-- mod_s2s_auth_dane
-- Copyright (C) 2013-2014 Kim Alvefur
--
-- This file is MIT/X11 licensed.
--
-- Could be done much cleaner if mod_s2s was 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 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
-- No encryption offered
-- This function is called when a new SRV target has been picked
-- the original function does A/AAAA resolution before continuing
local _try_connect = s2sout.try_connect;
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
srv_hosts[srv_choice].dane = dns_lookup(function(answer)
if answer and ( #answer > 0 or answer.bogus ) then
srv_hosts[srv_choice].dane = answer;
for i, tlsa in ipairs(answer) do
module:log("debug", "TLSA %s", tostring(tlsa));
end
else
srv_hosts[srv_choice].dane = false;
end
-- "blocking" until TLSA reply, but no race condition
return _try_connect(host_session, connect_host, connect_port, err);
end, ("_%d._tcp.%s"):format(connect_port, connect_host), "TLSA");
return true
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, match_found;
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;
-- PKIX-EE or DANE-EE
if use == 1 or use == 3 then
if select == 0 then
certdata = pem2der(cert:pem());
elseif select == 1 and cert.pubkey then
certdata = pem2der(cert:pubkey());
else
module:log("warn", "DANE selector %d is unsupported", select);
end
if match == 1 then
certdata = hashes.sha256(certdata);
elseif match == 2 then
certdata = hashes.sha512(certdata);
elseif match ~= 0 then
module:log("warn", "DANE match rule %d is unsupported", match);
certdata = nil;
end
-- Should we check if the cert subject matches?
if certdata and certdata == tlsa.data then
(session.log or module._log)("info", "DANE validation successful");
session.cert_identity_status = "valid";
if use == 3 then -- DANE-EE, chain status equals DNSSEC chain status
session.cert_chain_status = "valid";
-- for usage 1, PKIX-EE, the chain has to be valid already
end
match_found = true;
break;
end
else
module:log("warn", "DANE %s is unsupported", tlsa:getUsage() or ("usage "..tostring(use)));
-- TODO CA checks needs to loop over the chain and stuff
end
end
if not match_found then
-- No TLSA matched or response was bogus
(session.log or module._log)("warn", "DANE validation failed");
session.cert_identity_status = "invalid";
session.cert_chain_status = "invalid";
end
end
end);
function module.add_host(module)
module:hook("s2s-authenticated", function(event)
local session = event.session;
local srv_hosts = session.srv_hosts;
local srv_choice = session.srv_choice;
if srv_hosts[srv_choice].dane and not session.secure then
-- TLSA record but no TLS, not ok.
-- TODO Optional?
session:close({
condition = "policy-violation",
text = "Encrypted server-to-server communication is required but was not "
..((session.direction == "outgoing" and "offered") or "used")
});
return false;
end
end);
end
function module.unload()
-- Restore the original try_connect function
s2sout.try_connect = _try_connect;
end