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.
#!/usr/bin/env lua
-- 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.
--
-- prosody - main executable for Prosody XMPP server
-- Will be modified by configure script if run --
CFG_SOURCEDIR=CFG_SOURCEDIR or os.getenv("PROSODY_SRCDIR");
CFG_CONFIGDIR=CFG_CONFIGDIR or os.getenv("PROSODY_CFGDIR");
CFG_PLUGINDIR=CFG_PLUGINDIR or os.getenv("PROSODY_PLUGINDIR");
CFG_DATADIR=CFG_DATADIR or os.getenv("PROSODY_DATADIR");
-- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
local function is_relative(path)
local path_sep = package.config:sub(1,1);
return ((path_sep == "/" and path:sub(1,1) ~= "/")
or (path_sep == "\\" and (path:sub(1,1) ~= "/" and path:sub(2,3) ~= ":\\")))
end
-- Tell Lua where to find our libraries
if CFG_SOURCEDIR then
local function filter_relative_paths(path)
if is_relative(path) then return ""; end
end
local function sanitise_paths(paths)
return (paths:gsub("[^;]+;?", filter_relative_paths):gsub(";;+", ";"));
end
package.path = sanitise_paths(CFG_SOURCEDIR.."/?.lua;"..package.path);
package.cpath = sanitise_paths(CFG_SOURCEDIR.."/?.so;"..package.cpath);
end
-- Substitute ~ with path to home directory in data path
if CFG_DATADIR then
if os.getenv("HOME") then
CFG_DATADIR = CFG_DATADIR:gsub("^~", os.getenv("HOME"));
end
end
local startup = require "util.startup";
local async = require "util.async";
-- Note: it's important that this thread is not GC'd, as some C libraries
-- that are initialized here store a pointer to it ( :/ ).
local thread = async.runner();
thread:run(startup.prosody);
local function loop()
-- Error handler for errors that make it this far
local function catch_uncaught_error(err)
if type(err) == "string" and err:match("interrupted!$") then
return "quitting";
end
prosody.log("error", "Top-level error, please report:\n%s", tostring(err));
local traceback = debug.traceback("", 2);
if traceback then
prosody.log("error", "%s", traceback);
end
prosody.events.fire_event("very-bad-error", {error = err, traceback = traceback});
end
local sleep = require"socket".sleep;
local server = require "net.server";
while select(2, xpcall(server.loop, catch_uncaught_error)) ~= "quitting" do
sleep(0.2);
end
end
local function cleanup()
prosody.log("info", "Shutdown status: Cleaning up");
prosody.events.fire_event("server-cleanup");
end
loop();
prosody.log("info", "Shutting down...");
cleanup();
prosody.events.fire_event("server-stopped");
prosody.log("info", "Shutdown complete");
os.exit(prosody.shutdown_code);