Internet Engineering Task Force (IETF) V. Bertocci

Internet Engineering Task Force (IETF) V. Bertocci
Request for Comments: 9068 Auth0
Category: Standards Track October 2021
ISSN: 2070-1721

JSON Web Token (JWT) Profile for OAuth 2.0 Access Tokens

Abstract

This specification defines a profile for issuing OAuth 2.0 access
tokens in JSON Web Token (JWT) format. Authorization servers and
resource servers from different vendors can leverage this profile to
issue and consume access tokens in an interoperable manner.

Status of This Memo

This is an Internet Standards Track document.

This document is a product of the Internet Engineering Task Force
(IETF). It represents the consensus of the IETF community. It has
received public review and has been approved for publication by the
Internet Engineering Steering Group (IESG). Further information on
Internet Standards is available in Section 2 of RFC 7841.

Information about the current status of this document, any errata,
and how to provide feedback on it may be obtained at
https://www.rfc-editor.org/info/rfc9068.

Copyright Notice

Copyright (c) 2021 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
Provisions Relating to IETF Documents
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described in the Simplified BSD License.

Table of Contents

1. Introduction
1.1. Requirements Notation and Conventions
1.2. Terminology
2. JWT Access Token Header and Data Structure
2.1. Header
2.2. Data Structure
2.2.1. Authentication Information Claims
2.2.2. Identity Claims
2.2.3. Authorization Claims
2.2.3.1. Claims for Authorization Outside of Delegation
Scenarios
3. Requesting a JWT Access Token
4. Validating JWT Access Tokens
5. Security Considerations
6. Privacy Considerations
7. IANA Considerations
7.1. Media Type Registration
7.1.1. Registry Content
7.2. Claims Registration
7.2.1. Registry Content
7.2.1.1. Roles
7.2.1.2. Groups
7.2.1.3. Entitlements
8. References
8.1. Normative References
8.2. Informative References
Acknowledgements
Author's Address

1. Introduction

The original OAuth 2.0 Authorization Framework [RFC6749]
specification does not mandate any specific format for access tokens.
While that remains perfectly appropriate for many important
scenarios, in-market use has shown that many commercial OAuth 2.0
implementations elected to issue access tokens using a format that
can be parsed and validated by resource servers directly, without
further authorization server involvement. The approach is
particularly common in topologies where the authorization server and
resource server are not co-located, are not run by the same entity,
or are otherwise separated by some boundary. At the time of writing,
many commercial implementations leverage the JSON Web Token (JWT)
[RFC7519] format.

Many vendor-specific JWT access tokens share the same functional
layout, using JWT claims to convey the information needed to support
a common set of use cases: token validation, transporting
authorization information in the form of scopes and entitlements,
carrying identity information about the subject, and so on. The
differences are mostly confined to the claim names and syntax used to
represent the same entities, suggesting that interoperability could
be easily achieved by standardizing a common set of claims and
validation rules.

The assumption that access tokens are associated with specific
information doesn't appear only in commercial implementations.
Various specifications in the OAuth 2.0 family (such as resource
indicators [RFC8707], OAuth 2.0 bearer token usage [RFC6750], and
others) postulate the presence of scoping mechanisms, such as an
audience, in access tokens. The family of specifications associated
with introspection also indirectly suggests a fundamental set of
information that access tokens are expected to carry or at least be
associated with.

This specification aims to provide a standardized and interoperable
profile as an alternative to the proprietary JWT access token layouts
going forward. Besides defining a common set of mandatory and
optional claims, the profile provides clear indications on how
authorization request parameters determine the content of the issued
JWT access token, how an authorization server can publish metadata
relevant to the JWT access tokens it issues, and how a resource
server should validate incoming JWT access tokens.

Finally, this specification provides security and privacy
considerations meant to prevent common mistakes and anti-patterns
that are likely to occur in naive use of the JWT format to represent
access tokens.

Please note: Although both this document and [RFC7523] use JSON
Web Tokens in the context of the OAuth2 framework, the two
specifications differ in both intent and mechanics. Whereas
[RFC7523] defines how a JWT Bearer Token can be used to request an
access token, this document describes how to encode access tokens
in JWT format.

1.1. Requirements Notation and Conventions

The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in
BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all
capitals, as shown here.

1.2. Terminology

JWT access token: An OAuth 2.0 access token encoded in JWT format
and complying with the requirements described in this
specification.

This specification uses the terms "access token", "refresh token",
"authorization server", "resource server", "authorization endpoint",
"authorization request", "authorization response", "token endpoint",
"grant type", "access token request", "access token response", and
"client" defined by The OAuth 2.0 Authorization Framework [RFC6749].

2. JWT Access Token Header and Data Structure

2.1. Header

JWT access tokens MUST be signed. Although JWT access tokens can use
any signing algorithm, use of asymmetric cryptography is RECOMMENDED
as it simplifies the process of acquiring validation information for
resource servers (see Section 4). JWT access tokens MUST NOT use
"none" as the signing algorithm. See Section 4 for more details.

Authorization servers and resource servers conforming to this
specification MUST include RS256 (as defined in [RFC7518]) among
their supported signature algorithms.

This specification registers the "application/at+jwt" media type,
which can be used to indicate that the content is a JWT access token.
JWT access tokens MUST include this media type in the "typ" header
parameter to explicitly declare that the JWT represents an access
token complying with this profile. Per the definition of "typ" in
Section 4.1.9 of [RFC7515], it is RECOMMENDED that the "application/"
prefix be omitted. Therefore, the "typ" value used SHOULD be
"at+jwt". See the Security Considerations section for details on the
importance of preventing OpenID Connect ID Tokens (as defined by
Section 2 of [OpenID.Core]) from being accepted as access tokens by
resource servers implementing this profile.

2.2. Data Structure

The following claims are used in the JWT access token data structure.

iss REQUIRED - as defined in Section 4.1.1 of [RFC7519].

exp REQUIRED - as defined in Section 4.1.4 of [RFC7519].

aud REQUIRED - as defined in Section 4.1.3 of [RFC7519]. See
Section 3 for indications on how an authorization server should
determine the value of "aud" depending on the request.

sub REQUIRED - as defined in Section 4.1.2 of [RFC7519]. In cases
of access tokens obtained through grants where a resource owner is
involved, such as the authorization code grant, the value of "sub"
SHOULD correspond to the subject identifier of the resource owner.
In cases of access tokens obtained through grants where no
resource owner is involved, such as the client credentials grant,
the value of "sub" SHOULD correspond to an identifier the
authorization server uses to indicate the client application. See
Section 5 for more details on this scenario. Also, see Section 6
for a discussion about how different choices in assigning "sub"
values can impact privacy.

client_id REQUIRED - as defined in Section 4.3 of [RFC8693].

iat REQUIRED - as defined in Section 4.1.6 of [RFC7519]. This claim
identifies the time at which the JWT access token was issued.

jti REQUIRED - as defined in Section 4.1.7 of [RFC7519].

2.2.1. Authentication Information Claims

The claims listed in this section MAY be issued in the context of
authorization grants involving the resource owner and reflect the
types and strength of authentication in the access token that the
authentication server enforced prior to returning the authorization
response to the client. Their values are fixed and remain the same
across all access tokens that derive from a given authorization
response, whether the access token was obtained directly in the
response (e.g., via the implicit flow) or after one or more token
exchanges (e.g., obtaining a fresh access token using a refresh token
or exchanging one access token for another via [RFC8693] procedures).

auth_time OPTIONAL - as defined in Section 2 of [OpenID.Core].

acr OPTIONAL - as defined in Section 2 of [OpenID.Core].

amr OPTIONAL - as defined in Section 2 of [OpenID.Core].

2.2.2. Identity Claims

In the context of authorization grants involving the resource owner,
commercial authorization servers will often include resource owner
attributes directly in access tokens so that resource servers can
consume them directly for authorization or other purposes without any
further round trips to introspection ([RFC7662]) or UserInfo
([OpenID.Core]) endpoints. This is particularly common in scenarios
where the client and the resource server belong to the same entity
and are part of the same solution, as is the case for first-party
clients invoking their own backend API.

This profile does not introduce any mechanism for a client to
directly request the presence of specific claims in JWT access
tokens, as the authorization server can determine what additional
claims are required by a particular resource server by taking the
client_id of the client and the "scope" and the "resource" parameters
included in the request into consideration.

Any additional identity attribute whose semantic is well described by
an entry in the "JSON Web Token (JWT)" IANA registry introduced in
[RFC7519] SHOULD be encoded using the corresponding claim name, if
that attribute is to be included in the JWT access token. Note that
the JWT IANA registry includes the claims found in Section 5.1 of
[OpenID.Core].

Authorization servers MAY return arbitrary attributes not defined in
any existing specification, as long as the corresponding claim names
are collision resistant or the access tokens are meant to be used
only within a private subsystem. Please refer to Sections 4.2 and
4.3 of [RFC7519] for details.

Authorization servers including resource owner attributes in JWT
access tokens need to exercise care and verify that all privacy
requirements are met, as discussed in Section 6.

2.2.3. Authorization Claims

If an authorization request includes a scope parameter, the
corresponding issued JWT access token SHOULD include a "scope" claim
as defined in Section 4.2 of [RFC8693].

All the individual scope strings in the "scope" claim MUST have
meaning for the resources indicated in the "aud" claim. See
Section 5 for more considerations about the relationship between
scope strings and resources indicated by the "aud" claim.

2.2.3.1. Claims for Authorization Outside of Delegation Scenarios

Many authorization servers embed authorization attributes that go
beyond the delegated scenarios described by [RFC7519] in the access
tokens they issue. Typical examples include resource owner
memberships in roles and groups that are relevant to the resource
being accessed, entitlements assigned to the resource owner for the
targeted resource that the authorization server knows about, and so
on.

An authorization server wanting to include such attributes in a JWT
access token SHOULD use the "groups", "roles", and "entitlements"
attributes of the "User" resource schema defined by Section 4.1.2 of
[RFC7643]) as claim types.

Authorization servers SHOULD encode the corresponding claim values
according to the guidance defined in [RFC7643]. In particular, a
non-normative example of a "groups" attribute can be found in
Section 8.2 of [RFC7643]. No specific vocabulary is provided for
"roles" and "entitlements".

Section 7.2.1 of this document provides entries for registering
"groups", "roles", and "entitlements" attributes from [RFC7643] as
claim types to be used in this profile.

3. Requesting a JWT Access Token

An authorization server can issue a JWT access token in response to
any authorization grant defined by [RFC6749] and subsequent
extensions meant to result in an access token.

If the request includes a "resource" parameter (as defined in
[RFC8707]), the resulting JWT access token "aud" claim SHOULD have
the same value as the "resource" parameter in the request.

Example request below:

GET /as/authorization.oauth2?response_type=code
&client_id=s6BhdRkqt3
&state=xyz
&scope=openid%20profile%20reademail
&redirect_uri=https%3A%2F%2Fclient%2Eexample%2Ecom%2Fcb
&resource=https%3A%2F%2Frs.example.com%2F HTTP/1.1
Host: authorization-server.example.com

Figure 1: Authorization Request with Resource and Scope Parameters

Once redeemed, the code obtained from the request above will result
in a JWT access token in the form shown below:

Header:

{"typ":"at+JWT","alg":"RS256","kid":"RjEwOwOA"}

Claims:

{
"iss": "https://authorization-server.example.com/",
"sub": "5ba552d67",
"aud": "https://rs.example.com/",
"exp": 1639528912,
"iat": 1618354090,
"jti" : "dbe39bf3a3ba4238a513f51d6e1691c4",
"client_id": "s6BhdRkqt3",
"scope": "openid profile reademail"
}

Figure 2: The Header and JWT Claims Set of a JWT Access Token

The authorization server MUST NOT issue a JWT access token if the
authorization granted by the token would be ambiguous. See Section 5
for more details about common cases that might lead to ambiguity and
strategies an authorization server can enact to prevent them.

If the request does not include a "resource" parameter, the
authorization server MUST use a default resource indicator in the
"aud" claim. If a "scope" parameter is present in the request, the
authorization server SHOULD use it to infer the value of the default
resource indicator to be used in the "aud" claim. The mechanism
through which scopes are associated with default resource indicator
values is outside the scope of this specification. If the values in
the "scope" parameter refer to different default resource indicator
values, the authorization server SHOULD reject the request with
"invalid_scope" as described in Section 4.1.2.1 of [RFC6749].

4. Validating JWT Access Tokens

For the purpose of facilitating validation data retrieval, it is
RECOMMENDED here that authorization servers sign JWT access tokens
with an asymmetric algorithm.

Authorization servers SHOULD use OAuth 2.0 Authorization Server
Metadata [RFC8414] to advertise to resource servers their signing
keys via "jwks_uri" and what "iss" claim value to expect via the
"issuer" metadata value. Alternatively, authorization servers
implementing OpenID Connect MAY use the OpenID Connect discovery
[OpenID.Discovery] document for the same purpose. If an
authorization server supports both OAuth 2.0 Authorization Server
Metadata and OpenID Connect discovery, the values provided MUST be
consistent across the two publication methods.

An authorization server MAY elect to use different keys to sign
OpenID Connect ID Tokens and JWT access tokens. This specification
does not provide a mechanism for identifying a specific key as the
one used to sign JWT access tokens. An authorization server can sign
JWT access tokens with any of the keys advertised via authorization
server (AS) metadata or OpenID Connect discovery. See Section 5 for
further guidance on security implications.

Resource servers receiving a JWT access token MUST validate it in the
following manner.

* The resource server MUST verify that the "typ" header value is
"at+jwt" or "application/at+jwt" and reject tokens carrying any
other value.

* If the JWT access token is encrypted, decrypt it using the keys
and algorithms that the resource server specified during
registration. If encryption was negotiated with the authorization
server at registration time and the incoming JWT access token is
not encrypted, the resource server SHOULD reject it.

* The issuer identifier for the authorization server (which is
typically obtained during discovery) MUST exactly match the value
of the "iss" claim.

* The resource server MUST validate that the "aud" claim contains a
resource indicator value corresponding to an identifier the
resource server expects for itself. The JWT access token MUST be
rejected if "aud" does not contain a resource indicator of the
current resource server as a valid audience.

* The resource server MUST validate the signature of all incoming
JWT access tokens according to [RFC7515] using the algorithm
specified in the JWT "alg" Header Parameter. The resource server
MUST reject any JWT in which the value of "alg" is "none". The
resource server MUST use the keys provided by the authorization
server.

* The current time MUST be before the time represented by the "exp"
claim. Implementers MAY provide for some small leeway, usually no
more than a few minutes, to account for clock skew.

The resource server MUST handle errors as described in Section 3.1 of
[RFC6750]. In particular, in case of any failure in the validation
checks listed above, the authorization server response MUST include
the error code "invalid_token". Please note that this requirement
does not prevent JWT access tokens from using authentication schemes
other than "Bearer".

If the JWT access token includes authorization claims as described in
Section 2.2.3, the resource server SHOULD use them in combination
with any other contextual information available to determine whether
the current call should be authorized or rejected. Details about how
a resource server performs those checks is beyond the scope of this
profile specification.

5. Security Considerations

The JWT access token data layout described here is very similar to
that of the id_token as defined by [OpenID.Core]. The explicit
typing required in this profile, in line with the recommendations in
[RFC8725], helps the resource server to distinguish between JWT
access tokens and OpenID Connect ID Tokens.

Authorization servers should prevent scenarios where clients can
affect the value of the "sub" claim in ways that could confuse
resource servers. For example, if the authorization server elects to
use the client_id as the "sub" value for access tokens issued using
the client credentials grant, the authorization server should prevent
clients from registering an arbitrary client_id value, as this would
allow malicious clients to select the sub of a high-privilege
resource owner and confuse any authorization logic on the resource
server relying on the "sub" value. For more details, please refer to
Section 4.14 of [OAuth2.Security.BestPractices].

To prevent cross-JWT confusion, authorization servers MUST use a
distinct identifier as an "aud" claim value to uniquely identify
access tokens issued by the same issuer for distinct resources. For
more details on cross-JWT confusion, please refer to Section 2.8 of
[RFC8725].

Authorization servers should use particular care when handling
requests that might lead to ambiguous authorization grants. For
example, if a request includes multiple resource indicators, the
authorization server should ensure that each scope string included in
the resulting JWT access token, if any, can be unambiguously
correlated to a specific resource among the ones listed in the "aud"
claim. The details on how to recognize and mitigate this and other
ambiguous situations is highly scenario dependent and hence is out of
scope for this profile.

Authorization servers cannot rely on the use of different keys for
signing OpenID Connect ID Tokens and JWT tokens as a method to
safeguard against the consequences of leaking specific keys. Given
that resource servers have no way of knowing what key should be used
to validate JWT access tokens in particular, they have to accept
signatures performed with any of the keys published in AS metadata or
OpenID Connect discovery; consequently, an attacker just needs to
compromise any key among the ones published to be able to generate
and sign JWTs that will be accepted as valid by the resource server.

6. Privacy Considerations

As JWT access tokens carry information by value, it now becomes
possible for clients and potentially even end users to directly peek
inside the token claims collection of unencrypted tokens.

The client MUST NOT inspect the content of the access token: the
authorization server and the resource server might decide to change
the token format at any time (for example, by switching from this
profile to opaque tokens); hence, any logic in the client relying on
the ability to read the access token content would break without
recourse. The OAuth 2.0 framework assumes that access tokens are
treated as opaque by clients. Administrators of authorization
servers should also take into account that the content of an access
token is visible to the client. Whenever client access to the access
token content presents privacy issues for a given scenario, the
authorization server needs to take explicit steps to prevent them.

In scenarios in which JWT access tokens are accessible to the end
user, it should be evaluated whether the information can be accessed
without privacy violations (for example, if an end user would simply
access his or her own personal information) or if steps must be taken
to enforce confidentiality.

Possible measures to prevent leakage of information to clients and
end users include: encrypting the access token, encrypting the
sensitive claims, omitting the sensitive claims or not using this
profile, and falling back on opaque access tokens.

In every scenario, the content of the JWT access token will
eventually be accessible to the resource server. It's important to
evaluate whether the resource server gained the proper entitlement to
have access to any content received in the form of claims, for
example, through user consent in some form, policies and agreements
with the organization running the authorization servers, and so on.
For example, a user might not wish to consent to granting given
resource server information about any of the non-mandatory claims
enumerated in Section 2 (and its subsections).

This profile mandates the presence of the "sub" claim in every JWT
access token, making it possible for resource servers to rely on that
information for correlating incoming requests with data stored
locally for the authenticated principal. Although the ability to
correlate requests might be required by design in many scenarios,
there are scenarios where the authorization server might want to
prevent correlation. The "sub" claim should be populated by the
authorization servers according to a privacy impact assessment. For
instance, if a solution requires preventing tracking of principal
activities across multiple resource servers, the authorization server
should ensure that JWT access tokens meant for different resource
servers have distinct "sub" values that cannot be correlated in the
event of resource server collusion. Similarly, if a solution
requires preventing a resource server from correlating the
principal's activity within the resource itself, the authorization
server should assign different "sub" values for every JWT access
token issued. In turn, the client should obtain a new JWT access
token for every call to the resource server to ensure that the
resource server receives different "sub" and "jti" values at every
call, thus preventing correlation between distinct requests.

7. IANA Considerations

7.1. Media Type Registration

7.1.1. Registry Content

This section registers "application/at+jwt", a new media type
[RFC2046] in the "Media Types" registry [IANA.MediaTypes] in the
manner described in [RFC6838]. It can be used to indicate that the
content is an access token encoded in JWT format.

Type name: Application

Subtype name: at+jwt

Required parameters: N/A

Optional parameters: N/A

Encoding considerations: Binary; JWT values are encoded as a series
of base64url-encoded values (with trailing '=' characters
removed), some of which may be the empty string, separated by
period ('.') characters.

Security considerations: See the Security Considerations section of
RFC 9068.

Interoperability considerations: N/A

Published specification: RFC 9068

Applications that use this media type: Applications that access
resource servers using OAuth 2.0 access tokens encoded in JWT
format

Fragment identifier considerations: N/A

Additional information:

Magic number(s): N/A
File extension(s): N/A
Macintosh file type code(s): N/A

Person & email address to contact for further information:
Vittorio Bertocci <[email protected]>

Intended usage: COMMON

Restrictions on usage: None

Author: Vittorio Bertocci <[email protected]>

Change controller: IETF

Provisional registration? No

7.2. Claims Registration

Section 2.2.3.1 of this specification refers to the attributes
"roles", "groups", "entitlements" defined in [RFC7643] to express
authorization information in JWT access tokens. This section
registers those attributes as claims in the "JSON Web Token (JWT)"
IANA registry introduced in [RFC7519].

7.2.1. Registry Content

7.2.1.1. Roles

Claim Name: roles
Claim Description: Roles
Change Controller: IETF
Specification Document(s): Section 4.1.2 of [RFC7643] and
Section 2.2.3.1 of RFC 9068

7.2.1.2. Groups

Claim Name: groups
Claim Description: Groups
Change Controller: IETF
Specification Document(s): Section 4.1.2 of [RFC7643] and
Section 2.2.3.1 of RFC 9068

7.2.1.3. Entitlements

Claim Name: entitlements
Claim Description: Entitlements
Change Controller: IETF
Specification Document(s): Section 4.1.2 of [RFC7643] and
Section 2.2.3.1 of RFC 9068

8. References

8.1. Normative References

[OpenID.Core]
Sakimura, N., Bradley, J., Jones, M., de Medeiros, B., and
C. Mortimore, "OpenID Connect Core 1.0 incorporating
errata set 1", November 2014,
<https://openid.net/specs/openid-connect-core-1_0.html>.

[OpenID.Discovery]
Sakimura, N., Bradley, J., Jones, M., and E. Jay, "OpenID
Connect Discovery 1.0 incorporating errata set 1",
November 2014, <https://openid.net/specs/openid-connect-
discovery-1_0.html>.

[RFC2046] Freed, N. and N. Borenstein, "Multipurpose Internet Mail
Extensions (MIME) Part Two: Media Types", RFC 2046,
DOI 10.17487/RFC2046, November 1996,
<https://www.rfc-editor.org/info/rfc2046>.

[RFC2119] 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>.

[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>.

[RFC6838] Freed, N., Klensin, J., and T. Hansen, "Media Type
Specifications and Registration Procedures", BCP 13,
RFC 6838, DOI 10.17487/RFC6838, January 2013,
<https://www.rfc-editor.org/info/rfc6838>.

[RFC7515] 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>.

[RFC7518] Jones, M., "JSON Web Algorithms (JWA)", RFC 7518,
DOI 10.17487/RFC7518, May 2015,
<https://www.rfc-editor.org/info/rfc7518>.

[RFC7519] 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>.

[RFC7643] Hunt, P., Ed., Grizzle, K., Wahlstroem, E., and C.
Mortimore, "System for Cross-domain Identity Management:
Core Schema", RFC 7643, DOI 10.17487/RFC7643, September
2015, <https://www.rfc-editor.org/info/rfc7643>.

[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
May 2017, <https://www.rfc-editor.org/info/rfc8174>.

[RFC8414] Jones, M., Sakimura, N., and J. Bradley, "OAuth 2.0
Authorization Server Metadata", RFC 8414,
DOI 10.17487/RFC8414, June 2018,
<https://www.rfc-editor.org/info/rfc8414>.

[RFC8693] Jones, M., Nadalin, A., Campbell, B., Ed., Bradley, J.,
and C. Mortimore, "OAuth 2.0 Token Exchange", RFC 8693,
DOI 10.17487/RFC8693, January 2020,
<https://www.rfc-editor.org/info/rfc8693>.

[RFC8707] Campbell, B., Bradley, J., and H. Tschofenig, "Resource
Indicators for OAuth 2.0", RFC 8707, DOI 10.17487/RFC8707,
February 2020, <https://www.rfc-editor.org/info/rfc8707>.

[RFC8725] Sheffer, Y., Hardt, D., and M. Jones, "JSON Web Token Best
Current Practices", BCP 225, RFC 8725,
DOI 10.17487/RFC8725, February 2020,
<https://www.rfc-editor.org/info/rfc8725>.

8.2. Informative References

[IANA.MediaTypes]
IANA, "Media Types",
<https://www.iana.org/assignments/media-types/>.

[OAuth2.Security.BestPractices]
Lodderstedt, T., Bradley, J., Labunets, A., and D. Fett,
"OAuth 2.0 Security Best Current Practice", Work in
Progress, Internet-Draft, draft-ietf-oauth-security-
topics-18, 13 April 2021,
<https://datatracker.ietf.org/doc/html/draft-ietf-oauth-
security-topics-18>.

[RFC6750] 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>.

[RFC7523] Jones, M., Campbell, B., and C. Mortimore, "JSON Web Token
(JWT) Profile for OAuth 2.0 Client Authentication and
Authorization Grants", RFC 7523, DOI 10.17487/RFC7523, May
2015, <https://www.rfc-editor.org/info/rfc7523>.

[RFC7662] Richer, J., Ed., "OAuth 2.0 Token Introspection",
RFC 7662, DOI 10.17487/RFC7662, October 2015,
<https://www.rfc-editor.org/info/rfc7662>.

Acknowledgements

The initial set of requirements informing this specification was
extracted by numerous examples of access tokens issued in JWT format
by production systems. Thanks to Dominick Baier (IdentityServer),
Brian Campbell (Ping Identity), Daniel Dobalian (Microsoft), and Karl
Guinness (Okta) for providing sample tokens issued by their products
and services. Brian Campbell and Filip Skokan provided early
feedback that shaped the direction of the specification. This
profile was discussed at length during the OAuth Security Workshop
2019, with several individuals contributing ideas and feedback. The
author would like to acknowledge the contributions of:

John Bradley, Brian Campbell, Vladimir Dzhuvinov, Torsten
Lodderstedt, Nat Sakimura, Hannes Tschofenig, and everyone who
actively participated in the unconference discussions.

The following individuals contributed useful feedback and insights on
the drafts, both at the IETF OAuth 2.0 WG mailing list and during the
28th Internet Identity Workshop (IIW 28):

Dale Olds, George Fletcher, David Waite, Michael Engan, Mike Jones,
Hans Zandbelt, Vladimir Dzhuvinov, Martin Schanzenbach, Aaron
Parecki, Annabelle Richard Backman, Dick Hardt, Denis Pinkas,
Benjamin Kaduk, Dominick Baier, Andrii Deinega, Mike Jones, and
everyone who actively participated in the IIW 28 unconference
discussions and the IETF OAuth 2.0 WG mailing list discussions.
Thanks to Roman Danyliw for the AD review; Joseph Salowey and Roni
Even for the SECDIR and GENART reviews; and Francesca Palomini, Lars
Eggert, Murray Kucherawy, Roberto Polli, Martin Duke, Benjamin Kaduk
for the IESG reviews.

Author's Address

Vittorio Bertocci
Auth0

Email: [email protected]