XEP-0186: Invisible Command

This document specifies an XMPP-compatible protocol for user invisibility.

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: 0186
Publisher: XMPP Standards Foundation
Status: Experimental
Type: Standards Track
Version: 0.8
Last Updated: 2008-10-06
Approving Body: XMPP Council
Dependencies: XMPP Core, XMPP IM, XEP-0030
Supersedes: XEP-0018
Superseded By: None
Short Name: invisible

Author Information

Peter Saint-Andre

JabberID: stpeter@jabber.org
URI: https://stpeter.im/

Legal Notices

Copyright

This XMPP Extension Protocol is copyright (c) 1999 - 2008 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. 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. ##

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 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.

IPR Conformance

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://www.xmpp.org/extensions/ipr-policy.shtml> or obtained by writing to XSF, P.O. Box 1641, Denver, CO 80201 USA).

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
2. Requirements
3. Use Cases
    3.1. User Becomes Invisible
    3.2. User Becomes Visible
4. Discovering Support
5. Integration With Privacy Lists
6. Security Considerations
7. IANA Considerations
8. XMPP Registrar Considerations
    8.1. Protocol Namespaces
    8.2. Protocol Versioning
9. XML Schema
Notes
Revision History

1. Introduction

Some instant messaging implementations of the Jabber/XMPP protocols have long supported the ability for IM users to be online but appear invisible. The existing protocols for doing so are:

In order to provide a standards-compliant protocol that can be used in the long term, this document defines an IQ-based protocol that enables an IM user to become "invisible" and "visible" at will within the context of a given session. This protocol is intended to supersede the protocol described in XEP-0018 and to provide a more client-friendly approach to invisibility than XEP-0126.

2. Requirements

The requirements for invisible mode are straightforward:

  1. A user can become visible or invisible at any time within an XMPP session.
  2. Invisible mode is active only for the current session; if the user ends that session and starts another session, the invisibility mode set for the previous session does not carry over to the new session.
  3. When in invisible mode, a user can send directed presence to particular contacts.

3. Use Cases

3.1 User Becomes Invisible

In order for a client to go invisible, it shall send an IQ-set with no 'to' address (thus handled by the user's server) containing an <invisible/> element qualified by the 'urn:xmpp:invisible:0' namespace (see Namespace Versioning regarding the possibility of incrementing the version number).

Example 1. Invisible command

<iq from='bilbo@tolkien.lit/shire'
    id='inv1'
    type='set'>
  <invisible xmlns='urn:xmpp:invisible:0'/>
</iq>

If the server can successfully process the invisibility command, it MUST return an IQ-result.

Example 2. Invisible command is successful

<iq to='bilbo@tolkien.lit/shire'
    id='inv1'
    type='result'/>

(Standard XMPP stanza errors apply; see RFC 3920 and Error Condition Mappings [6].)

If the client enters invisible mode after having previously sent undirected presence with no 'type' attribute (e.g., after sending initial presence), the server MUST send <presence type='unavailable'/> presence from the specified resource to all contacts who would receive unavailable presence if the client sent <presence type='unavailable'/>.

While the client is in invisible mode, the server:

  1. MUST NOT broadcast presence notifications as a result of receiving any subsequent undirected presence notifications from the client.

  2. MUST deliver directed presence stanzas generated by the client.

  3. MUST deliver inbound <presence/> stanzas.

  4. SHOULD deliver inbound <message/> stanzas whose 'to' address is the bare JID <localpart@domain.tld> of the user (subject to standard XMPP stanza handling rules).

  5. MUST deliver inbound <message/> and <iq/> stanzas whose 'to' address is the full JID <localpart@domain.tld/resource> corresponding to the resource of the client.

  6. MUST deliver outbound <message/> and <iq/> stanzas generated by the client (for an important note regarding presence leaks, see the Security Considerations section of this document).

If after sending directed presence the client then sends <presence type='unavailable'/>, the server MUST deliver that unavailable presence only to the entities to which the client sent directed presence after going invisible.

3.2 User Becomes Visible

In order for a client to become visible again, it shall send an IQ-set with no 'to' address (thus handled by the user's server) containing a <visible/> element qualified by the 'urn:xmpp:invisible:0' namespace (see Namespace Versioning regarding the possibility of incrementing the version number).

Example 3. Visible command

<iq from='bilbo@tolkien.lit/shire'
    id='vis1'
    type='set'>
  <visible xmlns='urn:xmpp:invisible:0'/>
</iq>

If the server can successfully process the visibility command, it MUST return an IQ-result.

Example 4. Visible command is successful

<iq to='bilbo@tolkien.lit/shire'
    id='vis1'
    type='result'/>

When the client becomes visible, the server MUST treat that state as equivalent to an active session before receiving initial presence from the client.

It is the responsibility of the client to send an undirected presence notification to the server.

Example 5. Client sends presence

<presence/>

The server then MUST broadcast that presence to all entities who would normally receive presence broadcasts from the client (as well as any other entities to which the client sent directed presence while invisible).

4. Discovering Support

In order for a client to discover whether its server supports the protocol defined herein, it MUST send a Service Discovery [7] information request to the server:

Example 6. Service discovery request

<iq from='bilbo@tolkien.lit/shire'
    id='disco1'
    to='tolkien.lit'
    type='get'>
  <query xmlns='http://jabber.org/protocol/disco#info'/>
</iq>

If the server supports the protocol defined herein, it MUST return a feature of "urn:xmpp:invisible:0" (see Namespace Versioning regarding the possibility of incrementing the version number).

Example 7. Service discovery response

<iq from='bilbo@tolkien.lit/shire'
    id='disco1'
    to='tolkien.lit'
    type='result'>
  <query xmlns='http://jabber.org/protocol/disco#info'>
    <feature var='urn:xmpp:invisible:0'/>
  </query>
</iq>

A client SHOULD complete this service discovery process before sending initial presence to its server.

5. Integration With Privacy Lists

A server MAY use the same backend data store for invisibility mode as defined herein and Server-Based Privacy Rules [8] as used for invisibility (see XEP-0126). If so, the server MUST update the relevant privacy lists on behalf of the user when the client requests initiation or termination of invisible mode.

6. Security Considerations

It is important to recognize that invisibility can be defeated without the use of privacy lists, intelligent stanza handling by the server, and an awareness of context on the part of a client. For example:

7. IANA Considerations

No interaction with the Internet Assigned Numbers Authority (IANA) [14] is required as a result of this document.

8. XMPP Registrar Considerations

8.1 Protocol Namespaces

This specification defines the following XML namespace:

Upon advancement of this specification from a status of Experimental to a status of Draft, the XMPP Registrar [15] shall add the foregoing namespace to the registry located at <http://www.xmpp.org/registrar/namespaces.html>, as described in Section 4 of XMPP Registrar Function [16].

8.2 Protocol Versioning

If the protocol defined in this specification undergoes a major revision that is not fully backward-compatible with an older version, or that contains significant new features, the XMPP Registrar shall increment the protocol version number found at the end of the XML namespaces defined herein, as described in Section 4 of XEP-0053.

9. XML Schema

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

<xs:schema
    xmlns:xs='http://www.w3.org/2001/XMLSchema'
    targetNamespace='urn:xmpp:invisible:0'
    xmlns='urn:xmpp:invisible:0'
    elementFormDefault='qualified'>

  <xs:element name='invisible' type='empty'/>

  <xs:element name='visible' type='empty'/>

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

</xs:schema>

Notes

1. XEP-0018: Invisible Presence <http://www.xmpp.org/extensions/xep-0018.html>.

2. RFC 3920: Extensible Messaging and Presence Protocol (XMPP): Core <http://tools.ietf.org/html/rfc3920>.

3. RFC 3921: Extensible Messaging and Presence Protocol (XMPP): Instant Messaging and Presence <http://tools.ietf.org/html/rfc3921>.

4. XEP-0126: Invisibility <http://www.xmpp.org/extensions/xep-0126.html>.

5. XEP-0016: Server-Based Privacy Rules <http://www.xmpp.org/extensions/xep-0016.html>.

6. XEP-0086: Error Condition Mappings <http://www.xmpp.org/extensions/xep-0086.html>.

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

8. XEP-0016: Server-Based Privacy Rules <http://www.xmpp.org/extensions/xep-0016.html>.

9. XEP-0085: Chat State Notifications <http://www.xmpp.org/extensions/xep-0085.html>.

10. XEP-0012: Last Activity <http://www.xmpp.org/extensions/xep-0012.html>.

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

12. XEP-0090: Entity Time <http://www.xmpp.org/extensions/xep-0090.html>.

13. XEP-0092: Software Version <http://www.xmpp.org/extensions/xep-0092.html>.

14. 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/>.

15. 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://www.xmpp.org/registrar/>.

16. XEP-0053: XMPP Registrar Function <http://www.xmpp.org/extensions/xep-0053.html>.

Revision History

Version 0.8 (2008-10-06)

Modified namespace to incorporate namespace versioning.

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Version 0.7 (2008-05-12)

Added note about integration with privacy lists; removed XEP-0126 from list of protocols that this specification supersedes; changed temporary namespace to conform to XMPP Registrar procedures; copied several security considerations from XEP-0126.

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Version 0.6 (2007-09-05)

Clarified that this specification is intended to supersede XEP-0018 and XEP-0126; added several additional examples.

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Version 0.5 (2007-01-30)

Modified XML namespace name to conform to XEP-0053 processes.

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Version 0.4 (2006-08-09)

Added XMPP Registrar considerations and XML schema.

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Version 0.3 (2006-08-02)

Added inbound presence rule to server handling section.

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Version 0.2 (2006-07-07)

Clarified that invisibility mode does not carry across sessions.

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Version 0.1 (2006-05-30)

Initial version.

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Version 0.0.2 (2006-05-15)

Recommended delivery of messages sent to bare JID.

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Version 0.0.1 (2006-05-11)

First draft.

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END