Internet DRAFT - draft-sakimura-oauth-jpop
draft-sakimura-oauth-jpop
OAuth Working Group N. Sakimura
Internet-Draft Nomura Research Institute
Intended status: Standards Track K. Li
Expires: January 23, 2020 Alibaba Group
J. Bradley
Yubico
July 22, 2019
The OAuth 2.0 Authorization Framework: JWT Pop Token Usage
draft-sakimura-oauth-jpop-05
Abstract
This specification describes how to use JWT POP (Jpop) tokens that
were obtained through [POPKD] in HTTP requests to access OAuth 2.0
protected resources. Only the party in possession of the
corresponding cryptographic key for the Jpop token can use it to get
access to the associated resources unlike in the case of the bearer
token described in [RFC6750] where any party in posession of the
access token can access the resource.
Requirements Language
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 RFC 2119 [RFC2119].
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
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material or to cite them other than as "work in progress."
This Internet-Draft will expire on January 23, 2020.
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Copyright Notice
Copyright (c) 2019 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
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described in the Simplified BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
1.1. Notational Conventions . . . . . . . . . . . . . . . . . 3
2. Terms and definitions . . . . . . . . . . . . . . . . . . . . 3
3. JWT POP Token . . . . . . . . . . . . . . . . . . . . . . . . 3
4. Sender Constrained Token . . . . . . . . . . . . . . . . . . 4
4.1. Client ID Constrained Token . . . . . . . . . . . . . . . 4
4.2. Key Constrained Token . . . . . . . . . . . . . . . . . . 4
5. Resource access method . . . . . . . . . . . . . . . . . . . 6
5.1. Signature method . . . . . . . . . . . . . . . . . . . . 6
6. Authorization Error . . . . . . . . . . . . . . . . . . . . . 7
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 8
7.1. Jpop Authentication Scheme . . . . . . . . . . . . . . . 8
7.2. JWT Confirmation Methods . . . . . . . . . . . . . . . . 8
8. Security Considerations . . . . . . . . . . . . . . . . . . . 8
8.1. Certificate validation . . . . . . . . . . . . . . . . . 8
8.2. Key protection . . . . . . . . . . . . . . . . . . . . . 9
8.3. Audiance Restriction . . . . . . . . . . . . . . . . . . 9
8.4. Dynamic client registration elements . . . . . . . . . . 9
9. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 9
10. References . . . . . . . . . . . . . . . . . . . . . . . . . 9
10.1. Normative References . . . . . . . . . . . . . . . . . . 9
10.2. Informative References . . . . . . . . . . . . . . . . . 11
Appendix A. Document History . . . . . . . . . . . . . . . . . . 11
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 11
1. Introduction
This document specifies the method for the client to use a proof-of-
possestion token against a protected resource. The format of such
token is defined in section 3 of [RFC7800].
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The same methods and JWT schema elements can be used with opaque
tokens and OAuth 2.0 Token Introspection. [RFC7662]
[POPKD] can be used for a client to dynamically specify a key, or the
Authorization Server can use information provided by the client at
registration either through the dynamic registration or developer
portal to provide the confirmation element.
1.1. Notational 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 RFC
2119 [RFC2119].
Unless otherwise noted, all the protocol parameter names and values
are case sensitive.
2. Terms and definitions
For the purpose of this document, the terms defined in [RFC6749] and
[RFC7800] are used.
3. JWT POP Token
JWT PoP token is a JWS signed JWT whose payload is a JWT Claims Set.
The JWT claims set MUST include the following:
iss The issuer identifier of the auhtorization server.
aud The identifier of the resource server.
iat The issuance time of this token.
exp The expiry time of this token.
cnf The confirmation method.
Their semantics are defined in [RFC7519] and [RFC7800].
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Following is an example of such.
{
"iss": "https://server.example.com",
"aud": "https://resource.example.org",
"iat": "1360189224",
"exp": "1361398868",
"cnf":{...}
}
Figure 1: Example of JWT PoP Token.
4. Sender Constrained Token
There are several varieties of sender constrained token. Namely:
1. Client ID Constrained Token
2. Key Constrained Token
4.1. Client ID Constrained Token
The constraint in the Client ID constrained token is expressed by
including the following member at the top level of cnf claim.
cid The client_id of the client that the client used in the
authorization request. The combination of the "iss" of the access
token and this value forms a globally unique identifier for the
client.
The authorization server finds the client ID from the client ID used
in the client authentication at the token endpoint.
4.2. Key Constrained Token
Methods to express key constraints are extensively described in the
section 3 of [RFC7800]. Such cnf claim is used in the access token
described in section 3 to form a key constrained token. [RFC7800]
defines 4 confirmation methods.
jwk JSON Web Key Representing a Public Key
jwe Encrypted JSON Web Key
jwkt#s256 [RFC7638] Thumbprint of a JWK using the SHA-256 hash
function.
x5t#s256 [RFC7515] X.509 Certificate SHA-256 Thumbprint
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jku JWK Set URL
The client provides the corresponding keys or the pointers to the
authorization server as a part of the client configuration. It can
be done through out-of-band methods (e.g., developper portal) or
through some form of dynamic registration, etc.
Following is an example of a JWT payload containing a JWK with a raw
key.
{
"iss": "https://server.example.com",
"sub": "joe@example.com",
"aud": "https://resource.example.org",
"exp": "1361398824",
"nbf": "1360189224",
"cnf":{
"jwk":{
"kty": "EC",
"use": "sig",
"crv": "P-256",
"x": "18wHLeIgW9wVN6VD1Txgpqy2LszYkMf6J8njVAibvhM",
"y": "-V4dS4UaLMgP_4fY4j8ir7cl1TXlFdAgcx55o7TkcSA"
}
}
}
Figure 2: Example of a JWK Key Constrained JWT.
Following is an example of a JWT payload containing a jku URI.
{
"iss": "https://server.example.com",
"sub": "joe@example.com",
"aud": "https://resource.example.org",
"exp": "1361398824",
"nbf": "1360189224",
"cnf":{
"jku": "https://client.example.com/keys/client123-jwks"
}
}
Figure 3: Example of a jku Constrained JWT.
Following is an example of a JWT payload containing a x5t#s256
Certificate Thumbprint of a x509 certificate. .
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{
"iss": "https://server.example.com",
"sub": "joe@example.com",
"aud": "https://resource.example.org",
"exp": "1361398824",
"nbf": "1360189224",
"cnf":{
"x5t#s256": "w5cK0ebwmCZUYDB2Y5SlESsXE8o9yZg05O89jdNidgI"
}
}
Figure 4: Example of a x5t#s256 Certificate Thumbprint Constrained
JWT.
5. Resource access method
The resource server that supports this specification MUST
authenticate the Client by having it demonstrate that it is the
holder of the key associated with the access token being used. The
confirmation method can be broadly categorized in the method that
leverages mutual TLS client authentication and the method that
leverages client generated signature. Since the former is now dealt
with MTLS document, this document will only discuss the signature
method.
5.1. Signature method
For this, the following steps are taken:
STEP1: The client accesses the protected resource and gets an
authorization error as in Section 6. With it, the client
obtains a nonce.
STEP2: The client prepares a client nonce, "cnonce", and nounce
count, "nc" as defined in section 3.2.2 of [RFC2617].
STEP3: The client creates JWS compact serialization over the nonce.
To obtain it, first create a JSON with a name "nonce" and the value
being what was received in the previous step. The JWS MUST contain a
kid header element if the client has more than one signing key
published via JWKS URI e.g.,
{
"nonce":"dcd98b7102dd2f0e8b11d0f600bfb0c093",
"nc":"00000001",
"cnonce":"0a4f113b"
}
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Then, "jws-on-nonce" is obtained by creating a compact serialization
of JWS on this JSON.
STEP4: The client sends the request to the resource server, this
time with Authorization Request Header as defined in section
4.2 of [RFC7235] with the credential as follows:
credentials = "Jpop" jpop-response
jpop-response = at-response "," s-response
at-response = "at" "=" access-token (* As specified by [POPKD] *)
s-response = "s" "=" jws-on-nonce (* Created in the STEP3. *)
access-token = quoted-string
jws-on-nonce = quoted-string
In the following example, the access token and the jws-on-nonce are
represented as access.token.jwt and jws.of.nonce for the sake of
brevity.
GET /resource/1234 HTTP/1.0
Host: server.example.com
Authorization: Jpop at="access.token.jwt", s="jws.of.nonce"
Figure 5: Example resouce request
STEP5: The resource server finds the client's public key form the
access token through the methods described in [RFC7800].
STEP6: The resource server MUST verify the value of "s" of the
Authorization header. If it fails, the process stops here
and the resource access MUST be denied.
STEP7: The resource server MUST verify the access token. If it is
valid, the resource SHOULD be returned as HTTP response.
6. Authorization Error
If the client requests the resource without the proper authoization
header, the resource server returns a HTTP 401 response with "WWW-
Authenticate" header as defined in section 4.1 of [RFC7235] with the
challenge as follows:
challenge = "Jpop" jpop-challenge
jpop-challenge = "nonce" "=" nonce-value
nonce-value = quoted-string
Following example depicts what the response would look like.
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HTTP/1.0 401 Unauthorized
Server: HTTPd/0.9
Date: Wed, 14 March 2017 09:26:53 GMT
WWW-Authenticate: Jpop nonce="dcd98b7102dd2f0e8b11d0f600bfb0c093"
Figure 6: Example error response.
7. IANA Considerations
7.1. Jpop Authentication Scheme
A new scheme has been registered in the HTTP Authentication Scheme
Registry as follows:
Authentication Scheme Name: Jpop
Reference: Section 3 of this specification
Notes (optional): The Named Authentication scheme is intended to be
used only with OAuth Resource Access, and thus does not support proxy
authentication.
7.2. JWT Confirmation Methods
o Confirmation Method Value: "dn"
o Confirmation Method Description: DN match with the TLS client
auth.
o Change Controller: IESG
o Specification Document(s): This document.
o Confirmation Method Value: "cid"
o Confirmation Method Description: Client ID Confirmation
o Change Controller: IESG
o Specification Document(s): This document.
8. Security Considerations
8.1. Certificate validation
The "dn" JWT confirmation method relies its security property on the
X.509 client certificate authentication. In particular, the validity
of the certificate needs to be verified properly. It involves the
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traversal of all the certificate chain and the certificate validation
(e.g., with OCSP).
8.2. Key protection
The client's secret key must be kept securely. Otherwise, the notion
of PoP breaks down.
It should be noted that JWE confirmation method is significantly
weaker form of the PoP, as the resource server and the authorization
server can masquerade as the client.
8.3. Audiance Restriction
When using the signature method the client must specify to the AS the
aud it intends to send the token to, so that it can be included in
the AT.
A malicious RS could receive a AT with no aud or a logical audience
and then replay the AT and jws-on-nonce to the actual server.
NOTE another approach would be to include the resource in the jws-on-
nonce
8.4. Dynamic client registration elements
When a AS uses dynamic client registration it may accept software
statements supplied by a federation operator. Those software
statements can contain a JWKS-URI that is hosted by the federation
operator or protected by a certificate provisioned from a trusted
root. These methods would allow the federation operator to
administratively revoke the keys at the JWKS-URI without requiring
the JWKS to contain x5c elements with CA issued certificates and
having to have the RS perform full certificate validation for each
request.
9. Acknowledgements
The authors thank the following people for providing valuable
feedback to this document. Nov Matake (YAuth).
10. References
10.1. Normative References
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[POPKD] Bradley, J., Hunt, P., Jones, M., and H. Tschofenig,
"OAuth 2.0 Proof-of-Possession: Authorization Server to
Client Key Distribution", March 2017,
<https://tools.ietf.org/html/
draft-ietf-oauth-pop-key-distribution-03>.
[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>.
[RFC2617] Franks, J., Hallam-Baker, P., Hostetler, J., Lawrence, S.,
Leach, P., Luotonen, A., and L. Stewart, "HTTP
Authentication: Basic and Digest Access Authentication",
RFC 2617, DOI 10.17487/RFC2617, June 1999,
<https://www.rfc-editor.org/info/rfc2617>.
[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>.
[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>.
[RFC7235] Fielding, R., Ed. and J. Reschke, Ed., "Hypertext Transfer
Protocol (HTTP/1.1): Authentication", RFC 7235,
DOI 10.17487/RFC7235, June 2014,
<https://www.rfc-editor.org/info/rfc7235>.
[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>.
[RFC7517] Jones, M., "JSON Web Key (JWK)", RFC 7517,
DOI 10.17487/RFC7517, May 2015,
<https://www.rfc-editor.org/info/rfc7517>.
[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>.
[RFC7638] Jones, M. and N. Sakimura, "JSON Web Key (JWK)
Thumbprint", RFC 7638, DOI 10.17487/RFC7638, September
2015, <https://www.rfc-editor.org/info/rfc7638>.
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[RFC7662] Richer, J., Ed., "OAuth 2.0 Token Introspection",
RFC 7662, DOI 10.17487/RFC7662, October 2015,
<https://www.rfc-editor.org/info/rfc7662>.
[RFC7800] Jones, M., Bradley, J., and H. Tschofenig, "Proof-of-
Possession Key Semantics for JSON Web Tokens (JWTs)",
RFC 7800, DOI 10.17487/RFC7800, April 2016,
<https://www.rfc-editor.org/info/rfc7800>.
10.2. Informative References
[POPA] Hunt, P., Ed., "OAuth 2.0 Proof-of-Possession (PoP)
Security Architecture", March 2015,
<https://tools.ietf.org/html/
draft-ietf-oauth-pop-architecture-08>.
[RFC7636] Sakimura, N., Ed., Bradley, J., and N. Agarwal, "Proof Key
for Code Exchange by OAuth Public Clients", RFC 7636,
DOI 10.17487/RFC7636, September 2015,
<https://www.rfc-editor.org/info/rfc7636>.
[TINTRO] Richer, J., "OAuth 2.0 Token Introspection", July 2015.
Appendix A. Document History
-05 Removed the MTLS related contents as they are now dealt with
mTLS spec.
Authors' Addresses
Nat Sakimura
Nomura Research Institute
Otemachi Financial City Grand Cube, 1-9-2 Otemachi
Chiyoda-ku, Tokyo 100-0004
Japan
Phone: +81-3-5533-2111
Email: n-sakimura@nri.co.jp
URI: https://nat.sakimura.org/
Kepeng Li
Alibaba Group
Email: kepeng.lkp@alibaba-inc.com
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John Bradley
Yubico
Email: ve7jtb@ve7jtb.com
URI: http://www.thread-safe.com/
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