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# Copyright (C) 2009-2017 by the Free Software Foundation, Inc.
#
# This file is part of GNU Mailman.
#
# GNU Mailman 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.
#
# GNU Mailman 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
# GNU Mailman. If not, see <http://www.gnu.org/licenses/>.
"""MTA connections."""
import ssl
import logging
import smtplib
from contextlib import suppress
from lazr.config import as_boolean
from mailman.config import config
from mailman.interfaces.smtp import ISMTPConnection
from public import public
from zope.interface import implementer
log = logging.getLogger('mailman.smtp')
@implementer(ISMTPConnection)
class Connection:
def __init__(self, host, port, sessions_per_connection,
smtp_user=None, smtp_pass=None):
"""Create a connection manager.
:param host: The host name of the SMTP server to connect to.
:type host: string
:param port: The port number of the SMTP server to connect to.
:type port: integer
:param sessions_per_connection: The number of SMTP sessions per
connection to the SMTP server. After this number of sessions
has been reached, the connection is closed and a new one is
opened. Set to zero for an unlimited number of sessions per
connection (i.e. your MTA has no limit).
:type sessions_per_connection: integer
:param smtp_user: Optional SMTP authentication user name. If given,
`smtp_pass` must also be given.
:type smtp_user: str
:param smtp_pass: Optional SMTP authentication password. If given,
`smtp_user` must also be given.
"""
self._host = host
self._port = port
self._sessions_per_connection = sessions_per_connection
self._username = smtp_user
self._password = smtp_pass
self._session_count = None
self._connection = None
def _login(self):
"""Send login if both username and password are specified."""
if self._username is not None and self._password is not None:
log.debug('Logging in')
self._connection.login(self._username, self._password)
def sendmail(self, envsender, recipients, msgtext):
if as_boolean(config.devmode.enabled):
# Force the recipients to the specified address, but still deliver
# to the same number of recipients.
recipients = [config.devmode.recipient] * len(recipients)
if self._connection is None:
self._connect()
self._login()
try:
log.debug('envsender: %s, recipients: %s, size(msgtext): %s',
envsender, recipients, len(msgtext))
results = self._connection.sendmail(envsender, recipients, msgtext)
except smtplib.SMTPException:
# For safety, close this connection. The next send attempt will
# automatically re-open it. Pass the exception on up.
self.quit()
raise
# This session has been successfully completed.
self._session_count -= 1
# By testing exactly for equality to 0, we automatically handle the
# case for SMTP_MAX_SESSIONS_PER_CONNECTION <= 0 meaning never close
# the connection. We won't worry about wraparound <wink>.
if self._session_count == 0:
self.quit()
return results
def quit(self):
if self._connection is None:
return
with suppress(smtplib.SMTPException):
self._connection.quit()
self._connection = None
@public
class SMTPConnection(Connection):
"""Manage a clear connection to the SMTP server."""
def _connect(self):
"""Open a new connection."""
log.debug('Connecting to %s:%s', self._host, self._port)
self._connection = smtplib.SMTP(self._host, self._port)
self._session_count = self._sessions_per_connection
class _SSLConnection(Connection):
"""Manage a SMTP connection with a SSL context(either SMTPS or STARTTLS)"""
def __init__(self, host, port, sessions_per_connection,
verify_cert=False, verify_hostname=False,
smtp_user=None, smtp_pass=None):
"""
Create a connection manager with and SSL context.
:param host: The host name of the SMTP server to connect to.
:type host: string
:param port: The port number of the SMTP server to connect to.
:type port: integer
:param sessions_per_connection: The number of SMTP sessions per
connection to the SMTP server. After this number of sessions
has been reached, the connection is closed and a new one is
opened. Set to zero for an unlimited number of sessions per
connection (i.e. your MTA has no limit).
:type sessions_per_connection: integer
:param verify_cert: Whether to require a server cert and verify it.
Verification in this context means that the server needs to supply
a valid certificate signed by a CA from a set of the system's
default CA certs.
:type verify_cert: bool
:param verify_hostname: Whether to check that the server certificate
specifies the hostname as passed to this constructor.
RFC 2818 and RFC 6125 rules are followed.
:type verify_hostname: bool
:param smtp_user: Optional SMTP authentication user name. If given,
`smtp_pass` must also be given.
:type smtp_user: str
:param smtp_pass: Optional SMTP authentication password. If given,
`smtp_user` must also be given.
"""
super().__init__(host, port, sessions_per_connection,
smtp_user, smtp_pass)
self._tls_context = self._get_context(verify_cert, verify_hostname)
def _get_context(self, verify_cert, verify_hostname):
"""Create and return a new SSLContext."""
ssl_context = ssl.create_default_context()
ssl_context.check_hostname = verify_hostname
if verify_cert:
ssl_context.verify_mode = ssl.CERT_REQUIRED
else:
ssl_context.verify_mode = ssl.CERT_NONE
return ssl_context
@public
class SMTPSConnection(_SSLConnection):
"""Manage a SMTPS connection."""
def _connect(self):
log.debug('Connecting to %s:%s', self._host, self._port)
self._connection = smtplib.SMTP_SSL(self._host, self._port,
context=self._tls_context)
self._session_count = self._sessions_per_connection
@public
class STARTTLSConnection(_SSLConnection, SMTPConnection):
"""Manage a plain connection with STARTTLS."""
def _connect(self):
super()._connect()
log.debug('Starttls')
try:
self._connection.starttls(context=self._tls_context)
except smtplib.SMTPNotSupportedError as notls:
log.error('Starttls failed: ' + str(notls))
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