draft-ietf-ace-dtls-authorize-05.txt   draft-ietf-ace-dtls-authorize-06.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: April 11, 2019 Universitaet Bremen TZI Expires: September 1, 2019 Universitaet Bremen TZI
G. Selander G. Selander
Ericsson AB Ericsson AB
L. Seitz L. Seitz
RISE SICS RISE SICS
October 08, 2018 February 28, 2019
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-05 draft-ietf-ace-dtls-authorize-06
Abstract Abstract
This specification defines a profile that allows constrained servers This specification defines a profile of the ACE framework that allows
to delegate client authentication and authorization. The protocol constrained servers to delegate client authentication and
relies on DTLS for communication security between entities in a authorization. The protocol relies on DTLS for communication
constrained network using either raw public keys or pre-shared keys. security between entities in a constrained network using either raw
A resource-constrained server can use this protocol to delegate public keys or pre-shared keys. A resource-constrained server can
management of authorization information to a trusted host with less use this protocol to delegate management of authorization information
severe limitations regarding processing power and memory. 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
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 April 11, 2019. This Internet-Draft will expire on September 1, 2019.
Copyright Notice Copyright Notice
Copyright (c) 2018 IETF Trust and the persons identified as the Copyright (c) 2019 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
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carefully, as they describe your rights and restrictions with respect carefully, as they describe your rights and restrictions with respect
to this document. Code Components extracted from this document must to this document. Code Components extracted from this document must
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the Trust Legal Provisions and are provided without warranty as the Trust Legal Provisions and are provided without warranty as
skipping to change at page 2, line 25 skipping to change at page 2, line 25
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
3. Protocol Flow . . . . . . . . . . . . . . . . . . . . . . . . 5 3. Protocol Flow . . . . . . . . . . . . . . . . . . . . . . . . 5
3.1. Communication between C and AS . . . . . . . . . . . . . 5 3.1. Communication between C and AS . . . . . . . . . . . . . 5
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 C and RS . . . . . . . . . 7
3.3. PreSharedKey Mode . . . . . . . . . . . . . . . . . . . . 8 3.3. PreSharedKey Mode . . . . . . . . . . . . . . . . . . . . 8
3.3.1. DTLS Channel Setup Between C and RS . . . . . . . . . 10 3.3.1. DTLS Channel Setup Between C and RS . . . . . . . . . 11
3.4. Resource Access . . . . . . . . . . . . . . . . . . . . . 12 3.4. Resource Access . . . . . . . . . . . . . . . . . . . . . 12
4. Dynamic Update of Authorization Information . . . . . . . . . 13 4. Dynamic Update of Authorization Information . . . . . . . . . 13
5. Token Expiration . . . . . . . . . . . . . . . . . . . . . . 14 5. Token Expiration . . . . . . . . . . . . . . . . . . . . . . 14
6. Security Considerations . . . . . . . . . . . . . . . . . . . 15 6. Security Considerations . . . . . . . . . . . . . . . . . . . 15
7. Privacy Considerations . . . . . . . . . . . . . . . . . . . 15 7. Privacy Considerations . . . . . . . . . . . . . . . . . . . 15
8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 16 8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 16
9. References . . . . . . . . . . . . . . . . . . . . . . . . . 16 9. References . . . . . . . . . . . . . . . . . . . . . . . . . 16
9.1. Normative References . . . . . . . . . . . . . . . . . . 16 9.1. Normative References . . . . . . . . . . . . . . . . . . 16
9.2. Informative References . . . . . . . . . . . . . . . . . 17 9.2. Informative References . . . . . . . . . . . . . . . . . 17
9.3. URIs . . . . . . . . . . . . . . . . . . . . . . . . . . 18 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 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 obtains an access token, bound to a key (the proof-of- client obtains an access token, bound to a key (the proof-of-
possession key), from an authorization server to prove its 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 [RFC7250] requires the client and server to prove The DTLS handshake requires the client and server to prove that they
that they can use certain keying material. In the RPK mode, the can use certain keying material. In the RPK mode, the client proves
client proves with the DTLS handshake that it can use the RPK bound with the DTLS handshake that it can use the RPK bound to the token
to the token and the server shows that it can use a certain RPK. The and the server shows that it can use a certain RPK. The access token
access token must be presented to the resource server. For the RPK must be presented to the resource server. For the RPK mode, the
mode, the access token needs to be uploaded to the resource server access token needs to be uploaded to the resource server before the
before the handshake is initiated, as described in Section 5.8.1 of handshake is initiated, as described in Section 5.8.1 of the ACE
draft-ietf-ace-oauth-authz [1]. 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.
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 [2]. described in [I-D.ietf-ace-oauth-authz] and in
[I-D.ietf-ace-oauth-params].
The authz-info resource refers to the authz-info endpoint as The authz-info resource refers to the authz-info endpoint as
specified in I-D.ietf-ace-oauth-authz [3]. specified in [I-D.ietf-ace-oauth-authz].
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 C can use CoAP over DTLS to retrieve an access token from the
authorization server (AS) for a protected resource hosted on the authorization server (AS) for a protected resource hosted on the
resource server. resource server.
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 I- protected resource(s) it wants to access on RS as specified in
D.ietf-ace-oauth-authz [4]. Figure 1 shows the typical message flow [I-D.ietf-ace-oauth-authz]. Figure 1 shows the typical message flow
in this scenario (messages in square brackets are optional): in this scenario (messages in square brackets are optional):
C RS AS C RS AS
| [-- Resource Request --->] | | | [-- Resource Request --->] | |
| | | | | |
| [<----- AS Information --] | | | [<----- AS Information --] | |
| | | | | |
| --- 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 AS in charge of a resource hosted at the RS, C MAY
send an initial Unauthorized Resource Request message to the RS. The send an initial Unauthorized Resource Request message to the RS. The
RS then denies the request and sends an AS information message RS then denies the request and sends an AS information message
containing the address of its AS back to the client as specified in containing the address of its AS back to the client as specified in
Section 5.1.2 of draft-ietf-ace-oauth-authz [5]. 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 AS as specified
in I-D.ietf-ace-oauth-authz [6]. As the access token request as well in [I-D.ietf-ace-oauth-authz]. As the access token request as well
as the response may contain confidential data, the communication as the response may contain confidential data, the communication
between the client and the authorization server MUST be between the client and the authorization server MUST be
confidentiality-protected and ensure authenticity. C may have been confidentiality-protected and ensure authenticity. C may have been
registered at the AS via the OAuth 2.0 client registration mechanism 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]. 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 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, i.e. the authz-info the access token to the authz-info resource, i.e. the authz-info
endpoint, on the resource server before starting the DTLS handshake, endpoint, on the resource server before starting the DTLS handshake,
as described in Section 5.8.1 of draft-ietf-ace-oauth-authz [8]. If as described in Section 5.8.1 of [I-D.ietf-ace-oauth-authz]. If only
only symmetric cryptography is used between the client and the symmetric cryptography is used between the client and the resource
resource server, the access token MAY instead be transferred in the server, the access token MAY instead be transferred in the DTLS
DTLS ClientKeyExchange message (see Section 3.3.1). 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 ==> | |
| | | | | |
skipping to change at page 5, line 27 skipping to change at page 5, line 27
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 C and AS must be
secured. Depending on the used CoAP security mode (see also secured. Depending on the used CoAP security mode (see also
Section 9 of RFC 7252 [9]), the Client-to-AS request, AS-to-Client Section 9 of [RFC7252], the Client-to-AS request, AS-to-Client
response and DTLS session establishment carry slightly different response and DTLS session establishment carry slightly different
information. Section 3.2 addresses the use of raw public keys while 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. Section 3.3 defines how pre-shared keys are used in this profile.
3.1. Communication between C and AS 3.1. Communication between C and AS
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 C can request the access token, C and AS must
establish a secure communication channel. C must securely have establish a secure communication channel. C must securely have
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confidentiality, integrity and authenticity, and enable the client to confidentiality, integrity and authenticity, and enable the client to
determine if it is the intended recipient of a message, e.g., by 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 using an AEAD mechanism. C must also be able to determine if a
response from AS belongs to a certain request. Additionally, the response from AS belongs to a certain request. Additionally, the
protocol must offer replay protection. protocol must offer replay protection.
3.2. RawPublicKey Mode 3.2. RawPublicKey Mode
After C and AS mutually authenticated each other and validated each After C and AS mutually authenticated each other and validated each
other's authorization, C sends a token request to AS's token other's authorization, C sends a token request to AS's token
endpoint. The client MUST add a "cnf" object carrying either its raw endpoint. The client MUST add a "req_cnf" object carrying either its
public key or a unique identifier for a public key that it has raw 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, C MUST use the same keying client is in possession of this key, C MUST use the same keying
material that it uses to secure the communication with AS, e.g., the material that it uses to secure the communication with AS, e.g., the
DTLS session. DTLS session.
An example access token request from the client to the AS is depicted An example access token request from the client to the AS is depicted
in Figure 3. 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
skipping to change at page 7, line 26 skipping to change at page 7, line 26
3.2.1. DTLS Channel Setup Between C and RS 3.2.1. DTLS Channel Setup Between C and RS
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, C MUST send a "POST" request containing the new access token
to the authz-info resource hosted by the resource server. If this to the authz-info resource hosted by the resource server. If this
operation yields a positive response, the client SHOULD proceed to operation yields a positive response, the client SHOULD proceed to
establish a new DTLS channel with the resource server. To use the establish a new DTLS channel with the resource server. To use the
RawPublicKey mode, the client MUST specify the public key that AS RawPublicKey mode, the client MUST specify the public key that AS
defined in the "cnf" field of the access token response in the defined in the "cnf" field of the access token response in the
SubjectPublicKeyInfo structure in the DTLS handshake as specified in SubjectPublicKeyInfo structure in the DTLS handshake as specified in
RFC 7250 [10]. [RFC7250].
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 RFC 7252 [11], CoAP implementations MUST support Note: According to [RFC7252], CoAP implementations MUST support the
the ciphersuite TLS_ECDHE_ECDSA_WITH_AES_128_CCM_8 [RFC7251] and ciphersuite TLS_ECDHE_ECDSA_WITH_AES_128_CCM_8 [RFC7251] and the
the NIST P-256 curve. As discussed in RFC 7748 [12], new ECC NIST P-256 curve. As discussed in [RFC7748], new ECC curves have
curves have been defined recently that are considered superior to been defined recently that are considered superior to the so-
the so-called NIST curves. The curve that is mandatory to called NIST curves. The curve that is mandatory to implement in
implement in this specification is said to be efficient and less this specification is said to be efficient and less dangerous
dangerous regarding implementation errors than the secp256r1 curve regarding implementation errors than the secp256r1 curve mandated
mandated in RFC 7252 [13]. in [RFC7252].
RS MUST check if the access token is still valid, if RS is the RS MUST check if the access token is still valid, if RS is the
intended destination, i.e., the audience, of the token, and if the intended destination, i.e., the audience, of the token, and if the
token was issued by an authorized AS. The access token is token was issued by an authorized AS. The access token is
constructed by the authorization server such that the resource server constructed by the authorization server such that the resource server
can associate the access token with the Client's public key. The can associate the access token with the Client's public key. The
"cnf" claim MUST contain either C's RPK or, if the key is already "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 known by the resource server (e.g., from previous communication), a
reference to this key. If the authorization server has no certain reference to this key. If the authorization server has no certain
knowledge that the Client's key is already known to the resource knowledge that the Client's key is already known to the resource
server, the Client's public key MUST be included in the access server, the Client's public key MUST be included in the access
token's "cnf" parameter. If CBOR web tokens [RFC8392] are used as token's "cnf" parameter. If CBOR web tokens [RFC8392] are used as
recommended in I-D.ietf-ace-oauth-authz [14], unencrypted keys MUST recommended in [I-D.ietf-ace-oauth-authz], keys MUST be encoded as
be specified using a "COSE_Key" object, encrypted keys with a specified in [I-D.ietf-ace-cwt-proof-of-possession]. RS MUST use the
"COSE_Encrypt0" structure and references to the key as "key_id" keying material in the handshake that AS specified in the rs_cnf
parameters in a CBOR map. RS MUST use the keying material in the parameter in the access token. Thus, the handshake only finishes if
handshake that AS specified in the rs_cnf parameter in the access C and RS are able to use their respective keying material.
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. AS MUST check if the identifier refers to a symmetric key
that was previously generated by AS as a shared secret for the that was previously generated by AS as a shared secret for the
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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. AS
adds a "cnf" parameter to the access information carrying a adds a "cnf" parameter to the access information carrying a
"COSE_Key" object that informs the client about the symmetric key "COSE_Key" object that informs the client about the symmetric key
that is to be used between C and the resource server. that is to be used between C and the resource server.
An example access token response is illustrated in Figure 4. In this An example access token response is illustrated in Figure 4. In this
example, the authorization server returns a 2.01 response containing example, the authorization server returns a 2.01 response containing
a new access token and information for the client, including the a new access token and information for the client, including the
symmetric key in the cnf claim. The information is transferred as a symmetric key in the cnf claim. The information is transferred as a
CBOR data structure as specified in I-D.ietf-ace-oauth-authz [15]. 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: 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,
expires_in: 86400, expires_in: 86400,
profile: coap_dtls, profile: coap_dtls,
cnf: { cnf: {
COSE_Key: { COSE_Key: {
kty: symmetric, kty: symmetric,
alg: TLS_PSK_WITH_AES_128_CCM_8
kid: h'3d027833fc6267ce',
k: h'73657373696f6e6b6579' k: h'73657373696f6e6b6579'
} }
} }
} }
Figure 4: Example Access Token Response Figure 4: Example Access Token Response
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 or a key identifier that can be used by the resource server itself or a key identifier that can be used by the resource server to
to determine the shared secret. If the access token carries a determine the secret key shared with the client. If the access token
symmetric key, the access token MUST be encrypted using a carries a symmetric key, the access token MUST be encrypted using a
"COSE_Encrypt0" structure. The AS MUST use the keying material "COSE_Encrypt0" structure. The AS MUST use the keying material
shared with the RS to encrypt the token. shared with the RS to encrypt the token.
Instead of providing the keying material, the AS MAY include a key A response that declines any operation on the requested resource is
derivation function and a salt in the access token that enables the constructed according to Section 5.2 of [RFC6749], (cf.
Section 5.6.3. of [I-D.ietf-ace-oauth-authz]).
4.00 Bad Request
Content-Format: application/ace+cbor
{
error: invalid_request
}
Figure 5: Example Access Token Response With Reject
The method for how the resource server determines the symmetric key
from an access token containing only a key identifier is application
specific, the remainder of this section provides one example.
The AS and the resource server are assumed to share a key derivation
key used to derive the symmetric key shared with the client from the
key identifier in the access token. The key derivation key may be
derived from some other secret key shared between the AS and the
resource server. Knowledge of the symmetric key shared with the
client must not reveal any information about the key derivation key
or other secret keys shared between AS and resource server.
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
derivation key shared with the resource server to derive the
symmetric key as specified below. Instead of providing the keying
material in the access token, the AS includes the key identifier in
the "kid" parameter, see Figure 6. This key identifier enables the
resource server to calculate the keying material for the resource server to calculate the keying material for the
communication with C from the access token. In this case, the token communication with the client from the access token using the key
contains a "cnf" structure that specifies the key derivation derivation key and following Section 11 of [RFC8152] with parameters
algorithm and the salt that the AS has used to construct the shared as specified here. The KDF to be used needs to be defined by the
key. AS and RS MUST use their shared keying material for the key application, for example HKDF-SHA-256. The key identifier picked by
derivation, and the key derivation MUST follow Section 11 of RFC 8152 the AS needs to be unique for each access token where a unique
[16] with parameters as specified here. The KDF specified in the symmetric key is required.
"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" The fields in the context information "COSE_KDF_Context"
(Section 11.2 of RFC 8152 [17]) MUST have the following values: (Section 11.2 of [RFC8152]) have the following values:
o AlgorithmID = "ACE-CoAP-DTLS-salt" o AlgorithmID = "ACE-CoAP-DTLS-key-derivation"
o PartyUInfo = PartyVInfo = ( null, null, null ) 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 keyDataLength is a uint equal the length of the symmetric key
shared between C and RS in bits
o protected MUST be a zero length bstr o protected MUST be a zero length bstr
o other is a zero length bstr o other is a zero length bstr
o SuppPrivInfo is omitted o SuppPrivInfo is omitted
An example "cnf" structure specifying HMAC-based key derivation of a The "cnf" structure in the access token is provided in Figure 6.
symmetric key with SHA-256 as pseudo-random function and a random
salt value is provided in Figure 5.
cnf : { cnf : {
kty : symmetric, COSE_Key : {
alg : HKDF-SHA-256, kty : symmetric,
salt : h'eIiOFCa9lObw' alg : TLS_PSK_WITH_AES_128_CCM_8,
kid : h'eIiOFCa9lObw'
}
} }
Figure 5: Key Derivation Specification in an Access Token Figure 6: Access Token without Keying Material
A response that declines any operation on the requested resource is
constructed according to Section 5.2 of RFC 6749 [18], (cf.
Section 5.7.3. of draft-ietf-ace-oauth-authz [19]).
4.00 Bad Request
Content-Format: application/ace+cbor
{
error: invalid_request
}
Figure 6: Example Access Token Response With Reject
3.3.1. DTLS Channel Setup Between C and RS 3.3.1. DTLS Channel Setup Between C and RS
When a client receives an access token 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, C MUST ascertain that the access token response belongs to a
certain previously sent access token request, as the request may 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 C wants to communicate.
C checks if the payload of the access token response contains an C checks if the payload of the access token response contains an
"access_token" parameter and a "cnf" parameter. With this "access_token" parameter and a "cnf" parameter. With this
information the client can initiate the establishment of a new DTLS information the client can initiate the establishment of a new DTLS
channel with a resource server. To use DTLS with pre-shared keys, channel with a resource server. To use DTLS with pre-shared keys,
the client follows the PSK key exchange algorithm specified in the client follows the PSK key exchange algorithm specified in
Section 2 of RFC 4279 [20] using the key conveyed in the "cnf" Section 2 of [RFC4279] using the key conveyed in the "cnf" parameter
parameter of the AS response as PSK when constructing the premaster of the AS response as PSK when constructing the premaster secret.
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 RFC 7925 [21], the PSK identity Note: As stated in Section 4.2 of [RFC7925], the PSK identity should
should be treated as binary data in the Internet of Things space be treated as binary data in the Internet of Things space and not
and not assumed to have a human-readable form of any sort. 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. access tokens that are associated with the specified key.
If no key with a matching identifier is found, the resource server If no key with a matching identifier is found, the resource server
MAY process the contents of the "psk_identity" field as access token MAY process the contents of the "psk_identity" field as access token
that is stored with the authorization information endpoint, before 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 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 Note1: As a resource server cannot provide a client with a
meaningful PSK identity hint in response to the client's meaningful PSK identity hint in response to the client's
ClientHello message, the resource server SHOULD NOT send a ClientHello message, the resource server SHOULD NOT send a
ServerKeyExchange message. ServerKeyExchange message.
Note2: According to RFC 7252 [22], CoAP implementations MUST support Note2: According to [RFC7252], CoAP implementations MUST support the
the ciphersuite TLS_PSK_WITH_AES_128_CCM_8 [RFC6655]. A client is 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.
When RS receives an access token, RS MUST check if the access token When RS receives an access token, RS MUST check if the access token
is still valid, if RS is the intended destination, i.e., the audience is still valid, if RS is the intended destination, i.e., the audience
of the token, and if the token was issued by an authorized AS. This 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 specification assumes that the access token is a PoP token as
described in I-D.ietf-ace-oauth-authz [23] 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.
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 RS uses the
"COSE_KDF_Context" information as described above. "COSE_KDF_Context" information as described above.
skipping to change at page 12, line 28 skipping to change at page 12, line 44
With the successful establishment of the DTLS channel, C and RS have With the successful establishment of the DTLS channel, C and RS have
proven that they can use their respective keying material. An access proven that they can use their respective keying material. An access
token that is bound to the client's keying material is associated token that is bound to the client's keying material is associated
with the channel. Any request that the resource server receives on with the channel. Any request that the resource server receives on
this channel MUST be checked against these authorization rules. RS this channel MUST be checked against these authorization rules. RS
MUST check for every request if the access token is still valid. MUST check for every request if the access token is still valid.
Incoming CoAP requests that are not authorized with respect to any Incoming CoAP requests that are not authorized with respect to any
access token that is associated with the client MUST be rejected by 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 the resource server with 4.01 response as described in Section 5.1.1
of draft-ietf-ace-oauth-authz [24]. of [I-D.ietf-ace-oauth-authz].
The resource server SHOULD treat an incoming CoAP request as The resource server SHOULD treat 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.
4. The resource URI specified in the request is covered by the 4. The resource URI specified in the request is covered by the
authorization information. authorization information.
5. The request method is an authorized action on the resource with 5. The request method is an authorized action on the resource with
respect to the authorization information. respect to the authorization information.
Incoming CoAP requests received on a secure DTLS channel that are not 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- thus authorized MUST be rejected according to Section 5.8.2 of
ietf-ace-oauth-authz [25] [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 cannot always know a priori if an Authorized Resource
Request will succeed. If the client repeatedly gets error responses Request will succeed. It must check the validity of its keying
containing AS Information (cf. Section 5.1.2 of draft-ietf-ace- material before sending a request or processing a response. If the
oauth-authz [26]) as response to its requests, it SHOULD request a client repeatedly gets error responses containing AS Creation Hints
new access token from the authorization server in order to continue (cf. Section 5.1.2 of [I-D.ietf-ace-oauth-authz] as response to its
communication with the resource server. requests, it SHOULD request a new access token from the authorization
server in order to continue communication with the resource server.
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 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 The client can update the authorization information stored at the
resource server at any time without changing an established DTLS resource server at any time without changing an established DTLS
session. To do so, the Client requests a new access token from the session. To do so, the Client requests a new access token from the
authorization server for the intended action on the respective 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.
skipping to change at page 13, line 39 skipping to change at page 14, line 11
token after a security association between the client and the 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 existing DTLS channel request MUST specify the key identifier of the existing DTLS channel
between the client and the resource server in the "kid" parameter of between the client and the resource server in the "kid" parameter of
the Client-to-AS request. The authorization server MUST verify that the Client-to-AS request. The authorization server MUST verify that
the specified "kid" denotes a valid verifier for a proof-of- the specified "kid" denotes a valid verifier for a proof-of-
possession token that has previously been issued to the requesting possession token that has previously been issued to the requesting
client. Otherwise, the Client-to-AS request MUST be declined with 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 the error code "unsupported_pop_key" as defined in Section 5.6.3 of
draft-ietf-ace-oauth-authz [27]. [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 "kid" parameter in this access token. A resource server MUST replace
associate the updated authorization information with any existing the authorization information of any existing DTLS session that is
DTLS session that is identified by this key identifier. identified by this key identifier with the updated authorization
information.
Note: By associating the access tokens with the identifier of an Note: By associating the access tokens with the identifier of an
existing DTLS session, the authorization information can be existing DTLS session, the authorization information can be
updated without changing the cryptographic keys for the DTLS updated without changing the cryptographic keys for the DTLS
communication between the client and the resource server, i.e. an communication between the client and the resource server, i.e. an
existing session can be used with updated permissions. existing session can be used with updated permissions.
C RS AS C RS AS
| <===== DTLS channel =====> | | | <===== DTLS channel =====> | |
| + Access Token | | | + Access Token | |
skipping to change at page 14, line 33 skipping to change at page 15, line 7
5. Token Expiration 5. Token Expiration
DTLS sessions that have been established in accordance with this DTLS sessions that have been established in accordance with this
profile are always tied to a specific set of access tokens. As these 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 tokens may become invalid at any time (either because the token has
expired or the responsible authorization server has revoked the expired or the responsible authorization server has revoked the
token), the session may become useless at some point. A resource token), the session may become useless at some point. A resource
server therefore MUST terminate existing DTLS sessions after the last server therefore MUST terminate existing DTLS sessions after the last
valid access token for this session has been deleted. valid access token for this session has been deleted.
As specified in Section 5.8.3 of draft-ietf-ace-oauth-authz [28], 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 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 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. A similar issue exists with the
authorization information endpoint where the resource server needs to
[I-D.tiloca-tls-dos-handshake] specifies a TLS extension to prevent keep valid access tokens until their expiry. Adversaries can fill up
this type of attack which is applicable especially for constrained the constrained resource server's internal storage for a very long
environments where the authorization server can act as trust anchor. time with interjected or otherwise retrieved valid 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.
7. Privacy Considerations 7. Privacy Considerations
skipping to change at page 16, line 31 skipping to change at page 16, line 38
Profile ID: 1 Profile ID: 1
Change Controller: IESG Change Controller: IESG
Reference: [RFC-XXXX] Reference: [RFC-XXXX]
9. References 9. References
9.1. Normative References 9.1. Normative References
[I-D.ietf-ace-cwt-proof-of-possession]
Jones, M., Seitz, L., Selander, G., Erdtman, S., and H.
Tschofenig, "Proof-of-Possession Key Semantics for CBOR
Web Tokens (CWTs)", draft-ietf-ace-cwt-proof-of-
possession-06 (work in progress), February 2019.
[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-16 Framework (ACE-OAuth)", draft-ietf-ace-oauth-authz-21
(work in progress), October 2018. (work in progress), February 2019.
[I-D.tiloca-tls-dos-handshake] [I-D.ietf-ace-oauth-params]
Tiloca, M., Seitz, L., Hoeve, M., and O. Bergmann, Seitz, L., "Additional OAuth Parameters for Authorization
"Extension for protecting (D)TLS handshakes against Denial in Constrained Environments (ACE)", draft-ietf-ace-oauth-
of Service", draft-tiloca-tls-dos-handshake-02 (work in params-04 (work in progress), February 2019.
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>.
[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",
RFC 6749, DOI 10.17487/RFC6749, October 2012,
<https://www.rfc-editor.org/info/rfc6749>.
[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>.
skipping to change at page 18, line 20 skipping to change at page 18, line 35
[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>.
9.3. URIs
[1] https://tools.ietf.org/html/draft-ietf-ace-oauth-authz-
16#section-5.8.1
[2] https://tools.ietf.org/html/draft-ietf-ace-oauth-authz
[3] https://tools.ietf.org/html/draft-ietf-ace-oauth-authz
[4] https://tools.ietf.org/html/draft-ietf-ace-oauth-authz
[5] https://tools.ietf.org/html/draft-ietf-ace-oauth-authz-
16#section-5.1.2
[6] https://tools.ietf.org/html/draft-ietf-ace-oauth-authz
[7] https://tools.ietf.org/html/draft-ietf-ace-oauth-authz-
16#section-5.3
[8] https://tools.ietf.org/html/draft-ietf-ace-oauth-authz-
16#section-5.8.1
[9] https://tools.ietf.org/html/rfc7252#section-9
[10] https://tools.ietf.org/html/rfc7250
[11] https://tools.ietf.org/html/rfc7252
[12] https://tools.ietf.org/html/rfc7748
[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
Email: gerdes@tzi.org Email: gerdes@tzi.org
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