draft-ietf-ace-dtls-authorize-04.txt   draft-ietf-ace-dtls-authorize-05.txt 
ACE Working Group S. Gerdes ACE Working Group S. Gerdes
Internet-Draft O. Bergmann Internet-Draft O. Bergmann
Intended status: Standards Track C. Bormann Intended status: Standards Track C. Bormann
Expires: March 10, 2019 Universitaet Bremen TZI Expires: April 11, 2019 Universitaet Bremen TZI
G. Selander G. Selander
Ericsson Ericsson AB
L. Seitz L. Seitz
RISE SICS RISE SICS
September 06, 2018 October 08, 2018
Datagram Transport Layer Security (DTLS) Profile for Authentication and Datagram Transport Layer Security (DTLS) Profile for Authentication and
Authorization for Constrained Environments (ACE) Authorization for Constrained Environments (ACE)
draft-ietf-ace-dtls-authorize-04 draft-ietf-ace-dtls-authorize-05
Abstract Abstract
This specification defines a profile for delegating client This specification defines a profile that allows constrained servers
authentication and authorization in a constrained environment by to delegate client authentication and authorization. The protocol
establishing a Datagram Transport Layer Security (DTLS) channel relies on DTLS for communication security between entities in a
between resource-constrained nodes. The protocol relies on DTLS for constrained network using either raw public keys or pre-shared keys.
communication security between entities in a constrained network A resource-constrained server can use this protocol to delegate
using either raw public keys or pre-shared keys. A resource- management of authorization information to a trusted host with less
constrained node can use this protocol to delegate management of severe limitations regarding processing power and memory.
authorization information to a trusted host with less severe
limitations regarding processing power and memory.
Status of This Memo Status of This Memo
This Internet-Draft is submitted in full conformance with the This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79. provisions of BCP 78 and BCP 79.
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
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This Internet-Draft will expire on March 10, 2019. This Internet-Draft will expire on April 11, 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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Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
1.1. Terminology . . . . . . . . . . . . . . . . . . . . . . . 3 1.1. Terminology . . . . . . . . . . . . . . . . . . . . . . . 3
2. Protocol Overview . . . . . . . . . . . . . . . . . . . . . . 3 2. Protocol Overview . . . . . . . . . . . . . . . . . . . . . . 3
2.1. Resource Access . . . . . . . . . . . . . . . . . . . . . 5 3. Protocol Flow . . . . . . . . . . . . . . . . . . . . . . . . 5
2.2. Dynamic Update of Authorization Information . . . . . . . 7 3.1. Communication between C and AS . . . . . . . . . . . . . 5
2.3. Token Expiration . . . . . . . . . . . . . . . . . . . . 8 3.2. RawPublicKey Mode . . . . . . . . . . . . . . . . . . . . 6
3. RawPublicKey Mode . . . . . . . . . . . . . . . . . . . . . . 9 3.2.1. DTLS Channel Setup Between C and RS . . . . . . . . . 7
4. PreSharedKey Mode . . . . . . . . . . . . . . . . . . . . . . 10 3.3. PreSharedKey Mode . . . . . . . . . . . . . . . . . . . . 8
4.1. DTLS Channel Setup Between C and RS . . . . . . . . . . . 12 3.3.1. DTLS Channel Setup Between C and RS . . . . . . . . . 10
4.2. Updating Authorization Information . . . . . . . . . . . 13 3.4. Resource Access . . . . . . . . . . . . . . . . . . . . . 12
5. Security Considerations . . . . . . . . . . . . . . . . . . . 14 4. Dynamic Update of Authorization Information . . . . . . . . . 13
6. Privacy Considerations . . . . . . . . . . . . . . . . . . . 14 5. Token Expiration . . . . . . . . . . . . . . . . . . . . . . 14
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 14 6. Security Considerations . . . . . . . . . . . . . . . . . . . 15
8. References . . . . . . . . . . . . . . . . . . . . . . . . . 15 7. Privacy Considerations . . . . . . . . . . . . . . . . . . . 15
8.1. Normative References . . . . . . . . . . . . . . . . . . 15 8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 16
8.2. Informative References . . . . . . . . . . . . . . . . . 16 9. References . . . . . . . . . . . . . . . . . . . . . . . . . 16
8.3. URIs . . . . . . . . . . . . . . . . . . . . . . . . . . 17 9.1. Normative References . . . . . . . . . . . . . . . . . . 16
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 18 9.2. Informative References . . . . . . . . . . . . . . . . . 17
9.3. URIs . . . . . . . . . . . . . . . . . . . . . . . . . . 18
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 19
1. Introduction 1. Introduction
This specification defines a profile of the ACE framework This specification defines 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] over DTLS [RFC6347] to communicate. The server use CoAP [RFC7252] over DTLS [RFC6347] to communicate. The
client uses an access token, bound to a key (the proof-of-possession client obtains an access token, bound to a key (the proof-of-
key) to authorize its access to protected resources hosted by the possession key), from an authorization server to prove its
resource server. DTLS provides communication security, proof of authorization to access protected resources hosted by the resource
possession, and server authentication. Optionally the client and the server. Also, the client and the resource server are provided by the
resource server may also use CoAP over DTLS to communicate with the authorization server with the necessary keying material to establish
authorization server. This specification supports the DTLS handshake a DTLS session. The communication between client and authorization
with Raw Public Keys (RPK) [RFC7250] and the DTLS handshake with Pre- server may also be secured with DTLS. This specification supports
Shared Keys (PSK) [RFC4279]. DTLS with Raw Public Keys (RPK) [RFC7250] and with Pre-Shared Keys
(PSK) [RFC4279].
The DTLS RPK handshake [RFC7250] requires client authentication to The DTLS handshake [RFC7250] requires the client and server to prove
provide proof-of-possession for the key tied to the access token. that they can use certain keying material. In the RPK mode, the
Here the access token needs to be transferred to the resource server client proves with the DTLS handshake that it can use the RPK bound
before the handshake is initiated, as described in section 5.8.1 of to the token and the server shows that it can use a certain RPK. The
access token must be presented to the resource server. For the RPK
mode, the access token needs to be uploaded to the resource server
before the handshake is initiated, as described in Section 5.8.1 of
draft-ietf-ace-oauth-authz [1]. draft-ietf-ace-oauth-authz [1].
The DTLS PSK handshake [RFC4279] provides the proof-of-possession for In the PSK mode, client and server show with the DTLS handshake that
the key tied to the access token. Furthermore the psk_identity they can use the keying material that is bound to the access token.
parameter in the DTLS PSK handshake is used to transfer the access To transfer the access token from the client to the resource server,
token from the client to the resource server. the "psk_identity" parameter in the DTLS PSK handshake may be used
instead of uploading the token prior to the handshake.
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", "NOT RECOMMENDED", "MAY", and "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in BCP "OPTIONAL" in this document are to be interpreted as described in BCP
14 [RFC2119] [RFC8174] when, and only when, they appear in all 14 [RFC2119] [RFC8174] when, and only when, they appear in all
capitals, as shown here. capitals, as shown here.
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]. described in I-D.ietf-ace-oauth-authz [2].
The authz-info resource refers to the authz-info endpoint as
specified in I-D.ietf-ace-oauth-authz [3].
2. Protocol Overview 2. Protocol Overview
The CoAP-DTLS profile for ACE specifies the transfer of The CoAP-DTLS profile for ACE specifies the transfer of
authentication and, if necessary, authorization information between authentication information and, if necessary, authorization
the client C and the resource server RS during setup of a DTLS information between the client (C) and the resource server (RS)
session for CoAP messaging. It also specifies how a Client can use during setup of a DTLS session for CoAP messaging. It also specifies
CoAP over DTLS to retrieve an Access Token from the authorization how C can use CoAP over DTLS to retrieve an access token from the
server AS for a protected resource hosted on the resource server RS. authorization server (AS) for a protected resource hosted on the
resource server.
This profile requires a Client (C) to retrieve an Access Token for This profile requires the client to retrieve an access token for
the resource(s) it wants to access on a Resource Server (RS) as protected resource(s) it wants to access on RS as specified in I-
specified in [I-D.ietf-ace-oauth-authz]. Figure 1 shows the typical D.ietf-ace-oauth-authz [4]. Figure 1 shows the typical message flow
message flow in this scenario (messages in square brackets are in this scenario (messages in square brackets are optional):
optional):
C RS AS C RS AS
| [-- Resource Request --->] | | | [-- Resource Request --->] | |
| | | | | |
| [<----- AS Information --] | | | [<----- AS Information --] | |
| | | | | |
| --- Token Request ----------------------------> | | --- Token Request ----------------------------> |
| | | | | |
| <---------------------------- Access Token ----- | | <---------------------------- Access Token ----- |
| + RS Information | | + Access Information |
Figure 1: Retrieving an Access Token Figure 1: Retrieving an Access Token
To determine the AS in charge of a resource hosted at the RS, the To determine the AS in charge of a resource hosted at the RS, C MAY
client C MAY send an initial Unauthorized Resource Request message to send an initial Unauthorized Resource Request message to the RS. The
the RS. The RS then denies the request and sends the address of its RS then denies the request and sends an AS information message
AS back to the client C as specified in section 5.1.2 of draft-ietf- containing the address of its AS back to the client as specified in
ace-oauth-authz [2]. Section 5.1.2 of draft-ietf-ace-oauth-authz [5].
Once the client C knows the authorization server's address, it can
send an Access Token request to the token endpoint at the AS as
specified in [I-D.ietf-ace-oauth-authz]. As the Access Token request
as well as the response may contain confidential data, the
communication between the client and the authorization server MUST be
confidentiality-protected and ensure authenticity. How the mutual
authentication between the client and the authorization server is
achieved is out of scope for this document; the client may have been
configured with a public key of the authorization server and have
been registered at the AS via the OAuth client registration mechanism
as outlined in section 5.3 of draft-ietf-ace-oauth-authz [3].
If C wants to use the CoAP RawPublicKey mode as described in
Section 9 of RFC 7252 [4] it MUST provide a key or key identifier
within a "cnf" object in the token request. If the authorization
server AS decides that the request is to be authorized it generates
an access token response for the client C containing a "profile"
parameter with the value "coap_dtls" to indicate that this profile
MUST be used for communication between the client C and the resource
server.
For RPK mode, the authorization server also adds a "rs_cnf" parameter
containing information about the public that is used by the resource
server (see Section 3).
For PSK mode, the authorization server adds a "cnf" parameter Once the client knows the authorization server's address, it can send
containing information about the shared secret that C can use to an access token request to the token endpoint at the AS as specified
setup a DTLS session with the resource server (see Section 4). in I-D.ietf-ace-oauth-authz [6]. As the access token request as well
as the response may contain confidential data, the communication
between the client and the authorization server MUST be
confidentiality-protected and ensure authenticity. C may have been
registered at the AS via the OAuth 2.0 client registration mechanism
as outlined in Section 5.3 of draft-ietf-ace-oauth-authz [7].
The Access Token returned by the authorization server then can be The access token returned by the authorization server can then be
used by the client to establish a new DTLS session with the resource used by the client to establish a new DTLS session with the resource
server. When the client intends to use asymmetric cryptography in server. When the client intends to use asymmetric cryptography in
the DTLS handshake with the resource server, the client MUST upload the DTLS handshake with the resource server, the client MUST upload
the Access Token to the authz-info resource on the resource server the access token to the authz-info resource, i.e. the authz-info
before starting the DTLS handshake, as described in section 5.8.1 of endpoint, on the resource server before starting the DTLS handshake,
draft-ietf-ace-oauth-authz [5]. If only symmetric cryptography is as described in Section 5.8.1 of draft-ietf-ace-oauth-authz [8]. If
used between the client and the resource server, the Access Token MAY only symmetric cryptography is used between the client and the
instead be transferred in the DTLS ClientKeyExchange message (see resource server, the access token MAY instead be transferred in the
Section 4.1). DTLS ClientKeyExchange message (see Section 3.3.1).
Figure 2 depicts the common protocol flow for the DTLS profile after Figure 2 depicts the common protocol flow for the DTLS profile after
the client C has retrieved the Access Token from the authorization the client C has retrieved the access token from the authorization
server AS. server AS.
C RS AS C RS AS
| [--- Access Token ------>] | | | [--- Access Token ------>] | |
| | | | | |
| <== DTLS channel setup ==> | | | <== DTLS channel setup ==> | |
| | | | | |
| == Authorized Request ===> | | | == Authorized Request ===> | |
| | | | | |
| <=== Protected Resource == | | | <=== Protected Resource == | |
Figure 2: Protocol overview Figure 2: Protocol overview
The following sections specify how CoAP is used to interchange 3. Protocol Flow
access-related data between the resource server and the authorization
server so that the authorization server can provide the client and
the resource server with sufficient information to establish a secure
channel, and convey authorization information specific for this
communication relationship to the resource server.
Depending on the desired CoAP security mode, the Client-to-AS
request, AS-to-Client response and DTLS session establishment carry
slightly different information. Section 3 addresses the use of raw
public keys while Section 4 defines how pre-shared keys are used in
this profile.
2.1. Resource Access
Once a DTLS channel has been established as described in Section 3
and Section 4, respectively, the client is authorized to access
resources covered by the Access Token it has uploaded to the authz-
info resource hosted by the resource server.
On the resource server side, successful establishment of the DTLS
channel binds the client to the access token, functioning as a proof-
of-possession associated key. Any request that the resource server
receives on this channel MUST be checked against these authorization
rules that are associated with the identity of the client. Incoming
CoAP requests that are not authorized with respect to any Access
Token that is associated with the client MUST be rejected by the
resource server with 4.01 response as described in Section 5.1.1 of
draft-ietf-ace-oauth-authz [6].
Note: The identity of the client is determined by the authentication
process
during the DTLS handshake. In the asymmetric case, the public key
will define the client's identity, while in the PSK case, the
client's identity is defined by the shared secret generated by the
authorization server for this communication.
The resource server SHOULD treat an incoming CoAP request as
authorized if the following holds:
1. The message was received on a secure channel that has been
established using the procedure defined in this document.
2. The authorization information tied to the sending peer is valid.
3. The request is destined for the resource server.
4. The resource URI specified in the request is covered by the
authorization information.
5. The request method is an authorized action on the resource with
respect to the authorization information.
Incoming CoAP requests received on a secure DTLS channel MUST be
rejected according to [Section 5.1.1 of draft-ietf-ace-oauth-
authz](https://tools.ietf.org/html/draft-ietf-ace-oauth-authz-
13#section-5.1.1
1. with response code 4.03 (Forbidden) when the resource URI
specified in the request is not covered by the authorization
information, and
2. with response code 4.05 (Method Not Allowed) when the resource
URI specified in the request covered by the authorization
information but not the requested action.
The client cannot always know a priori if an Authorized Resource
Request will succeed. If the client repeatedly gets error responses
containing AS Information (cf. Section 5.1.1 of draft-ietf-ace-
oauth-authz [7] as response to its requests, it SHOULD request a new
Access Token from the authorization server in order to continue
communication with the resource server.
2.2. Dynamic Update of Authorization Information
The client can update the authorization information stored at the
resource server at any time without changing an established DTLS
session. To do so, the Client requests from the authorization server
a new Access Token for the intended action on the respective resource
and uploads this Access Token to the authz-info resource on the
resource server.
Figure 3 depicts the message flow where the client C requests a new
Access Token after a security association between the client and the
resource server RS has been established using this protocol. The
token request MUST specify the key identifier of the existing DTLS
channel between the client and the resource server in the "kid"
parameter of the Client-to-AS request. The authorization server MUST
verify that the specified "kid" denotes a valid verifier for a proof-
of-possession ticket that has previously been issued to the
requesting client. Otherwise, the Client-to-AS request MUST be
declined with a the error code "unsupported_pop_key" as defined in
Section 5.6.3 of draft-ietf-ace-oauth-authz [8].
When the authorization server issues a new access token to update
existing authorization information it MUST include the specified
"kid" parameter in this access token. A resource server MUST
associate the updated authorization information with any existing
DTLS session that is identified by this key identifier.
Note: By associating the access tokens with the identifier of an
existing DTLS session, the authorization information can be
updated without changing the cryptographic keys for the DTLS
communication between the client and the resource server, i.e. an
existing session can be used with updated permissions.
C RS AS
| <===== DTLS channel =====> | |
| + Access Token | |
| | |
| --- Token Request ----------------------------> |
| | |
| <---------------------------- New Access Token - |
| + RS Information |
| | |
| --- Update /authz-info --> | |
| New Access Token | |
| | |
| == Authorized Request ===> | |
| | |
| <=== Protected Resource == | |
Figure 3: Overview of Dynamic Update Operation
2.3. Token Expiration
DTLS sessions that have been established in accordance with this
profile are always tied to a specific set of access tokens. As these
tokens may become invalid at any time (either because the token has
expired or the responsible authorization server has revoked the
token), the session may become useless at some point. A resource
server therefore may decide to terminate existing DTLS sessions after
the last valid access token for this session has been deleted.
As specified in section 5.8.3 of draft-ietf-ace-oauth-authz [9], the The following sections specify how CoAP is used to interchange
resource server MUST notify the client with an error response with access-related data between the resource server, the client and the
code 4.01 (Unauthorized) for any long running request before authorization server so that the authorization server can provide the
terminating the session. client and the resource server with sufficient information to
establish a secure channel, and convey authorization information
specific for this communication relationship to the resource server.
The resource server MAY also keep the session alive for some time and Section 3.1 describes how the communication between C and AS must be
respond to incoming requests with a 4.01 (Unauthorized) error message secured. Depending on the used CoAP security mode (see also
including AS Information to signal that the client needs to upload a Section 9 of RFC 7252 [9]), the Client-to-AS request, AS-to-Client
new access token before it can continue using this DTLS session. The response and DTLS session establishment carry slightly different
AS Information is created as specified in section 5.1.2 of draft- information. Section 3.2 addresses the use of raw public keys while
ietf-ace-oauth-authz [10]. The resource server SHOULD add a "kid" Section 3.3 defines how pre-shared keys are used in this profile.
parameter to the AS Information denoting the identifier of the key
that it uses internally for this DTLS session. The client then
includes this "kid" parameter in a Client-to-AS request used to
retrieve a new access token to be used with this DTLS session. In
case the key identifier is already known by the client (e.g. because
it was included in the RS Information in an AS-to-Client response),
the "kid" parameter MAY be elided from the AS Information.
Table 1 updates Figure 2 in section 5.1.2 of draft-ietf-ace-oauth- 3.1. Communication between C and AS
authz [11] with the new "kid" parameter in accordance with [RFC8152].
+----------------+----------+-----------------+ To retrieve an access token for the resource that the client wants to
| Parameter name | CBOR Key | Major Type | access, the client requests an access token from the authorization
+----------------+----------+-----------------+ server. Before C can request the access token, C and AS must
| kid | 4 | 2 (byte string) | establish a secure communication channel. C must securely have
+----------------+----------+-----------------+ obtained keying material to communicate with AS, and C must securely
have received authorization information intended for C that states
that AS is authorized to provide keying material concerning RS to C.
Also, AS must securely have obtained keying material for C, and
obtained authorization rules approved by the resource owner (RO)
concerning C and RS that relate to this keying material. C and AS
must use their respective keying material for all exchanged messages.
How the security association between C and AS is established is not
part of this document. C and AS MUST ensure the confidentiality,
integrity and authenticity of all exchanged messages.
Table 1: Updated AS Information parameters If C is constrained, C and AS should use DTLS to communicate with
each other. But C and AS may also use other means to secure their
communication, e.g., TLS. The used security protocol must provide
confidentiality, integrity and authenticity, and enable the client to
determine if it is the intended recipient of a message, e.g., by
using an AEAD mechanism. C must also be able to determine if a
response from AS belongs to a certain request. Additionally, the
protocol must offer replay protection.
3. RawPublicKey Mode 3.2. RawPublicKey Mode
To retrieve an access token for the resource that the client wants to After C and AS mutually authenticated each other and validated each
access, the client requests an Access Token from the authorization other's authorization, C sends a token request to AS's token
server. The client MUST add a "cnf" object carrying either its raw endpoint. The client MUST add a "cnf" object carrying either its raw
public key or a unique identifier for a public key that it has public key or a unique identifier for a public key that it has
previously made known to the authorization server. To prove that the previously made known to the authorization server. To prove that the
client is in possession of this key, it MUST use the same public key client is in possession of this key, C MUST use the same keying
as in certificate message that is used to establish the DTLS session material that it uses to secure the communication with AS, e.g., the
with the authorization server. DTLS session.
An example Access Token request from the client to the resource An example access token request from the client to the AS is depicted
server is depicted in Figure 4. in Figure 3.
POST coaps://as.example.com/token POST coaps://as.example.com/token
Content-Format: application/cbor Content-Format: application/ace+cbor
{ {
grant_type: client_credentials, grant_type: client_credentials,
aud: "tempSensor4711", req_aud: "tempSensor4711",
cnf: { req_cnf: {
COSE_Key: { COSE_Key: {
kty: EC2, kty: EC2,
crv: P-256, crv: P-256,
x: h'TODOX', x: h'e866c35f4c3c81bb96a1...',
y: h'TODOY' y: h'2e25556be097c8778a20...'
} }
} }
} }
Figure 4: Access Token Request Example for RPK Mode Figure 3: Access Token Request Example for RPK Mode
The example shows an Access Token request for the resource identified The example shows an access token request for the resource identified
by the audience string "tempSensor4711" on the authorization server by the string "tempSensor4711" on the authorization server using a
using a raw public key. raw public key.
When the authorization server authorizes a request, it will return an AS MUST check if the client that it communicates with is associated
Access Token and a "cnf" object in the AS-to-Client response. Before with the RPK in the cnf object before issuing an access token to it.
the client initiates the DTLS handshake with the resource server, it If AS determines that the request is to be authorized according to
MUST send a "POST" request containing the new Access Token to the the respective authorization rules, it generates an access token
authz-info resource hosted by the resource server. If this operation response for C. The response SHOULD contain a "profile" parameter
yields a positive response, the client SHOULD proceed to establish a with the value "coap_dtls" to indicate that this profile must be used
new DTLS channel with the resource server. To use raw public key for communication between the client C and the resource server. The
mode, the client MUST pass the same public key that was used for response also contains an access token and an "rs_cnf" parameter
constructing the Access Token with the SubjectPublicKeyInfo structure containing information about the public key that is used by the
in the DTLS handshake as specified in [RFC7250]. resource server. AS MUST ascertain that the RPK specified in
"rs_cnf" belongs to the resource server that C wants to communicate
with. AS MUST protect the integrity of the token. If the access
token contains confidential data, AS MUST also protect the
confidentiality of the access token.
C MUST ascertain that the access token response belongs to a certain
previously sent access token request, as the request may specify the
resource server with which C wants to communicate.
3.2.1. DTLS Channel Setup Between C and RS
Before the client initiates the DTLS handshake with the resource
server, C MUST send a "POST" request containing the new access token
to the authz-info resource hosted by the resource server. If this
operation yields a positive response, the client SHOULD proceed to
establish a new DTLS channel with the resource server. To use the
RawPublicKey mode, the client MUST specify the public key that AS
defined in the "cnf" field of the access token response in the
SubjectPublicKeyInfo structure in the DTLS handshake as specified in
RFC 7250 [10].
An implementation that supports the RPK mode of this profile MUST at An implementation that supports the RPK mode of this profile MUST at
least support the ciphersuite TLS_ECDHE_ECDSA_WITH_AES_128_CCM_8 least support the ciphersuite TLS_ECDHE_ECDSA_WITH_AES_128_CCM_8
[RFC7251] with the ed25519 curve (cf. [RFC8032], [RFC8422]). [RFC7251] with the ed25519 curve (cf. [RFC8032], [RFC8422]).
Note: According to [RFC7252], CoAP implementations MUST support the Note: According to RFC 7252 [11], CoAP implementations MUST support
ciphersuite TLS_ECDHE_ECDSA_WITH_AES_128_CCM_8 [RFC7251] and the the ciphersuite TLS_ECDHE_ECDSA_WITH_AES_128_CCM_8 [RFC7251] and
NIST P-256 curve. As discussed in [RFC7748], new ECC curves have the NIST P-256 curve. As discussed in RFC 7748 [12], new ECC
been defined recently that are considered superior to the so- curves have been defined recently that are considered superior to
called NIST curves. The curve that is mandatory to implement in the so-called NIST curves. The curve that is mandatory to
this specification is said to be efficient and less dangerous implement in this specification is said to be efficient and less
regarding implementation errors than the secp256r1 curve mandated dangerous regarding implementation errors than the secp256r1 curve
in [RFC7252]. mandated in RFC 7252 [13].
The Access Token is constructed by the authorization server such that RS MUST check if the access token is still valid, if RS is the
the resource server can associate the Access Token with the Client's intended destination, i.e., the audience, of the token, and if the
public key. If CBOR web tokens [RFC8392] are used as recommended in token was issued by an authorized AS. The access token is
[I-D.ietf-ace-oauth-authz], the authorization server MUST include a constructed by the authorization server such that the resource server
"COSE_Key" object in the "cnf" claim of the Access Token. This can associate the access token with the Client's public key. The
"COSE_Key" object MAY contain a reference to a key for the client "cnf" claim MUST contain either C's RPK or, if the key is already
that is already known by the resource server (e.g., from previous known by the resource server (e.g., from previous communication), a
communication). If the authorization server has no certain knowledge reference to this key. If the authorization server has no certain
that the Client's key is already known to the resource server, the knowledge that the Client's key is already known to the resource
Client's public key MUST be included in the Access Token's "cnf" server, the Client's public key MUST be included in the access
parameter. token's "cnf" parameter. If CBOR web tokens [RFC8392] are used as
recommended in I-D.ietf-ace-oauth-authz [14], unencrypted keys MUST
be specified using a "COSE_Key" object, encrypted keys with a
"COSE_Encrypt0" structure and references to the key as "key_id"
parameters in a CBOR map. RS MUST use the keying material in the
handshake that AS specified in the rs_cnf parameter in the access
token. Thus, the handshake only finishes if C and RS are able to use
their respective keying material.
4. PreSharedKey Mode 3.3. PreSharedKey Mode
To retrieve an access token for the resource that the client wants to To retrieve an access token for the resource that the client wants to
access, the client MAY include a "cnf" object carrying an identifier access, the client MAY include a "cnf" object carrying an identifier
for a symmetric key in its Access Token request to the authorization for a symmetric key in its access token request to the authorization
server. This identifier can be used by the authorization server to server. This identifier can be used by the authorization server to
determine the shared secret to construct the proof-of-possession determine the shared secret to construct the proof-of-possession
token and therefore MUST specify a symmetric key that was previously token. AS MUST check if the identifier refers to a symmetric key
generated by the authorization server as a shared secret for the that was previously generated by AS as a shared secret for the
communication between the client and the resource server. communication between this client and the resource server.
Depending on the requested token type and algorithm in the Access The authorization server MUST determine the authorization rules for
Token request, the authorization server adds RS Information to the the C it communicates with as defined by RO and generate the access
response that provides the client with sufficient information to token accordingly. If the authorization server authorizes the
setup a DTLS channel with the resource server. For symmetric proof- client, it returns an AS-to-Client response. If the profile
of-possession keys (c.f. [I-D.ietf-ace-oauth-authz]), the client parameter is present, it is set to "coap_dtls". AS MUST ascertain
must ensure that the Access Token request is sent over a secure that the access token is generated for the resource server that C
channel that guarantees authentication, message integrity and wants to communicate with. Also, AS MUST protect the integrity of
confidentiality. the access token. If the token contains confidential data such as
the symmetric key, the confidentiality of the token MUST also be
protected. Depending on the requested token type and algorithm in
the access token request, the authorization server adds access
Information to the response that provides the client with sufficient
information to setup a DTLS channel with the resource server. AS
adds a "cnf" parameter to the access information carrying a
"COSE_Key" object that informs the client about the symmetric key
that is to be used between C and the resource server.
When the authorization server authorizes the client it returns an AS- An example access token response is illustrated in Figure 4. In this
to-Client response with the profile parameter set to "coap_dtls" and example, the authorization server returns a 2.01 response containing
a "cnf" parameter carrying a "COSE_Key" object that contains the a new access token and information for the client, including the
symmetric key to be used between the client and the resource server symmetric key in the cnf claim. The information is transferred as a
as illustrated in Figure 5. CBOR data structure as specified in I-D.ietf-ace-oauth-authz [15].
2.01 Created 2.01 Created
Content-Format: application/cbor Content-Format: application/ace+cbor
Location-Path: /token/asdjbaskd Max-Age: 86400
{ {
access_token: h'd08343a10... access_token: h'd08343a10...
(remainder of CWT omitted for brevity) (remainder of CWT omitted for brevity)
token_type: pop, token_type: pop,
alg: HS256, alg: HS256,
expires_in: 86400, expires_in: 86400,
profile: coap_dtls, profile: coap_dtls,
cnf: { cnf: {
COSE_Key: { COSE_Key: {
kty: symmetric, kty: symmetric,
k: h'73657373696f6e6b6579' k: h'73657373696f6e6b6579'
} }
} }
} }
Figure 5: Example Access Token response Figure 4: Example Access Token Response
In this example, the authorization server returns a 2.01 response The access token also comprises a "cnf" claim. This claim usually
containing a new Access Token. The information is transferred as a contains a "COSE_Key" object that carries either the symmetric key
CBOR data structure as specified in [I-D.ietf-ace-oauth-authz]. itself or or a key identifier that can be used by the resource server
to determine the shared secret. If the access token carries a
symmetric key, the access token MUST be encrypted using a
"COSE_Encrypt0" structure. The AS MUST use the keying material
shared with the RS to encrypt the token.
Instead of providing the keying material, the AS MAY include a key
derivation function and a salt in the access token that enables the
resource server to calculate the keying material for the
communication with C from the access token. In this case, the token
contains a "cnf" structure that specifies the key derivation
algorithm and the salt that the AS has used to construct the shared
key. AS and RS MUST use their shared keying material for the key
derivation, and the key derivation MUST follow Section 11 of RFC 8152
[16] with parameters as specified here. The KDF specified in the
"alg" parameter SHOULD be HKDF-SHA-256. The salt picked by the AS
must be uniformly random and is carried in the "salt" parameter.
The fields in the context information "COSE_KDF_Context"
(Section 11.2 of RFC 8152 [17]) MUST have the following values:
o AlgorithmID = "ACE-CoAP-DTLS-salt"
o PartyUInfo = PartyVInfo = ( null, null, null )
o keyDataLength is a uint equal the length of the key shared between
AS and RS in bits
o protected MUST be a zero length bstr
o other is a zero length bstr
o SuppPrivInfo is omitted
An example "cnf" structure specifying HMAC-based key derivation of a
symmetric key with SHA-256 as pseudo-random function and a random
salt value is provided in Figure 5.
cnf : {
kty : symmetric,
alg : HKDF-SHA-256,
salt : h'eIiOFCa9lObw'
}
Figure 5: Key Derivation Specification in an Access Token
A response that declines any operation on the requested resource is A response that declines any operation on the requested resource is
constructed according to Section 5.2 of RFC 6749 [12], (cf. constructed according to Section 5.2 of RFC 6749 [18], (cf.
Section 5.7.3 of [I-D.ietf-ace-oauth-authz]). Section 5.7.3. of draft-ietf-ace-oauth-authz [19]).
4.00 Bad Request 4.00 Bad Request
Content-Format: application/cbor Content-Format: application/ace+cbor
{ {
error: invalid_request error: invalid_request
} }
Figure 6: Example Access Token response with reject Figure 6: Example Access Token Response With Reject
4.1. DTLS Channel Setup Between C and RS 3.3.1. DTLS Channel Setup Between C and RS
When a client receives an Access Token from an authorization server, When a client receives an access token response from an authorization
it checks if the payload contains an "access_token" parameter and a server, C MUST ascertain that the access token response belongs to a
"cnf" parameter. With this information the client can initiate certain previously sent access token request, as the request may
establishment of a new DTLS channel with a resource server. To use specify the resource server with which C wants to communicate.
DTLS with pre-shared keys, the client follows the PSK key exchange
algorithm specified in Section 2 of [RFC4279] using the key conveyed C checks if the payload of the access token response contains an
in the "cnf" parameter of the AS response as PSK when constructing "access_token" parameter and a "cnf" parameter. With this
the premaster secret. information the client can initiate the establishment of a new DTLS
channel with a resource server. To use DTLS with pre-shared keys,
the client follows the PSK key exchange algorithm specified in
Section 2 of RFC 4279 [20] using the key conveyed in the "cnf"
parameter of the AS response as PSK when constructing the premaster
secret.
In PreSharedKey mode, the knowledge of the shared secret by the In PreSharedKey mode, the knowledge of the shared secret by the
client and the resource server is used for mutual authentication client and the resource server is used for mutual authentication
between both peers. Therefore, the resource server must be able to between both peers. Therefore, the resource server must be able to
determine the shared secret from the Access Token. Following the determine the shared secret from the access token. Following the
general ACE authorization framework, the client can upload the Access general ACE authorization framework, the client can upload the access
Token to the resource server's authz-info resource before starting token to the resource server's authz-info resource before starting
the DTLS handshake. Alternatively, the client MAY provide the most the DTLS handshake. Alternatively, the client MAY provide the most
recent Access Token in the "psk_identity" field of the recent access token in the "psk_identity" field of the
ClientKeyExchange message. To do so, the client MUST treat the ClientKeyExchange message. To do so, the client MUST treat the
contents of the "access_token" field from the AS-to-Client response contents of the "access_token" field from the AS-to-Client response
as opaque data and not perform any re-coding. as opaque data and not perform any re-coding.
Note: As stated in section 4.2 of [RFC7925], the PSK identity should Note: As stated in Section 4.2 of RFC 7925 [21], the PSK identity
be treated as binary data in the Internet of Things space and not should be treated as binary data in the Internet of Things space
assumed to have a human-readable form of any sort. and not assumed to have a human-readable form of any sort.
If a resource server receives a ClientKeyExchange message that If a resource server receives a ClientKeyExchange message that
contains a "psk_identity" with a length greater zero, it uses the contains a "psk_identity" with a length greater zero, it uses the
contents as index for its key store (i.e., treat the contents as key contents as index for its key store (i.e., treat the contents as key
identifier). The resource server MUST check if it has one or more identifier). The resource server MUST check if it has one or more
Access Tokens that are associated with the specified key. If no access tokens that are associated with the specified key.
valid Access Token is available for this key, the DTLS session setup
is terminated with an "illegal_parameter" DTLS alert message.
If no key with a matching identifier is found the resource server the If no key with a matching identifier is found, the resource server
resource server MAY process the decoded contents of the MAY process the contents of the "psk_identity" field as access token
"psk_identity" field as access token that is stored with the that is stored with the authorization information endpoint, before
authorization information endpoint before continuing the DTLS continuing the DTLS handshake. If the contents of the "psk_identity"
handshake. If the decoded contents of the "psk_identity" do not do not yield a valid access token for the requesting client, the DTLS
yield a valid access token for the requesting client, the DTLS
session setup is terminated with an "illegal_parameter" DTLS alert session setup is terminated with an "illegal_parameter" DTLS alert
message. message.
Note1: As a resource server cannot provide a client with a meaningful Note1: As a resource server cannot provide a client with a
PSK identity hint in meaningful PSK identity hint in response to the client's
response to the client's ClientHello message, the resource server ClientHello message, the resource server SHOULD NOT send a
SHOULD NOT send a ServerKeyExchange message. ServerKeyExchange message.
Note2: According to [RFC7252], CoAP implementations MUST support the Note2: According to RFC 7252 [22], CoAP implementations MUST support
ciphersuite TLS_PSK_WITH_AES_128_CCM_8 [RFC6655]. A client is the ciphersuite TLS_PSK_WITH_AES_128_CCM_8 [RFC6655]. A client is
therefore expected to offer at least this ciphersuite to the therefore expected to offer at least this ciphersuite to the
resource server. resource server.
This specification assumes that the Access Token is a PoP token as When RS receives an access token, RS MUST check if the access token
described in [I-D.ietf-ace-oauth-authz] unless specifically stated is still valid, if RS is the intended destination, i.e., the audience
otherwise. Therefore, the Access Token is bound to a symmetric PoP of the token, and if the token was issued by an authorized AS. This
specification assumes that the access token is a PoP token as
described in I-D.ietf-ace-oauth-authz [23] unless specifically stated
otherwise. Therefore, the access token is bound to a symmetric PoP
key that is used as shared secret between the client and the resource key that is used as shared secret between the client and the resource
server. server.
While the client can retrieve the shared secret from the contents of While the client can retrieve the shared secret from the contents of
the "cnf" parameter in the AS-to-Client response, the resource server the "cnf" parameter in the AS-to-Client response, the resource server
uses the information contained in the "cnf" claim of the Access Token uses the information contained in the "cnf" claim of the access token
to determine the actual secret when no explicit "kid" was provided in to determine the actual secret when no explicit "kid" was provided in
the "psk_identity" field. Usually, this is done by including a the "psk_identity" field. If key derivation is used, the RS uses the
"COSE_Key" object carrying either a key that has been encrypted with "COSE_KDF_Context" information as described above.
a shared secret between the authorization server and the resource
server, or a key identifier that can be used by the resource server
to lookup the shared secret.
Instead of the "COSE_Key" object, the authorization server MAY 3.4. Resource Access
include a "COSE_Encrypt" structure to enable the resource server to
calculate the shared key from the Access Token. The "COSE_Encrypt"
structure MUST use the _Direct Key with KDF_ method as described in
Section 12.1.2 of RFC 8152 [13]. The authorization server MUST
include a Context information structure carrying a PartyU "nonce"
parameter carrying the nonce that has been used by the authorization
server to construct the shared key.
This specification mandates that at least the key derivation Once a DTLS channel has been established as described in Section 3.2
algorithm "HKDF SHA-256" as defined in [RFC8152] MUST be supported. and Section 3.3, respectively, the client is authorized to access
This key derivation function is the default when no "alg" field is resources covered by the access token it has uploaded to the authz-
included in the "COSE_Encrypt" structure for the resource server. info resource hosted by the resource server.
4.2. Updating Authorization Information With the successful establishment of the DTLS channel, C and RS have
proven that they can use their respective keying material. An access
token that is bound to the client's keying material is associated
with the channel. Any request that the resource server receives on
this channel MUST be checked against these authorization rules. RS
MUST check for every request if the access token is still valid.
Incoming CoAP requests that are not authorized with respect to any
access token that is associated with the client MUST be rejected by
the resource server with 4.01 response as described in Section 5.1.1
of draft-ietf-ace-oauth-authz [24].
Usually, the authorization information that the resource server keeps The resource server SHOULD treat an incoming CoAP request as
for a client is updated by uploading a new Access Token as described authorized if the following holds:
in Section 2.2.
The Client MAY also perform a new DTLS handshake according to 1. The message was received on a secure channel that has been
Section 4.1 that replaces the existing DTLS session. After established using the procedure defined in this document.
successful completion of the DTLS handshake the resource server
updates the existing authorization information for the client
according to the new Access Token.
5. Security Considerations 2. The authorization information tied to the sending client is
valid.
3. The request is destined for the resource server.
4. The resource URI specified in the request is covered by the
authorization information.
5. The request method is an authorized action on the resource with
respect to the authorization information.
Incoming CoAP requests received on a secure DTLS channel that are not
thus authorized MUST be rejected according to Section 5.8.2 of draft-
ietf-ace-oauth-authz [25]
1. with response code 4.03 (Forbidden) when the resource URI
specified in the request is not covered by the authorization
information, and
2. with response code 4.05 (Method Not Allowed) when the resource
URI specified in the request covered by the authorization
information but not the requested action.
The client cannot always know a priori if an Authorized Resource
Request will succeed. If the client repeatedly gets error responses
containing AS Information (cf. Section 5.1.2 of draft-ietf-ace-
oauth-authz [26]) as response to its requests, it SHOULD request a
new access token from the authorization server in order to continue
communication with the resource server.
4. Dynamic Update of Authorization Information
The client can update the authorization information stored at the
resource server at any time without changing an established DTLS
session. To do so, the Client requests a new access token from the
authorization server for the intended action on the respective
resource and uploads this access token to the authz-info resource on
the resource server.
Figure 7 depicts the message flow where the C requests a new access
token after a security association between the client and the
resource server has been established using this protocol. If the
client wants to update the authorization information, the token
request MUST specify the key identifier of the existing DTLS channel
between the client and the resource server in the "kid" parameter of
the Client-to-AS request. The authorization server MUST verify that
the specified "kid" denotes a valid verifier for a proof-of-
possession token that has previously been issued to the requesting
client. Otherwise, the Client-to-AS request MUST be declined with
the error code "unsupported_pop_key" as defined in Section 5.6.3 of
draft-ietf-ace-oauth-authz [27].
When the authorization server issues a new access token to update
existing authorization information, it MUST include the specified
"kid" parameter in this access token. A resource server MUST
associate the updated authorization information with any existing
DTLS session that is identified by this key identifier.
Note: By associating the access tokens with the identifier of an
existing DTLS session, the authorization information can be
updated without changing the cryptographic keys for the DTLS
communication between the client and the resource server, i.e. an
existing session can be used with updated permissions.
C RS AS
| <===== DTLS channel =====> | |
| + Access Token | |
| | |
| --- Token Request ----------------------------> |
| | |
| <---------------------------- New Access Token - |
| + Access Information |
| | |
| --- Update /authz-info --> | |
| New Access Token | |
| | |
| == Authorized Request ===> | |
| | |
| <=== Protected Resource == | |
Figure 7: Overview of Dynamic Update Operation
5. Token Expiration
DTLS sessions that have been established in accordance with this
profile are always tied to a specific set of access tokens. As these
tokens may become invalid at any time (either because the token has
expired or the responsible authorization server has revoked the
token), the session may become useless at some point. A resource
server therefore MUST terminate existing DTLS sessions after the last
valid access token for this session has been deleted.
As specified in Section 5.8.3 of draft-ietf-ace-oauth-authz [28], the
resource server MUST notify the client with an error response with
code 4.01 (Unauthorized) for any long running request before
terminating the session.
Table 1 updates Figure 2 in Section 5.1.2 of draft-ietf-ace-oauth-
authz [29] with the new "kid" parameter in accordance with [RFC8152].
+----------------+----------+-----------------+
| Parameter name | CBOR Key | Major Type |
+----------------+----------+-----------------+
| kid | 4 | 2 (byte string) |
+----------------+----------+-----------------+
Table 1: Updated AS Information parameters
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]. As it follows this framework's general [I-D.ietf-ace-oauth-authz]. As it follows this framework's general
approach, the general security and privacy considerations from approach, the general security and privacy considerations from
section 6 and section 7 also apply to this profile. section 6 and section 7 also apply to this profile.
Constrained devices that use DTLS [RFC6347] are inherently vulnerable Constrained devices that use DTLS [RFC6347] are inherently vulnerable
to Denial of Service (DoS) attacks as the handshake protocol requires to Denial of Service (DoS) attacks as the handshake protocol requires
creation of internal state within the device. This is specifically creation of internal state within the device. This is specifically
of concern where an adversary is able to intercept the initial cookie of concern where an adversary is able to intercept the initial cookie
exchange and interject forged messages with a valid cookie to exchange and interject forged messages with a valid cookie to
continue with the handshake. continue with the handshake.
[I-D.tiloca-tls-dos-handshake] specifies a TLS extension to prevent [I-D.tiloca-tls-dos-handshake] specifies a TLS extension to prevent
this type of attack which is applicable especially for constrained this type of attack which is applicable especially for constrained
environments where the authorization server can act as trust anchor. environments where the authorization server can act as trust anchor.
6. Privacy Considerations The use of multiple access tokens for a single client increases the
strain on the resource server as it must consider every access token
and calculate the actual permissions of the client. Also, tokens may
contradict each other which may lead the server to enforce wrong
permissions. If one of the access tokens expires earlier than
others, the resulting permissions may offer insufficient protection.
Developers should avoid using multiple access tokens for a client.
7. Privacy Considerations
An unprotected response to an unauthorized request may disclose An unprotected response to an unauthorized request may disclose
information about the resource server and/or its existing information about the resource server and/or its existing
relationship with the client. It is advisable to include as little relationship with the client. It is advisable to include as little
information as possible in an unencrypted response. When a DTLS information as possible in an unencrypted response. When a DTLS
session between the client and the resource server already exists, session between the client and the resource server already exists,
more detailed information may be included with an error response to more detailed information may be included with an error response to
provide the client with sufficient information to react on that provide the client with sufficient information to react on that
particular error. particular error.
Also, unprotected requests to the resource server may reveal
information about the client, e.g., which resources the client
attempts to request or the data that the client wants to provide to
the resource server. The client should not send confidential data in
an unprotected request.
Note that some information might still leak after DTLS session is Note that some information might still leak after DTLS session is
established, due to observable message sizes, the source, and the established, due to observable message sizes, the source, and the
destination addresses. destination addresses.
7. IANA Considerations 8. IANA Considerations
The following registrations are done for the ACE OAuth Profile The following registrations are done for the ACE OAuth Profile
Registry following the procedure specified in Registry following the procedure specified in
[I-D.ietf-ace-oauth-authz]. [I-D.ietf-ace-oauth-authz].
Note to RFC Editor: Please replace all occurrences of "[RFC-XXXX]" Note to RFC Editor: Please replace all occurrences of "[RFC-XXXX]"
with the RFC number of this specification and delete this paragraph. with the RFC number of this specification and delete this paragraph.
Profile name: coap_dtls Profile name: coap_dtls
skipping to change at page 15, line 13 skipping to change at page 16, line 27
authorization in a constrained environment by establishing a Datagram authorization in a constrained environment by establishing a Datagram
Transport Layer Security (DTLS) channel between resource-constrained Transport Layer Security (DTLS) channel between resource-constrained
nodes. nodes.
Profile ID: 1 Profile ID: 1
Change Controller: IESG Change Controller: IESG
Reference: [RFC-XXXX] Reference: [RFC-XXXX]
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-13 Framework (ACE-OAuth)", draft-ietf-ace-oauth-authz-16
(work in progress), July 2018. (work in progress), October 2018.
[I-D.tiloca-tls-dos-handshake] [I-D.tiloca-tls-dos-handshake]
Tiloca, M., Seitz, L., Hoeve, M., and O. Bergmann, Tiloca, M., Seitz, L., Hoeve, M., and O. Bergmann,
"Extension for protecting (D)TLS handshakes against Denial "Extension for protecting (D)TLS handshakes against Denial
of Service", draft-tiloca-tls-dos-handshake-02 (work in of Service", draft-tiloca-tls-dos-handshake-02 (work in
progress), March 2018. progress), March 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>.
[RFC4279] Eronen, P., Ed. and H. Tschofenig, Ed., "Pre-Shared Key [RFC4279] Eronen, P., Ed. and H. Tschofenig, Ed., "Pre-Shared Key
Ciphersuites for Transport Layer Security (TLS)", Ciphersuites for Transport Layer Security (TLS)",
RFC 4279, DOI 10.17487/RFC4279, December 2005, RFC 4279, DOI 10.17487/RFC4279, December 2005,
<https://www.rfc-editor.org/info/rfc4279>. <https://www.rfc-editor.org/info/rfc4279>.
[RFC5746] Rescorla, E., Ray, M., Dispensa, S., and N. Oskov,
"Transport Layer Security (TLS) Renegotiation Indication
Extension", RFC 5746, DOI 10.17487/RFC5746, February 2010,
<https://www.rfc-editor.org/info/rfc5746>.
[RFC6347] Rescorla, E. and N. Modadugu, "Datagram Transport Layer [RFC6347] Rescorla, E. and N. Modadugu, "Datagram Transport Layer
Security Version 1.2", RFC 6347, DOI 10.17487/RFC6347, Security Version 1.2", RFC 6347, DOI 10.17487/RFC6347,
January 2012, <https://www.rfc-editor.org/info/rfc6347>. January 2012, <https://www.rfc-editor.org/info/rfc6347>.
[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>.
[RFC7925] Tschofenig, H., Ed. and T. Fossati, "Transport Layer [RFC7925] Tschofenig, H., Ed. and T. Fossati, "Transport Layer
skipping to change at page 16, line 24 skipping to change at page 17, line 28
<https://www.rfc-editor.org/info/rfc7925>. <https://www.rfc-editor.org/info/rfc7925>.
[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>.
[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
May 2017, <https://www.rfc-editor.org/info/rfc8174>. May 2017, <https://www.rfc-editor.org/info/rfc8174>.
8.2. Informative References 9.2. Informative References
[RFC6655] McGrew, D. and D. Bailey, "AES-CCM Cipher Suites for [RFC6655] McGrew, D. and D. Bailey, "AES-CCM Cipher Suites for
Transport Layer Security (TLS)", RFC 6655, Transport Layer Security (TLS)", RFC 6655,
DOI 10.17487/RFC6655, July 2012, DOI 10.17487/RFC6655, July 2012,
<https://www.rfc-editor.org/info/rfc6655>. <https://www.rfc-editor.org/info/rfc6655>.
[RFC7250] Wouters, P., Ed., Tschofenig, H., Ed., Gilmore, J., [RFC7250] Wouters, P., Ed., Tschofenig, H., Ed., Gilmore, J.,
Weiler, S., and T. Kivinen, "Using Raw Public Keys in Weiler, S., and T. Kivinen, "Using Raw Public Keys in
Transport Layer Security (TLS) and Datagram Transport Transport Layer Security (TLS) and Datagram Transport
Layer Security (DTLS)", RFC 7250, DOI 10.17487/RFC7250, Layer Security (DTLS)", RFC 7250, DOI 10.17487/RFC7250,
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[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>.
[RFC8422] Nir, Y., Josefsson, S., and M. Pegourie-Gonnard, "Elliptic [RFC8422] Nir, Y., Josefsson, S., and M. Pegourie-Gonnard, "Elliptic
Curve Cryptography (ECC) Cipher Suites for Transport Layer Curve Cryptography (ECC) Cipher Suites for Transport Layer
Security (TLS) Versions 1.2 and Earlier", RFC 8422, Security (TLS) Versions 1.2 and Earlier", RFC 8422,
DOI 10.17487/RFC8422, August 2018, DOI 10.17487/RFC8422, August 2018,
<https://www.rfc-editor.org/info/rfc8422>. <https://www.rfc-editor.org/info/rfc8422>.
8.3. URIs 9.3. URIs
[1] https://tools.ietf.org/html/draft-ietf-ace-oauth-authz- [1] https://tools.ietf.org/html/draft-ietf-ace-oauth-authz-
13#section-5.8.1 16#section-5.8.1
[2] https://tools.ietf.org/html/draft-ietf-ace-oauth-authz- [2] https://tools.ietf.org/html/draft-ietf-ace-oauth-authz
13#section-5.1.2
[3] https://tools.ietf.org/html/draft-ietf-ace-oauth-authz- [3] https://tools.ietf.org/html/draft-ietf-ace-oauth-authz
13#section-5.3
[4] https://tools.ietf.org/html/rfc7252#section-9 [4] https://tools.ietf.org/html/draft-ietf-ace-oauth-authz
[5] https://tools.ietf.org/html/draft-ietf-ace-oauth-authz- [5] https://tools.ietf.org/html/draft-ietf-ace-oauth-authz-
13#section-5.8.1 16#section-5.1.2
[6] https://tools.ietf.org/html/draft-ietf-ace-oauth-authz- [6] https://tools.ietf.org/html/draft-ietf-ace-oauth-authz
13#section-5.1.1
[7] https://tools.ietf.org/html/draft-ietf-ace-oauth-authz- [7] https://tools.ietf.org/html/draft-ietf-ace-oauth-authz-
13#section-5.1.1 16#section-5.3
[8] https://tools.ietf.org/html/draft-ietf-ace-oauth-authz- [8] https://tools.ietf.org/html/draft-ietf-ace-oauth-authz-
13#section-5.6.3 16#section-5.8.1
[9] https://tools.ietf.org/html/draft-ietf-ace-oauth-authz- [9] https://tools.ietf.org/html/rfc7252#section-9
13#section-5.8.3
[10] https://tools.ietf.org/html/draft-ietf-ace-oauth-authz- [10] https://tools.ietf.org/html/rfc7250
13#section-5.1.2
[11] https://tools.ietf.org/html/draft-ietf-ace-oauth-authz- [11] https://tools.ietf.org/html/rfc7252
13#section-5.1.2
[12] https://tools.ietf.org/html/rfc6749#section-5.2 [12] https://tools.ietf.org/html/rfc7748
[13] https://tools.ietf.org/html/rfc8152#section-12.1.2 [13] https://tools.ietf.org/html/rfc7252
[14] https://tools.ietf.org/html/draft-ietf-ace-oauth-authz
[15] https://tools.ietf.org/html/draft-ietf-ace-oauth-authz
[16] https://tools.ietf.org/html/rfc8152#section-11
[17] https://tools.ietf.org/html/rfc8152#section-11.2
[18] https://tools.ietf.org/html/rfc6749#section-5.2
[19] https://tools.ietf.org/html/draft-ietf-ace-oauth-authz#section-
5.7.3
[20] https://tools.ietf.org/html/rfc4279#section-2
[21] https://tools.ietf.org/html/rfc7925#section-4.2
[22] https://tools.ietf.org/html/rfc7252
[23] https://tools.ietf.org/html/draft-ietf-ace-oauth-authz
[24] https://tools.ietf.org/html/draft-ietf-ace-oauth-authz-
16#section-5.1.1
[25] https://tools.ietf.org/html/draft-ietf-ace-oauth-authz-
16#section-5.8.2
[26] https://tools.ietf.org/html/draft-ietf-ace-oauth-authz-
16#section-5.1.2
[27] https://tools.ietf.org/html/draft-ietf-ace-oauth-authz-
16#section-5.6.3
[28] https://tools.ietf.org/html/draft-ietf-ace-oauth-authz-
16#section-5.8.3
[29] https://tools.ietf.org/html/draft-ietf-ace-oauth-authz-
16#section-5.1.2
Authors' Addresses Authors' Addresses
Stefanie Gerdes Stefanie Gerdes
Universitaet Bremen TZI Universitaet Bremen TZI
Postfach 330440 Postfach 330440
Bremen D-28359 Bremen D-28359
Germany Germany
Phone: +49-421-218-63906 Phone: +49-421-218-63906
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Carsten Bormann Carsten Bormann
Universitaet Bremen TZI Universitaet Bremen TZI
Postfach 330440 Postfach 330440
Bremen D-28359 Bremen D-28359
Germany Germany
Phone: +49-421-218-63921 Phone: +49-421-218-63921
Email: cabo@tzi.org Email: cabo@tzi.org
Goeran Selander Goeran Selander
Ericsson Ericsson AB
Faroegatan 6
Kista 164 80
Sweden
Email: goran.selander@ericsson.com Email: goran.selander@ericsson.com
Ludwig Seitz Ludwig Seitz
RISE SICS RISE SICS
Scheelevaegen 17 Scheelevaegen 17
Lund 223 70 Lund 223 70
Sweden Sweden
Email: ludwig.seitz@ri.se Email: ludwig.seitz@ri.se
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