4 files changed, 113 insertions, 0 deletions
diff --git a/slixmpp/plugins/xep_0421/__init__.py b/slixmpp/plugins/xep_0421/__init__.py
new file mode 100644
index 00000000..4595ffad
--- /dev/null
+++ b/slixmpp/plugins/xep_0421/__init__.py
@@ -0,0 +1,13 @@
+"""
+    Slixmpp: The Slick XMPP Library
+    Copyright (C) 2020 "Maxime “pep” Buquet <pep@bouah.net>"
+    This file is part of Slixmpp.
+
+    See the file LICENSE for copying permission.
+"""
+
+from slixmpp.plugins.base import register_plugin
+from slixmpp.plugins.xep_0421.stanza import OccupantId
+from slixmpp.plugins.xep_0421.occupant_id import XEP_0421
+
+register_plugin(XEP_0421)
diff --git a/slixmpp/plugins/xep_0421/occupant_id.py b/slixmpp/plugins/xep_0421/occupant_id.py
new file mode 100644
index 00000000..116bf2d9
--- /dev/null
+++ b/slixmpp/plugins/xep_0421/occupant_id.py
@@ -0,0 +1,31 @@
+"""
+    Slixmpp: The Slick XMPP Library
+    Copyright (C) 2020 "Maxime “pep” Buquet <pep@bouah.net>"
+    This file is part of Slixmpp.
+
+    See the file LICENSE for copying permission.
+"""
+
+from slixmpp import JID, Message
+from slixmpp.plugins import BasePlugin
+from slixmpp.xmlstream import register_stanza_plugin
+from slixmpp.plugins.xep_0421 import stanza
+from slixmpp.plugins.xep_0421.stanza import OccupantId
+
+
+class XEP_0421(BasePlugin):
+    '''XEP-0421: Anonymous unique occupant identifiers for MUCs'''
+
+    name = 'xep_0421'
+    description = 'Anonymous unique occupant identifiers for MUCs'
+    dependencies = {'xep_0030', 'xep_0045'}
+    stanza = stanza
+    namespace = stanza.NS
+
+    def plugin_init(self) -> None:
+        # XXX: This should be MucMessage. Someday..
+        register_stanza_plugin(Message, OccupantId)
+
+    async def has_feature(self, jid: JID) -> bool:
+        info = await self.xmpp['xep_0030'].get_info(jid)
+        return self.namespace in info.get_features()
diff --git a/slixmpp/plugins/xep_0421/stanza.py b/slixmpp/plugins/xep_0421/stanza.py
new file mode 100644
index 00000000..0cb93959
--- /dev/null
+++ b/slixmpp/plugins/xep_0421/stanza.py
@@ -0,0 +1,40 @@
+"""
+    Slixmpp: The Slick XMPP Library
+    Copyright (C) 2020 "Maxime “pep” Buquet <pep@bouah.net>"
+    This file is part of Slixmpp.
+
+    See the file LICENSE for copying permission.
+"""
+
+from slixmpp.xmlstream import ElementBase
+
+
+NS = 'urn:xmpp:occupant-id:0'
+
+
+class OccupantId(ElementBase):
+    '''
+    An Occupant-id tag.
+
+    An <occupant-id/> tag is set by the MUC.
+
+    This is useful in semi-anon MUCs (and MUC-PMs) as a stable identifier to
+    prevent the usual races with nicknames.
+
+    Without occupant-id, getting the following messages from MUC history would
+    prevent a client from asserting senders are the same entity:
+
+    <message type='groupchat' from='foo@muc/nick1' id='message1'>
+        <body>Some message</body>
+        <occupant-id xmlns='urn:xmpp:occupant-id:0' id='unique-opaque-id1'/>
+    </message>
+    <message type='groupchat' from='foo@muc/nick2' id='message2'>
+        <body>Some correction</body>
+        <occupant-id xmlns='urn:xmpp:occupant-id:0' id='unique-opaque-id1'/>
+        <replace xmlns='urn:xmpp:message-correct:0' id='message1'/>
+    </message>
+    '''
+
+    name = 'occupant-id'
+    namespace = NS
+    interface = {'id'}
diff --git a/tests/test_stanza_xep_0421.py b/tests/test_stanza_xep_0421.py
new file mode 100644
index 00000000..dbd7a592
--- /dev/null
+++ b/tests/test_stanza_xep_0421.py
@@ -0,0 +1,29 @@
+import unittest
+from slixmpp import JID, Message
+from slixmpp.test import SlixTest
+import slixmpp.plugins.xep_0421 as xep_0421
+from slixmpp.xmlstream import register_stanza_plugin
+
+
+class TestOccupantId(SlixTest):
+
+    def setUp(self):
+        register_stanza_plugin(Message, xep_0421.stanza.OccupantId)
+
+    def testReadOccupantId(self):
+        result = """
+          <message type='groupchat' from='foo@muc/nick1'>
+            <body>Some message</body>
+            <occupant-id xmlns='urn:xmpp:occupant-id:0' id='unique-id1'/>
+          </message>
+        """
+
+        msg = self.Message()
+        msg['type'] = 'groupchat'
+        msg['from'] = JID('foo@muc/nick1')
+        msg['body'] = 'Some message'
+        msg['occupant-id']['id'] = 'unique-id1'
+
+        self.check(msg, result)
+
+suite = unittest.TestLoader().loadTestsFromTestCase(TestOccupantId)