mirror of
https://github.com/moparisthebest/xeps
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125 lines
4.8 KiB
XML
125 lines
4.8 KiB
XML
<?xml version='1.0' encoding='UTF-8'?>
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<!DOCTYPE xep SYSTEM 'xep.dtd' [
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<!ENTITY rfc5056 "<span class='ref'><link url='http://tools.ietf.org/html/rfc5056'>RFC 5056</link></span> <note>RFC 5056: On the Use of Channel Bindings to Secure Channels <<link url='http://tools.ietf.org/html/rfc5056'>http://tools.ietf.org/html/rfc5056</link>>.</note>" >
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<!ENTITY iana-cb-types "<span class='ref'><link url='https://www.iana.org/assignments/channel-binding-types/channel-binding-types.xhtml'>IANA Channel-Binding Types Registry</link></span> <note>IANA Channel-Binding Types Registry <<link url='https://www.iana.org/assignments/channel-binding-types/channel-binding-types.xhtml'>https://www.iana.org/assignments/channel-binding-types/channel-binding-types.xhtml</link>>.</note>" >
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<!ENTITY % ents SYSTEM 'xep.ent'>
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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>SASL Channel-Binding Type Capability</title>
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<abstract>This specification allows servers to annouce their supported SASL channel-binding types to clients.</abstract>
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&LEGALNOTICE;
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<number>0440</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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</dependencies>
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<supersedes/>
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<supersededby/>
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<shortname>sasl-cb-types</shortname>
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&flow;
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<revision>
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<version>0.1.0</version>
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<date>2020-06-14</date>
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<initials>XEP Editor (jsc)</initials>
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<remark>Accepted by vote of Council on 2020-05-27.</remark>
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</revision>
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<revision>
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<version>0.0.1</version>
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<date>2020-05-20</date>
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<initials>fs</initials>
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<remark><p>First draft.</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>SASL channel-binding is a technique to increase the security of
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connections (&rfc5056;). Unfortunately, the SASL profile specified
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in &rfc6120; lacks a method for the server to announce its supported
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channel-binding types. This hinders the adoption of channel-binding,
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especially since the error protocol to execute after a client
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requested a channel-binding type unsupported by the server is
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basically unspecified.</p>
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<p>The extension defined herein fills the gap left by &rfc6120;, by
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allowing the server the announce its supported channel-binding
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types.</p>
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</section1>
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<section1 topic='Announcing the SASL Channel-Binding Type Capability' anchor='sasl-cb-type'>
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<p>This protocol consists of a single optional extension element
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named 'sasl-channel-binding' qualified by the 'urn:xmpp:sasl-cb:0'
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namespace. The 'sasl-channel-binding' element MUST contain one or
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more 'channel-binding' elements, of which each MUST have an
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attribute with the name 'type'. The value of the 'type' attribute
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SHOULD be the "Channel-binding unique prefix" of a channel-binding
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type which was registered with the &iana-cb-types;.</p>
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<p>A server declares that it supports particular channel-binding
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types by listing the supported types via the 'sasl-channel-binding'
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element defined herein. The 'sasl-channel-binding' element could
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appear as child element to the SASL <mechanisms/>
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stream-feature element, qualified by the
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'urn:ietf:params:xml:ns:xmpp-sasl' namespace, as specified in
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&rfc6120;. Another potential appearance of
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<sasl-channel-binding> is as child element of the
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<mechanisms/> stream-feature element as specified in the
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&xep0388;.</p>
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<example caption='Example <mechanisms/> stream feature with SASL Channel-Binding Type Capability.'><![CDATA[
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<stream:features>
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<mechanisms xmlns='urn:ietf:params:xml:ns:xmpp-sasl'>
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<mechanism>EXTERNAL</mechanism>
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<mechanism>SCRAM-SHA-1-PLUS</mechanism>
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<mechanism>PLAIN</mechanism>
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<sasl-channel-binding xmlns='urn:xmpp:sasl-cb:0'>
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<channel-binding type='tls-server-end-point'/>
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<channel-binding type='tls-exporter'/>
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</sasl-channel-binding>
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</mechanisms>
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</stream:features>]]></example>
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</section1>
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<section1 topic='Security Considerations' anchor='security'>
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<p>The author belives that this document itself does not yield any
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new security considerations.<note>Hopefully somebody will correct him, in
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case he is wrong.</note></p>
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</section1>
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<section1 topic='IANA Considerations' anchor='iana'>
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<p>This document requires no interaction with &IANA;.</p>
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</section1>
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<section1 topic='XMPP Registrar Considerations' anchor='registrar'>
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<p>This document requires no interaction with the XMPP registrar.</p>
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</section1>
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<section1 topic='XML Schema' anchor='schema'>
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<p>TODO: Add if the XEP is scheduled for the state after 'experimental'.</p>
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</section1>
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<section1 topic='Acknowledgements' anchor='acknowledgements'>
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<p>Thanks to Sam Whited for the discussion about the underlying
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issue and incentivizing me to come up with this extension.</p>
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</section1>
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</xep>
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