-- mod_s2s_auth_dane

--

-- Between the DNS lookup and the chertificate validation, there is a race condition.

-- Solving that probably requires changes to mod_s2s, like using util.async

module:set_global();

local dns_lookup = require"net.adns".lookup;

local hashes = require"util.hashes";

local base64 = require"util.encodings".base64;

local s2sout = module:depends"s2s".route_to_new_session.s2sout;

local _try_connect = s2sout.try_connect

local pat = "%-%-%-%-%-BEGIN ([A-Z ]+)%-%-%-%-%-\r?\n"..

"([0-9A-Za-z=+/\r\n]*)\r?\n%-%-%-%-%-END %1%-%-%-%-%-";

local function pem2der(pem)

	local typ, data = pem:match(pat);

	if typ and data then

		return base64.decode(data), typ;

	end

end

-- TODO Things to test/handle:

-- Negative or bogus answers

-- No SRV records

function s2sout.try_connect(host_session, connect_host, connect_port, err)

	local srv_hosts = host_session.srv_hosts;

	local srv_choice = host_session.srv_choice;

	if srv_hosts and srv_hosts.answer.secure and not srv_hosts[srv_choice].dane then

		dns_lookup(function(answer)

			if answer and #answer > 0 then

				srv_hosts[srv_choice].dane = answer;

				for i, tlsa in ipairs(answer) do

					module:log("debug", "TLSA %s", tostring(tlsa));

				end

			end

		end, ("_%d._tcp.%s"):format(connect_port, connect_host), "TLSA")

	end

	return _try_connect(host_session, connect_host, connect_port, err)

end

module:hook("s2s-check-certificate", function(event)

	local session, cert = event.session, event.cert;

	local srv_hosts = session.srv_hosts;

	local srv_choice = session.srv_choice;

	local choosen = srv_hosts and srv_hosts[srv_choice];

	if choosen and choosen.dane then

		local use, select, match, tlsa, certdata

		for i, rr in ipairs(choosen.dane) do

			tlsa = rr.tlsa

			module:log("debug", "TLSA %s", tostring(tlsa));

			use, select, match, certdata = tlsa.use, tlsa.select, tlsa.match;

			if use == 1 or use == 3 then

				if select == 0 then

					certdata = pem2der(cert:pem());

				elseif select == 1 then

					certdata = pem2der(cert:pubkey());

				end

				if match == 1 then

					certdata = hashes.sha256(certdata);

				elseif match == 2 then

					certdata = hashes.sha512(certdata);

				end

				-- Should we check if the cert subject matches?

				if certdata == tlsa.data then

					(session.log or module._log)("info", "DANE validation successful");

					session.cert_identity_status = "valid"

					if use == 3 then

						session.cert_chain_status = "valid"

						-- for usage 1 the chain has to be valid already

					end

					break;

				end

			else

				module:log("warn", "DANE %s is unsupported", tlsa:getUsage());

				-- TODO Ca checks needs to loop over the chain and stuff

			end

		end

	end

	-- TODO Optionally, if no TLSA record matches, mark connection as untrusted.

end);

function module.unload()

	s2sout.try_connect = _try_connect;

end