XEP-0235: OAuth Over XMPP

This specification defines an XMPP extension for delegating access to protected resources over XMPP, using the OAuth protocol. In the language of OAuth, a User can authorize a Consumer to access a Protected Resource that is hosted by a Service Provider; this authorization is encapsulated in a token that the User requests from the Service Provider, that the User shares with the Consumer, and that the Consumer then presents to the Service Provider. This specification assumes that OAuth tokens will be acquired via HTTP as defined in the core OAuth specification, then presented over XMPP to a Service Provider. The Protected Resources accessible over XMPP might include groupchat rooms, data feeds hosted at publish-subscribe nodes, media relays, communication gateways, and other items of interest.

WARNING: This Standards-Track document is Experimental. Publication as an XMPP Extension Protocol does not imply approval of this proposal by the XMPP Standards Foundation. Implementation of the protocol described herein is encouraged in exploratory implementations, but production systems should not deploy implementations of this protocol until it advances to a status of Draft.

Document Information

Series: XEP
Number: 0235
Publisher: XMPP Standards Foundation
Status: Experimental
Type: Standards Track
Version: 0.4
Last Updated: 2008-08-07
Approving Body: XMPP Council
Dependencies: XMPP Core
Supersedes: None
Superseded By: None
Short Name: NOT_YET_ASSIGNED
Wiki Page: <http://wiki.jabber.org/index.php/OAuth Over XMPP (XEP-0235)>

Author Information

Legal Notices

Discussion Venue

The preferred venue for discussion of this document is the Standards discussion list: <http://mail.jabber.org/mailman/listinfo/standards>.

Errata may be sent to <editor@xmpp.org>.

Relation to XMPP

The Extensible Messaging and Presence Protocol (XMPP) is defined in the XMPP Core (RFC 3920) and XMPP IM (RFC 3921) specifications contributed by the XMPP Standards Foundation to the Internet Standards Process, which is managed by the Internet Engineering Task Force in accordance with RFC 2026. Any protocol defined in this document has been developed outside the Internet Standards Process and is to be understood as an extension to XMPP rather than as an evolution, development, or modification of XMPP itself.

Conformance Terms

The following keywords as used in this document are to be interpreted as described in RFC 2119: "MUST", "SHALL", "REQUIRED"; "MUST NOT", "SHALL NOT"; "SHOULD", "RECOMMENDED"; "SHOULD NOT", "NOT RECOMMENDED"; "MAY", "OPTIONAL".

Table of Contents

1. Introduction

Although authentication is required in order to access the XMPP network, in some situations it is desirable to require authorization in order for an authenticated entity to access certain resources on the network. For example, authorization may be required to join a Multi-User Chat [1] room, subscribe to a Publish-Subscribe [2] node, or to access other resources of interest (such as a media relay or communications gateway).

Dedicated technologies exist for authorization. One such technology is OAuth [3], as defined at <http://oauth.net/core/1.0/>. In the language of OAuth, a User can authorize a Consumer to access a Protected Resource that is hosted by a Service Provider; this authorization is encapsulated in a token that the User requests from the Service Provider, that the User shares with the Consumer, and that the Consumer then presents to the Service Provider.

This specification assumes that OAuth Access Tokens will be acquired outside the XMPP (i.e., via HTTP as defined in the core OAuth specification) and merely presented over XMPP.

2. Protocol Flow

The typical scenario is for a Consumer to request the authorization to act as a delegated authority on behalf of the User to access a Protected Resource owned by the User at a Service Provider. For example, the owner of a pubsub node could allow a remote entity to publish to that node (the single lines show protocol flows over HTTP and the double lines show protocol flows over XMPP):

Consumer                  Service Provider
   |                             |
   |  request a Request Token    |
   |---------------------------->|
   |  grant the Request Token    |
   |<----------------------------|
   |                             |
   |  [Consumer redirects User   |
   |   to Service Provider]      |
   |                             |
   |  request an Access Token    |
   |---------------------------->|
   |  grant the Access Token     |
   |<----------------------------|
   |  access Protected Resource  |
   |============================>|
   |                             |
  

Before presenting an access token to a Service Provider via XMPP, a Consumer SHOULD verify that the Service Provider supports this protocol, as described under the Determining Support section of this document.

Consider the example of a User (say, <world-traveler@example.com>) who wishes to authorize a Consumer (say, an application called FindMeNow as represented by the JID <travelbot@findemenow.tld>) to access the User's geolocation feed at a Service Provider called WorldGPS (as represented by a publish-subscribe node of <feeds.worldgps.tld/world-traveler>). The order of events might be as follows.

1. WorldGPS and FindMeNow have agreed upon a certificate and secret for FindMeNow to use when communicating with WorldGPS.
2. WorldGPS maintains a feed for the User's location data in an XMPP PubSub Node.
3. The User visits FindMeNow.tld and requests real-time updates from his WorldGPS feed.
4. FindMeNow, over HTTP, requests a "request token" from WorldGPS's pubsub service, signing it with the agreed-upon certificate and secret.
5. WorldGPS, if the signature was valid, sends FindMeNow a "request token."
6. FindMeNow then redirects the user to a WorldGPS webpage.
7. On the WorldGPS webpage, the User logs in (or is already logged in) and is then asked whether to approve of FindMeNow having read-only access to his geolocation information.
8. The User approves the request and WorldGPS redirects the User back to FindMeNow.
9. FindMeNow, over HTTP, requests an "access token" (again signing it) and now using the "request token" approved by the User.
10. WorldGPS, if the signature is correct and the request token was approved, replies with an access token.
11. FindMeNow, over XMPP, subscribes to the User's pubsub node using the access token.

As a result, FindMeNow gets updated every time the User publishes items to his geolocation node at WorldGPS.

Steps 1 through 10 occur via HTTP. Step 11 would be represented in XMPP as follows.

Example 1. Pubsub subscription request with token

<iq type='set'
    from='travelbot@findmenow.tld/bot'
    to='feeds.worldgps.tld'
    id='sub1'>
  <pubsub xmlns='http://jabber.org/protocol/pubsub'>
    <subscribe node='bard_geoloc'/>
    <oauth xmlns='urn:xmpp:tmp:oauth'>
      <oauth_consumer_key>0685bd9184jfhq22</oauth_consumer_key>
      <oauth_token>ad180jjd733klru7</oauth_token>
      <oauth_signature_method>HMAC-SHA1</oauth_signature_method>
      <oauth_signature>wOJIO9A2W5mFwDgiDvZbTSMK%2FPY%3D</oauth_signature>
    </oauth>
  </pubsub>
</iq>
  

3. Determining Support

If a service provides and accepts authorization tokens, it MUST advertise support for the 'urn:xmpp:tmp:oauth' namespace in its disco#info replies (if provided) its Entity Capabilities [4] notations (see Protocol Namespaces regarding issuance of one or more permanent namespaces).

4. Security Considerations

<iq to="x@example.com" from="y@example.org" id="1234">
  <pubsub xmlns='http://jabber.org/protocol/pubsub'>
    <subscribe node='mynode'/>
    <oauth xmlns='urn:xmpp:tmp:oauth'>
      <oauth_consumer_key>foo</oauth_consumer_key>
      <oauth_token>bar</oauth_token>
      <oauth_signature_method>HMAC-SHA1</oauth_signature_method>
      <oauth_signature>h2vvES3WQpdYmjzUK7Fl2G1Nez8=</oauth_signature>
    </oauth>
  </pubsub>
</iq>
    

iq&x%40example.com%26y%40example.org&oauth_consumer_key%3Dfoo\
%40oauth_signature_method%3DHMAC-SHA1%40oauth_token%3Dbar
    

    h2vvES3WQpdYmjzUK7Fl2G1Nez8=
    

5. IANA Considerations

This document requires no interaction with the Internet Assigned Numbers Authority (IANA) [9].

6. XMPP Registrar Considerations

7. XML Schema

<?xml version='1.0' encoding='UTF-8'?>

<xs:schema
    xmlns:xs='http://www.w3.org/2001/XMLSchema'
    targetNamespace='urn:xmpp:tmp:oauth'
    xmlns='urn:xmpp:tmp:oauth'
    elementFormDefault='qualified'>

  <xs:element name='oauth'>
    <xs:complexType>
      <xs:choice>
        <xs:element name='oauth_consumer_key' type='xs:string'/>
        <xs:element name='oauth_nonce' type='xs:string'/>
        <xs:element name='oauth_signature' type='xs:string'/>
        <xs:element name='oauth_signature_method' type='xs:string'/>
        <xs:element name='oauth_timestamp' type='xs:string'/>
        <xs:element name='oauth_token' type='xs:string'/>
        <xs:element name='oauth_token_secret' type='xs:string'/>
      </xs:choice>
    </xs:complexType>
  </xs:element>

  <xs:simpleType name='empty'>
    <xs:restriction base='xs:string'>
      <xs:enumeration value=''/>
    </xs:restriction>
  </xs:simpleType>

</xs:schema>
  

8. Acknowledgements

The author gratefully acknowledges the contributions of Blaine Cook, Leah Culver, Kellan Elliott-McCrea, Seth Fitzsimmons, Nathan Fritz, Evan Henshaw-Plath, Joe Hildebrand, and Ralph Meijer to the content of this specification, as provided during the XMPP Summit held in Portland, Oregon, on July 21 and 22, 2008. Thanks also to Dave Cridland and Pedro Melo for their comments on an early draft.

Notes

Revision History

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