OAuth Working Group R. Shekh-Yusef Internet-Draft Ernst & Young Intended status: Standards Track D. Hardt Expires: 27 December 2023 Hellō G. De Marco Dipartimento per la trasformazione digitale 25 June 2023 JSON Web Token (JWT) Embedded Tokens draft-yusef-oauth-nested-jwt-07 Abstract This specification defines a mechanism for embedding tokens into a JWT token. The JWT token and the embedded tokens are issued by different issuers. Status of This Memo This Internet-Draft is submitted in full conformance with the provisions of BCP 78 and BCP 79. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF). Note that other groups may also distribute working documents as Internet-Drafts. The list of current Internet- Drafts is at https://datatracker.ietf.org/drafts/current/. Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress." This Internet-Draft will expire on 27 December 2023. Copyright Notice Copyright (c) 2023 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 (https://trustee.ietf.org/ license-info) in effect on the date of publication of this document. Please review these documents carefully, as they describe your rights and restrictions with respect to this document. Code Components extracted from this document must include Revised BSD License text as described in Section 4.e of the Trust Legal Provisions and are provided without warranty as described in the Revised BSD License. Shekh-Yusef, et al. Expires 27 December 2023 [Page 1] Internet-Draft JWT Embedded Tokens June 2023 This document may contain material from IETF Documents or IETF Contributions published or made publicly available before November 10, 2008. The person(s) controlling the copyright in some of this material may not have granted the IETF Trust the right to allow modifications of such material outside the IETF Standards Process. Without obtaining an adequate license from the person(s) controlling the copyright in such materials, this document may not be modified outside the IETF Standards Process, and derivative works of it may not be created outside the IETF Standards Process, except to format it for publication as an RFC or to translate it into languages other than English. Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 1.1. Terminology . . . . . . . . . . . . . . . . . . . . . . . 3 2. Use Cases . . . . . . . . . . . . . . . . . . . . . . . . . . 3 2.1. STIR . . . . . . . . . . . . . . . . . . . . . . . . . . 3 2.2. Network Service Mesh (NSM) . . . . . . . . . . . . . . . 3 2.3. Multiple Issuers for same Subject . . . . . . . . . . . . 4 2.4. Multiple tokens for multiple resources . . . . . . . . . 4 3. Authorization Request and Response . . . . . . . . . . . . . 4 3.1. Authorization Request . . . . . . . . . . . . . . . . . . 4 3.2. Authorization Successful Response . . . . . . . . . . . . 6 3.2.1. Embedded Tokens By Value . . . . . . . . . . . . . . 6 3.2.2. Embedded Tokens By Reference . . . . . . . . . . . . 7 3.3. Authorization Error Response . . . . . . . . . . . . . . 8 4. JSON Web Token Claims . . . . . . . . . . . . . . . . . . . . 8 4.1. "tokens" Claim . . . . . . . . . . . . . . . . . . . . . 8 4.1.1. "type" Claim . . . . . . . . . . . . . . . . . . . . 9 4.1.2. "token" Claim . . . . . . . . . . . . . . . . . . . . 9 4.1.3. "digest" Claim . . . . . . . . . . . . . . . . . . . 9 5. Security Considerations . . . . . . . . . . . . . . . . . . . 9 6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 9 7. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 9 8. References . . . . . . . . . . . . . . . . . . . . . . . . . 9 8.1. Normative References . . . . . . . . . . . . . . . . . . 9 8.2. Informative References . . . . . . . . . . . . . . . . . 10 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 10 1. Introduction JWT is a mechanism that is used to transfer claims between two parties across security domains. There are a number of use cases that need to embed tokens into another JWT token. Shekh-Yusef, et al. Expires 27 December 2023 [Page 2] Internet-Draft JWT Embedded Tokens June 2023 This specification defines a mechanism for embedding tokens into a JWT token. The JWT token and the embedded tokens are issued by different issuers. Such a mechanism allows for a proper auditing trail that allows the Resource Server to identify who accessed what resource and on behalf of whom. In some cases, this allows the service consuming such a token to present some of the information contained in the nested token or claims to the end user in real-time. In addition, in some cases, this allows the Resource Server to apply authorization policies based on who requested the access to the resource and on behalf of whom is the request. 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: 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. 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. Shekh-Yusef, et al. Expires 27 December 2023 [Page 3] Internet-Draft JWT Embedded Tokens June 2023 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. 2.3. Multiple Issuers for same Subject A JWT may have embedded claims from one or more separate Issuers. An ID Token may have identity claims from independent issuers such as DOB and a professional accreditation. 2.4. Multiple tokens for multiple resources A JWT may embeds tokens for different audiences and scopes. An Authorization Server issues a JWT Token that contains multiple tokens. Each token has a specialized set of attributes and values. The tokens can be used by the client to consume protected resources or to obtain access tokens through a token exchange mechanism, over different domains, releasing the minimum possible number of information, related on the main subject, necessary for the operation. 3. Authorization Request and Response This section describes the mechanism to request an existing token or tokens to be embedded in a new token. The mechanism defines a new grant type embedded-tokens for this purpose. In some cases, the embedding of tokens into a new token could be done locally, if that entity is trusted to so. If this is the case, then this request/response process defined below is not needed, and the trusted entity can then issue the tokens in the format specified in section 4; see the examples provided in sections 3.2.1 or 3.2.2. 3.1. Authorization Request When a client receives a token, and it needs to transform or/and enhance the permissions of the token, the client will send a token request to the AS, and include the received token or tokens to be embedded in the newly issued token that contains the transformed token details or permissions. Shekh-Yusef, et al. Expires 27 December 2023 [Page 4] Internet-Draft JWT Embedded Tokens June 2023 The Client requests a token by sending an authorization request to the authorization server’s token endpoint and include the following parameters in a JSON payload: grant_type (REQUIRED) Carries the new grant type to indicate to the token endpoint that the provided token(s) to be embedded into the newly issued token. The parameter value MUST be urn:ietf:params:oauth:grant- type:embedded-tokens tokens (REQUIRED) An array of objects, where each object represents a token that contains the "type" claim and either the "token" claim, or the "digest" and "jti" claims, as defined in section 4 of this specification. The request MAY include any of the following parameters, defined in Section 2.1 of RFC8693: resource, audience, scope, and requested_token_type. The following is an example of this new token request: POST /token Host: as.example.com Content-Type: application/json { "grant_type": "urn:ietf:params:oauth:grant-type:embedded-tokens", "requested_token_type": "urn:ietf:params:oauth:token-type:access_token" "tokens": [ { "type": "urn:ietf:params:oauth:token-type:access_token", "token": "eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9. eyJzdWIiOiIyMzQ1Njc4OTAxIiwibmFtZSI6IkFsZXggRG9lIiwia WF0IjoxNTE2MjM5MDIyLCJqdGkiOiJYRkVYYlNDMHhpTXUifQ. wyycbcY9i0U5YldltNhp4WbM-gF3Q1-jtnc-Wvzyxcg" } ] } The following is the decoded example embedded token in the above example: Shekh-Yusef, et al. Expires 27 December 2023 [Page 5] Internet-Draft JWT Embedded Tokens June 2023 { "alg": "HS256", "typ": "JWT" } . { "sub": "2345678901", "name": "Alex Doe", "iat": 1516239022, "jti": "XFEXbSC0xiMu" } 3.2. Authorization Successful Response Before issuing the requested token, the authorization server MUST ensure that the request is valid and that the embedded token(s) provided in the subject_token is coming from a trusted and approved entity In the case that the authorization server validated and approved the request, the authorization server responds to the above request with the standard token exchange response, as defined in section 2.2.1 of [RFC8693]. The type of token issued is as specified in the requested_token_type parameter, if provided. Otherwise, the type of token issued is at the discretion of the authorization server. 3.2.1. Embedded Tokens By Value The authorization server will typically embed the provided tokens directly into the newly issued token, when there are no concerns around the size of the new token with the embedded tokens. The following is an example for a JWT token with an embedded token: Shekh-Yusef, et al. Expires 27 December 2023 [Page 6] Internet-Draft JWT Embedded Tokens June 2023 { "alg": "HS256", "typ": "JWT", } . { "sub": "1234567890", "name": "John Doe", "iat": 1516239022, "tokens": [ { "type": "urn:ietf:params:oauth:token-type:access_token", "token": "eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9. eyJzdWIiOiIyMzQ1Njc4OTAxIiwibmFtZSI6IkFsZXggRG9lIiwia WF0IjoxNTE2MjM5MDIyLCJqdGkiOiJYRkVYYlNDMHhpTXUifQ. wyycbcY9i0U5YldltNhp4WbM-gF3Q1-jtnc-Wvzyxcg" } ] } 3.2.2. Embedded Tokens By Reference In some cases, embedding the tokens into the JWT directly might cause the token size to become too large. In this case, instead of embedding the tokens, the AS will embed a hash of the token(s) and its associated 'jti' claim(s). This allows the Client to send these tokens directly to the RS with the newly issued JWT, to allow the RS to validate that the tokens are indeed associated with this new issued JWT. The following is an example for a JWT token with a reference to the token: Shekh-Yusef, et al. Expires 27 December 2023 [Page 7] Internet-Draft JWT Embedded Tokens June 2023 { "alg": "HS256", "typ": "JWT", } . { "sub": "1234567890", "name": "John Doe", "iat": 1516239022, "tokens": [ { "type": "urn:ietf:params:oauth:token-type:access_token:reference", "digest": { "alg": "sha-256", "hash": "68e439fd95964da902a8654d47c51d6bc0a7791ea9895173989b263374a9a125" } "jti": "XFEXbSC0xiMu" } ] } 3.3. Authorization Error Response If the authorization fails to validate the embedded token, then the authorization server MUST construct an error response, as specified in section 5.2 of RFC6749. The value of the error parameter MUST be invalid_embedded_token error code. The authorization server MAY include additional information regarding the reasons for the error using the error_description as discussed in Section 5.2 of [RFC6749]. 4. JSON Web Token Claims This section defines the new claims that will be used to represent the embedded tokens. It defines one top-level claim, "tokens" claim, and 3 sub claims under that, 'type', "token", and "digest" claims. 4.1. "tokens" Claim The "tokens" claim is an array of objects, where each object represents a token, that contains the “type” claim and either the “token” claim, or the “digest" and “jti” claims. Shekh-Yusef, et al. Expires 27 December 2023 [Page 8] Internet-Draft JWT Embedded Tokens June 2023 4.1.1. "type" Claim The "type" claim is used to indicate the type of embedded token, which takes one of the values defined in Section 3, RFC8693. 4.1.2. "token" Claim The "token" claim is used to hold the details of the embedded token. 4.1.3. "digest" Claim The "digest" claim is an object that is used to hold the hash of the token, to be used to reference the token instead of embedding it directly in the new JWT.ß The object contains the following two claims: 4.1.3.1. "alg" Claim Holds the algorithm used to hash the token. By default this is "sha- 256". 4.1.3.2. "hash" Claim Holds the hash value of the token using the algorithm defined in the "alg" claim. 5. Security Considerations The entity handling the incoming authorization request MUST validate the token and ensure that it is coming from a trusted entity, before attempting to embed that into a newly issued JWT. 6. IANA Considerations TODO 7. Acknowledgments TODO 8. References 8.1. Normative References [RFC7519] Jones, M., Bradley, J., and N. Sakimura, "JSON Web Token (JWT)", RFC 7519, DOI 10.17487/RFC7519, May 2015, . Shekh-Yusef, et al. Expires 27 December 2023 [Page 9] Internet-Draft JWT Embedded Tokens June 2023 [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, May 2017, . 8.2. Informative References [RFC8225] Wendt, C. and J. Peterson, "PASSporT: Personal Assertion Token", RFC 8225, DOI 10.17487/RFC8225, February 2018, . [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. Authors' Addresses Rifaat Shekh-Yusef Ernst & Young Ottawa, Ontario, Canada Email: rifaat.s.ietf@gmail.com Dick Hardt Hellō Seattle, Washington, USA Email: dick.hardt@gmail.com Giuseppe De Marco Dipartimento per la trasformazione digitale Italy Email: giuseppe.demarco@teamdigitale.governo.it Shekh-Yusef, et al. Expires 27 December 2023 [Page 10]