Open Authentication Protocol T. Lodderstedt, Ed.
Internet-Draft yes.com AG
Intended status: Standards Track V. Dzhuvinov
Expires: August 23, 2019 Connect2id Ltd.
February 19, 2019
JWT Response for OAuth Token Introspection
draft-ietf-oauth-jwt-introspection-response-02
Abstract
This draft proposes an additional JSON Web Token (JWT) based response
for OAuth 2.0 Token Introspection.
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 August 23, 2019.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Requesting a JWT Response . . . . . . . . . . . . . . . . . . 3
3. JWT Response . . . . . . . . . . . . . . . . . . . . . . . . 3
4. Client Metadata . . . . . . . . . . . . . . . . . . . . . . . 4
5. Authorization Server Metadata . . . . . . . . . . . . . . . . 5
6. Security Considerations . . . . . . . . . . . . . . . . . . . 5
6.1. Cross-JWT Confusion . . . . . . . . . . . . . . . . . . . 5
6.2. Token Data Leakage . . . . . . . . . . . . . . . . . . . 6
7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 6
8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 6
8.1. OAuth Dynamic Client Registration Metadata Registration . 7
8.1.1. Registry Contents . . . . . . . . . . . . . . . . . . 7
8.2. OAuth Authorization Server Metadata Registration . . . . 7
8.2.1. Registry Contents . . . . . . . . . . . . . . . . . . 7
8.3. OAuth Token Introspection Response . . . . . . . . . . . 8
9. References . . . . . . . . . . . . . . . . . . . . . . . . . 8
9.1. Normative References . . . . . . . . . . . . . . . . . . 8
9.2. Informative References . . . . . . . . . . . . . . . . . 10
Appendix A. Document History . . . . . . . . . . . . . . . . . . 10
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 11
1. Introduction
OAuth 2.0 Token Introspection [RFC7662] specifies a method for a
protected resource to query an OAuth 2.0 authorization server to
determine the state of an access token and obtain data associated
with the access token. This allows deployments to implement
identifier-based access tokens in an interoperable way.
The introspection response, as specified in OAuth 2.0 Token
Introspection [RFC7662], is a plain JSON object. However, there are
use cases where the resource server requires stronger assurance that
the authorization server issued the access token, including cases
where the authorization server assumes liability for the token's
content. An example is a resource server using verified person data
to create certificates, which in turn are used to create qualified
electronic signatures.
In such use cases it may be useful or even required to return a
signed JWT as the introspection response. This specification extends
the token introspection endpoint with the capability to return
responses as JWTs.
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2. Requesting a JWT Response
A resource server requests to receive a JWT introspection response by
including an Accept header with content type "application/jwt" in the
introspection request.
The following is a non-normative example request:
POST /introspect HTTP/1.1
Host: server.example.com
Accept: application/jwt
Content-Type: application/x-www-form-urlencoded
token=2YotnFZFEjr1zCsicMWpAA
3. JWT Response
The introspection endpoint responds with a JWT, setting the Content-
Type header to "application/jwt".
This JWT MUST contain the claims "iss" and "aud" in order to prevent
misuse of the JWT as ID or access token (see Section 6.1).
This JWT MAY furthermore contain all other claims described in
Section 2.2. of [RFC7662] and beyond (e.g. as defined in
[OpenID.Core]).
The following is a non-normative example response (with line breaks
for display purposes only):
HTTP/1.1 200 OK
Content-Type: application/jwt
eyJraWQiOiIxIiwiYWxnIjoiUlMyNTYifQ.eyJzdWIiOiJaNU8zdXBQQzg4UXJBa
ngwMGRpcyIsImF1ZCI6Imh0dHBzOlwvXC9wcm90ZWN0ZWQuZXhhbXBsZS5uZXRcL
3Jlc291cmNlIiwiZXh0ZW5zaW9uX2ZpZWxkIjoidHdlbnR5LXNldmVuIiwic2Nvc
GUiOiJyZWFkIHdyaXRlIGRvbHBoaW4iLCJpc3MiOiJodHRwczpcL1wvc2VydmVyL
mV4YW1wbGUuY29tXC8iLCJhY3RpdmUiOnRydWUsImV4cCI6MTQxOTM1NjIzOCwia
WF0IjoxNDE5MzUwMjM4LCJjbGllbnRfaWQiOiJsMjM4ajMyM2RzLTIzaWo0Iiwid
XNlcm5hbWUiOiJqZG9lIn0.HEQHf05vqVvWVnWuEjbzUnPz6JDQVR69QkxgzBNq5
kk-sK54ieg1STazXGsdFAT8nUhiiV1f_Z4HOKNnBs8TLKaFXokhA0MqNBOYI--2u
nVHDqI_RPmC3p0NmP02Xmv4hzxFmTmpgjSy3vpKQDihOjhwNBh7G81JNaJqjJQTR
v_1dHUPJotQjMK3k8_5FyiO2p64Y2VyxyQn1VWVlgOHlJwhj6BaGHk4Qf5F8DHQZ
1WCPg2p_-hwfINfXh1_buSjxyDRF4oe9pKy6ZB3ejh9qIMm-WrwltuU1uWMXxN6e
S6tUtpKo8UCHBwLWCHmJN7KU6ZojmaISspdS23lELAlyw
The example response contains the following JSON document:
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{
"sub": "Z5O3upPC88QrAjx00dis",
"aud": "https://protected.example.net/resource",
"scope": "read write dolphin",
"iss": "https://server.example.com/",
"active": true,
"exp": 1419356238,
"iat": 1419350238,
"client_id": "l238j323ds-23ij4",
"given_name": "John",
"family_name":"Doe",
"birthdate":"1982-02-01"
}
Depending on the specific resource server policy the JWT is either
signed, or signed and encrypted. If the JWT is signed and encrypted
it MUST be a Nested JWT, as defined in JWT [RFC7519].
Note: If the resource server policy requires a signed and encrypted
response and the authorization server receives an unauthenticated
request containing an Accept header with content type other than
"application/jwt", it MUST refuse to serve the request and return an
HTTP status code 400. This is done to prevent downgrading attacks to
obtain token data intended for release to legitimate recipients only
(see Section 6.2).
4. Client Metadata
The authorization server determines what algorithm to employ to
secure the JWT for a particular introspection response. This
decision can be based on registered metadata parameters for the
resource server, supplied via dynamic client registration with the
resource server posing as the client, as defined by this draft.
The parameter names follow the pattern established by OpenID Connect
Dynamic Client Registration [OpenID.Registration] for configuring
signing and encryption algorithms for JWT responses at the UserInfo
endpoint.
The following client metadata parameters are introduced by this
specification:
introspection_signed_response_alg JWS [RFC7515] "alg" algorithm JWA
[RFC7518] REQUIRED for signing introspection responses. If
this is specified, the response will be signed using JWS and
the configured algorithm. The default, if omitted, is
"RS256".
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introspection_encrypted_response_alg JWE [RFC7516] "alg" algorithm
JWA [RFC7518] REQUIRED for encrypting introspection
responses. If both signing and encryption are requested, the
response will be signed then encrypted, with the result being
a Nested JWT, as defined in JWT [RFC7519]. The default, if
omitted, is that no encryption is performed.
introspection_encrypted_response_enc JWE [RFC7516] "enc" algorithm
JWA [RFC7518] REQUIRED for encrypting introspection
responses. If "introspection_encrypted_response_alg" is
specified, the default for this value is A128CBC-HS256. When
"introspection_encrypted_response_enc" is included,
"introspection_encrypted_response_alg" MUST also be provided.
Resource servers may register their public encryption keys using the
"jwks_uri" or "jwks" metadata parameters.
5. Authorization Server Metadata
Authorization servers SHOULD publish the supported algorithms for
signing and encrypting the JWT of an introspection response by
utilizing OAuth 2.0 Authorization Server Metadata [RFC8414]
parameters.
The following parameters are introduced by this specification:
introspection_signing_alg_values_supported OPTIONAL. JSON array
containing a list of the JWS [RFC7515] signing algorithms
("alg" values) JWA [RFC7518] supported by the introspection
endpoint to sign the response.
introspection_encryption_alg_values_supported OPTIONAL. JSON array
containing a list of the JWE [RFC7516] encryption algorithms
("alg" values) JWA [RFC7518] supported by the introspection
endpoint to encrypt the response.
introspection_encryption_enc_values_supported OPTIONAL. JSON array
containing a list of the JWE [RFC7516] encryption algorithms
("enc" values) JWA [RFC7518] supported by the introspection
endpoint to encrypt the response.
6. Security Considerations
6.1. Cross-JWT Confusion
JWT introspection responses and OpenID Connect ID Tokens are
syntactically similar. An attacker could therefore attempt to
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impersonate an end-user at a OpenID Connect relying party by passing
the JWT as an ID token.
Such an attack can be prevented like any other token substitution
attack. The authorization server MUST include the claims "iss" and
"aud" in each JWT introspection response, with the "iss" value set to
the authorization server's issuer URL and the "aud" value set to the
resource server's identifier. This allows a correctly implemented
OpenID Connect relying party to detect substitution by checking the
"iss" and "aud" claims as described in Section 3.1.3.7. of
[OpenID.Core]. Relying parties SHOULD also use and check the "nonce"
parameter and claim to prevent token and code replay.
Resource servers utilizing JWTs to represent structured access tokens
could be susceptible to replay attacks. Resource servers should
therefore apply proper counter measures against replay as described
in [I-D.ietf-oauth-security-topics], section 2.2.
JWT Confusion and other attacks involving JWTs are discussed in
[I-D.ietf-oauth-jwt-bcp].
6.2. Token Data Leakage
If the authorization server supports unauthenticated requests an
attacker could potentially retrieve token data which must be kept
confidential. This attack can be prevented by either authenticating
any request to the token introspection endpoint or by setting up the
respective recipient for encrypted responses.
In the latter case, confidentiality is ensured by the fact that only
the legitimate recipient is able to decrypt the response. An
attacker could try to circumvent this measure by requesting a plain
JSON response, using an Accept header with the content type set to,
for example, "application/json" instead of "application/jwt". To
prevent this attack the authorization server MUST NOT serve requests
with content type other than "application/jwt" if the resource server
is set up to receive encrypted responses (see also Section 3).
7. Acknowledgements
We would like to thank Petteri Stenius, Neil Madden, Filip Skokan,
and Tony Nadalin for their valuable feedback.
8. IANA Considerations
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8.1. OAuth Dynamic Client Registration Metadata Registration
This specification requests registration of the following client
metadata definitions in the IANA "OAuth Dynamic Client Registration
Metadata" registry [IANA.OAuth.Parameters] established by [RFC7591]:
8.1.1. Registry Contents
o Client Metadata Name: "introspection_signed_response_alg"
o Client Metadata Description: String value indicating the client's
desired introspection response signing algorithm.
o Change Controller: IESG
o Specification Document(s): Section 4 of [[ this specification ]]
o Client Metadata Name: "introspection_encrypted_response_alg"
o Client Metadata Description: String value specifying the desired
introspection response encryption algorithm (alg value).
o Change Controller: IESG
o Specification Document(s): Section 4 of [[ this specification ]]
o Client Metadata Name: "introspection_encrypted_response_enc"
o Client Metadata Description: String value specifying the desired
introspection response encryption algorithm (enc value).
o Change Controller: IESG
o Specification Document(s): Section 4 of [[ this specification ]]
8.2. OAuth Authorization Server Metadata Registration
This specification requests registration of the following value in
the IANA "OAuth Authorization Server Metadata" registry
[IANA.OAuth.Parameters] established by [RFC8414].
8.2.1. Registry Contents
o Metadata Name: "introspection_signing_alg_values_supported"
o Metadata Description: JSON array containing a list of algorithms
supported by the authorization server for introspection response
signing.
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o Change Controller: IESG
o Specification Document(s): Section 5 of [[ this specification ]]
o Metadata Name: "introspection_encryption_alg_values_supported"
o Metadata Description: JSON array containing a list of algorithms
supported by the authorization server for introspection response
encryption (alg value).
o Change Controller: IESG
o Specification Document(s): Section 5 of [[ this specification ]]
o Metadata Name: "introspection_encryption_enc_values_supported"
o Metadata Description: JSON array containing a list of algorithms
supported by the authorization server for introspection response
encryption (enc value).
o Change Controller: IESG
o Specification Document(s): Section 5 of [[ this specification ]]
8.3. OAuth Token Introspection Response
TBD: add all OpenID Connect standard claims.
9. References
9.1. Normative References
[I-D.ietf-oauth-jwt-bcp]
Sheffer, Y., Hardt, D., and M. Jones, "JSON Web Token Best
Current Practices", draft-ietf-oauth-jwt-bcp-04 (work in
progress), November 2018.
[I-D.ietf-oauth-security-topics]
Lodderstedt, T., Bradley, J., Labunets, A., and D. Fett,
"OAuth 2.0 Security Best Current Practice", draft-ietf-
oauth-security-topics-11 (work in progress), December
2018.
[OpenID.Core]
NRI, Ping Identity, Microsoft, Google, and Salesforce,
"OpenID Connect Core 1.0 incorporating errata set 1", Nov
2014,
<http://openid.net/specs/openid-connect-core-1_0.html>.
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[OpenID.Registration]
NRI, Ping Identity, and Microsoft, "OpenID Connect Dynamic
Client Registration 1.0 incorporating errata set 1", Nov
2014, <https://openid.net/specs/
openid-connect-registration-1_0.html>.
[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>.
[RFC2246] Dierks, T. and C. Allen, "The TLS Protocol Version 1.0",
RFC 2246, DOI 10.17487/RFC2246, January 1999,
<https://www.rfc-editor.org/info/rfc2246>.
[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>.
[RFC7516] Jones, M. and J. Hildebrand, "JSON Web Encryption (JWE)",
RFC 7516, DOI 10.17487/RFC7516, May 2015,
<https://www.rfc-editor.org/info/rfc7516>.
[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>.
[RFC7591] Richer, J., Ed., Jones, M., Bradley, J., Machulak, M., and
P. Hunt, "OAuth 2.0 Dynamic Client Registration Protocol",
RFC 7591, DOI 10.17487/RFC7591, July 2015,
<https://www.rfc-editor.org/info/rfc7591>.
[RFC7662] Richer, J., Ed., "OAuth 2.0 Token Introspection",
RFC 7662, DOI 10.17487/RFC7662, October 2015,
<https://www.rfc-editor.org/info/rfc7662>.
[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>.
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9.2. Informative References
[IANA.OAuth.Parameters]
IANA, "OAuth Parameters",
<http://www.iana.org/assignments/oauth-parameters>.
Appendix A. Document History
[[ To be removed from the final specification ]]
-02
o updated references
-01
o adapted wording to preclude any accept header except "application/
jwt" if encrypted responses are required
o use registered alg value RS256 for default signing algorithm
o added text on claims in the token introspection response
-00
o initial version of the WG draft
o defined default signing algorithm
o changed behavior in case resource server is set up for encryption
o Added text on token data leakage prevention to the security
considerations
o moved Security Considerations section forward
WG draft
-01
o fixed typos in client meta data field names
o added OAuth Server Metadata parameters to publish algorithms
supported for signing and encrypting the introspection response
o added registration of new parameters for OAuth Server Metadata and
Client Registration
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o added explicit request for JWT introspection response
o made iss and aud claims mandatory in introspection response
o Stylistic and clarifying edits, updates references
-00
o initial version
Authors' Addresses
Torsten Lodderstedt (editor)
yes.com AG
Email: torsten@lodderstedt.net
Vladimir Dzhuvinov
Connect2id Ltd.
Email: vladimir@connect2id.com
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