#!/usr/bin/env python2.4
#
# This file is part of gpgpy-ezmlm - an encryption filter for the
# ezmlm-idx mailinglist manager.
#
# Copyright 02007 Sense.Lab e.V. <info@senselab.org>
#
# This script converts an existing plaintext ezmlm mailing list into an
# encrypted mailing list. This change does not interfere with the useal
# operation of ezmlm-idx.
# 
# Syntax:
#  gpgpy-ezmlm-manage MAILINGLIST_DIRECTORY [enable|disable] 
#    enable or disable encryption for the list
#
#  gpgpy-ezmlm-manage MAILINGLIST_DIRECTORY is_encrypted
#    check if encryption for this mailing list is enabled (exitcode = 0)
#
#  gpgpy-ezmlm-manage MAILINGLIST_DIRECTORY genkey [NAME [COMMENT [MAIL_ADDRESS]]]
#    generate the secret key of a list
#    NAME, COMMENT and MAIL_ADDRESS are optional parameters - otherwise
#      reasonable default values are generated
#
#  gpgpy-ezmlm-manage MAILINGLIST_DIRECTORY get_gnupg_dir
#    return the directory containing the keys of this list
#
# If no MAILINGLIST_DIRECTORY is given, then it will only run some self-tests.
#
#
# gpgpy-ezmlm 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.
# 
# gpgpy-ezmlm 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
#

## config file inside of a mailing list directory
CONF_FILE = "conf-gpgpy"

## default gnupg directory relative to a mailing list directory
DEFAULT_GNUPG_DIR = ".gnupg"

## default settings for mailing lists
CONFIG_SETTINGS = """plain_without_key = no
sign_messages = no
gnupg_dir = %s
""" % DEFAULT_GNUPG_DIR

## settings for new keys
GENERATE_KEY_SETTINGS = """
	<GnupgKeyParms format="internal">
		Key-Type: DSA
		Key-Length: 1024
		Subkey-Type: ELG-E
		Subkey-Length: 4096
		Name-Real: %(name)s
		Name-Comment: %(comment)s
		Name-Email: %(mail)s
	</GnupgKeyParms>
	"""


import sys, os


def check_for_errors():
	"""Check for environmental problems
	"""
	errors = False
	try:
		import pyme
	except ImportError:
		sys.stderr.write("Failed to import the python module 'pyme'.\n")
		errors = True
	return errors == False


def enable_encryption(list_dir):
	"""Turn on encryption for a mailing list
	"""
	conf_file = os.path.join(list_dir, CONF_FILE)
	if not os.path.isfile(conf_file):
		try:
			new_file = file(conf_file, "w")
			new_file.write(CONFIG_SETTINGS)
			new_file.close()
		except IOError, err_msg:
			sys.stderr.write("Failed to write the gpgpy-ezmlm configuration " \
					+ "file (%s): %s\n" % (conf_file, err_msg))
			return False
	return True


def disable_encryption(list_dir):
	"""Turn off encryption for a mailing list

	Secret and public keys are not removed.
	"""
	conf_file = os.path.join(list_dir, CONF_FILE)
	if os.path.isfile(conf_file):
		try:
			os.remove(conf_file)
		except OSError, err_msg:
			sys.stderr.write("Failed to delete the gpgpy-ezmlm configuration" \
					+ " file (%s): %s\n" % (conf_file, err_msg))
			return False
	return True


def is_encrypted(list_dir):
	"""Check if the mailing list is encrypted or not
	"""
	conf_file = os.path.join(list_dir, CONF_FILE)
	return os.path.isfile(conf_file)


def get_gnupg_setting(list_dir):
	conf_file = os.path.join(list_dir, CONF_FILE)
	gnupg_setting = DEFAULT_GNUPG_DIR
	if os.path.isfile(conf_file):
		for line in file(conf_file).readlines():
			key, value = line.split("=", 1)
			key, value = (key.strip().lower(), value.strip())
			## remove surrounding quotes
			if (len(value) > 1) and \
					((value.startswith('"') and value.endswith('"')) \
					or (value.startswith("'") and value.endswith("'"))):
				value = value[1:-1]
			if key == 'gnupg_dir':
				gnupg_setting = value
				break
	if gnupg_setting.startswith('~'):
		return os.path.expanduser(gnupg_setting)
	elif os.path.isabs(gnupg_setting):
		return gnupg_setting
	else:
		return os.path.realpath(os.path.join(list_dir, gnupg_setting))


def get_mail_address_of_list(list_dir):
	local_file = os.path.join(list_dir, "outlocal")
	host_file = os.path.join(list_dir, "outhost")
	local_mail = ""
	host_mail = ""
	if os.access(local_file, os.R_OK):
		try:
			local_mail = file(local_file).read().strip()
		except IOError:
			pass
	if os.access(host_file, os.R_OK):
		try:
			host_mail = file(host_file).read().strip()
		except IOError:
			pass
	if local_mail and host_mail:
		return "%s@%s" % (local_mail, host_mail)
	elif local_mail:
		return local_mail
	elif host_mail:
		return host_mail
	else:
		return "unknown"


def generate_key(list_dir, name, comment, mail):
	os.environ["GNUPGHOME"] = get_gnupg_setting(list_dir)
	import pyme
	import pyme.core
	import re
	context = pyme.core.Context()
	context.set_armor(1)
	context.set_progress_cb(None, None)
	values = { "name": name, "comment": comment, "mail": mail }
	if not name:
		values["name"] = "Mailing list %s" % os.path.basename(list_dir)
	if not comment:
		values["comment"] = "encrypted"
	if not mail:
		values["mail"] = get_mail_address_of_list(list_dir)
	bad_characters = re.compile("([\(\)<>])")
	for key, value in values.items():
		if bad_characters.search(value):
			sys.stderr.write("The description (%s) of the key to be " % key \
					+ "generated contains invalid characters: '%s'\n" % \
					str(bad_characters.search(value).groups()[0]))
			return False
	key_settings = GENERATE_KEY_SETTINGS % values
	try:
		context.op_genkey(key_settings, None, None)
	except pyme.errors.GPGMEError, err_msg:
		sys.stderr.write("Failed to create the gnupg key: %s\n" % err_msg)
		return False
	return True


def check_mailinglist_directory(list_dir):
	"""Check if the given directory contains an ezmlm mailing list
	"""
	## does the mailing list directory exist?
	if not os.path.isdir(list_dir):
		sys.stderr.write("The mailing list directory does not exist: %s\n" % list_dir)
		return False
	## is the mailing list directory accessible?
	if not os.access(list_dir, os.X_OK):
		sys.stderr.write("Could not access the mailing list directory: %s\n" % list_dir)
		return False
	if not os.path.isfile(os.path.join(list_dir, 'lock')):
		sys.stderr.write("The directory (%s) does not seem to" % list_dir \
				+ " contain an ezmlm mailing list.\n")
		return False
	return True


def output_help():
	prog_name = os.path.basename(sys.argv[0])
	print "Syntax:"
	print "\t%s MAILINGLIST_DIRECTORY [enable|disable]" % prog_name
	print "\t%s MAILINGLIST_DIRECTORY is_encrypted" % prog_name
	print "\t%s MAILINGLIST_DIRECTORY genkey [NAME [COMMENT [MAIL]]]" % prog_name
	print "\t%s MAILINGLIST_DIRECTORY get_gnupg_dir" % prog_name
	print


if __name__ == "__main__":
	if not check_for_errors():
		sys.exit(1)
	else:
		## no parameters - only self-testing was requested - we quit now
		if len(sys.argv) == 1:
			print "OK"
			sys.exit(0)
	if len(sys.argv) == 2:
		if sys.argv[1] == "--help":
			output_help()
			sys.exit(0)
		else:
			sys.stderr.write("Not enough parameters: %s\n" % sys.argv[1])
			output_help()
			sys.exit(2)
	else:
		list_dir = sys.argv[1]
		if not check_mailinglist_directory(list_dir):
			sys.exit(3)
		## is the action valid?
		action = sys.argv[2]
		if action == "enable":
			enable_encryption(list_dir)
		elif action == "disable":
			disable_encryption(list_dir)
		elif action == "is_encrypted":
			if is_encrypted(list_dir):
				print "The mailing list in %s is encrypted." % list_dir
				sys.exit(0)
			else:
				print "The mailing list in %s is not encrypted." % list_dir
				sys.exit(100)
		elif action == "get_gnupg_dir":
			print get_gnupg_setting(list_dir)
		elif action == "genkey":
			name, comment, mail = None, None, None
			if len(sys.argv) > 6:
				sys.stderr.write("Too many arguments (%d) - try '--help' for details.\n" % len(sys.argv)-1 )
				sys.exit(2)
			if len(sys.argv) > 5:
				mail = sys.argv[5]
			if len(sys.argv) > 4:
				comment = sys.argv[4]
			if len(sys.argv) > 3:
				name = sys.argv[3]
			if generate_key(list_dir, name, comment, mail):
				sys.exit(0)
			else:
				sys.exit(4)
		else:
			sys.stderr.write("Unknown action requested: %s\n" % sys.argv[2])
			sys.exit(2)