#!/usr/bin/env python

# pynslcd.py - main daemon module
#
# Copyright (C) 2010, 2011, 2012 Arthur de Jong
#
# This library is free software; you can redistribute it and/or
# modify it under the terms of the GNU Lesser General Public
# License as published by the Free Software Foundation; either
# version 2.1 of the License, or (at your option) any later version.
#
# This library is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
# Lesser General Public License for more details.
#
# You should have received a copy of the GNU Lesser General Public
# License along with this library; if not, write to the Free Software
# Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
# 02110-1301 USA

import daemon
import logging
import logging.handlers
import os
import signal
import sys
import syslog
import threading

import ldap

from tio import TIOStream
import cfg        # from nslcd.conf
import common
import config     # from configure
import constants  # from nslcd.h
import mypidfile


# the name of the program
program_name = 'pynslcd'

# flag to indicate whether we are in debugging mode
debugging = 0

# flag to indicate user requested the --check option
checkonly = False


class MyFormatter(logging.Formatter):

    def format(self, record):
        msg = super(MyFormatter, self).format(record)
        if record.levelno == logging.DEBUG:
            msg = 'DEBUG: %s' % msg
        return msg


class MySysLogHandler(logging.Handler):

    mapping = {
        logging.DEBUG: syslog.LOG_DEBUG,
        logging.INFO: syslog.LOG_INFO,
        logging.WARNING: syslog.LOG_WARNING,
        logging.ERROR: syslog.LOG_ERR,
        logging.CRITICAL: syslog.LOG_CRIT,
    }

    def __init__(self):
        super(MySysLogHandler, self).__init__()
        syslog.openlog(program_name, syslog.LOG_PID, syslog.LOG_DAEMON)

    def emit(self, record):
        priority = self.mapping.get(record.levelno, syslog.LOG_WARNING)
        msg = self.format(record)
        for l in msg.splitlines():
            syslog.syslog(priority, l)


# configure logging
formatter = MyFormatter('%(message)s')
stderrhandler = logging.StreamHandler(sys.stderr)
stderrhandler.setFormatter(formatter)
sysloghandler = MySysLogHandler()
sysloghandler.setFormatter(formatter)
logging.getLogger().addHandler(stderrhandler)
logging.getLogger().setLevel(logging.INFO)


def display_version(fp):
    fp.write('%(PACKAGE_STRING)s\n'
             'Written by Arthur de Jong.\n'
             '\n'
             'Copyright (C) 2010-2012 Arthur de Jong\n'
             'This is free software; see the source for copying conditions.  There is NO\n'
             'warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.\n'
             % {'PACKAGE_STRING': config.PACKAGE_STRING, })


def display_usage(fp):
    fp.write("Usage: %(program_name)s [OPTION]...\n"
             "Name Service LDAP connection daemon.\n"
             "  -c, --check        check if the daemon already is running\n"
             "  -d, --debug        don't fork and print debugging to stderr\n"
             "      --help         display this help and exit\n"
             "      --version      output version information and exit\n"
             "\n"
             "Report bugs to <%(PACKAGE_BUGREPORT)s>.\n"
             % {'program_name': program_name,
                'PACKAGE_BUGREPORT': config.PACKAGE_BUGREPORT, })


def parse_cmdline():
    """Parse command-line arguments."""
    import getopt
    global program_name
    program_name = sys.argv[0] or program_name
    try:
        optlist, args = getopt.gnu_getopt(sys.argv[1:],
          'cdhV', ('check', 'debug', 'help', 'version', ))
        for flag, arg in optlist:
            if flag in ('-c', '--check'):
                global checkonly
                checkonly = True
            elif flag in ('-d', '--debug'):
                global debugging
                debugging += 1
            elif flag in ('-h', '--help'):
                display_usage(sys.stdout)
                sys.exit(0)
            elif flag in ('-V', '--version'):
                display_version(sys.stdout)
                sys.exit(0)
        if len(args):
            raise getopt.GetoptError('unrecognized option \'%s\'' % args[0], args[0])
    except getopt.GetoptError, reason:
        sys.stderr.write("%(program_name)s: %(reason)s\n"
                         "Try '%(program_name)s --help' for more information.\n"
                          % {'program_name': program_name,
                             'reason': reason, })
        sys.exit(1)


def create_socket():
    """Returns a socket ready to answer requests from the client."""
    import socket
    import fcntl
    sock = socket.socket(socket.AF_UNIX, socket.SOCK_STREAM)
    # remove existing named socket
    try:
        os.unlink(config.NSLCD_SOCKET)
    except OSError:
        pass  # ignore any problems
    # bind to named socket
    sock.bind((config.NSLCD_SOCKET))
    # close the file descriptor on exit
    fcntl.fcntl(sock, fcntl.F_SETFD, fcntl.FD_CLOEXEC)
    # set permissions of socket so anybody can do requests
    os.chmod(config.NSLCD_SOCKET, 0666)
    # start listening for connections
    sock.listen(socket.SOMAXCONN)
    return sock


def log_newsession():
    pass
    # FIXME: implement


def getpeercred(fd):
    """Return uid, gid and pid of calling application."""
    import struct
    import socket
    SO_PEERCRED = 17
    creds = fd.getsockopt(socket.SOL_SOCKET, SO_PEERCRED, struct.calcsize('3i'))
    pid, uid, gid = struct.unpack('3i', creds)
    return uid, gid, pid


handlers = {}
handlers.update(common.get_handlers('alias'))
handlers.update(common.get_handlers('ether'))
handlers.update(common.get_handlers('group'))
handlers.update(common.get_handlers('host'))
handlers.update(common.get_handlers('netgroup'))
handlers.update(common.get_handlers('network'))
handlers.update(common.get_handlers('pam'))
handlers.update(common.get_handlers('passwd'))
handlers.update(common.get_handlers('protocol'))
handlers.update(common.get_handlers('rpc'))
handlers.update(common.get_handlers('service'))
handlers.update(common.get_handlers('shadow'))


def acceptconnection(session):
    # accept a new connection
    conn, addr = nslcd_serversocket.accept()
    # See: http://docs.python.org/library/socket.html#socket.socket.settimeout
    fp = None
    try:
        # probably use finally
        # indicate new connection to logging module (genrates unique id)
        log_newsession()
        # log connection
        try:
            uid, gid, pid = getpeercred(conn)
            logging.debug('connection from pid=%r uid=%r gid=%r', pid, uid, gid)
        except:
            raise  # FIXME: handle exception gracefully
        # create a stream object
        fp = TIOStream(conn)
        # read request
        version = fp.read_int32()
        if version != constants.NSLCD_VERSION:
            logging.debug('wrong nslcd version id (%r)', version)
            return
        action = fp.read_int32()
        try:
            handler = handlers[action]
        except KeyError:
            logging.warning('invalid action id: %r', action)
            return
        handler(fp, session, uid)()
    finally:
        if fp:
            fp.close()


def disable_nss_ldap():
    """Disable the nss_ldap module to avoid lookup loops."""
    import ctypes
    lib = ctypes.CDLL(config.NSS_LDAP_SONAME)
    ctypes.c_int.in_dll(lib, '_nss_ldap_enablelookups').value = 0


def get_connection():
    """Return a connection to the LDAP server."""
    session = ldap.initialize(cfg.uri)
    # set session-specific LDAP options
    if cfg.ldap_version:
        session.set_option(ldap.OPT_PROTOCOL_VERSION, cfg.ldap_version)
    if cfg.deref:
        session.set_option(ldap.OPT_DEREF, cfg.deref)
    if cfg.timelimit:
        session.set_option(ldap.OPT_TIMELIMIT, cfg.timelimit)
        session.set_option(ldap.OPT_TIMEOUT, cfg.timelimit)
        session.set_option(ldap.OPT_NETWORK_TIMEOUT, cfg.timelimit)
    if cfg.referrals:
        session.set_option(ldap.OPT_REFERRALS, cfg.referrals)
    if cfg.sasl_canonicalize is not None:
        session.set_option(ldap.OPT_X_SASL_NOCANON, not cfg.sasl_canonicalize)
    session.set_option(ldap.OPT_RESTART, True)
    # TODO: register a connection callback (like dis?connect_cb() in myldap.c)
    if cfg.ssl or cfg.uri.startswith('ldaps://'):
        session.set_option(ldap.OPT_X_TLS, ldap.OPT_X_TLS_HARD)
    return session


def worker():
    session = get_connection()
    while True:
        try:
            acceptconnection(session)
        except:
            logging.exception('exception in worker')
            # ignore all exceptions, just keep going


if __name__ == '__main__':
    # parse options
    parse_cmdline()
    # clean the environment
    os.environ.clear()
    os.putenv('HOME', '/')
    os.putenv('TMPDIR', '/tmp')
    os.putenv('LDAPNOINIT', '1')
    # disable ldap lookups of host names to avoid lookup loop
    disable_nss_ldap()
    # set log level
    if debugging:
        logging.getLogger().setLevel(logging.DEBUG)
    # TODO: implement
    #if myldap_set_debuglevel(cfg.debug) != LDAP_SUCCESS:
    #    sys.exit(1)
    # read configuration file
    cfg.read(config.NSLCD_CONF_PATH)
    # set process title
    try:
        import setproctitle
        setproctitle.setproctitle('pynslcd')
    except ImportError:
        pass
    # set a default umask for the pidfile and socket
    os.umask(0022)
    # see if someone already locked the pidfile
    pidfile = mypidfile.MyPIDLockFile(config.NSLCD_PIDFILE)
    # see if --check option was given
    if checkonly:
        if pidfile.is_locked():
            logging.debug('pidfile (%s) is locked', config.NSLCD_PIDFILE)
            sys.exit(0)
        else:
            logging.debug('pidfile (%s) is not locked', config.NSLCD_PIDFILE)
            sys.exit(1)
    # normal check for pidfile locked
    if pidfile.is_locked():
        logging.error('daemon may already be active, cannot acquire lock (%s)',
                      config.NSLCD_PIDFILE)
        sys.exit(1)
    # daemonize
    if debugging:
        daemon = pidfile
    else:
        daemon = daemon.DaemonContext(
                      pidfile=pidfile,
                      signal_map={
                          signal.SIGTERM: 'terminate',
                          signal.SIGINT: 'terminate',
                          signal.SIGPIPE: None,
                      })
    # start daemon
    with daemon:
        # start normal logging to syslog
        if not debugging:
            logging.getLogger().addHandler(sysloghandler)
        logging.info('version %s starting', config.VERSION)
        try:
            # create socket
            nslcd_serversocket = create_socket()
            # load supplementary groups
            if cfg.uid is not None:
                import pwd
                import grp
                u = pwd.getpwnam(cfg.uid)
                if cfg.gid is None:
                    gid = u.pw_gid
                else:
                    gid = grp.getgrnam(cfg.gid).gr_gid
                # set supplementary groups, gid and uid
                os.initgroups(u.pw_name, gid)
                os.setgid(gid)
                os.setuid(u.pw_uid)
                os.environ['HOME'] = u.pw_dir
            logging.info('accepting connections')
            # set global LDAP configuration
            if cfg.tls_reqcert is not None:
                ldap.set_option(ldap.OPT_X_TLS_REQUIRE_CERT, cfg.tls_reqcert)
            if cfg.tls_cacertdir:
                ldap.set_option(ldap.OPT_X_TLS_CACERTDIR, cfg.tls_cacertdir)
            if cfg.tls_cacertfile:
                ldap.set_option(ldap.OPT_X_TLS_CACERTFILE, cfg.tls_cacertfile)
            if cfg.tls_randfile:
                ldap.set_option(ldap.OPT_X_TLS_RANDOM_FILE, cfg.tls_randfile)
            if cfg.tls_ciphers:
                ldap.set_option(ldap.OPT_X_TLS_CIPHER_SUITE, cfg.tls_ciphers)
            if cfg.tls_cert:
                ldap.set_option(ldap.OPT_X_TLS_CERTFILE, cfg.tls_cert)
            if cfg.tls_key:
                ldap.set_option(ldap.OPT_X_TLS_KEYFILE, cfg.tls_key)
            # start worker threads
            threads = []
            for i in range(cfg.threads):
                thread = threading.Thread(target=worker, name='thread%d' % i)
                thread.setDaemon(True)
                thread.start()
                logging.debug('started thread %s', thread.getName())
                threads.append(thread)
            # wait for all threads to die
            for thread in threads:
                thread.join(10000)
        except:
            logging.exception('main loop exit')
            # no need to re-raise since we are exiting anyway