XEP-0074: Simple Access Control

Abstract:A simple protocol for querying information for permissions.
Author:Justin Kirby
Copyright:© 1999 - 2014 XMPP Standards Foundation. SEE LEGAL NOTICES.
Status:Retracted
Type:Standards Track
Version:0.2
Last Updated:2003-10-20

WARNING: This document has been retracted by the author(s). Implementation of the protocol described herein is not recommended. Developers desiring similar functionality are advised to implement the protocol that supersedes this one (if any).


Table of Contents


1. Introduction
2. A More Formal Tone
3. Query List of ACL operations
4. Integrating with Service Discovery
5. Security Considerations
6. IANA Considerations
7. XMPP Registrar Considerations
8. Open Issues

Appendices
    A: Document Information
    B: Author Information
    C: Legal Notices
    D: Relation to XMPP
    E: Discussion Venue
    F: Requirements Conformance
    G: Notes
    H: Revision History


1. Introduction

A Jabber travels further into the Jabber-as-Middleware world, it needs a protocol to determine "who can do what to whom". This proposal defines a protocol that enables any Jabber entity to determine the permissions of another Jabber entity, whether the context is a user JID querying a component for access, a client-to-client conversation, or a component asking another component about a request from a user.

All access control lists (ACLs) boil down to three aspects: Actor, Operation, and Target/Sink. With this in mind it becomes almost trivial to implement the basic query/response mechanism.

Example 1. A simple query

      
	<iq to="security.capulet.com"
	    from="inventory.capulet.com"
	    type="get" id="1234">
	  <acl xmlns="http://jabber.org/protocol/sac"
	       actor="juliet@capulet.com/church"
	       oper="uri://capulet.com/inventory#obtain"
	       target="poison"/>
	</iq> 
	
    

Here we have the inventory.capulet.com component querying the security component as to whether juliet@ may obtain the requested poison.

Example 2. A response to the above query

      
	<iq to="inventory.capulet.com"
	    from="security.capulet.com"
	    type="result" id="1234">
	  <acl xmlns="http://jabber.org/protocol/sac"
	       actor="juliet@capulet.com/church"
	       oper="uri://capulet.com/inventory#obtain"
	       target="poison">
	    <allowed/>
	  </acl>
	</iq> 
	
    

Unfortunately, the response is in the affirmative and the romantic tragedy follows.

2. A More Formal Tone

The <acl> element provides the container for the query. It MUST have the three attributes: actor, oper, and target.

The actor attribute is set to the Jabber ID which is attempting to perform an operation. This need not be the JID sending the acl, although it may be. Remember this is to allow for the question, "Can X do Y to Z?", which is a question anyone can ask.

The oper attribute is application-specific and refers to the operation for which a permission check is required (e.g., read/write operations). This also defines the scope of the ACL check, so the implementation is responsible for interpreting the actor and target values based on the value of the 'oper' attribute.

The target is the object which the actor is trying to perform the operation on. This MUST be a node queryable via Service Discovery (XEP-0030) [1].

Requests MUST be in the form of an empty <acl/> element with ALL the attributes specified. If not all attributes are specified, the request is incomplete and ambiguities arise; therefore the entity receving the request MUST return a "bad request" error to the sender.

Responses MUST be in one of three forms: allowed, denied, error.

The response is inserted into the <acl/> as a child element. If the response is allowed, then <allowed/> is inserted. If the JID is denied then <denied/> is returned. If there is inadequate information then <error/> is used following the standard Jabber error scheme.

Example 3. A positive response

      
	<iq to="inventory.capulet.com"
	    from="security.capulet.com"
	    type="result" id="1234">
	  <acl xmlns="http://jabber.org/protocol/sac"
	       actor="juliet@capulet.com/church"
	       oper="uri://capulet.com/inventory#obtain"
	       target="poison">
	    <allowed/>
	  </acl>
	</iq>       
	
    

Example 4. Negative response (denied)

      
	<iq to="inventory.capulet.com"
	    from="security.capulet.com"
	    type="result" id="1234">
	  <acl xmlns="http://jabber.org/protocol/sac"
	       actor="juliet@capulet.com/church"
	       oper="uri://capulet.com/inventory#obtain"
	       target="poison">
	    <denied/>
	  </acl>
	</iq> 
	
    

Example 5. Error response

      
	<iq to="inventory.capulet.com"
	    from="security.capulet.com"
	    type="error" id="1234">
	  <acl xmlns="http://jabber.org/protocol/sac"
	       actor="juliet@capulet.com/church"
	       oper="uri://capulet.com/inventory#obtain"
	       target="poison"/>
	  <error code="404">No information available</error>
	</iq> 
	
    

3. Query List of ACL operations

To obtain a list of acl operations that a jid supports, you must send an empty <query/>

Example 6. querying for list of acl operations

      
	<iq to="security.capulet.com"
	    from="inventory.capulet.com"
	    type="get" id="1234">
	  <query xmlns="http://jabber.org/protocol/sac"/>
	</iq> 
	
    

The to jid must then respond with a list of operations, if the jid supports SAC.

Example 7. response to the query

      
	<iq to="inventory.capulet.com"
	    from="security.capulet.com"
	    type="result" id="1234">
	  <query xmlns="http://jabber.org/protocol/sac">
	    <oper uri="uri://capulet.com/inventory#obtain"/>
	    <oper uri="uri://capulet.com/inventory#add"/>
	    <oper uri="uri://capulet.com/inventory#remove"/>
	  </query>
	</iq> 
	
    

4. Integrating with Service Discovery

To follow.

5. Security Considerations

To follow.

6. IANA Considerations

This document requires no interaction with the Internet Assigned Numbers Authority (IANA) [2].

7. XMPP Registrar Considerations

As a result of this document, the XMPP Registrar [3] will need to register the 'http://jabber.org/protocol/sac' namespace.

8. Open Issues

  1. Add disco integration section.
  2. Fill out error codes.
  3. Add DTD and Schema.
  4. Allow for query of all allowable operations for actor in relation to a target.
  5. Investigate possible integration with pubsub.

Appendices


Appendix A: Document Information

Series: XEP
Number: 0074
Publisher: XMPP Standards Foundation
Status: Retracted
Type: Standards Track
Version: 0.2
Last Updated: 2003-10-20
Approving Body: XMPP Council
Dependencies: None
Supersedes: None
Superseded By: None
Short Name: sac
Schema: <>
Source Control: HTML
This document in other formats: XML  PDF


Appendix B: Author Information

Justin Kirby

Email: justin@openaether.org
JabberID: zion@openaether.org


Appendix C: Legal Notices

Copyright

This XMPP Extension Protocol is copyright © 1999 - 2014 by the XMPP Standards Foundation (XSF).

Permissions

Permission is hereby granted, free of charge, to any person obtaining a copy of this specification (the "Specification"), to make use of the Specification without restriction, including without limitation the rights to implement the Specification in a software program, deploy the Specification in a network service, and copy, modify, merge, publish, translate, distribute, sublicense, or sell copies of the Specification, and to permit persons to whom the Specification is furnished to do so, subject to the condition that the foregoing copyright notice and this permission notice shall be included in all copies or substantial portions of the Specification. Unless separate permission is granted, modified works that are redistributed shall not contain misleading information regarding the authors, title, number, or publisher of the Specification, and shall not claim endorsement of the modified works by the authors, any organization or project to which the authors belong, or the XMPP Standards Foundation.

Disclaimer of Warranty

## NOTE WELL: This Specification is provided on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, express or implied, including, without limitation, any warranties or conditions of TITLE, NON-INFRINGEMENT, MERCHANTABILITY, or FITNESS FOR A PARTICULAR PURPOSE. ##

Limitation of Liability

In no event and under no legal theory, whether in tort (including negligence), contract, or otherwise, unless required by applicable law (such as deliberate and grossly negligent acts) or agreed to in writing, shall the XMPP Standards Foundation or any author of this Specification be liable for damages, including any direct, indirect, special, incidental, or consequential damages of any character arising from, out of, or in connection with the Specification or the implementation, deployment, or other use of the Specification (including but not limited to damages for loss of goodwill, work stoppage, computer failure or malfunction, or any and all other commercial damages or losses), even if the XMPP Standards Foundation or such author has been advised of the possibility of such damages.

IPR Conformance

This XMPP Extension Protocol has been contributed in full conformance with the XSF's Intellectual Property Rights Policy (a copy of which can be found at <http://xmpp.org/about-xmpp/xsf/xsf-ipr-policy/> or obtained by writing to XMPP Standards Foundation, 1899 Wynkoop Street, Suite 600, Denver, CO 80202 USA).

Appendix D: Relation to XMPP

The Extensible Messaging and Presence Protocol (XMPP) is defined in the XMPP Core (RFC 6120) and XMPP IM (RFC 6121) 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.


Appendix E: Discussion Venue

The primary venue for discussion of XMPP Extension Protocols is the <standards@xmpp.org> discussion list.

Discussion on other xmpp.org discussion lists might also be appropriate; see <http://xmpp.org/about/discuss.shtml> for a complete list.

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


Appendix F: Requirements Conformance

The following requirements 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".


Appendix G: Notes

1. XEP-0030: Service Discovery <http://xmpp.org/extensions/xep-0030.html>.

2. The Internet Assigned Numbers Authority (IANA) is the central coordinator for the assignment of unique parameter values for Internet protocols, such as port numbers and URI schemes. For further information, see <http://www.iana.org/>.

3. The XMPP Registrar maintains a list of reserved protocol namespaces as well as registries of parameters used in the context of XMPP extension protocols approved by the XMPP Standards Foundation. For further information, see <http://xmpp.org/registrar/>.


Appendix H: Revision History

Note: Older versions of this specification might be available at http://xmpp.org/extensions/attic/

Version 0.2 (2003-10-20)

At the request of the author, changed status to Retracted. (psa)

Version 0.1 (2003-03-05)

Initial version. (jk)

END