Admin Interface for the OSCORE Group Manager
draft-ietf-ace-oscore-gm-admin-12
| Document | Type | Active Internet-Draft (ace WG) | |
|---|---|---|---|
| Authors | Marco Tiloca , Rikard Höglund , Peter Van der Stok , Francesca Palombini | ||
| Last updated | 2024-09-23 (Latest revision 2024-07-08) | ||
| Replaces | draft-tiloca-ace-oscore-gm-admin | ||
| RFC stream | Internet Engineering Task Force (IETF) | ||
| Intended RFC status | Proposed Standard | ||
| Formats | |||
| Additional resources | Mailing list discussion | ||
| Stream | WG state | WG Document | |
| Associated WG milestone |
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| Document shepherd | (None) | ||
| IESG | IESG state | I-D Exists | |
| Consensus boilerplate | Yes | ||
| Telechat date | (None) | ||
| Responsible AD | (None) | ||
| Send notices to | (None) |
draft-ietf-ace-oscore-gm-admin-12
ACE Working Group M. Tiloca
Internet-Draft R. Höglund
Intended status: Standards Track RISE AB
Expires: 9 January 2025 P. van der Stok
F. Palombini
Ericsson AB
8 July 2024
Admin Interface for the OSCORE Group Manager
draft-ietf-ace-oscore-gm-admin-12
Abstract
Group communication for CoAP can be secured using Group Object
Security for Constrained RESTful Environments (Group OSCORE). A
Group Manager is responsible for handling the joining of new group
members, as well as managing and distributing the group keying
material. This document defines a RESTful admin interface at the
Group Manager that allows an Administrator entity to create and
delete OSCORE groups, as well as to retrieve and update their
configuration. The ACE framework for Authentication and
Authorization is used to enforce authentication and authorization of
the Administrator at the Group Manager. Protocol-specific transport
profiles of ACE are used to achieve communication security, proof-of-
possession, and server authentication.
Discussion Venues
This note is to be removed before publishing as an RFC.
Discussion of this document takes place on the Authentication and
Authorization for Constrained Environments Working Group mailing list
(ace@ietf.org), which is archived at
https://mailarchive.ietf.org/arch/browse/ace/.
Source for this draft and an issue tracker can be found at
https://github.com/ace-wg/ace-oscore-gm-admin.
Status of This Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
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This Internet-Draft will expire on 9 January 2025.
Copyright Notice
Copyright (c) 2024 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents (https://trustee.ietf.org/
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Please review these documents carefully, as they describe your rights
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 4
1.1. Terminology . . . . . . . . . . . . . . . . . . . . . . . 5
2. Group Administration . . . . . . . . . . . . . . . . . . . . 7
2.1. Managing OSCORE Groups . . . . . . . . . . . . . . . . . 8
2.2. Collection Representation . . . . . . . . . . . . . . . . 9
2.3. Discovery . . . . . . . . . . . . . . . . . . . . . . . . 9
3. Format of Scope . . . . . . . . . . . . . . . . . . . . . . . 10
3.1. On Using Group Name Patterns . . . . . . . . . . . . . . 14
4. Getting Access to the Group Manager . . . . . . . . . . . . . 14
4.1. Multiple Administrators for the Same OSCORE Group . . . . 18
5. Group Configurations . . . . . . . . . . . . . . . . . . . . 20
5.1. Group Configuration Representation . . . . . . . . . . . 20
5.1.1. Configuration Parameters . . . . . . . . . . . . . . 20
5.1.2. Status Parameters . . . . . . . . . . . . . . . . . . 23
5.2. Default Values . . . . . . . . . . . . . . . . . . . . . 24
5.2.1. Configuration Parameters . . . . . . . . . . . . . . 25
5.2.2. Status Parameters . . . . . . . . . . . . . . . . . . 26
6. Interactions with the Group Manager . . . . . . . . . . . . . 26
6.1. Retrieve the Full List of Group Configurations . . . . . 27
6.2. Retrieve a List of Group Configurations by Filters . . . 28
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6.3. Create a New Group Configuration . . . . . . . . . . . . 30
6.4. Retrieve a Group Configuration . . . . . . . . . . . . . 36
6.5. Retrieve Part of a Group Configuration by Filters . . . . 38
6.6. Overwrite a Group Configuration . . . . . . . . . . . . . 40
6.6.1. Effects on Joining Nodes . . . . . . . . . . . . . . 44
6.6.2. Effects on the Group Members . . . . . . . . . . . . 44
6.7. Selective Update of a Group Configuration . . . . . . . . 49
6.7.1. Effects on Joining Nodes . . . . . . . . . . . . . . 53
6.7.2. Effects on the Group Members . . . . . . . . . . . . 53
6.8. Delete a Group Configuration . . . . . . . . . . . . . . 53
6.8.1. Effects on the Group Members . . . . . . . . . . . . 55
7. ACE Groupcomm Parameters . . . . . . . . . . . . . . . . . . 56
8. ACE Groupcomm Error Identifiers . . . . . . . . . . . . . . . 58
9. Security Considerations . . . . . . . . . . . . . . . . . . . 60
9.1. Change of Group Configuration . . . . . . . . . . . . . . 61
9.2. Group Manager . . . . . . . . . . . . . . . . . . . . . . 62
9.3. Administrators . . . . . . . . . . . . . . . . . . . . . 62
10. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 63
10.1. ACE Groupcomm Parameters . . . . . . . . . . . . . . . . 63
10.2. ACE Groupcomm Errors . . . . . . . . . . . . . . . . . . 68
10.3. Resource Types . . . . . . . . . . . . . . . . . . . . . 68
10.4. Group OSCORE Admin Permissions . . . . . . . . . . . . . 69
10.5. Expert Review Instructions . . . . . . . . . . . . . . . 70
11. References . . . . . . . . . . . . . . . . . . . . . . . . . 70
11.1. Normative References . . . . . . . . . . . . . . . . . . 70
11.2. Informative References . . . . . . . . . . . . . . . . . 73
Appendix A. Processing of Group Name Patterns at the AS . . . . 75
Appendix B. CDDL Model . . . . . . . . . . . . . . . . . . . . . 77
Appendix C. Document Updates . . . . . . . . . . . . . . . . . . 78
C.1. Version -11 to -12 . . . . . . . . . . . . . . . . . . . 78
C.2. Version -10 to -11 . . . . . . . . . . . . . . . . . . . 79
C.3. Version -09 to -10 . . . . . . . . . . . . . . . . . . . 80
C.4. Version -08 to -09 . . . . . . . . . . . . . . . . . . . 80
C.5. Version -07 to -08 . . . . . . . . . . . . . . . . . . . 80
C.6. Version -06 to -07 . . . . . . . . . . . . . . . . . . . 81
C.7. Version -05 to -06 . . . . . . . . . . . . . . . . . . . 81
C.8. Version -04 to -05 . . . . . . . . . . . . . . . . . . . 82
C.9. Version -03 to -04 . . . . . . . . . . . . . . . . . . . 82
C.10. Version -02 to -03 . . . . . . . . . . . . . . . . . . . 82
C.11. Version -01 to -02 . . . . . . . . . . . . . . . . . . . 83
C.12. Version -00 to -01 . . . . . . . . . . . . . . . . . . . 83
Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . . 83
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 83
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1. Introduction
The Constrained Application Protocol (CoAP) [RFC7252] can also be
used for group communication [I-D.ietf-core-groupcomm-bis], where
messages are exchanged between members of a group, e.g., over IP
multicast. Applications relying on CoAP can achieve end-to-end
security at the application layer by using Object Security for
Constrained RESTful Environments (OSCORE) [RFC8613], and especially
Group OSCORE [I-D.ietf-core-oscore-groupcomm] in group communication
scenarios.
When group communication for CoAP is protected with Group OSCORE,
nodes are required to join the correct OSCORE group explicitly. To
this end, a joining node interacts with a Group Manager (GM) entity
responsible for that group, and retrieves the required keying
material to securely communicate with other group members using Group
OSCORE.
The method in [I-D.ietf-ace-key-groupcomm-oscore] specifies how nodes
can join an OSCORE group through the respective Group Manager. That
method builds on the ACE framework for Authentication and
Authorization [RFC9200], ensuring a secure joining process as well as
authentication and authorization of joining nodes (clients) at the
Group Manager (resource server).
In some deployments, the application running on the Group Manager may
know when a new OSCORE group has to be created, as well as how it
should be configured and later on updated or deleted, e.g., based on
the current application state or pre-installed policies. In this
case, the Group Manager application can create and configure OSCORE
groups when needed, by using a local application interface. However,
this requires the Group Manager to be application-specific, which in
turn may lead to error-prone deployments and is poorly flexible.
In other deployments, a separate Administrator entity, such as a
Commissioning Tool, is directly responsible for creating and
configuring the OSCORE groups at a Group Manager, as well as for
maintaining them during their whole lifetime until their deletion.
This allows the Group Manager to be agnostic of the specific
applications using secure group communication.
This document specifies a RESTful admin interface at the Group
Manager, intended for an Administrator as a separate entity external
to the Group Manager and its application. The interface allows the
Administrator to create and delete OSCORE groups, as well as to
specify and update their configuration.
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Interaction examples are provided in Link Format [RFC6690] and in
CBOR [RFC8949]. The examples in CBOR are expressed in CBOR
diagnostic notation.
Throughout this document, examples for CBOR data items are expressed
in CBOR extended diagnostic notation as defined in Section 8 of
[RFC8949] and Appendix G of [RFC8610] ("diagnostic notation").
Diagnostic notation comments are often used to provide a textual
representation of the numeric parameter names and values.
In the CBOR diagnostic notation used in this document, constructs of
the form e'SOME_NAME' are replaced by the value assigned to SOME_NAME
in the CDDL model shown in Figure 3 of Appendix B. For example,
{e'group_name': "gp1", e'gp_enc_alg': 10} stands for {-13: "gp1", -4:
10}.
Note to RFC Editor: Please delete the paragraph immediately preceding
this note. Also, in the CBOR diagnostic notation used in this
document, please replace the constructs of the form e'SOME_NAME' with
the value assigned to SOME_NAME in the CDDL model shown in Figure 3
of Appendix B. Finally, please delete this note.
The ACE framework is used to ensure authentication and authorization
of the Administrator (client) at the Group Manager (resource server).
In order to achieve communication security, proof-of-possession, and
server authentication, the Administrator and the Group Manager
leverage protocol-specific transport profiles of ACE, such as
[RFC9202][RFC9203]. These include also possible forthcoming
transport profiles that comply with the requirements in Appendix C of
[RFC9200].
1.1. Terminology
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in
BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all
capitals, as shown here.
Readers are expected to be familiar with the terms and concepts from
the following specifications.
* CDDL [RFC8610], CBOR [RFC8949] and COSE [RFC9052][RFC9053].
* The CoAP protocol [RFC7252], also in group communication scenarios
[I-D.ietf-core-groupcomm-bis]. These especially include the
following concepts.
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- "application group", as a set of CoAP nodes that share a common
set of resources.
- "security group", as a set of CoAP nodes that share the same
security material, and use it to protect and verify exchanged
messages.
* The OSCORE [RFC8613] and Group OSCORE
[I-D.ietf-core-oscore-groupcomm] security protocols. These
especially include the following concepts.
- Group Manager, as the entity responsible for a set of OSCORE
groups where communications among members are secured using
Group OSCORE. An OSCORE group is used as a security group for
one or many application groups.
- Authentication credential, as the set of information associated
with an entity, including that entity's public key and
parameters associated with the public key. Examples of
authentication credentials are CBOR Web Tokens (CWTs) and CWT
Claims Sets (CCSs) [RFC8392], X.509 certificates [RFC5280], and
C509 certificates [I-D.ietf-cose-cbor-encoded-cert].
* The ACE framework for authentication and authorization [RFC9200].
The terminology for entities in the considered architecture is
defined in OAuth 2.0 [RFC6749]. In particular, this includes
Client (C), Resource Server (RS), and Authorization Server (AS).
* The management of keying material for groups in ACE
[I-D.ietf-ace-key-groupcomm] and specifically for OSCORE groups
[I-D.ietf-ace-key-groupcomm-oscore]. These include the concept of
group-membership resource hosted by the Group Manager that new
members access to join the OSCORE group, and that current members
can access to retrieve updated keying material.
Note that the term "endpoint" is used here following its OAuth
definition [RFC6749], aimed at denoting resources such as /token and
/introspect at the AS, and /authz-info at the RS. This document does
not use the CoAP definition of "endpoint", which is "An entity
participating in the CoAP protocol".
This document also refers to the following terminology:
* Administrator: entity responsible for creating, configuring, and
deleting OSCORE groups at a Group Manager.
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* Group name: stable and invariant name of an OSCORE group. The
group name MUST be unique under the same Group Manager, and MUST
be consistent with the ABNF rule "segment = *pchar" defined in
Section 3.3 of [RFC3986].
* Group-collection resource: a single-instance resource hosted by
the Group Manager. An Administrator accesses a group-collection
resource to retrieve the list of existing OSCORE groups, or to
create a new OSCORE group, under that Group Manager.
When defining operations at the Group Manager and providing
examples, this document uses /manage as the url-path of the group-
collection resource; implementations can use a different url-path.
* Group-configuration resource: a resource hosted by the Group
Manager, associated with an OSCORE group under that Group Manager.
A group-configuration resource is identifiable with the invariant
group name of the respective OSCORE group. An Administrator
accesses a group-configuration resource to retrieve or change the
configuration of the respective OSCORE group, or to delete that
group.
The url-path to a group-configuration resource has GROUPNAME as
last segment, with GROUPNAME the invariant group name assigned
upon its creation. Building on the considered url-path of the
group-collection resource, this document uses /manage/GROUPNAME as
the url-path of a group-configuration resource; implementations
are not required to use this same construct, and can define their
own instead.
* Admin resource: a group-collection resource or a group-
configuration resource hosted by the Group Manager.
* Secure communication association: a security association
established between any two of the Administrator, the AS, and the
Group Manager and used for protecting their message exchanges.
For example, depending on the used transport profile of ACE, this
can rely on DTLS [RFC9147] as per [RFC9202], or on OSCORE
[RFC8613] as per [RFC9203].
2. Group Administration
With reference to the ACE framework and the terminology defined in
OAuth 2.0 [RFC6749]:
* The Group Manager acts as Resource Server (RS). The Group Manager
provides one single group-collection resource, and one group-
configuration resource per existing OSCORE group.
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* The Administrator acts as Client (C), and requests to access the
group-collection resource and group-configuration resources at the
Group Manager.
* The Authorization Server (AS) authorizes the Administrator to
access the group-collection resource and group-configuration
resources at a Group Manager. Multiple Group Managers can be
associated with the same AS.
The authorized access for an Administrator can be limited to
performing only a subset of operations, according to what is
allowed by the authorization information in the Access Token
issued to that Administrator (see Section 3 and Section 4). The
AS can authorize multiple Administrators to access the group-
collection resource and the (same) group-configuration resources
at the Group Manager.
The AS MAY issue Access Tokens to the Administrator for other
purposes than accessing admin resources of registered Group
Managers. For example, an Access Token can specify authorization
information for joining OSCORE groups at a Group Manager (see
[I-D.ietf-ace-key-groupcomm-oscore]), possibly combined with
authorization information for accessing admin resources at the
same Group Manager (see Section 3). Also, an AS can of course
issue an Access Token that specifies authorization information
unrelated to OSCORE groups, but instead pertaining to the access
of other resources hosted by the Group Manager or other Resource
Servers.
2.1. Managing OSCORE Groups
Figure 1 shows the resources of a Group Manager available to an
Administrator.
___
Group / \
Collection \___/
\
\____________________
\___ \___ \___
/ \ / \ ... / \ Group
\___/ \___/ \___/ Configurations
Figure 1: Admin Resources of a Group Manager
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The Group Manager exports a single group-collection resource, with
resource type "core.osc.gcoll" registered in Section 10.3 of this
document. The interface for the group-collection resource defined in
Section 6 allows the Administrator, if permitted, to:
* Retrieve the list of existing OSCORE groups.
* Retrieve a list of existing OSCORE groups matching with specified
filter criteria.
* Create a new OSCORE group, specifying its invariant group name
and, optionally, its configuration.
The Group Manager exports one group-configuration resource for each
of its OSCORE groups. Each group-configuration resource has resource
type "core.osc.gconf" registered in Section 10.3 of this document,
and is identified by the group name specified upon creating the
OSCORE group. The interface for a group-configuration resource
defined in Section 6 allows the Administrator, if permitted, to:
* Retrieve the complete current configuration of the OSCORE group.
* Retrieve part of the current configuration of the OSCORE group, by
applying filter criteria.
* Overwrite the current configuration of the OSCORE group.
* Selectively update only part of the current configuration of the
OSCORE group.
* Delete the OSCORE group.
2.2. Collection Representation
A collection of group configurations is represented as a Link Format
document [RFC6690] containing the list of corresponding group-
configuration resources.
Each group configuration is represented as a link, which specifies
the URI of the group-configuration resource as link target, and the
link target attribute 'rt' (Resource Type) with value
"core.osc.gconf".
2.3. Discovery
The Administrator can discover group-collection resources from a
Resource Directory [RFC9176] or from .well-known/core, by using the
resource type "core.osc.gcoll".
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The Administrator can discover group-configuration resources for the
group-collection resource as specified in Section 6.1 and
Section 6.2.
3. Format of Scope
Building on the definition in Section 3.3 of [RFC6749] considered in
the ACE framework [RFC9200], scope denotes: the permissions that the
Client (i.e., the Administrator) seeks to obtain from the AS for
accessing resources at a Resource Server (i.e., the Group Manager);
and the permissions that the AS actually issues to the Client
following its request. This process is detailed in Sections 5.8.1
and 5.8.2 of [RFC9200].
This section defines the exact format and encoding of scope to use,
in order to express authorization information for the Administrator
(see Section 4).
To this end, this document uses the Authorization Information Format
(AIF) [RFC9237]. In particular, it uses and extends the AIF data
model AIF-OSCORE-GROUPCOMM defined in Section 3 of
[I-D.ietf-ace-key-groupcomm-oscore].
The original definition of the data model AIF-OSCORE-GROUPCOMM
specifies a scope as structured into scope entries, which express
authorization information for users of an OSCORE group, i.e., actual
group members or external signature verifiers. Hereafter, these are
referred to as "user scope entries".
This document extends the same AIF data model AIF-OSCORE-GROUPCOMM as
defined below. In particular, it defines how the same scope can
(also) include scope entries that express authorization information
for Administrators of OSCORE groups. Hereafter, these are referred
to as "admin scope entries", or simply as "scope entries" unless
otherwise indicated.
Like in the original definition of the data model AIF-OSCORE-
GROUPCOMM, and with reference to the generic AIF model
AIF-Generic<Toid, Tperm> = [* [Toid, Tperm]]
the value of the CBOR byte string used as scope encodes the CBOR
array [* [Toid, Tperm]], where each [Toid, Tperm] element corresponds
to one scope entry.
Then, the following applies for each admin scope entry intended to
express authorization information for an Administrator, as defined in
this document.
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* The object identifier ("Toid") is specialized as either of the
following, and specifies a group name pattern P for the admin
scope entry.
- Wildcard pattern: "Toid" is specialized as the CBOR simple
value true (0xf5), specifying the wildcard pattern. That is,
any group name matches with this group name pattern.
- Literal pattern: "Toid" is specialized as a CBOR text string,
whose value specifies an exact group name as a literal string.
That is, only one specific group name expressed as a literal
text string matches with this group name pattern.
- Complex pattern: "Toid" is specialized as a tagged CBOR data
item, specifying a more complex group name pattern with the
semantics signaled by the CBOR tag. That is, multiple group
names expressed as a literal text string match with this group
name pattern.
For example, and as typically expected, the data item can be a
CBOR text string marked with the CBOR tag 21065. This
indicates that the group name pattern specified as value of the
CBOR text string is a regular expression (see [RFC9485] and
Section 3.4.5.3 of [RFC8949]).
In case the AIF data model AIF-OSCORE-GROUPCOMM is used in a
JSON payload, the semantics information conveyed by the CBOR
tag can be equivalently conveyed, for example, in a nested JSON
object.
The AS and the Group Manager are expected to have agreed on
commonly supported semantics for group name patterns. This can
happen, for instance, as part of the registration process of
the Group Manager at the AS.
* The permission set ("Tperm") is specialized as a CBOR unsigned
integer with value Q. This specifies the permissions that the
Administrator has with respect to performing operations on the
admin resources at the Group Manager, as pertaining to any OSCORE
group whose name matches with the pattern P. The value Q is
computed as follows.
- Each permission in the permission set is converted into the
corresponding numeric identifier X from the "Value" column of
the "Group OSCORE Admin Permissions" registry, for which this
document defines the entries in Table 1.
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- The set of N numbers is converted into the single value Q, by
taking two to the power of each numeric identifier X_1, X_2,
..., X_N, and then computing the inclusive OR of the binary
representations of all the power values.
In general, a single permission can be associated with multiple
different operations that are possible to be performed when
interacting with the Group Manager. For example, the "List"
permission allows the Administrator to retrieve a list of group
configurations (see Section 6.1) or only a subset of that
according to specified filter criteria (see Section 6.2), by
issuing a GET or FETCH request to the group-collection resource,
respectively.
+========+=======+=======================================+
| Name | Value | Description |
+========+=======+=======================================+
| List | 0 | Retrieve list of group configurations |
+--------+-------+---------------------------------------+
| Create | 1 | Create new group configurations |
+--------+-------+---------------------------------------+
| Read | 2 | Retrieve group configurations |
+--------+-------+---------------------------------------+
| Write | 3 | Change group configurations |
+--------+-------+---------------------------------------+
| Delete | 4 | Delete group configurations |
+--------+-------+---------------------------------------+
Table 1: Numeric identifier of permissions on the
admin resources at a Group Manager
The following CDDL [RFC8610] notation defines an admin scope entry
that uses the data model AIF-OSCORE-GROUPCOMM and expresses a set of
permissions from those in Table 1.
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;# include rfc9237
AIF-OSCORE-GROUPCOMM = AIF-Generic<oscore-gname, oscore-gperm>
oscore-gname = true / tstr / #6.<uint>(any) ; Group name pattern
oscore-gperm = uint .bits admin-permissions
admin-permissions = &(
List: 0,
Create: 1,
Read: 2,
Write: 3,
Delete: 4
)
scope_entry = [oscore-gname, oscore-gperm]
The following example in CBOR diagnostic notation shows a CBOR array
including five scope entries as its elements.
[[true, / Toid (wildcard pattern) /
5 / Tperm (List + Read) /
],
["gp1", / Toid (literal pattern) /
31 / Tperm (List + Create +
Read + Write + Delete) /
],
["gp2", / Toid (literal pattern) /
31 / Tperm (List + Create +
Read + Write + Delete) /
],
[21065("^[A-K][0-9][-a-z0-9]*$"), / Toid (complex pattern) /
31 / Tperm (List + Create +
Read + Write + Delete) /
],
[21065("^[J-Z][0-9][-a-z0-9]*$"), / Toid (complex pattern) /
13 / Tperm (List + Read + Write) /
]
]
Future specifications that define new permissions on the admin
resources at the Group Manager MUST register a corresponding numeric
identifier in the "Group OSCORE Admin Permissions" registry defined
in Section 10.4 of this document.
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When using the scope format as defined in this section, the
permission set ("Tperm") of each admin scope entry MUST include the
"List" permission. It follows that, when expressing permissions for
Administrators of OSCORE groups as defined in this document, an admin
scope entry has the least significant bit of "Tperm" always set to 1.
Therefore, an Administrator is always allowed to retrieve a list of
existing group configurations. The exact elements included in the
returned list are determined by the Group Manager, based on the group
name patterns specified in the admin scope entries of the
Administrator's Access Token, as well as on possible filter criteria
specified in the request from the Administrator (see Section 6.1 and
Section 6.2).
Building on the above, the same single scope can include user scope
entries as well as admin scope entries, whose specific format is
defined in Section 3 of [I-D.ietf-ace-key-groupcomm-oscore] and
earlier in this section, respectively. The two types of scope
entries can be unambiguously distinguished by means of the least
significant bit of their permission set "Tperm", which has value 0
for the user scope entries and 1 for the admin scope entries.
The coexistence of user scope entries and admin scope entries within
the same scope makes it possible to issue a single Access Token, in
case the requesting Client wishes to be a user for some OSCORE groups
and at the same time Administrator for some (other) OSCORE groups
under the same Group Manager.
3.1. On Using Group Name Patterns
Having the object identifier ("Toid") specialized as a pattern
confers a number of advantages.
* When relying on wildcard patterns and complex patterns, the
encoded scope can be compact in size while allowing the
Administrator to operate on large pools of group names.
* When relying on wildcard patterns and complex patterns, the
Administrator and the AS do not need to know the exact group names
for requesting and issuing an Access Token, respectively (see
Section 4). In turn, the Group Manager can effectively take the
final decision about the name to assign to an OSCORE group, upon
its creation (see Section 6.3).
4. Getting Access to the Group Manager
All communications between the involved entities rely on the CoAP
protocol and MUST be secured.
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In particular, communications between the Administrator and the Group
Manager leverage protocol-specific transport profiles of ACE to
achieve communication security, proof-of-possession, and server
authentication. To this end, the AS may explicitly signal the
specific transport profile to use, consistently with requirements and
assumptions defined in the ACE framework [RFC9200].
With reference to the AS, communications between the Administrator
and the AS (/token endpoint) as well as between the Group Manager and
the AS (/introspect endpoint) can be secured by different means, for
instance using DTLS [RFC9147] or OSCORE [RFC8613]. Further details
on how the AS secures communications (with the Administrator and the
Group Manager) depend on the transport profile of ACE in use, and are
out of the scope of this document.
In order to specify authorization information for Administrators, the
format and encoding of scope defined in Section 3 of this document
MUST be used, for both the 'scope' claim in the Access Token and the
'scope' parameter in the Authorization Request and Authorization
Response exchanged with the AS (see Sections 5.8.1 and 5.8.2 of
[RFC9200]).
If the 'scope' parameter in the Authorization Request includes scope
entries whose "Toid" specifies a complex pattern (see Section 3),
then all such scope entries MUST adhere to the same pattern
semantics. Also, in the 'scope' claim of the Access Token issued by
the AS, that semantics MUST be used for all the scope entries that
specify a complex pattern.
Furthermore, the AS MAY use the extended format of scope defined in
Section 7 of [I-D.ietf-ace-key-groupcomm] for the 'scope' claim of
the Access Token. In such a case, the AS MUST use the CBOR tag with
tag number TAG_NUMBER, associated with the CoAP Content-Format CF_ID
for the media type application/aif+cbor registered in Section 16.9 of
[I-D.ietf-ace-key-groupcomm-oscore].
Note to RFC Editor: In the previous paragraph, please replace
"TAG_NUMBER" with the CBOR tag number computed as TN(ct) in
Section 4.3 of [RFC9277], where ct is the ID assigned to the CoAP
Content-Format CF_ID registered in Section 16.9 of
[I-D.ietf-ace-key-groupcomm-oscore]. Then, please replace "CF_ID"
with the ID assigned to that CoAP Content-Format. Finally, please
delete this paragraph.
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This indicates that the binary encoded scope, as conveying the actual
access control information, follows the scope semantics of the AIF
data model AIF-OSCORE-GROUPCOMM defined in Section 3 of
[I-D.ietf-ace-key-groupcomm-oscore] and extended as per Section 3 of
this document.
In order to get access to the Group Manager for managing OSCORE
groups, an Administrator performs the following steps.
1. The Administrator requests an Access Token from the AS, in order
to access the group-collection and group-configuration resources
on the Group Manager. To this end, the Administrator sends to
the AS an Authorization Request as defined in Section 5.8.1 of
[RFC9200].
The Administrator will start or continue using a secure
communication association with the Group Manager, according to
the response from the AS and the transport profile of ACE in use.
2. The AS processes the Authorization Request as defined in
Section 5.8.2 of [RFC9200], especially verifying that the
Administrator is authorized to obtain the requested permissions,
or possibly a subset of those.
The AS specifies the information on the authorization granted to
the Administrator as the value of the 'scope' claim to include in
the Access Token, in accordance with the scope format specified
in Section 3. It is implementation specific which particular
approach the AS takes to evaluate the requested permissions
against the access policies pertaining to the Administrator for
the Group Manager in question. Appendix A provides an example of
such an approach that the AS can use.
The AS MUST include the 'scope' parameter in the Authorization
Response defined in Section 5.8.2 of [RFC9200], when the value
included in the Access Token differs from the one specified by
the Administrator in the Authorization Request. In such a case,
scope specifies the set of permissions that the Administrator
actually has, with respect to performing operations at the Group
Manager, encoded as specified in Section 3.
If the 'scope' parameter in the Authorization Request includes
scope entries whose "Toid" specifies a complex pattern and any of
the following conditions holds, then the AS MUST reply with a
4.00 (Bad Request) error response (see Section 5.8.3 of
[RFC9200]). The 'error_description' parameter carried out in the
response payload MUST specify the CBOR value 1 (invalid_scope).
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* The "Toid" of the different scope entries that specify a
complex pattern do not all adhere to the same pattern
semantics.
* The "Toid" of the different scope entries that specify a
complex pattern adhere to the same pattern semantics, but this
is not supported by the AS or by the Group Manager.
Finally, as discussed in Section 3, the authorization information
included in the Authorization Request or specified by the AS
might also include permissions for the same Client as a user of
an OSCORE group, i.e., as an actual group member or an external
signature verifier. As per Section 3, such authorization
information is expressed by "user scope entries", whose format
and processing is specified in
[I-D.ietf-ace-key-groupcomm-oscore].
3. The Administrator transfers authentication and authorization
information to the Group Manager by posting the obtained Access
Token, according to the used profile of ACE, such as [RFC9202]
and [RFC9203]. After that, the Administrator must have a secure
communication association established with the Group Manager,
before performing any administrative operation on that Group
Manager. Possible ways to provide secure communication are DTLS
[RFC9147] and OSCORE [RFC8613]. The Administrator and the Group
Manager maintain the secure association, to support possible
future communications.
4. Consistently with what is allowed by the authorization
information in the Access Token, the Administrator performs
administrative operations at the Group Manager, as described in
Section 6. These include retrieving a list of existing OSCORE
groups, creating new OSCORE groups, retrieving and changing
OSCORE group configurations, and removing OSCORE groups.
Messages exchanged among the Administrator and the Group Manager
are specified in Section 6.
Upon receiving a request from the Administrator targeting the
group-collection resource or a group-configuration resource, the
Group Manager MUST check that it is storing a valid Access Token
for that Administrator, and that the Access Token includes at
least one admin scope entry. If this is not the case, the Group
Manager MUST reply with a 4.01 (Unauthorized) error response.
If the request targets the group-collection resource for creating
a new group with name GROUPNAME or it targets the group-
configuration resource associated with an existing group with
name GROUPNAME, then the Group Manager MUST check that it is
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storing a valid Access Token from that Administrator, such that
the 'scope' claim specified in the Access Token: i) expresses
authorization information through scope entries as defined in
Section 3; and ii) specifically includes a scope entry where:
* The group name GROUPNAME matches with the pattern specified by
the "Toid" of the scope entry; and
* The permission set specified by the "Tperm" of the scope entry
allows the Administrator to perform the requested
administrative operation on the targeted group-configuration
resource.
Note that the checks defined above only consider scope entries
expressing permissions for administrative operations, namely
"admin scope entries" as defined in Section 3, while the
alternative "user scope entries" defined in
[I-D.ietf-ace-key-groupcomm-oscore] are not considered.
Further detailed checks to perform are defined separately for
each operation at the Group Manager, when specified in Section 6.
In case the Group Manager stores a valid Access Token but the
verifications above fail, the Group Manager MUST reply with a
4.03 (Forbidden) error response. This response MAY be an AS
Request Creation Hints, as defined in Section 5.3 of [RFC9200],
in which case the Content-Format MUST be set to application/
ace+cbor (i.e., ID: 19).
If the request is not formatted correctly (e.g., required fields
are not present or are not encoded as expected), the Group
Manager MUST reply with a 4.00 (Bad Request) error response.
4.1. Multiple Administrators for the Same OSCORE Group
It is possible that multiple Administrators are authorized to operate
on the same Group Manager in the interest of the same OSCORE group,
while also taking different responsibilities.
For example, in addition to a "main" primary Administrator
responsible for an OSCORE group at the Group Manager, it is also
possible to have "assistant" secondary Administrators that are
effectively authorized to perform some operations on the same OSCORE
group.
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With respect to the main Administrator, such assistant Administrators
are expected to have fewer permissions to perform administrative
operations related to the OSCORE group at the Group Manager. For
example, they may not be authorized to create an OSCORE group, or to
delete an OSCORE group and its configuration.
In case the main Administrator of an OSCORE group is dismissed or
relinquishes its role, one of the assistant Administrators can be
"promoted" and become main Administrator for that OSCORE group.
Practically, this requires that the access policies associated with
the promoted Administrator are updated accordingly at the
Authorization Server. Also, the promoted Administrator has to
request from the Authorization Server a new Access Token and to
upload it to the Group Manager. If allowed by the used transport
profile of ACE, this process can efficiently enforce a dynamic update
of access rights, thus preserving the current secure association
between the promoted Administrator and the Group Manager.
If an Administrator is not sure about being the only Administrator
responsible for an OSCORE group, then it is RECOMMENDED that the
Administrator regularly obtains a recent representation of the group-
configuration resource associated with the OSCORE group before
overwriting (see Section 6.6), updating (see Section 6.7), or
deleting (see Section 6.8) the group configuration. This can be
achieved in the following ways.
* The Administrator performs a regular polling of the group
configuration, by sending a GET request to the corresponding
group-configuration resource (see Section 6.4).
* If the group-configuration resource associated with the OSCORE
group is Observable, then the Administrator subscribes to that
resource by using CoAP Observe [RFC7641]. The Observation request
is a GET request sent to the group-configuration resource (see
Section 6.4). In such a case, the Group Manager will also send a
4.04 (Not Found) response in case another Administrator deletes
the group-configuration resource, as a result of deleting the
associated OSCORE group and its configuration.
If the Administrator gains knowledge that the group configuration has
changed compared to the latest known representation, then the
Administrator might hold the execution of writing or deletion
operation on the group-configuration resource, and first attempt
checking with other Administrators responsible for the same OSCORE
group about the changes they have made.
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In order to avoid race conditions due to possible concurrent updates
of the group-configuration resource (i.e., the "lost update"
problem), the Group Manager can include the ETag Option in the
responses to the GET requests sent to the group-configuration
resource (see Section 5.10.6 of [RFC7252]). Then, when sending to
the Group Manager a request for overwriting or updating the group-
configuration resource, the Administrator includes an If-Match Option
with value the most recent ETag that the Administrator knows for that
resource (see Section 5.10.8.1 of [RFC7252]).
5. Group Configurations
A group configuration consists of information related to an OSCORE
group, as organized into configuration parameters and status
parameters.
In particular, configuration parameters specify how members of the
OSCORE group use the Group OSCORE protocol to protect their
communications (e.g., by using which algorithms). Instead, status
parameters specify information concerning the management of the
OSCORE group and its current setting at the Group Manager (e.g., for
handling identifiers and the joining of group members).
5.1. Group Configuration Representation
The group configuration representation is a CBOR map, which includes
the configuration parameters specified in Section 5.1.1 and the
status parameters specified in Section 5.1.2.
Unless stated otherwise, these parameters are defined in this
document and their CBOR abbreviations are defined in Section 7.
5.1.1. Configuration Parameters
The CBOR map includes the following configuration parameters.
* 'hkdf', which specifies the HKDF Algorithm used in the OSCORE
group (see Section 2 of [I-D.ietf-core-oscore-groupcomm]), encoded
as a CBOR text string or a CBOR integer. This parameter can take
the same values as the 'hkdf' parameter of the
Group_OSCORE_Input_Material object, defined in Section 6.3 of
[I-D.ietf-ace-key-groupcomm-oscore].
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* 'cred_fmt', which specifies the Authentication Credential Format
used in the OSCORE group (see Section 2 of
[I-D.ietf-core-oscore-groupcomm]), encoded as a CBOR integer.
This parameter can take the same values as the 'cred_fmt'
parameter of the Group_OSCORE_Input_Material object, defined in
Section 6.3 of [I-D.ietf-ace-key-groupcomm-oscore].
* 'group_mode', encoded as a CBOR simple value. Its value is true
(0xf5) if the OSCORE group uses the group mode of Group OSCORE
(see Section 8 of [I-D.ietf-core-oscore-groupcomm]), or false
(0xf4) otherwise.
* 'gp_enc_alg', which is formatted as follows. If the configuration
parameter 'group_mode' has value false (0xf4), this parameter has
as value the CBOR simple value null (0xf6). Otherwise, this
parameter specifies the Group Encryption Algorithm used in the
OSCORE group to encrypt messages protected with the group mode
(see Section 2 of [I-D.ietf-core-oscore-groupcomm]), encoded as a
CBOR text string or a CBOR integer. This parameter can take the
same values as the 'sign_enc_alg' parameter of the
Group_OSCORE_Input_Material object, defined in Section 6.3 of
[I-D.ietf-ace-key-groupcomm-oscore].
Editor's note: as per the text above, the referred version of
[I-D.ietf-ace-key-groupcomm-oscore] still uses 'sign_enc_alg' as
parameter name. The next version of
[I-D.ietf-ace-key-groupcomm-oscore] will be updated in order to
use 'gp_enc_alg' instead, as already done for this document and
consistently with the naming used in the latest version of
[I-D.ietf-core-oscore-groupcomm].
* 'sign_alg', which is formatted as follows. If the configuration
parameter 'group_mode' has value false (0xf4), this parameter has
as value the CBOR simple value null (0xf6). Otherwise, this
parameter specifies the Signature Algorithm used in the OSCORE
group (see Section 2 of [I-D.ietf-core-oscore-groupcomm]), encoded
as a CBOR text string or a CBOR integer. This parameter can take
the same values as the 'sign_alg' parameter of the
Group_OSCORE_Input_Material object, defined in Section 6.3 of
[I-D.ietf-ace-key-groupcomm-oscore].
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* 'sign_params', which is formatted as follows. If the
configuration parameter 'group_mode' has value false (0xf4), this
parameter has as value the CBOR simple value null (0xf6).
Otherwise, this parameter specifies the additional parameters for
the Signature Algorithm used in the OSCORE group, encoded as a
CBOR array. This parameter can take the same values as the
'sign_params' parameter of the Group_OSCORE_Input_Material object,
defined in Section 6.3 of [I-D.ietf-ace-key-groupcomm-oscore].
* 'pairwise_mode', encoded as a CBOR simple value. Its value is
true (0xf5) if the OSCORE group uses the pairwise mode of Group
OSCORE (see Section 9 of [I-D.ietf-core-oscore-groupcomm]), or
false (0xf4) otherwise.
* 'alg', which is formatted as follows. If the configuration
parameter 'pairwise_mode' has value false (0xf4), this parameter
has as value the CBOR simple value null (0xf6). Otherwise, this
parameter specifies the AEAD Algorithm used in the OSCORE group to
encrypt messages protected with the pairwise mode (see Section 2
of [I-D.ietf-core-oscore-groupcomm]), encoded as a CBOR text
string or a CBOR integer. This parameter can take the same values
as the 'alg' parameter of the Group_OSCORE_Input_Material object,
defined in Section 6.3 of [I-D.ietf-ace-key-groupcomm-oscore].
* 'ecdh_alg', which is formatted as follows. If the configuration
parameter 'pairwise_mode' has value false (0xf4), this parameter
has as value the CBOR simple value null (0xf6). Otherwise, this
parameter specifies the Pairwise Key Agreement Algorithm used in
the OSCORE group (see Section 2 of
[I-D.ietf-core-oscore-groupcomm]), encoded as a CBOR text string
or a CBOR integer. This parameter can take the same values as the
'ecdh_alg' parameter of the Group_OSCORE_Input_Material object,
defined in Section 6.3 of [I-D.ietf-ace-key-groupcomm-oscore].
* 'ecdh_params', which is formatted as follows. If the
configuration parameter 'pairwise_mode' has value false (0xf4),
this parameter has as value the CBOR simple value null (0xf6).
Otherwise, this parameter specifies the parameters for the
Pairwise Key Agreement Algorithm used in the OSCORE group, encoded
as a CBOR array. This parameter can take the same values as the
'ecdh_params' parameter of the Group_OSCORE_Input_Material object,
defined in Section 6.3 of [I-D.ietf-ace-key-groupcomm-oscore].
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* 'det_req', encoded as a CBOR simple value. Its value is true
(0xf5) if the OSCORE group uses deterministic requests as defined
in [I-D.amsuess-core-cachable-oscore], or false (0xf4) otherwise.
This parameter can be present only if both the configuration
parameters 'group_mode' and 'pairwise_mode' have value true
(0xf5), and MUST NOT be present otherwise.
* 'det_hash_alg', encoded as a CBOR integer or text string. If
present, this parameter specifies the Hash Algorithm used in the
OSCORE group when producing deterministic requests, as defined in
[I-D.amsuess-core-cachable-oscore]. This parameter takes values
from the "Value" column of the "COSE Algorithms" Registry
[COSE.Algorithms].
This parameter MUST NOT be present if the configuration parameter
'det_req' is not present or if it is present with value false
(0xf4). If the configuration parameter 'det_req' is present with
value true (0xf5) and 'det_hash_alg' is not present, the choice of
the Hash Algorithm to use when producing deterministic requests is
left to the Group Manager.
5.1.2. Status Parameters
The CBOR map includes the following status parameters.
* 'rt', which specifies the resource type "core.osc.gconf"
associated with group-configuration resources, encoded as a CBOR
text string.
* 'active', which specifies whether the OSCORE group is currently
active, encoded as the CBOR simple value true (0xf5) of false
(0xf4).
* 'group_name', which specifies the group name of the OSCORE group
encoded as a CBOR text string.
* 'group_description', which specifies either a human-readable
description of the OSCORE group encoded as a CBOR text string, or
the CBOR simple value null (0xf6) if no description is specified.
* 'ace_groupcomm_profile', defined in Section 4.3.1 of
[I-D.ietf-ace-key-groupcomm], with value "coap_group_oscore_app"
defined in Section 16.5 of [I-D.ietf-ace-key-groupcomm-oscore]
encoded as a CBOR integer.
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* 'max_stale_sets', encoding a CBOR unsigned integer with value
strictly greater than 1. With reference to Section 7.1 of
[I-D.ietf-ace-key-groupcomm-oscore], this parameter specifies N,
i.e., the maximum number of sets of stale OSCORE Sender IDs that
the Group Manager stores for the group.
* 'exp', defined in Section 4.3.1 of [I-D.ietf-ace-key-groupcomm].
* 'gid_reuse', encoding the CBOR simple value true (0xf5) if, upon
rekeying the OSCORE group, the Group Manager can reassign the
values of the OSCORE Group ID used as OSCORE ID Context, as per
Section 3.2.1.1 of [I-D.ietf-core-oscore-groupcomm] and Section 11
of [I-D.ietf-ace-key-groupcomm-oscore]. Otherwise, this parameter
encodes the CBOR simple value false (0xf4).
* 'app_groups', with value a list of names of application groups,
encoded as a CBOR array. Each element of the array is a CBOR text
string, specifying the name of an application group using the
OSCORE group as security group (see Section 2.1 of
[I-D.ietf-core-groupcomm-bis]).
* 'joining_uri', with value the URI of the group-membership resource
for joining the newly created OSCORE group as per Section 6.2 of
[I-D.ietf-ace-key-groupcomm-oscore], encoded as a CBOR text
string.
* 'group_policies', defined in Section 4.3.1 of
[I-D.ietf-ace-key-groupcomm], and consistent with the format and
content defined in Section 6.3 of
[I-D.ietf-ace-key-groupcomm-oscore].
* 'as_uri', with value the URI of the Authorization Server
associated with the Group Manager for the OSCORE group, encoded as
a CBOR text string. Candidate group members will have to obtain
an Access Token from that Authorization Server, before starting
the joining process with the Group Manager to join the OSCORE
group (see Sections 5 and 6 of
[I-D.ietf-ace-key-groupcomm-oscore]).
5.2. Default Values
This section defines the default values that the Group Manager uses
for the configuration and status parameters.
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The Group Manager MAY choose different default values instead of
those recommended in this section. A possible reason is to ensure
that each of those are consistent with what the Group Manager
supports, e.g., in terms of signature algorithm and format of
authentication credentials used in the OSCORE group.
This ensures that the Group Manager is able to perform the operations
defined in [I-D.ietf-ace-key-groupcomm-oscore], as to its
interactions with joining nodes and current group members for an
OSCORE group (see Section 14 of [I-D.ietf-ace-key-groupcomm-oscore]).
5.2.1. Configuration Parameters
For each of the configuration parameters listed below, the Group
Manager uses the following pre-configured default value, if that
parameter is not specified by the Administrator.
* 'group_mode' - The Group Manager SHOULD use the CBOR simple value
true (0xf5).
* 'pairwise_mode' - The Group Manager SHOULD use the CBOR simple
value true (0xf5).
* 'gp_enc_alg', 'sign_alg', and 'sign_params' - If the value of
'group_mode' is determined to be the CBOR simple value true
(0xf5), the Group Manager SHOULD use the default values defined in
Section 14.2 of [I-D.ietf-ace-key-groupcomm-oscore] as follows:
the value of 'sign_enc_alg' for the parameter 'gp_enc_alg' defined
in this document; the value of 'sign_alg' and 'sign_params' for
the corresponding parameters defined in this document.
Editor's note: as per the text above, the referred version of
[I-D.ietf-ace-key-groupcomm-oscore] still uses 'sign_enc_alg' as
parameter name. The next version of
[I-D.ietf-ace-key-groupcomm-oscore] will be updated in order to
use 'gp_enc_alg' instead, as already done for this document and
consistently with the naming used in the latest version of
[I-D.ietf-core-oscore-groupcomm].
* 'alg', 'ecdh_alg', and 'ecdh_params' - If the value of
'pairwise_mode' is determined to be the CBOR simple value true
(0xf5), the Group Manager SHOULD use the same default values
defined in Section 14.3 of [I-D.ietf-ace-key-groupcomm-oscore] for
the parameters 'alg', 'ecdh_alg', and 'ecdh_params'.
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* 'det_req' - If the value of both 'group_mode' and 'pairwise_mode'
is determined to be the CBOR simple value true (0xf5), the Group
Manager SHOULD add the parameter 'det_req' to the group
configuration and SHOULD set its value to the CBOR simple value
false (0xf4).
* 'det_hash_alg' - If the value of 'det_req' is determined to be the
CBOR simple value true (0xf5), the Group Manager SHOULD add the
parameter 'det_hash_alg' to the group configuration and SHOULD set
its value to -16 (COSE algorithm encoding for SHA-256).
For any other configuration parameter, the Group Manager SHOULD use
the same default values defined in Section 14.1 of
[I-D.ietf-ace-key-groupcomm-oscore].
5.2.2. Status Parameters
For each of the status parameters listed below, the Group Manager
uses the following pre-configured default value, if that parameter is
not specified by the Administrator.
* 'active' - The Group Manager SHOULD use the CBOR simple value
false (0xf4).
* 'group_description' - The Group Manager SHOULD use the CBOR simple
value null (0xf6).
* 'max_stale_sets' - The Group Manager SHOULD use the CBOR unsigned
integer with value 3, consistent with what is defined in
Section 14.1 of [I-D.ietf-ace-key-groupcomm-oscore].
* 'gid_reuse' - The Group Manager SHOULD use the CBOR simple value
false (0xf4).
* 'app_groups' - The Group Manager SHOULD use the empty CBOR array.
* 'group_policies' - The Group Manager SHOULD use the default values
defined in Section 6.3 of [I-D.ietf-ace-key-groupcomm-oscore].
6. Interactions with the Group Manager
This section describes the operations that are possible to perform on
the group-collection resource and the group-configuration resources
at the Group Manager.
For each operation, it is defined whether that operation is required
or optional to support for an Administrator and for the Group
Manager. If an Administrator supports an operation, then the
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Administrator is able to produce and send the request associated with
that operation. If the Group Manager supports an operation, then the
Group Manager must be able to correctly handle authorized and valid
requests sent by the Administrator to carry out that operation. If
the Group Manager receives an authorized and valid request to perform
an operation that it does not support, then the Group Manager MUST
respond with a 5.01 (Not Implemented) response.
When checking the scope claim of a stored Access Token to verify that
any of the requests defined in the following is authorized, the Group
Manager only considers scope entries expressing permissions for
administrative operations, namely "admin scope entries" as defined in
Section 3. The alternative "user scope entries" defined in
[I-D.ietf-ace-key-groupcomm-oscore] are not considered. That is,
when handling any of the requests for administrative operations
defined in the following, the Group Manager ignores possible "user
scope entries" specified in the scope of a stored access token.
Upon receiving from the Administrator a POST request to the group-
collection resource or a request to a group-configuration resource,
the Group Manager performs the following authorization checks,
consistently with what is defined at step 4 of Section 4.
* The Group Manager MUST check whether the group name TARGETNAME
pertaining to the request matches with the group name pattern
specified in any scope entry of the 'scope' claim in the stored
Access Token for the Administrator.
* In case of a positive match, the Group Manager MUST check whether
the permission set in the found scope entry specifies the
permission PERMISSION required to perform the requested
administrative operation.
If there are no matching scope entries specifying the permission
PERMISSION, the Group Manager MUST reply with a 4.03 (Forbidden)
error response. Further details on TARGETNAME and PERMISSION are
defined separately for each operation at the Group Manager.
The Content-Format in messages containing a payload is set to
application/ace-groupcomm+cbor, defined in Section 11.2 of
[I-D.ietf-ace-key-groupcomm]. Furthermore, the CBOR abbreviations
defined in Section 7 of this document MUST be used when specifying
the corresponding configuration and status parameters.
6.1. Retrieve the Full List of Group Configurations
This operation MUST be supported by the Group Manager and an
Administrator.
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The Administrator can send a GET request to the group-collection
resource, in order to retrieve a list of the existing OSCORE groups
at the Group Manager. This is returned as a list of links to the
corresponding group-configuration resources.
The Group Manager MUST prepare the list L to include in the response
as follows. For each group-configuration resource R:
1. The Group Manager considers the group name GROUPNAME of the
OSCORE group associated with R.
2. The Group Manager retrieves the stored Access Token for the
Administrator. Then, it checks whether GROUPNAME matches with
the group name pattern specified in any scope entry of the
'scope' claim in the Access Token.
3. The link to the group-configuration resource R is added to the
list L only in case of a positive match.
An example of message exchange is shown below.
=> 0.01 GET
Uri-Path: manage
<= 2.05 Content
Content-Format: 40 (application/link-format)
Payload:
<coap://[2001:db8::ab]/manage/gp1>;rt="core.osc.gconf",
<coap://[2001:db8::ab]/manage/gp2>;rt="core.osc.gconf",
<coap://[2001:db8::ab]/manage/gp3>;rt="core.osc.gconf"
6.2. Retrieve a List of Group Configurations by Filters
This operation MUST be supported by the Group Manager and MAY be
supported by an Administrator.
The Administrator can send a FETCH request to the group-collection
resource, in order to retrieve a list of the existing OSCORE groups
that fully match a set of specified filter criteria. This is
returned as a list of links to the corresponding group-configuration
resources.
The filter criteria are specified in the request payload as a CBOR
map, whose possible entries are specified in Section 5.1.
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Entry values are the ones admitted for the corresponding labels in
the POST request for creating a group configuration (see
Section 6.3), with the exception that the parameter 'group_name' (if
present) can also be encoded as a tagged CBOR data item, specifying a
group name pattern with the semantics signaled by the CBOR tag.
In such a case, the parameter 'group_name' expresses a group name
pattern in the same way as a complex pattern Toid does in a scope
entry (see Section 3). In particular, the filter criterion is
satisfied by any group name that matches with the group name pattern
specified by the parameter 'group_name' in the payload of the FETCH
request.
The Group Manager MUST prepare the list L to include in the response
as follows.
1. The Group Manager prepares a preliminary version of the list L,
as specified in Section 6.1 for the processing of a GET request
to the group-collection resource.
2. The Group Manager applies the filter criteria specified in the
FETCH request to the list L from the previous step. The result
is the list L to include in the response.
An example of message exchange is shown below.
=> 0.05 FETCH
Uri-Path: manage
Content-Format: 261 (application/ace-groupcomm+cbor)
Payload:
{
e'group_mode' : true,
e'gp_enc_alg' : 10 / AES-CCM-16-64-128 /,
e'hkdf' : 5 / HMAC-256-256 /
}
<= 2.05 Content
Content-Format: 40 (application/link-format)
Payload:
<coap://[2001:db8::ab]/manage/gp1>;rt="core.osc.gconf",
<coap://[2001:db8::ab]/manage/gp2>;rt="core.osc.gconf",
<coap://[2001:db8::ab]/manage/gp3>;rt="core.osc.gconf"
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The following, additional example considers a request payload that
uses both configuration parameters and status parameters as filter
criteria. In particular, the following is assumed.
* In the URI of every group-configuration resource, the path
component is /manage/GROUPNAME, where GROUPNAME is the group name
of the associated OSCORE group.
* The Group Manager hosts four group-configuration resources, for
the OSCORE groups with names "gp4", "gp5", "gp6", and "foo". All
the OSCORE groups use the AEAD Algorithm AES-CCM-16-64-128 (COSE
algorithm encoding: 10). Also, all the OSCORE groups are
currently active, except for "gp6".
=> 0.05 FETCH
Uri-Path: manage
Content-Format: 261 (application/ace-groupcomm+cbor)
Payload:
{
e'gp_enc_alg' : 10 / AES-CCM-16-64-128 /,
e'group_name' : 21065("^gp[0-9]*$"),
e'active' : true
}
<= 2.05 Content
Content-Format: 40 (application/link-format)
Payload:
<coap://[2001:db8::ab]/manage/gp4>;rt="core.osc.gconf",
<coap://[2001:db8::ab]/manage/gp5>;rt="core.osc.gconf"
6.3. Create a New Group Configuration
This operation MUST be supported by the Group Manager and an
Administrator.
The Administrator can send a POST request to the group-collection
resource, in order to create a new OSCORE group at the Group Manager.
The request MUST specify the intended group name GROUPNAME, and MAY
specify the intended group title together with pieces of information
concerning the group configuration.
The request payload is a CBOR map, whose possible entries are
specified in Section 5.1. In particular:
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* The payload MAY include any of the configuration parameters
defined in Section 5.1.1.
* The payload MUST include the status parameter 'group_name' defined
in Section 5.1.2 and specifying the intended group name encoded as
a CBOR text string. As defined later in this section, the group
name specified in this parameter is simply a suggestion to the
Group Manager, which makes the final decision about the name to
assign to the new group.
* The payload MAY include any of the status parameters 'active',
'group_description', 'max_stale_sets', 'exp', 'gid_reuse',
'app_groups', 'group_policies', and 'as_uri' defined in
Section 5.1.2.
* The payload MUST NOT include any of the status parameters 'rt',
'ace_groupcomm_profile', and 'joining_uri' defined in
Section 5.1.2.
When performing the authorization checks, the Group Manager uses the
value of the 'group_name' parameter from the request as TARGETNAME,
and "Create" as PERMISSION.
If the group configuration to be created would include parameter
values that prevent the Group Manager from performing the operations
defined in [I-D.ietf-ace-key-groupcomm-oscore] (e.g., due to the
Group Manager not supporting a format of authentication credentials),
the Group Manager MUST respond with a 5.03 (Service Unavailable)
response. The response MUST have Content-Format set to application/
concise-problem-details+cbor [RFC9290] and is formatted as defined in
Section 4.1.2 of [I-D.ietf-ace-key-groupcomm]. Within the Custom
Problem Detail entry 'ace-groupcomm-error', the value of the 'error-
id' field MUST be set to 12 ("Unsupported group configuration"), and
the 'detail' field SHOULD be included in order to provide additional
context.
Otherwise, if any of the following occurs, the Group Manager MUST
respond with a 4.00 (Bad Request) response.
* Any of the received parameters is not recognized, or not valid, or
not consistent with respect to other related parameters. In
particular, the value of the status parameter 'exp' (if present)
is not valid if the indicated expiration date is not in the
future.
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* The Group Manager does not trust or deem acceptable the
Authorization Server with URI specified in the 'as_uri' parameter,
and has no alternative Authorization Server to consider for the
OSCORE group to create.
After a successful processing of the POST request, the Group Manager
performs the following actions.
If the 'group_name' parameter specifies the group name of an already
existing OSCORE group, the Group Manager MUST try to determine an
alternative name for the new OSCORE group to create.
In addition to that, the final decision about the name assigned to
the new OSCORE group is always of the Group Manager, which may have
more constraints than the Administrator can be aware of, possibly
beyond the availability of suggested names. For example, the Group
Manager may specifically want to use a randomized character string as
the name of a newly created group.
If the Group Manager has selected a name GROUPNAME different from the
name GROUPNAME* indicated in the parameter 'group_name' of the
request, then the following conditions MUST hold.
* The chosen name GROUPNAME is available to assign; and
* With reference to the 'scope' claim in the stored Access Token for
the Administrator, let us define PERM* as the union of the
permission sets associated with the scope entries such that
GROUPNAME* matches with the specified group name pattern. Also,
let us define PERM as the union of the permission sets associated
with the scope entries such that GROUPNAME matches with the
specified group name pattern. Then, PERM and PERM* MUST be equal.
If the Group Manager does not manage to determine a group name for
which both the above conditions hold, the Group Manager MUST respond
with a 5.03 (Service Unavailable) response. The response MUST have
Content-Format set to application/concise-problem-details+cbor
[RFC9290] and is formatted as defined in Section 4.1.2 of
[I-D.ietf-ace-key-groupcomm]. Within the Custom Problem Detail entry
'ace-groupcomm-error', the value of the 'error-id' field MUST be set
to 11 ("Unable to determine a group name").
Otherwise, the Group Manager creates a new group-configuration
resource, accessible to the Administrator at /manage/GROUPNAME, where
GROUPNAME is the name of the OSCORE group as either indicated in the
parameter 'group_name' of the request or uniquely assigned by the
Group Manager. The group-collection resource is also accordingly
updated.
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The operation of creating the new group-configuration resource and
accordingly updating the group-collection resource MUST be atomic.
That is, until the request processing fails, or the group-
configuration resource is fully created and the values of its
parameters set, the following applies.
* The group-configuration resource MUST NOT be accessible through
other operations.
* The group-collection resource MUST NOT be updated to reflect the
presence of the new group-configuration resource.
When the group-collection resource is eventually updated to reflect
the presence of the new group-configuration resource, this update
MUST NOT be interrupted by other updates to the group-collection
resource due to the creation or deletion of group-configuration
resources.
In the newly created group-configuration resource, the value of the
status parameter 'rt' is set to "core.osc.gconf". The values of
other parameters specified in the request are used as group
configuration information for the newly created OSCORE group.
If the request specifies the parameter 'gid_reuse' encoding the CBOR
simple value true (0xf5) and the Group Manager does not support the
reassignment of OSCORE Group ID values (see Section 3.2.1.1 of
[I-D.ietf-core-oscore-groupcomm] and Section 11 of
[I-D.ietf-ace-key-groupcomm-oscore]), then the Group Manager sets the
value of the 'gid_reuse' status parameter in the group-configuration
resource to the CBOR simple value false (0xf4).
For each parameter not specified in the request, the Group Manager
refers to the default values specified in Section 5.2.
After that, the Group Manager creates a new group-membership resource
accessible at /ace-group/GROUPNAME to nodes that want to join the
OSCORE group, as specified in Section 6.1 of
[I-D.ietf-ace-key-groupcomm-oscore]. Note that such group
membership-resource comprises a number of sub-resources intended to
current group members, as defined in Section 4.1 of
[I-D.ietf-ace-key-groupcomm] and Section 8 of
[I-D.ietf-ace-key-groupcomm-oscore].
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From then on, the Group Manager will rely on the current group
configuration to build the Join Response message defined in
Section 6.3 of [I-D.ietf-ace-key-groupcomm-oscore], when handling the
joining of a new group member. Furthermore, the Group Manager
generates the following pieces of information, and assigns them to
the newly created OSCORE group:
* The OSCORE Master Secret.
* The OSCORE Master Salt (optionally).
* The Group ID, used as OSCORE ID Context, which MUST be unique
within the set of OSCORE groups under the Group Manager.
Finally, the Group Manager replies to the Administrator with a 2.01
(Created) response. One or more Location-Path options MUST be
included in the response, indicating the location of the just created
group-configuration resource. The response MUST NOT include a
Location-Query option.
The response payload specifies the parameters 'group_name',
'joining_uri', and 'as_uri', from the status parameters of the newly
created OSCORE group (see Section 5.1), as detailed below.
The response payload is a CBOR map, whose possible entries are
specified in Section 5.1. In particular, the following applies.
* 'group_name', which specifies the group name of the OSCORE group.
This value can be different from the group name possibly specified
by the Administrator in the POST request, and reflects the final
choice of the Group Manager as value of the 'group_name' status
parameter for the OSCORE group. This parameter MUST be included.
* 'joining_uri', which specifies the URI of the group-membership
resource for joining the newly created OSCORE group. This
parameter MUST be included.
* 'as_uri', which specifies the URI of the Authorization Server
associated with the Group Manager for the newly created OSCORE
group. This parameter MUST be included. Its value can be
different from the URI possibly specified by the Administrator in
the POST request, and reflects the final choice of the Group
Manager as value of the 'as_uri' status parameter for the OSCORE
group.
If the POST request specified the parameter 'gid_reuse' encoding the
CBOR simple value true (0xf5) but the Group Manager has set the value
of the 'gid_reuse' status parameter in the group-configuration
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resource to the CBOR simple value false (0xf4), then the response
payload MUST include also the parameter 'gid_reuse' encoding the CBOR
simple value false (0xf4).
If the POST request did not specify certain parameters and the Group
Manager used default values different from the ones recommended in
Section 5.2, then the response payload MUST also include those
parameters, specifying the values chosen by the Group Manager for the
current group configuration.
The Group Manager can register the link to the group-membership
resource with URI specified in 'joining_uri' to a Resource Directory
[RFC9176], as defined in Section 2 of
[I-D.tiloca-core-oscore-discovery]. The Group Manager considers the
current group configuration when specifying additional information
for the link to register.
It is also possible that the Administrator performs the registration
in the Resource Directory on behalf of the Group Manager, acting as
Commissioning Tool. The Administrator considers the following when
specifying additional information for the link to register.
* The name of the OSCORE group MUST take the value specified in
'group_name' from the 2.01 (Created) response.
* The names of the application groups using the OSCORE group MUST
take the values possibly specified by the elements of the
'app_groups' parameter in the POST request.
* If also registering a related link to the Authorization Server
associated with the OSCORE group, the related link MUST have as
link target the URI in 'as_uri' from the 2.01 (Created) response.
* As to every other information element describing the current group
configuration, the following applies.
- If a certain parameter was specified in the POST request, the
Administrator MUST use either the value specified in the 2.01
(Created) response, if the Group Manager specified one, or the
value specified in the POST request otherwise.
- If a certain parameter was not specified in the POST request,
the Administrator MUST use either the value specified in the
2.01 (Created) response, if the Group Manager specified one, or
the corresponding default value recommended in Section 5.2.1
otherwise.
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Note that, compared to the Group Manager, the Administrator is less
likely to remain closely aligned with possible changes and updates
that would require a prompt update to the registration in the
Resource Directory. This applies especially to the address of the
Group Manager, as well as the URI of the group-membership resource or
of the Authorization Server associated with the Group Manager.
Therefore, it is RECOMMENDED that registrations of links to group-
membership resources in the Resource Directory are made (and possibly
updated) directly by the Group Manager, rather than by the
Administrator.
An example of message exchange is shown below.
=> 0.02 POST
Uri-Path: manage
Content-Format: 261 (application/ace-groupcomm+cbor)
Payload:
{
e'gp_enc_alg' : 10 / AES-CCM-16-64-128 /,
e'hkdf' : 5 / HMAC-256-256 /,
e'pairwise_mode' : true,
e'active' : true,
e'group_name' : "gp4",
e'group_description' : "rooms 1 and 2",
e'app_groups' : ["room1", "room2"],
e'as_uri' : "coap://as.example.com/token"
}
<= 2.01 Created
Location-Path: manage
Location-Path: gp4
Content-Format: 261 (application/ace-groupcomm+cbor)
Payload:
{
e'group_name' : "gp4",
e'joining_uri' : "coap://[2001:db8::ab]/ace-group/gp4/",
e'as_uri' : "coap://as.example.com/token"
}
6.4. Retrieve a Group Configuration
This operation MUST be supported by the Group Manager and an
Administrator.
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The Administrator can send a GET request to the group-configuration
resource manage/GROUPNAME associated with an OSCORE group with group
name GROUPNAME, in order to retrieve the complete current
configuration of that group.
When performing the authorization checks, the Group Manager uses
GROUPNAME as TARGETNAME, and "Read" as PERMISSION.
Otherwise, after a successful processing of the GET request, the
Group Manager replies to the Administrator with a 2.05 (Content)
response. The response has as payload the representation of the
group configuration as specified in Section 5.1. The exact content
of the payload reflects the current configuration of the OSCORE
group. This includes both configuration parameters and status
parameters.
The response payload is a CBOR map, whose possible entries are
specified in Section 5.1.
An example of message exchange is shown below.
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=> 0.01 GET
Uri-Path: manage
Uri-Path: gp4
<= 2.05 Content
Content-Format: 261 (application/ace-groupcomm+cbor)
Payload:
{
e'hkdf' : 5 / HMAC-256-256 /,
e'cred_fmt' : 33 / x5chain /,
e'group_mode' : true,
e'gp_enc_alg' : 10 / AES-CCM-16-64-128 /,
e'sign_alg' : -8 / EdDSA /,
e'sign_params' : [[1], [1, 6]]
/ [[OKP], [OKP, Ed25519]] /,
e'pairwise_mode' : true,
e'alg' : 10 / AES-CCM-16-64-128 /,
e'ecdh_alg' : -27 / ECDH-SS-HKDF-256 /,
e'ecdh_params' : [[1], [1, 4]]
/ [[OKP], [OKP, X25519]] /,
e'det_req' : false,
e'rt' : "core.osc.gconf",
e'active' : true,
e'group_name' : "gp4",
e'group_description' : "rooms 1 and 2",
e'ace_groupcomm_profile' : "coap_group_oscore_app",
e'max_stale_sets' : 3,
e'exp' : 1360289224,
e'gid_reuse' : false,
e'app_groups' : ["room1", "room2"],
e'joining_uri' : "coap://[2001:db8::ab]/ace-group/gp4/",
e'as_uri' : "coap://as.example.com/token"
}
6.5. Retrieve Part of a Group Configuration by Filters
This operation MUST be supported by the Group Manager and MAY be
supported by an Administrator.
The Administrator can send a FETCH request to the group-configuration
resource manage/GROUPNAME associated with an OSCORE group with group
name GROUPNAME, in order to retrieve part of the current
configuration of that group.
The request payload is a CBOR map, which contains the following
field:
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* 'conf_filter', encoded as a CBOR array. Each element of the array
specifies one requested configuration parameter or status
parameter of the current group configuration (see Section 5.1),
encoded with the corresponding CBOR abbreviation defined in
Section 7.
When performing the authorization checks, the Group Manager uses
GROUPNAME as TARGETNAME, and "Read" as PERMISSION.
After a successful processing of the FETCH request, the Group Manager
replies to the Administrator with a 2.05 (Content) response. The
response has as payload a partial representation of the group
configuration (see Section 5.1). The exact content of the payload
reflects the current configuration of the OSCORE group, and is
limited to the configuration parameters and status parameters
requested by the Administrator in the FETCH request.
The response payload includes the requested configuration parameters
and status parameters, and is formatted as in the response payload of
a GET request to a group-configuration resource (see Section 6.4).
If the request payload specifies a parameter that is not included in
the group configuration, then the response payload MUST NOT include a
corresponding parameter.
An example of message exchange is shown below.
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=> 0.05 FETCH
Uri-Path: manage
Uri-Path: gp4
Content-Format: 261 (application/ace-groupcomm+cbor)
Payload:
{
e'conf_filter' : [e'gp_enc_alg',
e'hkdf',
e'pairwise_mode',
e'active',
e'group_description',
e'app_groups']
}
<= 2.05 Content
Content-Format: 261 (application/ace-groupcomm+cbor)
Payload:
{
e'gp_enc_alg' : 10 / AES-CCM-16-64-128 /,
e'hkdf' : 5 / HMAC-256-256 /,
e'pairwise_mode' : true,
e'active' : true,
e'group_description' : "rooms 1 and 2",
e'app_groups' : ["room1", "room2"]
}
6.6. Overwrite a Group Configuration
This operation MAY be supported by the Group Manager and an
Administrator.
The Administrator can send a POST request to the group-configuration
resource manage/GROUPNAME associated with an OSCORE group with group
name GROUPNAME, in order to overwrite the current configuration of
that group with a new one.
The payload of the request has the same format of the POST request
defined in Section 6.3, with the exception that the configuration
parameters 'group_mode' and 'pairwise_mode' as well as the status
parameters 'group_name' and 'gid_reuse' MUST NOT be included.
The error handling for the POST request is the same as for the POST
request defined in Section 6.3, with the following difference in
terms of authorization checks.
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When performing the authorization checks, the Group Manager uses
GROUPNAME as TARGETNAME, and "Write" as PERMISSION.
If the group-configuration resource targeted by the POST request does
not currently exist, then the Group Manager MUST NOT create the
resource and MUST reply with a 4.04 (Not Found) error response.
If the updated group configuration would include parameter values
that prevent the Group Manager from performing the operations defined
in [I-D.ietf-ace-key-groupcomm-oscore] (e.g., due to the Group
Manager not supporting a format of authentication credentials), the
Group Manager MUST respond with a 5.03 (Service Unavailable)
response. The response MUST have Content-Format set to application/
concise-problem-details+cbor [RFC9290] and is formatted as defined in
Section 4.1.2 of [I-D.ietf-ace-key-groupcomm]. Within the Custom
Problem Detail entry 'ace-groupcomm-error', the value of the 'error-
id' field MUST be set to 12 ("Unsupported group configuration"), and
the 'detail' field SHOULD be included in order to provide additional
context.
If no error occurs and the POST request is successfully processed,
the Group Manager performs the following actions.
First, the Group Manager updates the group-configuration resource,
consistently with the values indicated in the POST request from the
Administrator. When doing so, the configuration parameters
'group_mode' and 'pairwise_mode' as well as the status parameters
'group_name' and 'gid_reuse' MUST remain unchanged.
For each other parameter not specified in the POST request, the Group
Manager MUST use default values as specified in Section 5.2. Note
that the default value recommended for the status parameter 'active'
is the CBOR simple value false (0xf4). Therefore, if the
Administrator intends to preserve the current status of the group as
active, then the payload of the POST request has to include the
parameter 'active' specifying the CBOR simple value true (0xf5).
When updating the group-configuration resource, the corresponding
group-membership resource is also accordingly updated. The operation
of overwriting such two resources MUST be atomic. That is, until the
request processing fails, or the group-configuration resource has
been fully updated and the values of its parameters set, the
following applies.
* The group-configuration resource MUST NOT be accessible through
other operations.
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* The group-membership resource MUST NOT be updated to reflect the
new group configuration.
* The filter criteria specified in a FETCH request to the group-
collection resource (see Section 6.2) MUST be compared against the
representation that the group-configuration resource had before
its update started.
When the group-membership resource is eventually updated to reflect
the new group configuration, this update MUST NOT be interrupted by
other operations performed on the group-membership resource.
If a new value N' is specified for the 'max_stale_sets' status
parameter and N' is smaller than the current value N, the Group
Manager preserves the (up to) N' most recent sets of stale OSCORE
Sender IDs associated with the group, and deletes any possible older
set (see Section 7.1 of [I-D.ietf-ace-key-groupcomm-oscore]).
From then on, the Group Manager relies on the latest updated
configuration to build the Join Response message defined in
Section 6.3 of [I-D.ietf-ace-key-groupcomm-oscore], when handling the
joining of a new group member. Similarly, the Group Manager relies
on the new group configuration when building responses specifying
(part of) the group configuration to a current group member. For
instance, this applies when a group member retrieves from the Group
Manager the updated group keying material (see Section 9.1 of
[I-D.ietf-ace-key-groupcomm-oscore]) or the current group status (see
Section 9.9 of [I-D.ietf-ace-key-groupcomm-oscore]).
Then, the Group Manager replies to the Administrator with a 2.04
(Changed) response. The payload of the response has the same format
of the 2.01 (Created) response defined in Section 6.3.
If the POST request did not specify certain parameters and the Group
Manager used default values different from the ones recommended in
Section 5.2, then the response payload MUST include also those
parameters, specifying the values chosen by the Group Manager for the
current group configuration.
If the link to the group-membership resource was registered in the
Resource Directory [RFC9176], the Group Manager is responsible to
refresh the registration, as defined in Section 3 of
[I-D.tiloca-core-oscore-discovery].
It is also possible that the Administrator updates the registration
in the Resource Directory on behalf of the Group Manager, acting as
Commissioning Tool. The Administrator considers the following when
specifying additional information for the link to update.
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* The name of the OSCORE group MUST take the value specified in
'group_name' from the 2.04 (Changed) response.
* The names of the application groups using the OSCORE group MUST
take the values possibly specified by the elements of the
'app_groups' parameter in the POST request.
* If also registering a related link to the Authorization Server
associated with the OSCORE group, the related link MUST have as
link target the URI in 'as_uri' from the 2.04 (Changed) response.
* As to every other information element describing the current group
configuration, the following applies.
- If a certain parameter was specified in the POST request, the
Administrator MUST use either the value specified in the 2.04
(Changed) response, if the Group Manager specified one, or the
value specified in the POST request otherwise.
- If a certain parameter was not specified in the POST request,
the Administrator MUST use either the value specified in the
2.04 (Changed) response, if the Group Manager specified one, or
the corresponding default value recommended in Section 5.2.1
otherwise.
As discussed in Section 6.3, it is RECOMMENDED that registrations of
links to group-membership resources in the Resource Directory are
made (and possibly updated) directly by the Group Manager, rather
than by the Administrator.
An example of message exchange is shown below.
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=> 0.02 POST
Uri-Path: manage
Uri-Path: gp4
Content-Format: 261 (application/ace-groupcomm+cbor)
Payload:
{
e'gp_enc_alg' : 11 / AES-CCM-16-64-256 /,
e'hkdf' : 5 / HMAC-256-256 /
}
<= 2.04 Changed
Content-Format: 261 (application/ace-groupcomm+cbor)
Payload:
{
e'group_name' : "gp4",
e'joining_uri' : "coap://[2001:db8::ab]/ace-group/gp4/",
e'as_uri' : "coap://as.example.com/token"
}
6.6.1. Effects on Joining Nodes
After having overwritten a group configuration, if the value of the
status parameter 'active' is changed from true (0xf5) to false
(0xf4), the Group Manager MUST stop admitting new members in the
OSCORE group. In particular, until the status parameter 'active' is
changed back to true (0xf5), the Group Manager MUST respond to a Join
Request with a 5.03 (Service Unavailable) response, as defined in
Section 6.2 of [I-D.ietf-ace-key-groupcomm-oscore].
If the value of the status parameter 'active' is changed from false
(0xf4) to true (0xf5), the Group Manager resumes admitting new
members in the OSCORE group, by processing their Join Requests (see
Section 6.2 of [I-D.ietf-ace-key-groupcomm-oscore]).
6.6.2. Effects on the Group Members
After having overwritten a group configuration, the Group Manager
informs the members of the OSCORE group, over the pairwise secure
communication channels established when joining the group (see
Section 6 of [I-D.ietf-ace-key-groupcomm-oscore]).
To this end, the Group Manager can individually target the
'control_uri' URI of each group member (see Section 4.3.1 of
[I-D.ietf-ace-key-groupcomm]), if provided by the intended recipient
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upon joining the OSCORE group (see Section 6.1 of
[I-D.ietf-ace-key-groupcomm-oscore]). Such messages sent by the
Group Manager to each group member MUST have Content-Format set to
application/ace-groupcomm+cbor, and MUST be formatted as the Join
Response defined in Section 6.3 of
[I-D.ietf-ace-key-groupcomm-oscore], with the following differences.
* Only the parameters 'gkty', 'key', 'num', 'exp', and
'ace_groupcomm_profile' are present.
* The 'key' parameter includes only the following parameters, with
values reflecting the new configuration of the OSCORE group.
- 'hkdf' and 'cred_fmt'.
- 'sign_enc_alg', 'sign_alg', and 'sign_params', only in case the
configuration parameter 'group_mode' in the group-configuration
resource has value true (0xf5), i.e., the OSCORE group uses the
group mode of Group OSCORE.
Editor's note: as per the text above, the referred version of
[I-D.ietf-ace-key-groupcomm-oscore] still uses 'sign_enc_alg'
as parameter name. The next version of
[I-D.ietf-ace-key-groupcomm-oscore] will be updated in order to
use 'gp_enc_alg' instead, as already done for this document and
consistently with the naming used in the latest version of
[I-D.ietf-core-oscore-groupcomm].
- 'alg', 'ecdh_alg', and 'ecdh_params', only in case the
configuration parameter 'pairwise_mode' in the group-
configuration resource has value true (0xf5), i.e., the OSCORE
group uses the pairwise mode of Group OSCORE.
- 'det_hash_alg' defined in Section 4 of
[I-D.amsuess-core-cachable-oscore], only in case the
configuration parameter 'det_req' is present with value true
(0xf5), and specifying the Hash Algorithm used in the OSCORE
group when producing deterministic requests, as defined in
[I-D.amsuess-core-cachable-oscore].
Alternatively, group members can obtain the information above by
accessing the group-membership resource associated with the OSCORE
group (see Section 9.1 of [I-D.ietf-ace-key-groupcomm-oscore]),
optionally by subscribing for updates to such a resource, e.g., by
using CoAP Observe [RFC7641].
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When receiving such information, each group member uses it to update
the corresponding parameters in the Group OSCORE Security Context of
the group in question (see Section 2 of
[I-D.ietf-core-oscore-groupcomm]. If any of 'sign_enc_alg',
'sign_alg', 'alg', and 'ecdh_alg' has as value the CBOR simple value
null (0xf6), then the corresponding parameter in the Group OSCORE
Security Context becomes unset if it is not already. According to
the new parameter values, each group member derives new Sender/
Recipient Keys, a new Common IV, and new Pairwise Keys. When doing
so, a group member MUST NOT reset the Sender Sequence Number in its
Sender Context or reset the Replay Window in its Recipient Contexts.
Editor's note: as per the text above, the referred version of
[I-D.ietf-ace-key-groupcomm-oscore] still uses 'sign_enc_alg' as
parameter name. The next version of
[I-D.ietf-ace-key-groupcomm-oscore] will be updated in order to use
'gp_enc_alg' instead, as already done for this document and
consistently with the naming used in the latest version of
[I-D.ietf-core-oscore-groupcomm].
The following holds when the value of specific parameters is updated.
* If the value of the status parameter 'active' is changed from true
(0xf5) to false (0xf4):
- The Group Manager MUST stop accepting requests for new
individual keying material from current group members (see
Section 9.2 of [I-D.ietf-ace-key-groupcomm-oscore]), until the
status parameter 'active' is changed back to true (0xf5).
Until then, the Group Manager MUST respond to a Key Renewal
Request with a 5.03 (Service Unavailable) response, as defined
in Section 9.2 of [I-D.ietf-ace-key-groupcomm-oscore].
- The Group Manager MUST stop accepting updated authentication
credentials uploaded by current group members (see Section 9.4
of [I-D.ietf-ace-key-groupcomm-oscore]), until the status
parameter 'active' is changed back to true (0xf5). Until then,
the Group Manager MUST respond to an Authentication Credential
Update Request with a 5.03 (Service Unavailable) response, as
defined in Section 9.4 of [I-D.ietf-ace-key-groupcomm-oscore].
* Every group member, upon learning that the OSCORE group has been
deactivated (i.e., 'active' has value false (0xf4)), SHOULD stop
communicating in the group.
Every group member, upon learning that the OSCORE group has been
reactivated (i.e., 'active' has value true (0xf5) again), can
resume communicating in the group.
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* If the value of 'gp_enc_alg' and/or 'alg' is changed, the Group
Manager determines the new maximum size NEW_MAX_SIZE that can be
used for the OSCORE Sender IDs of the group members, based on the
size of the AEAD nonce of such algorithms (see Section 2.2 of
[I-D.ietf-core-oscore-groupcomm]). In case NEW_MAX_SIZE is
strictly smaller than the old, maximum size of the OSCORE Sender
IDs used in the OSCORE group, the Group Manager MUST proceed as
follows.
- The Group Manager checks if any of the current group members
has an OSCORE Sender ID whose size is strictly larger than
NEW_MAX_SIZE.
- If any of such group members is found, the Group Manager MUST
evict them from the OSCORE group. That is, the Group Manager
MUST terminate their membership and MUST rekey the group in
such a way that the new keying material is not provided to
those evicted members. This also includes adding their
relinquished Sender IDs to the most recent set of stale Sender
IDs for the OSCORE group (see Section 7.1 of
[I-D.ietf-ace-key-groupcomm-oscore]), before rekeying the
group. Such evicted group members can rejoin the OSCORE group,
thus obtaining the new group keying material together with a
new, valid OSCORE Sender ID.
* Every group member, upon receiving updated values for 'hkdf',
'sign_enc_alg', and 'alg', MUST either:
- Leave the OSCORE group (see Section 9.11 of
[I-D.ietf-ace-key-groupcomm-oscore]), e.g., if not supporting
the indicated new algorithms; or
- Remain in the OSCORE group and use the Group OSCORE Security
Context after having updated it as defined above.
Editor's note: as per the text above, the referred version of
[I-D.ietf-ace-key-groupcomm-oscore] still uses 'sign_enc_alg' as
parameter name. The next version of
[I-D.ietf-ace-key-groupcomm-oscore] will be updated in order to
use 'gp_enc_alg' instead, as already done for this document and
consistently with the naming used in the latest version of
[I-D.ietf-core-oscore-groupcomm].
* Every group member, upon receiving updated values for 'cred_fmt',
'sign_alg', 'sign_params', 'ecdh_alg', and 'ecdh_params' MUST
either:
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- Leave the OSCORE group, e.g., if not supporting the indicated
new format, algorithms, parameters, and encoding; or
- Leave the OSCORE group and rejoin it (see Section 6 of
[I-D.ietf-ace-key-groupcomm-oscore]). When rejoining the
group, an authentication credential in the indicated format
used in the OSCORE group MUST be provided to the Group Manager.
The authentication credential as well as the included public
key MUST be compatible with the indicated algorithms and
parameters.
- Remain in the OSCORE group and use the Group OSCORE Security
Context after having updated it as defined above, and, if
required, perform the following actions.
o Provide the Group Manager with a new authentication
credential to use in the OSCORE group (see Section 9.4 of
[I-D.ietf-ace-key-groupcomm-oscore]). The new
authentication credential MUST be in the indicated format
used in the OSCORE group. The new authentication credential
as well as the included public key MUST be compatible with
the indicated algorithms and parameters.
Consistently, the group member has to retrieve the new
authentication credentials of other group members as they
are uploaded to the Group Manager (see Section 9.3 of
[I-D.ietf-ace-key-groupcomm-oscore]). In order to ensure
the retrieval of latest authentication credentials that are
consistent with the new group configuration, it is
preferable that the group member retrieves such
authentication credentials after a pre-configured time
interval has elapsed since uploading its own authentication
credential. Later on, the group member will need to
retrieve other group members' authentication credentials
that it is still missing and that it needs for processing
messages exchanged in the OSCORE group.
o Retrieve from the Group Manager the Group Manager's new
authentication credential (see Section 9.5 of
[I-D.ietf-ace-key-groupcomm-oscore]). The new Group
Manager's authentication credential is in the indicated
format used in the OSCORE group. The new authentication
credential as well as the included public key are compatible
with the indicated algorithms and parameters.
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As discussed above, after the group configuration has been updated,
some group members may leave the OSCORE group and rejoin it. Shortly
following an update of group configuration, the Group Manager SHOULD
prioritize the re-join of such current group members before
processing Join Requests from other, new group members.
6.7. Selective Update of a Group Configuration
This operation MAY be supported by the Group Manager and an
Administrator.
The Administrator can send a PATCH/iPATCH request [RFC8132] to the
group-configuration resource manage/GROUPNAME associated with an
OSCORE group with group name GROUPNAME, in order to update the value
of only part of the group configuration.
The request payload has the same format of the POST request defined
in Section 6.6, with the difference that it MAY also specify names of
application groups to be removed from or added to the 'app_groups'
status parameter. The names of such application groups are provided
as defined below.
The CBOR map in the request payload includes the field
'app_groups_diff'. This field is encoded as a CBOR array including
the following two elements.
* The first element is a CBOR array, namely 'app_groups_del'. Each
of its elements is a CBOR text string, with value the name of an
application group to remove from the 'app_groups' status
parameter.
* The second element is a CBOR array, namely 'app_groups_add'. Each
of its elements is a CBOR text string, with value the name of an
application group to add to the 'app_groups' status parameter.
The CDDL definition [RFC8610] of the CBOR array 'app_groups_diff'
formatted as in the request from the Administrator is provided below.
app-group-name = tstr
name-patch = [* app-group-name]
app_groups_diff = [app_groups_del: name-patch,
app_groups_add: name-patch]
Figure 2: CDDL definition of the 'app_groups_diff' field
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The Group Manager MUST respond with a 4.00 (Bad Request) response in
case: both the inner CBOR arrays 'app_groups_del' and
'app_groups_add' are empty; or the CBOR map in the request payload
includes both the 'app_groups' field and the 'app_groups_diff' field.
The error handling for the PATCH/iPATCH request is the same as for
the POST request defined in Section 6.6, with the following
additions.
* The set of group configuration parameters to update MUST NOT be
empty. That is, the Group Manager MUST respond with a 4.00 (Bad
Request) response, if the request payload includes an empty CBOR
map.
* If the Request-URI does not point to an existing group-
configuration resource, the Group Manager MUST NOT create a new
resource, and MUST respond with a 4.04 (Not Found) response.
* When applying the specified updated values would yield an
inconsistent group configuration, the Group Manager MUST respond
with a 4.09 (Conflict) response.
As an example, this is the case if the resulting group
configuration would include the parameter 'sign_alg' specifying
the signature algorithm EdDSA (COSE algorithm encoding: -8) and,
at the same time, the parameter 'sign_params' specifying EC2 as
COSE key type and P-256 as COSE elliptic curve (i.e., as the CBOR
array [[2], [2, 1]]).
The response MAY include the current representation of the group
configuration resource, like when responding to a GET request as
defined in Section 6.4. Otherwise, the response SHOULD include a
diagnostic payload with additional information for the
Administrator to recognize the source of the conflict.
* When the request uses specifically the iPATCH method, the Group
Manager MUST respond with a 4.00 (Bad Request) response, in case
the CBOR map includes the parameter 'app_groups_diff' and the name
of an application group is specified both in the 'app_groups_del'
and 'app_groups_add' inner arrays.
When performing the authorization checks, the Group Manager uses
GROUPNAME as TARGETNAME, and "Write" as PERMISSION.
If the updated group configuration would include parameter values
that prevent the Group Manager from performing the operations defined
in [I-D.ietf-ace-key-groupcomm-oscore] (e.g., due to the Group
Manager not supporting a format of authentication credentials), the
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Group Manager MUST respond with a 5.03 (Service Unavailable)
response. The response MUST have Content-Format set to application/
concise-problem-details+cbor [RFC9290] and is formatted as defined in
Section 4.1.2 of [I-D.ietf-ace-key-groupcomm]. Within the Custom
Problem Detail entry 'ace-groupcomm-error', the value of the 'error-
id' field MUST be set to 12 ("Unsupported group configuration"), and
the 'detail' field SHOULD be included in order to provide additional
context.
If no error occurs and the PATCH/iPATCH request is successfully
processed, the Group Manager performs the following actions.
First, the Group Manager updates the group-configuration resource,
consistently with the values indicated in the PATCH/iPATCH request
from the Administrator. The corresponding group-membership resource
is also accordingly updated.
The operation of updating the group-configuration resource and
accordingly updating the group-membership resource MUST be atomic.
That is, the same as defined in Section 6.6 when atomically
overwriting a group-configuration resource applies.
Unlike for the POST request defined in Section 6.6, the Group Manager
does not alter the value of configuration parameters and status
parameters for which updated values are not specified in the request
payload. In particular, the Group Manager does not assign possible
default values to those parameters.
Special processing occurs when updating the 'app_groups' status
parameter by difference, as defined below. The Administrator should
not expect the Group Manager to add or delete names of application
group names according to any particular order.
* If the name of an application group to add (delete) is specified
multiple times, the Group Manager considers it only once for
addition to (deletion from) the 'app_groups' status parameter.
* If the name of an application group to delete is not present in
the 'app_groups' status parameter before any change is applied,
the Group Manager ignores that name.
* If the name of an application group to add is already present in
the 'app_groups' status parameter before any change is applied,
the Group Manager ignores that name.
* The Group Manager deletes from the 'app_groups' status parameter
the names of the application groups specified in the inner
'app_groups_del' CBOR array of the 'app_groups_diff' field.
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* The Group Manager adds to the 'app_groups' status parameter the
names of the application groups specified in the inner
'app_groups_add' CBOR array of the 'app_groups_diff' field.
After having updated the group-configuration resource, from then on
the Group Manager relies on the new group configuration to build the
Join Response message defined in Section 6.3 of
[I-D.ietf-ace-key-groupcomm-oscore], when handling the joining of a
new group member. Similarly, the Group Manager relies on the new
group configuration when building responses specifying (part of) the
group configuration to a current group member. For instance, this
applies when a group member retrieves from the Group Manager the
updated group keying material (see Section 9.1 of
[I-D.ietf-ace-key-groupcomm-oscore]) or the current group status (see
Section 9.9 of [I-D.ietf-ace-key-groupcomm-oscore]).
Finally, the Group Manager replies to the Administrator with a 2.04
(Changed) response. The payload of the response has the same format
of the 2.01 (Created) response defined in Section 6.3.
The same considerations as for the POST request defined in
Section 6.6 hold also in this case, with respect to refreshing a
possible registration of the link to the group-membership resource in
the Resource Directory [RFC9176].
An example of message exchange is shown below.
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=> 0.06 PATCH
Uri-Path: manage
Uri-Path: gp4
Content-Format: 261 (application/ace-groupcomm+cbor)
Payload:
{
e'gp_enc_alg' : 10 / AES-CCM-16-64-128 /,
e'app_groups_diff' : [["room1"], ["room3", "room4"]]
}
<= 2.04 Changed
Content-Format: 261 (application/ace-groupcomm+cbor)
Payload:
{
e'group_name' : "gp4",
e'joining_uri' : "coap://[2001:db8::ab]/ace-group/gp4/",
e'as_uri' : "coap://as.example.com/token"
}
6.7.1. Effects on Joining Nodes
After having selectively updated part of a group configuration, the
effects on candidate joining nodes are the same as defined in
Section 6.6.1 for the case of group configuration overwriting.
6.7.2. Effects on the Group Members
After having selectively updated part of a group configuration, the
effects on the current group members are the same as defined in
Section 6.6.2 for the case of group configuration overwriting.
6.8. Delete a Group Configuration
This operation MUST be supported by the Group Manager and an
Administrator.
The Administrator can send a DELETE request to the group-
configuration resource manage/GROUPNAME associated with an OSCORE
group with group name GROUPNAME, in order to delete that OSCORE
group.
When performing the authorization checks, the Group Manager uses
GROUPNAME as TARGETNAME, and "Delete" as PERMISSION.
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Otherwise, the Group Manager continues processing the request, which
MUST fail it the OSCORE group is active. That is, the DELETE request
MUST yield the deletion of the OSCORE group only if the corresponding
status parameter 'active' has current value false (0xf4). The
Administrator can ensure that, by first performing an update of the
group-configuration resource associated with the OSCORE group (see
Section 6.6 and Section 6.7), and setting the corresponding status
parameter 'active' to false (0xf4).
If, upon receiving the DELETE request, the current value of the
status parameter 'active' is true (0xf5), the Group Manager MUST
respond with a 4.09 (Conflict) response. The response MUST have
Content-Format set to application/concise-problem-details+cbor
[RFC9290] and is formatted as defined in Section 4.1.2 of
[I-D.ietf-ace-key-groupcomm]. Within the Custom Problem Detail entry
'ace-groupcomm-error', the value of the 'error-id' field MUST be set
to 10 ("Group currently active").
After a successful processing of the DELETE request, the Group
Manager performs the following actions.
First, the Group Manager deletes the OSCORE group, deallocates both
the group-configuration resource as well as the group-membership
resource associated with that group, and accordingly updates the
group-collection resource.
The operation of deleting the group-configuration resource and the
corresponding group-membership resource, as well as of accordingly
updating the group-collection resource MUST be atomic. That is,
until the request processing fails, or the group-configuration
resource is deleted, the following applies.
* The group-configuration resource MUST NOT be accessible through
other operations.
* The group-membership resource MUST NOT be deleted.
* The group-collection resource MUST NOT be updated to reflect the
deletion of the group-configuration resource.
When the group-membership resource is eventually deleted, this
deletion MUST NOT be interrupted by other operations performed on the
group-membership resource.
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When the group-collection resource is eventually updated to reflect
the deletion of the group-configuration resource, this update MUST
NOT be interrupted by other updates to the group-collection resource
due to the creation or deletion of group-configuration resources, or
to other operations performed on those.
After deleting the group-configuration resource, the Group Manager
replies to the Administrator with a 2.02 (Deleted) response.
An example of message exchange is shown below.
=> 0.04 DELETE
Uri-Path: manage
Uri-Path: gp4
<= 2.02 Deleted
6.8.1. Effects on the Group Members
After having deleted an OSCORE group, the Group Manager can inform
the group members by means of the following two methods. When
contacting a group member, the Group Manager uses the pairwise secure
communication association established with that member during its
joining process (see Section 6 of
[I-D.ietf-ace-key-groupcomm-oscore]).
* The Group Manager sends an individual request message to each
group member, targeting the respective resource used to perform
the group rekeying process (see Section 11.1 of
[I-D.ietf-ace-key-groupcomm-oscore]). The Group Manager uses the
same format of the Join Response message in Section 6.3 of
[I-D.ietf-ace-key-groupcomm-oscore], where only the parameters
'gkty', 'key', and 'ace_groupcomm_profile' are present, and the
'key' parameter is the empty CBOR map.
* A group member may subscribe for updates to the group-membership
resource associated with the OSCORE group. In particular, if this
relies on CoAP Observe [RFC7641], a group member would receive a
4.04 (Not Found) notification response from the Group Manager,
since the group-configuration resource has been deallocated upon
deleting the OSCORE group (see Section 6.1 of
[I-D.ietf-ace-key-groupcomm]). The response MUST have Content-
Format set to application/concise-problem-details+cbor [RFC9290]
and is formatted as defined in Section 4.1.2 of
[I-D.ietf-ace-key-groupcomm]. Within the Custom Problem Detail
entry 'ace-groupcomm-error', the value of the 'error-id' field
MUST be set to 6 ("Group deleted").
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When being informed about the deletion of the OSCORE group, a group
member deletes the OSCORE Security Context that it stores as
associated with that group, and possibly deallocates any dedicated
control resource intended for the Group Manager that it has for that
group.
7. ACE Groupcomm Parameters
In addition to what is defined in Section 8 of
[I-D.ietf-ace-key-groupcomm], this document defines additional
parameters used in the messages exchanged between the Administrator
and the Group Manager (see Section 6). The table below summarizes
them and specifies the CBOR key to use instead of the full
descriptive name.
Note that the media type application/ace-groupcomm+cbor MUST be used
when these parameters are transported in the respective message
fields.
+===================+==========+=====================+============+
| Name | CBOR Key | CBOR Type | Reference |
+===================+==========+=====================+============+
| hkdf | -1 | tstr or int | [RFC-XXXX] |
+-------------------+----------+---------------------+------------+
| cred_fmt | -2 | int | [RFC-XXXX] |
+-------------------+----------+---------------------+------------+
| group_mode | -3 | True or False | [RFC-XXXX] |
+-------------------+----------+---------------------+------------+
| gp_enc_alg | -4 | Null or tstr or int | [RFC-XXXX] |
+-------------------+----------+---------------------+------------+
| sign_alg | -5 | Null or tstr or int | [RFC-XXXX] |
+-------------------+----------+---------------------+------------+
| sign_params | -6 | Null or array | [RFC-XXXX] |
+-------------------+----------+---------------------+------------+
| pairwise_mode | -7 | True or False | [RFC-XXXX] |
+-------------------+----------+---------------------+------------+
| alg | -8 | Null or tstr or int | [RFC-XXXX] |
+-------------------+----------+---------------------+------------+
| ecdh_alg | -9 | Null or tstr or int | [RFC-XXXX] |
+-------------------+----------+---------------------+------------+
| ecdh_params | -10 | Null or array | [RFC-XXXX] |
+-------------------+----------+---------------------+------------+
| det_req | -25 | True or False | [RFC-XXXX] |
+-------------------+----------+---------------------+------------+
| det_hash_alg | -26 | tstr or int | [RFC-XXXX] |
+-------------------+----------+---------------------+------------+
| rt | -11 | tstr | [RFC-XXXX] |
+-------------------+----------+---------------------+------------+
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| active | -12 | True or False | [RFC-XXXX] |
+-------------------+----------+---------------------+------------+
| group_name | -13 | tstr or | [RFC-XXXX] |
| | | #6.<uint>(any) | |
+-------------------+----------+---------------------+------------+
| group_description | -14 | Null or tstr | [RFC-XXXX] |
+-------------------+----------+---------------------+------------+
| max_stale_sets | -15 | uint | [RFC-XXXX] |
+-------------------+----------+---------------------+------------+
| gid_reuse | -16 | True or False | [RFC-XXXX] |
+-------------------+----------+---------------------+------------+
| app_groups | -17 | array | [RFC-XXXX] |
+-------------------+----------+---------------------+------------+
| joining_uri | -18 | tstr | [RFC-XXXX] |
+-------------------+----------+---------------------+------------+
| as_uri | -19 | tstr | [RFC-XXXX] |
+-------------------+----------+---------------------+------------+
| conf_filter | -27 | array | [RFC-XXXX] |
+-------------------+----------+---------------------+------------+
| app_groups_diff | -28 | array | [RFC-XXXX] |
+-------------------+----------+---------------------+------------+
Table 2: ACE Groupcomm Parameters
The following holds for the Group Manager.
* It MUST support the parameters 'ace_groupcomm_profile', 'exp', and
'group_policies', which are defined in Section 8 of
[I-D.ietf-ace-key-groupcomm].
This is consistent with what is defined in Section 8 of
[I-D.ietf-ace-key-groupcomm] for the Key Distribution Center, of
which the Group Manager defined in
[I-D.ietf-ace-key-groupcomm-oscore] is a specific instance.
* It MUST support all the parameters listed in Table 2, with the
exception of the 'app_groups_diff' parameter, which MUST be
supported only if the Group Manager supports the selective update
of a group configuration (see Section 6.7).
The following holds for an Administrator.
* It MUST support the parameters 'ace_groupcomm_profile', 'exp', and
'group_policies', which are defined in Section 8 of
[I-D.ietf-ace-key-groupcomm].
* It MUST support all the parameters listed in Table 2, with the
following exceptions.
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- 'conf_filter', which MUST be supported only if the
Administrator supports the partial retrieval of a group
configuration by filters (see Section 6.5).
- 'app_groups_diff' parameter, which MUST be supported only if
the Administrator supports the selective update of a group
configuration (see Section 6.7).
8. ACE Groupcomm Error Identifiers
In addition to what is defined in Section 9 of
[I-D.ietf-ace-key-groupcomm], this document defines new values that
the Group Manager can use as error identifiers. These are used in
error responses with Content-Format application/concise-problem-
details+cbor [RFC9290], as values of the 'error-id' field within the
Custom Problem Detail entry 'ace-groupcomm-error' (see Section 4.1.2
of [I-D.ietf-ace-key-groupcomm]).
+=======+==================================+============+
| Value | Description | Reference |
+=======+==================================+============+
| 10 | Group currently active | [RFC-XXXX] |
+-------+----------------------------------+------------+
| 11 | Unable to determine a group name | [RFC-XXXX] |
+-------+----------------------------------+------------+
| 12 | Unsupported group configuration | [RFC-XXXX] |
+-------+----------------------------------+------------+
Table 3: ACE Groupcomm Error Identifiers
If the Administrator supports the problem-details format [RFC9290]
and the Custom Problem Detail entry 'ace-groupcomm-error' defined in
Section 4.1.2 of [I-D.ietf-ace-key-groupcomm], and is able to
understand the error specified in the 'error-id' field therein, then
the Administrator may use that information to determine what actions
to take next. If the Concise Problem Details data item specified in
the error response includes the 'detail' entry and the Administrator
supports it, such an entry may provide additional context. In
particular, the following guidelines apply.
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* In case of error 10, the Administrator should stop sending the
DELETE request to the Group Manager (see Section 6.8), until the
group becomes inactive. As per this document, this error is
relevant only for the Administrator, if it tries to delete a group
without having set its status to inactive first (see Section 6.8).
In such a case, the Administrator should take the expected course
of actions, and set the group status to inactive first (see
Section 6.6 and Section 6.7), before sending a new request of
group deletion to the Group Manager.
* In case of error 11, the Administrator has the following options.
- The Administrator simply tries again later on. The new POST
request to the group-collection resource specifies the same
group name originally suggested in the previous request that
triggered the error response (see Section 6.3). This option
fundamentally relies on the Group Manager making the group name
available again before the Administrator sends the new POST
request. Hence, this option is not viable if it is
unacceptable for the Administrator to considerably or
indefinitely postpone the creation of the new group.
- The Administrator sends a new POST request to the group-
collection resource right away, specifying a different group
name than the one suggested in the previous request that
triggered the error response.
In order to not inadvertently suggest a new group name that is
already assigned to an existing OSCORE group, the Administrator
can first retrieve the list of existing groups from the Group
Manager, as defined in Section 6.1. In the payload of the
response from the Group Manager, each specified link indicates
the name of an existing OSCORE group as the last segment of its
url-path.
The Administrator should choose the new group name GROUPNAME to
suggest, in such a way that it does not renounce permissions
that were granted per the old group name GROUPNAME*. This is
the case if the following holds.
With reference to the 'scope' claim of the Administrator's
Access Token, let us define PERM* as the union of the
permission sets associated with the scope entries such that
GROUPNAME* matches with the specified group name pattern.
Also, let us define PERM as the union of the permission sets
associated with the scope entries such that GROUPNAME matches
with the specified group name pattern. Then, PERM specifies no
fewer permissions than PERM*.
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- The Administrator requests a new Access Token to the
Authorization Server, in order to update its access rights, and
have a new granted scope whose scope entries specify more and/
or different group name patterns than the old Access Token.
After uploading the new Access Token to the Group Manager, the
Administrator can send a new POST request to the group-
collection resource. When doing so, the Administrator suggests
a new group name to the Group Manager, according to the same
criteria discussed for the previous option.
* In case of error 12, the Administrator has the following options.
- If the Administrator has attempted to create a new group
configuration (see Section 6.3), the Administrator can take
into account what the Group Manager specifies in the 'detail'
entry of the Concise Problem Details data item [RFC9290]
specified in the error response, and send a new request to the
Group Manager for accordingly creating the group configuration.
This requires that the Administrator finds acceptable to create
a group configuration different from the originally intended
one.
- If the Administrator has attempted to overwrite (see
Section 6.6) or selectively update (see Section 6.7) an
existing group configuration, the Administrator can take into
account what the Group Manager specifies in the 'detail' entry
of the Concise Problem Details data item [RFC9290] specified in
the error response, and send a new request to the Group Manager
for accordingly overwriting or selectively updating the group
configuration.
This requires that the Administrator finds acceptable to
overwrite or update the current group configuration differently
than how it was originally intended. If this is not
attainable, the Administrator may decide to not take further
actions and keep the current group configuration as is, or
instead to delete the group configuration altogether (see
Section 6.8).
9. Security Considerations
Security considerations are inherited from the ACE framework for
Authentication and Authorization [RFC9200], and from the specific
transport profile of ACE used between the Administrator and the Group
Manager, such as [RFC9202] and [RFC9203].
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The same security considerations from [I-D.ietf-ace-key-groupcomm]
and [I-D.ietf-ace-key-groupcomm-oscore] also apply, with particular
reference to the process of rekeying OSCORE groups.
Further security considerations are compiled below.
9.1. Change of Group Configuration
With respect to changing group configurations, the following security
considerations hold.
* A change of the current group configuration (see Section 6.6 and
Section 6.7) might result in generating and distributing new group
keying material, consistently with the newly enforced algorithms
and related parameters. In such a case, the Group Manager can
perform a group rekeying as per Section 11 of
[I-D.ietf-ace-key-groupcomm-oscore], or provide the new group
keying material together with the new group configuration as per
Section 6.6 and Section 6.7 of this document.
After gaining knowledge of the new group configuration, current
group members may also leave the OSCORE group and rejoin it, hence
obtaining the new group configuration parameters and the up-to-
date group keying material. When this happens, the Group Manager
SHOULD NOT repeatedly rekey the group upon the re-join of every
current group member, each of which is identifiable by means of
the secure association that it has with the Group Manager.
* Following the enforcement of a new group configuration, a group
member might not deem it conducive to a sufficient security level
(e.g., in terms of security algorithms and related parameters).
In such a case, it is RECOMMENDED that the group member leaves the
group.
* A change of the current group configuration, possibly also
requiring a group rekeying, might result in temporarily preventing
communications among some group members altogether, until they
have aligned themselves to the new group configuration. This is
especially the case for a change of group configuration affecting
the security algorithms and related parameters used in the group.
Furthermore, a change of group configuration might interfere with
ongoing, extended exchanges between group members, especially
Block-Wise transfers [RFC7959][RFC9177] and the transmission of
Observe notifications for ongoing Observations [RFC7641].
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A group configuration (possibly together with the group keying
material) may have been updated while a Block-Wise transfer is
ongoing between two group members. This will result in blocks
being resent, if the block sender and recipient are not yet both
aligned with the new group configuration (and group keying
material), in which case the block recipient would reply with an
error message.
After a change of group configuration, a group member MUST
terminate an ongoing Observation if the new group configuration
would not have allowed to compute exactly the Observe request
associated with the ongoing Observation. This occurs, for
example, when the new group configuration specifies a signature
algorithm different from the one used in the group when the
Observe request was protected.
9.2. Group Manager
In addition to what is discussed in Section 10.1 of
[I-D.ietf-ace-key-groupcomm], a compromised Group Manager would allow
an adversary to also monitor the group configurations specified by an
Administrator, or to enforce group configurations different from the
specified ones, which can result in communications in the OSCORE
groups not attaining the originally intended security level.
Although this is undesirable, it is not worse than the control that
the adversary would gain on the group keying material through the
compromised Group Manager (see Section 10.1 of
[I-D.ietf-ace-key-groupcomm]).
Unlike what is defined in Section 10.2 of
[I-D.ietf-ace-key-groupcomm] with respect to renewing the group
keying material, the Group Manager does not have to change the group
configurations of the OSCORE groups it is responsible for, after
having experienced a reboot.
9.3. Administrators
If multiple Administrators are responsible for the same OSCORE group,
they are expected to be aware of each other and of their shared
responsibility, as well as to be aligned on what is in the best
interest of the OSCORE group and its secure operation. It is out of
the scope of this document to define how different Administrators are
appointed as responsible for an OSCORE group, and how they achieve
and maintain such an alignment with each other.
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A compromised Administrator may collude with unauthorized parties.
Within the extent of the granted access rights, the compromised
Administrator may leak group configurations, change them in such a
way that communications in the OSCORE groups do not attain the
originally intended security level, or delete OSCORE groups
altogether thus impeding their secure operation.
When an Administrator is found compromised, the pertaining Access
Tokens MUST be revoked by the Authorization Server. A possible way
for the Authorization Server to notify the affected Group Managers
about such revoked Access Tokens is defined in
[I-D.ietf-ace-revoked-token-notification].
10. IANA Considerations
This document has the following actions for IANA.
Note to RFC Editor: Please replace all occurrences of "[RFC-XXXX]"
with the RFC number of this specification and delete this paragraph.
10.1. ACE Groupcomm Parameters
IANA is asked to register the following entries in the "ACE Groupcomm
Parameters" registry within the "Authentication and Authorization for
Constrained Environments (ACE)" registry group.
* Name: hkdf
* CBOR Key: -1
* CBOR Type: tstr or int
* Reference: [RFC-XXXX]
* Name: cred_fmt
* CBOR Key: -2
* CBOR Type: int
* Reference: [RFC-XXXX]
* Name: group_mode
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* CBOR Key: -3
* CBOR Type: True or False
* Reference: [RFC-XXXX]
* Name: gp_enc_alg
* CBOR Key: -4
* CBOR Type: Null or tstr or int
* Reference: [RFC-XXXX]
* Name: sign_alg
* CBOR Key: -5
* CBOR Type: Null or tstr or int
* Reference: [RFC-XXXX]
* Name: sign_params
* CBOR Key: -6
* CBOR Type: Null or array
* Reference: [RFC-XXXX]
* Name: pairwise_mode
* CBOR Key: -7
* CBOR Type: True or False
* Reference: [RFC-XXXX]
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* Name: alg
* CBOR Key: -8
* CBOR Type: Null or tstr or int
* Reference: [RFC-XXXX]
* Name: ecdh_alg
* CBOR Key: -9
* CBOR Type: Null or tstr or int
* Reference: [RFC-XXXX]
* Name: ecdh_params
* CBOR Key: -10
* CBOR Type: Null or array
* Reference: [RFC-XXXX]
* Name: det_req
* CBOR Key: -25
* CBOR Type: True or False
* Reference: [RFC-XXXX]
* Name: det_hash_alg
* CBOR Key: -26
* CBOR Type: tstr or int
* Reference: [RFC-XXXX]
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* Name: rt
* CBOR Key: -11
* CBOR Type: tstr
* Reference: [RFC-XXXX]
* Name: active
* CBOR Key: -12
* CBOR Type: True or False
* Reference: [RFC-XXXX]
* Name: group_name
* CBOR Key: -13
* CBOR Type: tstr or #6.<uint>(any)
* Reference: [RFC-XXXX]
* Name: group_description
* CBOR Key: -14
* CBOR Type: Null or tstr
* Reference: [RFC-XXXX]
* Name: max_stale_sets
* CBOR Key: -15
* CBOR Type: uint
* Reference: [RFC-XXXX]
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* Name: gid_reuse
* CBOR Key: -16
* CBOR Type: True or False
* Reference: [RFC-XXXX]
* Name: app_groups
* CBOR Key: -17
* CBOR Type: array
* Reference: [RFC-XXXX]
* Name: joining_uri
* CBOR Key: -18
* CBOR Type: tstr
* Reference: [RFC-XXXX]
* Name: as_uri
* CBOR Key: -19
* CBOR Type: tstr
* Reference: [RFC-XXXX]
* Name: conf_filter
* CBOR Key: -27
* CBOR Type: array
* Reference: [RFC-XXXX]
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* Name: app_groups_diff
* CBOR Key: -28
* CBOR Type: array
* Reference: [RFC-XXXX]
10.2. ACE Groupcomm Errors
IANA is asked to register the following entries in the "ACE Groupcomm
Errors" registry within the "Authentication and Authorization for
Constrained Environments (ACE)" registry group.
* Value: 10
* Description: Group currently active
* Reference: [RFC-XXXX]
* Value: 11
* Description: Unable to determine a group name
* Reference: [RFC-XXXX]
* Value: 12
* Description: Unsupported group configuration
* Reference: [RFC-XXXX]
10.3. Resource Types
IANA is asked to enter the following entries in the "Resource Type
(rt=) Link Target Attribute Values" registry within the "Constrained
Restful Environments (CoRE) Parameters" registry group.
* Value: core.osc.gcoll
* Description: Group-collection resource of an OSCORE Group Manager
* Reference: [RFC-XXXX]
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* Value: core.osc.gconf
* Description: Group-configuration resource of an OSCORE Group
Manager
* Reference: [RFC-XXXX]
10.4. Group OSCORE Admin Permissions
This document establishes the IANA "Group OSCORE Admin Permissions"
registry. The registry has been created to use the "Expert Review"
registration procedure [RFC8126]. Expert review guidelines are
provided in Section 10.5.
This registry includes the possible permissions that Administrators
can have to perform operations on an OSCORE Group Manager, each in
combination with a numeric identifier. These numeric identifiers are
used to express authorization information about performing
administrative operations concerning OSCORE groups under the control
of the Group Manager, as specified in Section 3 of [RFC-XXXX].
The columns of this registry are:
* Name: A value that can be used in documents for easier
comprehension, to identify a possible permission that
Administrators can perform when interacting with an OSCORE Group
Manager.
* Value: The numeric identifier for this permission. Integer values
greater than 65535 are marked as "Private Use", all other values
use the registration policy "Expert Review" (see Section 4.5 of
[RFC8126]).
Note that, in general, a single permission can be associated with
multiple different operations that are possible to be performed
when interacting with the Group Manager.
* Description: This field contains a brief description of the
permission.
* Reference: This contains a pointer to the public specification for
the permission.
This registry will be initially populated by the values in Table 1.
The Reference column for all of these entries will be [RFC-XXXX].
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10.5. Expert Review Instructions
The IANA registry established in this document is 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:
* Clarity and correctness of registrations. Experts are expected to
check the clarity of purpose and use of the requested entries.
Experts should inspect the entry for the considered permission, to
verify the correctness of its description against the permission
as intended in the specification that defined it. Expert should
consider requesting an opinion on the correctness of registered
parameters from the Authentication and Authorization for
Constrained Environments (ACE) Working Group and the Constrained
RESTful Environments (CoRE) Working Group.
Entries that do not meet these objective of clarity and
completeness should not be registered.
* Duplicated registration and 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.
* Experts should take into account the expected usage of permissions
when approving point assignment. Given a 'Value' V as code point,
the length of the encoding of (2^(V+1) - 1) should be weighed
against the usage of the entry, considering the resources and
capabilities of devices it will be used on. Additionally, given a
'Value' V as code point, the length of the encoding of (2^(V+1) -
1) should be weighed against how many code points resulting in
that encoding length are left, and the resources and capabilities
of devices it will be used on.
* Specifications are recommended. When specifications are not
provided, the description provided needs to have sufficient
information to verify the points above.
11. References
11.1. Normative References
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[COSE.Algorithms]
IANA, "COSE Algorithms",
<https://www.iana.org/assignments/cose/
cose.xhtml#algorithms>.
[I-D.ietf-ace-key-groupcomm]
Palombini, F. and M. Tiloca, "Key Provisioning for Group
Communication using ACE", Work in Progress, Internet-
Draft, draft-ietf-ace-key-groupcomm-19, 30 April 2024,
<https://datatracker.ietf.org/doc/html/draft-ietf-ace-key-
groupcomm-19>.
[I-D.ietf-ace-key-groupcomm-oscore]
Tiloca, M., Park, J., and F. Palombini, "Key Management
for OSCORE Groups in ACE", Work in Progress, Internet-
Draft, draft-ietf-ace-key-groupcomm-oscore-16, 6 March
2023, <https://datatracker.ietf.org/doc/html/draft-ietf-
ace-key-groupcomm-oscore-16>.
[I-D.ietf-core-groupcomm-bis]
Dijk, E., Wang, C., and M. Tiloca, "Group Communication
for the Constrained Application Protocol (CoAP)", Work in
Progress, Internet-Draft, draft-ietf-core-groupcomm-bis-
11, 24 April 2024, <https://datatracker.ietf.org/doc/html/
draft-ietf-core-groupcomm-bis-11>.
[I-D.ietf-core-oscore-groupcomm]
Tiloca, M., Selander, G., Palombini, F., Mattsson, J. P.,
and R. Höglund, "Group Object Security for Constrained
RESTful Environments (Group OSCORE)", Work in Progress,
Internet-Draft, draft-ietf-core-oscore-groupcomm-21, 4
March 2024, <https://datatracker.ietf.org/doc/html/draft-
ietf-core-oscore-groupcomm-21>.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/rfc/rfc2119>.
[RFC3986] Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform
Resource Identifier (URI): Generic Syntax", STD 66,
RFC 3986, DOI 10.17487/RFC3986, January 2005,
<https://www.rfc-editor.org/rfc/rfc3986>.
[RFC6690] Shelby, Z., "Constrained RESTful Environments (CoRE) Link
Format", RFC 6690, DOI 10.17487/RFC6690, August 2012,
<https://www.rfc-editor.org/rfc/rfc6690>.
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[RFC6749] Hardt, D., Ed., "The OAuth 2.0 Authorization Framework",
RFC 6749, DOI 10.17487/RFC6749, October 2012,
<https://www.rfc-editor.org/rfc/rfc6749>.
[RFC7252] Shelby, Z., Hartke, K., and C. Bormann, "The Constrained
Application Protocol (CoAP)", RFC 7252,
DOI 10.17487/RFC7252, June 2014,
<https://www.rfc-editor.org/rfc/rfc7252>.
[RFC7641] Hartke, K., "Observing Resources in the Constrained
Application Protocol (CoAP)", RFC 7641,
DOI 10.17487/RFC7641, September 2015,
<https://www.rfc-editor.org/rfc/rfc7641>.
[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/rfc/rfc8126>.
[RFC8132] van der Stok, P., Bormann, C., and A. Sehgal, "PATCH and
FETCH Methods for the Constrained Application Protocol
(CoAP)", RFC 8132, DOI 10.17487/RFC8132, April 2017,
<https://www.rfc-editor.org/rfc/rfc8132>.
[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
May 2017, <https://www.rfc-editor.org/rfc/rfc8174>.
[RFC8610] Birkholz, H., Vigano, C., and C. Bormann, "Concise Data
Definition Language (CDDL): A Notational Convention to
Express Concise Binary Object Representation (CBOR) and
JSON Data Structures", RFC 8610, DOI 10.17487/RFC8610,
June 2019, <https://www.rfc-editor.org/rfc/rfc8610>.
[RFC8613] Selander, G., Mattsson, J., Palombini, F., and L. Seitz,
"Object Security for Constrained RESTful Environments
(OSCORE)", RFC 8613, DOI 10.17487/RFC8613, July 2019,
<https://www.rfc-editor.org/rfc/rfc8613>.
[RFC8949] Bormann, C. and P. Hoffman, "Concise Binary Object
Representation (CBOR)", STD 94, RFC 8949,
DOI 10.17487/RFC8949, December 2020,
<https://www.rfc-editor.org/rfc/rfc8949>.
[RFC9052] Schaad, J., "CBOR Object Signing and Encryption (COSE):
Structures and Process", STD 96, RFC 9052,
DOI 10.17487/RFC9052, August 2022,
<https://www.rfc-editor.org/rfc/rfc9052>.
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[RFC9053] Schaad, J., "CBOR Object Signing and Encryption (COSE):
Initial Algorithms", RFC 9053, DOI 10.17487/RFC9053,
August 2022, <https://www.rfc-editor.org/rfc/rfc9053>.
[RFC9200] Seitz, L., Selander, G., Wahlstroem, E., Erdtman, S., and
H. Tschofenig, "Authentication and Authorization for
Constrained Environments Using the OAuth 2.0 Framework
(ACE-OAuth)", RFC 9200, DOI 10.17487/RFC9200, August 2022,
<https://www.rfc-editor.org/rfc/rfc9200>.
[RFC9202] Gerdes, S., Bergmann, O., Bormann, C., Selander, G., and
L. Seitz, "Datagram Transport Layer Security (DTLS)
Profile for Authentication and Authorization for
Constrained Environments (ACE)", RFC 9202,
DOI 10.17487/RFC9202, August 2022,
<https://www.rfc-editor.org/rfc/rfc9202>.
[RFC9203] Palombini, F., Seitz, L., Selander, G., and M. Gunnarsson,
"The Object Security for Constrained RESTful Environments
(OSCORE) Profile of the Authentication and Authorization
for Constrained Environments (ACE) Framework", RFC 9203,
DOI 10.17487/RFC9203, August 2022,
<https://www.rfc-editor.org/rfc/rfc9203>.
[RFC9237] Bormann, C., "An Authorization Information Format (AIF)
for Authentication and Authorization for Constrained
Environments (ACE)", RFC 9237, DOI 10.17487/RFC9237,
August 2022, <https://www.rfc-editor.org/rfc/rfc9237>.
[RFC9277] Richardson, M. and C. Bormann, "On Stable Storage for
Items in Concise Binary Object Representation (CBOR)",
RFC 9277, DOI 10.17487/RFC9277, August 2022,
<https://www.rfc-editor.org/rfc/rfc9277>.
[RFC9290] Fossati, T. and C. Bormann, "Concise Problem Details for
Constrained Application Protocol (CoAP) APIs", RFC 9290,
DOI 10.17487/RFC9290, October 2022,
<https://www.rfc-editor.org/rfc/rfc9290>.
[RFC9485] Bormann, C. and T. Bray, "I-Regexp: An Interoperable
Regular Expression Format", RFC 9485,
DOI 10.17487/RFC9485, October 2023,
<https://www.rfc-editor.org/rfc/rfc9485>.
11.2. Informative References
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[I-D.amsuess-core-cachable-oscore]
Amsüss, C. and M. Tiloca, "Cacheable OSCORE", Work in
Progress, Internet-Draft, draft-amsuess-core-cachable-
oscore-08, 10 January 2024,
<https://datatracker.ietf.org/doc/html/draft-amsuess-core-
cachable-oscore-08>.
[I-D.ietf-ace-revoked-token-notification]
Tiloca, M., Palombini, F., Echeverria, S., and G. Lewis,
"Notification of Revoked Access Tokens in the
Authentication and Authorization for Constrained
Environments (ACE) Framework", Work in Progress, Internet-
Draft, draft-ietf-ace-revoked-token-notification-08, 24
June 2024, <https://datatracker.ietf.org/doc/html/draft-
ietf-ace-revoked-token-notification-08>.
[I-D.ietf-cose-cbor-encoded-cert]
Mattsson, J. P., Selander, G., Raza, S., Höglund, J., and
M. Furuhed, "CBOR Encoded X.509 Certificates (C509
Certificates)", Work in Progress, Internet-Draft, draft-
ietf-cose-cbor-encoded-cert-09, 4 March 2024,
<https://datatracker.ietf.org/doc/html/draft-ietf-cose-
cbor-encoded-cert-09>.
[I-D.tiloca-core-oscore-discovery]
Tiloca, M., Amsüss, C., and P. Van der Stok, "Discovery of
OSCORE Groups with the CoRE Resource Directory", Work in
Progress, Internet-Draft, draft-tiloca-core-oscore-
discovery-15, 4 March 2024,
<https://datatracker.ietf.org/doc/html/draft-tiloca-core-
oscore-discovery-15>.
[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/rfc/rfc5280>.
[RFC7959] Bormann, C. and Z. Shelby, Ed., "Block-Wise Transfers in
the Constrained Application Protocol (CoAP)", RFC 7959,
DOI 10.17487/RFC7959, August 2016,
<https://www.rfc-editor.org/rfc/rfc7959>.
[RFC8392] Jones, M., Wahlstroem, E., Erdtman, S., and H. Tschofenig,
"CBOR Web Token (CWT)", RFC 8392, DOI 10.17487/RFC8392,
May 2018, <https://www.rfc-editor.org/rfc/rfc8392>.
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[RFC9147] Rescorla, E., Tschofenig, H., and N. Modadugu, "The
Datagram Transport Layer Security (DTLS) Protocol Version
1.3", RFC 9147, DOI 10.17487/RFC9147, April 2022,
<https://www.rfc-editor.org/rfc/rfc9147>.
[RFC9176] Amsüss, C., Ed., Shelby, Z., Koster, M., Bormann, C., and
P. van der Stok, "Constrained RESTful Environments (CoRE)
Resource Directory", RFC 9176, DOI 10.17487/RFC9176, April
2022, <https://www.rfc-editor.org/rfc/rfc9176>.
[RFC9177] Boucadair, M. and J. Shallow, "Constrained Application
Protocol (CoAP) Block-Wise Transfer Options Supporting
Robust Transmission", RFC 9177, DOI 10.17487/RFC9177,
March 2022, <https://www.rfc-editor.org/rfc/rfc9177>.
Appendix A. Processing of Group Name Patterns at the AS
When processing an Authorization Request from an Administrator (see
Section 4), the AS builds the authorization information expressing
granted permissions as scope entries, according to the AIF data model
AIF-OSCORE-GROUPCOMM and to its extension specified in Section 3.
These scope entries are in turn specified as value of the 'scope'
claim to include in the Access Token.
This appendix provides an example of how the AS can evaluate the
requested permissions against the access policies pertaining to the
Administrator for the Group Manager in question.
The following specifically refers only to "admin scope entries",
i.e., scope entries that express authorization information for
Administrators of OSCORE groups.
Also, it is assumed that the AS stores the access policies as a set
of "admin policy entries", which have the same format of the scope
entries according to the AIF data model AIF-OSCORE-GROUPCOMM (see
Section 3). The following specifically considers only "admin policy
entries", i.e., policy entries for Administrators of OSCORE groups
hereafter shortly referred to as "policy entries".
The AS performs the following steps.
1. The AS initializes three empty sets of scope entries, namely
S_OUT.
2. For each scope entry E_S in the 'scope' parameter of the
Authorization Request, the AS performs the following actions.
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a. The AS initializes an empty set of policy entries, namely
S_AUX.
b. The AS considers all the policy entries related to the
Administrator and the Group Manager in question. For each policy
entry E_P among those policy entries, the AS determines whether
every group name matching with the Toid of E_S would also match
with the Toid of E_P. If that is the case, then the AS adds E_P
to the set S_AUX. The particular way that the AS uses to make a
determination is implementation specific.
c. If the set S_AUX is empty, the AS proceeds with the next
scope entry, if any. Otherwise, the AS computes TPERM_AUX as the
union of the permission sets associated with the policy entries
in the set S_AUX. That is, TPERM_AUX is the inclusive OR of the
binary representation of the Tperm values in the policy entries
within the set S_AUX.
d. The AS adds to the set S_OUT one scope entry, such that its
Toid is the same as in the scope entry E_S, while its Tperm is
the AND of TPERM_AUX with the Tperm in the scope entry E_S.
3. For each scope entry E_S in the 'scope' parameter of the
Authorization Request, the AS performs the following actions.
a. The AS initializes an empty set of policy entries, namely
S_AUX.
b. The AS considers all the policy entries related to the
Administrator and the Group Manager in question. For each policy
entry E_P among those policy entries, and such that the Toid of
E_P is different from the Toid of E_S, the AS determines whether
every group name matching with the Toid of E_P would also match
with the Toid of E_S. If that is the case, then the AS adds E_S
to the set S_AUX. The particular way that the AS uses to make a
determination is implementation specific.
c. If the set S_AUX is empty, the AS proceeds with the next
scope entry, if any. Otherwise, the AS adds to the set S_OUT one
scope entry, such that its Toid is the same as in the policy
entry E_P, while its Tperm is the AND of the Tperm in the policy
entry E_P with the Tperm in the scope entry E_S.
4. For each scope entry E_S in the 'scope' parameter of the
Authorization Request, the AS performs the following actions.
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a. The AS considers all the policy entries related to the
Administrator and the Group Manager in question, such that they
were never added to the set S_AUX during the previous steps 2 and
3. For each policy entry E_P among those policy entries, the AS
attempts to determine a group name pattern TOID_AUX such that
every group name matching with TOID_AUX would also match with the
Toid of E_P as well as with the Toid of E_S. The particular way
that the AS uses to make a determination is implementation
specific.
b. If the AS could not determine a group name pattern TOID_AUX,
then the AS proceeds with the next policy entry E_P, if any.
Otherwise, the AS adds to the set S_OUT one scope entry, such
that its Toid is TOID_AUX, while its Tperm is the AND of the
Tperm in the policy entry E_P with the Tperm in the scope entry
E_S.
5. If the set S_OUT is empty, the Authorization Request has not been
successfully verified, and the AS returns an error response as
per Section 5.8.3 of [RFC9200]. Otherwise, the AS uses the scope
entries in the set S_OUT as the scope entries for the 'scope'
claim to include in the Access Token, as per the format defined
in Section 3.
Appendix B. CDDL Model
This section is to be removed before publishing as an RFC.
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hkdf = -1
cred_fmt = -2
group_mode = -3
gp_enc_alg = -4
sign_alg = -5
sign_params = -6
pairwise_mode = -7
alg = -8
ecdh_alg = -9
ecdh_params = -10
det_req = -25
det_hash_alg = -26
rt = -11
active = -12
group_name = -13
group_description = -14
max_stale_sets = -15
gid_reuse = -16
app_groups = -17
joining_uri = -18
as_uri = -19
conf_filter = -27
app_groups_diff = -28
ace_groupcomm_profile = 10
exp = 11
Figure 3: CDDL model
Appendix C. Document Updates
This section is to be removed before publishing as an RFC.
C.1. Version -11 to -12
* CBOR diagnostic notation uses placeholders from a CDDL model.
* Clarified relation between group name and URI path segment.
* /manage is a url-path chosen as an example, but not a default one.
* Recapped concepts of scope and secure communication association.
* Main/optional Administrator is presented more as an example.
* The use of CBOR Tag 35 is not mentioned anymore.
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* Added considerations on race conditions with multiple
Administrators.
* Clarified requirement for some operations to be atomic.
* Early centralization of what it means to have permissions.
* Improved presentation of default values for the parameters.
* POST (instead of PUT) for overwriting a group-configuration
resource.
* Example of inconsistent configuration following a PATCH request.
* Clarified invalid semantics of an iPATCH request.
* Repositioned text from security to operational considerations.
* Revised appendix with an example of name pattern processing at the
AS.
* Minor clarifications and editorial improvements.
C.2. Version -10 to -11
* Early mentioned that issued Access Tokens can have other purposes.
* Added example of array of scope entries.
* Removed moot paragraph about the benefits of group name patterns.
* Use of CBOR tag 21065 to indicate a regular expression.
* Renamed 'group_title' as 'group_description'.
* Added a second example of FETCH to the group-collection resource.
* Avoiding accidental deactivation of a group when updating it.
* Avoid alternative ways to create a group configuration resource.
* RFC 9290 is used instead of the custom format for error responses.
* Added integer abbreviations for the new entries in the "ACE
Groupcomm Parameters" registry.
* Editorial fixes and improvements.
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C.3. Version -09 to -10
* Consistent use of 4.03 (Forbidden) error responses.
* Removed moot, remnant statements from when CoRAL was used.
* Clarified how the Group Manager may attempt to determine an
alternative group name upon creating a new group.
* Made explicit what parameters cannot change when overwriting a
group configuration.
* Improved guidelines to the Group Manager on selecting an
alternative group name.
* Improved guidelines to Administrators receiving an error after
trying to create a new group.
* Changed description of error 11 from "No available group names" to
"Unable to determine a group name".
* Editorial fixes and improvements.
C.4. Version -08 to -09
* Removed use of CoRAL.
* Use of the pairwise mode changed to true by default.
* Clarified effects on group members after a group configuration
change.
* Renamed "Signature Encryption Algorithm" to "Group Encryption
Algorithm".
* Renamed "sign_enc_alg" to "gp_enc_alg".
* Fixes and editorial improvements.
C.5. Version -07 to -08
* Consistency of parameter names.
* More details on consistency of message payload.
* New section on multiple, concurrent Administrators.
* Specified atomicity of write operations.
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* Clarified effects of configuration overwriting on group members.
* New ACE Groupcomm Error on unsupported configuration.
* Possible reason to deviate from default parameter values.
* Added security considerations.
* CoRAL examples use CBOR diagnostic notation and Packed CBOR.
* Various clarifications and editorial improvements.
C.6. Version -06 to -07
* Alignment with renaming in draft-ietf-ace-key-groupcomm.
* Updated signaling of semantics for binary encoded scopes.
* Split between parameter registration and their CBOR abbreviations.
* Classified parameters as must/should/may be supported.
* New error code "No available group names" and related guidelines.
* Fixes in the examples.
* Editorial improvements.
C.7. Version -05 to -06
* Use and extend the same AIF data model AIF-OSCORE-GROUPCOMM
defined in [I-D.ietf-ace-key-groupcomm-oscore].
* Revised Client-AS interaction, based on the used AIF data model.
* Categorized operations at the Group Manager as required and
optional to support.
* Added status parameter 'gid_reuse', on reassigning OSCORE Group
IDs upon group rekeying.
* Clarifications on the group name ultimately chosen by the Group
Manager.
* Moved the detailed processing of group name patterns at the AS to
an Appendix, as an example.
* Editorial improvements.
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C.8. Version -04 to -05
* Defined format of scope based on a new AIF data model.
* Specified authorization checks at the Group Manager.
* Revised resource handlers based on the new scope format.
* Renamed 'pub_key_enc' to 'cred_fmt'.
* Mandatory to include 'group_name' in the group creation request.
* Suggesting a used 'group_name' results in a new name, not in an
error.
* Distinction between authentication credentials and public keys.
* More details on informing group members about changes in the group
configuration.
* Revised order of sections; editorial improvements.
C.9. Version -03 to -04
* Clarifications on what to do in case of enhanced error responses.
* Clarifications on handling default values for group parameters.
* New configuration parameters to support OSCORE deterministic
requests.
* IANA considerations - Use RFC8126 terminology.
* Author's change of address.
* Editorial improvements.
C.10. Version -02 to -03
* Aligned new and old parameters to core-groupcomm-oscore and ace-
key-groupcomm-oscore.
* Removed 'cs_key_params' and 'ecdh_key_params' to avoid redundant
COSE capabilities of key types, consistently with draft-ietf-ace-
key-groupcomm-oscore.
* Revised examples and side effects due to parameter changes.
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* New error type "Group currently active".
C.11. Version -01 to -02
* Admit multiple Administrators and limited access to admin
resources.
* Early design considerations for defining the format of scope.
* Additional error handling, using also error types.
* Selective update of group-configuration resources with PATCH/
iPATCH.
* Editorial improvements.
C.12. Version -00 to -01
* Names of application groups as status parameter.
* Parameters related to the pairwise mode of Group OSCORE.
* Defined FETCH for group-configuration resources.
* Policies on registration of links to the Resource Directory.
* Added resource type for group-configuration resources.
* Fixes, clarifications and editorial improvements.
Acknowledgments
Klaus Hartke provided substantial contribution in defining the
resource model based on group collection and group configurations.
The authors sincerely thank Christian Amsüss, Carsten Bormann, Jim
Schaad, Göran Selander, and Cigdem Sengul for their comments and
feedback.
The work on this document has been partly supported by the Sweden's
Innovation Agency VINNOVA and the Celtic-Next projects CRITISEC and
CYPRESS; and by the H2020 project SIFIS-Home (Grant agreement
952652).
Authors' Addresses
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Marco Tiloca
RISE AB
Isafjordsgatan 22
SE-16440 Stockholm Kista
Sweden
Email: marco.tiloca@ri.se
Rikard Höglund
RISE AB
Isafjordsgatan 22
SE-16440 Stockholm Kista
Sweden
Email: rikard.hoglund@ri.se
Peter van der Stok
Email: stokcons@kpnmail.nl
Francesca Palombini
Ericsson AB
Torshamnsgatan 23
SE-16440 Stockholm Kista
Sweden
Email: francesca.palombini@ericsson.com
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