draft-ietf-ace-pubsub-profile-00.txt		draft-ietf-ace-pubsub-profile-01.txt
	ACE Working Group F. Palombini		ACE Working Group F. Palombini
	Internet-Draft Ericsson		Internet-Draft Ericsson
	Intended status: Standards Track January 04, 2020		Intended status: Standards Track July 03, 2020
	Expires: July 7, 2020		Expires: January 4, 2021
	Pub-Sub Profile for Authentication and Authorization for Constrained		Pub-Sub Profile for Authentication and Authorization for Constrained
	Environments (ACE)		Environments (ACE)
	draft-ietf-ace-pubsub-profile-00		draft-ietf-ace-pubsub-profile-01
	Abstract		Abstract
	This specification defines an application profile for authentication		This specification defines an application profile for authentication
	and authorization for publishers and subscribers in a pub-sub setting		and authorization for publishers and subscribers in a pub-sub setting
	scenario in a constrained environment, using the ACE framework. This		scenario in a constrained environment, using the ACE framework. This
	profile relies on transport layer or application layer security to		profile relies on transport layer or application layer security to
	authorize the publisher to the broker. Moreover, it relies on		authorize the publisher to the broker. Moreover, it relies on
	application layer security for publisher-broker and subscriber-broker		application layer security for publisher-broker and subscriber-broker
	communication.		communication.
	skipping to change at page 1, line 37 ¶		skipping to change at page 1, line 37 ¶
	Internet-Drafts are working documents of the Internet Engineering		Internet-Drafts are working documents of the Internet Engineering
	Task Force (IETF). Note that other groups may also distribute		Task Force (IETF). Note that other groups may also distribute
	working documents as Internet-Drafts. The list of current Internet-		working documents as Internet-Drafts. The list of current Internet-
	Drafts is at https://datatracker.ietf.org/drafts/current/.		Drafts is at https://datatracker.ietf.org/drafts/current/.
	Internet-Drafts are draft documents valid for a maximum of six months		Internet-Drafts are draft documents valid for a maximum of six months
	and may be updated, replaced, or obsoleted by other documents at any		and may be updated, replaced, or obsoleted by other documents at any
	time. It is inappropriate to use Internet-Drafts as reference		time. It is inappropriate to use Internet-Drafts as reference
	material or to cite them other than as "work in progress."		material or to cite them other than as "work in progress."
	This Internet-Draft will expire on July 7, 2020.		This Internet-Draft will expire on January 4, 2021.
	Copyright Notice		Copyright Notice
	Copyright (c) 2020 IETF Trust and the persons identified as the		Copyright (c) 2020 IETF Trust and the persons identified as the
	document authors. All rights reserved.		document authors. All rights reserved.
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	carefully, as they describe your rights and restrictions with respect		carefully, as they describe your rights and restrictions with respect
	to this document. Code Components extracted from this document must		to this document. Code Components extracted from this document must
	include Simplified BSD License text as described in Section 4.e of		include Simplified BSD License text as described in Section 4.e of
	the Trust Legal Provisions and are provided without warranty as		the Trust Legal Provisions and are provided without warranty as
	described in the Simplified BSD License.		described in the Simplified BSD License.
	Table of Contents		Table of Contents
	1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2		1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
	1.1. Terminology . . . . . . . . . . . . . . . . . . . . . . . 2		1.1. Terminology . . . . . . . . . . . . . . . . . . . . . . . 3
	2. Application Profile Overview . . . . . . . . . . . . . . . . 3		2. Application Profile Overview . . . . . . . . . . . . . . . . 3
	3. coap_pubsub_app Application Profile . . . . . . . . . . . . . 5		3. PubSub Application Profiles . . . . . . . . . . . . . . . . . 5
	3.1. Retrieval of COSE Key for protection of content . . . . . 5		3.1. Retrieval of COSE Key for protection of content . . . . . 6
	4. Publisher . . . . . . . . . . . . . . . . . . . . . . . . . . 8		3.2. coap_pubsub_app Application Profile . . . . . . . . . . . 9
	5. Subscriber . . . . . . . . . . . . . . . . . . . . . . . . . 10		3.3. mqtt_pubsub_app Application Profile . . . . . . . . . . . 9
	6. Pub-Sub Protected Communication . . . . . . . . . . . . . . . 12		4. Publisher . . . . . . . . . . . . . . . . . . . . . . . . . . 9
	6.1. Using COSE Objects To Protect The Resource Representation 13		4.1. CoAP Publisher . . . . . . . . . . . . . . . . . . . . . 11
	7. Security Considerations . . . . . . . . . . . . . . . . . . . 14		4.2. MQTT Publisher . . . . . . . . . . . . . . . . . . . . . 12
	8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 15		5. Subscriber . . . . . . . . . . . . . . . . . . . . . . . . . 12
	8.1. ACE Groupcomm Profile Registry . . . . . . . . . . . . . 15		5.1. CoAP Subscriber . . . . . . . . . . . . . . . . . . . . . 13
	8.2. ACE Groupcomm Key Registry . . . . . . . . . . . . . . . 16		5.2. MQTT Subscriber . . . . . . . . . . . . . . . . . . . . . 13
	9. References . . . . . . . . . . . . . . . . . . . . . . . . . 16		6. Pub-Sub Protected Communication . . . . . . . . . . . . . . . 13
	9.1. Normative References . . . . . . . . . . . . . . . . . . 16		6.1. Using COSE Objects To Protect The Resource Representation 14
	9.2. Informative References . . . . . . . . . . . . . . . . . 17		7. Security Considerations . . . . . . . . . . . . . . . . . . . 16
	Appendix A. Requirements on Application Profiles . . . . . . . . 17		8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 17
	Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . . 19		8.1. ACE Groupcomm Profile Registry . . . . . . . . . . . . . 17
	Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 19		8.1.1. CoAP Profile Registration . . . . . . . . . . . . . . 17
			8.1.2. CoAP Profile Registration . . . . . . . . . . . . . . 17
			8.2. ACE Groupcomm Key Registry . . . . . . . . . . . . . . . 18
			9. References . . . . . . . . . . . . . . . . . . . . . . . . . 18
			9.1. Normative References . . . . . . . . . . . . . . . . . . 18
			9.2. Informative References . . . . . . . . . . . . . . . . . 19
			Appendix A. Requirements on Application Profiles . . . . . . . . 19
			Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . . 21
			Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 21
	1. Introduction		1. Introduction
	The publisher-subscriber setting allows for devices with limited		The publisher-subscriber setting allows for devices with limited
	reachability to communicate via a broker that enables store-and-		reachability to communicate via a broker that enables store-and-
	forward messaging between the devices. The pub-sub scenario using		forward messaging between the devices. The pub-sub scenario using
	the Constrained Application Protocol (CoAP) is specified in		the Constrained Application Protocol (CoAP) is specified in
	[I-D.ietf-core-coap-pubsub]. This document defines a way to		[I-D.ietf-core-coap-pubsub], while the one using MQTT is specified in
	authorize nodes in a CoAP pub-sub type of setting, using the ACE		REF MQTT. This document defines a way to authorize nodes in a CoAP
	framework [I-D.ietf-ace-oauth-authz], and to provide the keys for		pub-sub type of setting, using the ACE framework
	protecting the communication between these nodes.		[I-D.ietf-ace-oauth-authz], and to provide the keys for protecting
			the communication between these nodes. This document gives detailed
			specifications for MQTT and CoAP pub-sub, but can easily be adapted
			for other transport protocol as well.
	1.1. Terminology		1.1. Terminology
	The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",		The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
	"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this		"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
	document are to be interpreted as described in RFC 2119 [RFC2119].		document are to be interpreted as described in RFC 2119 [RFC2119].
	Readers are expected to be familiar with the terms and concepts		Readers are expected to be familiar with the terms and concepts
	described in [I-D.ietf-ace-oauth-authz], [I-D.ietf-ace-key-groupcomm]		described in [I-D.ietf-ace-oauth-authz],
	and [I-D.ietf-core-coap-pubsub]. In particular, analogously to		[I-D.ietf-ace-key-groupcomm]. In particular, analogously to
	[I-D.ietf-ace-oauth-authz], terminology for entities in the		[I-D.ietf-ace-oauth-authz], terminology for entities in the
	architecture such as Client (C), Resource Server (RS), and		architecture such as Client (C), Resource Server (RS), and
	Authorization Server (AS) is defined in OAuth 2.0 [RFC6749] and		Authorization Server (AS) is defined in OAuth 2.0 [RFC6749] and
	[I-D.ietf-ace-actors], and terminology for entities such as the Key		[I-D.ietf-ace-actors], and terminology for entities such as the Key
	Distribution Center (KDC) and Dispatcher in		Distribution Center (KDC) and Dispatcher in
	[I-D.ietf-ace-key-groupcomm].		[I-D.ietf-ace-key-groupcomm].
			Readers are expected to be familiar with terms and concepts of pub-
			sub group communication, as described in [I-D.ietf-core-coap-pubsub],
			or MQTT (REF MQTT pubsub).
	2. Application Profile Overview		2. Application Profile Overview
	The objective of this document is to specify how to authorize nodes,		The objective of this document is to specify how to authorize nodes,
	provide keys, and protect a CoAP pub-sub communication, as described		provide keys, and protect a pub-sub communication, using
	in [I-D.ietf-core-coap-pubsub], using [I-D.ietf-ace-key-groupcomm],		[I-D.ietf-ace-key-groupcomm], which itself expands the Ace framework
	which itself expands the Ace framework ([I-D.ietf-ace-oauth-authz]),		([I-D.ietf-ace-oauth-authz]), and transport profiles
	and transport profiles ([I-D.ietf-ace-dtls-authorize],		([I-D.ietf-ace-dtls-authorize], [I-D.ietf-ace-oscore-profile], REF
	[I-D.ietf-ace-oscore-profile]).		MQTT profile). The pub-sub communication protocol can be based on
			CoAP, as described in [I-D.ietf-core-coap-pubsub], MQTT (see REF MQTT
			comm), or other transport.
	The architecture of the scenario is shown in Figure 1.		The architecture of the scenario is shown in Figure 1.
	+----------------+ +----------------+		+----------------+ +----------------+
	| | | |		| | | |
	| Authorization | | Authorization |		| Authorization | | Authorization |
	| Server 1 | | Server 2 |		| Server 1 | | Server 2 |
	| | | |		| | | |
	+----------------+ +----------------+		+----------------+ +----------------+
	^ ^ ^		^ ^ ^
	| | |		| | |
	+---------(A)----+ | +-----(D)------+		+---------(A)----+ | +-----(D)------+
	| +--------------------(B)--------+ |		| +--------------------(B)--------+ |
	v v v		v v v
	+------------+ +------------+ +------------+		+------------+ +------------+ +------------+
	| CoAP | ----(C)---> | CoAP | | CoAP |		| | | | | |
	| Client - | ----(E)---> | Server - | | Client - |		| Publisher | ----(E)---> | Broker | | Subscriber |
	| | | | <----(F)---- | |		| | | | <----(F)---- | |
	| Publisher | | Broker | -----(G)---> | Subscriber |		| | | | -----(G)---> | |
	+------------+ +------------+ +------------+		+------------+ +------------+ +------------+
	Figure 1: Architecture CoAP pubsub with Authorization Servers		Figure 1: Architecture CoAP pubsub with Authorization Servers
	The RS is the broker, which contains the topic. This node		The RS is the broker, which contains the topic. This node
	corresponds to the Dispatcher, in [I-D.ietf-ace-key-groupcomm]. The		corresponds to the Dispatcher, in [I-D.ietf-ace-key-groupcomm]. The
	AS1 hosts the policies about the Broker: what endpoints are allowed		AS1 hosts the policies about the Broker: what endpoints are allowed
	to Publish on the Broker. The Clients access this node to get write		to Publish on the Broker. The Clients access this node to get write
	access to the Broker. The AS2 hosts the policies about the topic:		access to the Broker. The AS2 hosts the policies about the topic:
	what endpoints are allowed to access what topic. This node		what endpoints are allowed to access what topic. This node
	skipping to change at page 4, line 34 ¶		skipping to change at page 5, line 16 ¶
	Note that, analogously to the Publisher, the Subscriber can also set		Note that, analogously to the Publisher, the Subscriber can also set
	up an additional security association with the Broker, using an AS,		up an additional security association with the Broker, using an AS,
	in the same way the Publisher does with AS1. In this case, only		in the same way the Publisher does with AS1. In this case, only
	authorized Subscribers would be able to get notifications from the		authorized Subscribers would be able to get notifications from the
	Broker. The overhead would be that each Subscriber should access the		Broker. The overhead would be that each Subscriber should access the
	AS and get all the information to start a secure exchange with the		AS and get all the information to start a secure exchange with the
	Broker.		Broker.
	+------------+ +------------+ +------------+		+------------+ +------------+ +------------+
	| CoAP | | CoAP | | CoAP |
	| Client - | | Server - | | Client - |
	| | | | | |		| | | | | |
	| Publisher | | Broker | | Subscriber |		| Publisher | | Broker | | Subscriber |
			| | | | | |
			| | | | | |
	+------------+ +------------+ +------------+		+------------+ +------------+ +------------+
	: : : :		: : : :
	: '------ Security -------' :		: '------ Security -------' :
	: Association 1 :		: Association 1 :
	'------------------------------- Security --------------'		'------------------------------- Security --------------'
	Association 2		Association 2
	Note that AS1 and AS2 might either be co-resident or be 2 separate		Note that AS1 and AS2 might either be co-resident or be 2 separate
	physical entities, in which case access control policies must be		physical entities, in which case access control policies must be
	exchanged between AS1 and AS2, so that they agree on rights for		exchanged between AS1 and AS2, so that they agree on rights for
	joining nodes about specific topics. How the policies are exchanged		joining nodes about specific topics. How the policies are exchanged
	is out of scope for this specification.		is out of scope for this specification.
	3. coap_pubsub_app Application Profile		3. PubSub Application Profiles
	This profile uses [I-D.ietf-ace-key-groupcomm], which expands the ACE		Each profile defined in this document uses
	framework. This document specifies which exact parameters from		[I-D.ietf-ace-key-groupcomm], which expands the ACE framework. This
			section defines which exact parameters from
	[I-D.ietf-ace-key-groupcomm] have to be used, and the values for each		[I-D.ietf-ace-key-groupcomm] have to be used, and the values for each
	parameter.		parameter. Since [I-D.ietf-ace-oauth-authz] recommends the use of
			CoAP anc CBOR, this document describes the exchanges assuming CoAP
			and CBOR are used. However, using HTTP instead of CoAP is possible,
			using the corresponding parameters and methods. Analogously, JSON
			[RFC8259] can be used instead of CBOR, using the conversion method
			specified in Sections 4.1 and 4.2 of [RFC7049]. In case JSON is
			used, the Content Format or Media Type of the message has to be
			changed accordingly.
	The Publisher and the Subscriber map to the Client in		The Publisher and the Subscriber map to the Client in
	[I-D.ietf-ace-key-groupcomm], the AS2 maps to the AS and to the KDC,		[I-D.ietf-ace-key-groupcomm], the AS2 maps to the AS and to the KDC,
	the Broker maps to the Dispatcher.		the Broker maps to the Dispatcher.
	Note that both publishers and subscribers use the same profile,		Note that both publishers and subscribers use the same profile.
	called "coap_pubsub_app".
	3.1. Retrieval of COSE Key for protection of content		3.1. Retrieval of COSE Key for protection of content
	This phase is common to both Publisher and Subscriber. To maintain		This phase is common to both Publisher and Subscriber. To maintain
	the generality, the Publisher or Subscriber is referred as Client in		the generality, the Publisher or Subscriber is referred as Client in
	this section.		this section.
	Client Broker AS2		Client Broker AS2
	| [----- Resource Request ---->] | |		| [----- Resource Request ---->] | |
	| | |		| | |
	skipping to change at page 5, line 48 ¶		skipping to change at page 6, line 36 ¶
	Figure 2: B: Access request - response		Figure 2: B: Access request - response
	Complementary to what is defined in [I-D.ietf-ace-oauth-authz]		Complementary to what is defined in [I-D.ietf-ace-oauth-authz]
	(Section 5.1.1), to determine the AS2 in charge of a topic hosted at		(Section 5.1.1), to determine the AS2 in charge of a topic hosted at
	the Broker, the Broker MAY send the address of both the AS in charge		the Broker, the Broker MAY send the address of both the AS in charge
	of the topic back to the Client in the 'AS' parameter in the AS		of the topic back to the Client in the 'AS' parameter in the AS
	Information, as a response to an Unauthorized Resource Request		Information, as a response to an Unauthorized Resource Request
	(Section 5.1.2). The uri of AS2 is concatenated to the uri of AS1,		(Section 5.1.2). The uri of AS2 is concatenated to the uri of AS1,
	and separated by a comma. An example using CBOR diagnostic notation		and separated by a comma. An example using CBOR diagnostic notation
	is given below:		and CoAP is given below:
	4.01 Unauthorized		4.01 Unauthorized
	Content-Format: application/ace+cbor		Content-Format: application/ace+cbor
	{"AS": "coaps://as1.example.com/token,		{"AS": "coaps://as1.example.com/token,
	coaps://as2.example.com/pubsubkey"}		coaps://as2.example.com/pubsubkey"}
	Figure 3: AS1, AS2 Information example		Figure 3: AS1, AS2 Information example
	After retrieving the AS2 address, the Client MAY send a request to		After retrieving the AS2 address, the Client MAY send a request to
	the AS, in order to retrieve necessary information concerning the		the AS, in order to retrieve necessary information concerning the
	skipping to change at page 7, line 23 ¶		skipping to change at page 8, line 8 ¶
	rsnonce concatenated with cnonce, if 'client_cred' is present,		rsnonce concatenated with cnonce, if 'client_cred' is present,
	* OPTIONALLY, if needed, the 'pub_keys_repos' parameter		* OPTIONALLY, if needed, the 'pub_keys_repos' parameter
	o the following fields from the Authorization Request (Section 3.1		o the following fields from the Authorization Request (Section 3.1
	of [I-D.ietf-ace-key-groupcomm]):		of [I-D.ietf-ace-key-groupcomm]):
	* OPTIONALLY, if needed, additional parameters such as		* OPTIONALLY, if needed, additional parameters such as
	'client_id'		'client_id'
			TODO: 'cnonce' might change name. TODO: register media type ace+json
			for HTTP?
	Note that the alg parameter in the 'client_cred' COSE_Key MUST be a		Note that the alg parameter in the 'client_cred' COSE_Key MUST be a
	signing algorithm, as defined in section 8 of [RFC8152], and that it		signing algorithm, as defined in section 8 of [RFC8152], and that it
	is the same algorithm used to compute the signature sent in		is the same algorithm used to compute the signature sent in
	'client_cred_verify'.		'client_cred_verify'.
	Examples of the payload of a Authorization + Joining Request are		Examples of the payload of a Authorization + Joining Request are
	specified in Figure 5 and Figure 8.		specified in Figure 5 and Figure 8.
	The AS2 verifies that the Client is authorized to access the topic		The AS2 verifies that the Client is authorized to access the topic
	and, if the 'client_cred' parameter is present, stores the public key		and, if the 'client_cred' parameter is present, stores the public key
	of the Client.		of the Client.
	The AS2 response is an Authorization + Joining Response, with		The AS2 response is an Authorization + Joining Response, with
	Content-Format = "application/ace+cbor". The payload (formatted as a		Content-Format = "application/ace+cbor". The payload (formatted as a
	CBOR map) MUST contain:		CBOR map) MUST contain:
	o the following fields from the Joining Response (Section 4.1 of		o the following fields from the Joining Response (Section 4.2 of
	[I-D.ietf-ace-key-groupcomm]):		[I-D.ietf-ace-key-groupcomm]):
	* 'kty' identifies a key type "COSE_Key", as defined in		* 'kty' identifies a key type "COSE_Key", as defined in
	Section 8.2.		Section 8.2.
	* 'key', which contains a "COSE_Key" object (defined in		* 'key', which contains a "COSE_Key" object (defined in
	[RFC8152], containing:		[RFC8152], containing:
	+ 'kty' with value 4 (symmetric)		+ 'kty' with value 4 (symmetric)
	skipping to change at page 8, line 21 ¶		skipping to change at page 9, line 8 ¶
	* OPTIONALLY, 'exp' with the expiration time of the key		* OPTIONALLY, 'exp' with the expiration time of the key
	* 'pub_keys', containing the public keys of all authorized		* 'pub_keys', containing the public keys of all authorized
	signing members formatted as COSE_Keys, if the 'get_pub_keys'		signing members formatted as COSE_Keys, if the 'get_pub_keys'
	parameter was present and set to the empty array in the		parameter was present and set to the empty array in the
	Authorization + Key Distribution Request		Authorization + Key Distribution Request
	o the following fields from the Authorization Response (Section 3.2		o the following fields from the Authorization Response (Section 3.2
	of [I-D.ietf-ace-key-groupcomm]):		of [I-D.ietf-ace-key-groupcomm]):
	* 'profile' set to "coap_pubsub_app", as specified in Section 8.1		* 'profile' set to the corresponding value, see Section 3.2 or
			Section 3.3
	* OPTIONALLY 'scope', set to a CBOR array containing:		* OPTIONALLY 'scope', set to a CBOR array containing:
	+ the broker's topic as first element, and		+ the broker's topic as first element, and
	+ the string "publisher" if the client is an authorized		+ the string "publisher" if the client is an authorized
	publisher, "subscriber" if the client is an authorized		publisher, "subscriber" if the client is an authorized
	subscriber, or a CBOR array containing both, if the client		subscriber, or a CBOR array containing both, if the client
	is authorized to be both.		is authorized to be both.
	Examples for the response payload are detailed in Figure 6 and		Examples for the response payload are detailed in Figure 6 and
	Figure 9.		Figure 9.
			3.2. coap_pubsub_app Application Profile
			In case CoAP PubSub is used as communication protocol:
			o 'profile' set to "coap_pubsub_app", as specified in Section 8.1.1.
			3.3. mqtt_pubsub_app Application Profile
			In case mQTT PubSub is used as communication protocol:
			o 'profile' set to "mqtt_pubsub_app", as specified in Section 8.1.2.
	4. Publisher		4. Publisher
	In this section, it is specified how the Publisher requests, obtains		In this section, it is specified how the Publisher requests, obtains
	and communicates to the Broker the access token, as well as the		and communicates to the Broker the access token, as well as the
	retrieval of the keying material to protect the publication.		retrieval of the keying material to protect the publication.
	+----------------+ +----------------+		+----------------+ +----------------+
	| | | |		| | | |
	| Authorization | | Authorization |		| Authorization | | Authorization |
	| Server 1 | | Server 2 |		| Server 1 | | Server 2 |
	| | | |		| | | |
	+----------------+ +----------------+		+----------------+ +----------------+
	^ ^		^ ^
	| |		| |
	+---------(A)----+ |		+---------(A)----+ |
	| +--------------------(B)--------+		| +--------------------(B)--------+
	v v		v v
	+------------+ +------------+		+------------+ +------------+
	| CoAP | ----(C)---> | CoAP |		| | ----(C)---> | |
	| Client - | | Server - |
	| | | |
	| Publisher | | Broker |		| Publisher | | Broker |
			| | | |
			| | | |
	+------------+ +------------+		+------------+ +------------+
	Figure 4: Phase 1: Publisher side		Figure 4: Phase 1: Publisher side
	This is a combination of two independent phases:		This is a combination of two independent phases:
	o one is the establishment of a secure connection between Publisher		o one is the establishment of a secure connection between Publisher
	and Broker, using an ACE transport profile such as DTLS		and Broker, using an ACE transport profile such as DTLS
	[I-D.ietf-ace-dtls-authorize] or OSCORE		[I-D.ietf-ace-dtls-authorize], OSCORE
	[I-D.ietf-ace-oscore-profile]. (A)(C)		[I-D.ietf-ace-oscore-profile] or REF MQTT Profile. (A)(C)
	o the other is the Publisher's retrieval of keying material to		o the other is the Publisher's retrieval of keying material to
	protect the publication. (B)		protect the publication. (B)
	In detail:		In detail:
	(A) corresponds to the Access Token Request and Response between		(A) corresponds to the Access Token Request and Response between
	Publisher and Authorization Server to retrieve the Access Token and		Publisher and Authorization Server to retrieve the Access Token and
	RS (Broker) Information. As specified, the Publisher has the role of		RS (Broker) Information. As specified, the Publisher has the role of
	a CoAP client, the Broker has the role of the CoAP server.		a CoAP client, the Broker has the role of the CoAP server.
	(C) corresponds to the exchange between Publisher and Broker, where		(C) corresponds to the exchange between Publisher and Broker, where
	the Publisher sends its access token to the Broker and establishes a		the Publisher sends its access token to the Broker and establishes a
	secure connection with the Broker. Depending on the Information		secure connection with the Broker. Depending on the Information
	received in (A), this can be for example DTLS handshake, or other		received in (A), this can be for example DTLS handshake, or other
	protocols. Depending on the application, there may not be the need		protocols. Depending on the application, there may not be the need
	for this set up phase: for example, if OSCORE is used directly.		for this set up phase: for example, if OSCORE is used directly. Note
			that, in line with what defined in the ACE transport profile used,
			the access token includes the scope (i.e. pubsub topics on the
			Broker) the Publisher is allowed to publish to. For implementation
			semplicity, it is RECOMMENDED that the ACE transport profile used and
			this specification use the same format of "scope".
	(A) and (C) details are specified in the profile used.		(A) and (C) details are specified in the profile used.
	(B) corresponds to the retrieval of the keying material to protect		(B) corresponds to the retrieval of the keying material to protect
	the publication end-to-end with the subscribers (see Section 6.1),		the publication end-to-end with the subscribers (see Section 6.1),
	and uses [I-D.ietf-ace-key-groupcomm]. The details are defined in		and uses [I-D.ietf-ace-key-groupcomm]. The details are defined in
	Section 3.1.		Section 3.1.
			4.1. CoAP Publisher
	An example of the payload of an Authorization + Joining Request and		An example of the payload of an Authorization + Joining Request and
	corresponding Response for a Publisher is specified in Figure 5 and		corresponding Response for a CoAP Publisher using CoAP and CBOR is
	Figure 6, where SIG is a signature computed using the private key		specified in Figure 5 and Figure 6, where SIG is a signature computed
	associated to the public key and the algorithm in "client_cred".		using the private key associated to the public key and the algorithm
			in "client_cred".
	{		{
	"scope" : ["Broker1/Temp", "publisher"],		"scope" : ["Broker1/Temp", "publisher"],
	"client_id" : "publisher1",		"client_id" : "publisher1",
	"client_cred" :		"client_cred" :
	{ / COSE_Key /		{ / COSE_Key /
	/ type / 1 : 2, / EC2 /		/ type / 1 : 2, / EC2 /
	/ kid / 2 : h'11',		/ kid / 2 : h'11',
	/ alg / 3 : -7, / ECDSA with SHA-256 /		/ alg / 3 : -7, / ECDSA with SHA-256 /
	/ crv / -1 : 1 , / P-256 /		/ crv / -1 : 1 , / P-256 /
	skipping to change at page 10, line 41 ¶		skipping to change at page 12, line 5 ¶
	{		{
	"profile" : "coap_pubsub_app",		"profile" : "coap_pubsub_app",
	"kty" : "COSE_Key",		"kty" : "COSE_Key",
	"key" : {1: 4, 2: h'1234', 3: 12, 5: h'1f389d14d17dc7',		"key" : {1: 4, 2: h'1234', 3: 12, 5: h'1f389d14d17dc7',
	-1: h'02e2cc3a9b92855220f255fff1c615bc'}		-1: h'02e2cc3a9b92855220f255fff1c615bc'}
	}		}
	Figure 6: Authorization + Joining Response payload for a Publisher		Figure 6: Authorization + Joining Response payload for a Publisher
			4.2. MQTT Publisher
			TODO
	5. Subscriber		5. Subscriber
	In this section, it is specified how the Subscriber retrieves the		In this section, it is specified how the Subscriber retrieves the
	keying material to protect the publication.		keying material to protect the publication.
	+----------------+		+----------------+
	| |		| |
	| Authorization |		| Authorization |
	| Server 2 |		| Server 2 |
	| |		| |
	+----------------+		+----------------+
	^		^
	|		|
	+-----(D)------+		+-----(D)------+
	|		|
	v		v
	+------------+		+------------+
	| CoAP |
	| Client - |
	| |		| |
	| Subscriber |		| Subscriber |
	| |		| |
			| |
	+------------+		+------------+
	Figure 7: Phase 2: Subscriber side		Figure 7: Phase 2: Subscriber side
	Step (D) between Subscriber and AS2 corresponds to the retrieval of		Step (D) between Subscriber and AS2 corresponds to the retrieval of
	the keying material to verify the publication end-to-end with the		the keying material to verify the publication end-to-end with the
	publishers (see Section 6.1). The details are defined in Section 3.1		publishers (see Section 6.1). The details are defined in Section 3.1
	This step is the same as (B) between Publisher and AS2 (Section 3.1),		This step is the same as (B) between Publisher and AS2 (Section 3.1),
	with the following differences:		with the following differences:
	skipping to change at page 11, line 43 ¶		skipping to change at page 13, line 5 ¶
	o The Authorization + Joining Request MUST NOT contain the		o The Authorization + Joining Request MUST NOT contain the
	'client_cred parameter', the role element in the 'scope' parameter		'client_cred parameter', the role element in the 'scope' parameter
	MUST be set to "subscriber". The Subscriber MUST have access to		MUST be set to "subscriber". The Subscriber MUST have access to
	the public keys of all the Publishers; this MAY be achieved in the		the public keys of all the Publishers; this MAY be achieved in the
	Authorization + Joining Request by using the parameter		Authorization + Joining Request by using the parameter
	'get_pub_keys' set to empty array.		'get_pub_keys' set to empty array.
	o The Authorization + Key Distribution Response MUST contain the		o The Authorization + Key Distribution Response MUST contain the
	'pub_keys' parameter.		'pub_keys' parameter.
			5.1. CoAP Subscriber
	An example of the payload of an Authorization + Joining Request and		An example of the payload of an Authorization + Joining Request and
	corresponding Response for a Subscriber is specified in Figure 8 and		corresponding Response for a CoAP Subscriber using CoAP and CBOR is
	Figure 9.		specified in Figure 8 and Figure 9.
	{		{
	"scope" : ["Broker1/Temp", "subscriber"],		"scope" : ["Broker1/Temp", "subscriber"],
	"get_pub_keys" : [ ]		"get_pub_keys" : [ ]
	}		}
	Figure 8: Authorization + Joining Request payload for a Subscriber		Figure 8: Authorization + Joining Request payload for a Subscriber
	{		{
	"profile" : "coap_pubsub_app",		"profile" : "coap_pubsub_app",
	skipping to change at page 12, line 27 ¶		skipping to change at page 13, line 40 ¶
	-2 : h'65eda5a12577c2bae829437fe338701a10aaa375e1bb5b5de108de43		-2 : h'65eda5a12577c2bae829437fe338701a10aaa375e1bb5b5de108de43
	9c08551d', / x /		9c08551d', / x /
	-3 : h'1e52ed75701163f7f9e40ddf9f341b3dc9ba860af7e0ca7ca7e9eecd		-3 : h'1e52ed75701163f7f9e40ddf9f341b3dc9ba860af7e0ca7ca7e9eecd
	0084d19c' / y /		0084d19c' / y /
	}		}
	]		]
	}		}
	Figure 9: Authorization + Joining Response payload for a Subscriber		Figure 9: Authorization + Joining Response payload for a Subscriber
			5.2. MQTT Subscriber
			TODO
	6. Pub-Sub Protected Communication		6. Pub-Sub Protected Communication
	This section specifies the communication Publisher-Broker and		This section specifies the communication Publisher-Broker and
	Subscriber-Broker, after the previous phases have taken place. The		Subscriber-Broker, after the previous phases have taken place. The
	operations of publishing and subscribing are defined in		operations of publishing and subscribing are defined in
	[I-D.ietf-core-coap-pubsub].		[I-D.ietf-core-coap-pubsub].
	+------------+ +------------+ +------------+		+------------+ +------------+ +------------+
	| CoAP | | CoAP | | CoAP |		| | | | | |
	| Client - | | Server - | | Client - |		| Publisher | ----(E)---> | Broker | | Subscriber |
	| | ----(E)---> | | | |		| | | | <----(F)---- | |
	| Publisher | | Broker | <----(F)---- | Subscriber |
	| | | | -----(G)---> | |		| | | | -----(G)---> | |
	+------------+ +------------+ +------------+		+------------+ +------------+ +------------+
	Figure 10: Phase 3: Secure communication between Publisher and		Figure 10: Phase 3: Secure communication between Publisher and
	Subscriber		Subscriber
	The (E) message corresponds to the publication of a topic on the		The (E) message corresponds to the publication of a topic on the
	Broker. The publication (the resource representation) is protected		Broker. The publication (the resource representation) is protected
	with COSE ([RFC8152]). The (F) message is the subscription of the		with COSE ([RFC8152]). The (F) message is the subscription of the
	Subscriber, which is unprotected, unless a profile of ACE		Subscriber, which is unprotected, unless a profile of ACE
	skipping to change at page 13, line 21 ¶		skipping to change at page 14, line 39 ¶
	| | |		| | |
	| | ---- response ------> |		| | ---- response ------> |
	| | protected with COSE |		| | protected with COSE |
	Figure 11: (E), (F), (G): Example of protected communication		Figure 11: (E), (F), (G): Example of protected communication
	6.1. Using COSE Objects To Protect The Resource Representation		6.1. Using COSE Objects To Protect The Resource Representation
	The Publisher uses the symmetric COSE Key received from AS2 in		The Publisher uses the symmetric COSE Key received from AS2 in
	exchange B (Section 3.1) to protect the payload of the PUBLISH		exchange B (Section 3.1) to protect the payload of the PUBLISH
	operation (Section 4.3 of [I-D.ietf-core-coap-pubsub]).		operation (Section 4.3 of [I-D.ietf-core-coap-pubsub] and REF MQTT).
	Specifically, the COSE Key is used to create a COSE_Encrypt0 with		Specifically, the COSE Key is used to create a COSE_Encrypt0 with
	algorithm specified by AS2. The Publisher uses the private key		algorithm specified by AS2. The Publisher uses the private key
	corresponding to the public key sent to the AS2 in exchange B		corresponding to the public key sent to the AS2 in exchange B
	(Section 3.1) to countersign the COSE Object as specified in		(Section 3.1) to countersign the COSE Object as specified in
	Section 4.5 of [RFC8152]. The CoAP payload is replaced by the COSE		Section 4.5 of [RFC8152]. The CoAP payload is replaced by the COSE
	object before the publication is sent to the Broker.		object before the publication is sent to the Broker.
	The Subscriber uses the kid in the countersignature field in the COSE		The Subscriber uses the kid in the countersignature field in the COSE
	object to retrieve the right public key to verify the		object to retrieve the right public key to verify the
	countersignature. It then uses the symmetric key received from AS2		countersignature. It then uses the symmetric key received from AS2
	skipping to change at page 15, line 40 ¶		skipping to change at page 17, line 29 ¶
	8.1. ACE Groupcomm Profile Registry		8.1. ACE Groupcomm Profile Registry
	The following registrations are done for the "ACE Groupcomm Profile"		The following registrations are done for the "ACE Groupcomm Profile"
	Registry following the procedure specified in		Registry following the procedure specified in
	[I-D.ietf-ace-key-groupcomm].		[I-D.ietf-ace-key-groupcomm].
	Note to RFC Editor: Please replace all occurrences of "[[This		Note to RFC Editor: Please replace all occurrences of "[[This
	document]]" with the RFC number of this specification and delete this		document]]" with the RFC number of this specification and delete this
	paragraph.		paragraph.
			8.1.1. CoAP Profile Registration
	Name: coap_pubsub_app		Name: coap_pubsub_app
	Description: Profile for delegating client authentication and		Description: Profile for delegating client authentication and
	authorization for publishers and subscribers in a pub-sub setting		authorization for publishers and subscribers in a CoAP pub-sub
	scenario in a constrained environment.		setting scenario in a constrained environment.
			CBOR Key: TBD
			Reference: [[This document]]
			8.1.2. CoAP Profile Registration
			Name: mqtt_pubsub_app
			Description: Profile for delegating client authentication and
			authorization for publishers and subscribers in a MQTT pub-sub
			setting scenario in a constrained environment.
	CBOR Key: TBD		CBOR Key: TBD
	Reference: [[This document]]		Reference: [[This document]]
	8.2. ACE Groupcomm Key Registry		8.2. ACE Groupcomm Key Registry
	The following registrations are done for the ACE Groupcomm Key		The following registrations are done for the ACE Groupcomm Key
	Registry following the procedure specified in		Registry following the procedure specified in
	[I-D.ietf-ace-key-groupcomm].		[I-D.ietf-ace-key-groupcomm].
	skipping to change at page 16, line 31 ¶		skipping to change at page 18, line 31 ¶
	Description: COSE_Key object		Description: COSE_Key object
	References: [RFC8152], [[This document]]		References: [RFC8152], [[This document]]
	9. References		9. References
	9.1. Normative References		9.1. Normative References
	[I-D.ietf-ace-key-groupcomm]		[I-D.ietf-ace-key-groupcomm]
	Palombini, F. and M. Tiloca, "Key Provisioning for Group		Palombini, F. and M. Tiloca, "Key Provisioning for Group
	Communication using ACE", draft-ietf-ace-key-groupcomm-03		Communication using ACE", draft-ietf-ace-key-groupcomm-07
	(work in progress), November 2019.		(work in progress), June 2020.
	[I-D.ietf-ace-oauth-authz]		[I-D.ietf-ace-oauth-authz]
	Seitz, L., Selander, G., Wahlstroem, E., Erdtman, S., and		Seitz, L., Selander, G., Wahlstroem, E., Erdtman, S., and
	H. Tschofenig, "Authentication and Authorization for		H. Tschofenig, "Authentication and Authorization for
	Constrained Environments (ACE) using the OAuth 2.0		Constrained Environments (ACE) using the OAuth 2.0
	Framework (ACE-OAuth)", draft-ietf-ace-oauth-authz-29		Framework (ACE-OAuth)", draft-ietf-ace-oauth-authz-35
	(work in progress), December 2019.		(work in progress), June 2020.
	[I-D.ietf-core-coap-pubsub]		[I-D.ietf-core-coap-pubsub]
	Koster, M., Keranen, A., and J. Jimenez, "Publish-		Koster, M., Keranen, A., and J. Jimenez, "Publish-
	Subscribe Broker for the Constrained Application Protocol		Subscribe Broker for the Constrained Application Protocol
	(CoAP)", draft-ietf-core-coap-pubsub-09 (work in		(CoAP)", draft-ietf-core-coap-pubsub-09 (work in
	progress), September 2019.		progress), September 2019.
	[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate		[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
	Requirement Levels", BCP 14, RFC 2119,		Requirement Levels", BCP 14, RFC 2119,
	DOI 10.17487/RFC2119, March 1997,		DOI 10.17487/RFC2119, March 1997,
	<https://www.rfc-editor.org/info/rfc2119>.		<https://www.rfc-editor.org/info/rfc2119>.
	[RFC6749] Hardt, D., Ed., "The OAuth 2.0 Authorization Framework",		[RFC6749] Hardt, D., Ed., "The OAuth 2.0 Authorization Framework",
	RFC 6749, DOI 10.17487/RFC6749, October 2012,		RFC 6749, DOI 10.17487/RFC6749, October 2012,
	<https://www.rfc-editor.org/info/rfc6749>.		<https://www.rfc-editor.org/info/rfc6749>.
			[RFC7049] Bormann, C. and P. Hoffman, "Concise Binary Object
			Representation (CBOR)", RFC 7049, DOI 10.17487/RFC7049,
			October 2013, <https://www.rfc-editor.org/info/rfc7049>.
	[RFC8152] Schaad, J., "CBOR Object Signing and Encryption (COSE)",		[RFC8152] Schaad, J., "CBOR Object Signing and Encryption (COSE)",
	RFC 8152, DOI 10.17487/RFC8152, July 2017,		RFC 8152, DOI 10.17487/RFC8152, July 2017,
	<https://www.rfc-editor.org/info/rfc8152>.		<https://www.rfc-editor.org/info/rfc8152>.
	9.2. Informative References		9.2. Informative References
	[I-D.ietf-ace-actors]		[I-D.ietf-ace-actors]
	Gerdes, S., Seitz, L., Selander, G., and C. Bormann, "An		Gerdes, S., Seitz, L., Selander, G., and C. Bormann, "An
	architecture for authorization in constrained		architecture for authorization in constrained
	environments", draft-ietf-ace-actors-07 (work in		environments", draft-ietf-ace-actors-07 (work in
	progress), October 2018.		progress), October 2018.
	[I-D.ietf-ace-dtls-authorize]		[I-D.ietf-ace-dtls-authorize]
	Gerdes, S., Bergmann, O., Bormann, C., Selander, G., and		Gerdes, S., Bergmann, O., Bormann, C., Selander, G., and
	L. Seitz, "Datagram Transport Layer Security (DTLS)		L. Seitz, "Datagram Transport Layer Security (DTLS)
	Profile for Authentication and Authorization for		Profile for Authentication and Authorization for
	Constrained Environments (ACE)", draft-ietf-ace-dtls-		Constrained Environments (ACE)", draft-ietf-ace-dtls-
	authorize-09 (work in progress), December 2019.		authorize-11 (work in progress), June 2020.
	[I-D.ietf-ace-oscore-profile]		[I-D.ietf-ace-oscore-profile]
	Palombini, F., Seitz, L., Selander, G., and M. Gunnarsson,		Palombini, F., Seitz, L., Selander, G., and M. Gunnarsson,
	"OSCORE profile of the Authentication and Authorization		"OSCORE profile of the Authentication and Authorization
	for Constrained Environments Framework", draft-ietf-ace-		for Constrained Environments Framework", draft-ietf-ace-
	oscore-profile-08 (work in progress), July 2019.		oscore-profile-11 (work in progress), June 2020.
			[RFC8259] Bray, T., Ed., "The JavaScript Object Notation (JSON) Data
			Interchange Format", STD 90, RFC 8259,
			DOI 10.17487/RFC8259, December 2017,
			<https://www.rfc-editor.org/info/rfc8259>.
	Appendix A. Requirements on Application Profiles		Appendix A. Requirements on Application Profiles
	This section lists the specifications on this profile based on the		This section lists the specifications on this profile based on the
	requirements defined in Appendix A of [I-D.ietf-ace-key-groupcomm]		requirements defined in Appendix A of [I-D.ietf-ace-key-groupcomm]
	o REQ1: Specify the encoding and value of the identifier of group or		o REQ1: Specify the encoding and value of the identifier of group or
	topic of 'scope': see Section 3.1).		topic of 'scope': see Section 3.1).
	o REQ2: Specify the encoding and value of roles of 'scope': see		o REQ2: Specify the encoding and value of roles of 'scope': see
	skipping to change at page 19, line 16 ¶		skipping to change at page 21, line 26 ¶
	'mgt_key_material': not defined		'mgt_key_material': not defined
	o OPT4: Optionally, specify policies that instruct clients to retain		o OPT4: Optionally, specify policies that instruct clients to retain
	unsuccessfully decrypted messages and for how long, so that they		unsuccessfully decrypted messages and for how long, so that they
	can be decrypted after getting updated keying material: not		can be decrypted after getting updated keying material: not
	defined		defined
	Acknowledgments		Acknowledgments
	The author wishes to thank Ari Keraenen, John Mattsson, Ludwig Seitz,		The author wishes to thank Ari Keraenen, John Mattsson, Ludwig Seitz,
	Goeran Selander, Jim Schaad and Marco Tiloca for the useful		Goeran Selander, Cigdem Sengul, Jim Schaad and Marco Tiloca for the
	discussion and reviews that helped shape this document.		useful discussion and reviews that helped shape this document.
	Author's Address		Author's Address
	Francesca Palombini		Francesca Palombini
	Ericsson		Ericsson
	Email: francesca.palombini@ericsson.com		Email: francesca.palombini@ericsson.com
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