Internet DRAFT - draft-ietf-oauth-pop-key-distribution
draft-ietf-oauth-pop-key-distribution
Network Working Group J. Bradley
Internet-Draft Ping Identity
Intended status: Standards Track P. Hunt
Expires: September 28, 2019 Oracle Corporation
M. Jones
Microsoft
H. Tschofenig
Arm Ltd.
M. Meszaros
GITDA
March 27, 2019
OAuth 2.0 Proof-of-Possession: Authorization Server to Client Key
Distribution
draft-ietf-oauth-pop-key-distribution-07
Abstract
RFC 6750 specified the bearer token concept for securing access to
protected resources. Bearer tokens need to be protected in transit
as well as at rest. When a client requests access to a protected
resource it hands-over the bearer token to the resource server.
The OAuth 2.0 Proof-of-Possession security concept extends bearer
token security and requires the client to demonstrate possession of a
key when accessing a protected resource.
Status of This Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet-
Drafts is at https://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."
This Internet-Draft will expire on September 28, 2019.
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Copyright Notice
Copyright (c) 2019 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
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described in the Simplified BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 4
3. Processing Instructions . . . . . . . . . . . . . . . . . . . 4
4. Examples . . . . . . . . . . . . . . . . . . . . . . . . . . 5
4.1. Symmetric Key Transport . . . . . . . . . . . . . . . . . 5
4.1.1. Client-to-AS Request . . . . . . . . . . . . . . . . 5
4.1.2. Client-to-AS Response . . . . . . . . . . . . . . . . 6
4.2. Asymmetric Key Transport . . . . . . . . . . . . . . . . 9
4.2.1. Client-to-AS Request . . . . . . . . . . . . . . . . 9
4.2.2. Client-to-AS Response . . . . . . . . . . . . . . . . 10
5. Security Considerations . . . . . . . . . . . . . . . . . . . 11
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 13
6.1. OAuth Access Token Types . . . . . . . . . . . . . . . . 13
6.2. OAuth Parameters Registration . . . . . . . . . . . . . . 13
6.3. OAuth Extensions Error Registration . . . . . . . . . . . 13
7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 13
8. References . . . . . . . . . . . . . . . . . . . . . . . . . 14
8.1. Normative References . . . . . . . . . . . . . . . . . . 14
8.2. Informative References . . . . . . . . . . . . . . . . . 15
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 16
1. Introduction
The work on proof-of-possession tokens, an extended token security
mechanisms for OAuth 2.0, is motivated in [22]. This document
defines the ability for the client request and to obtain PoP tokens
from the authorization server. After successfully completing the
exchange the client is in possession of a PoP token and the keying
material bound to it. Clients that access protected resources then
need to demonstrate knowledge of the secret key that is bound to the
PoP token.
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To best describe the scope of this specification, the OAuth 2.0
protocol exchange sequence is shown in Figure 1. The extension
defined in this document piggybacks on the message exchange marked
with (C) and (D). To demonstrate possession of the private/secret
key to the resource server protocol mechanisms outside the scope of
this document are used.
+--------+ +---------------+
| |--(A)- Authorization Request ->| Resource |
| | | Owner |
| |<-(B)-- Authorization Grant ---| |
| | +---------------+
| |
| | +---------------+
| |--(C)-- Authorization Grant -->| |
| Client | (resource, req_cnf) | Authorization |
| | | Server |
| |<-(D)-- PoP Access Token ------| |
| | (rs_cnf, token_type) +---------------+
| |
| | +---------------+
| |--(E)-- PoP Access Token ----->| |
| | (with proof of private key) | Resource |
| | | Server |
| |<-(F)--- Protected Resource ---| |
+--------+ +---------------+
Figure 1: Augmented OAuth 2.0 Protocol Flow
In OAuth 2.0 [2] access tokens can be obtained via authorization
grants and using refresh tokens. The core OAuth specification
defines four authorization grants, see Section 1.3 of [2], and [19]
adds an assertion-based authorization grant to that list. The token
endpoint, which is described in Section 3.2 of [2], is used with
every authorization grant except for the implicit grant type. In the
implicit grant type the access token is issued directly.
This specification extends the functionality of the token endpoint,
i.e., the protocol exchange between the client and the authorization
server, to allow keying material to be bound to an access token. Two
types of keying material can be bound to an access token, namely
symmetric keys and asymmetric keys. Conveying symmetric keys from
the authorization server to the client is described in Section 4.1
and the procedure for dealing with asymmetric keys is described in
Section 4.2.
This document describes how the client requests and obtains a PoP
access token from the authorization server for use with HTTPS-based
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transport. The use of alternative transports, such as Constrained
Application Protocol (CoAP), is described in [24].
2. Terminology
The key words 'MUST', 'MUST NOT', 'REQUIRED', 'SHALL', 'SHALL NOT',
'SHOULD', 'SHOULD NOT', 'RECOMMENDED', 'MAY', and 'OPTIONAL' in this
specification are to be interpreted as described in [1].
Session Key:
In the context of this specification 'session key' refers to fresh
and unique keying material established between the client and the
resource server. This session key has a lifetime that corresponds
to the lifetime of the access token, is generated by the
authorization server and bound to the access token.
This document uses the following abbreviations:
JWA: JSON Web Algorithms[7]
JWT: JSON Web Token[9]
JWS: JSON Web Signature[6]
JWK: JSON Web Key[5]
JWE: JSON Web Encryption[8]
CWT: CBOR Web Token[13]
COSE: CBOR Object Signing and Encryption[14]
3. Processing Instructions
Step (0): As an initial step the client typically determines the
resource server it wants to interact with. This may, for example,
happen as part of a discovery procedure or via manual
configuration.
Step (1): The client starts the OAuth 2.0 protocol interaction
based on the selected grant type.
Step (2): When the client interacts with the token endpoint to
obtain an access token it MUST use the resource identicator
parameter, defined in [16], or the audience parameter, defined in
[15], when symmetric PoP tokens are used. For asymmetric PoP
tokens the use of resource indicators and audience is optional but
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RECOMMENDED. The parameters 'audience' and 'resource' both allow
the client to express the location of the target service and the
difference between the two is described in [15]. As a summary,
'audience' allows expressing a logical name while 'resource'
contains an absolute URI. More details about the 'resource'
parameter can be found in [16].
Step (3): The authorization server parses the request from the
server and determines the suitable response based on OAuth 2.0 and
the PoP token credential procedures.
Note that PoP access tokens may be encoded in a variety of ways:
JWT The access token may be encoded using the JSON Web Token (JWT)
format [9]. The proof-of-possession token functionality is
described in [10]. A JWT encoded PoP token MUST be protected
against modification by either using a digital signature or a
keyed message digest, as described in [6]. The JWT may also be
encrypted using [8].
CWT [13] defines an alternative token format based on CBOR. The
proof-of-possession token functionality is defined in [12]. A CWT
encoded PoP token MUST be protected against modification by either
using a digital signature or a keyed message digest, as described
in [12].
If the access token is only a reference then a look-up by the
resource server is needed, as described in the token introspection
specification [23].
Note that the OAuth 2.0 framework nor this specification does not
mandate a specific PoP token format but using a standardized format
will improve interoperability and will lead to better code re-use.
Application layer interactions between the client and the resource
server are beyond the scope of this document.
4. Examples
This section provides a number of examples.
4.1. Symmetric Key Transport
4.1.1. Client-to-AS Request
The client starts with a request to the authorization server
indicating that it is interested to obtain a token for
https://resource.example.com
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POST /token HTTP/1.1
Host: authz.example.com
Authorization: Basic czZCaGRSa3F0MzpnWDFmQmF0M2JW
Content-Type: application/x-www-form-urlencoded;charset=UTF-8
grant_type=authorization_code
&code=SplxlOBeZQQYbYS6WxSbIA
&scope=calendar%20contacts
&redirect_uri=https%3A%2F%2Fclient%2Eexample%2Ecom%2Fcb
&resource=https%3A%2F%2Fresource.example.com
Example Request to the Authorization Server
4.1.2. Client-to-AS Response
If the access token request has been successfully verified by the
authorization server and the client is authorized to obtain a PoP
token for the indicated resource server, the authorization server
issues an access token and optionally a refresh token.
Figure 2 shows a response containing a token and a "cnf" parameter
with a symmetric proof-of-possession key both encoded in a JSON-based
serialization format. The "cnf" parameter contains the RFC 7517 [5]
encoded key element.
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HTTP/1.1 200 OK
Content-Type: application/json
Cache-Control: no-store
{
"access_token":"SlAV32hkKG ...
(remainder of JWT omitted for brevity;
JWT contains JWK in the cnf claim)",
"token_type":"pop",
"expires_in":3600,
"refresh_token":"8xLOxBtZp8",
"cnf":{
{"keys":
[
{"kty":"oct",
"alg":"A128KW",
"k":"GawgguFyGrWKav7AX4VKUg"
}
]
}
}
}
Figure 2: Example: Response from the Authorization Server (Symmetric
Variant)
Note that the cnf payload in Figure 2 is not encrypted at the
application layer since Transport Layer Security is used between the
AS and the client and the content of the cnf payload is consumed by
the client itself. Alternatively, a JWE could be used to encrypt the
key distribution, as shown in Figure 3.
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{
"access_token":"SlAV32hkKG ...
(remainder of JWT omitted for brevity;
JWT contains JWK in the cnf claim)",
"token_type":"pop",
"expires_in":3600,
"refresh_token":"8xLOxBtZp8",
"cnf":{
"jwe":
"eyJhbGciOiJSU0EtT0FFUCIsImVuYyI6IkExMjhDQkMtSFMyNTYifQ.
(remainder of JWE omitted for brevity)"
}
}
}
Figure 3: Example: Encrypted Symmmetric Key
The content of the 'access_token' in JWT format contains the 'cnf'
(confirmation) claim. The confirmation claim is defined in [10].
The digital signature or the keyed message digest offering integrity
protection is not shown in this example but has to be present in a
real deployment to mitigate a number of security threats.
The JWK in the key element of the response from the authorization
server, as shown in Figure 2, contains the same session key as the
JWK inside the access token, as shown in Figure 4. It is, in this
example, protected by TLS and transmitted from the authorization
server to the client (for processing by the client).
{
"iss": "https://server.example.com",
"sub": "24400320",
"aud": "s6BhdRkqt3",
"exp": 1311281970,
"iat": 1311280970,
"cnf":{
"jwe":
"eyJhbGciOiJSU0EtT0FFUCIsImVuYyI6IkExMjhDQkMtSFMyNTYifQ.
(remainder of JWE omitted for brevity)"
}
}
Figure 4: Example: Access Token in JWT Format
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Note: When the JWK inside the access token contains a symmetric key
it must be confidentiality protected using a JWE to maintain the
security goals of the PoP architecture since content is meant for
consumption by the selected resource server only. The details are
described in [22].
4.2. Asymmetric Key Transport
4.2.1. Client-to-AS Request
This example illustrates the case where an asymmetric key shall be
bound to an access token. The client makes the following HTTPS
request shown in Figure 5. Extra line breaks are for display
purposes only.
POST /token HTTP/1.1
Host: server.example.com
Authorization: Basic czZCaGRSa3F0MzpnWDFmQmF0M2JW
Content-Type: application/x-www-form-urlencoded;charset=UTF-8
grant_type=authorization_code
&code=SplxlOBeZQQYbYS6WxSbIA
&redirect_uri=https%3A%2F%2Fclient%2Eexample%2Ecom%2Fcb
&token_type=pop
&req_cnf=eyJhbGciOiJSU0ExXzUi ...
(remainder of JWK omitted for brevity)
Figure 5: Example Request to the Authorization Server (Asymmetric Key
Variant)
As shown in Figure 6 the content of the 'req_cnf' parameter contains
the ECC public key the client would like to associate with the access
token (in JSON format).
"jwk":{
"kty": "EC",
"use": "sig",
"crv": "P-256",
"x": "18wHLeIgW9wVN6VD1Txgpqy2LszYkMf6J8njVAibvhM",
"y": "-V4dS4UaLMgP_4fY4j8ir7cl1TXlFdAgcx55o7TkcSA"
}
Figure 6: Client Providing Public Key to Authorization Server
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4.2.2. Client-to-AS Response
If the access token request is valid and authorized, the
authorization server issues an access token and optionally a refresh
token. The authorization server also places information about the
public key used by the client into the access token to create the
binding between the two. The new token type "pop" is placed into the
'token_type' parameter.
An example of a successful response is shown in Figure 7.
HTTP/1.1 200 OK
Content-Type: application/json;charset=UTF-8
Cache-Control: no-store
Pragma: no-cache
{
"access_token":"2YotnFZFE....jr1zCsicMWpAA",
"token_type":"pop",
"expires_in":3600,
"refresh_token":"tGzv3JOkF0XG5Qx2TlKWIA"
}
Figure 7: Example: Response from the Authorization Server (Asymmetric
Variant)
The content of the 'access_token' field contains an encoded JWT, as
shown in Figure 8. The digital signature covering the access token
offering authenticity and integrity protection is not shown below
(but must be present).
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{
"iss":"https://authz.example.com",
"aud":"https://resource.example.com",
"exp":"1361398824",
"nbf":"1360189224",
"cnf":{
"jwk" : {
"kty" : "EC",
"crv" : "P-256",
"x" : "usWxHK2PmfnHKwXPS54m0kTcGJ90UiglWiGahtagnv8",
"y" : "IBOL+C3BttVivg+lSreASjpkttcsz+1rb7btKLv8EX4"
}
}
}
Figure 8: Example: Access Token Structure (Asymmetric Variant)
Note: In this example there is no need for the authorization server
to convey further keying material to the client since the client is
already in possession of the private key (as well as the public key).
5. Security Considerations
[22] describes the architecture for the OAuth 2.0 proof-of-possession
security architecture, including use cases, threats, and
requirements. This requirements describes one solution component of
that architecture, namely the mechanism for the client to interact
with the authorization server to either obtain a symmetric key from
the authorization server, to obtain an asymmetric key pair, or to
offer a public key to the authorization. In any case, these keys are
then bound to the access token by the authorization server.
To summarize the main security recommendations: A large range of
threats can be mitigated by protecting the contents of the access
token by using a digital signature or a keyed message digest.
Consequently, the token integrity protection MUST be applied to
prevent the token from being modified, particularly since it contains
a reference to the symmetric key or the asymmetric key. If the
access token contains the symmetric key (see Section 2.2 of [10] for
a description about how symmetric keys can be securely conveyed
within the access token) this symmetric key MUST be encrypted by the
authorization server with a long-term key shared with the resource
server.
To deal with token redirect, it is important for the authorization
server to include the identity of the intended recipient (the
audience), typically a single resource server (or a list of resource
servers), in the token. Using a single shared secret with multiple
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authorization server to simplify key management is NOT RECOMMENDED
since the benefit from using the proof-of-possession concept is
significantly reduced.
Token replay is also not possible since an eavesdropper will also
have to obtain the corresponding private key or shared secret that is
bound to the access token. Nevertheless, it is good practice to
limit the lifetime of the access token and therefore the lifetime of
associated key.
The authorization server MUST offer confidentiality protection for
any interactions with the client. This step is extremely important
since the client will obtain the session key from the authorization
server for use with a specific access token. Not using
confidentiality protection exposes this secret (and the access token)
to an eavesdropper thereby making the OAuth 2.0 proof-of-possession
security model completely insecure. OAuth 2.0 [2] relies on TLS to
offer confidentiality protection and additional protection can be
applied using the JWK [5] offered security mechanism, which would add
an additional layer of protection on top of TLS for cases where the
keying material is conveyed, for example, to a hardware security
module. Which version(s) of TLS ought to be implemented will vary
over time, and depend on the widespread deployment and known security
vulnerabilities at the time of implementation. At the time of this
writing, TLS version 1.2 [4] is the most recent version. The client
MUST validate the TLS certificate chain when making requests to
protected resources, including checking the validity of the
certificate.
Similarly to the security recommendations for the bearer token
specification [17] developers MUST ensure that the ephemeral
credentials (i.e., the private key or the session key) is not leaked
to third parties. An adversary in possession of the ephemeral
credentials bound to the access token will be able to impersonate the
client. Be aware that this is a real risk with many smart phone app
and Web development environments.
Clients can at any time request a new proof-of-possession capable
access token. Using a refresh token to regularly request new access
tokens that are bound to fresh and unique keys is important. Keeping
the lifetime of the access token short allows the authorization
server to use shorter key sizes, which translate to a performance
benefit for the client and for the resource server. Shorter keys
also lead to shorter messages (particularly with asymmetric keying
material).
When authorization servers bind symmetric keys to access tokens then
they SHOULD scope these access tokens to a specific permissions.
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6. IANA Considerations
6.1. OAuth Access Token Types
This specification registers the following error in the IANA "OAuth
Access Token Types" [25] established by [17].
o Name: pop
o Change controller: IESG
o Specification document(s): [[ this specification ]]
6.2. OAuth Parameters Registration
This specification registers the following value in the IANA "OAuth
Parameters" registry [25] established by [2].
o Parameter name: cnf_req
o Parameter usage location: authorization request, token request
o Change controller: IESG
o Specification document(s): [[ this specification ]]
o Parameter name: cnf
o Parameter usage location: authorization response, token response
o Change controller: IESG
o Specification document(s): [[ this specification ]]
o Parameter name: rs_cnf
o Parameter usage location: token response
o Change controller: IESG
o Specification document(s): [[ this specification ]]
6.3. OAuth Extensions Error Registration
This specification registers the following error in the IANA "OAuth
Extensions Error Registry" [25] established by [2].
o Error name: invalid_token_type
o Error usage location: implicit grant error response, token error
response
o Related protocol extension: token_type parameter
o Change controller: IESG
o Specification document(s): [[ this specification ]]
7. Acknowledgements
We would like to thank Chuck Mortimore and James Manger for their
review comments.
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8. References
8.1. Normative References
[1] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/info/rfc2119>.
[2] Hardt, D., Ed., "The OAuth 2.0 Authorization Framework",
RFC 6749, DOI 10.17487/RFC6749, October 2012,
<https://www.rfc-editor.org/info/rfc6749>.
[3] Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform
Resource Identifier (URI): Generic Syntax", STD 66,
RFC 3986, DOI 10.17487/RFC3986, January 2005,
<https://www.rfc-editor.org/info/rfc3986>.
[4] Dierks, T. and E. Rescorla, "The Transport Layer Security
(TLS) Protocol Version 1.2", RFC 5246,
DOI 10.17487/RFC5246, August 2008,
<https://www.rfc-editor.org/info/rfc5246>.
[5] Jones, M., "JSON Web Key (JWK)", RFC 7517,
DOI 10.17487/RFC7517, May 2015,
<https://www.rfc-editor.org/info/rfc7517>.
[6] Jones, M., Bradley, J., and N. Sakimura, "JSON Web
Signature (JWS)", RFC 7515, DOI 10.17487/RFC7515, May
2015, <https://www.rfc-editor.org/info/rfc7515>.
[7] Jones, M., "JSON Web Algorithms (JWA)", RFC 7518,
DOI 10.17487/RFC7518, May 2015,
<https://www.rfc-editor.org/info/rfc7518>.
[8] Jones, M. and J. Hildebrand, "JSON Web Encryption (JWE)",
RFC 7516, DOI 10.17487/RFC7516, May 2015,
<https://www.rfc-editor.org/info/rfc7516>.
[9] Jones, M., Bradley, J., and N. Sakimura, "JSON Web Token
(JWT)", RFC 7519, DOI 10.17487/RFC7519, May 2015,
<https://www.rfc-editor.org/info/rfc7519>.
[10] Jones, M., Bradley, J., and H. Tschofenig, "Proof-of-
Possession Key Semantics for JSON Web Tokens (JWTs)",
RFC 7800, DOI 10.17487/RFC7800, April 2016,
<https://www.rfc-editor.org/info/rfc7800>.
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[11] Jones, M. and N. Sakimura, "JSON Web Key (JWK)
Thumbprint", RFC 7638, DOI 10.17487/RFC7638, September
2015, <https://www.rfc-editor.org/info/rfc7638>.
[12] 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.
[13] Jones, M., Wahlstroem, E., Erdtman, S., and H. Tschofenig,
"CBOR Web Token (CWT)", RFC 8392, DOI 10.17487/RFC8392,
May 2018, <https://www.rfc-editor.org/info/rfc8392>.
[14] Schaad, J., "CBOR Object Signing and Encryption (COSE)",
RFC 8152, DOI 10.17487/RFC8152, July 2017,
<https://www.rfc-editor.org/info/rfc8152>.
[15] Jones, M., Nadalin, A., Campbell, B., Bradley, J., and C.
Mortimore, "OAuth 2.0 Token Exchange", draft-ietf-oauth-
token-exchange-16 (work in progress), October 2018.
[16] Campbell, B., Bradley, J., and H. Tschofenig, "Resource
Indicators for OAuth 2.0", draft-ietf-oauth-resource-
indicators-02 (work in progress), January 2019.
8.2. Informative References
[17] Jones, M. and D. Hardt, "The OAuth 2.0 Authorization
Framework: Bearer Token Usage", RFC 6750,
DOI 10.17487/RFC6750, October 2012,
<https://www.rfc-editor.org/info/rfc6750>.
[18] Crocker, D., Ed. and P. Overell, "Augmented BNF for Syntax
Specifications: ABNF", STD 68, RFC 5234,
DOI 10.17487/RFC5234, January 2008,
<https://www.rfc-editor.org/info/rfc5234>.
[19] Campbell, B., Mortimore, C., Jones, M., and Y. Goland,
"Assertion Framework for OAuth 2.0 Client Authentication
and Authorization Grants", RFC 7521, DOI 10.17487/RFC7521,
May 2015, <https://www.rfc-editor.org/info/rfc7521>.
[20] Sakimura, N., Ed., Bradley, J., and N. Agarwal, "Proof Key
for Code Exchange by OAuth Public Clients", RFC 7636,
DOI 10.17487/RFC7636, September 2015,
<https://www.rfc-editor.org/info/rfc7636>.
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[21] Richer, J., Ed., Jones, M., Bradley, J., Machulak, M., and
P. Hunt, "OAuth 2.0 Dynamic Client Registration Protocol",
RFC 7591, DOI 10.17487/RFC7591, July 2015,
<https://www.rfc-editor.org/info/rfc7591>.
[22] Hunt, P., Richer, J., Mills, W., Mishra, P., and H.
Tschofenig, "OAuth 2.0 Proof-of-Possession (PoP) Security
Architecture", draft-ietf-oauth-pop-architecture-08 (work
in progress), July 2016.
[23] Richer, J., Ed., "OAuth 2.0 Token Introspection",
RFC 7662, DOI 10.17487/RFC7662, October 2015,
<https://www.rfc-editor.org/info/rfc7662>.
[24] Seitz, L., Selander, G., Wahlstroem, E., Erdtman, S., and
H. Tschofenig, "Authentication and Authorization for
Constrained Environments (ACE) using the OAuth 2.0
Framework (ACE-OAuth)", draft-ietf-ace-oauth-authz-24
(work in progress), March 2019.
[25] IANA, "OAuth Parameters", October 2018.
[26] IANA, "JSON Web Token Claims", June 2018.
Authors' Addresses
John Bradley
Ping Identity
Email: ve7jtb@ve7jtb.com
URI: http://www.thread-safe.com/
Phil Hunt
Oracle Corporation
Email: phil.hunt@yahoo.com
URI: http://www.indepdentid.com
Michael B. Jones
Microsoft
Email: mbj@microsoft.com
URI: http://self-issued.info/
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Hannes Tschofenig
Arm Ltd.
Absam 6067
Austria
Email: Hannes.Tschofenig@gmx.net
URI: http://www.tschofenig.priv.at
Mihaly Meszaros
GITDA
Debrecen 4033
Hungary
Email: bakfitty@gmail.com
URI: https://github.com/misi
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