Network Working Group M. Jones
Internet-Draft Microsoft
Intended status: Standards Track B. Campbell
Expires: May 3, 2012 Ping Identity Corp.
C. Mortimore
Salesforce.com
Oct 31, 2011
JSON Web Token (JWT) Bearer Token Profiles for OAuth 2.0
draft-jones-oauth-jwt-bearer-01
Abstract
This specification defines the use of a JSON Web Token (JWT) Bearer
Token as means for requesting an OAuth 2.0 access token as well as
for use as a means of client authentication.
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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This Internet-Draft will expire on May 3, 2012.
Copyright Notice
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document authors. All rights reserved.
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described in the Simplified BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1. Notational Conventions . . . . . . . . . . . . . . . . . . 4
1.2. Terminology . . . . . . . . . . . . . . . . . . . . . . . 4
2. HTTP Parameter Bindings for Transporting Assertions . . . . . 4
2.1. Using JWTs as Authorization Grants . . . . . . . . . . . . 4
2.2. Using JWTs for Client Authentication . . . . . . . . . . . 4
3. JWT Format and Processing Requirements . . . . . . . . . . . . 5
3.1. Authorization Grant Processing . . . . . . . . . . . . . . 6
3.2. Client Authentication Processing . . . . . . . . . . . . . 6
4. Authorization Grant Example . . . . . . . . . . . . . . . . . 7
5. Security Considerations . . . . . . . . . . . . . . . . . . . 7
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 7
6.1. Sub-Namespace Registration of
urn:ietf:params:oauth:grant-type:jwt-bearer . . . . . . . 7
6.2. Sub-Namespace Registration of
urn:ietf:params:oauth:client-assertion-type:jwt-bearer . . 8
7. References . . . . . . . . . . . . . . . . . . . . . . . . . . 8
7.1. Normative References . . . . . . . . . . . . . . . . . . . 8
7.2. Informative References . . . . . . . . . . . . . . . . . . 9
Appendix A. Acknowledgements . . . . . . . . . . . . . . . . . . 9
Appendix B. Document History . . . . . . . . . . . . . . . . . . 9
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 10
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1. Introduction
JSON Web Token (JWT) [JWT] is a JSON-based security token encoding
that enables identity and security information to be shared across
security domains. JWTs utilize JSON data structures, as defined in
RFC 4627 [RFC4627]. A security token is generally issued by an
identity provider and consumed by a relying party that relies on its
content to identify the token's subject for security related
purposes.
The OAuth 2.0 Authorization Protocol [I-D.ietf.oauth-v2] provides a
method for making authenticated HTTP requests to a resource using an
access token. Access tokens are issued to third-party clients by an
authorization server (AS) with the (sometimes implicit) approval of
the resource owner. In OAuth, an authorization grant is an abstract
term used to describe intermediate credentials that represent the
resource owner authorization. An authorization grant is used by the
client to obtain an access token. Several authorization grant types
are defined to support a wide range of client types and user
experiences. OAuth also allows for the definition of new extension
grant types to support additional clients or to provide a bridge
between OAuth and other trust frameworks. Finally, OAuth allows the
definition of additional authentication mechanisms to be used by
clients when interacting with the authorization server.
The OAuth 2.0 Assertion Profile [I-D.ietf.oauth-assertions] is an
abstract extension to OAuth 2.0 that provides a general framework for
the use of Assertions (a.k.a. Security Tokens) as client credentials
and/or authorization grants with OAuth 2.0. This specification
profiles the OAuth 2.0 Assertion Profile [I-D.ietf.oauth-assertions]
to define an extension grant type that uses a JSON Web Token (JWT)
Bearer Token to request an OAuth 2.0 access token as well as for use
as client credentials. The format and processing rules for the JWT
defined in this specification are intentionally similar, though not
identical, to those in the closely related SAML 2.0 Bearer Assertion
Profiles for OAuth 2.0 [I-D.ietf-oauth-saml2-bearer].
This document defines how a JSON Web Token (JWT) Bearer Token can be
used to request an access token when a client wishes to utilize an
existing trust relationship, expressed through the semantics of (and
digital signature calculated over) the JWT, without a direct user
approval step at the authorization server. It also defines how a JWT
can be used as a client authentication mechanism. The use of a
security token for client authentication is orthogonal and separable
from using a security token as an authorization grant and the two can
be used either in combination or in isolation.
The process by which the client obtains the JWT, prior to exchanging
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it with the authorization server or using it for client
authentication, is out of scope.
1.1. Notational Conventions
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].
Unless otherwise noted, all the protocol parameter names and values
are case sensitive.
1.2. Terminology
All terms are as defined in [I-D.ietf.oauth-v2],
[I-D.ietf.oauth-assertions], and [JWT].
2. HTTP Parameter Bindings for Transporting Assertions
The OAuth 2.0 Assertion Profile [I-D.ietf.oauth-assertions] defines
generic HTTP parameters for transporting Assertions (a.k.a. Security
Tokens) during interactions with a token endpoint. This section
defines the values of those parameters for use with JWT Bearer
Tokens.
2.1. Using JWTs as Authorization Grants
To use a JWT Bearer Token as an authorization grant, use the
following parameter values and encodings.
The value of "grant_type" parameter MUST be
"urn:ietf:params:oauth:grant-type:jwt-bearer"
The value of the "assertion" parameter MUST contain a single JWT.
The SAML Assertion XML data MUST be encoded using base64url, where
the encoding adheres to the definition in Section 5 of RFC4648
[RFC4648] and where the padding bits are set to zero. To avoid the
need for subsequent encoding steps (by "application/
x-www-form-urlencoded" [W3C.REC-html401-19991224], for example), the
base64url encoded data SHOULD NOT be line wrapped and pad characters
("=") SHOULD NOT be included.
2.2. Using JWTs for Client Authentication
To use a JWT Bearer Token for client authentication grant, use the
following parameter values and encodings.
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The value of "client_assertion_type" parameter MUST be
"urn:ietf:params:oauth:client-assertion-type:jwt-bearer"
The value of the "client_assertion" parameter MUST contain a single
JWT. The SAML Assertion XML data MUST be encoded using base64url,
where the encoding adheres to the definition in Section 5 of RFC4648
[RFC4648] and where the padding bits are set to zero. To avoid the
need for subsequent encoding steps (by "application/
x-www-form-urlencoded" [W3C.REC-html401-19991224], for example), the
base64url encoded data SHOULD NOT be line wrapped and pad characters
("=") SHOULD NOT be included.
3. JWT Format and Processing Requirements
In order to issue an access token response as described in The OAuth
2.0 Authorization Protocol [I-D.ietf.oauth-v2] or to rely on a JWT
for client authentication, the authorization server MUST validate the
JWT according to the criteria below. Application of additional
restrictions and policy are at the discretion of the authorization
server.
o The JWT MUST contain an "iss" (issuer) claim that contains a
unique identifier for the entity that issued the JWT.
o The JWT MUST contain a "prn" (principal) claim identifying the
subject of the transaction. The principal MAY identify the
resource owner for whom the access token is being requested. For
client authentication, the principal MUST be the client_id of the
OAuth client. When using JWTs as an authorization grant, the
principal SHOULD identify an authorized accessor for whom the
access token is being requested (typically the resource owner, or
an authorized delegate).
o The JWT MUST contain an "aud" (audience) claim containing a URI
reference that identifies the authorization server, or the service
provider principal entity of its controlling domain, as an
intended audience. The token endpoint URL of the authorization
server MAY be used as an acceptable value for an "aud" element.
The authorization server MUST verify that it is an intended
audience for the JWT.
o The JWT MUST contain an "exp" (expiration) claim that limits the
time window during which the JWT can be used. The authorization
server MUST verify that the expiration time has not passed,
subject to allowable clock skew between systems. The
authorization server MAY reject JWTs with an "exp" claim value
that is unreasonably far in the future.
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o The JWT MAY contain an "nbf" (not before) claim that identifies
the time before which the token MUST NOT be accepted for
processing.
o The JWT MAY contain other claims.
o The JWT MUST be digitally signed by the issuer and the
authorization server MUST verify the signature.
o The authorization server MUST verify that the JWT is valid in all
other respects per [JWT].
3.1. Authorization Grant Processing
If present, the authorization server MUST also validate the client
credentials.
Authorization servers SHOULD issue access tokens with a limited
lifetime and require clients to refresh them by requesting a new
access token using the same JWT, if it is still valid, or with a new
JWT. The authorization server SHOULD NOT issue a refresh token.
If the JWT is not valid, or the current time is not within the
token's valid time window for use, the authorization server MUST
construct an error response as defined in [I-D.ietf.oauth-v2]. The
value of the error parameter MUST be the "invalid_grant" error code.
The authorization server MAY include additional information regarding
the reasons the JWT was considered invalid using the
error_description or error_uri parameters.
For example:
HTTP/1.1 400 Bad Request
Content-Type: application/json
Cache-Control: no-store
{
"error":"invalid_grant",
"error_description":"Audience validation failed"
}
3.2. Client Authentication Processing
If the client JWT is not valid, or its subject confirmation
requirements cannot be met, the authorization server MUST construct
an error response as defined in [I-D.ietf.oauth-v2]. The value of
the error parameter MUST be the "invalid_client" error code. The
authorization server MAY include additional information regarding the
reasons the JWT was considered invalid using the error_description or
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error_uri parameters.
4. Authorization Grant Example
Though non-normative, the following examples illustrate what a
conforming JWT and access token request would look like.
Below is an example JSON object that could be encoded to produce the
JWT Claims Object for a JWT:
{"iss":"https://jwt-idp.example.com",
"prn":"mailto:mike@example.com",
"aud":"https://jwt-rp.example.net",
"nbf":1300815780,
"exp":1300819380,
"http://claims.example.com/member":true}
The following example JSON object, used as the header of a JWT,
declares that the JWT is signed with the ECDSA P-256 SHA-256
algorithm.
{"alg":"ES256"}
To present the JWT with the claims and header shown in the previous
example as part of an access token request, for example, the client
might make the following HTTPS request (line breaks are for display
purposes only):
POST /token.oauth2 HTTP/1.1
Host: authz.example.net
Content-Type: application/x-www-form-urlencoded
grant_type=urn%3Aietf%3Aparams%3Aoauth%3Agrant-type%3Ajwt-
bearer&assertion=eyJhbGciOiJFUzI1NiJ9.
eyJpc3Mi[...omitted for brevity...].
J9l-ZhwP_2n[...omitted for brevity...]
5. Security Considerations
No additional security considerations apply beyond those described
within [I-D.ietf.oauth-v2], [I-D.ietf.oauth-assertions], and [JWT].
6. IANA Considerations
6.1. Sub-Namespace Registration of
urn:ietf:params:oauth:grant-type:jwt-bearer
This is a request to IANA to please register the value grant-
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type:jwt-bearer in the registry urn:ietf:params:oauth established in
[I-D.ietf.oauth-urn-sub-ns].
o URN: urn:ietf:params:oauth:grant-type:jwt-bearer
o Common Name: JWT Bearer Token Grant Type Profile for OAuth 2.0
o Change controller: IETF
o Description: [[this document]]
6.2. Sub-Namespace Registration of
urn:ietf:params:oauth:client-assertion-type:jwt-bearer
This is a request to IANA to please register the value client-
assertion-type:jwt-bearer in the registry urn:ietf:params:oauth
established in [I-D.ietf.oauth-urn-sub-ns].
o URN: urn:ietf:params:oauth:client-assertion-type:jwt-bearer
o Common Name: JWT Bearer Token Profile for OAuth 2.0 Client
Authentication
o Change controller: IETF
o Description: [[this document]]
7. References
7.1. Normative References
[I-D.ietf.oauth-assertions]
Mortimore, C., Ed., Campbell, B., Jones, M., and Y.
Goland, "OAuth 2.0 Assertion Profile",
ID draft-ietf-oauth-assertions-01 (work in progress),
October 2011.
[I-D.ietf.oauth-urn-sub-ns]
Campbell, B., Ed. and H. Tschofenig, "An IETF URN Sub-
Namespace for OAuth", ID draft-ietf-oauth-urn-sub-ns-00
(work in progress), Aug 2011.
[I-D.ietf.oauth-v2]
Hammer-Lahav, E., Ed., Recordon, D., and D. Hardt, "The
OAuth 2.0 Authorization Protocol",
ID draft-ietf-oauth-v2-22 (work in progress),
September 2011.
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[JWT] Jones, M., Balfanz, D., Bradley, J., Goland, Y., Panzer,
J., Sakimura, N., and P. Tarjan, "JSON Web Token (JWT)",
October 2011.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC4627] Crockford, D., "The application/json Media Type for
JavaScript Object Notation (JSON)", RFC 4627, July 2006.
[RFC4648] Josefsson, S., "The Base16, Base32, and Base64 Data
Encodings", RFC 4648, October 2006.
7.2. Informative References
[I-D.ietf-oauth-saml2-bearer]
Mortimore, C., "SAML 2.0 Bearer Assertion Profiles for
OAuth 2.0", draft-ietf-oauth-saml2-bearer-09 (work in
progress), October 2011.
[W3C.REC-html401-19991224]
Raggett, D., Jacobs, I., and A. Hors, "HTML 4.01
Specification", World Wide Web Consortium
Recommendation REC-html401-19991224, December 1999,
<http://www.w3.org/TR/1999/REC-html401-19991224>.
Appendix A. Acknowledgements
This profile was derived from the SAML 2.0 Bearer Assertion Profiles
for OAuth 2.0 [I-D.ietf-oauth-saml2-bearer] by Brian Campbell and
Chuck Mortimore.
Appendix B. Document History
[[ to be removed by RFC editor before publication as an RFC ]]
-01
o Merged in changes from draft-ietf-oauth-saml2-bearer-09. In
particular, this draft now uses draft-ietf-oauth-assertions,
rather than being standalone. It also now defines how to use JWT
bearer tokens both for Authorization Grants and for Client
Authentication.
-00
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o Initial draft.
Authors' Addresses
Michael B. Jones
Microsoft
Email: mbj@microsoft.com
URI: http://self-issued.info/
Brian Campbell
Ping Identity Corp.
Email: brian.d.campbell@gmail.com
Chuck Mortimore
Salesforce.com
Email: cmortimore@salesforce.com
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