-- Dovecot authentication backend for Prosody

--

-- Copyright (C) 2010 Javier Torres

-- Copyright (C) 2008-2010 Matthew Wild

-- Copyright (C) 2008-2010 Waqas Hussain

--

local socket_unix = require "socket.unix";

local datamanager = require "util.datamanager";

local usermanager = require "core.usermanager";

local log = require "util.logger".init("auth_dovecot");

local new_sasl = require "util.sasl".new;

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

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

local sha1 = require "util.hashes".sha1;

local prosody = prosody;

local socket_path = module:get_option_string("dovecot_auth_socket", "/var/run/dovecot/auth-login");

function new_provider(host)

	local provider = { name = "dovecot", request_id = 0 };

	log("debug", "initializing dovecot authentication provider for host '%s'", host);

	local conn;

	-- Generate an id for this connection (must be a 31-bit number, unique per process)

	local pid = tonumber(sha1(host, true):sub(1, 6), 16);

	-- Closes the socket

	function provider.close(self)

		if conn then

			conn:close();

			conn = nil;

		end

	end

	-- The following connects to a new socket and send the handshake

	function provider.connect(self)

		-- Destroy old socket

		provider:close();

		conn = socket.unix();

		-- Create a connection to dovecot socket

		log("debug", "connecting to dovecot socket at '%s'", socket_path);

		local ok, err = conn:connect(socket_path);

		if not ok then

			log("error", "error connecting to dovecot socket at '%s'. error was '%s'. check permissions", socket_path, err);

			provider:close();

			return false;

		end

		-- Send our handshake

		log("debug", "sending handshake to dovecot. version 1.1, cpid '%d'", pid);

		if not provider:send("VERSION\t1\t1\n") then

			return false

		end

		if not provider:send("CPID\t" .. pid .. "\n") then

			return false

		end

		-- Parse Dovecot's handshake

		local done = false;

		local supported_mechs = {};

		while (not done) do

			local line = provider:receive();

			if not line then

				return false;

			end

			log("debug", "dovecot handshake: '%s'", line);

			local parts = line:gmatch("[^\t]+");

			local first = parts();

			if first == "VERSION" then

				-- Version should be 1.1

				local major_version = parts();

				if major_version ~= "1" then

					log("error", "dovecot server version is not 1.x. it is %s.x", major_version);

					provider:close();

					return false;

				end

			elseif first == "MECH" then

				local mech = parts();

				supported_mechs[mech] = true;

			elseif first == "DONE" then

				-- We need PLAIN

				if not supported_mechs.PLAIN then

					log("warn", "server doesn't support PLAIN mechanism.");

					provider:close();

					return false;

				end

				done = true;

			end

		end

		return true;

	end

	-- Wrapper for send(). Handles errors

	function provider.send(self, data)

		local ok, err = conn:send(data);

		if not ok then

			log("error", "error sending '%s' to dovecot. error was '%s'", data, err);

			provider:close();

			return false;

		end

		return true;

	end

	-- Wrapper for receive(). Handles errors

	function provider.receive(self)

		local line, err = conn:receive();

		if not line then

			log("error", "error receiving data from dovecot. error was '%s'", err);

			provider:close();

			return false;

		end

		return line;

	end

	function provider.send_auth_request(self, username, password)

		if not conn then

			if not provider:connect() then

				return nil, "Auth failed. Dovecot communications error";

			end

		end

		-- Send auth data

		username = username .. "@" .. module.host; -- FIXME: this is actually a hack for my server

		local b64 = base64.encode(username .. "\0" .. username .. "\0" .. password);

		provider.request_id = provider.request_id + 1 % 4294967296

		local msg = "AUTH\t" .. provider.request_id .. "\tPLAIN\tservice=XMPP\tresp=" .. b64;

		log("debug", "sending auth request for '%s' with password '%s': '%s'", username, password, msg);

		if not provider:send(msg .. "\n") then

			return nil, "Auth failed. Dovecot communications error";

		end

		-- Get response

		local line = provider:receive();

		log("debug", "got auth response: '%s'", line);

		if not line then

			return nil, "Auth failed. Dovecot communications error";

		end

		local parts = line:gmatch("[^\t]+");

		-- Check response

		local status = parts();

		local resp_id = tonumber(parts());

		if resp_id  ~= provider.request_id then

			log("warn", "dovecot response_id(%s) doesn't match request_id(%s)", resp_id, provider.request_id);

			provider:close();

			return nil, "Auth failed. Dovecot communications error";

		end

		return status, parts;

	end

	function provider.test_password(username, password)

		log("debug", "test password '%s' for user %s at host %s", password, username, module.host);

		local status, extra = provider:send_auth_request(username, password);

		if status == "OK" then

			log("info", "login ok for '%s'", username);

			return true;

		else

			log("info", "login failed for '%s'", username);

			return nil, "Auth failed. Invalid username or password.";

		end

	end

	function provider.get_password(username)

		return nil, "Cannot get_password in dovecot backend.";

	end

	function provider.set_password(username, password)

		return nil, "Cannot set_password in dovecot backend.";

	end

	function provider.user_exists(username)

		log("debug", "user_exists for user %s at host %s", username, module.host);

		-- Send a request. If the response (FAIL) contains an extra

		-- parameter like user=<username> then it exists.

		local status, extra = provider:send_auth_request(username, "");

		local param = extra();

		while param do

			local parts = param:gmatch("[^=]+");

			local name = parts();

			local value = parts();

			if name == "user" then

				log("debug", "user '%s' exists", username);

				return true;

			end

			param = extra();

		end

		log("debug", "user '%s' does not exists (or dovecot didn't send user=<username> parameter)", username);

		return false;

	end

	function provider.create_user(username, password)

		return nil, "Cannot create_user in dovecot backend.";

	end

	function provider.get_sasl_handler()

		local getpass_authentication_profile = {

			plain_test = function(sasl, username, password, realm)

			local prepped_username = nodeprep(username);

			if not prepped_username then

				log("debug", "NODEprep failed on username: %s", username);

				return "", nil;

			end

			return usermanager.test_password(prepped_username, realm, password), true;

		end

		};

		return new_sasl(module.host, getpass_authentication_profile);

	end

	return provider;

end

module:add_item("auth-provider", new_provider(module.host));