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privileged entity This specification provides a way for XMPP entities to have a privileged access to some other entities data This XMPP Extension Protocol is copyright (c) 1999 - 2014 by the XMPP Standards Foundation (XSF). 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. ## 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. In no event shall the XMPP Standards Foundation or the authors of this Specification be liable for any claim, damages, or other liability, whether in an action of contract, tort, or otherwise, arising from, out of, or in connection with the Specification or the implementation, deployment, or other use of the Specification. ## 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 out of the use or inability to use 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. This XMPP Extension Protocol has been contributed in full conformance with the XSF's Intellectual Property Rights Policy (a copy of which may be found at <http://xmpp.org/extensions/ipr-policy.shtml> or obtained by writing to XSF, P.O. Box 1641, Denver, CO 80201 USA). xxxx ProtoXEP Standards Track Standards Council XMPP Core NOT_YET_ASSIGNED Jérôme Poisson goffi@goffi.org goffi@jabber.fr 0.0.4 2014-12-18 jp
  • Big simplification and restriction following council's veto and standard@ discussions
  • Configuration is now done only on server own configuration
  • No more client mode
  • Permissions are adverised using &MESSAGE;
  • The only &IQ; privilege still available is jabber:iq:roster
 0.0.3 2014-11-13 jp
  • giving permission to manage this XEP namespace is forbidden
  • Added configuration section; with well-defined command node
  • better specification of persistent permissions
  • fixed erroneous example (server returns bookmarks)
  • added special permissions
  • better specification of &QUERY; element
 0.0.2 2014-09-17 jp
  • changed for privileged entity
  • fixes after feedbacks on standard mailing list
  • completed missing required parts
 0.0.1 2014-05-09 jp

First draft.

XMPP components are used for long through &xep0114;, but are quite limited: they have a restricted access to other entities data, similar to what a client can do. This is sufficient for components like gateways, but very limiting for more complex components like a PubSub service. The goal of this XEP is to allow a component or any entity to have a "privileged" status, and access some other entity data with the same privileges than the entity itself, that means manage an entity roster on its behalf, send &MESSAGE; or receive &PRESENCE; stanzas in the name of the server.

Privileged entities have numerous advantages, including:

Privileged entity has been created with the main goal to create an external, server agnostic, PEP service. It is restricted to only a couple of features, see Acknowledgements section for more details

A privileged entity must be able to do what a PEP service can do and to access roster, so it must be able to (according to configuration):

The privilege mechanism MUST be totally transparent for the managed entities.

Roster access is granted in the server configuration. Roster access can have 4 types:

  • none — the entity is not allowed to access managed entity roster at all. This MUST be the default value.
  • get — the entity is allowed to send &IQ; stanzas of type 'get' for the namespace 'jabber:iq:roster'.
  • set — the entity is allowed to send &IQ; stanzas of type 'set' for namespace 'jabber:iq:roster'.
  • both — the entity is allowed to send &IQ; stanzas of type 'get' and 'set' for namespace 'jabber:iq:roster'.

Once an entity is authenticated and stream is started, the server send it a &MESSAGE; stanza with a <privilege> elements which MUST have the namespace 'urn:xmpp:privilege:0'. This element contains <perm> elements which MUST contain a 'namespace' attribute of the value "jabber:iq:roster" and a 'type' attribute which must correspond to the type configured as specified in "Server Allows Roster Access" section

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Here pubsub.capulet.lit is allowed to do get and set operations on all entities managed by capulet.lit

Doing a get or set operation on the roster of a managed entity is done in the usual way (as described in &rfc6121; section 2), except that the 'to' attribute is set to the attribute of the managed entity. The server MUST check that the privileged entity has right to get or set the roster of managed entity, and MUST return a &forbidden; error if it is not the case:

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The server then answers normally, as it would have done to the managed entity:

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In some cases, it can be desirable to send notifications (e.g. PEP service), so the privileged entity must be able to send &MESSAGE; stanzas. This is allowed in server configuration in the same way as for roster permission. The permission type can have the following values:

  • none — the entity is not allowed to send &MESSAGE; stanza in the name of the server. This MUST be the default value.
  • outgoing — the entity is allowed to send &MESSAGE; stanzas in the name of the server, according to following restrictions.

A privileged entity can then send message on the behalf either of the server or of a bare JID of the server, using &xep0297;, with the following restrictions:

  1. forwarded &MESSAGE; 'type' attribute has the value of "headline"
  2. forwarded &MESSAGE; 'from' attribute MUST be a bare JID from the server, no resource is allowed

If any of this rules is violated, the server MUST return a <not-authorized/> stream error and close the connection, as explained in &rfc6120; section 4.9.3.12.

Server advertise "message" permission in the same way as for "roster" permission, except that 'namespace' attribute has the value of "message", and the 'type' attribute as a value of 'outgoing':

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Now that pubsub.capulet.lit is allowed, it can send messages using <forwarded/> elements.

Gerald Finzi 255 Music for "Love's Labors Lost" (Suite for small orchestra) Introduction (Allegro vigoroso) 1 ]]>

The server sees that forwarded message type is 'headline', that juliet@capulet.lit is a bare JID of the server, and that outgoing message permission was granted in admin mode (so all bare JIDs from server are allowed); it can now send the notification:

Gerald Finzi 255 Music for "Love's Labors Lost" (Suite for small orchestra) Introduction (Allegro vigoroso) 1 ]]>

It can be often desirable for a privileged entity to have presence information of the managed entities (e.g. to know when to send them notificiations). As privileges must be transparent for the managed entity, this presence has to be sent by the server without modifying managed entity roster.

This is allowed in server configuration in the same way as for roster and message permissions. The "presence" type can have the following values:

  • none — the entity is not allowed to access &PRESENCE; informations at all. This MUST be the default value.
  • managed_entity — the entity is allowed to receive managed entity presence (see below).
  • roster — the entity is allowed to receive presence informations of managed entity contacts, see Roster Presence section.

If the privilege is granted, the server MUST use a directed presence, as specified in &rfc6121; section 4.6 on the behalf of managed entity each time its presence information change.

Server advertise "presence" permission in the same way as for "roster" or "message" permissions, except that 'namespace' attribute has the value of "presence", and the 'type' attribute has a value of "managed_entity"

Once the "presence" permission is granted, the server send presence informations:

chat Staying on the balcony ]]> chat Staying on the balcony ]]>

In addition to "managed entity presence", a privileged entity may need to know when a contact in managed entity roster is online (for example, it's necessary for a PEP service because of the presence default access model).

As for other permissions, the access in granted in server's configuration, but there is a additional restriction: the privileged entity MUST have read permission on roster namespace (i.e. 'type' attribute in allowed <perm> of namespace jabber:iq:roster MUST have a value of either get or both).

If the delegation is granted, the server MUST send to the privileged entity every presence information that the privileged entity is receiving. Having "roster" type for "presence" permission imply that you have also implicitly "managed_entity" type.

The server MUST reject the permission if the privileged entity doesn't have read permission on roster namespace.

Note: this permission should be given carefully, as it gives access to presence of potentially a lot of entities to the privileged entity (see security considerations).

Server advertise roster "presence" permission in the same way as for other permissions, except that the 'namespace' attribute has the value of "presence", and the 'type' attribute has a value of "roster"

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Note the presence of jabber:iq:roster permission request.

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  1. Privileged entitiy has access to sensitive data, and can act as the server itself, permissions should be granted carefuly, only if you absolutely trust the entity.
  2. Roster presence is particulary sensitive, because presence informations of whole rosters are shared.

This document requires no interaction with &IANA;.

The ®ISTRAR; includes 'urn:xmpp:privilege:0' in its registry of protocol namespaces (see &NAMESPACES;).

  • urn:xmpp:privilege:0
 &NSVER; ]]>

Thanks to Sergey Dobrov, Dave Cridland, Steven Lloyd Watkin, Lance Stout and Johannes Hund for their feedbacks. Thanks to Adrien Cossa for his typos/style corrections.

Privileged entity was initialy written to be a generic identity based access control (IBAC) which allows an entity to access sensitive data. After a discussion on standard mailing list, it has been decided to restrict the current XEP to immediate needs to build an external PEP service, and to implement separately an Attribute Based Access Control (ABAC) which is more modern, generic and flexible. This XEP is still interesting for being easy to implement and doing the job.