draft-ietf-ace-oscore-profile-02.txt		draft-ietf-ace-oscore-profile-03.txt
	ACE Working Group L. Seitz		ACE Working Group L. Seitz
	Internet-Draft RISE SICS AB		Internet-Draft RISE SICS AB
	Intended status: Standards Track F. Palombini		Intended status: Standards Track F. Palombini
	Expires: December 30, 2018 Ericsson AB		Expires: April 4, 2019 Ericsson AB
	M. Gunnarsson		M. Gunnarsson
	RISE SICS AB		RISE SICS AB
	G. Selander		G. Selander
	Ericsson AB		Ericsson AB
	June 28, 2018		October 1, 2018
	OSCORE profile of the Authentication and Authorization for Constrained		OSCORE profile of the Authentication and Authorization for Constrained
	Environments Framework		Environments Framework
	draft-ietf-ace-oscore-profile-02		draft-ietf-ace-oscore-profile-03
	Abstract		Abstract
	This memo specifies a profile for the Authentication and		This memo specifies a profile for the Authentication and
	Authorization for Constrained Environments (ACE) framework. It		Authorization for Constrained Environments (ACE) framework. It
	utilizes Object Security for Constrained RESTful Environments		utilizes Object Security for Constrained RESTful Environments
	(OSCORE) to provide communication security, server authentication,		(OSCORE) to provide communication security, server authentication,
	and proof-of-possession for a key owned by the client and bound to an		and proof-of-possession for a key owned by the client and bound to an
	OAuth 2.0 access token.		OAuth 2.0 access token.
	skipping to change at page 1, line 41 ¶		skipping to change at page 1, line 41 ¶
	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 December 30, 2018.		This Internet-Draft will expire on April 4, 2019.
	Copyright Notice		Copyright Notice
	Copyright (c) 2018 IETF Trust and the persons identified as the		Copyright (c) 2018 IETF Trust and the persons identified as the
	document authors. All rights reserved.		document authors. All rights reserved.
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	to this document. Code Components extracted from this document must		to this document. Code Components extracted from this document must
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	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 . . . . . . . . . . . . . . . . . . . . . . . 3		1.1. Terminology . . . . . . . . . . . . . . . . . . . . . . . 3
	2. Client to Resource Server . . . . . . . . . . . . . . . . . . 3		2. Protocol Overview . . . . . . . . . . . . . . . . . . . . . . 3
	2.1. Signaling the use of OSCORE . . . . . . . . . . . . . . . 3		3. Client-AS Communication . . . . . . . . . . . . . . . . . . . 5
	2.2. Key establishment for OSCORE . . . . . . . . . . . . . . 4		3.1. C-to-AS: POST /token . . . . . . . . . . . . . . . . . . 5
	3. Client to Authorization Server . . . . . . . . . . . . . . . 8		3.2. AS-to-C: Access Token . . . . . . . . . . . . . . . . . . 6
	4. Resource Server to Authorization Server . . . . . . . . . . . 8		4. Client-RS Communication . . . . . . . . . . . . . . . . . . . 11
	5. Security Considerations . . . . . . . . . . . . . . . . . . . 8		4.1. C-to-RS: POST /authz-info . . . . . . . . . . . . . . . . 11
	6. Privacy Considerations . . . . . . . . . . . . . . . . . . . 9		4.2. RS-to-C: 2.01 (Created) . . . . . . . . . . . . . . . . . 11
	7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 9		4.3. OSCORE Setup . . . . . . . . . . . . . . . . . . . . . . 12
	8. References . . . . . . . . . . . . . . . . . . . . . . . . . 10		4.4. Access rights verification . . . . . . . . . . . . . . . 13
	8.1. Normative References . . . . . . . . . . . . . . . . . . 10		5. Secure Communication with AS . . . . . . . . . . . . . . . . 14
	8.2. Informative References . . . . . . . . . . . . . . . . . 11		6. Security Considerations . . . . . . . . . . . . . . . . . . . 14
	Appendix A. Profile Requirements . . . . . . . . . . . . . . . . 11		7. Privacy Considerations . . . . . . . . . . . . . . . . . . . 15
	Appendix B. Using the pop-key with EDHOC (EDHOC+OSCORE) . . . . 12		8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 15
	B.1. Using Asymmetric Keys . . . . . . . . . . . . . . . . . . 13		9. References . . . . . . . . . . . . . . . . . . . . . . . . . 16
	B.2. Using Symmetric Keys . . . . . . . . . . . . . . . . . . 14		9.1. Normative References . . . . . . . . . . . . . . . . . . 16
	B.3. Processing . . . . . . . . . . . . . . . . . . . . . . . 16		9.2. Informative References . . . . . . . . . . . . . . . . . 17
	Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . . 17		Appendix A. Profile Requirements . . . . . . . . . . . . . . . . 17
	Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 18		Appendix B. Using the pop-key with EDHOC (EDHOC+OSCORE) . . . . 18
			B.1. Using Asymmetric Keys . . . . . . . . . . . . . . . . . . 18
			B.2. Using Symmetric Keys . . . . . . . . . . . . . . . . . . 20
			B.3. Processing . . . . . . . . . . . . . . . . . . . . . . . 22
			Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . . 23
			Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 24
	1. Introduction		1. Introduction
	This memo specifies a profile of the ACE framework		This memo specifies a profile of the ACE framework
	[I-D.ietf-ace-oauth-authz]. In this profile, a client and a resource		[I-D.ietf-ace-oauth-authz]. In this profile, a client and a resource
	server use CoAP [RFC7252] to communicate. The client uses an access		server use CoAP [RFC7252] to communicate. The client uses an access
	token, bound to a key (the proof-of-possession key) to authorize its		token, bound to a key (the proof-of-possession key) to authorize its
	access to the resource server. In order to provide communication		access to the resource server. In order to provide communication
	security, proof of possession, and server authentication they use		security, proof of possession, and server authentication they use
	Object Security for Constrained RESTful Environments (OSCORE)		Object Security for Constrained RESTful Environments (OSCORE)
	[I-D.ietf-core-object-security]. Optionally the client and the		[I-D.ietf-core-object-security].
	resource server may also use CoAP and OSCORE to communicate with the
	authorization server.
	OSCORE specifies how to use CBOR Object Signing and Encryption (COSE)		OSCORE specifies how to use CBOR Object Signing and Encryption (COSE)
	[RFC8152] to secure CoAP messages. In order to provide replay and		[RFC8152] to secure CoAP messages. Note that OSCORE can be used to
	reordering protection OSCORE also introduces sequence numbers that		secure CoAP messages, as well as HTTP and combinations of HTTP and
	are used together with COSE.		CoAP; a profile of ACE similar to the one described in this document,
			with the difference of using HTTP instead of CoAP as communication
	Note that OSCORE can be used to secure CoAP messages, as well as HTTP		protocol, could be specified analogously to this one.
	and combinations of HTTP and CoAP; a profile of ACE similar to the
	one described in this document, with the difference of using HTTP
	instead of CoAP as communication protocol, could be specified
	analogously to this one.
	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 [RFC2119]. These		document are to be interpreted as described in [RFC2119]. These
	words may also appear in this document in lowercase, absent their		words may also appear in this document in lowercase, absent their
	normative meanings.		normative meanings.
	Certain security-related terms such as "authentication",		Certain security-related terms such as "authentication",
	"authorization", "confidentiality", "(data) integrity", "message		"authorization", "confidentiality", "(data) integrity", "message
	authentication code", and "verify" are taken from [RFC4949].		authentication code", and "verify" are taken from [RFC4949].
	Since we describe exchanges as RESTful protocol interactions HTTP		RESTful terminology follows HTTP [RFC7231].
	[RFC7231] offers useful terminology.
	Terminology for entities in the architecture is defined in OAuth 2.0		Terminology for entities in the architecture is defined in OAuth 2.0
	[RFC6749] and [I-D.ietf-ace-actors], such as client (C), resource		[RFC6749], such as client (C), resource server (RS), and
	server (RS), and authorization server (AS). It is assumed in this		authorization server (AS). It is assumed in this document that a
	document that a given resource on a specific RS is associated to a		given resource on a specific RS is associated to a unique AS.
	unique AS.
	2. Client to Resource Server		2. Protocol Overview
	The use of OSCORE for arbitrary CoAP messages is specified in		This section gives an overview on how to use the ACE Framework
	[I-D.ietf-core-object-security]. This section defines the specific		[I-D.ietf-ace-oauth-authz] to secure the communication between a
	uses and their purpose for securing the communication between a		client and a resource server using OSCORE
	client and a resource server, and the parameters needed to negotiate		[I-D.ietf-core-object-security]. The parameters needed to negotiate
	the use of this profile with the token resource at the authorization		the use of this profile with the token resource at the authorization
	server as specified in section 5.6 of [I-D.ietf-ace-oauth-authz].		server as specified in section 5.6 of [I-D.ietf-ace-oauth-authz] are
			described in detail in the following sections.
	2.1. Signaling the use of OSCORE		This profile requires a client to retrieve an access token from the
			AS for the resource it wants to access on a RS, using the token
			endpoint, as specified in section 5.6.1 of
			[I-D.ietf-ace-oauth-authz]. To determine the AS in charge of a
			resource hosted at the RS, the client C MAY send an initial
			Unauthorized Resource Request message to the RS. The RS then denies
			the request and sends the address of its AS back to the client C as
			specified in section 5.1 of [I-D.ietf-ace-oauth-authz]. The access
			token request and response MUST be confidentiality-protected and
			ensure authenticity. This profile RECOMMENDS the use of OSCORE
			between client and AS, but TLS or DTLS MAY be used additionally or
			instead.
	A client requests a token at an AS via the /token resource. This		Once the client has retrieved the access token, it forwards it to the
	follows the message formats specified in section 5.6.1 of		RS using the authz-info endpoint and mechanisms specified in section
			5.8.1. of [I-D.ietf-ace-oauth-authz]. If the access token is valid,
			the RS replies to this request with a 2.01 (Created) response, which
			contains a nonce N1.
			After receiving the nonce N1, the client generates a nonce N2,
			concatenates it with N1 and sets the ID Context in its Security
			Context (see section 3 of [I-D.ietf-core-object-security]) to N1
			concatenated with N2. The client then derives the complete Security
			Context from the ID Context plus the parameters received from the AS.
			Finally, the client sends a request protected with OSCORE to the RS.
			This message contains the ID Context value. When receiving this
			request after the 2.01 (Created) response, the server extract the ID
			Context from it, verifies that the first part is equal to the nonce
			N1 it previously sent, and if so, sets its own ID Context and derives
			the complete Security Context from it plus the parameters received in
			the AS, following section 3.2 of [I-D.ietf-core-object-security]. If
			the request verifies, then this Security Context is stored in the
			server, and used in the response, and in further communications with
			the client, until token expiration. The client will not include the
			ID Context value in further requests.
			An overview of the profile flow for the OSCORE profile is given in
			Figure 1.
			C RS AS
			| [-- Resource Request --->] | |
			| | |
			| [<----- AS Information --] | |
			| | |
			| ----- POST /token ----------------------------> |
			| | |
			| <---------------------------- Access Token ----- |
			| + RS Information |
			| ---- POST /authz-info ---> | |
			| | |
			| <--- 2.01 Created (N1) --- | |
			| | |
			/Sec Context Derivation/ | |
			| | |
			| ---- OSCORE Request -----> | |
			| (N1, N2) | |
			| | |
			| /Sec Context Derivation/ |
			| | |
			| <--- OSCORE Response ----- | |
			| | |
			| ---- OSCORE Request -----> | |
			| | |
			| <--- OSCORE Response ----- | |
			| ... | |
			Figure 1: Protocol Overview
			3. Client-AS Communication
			The following subsections describe the details of the POST /token
			request and response between client and AS. Section 3.2 of
			[I-D.ietf-core-object-security] defines how to derive a security
			context based on a shared master secret and a set of other
			parameters, established between client and server, which the client
			receives from the AS in this exchange. The proof-of-possession key
			(pop-key) provisioned from the AS MUST be used as master secret in
			OSCORE.
			3.1. C-to-AS: POST /token
			The client-to-AS request is specified in Section 5.6.1 of
	[I-D.ietf-ace-oauth-authz].		[I-D.ietf-ace-oauth-authz].
	The AS responding to a successful access token request as defined in		If the client wants to update its access rights using the same OSCORE
	section 5.6.2 of [I-D.ietf-ace-oauth-authz] can signal that the use		Security Context, it MUST include in its POST /token request a cnf
	of OSCORE is REQUIRED for a specific access token by including the		object carrying the Sender ID in the kid field. This identifier can
	"profile" parameter with the value "coap_oscore" in the access token		be used by the AS to determine the shared secret to construct the
	response. This means that the client MUST use OSCORE towards all		proof-of-possession token and therefore MUST specify a symmetric key
	resource servers for which this access token is valid, and follow		that was previously generated by the AS as a shared secret for the
	Section 2.2 to derive the security context to run OSCORE.		communication between the client and the RS.
	The error response procedures defined in section 5.6.3 of the ACE		The client MUST send this POST /token request over a secure channel
	framework are unchanged by this profile.		that guarantees authentication, message integrity and confidentiality
			(see Section 5).
	Note the the client and the authorization server MAY OPTIONALLY use		An example of such a request, in CBOR diagnostic notation without the
	OSCORE to protect the interaction via the /token resource. See		tag and value abbreviations is reported in Figure 2
	Section 3 for details.
	2.2. Key establishment for OSCORE		Header: POST (Code=0.02)
			Uri-Host: "as.example.com"
			Uri-Path: "token"
			Content-Format: "application/ace+cbor"
			Payload:
			{
			"grant_type" : "client_credentials",
			"client_id" : "myclient",
			"aud" : "tempSensor4711"
			}
	Section 3.2 of [I-D.ietf-core-object-security] defines how to derive		Figure 2: Example C-to-AS POST /token request for an access token
	a security context based on a shared master secret and a set of other		bound to a symmetric key.
	parameters, established between client and server. The proof-of-
	possession key (pop-key) provisioned from the AS MAY, in case of pre-
	shared keys, be used directly as master secret in OSCORE.
	If OSCORE is used directly with the symmetric pop-key as master		3.2. AS-to-C: Access Token
	secret, then the AS MUST provision the following data, in response to
	the access token request:
	o a master secret		After verifying the POST /token request and that the client is
			authorized to obtain an access token corresponding to its access
			token request, the AS responds as defined in section 5.6.2 of
			[I-D.ietf-ace-oauth-authz]. It signals that the use of OSCORE is
			REQUIRED for a specific access token by including the "profile"
			parameter with the value "coap_oscore" in the access token response.
			This means that the client MUST use OSCORE towards all resource
			servers for which this access token is valid, and follow Section 4.3
			to derive the security context to run OSCORE.
	o the sender identifier		The error response procedures defined in section 5.6.3 of the ACE
			framework are unchanged by this profile.
	o the recipient identifier		Moreover, the AS MUST provision the following data:
			o a master secret
			o a client identifier
			o a server identifier
	Additionally, the AS MAY provision the following data, in the same		Additionally, the AS MAY provision the following data, in the same
	response. In case these parameters are omitted, the default values		response.
	are used as described in section 3.2 of
	[I-D.ietf-core-object-security].
	o an AEAD algorithm		o an AEAD algorithm
	o a KDF algorithm		o an HKDF algorithm
	o a salt		o a salt
	o a replay window type and size		o a replay window type and size
	The master secret MUST be communicated as COSE_Key in the 'cnf'		The master secret MUST be communicated as COSE_Key in the 'cnf'
	parameter of the access token response as defined in Section 5.6.4.5		parameter of the access token response as defined in Section 5.6.4.5
	of [I-D.ietf-ace-oauth-authz]. The AEAD algorithm MAY be included as		of [I-D.ietf-ace-oauth-authz]. The AEAD algorithm MAY be included as
	the 'alg' parameter in the COSE_Key; the KDF algorithm MAY be		the 'alg' parameter in the COSE_Key; the HKDF algorithm MAY be
	included as the 'kdf' parameter of the COSE_Key and the salt MAY be		included as the 'hkdf' parameter of the COSE_Key and the salt MAY be
	included as the 'slt' parameter of the COSE_Key as defined in table		included as the 'slt' parameter of the COSE_Key as defined in
	1.		Figure 3.
	The same parameters MUST be included as metadata of the access token;		The same parameters MUST be included as metadata of the access token.
	if the token is a CWT [RFC8392], the same COSE_Key structure MUST be		This profile RECOMMENDS the use of CBOR web token (CWT) as specified
	placed in the 'cnf' claim of this token. If a CWT is used it MUST be		in [RFC8392]. If the token is a CWT, the same COSE_Key structure
	encrypted, since the token is transferred from the client to the RS		defined above MUST be placed in the 'cnf' claim of this token.
	over an unprotected channel.
	The AS MUST also assign identifiers to both client and RS, which are		The AS MUST also assign identifiers to both client and RS, which are
	then used as Sender ID and Recipient ID in the OSCORE context as		then used as Sender ID and Recipient ID in the OSCORE context as
	described in section 3.1 of [I-D.ietf-core-object-security]. These		described in section 3.1 of [I-D.ietf-core-object-security]. These
	identifiers MUST be unique in the set of all clients and RS		identifiers MUST be unique in the set of all clients and RS
	identifiers for a certain AS. Moreover, these MUST be included in		identifiers for a certain AS. Moreover, these MUST be included in
	the COSE_Key as header parameters, as defined in table 1.		the COSE_Key as header parameters, as defined in Figure 3.
	We assume in this document that a resource is associated to one		We assume in this document that a resource is associated to one
	single AS, which makes it possible to assume unique identifiers for		single AS, which makes it possible to assume unique identifiers for
	each client requesting a particular resource to a RS. If this is not		each client requesting a particular resource to a RS. If this is not
	the case, collisions of identifiers may appear in the RS, in which		the case, collisions of identifiers may appear in the RS, in which
	case the RS needs to have a mechanism in place to disambiguate		case the RS needs to have a mechanism in place to disambiguate
	identifiers or mitigate their effect.		identifiers or mitigate their effect.
	Note that C should set the Sender ID of its security context to the		Note that C should set the Sender ID of its Security Context to the
	clientId value received and the Recipient ID to the serverId value,		clientId value received and the Recipient ID to the serverId value,
	and RS should do the opposite.		and RS should do the opposite.
	+----------+-------+--------------+------------+-------------------+		+----------+-------+--------------+------------+-------------------+
	| name | label | CBOR type | registry | description |		| name | label | CBOR type | registry | description |
	+----------+-------+--------------+------------+-------------------+		+----------+-------+--------------+------------+-------------------+
	| clientId | TBD1 | bstr | | Identifies the |		| clientId | TBD1 | bstr | | Identifies the |
	| | | | | client in an |		| | | | | client in an |
	| | | | | OSCORE context |		| | | | | OSCORE context |
	| | | | | using this key |		| | | | | using this key |
	| | | | | |		| | | | | |
	| serverId | TBD2 | bstr | | Identifies the |		| serverId | TBD2 | bstr | | Identifies the |
	| | | | | server in an |		| | | | | server in an |
	| | | | | OSCORE context |		| | | | | OSCORE context |
	| | | | | using this key |		| | | | | using this key |
	| | | | | |		| | | | | |
	| kdf | TBD3 | bstr | | Identifies the |		| hkdf | TBD3 | bstr | | Identifies the |
	| | | | | KDF algorithm in |		| | | | | KDF algorithm in |
	| | | | | an OSCORE context |		| | | | | an OSCORE context |
	| | | | | using this key |		| | | | | using this key |
	| | | | | |		| | | | | |
	| slt | TBD4 | bstr | | Identifies the |		| slt | TBD4 | bstr | | Identifies the |
	| | | | | master salt in |		| | | | | master salt in |
	| | | | | an OSCORE context |		| | | | | an OSCORE context |
	| | | | | using this key |		| | | | | using this key |
	+----------+-------+--------------+------------+-------------------+		+----------+-------+--------------+------------+-------------------+
	Table 1: Additional COSE_Key Common Parameters
	Figure 1 shows an example of such an AS response, in CBOR diagnostic		Figure 3: Additional COSE_Key Common Parameters
			Figure 4 shows an example of such an AS response, in CBOR diagnostic
	notation without the tag and value abbreviations.		notation without the tag and value abbreviations.
	Header: Created (Code=2.01)		Header: Created (Code=2.01)
	Content-Type: "application/cose+cbor"		Content-Type: "application/cose+cbor"
	Payload:		Payload:
	{		{
	"access_token" : b64'SlAV32hkKG ...		"access_token" : b64'SlAV32hkKG ...
	(remainder of access token omitted for brevity)',		(remainder of access token omitted for brevity)',
	"profile" : "coap_oscore",		"profile" : "coap_oscore",
	"expires_in" : "3600",		"expires_in" : "3600",
	skipping to change at page 7, line 24 ¶		skipping to change at page 9, line 24 ¶
	"COSE_Key" : {		"COSE_Key" : {
	"kty" : "Symmetric",		"kty" : "Symmetric",
	"alg" : "AES-CCM-16-64-128",		"alg" : "AES-CCM-16-64-128",
	"clientId" : b64'qA',		"clientId" : b64'qA',
	"serverId" : b64'Qg',		"serverId" : b64'Qg',
	"k" : b64'+a+Dg2jjU+eIiOFCa9lObw'		"k" : b64'+a+Dg2jjU+eIiOFCa9lObw'
	}		}
	}		}
	}		}
	Figure 1: Example AS response with OSCORE parameters.		Figure 4: Example AS-to-C Access Token response with OSCORE profile.
	Figure 2 shows an example CWT, containing the necessary OSCORE		Figure 5 shows an example CWT, containing the necessary OSCORE
	parameters in the 'cnf' claim, in CBOR diagnostic notation without		parameters in the 'cnf' claim, in CBOR diagnostic notation without
	tag and value abbreviations.		tag and value abbreviations.
	{		{
	"aud" : "tempSensorInLivingRoom",		"aud" : "tempSensorInLivingRoom",
	"iat" : "1360189224",		"iat" : "1360189224",
	"exp" : "1360289224",		"exp" : "1360289224",
	"scope" : "temperature_g firmware_p",		"scope" : "temperature_g firmware_p",
	"cnf" : {		"cnf" : {
	"COSE_Key" : {		"COSE_Key" : {
	"kty" : "Symmetric",		"kty" : "Symmetric",
	"alg" : "AES-CCM-16-64-128",		"alg" : "AES-CCM-16-64-128",
	"clientId" : b64'Qg',		"clientId" : b64'Qg',
	"serverId" : b64'qA',		"serverId" : b64'qA',
	"k" : b64'+a+Dg2jjU+eIiOFCa9lObw'		"k" : b64'+a+Dg2jjU+eIiOFCa9lObw'
	}		}
	}		}
	Figure 2: Example CWT with OSCORE parameters.		Figure 5: Example CWT with OSCORE parameters.
			If the client has requested an update to its access rights using the
			same OSCORE Security Context, and the token associated with it is not
			expired, the AS MAY omit the master secret and server identifier both
			in the COSE_Key in the 'cnf' parameter and in the token. The client
			identifier needs to be provisioned, in order for the RS to identify
			the previously generated Security Context.
			Figure 6 shows an example of such an AS response, in CBOR diagnostic
			notation without the tag and value abbreviations.
			Header: Created (Code=2.01)
			Content-Type: "application/cose+cbor"
			Payload:
			{
			"access_token" : b64'SlAV32hkKG ...
			(remainder of access token omitted for brevity)',
			"profile" : "coap_oscore",
			"expires_in" : "3600",
			"cnf" : {
			"COSE_Key" : {
			"clientId" : b64'qA'
			}
			}
			}
			Figure 6: Example AS-to-C Access Token response with OSCORE profile,
			for update of access rights.
			Figure 7 shows an example CWT, containing the necessary OSCORE
			parameters in the 'cnf' claim for update of access rights, in CBOR
			diagnostic notation without tag and value abbreviations.
			{
			"aud" : "tempSensorInLivingRoom",
			"iat" : "1360189224",
			"exp" : "1360289224",
			"scope" : "temperature_h",
			"cnf" : {
			"COSE_Key" : {
			"clientId" : b64'Qg'
			}
			}
			Figure 7: Example CWT with OSCORE parameters for update of access
			rights.
			4. Client-RS Communication
			The following subsections describe the details of the POST /authz-
			info request and response between client and RS. The client posts
			the token that includes the materials provisioned by the AS to the
			RS, which can then use Section 3.2 of [I-D.ietf-core-object-security]
			to derive a security context based on a shared master secret and a
			set of other parameters, established between client and server.
	Note that the proof-of-possession required to bind the access token		Note that the proof-of-possession required to bind the access token
	to the client is implicitly performed by generating the shared OSCORE		to the client is implicitly performed by generating the shared OSCORE
	context using the pop-key as master secret, both on the client and RS		Security Context using the pop-key as master secret, for both client
	side. An attacker using a stolen token will not be able to generate		and RS. An attacker using a stolen token will not be able to
	a valid OSCORE context and thus not be able to prove possession of		generate a valid OSCORE context and thus not be able to prove
	the pop-key.		possession of the pop-key.
	3. Client to Authorization Server		4.1. C-to-RS: POST /authz-info
	As specified in the ACE framework (section 5.6 of		The client MUST use CoAP and the Authorization Information endpoint
	[I-D.ietf-ace-oauth-authz]), the Client and AS can also use CoAP		as described in section 5.8.1 of [I-D.ietf-ace-oauth-authz] to
	instead of HTTP to communicate via the token resource. This section		transport the token to the RS.
	specifies how to use OSCORE between Client and AS together with CoAP.
	The use of OSCORE for this communication is OPTIONAL in this profile,
	other security protocols (such as DTLS) MAY be used instead.
	The client and the AS are expected to have pre-established security		The authz-info endpoint is not protected, nor are the responses from
	contexts in place. How these security contexts are established is		this endpoint.
	out of scope for this profile. Furthermore the client and the AS
	communicate using OSCORE ([I-D.ietf-core-object-security]) through
	the introspection resource as specified in section 5.7 of
	[I-D.ietf-ace-oauth-authz].
	4. Resource Server to Authorization Server		The access token MUST be encrypted, since it is transferred from the
			client to the RS over an unprotected channel.
			Figure 8 shows an example of the request sent from the client to the
			RS.
			Header: POST (Code=0.02)
			Uri-Host: "rs.example.com"
			Uri-Path: "authz-info"
			Content-Format: "application/cwt"
			Payload:
			b64'SlAV32hkKG ...
			(remainder of access token omitted for brevity)',
			Figure 8: Example C-to-RS POST /authz-info request using CWT
			4.2. RS-to-C: 2.01 (Created)
			The RS MUST follow the procedures defined in section 5.8.1 of
			[I-D.ietf-ace-oauth-authz]: the RS MUST verify the validity of the
			token. If the token is valid, the RS MUST respond to the POST
			request with 2.01 (Created). This response MAY contain an identifier
			of the token (e.g., the cti for a CWT) as a payload, in order to
			allow the client to refer to the token. If the token is valid but is
			associated to claims that the RS cannot process (e.g., an unknown
			scope) the RS MUST respond with a response code equivalent to the
			CoAP code 4.00 (Bad Request). In the latter case the RS MAY provide
			additional information in the error response, in order to clarify
			what went wrong. The RS MAY make an introspection request to
			validate the token before responding to the POST request to the
			authz-info endpoint.
			Additionally, the RS MUST generate a nonce (N1) with a good amount of
			randomness, and include it in the payload of the 2.01 (Created)
			response as a CBOR byte string. This profile RECOMMENDS to use a
			nonce of 64 bits. The RS MUST store this nonce as long as the access
			token related to it is still valid.
			Figure 9 shows an example of the response sent from the RS to the
			client.
			Header: Created (Code=2.01)
			Content-Format: "application/cbor"
			Payload:
			h'018a278f7faab55a',
			Figure 9: Example RS-to-C 2.01 (Created) response
			As specified in section 5.8.3 of [I-D.ietf-ace-oauth-authz], the RS
			MUST notify the client with an error response with code 4.01
			(Unauthorized) for any long running request before terminating the
			session, when the access token expires.
			4.3. OSCORE Setup
			Once receiving the 2.01 (Created) response from the RS, following the
			POST /authz-info request, the client MUST extract the nonce N1 from
			the CBOR byte string in the payload of the response. The client MUST
			generate itself a nonce (N2) with a good amount of randomness. This
			profile RECOMMENDS to use a nonce of 64 bits. Then, the client MUST
			set the ID Context of the Security Context created to communicate
			with the RS to the concatenation of N1 and N2, in this order: ID
			Context = N1 | N2, where | denotes byte string concatenation. The
			client MUST set the Master Secret, Sender ID and Recipient ID from
			the parameters received from the AS in Section 3.2. The client MUST
			set the AEAD Algorithm, Master Salt, HKDF and Replay Window from the
			parameters received from the AS in Section 3.2, if present. In case
			these parameters are omitted, the default values are used as
			described in section 3.2 of [I-D.ietf-core-object-security]. After
			that, the client MUST derive the complete Security Context following
			section 3.2.1 of [I-D.ietf-core-object-security]. From this point
			on, the client MUST use this Security Context to communicate with the
			RS when accessing the resources as specified by the authorization
			information.
			The client then uses this Security Context to send requests to RS
			using OSCORE. In the first request sent to the RS, the client MUST
			include the kid context, with value ID Context, i.e. N1 concatenated
			with N2. The client needs to make sure the RS receives the kid
			context, possibly adding the kid context to later requests, until it
			receives a valid OSCORE response from the RS using the same Security
			Context.
			When the RS receives this first OSCORE-protected request, it MUST
			extract the kid context from the message first. Then, it needs to
			verify that the first part of the kid context corresponds to the
			nonce N1 it previously sent, and that it is followed by a non-zero-
			length byte string. If that is verified, the RS MUST set the ID
			Context to the kid context value. Then, the RS MUST set the Master
			Secret, Sender ID and Recipient ID from the parameters received from
			the client in the access token in Section 4.1. The RS MUST set the
			AEAD Algorithm, Master Salt, HKDF and Replay Window from the
			parameters received from the client in the access token in
			Section 4.1, if present. In case these parameters are omitted, the
			default values are used as described in section 3.2 of
			[I-D.ietf-core-object-security]. After that, the RS MUST derive the
			complete Security Context following section 3.2.1 of
			[I-D.ietf-core-object-security], and MUST associate this Security
			Context with the authorization information from the access token.
			Then, the RS MUST delete the nonce N1 from memory.
			The RS then uses this Security Context to verify the request and send
			responses to RS using OSCORE. If OSCORE verification fails, error
			responses are used, as specified in section 8 of
			[I-D.ietf-core-object-security]. Additionally, if OSCORE
			verification succeeds, the verification of access rights is performed
			as described in section Section 4.4. The RS MUST NOT use the
			Security Context after the related token has expired, and MUST
			respond with a unprotected 4.01 (Unauthorized) error message.
			4.4. Access rights verification
			The RS MUST follow the procedures defined in section 5.8.2 of
			[I-D.ietf-ace-oauth-authz]: if an RS receives a OSCORE-protected
			request from a client, then it processes according to
			[I-D.ietf-core-object-security]. If OSCORE verification succeeds,
			and the target resource requires authorization, the RS retrieves the
			authorization information from the access token associated to the
			Security Context. The RS then MUST verify that the authorization
			information covers the resource and the action requested.
			The response code MUST be 4.01 (Unauthorized) in case the client has
			not used the Security Context associated with the access token, or if
			RS has no valid access token for the client. If RS has an access
			token for the client but not for the resource that was requested, RS
			MUST reject the request with a 4.03 (Forbidden). If RS has an access
			token for the client but it does not cover the action that was
			requested on the resource, RS MUST reject the request with a 4.05
			(Method Not Allowed).
			5. Secure Communication with AS
	As specified in the ACE framework (section 5.7 of		As specified in the ACE framework (section 5.7 of
	[I-D.ietf-ace-oauth-authz]), the RS and AS can also use CoAP instead		[I-D.ietf-ace-oauth-authz]), the requesting entity (RS and/or client)
	of HTTP to communicate via the introspection resource. This section		and the AS communicates via the introspection or token endpoint. The
	specifies how to use OSCORE between RS and AS. The use of OSCORE for		use of CoAP and OSCORE for this communication is RECOMMENDED in this
	this communication is OPTIONAL in this profile, other security		profile, other protocols (such as HTTP and DTLS or TLS) MAY be used
	protocols (such as DTLS) MAY be used instead.		instead.
	The RS and the AS are expected to have pre-established security		If OSCORE is used, the requesting entity and the AS are expected to
	contexts in place. How these security contexts are established is		have pre-established security contexts in place. How these security
	out of scope for this profile. Furthermore the RS and the AS		contexts are established is out of scope for this profile.
	communicate using OSCORE ([I-D.ietf-core-object-security]) through		Furthermore the requesting entity and the AS communicate using OSCORE
	the introspection resource as specified in section 5.7 of		([I-D.ietf-core-object-security]) through the introspection endpoint
			as specified in section 5.7 of [I-D.ietf-ace-oauth-authz] and through
			the token endpoint as specified in section 5.6 of
	[I-D.ietf-ace-oauth-authz].		[I-D.ietf-ace-oauth-authz].
	5. Security Considerations		6. Security Considerations
	This document specifies a profile for the Authentication and		This document specifies a profile for the Authentication and
	Authorization for Constrained Environments (ACE) framework		Authorization for Constrained Environments (ACE) framework
	[I-D.ietf-ace-oauth-authz]. Thus the general security considerations		[I-D.ietf-ace-oauth-authz]. Thus the general security considerations
	from the framework also apply to this profile.		from the framework also apply to this profile.
	Furthermore the general security considerations of OSCORE		Furthermore the general security considerations of OSCORE
	[I-D.ietf-core-object-security] also apply to this specific use of		[I-D.ietf-core-object-security] also apply to this specific use of
	the OSCORE protocol.		the OSCORE protocol.
	OSCORE is designed to secure point-to-point communication, providing		OSCORE is designed to secure point-to-point communication, providing
	a secure binding between the request and the response(s). Thus the		a secure binding between the request and the response(s). Thus the
	basic OSCORE protocol is not intended for use in point-to-multipoint		basic OSCORE protocol is not intended for use in point-to-multipoint
	communication (e.g. multicast, publish-subscribe). Implementers of		communication (e.g. multicast, publish-subscribe). Implementers of
	this profile should make sure that their usecase corresponds to the		this profile should make sure that their usecase corresponds to the
	expected use of OSCORE, to prevent weakening the security assurances		expected use of OSCORE, to prevent weakening the security assurances
	provided by OSCORE.		provided by OSCORE.
	6. Privacy Considerations		TODO: explain the rationale for the nonces construction, and the
			security implications for Man-in-the-Middle attacks.
			7. Privacy Considerations
	TBD.		TBD.
	7. IANA Considerations		8. IANA Considerations
	Note to RFC Editor: Please replace all occurrences of "[[this		Note to RFC Editor: Please replace all occurrences of "[[this
	specification]]" with the RFC number of this specification and delete		specification]]" with the RFC number of this specification and delete
	this paragraph.		this paragraph.
	The following registration is done for the ACE OAuth Profile Registry		The following registration is done for the ACE OAuth Profile Registry
	following the procedure specified in section 8.6 of		following the procedure specified in section 8.6 of
	[I-D.ietf-ace-oauth-authz]:		[I-D.ietf-ace-oauth-authz]:
	o Profile name: coap_oscore		o Profile name: coap_oscore
	skipping to change at page 9, line 46 ¶		skipping to change at page 15, line 49 ¶
	o Description: Identifies the client in an OSCORE context		o Description: Identifies the client in an OSCORE context
	o Reference: [[this specification]]		o Reference: [[this specification]]
	o Name: serverId		o Name: serverId
	o Label: TBD2 (value between 1 and 255)		o Label: TBD2 (value between 1 and 255)
	o Value Type: bstr		o Value Type: bstr
	o Value Registry: N/A		o Value Registry: N/A
	o Description: Identifies the server in an OSCORE context		o Description: Identifies the server in an OSCORE context
	o Reference: [[this specification]]		o Reference: [[this specification]]
	o Name: kdf		o Name: hkdf
	o Label: TBD3 (value between 1 and 255)		o Label: TBD3 (value between 1 and 255)
	o Value Type: bstr		o Value Type: bstr
	o Value Registry: COSE Algorithms registry		o Value Registry: COSE Algorithms registry
	o Description: Identifies the KDF algorithm to be used in an OSCORE		o Description: Identifies the KDF algorithm to be used in an OSCORE
	context		context
	o Reference: [[this specification]]		o Reference: [[this specification]]
	o Name: slt		o Name: slt
	o Label: TBD4 (value between 1 and 255)		o Label: TBD4 (value between 1 and 255)
	o Value Type: bstr		o Value Type: bstr
	o Value Registry: N/A		o Value Registry: N/A
	o Description: Identifies the master salt of to be used in an OSCORE		o Description: Identifies the master salt of to be used in an OSCORE
	context		context
	o Reference: [[this specification]]		o Reference: [[this specification]]
	skipping to change at page 10, line 15 ¶		skipping to change at page 16, line 17 ¶
	o Reference: [[this specification]]		o Reference: [[this specification]]
	o Name: slt		o Name: slt
	o Label: TBD4 (value between 1 and 255)		o Label: TBD4 (value between 1 and 255)
	o Value Type: bstr		o Value Type: bstr
	o Value Registry: N/A		o Value Registry: N/A
	o Description: Identifies the master salt of to be used in an OSCORE		o Description: Identifies the master salt of to be used in an OSCORE
	context		context
	o Reference: [[this specification]]		o Reference: [[this specification]]
	8. References		9. References
	8.1. Normative References		9.1. Normative References
	[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-12		Framework (ACE-OAuth)", draft-ietf-ace-oauth-authz-15
	(work in progress), May 2018.		(work in progress), September 2018.
	[I-D.ietf-core-object-security]		[I-D.ietf-core-object-security]
	Selander, G., Mattsson, J., Palombini, F., and L. Seitz,		Selander, G., Mattsson, J., Palombini, F., and L. Seitz,
	"Object Security for Constrained RESTful Environments		"Object Security for Constrained RESTful Environments
	(OSCORE)", draft-ietf-core-object-security-13 (work in		(OSCORE)", draft-ietf-core-object-security-15 (work in
	progress), June 2018.		progress), August 2018.
	[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>.
	[RFC7252] Shelby, Z., Hartke, K., and C. Bormann, "The Constrained		[RFC7252] Shelby, Z., Hartke, K., and C. Bormann, "The Constrained
	Application Protocol (CoAP)", RFC 7252,		Application Protocol (CoAP)", RFC 7252,
	DOI 10.17487/RFC7252, June 2014,		DOI 10.17487/RFC7252, June 2014,
	<https://www.rfc-editor.org/info/rfc7252>.		<https://www.rfc-editor.org/info/rfc7252>.
	[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>.
	[RFC8392] Jones, M., Wahlstroem, E., Erdtman, S., and H. Tschofenig,		[RFC8392] Jones, M., Wahlstroem, E., Erdtman, S., and H. Tschofenig,
	"CBOR Web Token (CWT)", RFC 8392, DOI 10.17487/RFC8392,		"CBOR Web Token (CWT)", RFC 8392, DOI 10.17487/RFC8392,
	May 2018, <https://www.rfc-editor.org/info/rfc8392>.		May 2018, <https://www.rfc-editor.org/info/rfc8392>.
	8.2. Informative References		9.2. Informative References
	[I-D.gerdes-ace-dcaf-authorize]		[I-D.gerdes-ace-dcaf-authorize]
	Gerdes, S., Bergmann, O., and C. Bormann, "Delegated CoAP		Gerdes, S., Bergmann, O., and C. Bormann, "Delegated CoAP
	Authentication and Authorization Framework (DCAF)", draft-		Authentication and Authorization Framework (DCAF)", draft-
	gerdes-ace-dcaf-authorize-04 (work in progress), October		gerdes-ace-dcaf-authorize-04 (work in progress), October
	2015.		2015.
	[I-D.ietf-ace-actors]
	Gerdes, S., Seitz, L., Selander, G., and C. Bormann, "An
	architecture for authorization in constrained
	environments", draft-ietf-ace-actors-06 (work in
	progress), November 2017.
	[I-D.selander-ace-cose-ecdhe]		[I-D.selander-ace-cose-ecdhe]
	Selander, G., Mattsson, J., and F. Palombini, "Ephemeral		Selander, G., Mattsson, J., and F. Palombini, "Ephemeral
	Diffie-Hellman Over COSE (EDHOC)", draft-selander-ace-		Diffie-Hellman Over COSE (EDHOC)", draft-selander-ace-
	cose-ecdhe-08 (work in progress), March 2018.		cose-ecdhe-10 (work in progress), September 2018.
	[RFC4949] Shirey, R., "Internet Security Glossary, Version 2",		[RFC4949] Shirey, R., "Internet Security Glossary, Version 2",
	FYI 36, RFC 4949, DOI 10.17487/RFC4949, August 2007,		FYI 36, RFC 4949, DOI 10.17487/RFC4949, August 2007,
	<https://www.rfc-editor.org/info/rfc4949>.		<https://www.rfc-editor.org/info/rfc4949>.
	[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		[RFC7049] Bormann, C. and P. Hoffman, "Concise Binary Object
	skipping to change at page 17, line 47 ¶		skipping to change at page 23, line 47 ¶
	| |		| |
	|<---------+ CoAP response +		|<---------+ CoAP response +
	| OSCORE | Object-Security option		| OSCORE | Object-Security option
	| response |		| response |
	| |		| |
	Figure 7: Access token and key establishment with EDHOC		Figure 7: Access token and key establishment with EDHOC
	Acknowledgments		Acknowledgments
	The authors wish to thank Jim Schaad, Goeran Selander and Marco		The authors wish to thank Jim Schaad and Marco Tiloca for the input
	Tiloca for the input on this memo. The error responses specified in		on this memo. The error responses specified in Appendix B.3 were
	Appendix B.3 were originally specified by Gerdes et al. in		originally specified by Gerdes et al. in
	[I-D.gerdes-ace-dcaf-authorize].		[I-D.gerdes-ace-dcaf-authorize].
	Authors' Addresses		Authors' Addresses
	Ludwig Seitz		Ludwig Seitz
	RISE SICS AB		RISE SICS AB
	Scheelevagen 17		Scheelevagen 17
	Lund 22370		Lund 22370
	Sweden		Sweden
End of changes. 55 change blocks.
	144 lines changed or deleted		413 lines changed or added
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