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 full_sessions = prosody.full_sessions;
if module:get_host_type() == "local" then
module:hook("iq/full", function(data)
-- IQ to full JID received
local origin, stanza = data.origin, data.stanza;
local session = full_sessions[stanza.attr.to];
if not (session and session.send(stanza)) then
if stanza.attr.type == "get" or stanza.attr.type == "set" then
origin.send(st.error_reply(stanza, "cancel", "service-unavailable"));
end
end
return true;
end);
end
module:hook("iq/bare", function(data)
-- IQ to bare JID received
local stanza = data.stanza;
local type = stanza.attr.type;
-- TODO fire post processing events
if type == "get" or type == "set" then
local child = stanza.tags[1];
local xmlns = child.attr.xmlns or "jabber:client";
local ret = module:fire_event("iq/bare/"..xmlns..":"..child.name, data);
if ret ~= nil then return ret; end
return module:fire_event("iq-"..type.."/bare/"..xmlns..":"..child.name, data);
else
return module:fire_event("iq-"..type.."/bare/"..stanza.attr.id, data);
end
end);
module:hook("iq/self", function(data)
-- IQ to self JID received
local stanza = data.stanza;
local type = stanza.attr.type;
if type == "get" or type == "set" then
local child = stanza.tags[1];
local xmlns = child.attr.xmlns or "jabber:client";
local ret = module:fire_event("iq/self/"..xmlns..":"..child.name, data);
if ret ~= nil then return ret; end
return module:fire_event("iq-"..type.."/self/"..xmlns..":"..child.name, data);
else
return module:fire_event("iq-"..type.."/self/"..stanza.attr.id, data);
end
end);
module:hook("iq/host", function(data)
-- IQ to a local host received
local stanza = data.stanza;
local type = stanza.attr.type;
if type == "get" or type == "set" then
local child = stanza.tags[1];
local xmlns = child.attr.xmlns or "jabber:client";
local ret = module:fire_event("iq/host/"..xmlns..":"..child.name, data);
if ret ~= nil then return ret; end
return module:fire_event("iq-"..type.."/host/"..xmlns..":"..child.name, data);
else
return module:fire_event("iq-"..type.."/host/"..stanza.attr.id, data);
end
end);