--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/mod_block_registrations/mod_block_registrations.lua	Thu Jun 06 15:52:36 2013 +0100
@@ -0,0 +1,34 @@
+local st = require "util.stanza";
+local nodeprep = require "util.encodings".stringprep.nodeprep;
+
+local block_users = module:get_option_set("block_registrations_users", { "admin" });
+local block_patterns = module:get_option_set("block_registrations_matching", {});
+local require_pattern = module:get_option_string("block_registrations_require");
+
+function is_blocked(username)
+        -- Check if the username is simply blocked
+        if block_users:contains(username) then return true; end
+
+        for pattern in block_patterns do
+                if username:match(pattern) then
+                        return true;
+                end
+        end
+        -- Not blocked, but check that username matches allowed pattern
+        if require_pattern and not username:match(require_pattern) then
+                return true;
+        end
+end
+
+module:hook("stanza/iq/jabber:iq:register:query", function(event)
+        local session, stanza = event.origin, event.stanza;
+
+        if stanza.attr.type == "set" then
+                local query = stanza.tags[1];
+                local username = nodeprep(query:get_child_text("username"));
+                if username and is_blocked(username) then
+                        session.send(st.error_reply(stanza, "modify", "policy-violation", "Username is blocked"));
+                        return true;
+                end
+        end
+end, 10);