RISE AB

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RISE AB

Isafjordsgatan 22 Kista 16440 Stockholm Sweden rikard.hoglund@ri.se

Consultant

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Ericsson AB

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Internet ACE Working Group Internet-Draft Group communication for CoAP can be secured using Group Object Security for Constrained RESTful Environments (Group OSCORE). A Group Manager is responsible to handle the joining of new group members, as well as to manage and distribute 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 Discussion of this document takes place on the ACE Working Group mailing list (ace@ietf.org), which is archived at . Source for this draft and an issue tracker can be found at .

Introduction The Constrained Application Protocol (CoAP) can be used in group communication environments where messages are also exchanged 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) , and especially Group OSCORE in group communication scenarios. When group communication for CoAP is protected with Group OSCORE, nodes are required to explicitly join the correct OSCORE group. 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 specifies how nodes can join an OSCORE group through the respective Group Manager. Such a method builds on the ACE framework for Authentication and Authorization , so 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 on 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 leads 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 configure and update their configuration. Interaction examples are provided, in Link Format and CBOR , as well as in CoRAL . While all the CoRAL examples show the CoRAL textual serialization format, its binary serialization format is used on the wire. 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 . These include also possible forthcoming transport profiles that comply with the requirements in Appendix C of .

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 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:

• CBOR and COSE .
• The CoAP protocol , also in group communication scenarios . These include the concepts of:
  • "application group", as a set of CoAP nodes that share a common set of resources; and of
  • "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 and Group OSCORE security protocols. These include the concept of 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 security group for one or many application groups.
• The ACE framework for authentication and authorization . The terminology for entities in the considered architecture is defined in OAuth 2.0 . In particular, this includes Client (C), Resource Server (RS), and Authorization Server (AS).
• The management of keying material for groups in ACE and specifically for OSCORE groups . These include the concept of group-membership resource hosted by the Group Manager, that new members access to join the OSCORE group, while current members can access to retrieve updated keying material.

Note that, unless otherwise indicated, the term "endpoint" is used here following its OAuth definition, 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 to create, configure and delete OSCORE groups at a Group Manager.
• Group name: stable and invariant name of an OSCORE group. The group name MUST be unique under the same Group Manager, and MUST include only characters that are valid for a URI path segment.
• Group-collection resource: a single-instance resource hosted by the Group Manager. An Administrator accesses a group-collection resource to create a new OSCORE group, or to retrieve the list of existing OSCORE groups, under that Group Manager. As an example, this document uses /manage as the url-path of the group-collection resource; implementations are not required to use this name, and can define their own instead.
• Group-configuration resource: a resource hosted by the Group Manager, associated to 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 update 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 name, and can define their own instead.
• Admin endpoint: an endpoint at the Group Manager associated to the group-collection resource or to a group-configuration resource hosted by that Group Manager.

Group Administration With reference to the ACE framework and the terminology defined in OAuth 2.0 :

• The Group Manager acts as Resource Server (RS). It provides one single group-collection resource, and one group-configuration resource per existing OSCORE group. Each of those is exported by a distinct admin endpoint.
• The Administrator acts as Client (C), and requests to access the group-collection resource and group-configuration resources, by accessing the respective admin endpoint 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 to the same AS. The authorized access for an Administrator can be limited to performing only a subset of operations. The AS can authorize multiple Administrators to access the collection resource and the (same) group-configuration resources at the Group Manager. [ NOTE: This will be enabled by defining the format to use for the 'scope' claim in the Access Token, as encoding permitted actions on groups whose name matches with a name pattern. ] The AS MAY release Access Tokens to the Administrator for other purposes than accessing admin endpoints of registered Group Managers.

Getting Access to the Group Manager All communications between the involved entities rely on the CoAP protocol and MUST be secured. 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 . 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 or OSCORE . Further details on how the AS secures communications (with the Administrator and the Group Manager) depend on the specifically used transport profile of ACE, and are out of the scope of this document. In order to get access to the Group Manager for managing OSCORE groups, an Administrator performs the following steps. The format and encoding of scope defined in of this document MUST be used, for both the 'scope' claim in the Access Token, as well as for the 'scope' parameter in the Authorization Request and Authorization Response exchanged with the AS (see Sections and of ).

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. The Administrator will start or continue using secure communications with the Group Manager, according to the response from the AS.
2. 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 and . After that, the Administrator must have secure communication established with the Group Manager, before performing any admin operation on that Group Manager. Possible ways to provide secure communication are DTLS and OSCORE . The Administrator and the Group Manager maintain the secure association, to support possible future communications.
3. Consistently with what allowed by the authorization information in the Access Token, the Administrator performs admin operations at the Group Manager, as described in the following sections. These include the retrieval of the existing OSCORE groups, the creation of new OSCORE groups, the update and retrieval of OSCORE group configurations, and the removal of OSCORE groups. Messages exchanged among the Administrator and the Group Manager are specified in .

Format of Scope This section defines the exact format and encoding of scope to use, in order to express authorization information for the Administrator (see ). TODO [ DESIGN CONSIDERATIONS

• Define a new AIF specific data model, as loosely aligned with the data model AIF-OSCORE-GROUPCOMM defined in .
  • The overall scope is an array of scope entries, each as a pair (Toid, Tperm).
  • Toid is a text string, i.e., a wildcard pattern against which group names can be matched.
  • Tperm is a set of specific permissions encoded as a bitmap, applied to groups whose name matches with the wildcard pattern.
• A valid Access Token should always allow to at least retrieve the list of existing group configurations.
• An Administrator authorized to create a group, should later be able to perform any possible operation on it.
• An Administrator can be authorized to perform selected operations on a group earlier created by a different Administrator, still barring the group name matching with the wildcard pattern.

]

Managing OSCORE Groups shows the resources of a Group Manager available to an Administrator.

Resources of a Group Manager

The Group Manager exports a single group-collection resource, with resource type "core.osc.gcoll" defined in of this document. The interface for the group-collection resource defined in allows the Administrator to:

• Retrieve the complete list of existing OSCORE groups.
• Retrieve a partial list of existing OSCORE groups, by applying 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" defined in 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 allows the Administrator 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.

Collection Representation A list of group configurations is represented as a document containing the corresponding group-configuration resources in the list. Each group-configuration is represented as a link, where the link target is the URI of the group-configuration resource. The list can be represented as a Link Format document or a CoRAL document . In the former case, the link to each group-configuration resource specifies the link target attribute 'rt' (Resource Type), with value "core.osc.gconf" defined in of this document. In the latter case, the CoRAL document specifies the group-configuration resources in the list as top-level elements. In particular, the link to each group-configuration resource has http://coreapps.org/core.osc.gcoll#item as relation type.

Discovery The Administrator can discover the group-collection resource from a Resource Directory, for instance and , or from .well-known/core, by using the resource type "core.osc.gcoll" defined in of this document. The Administrator can discover group-configuration resources for the group-collection resource as specified in and .

Group Configurations A group configuration consists of a set of parameters.

Group Configuration Representation The group configuration representation is a CBOR map which MUST include configuration properties and status properties.

Configuration Properties The CBOR map MUST include the following configuration parameters, which are defined in of this document.

• 'hkdf', which specifies the HKDF Algorithm used in the OSCORE group, encoded as a CBOR text string or a CBOR integer. Possible values are the same ones admitted for the 'hkdf' parameter of the "OSCORE Security Context Parameters" registry, defined in .
• 'pub_key_enc', which specifies the encoding of public keys used in the OSCORE group, encoded as a CBOR integer. Possible values are the same ones admitted for the 'pub_key_enc' parameter of the "OSCORE Security Context Parameters" registry, defined in .
• 'group_mode', encoded as a CBOR simple value. Its value is True if the OSCORE group uses the group mode of Group OSCORE , or False otherwise.
• 'sign_enc_alg', which is formatted as follows. If the configuration parameter 'group_mode' has value False, this parameter has as value the CBOR simple value Null. Otherwise, this parameter specifies the Signature Encryption Algorithm used in the OSCORE group to encrypt messages protected with the group mode, encoded as a CBOR text string or a CBOR integer. Possible values are the same ones admitted for the 'sign_enc_alg' parameter of the "OSCORE Security Context Parameters" registry, defined in .
• 'sign_alg', which is formatted as follows. If the configuration parameter 'group_mode' has value False, this parameter has as value the CBOR simple value Null. Otherwise, this parameter specifies the Signature Algorithm used in the OSCORE group, encoded as a CBOR text string or a CBOR integer. Possible values are the same ones admitted for the 'sign_alg' parameter of the "OSCORE Security Context Parameters" registry, defined in .
• 'sign_params', which is formatted as follows. If the configuration parameter 'group_mode' has value False, this parameter has as value the CBOR simple value Null. Otherwise, this parameter specifies the additional parameters for the Signature Algorithm used in the OSCORE group, encoded as a CBOR array. Possible formats and values are the same ones admitted for the 'sign_params' parameter of the "OSCORE Security Context Parameters" registry, defined in .
• 'pairwise_mode', encoded as a CBOR simple value. Its value is True if the OSCORE group uses the pairwise mode of Group OSCORE , or False otherwise.
• 'alg', which is formatted as follows. If the configuration parameter 'pairwise_mode' has value False, this parameter has as value the CBOR simple value Null. Otherwise, this parameter specifies the AEAD Algorithm used in the OSCORE group to encrypt messages protected with the pairwise mode, encoded as a CBOR text string or a CBOR integer. Possible values are the same ones admitted for the 'alg' parameter of the "OSCORE Security Context Parameters" registry, defined in .
• 'ecdh_alg', which is formatted as follows. If the configuration parameter 'pairwise_mode' has value False, this parameter has as value the CBOR simple value Null. Otherwise, this parameter specifies the Pairwise Key Agreement Algorithm used in the OSCORE group, encoded as a CBOR text string or a CBOR integer. Possible values are the same ones admitted for the 'ecdh_alg' parameter of the "OSCORE Security Context Parameters" registry, defined in .
• 'ecdh_params', which is formatted as follows. If the configuration parameter 'pairwise_mode' has value False, this parameter has as value the CBOR simple value Null. Otherwise, this parameter specifies the parameters for the Pairwise Key Agreement Algorithm used in the OSCORE group, encoded as a CBOR array. Possible formats and values are the same ones admitted for the 'ecdh_params' parameter of the "OSCORE Security Context Parameters" registry, defined in .

Status Properties The CBOR map MUST include the following status parameters:

• 'rt', with value the resource type "core.osc.gconf" associated to group-configuration resources, encoded as a CBOR text string.
• 'active', encoding the CBOR simple value True if the OSCORE group is currently active, or the CBOR simple value False otherwise. This parameter is defined in of this document.
• 'group_name', with value the group name of the OSCORE group encoded as a CBOR text string. This parameter is defined in of this document.
• 'group_title', with value either a human-readable description of the OSCORE group encoded as a CBOR text string, or the CBOR simple value Null if no description is specified. This parameter is defined in of this document.
• 'ace-groupcomm-profile', defined in Section 4.1.2.1 of , with value "coap_group_oscore_app" defined in encoded as a CBOR integer.
• 'exp', defined in .
• '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 ).
• 'joining_uri', with value the URI of the group-membership resource for joining the newly created OSCORE group as per , encoded as a CBOR text string. This parameter is defined in of this document.

The CBOR map MAY include the following status parameters:

• 'group_policies', defined in , and consistent with the format and content defined in .
• 'max_stale_sets', defined in of this document and encoded as a CBOR unsigned integer, with value strictly greater than 1. With reference to , this parameter specifies N, i.e., the maximum number of sets of stale OSCORE Sender IDs that the Group Manager stores in the collection associated to the group.
• 'as_uri', defined in of this document, specifies the URI of the Authorization Server associated to 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 and of ).

Default Values This section defines the default values that the Group Manager assumes for configuration and status parameters.

Configuration Parameters For each configuration parameter, the Group Manager MUST use a pre-configured default value, if none is specified by the Administrator. In particular:

• For 'group_mode', the Group Manager SHOULD use the CBOR simple value True.
• For 'pairwise_mode', the Group Manager SHOULD use the CBOR simple value False.
• If 'group_mode' has value True, the Group Manager SHOULD use the same default values defined in for the parameters 'sign_enc_alg', 'sign_alg' and 'sign_params'.
• If 'pairwise_mode' has value True, the Group Manager SHOULD use the same default values defined in for the parameters 'alg', 'ecdh_alg' and 'ecdh_params'.
• For any other configuration parameter, the Group Manager SHOULD use the same default values defined in .

Status Parameters For the following status parameters, the Group Manager MUST use a pre-configured default value, if none is specified by the Administrator. In particular:

• For 'active', the Group Manager SHOULD use the CBOR simple value False.
• For 'group_title', the Group Manager SHOULD use the CBOR simple value Null.
• For 'app_groups', the Group Manager SHOULD use the empty CBOR array.
• For 'group_policies', the Group Manager SHOULD use the default values defined in .

Interactions with the Group Manager This section describes the operations available on the group-collection resource and the group-configuration resources. When custom CBOR is used, the Content-Format in messages containing a payload is set to application/ace-groupcomm+cbor, defined in . Furthermore, the entry labels defined in of this document MUST be used, when specifying the corresponding configuration and status parameters.

Retrieve the Full List of Groups Configurations The Administrator can send a GET request to the group-collection resource, in order to retrieve the complete list of the existing OSCORE groups at the Group Manager. This is returned as a list of links to the corresponding group-configuration resources. Example in Link Format: 0.01 GET Uri-Path: manage <= 2.05 Content Content-Format: 40 (application/link-format) ;rt="core.osc.gconf", ;rt="core.osc.gconf", ;rt="core.osc.gconf" ]]> Example in CoRAL: 0.01 GET Uri-Path: manage <= 2.05 Content Content-Format: TBD1 (application/coral+cbor) #using #base item item item ]]>

Retrieve a List of Group Configurations by Filters The Administrator can send a FETCH request to the group-collection resource, in order to retrieve the 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. When custom CBOR is used, the set of filter criteria is specified in the request payload as a CBOR map, whose possible entries are specified in and use the same abbreviations defined in . Entry values are the ones admitted for the corresponding labels in the POST request for creating a group configuration (see ). A valid request MUST NOT include the same entry multiple times. When CoRAL is used, the filter criteria are specified in the request payload with top-level elements, each of which corresponds to an entry specified in , with the exception of the 'app_groups' status parameter. If names of application groups are used as filter criteria, each element of the 'app_groups' array from the status properties is included as a separate element with name 'app_group'. With the exception of the 'app_group' element, a valid request MUST NOT include the same element multiple times. Element values are the ones admitted for the corresponding labels in the POST request for creating a group configuration (see ). Example in custom CBOR and Link Format: 0.05 FETCH Uri-Path: manage Content-Format: TBD2 (application/ace-groupcomm+cbor) { "group_mode" : True, "sign_enc_alg" : 10, "hkdf" : 5 } <= 2.05 Content Content-Format: 40 (application/link-format) ;rt="core.osc.gconf", ;rt="core.osc.gconf", ;rt="core.osc.gconf" ]]> Example in CoRAL: 0.05 FETCH Uri-Path: manage Content-Format: TBD1 (application/coral+cbor) group_mode True sign_enc_alg 10 hkdf 5 <= 2.05 Content Content-Format: TBD1 (application/coral+cbor) #using #base item item item ]]>

Create a New Group Configuration 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 MAY specify the intended group name GROUPNAME and group title, and MAY specify pieces of information concerning the group configuration. When custom CBOR is used, the request payload is a CBOR map, whose possible entries are specified in and use the same abbreviations defined in . When CoRAL is used, each element of the request payload corresponds to an entry specified in , with the exception of the 'app_groups' status parameter (see below). In particular:

• The payload MAY include any of the configuration parameter defined in .
• The payload MAY include any of the status parameter 'group_name', 'group_title', 'max_stale_sets', 'exp', 'app_groups, 'group_policies', 'as_uri' and 'active' defined in .
  • When CoRAL is used, each element of the 'app_groups' array from the status properties is included as a separate element with name 'app_group'.
• The payload MUST NOT include any of the status parameter 'rt', 'ace-groupcomm-profile' and 'joining_uri' defined in .

If any of the following occurs, the Group Manager MUST respond with a 4.00 (Bad Request) response.

• Any of the received parameters is specified multiple times, with the exception of the 'app_group' element when using CoRAL.
• Any of the received parameters is not recognized, or not valid, or not consistent with respect to other related parameters.
• The 'group_name' parameter specifies the group name of an already existing OSCORE group.
• The Group Manager does not trust 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 request above, the Group Manager performs the following actions. First, 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. Note that the final decision about the name assigned to the OSCORE group is of the Group Manager, which may have more constraints than the Administrator can be aware of, possibly beyond the availability of suggested names. 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. For each configuration parameter not specified in the request, the Group Manager MUST use default values as specified in . 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 . Note that such group membership-resource comprises a number of sub-resources intended to current group members, as defined in and . From then on, the Group Manager will rely on the current group configuration to build the Joining Response message defined in , 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. The Location-Path option 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 properties of the newly created OSCORE group (see ), as detailed below. When custom CBOR is used, the response payload is a CBOR map, where entries use the same abbreviations defined in . When CoRAL is used, the response payload includes one element for each specified parameter.

• 'group_name', with value 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 'group_name' status property for the OSCORE group. This parameter MUST be included.
• 'joining_uri', with value the URI of the group-membership resource for joining the newly created OSCORE group. This parameter MUST be included.
• 'as_uri', with value the URI of the Authorization Server associated to the Group Manager for the newly created OSCORE group. This parameter MUST be included if specified in the status properties of the group. This 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 'as_uri' status property for the OSCORE group.

The Group Manager can register the link to the group-membership resource with URI specified in 'joining_uri' to a Resource Directory , as defined in . The Group Manager considers the current group configuration when specifying additional information for the link to register. Alternatively, the Administrator can perform 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 above.
• The names of the application groups using the OSCORE group MUST take the values possibly specified by the elements of the 'app_groups' parameter (when custom CBOR is used) or by the different 'app_group' elements (when CoRAL is used) in the POST request above.
• If present, parameters describing the cryptographic algorithms used in the OSCORE group MUST follow the values that the Administrator specified in the POST request above, or the corresponding default values specified in otherwise.
• If also registering a related link to the Authorization Server associated to the OSCORE group, the related link MUST have as link target the URI in 'as_uri' from the 2.01 (Created) response above, if the 'as_uri' parameter was included in the response.

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 to 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. Example in custom CBOR: 0.02 POST Uri-Path: manage Content-Format: TBD2 (application/ace-groupcomm+cbor) { "sign_enc_alg" : 10, "hkdf" : 5, "pairwise_mode" : True, "active" : True, "group_title" : "rooms 1 and 2", "app_groups": : ["room1", "room2"], "as_uri" : "coap://as.example.com/token" } <= 2.01 Created Location-Path: manage Location-Path: gp4 Content-Format: TBD2 (application/ace-groupcomm+cbor) { "group_name" : "gp4", "joining_uri" : "coap://[2001:db8::ab]/ace-group/gp4/", "as_uri" : "coap://as.example.com/token" } ]]> Example in CoRAL: 0.02 POST Uri-Path: manage Content-Format: TBD1 (application/coral+cbor) #using sign_enc_alg 10 hkdf 5 pairwise_mode True active True group_title "rooms 1 and 2" app_group "room1" app_group "room2" as_uri <= 2.01 Created Location-Path: manage Location-Path: gp4 Content-Format: TBD1 (application/coral+cbor) #using group_name "gp4" joining_uri as_uri ]]>

Retrieve a Group Configuration The Administrator can send a GET request to the group-configuration resource manage/GROUPNAME associated to an OSCORE group with group name GROUPNAME, in order to retrieve the complete current configuration of that group. After a successful processing of the request above, 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 . The exact content of the payload reflects the current configuration of the OSCORE group. This includes both configuration properties and status properties. When custom CBOR is used, the response payload is a CBOR map, whose possible entries are specified in and use the same abbreviations defined in . When CoRAL is used, the response payload includes one element for each entry specified in , with the exception of the 'app_groups' status parameter. That is, each element of the 'app_groups' array from the status properties is included as a separate element with name 'app_group'. Example in custom CBOR: 0.01 GET Uri-Path: manage Uri-Path: gp4 <= 2.05 Content Content-Format: TBD2 (application/ace-groupcomm+cbor) { "hkdf" : 5, "pub_key_enc" : 33, "group_mode" : True, "sign_enc_alg" : 10, "sign_alg" : -8, "sign_params" : [[1], [1, 6]], "pairwise_mode" : True, "alg" : 10, "ecdh_alg" : -27, "ecdh_params" : [[1], [1, 6]], "rt" : "core.osc.gconf", "active" : True, "group_name" : "gp4", "group_title" : "rooms 1 and 2", "ace-groupcomm-profile" : "coap_group_oscore_app", "max_stale_sets" : 3, "exp" : 1360289224, "app_groups": : ["room1", "room2"], "joining_uri" : "coap://[2001:db8::ab]/ace-group/gp4/", "as_uri" : "coap://as.example.com/token" } ]]> Example in CoRAL: 0.01 GET Uri-Path: manage Uri-Path: gp4 <= 2.05 Content Content-Format: TBD1 (application/coral+cbor) #using hkdf 5 pub_key_enc 33 group_mode True sign_enc_alg 10 sign_alg -8 sign_params.alg_capab.key_type 1 sign_params.key_type_capab.key_type 1 sign_params.key_type_capab.curve 6 pairwise_mode True alg 10 ecdh_alg -27 ecdh_params.alg_capab.key_type 1 ecdh_params.key_type_capab.key_type 1 ecdh_params.key_type_capab.curve 6 rt "core.osc.gconf", active True group_name "gp4" group_title "rooms 1 and 2" ace-groupcomm-profile "coap_group_oscore_app" max_stale_sets 3 exp 1360289224 app_group "room1" app_group "room2" joining_uri as_uri ]]>

Retrieve Part of a Group Configuration by Filters The Administrator can send a FETCH request to the group-configuration resource manage/GROUPNAME associated to an OSCORE group with group name GROUPNAME, in order to retrieve part of the current configuration of that group. When custom CBOR is used, the request payload is a CBOR map, which contains the following fields:

• 'conf_filter', defined in of this document and encoded as a CBOR array. Each element of the array specifies one requested configuration parameter or status parameter of the current group configuration (see ), using the corresponding abbreviation defined in .

When CoRAL is used, the request payload includes one element for each requested configuration parameter or status parameter of the current group configuration (see ). All the specified elements have no value. After a successful processing of the request above, 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 ). The exact content of the payload reflects the current configuration of the OSCORE group, and is limited to the configuration properties and status properties 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 ). Example in custom CBOR: 0.05 FETCH Uri-Path: manage Uri-Path: gp4 Content-Format: TBD2 (application/ace-groupcomm+cbor) { "conf_filter" : ["sign_enc_alg", "hkdf", "pairwise_mode", "active", "group_title", "app_groups"] } <= 2.05 Content Content-Format: TBD2 (application/ace-groupcomm+cbor) { "sign_enc_alg" : 10, "hkdf" : 5, "pairwise_mode" : True, "active" : True, "group_title" : "rooms 1 and 2", "app_groups": : ["room1", "room2"] } ]]> Example in CoRAL: 0.05 FETCH Uri-Path: manage Uri-Path: gp4 Content-Format: TBD1 (application/coral+cbor) #using sign_enc_alg hkdf pairwise_mode active group_title app_groups <= 2.05 Content Content-Format: TBD1 (application/coral+cbor) #using sign_enc_alg 10 hkdf 5 pairwise_mode True active True group_title "rooms 1 and 2" app_group "room1" app_group "room2" ]]>

Overwrite a Group Configuration The Administrator can send a PUT request to the group-configuration resource associated to an OSCORE group, 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 , with the exception that the configuration parameters 'group_mode' and 'pairwise_mode' as well as the status parameter 'group_name' MUST NOT be included. The error handling for the PUT request is the same as for the POST request defined in . If no error occurs, the Group Manager performs the following actions. First, the Group Manager updates the group-configuration resource, consistently with the values indicated in the PUT request from the Administrator. For each parameter not specified in the PUT request, the Group Manager MUST use the default value as specified in . 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 in the collection of sets of stale OSCORE Sender IDs associated to the group, and deletes any possible older set from the collection (see ). From then on, the Group Manager relies on the latest updated configuration to build the Joining Response message defined in , 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 ) or the current group status (see ). 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 . If the link to the group-membership resource was registered in the Resource Directory , the GM is responsible to refresh the registration, as defined in . Alternatively, the Administrator can update 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.

• The name of the OSCORE group MUST take the value specified in 'group_name' from the 2.04 (Changed) response above.
• The names of the application groups using the OSCORE group MUST take the values possibly specified by the elements of the 'app_groups' parameter (when custom CBOR is used) or by the different 'app_group' elements (when CoRAL is used) in the PUT request above.
• If present, parameters describing the cryptographic algorithms used in the OSCORE group MUST follow the values that the Administrator specified in the PUT request above, or the corresponding default values as specified in otherwise.
• If also registering a related link to the Authorization Server associated to the OSCORE group, the related link MUST have as link target the URI in 'as_uri' from the 2.04 (Changed) response above, if the 'as_uri' parameter was included in the response.

As discussed in , 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. Example in custom CBOR: 0.03 PUT Uri-Path: manage Uri-Path: gp4 Content-Format: TBD2 (application/ace-groupcomm+cbor) { "sign_enc_alg" : 11, "hkdf" : 5 } <= 2.04 Changed Content-Format: TBD2 (application/ace-groupcomm+cbor) { "group_name" : "gp4", "joining_uri" : "coap://[2001:db8::ab]/ace-group/gp4/", "as_uri" : "coap://as.example.com/token" } ]]> Example in CoRAL: 0.03 PUT Uri-Path: manage Uri-Path: gp4 Content-Format: TBD1 (application/coral+cbor) #using sign_enc_alg 11 hkdf 5 <= 2.04 Changed Content-Format: TBD1 (application/coral+cbor) #using group_name "gp4" joining_uri as_uri ]]>

Effects on Joining Nodes After having overwritten a group configuration, if the value of the status parameter 'active' is changed from True to False, the Group Manager MUST stop admitting new members in the OSCORE group. In particular, until the status parameter 'active' is changed back to True, the Group Manager MUST respond to a Joining Request with a 5.03 (Service Unavailable) response, as defined in . If the value of the status parameter 'active' is changed from False to True, the Group Manager resumes admitting new members in the OSCORE group, by processing their Joining Requests (see ).

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 ). To this end, the Group Manager can individually target the 'control_uri' URI of each group member (see ), if provided by the intended recipient upon joining the OSCORE group (see ). Alternatively, group members can subscribe for updates to the group-membership resource of the OSCORE group, e.g., by using CoAP Observe . If the value of the status parameter 'active' is changed from True to False:

• The Group Manager MUST stop accepting requests for new keying material from current group members (see ). In particular, until the status parameter 'active' is changed back to True, the Group Manager MUST respond to a Key Renewal Request with a 5.03 (Service Unavailable) response, as defined in .
• The Group Manager MUST stop accepting updated public keys uploaded by current group members (see ). In particular, until the status parameter 'active' is changed back to True, the Group Manager MUST respond to a Public Key Update Request with a 5.03 (Service Unavailable) response, as defined in .

Every group member, upon learning that the OSCORE group has been deactivated (i.e., 'active' has value False), SHOULD stop communicating in the group. Every group member, upon learning that the OSCORE group has been reactivated (i.e., 'active' has value True again), can resume communicating in the group. Every group member, upon receiving updated values for 'hkdf', 'sign_enc_alg' and 'alg', MUST either:

• Leave the OSCORE group (see ), e.g., if not supporting the indicated new algorithms; or
• Use the new parameter values, and accordingly re-derive the OSCORE Security Context for the OSCORE group (see ).

Every group member, upon receiving updated values for 'pub_key_enc', 'sign_alg', 'sign_params', 'ecdh_alg' and 'ecdh_params' MUST either:

• Leave the OSCORE group, e.g., if not supporting the indicated new algorithms, parameters and encoding; or
• Leave the OSCORE group and rejoin it (see ), providing the Group Manager with a public key which is compatible with the indicated new algorithms, parameters and encoding; or
• Use the new parameter values, and, if required, performs the following actions: i) provide the Group Manager with a new public key to use in the OSCORE group, as compatible with the indicated parameters (see ); ii) retrieve from the Group Manager the new Group Manager's public key (see ), as also compatible with the indicated new algorithms, parameters and encoding.

Selective Update of a Group Configuration The Administrator can send a PATCH/iPATCH request to the group-configuration resource associated to an OSCORE group, in order to update the value of only part of the group configuration. The request payload has the same format of the PUT request defined in , 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.

• When custom CBOR is used, the CBOR map in the request payload includes the field 'app_groups_diff'. This field MUST NOT be present multiple times, and it 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 of the CBOR array 'app_groups_diff' formatted as in the response from the Group Manager is provided below.

CDDL definition of the 'app_groups_diff' field

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 in case the 'app_groups_diff' field occurs more than once. The Group Manager MUST respond with a 4.00 (Bad Request) response, in case the CBOR map in the request payload includes both the 'app_groups' field and the 'app_groups_diff' field.

• When CoRAL is used, the request payload includes the following top-level elements.
  • 'app_group_del', with value a text string specifying the name of an application group to remove from the 'app_groups' status parameter. This element can be included multiple times.
  • 'app_group_add', with value a text string specifying the name of an application group to add to the 'app_groups' status parameter. This element can be included multiple times.
  The Group Manager MUST respond with a 4.00 (Bad Request) response, in case the request payload includes both any 'app_group' element as well as any 'app_group_del' and/or 'app_group_add' element.

The error handling for the PATCH/iPATCH request is the same as for the PUT request defined in , 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 (when custom CBOR is used) or no elements (when CoRAL is used).
• 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. The response, MAY include the current representation of the group configuration resource, like when responding to a GET request as defined in . 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:
  • When custom CBOR is used, the CBOR map includes the parameter 'app_groups_diff'; or
  • When CoRAL is used, any element 'app_group_del' and/or 'app_group_add' is included.

If no error occurs, 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. Unlike for the PUT request defined in , 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.
• When custom CBOR is used, 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.
  • 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.
• When CoRAL is used, the Group Manager:
  • Deletes from the 'app_groups' status parameter the names of the application groups specified in the different 'app_group_del' elements.
  • Adds to the 'app_groups' status parameter the names of the application groups specified in the different 'app_group_add' elements.

After having updated the group-configuration resource, from then on the Group Manager relies on the new group configuration to build the Joining Response message defined in , 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 ) or the current group status (see ). 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 . The same considerations as for the PUT request defined in hold also in this case, with respect to refreshing a possible registration of the link to the group-membership resource in the Resource Directory . Example in custom CBOR: 0.06 PATCH Uri-Path: manage Uri-Path: gp4 Content-Format: TBD2 (application/ace-groupcomm+cbor) { "sign_enc_alg" : 10, "app_groups_diff" : [["room1"], ["room3", "room4"]] } <= 2.04 Changed Content-Format: TBD2 (application/ace-groupcomm+cbor) { "group_name" : "gp4", "joining_uri" : "coap://[2001:db8::ab]/ace-group/gp4/", "as_uri" : "coap://as.example.com/token" } ]]> Example in CoRAL: 0.06 PATCH Uri-Path: manage Uri-Path: gp4 Content-Format: TBD1 (application/coral+cbor) #using sign_enc_alg 10 app_group_del "room1" app_group_add "room3" app_group_add "room4" <= 2.04 Changed Content-Format: TBD1 (application/coral+cbor) #using group_name "gp4" joining_uri as_uri ]]>

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 for the case of group configuration overwriting.

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 for the case of group configuration overwriting.

Delete a Group Configuration The Administrator can send a DELETE request to the group-configuration resource, in order to delete that OSCORE group. The deletion would be successful only on an inactive OSCORE group. That is, the DELETE request actually yields a successful deletion of the OSCORE group, only if the corresponding status parameter 'active' has current value False. The Administrator can ensure that, by first performing an update of the group-configuration resource associated to the OSCORE group (see ), and setting the corresponding status parameter 'active' to False. If, upon receiving the DELETE request, the current value of the status parameter 'active' is True, the Group Manager MUST respond with a 4.09 (Conflict) response. The response MUST have Content-Format set to application/ace-groupcomm+cbor and is formatted as defined in . The value of the 'error' field MUST be set to 8 ("Group currently active"). After a successful processing of the request above, the Group Manager performs the following actions. First, the Group Manager deletes the OSCORE group and deallocates both the group-configuration resource as well as the group-membership resource associated to that group. Then, the Group Manager replies to the Administrator with a 2.02 (Deleted) response. Example: 0.04 DELETE Uri-Path: manage Uri-Path: gp4 <= 2.02 Deleted ]]>

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 ).

• The Group Manager sends an individual request message to each group member, targeting the respective resource used to perform the group rekeying process (see ). The Group Manager uses the same format of the Joining Response message in , 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 to the OSCORE group. In particular, if this relies on CoAP Observe , 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 ). The response MUST have Content-Format set to application/ace-groupcomm+cbor and is formatted as defined in . The value of the 'error' field MUST be set to 5 ("Group deleted").

When being informed about the deletion of the OSCORE group, a group member deletes the OSCORE Security Context that it stores as associated to that group, and possibly deallocates any dedicated control resource intended for the Group Manager that it has for that group.

Security Considerations Security considerations are inherited from the ACE framework for Authentication and Authorization , and from the specific transport profile of ACE used between the Administrator and the Group Manager, such as and .

IANA Considerations RFC Editor: Please replace "[[this document]]" with the RFC number of this document and delete this paragraph. This document has the following actions for IANA.

ACE Groupcomm Parameters Registry IANA is asked to register the following entries in the "ACE Groupcomm Parameters" Registry defined in .

ACE Groupcomm Errors IANA is asked to register the following entry in the "ACE Groupcomm Errors" registry defined in .

• Value: 10
• Description: Group currently active.
• Reference: [[This document]]

Resource Types IANA is asked to enter the following values into the Resource Type (rt=) Link Target Attribute Values subregistry within the Constrained Restful Environments (CoRE) Parameters registry defined in .

References Normative References RISE AB Ericsson AB Ericsson AB Ericsson AB Universitaet Duisburg-Essen This document defines Group Object Security for Constrained RESTful Environments (Group OSCORE), providing end-to-end security of CoAP messages exchanged between members of a group, e.g. sent over IP multicast. In particular, the described approach defines how OSCORE is used in a group communication setting to provide source authentication for CoAP group requests, sent by a client to multiple servers, and for protection of the corresponding CoAP responses. Combitech Ericsson Spotify AB Arm Ltd. This specification defines a framework for authentication and authorization in Internet of Things (IoT) environments called ACE- OAuth. The framework is based on a set of building blocks including OAuth 2.0 and the Constrained Application Protocol (CoAP), thus transforming a well-known and widely used authorization solution into a form suitable for IoT devices. Existing specifications are used where possible, but extensions are added and profiles are defined to better serve the IoT use cases. Ericsson AB RISE AB This document defines message formats and procedures for requesting and distributing group keying material using the ACE framework, to protect communications between group members. RISE AB Universitaet Duisburg-Essen Ericsson AB This specification defines an application profile of the ACE framework for Authentication and Authorization, to request and provision keying material in group communication scenarios that are based on CoAP and secured with Group Object Security for Constrained RESTful Environments (OSCORE). This application profile delegates the authentication and authorization of Clients that join an OSCORE group through a Resource Server acting as Group Manager for that group. This application profile leverages protocol-specific transport profiles of ACE to achieve communication security, server authentication and proof-of-possession for a key owned by the Client and bound to an OAuth 2.0 Access Token. Ericsson AB Combitech Ericsson AB RISE This document specifies a profile for the Authentication and Authorization for Constrained Environments (ACE) framework. It utilizes Object Security for Constrained RESTful Environments (OSCORE) to provide communication security and proof-of-possession for a key owned by the client and bound to an OAuth 2.0 access token. Ericsson The Constrained RESTful Application Language (CoRAL) defines a data model and interaction model as well as two specialized serialization formats for the description of typed connections between resources on the Web ("links"), possible operations on such resources ("forms"), and simple resource metadata. August Cellars Concise Binary Object Representation (CBOR) is a data format designed for small code size and small message size. There is a need for the ability to have basic security services defined for this data format. This document defines the CBOR Object Signing and Encryption (COSE) protocol. This specification describes how to create and process signatures, message authentication codes, and encryption using CBOR for serialization. This specification additionally describes how to represent cryptographic keys using CBOR. This document along with [I-D.ietf-cose-rfc8152bis-algs] obsoletes RFC8152. August Cellars Concise Binary Object Representation (CBOR) is a data format designed for small code size and small message size. There is a need for the ability to have basic security services defined for this data format. THis document defines a set of algorithms that can be used with the CBOR Object Signing and Encryption (COSE) protocol RFC XXXX. IoTconsultancy.nl InterDigital RISE AB This document specifies the use of the Constrained Application Protocol (CoAP) for group communication, using UDP/IP multicast as the underlying data transport. Both unsecured and secured CoAP group communication are specified. Security is achieved by use of the Group Object Security for Constrained RESTful Environments (Group OSCORE) protocol. The target application area of this specification is any group communication use cases that involve resource- constrained devices or networks. This document replaces RFC7390, while it updates RFC7252 and RFC7641. In many standards track documents several words are used to signify the requirements in the specification. These words are often capitalized. This document defines these words as they should be interpreted in IETF documents. This document specifies an Internet Best Current Practices for the Internet Community, and requests discussion and suggestions for improvements. This specification defines Web Linking using a link format for use by constrained web servers to describe hosted resources, their attributes, and other relationships between links. Based on the HTTP Link Header field defined in RFC 5988, the Constrained RESTful Environments (CoRE) Link Format is carried as a payload and is assigned an Internet media type. "RESTful" refers to the Representational State Transfer (REST) architecture. A well-known URI is defined as a default entry point for requesting the links hosted by a server. [STANDARDS-TRACK] The OAuth 2.0 authorization framework enables a third-party application to obtain limited access to an HTTP service, either on behalf of a resource owner by orchestrating an approval interaction between the resource owner and the HTTP service, or by allowing the third-party application to obtain access on its own behalf. This specification replaces and obsoletes the OAuth 1.0 protocol described in RFC 5849. [STANDARDS-TRACK] The Constrained Application Protocol (CoAP) is a specialized web transfer protocol for use with constrained nodes and constrained (e.g., low-power, lossy) networks. The nodes often have 8-bit microcontrollers with small amounts of ROM and RAM, while constrained networks such as IPv6 over Low-Power Wireless Personal Area Networks (6LoWPANs) often have high packet error rates and a typical throughput of 10s of kbit/s. The protocol is designed for machine- to-machine (M2M) applications such as smart energy and building automation. CoAP provides a request/response interaction model between application endpoints, supports built-in discovery of services and resources, and includes key concepts of the Web such as URIs and Internet media types. CoAP is designed to easily interface with HTTP for integration with the Web while meeting specialized requirements such as multicast support, very low overhead, and simplicity for constrained environments. The Constrained Application Protocol (CoAP) is a RESTful application protocol for constrained nodes and networks. The state of a resource on a CoAP server can change over time. This document specifies a simple protocol extension for CoAP that enables CoAP clients to "observe" resources, i.e., to retrieve a representation of a resource and keep this representation updated by the server over a period of time. The protocol follows a best-effort approach for sending new representations to clients and provides eventual consistency between the state observed by each client and the actual resource state at the server. The methods defined in RFC 7252 for the Constrained Application Protocol (CoAP) only allow access to a complete resource, not to parts of a resource. In case of resources with larger or complex data, or in situations where resource continuity is required, replacing or requesting the whole resource is undesirable. Several applications using CoAP need to access parts of the resources. This specification defines the new CoAP methods, FETCH, PATCH, and iPATCH, which are used to access and update parts of a resource. RFC 2119 specifies common key words that may be used in protocol specifications. This document aims to reduce the ambiguity by clarifying that only UPPERCASE usage of the key words have the defined special meanings. This document proposes a notational convention to express Concise Binary Object Representation (CBOR) data structures (RFC 7049). Its main goal is to provide an easy and unambiguous way to express structures for protocol messages and data formats that use CBOR or JSON. This document defines Object Security for Constrained RESTful Environments (OSCORE), a method for application-layer protection of the Constrained Application Protocol (CoAP), using CBOR Object Signing and Encryption (COSE). OSCORE provides end-to-end protection between endpoints communicating using CoAP or CoAP-mappable HTTP. OSCORE is designed for constrained nodes and networks supporting a range of proxy operations, including translation between different transport protocols. Although an optional functionality of CoAP, OSCORE alters CoAP options processing and IANA registration. Therefore, this document updates RFC 7252. The Concise Binary Object Representation (CBOR) is a data format whose design goals include the possibility of extremely small code size, fairly small message size, and extensibility without the need for version negotiation. These design goals make it different from earlier binary serializations such as ASN.1 and MessagePack. This document obsoletes RFC 7049, providing editorial improvements, new details, and errata fixes while keeping full compatibility with the interchange format of RFC 7049. It does not create a new version of the format. Informative References Universität Bremen TZI Universität Bremen TZI Universität Bremen TZI Ericsson AB Combitech This specification defines a profile of the ACE framework that allows constrained servers to delegate client authentication and authorization. The protocol relies on DTLS version 1.2 for communication security between entities in a constrained network using either raw public keys or pre-shared keys. A resource- constrained server can use this protocol to delegate management of authorization information to a trusted host with less severe limitations regarding processing power and memory. This document specifies Version 1.3 of the Datagram Transport Layer Security (DTLS) protocol. DTLS 1.3 allows client/server applications to communicate over the Internet in a way that is designed to prevent eavesdropping, tampering, and message forgery. The DTLS 1.3 protocol is intentionally based on the Transport Layer Security (TLS) 1.3 protocol and provides equivalent security guarantees with the exception of order protection/non-replayability. Datagram semantics of the underlying transport are preserved by the DTLS protocol. This document obsoletes RFC 6347. ARM SmartThings Universitaet Bremen TZI consultant In many IoT applications, direct discovery of resources is not practical due to sleeping nodes, or networks where multicast traffic is inefficient. These problems can be solved by employing an entity called a Resource Directory (RD), which contains information about resources held on other servers, allowing lookups to be performed for those resources. The input to an RD is composed of links and the output is composed of links constructed from the information stored in the RD. This document specifies the web interfaces that an RD supports for web servers to discover the RD and to register, maintain, lookup and remove information on resources. Furthermore, new target attributes useful in conjunction with an RD are defined. RISE AB Consultant Group communication over the Constrained Application Protocol (CoAP) can be secured by means of Group Object Security for Constrained RESTful Environments (Group OSCORE). At deployment time, devices may not know the exact security groups to join, the respective Group Manager, or other information required to perform the joining process. This document describes how a CoAP endpoint can use descriptions and links of resources registered at the CoRE Resource Directory to discover security groups and to acquire information for joining them through the respective Group Manager. A given security group may protect multiple application groups, which are separately announced in the Resource Directory as sets of endpoints sharing a pool of resources. This approach is consistent with, but not limited to, the joining of security groups based on the ACE framework for Authentication and Authorization in constrained environments. Ericsson This document explores how the Constrained RESTful Application Language (CoRAL) might be used for two use cases in Constrained RESTful Environments (CoRE): CoRE Resource Discovery, which allows a client to discover the resources of a server given a host name or IP address, and CoRE Resource Directory, which provides a directory of resources on many servers. This document specifies version 1.2 of the Datagram Transport Layer Security (DTLS) protocol. The DTLS protocol provides communications privacy for datagram protocols. The protocol allows client/server applications to communicate in a way that is designed to prevent eavesdropping, tampering, or message forgery. The DTLS protocol is based on the Transport Layer Security (TLS) protocol and provides equivalent security guarantees. Datagram semantics of the underlying transport are preserved by the DTLS protocol. This document updates DTLS 1.0 to work with TLS version 1.2. [STANDARDS-TRACK]

Document Updates RFC EDITOR: PLEASE REMOVE THIS SECTION.

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.
• New error type "Group currently active".

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.

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, as well as the interactions with the Group Manager using CoRAL. The authors sincerely thank Christian Amsuess, Carsten Bormann and Jim Schaad for their comments and feedback. The work on this document has been partly supported by VINNOVA and the Celtic-Next project CRITISEC; and by the H2020 project SIFIS-Home (Grant agreement 952652).