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 = require "util.stanza";
local usermanager_set_password = require "core.usermanager".set_password;
local usermanager_delete_user = require "core.usermanager".delete_user;
local nodeprep = require "util.encodings".stringprep.nodeprep;
local jid_bare = require "util.jid".bare;
local compat = module:get_option_boolean("registration_compat", true);
module:add_feature("jabber:iq:register");
-- Password change and account deletion handler
local function handle_registration_stanza(event)
local session, stanza = event.origin, event.stanza;
local log = session.log or module._log;
local query = stanza.tags[1];
if stanza.attr.type == "get" then
local reply = st.reply(stanza);
reply:tag("query", {xmlns = "jabber:iq:register"})
:tag("registered"):up()
:tag("username"):text(session.username):up()
:tag("password"):up();
session.send(reply);
else -- stanza.attr.type == "set"
if query.tags[1] and query.tags[1].name == "remove" then
local username, host = session.username, session.host;
-- This one weird trick sends a reply to this stanza before the user is deleted
local old_session_close = session.close;
session.close = function(self, ...)
self.send(st.reply(stanza));
return old_session_close(self, ...);
end
local ok, err = usermanager_delete_user(username, host);
if not ok then
log("debug", "Removing user account %s@%s failed: %s", username, host, err);
session.close = old_session_close;
session.send(st.error_reply(stanza, "cancel", "service-unavailable", err));
return true;
end
log("info", "User removed their account: %s@%s", username, host);
module:fire_event("user-deregistered", { username = username, host = host, source = "mod_register", session = session });
else
local username = nodeprep(query:get_child_text("username"));
local password = query:get_child_text("password");
if username and password then
if username == session.username then
if usermanager_set_password(username, password, session.host, session.resource) then
session.send(st.reply(stanza));
else
-- TODO unable to write file, file may be locked, etc, what's the correct error?
session.send(st.error_reply(stanza, "wait", "internal-server-error"));
end
else
session.send(st.error_reply(stanza, "modify", "bad-request"));
end
else
session.send(st.error_reply(stanza, "modify", "bad-request"));
end
end
end
return true;
end
module:hook("iq/self/jabber:iq:register:query", handle_registration_stanza);
if compat then
module:hook("iq/host/jabber:iq:register:query", function (event)
local session, stanza = event.origin, event.stanza;
if session.type == "c2s" and jid_bare(stanza.attr.to) == session.host then
return handle_registration_stanza(event);
end
end);
end