draft-ietf-ace-dtls-authorize-09.txt   draft-ietf-ace-dtls-authorize-10.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: June 20, 2020 Universitaet Bremen TZI Expires: November 14, 2020 Universitaet Bremen TZI
G. Selander G. Selander
Ericsson AB Ericsson AB
L. Seitz L. Seitz
Combitech Combitech
December 18, 2019 May 13, 2020
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-09 draft-ietf-ace-dtls-authorize-10
Abstract Abstract
This specification defines a profile of the ACE framework that allows This specification defines a profile of the ACE framework that allows
constrained servers to delegate client authentication and constrained servers to delegate client authentication and
authorization. The protocol relies on DTLS for communication authorization. The protocol relies on DTLS version 1.2 for
security between entities in a constrained network using either raw communication security between entities in a constrained network
public keys or pre-shared keys. A resource-constrained server can using either raw public keys or pre-shared keys. A resource-
use this protocol to delegate management of authorization information constrained server can use this protocol to delegate management of
to a trusted host with less severe limitations regarding processing authorization information to a trusted host with less severe
power and memory. 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
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 June 20, 2020. This Internet-Draft will expire on November 14, 2020.
Copyright Notice Copyright Notice
Copyright (c) 2019 IETF Trust and the persons identified as the Copyright (c) 2020 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents Provisions Relating to IETF Documents
(https://trustee.ietf.org/license-info) in effect on the date of (https://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents publication of this document. Please review these documents
carefully, as they describe your rights and restrictions with respect carefully, as they describe your rights and restrictions with respect
to this document. Code Components extracted from this document must to this document. Code Components extracted from this document must
include Simplified BSD License text as described in Section 4.e of include Simplified BSD License text as described in Section 4.e of
the Trust Legal Provisions and are provided without warranty as the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License. described in the Simplified BSD License.
Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
1.1. Terminology . . . . . . . . . . . . . . . . . . . . . . . 3 1.1. Terminology . . . . . . . . . . . . . . . . . . . . . . . 3
2. Protocol Overview . . . . . . . . . . . . . . . . . . . . . . 3 2. Protocol Overview . . . . . . . . . . . . . . . . . . . . . . 4
3. Protocol Flow . . . . . . . . . . . . . . . . . . . . . . . . 5 3. Protocol Flow . . . . . . . . . . . . . . . . . . . . . . . . 5
3.1. Communication between C and AS . . . . . . . . . . . . . 5 3.1. Communication Between the Client and the Authorization
Server . . . . . . . . . . . . . . . . . . . . . . . . . 6
3.2. RawPublicKey Mode . . . . . . . . . . . . . . . . . . . . 6 3.2. RawPublicKey Mode . . . . . . . . . . . . . . . . . . . . 6
3.2.1. DTLS Channel Setup Between C and RS . . . . . . . . . 7 3.2.1. DTLS Channel Setup Between Client and Resource Server 9
3.3. PreSharedKey Mode . . . . . . . . . . . . . . . . . . . . 8 3.3. PreSharedKey Mode . . . . . . . . . . . . . . . . . . . . 10
3.3.1. DTLS Channel Setup Between C and RS . . . . . . . . . 12 3.3.1. DTLS Channel Setup Between Client and Resource Server 14
3.4. Resource Access . . . . . . . . . . . . . . . . . . . . . 13 3.4. Resource Access . . . . . . . . . . . . . . . . . . . . . 15
4. Dynamic Update of Authorization Information . . . . . . . . . 14 4. Dynamic Update of Authorization Information . . . . . . . . . 17
5. Token Expiration . . . . . . . . . . . . . . . . . . . . . . 16 5. Token Expiration . . . . . . . . . . . . . . . . . . . . . . 18
6. Secure Communication with AS . . . . . . . . . . . . . . . . 16 6. Secure Communication with an Authorization Server . . . . . . 18
7. Security Considerations . . . . . . . . . . . . . . . . . . . 16 7. Security Considerations . . . . . . . . . . . . . . . . . . . 19
8. Privacy Considerations . . . . . . . . . . . . . . . . . . . 17 7.1. Reuse of Existing Sessions . . . . . . . . . . . . . . . 20
9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 17 7.2. Multiple Access Tokens . . . . . . . . . . . . . . . . . 21
10. References . . . . . . . . . . . . . . . . . . . . . . . . . 18 7.3. Out-of-Band Configuration . . . . . . . . . . . . . . . . 21
10.1. Normative References . . . . . . . . . . . . . . . . . . 18 8. Privacy Considerations . . . . . . . . . . . . . . . . . . . 22
10.2. Informative References . . . . . . . . . . . . . . . . . 19 9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 22
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 20 10. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 23
11. References . . . . . . . . . . . . . . . . . . . . . . . . . 23
11.1. Normative References . . . . . . . . . . . . . . . . . . 23
11.2. Informative References . . . . . . . . . . . . . . . . . 24
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 25
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 version 1.2 [RFC6347] to
client obtains an access token, bound to a key (the proof-of- communicate. The client obtains an access token, bound to a key (the
possession key), from an authorization server to prove its proof-of-possession key), from an authorization server to prove its
authorization to access protected resources hosted by the resource authorization to access protected resources hosted by the resource
server. Also, the client and the resource server are provided by the server. Also, the client and the resource server are provided by the
authorization server with the necessary keying material to establish authorization server with the necessary keying material to establish
a DTLS session. The communication between client and authorization a DTLS session. The communication between client and authorization
server may also be secured with DTLS. This specification supports server may also be secured with DTLS. This specification supports
DTLS with Raw Public Keys (RPK) [RFC7250] and with Pre-Shared Keys DTLS with Raw Public Keys (RPK) [RFC7250] and with Pre-Shared Keys
(PSK) [RFC4279]. (PSK) [RFC4279].
The DTLS handshake requires the client and server to prove that they The ACE framework requires that client and server mutually
can use certain keying material. In the RPK mode, the client proves authenticate each other before any application data is exchanged.
with the DTLS handshake that it can use the RPK bound to the token DTLS enables mutual authentication if both client and server prove
and the server shows that it can use a certain RPK. The access token their ability to use certain keying material in the DTLS handshake.
must be presented to the resource server. For the RPK mode, the The authorization server assists in this process on the server side
access token needs to be uploaded to the resource server before the by incorporating keying material (or information about keying
handshake is initiated, as described in Section 5.8.1 of the ACE material) into the access token, which is considered a "proof of
framework [I-D.ietf-ace-oauth-authz]. possession" token.
In the RPK mode, the client proves that it can use the RPK bound to
the token and the server shows that it can use a certain RPK.
The resource server needs access to the token in order to complete
this exchange. For the RPK mode, the client must upload the access
token to the resource server before initiating the handshake, as
described in Section 5.8.1 of the ACE framework
[I-D.ietf-ace-oauth-authz].
In the PSK mode, client and server show with the DTLS handshake that In the PSK mode, client and server show with the DTLS handshake that
they can use the keying material that is bound to the access token. they can use the keying material that is bound to the access token.
To transfer the access token from the client to the resource server, To transfer the access token from the client to the resource server,
the "psk_identity" parameter in the DTLS PSK handshake may be used the "psk_identity" parameter in the DTLS PSK handshake may be used
instead of uploading the token prior to the handshake. instead of uploading the token prior to the handshake.
As recommended in Section 5.8 of [I-D.ietf-ace-oauth-authz], this
specification uses CBOR web tokens to convey claims within an access
token issued by the server. While other formats could be used as
well, those are out of scope for this document.
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] and in described in [I-D.ietf-ace-oauth-authz] and in
[I-D.ietf-ace-oauth-params]. [I-D.ietf-ace-oauth-params].
The authorization information (authz-info) resource refers to the The authorization information (authz-info) resource refers to the
authorization information endpoint as specified in authorization information endpoint as specified in
[I-D.ietf-ace-oauth-authz].
[I-D.ietf-ace-oauth-authz]. The term "claim" is used in this
document with the same semantics as in [I-D.ietf-ace-oauth-authz],
i.e., it denotes information carried in the access token or returned
from introspection.
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 information and, if necessary, authorization authentication information and, if necessary, authorization
information between the client (C) and the resource server (RS) information between the client (C) and the resource server (RS)
during setup of a DTLS session for CoAP messaging. It also specifies during setup of a DTLS session for CoAP messaging. It also specifies
how C can use CoAP over DTLS to retrieve an access token from the how the client can use CoAP over DTLS to retrieve an access token
authorization server (AS) for a protected resource hosted on the from the authorization server (AS) for a protected resource hosted on
resource server. the resource server. As specified in Section 6.7 of
[I-D.ietf-ace-oauth-authz], use of DTLS for one or both of these
interactions is completely independent
This profile requires the client to retrieve an access token for This profile requires the client to retrieve an access token for
protected resource(s) it wants to access on RS as specified in protected resource(s) it wants to access on the resource server as
[I-D.ietf-ace-oauth-authz]. Figure 1 shows the typical message flow specified in [I-D.ietf-ace-oauth-authz]. Figure 1 shows the typical
in this scenario (messages in square brackets are optional): message flow in this scenario (messages in square brackets are
optional):
C RS AS C RS AS
| [---- Resource Request ------>]| | | [---- Resource Request ------>]| |
| | | | | |
| [<-AS Request Creation Hints-] | | | [<-AS Request Creation Hints-] | |
| | | | | |
| ------- Token Request ----------------------------> | | ------- Token Request ----------------------------> |
| | | | | |
| <---------------------------- Access Token --------- | | <---------------------------- Access Token --------- |
| + Access 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, C MAY To determine the authorization server in charge of a resource hosted
send an initial Unauthorized Resource Request message to the RS. The at the resource server, the client can send an initial Unauthorized
RS then denies the request and sends an AS Request Creation Hints Resource Request message to the resource server. The resource server
message containing the address of its AS back to the client as then denies the request and sends an AS Request Creation Hints
specified in Section 5.1.2 of [I-D.ietf-ace-oauth-authz]. message containing the address of its authorization server back to
the client as specified in Section 5.1.2 of
[I-D.ietf-ace-oauth-authz].
Once the client knows the authorization server's address, it can send Once the client knows the authorization server's address, it can send
an access token request to the token endpoint at the AS as specified an access token request to the token endpoint at the authorization
in [I-D.ietf-ace-oauth-authz]. As the access token request as well server as specified in [I-D.ietf-ace-oauth-authz]. As the access
as the response may contain confidential data, the communication token request as well as the response may contain confidential data,
between the client and the authorization server MUST be the communication between the client and the authorization server
confidentiality-protected and ensure authenticity. C may have been must be confidentiality-protected and ensure authenticity. The
registered at the AS via the OAuth 2.0 client registration mechanism client may have been registered at the authorization server via the
as outlined in Section 5.3 of [I-D.ietf-ace-oauth-authz]. OAuth 2.0 client registration mechanism as outlined in Section 5.3 of
[I-D.ietf-ace-oauth-authz].
The access token returned by the authorization server can then 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 an asymmetric proof-of- server. When the client intends to use an asymmetric proof-of-
possession key in the DTLS handshake with the resource server, the possession key in the DTLS handshake with the resource server, the
client MUST upload the access token to the authz-info resource, i.e. client MUST upload the access token to the authz-info resource, i.e.
the authz-info endpoint, on the resource server before starting the the authz-info endpoint, on the resource server before starting the
DTLS handshake, as described in Section 5.8.1 of DTLS handshake, as described in Section 5.8.1 of
[I-D.ietf-ace-oauth-authz]. In case the client uses a symmetric [I-D.ietf-ace-oauth-authz]. In case the client uses a symmetric
proof-of-possession key in the DTLS handshake, the procedure as above proof-of-possession key in the DTLS handshake, the procedure as above
MAY be used, or alternatively, the access token MAY instead be MAY be used, or alternatively, the access token MAY instead be
transferred in the DTLS ClientKeyExchange message (see transferred in the DTLS ClientKeyExchange message (see
Section 3.3.1). Section 3.3.1). In any case, DTLS MUST be used in a mode that
provides replay protection.
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 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 == | |
skipping to change at page 5, line 25 skipping to change at page 5, line 48
3. Protocol Flow 3. Protocol Flow
The following sections specify how CoAP is used to interchange The following sections specify how CoAP is used to interchange
access-related data between the resource server, the client and the access-related data between the resource server, the client and the
authorization server so that the authorization server can provide the authorization server so that the authorization server can provide the
client and the resource server with sufficient information to client and the resource server with sufficient information to
establish a secure channel, and convey authorization information establish a secure channel, and convey authorization information
specific for this communication relationship to the resource server. specific for this communication relationship to the resource server.
Section 3.1 describes how the communication between C and AS must be Section 3.1 describes how the communication between the client (C)
secured. Depending on the used CoAP security mode (see also and the authorization server (AS) must be secured. Depending on the
Section 9 of [RFC7252], the Client-to-AS request, AS-to-Client used CoAP security mode (see also Section 9 of [RFC7252], the Client-
response and DTLS session establishment carry slightly different to-AS request, AS-to-Client response (see Section 5.6 of
information. Section 3.2 addresses the use of raw public keys while [I-D.ietf-ace-oauth-authz]) and DTLS session establishment carry
Section 3.3 defines how pre-shared keys are used in this profile. slightly different information. Section 3.2 addresses the use of raw
public keys while Section 3.3 defines how pre-shared keys are used in
this profile.
3.1. Communication between C and AS 3.1. Communication Between the Client and the Authorization Server
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 requests an access token from the authorization access, the client requests an access token from the authorization
server. Before C can request the access token, C and AS MUST server. Before the client can request the access token, the client
establish a secure communication channel. C MUST securely have and the authorization server MUST establish a secure communication
obtained keying material to communicate with AS. Furthermore, C MUST channel. This profile assumes that the keying material to secure
verify that AS is authorized to provide access tokens (including this communication channel has securely been obtained either by
authorization information) about RS to C. Also, AS MUST securely manual configuration or in an automated provisioning process. The
have obtained keying material for C, and obtained authorization rules following requirements in alignment with Section 6.5 of
approved by the resource owner (RO) concerning C and RS that relate [I-D.ietf-ace-oauth-authz] therefore must be met:
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 bootstrapped is not part of this document. C and
AS MUST ensure the confidentiality, integrity and authenticity of all
exchanged messages.
Section Section 6 specifies how communication with the AS is secured. o The client MUST securely have obtained keying material to
communicate with the authorization server.
o Furthermore, the client MUST verify that the authorization server
is authorized to provide access tokens (including authorization
information) about the resource server to the client, and that
this authorization information about the authorization server is
still valid.
o Also, the authorization server MUST securely have obtained keying
material for the client, and obtained authorization rules approved
by the resource owner (RO) concerning the client and the resource
server that relate to this keying material.
The client and the authorization server MUST use their respective
keying material for all exchanged messages. How the security
association between the client and the authorization server is
bootstrapped is not part of this document. The client and the
authorization server must ensure the confidentiality, integrity and
authenticity of all exchanged messages within the ACE protocol.
Section Section 6 specifies how communication with the authorization
server is secured.
3.2. RawPublicKey Mode 3.2. RawPublicKey Mode
After C and AS mutually authenticated each other and validated each When the client and the resource server use RawPublicKey
other's authorization, C sends a token request to AS's token authentication, the procedure is as follows: After the client and the
endpoint. The client MUST add a "req_cnf" object carrying either its authorization server mutually authenticated each other and validated
raw public key or a unique identifier for a public key that it has each other's authorization, the client sends a token request to the
previously made known to the authorization server. To prove that the authorization server's token endpoint. The client MUST add a
client is in possession of this key, C MUST use the same keying "req_cnf" object carrying either its raw public key or a unique
material that it uses to secure the communication with AS, e.g., the identifier for a public key that it has previously made known to the
DTLS session. authorization server. It is RECOMMENDED that the client uses DTLS
with the same keying material to secure the communication with the
authorization server, proving possession of the key as part of the
token request. Other mechanisms for proving possession of the key
may be defined in the future.
An example access token request from the client to the AS is depicted An example access token request from the client to the authorization
in Figure 3. server is depicted in Figure 3.
POST coaps://as.example.com/token POST coaps://as.example.com/token
Content-Format: application/ace+cbor Content-Format: application/ace+cbor
Payload: Payload:
{ {
grant_type : client_credentials, grant_type : client_credentials,
req_aud : "tempSensor4711", req_aud : "tempSensor4711",
req_cnf : { req_cnf : {
COSE_Key : { COSE_Key : {
kty : EC2, kty : EC2,
skipping to change at page 6, line 41 skipping to change at page 7, line 38
} }
} }
} }
Figure 3: 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 string "tempSensor4711" on the authorization server using a by the string "tempSensor4711" on the authorization server using a
raw public key. raw public key.
AS MUST check if the client that it communicates with is associated The authorization server MUST check if the client that it
with the RPK in the cnf object before issuing an access token to it. communicates with is associated with the RPK in the "req_cnf"
If AS determines that the request is to be authorized according to parameter before issuing an access token to it. If the authorization
server determines that the request is to be authorized according to
the respective authorization rules, it generates an access token the respective authorization rules, it generates an access token
response for C. The access token MUST be bound to the RPK of the response for the client. The access token MUST be bound to the RPK
client by means of the cnf claim. The response MAY contain a of the client by means of the "cnf" claim.
"profile" parameter with the value "coap_dtls" to indicate that this
profile MUST be used for communication between the client C and the The response MAY contain a "profile" parameter with the value
resource server. The "profile" may be specified out-of-band, in "coap_dtls" to indicate that this profile MUST be used for
which case it does not have to be sent. The response also contains communication between the client and the resource server. The
an access token and an "rs_cnf" parameter containing information "profile" may be specified out-of-band, in which case it does not
about the public key that is used by the resource server. AS MUST have to be sent. The response also contains an access token with
information for the resource server about the client's public key.
The authorization server MUST return in its response the parameter
"rs_cnf" unless it is certain that the client already knows the
public key of the resource server. The authorization server MUST
ascertain that the RPK specified in "rs_cnf" belongs to the resource ascertain that the RPK specified in "rs_cnf" belongs to the resource
server that C wants to communicate with. AS MUST protect the server that the client wants to communicate with. The authorization
integrity of the token. If the access token contains confidential server MUST protect the integrity of the access token such that the
data, AS MUST also protect the confidentiality of the access token. resource server can detect unauthorized changes. If the access token
contains confidential data, the authorization server MUST also
protect the confidentiality of the access token.
C MUST ascertain that the access token response belongs to a certain The client MUST ascertain that the access token response belongs to a
previously sent access token request, as the request may specify the certain previously sent access token request, as the request may
resource server with which C wants to communicate. specify the resource server with which the client wants to
communicate.
An example access token response from the AS to the client is An example access token response from the authorization to the client
depicted in Figure 4. is depicted in Figure 4. Here, the contents of the "access_token"
claim have been truncated to improve readability. Caching proxies
process the Max-Age option in the CoAP response which has a default
value of 60 seconds (Section 5.6.1 of [RFC7252]). The authorization
server SHOULD adjust the Max-Age option such that it does not exceed
the "expires_in" parameter to avoid stale responses.
2.01 Created 2.01 Created
Content-Format: application/ace+cbor Content-Format: application/ace+cbor
Max-Age: 3600 Max-Age: 3560
Payload: Payload:
{ {
access_token : b64'SlAV32hkKG... access_token : b64'SlAV32hkKG...
(remainder of CWT omitted for brevity; (remainder of CWT omitted for brevity;
CWT contains clients RPK in the cnf claim)', CWT contains the client's RPK in the cnf claim)',
expires_in : 3600, expires_in : 3600,
rs_cnf : { rs_cnf : {
COSE_Key : { COSE_Key : {
kty : EC2, kty : EC2,
crv : P-256, crv : P-256,
x : h'd7cc072de2205bdc1537...', x : h'd7cc072de2205bdc1537...',
y : h'f95e1d4b851a2cc80fff...' y : h'f95e1d4b851a2cc80fff...'
} }
} }
} }
Figure 4: Access Token Response Example for RPK Mode Figure 4: Access Token Response Example for RPK Mode
3.2.1. DTLS Channel Setup Between C and RS 3.2.1. DTLS Channel Setup Between Client and Resource Server
Before the client initiates the DTLS handshake with the resource Before the client initiates the DTLS handshake with the resource
server, C MUST send a "POST" request containing the new access token server, the client MUST send a "POST" request containing the obtained
to the authz-info resource hosted by the resource server. After the access token to the authz-info resource hosted by the resource
client server. After the client receives a confirmation that the resource
receives a confirmation that the RS has accepted the access token, it server has accepted the access token, it SHOULD proceed to establish
SHOULD proceed to establish a new DTLS channel with the resource a new DTLS channel with the resource server. The client MUST use its
server. To use the RawPublicKey mode, the client MUST specify the correct public key in the DTLS handshake. If the authorization
public key that AS defined in the "cnf" field of the access token server has specified a "cnf" field in the access token response, the
response in the SubjectPublicKeyInfo structure in the DTLS handshake client MUST use this key. Otherwise, the client MUST use the public
as specified in [RFC7250]. key that it specified in the "req_cnf" of the access token request.
The client MUST specify this public key in the SubjectPublicKeyInfo
structure of the DTLS handshake as described in [RFC7250].
An implementation that supports the RPK mode of this profile MUST at To be consistent with [RFC7252] which allows for shortened MAC tags
least support the ciphersuite TLS_ECDHE_ECDSA_WITH_AES_128_CCM_8 in constrained environments, an implementation that supports the RPK
[RFC7251] with the ed25519 curve (cf. [RFC8032], [RFC8422]). mode of this profile MUST at least support the ciphersuite
TLS_ECDHE_ECDSA_WITH_AES_128_CCM_8 [RFC7251]. As discussed in
[RFC7748], new ECC curves have been defined recently that are
considered superior to the so-called NIST curves. This specification
therefore mandates implementation support for curve25519 (cf.
[RFC8032], [RFC8422]) as this curve said to be efficient and less
dangerous regarding implementation errors than the secp256r1 curve
mandated in [RFC7252].
Note: According to [RFC7252], CoAP implementations MUST support the The resource server MUST check if the access token is still valid, if
ciphersuite TLS_ECDHE_ECDSA_WITH_AES_128_CCM_8 [RFC7251] and the the resource server is the intended destination (i.e., the audience)
NIST P-256 curve. As discussed in [RFC7748], new ECC curves have of the token, and if the token was issued by an authorized
been defined recently that are considered superior to the so- authorization server. The access token is constructed by the
called NIST curves. The curve that is mandatory to implement in authorization server such that the resource server can associate the
this specification is said to be efficient and less dangerous access token with the Client's public key. The "cnf" claim MUST
regarding implementation errors than the secp256r1 curve mandated contain either the client's RPK or, if the key is already known by
in [RFC7252]. the resource server (e.g., from previous communication), a reference
to this key. If the authorization server has no certain knowledge
that the Client's key is already known to the resource server, the
Client's public key MUST be included in the access token's "cnf"
parameter. If CBOR web tokens [RFC8392] are used as recommended in
[I-D.ietf-ace-oauth-authz], keys MUST be encoded as specified in
[RFC8747]. The resource server MUST use its own raw public key in
the DTLS handshake with the client. If the resource server has
several raw public keys, it must already know which key it is
supposed to use with this client. How this is achieved is not part
of this profile.
RS MUST check if the access token is still valid, if RS is the The resource server MUST use the keying material that the
intended destination, i.e., the audience, of the token, and if the authorizations server has specified in the "cnf" parameter in the
token was issued by an authorized AS. The access token is access token for the DTLS handshake with the client. Thus, the
constructed by the authorization server such that the resource server handshake only finishes if the client and the resource server are
can associate the access token with the Client's public key. The able to use their respective keying material.
"cnf" claim MUST contain either C's RPK or, if the key is already
known by the resource server (e.g., from previous communication), a
reference to this key. If the authorization server has no certain
knowledge that the Client's key is already known to the resource
server, the Client's public key MUST be included in the access
token's "cnf" parameter. If CBOR web tokens [RFC8392] are used as
recommended in [I-D.ietf-ace-oauth-authz], keys MUST be encoded as
specified in [I-D.ietf-ace-cwt-proof-of-possession]. 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.
3.3. 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. AS MUST check if the identifier refers to a symmetric key token. The authorization server MUST check if the identifier refers
that was previously generated by AS as a shared secret for the to a symmetric key that was previously generated by the authorization
communication between this client and the resource server. server as a shared secret for the communication between this client
and the resource server. If no such symmetric key was found, the
authorization server MUST generate a new symmetric key that is
returned in its response to the client.
The authorization server MUST determine the authorization rules for The authorization server MUST determine the authorization rules for
the C it communicates with as defined by RO and generate the access the client it communicates with as defined by the resource owner and
token accordingly. If the authorization server authorizes the generate the access token accordingly. If the authorization server
client, it returns an AS-to-Client response. If the profile authorizes the client, it returns an AS-to-Client response. If the
parameter is present, it is set to "coap_dtls". AS MUST ascertain profile parameter is present, it is set to "coap_dtls". The
that the access token is generated for the resource server that C authorization server MUST ascertain that the access token is
wants to communicate with. Also, AS MUST protect the integrity of generated for the resource server that the client wants to
the access token. If the token contains confidential data such as communicate with. Also, the authorization server MUST protect the
the symmetric key, the confidentiality of the token MUST also be integrity of the access token to ensure that the resource server can
protected. Depending on the requested token type and algorithm in detect unauthorized changes. 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 the access token request, the authorization server adds access
Information to the response that provides the client with sufficient Information to the response that provides the client with sufficient
information to setup a DTLS channel with the resource server. AS information to setup a DTLS channel with the resource server. The
adds a "cnf" parameter to the access information carrying a authorization server adds a "cnf" parameter to the access information
"COSE_Key" object that informs the client about the symmetric key carrying a "COSE_Key" object that informs the client about the shared
that is to be used between C and the resource server. The access secret that is to be used between the client and the resource server.
token MUST be bound to the same symmetric key by means of the cnf To convey the same secret to the resource server, the authorization
claim. server either includes it directly in the access token by means of
the "cnf" claim or it provides sufficient information to enable the
resource server to derive the key from the access token using key
derivation.
An example access token request for an access token with a symmetric An example access token request for an access token with a symmetric
proof-of-possession key is illustrated in Figure 5. proof-of-possession key is illustrated in Figure 5.
POST coaps://as.example.com/token POST coaps://as.example.com/token
Content-Format: application/ace+cbor Content-Format: application/ace+cbor
Payload: Payload:
{ {
audience : "smokeSensor1807", audience : "smokeSensor1807",
} }
Figure 5: Example Access Token Request, symmetric PoP-key Figure 5: Example Access Token Request, (implicit) symmetric PoP-key
An example access token response is illustrated in Figure 6. In this A corresponding example access token response is illustrated in
example, the authorization server returns a 2.01 response containing Figure 6. In this example, the authorization server returns a 2.01
a new access token and information for the client, including the response containing a new access token (truncated to improve
symmetric key in the cnf claim. The information is transferred as a readability) and information for the client, including the symmetric
CBOR data structure as specified in [I-D.ietf-ace-oauth-authz]. key in the cnf claim. The information is transferred as a CBOR data
structure as specified in [I-D.ietf-ace-oauth-authz].
2.01 Created 2.01 Created
Content-Format: application/ace+cbor Content-Format: application/ace+cbor
Max-Age: 86400 Max-Age: 85800
Payload: Payload:
{ {
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,
expires_in : 86400, expires_in : 86400,
profile : coap_dtls, profile : coap_dtls,
cnf : { cnf : {
COSE_Key : { COSE_Key : {
kty : symmetric, kty : symmetric,
kid : h'3d027833fc6267ce', kid : h'3d027833fc6267ce',
k : h'73657373696f6e6b6579' k : h'73657373696f6e6b6579'
} }
} }
} }
Figure 6: Example Access Token Response, symmetric PoP-key Figure 6: Example Access Token Response, symmetric PoP-key
The access token also comprises a "cnf" claim. This claim usually The access token also comprises a "cnf" claim. This claim usually
contains a "COSE_Key" object that carries either the symmetric key contains a "COSE_Key" object that carries either the symmetric key
itself or a key identifier that can be used by the resource server to itself or a key identifier that can be used by the resource server to
determine the secret key shared with the client. If the access token determine the secret key it shares with the client. If the access
carries a symmetric key, the access token MUST be encrypted using a token carries a symmetric key, the access token MUST be encrypted
"COSE_Encrypt0" structure. The AS MUST use the keying material using a "COSE_Encrypt0" structure. The authorization server MUST use
shared with the RS to encrypt the token. the keying material shared with the resource server to encrypt the
token.
The "cnf" structure in the access token is provided in Figure 7. The "cnf" structure in the access token is provided in Figure 7.
cnf : { cnf : {
COSE_Key : { COSE_Key : {
kty : symmetric, kty : symmetric,
kid : h'6549694f464361396c4f6277' kid : h'3d027833fc6267ce'
} }
} }
Figure 7: Access Token without Keying Material Figure 7: Access Token without Keying Material
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 [RFC6749], (cf. constructed according to Section 5.2 of [RFC6749], (cf.
Section 5.6.3. of [I-D.ietf-ace-oauth-authz]). Section 5.6.3. of [I-D.ietf-ace-oauth-authz]). Figure 8 shows an
example for a request that has been rejected due to invalid request
parameters.
4.00 Bad Request 4.00 Bad Request
Content-Format: application/ace+cbor Content-Format: application/ace+cbor
Payload: Payload:
{ {
error : invalid_request error : invalid_request
} }
Figure 8: Example Access Token Response With Reject Figure 8: Example Access Token Response With Reject
The method for how the resource server determines the symmetric key The method for how the resource server determines the symmetric key
from an access token containing only a key identifier is application from an access token containing only a key identifier is application-
specific, the remainder of this section provides one example. specific; the remainder of this section provides one example.
The AS and the resource server are assumed to share a key derivation The authorization server and the resource server are assumed to share
key used to derive the symmetric key shared with the client from the a key derivation key used to derive the symmetric key shared with the
key identifier in the access token. The key derivation key may be client from the key identifier in the access token. The key
derived from some other secret key shared between the AS and the derivation key may be derived from some other secret key shared
resource server. This key needs to be securely stored and processed between the authorization server and the resource server. This key
in the same way as the key used to protect the communication between needs to be securely stored and processed in the same way as the key
AS and RS. used to protect the communication between the authorization server
and the resource server.
Knowledge of the symmetric key shared with the client must not reveal Knowledge of the symmetric key shared with the client must not reveal
any information about the key derivation key or other secret keys any information about the key derivation key or other secret keys
shared between AS and resource server. shared between the authorization server and resource server.
In order to generate a new symmetric key to be used by client and In order to generate a new symmetric key to be used by client and
resource server, the AS generates a key identifier and uses the key resource server, the authorization server generates a new key
identifier which MUST be unique among all key identifiers used by the
authorization server. The authorization server then uses the key
derivation key shared with the resource server to derive the derivation key shared with the resource server to derive the
symmetric key as specified below. Instead of providing the keying symmetric key as specified below. Instead of providing the keying
material in the access token, the AS includes the key identifier in material in the access token, the authorization server includes the
the "kid" parameter, see Figure 7. This key identifier enables the key identifier in the "kid" parameter, see Figure 7. This key
resource server to calculate the keying material for the identifier enables the resource server to calculate the symmetric key
communication with the client from the access token using the key used for the communication with the client using the key derivation
derivation key and following Section 11 of [RFC8152] with parameters key and a KDF to be defined by the application, for example HKDF-SHA-
as specified here. The KDF to be used needs to be defined by the 256. The key identifier picked by the authorization server needs to
application, for example HKDF-SHA-256. The key identifier picked by be unique for each access token where a unique symmetric key is
the AS needs to be unique for each access token where a unique required.
symmetric key is required.
The fields in the context information "COSE_KDF_Context" In this example, HKDF consists of the composition of the HKDF-Extract
(Section 11.2 of [RFC8152]) have the following values: and HKDF-Expand steps [RFC5869]. The symmetric key is derived from
the key identifier, the key derivation key and other data:
o AlgorithmID = "ACE-CoAP-DTLS-key-derivation" OKM = HKDF(salt, IKM, info, L),
o PartyUInfo = PartyVInfo = ( null, null, null ) where:
o keyDataLength needs to be defined by the application o OKM, the output keying material, is the derived symmetric key
o protected MUST be a zero length bstr
o other is a zero length bstr o salt is the empty byte string
o SuppPrivInfo is omitted o IKM, the input keying material, is the key derivation key as
defined above
3.3.1. DTLS Channel Setup Between C and RS o info is the serialization of a CBOR array consisting of
([RFC8610]):
info = [
type : tstr,
L : uint,
access_token: map
]
where:
o type is set to the constant text string "ACE-CoAP-DTLS-key-
derivation",
o L is the size of the symmetric key in bytes,
o access_token is the decrypted access_token as transferred from the
authorization server to the resource server.
To ensure uniqueness of the derived shared secret, the authorization
server SHOULD generate a sufficiently random kid value and include
the claims "iat" and either "exp" or "exi" in the access token.
3.3.1. DTLS Channel Setup Between Client and Resource Server
When a client receives an access token response from an authorization When a client receives an access token response from an authorization
server, C MUST ascertain that the access token response belongs to a server, the client MUST check if the access token response is bound
certain previously sent access token request, as the request may to a certain previously sent access token request, as the request may
specify the resource server with which C wants to communicate. specify the resource server with which the client wants to
communicate.
C checks if the payload of the access token response contains an The client checks if the payload of the access token response
"access_token" parameter and a "cnf" parameter. With this contains an "access_token" parameter and a "cnf" parameter. With
information the client can initiate the establishment of a new DTLS this information the client can initiate the establishment of a new
channel with a resource server. To use DTLS with pre-shared keys, DTLS channel with a resource server. To use DTLS with pre-shared
the client follows the PSK key exchange algorithm specified in keys, the client follows the PSK key exchange algorithm specified in
Section 2 of [RFC4279] using the key conveyed in the "cnf" parameter Section 2 of [RFC4279] using the key conveyed in the "cnf" parameter
of the AS response as PSK when constructing the premaster secret. of the AS response as PSK when constructing the premaster secret. To
be consistent with the recommendations in [RFC7252] a client is
expected to offer at least the ciphersuite TLS_PSK_WITH_AES_128_CCM_8
[RFC6655] to the resource server.
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. The client then needs to indicate during the
recent access token in the "psk_identity" field of the DTLS handshake which previously uploaded access token it intends to
use. To do so, it MUST create a "COSE_Key" structure with the "kid"
that was conveyed in the "rs_cnf" claim in the token response from
the authorization server and the key type "symmetric". This
structure then is included as the only element in the "cnf" structure
that is used as value for "psk_identity" as shown in Figure 9.
{ cnf : {
COSE_Key : {
kty: symmetric,
kid : h'3d027833fc6267ce'
}
}
}
Figure 9: Access token containing a single kid parameter
As an alternative to the access token upload, the client can provide
the most 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 as specified in Section 4.2 of [RFC7925] and not
perform any re-coding. This allows the resource server to retrieve
Note: As stated in Section 4.2 of [RFC7925], the PSK identity should the shared secret directly from the "cnf" claim of the access token.
be treated as binary data in the Internet of Things space 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 than zero, it MUST
contents as index for its key store (i.e., treat the contents as key process the contents of the "psk_identity" field as access token that
identifier). The resource server MUST check if it has one or more is stored with the authorization information endpoint, before
access tokens that are associated with the specified key.
If no key with a matching identifier is found, the resource server
MAY process the contents of the "psk_identity" field as access token
that is stored with the authorization information endpoint, before
continuing the DTLS handshake. If the contents of the "psk_identity" continuing the DTLS handshake. If the contents of the "psk_identity"
do not yield a valid access token for the requesting client, the DTLS do not yield a valid access token for the requesting client, the
session setup is terminated with an "illegal_parameter" DTLS alert resource server aborts the DTLS handshake with an "illegal_parameter"
message. alert.
Note1: As a resource server cannot provide a client with a
meaningful PSK identity hint in response to the client's
ClientHello message, the resource server SHOULD NOT send a
ServerKeyExchange message.
Note2: According to [RFC7252], CoAP implementations MUST support the
ciphersuite TLS_PSK_WITH_AES_128_CCM_8 [RFC6655]. A client is
therefore expected to offer at least this ciphersuite to the
resource server.
When RS receives an access token, RS MUST check if the access token When the resource server receives an access token, it MUST check if
is still valid, if RS is the intended destination, i.e., the audience the access token is still valid, if the resource server is the
of the token, and if the token was issued by an authorized AS. This intended destination (i.e., the audience of the token), and if the
token was issued by an authorized authorization server. This
specification assumes that the access token is a PoP token as specification assumes that the access token is a PoP token as
described in [I-D.ietf-ace-oauth-authz] unless specifically stated described in [I-D.ietf-ace-oauth-authz] unless specifically stated
otherwise. Therefore, the access token is bound to a symmetric PoP 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. The resource server may use token introspection [RFC7662] on
the access token to retrieve more information about the specific
token. The use of introspection is out of scope for this
specification.
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. If key derivation is used, the RS uses the the "psk_identity" field. If key derivation is used, the resource
"COSE_KDF_Context" information as described above. server uses the "COSE_KDF_Context" information as described above.
3.4. Resource Access 3.4. Resource Access
Once a DTLS channel has been established as described in Section 3.2 Once a DTLS channel has been established as described in Section 3.2
and Section 3.3, respectively, the client is authorized to access or Section 3.3, respectively, the client is authorized to access
resources covered by the access token it has uploaded to the authz- resources covered by the access token it has uploaded to the authz-
info resource hosted by the resource server. info resource hosted by the resource server.
With the successful establishment of the DTLS channel, C and RS have With the successful establishment of the DTLS channel, the client and
proven that they can use their respective keying material. An access the resource server have proven that they can use their respective
token that is bound to the client's keying material is associated keying material. An access token that is bound to the client's
with the channel. Any request that the resource server receives on keying material is associated with the channel. According to section
this channel MUST be checked against these authorization rules. RS 5.8.1 of [I-D.ietf-ace-oauth-authz], there should be only one access
MUST check for every request if the access token is still valid. token for each client. New access tokens issued by the authorization
Incoming CoAP requests that are not authorized with respect to any server are supposed to replace previously issued access tokens for
access token that is associated with the client MUST be rejected by the respective client. The resource server therefore must have a
the resource server with 4.01 response as described in Section 5.1.1 common understanding with the authorization server how access tokens
of [I-D.ietf-ace-oauth-authz]. are ordered.
The resource server SHOULD treat an incoming CoAP request as Any request that the resource server receives on a DTLS channel that
is tied to an access token via its keying material MUST be checked
against the authorization rules that can be determined with the
access token. The resource server MUST check for every request if
the access token is still valid. If the token has expired, the
resource server MUST remove it. 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. The response MAY include AS Request Creation Hints as
described in Section 5.1.1 of [I-D.ietf-ace-oauth-authz].
The resource server MUST only accept an incoming CoAP request as
authorized if the following holds: authorized if the following holds:
1. The message was received on a secure channel that has been 1. The message was received on a secure channel that has been
established using the procedure defined in this document. established using the procedure defined in this document.
2. The authorization information tied to the sending client is 2. The authorization information tied to the sending client is
valid. valid.
3. The request is destined for the resource server. 3. The request is destined for the resource server.
skipping to change at page 14, line 34 skipping to change at page 16, line 47
[I-D.ietf-ace-oauth-authz] [I-D.ietf-ace-oauth-authz]
1. with response code 4.03 (Forbidden) when the resource URI 1. with response code 4.03 (Forbidden) when the resource URI
specified in the request is not covered by the authorization specified in the request is not covered by the authorization
information, and information, and
2. with response code 4.05 (Method Not Allowed) when the resource 2. with response code 4.05 (Method Not Allowed) when the resource
URI specified in the request covered by the authorization URI specified in the request covered by the authorization
information but not the requested action. information but not the requested action.
The client cannot always know a priori if an Authorized Resource The client MUST ascertain that its keying material is still valid
Request will succeed. It MUST check the validity of its keying before sending a request or processing a response. If the client
material before sending a request or processing a response. If the gets an error response containing AS Request Creation Hints (cf.
client repeatedly gets error responses containing AS Creation Hints Section 5.1.2 of [I-D.ietf-ace-oauth-authz] as response to its
(cf. Section 5.1.2 of [I-D.ietf-ace-oauth-authz] as response to its
requests, it SHOULD request a new access token from the authorization requests, it SHOULD request a new access token from the authorization
server in order to continue communication with the resource server. server in order to continue communication with the resource server.
Unauthorized requests that have been received over a DTLS session Unauthorized requests that have been received over a DTLS session
SHOULD be treated as non-fatal by the RS, i.e., the DTLS session SHOULD be treated as non-fatal by the resource server, i.e., the DTLS
SHOULD be kept alive until the associated access token has expired. session SHOULD be kept alive until the associated access token has
expired.
4. Dynamic Update of Authorization Information 4. Dynamic Update of Authorization Information
The client can update the authorization information stored at the Resource servers must only use a new access token to update the
resource server at any time without changing an established DTLS authorization information for a DTLS session if the keying material
session. To do so, the Client requests a new access token from the that is bound to the token is the same that was used in the DTLS
authorization server for the intended action on the respective handshake. 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.
The client can therefore 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 resource and uploads this access token to the authz-info resource on
the resource server. the resource server.
Figure 9 depicts the message flow where the C requests a new access Figure 10 depicts the message flow where the client requests a new
token after a security association between the client and the access token after a security association between the client and the
resource server has been established using this protocol. If the resource server has been established using this protocol. If the
client wants to update the authorization information, the token client wants to update the authorization information, the token
request MUST specify the key identifier of the proof-of-possession request MUST specify the key identifier of the proof-of-possession
key used for the existing DTLS channel between the client and the key used for the existing DTLS channel between the client and the
resource server in the "kid" parameter of the Client-to-AS request. resource server in the "kid" parameter of the Client-to-AS request.
The authorization server MUST verify that the specified "kid" denotes The authorization server MUST verify that the specified "kid" denotes
a valid verifier for a proof-of-possession token that has previously a valid verifier for a proof-of-possession token that has previously
been issued to the requesting client. Otherwise, the Client-to-AS been issued to the requesting client. Otherwise, the Client-to-AS
request MUST be declined with the error code "unsupported_pop_key" as request MUST be declined with the error code "unsupported_pop_key" as
defined in Section 5.6.3 of [I-D.ietf-ace-oauth-authz]. defined in Section 5.6.3 of [I-D.ietf-ace-oauth-authz].
When the authorization server issues a new access token to update When the authorization server issues a new access token to update
existing authorization information, it MUST include the specified existing authorization information, it MUST include the specified
"kid" parameter in this access token. A resource server MUST replace "kid" parameter in this access token. A resource server MUST replace
the authorization information of any existing DTLS session that is the authorization information of any existing DTLS session that is
identified by this key identifier with the updated authorization identified by this key identifier with the updated authorization
information. information.
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 C RS AS
| <===== DTLS channel =====> | | | <===== DTLS channel =====> | |
| + Access Token | | | + Access Token | |
| | | | | |
| --- Token Request ----------------------------> | | --- Token Request ----------------------------> |
| | | | | |
| <---------------------------- New Access Token - | | <---------------------------- New Access Token - |
| + Access Information | | + Access Information |
| | | | | |
| --- Update /authz-info --> | | | --- Update /authz-info --> | |
| New Access Token | | | New Access Token | |
| | | | | |
| == Authorized Request ===> | | | == Authorized Request ===> | |
| | | | | |
| <=== Protected Resource == | | | <=== Protected Resource == | |
Figure 9: Overview of Dynamic Update Operation Figure 10: Overview of Dynamic Update Operation
5. Token Expiration 5. Token Expiration
DTLS sessions that have been established in accordance with this The resource server MUST delete access tokens that are no longer
profile are always tied to a specific access token. As this token valid. DTLS associations that have been setup in accordance with
may become invalid at any time (e.g. because it has expired), the this profile are always tied to specific tokens (which may be
session may become useless at some point. A resource server exchanged with a dynamic update as described in Section 4). As
therefore MUST terminate existing DTLS sessions after the access tokens may become invalid at any time (e.g., because they have
token for this session has been deleted. expired), the association may become useless at some point. A
resource server therefore MUST terminate existing DTLS association
after the last access token associated with this association has
expired.
As specified in Section 5.8.3 of [I-D.ietf-ace-oauth-authz], the As specified in Section 5.8.3 of [I-D.ietf-ace-oauth-authz], the
resource server MUST notify the client with an error response with resource server MUST notify the client with an error response with
code 4.01 (Unauthorized) for any long running request before code 4.01 (Unauthorized) for any long running request before
terminating the session. terminating the association.
6. Secure Communication with AS 6. Secure Communication with an Authorization Server
As specified in the ACE framework (sections 5.6 and 5.7 of As specified in the ACE framework (sections 5.6 and 5.7 of
[I-D.ietf-ace-oauth-authz]), the requesting entity (RS and/or client) [I-D.ietf-ace-oauth-authz]), the requesting entity (the resource
and the AS communicate via the token endpoint or introspection server and/or the client) and the authorization server communicate
endpoint. The use of CoAP and DTLS for this communication is via the token endpoint or introspection endpoint. The use of CoAP
RECOMMENDED in this profile, other protocols (such as HTTP and TLS or and DTLS for this communication is RECOMMENDED in this profile, other
CoAP and OSCORE) MAY be used instead. protocols (such as HTTP and TLS, or CoAP and OSCORE [RFC8613]) MAY be
used instead.
How credentials (e.g., PSK, RPK, X.509 cert) for using DTLS with the How credentials (e.g., PSK, RPK, X.509 cert) for using DTLS with the
AS are established is out of scope for this profile. authorization server are established is out of scope for this
profile.
If other means of securing the communication with the AS are used, If other means of securing the communication with the authorization
the security protocol MUST fulfill the communication security server are used, the communication security requirements from
requirements in Section 6.2 of [I-D.ietf-ace-oauth-authz]. Section 6.2 of [I-D.ietf-ace-oauth-authz] remain applicable.
7. Security Considerations 7. 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 considerations from section 6 also approach, the general security considerations from section 6 of
apply to this profile. [I-D.ietf-ace-oauth-authz] also apply to this profile.
When using pre-shared keys provisioned by the AS, the security level The authorization server must ascertain that the keying material for
depends on the randomness of PSK, and the security of the TLS cipher the client that it provides to the resource server actually is
suite and key exchange algorithm. associated with this client. Malicious clients may hand over access
tokens containing their own access permissions to other entities.
This problem cannot be completely eliminated. Nevertheless, in RPK
mode it should not be possible for clients to request access tokens
for arbitrary public keys, since that would allow the client to relay
tokens without the need to share its own credentials with others.
The authorization server therefore at some point needs to validate
that the client can actually use the private key corresponding to the
client's public key.
When using pre-shared keys provisioned by the authorization server,
the security level depends on the randomness of PSK, and the security
of the TLS cipher suite and key exchange algorithm. As this
specification targets at constrained environments, message payloads
exchanged between the client and the resource server are expected to
be small and rare. CoAP [RFC7252] mandates the implementation of
cipher suites with abbreviated, 8-byte tags for message integrity
protection. For consistency, this profile requires implementation of
the same cipher suites. For application scenarios where the cost of
full-width authentication tags is low compared to the overall amount
of data being transmitted, the use of cipher suites with 16-byte
integrity protection tags is preferred.
The PSK mode of this profile offers a distribution mechanism to
convey authorization tokens together with a shared secret to a client
and a server. As this specification aims at constrained devices and
uses CoAP [RFC7252] as transfer protocol, at least the ciphersuite
TLS_PSK_WITH_AES_128_CCM_8 [RFC6655] should be supported. The access
tokens and the corresponding shared secrets generated by the
authorization server are expected to be sufficiently short-lived to
provide similar forward-secrecy properties to using ephemeral Diffie-
Hellman (DHE) key exchange mechanisms. For longer-lived access
tokens, DHE ciphersuites should be used.
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. A similar issue exists with the continue with the handshake. A similar issue exists with the
authorization information endpoint where the resource server needs to unprotected authorization information endpoint where the resource
keep valid access tokens until their expiry. Adversaries can fill up server needs to keep valid access tokens until their expiry.
the constrained resource server's internal storage for a very long Adversaries can fill up the constrained resource server's internal
time with interjected or otherwise retrieved valid access tokens. storage for a very long time with interjected or otherwise retrieved
valid access tokens. The protection of access tokens that are stored
in the authorization information endpoint depends on the keying
material that is used between the authorization server and the
resource server: The resource server must ensure that it processes
only access tokens that are encrypted and integrity-protected by an
authorization server that is authorized to provide access tokens for
the resource server.
7.1. Reuse of Existing Sessions
To avoid the overhead of a repeated DTLS handshake, [RFC7925]
recommends session resumption [RFC5077] to reuse session state from
an earlier DTLS association and thus requires client side
implementation. In this specification, the DTLS session is subject
to the authorization rules denoted by the access token that was used
for the initial setup of the DTLS association. Enabling session
resumption would require the server to transfer the authorization
information with the session state in an encrypted SessionTicket to
the client. Assuming that the server uses long-lived keying
material, this could open up attacks due to the lack of forward
secrecy. Moreover, using this mechanism, a client can resume a DTLS
session without proving the possession of the PoP key again.
Therefore, the use of session resumption is NOT RECOMMENDED for
resource servers.
Since renogiation of DTLS associations is prone to attacks as well,
[RFC7925] requires clients to decline any renogiation attempt. A
server that wants to initiate re-keying therefore SHOULD periodically
force a full handshake.
7.2. Multiple Access Tokens
The use of multiple access tokens for a single client increases the The use of multiple access tokens for a single client increases the
strain on the resource server as it must consider every access token strain on the resource server as it must consider every access token
and calculate the actual permissions of the client. Also, tokens may and calculate the actual permissions of the client. Also, tokens may
contradict each other which may lead the server to enforce wrong contradict each other which may lead the server to enforce wrong
permissions. If one of the access tokens expires earlier than permissions. If one of the access tokens expires earlier than
others, the resulting permissions may offer insufficient protection. others, the resulting permissions may offer insufficient protection.
Developers SHOULD avoid using multiple access tokens for a client. Developers SHOULD avoid using multiple access tokens for a client.
Even when a single access token per client is used, an attacker could
compromise the dynamic update mechanism for existing DTLS connections
by delaying or reordering packets destined for the authz-info
endpoint. Thus, the order in which operations occur at the resource
server (and thus which authorization info is used to process a given
client request) cannot be guaranteed. Especially in the presence of
later-issued access tokens that reduce the client's permissions from
the initial access token, it is impossible to guarantee that the
reduction in authorization will take effect prior to the expiration
of the original token.
7.3. Out-of-Band Configuration
To communicate securely, the authorization server, the client and the
resource server require certain information that must be exchanged
outside the protocol flow described in this document. The
authorization server must have obtained authorization information
concerning the client and the resource server that is approved by the
resource owner as well as corresponding keying material. The
resource server must have received authorization information approved
by the resource owner concerning its authorization managers and the
respective keying material. The client must have obtained
authorization information concerning the authorization server
approved by its owner as well as the corresponding keying material.
Also, the client's owner must have approved of the client's
communication with the resource server. The client and the
authorization server must have obtained a common understanding how
this resource server is identified to ensure that the client obtains
access token and keying material for the correct resource server. If
the client is provided with a raw public key for the resource server,
it must be ascertained to which resource server (which identifier and
authorization information) the key is associated. All authorization
information and keying material must be kept up to date.
8. Privacy Considerations 8. Privacy Considerations
This privacy considerations from section 7 of the This privacy considerations from section 7 of the
[I-D.ietf-ace-oauth-authz] apply also to this profile. [I-D.ietf-ace-oauth-authz] apply also to this profile.
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 an authenticated client and the resource server
more detailed information MAY be included with an error response to already exists, more detailed information MAY be included with an
provide the client with sufficient information to react on that error response to provide the client with sufficient information to
particular error. react on that particular error.
Also, unprotected requests to the resource server may reveal Also, unprotected requests to the resource server may reveal
information about the client, e.g., which resources the client information about the client, e.g., which resources the client
attempts to request or the data that the client wants to provide to attempts to request or the data that the client wants to provide to
the resource server. The client SHOULD NOT send confidential data in the resource server. The client SHOULD NOT send confidential data in
an unprotected request. 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.
skipping to change at page 18, line 4 skipping to change at page 22, line 39
9. IANA Considerations 9. 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
Profile Description: Profile for delegating client authentication and Profile Description: Profile for delegating client authentication and
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: TBD (suggested: 1)
Change Controller: IESG Change Controller: IESG
Reference: [RFC-XXXX] Reference: [RFC-XXXX]
10. References 10. Acknowledgments
10.1. Normative References Thanks to Jim Schaad for his contributions and reviews of this
document. Special thanks to Ben Kaduk for his thorough review of
this document.
[I-D.ietf-ace-cwt-proof-of-possession] Ludwig Seitz worked on this document as part of the CelticNext
Jones, M., Seitz, L., Selander, G., Erdtman, S., and H. projects CyberWI, and CRITISEC with funding from Vinnova.
Tschofenig, "Proof-of-Possession Key Semantics for CBOR
Web Tokens (CWTs)", draft-ietf-ace-cwt-proof-of- 11. References
possession-11 (work in progress), October 2019.
11.1. 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-29 Framework (ACE-OAuth)", draft-ietf-ace-oauth-authz-33
(work in progress), December 2019. (work in progress), February 2020.
[I-D.ietf-ace-oauth-params] [I-D.ietf-ace-oauth-params]
Seitz, L., "Additional OAuth Parameters for Authorization Seitz, L., "Additional OAuth Parameters for Authorization
in Constrained Environments (ACE)", draft-ietf-ace-oauth- in Constrained Environments (ACE)", draft-ietf-ace-oauth-
params-07 (work in progress), December 2019. params-13 (work in progress), April 2020.
[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>.
[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>.
[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>.
[RFC7250] Wouters, P., Ed., Tschofenig, H., Ed., Gilmore, J.,
Weiler, S., and T. Kivinen, "Using Raw Public Keys in
Transport Layer Security (TLS) and Datagram Transport
Layer Security (DTLS)", RFC 7250, DOI 10.17487/RFC7250,
June 2014, <https://www.rfc-editor.org/info/rfc7250>.
[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
Security (TLS) / Datagram Transport Layer Security (DTLS) Security (TLS) / Datagram Transport Layer Security (DTLS)
Profiles for the Internet of Things", RFC 7925, Profiles for the Internet of Things", RFC 7925,
DOI 10.17487/RFC7925, July 2016, DOI 10.17487/RFC7925, July 2016,
<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>.
10.2. Informative References [RFC8422] Nir, Y., Josefsson, S., and M. Pegourie-Gonnard, "Elliptic
Curve Cryptography (ECC) Cipher Suites for Transport Layer
Security (TLS) Versions 1.2 and Earlier", RFC 8422,
DOI 10.17487/RFC8422, August 2018,
<https://www.rfc-editor.org/info/rfc8422>.
[RFC8747] Jones, M., Seitz, L., Selander, G., Erdtman, S., and H.
Tschofenig, "Proof-of-Possession Key Semantics for CBOR
Web Tokens (CWTs)", RFC 8747, DOI 10.17487/RFC8747, March
2020, <https://www.rfc-editor.org/info/rfc8747>.
11.2. Informative References
[RFC5077] Salowey, J., Zhou, H., Eronen, P., and H. Tschofenig,
"Transport Layer Security (TLS) Session Resumption without
Server-Side State", RFC 5077, DOI 10.17487/RFC5077,
January 2008, <https://www.rfc-editor.org/info/rfc5077>.
[RFC5869] Krawczyk, H. and P. Eronen, "HMAC-based Extract-and-Expand
Key Derivation Function (HKDF)", RFC 5869,
DOI 10.17487/RFC5869, May 2010,
<https://www.rfc-editor.org/info/rfc5869>.
[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.,
Weiler, S., and T. Kivinen, "Using Raw Public Keys in
Transport Layer Security (TLS) and Datagram Transport
Layer Security (DTLS)", RFC 7250, DOI 10.17487/RFC7250,
June 2014, <https://www.rfc-editor.org/info/rfc7250>.
[RFC7251] McGrew, D., Bailey, D., Campagna, M., and R. Dugal, "AES- [RFC7251] McGrew, D., Bailey, D., Campagna, M., and R. Dugal, "AES-
CCM Elliptic Curve Cryptography (ECC) Cipher Suites for CCM Elliptic Curve Cryptography (ECC) Cipher Suites for
TLS", RFC 7251, DOI 10.17487/RFC7251, June 2014, TLS", RFC 7251, DOI 10.17487/RFC7251, June 2014,
<https://www.rfc-editor.org/info/rfc7251>. <https://www.rfc-editor.org/info/rfc7251>.
[RFC7662] Richer, J., Ed., "OAuth 2.0 Token Introspection",
RFC 7662, DOI 10.17487/RFC7662, October 2015,
<https://www.rfc-editor.org/info/rfc7662>.
[RFC7748] Langley, A., Hamburg, M., and S. Turner, "Elliptic Curves [RFC7748] Langley, A., Hamburg, M., and S. Turner, "Elliptic Curves
for Security", RFC 7748, DOI 10.17487/RFC7748, January for Security", RFC 7748, DOI 10.17487/RFC7748, January
2016, <https://www.rfc-editor.org/info/rfc7748>. 2016, <https://www.rfc-editor.org/info/rfc7748>.
[RFC8032] Josefsson, S. and I. Liusvaara, "Edwards-Curve Digital [RFC8032] Josefsson, S. and I. Liusvaara, "Edwards-Curve Digital
Signature Algorithm (EdDSA)", RFC 8032, Signature Algorithm (EdDSA)", RFC 8032,
DOI 10.17487/RFC8032, January 2017, DOI 10.17487/RFC8032, January 2017,
<https://www.rfc-editor.org/info/rfc8032>. <https://www.rfc-editor.org/info/rfc8032>.
[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 [RFC8610] Birkholz, H., Vigano, C., and C. Bormann, "Concise Data
Curve Cryptography (ECC) Cipher Suites for Transport Layer Definition Language (CDDL): A Notational Convention to
Security (TLS) Versions 1.2 and Earlier", RFC 8422, Express Concise Binary Object Representation (CBOR) and
DOI 10.17487/RFC8422, August 2018, JSON Data Structures", RFC 8610, DOI 10.17487/RFC8610,
<https://www.rfc-editor.org/info/rfc8422>. June 2019, <https://www.rfc-editor.org/info/rfc8610>.
[RFC8613] Selander, G., Mattsson, J., Palombini, F., and L. Seitz,
"Object Security for Constrained RESTful Environments
(OSCORE)", RFC 8613, DOI 10.17487/RFC8613, July 2019,
<https://www.rfc-editor.org/info/rfc8613>.
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
 End of changes. 101 change blocks. 
337 lines changed or deleted 609 lines changed or added

This html diff was produced by rfcdiff 1.47. The latest version is available from http://tools.ietf.org/tools/rfcdiff/