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.
local dbg = require "util.debug";
describe("util.debug", function ()
describe("traceback()", function ()
it("works", function ()
local tb = dbg.traceback();
assert.is_string(tb);
end);
end);
describe("get_traceback_table()", function ()
it("works", function ()
local count = 0;
-- MUST stay in sync with the line numbers of these functions:
local f1_defined, f3_defined = 43, 15;
local function f3(f3_param) --luacheck: ignore 212/f3_param
count = count + 1;
for i = 1, 2 do
local tb = dbg.get_traceback_table(i == 1 and coroutine.running() or nil, 0);
assert.is_table(tb);
--print(dbg.traceback(), "\n\n\n", require "util.serialization".serialize(tb, { fatal = false, unquoted = true}));
local found_f1, found_f3;
for _, frame in ipairs(tb) do
if frame.info.linedefined == f1_defined then
assert.equal(0, #frame.locals);
assert.equal("f2", frame.upvalues[1].name);
assert.equal("f1_upvalue", frame.upvalues[2].name);
found_f1 = true;
elseif frame.info.linedefined == f3_defined then
assert.equal("f3_param", frame.locals[1].name);
found_f3 = true;
end
end
assert.is_true(found_f1);
assert.is_true(found_f3);
end
end
local function f2()
local f2_local = "hello";
return f3(f2_local);
end
local f1_upvalue = "upvalue1";
local function f1()
f2(f1_upvalue);
end
-- ok/err are caught and re-thrown so that
-- busted gets to handle them in its own way
local ok, err;
local function hook()
debug.sethook();
ok, err = pcall(f1);
end
-- Test the traceback is correct in various
-- types of caller environments
-- From a Lua hook
debug.sethook(hook, "crl", 1);
local a = string.sub("abcdef", 3, 4);
assert.equal("cd", a);
debug.sethook();
assert.equal(1, count);
if not ok then
error(err);
end
ok, err = nil, nil;
-- From a signal handler (C hook)
require "util.signal".signal("SIGUSR1", hook);
require "util.signal".raise("SIGUSR1");
assert.equal(2, count);
if not ok then
error(err);
end
ok, err = nil, nil;
-- Inside a coroutine
local co = coroutine.create(function ()
hook();
end);
coroutine.resume(co);
if not ok then
error(err);
end
assert.equal(3, count);
end);
end);
end);