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 serialization = require "util.serialization";
describe("util.serialization", function ()
describe("serialize", function ()
it("makes a string", function ()
assert.is_string(serialization.serialize({}));
assert.is_string(serialization.serialize(nil));
assert.is_string(serialization.serialize(1));
assert.is_string(serialization.serialize(true));
end);
it("rejects function by default", function ()
assert.has_error(function ()
serialization.serialize(function () end)
end);
end);
it("makes a string in debug mode", function ()
assert.is_string(serialization.serialize(function () end, "debug"));
end);
it("rejects cycles", function ()
assert.has_error(function ()
local t = {}
t[t] = { t };
serialization.serialize(t)
end);
-- also with multirefs allowed
assert.has_error(function ()
local t = {}
t[t] = { t };
serialization.serialize(t, { multirefs = true })
end);
end);
it("rejects multiple references to same table", function ()
assert.has_error(function ()
local t1 = {};
local t2 = { t1, t1 };
serialization.serialize(t2, { multirefs = false });
end);
end);
it("optionally allows multiple references to same table", function ()
assert.has_error(function ()
local t1 = {};
local t2 = { t1, t1 };
serialization.serialize(t2, { multirefs = true });
end);
end);
it("roundtrips", function ()
local function test(data)
local serialized = serialization.serialize(data);
assert.is_string(serialized);
local deserialized, err = serialization.deserialize(serialized);
assert.same(data, deserialized, err);
end
test({});
test({hello="world"});
test("foobar")
test("\0\1\2\3");
test("nödåtgärd");
test({1,2,3,4});
test({foo={[100]={{"bar"},{baz=1}}}});
test({["goto"] = {["function"]={["do"]="keywords"}}});
end);
it("can serialize with metatables", function ()
local s = serialization.new({ freeze = true });
local t = setmetatable({ a = "hi" }, { __freeze = function (t) return { t.a } end });
local rt = serialization.deserialize(s(t));
assert.same({"hi"}, rt);
end);
end);
end);