-- 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.

--

-- luacheck: ignore 431/log

local st = require "prosody.util.stanza";

local sm_bind_resource = require "prosody.core.sessionmanager".bind_resource;

local sm_make_authenticated = require "prosody.core.sessionmanager".make_authenticated;

local base64 = require "prosody.util.encodings".base64;

local set = require "prosody.util.set";

local errors = require "prosody.util.error";

local hex = require "prosody.util.hex";

local pem2der = require"util.x509".pem2der;

local hashes = require"util.hashes";

local ssl = require "ssl"; -- FIXME Isolate LuaSec from the rest of the code

local certmanager = require "core.certmanager";

local pm_get_tls_config_at = require "prosody.core.portmanager".get_tls_config_at;

local usermanager_get_sasl_handler = require "prosody.core.usermanager".get_sasl_handler;

local secure_auth_only = module:get_option_boolean("c2s_require_encryption", module:get_option_boolean("require_encryption", true));

local allow_unencrypted_plain_auth = module:get_option_boolean("allow_unencrypted_plain_auth", false)

local insecure_mechanisms = module:get_option_set("insecure_sasl_mechanisms", allow_unencrypted_plain_auth and {} or {"PLAIN", "LOGIN"});

local disabled_mechanisms = module:get_option_set("disable_sasl_mechanisms", { "DIGEST-MD5" });

local tls_server_end_point_hash = module:get_option_string("tls_server_end_point_hash");

local log = module._log;

local xmlns_sasl ='urn:ietf:params:xml:ns:xmpp-sasl';

local xmlns_bind ='urn:ietf:params:xml:ns:xmpp-bind';

local function build_reply(status, ret, err_msg)

	local reply = st.stanza(status, {xmlns = xmlns_sasl});

	if status == "failure" then

		reply:tag(ret):up();

		if err_msg then reply:tag("text"):text(err_msg); end

	elseif status == "challenge" or status == "success" then

		if ret == "" then

			reply:text("=")

		elseif ret then

			reply:text(base64.encode(ret));

		end

	else

		module:log("error", "Unknown sasl status: %s", status);

	end

	return reply;

end

local function handle_status(session, status, ret, err_msg)

	if not session.sasl_handler then

		return "failure", "temporary-auth-failure", "Connection gone";

	end

	if status == "failure" then

		local event = { session = session, condition = ret, text = err_msg };

		module:fire_event("authentication-failure", event);

		session.sasl_handler = session.sasl_handler:clean_clone();

		ret, err_msg = event.condition, event.text;

	elseif status == "success" then

		local ok, err = sm_make_authenticated(session, session.sasl_handler.username, session.sasl_handler.role);

		if ok then

			session.sasl_resource = session.sasl_handler.resource;

			module:fire_event("authentication-success", { session = session });

			session.sasl_handler = nil;

			session:reset_stream();

		else

			module:log("warn", "SASL succeeded but username was invalid");

			module:fire_event("authentication-failure", { session = session, condition = "not-authorized", text = err });

			session.sasl_handler = session.sasl_handler:clean_clone();

			return "failure", "not-authorized", "User authenticated successfully, but username was invalid";

		end

	end

	return status, ret, err_msg;

end

local function sasl_process_cdata(session, stanza)

	local text = stanza[1];

	if text then

		text = base64.decode(text);

		if not text then

			session.sasl_handler = nil;

			session.send(build_reply("failure", "incorrect-encoding"));

			return true;

		end

	end

	local sasl_handler = session.sasl_handler;

	local status, ret, err_msg = sasl_handler:process(text);

	status, ret, err_msg = handle_status(session, status, ret, err_msg);

	local event = { session = session, message = ret, error_text = err_msg };

	module:fire_event("sasl/"..session.base_type.."/"..status, event);

	local s = build_reply(status, event.message, event.error_text);

	session.send(s);

	return true;

end

module:hook_tag(xmlns_sasl, "success", function (session)

	if session.type ~= "s2sout_unauthed" or session.external_auth ~= "attempting" then return; end

	module:log("debug", "SASL EXTERNAL with %s succeeded", session.to_host);

	session.external_auth = "succeeded"

	session:reset_stream();

	session:open_stream(session.from_host, session.to_host);

	module:fire_event("s2s-authenticated", { session = session, host = session.to_host, mechanism = "EXTERNAL" });

	return true;

end)

module:hook_tag(xmlns_sasl, "failure", function (session, stanza)

	if session.type ~= "s2sout_unauthed" or session.external_auth ~= "attempting" then return; end

	local text = stanza:get_child_text("text");

	local condition = "unknown-condition";

	for child in stanza:childtags() do

		if child.name ~= "text" then

			condition = child.name;

			break;

		end

	end

	local err = errors.new({

			-- TODO type = what?

			text = text,

			condition = condition,

		}, {

			session = session,

			stanza = stanza,

		});

	module:log("info", "SASL EXTERNAL with %s failed: %s", session.to_host, err);

	session.external_auth = "failed"

	session.external_auth_failure_reason = err;

end, 500)

module:hook_tag(xmlns_sasl, "failure", function (session, stanza) -- luacheck: ignore 212/stanza

	session.log("debug", "No fallback from SASL EXTERNAL failure, giving up");

	session:close(nil, session.external_auth_failure_reason, errors.new({

				type = "wait", condition = "remote-server-timeout",

				text = "Could not authenticate to remote server",

		}, { session = session, sasl_failure = session.external_auth_failure_reason, }));

	return true;

end, 90)

module:hook_tag("http://etherx.jabber.org/streams", "features", function (session, stanza)

	if session.type ~= "s2sout_unauthed" or not session.secure then return; end

	local mechanisms = stanza:get_child("mechanisms", xmlns_sasl)

	if mechanisms then

		for mech in mechanisms:childtags() do

			if mech[1] == "EXTERNAL" then

				module:log("debug", "Initiating SASL EXTERNAL with %s", session.to_host);

				local reply = st.stanza("auth", {xmlns = xmlns_sasl, mechanism = "EXTERNAL"});

				reply:text(base64.encode(session.from_host))

				session.sends2s(reply)

				session.external_auth = "attempting"

				return true

			end

		end

	end

end, 150);

local function s2s_external_auth(session, stanza)

	if session.external_auth ~= "offered" then return end -- Unexpected request

	local mechanism = stanza.attr.mechanism;

	if mechanism ~= "EXTERNAL" then

		session.sends2s(build_reply("failure", "invalid-mechanism"));

		return true;

	end

	if not session.secure then

		session.sends2s(build_reply("failure", "encryption-required"));

		return true;

	end

	local text = stanza[1];

	if not text then

		session.sends2s(build_reply("failure", "malformed-request"));

		return true;

	end

	text = base64.decode(text);

	if not text then

		session.sends2s(build_reply("failure", "incorrect-encoding"));

		return true;

	end

	-- The text value is either "" or equals session.from_host

	if not ( text == "" or text == session.from_host ) then

		session.sends2s(build_reply("failure", "invalid-authzid"));

		return true;

	end

	-- We've already verified the external cert identity before offering EXTERNAL

	if session.cert_chain_status ~= "valid" or session.cert_identity_status ~= "valid" then

		session.sends2s(build_reply("failure", "not-authorized"));

		session:close();

		return true;

	end

	-- Success!

	session.external_auth = "succeeded";

	session.sends2s(build_reply("success"));

	module:log("info", "Accepting SASL EXTERNAL identity from %s", session.from_host);

	module:fire_event("s2s-authenticated", { session = session, host = session.from_host, mechanism = mechanism });

	session:reset_stream();

	return true;

end

module:hook("stanza/urn:ietf:params:xml:ns:xmpp-sasl:auth", function(event)

	local session, stanza = event.origin, event.stanza;

	if session.type == "s2sin_unauthed" then

		return s2s_external_auth(session, stanza)

	end

	if session.type ~= "c2s_unauthed" or module:get_host_type() ~= "local" then return; end

	-- event for preemptive checks, rate limiting etc

	module:fire_event("authentication-attempt", event);

	if event.allowed == false then

		session.send(build_reply("failure", event.error_condition or "not-authorized", event.error_text));

		return true;

	end

	if session.sasl_handler and session.sasl_handler.selected then

		session.sasl_handler = nil; -- allow starting a new SASL negotiation before completing an old one

	end

	if not session.sasl_handler then

		session.sasl_handler = usermanager_get_sasl_handler(module.host, session);

	end

	local mechanism = stanza.attr.mechanism;

	if not session.secure and (secure_auth_only or insecure_mechanisms:contains(mechanism)) then

		session.send(build_reply("failure", "encryption-required"));

		return true;

	elseif disabled_mechanisms:contains(mechanism) then

		session.send(build_reply("failure", "invalid-mechanism"));

		return true;

	end

	local valid_mechanism = session.sasl_handler:select(mechanism);

	if not valid_mechanism then

		session.send(build_reply("failure", "invalid-mechanism"));

		return true;

	end

	return sasl_process_cdata(session, stanza);

end);

module:hook("stanza/urn:ietf:params:xml:ns:xmpp-sasl:response", function(event)

	local session = event.origin;

	if not(session.sasl_handler and session.sasl_handler.selected) then

		session.send(build_reply("failure", "not-authorized", "Out of order SASL element"));

		return true;

	end

	return sasl_process_cdata(session, event.stanza);

end);

module:hook("stanza/urn:ietf:params:xml:ns:xmpp-sasl:abort", function(event)

	local session = event.origin;

	session.sasl_handler = nil;

	session.send(build_reply("failure", "aborted"));

	return true;

end);

local function tls_unique(self)

	return self.userdata["tls-unique"]:ssl_peerfinished();

end

local function tls_exporter(conn)

	if not conn.ssl_exportkeyingmaterial then return end

	return conn:ssl_exportkeyingmaterial("EXPORTER-Channel-Binding", 32, "");

end

local function sasl_tls_exporter(self)

	return tls_exporter(self.userdata["tls-exporter"]);

end

local function tls_server_end_point(self)

	local cert_hash = self.userdata["tls-server-end-point"];

	if cert_hash then return hex.from(cert_hash); end

	local conn = self.userdata["tls-server-end-point-conn"];

	local cert = conn.getlocalcertificate and conn:getlocalcertificate();

	if not cert then

		-- We don't know that this is the right cert, it could have been replaced on

		-- disk since we started.

		local certfile = self.userdata["tls-server-end-point-cert"];

		if not certfile then return end

		local f = io.open(certfile);

		if not f then return end

		local certdata = f:read("*a");

		f:close();

		cert = ssl.loadcertificate(certdata);

	end

	-- Hash function selection, see RFC 5929 §4.1

	local hash, hash_name = hashes.sha256, "sha256";

	if cert.getsignaturename then

		local sigalg = cert:getsignaturename():lower():match("sha%d+");

		if sigalg and sigalg ~= "sha1" and hashes[sigalg] then

			-- This should have ruled out MD5 and SHA1

			hash, hash_name = hashes[sigalg], sigalg;

		end

	end

	local certdata_der = pem2der(cert:pem());

	local hashed_der = hash(certdata_der);

	module:log("debug", "tls-server-end-point: hex(%s(der)) = %q, hash = %s", hash_name, hex.encode(hashed_der));

	return hashed_der;

end

local mechanisms_attr = { xmlns='urn:ietf:params:xml:ns:xmpp-sasl' };

local bind_attr = { xmlns='urn:ietf:params:xml:ns:xmpp-bind' };

local xmpp_session_attr = { xmlns='urn:ietf:params:xml:ns:xmpp-session' };

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

	local origin, features = event.origin, event.features;

	local log = origin.log or log;

	if not origin.username then

		if secure_auth_only and not origin.secure then

			log("debug", "Not offering authentication on insecure connection");

			return;

		end

		local sasl_handler = usermanager_get_sasl_handler(module.host, origin)

		origin.sasl_handler = sasl_handler;

		local channel_bindings = set.new()

		if origin.encrypted then

			-- check whether LuaSec has the nifty binding to the function needed for tls-unique

			-- FIXME: would be nice to have this check only once and not for every socket

			if sasl_handler.add_cb_handler then

				local info = origin.conn:ssl_info();

				if info and info.protocol == "TLSv1.3" then

					log("debug", "Channel binding 'tls-unique' undefined in context of TLS 1.3");

					if tls_exporter(origin.conn) then

						log("debug", "Channel binding 'tls-exporter' supported");

						sasl_handler:add_cb_handler("tls-exporter", sasl_tls_exporter);

						channel_bindings:add("tls-exporter");

					end

				elseif origin.conn.ssl_peerfinished and origin.conn:ssl_peerfinished() then

					log("debug", "Channel binding 'tls-unique' supported");

					sasl_handler:add_cb_handler("tls-unique", tls_unique);

					channel_bindings:add("tls-unique");

				else

					log("debug", "Channel binding 'tls-unique' not supported (by LuaSec?)");

				end

				local certfile;

				if tls_server_end_point_hash == "auto" then

					tls_server_end_point_hash = nil;

					local ssl_cfg = origin.ssl_cfg;

					if not ssl_cfg then

						local server = origin.conn:server();

						local tls_config = pm_get_tls_config_at(server:ip(), server:serverport());

						local autocert = certmanager.find_host_cert(origin.conn:socket():getsniname());