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mod_s2s_auth_dane/mod_s2s_auth_dane.lua @ 5314:7c123d3285de
mod_client_management: README: Update docs to detail shell and XMPP interfaces
author | Matthew Wild <mwild1@gmail.com> |
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date | Thu, 06 Apr 2023 19:31:29 +0100 |
parent | 4491:35381608d323 |
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-- mod_s2s_auth_dane -- Copyright (C) 2013-2014 Kim Alvefur -- -- This file is MIT/X11 licensed. -- -- Implements DANE and Secure Delegation using DNS SRV as described in -- http://tools.ietf.org/html/draft-miller-xmpp-dnssec-prooftype -- -- Known issues: -- Could be done much cleaner if mod_s2s was using util.async -- -- TODO Things to test/handle: -- Negative or bogus answers -- No encryption offered -- Different hostname before and after STARTTLS - mod_s2s should complain -- Interaction with Dialback -- -- luacheck: ignore module module:set_global(); local have_async, async = pcall(require, "util.async"); local noop = function () end local unpack = table.unpack or _G.unpack; local type = type; local t_insert = table.insert; local set = require"util.set"; local dns_lookup = require"net.adns".lookup; local hashes = require"util.hashes"; local base64 = require"util.encodings".base64; local idna_to_ascii = require "util.encodings".idna.to_ascii; local idna_to_unicode = require"util.encodings".idna.to_unicode; local nameprep = require"util.encodings".stringprep.nameprep; local cert_verify_identity = require "util.x509".verify_identity; do local net_dns = require"net.dns"; if not net_dns.types or not net_dns.types[52] then module:log("error", "No TLSA support available, DANE will not be supported"); return end end 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 local use_map = { ["DANE-EE"] = 3; ["DANE-TA"] = 2; ["PKIX-EE"] = 1; ["PKIX-CA"] = 0 } local implemented_uses = set.new { "DANE-EE", "PKIX-EE" }; do local cert_mt = debug.getregistry()["SSL:Certificate"]; if cert_mt and cert_mt.__index.issued then -- Need cert:issued() for these implemented_uses:add("DANE-TA"); implemented_uses:add("PKIX-CA"); else module:log("debug", "The cert:issued() method is unavailable, DANE-TA and PKIX-CA can't be enabled"); end if not cert_mt.__index.pubkey then module:log("debug", "The cert:pubkey() method is unavailable, the SPKI usage can't be supported"); end end local configured_uses = module:get_option_set("dane_uses", { "DANE-EE", "DANE-TA" }); local enabled_uses = set.intersection(implemented_uses, configured_uses) / function(use) return use_map[use] end; local unsupported = configured_uses - implemented_uses; if not unsupported:empty() then module:log("warn", "Unable to support DANE uses %s", tostring(unsupported)); end -- Find applicable TLSA records -- Takes a s2sin/out and a callback local function dane_lookup(host_session, cb) cb = cb or noop; local log = host_session.log or module._log; if host_session.dane ~= nil then return end -- Has already done a lookup if host_session.direction == "incoming" then if not host_session.from_host then log("debug", "Session doesn't have a 'from' host set"); return; end -- We don't know what hostname or port to use for Incoming connections -- so we do a SRV lookup and then request TLSA records for each SRV -- Most servers will probably use the same certificate on outgoing -- and incoming connections, so this should work well local name = host_session.from_host and idna_to_ascii(host_session.from_host); if not name then log("warn", "Could not convert '%s' to ASCII for DNS lookup", tostring(host_session.from_host)); return; end log("debug", "Querying SRV records from _xmpp-server._tcp.%s.", name); host_session.dane = dns_lookup(function (answer, err) host_session.dane = false; -- Mark that we already did the lookup if not answer then log("debug", "Resolver error: %s", tostring(err)); return cb(host_session); end if answer.bogus then log("warn", "Results are bogus!"); -- Bad sign, probably not a good idea to do any fallback here host_session.dane = answer; elseif not answer.secure then log("debug", "Results are not secure"); return cb(host_session); end local n = answer.n or #answer; if n == 0 then -- No SRV records, synthesize fallback host and port -- this may behave oddly for connections in the other direction if -- mod_s2s doesn't keep the answer around answer[1] = { srv = { target = name, port = 5269 } }; n = 1; elseif n == 1 and answer[1].srv.target == '.' then return cb(host_session); -- No service ... This shouldn't happen? end local srv_hosts = { answer = answer }; host_session.srv_hosts = srv_hosts; local dane; for _, record in ipairs(answer) do t_insert(srv_hosts, record.srv); log("debug", "Querying TLSA record for %s:%d", record.srv.target, record.srv.port); dns_lookup(function(dane_answer) log("debug", "Got answer for %s:%d", record.srv.target, record.srv.port); n = n - 1; -- There are three kinds of answers -- Insecure, Secure and Bogus -- -- We collect Secure answers for later use -- -- Insecure (legacy) answers are simply ignored -- -- If we get a Bogus (dnssec error) reply, keep the -- status around. If there were only bogus replies, the -- connection will be aborted. If there were at least -- one non-Bogus reply, we proceed. If none of the -- replies matched, we consider the connection insecure. if (dane_answer.bogus or dane_answer.secure) and not dane then -- The first answer we care about -- For services with only one SRV record, this will be the only one log("debug", "First secure (or bogus) TLSA") dane = dane_answer; elseif dane_answer.bogus then log("debug", "Got additional bogus TLSA") dane.bogus = dane_answer.bogus; elseif dane_answer.secure then log("debug", "Got additional secure TLSA") for _, dane_record in ipairs(dane_answer) do t_insert(dane, dane_record); end end if n == 0 then if dane then host_session.dane = dane; if #dane > 0 and dane.bogus then -- Got at least one non-bogus reply, -- This should trigger a failure if one of them did not match log("warn", "Ignoring bogus replies"); dane.bogus = nil; end if #dane == 0 and dane.bogus == nil then -- Got no usable data host_session.dane = false; end end return cb(host_session); end end, ("_%d._tcp.%s."):format(record.srv.port, record.srv.target), "TLSA"); end end, "_xmpp-server._tcp."..name..".", "SRV"); return true; elseif host_session.direction == "outgoing" then -- Prosody has already done SRV lookups for outgoing session, so check if those are secure local srv_hosts = host_session.srv_hosts; if not ( srv_hosts and srv_hosts.answer and srv_hosts.answer.secure ) then return; -- No secure SRV records, fall back to non-DANE mode -- Empty response were not kept by older mod_s2s/s2sout end -- Do TLSA lookup for currently selected SRV record local srv_choice = srv_hosts[host_session.srv_choice or 0] or { target = idna_to_ascii(host_session.to_host), port = 5269 }; log("debug", "Querying TLSA record for %s:%d", srv_choice.target, srv_choice.port); host_session.dane = dns_lookup(function(answer) if answer and ((answer.secure and #answer > 0) or answer.bogus) then srv_choice.dane = answer; else srv_choice.dane = false; end host_session.dane = srv_choice.dane; return cb(host_session); end, ("_%d._tcp.%s."):format(srv_choice.port, srv_choice.target), "TLSA"); return true; end end local function pause(host_session) host_session.log("debug", "Pausing connection until DANE lookup is completed"); host_session.conn:pause() end local function resume(host_session) host_session.log("debug", "DANE lookup completed, resuming connection"); host_session.conn:resume() end if have_async then function pause(host_session) host_session.log("debug", "Pausing connection until DANE lookup is completed"); local wait, done = async.waiter(); host_session._done_waiting_for_dane = done; wait(); end local function _resume(_, host_session) if host_session._done_waiting_for_dane then host_session.log("debug", "DANE lookup completed, resuming connection"); host_session._done_waiting_for_dane(); host_session._done_waiting_for_dane = nil; end end function resume(host_session) -- Something about the way luaunbound calls callbacks is messed up if host_session._done_waiting_for_dane then module:add_timer(0, _resume, host_session); end end end local new_dane = module:get_option_boolean("use_dane", false); function module.add_host(module) local function on_new_s2s(event) local host_session = event.origin; if host_session.type == "s2sout" or host_session.type == "s2sin" then return; -- Already authenticated end if host_session.dane ~= nil then return; -- Already done DANE lookup end dane_lookup(host_session, resume); -- Let it run in parallel until we need to check the cert end if not new_dane then -- New outgoing connections module:hook("stanza/http://etherx.jabber.org/streams:features", on_new_s2s, 501); module:hook("s2sout-authenticate-legacy", on_new_s2s, 200); end -- New incoming connections module:hook("s2s-stream-features", on_new_s2s, 10); module:hook("s2s-authenticated", function(event) local session = event.session; if session.dane and type(session.dane) == "table" and next(session.dane) ~= nil and not session.secure then -- TLSA record but no TLS, not ok. -- TODO Optional? -- Bogus replies should trigger this path -- How does this interact with Dialback? 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 -- Cleanup session.srv_hosts = nil; end); end -- Compare one TLSA record against a certificate local function one_dane_check(tlsa, cert, log) local select, match, certdata = tlsa.select, tlsa.match; if select == 0 then certdata = pem2der(cert:pem()); elseif select == 1 and cert.pubkey then certdata = pem2der(cert:pubkey()); else log("warn", "DANE selector %s is unsupported", tlsa:getSelector() or select); return; end if match == 1 then certdata = hashes.sha256(certdata); elseif match == 2 then certdata = hashes.sha512(certdata); elseif match ~= 0 then log("warn", "DANE match rule %s is unsupported", tlsa:getMatchType() or match); return; end if #certdata ~= #tlsa.data then log("warn", "Length mismatch: Cert: %d, TLSA: %d", #certdata, #tlsa.data); end return certdata == tlsa.data; end module:hook("s2s-check-certificate", function(event) local session, cert, host = event.session, event.cert, event.host; if not cert then return end local log = session.log or module._log; local dane = session.dane; if type(dane) ~= "table" then if dane == nil and dane_lookup(session, resume) then pause(session); dane = session.dane; end end if type(dane) == "table" then local match_found, supported_found; for i = 1, #dane do local tlsa = dane[i].tlsa; log("debug", "TLSA #%d: %s", i, tostring(tlsa)) local use = tlsa.use; if enabled_uses:contains(use) then -- DANE-EE or PKIX-EE if use == 3 or use == 1 then -- Should we check if the cert subject matches? local is_match = one_dane_check(tlsa, cert, log); if is_match ~= nil then supported_found = true; end if is_match and use == 1 and session.cert_chain_status ~= "valid" then -- for usage 1, PKIX-EE, the chain has to be valid already log("debug", "PKIX-EE TLSA matches untrusted certificate"); is_match = false; end if is_match then log("info", "DANE validated ok for %s using %s", host, tlsa:getUsage()); session.cert_identity_status = "valid"; if use == 3 then -- DANE-EE, chain status equals DNSSEC chain status session.cert_chain_status = "valid"; end match_found = true; dane.matching = tlsa; break; end -- DANE-TA or PKIX-CA elseif use == 2 or use == 0 then supported_found = true; local chain = session.conn:socket():getpeerchain(); for c = 1, #chain do local cacert = chain[c]; local is_match = one_dane_check(tlsa, cacert, log); if is_match ~= nil then supported_found = true; end if is_match and not cacert:issued(cert, unpack(chain)) then is_match = false; end if is_match and use == 0 and session.cert_chain_status ~= "valid" then -- for usage 0, PKIX-CA, identity and chain has to be valid already is_match = false; end if is_match then log("info", "DANE validated ok for %s using %s", host, tlsa:getUsage()); if use == 2 then -- DANE-TA session.cert_identity_status = "valid"; if cert_verify_identity(host, "xmpp-server", cert) then session.cert_chain_status = "valid"; -- else -- TODO Check against SRV target? end end match_found = true; dane.matching = tlsa; break; end end if match_found then break end end end end if supported_found and not match_found or dane.bogus then -- No TLSA matched or response was bogus local why = "No TLSA matched certificate"; if dane.bogus then why = "Bogus: "..tostring(dane.bogus); end log("warn", "DANE validation failed for %s: %s", host, why); session.cert_identity_status = "invalid"; session.cert_chain_status = "invalid"; end else if session.cert_chain_status == "valid" and session.cert_identity_status ~= "valid" and session.srv_hosts 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 = session.srv_hosts[i].target:gsub("%.?$",""); log("debug", "Comparing certificate with Secure SRV target %s", srv_target); srv_target = nameprep(idna_to_unicode(srv_target)); if srv_target and cert_verify_identity(srv_target, "xmpp-server", cert) then log("info", "Certificate for %s matches Secure SRV target %s", host, srv_target); session.cert_identity_status = "valid"; return; end end end end end); -- Telnet command if module:get_option_set("modules_enabled", {}):contains("admin_telnet") then module:depends("admin_telnet"); -- Make sure the env is there local def_env = module:shared("admin_telnet/env"); local function annotate(session, line) line = line or {}; table.insert(line, "--"); if session.dane == nil then table.insert(line, "No DANE attempted, probably insecure SRV response"); elseif session.dane == false then table.insert(line, "DANE failed or response was insecure"); elseif type(session.dane) ~= "table" then table.insert(line, "Waiting for DANE records..."); elseif session.dane.matching then table.insert(line, "Matching DANE record:\n| " .. tostring(session.dane.matching)); else table.insert(line, "DANE records:\n| " .. tostring(session.dane)); end return table.concat(line, " "); end function def_env.s2s:show_dane(...) return self:show(..., annotate); end end