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) 2008-2011 Florian Zeitz
--
-- This project is MIT/X11 licensed. Please see the
-- COPYING file in the source package for more information.
--
-- luacheck: ignore 113/setfenv 113/loadstring
local load, loadstring, setfenv = load, loadstring, setfenv;
local io_open = io.open;
local envload;
local envloadfile;
if setfenv then
function envload(code, source, env)
local f, err = loadstring(code, source);
if f and env then setfenv(f, env); end
return f, err;
end
function envloadfile(file, env)
local fh, err, errno = io_open(file);
if not fh then return fh, err, errno; end
local f, err = load(function () return fh:read(2048); end, "@"..file);
fh:close();
if f and env then setfenv(f, env); end
return f, err;
end
else
function envload(code, source, env)
return load(code, source, nil, env);
end
function envloadfile(file, env)
local fh, err, errno = io_open(file);
if not fh then return fh, err, errno; end
local f, err = load(fh:lines(2048), "@"..file, nil, env);
fh:close();
return f, err;
end
end
return { envload = envload, envloadfile = envloadfile };