prosody/plugins/mod_tls.lua

-- Prosody IM
-- Copyright (C) 2008-2010 Matthew Wild
-- Copyright (C) 2008-2010 Waqas Hussain
--
-- This project is MIT/X11 licensed. Please see the
-- COPYING file in the source package for more information.
--

local create_context = require "core.certmanager".create_context;
local rawgetopt = require"core.configmanager".rawget;
local st = require "util.stanza";

local c2s_require_encryption = module:get_option("c2s_require_encryption", module:get_option("require_encryption", true));
local s2s_require_encryption = module:get_option("s2s_require_encryption", true);
local allow_s2s_tls = module:get_option("s2s_allow_encryption") ~= false;
local s2s_secure_auth = module:get_option("s2s_secure_auth");

if s2s_secure_auth and s2s_require_encryption == false then
	module:log("warn", "s2s_secure_auth implies s2s_require_encryption, but s2s_require_encryption is set to false");
	s2s_require_encryption = true;
end

local xmlns_starttls = 'urn:ietf:params:xml:ns:xmpp-tls';
local starttls_attr = { xmlns = xmlns_starttls };
local starttls_initiate= st.stanza("starttls", starttls_attr);
local starttls_proceed = st.stanza("proceed", starttls_attr);
local starttls_failure = st.stanza("failure", starttls_attr);
local c2s_feature = st.stanza("starttls", starttls_attr);
local s2s_feature = st.stanza("starttls", starttls_attr);
if c2s_require_encryption then c2s_feature:tag("required"):up(); end
if s2s_require_encryption then s2s_feature:tag("required"):up(); end

local hosts = prosody.hosts;
local host = hosts[module.host];

local ssl_ctx_c2s, ssl_ctx_s2sout, ssl_ctx_s2sin;
local ssl_cfg_c2s, ssl_cfg_s2sout, ssl_cfg_s2sin;
local err_c2s, err_s2sin, err_s2sout;

function module.load(reload)
	local NULL = {};
	local modhost = module.host;
	local parent = modhost:match("%.(.*)$");

	local parent_ssl = rawgetopt(parent,  "ssl") or NULL;
	local host_ssl   = rawgetopt(modhost, "ssl") or parent_ssl;

	local global_c2s = rawgetopt("*",     "c2s_ssl") or NULL;
	local parent_c2s = rawgetopt(parent,  "c2s_ssl") or NULL;
	local host_c2s   = rawgetopt(modhost, "c2s_ssl") or parent_c2s;

	local global_s2s = rawgetopt("*",     "s2s_ssl") or NULL;
	local parent_s2s = rawgetopt(parent,  "s2s_ssl") or NULL;
	local host_s2s   = rawgetopt(modhost, "s2s_ssl") or parent_s2s;

	module:log("debug", "Creating context for c2s");
	local request_client_certs = { verify = { "peer", "client_once", }; };
	local xmpp_alpn = { alpn = "xmpp-server" };

	ssl_ctx_c2s, err_c2s, ssl_cfg_c2s = create_context(host.host, "server", host_c2s, host_ssl, global_c2s); -- for incoming client connections
	if not ssl_ctx_c2s then module:log("error", "Error creating context for c2s: %s", err_c2s); end

	module:log("debug", "Creating context for s2sout");
	-- for outgoing server connections
	ssl_ctx_s2sout, err_s2sout, ssl_cfg_s2sout = create_context(host.host, "client", host_s2s, host_ssl, global_s2s, request_client_certs, xmpp_alpn);
	if not ssl_ctx_s2sout then module:log("error", "Error creating contexts for s2sout: %s", err_s2sout); end

	module:log("debug", "Creating context for s2sin");
	-- for incoming server connections
	ssl_ctx_s2sin, err_s2sin, ssl_cfg_s2sin = create_context(host.host, "server", host_s2s, host_ssl, global_s2s, request_client_certs);
	if not ssl_ctx_s2sin then module:log("error", "Error creating contexts for s2sin: %s", err_s2sin); end

	if reload then
		module:log("info", "Certificates reloaded");
	else
		module:log("info", "Certificates loaded");
	end
end

module:hook_global("config-reloaded", module.load);

local function can_do_tls(session)
	if session.secure then
		return false;
	end
	if session.conn and not session.conn.starttls then
		if not session.secure then
			session.log("debug", "Underlying connection does not support STARTTLS");
		end
		return false;
	elseif session.ssl_ctx ~= nil then
		return session.ssl_ctx;
	end
	if session.type == "c2s_unauthed" then
		if not ssl_ctx_c2s and c2s_require_encryption then
			session.log("error", "No TLS context available for c2s. Earlier error was: %s", err_c2s);
		end
		session.ssl_ctx = ssl_ctx_c2s;
		session.ssl_cfg = ssl_cfg_c2s;
	elseif session.type == "s2sin_unauthed" and allow_s2s_tls then
		if not ssl_ctx_s2sin and s2s_require_encryption then
			session.log("error", "No TLS context available for s2sin. Earlier error was: %s", err_s2sin);
		end
		session.ssl_ctx = ssl_ctx_s2sin;
		session.ssl_cfg = ssl_cfg_s2sin;
	elseif session.direction == "outgoing" and allow_s2s_tls then
		if not ssl_ctx_s2sout and s2s_require_encryption then
			session.log("error", "No TLS context available for s2sout. Earlier error was: %s", err_s2sout);
		end
		session.ssl_ctx = ssl_ctx_s2sout;
		session.ssl_cfg = ssl_cfg_s2sout;
	else
		session.log("debug", "Unknown session type, don't know which TLS context to use");
		return false;
	end
	if not session.ssl_ctx then
		session.log("debug", "Should be able to do TLS but no context available");
		return false;
	end
	return session.ssl_ctx;
end

module:hook("s2sout-created", function (event)
	-- Initialize TLS context for outgoing connections
	can_do_tls(event.session);
end);

-- Hook <starttls/>
module:hook("stanza/urn:ietf:params:xml:ns:xmpp-tls:starttls", function(event)
	local origin = event.origin;
	origin.starttls = "requested";
	if can_do_tls(origin) then
		if origin.conn.block_reads then
			-- we need to ensure that no data is read anymore, otherwise we could end up in a situation where
			-- <proceed/> is sent and the socket receives the TLS handshake (and passes the data to lua) before
			-- it is asked to initiate TLS
			-- (not with the classical single-threaded server backends)
			origin.conn:block_reads()
		end
		(origin.sends2s or origin.send)(starttls_proceed);
		if origin.destroyed then return end
		origin:reset_stream();
		origin.conn:starttls(origin.ssl_ctx);
		origin.log("debug", "TLS negotiation started for %s...", origin.type);
		origin.secure = false;
	else
		origin.log("warn", "Attempt to start TLS, but TLS is not available on this %s connection", origin.type);
		(origin.sends2s or origin.send)(starttls_failure);
		origin:close();
	end
	return true;
end);

-- Advertise stream feature
module:hook("stream-features", function(event)
	local origin, features = event.origin, event.features;
	if can_do_tls(origin) then
		features:add_child(c2s_feature);
	end
end);
module:hook("s2s-stream-features", function(event)
	local origin, features = event.origin, event.features;
	if can_do_tls(origin) then
		features:add_child(s2s_feature);
	end
end);

-- For s2sout connections, start TLS if we can
module:hook_tag("http://etherx.jabber.org/streams", "features", function (session, stanza)
	module:log("debug", "Received features element");
	if can_do_tls(session) then
		if stanza:get_child("starttls", xmlns_starttls) then
			module:log("debug", "%s is offering TLS, taking up the offer...", session.to_host);
		elseif s2s_require_encryption then
			module:log("debug", "%s is *not* offering TLS, trying anyways!", session.to_host);
		else
			module:log("debug", "%s is not offering TLS", session.to_host);
			return;
		end
		session.starttls = "initiated";
		session.sends2s(starttls_initiate);
		return true;
	end
end, 500);

module:hook("s2sout-authenticate-legacy", function(event)
	local session = event.origin;
	if s2s_require_encryption and can_do_tls(session) then
		session.sends2s(starttls_initiate);
		return true;
	end
end, 200);

module:hook_tag(xmlns_starttls, "proceed", function (session, stanza) -- luacheck: ignore 212/stanza
	if session.type == "s2sout_unauthed" and can_do_tls(session) then
		module:log("debug", "Proceeding with TLS on s2sout...");
		session:reset_stream();
		session.starttls = "proceeding"
		session.conn:starttls(session.ssl_ctx, session.to_host);
		session.secure = false;
		return true;
	end
end);

module:hook_tag(xmlns_starttls, "failure", function (session, stanza) -- luacheck: ignore 212/stanza
	module:log("warn", "TLS negotiation with %s failed.", session.to_host);
	session:close(nil, "TLS negotiation failed");
	return false;
end);