util.xml: Do not allow doctypes, comments or processing instructions
Yes. This is as bad as it sounds. CVE pending.
In Prosody itself, this only affects mod_websocket, which uses util.xml
to parse the <open/> frame, thus allowing unauthenticated remote DoS
using Billion Laughs. However, third-party modules using util.xml may
also be affected by this.
This commit installs handlers which disallow the use of doctype
declarations and processing instructions without any escape hatch. It,
by default, also introduces such a handler for comments, however, there
is a way to enable comments nontheless.
This is because util.xml is used to parse human-facing data, where
comments are generally a desirable feature, and also because comments
are generally harmless.
-- Prosody IM
-- Copyright (C) 2008-2010 Matthew Wild
-- Copyright (C) 2008-2010 Waqas Hussain
--
-- This project is MIT/X11 licensed. Please see the
-- COPYING file in the source package for more information.
--
local st, jid = require "util.stanza", require "util.jid";
local hosts = prosody.hosts;
local is_admin = require "core.usermanager".is_admin;
function send_to_online(message, host)
local sessions;
if host then
sessions = { [host] = hosts[host] };
else
sessions = hosts;
end
local c = 0;
for hostname, host_session in pairs(sessions) do
if host_session.sessions then
message.attr.from = hostname;
for username in pairs(host_session.sessions) do
c = c + 1;
message.attr.to = username.."@"..hostname;
module:send(message);
end
end
end
return c;
end
-- Old <message>-based jabberd-style announcement sending
function handle_announcement(event)
local stanza = event.stanza;
local node, host, resource = jid.split(stanza.attr.to);
if resource ~= "announce/online" then
return; -- Not an announcement
end
if not is_admin(stanza.attr.from, host) then
-- Not an admin? Not allowed!
module:log("warn", "Non-admin '%s' tried to send server announcement", stanza.attr.from);
return;
end
module:log("info", "Sending server announcement to all online users");
local message = st.clone(stanza);
message.attr.type = "headline";
message.attr.from = host;
local c = send_to_online(message, host);
module:log("info", "Announcement sent to %d online users", c);
return true;
end
module:hook("message/host", handle_announcement);
-- Ad-hoc command (XEP-0133)
local dataforms_new = require "util.dataforms".new;
local announce_layout = dataforms_new{
title = "Making an Announcement";
instructions = "Fill out this form to make an announcement to all\nactive users of this service.";
{ name = "FORM_TYPE", type = "hidden", value = "http://jabber.org/protocol/admin" };
{ name = "subject", type = "text-single", label = "Subject" };
{ name = "announcement", type = "text-multi", required = true, label = "Announcement" };
};
function announce_handler(_, data, state)
if state then
if data.action == "cancel" then
return { status = "canceled" };
end
local fields = announce_layout:data(data.form);
module:log("info", "Sending server announcement to all online users");
local message = st.message({type = "headline"}, fields.announcement):up()
:tag("subject"):text(fields.subject or "Announcement");
local count = send_to_online(message, data.to);
module:log("info", "Announcement sent to %d online users", count);
return { status = "completed", info = ("Announcement sent to %d online users"):format(count) };
else
return { status = "executing", actions = {"next", "complete", default = "complete"}, form = announce_layout }, "executing";
end
end
module:depends "adhoc";
local adhoc_new = module:require "adhoc".new;
local announce_desc = adhoc_new("Send Announcement to Online Users", "http://jabber.org/protocol/admin#announce", announce_handler, "admin");
module:provides("adhoc", announce_desc);