OAuth Working Group J. Richer, Ed.
Internet-Draft The MITRE Corporation
Intended status: Standards Track May 01, 2013
Expires: November 02, 2013
OAuth Token Introspection
draft-richer-oauth-introspection-04
Abstract
This specification defines a method for a client or protected
resource to query an OAuth authorization server to determine meta-
information about an OAuth token.
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.
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This Internet-Draft will expire on November 02, 2013.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Introspection Endpoint . . . . . . . . . . . . . . . . . . . 2
2.1. Introspection Request . . . . . . . . . . . . . . . . . . 3
2.2. Introspection Response . . . . . . . . . . . . . . . . . 3
2.3. Non-normative Example . . . . . . . . . . . . . . . . . . 4
3. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 5
4. Security Considerations . . . . . . . . . . . . . . . . . . . 5
5. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 6
6. Normative References . . . . . . . . . . . . . . . . . . . . 6
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 6
1. Introduction
In OAuth, the contents of tokens are opaque to clients. This means
that the client does not need to know anything about the content or
structure of the token itself, if there is any. However, there is
still a large amount of metadata that may be attached to a token,
such as its current validity, approved scopes, and extra information
about the authentication context in which the token was issued.
These pieces of information are often vital to Protected Resources
making authorization decisions based on the tokens being presented.
Since OAuth2 defines no direct relationship between the Authorization
Server and the Protected Resource, only that they must have an
agreement on the tokens themselves, there have been many different
approaches to bridging this gap.
This specification defines an Introspection Endpoint that allows the
holder of a token to query the Authorization Server to discover the
set of metadata for a token. A Protected Resource may use the
mechanism described in this draft to query the Introspection Endpoint
in a particular authorization decision context and ascertain the
relevant metadata about the token in order to make this authorization
decision appropriately.
2. Introspection Endpoint
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The Introspection Endpoint is an OAuth 2 Endpoint that responds to
HTTP POST requests (and optionally HTTP GET requests) from token
holders, particularly including Resource Servers and Clients. The
endpoint takes a single parameter representing the token (and
optionally further authentication) and returns a JSON document
representing the meta information surrounding the token.
The endpoint MUST be protected by TLS or equivalent.
2.1. Introspection Request
token REQUIRED. The string value of the token.
resource_id OPTIONAL. A service-specific string identifying the
resource that the client doing the introspection is asking about.
token_type_hint OPTIONAL. A hint about the type of the token
submitted for revocation. Clients MAY pass this parameter in
order to help the authorization server to optimize the token
lookup. If the server is unable to locate the token using the
given hint, it MUST extend its search accross all of its supported
token types. An authorization server MAY ignore this parameter,
particularly if it is able to detect the token type automatically.
Values for this field are defined in OAuth Token Revocation
[Revocation].
The endpoint MAY allow other parameters to provide context to the
query. For instance, an authorization service may need to know the
IP address of the Client in order to determine the appropriateness of
the token being presented.
The endpoint SHOULD also require some form of authentication to
access this endpoint, such as the Client Authentication as described
in OAuth 2 Core Specification [RFC6749] or a separate OAuth 2.0
Access Token. The methods of managing and validating these
authentication credentials are out of scope of this specification.
2.2. Introspection Response
The server responds with a JSON object [RFC4627] in "application/
json" format with the following top-level members. Specific
implementations MAY extend this structure with their own service-
specific pieces of information.
active REQUIRED. Boolean indicator of whether or not the presented
token is currently active.
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exp OPTIONAL. Integer timestamp, measured in the number of seconds
since January 1 1970 UTC, indicating when this token will expire.
iat OPTIONAL. Integer timestamp, measured in the number of seconds
since January 1 1970 UTC, indicating when this token was
originally issued.
scope OPTIONAL. A space-separated list of strings representing the
scopes associated with this token, in the format described in
Section 3.3 of OAuth 2.0 [RFC6749].
client_id OPTIONAL. Client Identifier for the OAuth Client that
requested this token.
sub OPTIONAL. Local identifier of the Resource Owner who authorized
this token.
aud OPTIONAL. Service-specific string identifier or list of string
identifiers representing the intended audience for this token.
token_type OPTIONAL. Type of the token as defined in OAuth 2.0
section 5.1.
2.3. Non-normative Example
For example, a Protected Resource accepts a request from a Client
carrying an OAuth2 Bearer Token. In order to know how and whether to
serve the request, the Protected Resource then makes the following
request to the Introspection Endpoint of the Authorization Server.
The Protected Resource is here authenticating with its own Client ID
and Client Secret as per OAuth2 [RFC6749] Section 2.3.1.
Following is a non-normative example request (with line wraps for
display purposes only):
POST /register HTTP/1.1
Accept: application/x-www-form-urlencoded
Host: server.example.com
Authorization: Basic czZCaGRSa3F0Mzo3RmpmcDBaQnIxS3REUmJuZlZkbUl3
token=X3241Affw.4233-99JXJ
The Authorization Server validates the client credentials and looks
up the information in the token. If the token is currently active,
it returns the following JSON document.
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Following is a non-normative example active token response (with line
wraps for display purposes only):
HTTP/1.1 200 OK
Content-Type: application/json
Cache-Control: no-store
{
"active": true,
"client_id":"s6BhdRkqt3",
"scope": "read write dolphin",
"sub": "2309fj32kl",
"aud": "http://example.org/protected-resource/*"
}
If the token presented is not currently active (but the
authentication presented is valid), it returns the following JSON
document.
Following is a non-normative example response to an inactive or
invalid token (with line wraps for display purposes only):
HTTP/1.1 200 OK
Content-Type: application/json
Cache-Control: no-store
{
"active": false
}
If the client credentials are invalid or there is another error, the
Authorization Server responds with an HTTP 400 (Bad Request) as
described in OAuth 2.0 section 5.2 [RFC6749].
3. IANA Considerations
This document makes no request of IANA.
4. Security Considerations
If left unprotected and un-throttled, the Introspection Endpoint
could present a means for an attacker to poll a series of possible
token values, fishing for a valid token. Therefore, the
Authorization Server SHOULD issue special client credentials to any
protected resources or clients that need to access the introspection
endpoint. These credentials may be used directly at the endpoint, or
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they may be exchanged for an OAuth2 Access token scoped specifically
for the Introspection Endpoint.
Since the introspection endpoint takes in OAuth 2 tokens as
parameters, it MUST be protected by TLS or equivalent. A server MAY
require an HTTP POST method only to the endpoint.
5. Acknowledgements
Thanks to the OAuth Working Group and the UMA Working Group for
feedback.
6. Normative References
[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.
[RFC6749] Hardt, D., "The OAuth 2.0 Authorization Framework", RFC
6749, October 2012.
[RFC6750] Jones, M. and D. Hardt, "The OAuth 2.0 Authorization
Framework: Bearer Token Usage", RFC 6750, October 2012.
[Revocation]
Lodderstedt, T., "OAuth Token Revocation", April 2013.
Author's Address
Justin Richer (editor)
The MITRE Corporation
Email: jricher@mitre.org
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