#!/usr/bin/env python
#
# The daemon script to run the CryptoBox webserver.
#
# run the script with "--help" to see all possible paramters
#
#
# Copyright 2006 sense.lab e.V.
# 
# This file is part of the CryptoBox.
#
# The CryptoBox is free software; you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation; either version 2 of the License, or
# (at your option) any later version.
# 
# The CryptoBox 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 General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with the CryptoBox; if not, write to the Free Software
# Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
#

__revision__ = "$Id"

import os, sys
import cryptobox.web.sites
from cryptobox.core.exceptions import *
from optparse import OptionParser

## check python version
(ver_major, ver_minor, ver_sub, ver_desc, ver_subsub) = sys.version_info
if (ver_major < 2) or ((ver_major == 2) and (ver_minor < 4)):
	sys.stderr.write("You need a python version >= 2.4\n")
	sys.stderr.write("Current version is: %s\n" % sys.version)
	sys.exit(1)

## check cherrypy dependency
try:
	import cherrypy
except: 
	sys.stderr.write("Could not import the cherrypy module!\n")
	sys.stderr.write("Try 'apt-get install python-cherrypy'.\n")
	sys.exit(1)

## check clearsilver dependency
try:
	import neo_cgi, neo_util
except: 
	sys.stderr.write("Could not import the clearsilver module!\n")
	sys.stderr.write("Try 'apt-get install python-clearsilver'.\n")
	sys.exit(1)

## check configobj dependency
try:
	import configobj, validate
except: 
	sys.stderr.write("Could not import the configobj or validate module!\n")
	sys.stderr.write("Try 'apt-get install python-configobj'.\n")
	sys.exit(1)


# TODO: change this for the release version [development|production]
SERVER_ENVIRONMENT = "production"

class CryptoBoxWebserver:
	'''this class starts the cherrypy webserver and serves the single sites'''

	def __init__(self, opts):
		self.opts = opts
		## check conffile
		if not os.access(opts.conffile, os.R_OK) or not os.path.isfile(opts.conffile):
			sys.stderr.write("Error: could not read configuration file (%s)\n" % opts.conffile)
			sys.exit(1)
		## store the absolute path as we will chdir later (for daemons)
		self.conffile = os.path.realpath(opts.conffile)
		## drop privileges to run the cryptobox without root permissions
		self.drop_privileges_temporarily()
		## initialize site class
		try:
			cherrypy.root = cryptobox.web.sites.WebInterfaceSites(self.conffile)
			self.website = cherrypy.root
		except (CBConfigError,CBEnvironmentError), err_msg:
			sys.stderr.write("Error: the CryptoBox is misconfigured - please fix it!\n")
			sys.stderr.write("%s\n" % str(err_msg))
			sys.exit(1)
		## restore privileges, as we need them to connect to a low socket (<1024)
		self.restore_privileges()
		## expose static content and set options
		## beware: 
		cherrypy.config.update({
			"global": {
				"server.socket_port" : int(opts.port),
				"server.socket_host" : opts.host,
				"server.log_to_screen" : not opts.background and opts.verbose,
				"server.log_tracebacks" : opts.verbose,
				"server.log_request_headers": opts.verbose,
				"server.environment": SERVER_ENVIRONMENT,
				"server.log_file" : opts.logfile },
			"/cryptobox-misc": { 
					"staticFilter.on" : True, 
					"staticFilter.dir": os.path.realpath(opts.datadir)},
			"/favicon.ico": { 
					"staticFilter.on" : True, 
					"staticFilter.file": os.path.realpath(os.path.join(opts.datadir, 'favicon.ico'))}

			})


	def get_user_info(self):
		"""Retrieve the uid, gid and additional groups of the given user
		"""
		import pwd, grp
		user_entry = pwd.getpwuid(self.opts.user)
		## get the new uid and gid
		pw_uid, pw_gid = user_entry[2], user_entry[3]
		## change the owner of the webserver log file
		try:
			os.chown(self.opts.logfile, pw_uid, pw_gid)
		except OSError:
			## fail silently
			pass
		## calculate additional groups of the given user
		additional_groups = [ entry[2]
				for entry in grp.getgrall()
				if pw_uid in entry[3] ]
		return (pw_uid, pw_gid, additional_groups)


	def drop_privileges_temporarily(self):
		"""Temporarily drop privileges.
		"""
		if self.opts.user is None:
			return
		(pw_uid, pw_gid, additional_groups) = self.get_user_info()
		try:
			os.setegid(pw_gid)
			os.seteuid(pw_uid)
		except OSError, err_msg:
			sys.stderr.write("Failed to drop privileges temporarily: %s\n" % err_msg)


	def restore_privileges(self):
		"""Restore previously temporarily dropped privileges.
		"""
		if self.opts.user is None:
			return
		try:
			os.setegid(os.getgid())
			os.seteuid(os.getuid())
		except OSError, err_msg:
			sys.stderr.write("Failed to restore privileges: %s\n" % err_msg)


	def drop_privileges_permanently(self):
		"""Drop all privileges of the current process and acquire the privileges of the
		given user instead.
		"""
		if self.opts.user is None:
			return
		(pw_uid, pw_gid, additional_groups) = self.get_user_info()
		try:
			os.setgroups(additional_groups)
			os.setregid(pw_gid, pw_gid)
			os.setreuid(pw_uid, pw_uid)
		except OSError, err_msg:
			sys.stderr.write("Failed to drop privileges permanently: %s\n" % err_msg)



	def start(self):
		try:
			cherrypy.server.start(initOnly=True)
			self.drop_privileges_permanently()
			cherrypy.server.wait_for_http_ready()
		except cherrypy._cperror.NotReady, err_msg:
			sys.stderr.write("Failed to start CryptoBox: %s\n" % err_msg)
			sys.exit(1)
		except Exception, err_msg:
			if err_msg == "(98, 'Address already in use')":
				sys.stderr.write("Failed to start CryptoBox: %s\n" % err_msg)
				sys.exit(1)
			else:
				raise
	


def fork_to_background():
	## this is just copy'n'pasted from http://aspn.activestate.com/ASPN/Cookbook/Python/Recipe/278731
	## check the original for exhaustive comments
	try:
		pid = os.fork()
	except OSError, err_msg:
		sys.stderr.write("Error: failed to fork cryptobox daemon process!\n")
		sys.stderr.write("%s\n" % err_msg)
		sys.exit(1)
	if pid == 0:	# the first child
		os.setsid()
		try:
			pid = os.fork()
		except OSError, err_msg:
			sys.stderr.write("Error: failed to fork second cryptobox daemon process!\n")
			sys.stderr.write("%s\n" % err_msg)
			sys.exit(1)
		if pid == 0:	# the second child
			## we do not change the directory - otherwise there seems to be a race condition with the python interpreter loading this script file
			#os.chdir(os.path.sep)
			os.umask(0)
		else:
			os._exit(0)
	else:
		os._exit(0)


def close_open_files():
	"""this is only necessary if we want to go into background
	we will only close stdin, stdout and stderr
	"""
	import resource		# Resource usage information.
	## use the following lines to close all open files (including the log file)
	# maxfd = resource.getrlimit(resource.RLIMIT_NOFILE)[1]
	# if (maxfd == resource.RLIM_INFINITY):
	# 	maxfd = 1024
	maxfd = 2
	for fd in range(0, maxfd):
		try:
			## close all except for stderr - we will redirect it later
			if fd != 2:
				os.close(fd)
		except OSError:		# ERROR, fd wasn't open to begin with (ignored)
			pass
	os.open(os.devnull, os.O_RDWR)		# standard input (0)
	os.dup2(0, 1)			# standard output (1)


def write_pid_file(pid_file):
	if os.path.exists(pid_file):
		sys.stderr.write(
			"Warning: pid file (%s) already exists - overwriting ...\n" % pid_file)
	try:
		pidf = open(pid_file,"w")
		pidf.write(str(os.getpid()))
		pidf.close()
	except (IOError, OSError), err_msg:
		sys.stderr.write(
			"Warning: failed to write pid file (%s): %s\n" % (pid_file, err_msg))
		## it is just a warning - no need to break


def parseOptions():
	import cryptobox
	import pwd
	version = "%prog" + cryptobox.__version__
	parser = OptionParser(version=version)
	parser.set_defaults(conffile="/etc/cryptobox-server/cryptobox.conf",
		pidfile="/var/run/cryptobox-server/webserver.pid",
		background=False,
		datadir="/usr/share/cryptobox-server/www-data",
		logfile="/var/log/cryptobox-server/webserver.log",
		port="8080",
		host="",
		verbose=True,
		user=None)
	parser.add_option("-c", "--config", dest="conffile",
		help="read configuration from FILE", metavar="FILE")
	parser.add_option("","--pidfile", dest="pidfile",
		help="write process id to FILE", metavar="FILE")
	parser.add_option("-B","", dest="background", action="store_true",
		help="run webserver in background (as daemon)")
	parser.add_option("-q","", dest="verbose", action="store_false",
		help="output only errors")
	parser.add_option("","--datadir", dest="datadir", metavar="DIR",
		help="set data directory to DIR")
	parser.add_option("-p","--port", dest="port", metavar="PORT",
		help="listen on PORT")
	parser.add_option("-l","--logfile", dest="logfile", metavar="FILE",
		help="write webserver log to FILE")
	parser.add_option("","--host", dest="host", metavar="HOST",
		help="attach to HOST")
	parser.add_option("-u","--user", dest="user", metavar="USER",
		help="change to USER after starting the webserver")
	(options, args) = parser.parse_args()
	## we do not expect any remaining arguments
	if len(args) != 0:
		parser.error("unknown argument: %s" % str(args[0]))
	if not ((not os.path.exists(options.logfile) \
			and os.access(os.path.dirname(options.logfile), os.W_OK)) \
			or os.access(options.logfile, os.W_OK)):
		parser.error("could not write to logfile (%s)" % options.logfile)
	if not os.path.isdir(options.datadir) or not os.access(options.datadir,os.X_OK):
		parser.error("could not access the data directory (%s)" % options.datadir)
	try:
		if (int(options.port) < 0) or (int(options.port) > 65535):
			parser.error("invalid port number: %s" % str(options.port))
	except ValueError:
		parser.error("invalid port specified (%s) - it must be a number" % (options.port))
	if options.user:
		try:
			try:
				## check for the user given as uid
				uid = pwd.getpwuid(int(options.user))[2]
			except ValueError:
				## check for the user given as name
				uid = pwd.getpwnam(options.user)[2]
		except KeyError:
			## invalid user specified
			parser.error("invalid user specified (%s)" % options.user)
		## we will use the uid
		options.user = uid
	return options




if __name__ == "__main__":
	## process arguments
	options = parseOptions()
	## set umask to 022 (aka 755) - octal value
	os.umask(022)
	## initialize the webserver class (before forking to get some error messages)
	cbw = CryptoBoxWebserver(options)
	## fork to background before cbw.start() - otherwise we lose the socket
	if options.background:
		fork_to_background()
	## start the webserver
	try:
		cbw.start()
	except CBError, err_msg:
		sys.stderr.write("Failed to start the CryptoBox webserver!\n")
		sys.stderr.write("%s\n" % str(err_msg))
		sys.stderr.write("Check the log file for details.\n")
		sys.exit(1)
	## redirect stderr to the webserver's logfile
	if options.background:
		## replace stdin and stdout by /dev/null
		close_open_files()
		## replace stderr by the webserver logfile
		os.close(2)
		os.open(options.logfile, os.O_APPEND)
	## startup went fine - fork is done - now we may write the pid file
	## write pid file
	write_pid_file(options.pidfile)
	def exit_handler(signum, sigframe):
		cbw.website.cbox.log.info("Shutting down ...")
		cbw.website.cleanup()
		try:
			os.remove(options.pidfile)
		except OSError:
			pass
		os._exit(0)
	## the signal handler gets called by a kill signal (usually in background mode)
	import signal
	signal.signal(signal.SIGTERM, exit_handler)
	## this exit handler gets called by KeyboardInterrupt and similar ones (foreground)
	import atexit
	atexit.register(exit_handler, None, None)
	## this will never exit - one of the above exit handlers will get triggered
	cherrypy.server.block()