-- Copyright (C) 2013 Kim Alvefur

--

-- This file is MIT/X11 licensed.

local jid_compare = require "util.jid".compare;

local jid_split = require "util.jid".prepped_split;

local new_sasl = require "util.sasl".new;

local log = module._log;

local subject_alternative_name = "2.5.29.17";

local id_on_xmppAddr = "1.3.6.1.5.5.7.8.5";

local cert_match = module:get_option("certificate_match", "xmppaddr");

local username_extractor = {};

function username_extractor.xmppaddr(cert, authz, session)

	local extensions = cert:extensions();

	local SANs = extensions[subject_alternative_name];

	local xmppAddrs = SANs and SANs[id_on_xmppAddr];

	if not xmppAddrs then

		(session.log or log)("warn", "Client certificate contains no xmppAddrs");

		return nil, false;

	end

	for i=1,#xmppAddrs do

		if authz == "" or jid_compare(authz, xmppAddrs[i]) then

			(session.log or log)("debug", "xmppAddrs[%d] %q matches authz %q", i, xmppAddrs[i], authz)

			local username, host = jid_split(xmppAddrs[i]);

			if host == module.host then

				return username, true

			end

		end

	end

end

function username_extractor.email(cert)

	local subject = cert:subject();

	for i=1,#subject do

		local ava = subject[i];

		if ava.oid == oid_emailAddress then

			local username, host = jid_split(ava.value);

			if host == module.host then

				return username, true

			end

		end

	end

end

local find_username = username_extractor[cert_match];

if not find_username then

	module:log("error", "certificate_match = %q is not supported");

	return

end

function get_sasl_handler(session)

	return new_sasl(module.host, {

		external = session.secure and function(authz)

			if not session.secure then

				-- getpeercertificate() on a TCP connection would be bad, abort!

				(session.log or log)("error", "How did you manage to select EXTERNAL without TLS?");

				return nil, false;

			end

			local sock = session.conn:socket();

			local cert = sock:getpeercertificate();

			if not cert then

				(session.log or log)("warn", "No certificate provided");

				return nil, false;

			end

			if not cert:validat(now()) then

				(session.log or log)("warn", "Client certificate expired")

				return nil, "expired";

			end

			local chain_valid, chain_errors = sock:getpeerverification();

			if not chain_valid then

				(session.log or log)("warn", "Invalid client certificate chain");

				for i, error in ipairs(chain_errors) do

					(session.log or log)("warn", "%d: %s", i, table.concat(chain_errors, ", "));

				end

				return nil, false;

			end

			return find_username(cert, authz, session);

		end

	});

end

module:provides "auth";