gpg-lacre/gpg-mailgate.py

466 lines
16 KiB
Python
Executable file

#!/usr/bin/python
#
# gpg-mailgate
#
# This file is part of the gpg-mailgate source code.
#
# gpg-mailgate 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 3 of the License, or
# (at your option) any later version.
#
# gpg-mailgate source code 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 gpg-mailgate source code. If not, see <http://www.gnu.org/licenses/>.
#
from configparser import RawConfigParser
from email.mime.base import MIMEBase
from email.mime.multipart import MIMEMultipart
import copy
import email
import email.message
import email.utils
import GnuPG
import os
import re
import smtplib
import sys
import syslog
import traceback
# imports for S/MIME
from M2Crypto import BIO, Rand, SMIME, X509
from email.mime.message import MIMEMessage
# Environment variable name we read to retrieve configuration path. This is to
# enable non-root users to set up and run GPG Mailgate and to make the software
# testable.
CONFIG_PATH_ENV = "GPG_MAILGATE_CONFIG"
# Read configuration from /etc/gpg-mailgate.conf
_cfg = RawConfigParser()
_cfg.read(os.getenv(CONFIG_PATH_ENV, '/etc/gpg-mailgate.conf'))
cfg = dict()
for sect in _cfg.sections():
cfg[sect] = dict()
for (name, value) in _cfg.items(sect):
cfg[sect][name] = value
def log( msg ):
if 'logging' in cfg and 'file' in cfg['logging']:
if cfg['logging'].get('file') == "syslog":
syslog.syslog(syslog.LOG_INFO | syslog.LOG_MAIL, msg)
else:
logfile = open(cfg['logging']['file'], 'a')
logfile.write(msg + "\n")
logfile.close()
verbose = 'logging' in cfg and 'verbose' in cfg['logging'] and cfg['logging'].get('verbose') == 'yes'
# Read e-mail from stdin
raw = sys.stdin.read()
raw_message = email.message_from_string( raw )
from_addr = raw_message['From']
to_addrs = sys.argv[1:]
def gpg_encrypt( raw_message, recipients ):
if not get_bool_from_cfg('gpg', 'keyhome'):
log("No valid entry for gpg keyhome. Encryption aborted.")
return recipients
keys = GnuPG.public_keys( cfg['gpg']['keyhome'] )
for fingerprint in keys:
keys[fingerprint] = sanitize_case_sense(keys[fingerprint])
gpg_to = list()
ungpg_to = list()
for to in recipients:
# Check if recipient is in keymap
if get_bool_from_cfg('enc_keymap', to):
log("Encrypt keymap has key '%s'" % cfg['enc_keymap'][to] )
# Check we've got a matching key!
if cfg['enc_keymap'][to] in keys:
gpg_to.append( (to, cfg['enc_keymap'][to]) )
continue
else:
log("Key '%s' in encrypt keymap not found in keyring for email address '%s'." % (cfg['enc_keymap'][to], to))
# Check if key in keychain is present
if to in keys.values() and not get_bool_from_cfg('default', 'enc_keymap_only', 'yes'):
gpg_to.append( (to, to) )
continue
# Check if there is a default key for the domain
splitted_to = to.split('@')
if len(splitted_to) > 1:
domain = splitted_to[1]
if get_bool_from_cfg('enc_domain_keymap', domain):
log("Encrypt domain keymap has key '%s'" % cfg['enc_dec_keymap'][domain] )
# Check we've got a matching key!
if cfg['enc_domain_keymap'][domain] in keys:
log("Using default domain key for recipient '%s'" % to)
gpg_to.append( (to, cfg['enc_domain_keymap'][domain]) )
continue
else:
log("Key '%s' in encrypt domain keymap not found in keyring for email address '%s'." % (cfg['enc_domain_keymap'][domain], to))
# At this point no key has been found
if verbose:
log("Recipient (%s) not in PGP domain list for encrypting." % to)
ungpg_to.append(to)
if gpg_to != list():
log("Encrypting email to: %s" % ' '.join( x[0] for x in gpg_to ))
# Getting PGP style for recipient
gpg_to_smtp_mime = list()
gpg_to_cmdline_mime = list()
gpg_to_smtp_inline = list()
gpg_to_cmdline_inline = list()
for rcpt in gpg_to:
# Checking pre defined styles in settings first
if get_bool_from_cfg('pgp_style', rcpt[0], 'mime'):
gpg_to_smtp_mime.append(rcpt[0])
gpg_to_cmdline_mime.extend(rcpt[1].split(','))
elif get_bool_from_cfg('pgp_style', rcpt[0], 'inline'):
gpg_to_smtp_inline.append(rcpt[0])
gpg_to_cmdline_inline.extend(rcpt[1].split(','))
else:
# Log message only if an unknown style is defined
if get_bool_from_cfg('pgp_style', rcpt[0]):
log("Style %s for recipient %s is not known. Use default as fallback." % (cfg['pgp_style'][rcpt[0]], rcpt[0]))
# If no style is in settings defined for recipient, use default from settings
if get_bool_from_cfg('default', 'mime_conversion', 'yes'):
gpg_to_smtp_mime.append(rcpt[0])
gpg_to_cmdline_mime.extend(rcpt[1].split(','))
else:
gpg_to_smtp_inline.append(rcpt[0])
gpg_to_cmdline_inline.extend(rcpt[1].split(','))
if gpg_to_smtp_mime != list():
# Encrypt mail with PGP/MIME
raw_message_mime = copy.deepcopy(raw_message)
if get_bool_from_cfg('default', 'add_header', 'yes'):
raw_message_mime['X-GPG-Mailgate'] = 'Encrypted by GPG Mailgate'
if 'Content-Transfer-Encoding' in raw_message_mime:
raw_message_mime.replace_header('Content-Transfer-Encoding', '8BIT')
else:
raw_message_mime['Content-Transfer-Encoding'] = '8BIT'
encrypted_payloads = encrypt_all_payloads_mime( raw_message_mime, gpg_to_cmdline_mime )
raw_message_mime.set_payload( encrypted_payloads )
send_msg( raw_message_mime.as_string(), gpg_to_smtp_mime )
if gpg_to_smtp_inline != list():
# Encrypt mail with PGP/INLINE
raw_message_inline = copy.deepcopy(raw_message)
if get_bool_from_cfg('default', 'add_header', 'yes'):
raw_message_inline['X-GPG-Mailgate'] = 'Encrypted by GPG Mailgate'
if 'Content-Transfer-Encoding' in raw_message_inline:
raw_message_inline.replace_header('Content-Transfer-Encoding', '8BIT')
else:
raw_message_inline['Content-Transfer-Encoding'] = '8BIT'
encrypted_payloads = encrypt_all_payloads_inline( raw_message_inline, gpg_to_cmdline_inline )
raw_message_inline.set_payload( encrypted_payloads )
send_msg( raw_message_inline.as_string(), gpg_to_smtp_inline )
return ungpg_to
def encrypt_all_payloads_inline( message, gpg_to_cmdline ):
# This breaks cascaded MIME messages. Blame PGP/INLINE.
encrypted_payloads = list()
if isinstance(message.get_payload(), str):
return encrypt_payload( message, gpg_to_cmdline ).get_payload()
for payload in message.get_payload():
if( isinstance(payload.get_payload(), list) ):
encrypted_payloads.extend( encrypt_all_payloads_inline( payload, gpg_to_cmdline ) )
else:
encrypted_payloads.append( encrypt_payload( payload, gpg_to_cmdline ) )
return encrypted_payloads
def encrypt_all_payloads_mime( message, gpg_to_cmdline ):
# Convert a plain text email into PGP/MIME attachment style. Modeled after enigmail.
submsg1 = email.message.Message()
submsg1.set_payload("Version: 1\n")
submsg1.set_type("application/pgp-encrypted")
submsg1.set_param('PGP/MIME version identification', "", 'Content-Description' )
submsg2 = email.message.Message()
submsg2.set_type("application/octet-stream")
submsg2.set_param('name', "encrypted.asc")
submsg2.set_param('OpenPGP encrypted message', "", 'Content-Description' )
submsg2.set_param('inline', "", 'Content-Disposition' )
submsg2.set_param('filename', "encrypted.asc", 'Content-Disposition' )
if isinstance(message.get_payload(), str):
# WTF! It seems to swallow the first line. Not sure why. Perhaps
# it's skipping an imaginary blank line someplace. (ie skipping a header)
# Workaround it here by prepending a blank line.
# This happens only on text only messages.
additionalSubHeader=""
if 'Content-Type' in message and not message['Content-Type'].startswith('multipart'):
additionalSubHeader="Content-Type: "+message['Content-Type']+"\n"
submsg2.set_payload(additionalSubHeader+"\n" +message.get_payload(decode=True))
check_nested = True
else:
processed_payloads = generate_message_from_payloads(message)
submsg2.set_payload(processed_payloads.as_string())
check_nested = False
message.preamble = "This is an OpenPGP/MIME encrypted message (RFC 2440 and 3156)"
# Use this just to generate a MIME boundary string.
junk_msg = MIMEMultipart()
junk_str = junk_msg.as_string() # WTF! Without this, get_boundary() will return 'None'!
boundary = junk_msg.get_boundary()
# This also modifies the boundary in the body of the message, ie it gets parsed.
if 'Content-Type' in message:
message.replace_header('Content-Type', "multipart/encrypted; protocol=\"application/pgp-encrypted\";\nboundary=\"%s\"\n" % boundary)
else:
message['Content-Type'] = "multipart/encrypted; protocol=\"application/pgp-encrypted\";\nboundary=\"%s\"\n" % boundary
return [ submsg1, encrypt_payload(submsg2, gpg_to_cmdline, check_nested) ]
def encrypt_payload( payload, gpg_to_cmdline, check_nested = True ):
raw_payload = payload.get_payload(decode=True)
if check_nested and b"-----BEGIN PGP MESSAGE-----" in raw_payload and b"-----END PGP MESSAGE-----" in raw_payload:
if verbose:
log("Message is already pgp encrypted. No nested encryption needed.")
return payload
# No check is needed for cfg['gpg']['keyhome'] as this is already done in method gpg_encrypt
gpg = GnuPG.GPGEncryptor( cfg['gpg']['keyhome'], gpg_to_cmdline, payload.get_content_charset() )
gpg.update( raw_payload )
encrypted_data, returncode = gpg.encrypt()
if verbose:
log("Return code from encryption=%d (0 indicates success)." % returncode)
if returncode != 0:
log("Encrytion failed with return code %d. Encryption aborted." % returncode)
return payload
payload.set_payload( encrypted_data )
isAttachment = payload.get_param( 'attachment', None, 'Content-Disposition' ) is not None
if isAttachment:
filename = payload.get_filename()
if filename:
pgpFilename = filename + ".pgp"
if not (payload.get('Content-Disposition') is None):
payload.set_param( 'filename', pgpFilename, 'Content-Disposition' )
if not (payload.get('Content-Type') is None) and not (payload.get_param( 'name' ) is None):
payload.set_param( 'name', pgpFilename )
if not (payload.get('Content-Transfer-Encoding') is None):
payload.replace_header( 'Content-Transfer-Encoding', "7bit" )
return payload
def smime_encrypt( raw_message, recipients ):
if not get_bool_from_cfg('smime', 'cert_path'):
log("No valid path for S/MIME certs found in config file. S/MIME encryption aborted.")
return recipients
cert_path = cfg['smime']['cert_path']+"/"
s = SMIME.SMIME()
sk = X509.X509_Stack()
smime_to = list()
unsmime_to = list()
for addr in recipients:
cert_and_email = get_cert_for_email(addr, cert_path)
if not (cert_and_email is None):
(to_cert, normal_email) = cert_and_email
if verbose:
log("Found cert " + to_cert + " for " + addr + ": " + normal_email)
smime_to.append(addr)
x509 = X509.load_cert(to_cert, format=X509.FORMAT_PEM)
sk.push(x509)
else:
unsmime_to.append(addr)
if smime_to != list():
s.set_x509_stack(sk)
s.set_cipher(SMIME.Cipher('aes_192_cbc'))
p7 = s.encrypt( BIO.MemoryBuffer( raw_message.as_string() ) )
# Output p7 in mail-friendly format.
out = BIO.MemoryBuffer()
out.write('From: ' + from_addr + '\n')
out.write('To: ' + raw_message['To'] + '\n')
if raw_message['Cc']:
out.write('Cc: ' + raw_message['Cc'] + '\n')
if raw_message['Bcc']:
out.write('Bcc: ' + raw_message['Bcc'] + '\n')
if raw_message['Subject']:
out.write('Subject: '+ raw_message['Subject'] + '\n')
if get_bool_from_cfg('default', 'add_header', 'yes'):
out.write('X-GPG-Mailgate: Encrypted by GPG Mailgate\n')
s.write(out, p7)
if verbose:
log("Sending message from " + from_addr + " to " + str(smime_to))
send_msg(out.read(), smime_to)
if unsmime_to != list():
if verbose:
log("Unable to find valid S/MIME certificates for " + str(unsmime_to))
return unsmime_to
def get_cert_for_email( to_addr, cert_path ):
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 get_bool_from_cfg('default', 'mail_case_insensitive', 'yes'):
if filename.lower() == 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
multi_email = re.match('^([^\+]+)\+([^@]+)@(.*)$', to_addr)
if multi_email:
fixed_up_email = "%s@%s" % (multi_email.group(1), multi_email.group(3))
if verbose:
log("Multi-email %s converted to %s" % (to_addr, fixed_up_email))
return get_cert_for_email(fixed_up_email)
return None
def get_bool_from_cfg( section, key = None, evaluation = None ):
if not (key is None) and not (evaluation is None):
return section in cfg and cfg[section].get(key) == evaluation
elif not (key is None) and (evaluation is None):
return section in cfg and not (cfg[section].get(key) is None)
else:
return section in cfg
def sanitize_case_sense( address ):
if get_bool_from_cfg('default', 'mail_case_insensitive', 'yes'):
address = address.lower()
else:
if isinstance(address, str):
sep = '@'
else:
sep = b'@'
splitted_address = address.split(sep)
if len(splitted_address) > 1:
address = splitted_address[0] + sep + splitted_address[1].lower()
return address
def generate_message_from_payloads( payloads, message = None ):
if message == 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, recipients ):
recipients = [_f for _f in recipients if _f]
if recipients:
if not (get_bool_from_cfg('relay', 'host') and get_bool_from_cfg('relay', 'port')):
log("Missing settings for relay. Sending email aborted.")
return None
log("Sending email to: <%s>" % '> <'.join( recipients ))
relay = (cfg['relay']['host'], int(cfg['relay']['port']))
smtp = smtplib.SMTP(relay[0], relay[1])
if 'relay' in cfg and 'starttls' in cfg['relay'] and cfg['relay']['starttls'] == 'yes':
smtp.starttls()
smtp.sendmail( from_addr, recipients, message )
else:
log("No recipient found")
def sort_recipients( raw_message, from_addr, to_addrs ):
recipients_left = list()
for recipient in to_addrs:
recipients_left.append(sanitize_case_sense(recipient))
# There is no need for nested encryption
first_payload = get_first_payload(raw_message)
if first_payload.get_content_type() == 'application/pkcs7-mime':
if verbose:
log("Message is already encrypted with S/MIME. Encryption aborted.")
send_msg(raw_message.as_string(), recipients_left)
return
first_payload = first_payload.get_payload(decode=True)
if b"-----BEGIN PGP MESSAGE-----" in first_payload and b"-----END PGP MESSAGE-----" in first_payload:
if verbose:
log("Message is already encrypted as PGP/INLINE. Encryption aborted.")
send_msg(raw_message.as_string(), recipients_left)
return
if raw_message.get_content_type() == 'multipart/encrypted':
if verbose:
log("Message is already encrypted. Encryption aborted.")
send_msg(raw_message.as_string(), recipients_left)
return
# Encrypt mails for recipients with known public PGP keys
recipients_left = gpg_encrypt(raw_message, recipients_left)
if recipients_left == list():
return
# Encrypt mails for recipients with known S/MIME certificate
recipients_left = smime_encrypt(raw_message, recipients_left)
if recipients_left == list():
return
# Send out mail to recipients which are left
send_msg(raw_message.as_string(), recipients_left)
# Let's start
sort_recipients(raw_message, from_addr, to_addrs)