-- 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 st = require "util.stanza";

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

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

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

local nodeprep = require "util.encodings".stringprep.nodeprep;

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

local usermanager_user_exists = require "core.usermanager".user_exists;

local t_concat, t_insert = table.concat, table.insert;

local tostring = tostring;

local secure_auth_only = module:get_option("c2s_require_encryption") or module:get_option("require_encryption");

local sasl_backend = module:get_option("sasl_backend") or "builtin";

local anonymous_login = module:get_option("anonymous_login");

local allow_unencrypted_plain_auth = module:get_option("allow_unencrypted_plain_auth")

-- Cyrus config options

local require_provisioning = module:get_option("cyrus_require_provisioning") or false;

local cyrus_service_realm = module:get_option("cyrus_service_realm");

local cyrus_service_name = module:get_option("cyrus_service_name");

local cyrus_application_name = module:get_option("cyrus_application_name");

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 xmlns_stanzas ='urn:ietf:params:xml:ns:xmpp-stanzas';

local new_sasl;

if sasl_backend == "builtin" then

	new_sasl = require "util.sasl".new;

elseif sasl_backend == "cyrus" then

	prosody.unlock_globals(); --FIXME: Figure out why this is needed and

	                          -- why cyrussasl isn't caught by the sandbox

	local ok, cyrus = pcall(require, "util.sasl_cyrus");

	prosody.lock_globals();

	if ok then

		local cyrus_new = cyrus.new;

		new_sasl = function(realm)

			return cyrus_new(

				cyrus_service_realm or realm,

				cyrus_service_name or "xmpp",

				cyrus_application_name or "prosody"

			);

		end

	else

		module:log("error", "Failed to load Cyrus SASL because: %s", cyrus);

		error("Failed to load Cyrus SASL");

	end

else

	module:log("error", "Unknown SASL backend: %s", sasl_backend);

	error("Unknown SASL backend");

end

local anonymous_authentication_profile = {

	anonymous = function(username, realm)

		return true; -- for normal usage you should always return true here

	end

};

local function build_reply(status, ret, err_msg)

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

	if status == "challenge" then

		--log("debug", "CHALLENGE: %s", ret or "");

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

	elseif status == "failure" then

		reply:tag(ret):up();

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

	elseif status == "success" then

		--log("debug", "SUCCESS: %s", ret or "");

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

	else

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

	end

	return reply;

end

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

	if status == "failure" then

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

	elseif status == "success" then

		local username = nodeprep(session.sasl_handler.username);

		if not(require_provisioning) or usermanager_user_exists(username, session.host) then

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

			if ok then

				session.sasl_handler = nil;

				session:reset_stream();

			else

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

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

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

			end

		else

			module:log("warn", "SASL succeeded but we don't have an account provisioned for %s", username);

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

			return "failure", "not-authorized", "User authenticated successfully, but not provisioned for XMPP";

		end

	end

	return status, ret, err_msg;

end

local function sasl_handler(session, stanza)

	if stanza.name == "auth" then

		-- FIXME ignoring duplicates because ejabberd does

		if anonymous_login then

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

			end

			return session.send(build_reply("failure", "mechanism-too-weak"));

		end

		if not session.secure and (secure_auth_only or (mechanism == "PLAIN" and not allow_unencrypted_plain_auth)) then

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

		end

		if not valid_mechanism then

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

		end

	elseif not session.sasl_handler then

		return; -- FIXME ignoring out of order stanzas because ejabberd does

	end

	local text = stanza[1];

	if text then

		text = base64.decode(text);

		--log("debug", "AUTH: %s", text:gsub("[%z\001-\008\011\012\014-\031]", " "));

		if not text then

			session.sasl_handler = nil;

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

			return;

		end

	end

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

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

	local s = build_reply(status, ret, err_msg);

	log("debug", "sasl reply: %s", tostring(s));

	session.send(s);

end

module:add_handler("c2s_unauthed", "auth", xmlns_sasl, sasl_handler);

module:add_handler("c2s_unauthed", "abort", xmlns_sasl, sasl_handler);

module:add_handler("c2s_unauthed", "response", xmlns_sasl, sasl_handler);

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;

	if not origin.username then

		if secure_auth_only and not origin.secure then

			return;

		end

		if anonymous_login then

			origin.sasl_handler = new_sasl(module.host, anonymous_authentication_profile);

		else

			origin.sasl_handler = usermanager_get_sasl_handler(module.host);

		end

		features:tag("mechanisms", mechanisms_attr);

		for mechanism in pairs(origin.sasl_handler:mechanisms()) do

			if mechanism ~= "PLAIN" or origin.secure or allow_unencrypted_plain_auth then

				features:tag("mechanism"):text(mechanism):up();

			end

		end

		features:up();

	else

		features:tag("bind", bind_attr):tag("required"):up():up();

		features:tag("session", xmpp_session_attr):tag("optional"):up():up();

	end

end);

module:add_iq_handler("c2s", "urn:ietf:params:xml:ns:xmpp-bind", function(session, stanza)

	log("debug", "Client requesting a resource bind");

	local resource;

	if stanza.attr.type == "set" then

		local bind = stanza.tags[1];

		if bind and bind.attr.xmlns == xmlns_bind then

			resource = bind:child_with_name("resource");

			if resource then

				resource = resource[1];

			end

		end

	end

	local success, err_type, err, err_msg = sm_bind_resource(session, resource);

	if not success then

		session.send(st.error_reply(stanza, err_type, err, err_msg));

	else

		session.send(st.reply(stanza)

			:tag("bind", { xmlns = xmlns_bind})

			:tag("jid"):text(session.full_jid));

	end

end);

module:add_iq_handler("c2s", "urn:ietf:params:xml:ns:xmpp-session", function(session, stanza)

	log("debug", "Client requesting a session");

	session.send(st.reply(stanza));

end);