-- Dovecot authentication backend for Prosody

--

-- Copyright (C) 2008-2009 Tobias Markmann

-- Copyright (C) 2010 Javier Torres

-- Copyright (C) 2010-2011 Matthew Wild

-- Copyright (C) 2010-2011 Waqas Hussain

-- Copyright (C) 2011 Kim Alvefur

--

--    Redistribution and use in source and binary forms, with or without modification, are permitted provided that the following conditions are met:

--

--        * Redistributions of source code must retain the above copyright notice, this list of conditions and the following disclaimer.

--        * Redistributions in binary form must reproduce the above copyright notice, this list of conditions and the following disclaimer in the documentation and/or other materials provided with the distribution.

--        * Neither the name of Tobias Markmann nor the names of its contributors may be used to endorse or promote products derived from this software without specific prior written permission.

--

--    THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

-- This code is based on util.sasl_cyrus and the old mod_auth_dovecot

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

local setmetatable = setmetatable;

local s_match, s_gmatch = string.match, string.gmatch

local t_concat = table.concat;

local m_random = math.random;

local tostring, tonumber = tostring, tonumber;

local socket = require "socket"

pcall(require, "socket.unix");

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

local b64, unb64 = base64.encode, base64.decode;

local jid_escape = require "util.jid".escape;

local prepped_split = require "util.jid".prepped_split;

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

--module "sasl_dovecot"

local _M = {};

local request_id = 0;

local method = {};

method.__index = method;

local conn, supported_mechs, pid;

local function connect(socket_info)

	--log("debug", "connect(%q)", socket_path);

	if conn then conn:close(); pid = nil; end

	if not pid then pid = tonumber(tostring(conn):match("0x%x*$")) end

	local socket_type = (type(socket_info) == "string") and "UNIX" or "TCP";

	local ok, err;

	if socket_type == "TCP" then

		local socket_host, socket_port = unpack(socket_info);

		conn = socket.tcp();

		ok, err = conn:connect(socket_host, socket_port);

		socket_path = ("%s:%d"):format(socket_host, socket_port);

	elseif socket.unix then

		conn = socket.unix();

		ok, err = conn:connect(socket_path);

	else

		err = "luasocket was not compiled with UNIX sockets support";

	end

	if not ok then

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

		return false;

	end

	-- Send our handshake

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

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

		return false

	end

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

		return false

	end

	-- Parse Dovecot's handshake

	local done = false;

	supported_mechs = {};

	while (not done) do

		local line = conn: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);

				conn:close();

				return false;

			end

		elseif first == "MECH" then

			local mech = parts();

			supported_mechs[mech] = true;

		elseif first == "DONE" then

			done = true;

		end

	end

	return conn, supported_mechs;

end

-- create a new SASL object which can be used to authenticate clients

function _M.new(realm, service_name, socket_info, config)

	--log("debug", "new(%q, %q, %q)", realm or "", service_name or "", socket_info or "");

	local sasl_i = { realm = realm, service_name = service_name, socket_info = socket_info, config = config or {} };

	request_id = request_id + 1;

	sasl_i.request_id = request_id;

	local conn, mechs = conn, supported_mechs;

	if not conn then

		conn, mechs = connect(socket_info);

		if not conn then

			return nil, "Socket connection failure";

		end

	end

	sasl_i.conn, sasl_i.mechs = conn, mechs;

	return setmetatable(sasl_i, method);

end

-- [[

function method:send(...)

	local msg = t_concat({...}, "\t");

	local ok, err = self.conn:send(authmsg.."\n");

	if not ok then

		log("error", "Could not write to socket: %s", err);

		return nil, err;

	end

	return true;

end

function method:recv()

	local line, err = self.conn:receive();

	--log("debug", "Sent %d bytes to socket", ok);

	local line, err = self.conn:receive();

	if not line then

		log("error", "Could not read from socket: %s", err);

		return nil, err;

	end

	return line;

end

-- ]]

function method:plain_test(username, password, realm)

	if self:select("PLAIN") then

		return self:process(("\0%s\0%s"):format(username, password));

	end

end

-- get a fresh clone with the same realm and service name

function method:clean_clone()

	--log("debug", "method:clean_clone()");

	return _M.new(self.realm, self.service_name, self.socket_info, self.config)

end

-- get a list of possible SASL mechanims to use

function method:mechanisms()

	--log("debug", "method:mechanisms()");

	return self.mechs;

end

-- select a mechanism to use

function method:select(mechanism)

	--log("debug", "method:select(%q)", mechanism);

	if not self.selected and self.mechs[mechanism] then

		self.selected = mechanism;

		return true;

	end

end

-- feed new messages to process into the library

function method:process(message)

	--log("debug", "method:process"..(message and "(%q)" or "()"), message);

	--if not message then

		--return "challenge";

		--return "failure", "malformed-request";

	--end

	local request_id = self.request_id;

	local authmsg;

	if not self.started then

		self.started = true;

		authmsg = t_concat({

			"AUTH",

			request_id,

			self.selected,

			"service="..self.service_name,

			"resp="..(message and b64(message) or "=")

		}, "\t");

	else

		authmsg = t_concat({

			"CONT",

			request_id,

			(message and b64(message) or "=")

		}, "\t");

	end

	--log("debug", "Sending %d bytes: %q", #authmsg, authmsg);

	local ok, err = self.conn:send(authmsg.."\n");

	if not ok then

		log("error", "Could not write to socket: %s", err);

		return "failure", "internal-server-error", err

	end

	--log("debug", "Sent %d bytes to socket", ok);

	local line, err = self.conn:receive();

	if not line then

		log("error", "Could not read from socket: %s", err);

		return "failure", "internal-server-error", err

	end

	--log("debug", "Received %d bytes from socket: %s", #line, line);

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

	local resp = parts();

	local id = tonumber(parts());

	if id ~= request_id then

		return "failure", "internal-server-error", "Unexpected request id"

	end

	local data = {};

	for param in parts do

		data[#data+1]=param;

		local k,v = param:match("^([^=]*)=?(.*)$");

		if k and #k>0 then

			data[k]=v or true;

		end

	end

	if data.user then

		local handle_domain = self.config.handle_domain;

		local validate_domain = self.config.validate_domain;

		if handle_domain == "split" then

			local domain;

			self.username, domain = prepped_split(data.user);

			if validate_domain and domain ~= self.realm then

				return "failure", "not-authorized", "Domain mismatch";

			end

		elseif handle_domain == "escape" then

			self.username = nodeprep(jid_escape(data.user));

		else

			self.username = nodeprep(data.user);

		end

		if not self.username then 

			return "failure", "not-authorized", "Username failed NODEprep"

		end

	end

	if resp == "FAIL" then

		if data.temp then

			return "failure", "temporary-auth-failure", data.reason;

		elseif data.authz then

			return "failure", "invalid-authzid", data.reason;

		else

			return "failure", "not-authorized", data.reason;

		end

	elseif resp == "CONT" then

		return "challenge", unb64(data[1]);

	elseif resp == "OK" then

		return "success", data.resp and unb64(data.resp) or nil; 

	end

end

return _M;