331 lines
11 KiB
Text
331 lines
11 KiB
Text
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#!/usr/bin/env python2.4
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#
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# This file is part of gpgpy-ezmlm - an encryption filter for the
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# ezmlm-idx mailinglist manager.
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#
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# Copyright 02007 Sense.Lab e.V. <info@senselab.org>
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#
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# This script decrypts an incoming mail and encrypts it for each recipient
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# separately. Afterwards it calls qmail-queue for each recipient.
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# It is meant as a wrapper around qmail-queue. See 'man qmail-queue' for
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# details of the qmail-queue interface.
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#
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# Syntax:
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# gpgpy-ezmlm-encrypt [MAILINGLIST_DIRECTORY]
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#
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# If no MAILINGLIST_DIRECTORY is given, then it will only run some self-tests.
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#
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# Environment settings:
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# - QMAILQUEUE should contain the path of the qmail-queue program (or a
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# substitute - e.g. for spam filtering) - otherwise the default location
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# /var/qmail/bin/qmail-queue is used
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#
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#
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# gpgpy-ezmlm is free software; you can redistribute it and/or modify
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# it under the terms of the GNU General Public License as published by
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# the Free Software Foundation; either version 2 of the License, or
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# (at your option) any later version.
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#
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# gpgpy-ezmlm is distributed in the hope that it will be useful,
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# but WITHOUT ANY WARRANTY; without even the implied warranty of
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# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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# GNU General Public License for more details.
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#
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# You should have received a copy of the GNU General Public License
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# along with the CryptoBox; if not, write to the Free Software
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# Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
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#
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# TODO: implement 'sign_messages' setting
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import sys, os, re
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import email
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import email.Parser
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import email.Message
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import subprocess
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############### some default settings ##################
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## we will finally deliver via the original qmail-queue
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if os.environ.has_key("QMAILQUEUE"):
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QMAILQUEUE_BIN = os.environ["QMAILQUEUE"]
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else:
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QMAILQUEUE_BIN = '/var/qmail/bin/qmail-queue'
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## the list specific configuration file
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CONF_FILE = 'conf-gpgpy'
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## default settings - the setting keys must always be lower case!
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DEFAULT_SETTINGS = {
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"plain_without_key": False,
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"sign_messages": False,
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"gnupg_dir": ".gnupg"
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}
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## put this warning into a mail instead of the encrypted content, in case
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## the key of the recipient is missing
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NOKEY_WARNING = "No valid encryption key found!"
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## in case of 'cannot decrypt' errors
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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?"
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################ the encryption handler ################
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class MailEncryption:
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def __init__(self, list_dir):
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self.list_dir = os.path.abspath(list_dir)
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## does the list directory exist?
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if not os.access(self.list_dir, os.X_OK):
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internal_error("Could not access mailinglist directory: %s" \
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% self.list_dir)
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## read the config file
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self.config = self.read_config()
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## does the gnupg directory exist?
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if not os.access(self.config["gnupg_dir"], os.X_OK):
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internal_error("Could not access gnupg directory: %s" \
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% self.config["gnupg_dir"])
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## set GPGHOME environment - this should be used by pyme
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os.environ["GNUPGHOME"] = self.config["gnupg_dir"]
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## we _must_ import pyme after configuring the GNUPGHOME setting
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import pyme.core
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self.pyme = pyme
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self.context = self.pyme.core.Context()
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self.context.set_armor(1)
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def read_config(self):
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"""Read the config file.
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If a value is not defined in the config file, then the default value
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is used.
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Any line that does not really look like a config setting is ignored.
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Any unknown configuration settings are ignored, too.
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"""
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result = DEFAULT_SETTINGS
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## retrieve the absolute path of the configuration file
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## by default it is relative to the mailinglist's directory
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if os.path.isabs(CONF_FILE):
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conf_file = CONF_FILE
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else:
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conf_file = os.path.join(self.list_dir, CONF_FILE)
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if not os.access(conf_file, os.R_OK):
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internal_error("Could not read gpgpy-ezmlm config file: %s" % conf_file)
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## read all lines of the configuration file
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all_lines = [ e.strip() for e in file(conf_file).readlines() ]
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for line in all_lines:
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## ignore empty lines, comments and lines without "="
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if (not line) or e.startswith("#") or (e.find("=") == -1):
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continue
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key, value = line.split("=", 1)
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## turn everything to lower case and remove surrounding whitespace
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key, value = (key.strip().lower(), value.strip())
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if (len(value) > 1) and \
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((value.startswith('"') and value.endswith('"')) \
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or (value.startswith("'") and value.endswith("'"))):
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value = value[1:-1]
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## ignore empty values or keys
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if not key or not value:
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continue
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## check boolean values
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if key in ['plain_without_key', 'sign_messages']:
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if value.lower() == 'no':
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result[key] = False
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elif value.lower() == 'yes':
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result[key] = True
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else:
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continue
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## process the key directory
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elif key == 'gnupg_dir':
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result[key] = value
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## unknown setting - ignore
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else:
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continue
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if result["gnupg_dir"].startswith('~'):
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result["gnupg_dir"] = os.path.expanduser(result["gnupg_dir"])
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elif not os.path.isabs(result["gnupg_dir"]):
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result["gnupg_dir"] = os.path.abspath(os.path.join(
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self.list_dir, result["gnupg_dir"]))
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return result
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def get_valid_keys(self, pattern=""):
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return [ key for key in self.context.op_keylist_all(pattern, 0)
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if (key.can_encrypt != 0) ]
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def encrypt_to_keys(self, plain, keylist):
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plaindata = self.pyme.core.Data(plain)
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cipher = self.pyme.core.Data(plain)
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self.context.op_encrypt(keylist, 1, plaindata, cipher)
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cipher.seek(0, 0)
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return cipher.read()
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def reencrypt_mail(self, mail, keys):
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if mail.is_multipart():
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payloads = mail.get_payload()
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index = 0
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while index < len(payloads):
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if self.is_encrypted(payloads[index].get_payload()):
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decrypted_part = email.message_from_string(
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self.decrypt_block(payloads[index].get_payload()))
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if keys:
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payloads[index].set_payload(self.encrypt_to_keys(
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decrypted_part.as_string(), keys))
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else:
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if self.config["plain_without_key"]:
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payloads[index].set_payload(decrypted_part.as_string())
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else:
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payloads[index].set_payload(NOKEY_WARNING)
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index += 1
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else:
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if self.is_encrypted(mail.get_payload()):
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if keys:
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mail.set_payload(self.encrypt_to_keys(
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self.decrypt_block(mail.get_payload()), keys))
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else:
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if self.config["plain_without_key"]:
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mail.set_payload(self.decrypt_block(mail.get_payload()))
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else:
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mail.set_payload(NOKEY_WARNING)
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def is_encrypted(self, text):
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return text.find("-----BEGIN PGP MESSAGE-----") != -1
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def decrypt_block(self, text):
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cipher = self.pyme.core.Data(text)
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plain = self.pyme.core.Data()
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try:
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self.context.op_decrypt(cipher, plain)
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except self.pyme.errors.GPGMEError:
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## decryption failed - we do not do anything
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plain = self.pyme.core.Data(DECRYPT_ERROR)
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plain.seek(0, 0)
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return plain.read()
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def process_mail(self, sender, recipient, mail_text):
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"""Decrypt the mail and encrypt it again for the specified recipient
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"""
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mail = email.message_from_string(mail_text)
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keys = self.get_valid_keys(recipient)
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## reencrypt the whole mail for the specific recipient
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self.reencrypt_mail(mail, keys)
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## use tmpfile as input for qmail-queue
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## we have to complicate things a little bit, as qmail-queue expects input
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## at file handle 1 - this is usually stdout
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tmpfile = os.tmpfile()
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tmpfile.write('F%s\0T%s\0\0' % (sender, recipient))
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tmpfile.seek(0)
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## execute the original qmail-queue
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proc = subprocess.Popen(
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shell = False,
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stdin = subprocess.PIPE,
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stdout = tmpfile.fileno(),
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env = os.environ,
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args = [ QMAILQUEUE_BIN ] )
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proc.stdin.write(mail.as_string())
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## tmpfile is deleted automatically after closing
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tmpfile.close()
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proc.stdin.close()
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proc.wait()
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## exit immediately, if qmail-queue failed once
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if proc.returncode != 0:
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sys.exit(proc.returncode)
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#################### input/output stuff ###################
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def internal_error(message=None, exitcode=81):
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if message:
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sys.stderr.write(message + "\n")
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sys.exit(exitcode)
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def process_input_and_output(handler):
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"""Read mail content and the envelopement information from fd1 and fd2
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see 'main qmail-queue' for details
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"""
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in_mail = os.fdopen(0, "r")
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in_envelope = os.fdopen(1, "rb")
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## try to read mail and
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try:
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mail_text = in_mail.read()
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envelope = in_envelope.read()
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except IOError:
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## report "Unable to read the message or envelope." (see 'man qmail-queue')
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sys.exit(54)
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## see 'man qmail-queue' for details of the envelope format
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envelope_addresses = re.match(u'F(.+?)\0((?:T[^\0]+?\0)+)\0$', envelope)
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if not envelope_addresses or (len(envelope_addresses.groups()) != 2):
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## report "Envelope format error." (see 'man qmail-queue')
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sys.exit(91)
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## the first match is the sender address
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envelope_sender = envelope_addresses.groups()[0]
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## the second match is the list of all recipients
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## each preceded by "T" and followed by "\0"
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envelope_recipients = envelope_addresses.groups()[1].split("\0")
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## remove leading "T" and skip empty values
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envelope_recipients = [ e[1:] for e in envelope_recipients if e ]
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for recipient in envelope_recipients:
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handler.process_mail(envelope_sender, recipient, mail_text)
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def check_for_errors():
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errors = False
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## check the original qmail-queue binary
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if not os.access(QMAILQUEUE_BIN, os.X_OK):
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sys.stderr.write("Could not find executable qmail-queue: %s\n" % QMAILQUEUE_BIN)
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errors = True
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## check the existence of the pyme module
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try:
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import pyme
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except ImportError:
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sys.stderr.write("Failed to import python-pyme!\n")
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errors = True
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## check if the subprocess module is available (python >= 2.4)
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try:
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import subprocess
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except ImportError:
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sys.stderr.write("Failed to import the python module 'subprocess'! It requires python2.4.\n")
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errors = True
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return errors == False
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if __name__ == '__main__':
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if not check_for_errors():
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internal_error()
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if len(sys.argv) == 1:
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## we were only supposed to run the self-tests - exiting successfully
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sys.exit(0)
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## we expect exactly one parameter - the mailinglist directory
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if len(sys.argv) != 2:
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internal_error("More than one parameter (the mailinglist directory) given!")
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## print some help if it was requested
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if sys.argv[0] == '--help':
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sys.stderr.write("Syntax: %s [MAILINGLIST_DIRECTORY]\n\n" % \
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os.path.basename(sys.argv[0]))
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sys.stderr.write("If you omit the MAILINGLIST_DIRECTORY, " \
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+ "then only some self-tests are done.\n\n")
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sys.exit(0)
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## retrieve the mailing list directory by reading the dotqmail file
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list_dir = sys.argv[1]
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## does the mailinglist directory exist?
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if not os.access(list_dir, os.X_OK):
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internal_error("Could not access the mailinglist directory: %s" % list_dir)
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## reencrypt the mail for each recipient
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mail_handler = MailEncryption(list_dir)
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process_input_and_output(mail_handler)
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