OAuth Working Group R. Shekh-Yusef
Internet-Draft Okta
Intended status: Standards Track 14 June 2022
Expires: 16 December 2022
Multi-Subject JSON Web Token (JWT)
draft-yusef-oauth-nested-jwt-05
Abstract
This specification defines a mechanism for including multiple
subjects in a JWT. A primary subject in an enclosing JWT with its
own claims, and a related secondary subject in a nested JWT with its
own claims.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
1.1. Terminology . . . . . . . . . . . . . . . . . . . . . . . 3
2. Use Cases . . . . . . . . . . . . . . . . . . . . . . . . . . 3
2.1. One Issuer Category . . . . . . . . . . . . . . . . . . . 3
2.1.1. Primary Subject with Secondary Authority Subject . . 3
2.1.2. Multiple Primary Subjects . . . . . . . . . . . . . . 3
2.1.3. Delegation of Authority . . . . . . . . . . . . . . . 4
2.2. Multiple Issuers Category . . . . . . . . . . . . . . . . 4
2.2.1. STIR . . . . . . . . . . . . . . . . . . . . . . . . 4
2.2.2. Network Service Mesh (NSM) . . . . . . . . . . . . . 4
3. Authorization Request . . . . . . . . . . . . . . . . . . . . 4
4. JWT Content . . . . . . . . . . . . . . . . . . . . . . . . . 5
5. Token Relationship . . . . . . . . . . . . . . . . . . . . . 5
6. Example . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
7. Security Considerations . . . . . . . . . . . . . . . . . . . 7
8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 7
9. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 7
10. References . . . . . . . . . . . . . . . . . . . . . . . . . 7
10.1. Normative References . . . . . . . . . . . . . . . . . . 7
10.2. Informative References . . . . . . . . . . . . . . . . . 7
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 7
1. Introduction
JSON Web Token (JWT) [RFC7519] is a mechanism that is used to
transfer claims between two parties across security domains. Nested
JWT is a JWT in which the payload is another JWT. The current
specification does not define a means by which the enclosing JWT
could have its own Claims Set, only the enclosed JWT would have
claims.
There are a number of use cases where there is a need to represent
multiple related subjects in one JWT; a primary subject and a related
secondary subject.
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This specification defines a mechanism for including multiple
subjects in a JWT. A primary subject in an enclosing JWT with its
own claims, and a related secondary subject in a nested JWT with its
own claims.
1.1. Terminology
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in [RFC8174].
2. Use Cases
The following are few use cases that might benefit from such a
concept, that fall into two different categories:
2.1. One Issuer Category
In the following cases, both JWTs are issued by the same issuer.
2.1.1. Primary Subject with Secondary Authority Subject
A primary subject with a related secondary subject that has authority
over the primary subject, e.g. Child/Parent, Pet/Owner.
The secondary user (e.g., parent) logs in to an application (e.g.,
pharmacy application), gets redirected to the authorization server,
authenticates, and asks for permission to access resources (e.g.,
medication) for the primary subject (e.g., child). The authorization
server then issues a JWT with the primary subject in the enclosing
JWT and the secondary subject in the nested JWT.
2.1.2. Multiple Primary Subjects
Two or more primary related subjects e.g. a married couple. The
authorization server is setup to provide one of the subjects with
permissions to access the other related subject resources.
One user (e.g., wife) logs in to a application (e.g., pharmacy
application), gets redirected to the authorization server,
authenticates, and asks for permission to access resources (e.g.,
medication) for the other primary subject (e.g., husband). The
authorization server then issues a JWT with the primary subject in
the enclosing JWT and the other primary subject in the nested JWT.
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2.1.3. Delegation of Authority
A primary subject delegates authority over a resource to a secondary
subject who acts on behalf of the primary subject, as defined in
[RFC8693].
2.2. Multiple Issuers Category
In the following cases, the JWTs are issued by different issuers.
2.2.1. STIR
[RFC8225] defines a PASSporT, which is a JWT, that is used to verify
the identity of a caller in an incoming call.
The PASSporT Extension for Diverted Calls draft [STIR] uses a nested
PASSporT to deliver the details of an incoming call that get
redirected. An authentication service acting for a retargeting
entity generates new PASSporT and embeds the original PASSporT inside
the new one. When the new target receives the nested PASSporT it
will be able to validate the enclosing PASSporT and use the details
of the enclosed PASSporT to identify the original target.
In this case, the original JWT is issued by the calling service, and
the new enclosing JWT is issued by the retargeting service.
2.2.2. Network Service Mesh (NSM)
Network Service Mesh [NSM] is a mechanism that maps the concept of a
service mesh in Kubernetes to L2/L3 payloads.
NSM GRPS messages may pass through multiple intermediaries, each of
which may transform the message. Each intermediary is expected to
create its own JWT token, and include a claim that contains the JWT
it received with the message it has transformed.
In this case, the original JWT is issued by the entity sending the
initial message, and the new enclosing JWT is issued by the
intermediate entity.
3. Authorization Request
To allow the AS to differentiate between an authorization request for
a single subject and an authorization request for multiple subjects,
this document defines the following parameter:
issuer-hint:
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A hint to the AS that the request is for a multi-subject token,
which can take one of two values:
Internal
Indicates that the AS handling the current request will be
issuing both enclosing and enclosed JWTs.
External
Indicates that an external entity has issued the JWT to be
enclosed, which will be carried in access_token parameter.
If the access_token query parameter is included in the request, then
the AS SHOULD embed the provided token in the issued token, if the
issuer-hint has the "External" value.
4. JWT Content
The payload of the enclosing JWT is JSON object that contains the
Claims Set of the primary subject, and one new claim that is used to
hold the enclosed JWT and its relation to the primary subject.
This document defines a new claim, "rsub" (Related Subject) Claim,
that is used to contain the enclosed JWT and its relation to the
primary subject. The "rsub" contains two claims:
rel:
Defines the relationship between the enclosed JWT and the
enclosing JWT. It can take one of the values defined in section
Section 5
jwt:
Contains the enclosed JWT.
5. Token Relationship
The following relathionship types are defined by this specification:
urn:ietf:params:oauth:subject-type:authority
Indicates that the subject in the enclosed JWT has authority over
the subject in the enclosing JWT.
This URN could be used in the child/parent use case described in
Section 2.1.1.
urn:ietf:params:oauth:subject-type:primary
Indicates that the subject in the enclosed JWT is related primary
subject
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This URN could be used in the married couple use case described in
Section 2.1.2.
urn:ietf:params:oauth:subject-type:actor
Indicates that the subject in the enclosed JWT is acting on behalf
of the primary subject
This URN could be used in the delegation use case described in
Section 2.1.3.
urn:ietf:params:oauth:subject-type:original
Indicates that the subject in the enclosed JWT is the original JWT
that resulted in the primary subject JWT
This URN could be used in all the use cases described in
Section 2.2.
6. Example
The following example is for a multi-subject token that represents a
child/parent relashionship. The enclosing JWT represents the primary
user, the child in this case, and the enclosed token in the "rsub"
claim represents the secondary user, the parent in this case.
{
"alg": "HS256",
"typ": "JWT",
}
{
"sub": "1234567890",
"name": "John Doe",
"iat": 1516239022,
"rsub": {
“rel” : "urn:ietf:params:oauth:subject-type:authority"
“jwt” : {
"sub": "9876543210",
"name": "Alice Doe",
"iat": 1516239022,
}
}
}
In this use case, both JWTs are issued by the same entity handling
the authorization request.
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7. Security Considerations
The existing security considerations apply to the use cases where the
JWTs are issued by the same entity. Allowing more than one subject
to access the same account might open the door for potential abuse.
Care must be taken to ensure that when a secondary subject is added
to an account that an adequate approval process is in place.
In the multiple issuers use cases, the entity handling the incoming
authorization request that contains a JWT MUST validate the token and
ensure that it is coming from a trusted entity, before attempting to
embed that JWT into a new multi-subject JWT issued by the AS.
8. IANA Considerations
TODO
9. Acknowledgments
TODO
10. References
10.1. Normative References
[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>.
[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>.
10.2. Informative References
[RFC8225] Wendt, C. and J. Peterson, "PASSporT: Personal Assertion
Token", RFC 8225, DOI 10.17487/RFC8225, February 2018,
<https://www.rfc-editor.org/info/rfc8225>.
[RFC8693] Jones, M., Nadalin, A., Campbell, B., Bradley, J., and C.
Mortimore, "OAuth 2.0 Token Exchange", October 2018.
[STIR] Peterson, J., "PASSporT Extension for Diverted Calls",
October 2018.
Author's Address
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Rifaat Shekh-Yusef
Okta
Ottawa, Ontario, Canada
Email: rifaat.s.ietf@gmail.com
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