OAuth Working Group M. Jones
Internet-Draft Microsoft
Intended status: Standards Track B. Campbell
Expires: November 23, 2012 Ping Identity
C. Mortimore
Salesforce
May 22, 2012
JSON Web Token (JWT) Bearer Token Profiles for OAuth 2.0
draft-ietf-oauth-jwt-bearer-00
Abstract
This specification defines the use of a JSON Web Token (JWT) Bearer
Token as a means for requesting an OAuth 2.0 access token as well as
for use as a means of client authentication.
Status of this Memo
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This Internet-Draft will expire on November 23, 2012.
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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 . . . . . . . . . . . . . . . . . . 6
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 . . . . . . . . . . . . . . . . . . . . . . . . 9
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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 The OAuth 2.0 Authorization Protocol
[I-D.ietf-oauth-v2], OAuth 2.0 Assertion Profile
[I-D.ietf-oauth-assertions], and JSON Web Token (JWT) [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 the "grant_type" parameter MUST be
"urn:ietf:params:oauth:grant-type:jwt-bearer".
The value of the "assertion" parameter MUST contain a single JWT.
2.2. Using JWTs for Client Authentication
To use a JWT Bearer Token for client authentication grant, use the
following parameter values and encodings.
The value of the "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.
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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 a JWT 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.
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 an "iat" (issued at) claim that identifies the
time at which the JWT was issued. The authorization server MAY
reject JWTs with an "iat" claim value that is unreasonably far in
the past.
o The JWT MAY contain a "jti" (JWT ID) claim that provides a unique
identifier for the token. The authorization server MAY ensure
that JWTs are not replayed by maintaining the set of used "jti"
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values for the length of time for which the JWT would be
considered valid based on the applicable "exp" instant.
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 JSON Web Token (JWT) [JWT].
3.1. Authorization Grant Processing
If present, the authorization server MUST also validate the client
credentials.
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 OAuth 2.0
[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 OAuth 2.0 [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 "error_uri" parameters.
4. Authorization Grant Example
Though non-normative, the following examples illustrate what a
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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 (with line breaks 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 The OAuth 2.0 Authorization Protocol [I-D.ietf-oauth-v2], the
OAuth 2.0 Assertion Profile [I-D.ietf-oauth-assertions], and the JSON
Web Token (JWT) [JWT] specification.
6. IANA Considerations
6.1. Sub-Namespace Registration of
urn:ietf:params:oauth:grant-type:jwt-bearer
This specification registers the value "grant-type:jwt-bearer" in the
registry urn:ietf:params:oauth established in An IETF URN Sub-
Namespace for OAuth [I-D.ietf-oauth-urn-sub-ns].
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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 specification registers the value
"client-assertion-type:jwt-bearer" in the registry
urn:ietf:params:oauth established in An IETF URN Sub-Namespace for
OAuth [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]
Jones, M., Campbell, B., and Y. Goland, "OAuth 2.0
Assertion Profile", draft-ietf-oauth-assertions-03 (work
in progress), May 2012.
[I-D.ietf-oauth-urn-sub-ns]
Tschofenig, H., "An IETF URN Sub-Namespace for OAuth",
draft-ietf-oauth-urn-sub-ns-02 (work in progress),
January 2012.
[I-D.ietf-oauth-v2]
Hammer-Lahav, E., Recordon, D., and D. Hardt, "The OAuth
2.0 Authorization Framework", draft-ietf-oauth-v2-26 (work
in progress), May 2012.
[JWT] Jones, M., Bradley, J., and N. Sakimura, "JSON Web Token
(JWT)", May 2012.
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[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.
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-12 (work in
progress), May 2012.
Appendix A. Acknowledgements
This profile was derived from 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 the RFC editor before publication as an RFC ]]
-00
o Created the initial IETF draft based upon
draft-jones-oauth-jwt-bearer-04 with no normative changes.
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
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Chuck Mortimore
Salesforce
Email: cmortimore@salesforce.com
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