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.

-- luacheck: ignore 212

local driver = {};
local driver_mt = { __index = driver };

function driver:open(store, typ)
	if typ and typ ~= "keyval" and typ ~= "archive" then
		return nil, "unsupported-store";
	end
	return setmetatable({ store = store, type = typ }, driver_mt);
end
function driver:get(user)
	return {};
end

function driver:set(user, data)
	return nil, "Storage disabled";
end

function driver:stores(username)
	return { "roster" };
end

function driver:purge(user)
	return true;
end

function driver:append()
	return nil, "Storage disabled";
end

function driver:find()
	return function () end, 0;
end

function driver:delete()
	return true;
end

module:provides("storage", driver);