This XMPP extension protocol specifies a profile of Pubsub Signing to use OpenPGP for signature.
Signing an item with OpenPGP requires to have OpenPGP for XMPP (XEP-0373) [1] implemented to handle keys, however this specification uses its own <sign/> element because it uses wrapper element from Pubsub Signing XEP, and signed data MUST NOT be included with the signature.
To sign an element, a client process as explained in XEP-0XXX § Signing a Pubsub Item where the "signing profile" element used is a <sign/> element qualified by the 'urn:xmpp:pubsub-signing:openpgp:0' namespace. This element MUST contain a Base64 encoded (RFC 4648 [2] § 4) OpenPGP message as specified in RFC 4880 [3] which MUST contain a detached signature as defined in RFC 4880 [3] § 11.4 of the signed data as specified in XEP-0XXX § Signing a Pubsub Item.
<iq xmlns="jabber:client" from="juliet@capulet.lit/chamber" to="juliet@capulet.lit" id="signature_1" type="set">
<pubsub xmlns="http://jabber.org/protocol/pubsub">
<items node="urn:xmpp:pubsub-attachments:1/xmpp:juliet@capulet.lit?;node=urn%3Axmpp%3Amicroblog%3A0;item=random-thoughts-12bd">
<item id="juliet@capulet.lit">
<attachments xmlns="urn:xmpp:pubsub-attachments:1">
<signature xmlns="urn:xmpp:pubsub-signing:0">
<time stamp="2022-10-16T18:39:03Z"/>
<signer>juliet@capulet.lit</signer>
<sign xmlns="urn:xmpp:pubsub-signing:openpgp:0">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</sign>
</signature>
</attachments>
</item>
</items>
</pubsub>
</iq>
If a client supports the protocol specified in this XEP, it MUST advertise it by including the "urn:xmpp:pubsub-signing:openpgp:0" discovery feature in response to a Service Discovery (XEP-0030) [4] information request:
<iq type='get'
from='juliet@example.org/chamber'
to='romeo@example.org/orchard'
id='disco1'>
<query xmlns='http://jabber.org/protocol/disco#info'/>
</iq>
<iq type='result'
from='romeo@example.org/orchard'
to='juliet@example.org/chamber'
id='disco1'>
<query xmlns='http://jabber.org/protocol/disco#info'>
...
<feature var='urn:xmpp:pubsub-signing:openpgp:0'/>
...
</query>
</iq>Security considerations of OpenPGP for XMPP (XEP-0373) [1] and XEP-0XXX apply.
TODO
TODO
TODO
Thanks to NLnet foundation/NGI0 Discovery for funding.
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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.
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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. XEP-0373: OpenPGP for XMPP <https://xmpp.org/extensions/xep-0373.html>.
2. RFC 4648: The Base16, Base32, and Base64 Data Encodings <http://tools.ietf.org/html/rfc4648>.
3. RFC 4880: OpenPGP Message Format <http://tools.ietf.org/html/rfc4880>.
4. XEP-0030: Service Discovery <https://xmpp.org/extensions/xep-0030.html>.
Note: Older versions of this specification might be available at https://xmpp.org/extensions/attic/
First draft.
@report{poisson2022pss-ox,
title = {Pubsub Signing: OpenPGP Profile},
author = {Poisson, Jérôme},
type = {XEP},
number = {0476},
version = {0.1.0},
institution = {XMPP Standards Foundation},
url = {https://xmpp.org/extensions/xep-0476.html},
date = {2022-10-29/2022-12-20},
}END