-- Copyright (C) 2013 Kim Alvefur

-- This file is MIT/X11 licensed.

--

-- Implements Secure Delegation using DNS SRV as described in

-- http://tools.ietf.org/html/draft-miller-xmpp-dnssec-prooftype

--

-- Dependecies:

-- Prosody above hg:43059357b2f0

-- DNSSEC-validating DNS resolver

--  https://github.com/Zash/luaunbound

--   libunbound binding using LuaJIT FFI

module:set_global();

local nameprep = require"util.encodings".stringprep.nameprep;

local to_unicode = require"util.encodings".idna.to_unicode;

local to_ascii = require "util.encodings".idna.to_ascii;

local cert_verify_identity = require "util.x509".verify_identity;

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

local t_insert = table.insert;

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

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

	if session.cert_chain_status == "valid" and session.cert_identity_status ~= "valid"

	and session.srv_hosts.answer and session.srv_hosts.answer.secure then

		local srv_hosts, srv_choice, srv_target = session.srv_hosts, session.srv_choice;

		for i = srv_choice or 1, srv_choice or #srv_hosts do

			srv_target = nameprep(to_unicode(session.srv_hosts[i].target:gsub("%.?$","")));

			(session.log or module._log)("debug", "Comparing certificate with Secure SRV target %s", srv_target);

			if srv_target and cert_verify_identity(srv_target, "xmpp-server", cert) then

				(session.log or module._log)("info", "Certificate matches Secure SRV target %s", srv_target);

				session.cert_identity_status = "valid";

				return;

			end

		end

	end

end);

function module.add_host(module)

	module:hook("s2s-stream-features", function(event)

		local host_session = event.origin;

		if not name then return end

		dns_lookup(function (answer)

			if host_session.dane ~= nil then return end

			if not answer.secure or #answer == 1

				and answer[1].srv.target == "." then return end

			local srv_hosts = { answer = answer };

			for _, record in ipairs(answer) do

				t_insert(srv_hosts, record.srv);

			end

			host_session.srv_hosts = srv_hosts;

		end, "_xmpp-server._tcp."..name..".", "SRV");

	end);

end