--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/mod_muc_rtbl/mod_muc_rtbl.lua	Sun Dec 05 18:22:47 2021 +0000
@@ -0,0 +1,49 @@
+local jid = require "util.jid";
+local sha256 = require "util.hashes".sha256;
+local st = require "util.stanza";
+
+local rtbl_service_jid = assert(module:get_option_string("muc_rtbl_jid"), "No RTBL JID supplied");
+local rtbl_node = module:get_option_string("muc_rtbl_node", "muc_bans_sha256");
+
+local banned_hashes = module:shared("banned_hashes");
+
+module:depends("pubsub_subscription");
+
+module:add_item("pubsub-subscription", {
+	service = rtbl_service_jid;
+	node = rtbl_node;
+
+	-- Callbacks:
+	on_subscribed = function()
+		module:log("info", "RTBL active");
+	end;
+
+	on_error = function(err)
+		module:log("error", "Failed to subscribe to RTBL: %s::%s:  %s", err.type, err.condition, err.text);
+	end;
+
+	on_item = function(event)
+		local hash = event.item.attr.id;
+		if not hash then return; end
+		module:log("debug", "Received new hash: %s", hash);
+		banned_hashes[hash] = hash;
+	end;
+
+	on_retract = function (event)
+		local hash = event.item.attr.id;
+		if not hash then return; end
+		module:log("debug", "Retracted hash: %s", hash);
+		banned_hashes[hash] = nil;
+	end;
+});
+
+module:hook("muc-occupant-pre-join", function (event)
+	local from_bare = jid.bare(event.stanza.attr.from);
+	local hash = sha256(jid.bare(event.stanza.attr.from), true);
+	if banned_hashes[hash] then
+		module:log("info", "Blocked user <%s> from room <%s> due to RTBL match", from_bare, event.stanza.attr.to);
+		local error_reply = st.error_reply(event.stanza, "cancel", "forbidden", "You are banned from this service", event.room.jid);
+		event.origin.send(error_reply);
+		return true;
+	end
+end);