mirror of
https://github.com/moparisthebest/xeps
synced 2024-12-22 07:38:52 -05:00
135 lines
7.0 KiB
XML
135 lines
7.0 KiB
XML
<?xml version='1.0' encoding='UTF-8'?>
|
|
<!DOCTYPE xep SYSTEM 'xep.dtd' [
|
|
<!ENTITY secret "<secret/>">
|
|
<!ENTITY % ents SYSTEM 'xep.ent'>
|
|
%ents;
|
|
]>
|
|
<?xml-stylesheet type='text/xsl' href='xep.xsl'?>
|
|
<xep>
|
|
<header>
|
|
<title>Jingle Encrypted Transports - OMEMO</title>
|
|
<abstract>Extension for JET introducing OMEMO End-to-End Encrypted Jingle Transports.</abstract>
|
|
&LEGALNOTICE;
|
|
<number>0396</number>
|
|
<status>Experimental</status>
|
|
<type>Standards Track</type>
|
|
<sig>Standards</sig>
|
|
<approver>Council</approver>
|
|
<dependencies>
|
|
<spec>XEP-0391</spec>
|
|
<spec>XEP-0234</spec>
|
|
<spec>XEP-0384</spec>
|
|
</dependencies>
|
|
<supersedes/>
|
|
<supersededby/>
|
|
<shortname>jet-omemo</shortname>
|
|
<schemaloc>
|
|
<ns>jingle</ns>
|
|
<url>http://xmpp.org/schemas/jingle.xsd</url>
|
|
</schemaloc>
|
|
<schemaloc>
|
|
<ns>jingle:errors</ns>
|
|
<url>http://xmpp.org/schemas/jingle-errors.xsd</url>
|
|
</schemaloc>
|
|
<registry/>
|
|
<discuss>jingle</discuss>
|
|
&paulschaub;
|
|
<revision>
|
|
<version>0.1</version>
|
|
<date>2017-11-29</date>
|
|
<initials>XEP Editor (jwi)</initials>
|
|
<remark><p>Accepted by Council as Expremental XEP</p></remark>
|
|
</revision>
|
|
<revision>
|
|
<version>0.0.1</version>
|
|
<date>2017-10-06</date>
|
|
<initials>vv</initials>
|
|
<remark><p>First draft</p></remark>
|
|
</revision>
|
|
</header>
|
|
<section1 topic='Introduction' anchor='intro'>
|
|
<p>&xep0391; can be used to utilize different end-to-end encryption methods to secure Jingle Transports, eg. in the context of &xep0234;. This document aims to extend &xep0391; to allow the use of OMEMO encryption with Jingle transports. To achieve this goal, this protocol extension makes use of OMEMOs <link url='https://xmpp.org/extensions/xep-0384.html#usecases-keysend'>KeyTransportElements</link>.</p>
|
|
</section1>
|
|
<section1 topic='Mappings' anchor='mappings'>
|
|
<p>Conveniently the OMEMO protocol already provides a way to transport key material to another entity. So called KeyTransportElements are basically normal OMEMO MessageElements, but without a payload, so the contained key can be used for something else (see Section 4.6 of <cite>XEP-0384</cite>). This extension uses the key encrypted in the KeyTransportMessages <key> attribute and initialization vector from the <iv> attribute to secure Jingle Transports. The key corresponds to the <cite>Transport Key</cite> of <cite>XEP-0391</cite>, while the iv corresponds to the <cite>Initialization Vector</cite>. The KeyTransportMessage is the equivalent to the <cite>Envelope Element</cite>. Note that within the Envelope Element, the Transport Key is encrypted with the OMEMO ratchet.</p>
|
|
</section1>
|
|
<section1 topic='Limitations' anchor='limitations'>
|
|
<p>Unfortunately &xep0384; determines the type of the transported key to be AES-128-GCM-NoPadding, so no other configuration can be used in the context of this extension.</p>
|
|
<p>Since OMEMO deviceIds are not bound to XMPP resources, the initiator MUST encrypt the Transport Key for every device of the recipient.</p>
|
|
</section1>
|
|
<section1 topic='Key Transport' anchor='transport'>
|
|
<p>In order to transport a key to the responder, the initiator creates a fresh AES-128-GCM-NoPadding Transport Key and Initialization Vector and generates an OMEMO KeyTransportElement from it as described in <cite>XEP-0384</cite>. This is then added as a child of the JET <security> element. The 'cipher' attribute MUST be set to 'aes-128-gcm-nopadding:0' (see the <link url='https://xmpp.org/extensions/xep-0391.html#ciphers'>ciphers</link> section of <cite>XEP-0391</cite>). The value of the 'type' attribute must be set to the namespace of the used version of <cite>XEP-0384</cite> &VNOTE;.</p>
|
|
<p></p>
|
|
<example caption="Romeo initiates an OMEMO encrypted file offer"><![CDATA[
|
|
<iq from='romeo@montague.example/dr4hcr0st3lup4c'
|
|
id='nzu25s8'
|
|
to='juliet@capulet.example/yn0cl4bnw0yr3vym'
|
|
type='set'>
|
|
<jingle xmlns='urn:xmpp:jingle:1'
|
|
action='session-initiate'
|
|
initiator='romeo@montague.example/dr4hcr0st3lup4c'
|
|
sid='851ba2'>
|
|
<content creator='initiator' name='a-file-offer' senders='initiator'>
|
|
<description xmlns='urn:xmpp:jingle:apps:file-transfer:5'>
|
|
<file>
|
|
<date>1969-07-21T02:56:15Z</date>
|
|
<desc>This is a test. If this were a real file...</desc>
|
|
<media-type>text/plain</media-type>
|
|
<name>test.txt</name>
|
|
<range/>
|
|
<size>6144</size>
|
|
<hash xmlns='urn:xmpp:hashes:2'
|
|
algo='sha-1'>w0mcJylzCn+AfvuGdqkty2+KP48=</hash>
|
|
</file>
|
|
</description>
|
|
<transport xmlns='urn:xmpp:jingle:transports:s5b:1'
|
|
mode='tcp'
|
|
sid='vj3hs98y'>
|
|
<candidate cid='hft54dqy'
|
|
host='192.168.4.1'
|
|
jid='romeo@montague.example/dr4hcr0st3lup4c'
|
|
port='5086'
|
|
priority='8257636'
|
|
type='direct'/>
|
|
</transport>
|
|
<security xmlns='urn:xmpp:jingle:jet:0'
|
|
name='a-file-offer'
|
|
cipher='urn:xmpp:ciphers:aes-128-gcm-nopadding'
|
|
type='eu.siacs.conversations.axolotl'>
|
|
<encrypted xmlns='eu.siacs.conversations.axolotl'>
|
|
<header sid='27183'>
|
|
<key rid='31415'>BASE64ENCODED...</key>
|
|
<key prekey="true" rid='12321'>BASE64ENCODED...</key>
|
|
<!-- ... -->
|
|
<iv>BASE64ENCODED...</iv>
|
|
</header>
|
|
</encrypted>
|
|
</security>
|
|
</content>
|
|
</jingle>
|
|
</iq>]]></example>
|
|
<p>The recipient decrypts the OMEMO KeyTransportElement to retrieve the Transport Secret. Transport Key and Initialization Vector are later used to encrypt/decrypt data as described in &xep0391;.</p>
|
|
</section1>
|
|
<section1 topic='Determining Support' anchor='support'>
|
|
<p>To advertise its support for JET-OMEMO, when replying to service discovery information ("disco#info") requests an entity MUST return URNs for any version of this extension, as well as of the JET extension that the entity supports -- e.g., "urn:xmpp:jingle:jet-omemo:0" for this version, or "urn:xmpp:jingle:jet:0" for &xep0391; &VNOTE;.</p>
|
|
<example caption="Service discovery information request"><![CDATA[
|
|
<iq from='romeo@montague.example/dr4hcr0st3lup4c'
|
|
id='uw72g176'
|
|
to='juliet@capulet.example/yn0cl4bnw0yr3vym'
|
|
type='get'>
|
|
<query xmlns='http://jabber.org/protocol/disco#info'/>
|
|
</iq>]]></example>
|
|
<example caption="Service discovery information response"><![CDATA[
|
|
<iq from='juliet@capulet.example/yn0cl4bnw0yr3vym'
|
|
id='uw72g176'
|
|
to='romeo@montague.example/dr4hcr0st3lup4c'
|
|
type='result'>
|
|
<query xmlns='http://jabber.org/protocol/disco#info'>
|
|
<feature var='urn:xmpp:jingle:jet:0'/>
|
|
<feature var='urn:xmpp:jingle:jet-omemo:0'/>
|
|
</query>
|
|
</iq>]]></example>
|
|
<p>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 &xep0115;. However, if an application has not received entity capabilities information from an entity, it SHOULD use explicit service discovery instead.</p>
|
|
</section1>
|
|
</xep>
|