prosody: Add module to expose stable client id across sessions

ansible/files/prosody.cfg.lua

@@ -75,6 +75,7 @@ modules_enabled = {
 		"update_notify";
 		"turncredentials";
 		"admin_shell";
+		"snikket_client_id";
 
 	-- Spam/abuse management
 		"spam_reporting"; -- Allow users to report spam/abuse

ansible/tasks/prosody.yml

@@ -131,6 +131,7 @@
     - mod_update_notify
     - mod_invites_default_group
     - mod_invites_bootstrap
+    - mod_snikket_client_id
 
 - name: "Install lua-ossl for encrypted push notifications"
   apt:

snikket-modules/mod_snikket_client_id/mod_snikket_client_id.lua

@@ -0,0 +1,13 @@
+-- This module assigns a client_id to sessions if they are using a "Snikket.*"
+-- resource identifier. We assume that a resource string in this format is
+-- static for the same client instance across every session.
+--
+-- In the future it is anticipated that this "hack" will be replaced by SASL 2
+-- (XEP-0388) and/or Bind 2 (XEP-0386), however this is not yet implemented in
+-- Prosody or any clients.
+
+module:hook("resource-bind", function (event)
+	local id = event.session.resource:match("^Snikket%..+$");
+	if not id then return; end
+	event.session.client_id = id;
+end, 1000);