Security Association Policy Substructure
specifies the transform information. The format is defined in
IKEv2 [RFC7296], section 3.3.2, and values are described in the
IKEv2 registries [IKEV2-IANA]. Valid Transform Types are ENCR,
INTEG. The Last Substruc value in each Transform Substructure
will be set to 3 except for the last one in the list, which is set
to 0.
o KEK Attributes -- Contains KEK policy attributes associated with The GSA policy substructure contains parameters for the SA used with
the group. The following sections describe the possible this group. Depending on the security protocol the SA is either a
attributes. Any or all attributes may be optional, depending on rekey SA or a data security SA (ESP and AH). It is NOT RECOMMENDED
the group policy. that the GCKS distribute both ESP and AH policies for the same set of
Traffic Selectors.
2.4.2.1. KEK Attributes 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> ~
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
The following attributes may be present in a GSA KEK policy. The Figure 14: GSA Policy Substructure Format
attributes must follow the format defined in the IKEv2 [RFC7296]
section 3.3.5. In the table, attributes that are defined as TV are
marked as Basic (B); attributes that are defined as TLV are marked as
Variable (V). The terms Reserved, Unassigned, and Private Use are to
be applied as defined in [RFC8126]. The registration procedure is
Expert Review.
KEK Attributes Value Type Mandatory The GSA policy fields are defined as follows:
-------------- ----- ---- ---------
Reserved 0
KEK_MANAGEMENT_ALGORITHM 1 B N
Reserved 2
Reserved 3
KEK_KEY_LIFETIME 4 V Y
Reserved 5
KEK_AUTH_METHOD 6 B Y
KEK_AUTH_HASH 7 B N
KEK_MESSAGE_ID 8 V Y (*)
KEK_NEXT_SPI 9 V N
Unassigned 10-16383
Private Use 16384-32767
(*) the KEK_MESSAGE_ID MUST be included in a G-IKEv2 registration o Protocol (1 octet) - Identifies the security protocol for this
message and MUST NOT be included in rekey messages. group SA. The values are defined in the IKEv2 Security Protocol
Identifiers in [IKEV2-IANA]. The valid values for this field are:
<TBA> (GIKE_REKEY) for GSA KEK policy and 2 (AH) or 3 (ESP) for
GSA TEK policy.
The following attributes may only be included in a G-IKEv2 o SPI Size (1 octet) - Size of Security Parameter Index (SPI) for
registration message: KEK_MANAGEMENT_ALGORITHM, KEK_MESSAGE_ID. the group SA. SPI size depends on the SA protocol. For
GIKE_REKEY it is 16 octets, while for AH and ESP it is 4 octets.
2.4.2.1.1. KEK_MANAGEMENT_ALGORITHM o Length (2 octets, unsigned integer) - Length of this substructure
including the header.
The KEK_MANAGEMENT_ALGORITHM attribute specifies the group KEK o SPI (variable) - Security Parameter Index for the group SA. The
management algorithm used to provide forward or backward access size of this field is determined by the SPI Size field. As
control (i.e., used to exclude group members). Defined values are described above, these SPIs are assigned by the GCKS. In case of
specified in the following table. The terms Reserved, Unassigned, GIKE_REKEY the SPI must be the IKEv2 Header SPI pair where the
and Private Use are to be applied as defined in [RFC8126]. The first 8 octets become the "Initiator's SPI" field in the G-IKEv2
registration procedure is Expert Review. rekey message IKEv2 HDR, and the second 8 octets become the
"Responder's SPI" in the same HDR. When selecting SPI the GCKS
MUST make sure that the sole first 8 octets (corresponding to
"Initiator's SPI" field in the IKEv2 header) uniquely identify the
Rekey SA.
KEK Management Type Value o Source & Destination Traffic Selectors - (variable) -
------------------- ----- Substructures describing the source and destination of the network
Reserved 0 identities. The format for these substructures is defined in
LKH 1 IKEv2 [RFC7296], section 3.13.1. For the group rekey SA (protocol
Unassigned 2-16383 GIKE_REKEY) the destination traffic selectors MUST define a single
Private Use 16384-32767 IP address, IP protocol and port the GSA_REKEY messages will be
destined to. The source traffic selector in this case MUST either
define a single IP address, IP protocol and port the GSA_REKEY
messages will be originated from or be a wildcard selector. For
the data security (AH and ESP) SAs the traffic selectors instead
specify characteristics of the traffic to be protected by the
corresponding SA.
2.4.2.1.2. KEK_KEY_LIFETIME o GSA Transforms (variable) - A list of Transform Substructures
specifies the policy information for the group SA. The format is
defined in IKEv2 [RFC7296], section 3.3.2. The Last Substruc
value in each Transform Substructure will be set to 3 except for
the last one in the list, which is set to 0. Section 3.4.2.1
describes using IKEv2 transforms in GSA policy substructure.
The KEK_KEY_LIFETIME attribute specifies the maximum time for which o GSA Attributes (variable) - Contains policy attributes associated
the KEK is valid. The GCKS may refresh the KEK at any time before with the group SA. The following sections describe the possible
the end of the valid period. The value is a four (4) octet number attributes. Any or all attributes may be optional, depending on
defining a valid time period in seconds. the group SA protocol and the group policy. Section 3.4.2.2
defines attributes used in GSA policy.
2.4.2.1.3. KEK_AUTH_METHOD 3.4.2.1. GSA Transforms
The KEK_AUTH_METHOD attribute specifies the method of authentication GSA policy is defined by means of transforms in GSA policy
used. This value is from the IKEv2 Authentication Method registry substructure. For this purpose the transforms defined in [RFC7296]
[IKEV2-IANA]. The method must either specify using some public key are used. In addition, new transform types are defined for using in
signatures or Shared Key Message Integrity Code. Other G-IKEv2: Authentication Method (AUTH) and Group Key Management Method
authentication methods MUST NOT be used. (GKM), see Section 6.
2.4.2.1.4. KEK_AUTH_HASH Valid Transform Types depend on group SA protocol and are summarized
in the table below.
The KEK_AUTH_HASH attribute specifies the hash algorithm used to Protocol Mandatory Types Optional Types
generate the AUTH key to authenticate GSA_REKEY messages. Hash ----------------------------------------------------------
algorithms are defined in IANA registry IKEv2 Hash Algorithms GIKE_REKEY ENCR, INTEG*, PRF, AUTH, GKM
[IKEV2-IANA]. ESP ENCR INTEG
AH INTEG
This attribute SHOULD NOT be sent if the KEK_AUTH_METHOD implies a Figure 15: Valid Transform Types
particular hash algorithm (e.g., for DSA-based algorithms).
Furthermore, it is not necessary for the GCKS to send it if the GM is
known to support the algorithm because it declared it in a
SIGNATURE_HASH_ALGORITHMS notification during registration (see
[RFC7427]).
2.4.2.1.5. KEK_MESSAGE_ID (*) If AEAD encryption algorithm is used, then INTEG transform MUST
NOT be specified, otherwise it MUST be specified.
The KEK_MESSAGE_ID attribute defines the initial Message ID to be 3.4.2.1.1. Authentication Method Transform
used by the GCKS in the GSA_REKEY messages. The Message ID is a 4
octet unsigned integer in network byte order.
2.4.2.1.6. KEK_NEXT_SPI The Authentication Method (AUTH) transform is used in the GIKE_REKEY
policy to convey information of how GCKS will authenticate the
GSA_REKEY messages. This values are from the IKEv2 Authentication
Method registry [IKEV2-IANA]. Note, that this registry defines only
256 possible values, so even that Transform ID field in the Transform
substructure allows for 65536 possible values, in case of the
Authentication Method transform the values 257-65535 MUST NOT be
used.
The KEK_NEXT_SPI attribute may optionally be included by GCKS in Among the currently defined authentication methods in the IKEv2
GSA_REKEY message, indicating what IKE SPIs are intended be used for Authentication Method registry, only the following are allowed to be
the next rekey SA. The attribute data MUST be 16 octets in length used in the Authentication Method transform: Shared Key Message
specifying the pair of IKE SPIs as they appear in the IKE header. Integrity Code, NULL Authentication and Digital Signature. Other
Multiple attributes of this type MAY be included, meaning that any of currently defined authentication methods MUST NOT be used. The
the supplied SPIs can be used for the next rekey. following semantics is associated with each of the allowed methods.
The GM may save these values and if later the GM starts receiving IKE Shared Key Message Integrity Code - GCKS will authenticates the
messages with one of these SPIs without seeing a rekey message over GSA_REKEY messages by means of shared secret. In this case the
the current rekey SA, this may be used as an indication, that the GCKS MUST include the AUTH_KEY attribute containing the shared key
rekey message was lost on its way to this GM. In this case the GM into the KD payload at the time the GM is registered to the group.
SHOULD re-register to the group.
Note, that this method of detecting missed rekeys can only be used by NULL Authentication - No additional authentication of the
passive GMs, i.e. those, that only listen and don't send data. It's GSA_REKEY messages will be provided by the GCKS (besides the
also no point to include this attribute in the GSA_INBAND_REKEY ability for the GMs to correctly decrypt them and verify their
messages, since they use reliable transport. Note also, that the ICV). In this case the GCKS MUST NOT include the AUTH_KEY
GCKS is free to forget its promises and not to use the SPIs it sent attribute into the KD payload.
in the KEK_NEXT_SPI attributes before (e.g. in case of GCKS reboot),
so the GM must only treat these information as a "best effort" made
by GCKS to prepare for future rekeys.
2.4.3. GSA TEK Policy Digital Signature - Digital signatures will be used by the GCKS to
authenticate the GSA_REKEY messages. In this 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 a new attribute
Algorithm Identifier (<TBA by IANA>) is defined. This attribute
contains DER-encoded ASN.1 object AlgorithmIdentifier, which would
specify 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 [RFC5280], see also [RFC7427] for
the list of common AlgorithmIdentifier values used in IKEv2. In
case of using digital signature the GCKS MUST include the
Algorithm Identifier attribute in the Authentication Method
transform.
The GSA TEK policy contains security attributes for a single TEK The type of the Authentication Method Transform is <TBA by IANA>.
associated with a group.
1 2 3 3.4.2.1.2. Group Key Management Method Transform
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type = 3 | RESERVED | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Protocol-ID | TEK Protocol-Specific Payload |
+-+-+-+-+-+-+-+-+ ~
~ |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 21: TEK Policy Generic Header Format The Group Key Management Method (GKM) transform is used in the
GIKE_REKEY policy to convey information of how GCKS will manage the
group keys to provide forward and backward access control (i.e., used
to exclude group members). Possible key management methods are
defined in a new IKEv2 registry "Transform Type <TBA> - Group Key
Management Methods" (see Section 6). This document defines one
values for this registry:
The GSA TEK Payload fields are defined as follows: Wrapped Key Download (<TBA by IANA>) - Keys are downloaded by GCKS
to the GMs in encrypted form. This algorithm may provide forward
and backward access control if some form of key hierarchy is used
and each GM is provided with a personal key at the time of
registration. Otherwise no access control is provided.
o Type = 3 (1 octet) -- Identifies the GSA payload type as TEK in The type of the Group Key Management Method transform is <TBA by
the G-IKEv2 registration or the G-IKEv2 rekey message. IANA>.
o RESERVED (1 octet) -- Must be zero. 3.4.2.2. GSA Attributes
o Length (2 octets) -- Length of this structure, including the TEK GSA attributes are generally used to provide GMs with additional
Protocol-Specific Payload. parameters for the GSA policy. Unlike security parameters
distributed via transforms, which are expected not to change over
time (unless policy changes), the parameters distributed via GSA
attributes may depend on the time the distribution takes place, on
the existence of others group SAs or on other conditions.
o Protocol-ID (1 octet) -- Value specifying the Security Protocol. This document creates a new IKEv2 IANA registry for the types of the
The following table defines values for the Security Protocol. GSA attributes which is initially filled as described in Section 6.
Support for the GSA_PROTO_IPSEC_AH GSA TEK is OPTIONAL. The terms In particular, the following attributes are initially added.
Reserved, Unassigned, and Private Use are to be applied as defined
in [RFC8126]. The registration procedure is Expert Review.
Protocol ID Value GSA Attributes Value Type Multiple Used In
----------- ----- ---------------------------------------------------------------------
Reserved 0 Reserved 0
GSA_PROTO_IPSEC_ESP 1 GSA_KEY_LIFETIME 1 V N (GIKE_REKEY, AH, ESP)
GSA_PROTO_IPSEC_AH 2 GSA_INITIAL_MESSAGE_ID 2 V N (GIKE_REKEY)
Unassigned 3-127 GSA_NEXT_SPI 3 V Y (GIKE_REKEY, AH, ESP)
Private Use 128-255 The attributes must follow the format defined in the IKEv2 [RFC7296]
section 3.3.5. In the table, attributes that are defined as TV are
marked as Basic (B); attributes that are defined as TLV are marked as
Variable (V).
o TEK Protocol-Specific Payload (variable) -- Payload which 3.4.2.2.1. GSA_KEY_LIFETIME Attribute
describes the attributes specific for the Protocol-ID.
2.4.3.1. TEK ESP and AH Protocol-Specific Policy The GSA_KEY_LIFETIME attribute specifies the maximum time for which
the group SA is valid. The value is a 4 octet number defining a
valid time period in seconds. A single attribute of this type MUST
be included into any GSA policy substructure.
The TEK Protocol-Specific policy contains two traffic selectors one When the lifetime expires, the group security association and all
for the source and one for the destination of the protected traffic, associated keys MUST be deleted. The GCKS may delete the SA at any
SPI, Transforms, and Attributes. time before the end of the valid period.
The TEK Protocol-Specific policy for ESP and AH is as follows: 3.4.2.2.2. GSA_INITIAL_MESSAGE_ID Attribute
1 2 3 The GSA_INITIAL_MESSAGE_ID attribute defines the initial Message ID
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 to be used by the GCKS in the GSA_REKEY messages. The Message ID is
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ a 4 octet unsigned integer in network byte order.
| SPI |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
~ <Source Traffic Selector> ~
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
~ <Destination Traffic Selector> ~
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
~ <Transform Substructure List> ~
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
~ TEK Attributes ~
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 22: AH and ESP TEK Policy Format A single attribute of this type MUST be included into the GSA KEK
policy substructure if the initial Message ID is non-zero. 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 this
attribute will be included into the GSA policy at the time of GMs'
registration.
The GSA TEK Policy fields are defined as follows: 3.4.2.2.3. GSA_NEXT_SPI Attribute
o SPI (4 octets) -- Security Parameter Index. The optional GSA_NEXT_SPI attribute contains SPI that the GCKS
reserved for the next group SA replacing this group SA. The length
of the attribute data is determined by the SPI Size field in the GSA
Policy substructure the attribute resides in (see Section 3.4.2), and
the attribute data contains 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.
o Source & Destination Traffic Selectors - The traffic selectors The GM may store these values and if later the GM starts receiving
describe the source and the destination of the protected traffic. group SA messages with one of these SPIs without seeing a rekey
The format and values are defined in IKEv2 [RFC7296], section message over the current rekey SA, this may be used as an indication,
3.13.1. that the rekey message got lost on its way to this GM. In this case
the GM SHOULD re-register to the group.
o Transform Substructure List -- A list of Transform Substructures Note, that this method of detecting lost rekey messages can only be
specifies the transform information. The format is defined in used by passive GMs, i.e. those, that only listen and don't send
IKEv2 [RFC7296], section 3.3.2, and values are described in the data. There is also no point to include this attribute in the
IKEv2 registries [IKEV2-IANA]. Valid Transform Types for ESP are GSA_INBAND_REKEY messages, since they use reliable transport. Note
ENCR, INTEG, and ESN. Valid Transform Types for AH are INTEG and also, that the GCKS is free to forget its promises and not to use the
ESN. The Last Substruc value in each Transform Substructure will SPIs it sent in the GSA_NEXT_SPI attributes before (e.g. in case of
be set to 3 except for the last one in the list, which is set to the GCKS reboot), so the GM must only treat these information as a
0. A Transform Substructure with attributes (e.g., the ENCR Key "best effort" made by GCKS to prepare for future rekeys.
Length), they are included within the Transform Substructure as
usual.
o TEK Attributes -- Contains the TEK policy attributes associated 3.4.3. Group Associated Policy Substructure
with the group, in the format defined in Section 3.3.5 of
[RFC7296]. All attributes are optional, depending on the group
policy.
Attribute Types are as follows. The terms Reserved, Unassigned, and Group specific policy that does not belong to any SA policy can be
Private Use are to be applied as defined in [RFC8126]. The distributed to all group member using Group Associated Policy (GAP)
registration procedure is Expert Review. substructure.
TEK Attributes Value Type Mandatory The GAP substructure is defined as follows:
-------------- ----- ---- ---------
Reserved 0
TEK_KEY_LIFETIME 1 V N
TEK_MODE 2 B Y
TEK_REKEY_SPI 3 V N
TEK_NEXT_SPI 4 V N
Unassigned 5-16383
Private Use 16384-32767
It is NOT RECOMMENDED that the GCKS distribute both ESP and AH 1 2 3
Protocol-Specific Policies for the same set of Traffic Selectors. 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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| ZERO | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
~ <GAP Attributes> ~
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
2.4.3.1.1. TEK_KEY_LIFETIME Figure 16: GAP Substructure Format
The TEK_KEY_LIFETIME attribute specifies the maximum time for which The GAP substructure fields are defined as follows:
the TEK is valid. When the TEK expires, the AH or ESP security
association and all keys downloaded under the security association
are discarded. The GCKS may refresh the TEK at any time before the
end of the valid period.
The value is a four (4) octet number defining a valid time period in o ZERO (2 octets) - MUST be zero.
seconds. If unspecified the default value of 28800 seconds (8 hours)
shall be assumed.
2.4.3.1.2. TEK_MODE o Length (2 octets, unsigned integer) - Length of this substructure
including the header.
The value of 0 is used for tunnel mode and 1 for transport mode. In o GAP Attributes (variable) - Contains policy attributes associated
the absence of this attribute tunnel mode will be used. with no specific SA. The following sections describe the possible
attributes. Any or all attributes may be optional, depending on
the group policy.
2.4.3.1.3. TEK_REKEY_SPI This document creates a new IKEv2 IANA registry for the types of the
GAP attributes which is initially filled as described in Section 6.
In particular, the following attributes are initially added.
This attribute contains an SPI for the SA that is being rekeyed. The GAP Attributes Value Type Multiple
size of SPI depends on the protocol, for ESP and AH it is 4 octets, ----------------------------------------------------
so the size of the data MUST be 4 octets for AH and ESP. Reserved 0
GAP_ATD 1 B N
GAP_DTD 2 B N
GAP_SID_BITS 3 B N
If this attribute is included in the rekey message, the GM SHOULD The attributes must follow the format defined in the IKEv2 [RFC7296]
delete the SA corresponding to this SPI once the new SA is installed section 3.3.5. In the table, attributes that are defined as TV are
and regardless of the expiration time of the SA to be deleted (but marked as Basic (B); attributes that are defined as TLV are marked as
after waiting DEACTIVATION_TIME_DELAY time period). Variable (V).
2.4.3.1.4. TEK_NEXT_SPI 3.4.3.1. GAP_ATD And GAP_DTD Attributes
This attribute contains an SPI that the GCKS reserved for the next Section 4.2.1 of [RFC5374] specifies a key rollover method that
rekey. The size of SPI depends on the protocol, for ESP and AH it is requires two values be provided to group members - Activation Time
4 octets, so the size of the data MUST be 4 octets for AH and ESP. Delay (ATD) and Deactivation Time Delay (DTD).
Multiple attributes of this type MAY be included, which means that
any of the provided SPIs can be used in the next rekey.
The GM may save these values and if later the GM starts receiving The GAP_ATD attribute allows a GCKS to set the Activation Time Delay
IPsec messages with one of these SPIs without seeing a rekey message for data security SAs of the group. The ATD defines how long active
for it, this may be used as an indication, that the rekey message was members of the group (those who sends traffic) should wait after
lost on its way to this GM. In this case the GM SHOULD re-register receiving new SAs before staring sending traffic over them. Note,
to the group. that to achieve smooth rollover passive members of the group should
activate the SAs immediately once they receive them.
Note, that this method of detecting missed rekey messages can only be The GAP_DTD attribute allows the GCKS to set the Deactivation Time
used by passive GMs, i.e. those, that only listen and don't send Delay for previously distributed SAs. The DTD defines how long after
data. It's also no point to include this attribute in the receiving a request to delete data security SAs passive group members
GSA_INBAND_REKEY messages, since they use reliable transport. Note should wait before actually deleting them. Note that active members
also, that the GCKS is free to forget its promises and not to use the of the group should stop sending traffic over these old SAs once new
SPIs it sent in the TEK_NEXT_SPI attributes before (e.g. in case of replacement SAs are activated (after time specified in the GAP_ATD
GCKS reboot), so the GM must only treat these information as a "best attribute).
effort" made by GCKS to prepare for future rekeys.
2.4.4. GSA Group Associated Policy The GAP_ATD and GAP_DTD attributes contain 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, the GMs should use default values for activation and
deactivation time delays.
Group specific policy that does not belong to rekey policy (GSA KEK) 3.4.3.2. GAP_SID_BITS Attribute
or traffic encryption policy (GSA TEK) can be distributed to all
group member using GSA GAP (Group Associated Policy).
The GSA GAP payload is defined as follows: The GAP_SID_BITS attribute declares how many bits of the cipher nonce
are taken to represent an SID value. The bits are applied as the
most significant bits of the IV, as shown in Figure 1 of [RFC6054]
and specified in Section 1.4.6.2. Guidance for a GCKS choosing the
NUMBER_OF_SID_BITS is provided in Section 3 of [RFC6054]. This value
is applied to each SID value distributed in the KD payload.
1 2 3 The GCKS MUST include this attribute if there are more than one
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 sender in the group and any of the data security SAs use counter-
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ based cipher mode. The number of SID bits is represented as 16 bit
| Type = 2 | RESERVED | Length | unsigned integer in network byte order.
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
~ Group Associated Policy Attributes ~
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 23: GAP Policy Format 3.5. Key Download Payload
The GSA GAP payload fields are defined as follows: The Key Download (KD) payload contains the group keys for the group
specified in the GSA Payload. The Payload Type for the Key Download
payload is fifty-two (52).
o Type = 2 (1 octet) -- Identifies the GSA payload type as GAP in 1 2 3
the G-IKEv2 registration or the G-IKEv2 rekey message. 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 Packets> ~
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
o RESERVED (1 octet) -- Must be zero. Figure 17: Key Download Payload Format
o Length (2 octets) -- Length of this structure, including the GSA The Key Download payload fields are defined as follows:
GAP header and Attributes.
o Group Associated Policy Attributes (variable) -- Contains o Next Payload, C, RESERVED, Payload Length fields comprise the
attributes following the format defined in Section 3.3.5 of IKEv2 Generic Payload Header and are defined in Section 3.2. of
[RFC7296]. [RFC7296].
Attribute Types are as follows. The terms Reserved, Unassigned, and o Key Packets (variable) - Contains Group Key Packet and Member Key
Private Use are to be applied as defined in [RFC8126]. The Packet substructures. Each Key Packet contains keys for a single
registration procedure is Expert Review. group rekey or data security SA or a keys and security parameters
for a GM.
Attribute Type Value Type
-------------- ----- ----
Reserved 0
ACTIVATION_TIME_DELAY 1 B
DEACTIVATION_TIME_DELAY 2 B
Unassigned 3-16383
Private Use 16384-32767
2.4.4.1. ACTIVATION_TIME_DELAY/DEACTIVATION_TIME_DELAY Two types of Key Packets are used - Group Key Packet and Member Key
Packet.
Section 4.2.1 of [RFC5374] specifies a key rollover method that 3.5.1. Wrapped Key Format
requires two values be provided to group members. The
ACTIVATION_TIME_DELAY attribute allows a GCKS to set the Activation
Time Delay (ATD) for SAs generated from TEKs. The ATD defines how
long after receiving new SAs that they are to be activated by the GM.
The ATD value is in seconds.
The DEACTIVATION_TIME_DELAY allows the GCKS to set the Deactivation The symmetric keys in G-IKEv2 are never sent in clear. They are
Time Delay (DTD) for previously distributed SAs. The DTD defines how always encrypted with other keys using the format called Wrapped Key
long after receiving new SAs it should deactivate SAs that are that is shown below (Figure 18).
destroyed by the rekey event. The value is in seconds.
The values of ATD and DTD are independent. However, the DTD value The keys are encrypted using algorithm that is used to encrypt the
should be larger, which allows new SAs to be activated before older message the keys are sent in. It means, that in case of unicast IKE
SAs are deactivated. Such a policy ensures that protected group SA (used for GMs registration and rekeying using GSA_INBAND_REKEY)
traffic will always flow without interruption. the encryption algorithm will be the one negotiated during the SA
establishment, while for the GSA_REKEY messages the algorithm will be
provided by the GCKS in the Encryption Algorithm transform in the GSA
payload when this multicast SA was being established (not in the same
GSA_REKEY message).
2.5. Key Download Payload If AEAD mode is used for encryption, then for the purpose of key
encryption the authentication tag MUST NOT be used (both not
calculated and not verified), since the G-IKEv2 provides
authentication of all its messages. In addition there is no AAD in
this case. If encryption algorithm requires padding, then the
encrypted key MUST be padded before encryption to have the required
size. If the encryption algorithm doesn't define the padding
content, then the following scheme SHOULD be used: the Padding bytes
are initialized with a series of (unsigned, 1-byte) integer values.
The first padding byte appended to the plaintext is numbered 1, with
subsequent padding bytes making up a monotonically increasing
sequence: 1, 2, 3, .... The length of the padding is not transmitted
and is implicitly determined, since the length of the key is known.
The Key Download Payload contains the group keys for the group 1 2 3
specified in the GSA Payload. These key download payloads can have 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
several security attributes applied to them based upon the security +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
policy of the group as defined by the associated GSA Payload. | Key ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| KWK ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
~ IV ~
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
~ Encrypted Key ~
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1 2 3 Figure 18: Wrapped Key Format
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 Packets ~
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 24: Key Download Payload Format The Wrapped Key fields are defined as follows:
The Key Download Payload fields are defined as follows: o Key ID (4 octets) - ID of the encrypted key. The value zero means
that the encrypted key contains keying material for the group SA,
otherwise it contains some intermediate key.
o Next Payload (1 octet) -- Identifier for the payload type of the o Key Wrap Key (KWK) ID (4 octets) - ID of the key that was used to
next payload in the message. If the current payload is the last encrypt this key. The value zero means that the default KWK was
in the message, then this field will be zero. used to encrypt the key, otherwise some other key was used.
o Critical (1 bit) -- Set according to [RFC7296]. o IV (variable) - Initialization Vector used for encryption. The
size and the content of IV is defined by the encryption algorithm
employed.
o RESERVED (7 bits) -- Unused, set to zero. o Encrypted Key (variable) - The encrypted key bits. These bits may
comprise either a single encrypted key or a result of encryption
of a concatenation of keys (key material) for several algorithms.
o Payload Length (2 octets) -- Length in octets of the current 3.5.2. Group Key Packet Substructure
payload, including the generic payload header.
o Key Packets (variable) -- Contains Key Packets. Several types of Group Key Packet substructure contains SA key information. This key
key packets are defined. Each Key Packet has the following information is associated with some group SAs: either with data
format. security SAs or with group rekey SA.
1 2 3 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| KD Type | RESERVED | KD Length | | Protocol | SPI Size | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| SPI Size | SPI (variable) ~ | |
~ SPI ~
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
~ Key Packet Attributes ~ | |
~ <Group Key Download Attributes> ~
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 25: Key Packet Format Figure 19: Group Key Packet Substructure Format
o Key Download (KD) Type (1 octet) -- Identifier for the Key Data
field of this Key Packet. In the following table the terms
Reserved, Unassigned, and Private Use are to be applied as defined
in [RFC8126]. The registration procedure is Expert Review.
Key Download Type Value
----------------- -----
Reserved 0
TEK 1
KEK 2
LKH 3
SID 4
Unassigned 5-127
Private Use 128-255
o RESERVED (1 octet) -- Unused, set to zero.
o Key Download Length (2 octets) -- Length in octets of the Key
Packet data, including the Key Packet header.
o SPI Size (1 octet) -- Value specifying the length in octets of the
SPI as defined by the Protocol-Id.
o SPI (variable length) -- Security Parameter Index which matches a
SPI previously sent in an GSA KEK or GSA TEK Payload.
o Key Packet Attributes (variable length) -- Contains Key o Protocol (1 octet) - Identifies the security protocol for this key
information. The format of this field is specific to the value of packet. The values are defined in the IKEv2 Security Protocol
the KD Type field. The following sections describe the format of Identifiers in [IKEV2-IANA]. The valid values for this field are:
each KD Type. <TBA> (GIKE_REKEY) for KEK Key packet and 2 (AH) or 3 (ESP) for
TEK key packet.
2.5.1. TEK Download Type o SPI Size (1 octet) - Size of Security Parameter Index (SPI) for
the corresponding SA. SPI size depends on the security protocol.
For GIKE_REKEY it is 16 octets, while for AH and ESP it is 4
octets.
The following attributes may be present in a TEK Download Type. o Length (2 octets, unsigned integer) - Length of this substructure
Exactly one attribute matching each type sent in the GSA TEK payload including the header.
MUST be present. The attributes must follow the format defined in
IKEv2 (Section 3.3.5 of [RFC7296]). In the table, attributes defined
as TV are marked as Basic (B); attributes defined as TLV are marked
as Variable (V). The terms Reserved, Unassigned, and Private Use are
to be applied as defined in [RFC8126]. The registration procedure is
Expert Review.
TEK KD Attributes Value Type Mandatory o SPI (variable) - Security Parameter Index for the corresponding
----------------- ----- ---- --------- SA. The size of this field is determined by the SPI Size field.
Reserved 0-2 In case of GIKE_REKEY the SPI must be the IKEv2 Header SPI pair
TEK_KEYMAT 3 V Y where the first 8 octets become the "Initiator's SPI" field in the
Unassigned 4-16383 G-IKEv2 rekey message IKEv2 HDR, and the second 8 octets become
Private Use 16384-32767 the "Responder's SPI" in the same HDR. When selecting SPI the
GCKS MUST make sure that the sole first 8 octets (corresponding to
"Initiator's SPI" field in the IKEv2 header) uniquely identify the
Rekey SA.
It is possible that the GCKS will send no TEK key packets in a o Group Key Download Attributes (variable length) - Contains Key
Registration KD payload (as well as no corresponding GSA TEK payloads information for the corresponding SA.
in the GSA payload), after which the TEK payloads will be sent in a
rekey message.
2.5.1.1. TEK_KEYMAT This document creates a new IKEv2 IANA registry for the types of the
Group Key Download attributes which is initially filled as described
in Section 6. In particular, the following attributes are initially
added.
The TEK_KEYMAT attribute contains keying material for the GKD Attributes Value Type Multiple Used In
corresponding SPI. This keying material will be used with the ------------------------------------------------------------
transform specified in the GSA TEK payload. The keying material is Reserved 0
treated equivalent to IKEv2 KEYMAT derived for that IPsec transform. SA_KEY 1 V Y (GIKE_REKEY)
N (AH, ESP)
2.5.2. KEK Download Type The attributes must follow the format defined in the IKEv2 [RFC7296]
section 3.3.5. In the table, attributes that are defined as TV are
marked as Basic (B); attributes that are defined as TLV are marked as
Variable (V).
The following attributes may be present in a KEK Download Type. 3.5.2.1. SA_KEY Attribute
Exactly one attribute matching each type sent in the GSA KEK payload
MUST be present. The attributes must follow the format defined in
IKEv2 (Section 3.3.5 of [RFC7296]). In the table, attributes defined
as TV are marked as Basic (B); attributes defined as TLV are marked
as Variable (V). The terms Reserved, Unassigned, and Private Use are
to be applied as defined in [RFC8126]. The registration procedure is
Expert Review.
KEK KD Attributes Value Type Mandatory The SA_KEY attribute contains a keying material for the corresponding
----------------- ----- ---- --------- SA. The content of the attribute is formatted according to
Reserved 0 Section 3.5.1 with a precondition that the Key ID field MUST be zero.
KEK_ENCR_KEY 1 V Y The size of the keying material MUST be equal to the total size of
KEK_INTEGRITY_KEY 2 V N the keys needed to be taken from this keying material (see
KEK_AUTH_KEY 3 V N Section 2.4) for the corresponding SA.
Unassigned 4-16383
Private Use 16384-32767
If the KEK Key Packet is included, there MUST be only one present in If the Key Packet is for a data security SA (AH or ESP protocols),
the KD payload. then exactly one SA_KEY attribute MUST be present with both Key ID
and KWK ID fields set to zero.
2.5.2.1. KEK_ENCR_KEY If the Key Packet is for a rekey SA (GIKE_REKEY protocol), then at
least one SA_KEY attribute with zero Key ID MUST be present.
Depending on GCKS key management policy more SA_KEY attributes MAY be
present.
The KEK_ENCR_KEY attribute type declares that the encryption key for 3.5.3. Member Key Packet Substructure
the corresponding SPI is contained in the Key Packet Attribute. The
encryption algorithm that will use this key was specified in the GSA
KEK payload.
2.5.2.2. KEK_INTEGRITY_KEY The Member Key Packet substructure contains keys and other parameters
that are specific for the member of the group and are not associated
with any particular group SA.
The KEK_INTEGRITY_KEY attribute type declares the integrity key for 1 2 3
this SPI is contained in the Key Packet Attribute. The integrity 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
algorithm that will use this key was specified in the GSA KEK +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
payload. | ZERO | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
~ <Member Key Download Attributes> ~
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
2.5.2.3. KEK_AUTH_KEY Figure 20: Member Key Packet Substructure Format
The KEK_AUTH_KEY attribute type declares that the authentication key The Member Key Packet substructure fields are defined as follows:
for this SPI is contained in the Key Packet Attribute. The signature
algorithm that will use this key was specified in the GSA KEK
payload. An RSA public key format is defined in [RFC3447],
Section A.1.1. DSS public key format is defined in [RFC3279]
Section 2.3.2. For ECDSA Public keys, use format described in
[RFC5480] Section 2.2. Other algorithms added to the IKEv2
Authentication Method registry are also expected to include a format
of the public key included in the algorithm specification.
2.5.3. LKH Download Type o ZERO (2 octets) - MUST be zero.
The LKH key packet is comprised of attributes representing different o Length (2 octets, unsigned integer) - Length of this substructure
leaves in the LKH key tree. including the header.
The following attributes are used to pass an LKH KEK array in the KD o Member Key Download Attributes (variable length) - Contains Key
payload. The attributes must follow the format defined in IKEv2 information and other parameters exclusively for a particular
(Section 3.3.5 of [RFC7296]). In the table, attributes defined as TV member of the group.
are marked as Basic (B); attributes defined as TLV are marked as
Variable (V). The terms Reserved, Unassigned, and Private Use are to
be applied as defined in [RFC8126]. The registration procedure is
Expert Review.
LKH KD Attributes Value Type Member Key Packet substructure contains sensitive information for a
----------------- ----- ---- single GM, for this reason it MUST NOT be sent in GSA_REKEY messages
Reserved 0 and MUST only be sent via unicast SA at the time the GM registers to
LKH_DOWNLOAD_ARRAY 1 V the group (in either GSA_AUTH or GSA_REGISTRATION exchanges).
LKH_UPDATE_ARRAY 2 V
Unassigned 3-16383
Private Use 16384-32767
If an LKH key packet is included in the KD payload, there MUST be This document creates a new IKEv2 IANA registry for the types of the
only one present. Member Key Download attributes which is initially filled as described
in Section 6. In particular, the following attributes are initially
added.
2.5.3.1. LKH_DOWNLOAD_ARRAY MKD Attributes Value Type Multiple
------------------------------------------------
Reserved 0
KEY_WRAP_KEY 1 V Y
GM_SID 2 V Y
AUTH_KEY 3 V N
The LKH_DOWNLOAD_ARRAY attribute type is used to download a set of The attributes must follow the format defined in the IKEv2 [RFC7296]
LKH keys to a group member. It MUST NOT be included in a IKEv2 rekey section 3.3.5. In the table, attributes that are defined as TV are
message KD payload if the IKEv2 rekey is sent to more than one group marked as Basic (B); attributes that are defined as TLV are marked as
member. If an LKH_DOWNLOAD_ARRAY attribute is included in a KD Variable (V).
payload, there MUST be only one present.
This attribute consists of a header block, followed by one or more 3.5.3.1. KEY_WRAP_KEY Attribute
LKH keys.
1 2 3 The KEY_WRAP_KEY attribute contains a key that is used to encrypt
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 other keys. One or more the these attributes are sent to GMs if the
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ GCKS key management policy relies on some key hierarchy (e.g. LKH).
| # of LKH Keys | RESERVED |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
~ LKH Keys ~
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 26: LKH_DOWNLOAD_ARRAY Format The content of the attribute has a format defined in Section 3.5.1
with a precondition that the Key ID field MUST NOT be zero. The
algorithm associated with the key is from the Encryption Transform
for the SA the KEY_WRAP_KEY attributes was sent in. The size of the
key MUST be equal to the key size for this algorithm.
The KEK_LKH attribute fields are defined as follows: Multiple instances of the KEY_WRAP_KEY attributes MAY be present in
the key packet.
o Number of LKH Keys (2 octets) -- This value is the number of 3.5.3.2. GM_SID Attribute
distinct LKH keys in this sequence.
o RESERVED (2 octets) -- Unused, set to zero. The GM_SID attribute is used to download one or more Sender-ID (SID)
values for the exclusive use of a group member. One or more of this
attributes MUST be sent by the GCKS if the GM informed the GCKS that
it would be a sender (by inclusion the SENDER notification to the
request) and at least one of the data security SAs included in the
GSA payload uses counter-based mode of encryption.
Each LKH Key is defined as follows: If the GMs has requested multiple SID values in the SENDER
notification, then the GCKS SHOULD provide it with the requested
number of SIDs by sending multiple instances of the GM_SID attribute.
The GCKS MAY send fewer SIDs than requested by the GM (e.g. if it is
running out of SIDs), but it MUST NOT send more than requested.
1 2 3 3.5.3.3. AUTH_KEY Attribute
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| LKH ID | Encr Alg |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Key Handle |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
~ Key Data ~
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 27: LKH Key Format The AUTH_KEY attribute 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 Authentication Method
transform in the GSA payload.
o LKH ID (2 octets) -- This is the position of this key in the o If a shared secret is used for the GSA_REKEY messages
binary tree structure used by LKH. authentication then the content of the AUTH_KEY attribute is the
shared secret that MUST be represented in the form of Wrapped Key
(see Section 3.5.1) with zero KWK ID. The Key ID in this case is
arbitrary and MUST be ignored by the GM.
o Encr Alg (2 octets) -- This is the encryption algorithm for which o If digital signatures are used for the GSA_REKEY messages
this key data is to be used. This value is specified in the ENCR authentication then the content of the AUTH_KEY attribute is a
transform in the GSA payload. 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 [RFC5280].
o Key Handle (4 octets) -- This is a randomly generated value to The signature algorithm that will use this key was specified in
uniquely identify a key within an LKH ID. the Algorithm Identifier attribute of the Authentication Method
transform. The key MUST be compatible with this algorithm. An
RSA public key format is defined in [RFC3447], Section A.1. DSS
public key format is defined in [RFC3279] Section 2.3.2. For
ECDSA Public keys, use format described in [RFC5480] Section 2.
Other algorithms added to the IKEv2 Authentication Method registry
are also expected to include a format of the SubjectPublicKeyInfo
object included in the algorithm specification.
o Key Data (variable length) -- This is the actual encryption key Multiple instances of the AUTH_KEY attributes MUST NOT be sent.
data, which is dependent on the Encr Alg algorithm for its format.
The first LKH Key structure in an LKH_DOWNLOAD_ARRAY attribute 3.6. Delete Payload
contains the Leaf identifier and key for the group member. The rest
of the LKH Key structures contain keys along the path of the key tree
in the order starting from the leaf, culminating in the group KEK.
2.5.3.2. LKH_UPDATE_ARRAY There are occasions when the GCKS may want to signal to group members
to delete policy at the end of a broadcast, if group policy has
changed, or the GCKS needs to reset the policy and keying material
for the group due to an emergency. Deletion of keys MAY be
accomplished by sending an IKEv2 Delete Payload, section 3.11 of
[RFC7296] as part of a registration or rekey Exchange. Whenever an
SA is to be deleted, the GKCS SHOULD send the Delete Payload in both
registration and rekey exchanges, because GMs with previous group
policy may contact the GCKS using either exchange.
The LKH_UPDATE_ARRAY attribute type is used to update the LKH keys The Protocol ID MUST be GIKE_REKEY (<TBA>) for GSA_REKEY pseudo-
for a group. It is most likely to be included in a G-IKEv2 rekey exchange, 2 for AH or 3 for ESP. Note that only one protocol id
message KD payload to rekey the entire group. This attribute value can be defined in a Delete payload. If a TEK and a KEK SA for
consists of a header block, followed by one or more LKH keys, as GSA_REKEY pseudo-exchange must be deleted, they must be sent in
defined in Section 2.5.3.1. different Delete payloads. Similarly, if a TEK specifying ESP and a
TEK specifying AH need to be deleted, they must be sent in different
Delete payloads.
There may be any number of LKH_UPDATE_ARRAY attributes included in a There may be circumstances where the GCKS may want to reset the
KD payload. policy and keying material for the group. The GCKS can signal
deletion of all policy of a particular TEK by sending a TEK with a
SPI value equal to zero in the delete payload. In the event that the
administrator is no longer confident in the integrity of the group
they may wish to remove all KEK and all the TEKs in the group. This
is done by having the GCKS send a delete payload with a SPI of zero
and a Protocol-ID of AH or ESP to delete all TEKs, followed by
another delete payload with a SPI value of zero and Protocol-ID of
KEK SA to delete the KEK SA.
1 2 3 3.7. Notify Payload
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| # of LKH Keys | LKH ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Key Handle |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
~ LKH Keys ~
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 28: LKH_UPDATE_ARRAY Format G-IKEv2 uses the same Notify payload as specified in [RFC7296],
section 3.10.
o Number of LKH Keys (2 octets) -- This value is the number of There are additional Notify Message types introduced by G-IKEv2 to
distinct LKH keys in this sequence. communicate error conditions and status (see Section 6).
o LKH ID (2 octets) -- This is the node identifier associated with o INVALID_GROUP_ID (45) - error type notification that indicates
the key used to encrypt the first LKH Key. 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.
o Key Handle (4 octets) -- This is the value that uniquely o AUTHORIZATION_FAILED (46) - error type notification that is sent
identifies the key within the LKH ID which was used to encrypt the in the response to a GSA_AUTH message when authorization failed.
first LKH key. 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.
The LKH Keys are as defined in Section 2.5.3.1. The LKH Key o REGISTRATION_FAILED (<TBA>) - error type notification that is sent
structures contain keys along the path of the key tree in the order by the GCKS when the GM registration request cannot be satisfied.
from the LKH ID found in the LKH_UPDATE_ARRAY header, culminating in The Protocol ID and SPI Size fields in the Notify payload MUST be
the group KEK. The Key Data field of each LKH Key is encrypted with zero. There is no data associated with this notification and the
the LKH key preceding it in the LKH_UPDATE_ARRAY attribute. The content of the Notification Data field MUST be ignored on receipt.
first LKH Key is encrypted under the key defined by the LKH ID and
Key Handle found in the LKH_UPDATE_ARRAY header.
2.5.4. SID Download Type o SENDER (16429) - 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 SID values the GM desires. The count MUST be 4 octets
long and contain the big endian representation of the number of
requested SIDs. The Protocol ID and SPI Size fields in the Notify
payload MUST be zero.
The SID attribute is used to download one or more Sender-ID (SID) o REKEY_IS_NEEDED (<TBA>) - status type notification that is sent in
values for the exclusive use of a group member. The terms Reserved, the GSA_AUTH response message to indicate that the GM must perform
Unassigned, and Private Use are to be applied as defined in an immediate rekey of IKE SA to make it secure against quantum
[RFC8126]. The registration procedure is Expert Review. computers and then start a registration request over. 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.
SID KD Attributes Value Type 3.7.1. USE_TRANSPORT_MODE Notification
----------------- ----- ----
Reserved 0
NUMBER_OF_SID_BITS 1 B
SID_VALUE 2 V
Unassigned 3-16383
Private Use 16384-32767
Because a SID value is intended for a single group member, the SID This specification uses USE_TRANSPORT_MODE notification defined in
Download type MUST NOT be distributed in a GSA_REKEY message section 3.10.1 of [RFC7296] to specify which mode data security SAs
distributed to multiple group members. should be created in. The GCKS MUST include one USE_TRANSPORT_MODE
notification in a message containing the GSA payload for every data
security SAs specified in this payload that is to be created in
transport mode. In other words, there must be as many these
notifications included in the message as many SAs are created in
transport mode. The Protocol ID, SPI Size and SPI fields of the
Notify Payload MUST correctly specify each such SA.
2.5.4.1. NUMBER_OF_SID_BITS 3.8. Authentication Payload
The NUMBER_OF_SID_BITS attribute type declares how many bits of the G-IKEv2 uses the same Authentication payload as specified in
cipher nonce in which to represent an SID value. The bits are [RFC7296], section 3.8, to authenticate the rekey message. However,
applied as the most significant bits of the IV, as shown in Figure 1 if it is used in the GSA_REKEY messages the content of the payload is
of [RFC6054] and specified in Section 1.4.6.2. Guidance for a GCKS computed differently, as described in Section 1.4.5.1.1.
choosing the NUMBER_OF_SID_BITS is provided in Section 3 of
[RFC6054].
This value is applied to each SID value distributed in the SID 4. Interaction with other IKEv2 Protocol Extensions
Download.
2.5.4.2. SID_VALUE A number of IKEv2 extensions is 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 Secure Password
authentication ([RFC6467]). G-IKEv2 is compatible with and can use
IKEv2 Session Resumption [RFC5723] except that a GM would include the
initial ticket request in a GSA_AUTH exchange instead of an IKE_AUTH
exchange. G-IKEv2 is also compatible with Multiple Key Exchanges in
IKEv2 framework, defined in [I-D.ietf-ipsecme-ikev2-multiple-ke].
The SID_VALUE attribute type declares a single SID value for the Some IKEv2 extensions however require special handling if used in
exclusive use of this group member. Multiple SID_VALUE attributes G-IKEv2.
MAY be included in a SID Download.
2.5.4.3. GM Semantics 4.1. Mixing Preshared Keys in IKEv2 for Post-quantum Security
The SID_VALUE attribute value distributed to the group member MUST be G-IKEv2 can take advantage of the protection provided by Postquantum
used by that group member as the SID field portion of the IV for all Preshared Keys (PPK) for IKEv2 [RFC8784]. However, the use of PPK
Data-Security SAs including a counter-based mode of operation leaves the initial IKE SA susceptible to quantum computer (QC)
distributed by the GCKS as a part of this group. When the Sender- attacks. For this reason an alternative approach for using PPK in
Specific IV (SSIV) field for any Data-Security SA is exhausted, the IKEv2 defined in [I-D.smyslov-ipsecme-ikev2-qr-alt] SHOULD be used.
group member MUST NOT act as a sender on that SA using its active
SID. The group member SHOULD re-register, at which time the GCKS
will issue a new SID to the group member, along with either the same
Data-Security SAs or replacement ones. The new SID replaces the
existing SID used by this group member, and also resets the SSIV
value to its starting value. A group member MAY re-register prior to
the actual exhaustion of the SSIV field to avoid dropping data
packets due to the exhaustion of available SSIV values combined with
a particular SID value.
A group member MUST ignore an SID Download Type KD payload present in If the alternative approach is not supported by the peers, then the
a GSA-REKEY message, otherwise more than one GM may end up using the GCKS MUST NOT send GSA and KD payloads in the GSA_AUTH response
same SID. message. Instead, the GCKS MUST return a new notification
REKEY_IS_NEEDED. Upon receiving this notification in the GSA_AUTH
response the GM MUST perform an IKE SA rekey and then initiate a new
GSA_REGISTRATION request for the same group. Below are possible
scenarios involving using PPK.
2.5.4.4. GCKS Semantics The GM starts the IKE_SA_INIT exchange requesting using PPK, and the
GCKS responds with agreement to do it, or aborts according to its
"mandatory_or_not" flag:
If any KD payload includes keying material that is associated with a Initiator (Member) Responder (GCKS)
counter-mode of operation, an SID Download Type KD payload containing -------------------- ------------------
at least one SID_VALUE attribute MUST be included. The GCKS MUST NOT HDR, SAi1, KEi, Ni, N(USE_PPK) -->
send the SID Download Type KD payload as part of a GSA_REKEY message, <-- DR, SAr1, KEr, Nr, [CERTREQ],
because distributing the same sender-specific policy to more than one N(USE_PPK)
group member will reduce the security of the group.
2.6. Delete Payload Figure 21: IKE_SA_INIT Exchange requesting using PPK
There are occasions when the GCKS may want to signal to group members The GM then starts the GSA_AUTH exchange with the PPK_ID; if using
to delete policy at the end of a broadcast, if group policy has PPK is not mandatory for the GM, the NO_PPK_AUTH notification is
changed, or the GCKS needs to reset the policy and keying material included in the request:
for the group due to an emergency. Deletion of keys MAY be
accomplished by sending an IKEv2 Delete Payload, section 3.11 of
[RFC7296] as part of a registration or rekey Exchange. Whenever an
SA is to be deleted, the GKCS SHOULD send the Delete Payload in both
registration and rekey exchanges, because GMs with previous group
policy may contact the GCKS using either exchange.
The Protocol ID MUST be 41 for GSA_REKEY Exchange, 2 for AH or 3 for Initiator (Member) Responder (GCKS)
ESP. Note that only one protocol id value can be defined in a Delete -------------------- ------------------
payload. If a TEK and a KEK SA for GSA_REKEY Exchange must be HDR, SK{IDi, AUTH, IDg,
deleted, they must be sent in different Delete payloads. Similarly, N(PPK_IDENTITY), N(NO_PPK_AUTH)} -->
if a TEK specifying ESP and a TEK specifying AH need to be deleted,
they must be sent in different Delete payloads.
There may be circumstances where the GCKS may want to reset the Figure 22: GSA_AUTH Request using PPK
policy and keying material for the group. The GCKS can signal
deletion of all policy of a particular TEK by sending a TEK with a
SPI value equal to zero in the delete payload. In the event that the
administrator is no longer confident in the integrity of the group
they may wish to remove all KEK and all the TEKs in the group. This
is done by having the GCKS send a delete payload with a SPI of zero
and a Protocol-ID of AH or ESP to delete all TEKs, followed by
another delete payload with a SPI value of zero and Protocol-ID of
KEK SA to delete the KEK SA.
2.7. Notify Payload If the GCKS has no such PPK and using PPK is not mandatory for it and
the NO_PPK_AUTH is included, then the GCKS continues without PPK; in
this case no rekey is needed:
G-IKEv2 uses the same Notify payload as specified in [RFC7296], Initiator (Member) Responder (GCKS)
section 3.10. -------------------- ------------------
<-- HDR, SK{IDr, AUTH, GSA, KD}
There are additional Notify Message types introduced by G-IKEv2 to Figure 23: GSA_AUTH Response using no PPK
communicate error conditions and status.
NOTIFY messages - error types Value If the GCKS has no such PPK and either the NO_PPK_AUTH is missing or
------------------------------------------------------------------- using PPK is mandatory for the GCKS, the GCKS aborts the exchange:
INVALID_GROUP_ID - 45
AUTHORIZATION_FAILED - 46
REGISTRATION_FAILED - TBD
INVALID_GROUP_ID indicates the group id sent during the registration Initiator (Member) Responder (GCKS)
process is invalid. -------------------- ------------------
<-- HDR, SK{N(AUTHENTICATION_FAILED)}
AUTHORIZATION_FAILED is sent in the response to a GSA_AUTH message Figure 24: GSA_AUTH Error Response
when authorization failed.
REGISTRATION_FAILED is sent by the GCKS when the GM registration Assuming the GCKS has the proper PPK it continues with a request to
request cannot be satisfied. the GM to immediately perform a rekey by sending the REKEY_IS_NEEDED
notification:
NOTIFY messages - status types Value Initiator (Member) Responder (GCKS)
------------------------------------------------------------------- -------------------- ------------------
SENDER - 16429 <-- HDR, SK{IDr, AUTH, N(PPK_IDENTITY),
REKEY_IS_NEEDED - TBD N(REKEY_IS_NEEDED) }
SENDER notification is sent in GSA_AUTH or GSA_REGISTRATION to Figure 25: GSA_AUTH Response using PPK
indicate that the GM intends to be sender of data traffic. The data
includes a count of how many SID values the GM desires. The count
MUST be 4 octets long and contain the big endian representation of
the number of requested SIDs.
REKEY_IS_NEEDED is sent in GSA_AUTH response message to indicate that The GM initiates the CREATE_CHILD_SA exchange to rekey the initial
the GM must perform an immediate rekey of IKE SA to make it secure IKE SA and then makes a new registration request for the same group
against quantum computers and then start a registration request over. over the new IKE SA:
2.8. Authentication Payload Initiator (Member) Responder (GCKS)
-------------------- ------------------
HDR, SK{SA, Ni, KEi} -->
<-- HDR, SK{SA, Nr, KEr}
HDR, SK{IDg} --->
<-- HDR, SK{GSA, KD}
G-IKEv2 uses the same Authentication payload as specified in Figure 26: Rekeying IKE SA followed by GSA_REGISTRATION Exchange
[RFC7296], section 3.8, to sign the rekey message.
3. Security Considerations 5. Security Considerations
3.1. GSA Registration and Secure Channel 5.1. GSA Registration and Secure Channel
G-IKEv2 registration exchange uses IKEv2 IKE_SA_INIT protocols, G-IKEv2 registration exchange uses IKEv2 IKE_SA_INIT protocols,
inheriting all the security considerations documented in [RFC7296] inheriting all the security considerations documented in [RFC7296]
section 5 Security Considerations, including authentication, section 5 Security Considerations, including authentication,
confidentiality, protection against man-in-the-middle, protection confidentiality, protection against man-in-the-middle, protection
against replay/reflection attacks, and denial of service protection. against replay/reflection attacks, and denial of service protection.
The GSA_AUTH and GSA_REGISTRATION exchanges also take advantage of The GSA_AUTH and GSA_REGISTRATION exchanges also take advantage of
those protections. In addition, G-IKEv2 brings in the capability to those protections. In addition, G-IKEv2 brings in the capability to
authorize a particular group member regardless of whether they have authorize a particular group member regardless of whether they have
the IKEv2 credentials. the IKEv2 credentials.
3.2. GSA Maintenance Channel 5.2. GSA Maintenance Channel
The GSA maintenance channel is cryptographically and integrity The GSA maintenance channel is cryptographically and integrity
protected using the cryptographic algorithm and key negotiated in the protected using the cryptographic algorithm and key negotiated in the
GSA member registration exchanged. GSA member registration exchanged.
3.2.1. Authentication/Authorization 5.2.1. Authentication/Authorization
Authentication is implicit, the public key of the identity is Authentication is implicit, the public key of the identity is
distributed during the registration, and the receiver of the rekey distributed during the registration, and the receiver of the rekey
message uses that public key and identity to verify the message came message uses that public key and identity to verify the message came
from the authorized GCKS. from the authorized GCKS.
3.2.2. Confidentiality 5.2.2. Confidentiality
Confidentiality is provided by distributing a confidentiality key as Confidentiality is provided by distributing a confidentiality key as
part of the GSA member registration exchange. part of the GSA member registration exchange.
3.2.3. Man-in-the-Middle Attack Protection 5.2.3. Man-in-the-Middle Attack Protection
GSA maintenance channel is integrity protected by using a digital GSA maintenance channel is integrity protected by using a digital
signature. signature.
3.2.4. Replay/Reflection Attack Protection 5.2.4. Replay/Reflection Attack Protection
The GSA_REKEY message includes a monotonically increasing sequence The GSA_REKEY message includes a monotonically increasing sequence
number to protect against replay and reflection attacks. A group number to protect against replay and reflection attacks. A group
member will recognize a replayed message by comparing the Message ID member will recognize a replayed message by comparing the Message ID
number to that of the last received rekey message, any rekey message number to that of the last received rekey message, any rekey message
containing a Message ID number less than or equal to the last containing a Message ID number less than or equal to the last
received value MUST be discarded. Implementations should keep a received value MUST be discarded. Implementations should keep a
record of recently received GSA rekey messages for this comparison. record of recently received GSA rekey messages for this comparison.
4. IANA Considerations 6. IANA Considerations
4.1. New Registries 6.1. New Registries
A new set of registries should be created for G-IKEv2, on a new page A new set of registries is created for G-IKEv2 on IKEv2 parameters
titled Group Key Management using IKEv2 (G-IKEv2) Parameters. The page [IKEV2-IANA]. The terms Reserved, Expert Review and Private Use
following registries should be placed on that page. The terms are to be applied as defined in [RFC8126].
Reserved, Expert Review and Private Use are to be applied as defined
in [RFC8126].
GSA Policy Type Registry, see Section 2.4.1 This document creates a new IANA registry "Transform Type <TBA> -
KEK Attributes Registry, see Section 2.4.2.1 Group Key Management Methods". The initial values of the new
registry are:
KEK Management Algorithm Registry, see Section 2.4.2.1.1 Value Group Key Management Method
-------------------------------------------------------
Reserved 0
Wrapped Key Download 1
Unassigned 2-1023
Private Use 1024-65535
GSA TEK Payload Protocol ID Type Registry, see Section 2.4.3 Changes and additions to the unassigned range of this registry are by
the Expert Review Policy [RFC8126].
TEK Attributes Registry, see Section 2.4.3 This document creates a new IANA registry "GSA Attributes". The
initial values of the new registry are:
Key Download Type Registry, see Section 2.5 GSA Attributes Value Type Multiple Used In
---------------------------------------------------------------------
Reserved 0
GSA_KEY_LIFETIME 1 V N (GIKE_REKEY, AH, ESP)
GSA_INITIAL_MESSAGE_ID 2 V N (GIKE_REKEY)
GSA_NEXT_SPI 3 V Y (GIKE_REKEY, AH, ESP)
Unassigned 5-16383
Private Use 16384-32767
Changes and additions to the unassigned range of this registry are by
the Expert Review Policy [RFC8126].
TEK Download Type Attributes Registry, see Section 2.5.1 This document creates a new IANA registry "GAP Attributes". The
initial values of the new registry are:
KEK Download Type Attributes Registry, see Section 2.5.2 GAP Attributes Value Type Multiple
----------------------------------------------------
Reserved 0
GAP_ATD 1 B N
GAP_DTD 2 B N
GAP_SID_BITS 3 B N
Unassigned 4-16383
Private Use 16384-32767
LKH Download Type Attributes Registry, see Section 2.5.3 Changes and additions to the unassigned range of this registry are by
the Expert Review Policy [RFC8126].
SID Download Type Attributes Registry, see Section 2.5.4 This document creates a new IANA registry "Group Key Download
Attributes". The initial values of the new registry are:
4.2. New Payload and Exchange Types Added to the Existing IKEv2 GKD Attributes Value Type Multiple Used In
Registry ------------------------------------------------------------
Reserved 0
SA_KEY 1 V Y (GIKE_REKEY)
N (AH, ESP)
Unassigned 2-16383
Private Use 16384-32767
The following new payloads and exchange types specified in this memo Changes and additions to the unassigned range of this registry are by
have already been allocated by IANA and require no further action, the Expert Review Policy [RFC8126].
other than replacing the draft name with an RFC number.
The present document describes new IKEv2 Next Payload types, see This document creates a new IANA registry "Member Key Download
Section 2.1 Attributes". The initial values of the new registry are:
The present document describes new IKEv2 Exchanges types, see MKD Attributes Value Type Multiple
Section 2.1 ------------------------------------------------
Reserved 0
KEY_WRAP_KEY 1 V Y
GM_SID 2 V Y
AUTH_KEY 3 V N
Unassigned 4-16383
Private Use 16384-32767
The present document describes new IKEv2 notification types, see Changes and additions to the unassigned range of this registry are by
Section 2.7 the Expert Review Policy [RFC8126].
4.3. Changes to Previous Allocations 6.2. Changes in the Existing IKEv2 Registries
Section 4.7 indicates an allocation in the IKEv2 Notify Message Types This document defines new Exchange Types in the "IKEv2 Exchange
- Status Types registry has been made. This NOTIFY type was Types" registry:
allocated earlier in the development of G-IKEv2. The number is
16429, and was allocated with the name SENDER_REQUEST_ID. The name
should be changed to SENDER.
5. Acknowledgements Value Exchange Type
----------------------------
39 GSA_AUTH
40 GSA_REGISTRATION
41 GSA_REKEY
<TBA> GSA_INBAND_REKEY
This document defines new Payload Types in the "IKEv2 Payload Types"
registry:
Value Next Payload Type Notation
----------------------------------------------------
50 Group Identification IDg
51 Group Security Association GSA
52 Key Download KD
This document defines a new Security Protocol Identifier in the
"IKEv2 Security Protocol Identifiers" registry:
<TBA> GIKE_REKEY
This document defines new Transform Types in the "Transform Type
Values" registry and changes the "Used In" column for the existing
allocations:
Type Description Used In
---------------------------------------------------------------------
1 Encryption Algorithm (ENCR) (IKE, GIKE_REKEY and ESP)
2 Pseudo-random Function (PRF) (IKE, GIKE_REKEY)
3 Integrity Algorithm (INTEG) (IKE, GIKE_REKEY, AH,
optional in ESP)
4 Diffie-Hellman Group (D-H) (IKE, optional in AH, ESP)
5 Extended Sequence Numbers (ESN) (AH and ESP)
<TBA> Authentication Method (AUTH) (GIKE_REKEY)
<TBA> Group Key Management Method (GKM) (GIKE_REKEY)
This document defines a new Attribute Type in the "IKEv2 Transform
Attribute Types" registry:
Value Attribute Type Format
----------------------------------------------
<TBA> Algorithm Identifier TLV
This document defines new Notify Message Types in the "Notify Message
Types - Status Types" registry:
Value Notify Messages - Status Types
------------------------------------------
16429 SENDER
The Notify type with the value 16429 was allocated earlier in the
development of G-IKEv2 document with the name SENDER_REQUEST_ID.
This specification changes its name to SENDER.
This document defines new Notify Message Types in the "Notify Message
Types - Error Types" registry:
Value Notify Messages - Error Types
-----------------------------------------
45 INVALID_GROUP_ID
46 AUTHORIZATION_FAILED
<TBA> REGISTRATION_FAILED
7. Acknowledgements
The authors thank Lakshminath Dondeti and Jing Xiang for first The authors thank Lakshminath Dondeti and Jing Xiang for first
exploring the use of IKEv2 for group key management and providing the exploring the use of IKEv2 for group key management and providing the
basis behind the protocol. Mike Sullenberger and Amjad Inamdar were basis behind the protocol. Mike Sullenberger and Amjad Inamdar were
instrumental in helping resolve many issues in several versions of instrumental in helping resolve many issues in several versions of
the document. the document.
6. Contributors 8. Contributors
The following individuals made substantial contributions to early The following individuals made substantial contributions to early
versions of this memo. versions of this memo.
Sheela Rowles Sheela Rowles
Cisco Systems Cisco Systems
170 W. Tasman Drive 170 W. Tasman Drive
San Jose, California 95134-1706 San Jose, California 95134-1706
USA USA
skipping to change at page 46, line 47 skipping to change at page 52, line 30
Email: ptran@cisco.com Email: ptran@cisco.com
Yoav Nir Yoav Nir
Dell EMC Dell EMC
9 Andrei Sakharov St 9 Andrei Sakharov St
Haifa 3190500 Haifa 3190500
Israel Israel
Email: ynir.ietf@gmail.com Email: ynir.ietf@gmail.com
7. References 9. References
7.1. Normative References
9.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997, DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/info/rfc2119>. <https://www.rfc-editor.org/info/rfc2119>.
[RFC2627] Wallner, D., Harder, E., and R. Agee, "Key Management for [RFC2627] Wallner, D., Harder, E., and R. Agee, "Key Management for
Multicast: Issues and Architectures", RFC 2627, Multicast: Issues and Architectures", RFC 2627,
DOI 10.17487/RFC2627, June 1999, DOI 10.17487/RFC2627, June 1999,
<https://www.rfc-editor.org/info/rfc2627>. <https://www.rfc-editor.org/info/rfc2627>.
skipping to change at page 47, line 29 skipping to change at page 53, line 9
[RFC4046] Baugher, M., Canetti, R., Dondeti, L., and F. Lindholm, [RFC4046] Baugher, M., Canetti, R., Dondeti, L., and F. Lindholm,
"Multicast Security (MSEC) Group Key Management "Multicast Security (MSEC) Group Key Management
Architecture", RFC 4046, DOI 10.17487/RFC4046, April 2005, Architecture", RFC 4046, DOI 10.17487/RFC4046, April 2005,
<https://www.rfc-editor.org/info/rfc4046>. <https://www.rfc-editor.org/info/rfc4046>.
[RFC4301] Kent, S. and K. Seo, "Security Architecture for the [RFC4301] Kent, S. and K. Seo, "Security Architecture for the
Internet Protocol", RFC 4301, DOI 10.17487/RFC4301, Internet Protocol", RFC 4301, DOI 10.17487/RFC4301,
December 2005, <https://www.rfc-editor.org/info/rfc4301>. December 2005, <https://www.rfc-editor.org/info/rfc4301>.
[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 [RFC6054] McGrew, D. and B. Weis, "Using Counter Modes with
Encapsulating Security Payload (ESP) and Authentication Encapsulating Security Payload (ESP) and Authentication
Header (AH) to Protect Group Traffic", RFC 6054, Header (AH) to Protect Group Traffic", RFC 6054,
DOI 10.17487/RFC6054, November 2010, DOI 10.17487/RFC6054, November 2010,
<https://www.rfc-editor.org/info/rfc6054>. <https://www.rfc-editor.org/info/rfc6054>.
[RFC7296] Kaufman, C., Hoffman, P., Nir, Y., Eronen, P., and T. [RFC7296] Kaufman, C., Hoffman, P., Nir, Y., Eronen, P., and T.
Kivinen, "Internet Key Exchange Protocol Version 2 Kivinen, "Internet Key Exchange Protocol Version 2
(IKEv2)", STD 79, RFC 7296, DOI 10.17487/RFC7296, October (IKEv2)", STD 79, RFC 7296, DOI 10.17487/RFC7296, October
2014, <https://www.rfc-editor.org/info/rfc7296>. 2014, <https://www.rfc-editor.org/info/rfc7296>.
[RFC8126] Cotton, M., Leiba, B., and T. Narten, "Guidelines for [RFC8126] Cotton, M., Leiba, B., and T. Narten, "Guidelines for
Writing an IANA Considerations Section in RFCs", BCP 26, Writing an IANA Considerations Section in RFCs", BCP 26,
RFC 8126, DOI 10.17487/RFC8126, June 2017, RFC 8126, DOI 10.17487/RFC8126, June 2017,
<https://www.rfc-editor.org/info/rfc8126>. <https://www.rfc-editor.org/info/rfc8126>.
[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
May 2017, <https://www.rfc-editor.org/info/rfc8174>. May 2017, <https://www.rfc-editor.org/info/rfc8174>.
7.2. Informative References 9.2. Informative References
[I-D.ietf-ipsecme-qr-ikev2]
Fluhrer, S., McGrew, D., Kampanakis, P., and V. Smyslov,
"Mixing Preshared Keys in IKEv2 for Post-quantum
Resistance", draft-ietf-ipsecme-qr-ikev2-10 (work in
progress), December 2019.
[I-D.smyslov-ipsecme-ikev2-qr-alt]
Smyslov, V., "An Alternative Approach for Postquantum
Preshared Keys in IKEv2", draft-smyslov-ipsecme-ikev2-qr-
alt-00 (work in progress), October 2019.
[I-D.tjhai-ipsecme-hybrid-qske-ikev2] [I-D.ietf-ipsecme-ikev2-multiple-ke]
Tjhai, C., Tomlinson, M., grbartle@cisco.com, g., Fluhrer, Tjhai, C., Tomlinson, M., grbartle@cisco.com, g., Fluhrer,
S., Geest, D., Garcia-Morchon, O., and V. Smyslov, S., Geest, D., Garcia-Morchon, O., and V. Smyslov,
"Framework to Integrate Post-quantum Key Exchanges into "Multiple Key Exchanges in IKEv2", draft-ietf-ipsecme-
Internet Key Exchange Protocol Version 2 (IKEv2)", draft- ikev2-multiple-ke-00 (work in progress), January 2020.
tjhai-ipsecme-hybrid-qske-ikev2-04 (work in progress),
July 2019. [I-D.smyslov-ipsecme-ikev2-qr-alt]
Smyslov, V., "Alternative Approach for Mixing Preshared
Keys in IKEv2 for Post-quantum Security", draft-smyslov-
ipsecme-ikev2-qr-alt-01 (work in progress), February 2020.
[IKEV2-IANA] [IKEV2-IANA]
IANA, "Internet Key Exchange Version 2 (IKEv2) IANA, "Internet Key Exchange Version 2 (IKEv2)
Parameters", <http://www.iana.org/assignments/ikev2- Parameters", <http://www.iana.org/assignments/ikev2-
parameters/ikev2-parameters.xhtml#ikev2-parameters-7>. parameters/ikev2-parameters.xhtml#ikev2-parameters-7>.
[NNL] Naor, D., Noal, M., and J. Lotspiech, "Revocation and [NNL] Naor, D., Noal, M., and J. Lotspiech, "Revocation and
Tracing Schemes for Stateless Receivers", Advances in Tracing Schemes for Stateless Receivers", Advances in
Cryptology, Crypto '01, Springer-Verlag LNCS 2139, 2001, Cryptology, Crypto '01, Springer-Verlag LNCS 2139, 2001,
pp. 41-62, 2001, pp. 41-62, 2001,
<http://www.wisdom.weizmann.ac.il/~naor/>. <http://www.wisdom.weizmann.ac.il/~naor/PAPERS/2nl.pdf>.
[OFT] McGrew, D. and A. Sherman, "Key Establishment in Large [OFT] McGrew, D. and A. Sherman, "Key Establishment in Large
Dynamic Groups Using One-Way Function Trees", Manuscript, Dynamic Groups Using One-Way Function Trees", Manuscript,
submitted to IEEE Transactions on Software Engineering, submitted to IEEE Transactions on Software Engineering,
1998, <http://download.nai.com/products/media/nai/misc/ 1998, <https://pdfs.semanticscholar.org/
oft052098.ps>. d24c/7b41f7bcc2b6690e1b4d80eaf8c3e1cc5ee5.pdf>.
[RFC2409] Harkins, D. and D. Carrel, "The Internet Key Exchange [RFC2409] Harkins, D. and D. Carrel, "The Internet Key Exchange
(IKE)", RFC 2409, DOI 10.17487/RFC2409, November 1998, (IKE)", RFC 2409, DOI 10.17487/RFC2409, November 1998,
<https://www.rfc-editor.org/info/rfc2409>. <https://www.rfc-editor.org/info/rfc2409>.
[RFC3279] Bassham, L., Polk, W., and R. Housley, "Algorithms and [RFC3279] Bassham, L., Polk, W., and R. Housley, "Algorithms and
Identifiers for the Internet X.509 Public Key Identifiers for the Internet X.509 Public Key
Infrastructure Certificate and Certificate Revocation List Infrastructure Certificate and Certificate Revocation List
(CRL) Profile", RFC 3279, DOI 10.17487/RFC3279, April (CRL) Profile", RFC 3279, DOI 10.17487/RFC3279, April
2002, <https://www.rfc-editor.org/info/rfc3279>. 2002, <https://www.rfc-editor.org/info/rfc3279>.
skipping to change at page 50, line 15 skipping to change at page 55, line 39
[RFC7383] Smyslov, V., "Internet Key Exchange Protocol Version 2 [RFC7383] Smyslov, V., "Internet Key Exchange Protocol Version 2
(IKEv2) Message Fragmentation", RFC 7383, (IKEv2) Message Fragmentation", RFC 7383,
DOI 10.17487/RFC7383, November 2014, DOI 10.17487/RFC7383, November 2014,
<https://www.rfc-editor.org/info/rfc7383>. <https://www.rfc-editor.org/info/rfc7383>.
[RFC7427] Kivinen, T. and J. Snyder, "Signature Authentication in [RFC7427] Kivinen, T. and J. Snyder, "Signature Authentication in
the Internet Key Exchange Version 2 (IKEv2)", RFC 7427, the Internet Key Exchange Version 2 (IKEv2)", RFC 7427,
DOI 10.17487/RFC7427, January 2015, DOI 10.17487/RFC7427, January 2015,
<https://www.rfc-editor.org/info/rfc7427>. <https://www.rfc-editor.org/info/rfc7427>.
[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>.
[RFC8229] Pauly, T., Touati, S., and R. Mantha, "TCP Encapsulation [RFC8229] Pauly, T., Touati, S., and R. Mantha, "TCP Encapsulation
of IKE and IPsec Packets", RFC 8229, DOI 10.17487/RFC8229, of IKE and IPsec Packets", RFC 8229, DOI 10.17487/RFC8229,
August 2017, <https://www.rfc-editor.org/info/rfc8229>. August 2017, <https://www.rfc-editor.org/info/rfc8229>.
[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>.
Appendix A. Use of LKH in G-IKEv2 Appendix A. Use of LKH in G-IKEv2
Section 5.4 of [RFC2627] describes the LKH architecture, and how a Section 5.4 of [RFC2627] describes the LKH architecture, and how a
GCKS uses LKH to exclude group members. This section clarifies how GCKS uses LKH to exclude group members. This section clarifies how
the LKH architecture is used with G-IKEv2. the LKH architecture is used with G-IKEv2.
A.1. Group Creation A.1. Notation
In this section we will use the notation X{Y} where a key with ID Y
is encrypted with the key with ID X. The notation 0{Y} means that
the default wrap key (SK_w) is used to encrypt key Y, and the
notation X{0} means key X is used to encrypt the group SA key. Note,
that 0{0} means that the group SA key is encrypted with default wrap
key.
The content of the KD payload will be shown as a sequence of Key
Packets. The Group Key Packet substructure will be denoted as SAn(),
when n is an SPI for the SA, and The Member Key Packet substructure
will be denoted as GM(). The content of the Key Packets is shown as
SA_KEY and KEY_WRAP_KEY attributes with the notation described above.
Here is the example of KD payload.
KD(SA1(X{0}),GM(Y{X},Z{Y},0{Z})
For simplicity any other attributes in the KD payload are omitted.
We will also use the notation X->Y->Z to describe the Key Path, i.e.
the relation between the keys. In this case the keys had the
following relation: Z{Y}, Y{X}.
A.2. Group Creation
When a GCKS forms a group, it creates a key tree as shown in the When a GCKS forms a group, it creates a key tree as shown in the
figure below. The key tree contains logical keys (represented as figure below. The key tree contains logical keys (which are
numbers in the figure) and a private key shared with only a single GM represented as the values of their Key IDs in the figure) and a
(represented as letters in the figure). Note that the use of numbers private key shared with only a single GM (the GMs are represented as
and letters is used for explanatory purposes; in fact, each key would letters followed by the corresponding key ID in parentheses in the
have an LKH ID, which is two-octet identifier chosen by the GCKS. figure). The root of the tree contains the multicast rekey SA key
The GCKS may create a complete tree as shown, or a partial tree which (which is represented as SAn(0), showing that its Key ID is always
is created on demand as members join the group. The top of the key zero). The figure below assumes that the Key IDs are assigned
tree (i.e., "1" in Figure 29) is used as the KEK for the group. sequentially; this is not a requirement and only used for
illustrative purposes. The GCKS may create a complete tree as shown,
or a partial tree which is created on demand as members join the
group.
1 SA1(0)
+------------------------------+ +------------------------------+
2 3 1 2
+---------------+ +---------------+ +---------------+ +---------------+
4 5 6 7 3 4 5 6
+-------+ +-------+ +--------+ +--------+ +-------+ +-------+ +--------+ +--------+
A B C D E F G H A(7) B(8) C(9) D(10) E(11) F(12) G(13) H(14)
Figure 29: Initial LKH tree Figure 27: Initial LKH tree
When GM "A" joins the group, the GCKS provides an LKH_DOWNLOAD_ARRAY When GM A joins the group, the GCKS provides it with the keys in the
in the KD payload of the GSA_AUTH or GSA_REGISTRATION exchange. KEY_WRAP_KEY attributes in the KD payload of the GSA_AUTH or
Given the tree shown in figure above, the LKH_DOWNLOAD_ARRAY will GSA_REGISTRATION exchange. Given the tree shown in figure above, the
contain four LKH Key payloads, each containing an LKH ID and Key KD payload will be:
Data. If the LKH ID values were chosen as shown in the figure, four
LKH Keys would be provided to GM "A", in the following order: A, 4,
2, 1. When GM "B" joins the group, it would also be given four LKH
Keys in the following order: B, 4, 2, 1. And so on, until GM "H"
joins the group and is given H, 7, 3, 1.
A.2. Group Member Exclusion KD(SA1(1{0}),GM(3{1},7{3},0{7})
KD Payload for the Group Member A
From these attributes the GM A will construct the Key Path
0->1->3->7->0 and since it ends up with SK_w, it will use all the
KEY_WRAP_KEY attributes present in the path as its working Key Path:
1->3->7.
Similarly, when other GMs will be joining the group they will be
provided with the corresponding keys, so after 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
A.3. Simple Group SA Rekey
If the GCKS performs a simple SA rekey without changing group
membership, it will only send Group Key Packet in the KD payload with
a new SA key encrypted with the default KWK.
KD(SA2(0{0}))
KD Payload for the Group Member F
All the GMs will be able to decrypt it and no changes in their
working Key Paths will take place.
A.4. Group Member Exclusion
If the GKCS has reason to believe that a GM should be excluded, then If the GKCS has reason to believe that a GM should be excluded, then
it can do so by sending a GSA_REKEY exchange that includes a set of it can do so by sending a GSA_REKEY message that includes a set of
LKH_UPDATE_ARRAY attributes in the KD payload. Each LKH_UPDATE_ARRAY GM_KEY attributes which would allow all GMs except for the excluded
contains a set of LKH Key payloads, in which every GM other than the one to get a new SA key.
excluded GM will be able to determine a set of new logical keys,
which culminate in a new key "1". The excluded GM will observe the
set of LKH_UPDATE_ARRAY attributes, but cannot determine the new
logical keys because each of the "Key Data" fields is encrypted with
a key held by other GMs. The GM will hold no keys to properly
decrypt any of the "Key Data" fields, including key "1" (i.e., the
new KEK). When a subsequent GSA_REKEY exchange is delivered by the
GCKS and protected by the new KEK, the excluded GM will no longer be
able to see the contents of the GSA_REKEY, including new TEKs that
will be delivered to replace existing TEKs. At this point, the GM
will no longer be able to participate in the group.
In the example below, new keys are represented as the number followed In the example below the GCKS excludes GM F. For this purpose it
by a "prime" symbol (e.g., "1" becomes "1'"). Each key is encrypted changes the key tree as follows, replacing the key 2 with the key 15
by another key. This is represented as "{key1}key2", where key2 and the key 5 with the key 16. It also a new SA key for a new SA3.
encrypts key1. For example, "{1'}2' states that a new key "1'" is
encrypted with a new key "2'".
If GM "B" is to be excluded, the GCKS will need to include three SA3(0)
LKH_UPDATE_ARRAY attributes in the GSA_REKEY message. The order of +------------------------------+
the attributes does not matter; only the order of the keys within 1 15
each attribute. +---------------+ +---------------+
3 4 16 6
+-------+ +-------+ +---- +--------+
A(7) B(8) C(9) D(10) E(11) F(12) G(13) H(14)
o One will provide GM "A" with new logical keys that are shared with Figure 28: LKH tree after F has been excluded
B: {4'}A, {2'}4', {1'}2'
o One will provide all GMs holding key "5" with new logical keys: Then it sends the following KD payload for the new rekey SA3:
{2'}5, {1'}2'
o One will provide all GMs holding key "3" with a new KEK: {1'}3 KD(SA3(1{0},SA3(15{0})),GM(6{15},16{15},11{16})
Each GM will look at each LKH_UPDATE_ARRAY attribute and observe an KD Payload for the Group Member F
LKH ID which is present in an LKH Key delivered to them in the
LKH_DOWNLOAD_ARRAY they were given. If they find a matching LKH ID,
then they will decrypt the new key with the logical key immediately
preceding that LKH Key, and so on until they have received the new 1'
key.
The resulting key tree from this rekey event would would be shown in While processing this KD payload:
Figure 30.
1' o GMs A, B, C and D will be able to decrypt the SA_KEY attribute
+------------------------------+ 1{0} by using the "1" key from their key path. Since no new
2' 3 GM_KEY attributes are in the new Key Path, they won't update their
+---------------+ +---------------+ working Key Paths.
4' 5 6 7
+---+ +-------+ +--------+ +--------+
A B C D E F G H
Figure 30: LKH tree after B has been excluded o GMs G and H will construct new Key Path 15->0 and will be able to
decrypt the new GM_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).
Authors' Addresses o GM E will construct new Key Path 16->15->0 and will be able to
decrypt the new GM_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).
Brian Weis o GM F won't be able to construct any Key Path leading to any key he
Independent possesses, so it will be unable to decrypt the new SA key for the
USA SA3 and thus it will be excluded from the group once the GCKS
starts sending TEK keys using SA3.
Email: bew.stds@gmail.com 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
Authors' Addresses
Valery Smyslov Valery Smyslov
ELVIS-PLUS ELVIS-PLUS
PO Box 81 PO Box 81
Moscow (Zelenograd) 124460 Moscow (Zelenograd) 124460
Russian Federation Russian Federation
Phone: +7 495 276 0211 Phone: +7 495 276 0211
Email: svan@elvis.ru Email: svan@elvis.ru
Brian Weis
Independent
USA
Email: bew.stds@gmail.com
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