RFC 3514 [1], published just today (2003-04-01), defines a mechanism for specifying the "evil bit" in IPv4 in order to determine if a packet was sent with malicious intent. In Section 5 ("Related Work") of that RFC, reference is made to complementary mechanisms for other forms of evil such as IPv6 support and the application/evil MIME type. Because the XMPP Standards Foundation (XSF) [2] desires to maintain compliance with protocols developed by core Internet standards bodies, the current document defines a complementary mechanism for XMPP support of evil.
There are three basic XMPP stanza types that may be sent within XML streams:
Any one of the foregoing data elements can be used with malicious intent. Therefore a generalized mechanism is needed. Because XML namespaces are used within XMPP to properly scope data, this document proposes a new namespace ('http://jabber.org/protocol/evil') to implement the desired functionality.
If an evil entity sends an evil message, it MUST include an appropriately namespaced extension in the message stanza:
<message
from='iago@shakespeare.lit/pda'
to='emilia@shakespeare.lit/mobile'>
<body>
I told him what I thought, and told no more
Than what he found himself was apt and true.
</body>
<evil xmlns='http://jabber.org/protocol/evil'/>
</message>
If an evil entity sends evil presence information, it MUST include an appropriately namespaced extension in the presence stanza:
<presence from='iago@shakespeare.lit/pda'> <show>dnd</show> <status>Fomenting dissension</status> <evil xmlns='http://jabber.org/protocol/evil'/> </presence>
If an evil entity provides evil information in an IQ exchange, it MUST include an appropriately namespaced extension in the IQ stanza:
<iq from='iago@shakespeare.lit/pda'
id='evil1'
type='result'
to='emilia@shakespeare.lit/mobile'>
<query xmlns='jabber:iq:version'>
<name>Stabber</name>
<version>666</version>
<os>FiendOS</os>
<evil xmlns='http://jabber.org/protocol/evil'/>
</query>
</iq>
Evil entities MUST advertise their support for this protocol in their responses to Service Discovery (XEP-0030) [3] information ("disco#info") requests by returning a feature of "http://jabber.org/protocol/evil":
<iq from='emilia@shakespeare.lit/mobile'
id='disco1'
to='iago@shakespeare.lit/pda'
type='get'>
<query xmlns='http://jabber.org/protocol/disco#info'/>
</iq>
<iq from='iago@shakespeare.lit/pda'
id='disco1'
to='emilia@shakespeare.lit/mobile'
type='result'>
<query xmlns='http://jabber.org/protocol/disco#info'>
<feature var='http://jabber.org/protocol/evil'/>
</query>
</iq>
In order for an application to determine whether an entity supports this protocol, where possible it SHOULD use the dynamic, presence-based profile of service discovery defined in Entity Capabilities (XEP-0115) [4]. However, if an application has not received entity capabilities information from an entity, it SHOULD use explicit service discovery instead.
Because the 'http://jabber.org/protocol/evil' namespace flags an XML stanza as malicious, it is critically important that an entity appropriately process an XML stanza that contains the evil extension. Mission-critical applications SHOULD ignore any stanzas tagged with the evil extension. Evil servers MAY pass through evil stanzas unmodified. Really evil servers MAY silently delete the evil extension. Entities that are evil to the core SHOULD support channel-level evil as defined in RFC 3514, since this document defines per-stanza evil only.
This document requires no interaction with the Internet Assigned Numbers Authority (IANA) [5].
The XMPP Registrar [6] shall register the 'http://jabber.org/protocol/evil' namespace as a result of this document.
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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.
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.
Given that this XMPP Extension Protocol normatively references IETF technologies, discussion on the <xsf-ietf@xmpp.org> list might also be appropriate.
Errata can be sent to <editor@xmpp.org>.
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".
1. RFC 3514: The Security Flag in the IPv4 Header <http://tools.ietf.org/html/rfc3514>.
2. The XMPP Standards Foundation (XSF) is an independent, non-profit membership organization that develops open extensions to the IETF's Extensible Messaging and Presence Protocol (XMPP). For further information, see <https://xmpp.org/about/xmpp-standards-foundation>.
3. XEP-0030: Service Discovery <https://xmpp.org/extensions/xep-0030.html>.
4. XEP-0115: Entity Capabilities <https://xmpp.org/extensions/xep-0115.html>.
5. 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/>.
6. 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 <https://xmpp.org/registrar/>.
Note: Older versions of this specification might be available at http://xmpp.org/extensions/attic/
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