crypto-exmlm: added python interface

crypto-ezmlm/trunk/python/lispet/config.py

@@ -0,0 +1,124 @@
+#!/usr/bin/env python2.4
+#
+# This file is part of lispet - an encryption filter for the
+# ezmlm-idx mailinglist manager.
+#
+# Copyright 02007 Sense.Lab e.V. <info@senselab.org>
+#
+# This script decrypts an incoming mail and encrypts it for each recipient
+# separately. Afterwards it calls qmail-queue for each recipient.
+# It is meant as a wrapper around qmail-queue. See 'man qmail-queue' for
+# details of the qmail-queue interface.
+#
+# Syntax:
+#  lispet-encrypt [MAILINGLIST_DIRECTORY]
+# 
+# If no MAILINGLIST_DIRECTORY is given, then it will only run some self-tests.
+#
+# Environment settings:
+#  - QMAILQUEUE should contain the path of the qmail-queue program (or a
+#    substitute - e.g. for spam filtering) - otherwise the default location
+#    /var/qmail/bin/qmail-queue is used
+#
+#
+# lispet 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.
+# 
+# lispet 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
+#
+
+
+# TODO:
+#	implement 'sign_messages'
+#	implement 'hide_subject'
+
+
+import sys
+import os
+import re
+#the following modules are imported later
+# import configobj
+
+
+# try to load the module configobj
+try:
+	import configobj
+except ImportError:
+	sys.stderr.write("Failed to import the required module 'configobj'. "
+			. "Please check if it is installed!\n")
+	sys.exit(1)
+
+
+############### some default settings ##################
+
+
+## default settings - the setting keys must always be lower case!
+DEFAULT_SETTINGS = {
+		"plain_without_key": False,
+		"sign_messages": False,
+		"gnupg_dir": ".gnupg"
+	}
+
+	def read_config(self):
+		"""Read the config file.
+
+		If a value is not defined in the config file, then the default value
+		is used.
+		Any line that does not really look like a config setting is ignored.
+		Any unknown configuration settings are ignored, too.
+		"""
+		result = DEFAULT_SETTINGS
+		## retrieve the absolute path of the configuration file
+		## by default it is relative to the mailinglist's directory
+		if os.path.isabs(CONF_FILE):
+			conf_file = CONF_FILE
+		else:
+			conf_file = os.path.join(self.list_dir, CONF_FILE)
+		if not os.access(conf_file, os.R_OK):
+			internal_error("Could not read gpgpy-ezmlm config file: %s" % conf_file)
+		## read all lines of the configuration file
+		all_lines = [ e.strip() for e in file(conf_file).readlines() ]
+		for line in all_lines:
+			## ignore empty lines, comments and lines without "="
+			if (not line) or e.startswith("#") or (e.find("=") == -1):
+				continue
+			key, value = line.split("=", 1)
+			## turn everything to lower case and remove surrounding whitespace
+			key, value = (key.strip().lower(), value.strip())
+			if (len(value) > 1) and \
+					((value.startswith('"') and value.endswith('"')) \
+					or (value.startswith("'") and value.endswith("'"))):
+				value = value[1:-1]
+			## ignore empty values or keys
+			if not key or not value:
+				continue
+			## check boolean values
+			if key in ['plain_without_key', 'sign_messages']:
+				if value.lower() == 'no':
+					result[key] = False
+				elif value.lower() == 'yes':
+					result[key] = True
+				else:
+					continue
+			## process the key directory
+			elif key == 'gnupg_dir':
+				result[key] = value
+			## unknown setting - ignore
+			else:
+				continue
+		if result["gnupg_dir"].startswith('~'):
+			result["gnupg_dir"] = os.path.expanduser(result["gnupg_dir"])
+		elif not os.path.isabs(result["gnupg_dir"]):
+			result["gnupg_dir"] = os.path.abspath(os.path.join(
+					self.list_dir, result["gnupg_dir"]))
+		return result
+

crypto-ezmlm/trunk/python/lispet/interfaces/ezmlm.py

@@ -0,0 +1,162 @@
+#!/usr/bin/env python2.4
+#
+# This file is part of lispet - an encryption filter for different
+# mailing list manager.
+#
+# Copyright 02007-02008 Sense.Lab e.V. <info@senselab.org>
+#
+#
+# lispet 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.
+# 
+# lispet 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
+#
+
+
+
+import sys
+import os
+import re
+# the following modules are imported later
+#import subprocess
+
+# check if the subprocess module is available (python >= 2.4)
+try:
+	import subprocess
+except ImportError:
+	sys.stderr.write("Failed to import the python module 'subprocess'! "
+			. "It requires python2.4 or higher.\n")
+	sys.exit(1)
+
+
+############### some default settings ##################
+
+## we will finally deliver via the original qmail-queue
+if os.environ.has_key("QMAILQUEUE"):
+	QMAILQUEUE_BIN = os.environ["QMAILQUEUE"]
+else:
+	QMAILQUEUE_BIN = '/var/qmail/bin/qmail-queue'
+
+
+
+def write_to_qmailqueue:
+		## use tmpfile as input for qmail-queue
+		## we have to complicate things a little bit, as qmail-queue expects input
+		## at file handle 1 - this is usually stdout
+		# TODO: use something like StringIO instead
+		tmpfile = os.tmpfile()
+		tmpfile.write('F%s\0T%s\0\0' % (sender, recipient))
+		tmpfile.seek(0)
+		## execute the original qmail-queue
+		proc = subprocess.Popen(
+			shell = False,
+			stdin = subprocess.PIPE,
+			stdout = tmpfile.fileno(),
+			env = os.environ,
+			args = [ QMAILQUEUE_BIN ] )
+		proc.stdin.write(mail.as_string())
+		## tmpfile is deleted automatically after closing
+		tmpfile.close()
+		proc.stdin.close()
+		proc.wait()
+		## exit immediately, if qmail-queue failed once
+		if proc.returncode != 0:
+			sys.exit(proc.returncode)
+
+
+
+#################### input/output stuff ###################
+
+def internal_error(message=None, exitcode=81):
+	if message:
+		sys.stderr.write(message + "\n")
+	sys.exit(exitcode)
+
+
+def process_input_and_output(handler):
+	"""Read mail content and the envelopement information from fd1 and fd2
+
+	see 'main qmail-queue' for details
+	"""
+	in_mail = os.fdopen(0, "r")
+	in_envelope = os.fdopen(1, "rb")
+	## try to read mail and 
+	try:
+		mail_text = in_mail.read()
+		envelope = in_envelope.read()
+	except IOError:
+		## report "Unable to read the message or envelope." (see 'man qmail-queue')
+		sys.exit(54)
+	## see 'man qmail-queue' for details of the envelope format
+	envelope_addresses = re.match(u'F(.+?)\0((?:T[^\0]+?\0)+)\0$', envelope)
+	if not envelope_addresses or (len(envelope_addresses.groups()) != 2):
+		## report "Envelope format error." (see 'man qmail-queue')
+		sys.exit(91)
+	## the first match is the sender address
+	envelope_sender = envelope_addresses.groups()[0]
+	## the second match is the list of all recipients
+	## each preceded by "T" and followed by "\0"
+	envelope_recipients = envelope_addresses.groups()[1].split("\0")
+	## remove leading "T" and skip empty values
+	envelope_recipients = [ e[1:] for e in envelope_recipients if e ]
+	for recipient in envelope_recipients:
+		handler.process_mail(envelope_sender, recipient, mail_text)
+
+
+def check_for_errors():
+	errors = False
+	## check the original qmail-queue binary
+	if not os.access(QMAILQUEUE_BIN, os.X_OK):
+		sys.stderr.write("Could not find executable qmail-queue: %s\n" % QMAILQUEUE_BIN)
+		errors = True
+	## check the existence of the pyme module
+	try:
+		import pyme
+	except ImportError:
+		sys.stderr.write("Failed to import python-pyme!\n")
+		errors = True
+	## check if the subprocess module is available (python >= 2.4)
+	try:
+		import subprocess
+	except ImportError:
+		sys.stderr.write("Failed to import the python module 'subprocess'! It requires python2.4.\n")
+		errors = True
+	return errors == False
+
+
+if __name__ == '__main__':
+	# reduce priority
+	os.nice(5)
+	if not check_for_errors():
+		internal_error()
+	if len(sys.argv) == 1:
+		## we were only supposed to run the self-tests - exiting successfully
+		sys.exit(0)
+	## we expect exactly one parameter - the mailinglist directory
+	if len(sys.argv) != 2:
+		internal_error("More than one parameter (the mailinglist directory) given!")
+	## print some help if it was requested
+	if sys.argv[0] == '--help':
+		sys.stderr.write("Syntax: %s [MAILINGLIST_DIRECTORY]\n\n" % \
+				os.path.basename(sys.argv[0]))
+		sys.stderr.write("If you omit the MAILINGLIST_DIRECTORY, " \
+				+ "then only some self-tests are done.\n\n")
+		sys.exit(0)
+	## retrieve the mailing list directory by reading the dotqmail file
+	list_dir = sys.argv[1]
+	## does the mailinglist directory exist?
+	if not os.access(list_dir, os.X_OK):
+		internal_error("Could not access the mailinglist directory: %s" % list_dir)
+	## reencrypt the mail for each recipient
+	mail_handler = MailEncryption(list_dir)
+	process_input_and_output(mail_handler)
+

crypto-ezmlm/trunk/python/lispet/mail.py

@@ -0,0 +1,178 @@
+#!/usr/bin/env python
+#
+# This file is part of lispet - an encryption filter for the different
+# mailinglist manager.
+#
+# Copyright 02007-2008 Sense.Lab e.V. <info@senselab.org>
+#
+# lispet 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.
+# 
+# lispet 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
+#
+
+
+# TODO:
+#	implement 'sign_messages'
+#	implement 'hide_subject'
+
+
+import sys
+import os
+import email
+# the following modules are imported later
+#import pyme
+#import subprocess
+
+
+## try to import the pyme module
+try:
+	import pyme
+except ImportError:
+	sys.stderr.write("Failed to import python-pyme!\n")
+	sys.exit(1)
+## check if the subprocess module is available (python >= 2.4)
+try:
+	import subprocess
+except ImportError:
+	sys.stderr.write("Failed to import the python module 'subprocess'! "
+			. "It requires python2.4 or higher.\n")
+	sys.exit(1)
+
+#################### some strings ######################
+
+
+## put this warning into a mail instead of the encrypted content, in case
+## the key of the recipient is missing
+NOKEY_WARNING = "No valid encryption key found!"
+
+
+## in case of 'cannot decrypt' errors
+DECRYPT_ERROR = "Failed to decrypt the mail that was sent to the mailinglist. Please check the configuration of the mailinglist. Maybe the sender used an invalid encryption key?"
+
+
+################ the encryption handler ################
+
+class MailEncryption:
+
+	def __init__(self, list_dir):
+		self.list_dir = os.path.abspath(list_dir)
+		## does the list directory exist?
+		if not os.access(self.list_dir, os.X_OK):
+			internal_error("Could not access mailinglist directory: %s" \
+					% self.list_dir)
+		## read the config file
+		self.config = self.read_config()
+		## does the gnupg directory exist?
+		if not os.access(self.config["gnupg_dir"], os.X_OK):
+			internal_error("Could not access gnupg directory: %s" \
+					% self.config["gnupg_dir"])
+		## set GPGHOME environment - this should be used by pyme
+		os.environ["GNUPGHOME"] = self.config["gnupg_dir"]
+		## we _must_ import pyme after configuring the GNUPGHOME setting
+		import pyme.core
+		self.pyme = pyme
+		self.context = self.pyme.core.Context()
+		self.context.set_armor(1)
+	
+
+	def get_valid_keys(self, pattern=""):
+		for key in self.context.op_keylist_all(pattern, 0):
+			if key.can_encrypt != 0:
+				yield key
+
+
+	def encrypt_to_keys(self, plain, keylist):
+		plaindata = self.pyme.core.Data(plain)
+		cipher = self.pyme.core.Data(plain)
+		self.context.op_encrypt(keylist, 1, plaindata, cipher)
+		cipher.seek(0, 0)
+		return cipher.read()
+
+
+	def reencrypt_mail(self, mail, keys):
+		if mail.is_multipart():
+			payloads = mail.get_payload()
+			index = 0
+			while index < len(payloads):
+				if self.is_encrypted(payloads[index].get_payload()):
+					decrypted_part = email.message_from_string(
+							self.decrypt_block(payloads[index].get_payload()))
+					if keys:
+						payloads[index].set_payload(self.encrypt_to_keys(
+								decrypted_part.as_string(), keys))
+					else:
+						if self.config["plain_without_key"]:
+							payloads[index].set_payload(decrypted_part.as_string())
+						else:
+							payloads[index].set_payload(NOKEY_WARNING)
+				index += 1
+		else:
+			if self.is_encrypted(mail.get_payload()):
+				if keys:
+					mail.set_payload(self.encrypt_to_keys(
+							self.decrypt_block(mail.get_payload()), keys))
+				else:
+					if self.config["plain_without_key"]:
+						mail.set_payload(self.decrypt_block(mail.get_payload()))
+					else:
+						mail.set_payload(NOKEY_WARNING)
+					
+
+
+	def is_encrypted(self, text):
+		# TODO: check for base64 encoded mails!
+		return text.find("-----BEGIN PGP MESSAGE-----") != -1
+
+
+	def decrypt_block(self, text):
+		cipher = self.pyme.core.Data(text)
+		plain = self.pyme.core.Data()
+		try:
+			self.context.op_decrypt(cipher, plain)
+		except self.pyme.errors.GPGMEError:
+			## decryption failed - we do not do anything
+			plain = self.pyme.core.Data(DECRYPT_ERROR)
+		plain.seek(0, 0)
+		# this function should write to a stream
+		return plain.read()
+
+
+	def process_mail(self, sender, recipient, mail_text):
+		"""Decrypt the mail and encrypt it again for the specified recipient
+		"""
+		mail = email.message_from_string(mail_text)
+		keys = self.get_valid_keys(recipient)
+		## reencrypt the whole mail for the specific recipient
+		self.reencrypt_mail(mail, keys)
+		## use tmpfile as input for qmail-queue
+		## we have to complicate things a little bit, as qmail-queue expects input
+		## at file handle 1 - this is usually stdout
+		tmpfile = os.tmpfile()
+		tmpfile.write('F%s\0T%s\0\0' % (sender, recipient))
+		tmpfile.seek(0)
+		## execute the original qmail-queue
+		proc = subprocess.Popen(
+			shell = False,
+			stdin = subprocess.PIPE,
+			stdout = tmpfile.fileno(),
+			env = os.environ,
+			args = [ QMAILQUEUE_BIN ] )
+		proc.stdin.write(mail.as_string())
+		## tmpfile is deleted automatically after closing
+		tmpfile.close()
+		proc.stdin.close()
+		proc.wait()
+		## exit immediately, if qmail-queue failed once
+		if proc.returncode != 0:
+			sys.exit(proc.returncode)
+