OAuth Working Group M. Jones
Internet-Draft A. Nadalin
Intended status: Standards Track Microsoft
Expires: April 22, 2019 B. Campbell, Ed.
J. Bradley
Ping Identity
C. Mortimore
Salesforce
October 19, 2018
OAuth 2.0 Token Exchange
draft-ietf-oauth-token-exchange-16
Abstract
This specification defines a protocol for an HTTP- and JSON- based
Security Token Service (STS) by defining how to request and obtain
security tokens from OAuth 2.0 authorization servers, including
security tokens employing impersonation and delegation.
Status of This Memo
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provisions of BCP 78 and BCP 79.
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This Internet-Draft will expire on April 22, 2019.
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document authors. All rights reserved.
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to this document. Code Components extracted from this document must
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1. Delegation vs. Impersonation Semantics . . . . . . . . . 4
1.2. Requirements Notation and Conventions . . . . . . . . . . 5
1.3. Terminology . . . . . . . . . . . . . . . . . . . . . . . 6
2. Token Exchange Request and Response . . . . . . . . . . . . . 6
2.1. Request . . . . . . . . . . . . . . . . . . . . . . . . . 6
2.1.1. Relationship Between Resource, Audience and Scope . . 8
2.2. Response . . . . . . . . . . . . . . . . . . . . . . . . 9
2.2.1. Successful Response . . . . . . . . . . . . . . . . . 9
2.2.2. Error Response . . . . . . . . . . . . . . . . . . . 10
2.3. Example Token Exchange . . . . . . . . . . . . . . . . . 11
3. Token Type Identifiers . . . . . . . . . . . . . . . . . . . 13
4. JSON Web Token Claims and Introspection Response Parameters . 14
4.1. "act" (Actor) Claim . . . . . . . . . . . . . . . . . . . 14
4.2. "scope" (Scopes) Claim . . . . . . . . . . . . . . . . . 16
4.3. "client_id" (Client Identifier) Claim . . . . . . . . . . 17
4.4. "may_act" (May Act For) Claim . . . . . . . . . . . . . . 17
5. Security Considerations . . . . . . . . . . . . . . . . . . . 18
6. Privacy Considerations . . . . . . . . . . . . . . . . . . . 19
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 19
7.1. OAuth URI Registration . . . . . . . . . . . . . . . . . 19
7.1.1. Registry Contents . . . . . . . . . . . . . . . . . . 19
7.2. OAuth Parameters Registration . . . . . . . . . . . . . . 20
7.2.1. Registry Contents . . . . . . . . . . . . . . . . . . 20
7.3. OAuth Access Token Type Registration . . . . . . . . . . 21
7.3.1. Registry Contents . . . . . . . . . . . . . . . . . . 21
7.4. JSON Web Token Claims Registration . . . . . . . . . . . 21
7.4.1. Registry Contents . . . . . . . . . . . . . . . . . . 21
7.5. OAuth Token Introspection Response Registration . . . . . 22
7.5.1. Registry Contents . . . . . . . . . . . . . . . . . . 22
7.6. OAuth Extensions Error Registration . . . . . . . . . . . 22
7.6.1. Registry Contents . . . . . . . . . . . . . . . . . . 22
8. References . . . . . . . . . . . . . . . . . . . . . . . . . 22
8.1. Normative References . . . . . . . . . . . . . . . . . . 22
8.2. Informative References . . . . . . . . . . . . . . . . . 23
Appendix A. Additional Token Exchange Examples . . . . . . . . . 24
A.1. Impersonation Token Exchange Example . . . . . . . . . . 24
A.1.1. Token Exchange Request . . . . . . . . . . . . . . . 24
A.1.2. Subject Token Claims . . . . . . . . . . . . . . . . 25
A.1.3. Token Exchange Response . . . . . . . . . . . . . . . 25
A.1.4. Issued Token Claims . . . . . . . . . . . . . . . . . 26
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A.2. Delegation Token Exchange Example . . . . . . . . . . . . 26
A.2.1. Token Exchange Request . . . . . . . . . . . . . . . 26
A.2.2. Subject Token Claims . . . . . . . . . . . . . . . . 27
A.2.3. Actor Token Claims . . . . . . . . . . . . . . . . . 28
A.2.4. Token Exchange Response . . . . . . . . . . . . . . . 28
A.2.5. Issued Token Claims . . . . . . . . . . . . . . . . . 28
Appendix B. Acknowledgements . . . . . . . . . . . . . . . . . . 29
Appendix C. Document History . . . . . . . . . . . . . . . . . . 29
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 33
1. Introduction
A security token is a set of information that facilitates the sharing
of identity and security information in heterogeneous environments or
across security domains. Examples of security tokens include JSON
Web Tokens (JWTs) [JWT] and SAML 2.0 Assertions
[OASIS.saml-core-2.0-os]. Security tokens are typically signed to
achieve integrity and sometimes also encrypted to achieve
confidentiality. Security tokens are also sometimes described as
Assertions, such as in [RFC7521].
A Security Token Service (STS) is a service capable of validating and
issuing security tokens, which enables clients to obtain appropriate
access credentials for resources in heterogeneous environments or
across security domains. Web Service clients have used WS-Trust
[WS-Trust] as the protocol to interact with an STS for token
exchange. While WS-Trust uses XML and SOAP, the trend in modern Web
development has been towards RESTful patterns and JSON. The OAuth
2.0 Authorization Framework [RFC6749] and OAuth 2.0 Bearer Tokens
[RFC6750] have emerged as popular standards for authorizing third-
party applications access to HTTP and RESTful resources. The
conventional OAuth 2.0 interaction involves the exchange of some
representation of resource owner authorization for an access token,
which has proven to be an extremely useful pattern in practice,
however, its input and output are somewhat too constrained as is to
fully accommodate a security token exchange framework.
This specification defines a protocol extending OAuth 2.0 that
enables clients to request and obtain security tokens from
authorization servers acting in the role of an STS. Similar to OAuth
2.0, this specification focuses on client developer simplicity and
requires only an HTTP client and JSON parser, which are nearly
universally available in modern development environments. The STS
protocol defined in this specification is not itself RESTful (an STS
doesn't lend itself particularly well to a REST approach) but does
utilize communication patterns and data formats that should be
familiar to developers accustomed to working with RESTful systems.
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A new grant type for a token exchange request and the associated
specific parameters for such a request to the token endpoint are
defined by this specification. A token exchange response is a normal
OAuth 2.0 response from the token endpoint with a few additional
parameters defined herein to provide information to the client.
The entity that makes the request to exchange tokens is considered
the client in the context of the token exchange interaction.
However, that does not restrict usage of this profile to traditional
OAuth clients. An OAuth resource server, for example, might assume
the role of the client during token exchange in order to trade an
access token, which it received in a protected resource request, for
a new token that is appropriate to include in a call to a backend
service. The new token might be an access token that is more
narrowly scoped for the downstream service or it could be an entirely
different kind of token.
The scope of this specification is limited to the definition of a
basic request and response protocol for an STS-style token exchange
utilizing OAuth 2.0. Although a few new JWT claims are defined that
enable delegation semantics to be expressed, the specific syntax,
semantics and security characteristics of the tokens themselves (both
those presented to the authorization server and those obtained by the
client) are explicitly out of scope and no requirements are placed on
the trust model in which an implementation might be deployed.
Additional profiles may provide more detailed requirements around the
specific nature of the parties and trust involved, such as whether
signing and/or encryption of tokens is needed or if proof-of-
possession style tokens will be required or issued; however, such
details will often be policy decisions made with respect to the
specific needs of individual deployments and will be configured or
implemented accordingly.
The security tokens obtained may be used in a number of contexts, the
specifics of which are also beyond the scope of this specification.
1.1. Delegation vs. Impersonation Semantics
When principal A impersonates principal B, A is given all the rights
that B has within some defined rights context and is
indistinguishable from B in that context. Thus, when principal A
impersonates principal B, then in so far as any entity receiving such
a token is concerned, they are actually dealing with B. It is true
that some members of the identity system might have awareness that
impersonation is going on, but it is not a requirement. For all
intents and purposes, when A is impersonating B, A is B.
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Delegation semantics are different than impersonation semantics,
though the two are closely related. With delegation semantics,
principal A still has its own identity separate from B and it is
explicitly understood that while B may have delegated some of its
rights to A, any actions taken are being taken by A representing B.
In a sense, A is an agent for B.
Delegation and impersonation are not inclusive of all situations.
When a principal is acting directly on its own behalf, for example,
neither delegation nor impersonation are in play. They are, however,
the more common semantics operating for token exchange and, as such,
are given more direct treatment in this specification.
Delegation semantics are typically expressed in a token by including
information about both the primary subject of the token as well as
the actor to whom that subject has delegated some of its rights.
Such a token is sometimes referred to as a composite token because it
is composed of information about multiple subjects. Typically, in
the request, the "subject_token" represents the identity of the party
on behalf of whom the token is being requested while the
"actor_token" represents the identity of the party to whom the access
rights of the issued token are being delegated. A composite token
issued by the authorization server will contain information about
both parties. When and if a composite token is issued is at the
discretion of the authorization server and applicable policy and
configuration.
The specifics of representing a composite token and even whether or
not such a token will be issued depend on the details of the
implementation and the kind of token. The representations of
composite tokens that are not JWTs are beyond the scope of this
specification. The "actor_token" request parameter, however, does
provide a means for providing information about the desired actor and
the JWT "act" claim can provide a representation of a chain of
delegation.
1.2. 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.
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1.3. Terminology
This specification uses the terms "access token type", "authorization
server", "client", "client identifier", "resource server", "token
endpoint", "token request", and "token response" defined by OAuth 2.0
[RFC6749], and the terms "Base64url Encoding", "Claim", and "JWT
Claims Set" defined by JSON Web Token (JWT) [JWT].
2. Token Exchange Request and Response
2.1. Request
A client requests a security token by making a token request to the
authorization server's token endpoint using the extension grant type
mechanism defined in Section 4.5 of OAuth 2.0 [RFC6749].
Client authentication to the authorization server is done using the
normal mechanisms provided by OAuth 2.0. Section 2.3.1 of The OAuth
2.0 Authorization Framework [RFC6749] defines password-based
authentication of the client, however, client authentication is
extensible and other mechanisms are possible. For example, [RFC7523]
defines client authentication using JSON Web Tokens (JWTs) [JWT].
The supported methods of client authentication and whether or not to
allow unauthenticated or unidentified clients are deployment
decisions that are at the discretion of the authorization server.
The client makes a token exchange request to the token endpoint with
an extension grant type by including the following parameters using
the "application/x-www-form-urlencoded" format with a character
encoding of UTF-8 in the HTTP request entity-body:
grant_type
REQUIRED. The value "urn:ietf:params:oauth:grant-type:token-
exchange" indicates that a token exchange is being performed.
resource
OPTIONAL. Indicates the location of the target service or
resource where the client intends to use the requested security
token. This enables the authorization server to apply policy as
appropriate for the target, such as determining the type and
content of the token to be issued or if and how the token is to be
encrypted. In many cases, a client will not have knowledge of the
logical organization of the systems with which it interacts and
will only know the location of the service where it intends to use
the token. The "resource" parameter allows the client to indicate
to the authorization server where it intends to use the issued
token by providing the location, typically as an https URL, in the
token exchange request in the same form that will be used to
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access that resource. The authorization server will typically
have the capability to map from a resource URI value to an
appropriate policy. The value of the "resource" parameter MUST be
an absolute URI, as specified by Section 4.3 of [RFC3986], which
MAY include a query component and MUST NOT include a fragment
component. Multiple "resource" parameters may be used to indicate
that the issued token is intended to be used at the multiple
resources listed.
audience
OPTIONAL. The logical name of the target service where the client
intends to use the requested security token. This serves a
purpose similar to the "resource" parameter, but with the client
providing a logical name rather than a location. Interpretation
of the name requires that the value be something that both the
client and the authorization server understand. An OAuth client
identifier, a SAML entity identifier [OASIS.saml-core-2.0-os], an
OpenID Connect Issuer Identifier [OpenID.Core], or a URI are
examples of things that might be used as "audience" parameter
values. Multiple "audience" parameters may be used to indicate
that the issued token is intended to be used at the multiple
audiences listed. The "audience" and "resource" parameters may be
used together to indicate multiple target services with a mix of
logical names and locations.
scope
OPTIONAL. A list of space-delimited, case-sensitive strings, as
defined in Section 3.3 of [RFC6749], that allow the client to
specify the desired scope of the requested security token in the
context of the service or resource where the token will be used.
The values and associated semantics of scope are service specific
and expected to be described in the relevant service
documentation.
requested_token_type
OPTIONAL. An identifier, as described in Section 3, for the type
of the requested security token. If the requested type is
unspecified, the issued token type is at the discretion of the
authorization server and may be dictated by knowledge of the
requirements of the service or resource indicated by the
"resource" or "audience" parameter.
subject_token
REQUIRED. A security token that represents the identity of the
party on behalf of whom the request is being made. Typically, the
subject of this token will be the subject of the security token
issued in response to this request.
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subject_token_type
REQUIRED. An identifier, as described in Section 3, that
indicates the type of the security token in the "subject_token"
parameter.
actor_token
OPTIONAL. A security token that represents the identity of the
acting party. Typically, this will be the party that is
authorized to use the requested security token and act on behalf
of the subject.
actor_token_type
An identifier, as described in Section 3, that indicates the type
of the security token in the "actor_token" parameter. This is
REQUIRED when the "actor_token" parameter is present in the
request but MUST NOT be included otherwise.
In processing the request, the authorization sever MUST validate the
subject token as appropriate for the indicated token type and, if the
actor token is present, also validate it according to its token type.
The validity criteria and details of any particular token are beyond
the scope of this document and are specific to the respective type of
token and its content.
In the absence of one-time-use or other semantics specific to the
token type, the act of performing a token exchange has no impact on
the validity of the subject token or actor token. Furthermore, the
validity of the subject token or actor token have no impact on the
validity of the issued token after the exchange has occurred.
2.1.1. Relationship Between Resource, Audience and Scope
When requesting a token, the client can indicate the desired target
service(s) where it intends to use that token by way of the
"audience" and "resource" parameters, as well as indicating the
desired scope of the requested token using the "scope" parameter.
The semantics of such a request are that the client is asking for a
token with the requested scope that is usable at all the requested
target services. Effectively, the requested access rights of the
token are the cartesian product of all the scopes at all the target
services.
An authorization server may be unwilling or unable to fulfill any
token request but the likelihood of an unfulfillable request is
significantly higher when very broad access rights are being
solicited. As such, in the absence of specific knowledge about the
relationship of systems in a deployment, clients should exercise
discretion in the breadth of the access requested, particularly the
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number of target services. An authorization server can use the
"invalid_target" error code, defined in Section 2.2.2, to inform a
client that it requested access to too many target services
simultaneously.
2.2. Response
The authorization server responds to a token exchange request with a
normal OAuth 2.0 response from the token endpoint, as specified in
Section 5 of [RFC6749]. Additional details and explanation are
provided in the following subsections.
2.2.1. Successful Response
If the request is valid and meets all policy and other criteria of
the authorization server, a successful token response is constructed
by adding the following parameters to the entity-body of the HTTP
response using the "application/json" media type, as specified by
[RFC7159], and an HTTP 200 status code. The parameters are
serialized into a JavaScript Object Notation (JSON) structure by
adding each parameter at the top level. Parameter names and string
values are included as JSON strings. Numerical values are included
as JSON numbers. The order of parameters does not matter and can
vary.
access_token
REQUIRED. The security token issued by the authorization server
in response to the token exchange request. The "access_token"
parameter from Section 5.1 of [RFC6749] is used here to carry the
requested token, which allows this token exchange protocol to use
the existing OAuth 2.0 request and response constructs defined for
the token endpoint. The identifier "access_token" is used for
historical reasons and the issued token need not be an OAuth
access token.
issued_token_type
REQUIRED. An identifier, as described in Section 3, for the
representation of the issued security token.
token_type
REQUIRED. A case-insensitive value specifying the method of using
the access token issued, as specified in Section 7.1 of [RFC6749].
It provides the client with information about how to utilize the
access token to access protected resources. For example, a value
of "Bearer", as specified in [RFC6750], indicates that the
security token is a bearer token and the client can simply present
it as is without any additional proof of eligibility beyond the
contents of the token itself. Note that the meaning of this
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parameter is different from the meaning of the "issued_token_type"
parameter, which declares the representation of the issued
security token; the term "token type" is typically used with this
meaning, as it is in all "*_token_type" parameters in this
specification. If the issued token is not an access token or
usable as an access token, then the "token_type" value "N_A" is
used to indicate that an OAuth 2.0 "token_type" identifier is not
applicable in that context.
expires_in
RECOMMENDED. The validity lifetime, in seconds, of the token
issued by the authorization server. Oftentimes the client will
not have the inclination or capability to inspect the content of
the token and this parameter provides a consistent and token type
agnostic indication of how long the token can be expected to be
valid. For example, the value 1800 denotes that the token will
expire in thirty minutes from the time the response was generated.
scope
OPTIONAL, if the scope of the issued security token is identical
to the scope requested by the client; otherwise, REQUIRED.
refresh_token
OPTIONAL. A refresh token will typically not be issued when the
exchange is of one temporary credential (the subject_token) for a
different temporary credential (the issued token) for use in some
other context. A refresh token can be issued in cases where the
client of the token exchange needs the ability to access a
resource even when the original credential is no longer valid
(e.g., user-not-present or offline scenarios where there is no
longer any user entertaining an active session with the client).
Profiles or deployments of this specification should clearly
document the conditions under which a client should expect a
refresh token in response to "urn:ietf:params:oauth:grant-
type:token-exchange" grant type requests.
2.2.2. Error Response
If the request itself is not valid or if either the "subject_token"
or "actor_token" are invalid for any reason, or are unacceptable
based on policy, the authorization server MUST construct an error
response, as specified in Section 5.2 of [RFC6749]. The value of the
"error" parameter MUST be the "invalid_request" error code.
If the authorization server is unwilling or unable to issue a token
for all the target services indicated by the "resource" or "audience"
parameters, the "invalid_target" error code SHOULD be used in the
error response.
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The authorization server MAY include additional information regarding
the reasons for the error using the "error_description" and/or
"error_uri" parameters.
Other error codes may also be used, as appropriate.
2.3. Example Token Exchange
The following example demonstrates a hypothetical token exchange in
which an OAuth resource server assumes the role of the client during
token exchange in order to trade an access token that it received in
a protected resource request for a token that it will use to call to
a backend service (extra line breaks and indentation in the examples
are for display purposes only).
The resource server receives the following request containing an
OAuth access token in the Authorization request header, as specified
in Section 2.1 of [RFC6750].
GET /resource HTTP/1.1
Host: frontend.example.com
Authorization: Bearer accVkjcJyb4BWCxGsndESCJQbdFMogUC5PbRDqceLTC
Figure 1: Protected Resource Request
The resource server assumes the role of the client for the token
exchange and the access token from the request above is sent to the
authorization server using a request as specified in Section 2.1.
The value of the "subject_token" parameter carries the access token
and the value of the "subject_token_type" parameter indicates that it
is an OAuth 2.0 access token. The resource server, acting in the
role of the client, uses its identifier and secret to authenticate to
the authorization server using the HTTP Basic authentication scheme.
The "resource" parameter indicates the location of the backend
service, https://backend.example.com/api, where the issued token will
be used.
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POST /as/token.oauth2 HTTP/1.1
Host: as.example.com
Authorization: Basic cnMwODpsb25nLXNlY3VyZS1yYW5kb20tc2VjcmV0
Content-Type: application/x-www-form-urlencoded
grant_type=urn%3Aietf%3Aparams%3Aoauth%3Agrant-type%3Atoken-exchange
&resource=https%3A%2F%2Fbackend.example.com%2Fapi%20
&subject_token=accVkjcJyb4BWCxGsndESCJQbdFMogUC5PbRDqceLTC
&subject_token_type=
urn%3Aietf%3Aparams%3Aoauth%3Atoken-type%3Aaccess_token
Figure 2: Token Exchange Request
The authorization server validates the client credentials and the
"subject_token" presented in the token exchange request. From the
"resource" parameter, the authorization server is able to determine
the appropriate policy to apply to the request and issues a token
suitable for use at https://backend.example.com. The "access_token"
parameter of the response contains the new token, which is itself a
bearer OAuth access token that is valid for one minute. The token
happens to be a JWT; however, its structure and format are opaque to
the client so the "issued_token_type" indicates only that it is an
access token.
HTTP/1.1 200 OK
Content-Type: application/json
Cache-Control: no-cache, no-store
{
"access_token":"eyJhbGciOiJFUzI1NiIsImtpZCI6IjllciJ9.eyJhdWQiOiJo
dHRwczovL2JhY2tlbmQuZXhhbXBsZS5jb20iLCJpc3MiOiJodHRwczovL2FzLmV
4YW1wbGUuY29tIiwiZXhwIjoxNDQxOTE3NTkzLCJpYXQiOjE0NDE5MTc1MzMsIn
N1YiI6ImJjQGV4YW1wbGUuY29tIiwic2NvcGUiOiJhcGkifQ.K4Ik-igqOKi_4C
nBu4dG3-gGUObfgv-rJhgXVDNOWW_MHgVwddhgVLLQf_bm3xlpQM6wHrLbMaZC4
LicsQC23g",
"issued_token_type":
"urn:ietf:params:oauth:token-type:access_token",
"token_type":"Bearer",
"expires_in":60
}
Figure 3: Token Exchange Response
The resource server can then use the newly acquired access token in
making a request to the backend server.
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GET /api HTTP/1.1
Host: backend.example.com
Authorization: Bearer eyJhbGciOiJFUzI1NiIsImtpZCI6IjllciJ9.eyJhdWQ
iOiJodHRwczovL2JhY2tlbmQuZXhhbXBsZS5jb20iLCJpc3MiOiJodHRwczovL2
FzLmV4YW1wbGUuY29tIiwiZXhwIjoxNDQxOTE3NTkzLCJpYXQiOjE0NDE5MTc1M
zMsInN1YiI6ImJjQGV4YW1wbGUuY29tIiwic2NwIjpbImFwaSJdfQ.MXgnpvPMo
0nhcePwnQbunD2gw_pDyCFA-Saobl6gyLAdyPbaALFuAOyFc4XTWaPEnHV_LGmX
klSTpz0yC7hlSQ
Figure 4: Backend Protected Resource Request
Additional examples can be found in Appendix A.
3. Token Type Identifiers
Several parameters in this specification utilize an identifier as the
value to describe the token in question. Specifically, they are the
"requested_token_type", "subject_token_type", "actor_token_type"
parameters of the request and the "issued_token_type" member of the
response. Token type identifiers are URIs. Token Exchange can work
with both tokens issued by other parties and tokens from the given
authorization server. For the former the token type identifier
indicates the syntax (e.g., JWT or SAML 2.0) so the authorization
server can parse it; for the latter it indicates what the given
authorization server issued it for (e.g., access_token or
refresh_token).
The following token type identifiers are defined by this
specification. Other URIs MAY be used to indicate other token types.
urn:ietf:params:oauth:token-type:access_token
Indicates that the token is an OAuth 2.0 access token issued by
the given authorization server.
urn:ietf:params:oauth:token-type:refresh_token
Indicates that the token is an OAuth 2.0 refreshe token issued by
the given authorization server.
urn:ietf:params:oauth:token-type:id_token
Indicates that the token is an ID Token, as defined in Section 2
of [OpenID.Core].
urn:ietf:params:oauth:token-type:saml1
Indicates that the token is a base64url-encoded SAML 1.1
[OASIS.saml-core-1.1] assertion.
urn:ietf:params:oauth:token-type:saml2
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Indicates that the token is a base64url-encoded SAML 2.0
[OASIS.saml-core-2.0-os] assertion.
The value "urn:ietf:params:oauth:token-type:jwt", which is defined in
Section 9 of [JWT], indicates that the token is a JWT.
The distinction between an access token and a JWT is subtle. An
access token represents a delegated authorization decision, whereas
JWT is a token format. An access token can be formatted as a JWT but
doesn't necessarily have to be. And a JWT might well be an access
token but not all JWTs are access tokens. The intent of this
specification is that "urn:ietf:params:oauth:token-type:access_token"
be an indicator that the token is a typical OAuth access token issued
by the authorization server in question, opaque to the client, and
usable the same manner as any other access token obtained from that
authorization server. (It could well be a JWT, but the client isn't
and needn't be aware of that fact.) Whereas,
"urn:ietf:params:oauth:token-type:jwt" is to indicate specifically
that a JWT is being requested or sent (perhaps in a cross-domain use-
case where the JWT is used as an authorization grant to obtain an
access token from a different authorization server as is facilitated
by [RFC7523]).
4. JSON Web Token Claims and Introspection Response Parameters
It is useful to have defined mechanisms to express delegation within
a token as well as to express authorization to delegate or
impersonate. Although the token exchange protocol described herein
can be used with any type of token, this section defines claims to
express such semantics specifically for JWTs and in an OAuth 2.0
Token Introspection [RFC7662] response. Similar definitions for
other types of tokens are possible but beyond the scope of this
specification.
Note that the claims not established herein but used in examples and
descriptions, such as "iss", "sub", "exp", etc., are defined by
[JWT].
4.1. "act" (Actor) Claim
The "act" (actor) claim provides a means within a JWT to express that
delegation has occurred and identify the acting party to whom
authority has been delegated. The "act" claim value is a JSON object
and members in the JSON object are claims that identify the actor.
The claims that make up the "act" claim identify and possibly provide
additional information about the actor. For example, the combination
of the two claims "iss" and "sub" might be necessary to uniquely
identify an actor.
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However, claims within the "act" claim pertain only to the identity
of the actor and are not relevant to the validity of the containing
JWT in the same manner as the top-level claims. Consequently, non-
identity claims (e.g., "exp", "nbf", and "aud") are not meaningful
when used within an "act" claim, and therefore must not be used.
The following example illustrates the "act" (actor) claim within a
JWT Claims Set. The claims of the token itself are about
user@example.com while the "act" claim indicates that
admin@example.com is the current actor.
{
"aud":"https://consumer.example.com",
"iss":"https://issuer.example.com",
"exp":1443904177,
"nbf":1443904077,
"sub":"user@example.com",
"act":
{
"sub":"admin@example.com"
}
}
Figure 5: Actor Claim
A chain of delegation can be expressed by nesting one "act" claim
within another. The outermost "act" claim represents the current
actor while nested "act" claims represent prior actors. The least
recent actor is the most deeply nested.
For the purpose of applying access control policy, the consumer of a
token MUST only consider the token's top-level claims and the party
identified as the current actor by the "act" claim. Prior actors
identified by any nested "act" claims are informational only and are
not to be considered in access control decisions.
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The following example illustrates nested "act" (actor) claims within
a JWT Claims Set. The claims of the token itself are about
user@example.com while the "act" claim indicates that the system
https://service16.example.com is the current actor and
https://service77.example.com was a prior actor. Such a token might
come about as the result of service16 receiving a token in a call
from service77 and exchanging it for a token suitable to call
service26 while the authorization server notes the situation in the
newly issued token.
{
"aud":"https://service26.example.com",
"iss":"https://issuer.example.com",
"exp":1443904100,
"nbf":1443904000,
"sub":"user@example.com",
"act":
{
"sub":"https://service16.example.com",
"act":
{
"sub":"https://service77.example.com",
}
}
}
Figure 6: Nested Actor Claim
When included as a top-level member of an OAuth token introspection
response, "act" has the same semantics and format as the claim of the
same name.
4.2. "scope" (Scopes) Claim
The value of the "scope" claim is a JSON string containing a space-
separated list of scopes associated with the token, in the format
described in Section 3.3 of OAuth 2.0 [RFC6749].
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The following example illustrates the "scope" claim within a JWT
Claims Set.
{
"aud":"https://consumer.example.com",
"iss":"https://issuer.example.com",
"exp":1443904177,
"nbf":1443904077,
"sub":"dgaf4mvfs75Fci_FL3heQA",
"scope":"email profile phone address"
}
Figure 7: Scopes Claim
OAuth 2.0 Token Introspection [RFC7662] already defines the "scope"
parameter to convey the scopes associated with the token.
4.3. "client_id" (Client Identifier) Claim
The "client_id" claim carries the client identifier of the OAuth 2.0
[RFC6749] client that requested the token.
The following example illustrates the "client_id" claim within a JWT
Claims Set indicating an OAuth 2.0 client with "s6BhdRkqt3" as its
identifier.
{
"aud":"https://consumer.example.com",
"iss":"https://issuer.example.com",
"exp":1443904177,
"sub":"user@example.com",
"client_id":"s6BhdRkqt3"
}
Figure 8: Client Identifier Claim
OAuth 2.0 Token Introspection [RFC7662] already defines the
"client_id" parameter as the client identifier for the OAuth 2.0
client that requested the token.
4.4. "may_act" (May Act For) Claim
The "may_act" claim makes a statement that one party is authorized to
become the actor and act on behalf of another party. The claim value
is a JSON object and members in the JSON object are claims that
identify the party that is asserted as being eligible to act for the
party identified by the JWT containing the claim. The claims that
make up the "may_act" claim identify and possibly provide additional
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information about the authorized actor. For example, the combination
of the two claims "iss" and "sub" are sometimes necessary to uniquely
identify an authorized actor, while the "email" claim might be used
to provide additional useful information about that party.
However, claims within the "may_act" claim pertain only to the
identity of that party and are not relevant to the validity of the
containing JWT in the same manner as top-level claims. Consequently,
claims such as "exp", "nbf", and "aud" are not meaningful when used
within a "may_act" claim, and therefore should not be used.
The following example illustrates the "may_act" claim within a JWT
Claims Set. The claims of the token itself are about
user@example.com while the "may_act" claim indicates that
admin@example.com is authorized to act on behalf of user@example.com.
{
"aud":"https://consumer.example.com",
"iss":"https://issuer.example.com",
"exp":1443904177,
"nbf":1443904077,
"sub":"user@example.com",
"may_act":
{
"sub":"admin@example.com"
}
}
Figure 9: May Act For Claim
When included as a top-level member of an OAuth token introspection
response, "may_act" has the same semantics and format as the claim of
the same name.
5. Security Considerations
All of the normal security issues that are discussed in [JWT],
especially in relationship to comparing URIs and dealing with
unrecognized values, also apply here.
In addition, both delegation and impersonation introduce unique
security issues. Any time one principal is delegated the rights of
another principal, the potential for abuse is a concern. The use of
the "scope" claim is suggested to mitigate potential for such abuse,
as it restricts the contexts in which the delegated rights can be
exercised.
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6. Privacy Considerations
Tokens employed in the context of the functionality described herein
may contain privacy-sensitive information and, to prevent disclosure
of such information to unintended parties, should only be transmitted
over encrypted channels, such as Transport Layer Security (TLS). In
cases where it is desirable to prevent disclosure of certain
information to the client, the token should be encrypted to its
intended recipient. Deployments should determine the minimally
necessary amount of data and only include such information in issued
tokens. In some cases, data minimization may include representing
only an anonymous or pseudonymous user.
7. IANA Considerations
7.1. OAuth URI Registration
This specification registers the following values in the IANA "OAuth
URI" registry [IANA.OAuth.Parameters] established by [RFC6755].
7.1.1. Registry Contents
o URN: urn:ietf:params:oauth:grant-type:token-exchange
o Common Name: Token exchange grant type for OAuth 2.0
o Change controller: IESG
o Specification Document: Section 2.1 of [[ this specification ]]
o URN: urn:ietf:params:oauth:token-type:access_token
o Common Name: Token type URI for an OAuth 2.0 access token
o Change controller: IESG
o Specification Document: Section 3 of [[this specification]]
o URN: urn:ietf:params:oauth:token-type:refresh_token
o Common Name: Token type URI for an OAuth 2.0 refresh token
o Change controller: IESG
o Specification Document: Section 3 of [[this specification]]
o URN: urn:ietf:params:oauth:token-type:id_token
o Common Name: Token type URI for an ID Token
o Change controller: IESG
o Specification Document: Section 3 of [[this specification]]
o URN: urn:ietf:params:oauth:token-type:saml1
o Common Name: Token type URI for a base64url-encoded SAML 1.1
assertion
o Change Controller: IESG
o Specification Document: Section 3 of [[this specification]]
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o URN: urn:ietf:params:oauth:token-type:saml2
o Common Name: Token type URI for a base64url-encoded SAML 2.0
assertion
o Change Controller: IESG
o Specification Document: Section 3 of [[this specification]]
7.2. OAuth Parameters Registration
This specification registers the following values in the IANA "OAuth
Parameters" registry [IANA.OAuth.Parameters] established by
[RFC6749].
7.2.1. Registry Contents
o Parameter name: resource
o Parameter usage location: token request
o Change controller: IESG
o Specification document(s): Section 2.1 of [[ this specification ]]
o Parameter name: audience
o Parameter usage location: token request
o Change controller: IESG
o Specification document(s): Section 2.1 of [[ this specification ]]
o Parameter name: requested_token_type
o Parameter usage location: token request
o Change controller: IESG
o Specification document(s): Section 2.1 of [[ this specification ]]
o Parameter name: subject_token
o Parameter usage location: token request
o Change controller: IESG
o Specification document(s): Section 2.1 of [[ this specification ]]
o Parameter name: subject_token_type
o Parameter usage location: token request
o Change controller: IESG
o Specification document(s): Section 2.1 of [[ this specification ]]
o Parameter name: actor_token
o Parameter usage location: token request
o Change controller: IESG
o Specification document(s): Section 2.1 of [[ this specification ]]
o Parameter name: actor_token_type
o Parameter usage location: token request
o Change controller: IESG
o Specification document(s): Section 2.1 of [[ this specification ]]
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o Parameter name: issued_token_type
o Parameter usage location: token response
o Change controller: IESG
o Specification document(s): Section 2.2.1 of [[ this specification
]]
7.3. OAuth Access Token Type Registration
This specification registers the following access token type in the
IANA "OAuth Access Token Types" registry [IANA.OAuth.Parameters]
established by [RFC6749].
7.3.1. Registry Contents
o Type name: N_A
o Additional Token Endpoint Response Parameters: (none)
o HTTP Authentication Scheme(s): (none)
o Change controller: IESG
o Specification document(s): Section 2.2.1 of [[ this specification
]]
7.4. JSON Web Token Claims Registration
This specification registers the following Claims in the IANA "JSON
Web Token Claims" registry [IANA.JWT.Claims] established by [JWT].
7.4.1. Registry Contents
o Claim Name: "act"
o Claim Description: Actor
o Change Controller: IESG
o Specification Document(s): Section 4.1 of [[ this specification ]]
o Claim Name: "scope"
o Claim Description: Scope Values
o Change Controller: IESG
o Specification Document(s): Section 4.2 of [[ this specification ]]
o Claim Name: "client_id"
o Claim Description: Client Identifier
o Change Controller: IESG
o Specification Document(s): Section 4.3 of [[ this specification ]]
o Claim Name: "may_act"
o Claim Description: May Act For
o Change Controller: IESG
o Specification Document(s): Section 4.4 of [[ this specification ]]
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7.5. OAuth Token Introspection Response Registration
This specification registers the following values in the IANA "OAuth
Token Introspection Response" registry [IANA.OAuth.Parameters]
established by [RFC7662].
7.5.1. Registry Contents
o Claim Name: "act"
o Claim Description: Actor
o Change Controller: IESG
o Specification Document(s): Section 4.1 of [[ this specification ]]
o Claim Name: "may_act"
o Claim Description: May Act For
o Change Controller: IESG
o Specification Document(s): Section 4.4 of [[ this specification ]]
7.6. OAuth Extensions Error Registration
This specification registers the following values in the IANA "OAuth
Extensions Error" registry [IANA.OAuth.Parameters] established by
[RFC6749].
7.6.1. Registry Contents
o Error Name: "invalid_target"
o Error Usage Location: token error response
o Related Protocol Extension: OAuth 2.0 Token Exchange
o Change Controller: IETF
o Specification Document(s): Section 2.2.2 of [[ this specification
]]
8. References
8.1. Normative References
[IANA.JWT.Claims]
IANA, "JSON Web Token Claims",
<http://www.iana.org/assignments/jwt>.
[IANA.OAuth.Parameters]
IANA, "OAuth Parameters",
<http://www.iana.org/assignments/oauth-parameters>.
[JWT] Jones, M., Bradley, J., and N. Sakimura, "JSON Web Token
(JWT)", RFC 7519, DOI 10.17487/RFC7519, May 2015,
<http://tools.ietf.org/html/rfc7519>.
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[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>.
[RFC3986] 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>.
[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>.
[RFC7159] Bray, T., Ed., "The JavaScript Object Notation (JSON) Data
Interchange Format", RFC 7159, DOI 10.17487/RFC7159, March
2014, <https://www.rfc-editor.org/info/rfc7159>.
[RFC7662] Richer, J., Ed., "OAuth 2.0 Token Introspection",
RFC 7662, DOI 10.17487/RFC7662, October 2015,
<https://www.rfc-editor.org/info/rfc7662>.
8.2. Informative References
[OASIS.saml-core-1.1]
Maler, E., Mishra, P., and R. Philpott, "Assertions and
Protocol for the OASIS Security Assertion Markup Language
(SAML) V1.1", OASIS Standard oasis-sstc-saml-core-1.1,
September 2003.
[OASIS.saml-core-2.0-os]
Cantor, S., Kemp, J., Philpott, R., and E. Maler,
"Assertions and Protocol for the OASIS Security Assertion
Markup Language (SAML) V2.0", OASIS Standard saml-core-
2.0-os, March 2005.
[OpenID.Core]
Sakimura, N., Bradley, J., Jones, M., de Medeiros, B., and
C. Mortimore, "OpenID Connect Core 1.0", August 2015,
<http://openid.net/specs/openid-connect-core-1_0.html>.
[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>.
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[RFC6755] Campbell, B. and H. Tschofenig, "An IETF URN Sub-Namespace
for OAuth", RFC 6755, DOI 10.17487/RFC6755, October 2012,
<https://www.rfc-editor.org/info/rfc6755>.
[RFC7521] 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>.
[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>.
[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>.
[WS-Trust]
Nadalin, A., Goodner, M., Gudgin, M., Barbir, A., and H.
Granqvist, "WS-Trust 1.4", February 2012,
<http://docs.oasis-open.org/ws-sx/ws-trust/v1.4/
ws-trust.html>.
Appendix A. Additional Token Exchange Examples
Two example token exchanges are provided in the following sections
illustrating impersonation and delegation, respectively (with extra
line breaks and indentation for display purposes only).
A.1. Impersonation Token Exchange Example
A.1.1. Token Exchange Request
In the following token exchange request, a client is requesting a
token with impersonation semantics. The client tells the
authorization server that it needs a token for use at the target
service with the logical name "urn:example:cooperation-context".
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POST /as/token.oauth2 HTTP/1.1
Host: as.example.com
Content-Type: application/x-www-form-urlencoded
grant_type=urn%3Aietf%3Aparams%3Aoauth%3Agrant-type%3Atoken-exchange
&audience=urn%3Aexample%3Acooperation-context
&subject_token=eyJhbGciOiJFUzI1NiIsImtpZCI6IjE2In0.eyJhdWQiOiJodHRwc
zovL2FzLmV4YW1wbGUuY29tIiwiaXNzIjoiaHR0cHM6Ly9vcmlnaW5hbC1pc3N1ZXI
uZXhhbXBsZS5uZXQiLCJleHAiOjE0NDE5MTA2MDAsIm5iZiI6MTQ0MTkwOTAwMCwic
3ViIjoiYmNAZXhhbXBsZS5uZXQiLCJzY29wZSI6Im9yZGVycyBwcm9maWxlIGhpc3R
vcnkifQ.u0slqvbnqU43EvI_itGdFJ11StrAwXlxczYfMYsaR5p4J_gBp019mxljSx
xmD3FfbrjTGyZ4eDh1JKJVpsnnPg
&subject_token_type=urn%3Aietf%3Aparams%3Aoauth%3Atoken-type%3Ajwt
Figure 10: Token Exchange Request
A.1.2. Subject Token Claims
The "subject_token" in the prior request is a JWT and the decoded JWT
Claims Set is shown here. The JWT is intended for consumption by the
authorization server within a specific time window. The subject of
the JWT ("bc@example.net") is the party on behalf of whom the new
token is being requested.
{
"aud":"https://as.example.com",
"iss":"https://original-issuer.example.net",
"exp":1441910600,
"nbf":1441909000,
"sub":"bc@example.net",
"scope":"orders profile history"
}
Figure 11: Subject Token Claims
A.1.3. Token Exchange Response
The "access_token" parameter of the token exchange response shown
below contains the new token that the client requested. The other
parameters of the response indicate that the token is a bearer access
token that expires in an hour.
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HTTP/1.1 200 OK
Content-Type: application/json
Cache-Control: no-cache, no-store
{
"access_token":"eyJhbGciOiJFUzI1NiIsImtpZCI6IjcyIn0.eyJhdWQiOiJ1cm4
6ZXhhbXBsZTpjb29wZXJhdGlvbi1jb250ZXh0IiwiaXNzIjoiaHR0cHM6Ly9hcy5l
eGFtcGxlLmNvbSIsImV4cCI6MTQ0MTkxMzYxMCwic3ViIjoiYmNAZXhhbXBsZS5uZ
XQiLCJzY29wZSI6Im9yZGVycyBwcm9maWxlIGhpc3RvcnkifQ._OnH9oHT2cd0-Sz
OfBrNkVYlRdn48X8kI4_Is3LHeQmtkd-nDdR63IuuQ_GeZd7UafMV3bk8jqUDgi-l
rTfSwA",
"issued_token_type":
"urn:ietf:params:oauth:token-type:access_token",
"token_type":"Bearer",
"expires_in":3600
}
Figure 12: Token Exchange Response
A.1.4. Issued Token Claims
The decoded JWT Claims Set of the issued token is shown below. The
new JWT is issued by the authorization server and intended for
consumption by a system entity known by the logical name
"urn:example:cooperation-context" any time before its expiration.
The subject ("sub") of the JWT is the same as the subject the token
used to make the request, which effectively enables the client to
impersonate that subject at the system entity known by the logical
name of "urn:example:cooperation-context" by using the token.
{
"aud":"urn:example:cooperation-context",
"iss":"https://as.example.com",
"exp":1441913610,
"sub":"bc@example.net",
"scope":"orders profile history"
}
Figure 13: Issued Token Claims
A.2. Delegation Token Exchange Example
A.2.1. Token Exchange Request
In the following token exchange request, a client is requesting a
token and providing both a "subject_token" and an "actor_token". The
client tells the authorization server that it needs a token for use
at the target service with the logical name "urn:example:cooperation-
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context". Policy at the authorization server dictates that the
issued token be a composite.
POST /as/token.oauth2 HTTP/1.1
Host: as.example.com
Content-Type: application/x-www-form-urlencoded
grant_type=urn%3Aietf%3Aparams%3Aoauth%3Agrant-type%3Atoken-exchange
&audience=urn%3Aexample%3Acooperation-context
&subject_token=eyJhbGciOiJFUzI1NiIsImtpZCI6IjE2In0.eyJhdWQiOiJodHRwc
zovL2FzLmV4YW1wbGUuY29tIiwiaXNzIjoiaHR0cHM6Ly9vcmlnaW5hbC1pc3N1ZXI
uZXhhbXBsZS5uZXQiLCJleHAiOjE0NDE5MTAwNjAsInNjb3BlIjoic3RhdHVzIGZlZ
WQiLCJzdWIiOiJ1c2VyQGV4YW1wbGUubmV0IiwibWF5X2FjdCI6eyJzdWIiOiJhZG1
pbkBleGFtcGxlLm5ldCJ9fQ.4rPRSWihQbpMIgAmAoqaJojAxj-p2X8_fAtAGTXrvM
xU-eEZHnXqY0_AOZgLdxw5DyLzua8H_I10MCcckF-Q_g
&subject_token_type=urn%3Aietf%3Aparams%3Aoauth%3Atoken-type%3Ajwt
&actor_token=eyJhbGciOiJFUzI1NiIsImtpZCI6IjE2In0.eyJhdWQiOiJodHRwczo
vL2FzLmV4YW1wbGUuY29tIiwiaXNzIjoiaHR0cHM6Ly9vcmlnaW5hbC1pc3N1ZXIuZ
XhhbXBsZS5uZXQiLCJleHAiOjE0NDE5MTAwNjAsInN1YiI6ImFkbWluQGV4YW1wbGU
ubmV0In0.7YQ-3zPfhUvzje5oqw8COCvN5uP6NsKik9CVV6cAOf4QKgM-tKfiOwcgZ
oUuDL2tEs6tqPlcBlMjiSzEjm3yBg
&actor_token_type=urn%3Aietf%3Aparams%3Aoauth%3Atoken-type%3Ajwt
Figure 14: Token Exchange Request
A.2.2. Subject Token Claims
The "subject_token" in the prior request is a JWT and the decoded JWT
Claims Set is shown here. The JWT is intended for consumption by the
authorization server before a specific expiration time. The subject
of the JWT ("user@example.net") is the party on behalf of whom the
new token is being requested.
{
"aud":"https://as.example.com",
"iss":"https://original-issuer.example.net",
"exp":1441910060,
"scope":"status feed",
"sub":"user@example.net",
"may_act":
{
"sub":"admin@example.net"
}
}
Figure 15: Subject Token Claims
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A.2.3. Actor Token Claims
The "actor_token" in the prior request is a JWT and the decoded JWT
Claims Set is shown here. This JWT is also intended for consumption
by the authorization server before a specific expiration time. The
subject of the JWT ("admin@example.net") is the actor that will wield
the security token being requested.
{
"aud":"https://as.example.com",
"iss":"https://original-issuer.example.net",
"exp":1441910060,
"sub":"admin@example.net"
}
Figure 16: Actor Token Claims
A.2.4. Token Exchange Response
The "access_token" parameter of the token exchange response shown
below contains the new token that the client requested. The other
parameters of the response indicate that the token is a JWT that
expires in an hour and that the access token type is not applicable
since the issued token is not an access token.
HTTP/1.1 200 OK
Content-Type: application/json
Cache-Control: no-cache, no-store
{
"access_token":"eyJhbGciOiJFUzI1NiIsImtpZCI6IjcyIn0.eyJhdWQiOiJ1cm4
6ZXhhbXBsZTpjb29wZXJhdGlvbi1jb250ZXh0IiwiaXNzIjoiaHR0cHM6Ly9hcy5l
eGFtcGxlLmNvbSIsImV4cCI6MTQ0MTkxMzYxMCwic2NvcGUiOiJzdGF0dXMgZmVlZ
CIsInN1YiI6InVzZXJAZXhhbXBsZS5uZXQiLCJhY3QiOnsic3ViIjoiYWRtaW5AZX
hhbXBsZS5uZXQifX0.3paKl9UySKYB5ng6_cUtQ2qlO8Rc_y7Mea7IwEXTcYbNdwG
9-G1EKCFe5fW3H0hwX-MSZ49Wpcb1SiAZaOQBtw",
"issued_token_type":"urn:ietf:params:oauth:token-type:jwt",
"token_type":"N_A",
"expires_in":3600
}
Figure 17: Token Exchange Response
A.2.5. Issued Token Claims
The decoded JWT Claims Set of the issued token is shown below. The
new JWT is issued by the authorization server and intended for
consumption by a system entity known by the logical name
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"urn:example:cooperation-context" any time before its expiration.
The subject ("sub") of the JWT is the same as the subject of the
"subject_token" used to make the request. The actor ("act") of the
JWT is the same as the subject of the "actor_token" used to make the
request. This indicates delegation and identifies
"admin@example.net" as the current actor to whom authority has been
delegated to act on behalf of "user@example.net".
{
"aud":"urn:example:cooperation-context",
"iss":"https://as.example.com",
"exp":1441913610,
"scope":"status feed",
"sub":"user@example.net",
"act":
{
"sub":"admin@example.net"
}
}
Figure 18: Issued Token Claims
Appendix B. Acknowledgements
This specification was developed within the OAuth Working Group,
which includes dozens of active and dedicated participants. It was
produced under the chairmanship of Hannes Tschofenig, Derek Atkins,
and Rifaat Shekh-Yusef with Kathleen Moriarty, Stephen Farrell, Eric
Rescorla, and Benjamin Kaduk serving as Security Area Directors. The
following individuals contributed ideas, feedback, and wording to
this specification:
Caleb Baker, Vittorio Bertocci, Thomas Broyer, William Denniss,
Vladimir Dzhuvinov, Phil Hunt, Benjamin Kaduk, Jason Keglovitz,
Torsten Lodderstedt, Adam Lewis, James Manger, Nov Matake, Matt
Miller, Hilarie Orman, Matthew Perry, Eric Rescorla, Justin Richer,
Rifaat Shekh-Yusef, Scott Tomilson, and Hannes Tschofenig.
Appendix C. Document History
[[ to be removed by the RFC Editor before publication as an RFC ]]
-16
o Fixed typo and added an AD to Acknowledgements.
-15
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o Updated the nested actor claim example to (hopefully) be more
straightforward.
o Reworked Privacy Considerations to say to use TLS in transit,
minimize the amount of information in the token, and encrypt the
token if disclosure of its information to the client is a concern
per https://mailarchive.ietf.org/arch/msg/secdir/
KJhx4aq_U5uk3k6zpYP-CEHbpVM
o Moved the Security and Privacy Considerations sections to before
the IANA Considerations.
-14
o Added text in Section 4.1 about the "act" claim stating that only
the top-level claims and the current actor are to be considered in
applying access control decisions.
-13
o Updated the claim name and value syntax for scope to be consistent
with the treatment of scope in RFC 7662 OAuth 2.0 Token
Introspection.
o Updated the client identifier claim name to be consistent with the
treatment of client id in RFC 7662 OAuth 2.0 Token Introspection.
-12
o Updated to use the boilerplate from RFC 8174.
-11
o Added new WG chair and AD to the Acknowledgements.
o Applied clarifications suggested during AD review by EKR.
-10
o Defined token type URIs for base64url-encoded SAML 1.1 and SAML
2.0 assertions.
o Applied editorial fixes.
-09
o Changed "security tokens obtained could be used in a number of
contexts" to "security tokens obtained may be used in a number of
contexts" per a WGLC suggestion.
o Clarified that the validity of the subject or actor token have no
impact on the validity of the issued token after the exchange has
occurred per a WGLC comment.
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o Changed use of invalid_target error code to a SHOULD per a WGLC
comment.
o Clarified text about non-identity claims within the "act" claim
being meaningless per a WGLC comment.
o Added brief Privacy Considerations section per WGLC comments.
-08
o Use the bibxml reference for OpenID.Core rather than defining it
inline.
o Added editor role for Campbell.
o Minor clarification of the text for actor_token.
-07
o Fixed typo (desecration -> discretion).
o Added an explanation of the relationship between scope, audience
and resource in the request and added an "invalid_target" error
code enabling the AS to tell the client that the requested
audiences/resources were too broad.
-06
o Drop "An STS for the REST of Us" from the title.
o Drop "heavyweight" and "lightweight" from the abstract and
introduction.
o Clarifications on the language around xxxxxx_token_type.
o Remove the want_composite parameter.
o Add a short mention of proof-of-possession style tokens to the
introduction and remove the respective open issue.
-05
o Defined the JWT claim "cid" to express the OAuth 2.0 client
identifier of the client that requested the token.
o Defined and requested registration for "act" and "may_act" as
Token introspection response parameters (in addition to being JWT
claims).
o Loosen up the language about refresh_token in the response to
OPTIONAL from NOT RECOMMENDED based on feedback form real world
deployment experience.
o Add clarifying text about the distinction between JWT and access
token URIs.
o Close out (remove) some of the Open Issues bullets that have been
resolved.
-04
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o Clarified that the "resource" and "audience" request parameters
can be used at the same time (via http://www.ietf.org/mail-
archive/web/oauth/current/msg15335.html).
o Clarified subject/actor token validity after token exchange and
explained a bit more about the recommendation to not issue refresh
tokens (via http://www.ietf.org/mail-archive/web/oauth/current/
msg15318.html).
o Updated the examples appendix to use an issuer value that doesn't
imply that the client issued and signed the tokens and used
"Bearer" and "urn:ietf:params:oauth:token-type:access_token" in
one of the responses (via http://www.ietf.org/mail-
archive/web/oauth/current/msg15335.html).
o Defined and registered urn:ietf:params:oauth:token-type:id_token,
since some use cases perform token exchanges for ID Tokens and no
URI to indicate that a token is an ID Token had previously been
defined.
-03
o Updated the document editors (adding Campbell, Bradley, and
Mortimore).
o Added to the title.
o Added to the abstract and introduction.
o Updated the format of the request to use application/x-www-form-
urlencoded request parameters and the response to use the existing
token endpoint JSON parameters defined in OAuth 2.0.
o Changed the grant type identifier to urn:ietf:params:oauth:grant-
type:token-exchange.
o Added RFC 6755 registration requests for
urn:ietf:params:oauth:token-type:refresh_token,
urn:ietf:params:oauth:token-type:access_token, and
urn:ietf:params:oauth:grant-type:token-exchange.
o Added RFC 6749 registration requests for request/response
parameters.
o Removed the Implementation Considerations and the requirement to
support JWTs.
o Clarified many aspects of the text.
o Changed "on_behalf_of" to "subject_token",
"on_behalf_of_token_type" to "subject_token_type", "act_as" to
"actor_token", and "act_as_token_type" to "actor_token_type".
o Added an "audience" request parameter used to indicate the logical
names of the target services at which the client intends to use
the requested security token.
o Added a "want_composite" request parameter used to indicate the
desire for a composite token rather than trying to infer it from
the presence/absence of token(s) in the request.
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o Added a "resource" request parameter used to indicate the URLs of
resources at which the client intends to use the requested
security token.
o Specified that multiple "audience" and "resource" request
parameter values may be used.
o Defined the JWT claim "act" (actor) to express the current actor
or delegation principal.
o Defined the JWT claim "may_act" to express that one party is
authorized to act on behalf of another party.
o Defined the JWT claim "scp" (scopes) to express OAuth 2.0 scope-
token values.
o Added the "N_A" (not applicable) OAuth Access Token Type
definition for use in contexts in which the token exchange syntax
requires a "token_type" value, but in which the token being issued
is not an access token.
o Added examples.
-02
o Enabled use of Security Token types other than JWTs for "act_as"
and "on_behalf_of" request values.
o Referenced the JWT and OAuth Assertions RFCs.
-01
o Updated references.
-00
o Created initial working group draft from draft-jones-oauth-token-
exchange-01.
Authors' Addresses
Michael B. Jones
Microsoft
Email: mbj@microsoft.com
URI: http://self-issued.info/
Anthony Nadalin
Microsoft
Email: tonynad@microsoft.com
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Brian Campbell (editor)
Ping Identity
Email: brian.d.campbell@gmail.com
John Bradley
Ping Identity
Email: ve7jtb@ve7jtb.com
Chuck Mortimore
Salesforce
Email: cmortimore@salesforce.com
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