ACE Working Group F. Palombini
Internet-Draft Ericsson AB
Intended status: Standards Track M. Tiloca
Expires: September 9, 2019 RISE AB
March 08, 2019
Key Provisioning for Group Communication using ACE
draft-ietf-ace-key-groupcomm-01
Abstract
This document defines message formats and procedures for requesting
and distributing group keying material using the ACE framework, to
protect communications between group members.
Status of This Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute
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This Internet-Draft will expire on September 9, 2019.
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document authors. All rights reserved.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
1.1. Terminology . . . . . . . . . . . . . . . . . . . . . . . 3
2. Overview . . . . . . . . . . . . . . . . . . . . . . . . . . 3
3. Authorization to Join a Group . . . . . . . . . . . . . . . . 5
3.1. Authorization Request . . . . . . . . . . . . . . . . . . 6
3.2. Authorization Response . . . . . . . . . . . . . . . . . 7
3.3. Token Post . . . . . . . . . . . . . . . . . . . . . . . 8
4. Key Distribution . . . . . . . . . . . . . . . . . . . . . . 8
4.1. Key Distribution Request . . . . . . . . . . . . . . . . 9
4.2. Key Distribution Response . . . . . . . . . . . . . . . . 10
5. Removal of a Node from the Group . . . . . . . . . . . . . . 12
5.1. Expired Authorization . . . . . . . . . . . . . . . . . . 12
5.2. Request to Leave the Group . . . . . . . . . . . . . . . 12
6. Retrieval of Updated Keying Material . . . . . . . . . . . . 13
6.1. Key Re-Distribution Request . . . . . . . . . . . . . . . 14
6.2. Key Re-Distribution Response . . . . . . . . . . . . . . 14
7. Retrieval of Public Keys for Group Members . . . . . . . . . 15
7.1. Public Key Request . . . . . . . . . . . . . . . . . . . 15
7.2. Public Key Response . . . . . . . . . . . . . . . . . . . 16
8. Security Considerations . . . . . . . . . . . . . . . . . . . 16
9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 16
9.1. ACE Groupcomm Key Registry . . . . . . . . . . . . . . . 16
9.2. ACE Groupcomm Profile Registry . . . . . . . . . . . . . 17
9.3. Expert Review Instructions . . . . . . . . . . . . . . . 18
10. References . . . . . . . . . . . . . . . . . . . . . . . . . 18
10.1. Normative References . . . . . . . . . . . . . . . . . . 18
10.2. Informative References . . . . . . . . . . . . . . . . . 19
Appendix A. Document Updates . . . . . . . . . . . . . . . . . . 20
A.1. Version -00 to -01 . . . . . . . . . . . . . . . . . . . 20
Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . . 20
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 21
1. Introduction
This document expands the ACE framework [I-D.ietf-ace-oauth-authz] to
define the format of messages used to request, distribute and renew
the keying material in a group communication scenario, e.g. based on
multicast [RFC7390] or on publishing-subscribing
[I-D.ietf-core-coap-pubsub].
Profiles that use group communication can build on this document to
specify the selection of the message parameters defined in this
document to use and their values. Known applications that can
benefit from this document would be, for example, profiles addressing
group communication based on multicast [RFC7390] or publishing/
subscribing [I-D.ietf-core-coap-pubsub] in ACE.
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If the application requires backward and forward security, updated
keying material is generated and distributed to the group members
(rekeying), when membership changes. A key management scheme
performs the actual distribution of the updated keying material to
the group. In particular, the key management scheme rekeys the
current group members when a new node joins the group, and the
remaining group members when a node leaves the group. This document
provides a message format for group rekeying that allows to fulfill
these requirements. Rekeying mechanisms can be based on [RFC2093],
[RFC2094] and [RFC2627].
1.1. Terminology
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in [RFC2119]. These
words may also appear in this document in lowercase, absent their
normative meanings.
Readers are expected to be familiar with the terms and concepts
described in [I-D.ietf-ace-oauth-authz] and [RFC8152], such as
Authorization Server (AS) and Resource Server (RS).
2. Overview
+------------+ +-----------+
| AS | | KDC |
| | .-------->| |
+------------+ / +-----------+
^ /
| /
v / +-----------+
+------------+ / +------------+ |+-----------+
| Client |<-' | Dispatcher | ||+-----------+
| |<-------->| (RS) |<------->|| Group |
+------------+ +------------+ +| members |
+-----------+
Figure 1: Key Distribution Participants
The following participants (see Figure 1) take part in the
authorization and key distribution.
o Client (C): node that wants to join the group communication. It
can request write and/or read rights.
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o Authorization Server (AS): same as AS in the ACE Framework; it
enforces access policies, and knows if a node is allowed to join
the group with write and/or read rights.
o Key Distribution Center (KDC): maintains the keying material to
protect group communications, and provides it to Clients
authorized to join the group. During the first part of the
exchange (Section 3), it takes the role of the RS in the ACE
Framework. During the second part (Section 4), which is not based
on the ACE Framework, it distributes the keying material. In
addition, it provides the latest keying material to group members
when requested. If required by the application, the KDC renews
and re-distributes the keying material in the group when
membership changes.
o Dispatcher: entity through which the Clients communicate with the
group and which distributes messages to the group members.
Examples of dispatchers are: the Broker node in a pub-sub setting;
a relayer node for group communication that delivers group
messages as multiple unicast messages to all group members; an
implicit entity as in a multicast communication setting, where
messages are transmitted to a multicast IP address and delivered
on the transport channel.
This document specifies the message flows and formats for:
o Authorizing a new node to join the group (Section 3), and
providing it with the group keying material to communicate with
the other group members (Section 4).
o Removing of a current member from the group (Section 5).
o Retrieving keying material as a current group member (Section 6
and Section 7).
o Renewing and re-distributing the group keying material (rekeying)
upon a membership change in the group (Section 4.2 and Section 5).
Figure 2 provides a high level overview of the message flow for a
node joining a group communication setting.
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C AS KDC Dispatcher Group
| | | | Member
| | | | \ |
| Authorization Request | | | | Defined |
|----------------------------->| | | | in the ACE |
| | | | | framework |
| Authorization Response | | | | |
|<-----------------------------| | | | |
| | | | | |
|--------- Token Post ---------------->| | / |
| | | |
|---- Key Distribution Request ------->| | |
| | | |
|<--- Key Distribution Response ------ | --- Group Rekeying ----->|
| | |
|<================== Protected communication ===|================>|
| | |
Figure 2: Message Flow Upon New Node's Joining
The exchange of Authorization Request and Authorization Response
between Client and AS MUST be secured, as specified by the ACE
profile used between Client and KDC.
The exchange of Key Distribution Request and Key Distribution
Response between Client and KDC MUST be secured, as a result of the
ACE profile used between Client and KDC.
All further communications between the Client and the KDC MUST be
secured, for instance with the same security mechanism used for the
Key Distribution exchange.
All further communications between a Client and the other group
members MUST be secured using the keying material provided in
Section 4.
3. Authorization to Join a Group
This section describes in detail the format of messages exchanged by
the participants when a node requests access to a group. The first
part of the exchange is based on ACE [I-D.ietf-ace-oauth-authz].
As defined in [I-D.ietf-ace-oauth-authz], the Client requests from
the AS an authorization to join the group through the KDC (see
Section 3.1). If the request is approved and authorization is
granted, the AS provides the Client with a proof-of-possession access
token and parameters to securely communicate with the KDC (see
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Section 3.2). Communications between the Client and the AS MUST be
secured, and depends on the profile of ACE used.
Figure 3 gives an overview of the exchange described above.
Client AS KDC
| | |
|---- Authorization Request: POST /token ------>| |
| | |
|<--- Authorization Response: 2.01 (Created) ---| |
| | |
|----- POST Token: POST /authz-info --------------->|
| |
Figure 3: Message Flow of Join Authorization
3.1. Authorization Request
The Authorization Request sent from the Client to the AS is as
defined in Section 5.6.1 of [I-D.ietf-ace-oauth-authz] and MUST
contain the following parameters:
o 'grant_type', with value "client_credentials".
Additionally, the Authorization Request MAY contain the following
parameters, which, if included, MUST have the corresponding values:
o 'scope', containing the identifier of the specific group (or topic
in the case of pub-sub) that the Client wishes to access, and
optionally the role(s) that the Client wishes to take. This value
is a CBOR array encoded as a byte string, which contains:
* As first element, the identifier of the specific group or
topic.
* Optionally, as second element, the role (or CBOR array of
roles) the Client wishes to take in the group.
The encoding of the group or topic identifier and of the role
identifiers is application specific.
o 'audience', with an identifier of a KDC.
o 'req_cnf', as defined in Section 3.1 of
[I-D.ietf-ace-oauth-params], optionally containing the public key
or a reference to the public key of the Client, if it wishes to
communicate that to the AS.
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o Other additional parameters as defined in
[I-D.ietf-ace-oauth-authz], if necessary.
3.2. Authorization Response
The Authorization Response sent from the AS to the Client is as
defined in Section 5.6.2 of [I-D.ietf-ace-oauth-authz] and MUST
contain the following parameters:
o 'access_token', containing the proof-of-possession access token.
o 'cnf' if symmetric keys are used, not present if asymmetric keys
are used. This parameter is defined in Section 3.2 of
[I-D.ietf-ace-oauth-params] and contains the symmetric proof-of-
possession key that the Client is supposed to use with the KDC.
o 'rs_cnf' if asymmetric keys are used, not present if symmetric
keys are used. This parameter is as defined in Section 3.2 of
[I-D.ietf-ace-oauth-params] and contains information about the
public key of the KDC.
o 'exp', contains the lifetime in seconds of the access token. This
parameter MAY be omitted if the application defines how the
expiration time is communicated to the Client via other means, or
if it establishes a default value.
Additionally, the Authorization Response MAY contain the following
parameters, which, if included, MUST have the corresponding values:
o 'scope', which mirrors the 'scope' parameter in the Authorization
Request (see Section 3.1). Its value is a CBOR array encoded as a
byte string, containing:
* As first element, the identifier of the specific group or topic
the Client is authorized to access.
* Optionally, as second element, the role (or CBOR array of
roles) the Client is authorized to take in the group.
The encoding of the group or topic identifier and of the role
identifiers is application specific.
o Other additional parameters as defined in
[I-D.ietf-ace-oauth-authz], if necessary.
The access token MUST contain all the parameters defined above
(including the same 'scope' as in this message, if present, or the
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'scope' of the Authorization Request otherwise), and additionally
other optional parameters the profile requires.
When receiving an Authorization Request from a Client that was
previously authorized, and which still owns a valid non expired
access token, the AS can simply reply with an Authorization Response
including a new access token.
3.3. Token Post
The Client sends a CoAP POST request including the access token to
the KDC, as specified in section 5.8.1 of [I-D.ietf-ace-oauth-authz].
If the specific ACE profile defines it, the Client MAY use a
different endpoint than /authz-info at the KDC to post the access
token to. After successful verification, the Client is authorized to
receive the group keying material from the KDC and join the group.
Note that this step could be merged with the following message from
the Client to the KDC, namely Key Distribution Request.
4. Key Distribution
This section defines how the keying material used for group
communication is distributed from the KDC to the Client, when joining
the group as a new member.
If not previously established, the Client and the KDC MUST first
establish a pairwise secure communication channel using ACE. The
exchange of Key Distribution Request-Response MUST occur over that
secure channel. The Client and the KDC MAY use that same secure
channel to protect further pairwise communications, that MUST be
secured.
During this exchange, the Client sends a request to the AS,
specifying the group it wishes to join (see Section 4.1). Then, the
KDC verifies the access token and that the Client is authorized to
join that group; if so, it provides the Client with the keying
material to securely communicate with the member of the group (see
Section 4.2).
Figure 4 gives an overview of the exchange described above.
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Client KDC
| |
|---- Key Distribution Request: POST /group-id --->|
| |
|<--- Key Distribution Response: 2.01 (Created) ---|
| |
Figure 4: Message Flow of Key Distribution to a New Group Member
The same set of message can also be used for the following cases,
when the Client is already a group member:
o The Client wishes to (re-)get the current keying material, for
cases such as expiration, loss or suspected mismatch, due to e.g.
reboot or missed group rekeying. This is further discussed in
Section 6.
o The Client wishes to (re-)get the public keys of other group
members, e.g. if it is aware of new nodes joining the group after
itself. This is further discussed in Section 7.
Additionally, the format of the payload of the Key Distribution
Response (Section 4.2) can be reused for messages sent by the KDC to
distribute updated group keying material, in case of a new node
joining the group or of a current member leaving the group. The key
management scheme used to send such messages could rely on, e.g.,
multicast in case of a new node joining or unicast in case of a node
leaving the group.
Note that proof-of-possession to bind the access token to the Client
is performed by using the proof-of-possession key bound to the access
token for establishing secure communication between the Client and
the KDC.
4.1. Key Distribution Request
The Client sends a Key Distribution Request to the KDC. This
corresponds to a CoAP POST request to the endpoint in the KDC
associated to the group to join. The endpoint in the KDC is
associated to the 'scope' value of the Authorization Request/
Response. The payload of this request is a CBOR Map which MAY
contain the following fields, which, if included, MUST have the
corresponding values:
o 'scope', with value the specific resource that the Client is
authorized to access (i.e. group or topic identifier) and role(s),
encoded as in Section 3.1.
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o 'get_pub_keys', if the Client wishes to receive the public keys of
the other nodes in the group from the KDC. The value is an empty
CBOR Array. This parameter may be present if the KDC stores the
public keys of the nodes in the group and distributes them to the
Client; it is useless to have here if the set of public keys of
the members of the group is known in another way, e.g. it was
provided by the AS.
o 'client_cred', with value the public key or certificate of the
Client. If the KDC is managing (collecting from/distributing to
the Client) the public keys of the group members, this field
contains the public key of the Client.
o 'pub_keys_repos', can be present if a certificate is present in
the 'client_cred' field, with value a list of public key
repositories storing the certificate of the Client.
4.2. Key Distribution Response
The KDC verifies the 'scope' received in the Key Distribution
Request, if present, against the 'scope' stored in the access token
associated to this client. If verification fails, the KDC MUST
respond with a 4.01 (Unauthorized) error message. If the Key
Distribution Request is not formatted correctly (e.g. no 'scope'
field present while expected, or unknown fields present), the KDC
MUST respond with 4.00 (Bad Request) error message.
If verification succeeds, the KDC sends a Key Distribution success
Response to the Client. The Key Distribution success Response
corresponds to a 2.01 Created message. The payload of this response
is a CBOR map, which MUST contain:
o 'kty', identifying the key type of the 'key' parameter. The set
of values can be found in the "Key Type" column of the "ACE
Groupcomm Key" Registry. Implementations MUST verify that the key
type matches the profile being used, if present, as registered in
the "ACE Groupcomm Key" registry.
o 'key', containing the keying material for the group communication,
or information required to derive it.
The exact format of the 'key' value MUST be defined in applications
of this specification. Additionally, documents specifying the key
format MUST register it in the "ACE Groupcomm Key" registry,
including its name, type and profile to be used with, as defined in
the "ACE Groupcomm Key" registry, defined in Section 9.1.
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+----------+----------------+---------+-------------------------+
| Name | Key Type Value | Profile | Description |
+----------+----------------+---------+-------------------------+
| Reserved | 0 | | This value is reserved |
+----------+----------------+---------+-------------------------+
Figure 5: Key Type Values
Optionally, the Key Distribution Response MAY contain the following
parameters, which, if included, MUST have the corresponding values:
o 'profile', with value an identifier that MUST be used to uniquely
identify itself. The identifier MUST be registered in the "ACE
Groupcomm Profile" Registry.
o 'exp', with value the expiration time of the keying material for
the group communication, encoded as a CBOR unsigned integer or
floating-point number.
o 'pub_keys', may only be present if 'get_pub_keys' was present in
the Key Distribution Request. This parameter is a CBOR Byte
String, which encodes the public keys of all the group members
paired with the respective member identifiers. In case public
keys in the group are represented as COSE Keys, the CBOR Byte
String encodes a COSE_KeySet (see [RFC8152]), which contains the
public keys of all the members of the group. In particular, each
COSE Key in the COSE_KeySet includes the identifier of the
corresponding group member as value of its 'kid' key parameter.
Alternative specific encodings of this parameter MUST be defined
in applications of this specification.
o 'group_policies', with value a list of parameters indicating how
the group handles specific management aspects. This includes, for
instance, approaches to achieve synchronization of sequence
numbers among group members. The exact format of this parameter
is specific to the profile.
o 'mgt_key_material', with value the administrative keying material
to participate in the group rekeying performed by the KDC. The
exact format and content depend on the specific rekeying scheme
used in the group, which may be specified in the profile.
Specific profiles need to specify how exactly the keying material is
used to protect the group communication.
If the application requires backward security, the KDC SHALL generate
new group keying material and securely distribute it to all the
current group members, using the message format defined in this
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section. Application profiles may define alternative message
formats.
5. Removal of a Node from the Group
This section describes at a high level how a node can be removed from
the group.
If the application requires forward security, the KDC SHALL generate
new group keying material and securely distribute it to all the
current group members but the leaving node, using the message format
defined in Section 4.2. Application profiles may define alternative
message formats.
5.1. Expired Authorization
If the node is not authorized anymore, the AS can directly
communicate that to the KDC. Alternatively, the access token might
have expired. If Token introspection is provided by the AS, the KDC
can use it as per Section 5.7 of [I-D.ietf-ace-oauth-authz], in order
to verify that the access token is still valid.
Either case, once aware that a node is not authorized anymore, the
KDC has to remove the unauthorized node from the list of group
members, if the KDC keeps track of that.
5.2. Request to Leave the Group
A node can actively request to leave the group. In this case, the
Client can send a request formatted as follows to the KDC, to abandon
the group. The client MUST use the protected channel established
with ACE, mentioned in Section 4.
To request to leave a group, the client MUST send a CoAP POST request
to the endpoint in the KDC associated to the group to leave (same
endpoint used in Section 4.1 for Key Distribution requests). The
payload of this Leave Request is a CBOR Map which MUST contain:
o 'leave', with value an empty CBOR array.
o 'scope', with value the specific resource that the Client is
authorized to access (i.e. group or topic identifier) and wants to
leave, encoded as in Section 3.1. The 'role' field is omitted.
Additionally, the Leave request MAY contain the following parameters,
which, if included, MUST have the corresponding values:
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o 'client_cred', with value the identifier of the public key or
certificate of the Client. This field is used if the KDC is
managing (collecting from/distributing to the Client) the public
keys of the group members.
Note that the 'role' field is omitted since such a request should
only be used to leave a group altogether. If the leaving node wants
to be part of a group with fewer roles, it does not need to
communicate that to the KDC, and can simply stop acting according to
such roles.
If the Leave Request is not formatted correctly (e.g. no 'scope'
field present, or unknown fields present), the KDC MUST respond with
a 4.00 (Bad Request) error message. Otherwise, the KDC MUST remove
the leaving node from the list of group members, if the KDC keeps
track of that.
Note that, after having left the group, a node may wish to join it
again. Then, as long as the node is still authorized to join the
group, i.e. it has a still valid access token, it can re-request to
join the group directly to the KDC without needing to retrieve a new
access token from the AS. This means that the KDC needs to keep
track of nodes with valid access tokens, before deleting all
information about the leaving node.
6. Retrieval of Updated Keying Material
A node stops using the group keying material upon its expiration,
according to the 'exp' parameter specified in the retained COSE Key.
Then, if it wants to continue participating in the group
communication, the node has to request new updated keying material to
the KDC.
The Client may perform the same request to the KDC also upon
receiving messages from other group members without being able to
correctly decrypt them. This may be due to a previous update of the
group keying material (rekeying) triggered by the KDC, that the
Client was not able to receive or decrypt.
Note that policies can be set up so that the Client sends a request
to the KDC only after a given number of unsuccessfully decrypted
incoming messages.
Alternatively, the re-distribution of keying material can be
initiated by the KDC, which e.g.:
o Can maintain an Observable resource to send notifications to
Clients when the keying material is updated. Such a notification
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would have the same payload as the Key Re-Distribution Response
defined in Section 6.2.
o Can send the payload of the Key Re-Distribution Response in a
multicast request to the members of the group.
o Can send unicast requests to each Client over a secure channel,
with the Key Re-Distribution Response as payload.
o Can act as a publisher in a pub-sub scenario, and update the
keying material by publishing on a specific topic on a broker,
which all the members of the group are subscribed to.
Note that these methods of KDC-initiated key re-distribution have
different security properties and require different security
associations.
6.1. Key Re-Distribution Request
To request a re-distribution of keying material, the Client sends a
shortened Key Distribution Request to the KDC (Section 4.1),
formatted as follows. The payload MUST contain only the following
field:
o 'scope', which contains only the identifier of the specific group
or topic, encoded as in Section 3.1. That is, the role field is
not present.
6.2. Key Re-Distribution Response
The KDC receiving a Key Re-Distribution Request MUST check that it is
storing a valid access token from that client for that scope.
If that is not the case, i.e. it does not store the token or the
token is not valid for that client for the scope requested, the KDC
MUST respond with a 4.01 (Unauthorized) error message. Analogously
to Section 4.2, if the Key Re-Distribution Request is not formatted
correctly (e.g. no 'scope' field present, or unknown fields present),
the KDC MUST respond with a 4.00 (Bad Request) error message.
Otherwise, the KDC replies to the Client with a Key Distribution
Response, which MUST include the 'kty' and 'key' parameters specified
in Section 4.2. The Key Distribution Response MAY also include the
'profile', 'exp', 'group_policies' and 'mgt_key_material' parameters
specified in Section 4.2.
Note that this response might simply re-provide the same keying
material currently owned by the Client, if it has not been renewed.
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7. Retrieval of Public Keys for Group Members
In case the KDC maintains the public keys of group members, a node in
the group can contact the KDC to request public keys of either all
group members or a specified subset, using the messages defined
below.
Figure 6 gives an overview of the exchange described above.
Client KDC
| |
|---- Public Key Request: POST /group-id --->|
| |
|<--- Public Key Response: 2.01 (Created) ---|
| |
Figure 6: Message Flow of Public Key Request-Response
Note that these messages can be combined with the Key Re-Distribution
messages in Section 6, to request at the same time the keying
material and the public keys. In this case, either a new endpoint at
the KDC may be used, or additional information needs to be sent in
the request payload, to distinguish these combined messages from the
Public Key messages described below, since they would be identical
otherwise.
7.1. Public Key Request
To request public keys, the Client sends a shortened Key Distribution
Request to the KDC (Section 4.1), formatted as follows. The payload
of this request MUST contain the following fields:
o 'get_pub_keys', which has as value a CBOR array including either:
* no elements, i.e. an empty array, in order to request the
public key of all current group members; or
* N elements, each of which is the identifier of a group member,
in order to request the public key of the specified nodes.
o 'scope', which contains only the identifier of the specific group
or topic, encoded as in Section 3.1. That is, the role field is
not present.
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7.2. Public Key Response
The KDC replies to the Client with a Key Distribution Response
containing only the 'pub_keys' parameter, as specified in
Section 4.2. The payload of this response contains the following
field:
o 'pub_keys', which contains either:
* the public keys of all the members of the group, if the
'get_pub_keys' parameter of the Public Key request was an empty
array; or
* the public keys of the group members with the identifiers
specified in the 'get_pub_keys' parameter of the Public Key
request.
The KDC ignores possible identifiers included in the 'get_pub_keys'
parameter of the Public Key request if they are not associated to any
current group member.
8. Security Considerations
The KDC must renew the group keying material upon its expiration.
The KDC should renew the keying material upon group membership
change, and should provide it to the current group members through
the rekeying scheme used in the group.
When a Client receives a message from a sender for the first time, it
needs to have a mechanism in place to avoid replay, e.g.
Appendix B.2 of [I-D.ietf-core-object-security].
9. IANA Considerations
This document has the following actions for IANA.
9.1. ACE Groupcomm Key Registry
This specification establishes the IANA "ACE Groupcomm Key" Registry.
The Registry has been created to use the "Expert Review Required"
registration procedure [RFC8126]. Expert review guidelines are
provided in Section 9.3.
The columns of this Registry are:
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o Name: This is a descriptive name that enables easier reference to
the item. The name MUST be unique. It is not used in the
encoding.
o Key Type Value: This is the value used to identify the keying
material. These values MUST be unique. The value can be a
positive integer, a negative integer, or a string.
o Profile: This field may contain a descriptive string of a profile
to be used with this item. This should be a value that is in the
Name column of the "ACE Groupcomm Profile" Registry.
o Description: This field contains a brief description of the keying
material.
o References: This contains a pointer to the public specification
for the format of the keying material, if one exists.
This Registry has been initially populated by the values in Figure 5.
The specification column for all of these entries will be this
document.
9.2. ACE Groupcomm Profile Registry
This specification establishes the IANA "ACE Groupcomm Profile"
Registry. The Registry has been created to use the "Expert Review
Required" registration procedure [RFC8126]. Expert review guidelines
are provided in Section 9.3. It should be noted that, in addition to
the expert review, some portions of the Registry require a
specification, potentially a Standards Track RFC, be supplied as
well.
The columns of this Registry are:
o Name: The name of the profile, to be used as value of the profile
attribute.
o Description: Text giving an overview of the profile and the
context it is developed for.
o CBOR Value: CBOR abbreviation for this profile name. Different
ranges of values use different registration policies [RFC8126].
Integer values from -256 to 255 are designated as Standards
Action. Integer values from -65536 to -257 and from 256 to 65535
are designated as Specification Required. Integer values greater
than 65535 are designated as Expert Review. Integer values less
than -65536 are marked as Private Use.
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o Reference: This contains a pointer to the public specification of
the profile abbreviation, if one exists.
9.3. Expert Review Instructions
The IANA Registries established in this document are defined as
expert review. This section gives some general guidelines for what
the experts should be looking for, but they are being designated as
experts for a reason so they should be given substantial latitude.
Expert reviewers should take into consideration the following points:
o Point squatting should be discouraged. Reviewers are encouraged
to get sufficient information for registration requests to ensure
that the usage is not going to duplicate one that is already
registered and that the point is likely to be used in deployments.
The zones tagged as private use are intended for testing purposes
and closed environments, code points in other ranges should not be
assigned for testing.
o Specifications are required for the standards track range of point
assignment. Specifications should exist for specification
required ranges, but early assignment before a specification is
available is considered to be permissible. Specifications are
needed for the first-come, first-serve range if they are expected
to be used outside of closed environments in an interoperable way.
When specifications are not provided, the description provided
needs to have sufficient information to identify what the point is
being used for.
o Experts should take into account the expected usage of fields when
approving point assignment. The fact that there is a range for
standards track documents does not mean that a standards track
document cannot have points assigned outside of that range. The
length of the encoded value should be weighed against how many
code points of that length are left, the size of device it will be
used on, and the number of code points left that encode to that
size.
10. References
10.1. Normative References
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[I-D.ietf-ace-oauth-authz]
Seitz, L., Selander, G., Wahlstroem, E., Erdtman, S., and
H. Tschofenig, "Authentication and Authorization for
Constrained Environments (ACE) using the OAuth 2.0
Framework (ACE-OAuth)", draft-ietf-ace-oauth-authz-22
(work in progress), March 2019.
[I-D.ietf-ace-oauth-params]
Seitz, L., "Additional OAuth Parameters for Authorization
in Constrained Environments (ACE)", draft-ietf-ace-oauth-
params-04 (work in progress), February 2019.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/info/rfc2119>.
[RFC8126] Cotton, M., Leiba, B., and T. Narten, "Guidelines for
Writing an IANA Considerations Section in RFCs", BCP 26,
RFC 8126, DOI 10.17487/RFC8126, June 2017,
<https://www.rfc-editor.org/info/rfc8126>.
[RFC8152] Schaad, J., "CBOR Object Signing and Encryption (COSE)",
RFC 8152, DOI 10.17487/RFC8152, July 2017,
<https://www.rfc-editor.org/info/rfc8152>.
10.2. Informative References
[I-D.ietf-core-coap-pubsub]
Koster, M., Keranen, A., and J. Jimenez, "Publish-
Subscribe Broker for the Constrained Application Protocol
(CoAP)", draft-ietf-core-coap-pubsub-06 (work in
progress), January 2019.
[I-D.ietf-core-object-security]
Selander, G., Mattsson, J., Palombini, F., and L. Seitz,
"Object Security for Constrained RESTful Environments
(OSCORE)", draft-ietf-core-object-security-16 (work in
progress), March 2019.
[RFC2093] Harney, H. and C. Muckenhirn, "Group Key Management
Protocol (GKMP) Specification", RFC 2093,
DOI 10.17487/RFC2093, July 1997,
<https://www.rfc-editor.org/info/rfc2093>.
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[RFC2094] Harney, H. and C. Muckenhirn, "Group Key Management
Protocol (GKMP) Architecture", RFC 2094,
DOI 10.17487/RFC2094, July 1997,
<https://www.rfc-editor.org/info/rfc2094>.
[RFC2627] Wallner, D., Harder, E., and R. Agee, "Key Management for
Multicast: Issues and Architectures", RFC 2627,
DOI 10.17487/RFC2627, June 1999,
<https://www.rfc-editor.org/info/rfc2627>.
[RFC7390] Rahman, A., Ed. and E. Dijk, Ed., "Group Communication for
the Constrained Application Protocol (CoAP)", RFC 7390,
DOI 10.17487/RFC7390, October 2014,
<https://www.rfc-editor.org/info/rfc7390>.
Appendix A. Document Updates
RFC EDITOR: PLEASE REMOVE THIS SECTION.
A.1. Version -00 to -01
o Changed name of 'req_aud' to 'audience' in the Authorization
Request (Section 3.1).
o Defined error handling on the KDC (Sections 4.2 and 6.2).
o Updated format of the Key Distribution Response as a whole
(Section 4.2).
o Generalized format of 'pub_keys' in the Key Distribution Response
(Section 4.2).
o Defined format for the message to request leaving the group
(Section 5.2).
o Mentioned methods for group rekeying initiated by the KDC
(Section 6).
o Added security consideration on replay protection (Section 8).
o New IANA registries "ACE Groupcomm Key Registry" and "ACE
Groupcomm Profile Registry" (Section 9).
Acknowledgments
The following individuals were helpful in shaping this document: Ben
Kaduk, John Mattsson, Jim Schaad, Ludwig Seitz, Goeran Selander and
Peter van der Stok.
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The work on this document has been partly supported by VINNOVA and
the Celtic-Next project CRITISEC; and by the EIT-Digital High Impact
Initiative ACTIVE.
Authors' Addresses
Francesca Palombini
Ericsson AB
Torshamnsgatan 23
Kista SE-16440 Stockholm
Sweden
Email: francesca.palombini@ericsson.com
Marco Tiloca
RISE AB
Isafjordsgatan 22
Kista SE-16440 Stockholm
Sweden
Email: marco.tiloca@ri.se
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