mirror of
https://github.com/moparisthebest/xeps
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98 lines
3.6 KiB
XML
98 lines
3.6 KiB
XML
<?xml version='1.0' encoding='UTF-8'?>
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<!DOCTYPE xep SYSTEM 'xep.dtd' [
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<!ENTITY % ents SYSTEM 'xep.ent'>
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<!ENTITY otr3 "<span class='ref'><link url='https://otr.cypherpunks.ca/Protocol-v3-4.0.0.html'>Off-the-Record Messaging Protocol version 3</link></span> <note>Off-the-Record Messaging Protocol (OTR) version 3 <<link url='https://otr.cypherpunks.ca/Protocol-v3-4.0.0.html'>https://otr.cypherpunks.ca/Protocol-v3-4.0.0.html</link>> (Accessed 2015-08-30).</note>" >
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%ents;
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]>
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<?xml-stylesheet type='text/xsl' href='xep.xsl'?>
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<xep>
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<header>
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<title>OTR Discovery</title>
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<abstract>
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This document provides a mechanism by which OTR encryption support can be
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discovered in XMPP, without relying on OTRs protocol agnostic discovery
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mechanism.
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</abstract>
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&LEGALNOTICE;
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<number>0378</number>
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<status>Experimental</status>
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<type>Standards Track</type>
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<sig>Standards</sig>
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<approver>Council</approver>
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<dependencies>
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<spec>XMPP Core</spec>
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<spec>XEP-0030</spec>
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</dependencies>
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<supersedes/>
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<supersededby/>
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<shortname>OTR-DISCO</shortname>
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&sam;
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<revision>
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<version>0.0.1</version>
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<date>2016-07-15</date>
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<initials>ssw</initials>
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<remark><p>Initial version approved by the Council.</p></remark>
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</revision>
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</header>
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<section1 topic='Introduction' anchor='intro'>
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<p>
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The Off-the-Record messaging protocol (OTR) is widely layered on top of
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XMPP to provide end-to-end encryption. Current use of the protocol is
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described in &xep0364;. OTR provides its own discovery mechanism in which
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it sends messages with special whitespace characters to indicate support.
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While this works when initializing a session, there is no way to query a
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client for support and to know in advance that a particular version of
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OTR is supported. This specification aims to solve that by providing an
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in-band mechanism for discovering OTR support in XMPP.
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</p>
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<p>
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It should be noted that newer, more secure encryption protocols exist for
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XMPP, and that new implementations of OTR are discouraged. This protocol
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is primarily intended to solve issues with existing implementations of
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OTR.
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</p>
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</section1>
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<section1 topic='Discovering support' anchor='disco'>
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<p>
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If an entity supports OTR it MUST advertise the fact by returning a
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feature of 'urn:xmpp:otr:0' &VNOTE; in response to a &xep0030; information
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request. This indicates support for OTRv3 as defined by &otr3;.
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</p>
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<example caption='Disco response'><![CDATA[
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<feature var='urn:xmpp:otr:0' />]]></example>
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<p>
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If older versions of OTR are required, they may be discovered out of band
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using OTRs built in mechanism which is beyond the scope of this document.
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</p>
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</section1>
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<section1 topic='Security Considerations' anchor='security'>
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<p>
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Because OTR support is advertised outside of any end-to-end encrypted
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stream, it may be subject to downgrade attacks (eg. the server operator
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may remove OTR from the features list).
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</p>
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</section1>
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<section1 topic='IANA Considerations' anchor='iana'>
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<p>
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This document requires no interaction with the Internet Assigned Numbers
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Authority (IANA).
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</p>
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</section1>
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<section1 topic='XMPP Registrar Considerations' anchor='registrar'>
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<p>This specification defines the following XML namespaces:</p>
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<ul>
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<li>urn:xmpp:otr:0</li>
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</ul>
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<p>
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The ®ISTRAR; shall include the foregoing namespaces in its disco
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features registry as defined in &xep0030;.
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</p>
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<code caption='Registry Submission'><![CDATA[
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<var>
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<name>urn:xmpp:otr:0</name>
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<desc>Indicates support for Off-the-Record Messaging (OTR) version 3</desc>
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<doc>XEP-0378</doc>
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</var>]]></code>
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</section1>
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</xep>
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