698 lines
23 KiB
Python
698 lines
23 KiB
Python
#
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# gpg-mailgate
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#
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# This file is part of the gpg-mailgate source code.
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#
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# gpg-mailgate 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 3 of the License, or
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# (at your option) any later version.
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#
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# gpg-mailgate source code 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 gpg-mailgate source code. If not, see <http://www.gnu.org/licenses/>.
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#
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"""Lacre's actual mail-delivery module.
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IMPORTANT: This module has to be loaded _after_ initialisation of the logging
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module.
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"""
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from email.mime.multipart import MIMEMultipart
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import copy
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import email
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from email.message import EmailMessage, MIMEPart
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import email.utils
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from email.policy import SMTPUTF8
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import GnuPG
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import os
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import smtplib
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import asyncio
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from typing import Tuple
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# imports for S/MIME
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from M2Crypto import BIO, SMIME, X509
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import logging
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import lacre.text as text
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import lacre.config as conf
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import lacre.keyring as kcache
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from lacre.mailop import KeepIntact, InlineOpenPGPEncrypt, MimeOpenPGPEncrypt
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LOG = logging.getLogger(__name__)
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class GpgRecipient:
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"""A tuple-like object that contains GPG recipient data."""
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def __init__(self, left, right):
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"""Initialise a tuple-like object that contains GPG recipient data."""
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self._left = left
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self._right = right
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def __getitem__(self, index):
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"""Pretend this object is a tuple by returning an indexed tuple element."""
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if index == 0:
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return self._left
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elif index == 1:
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return self._right
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else:
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raise IndexError()
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def __repr__(self):
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"""Return textual representation of this GPG Recipient."""
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return f"GpgRecipient({self._left!r}, {self._right!r})"
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def email(self):
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"""Return this recipient's email address."""
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return self._left
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def key(self):
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"""Return this recipient's key ID."""
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return self._right
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class RecipientList:
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"""Encalsulates two lists of recipients.
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First list contains addresses, the second - GPG identities.
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"""
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def __init__(self, recipients=[], keys=[]):
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"""Initialise lists of recipients and identities."""
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self._recipients = [GpgRecipient(email, key) for (email, key) in zip(recipients, keys)]
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def emails(self):
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"""Return list of recipients."""
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LOG.debug('Recipient emails from: %s', self._recipients)
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return [r.email() for r in self._recipients]
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def keys(self):
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"""Return list of GPG identities."""
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LOG.debug('Recipient keys from: %s', self._recipients)
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return [r.key() for r in self._recipients]
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def __iadd__(self, recipient: GpgRecipient):
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"""Append a recipient."""
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LOG.debug('Adding %s to %s', recipient, self._recipients)
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self._recipients.append(recipient)
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LOG.debug('Added; got: %s', self._recipients)
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return self
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def __len__(self):
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"""Provide len().
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With this method, it is possible to write code like:
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rl = RecipientList()
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if rl:
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# do something
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"""
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return len(self._recipients)
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def _gpg_encrypt(raw_message, recipients):
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if not conf.config_item_set('gpg', 'keyhome'):
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LOG.error("No valid entry for gpg keyhome. Encryption aborted.")
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return recipients
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gpg_recipients, cleartext_recipients = _identify_gpg_recipients(recipients, _load_keys())
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LOG.info(f"Got addresses: gpg_to={gpg_recipients!r}, ungpg_to={cleartext_recipients!r}")
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if gpg_recipients:
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LOG.info("Encrypting email to: %s", gpg_recipients)
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mime, inline = _sort_gpg_recipients(gpg_recipients)
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if mime:
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# Encrypt mail with PGP/MIME
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_gpg_encrypt_and_deliver(raw_message,
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mime.keys(), mime.emails(),
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_encrypt_all_payloads_mime)
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if inline:
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# Encrypt mail with PGP/INLINE
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_gpg_encrypt_and_deliver(raw_message,
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inline.keys(), inline.emails(),
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_encrypt_all_payloads_inline)
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LOG.info('Not processed emails: %s', cleartext_recipients)
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return cleartext_recipients
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def _sort_gpg_recipients(gpg_to) -> Tuple[RecipientList, RecipientList]:
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mime = RecipientList()
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inline = RecipientList()
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recipients_mime = list()
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keys_mime = list()
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recipients_inline = list()
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keys_inline = list()
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default_to_pgp_mime = conf.flag_enabled('default', 'mime_conversion')
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for rcpt in gpg_to:
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# Checking pre defined styles in settings first
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if conf.config_item_equals('pgp_style', rcpt.email(), 'mime'):
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recipients_mime.append(rcpt.email())
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keys_mime.extend(rcpt.key().split(','))
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mime += rcpt
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elif conf.config_item_equals('pgp_style', rcpt.email(), 'inline'):
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recipients_inline.append(rcpt.email())
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keys_inline.extend(rcpt.key().split(','))
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inline += rcpt
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else:
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# Log message only if an unknown style is defined
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if conf.config_item_set('pgp_style', rcpt.email()):
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LOG.debug("Style %s for recipient %s is not known. Use default as fallback."
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% (conf.get_item("pgp_style", rcpt.email()), rcpt.email()))
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# If no style is in settings defined for recipient, use default from settings
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if default_to_pgp_mime:
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recipients_mime.append(rcpt.email())
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keys_mime.extend(rcpt.key().split(','))
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mime += rcpt
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else:
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recipients_inline.append(rcpt.email())
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keys_inline.extend(rcpt.key().split(','))
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inline += rcpt
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mime = RecipientList(recipients_mime, keys_mime)
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inline = RecipientList(recipients_inline, keys_inline)
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LOG.debug('Loaded recipients: MIME %s; Inline %s', repr(mime), repr(inline))
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return mime, inline
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def _gpg_encrypt_copy(message: EmailMessage, keys, recipients, encrypt_f):
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msg_copy = copy.deepcopy(message)
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_customise_headers(msg_copy)
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encrypted_payloads = encrypt_f(msg_copy, keys)
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msg_copy.set_payload(encrypted_payloads)
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return msg_copy
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def _gpg_encrypt_to_bytes(message: EmailMessage, keys, recipients, encrypt_f) -> bytes:
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msg_copy = _gpg_encrypt_copy(message, keys, recipients, encrypt_f)
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return msg_copy.as_bytes(policy=SMTPUTF8)
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def _gpg_encrypt_to_str(message: EmailMessage, keys, recipients, encrypt_f) -> str:
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msg_copy = _gpg_encrypt_copy(message, keys, recipients, encrypt_f)
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return msg_copy.as_string(policy=SMTPUTF8)
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def _gpg_encrypt_and_deliver(message: EmailMessage, keys, recipients, encrypt_f):
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out = _gpg_encrypt_to_str(message, keys, recipients, encrypt_f)
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send_msg(out, recipients)
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def _customise_headers(message: EmailMessage):
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if conf.config_item_equals('default', 'add_header', 'yes'):
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message['X-GPG-Mailgate'] = 'Encrypted by GPG Mailgate'
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if 'Content-Transfer-Encoding' in message:
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message.replace_header('Content-Transfer-Encoding', '8BIT')
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else:
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message['Content-Transfer-Encoding'] = '8BIT'
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def _load_keys():
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"""Return a map from a key's fingerprint to email address."""
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keyring = kcache.KeyRing(conf.get_item('gpg', 'keyhome'))
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return asyncio.run(keyring.freeze_identities())
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def _identify_gpg_recipients(recipients, keys: kcache.KeyCache):
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# This list will be filled with pairs (M, N), where M is the destination
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# address we're going to deliver the message to and N is the identity we're
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# going to encrypt it for.
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gpg_recipients = list()
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# This will be the list of recipients that haven't provided us with their
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# public keys.
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cleartext_recipients = list()
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# In "strict mode", only keys included in configuration are used to encrypt
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# email.
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strict_mode = conf.strict_mode()
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# GnuPG keys found in our keyring.
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for to in recipients:
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own_key = _try_configured_key(to, keys)
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if own_key is not None:
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gpg_recipients.append(GpgRecipient(own_key[0], own_key[1]))
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continue
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direct_key = _try_direct_key_lookup(to, keys, strict_mode)
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if direct_key is not None:
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gpg_recipients.append(GpgRecipient(direct_key[0], direct_key[1]))
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continue
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domain_key = _try_configured_domain_key(to, keys)
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if domain_key is not None:
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gpg_recipients.append(GpgRecipient(domain_key[0], domain_key[1]))
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continue
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cleartext_recipients.append(to)
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LOG.debug('Collected recipients; GPG: %s; cleartext: %s', gpg_recipients, cleartext_recipients)
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return gpg_recipients, cleartext_recipients
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def _find_key(recipient, keys, strict_mode):
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own_key = _try_configured_key(recipient, keys)
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if own_key is not None:
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return own_key
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direct_key = _try_direct_key_lookup(recipient, keys, strict_mode)
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if direct_key is not None:
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return direct_key
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domain_key = _try_configured_domain_key(recipient, keys)
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if domain_key is not None:
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return domain_key
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return None
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def _try_configured_key(recipient, keys):
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if conf.config_item_set('enc_keymap', recipient):
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key = conf.get_item('enc_keymap', recipient)
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if key in keys:
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LOG.debug(f"Found key {key} configured for {recipient}")
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return (recipient, key)
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LOG.debug(f"No configured key found for {recipient}")
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return None
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def _try_direct_key_lookup(recipient, keys, strict_mode):
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if strict_mode:
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return None
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if keys.has_email(recipient):
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LOG.info(f"Found key for {recipient}")
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return recipient, recipient
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(newto, topic) = text.parse_delimiter(recipient)
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if keys.has_email(newto):
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LOG.info(f"Found key for {newto}, stripped {recipient}")
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return recipient, newto
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return None
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def _try_configured_domain_key(recipient, keys):
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parts = recipient.split('@')
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if len(parts) != 2:
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return None
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domain = parts[1]
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if conf.config_item_set('enc_domain_keymap', domain):
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domain_key = conf.get_item('enc_domain_keymap', domain)
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if domain_key in keys:
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LOG.debug(f"Found domain key {domain_key} for {recipient}")
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return recipient, domain_key
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LOG.debug(f"No domain key for {recipient}")
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return None
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def _encrypt_all_payloads_inline(message: EmailMessage, gpg_to_cmdline):
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# This breaks cascaded MIME messages. Blame PGP/INLINE.
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encrypted_payloads = list()
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if isinstance(message.get_payload(), str):
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return _encrypt_payload(message, gpg_to_cmdline).get_payload()
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for payload in message.get_payload():
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if(isinstance(payload.get_payload(), list)):
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encrypted_payloads.extend(_encrypt_all_payloads_inline(payload, gpg_to_cmdline))
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else:
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encrypted_payloads.append(_encrypt_payload(payload, gpg_to_cmdline))
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return encrypted_payloads
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def _encrypt_all_payloads_mime(message: EmailMessage, gpg_to_cmdline):
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# Convert a plain text email into PGP/MIME attachment style. Modeled after enigmail.
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pgp_ver_part = MIMEPart()
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pgp_ver_part.set_content('Version: 1' + text.EOL_S)
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pgp_ver_part.set_type("application/pgp-encrypted")
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pgp_ver_part.set_param('PGP/MIME version identification', "", 'Content-Description')
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encrypted_part = MIMEPart()
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encrypted_part.set_type("application/octet-stream")
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encrypted_part.set_param('name', "encrypted.asc")
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encrypted_part.set_param('OpenPGP encrypted message', "", 'Content-Description')
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encrypted_part.set_param('inline', "", 'Content-Disposition')
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encrypted_part.set_param('filename', "encrypted.asc", 'Content-Disposition')
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message.preamble = "This is an OpenPGP/MIME encrypted message (RFC 2440 and 3156)"
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boundary = _make_boundary()
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if isinstance(message.get_payload(), str):
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wrapped_payload = _rewrap_payload(message)
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encrypted_part.set_payload(wrapped_payload.as_string())
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_set_type_and_boundary(message, boundary)
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return [pgp_ver_part, _encrypt_payload(encrypted_part, gpg_to_cmdline, True)]
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else:
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processed_payloads = _generate_message_from_payloads(message)
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encrypted_part.set_payload(processed_payloads.as_string())
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_set_type_and_boundary(message, boundary)
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return [pgp_ver_part, _encrypt_payload(encrypted_part, gpg_to_cmdline, False)]
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def _rewrap_payload(message: EmailMessage) -> MIMEPart:
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# In PGP/MIME (RFC 3156), the payload has to be a valid MIME entity. In
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# other words, we need to wrap text/plain message's payload in a new MIME
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# entity.
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pld = MIMEPart()
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pld.set_type(message.get_content_type())
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pld.set_content(message.get_content())
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# Make sure all Content-Type parameters are included.
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for (k, v) in message.get_params():
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pld.set_param(k, v)
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return pld
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def _make_boundary():
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junk_msg = MIMEMultipart()
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# XXX See EmailTest.test_boundary_generated_after_as_string_call.
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_ = junk_msg.as_string()
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return junk_msg.get_boundary()
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def _set_type_and_boundary(message: EmailMessage, boundary):
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message.set_type('multipart/encrypted')
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message.set_param('protocol', 'application/pgp-encrypted')
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message.set_param('boundary', boundary)
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def _encrypt_payload(payload: EmailMessage, recipients, check_nested=True, **kwargs):
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raw_payload = payload.get_payload(decode=True)
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LOG.debug('About to encrypt raw payload: %s', raw_payload)
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LOG.debug('Original message: %s', payload)
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if check_nested and text.is_payload_pgp_inline(raw_payload):
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LOG.debug("Message is already pgp encrypted. No nested encryption needed.")
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return payload
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gpg = _make_encryptor(raw_payload, recipients)
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gpg.update(raw_payload)
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encrypted_data, exit_code = gpg.encrypt()
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payload.set_payload(encrypted_data)
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isAttachment = payload.get_param('attachment', None, 'Content-Disposition') is not None
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if isAttachment:
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_append_gpg_extension(payload)
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if not (payload.get('Content-Transfer-Encoding') is None):
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payload.replace_header('Content-Transfer-Encoding', "7bit")
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return payload
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def _make_encryptor(raw_data, recipients):
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# No check is needed for conf.get_item('gpg', 'keyhome') as this is already
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# done in method gpg_encrypt
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keyhome = conf.get_item('gpg', 'keyhome')
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if isinstance(raw_data, str):
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return GnuPG.GPGEncryptor(keyhome, recipients, 'utf-8')
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else:
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return GnuPG.GPGEncryptor(keyhome, recipients)
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def _append_gpg_extension(attachment):
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filename = attachment.get_filename()
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if not filename:
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return
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pgpFilename = filename + ".pgp"
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# Attachment name can come from one of two places: Content-Disposition or
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# Content-Type header, hence the two cases below.
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if not (attachment.get('Content-Disposition') is None):
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attachment.set_param('filename', pgpFilename, 'Content-Disposition')
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if not (attachment.get('Content-Type') is None) and not (attachment.get_param('name') is None):
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attachment.set_param('name', pgpFilename)
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def _smime_encrypt(raw_message, recipients):
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global LOG
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global from_addr
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if not conf.config_item_set('smime', 'cert_path'):
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LOG.info("No valid path for S/MIME certs found in config file. S/MIME encryption aborted.")
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return recipients
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cert_path = conf.get_item('smime', 'cert_path')+"/"
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s = SMIME.SMIME()
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sk = X509.X509_Stack()
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smime_to = list()
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unsmime_to = list()
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for addr in recipients:
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cert_and_email = _get_cert_for_email(addr, cert_path)
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if not (cert_and_email is None):
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(to_cert, normal_email) = cert_and_email
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LOG.debug("Found cert " + to_cert + " for " + addr + ": " + normal_email)
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smime_to.append(addr)
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x509 = X509.load_cert(to_cert, format=X509.FORMAT_PEM)
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sk.push(x509)
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else:
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unsmime_to.append(addr)
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if smime_to:
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s.set_x509_stack(sk)
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s.set_cipher(SMIME.Cipher('aes_192_cbc'))
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p7 = s.encrypt(BIO.MemoryBuffer(raw_message.as_string()))
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# Output p7 in mail-friendly format.
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out = BIO.MemoryBuffer()
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out.write('From: ' + from_addr + text.EOL_S)
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out.write('To: ' + raw_message['To'] + text.EOL_S)
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if raw_message['Cc']:
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out.write('Cc: ' + raw_message['Cc'] + text.EOL_S)
|
|
if raw_message['Bcc']:
|
|
out.write('Bcc: ' + raw_message['Bcc'] + text.EOL_S)
|
|
if raw_message['Subject']:
|
|
out.write('Subject: ' + raw_message['Subject'] + text.EOL_S)
|
|
|
|
if conf.config_item_equals('default', 'add_header', 'yes'):
|
|
out.write('X-GPG-Mailgate: Encrypted by GPG Mailgate' + text.EOL_S)
|
|
|
|
s.write(out, p7)
|
|
|
|
LOG.debug(f"Sending message from {from_addr} to {smime_to}")
|
|
|
|
send_msg(out.read(), smime_to)
|
|
if unsmime_to:
|
|
LOG.debug(f"Unable to find valid S/MIME certificates for {unsmime_to}")
|
|
|
|
return unsmime_to
|
|
|
|
|
|
def _get_cert_for_email(to_addr, cert_path):
|
|
insensitive = conf.config_item_equals('default', 'mail_case_insensitive', 'yes')
|
|
|
|
LOG.info(f'Retrieving certificate for {to_addr!r} from {cert_path!r}, sensitivity={insensitive!r}')
|
|
|
|
files_in_directory = os.listdir(cert_path)
|
|
for filename in files_in_directory:
|
|
file_path = os.path.join(cert_path, filename)
|
|
if not os.path.isfile(file_path):
|
|
continue
|
|
|
|
if insensitive:
|
|
if filename.casefold() == to_addr:
|
|
return (file_path, to_addr)
|
|
else:
|
|
if filename == to_addr:
|
|
return (file_path, to_addr)
|
|
|
|
# support foo+ignore@bar.com -> foo@bar.com
|
|
LOG.info(f"An email with topic? {to_addr}")
|
|
(fixed_up_email, topic) = text.parse_delimiter(to_addr)
|
|
LOG.info(f'Got {fixed_up_email!r} and {topic!r}')
|
|
if topic is None:
|
|
# delimiter not used
|
|
LOG.info('Topic not found')
|
|
return None
|
|
else:
|
|
LOG.info(f"Looking up certificate for {fixed_up_email} after parsing {to_addr}")
|
|
return _get_cert_for_email(fixed_up_email, cert_path)
|
|
|
|
|
|
def _generate_message_from_payloads(payloads, message=None):
|
|
if message is None:
|
|
message = email.mime.multipart.MIMEMultipart(payloads.get_content_subtype())
|
|
|
|
for payload in payloads.get_payload():
|
|
if(isinstance(payload.get_payload(), list)):
|
|
message.attach(_generate_message_from_payloads(payload))
|
|
else:
|
|
message.attach(payload)
|
|
|
|
return message
|
|
|
|
|
|
def _get_first_payload(payloads):
|
|
if payloads.is_multipart():
|
|
return _get_first_payload(payloads.get_payload(0))
|
|
else:
|
|
return payloads
|
|
|
|
|
|
def send_msg(message: str, recipients, fromaddr=None):
|
|
"""Send MESSAGE to RECIPIENTS to the mail relay."""
|
|
global from_addr
|
|
|
|
if fromaddr is not None:
|
|
from_addr = fromaddr
|
|
|
|
recipients = [_f for _f in recipients if _f]
|
|
if recipients:
|
|
LOG.info(f"Sending email to: {recipients!r}")
|
|
relay = conf.relay_params()
|
|
smtp = smtplib.SMTP(relay[0], relay[1])
|
|
if conf.flag_enabled('relay', 'starttls'):
|
|
smtp.starttls()
|
|
smtp.sendmail(from_addr, recipients, message)
|
|
else:
|
|
LOG.info("No recipient found")
|
|
|
|
|
|
def send_msg_bytes(message: bytes, recipients, fromaddr=None):
|
|
"""Send MESSAGE to RECIPIENTS to the mail relay."""
|
|
global from_addr
|
|
|
|
if fromaddr is not None:
|
|
from_addr = fromaddr
|
|
|
|
recipients = [_f for _f in recipients if _f]
|
|
if recipients:
|
|
LOG.info(f"Sending email to: {recipients!r}")
|
|
relay = conf.relay_params()
|
|
smtp = smtplib.SMTP(relay[0], relay[1])
|
|
if conf.flag_enabled('relay', 'starttls'):
|
|
smtp.starttls()
|
|
smtp.sendmail(from_addr, recipients, message)
|
|
else:
|
|
LOG.info("No recipient found")
|
|
|
|
|
|
def _recode(m: EmailMessage):
|
|
payload = m.get_payload()
|
|
m.set_content(payload)
|
|
|
|
|
|
def failover_delivery(message: EmailMessage, recipients):
|
|
"""Try delivering message just one last time."""
|
|
LOG.debug('Failover delivery')
|
|
|
|
if message.get_content_maintype() == 'text':
|
|
LOG.debug('Flat text message, adjusting coding')
|
|
_recode(message)
|
|
b = message.as_bytes(policy=SMTPUTF8)
|
|
send_msg_bytes(b, recipients)
|
|
elif message.get_content_maintype() == 'multipart':
|
|
LOG.debug('Multipart message, adjusting coding of text entities')
|
|
for part in message.iter_parts():
|
|
if part.get_content_maintype() == 'text':
|
|
_recode(part)
|
|
b = message.as_bytes(policy=SMTPUTF8)
|
|
send_msg_bytes(b, recipients)
|
|
else:
|
|
LOG.warning('No failover strategy, giving up')
|
|
|
|
|
|
def _is_encrypted(raw_message: EmailMessage):
|
|
if raw_message.get_content_type() == 'multipart/encrypted':
|
|
return True
|
|
|
|
first_part = _get_first_payload(raw_message)
|
|
if first_part.get_content_type() == 'application/pkcs7-mime':
|
|
return True
|
|
|
|
return text.is_message_pgp_inline(first_part)
|
|
|
|
|
|
def delivery_plan(recipients, message: EmailMessage, key_cache: kcache.KeyCache):
|
|
"""Generate a sequence of delivery strategies."""
|
|
if _is_encrypted(message):
|
|
LOG.debug('Message is already encrypted: %s', message)
|
|
return [KeepIntact(recipients)]
|
|
|
|
gpg_recipients, cleartext_recipients = _identify_gpg_recipients(recipients, key_cache)
|
|
|
|
mime, inline = _sort_gpg_recipients(gpg_recipients)
|
|
|
|
keyhome = conf.get_item('gpg', 'keyhome')
|
|
|
|
plan = []
|
|
if mime:
|
|
plan.append(MimeOpenPGPEncrypt(mime.emails(), mime.keys(), keyhome))
|
|
if inline:
|
|
plan.append(InlineOpenPGPEncrypt(inline.emails(), inline.keys(), keyhome))
|
|
if cleartext_recipients:
|
|
plan.append(KeepIntact(cleartext_recipients))
|
|
|
|
return plan
|
|
|
|
|
|
def deliver_message(raw_message: EmailMessage, from_address, to_addrs):
|
|
"""Send RAW_MESSAGE to all TO_ADDRS using the best encryption method available."""
|
|
global from_addr
|
|
|
|
# Ugly workaround to keep the code working without too many changes.
|
|
from_addr = from_address
|
|
|
|
sanitize = text.choose_sanitizer(conf.get_item('default', 'mail_case_insensitive'))
|
|
recipients_left = [sanitize(recipient) for recipient in to_addrs]
|
|
|
|
# There is no need for nested encryption
|
|
LOG.debug("Seeing if it's already encrypted")
|
|
if _is_encrypted(raw_message):
|
|
LOG.debug("Message is already encrypted. Encryption aborted.")
|
|
send_msg(raw_message.as_string(), recipients_left)
|
|
return
|
|
|
|
# Encrypt mails for recipients with known public PGP keys
|
|
LOG.debug("Encrypting with OpenPGP")
|
|
recipients_left = _gpg_encrypt(raw_message, recipients_left)
|
|
if not recipients_left:
|
|
return
|
|
|
|
# Encrypt mails for recipients with known S/MIME certificate
|
|
LOG.debug("Encrypting with S/MIME")
|
|
recipients_left = _smime_encrypt(raw_message, recipients_left)
|
|
if not recipients_left:
|
|
return
|
|
|
|
# Send out mail to recipients which are left
|
|
LOG.debug("Sending the rest as text/plain")
|
|
send_msg(raw_message.as_string(), recipients_left)
|