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# Copyright 2021 The Matrix.org C.I.C. Foundation
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
# http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
import email.utils
import logging
from email.mime.multipart import MIMEMultipart
from email.mime.text import MIMEText
from io import BytesIO
from typing import TYPE_CHECKING, Any, Optional
from pkg_resources import parse_version
import twisted
from twisted.internet.defer import Deferred
from twisted.internet.interfaces import IOpenSSLContextFactory, IReactorTCP
from twisted.mail.smtp import ESMTPSender, ESMTPSenderFactory
from synapse.logging.context import make_deferred_yieldable
if TYPE_CHECKING:
from synapse.server import HomeServer
logger = logging.getLogger(__name__)
_is_old_twisted = parse_version(twisted.__version__) < parse_version("21")
class _NoTLSESMTPSender(ESMTPSender):
"""Extend ESMTPSender to disable TLS
Unfortunately, before Twisted 21.2, ESMTPSender doesn't give an easy way to disable
TLS, so we override its internal method which it uses to generate a context factory.
"""
def _getContextFactory(self) -> Optional[IOpenSSLContextFactory]:
return None
async def _sendmail(
reactor: IReactorTCP,
smtphost: str,
smtpport: int,
from_addr: str,
to_addr: str,
msg_bytes: bytes,
username: Optional[bytes] = None,
password: Optional[bytes] = None,
require_auth: bool = False,
require_tls: bool = False,
enable_tls: bool = True,
) -> None:
"""A simple wrapper around ESMTPSenderFactory, to allow substitution in tests
Params:
reactor: reactor to use to make the outbound connection
smtphost: hostname to connect to
smtpport: port to connect to
from_addr: "From" address for email
to_addr: "To" address for email
msg_bytes: Message content
username: username to authenticate with, if auth is enabled
password: password to give when authenticating
require_auth: if auth is not offered, fail the request
require_tls: if TLS is not offered, fail the reqest
enable_tls: True to enable TLS. If this is False and require_tls is True,
the request will fail.
"""
msg = BytesIO(msg_bytes)
d: "Deferred[object]" = Deferred()
def build_sender_factory(**kwargs: Any) -> ESMTPSenderFactory:
return ESMTPSenderFactory(
username,
password,
from_addr,
to_addr,
msg,
d,
heloFallback=True,
requireAuthentication=require_auth,
requireTransportSecurity=require_tls,
**kwargs,
)
if _is_old_twisted:
# before twisted 21.2, we have to override the ESMTPSender protocol to disable
# TLS
factory = build_sender_factory()
if not enable_tls:
factory.protocol = _NoTLSESMTPSender
else:
# for twisted 21.2 and later, there is a 'hostname' parameter which we should
# set to enable TLS.
factory = build_sender_factory(hostname=smtphost if enable_tls else None)
reactor.connectTCP(
smtphost,
smtpport,
factory,
timeout=30,
bindAddress=None,
)
await make_deferred_yieldable(d)
class SendEmailHandler:
def __init__(self, hs: "HomeServer"):
self.hs = hs
self._reactor = hs.get_reactor()
self._from = hs.config.email.email_notif_from
self._smtp_host = hs.config.email.email_smtp_host
self._smtp_port = hs.config.email.email_smtp_port
user = hs.config.email.email_smtp_user
self._smtp_user = user.encode("utf-8") if user is not None else None
passwd = hs.config.email.email_smtp_pass
self._smtp_pass = passwd.encode("utf-8") if passwd is not None else None
self._require_transport_security = hs.config.email.require_transport_security
self._enable_tls = hs.config.email.enable_smtp_tls
self._sendmail = _sendmail
async def send_email(
self,
email_address: str,
subject: str,
app_name: str,
html: str,
text: str,
) -> None:
"""Send a multipart email with the given information.
Args:
email_address: The address to send the email to.
subject: The email's subject.
app_name: The app name to include in the From header.
html: The HTML content to include in the email.
text: The plain text content to include in the email.
"""
try:
from_string = self._from % {"app": app_name}
except (KeyError, TypeError):
from_string = self._from
raw_from = email.utils.parseaddr(from_string)[1]
raw_to = email.utils.parseaddr(email_address)[1]
if raw_to == "":
raise RuntimeError("Invalid 'to' address")
html_part = MIMEText(html, "html", "utf8")
text_part = MIMEText(text, "plain", "utf8")
multipart_msg = MIMEMultipart("alternative")
multipart_msg["Subject"] = subject
multipart_msg["From"] = from_string
multipart_msg["To"] = email_address
multipart_msg["Date"] = email.utils.formatdate()
multipart_msg["Message-ID"] = email.utils.make_msgid()
multipart_msg.attach(text_part)
multipart_msg.attach(html_part)
logger.info("Sending email to %s" % email_address)
await self._sendmail(
self._reactor,
self._smtp_host,
self._smtp_port,
raw_from,
raw_to,
multipart_msg.as_string().encode("utf8"),
username=self._smtp_user,
password=self._smtp_pass,
require_auth=self._smtp_user is not None,
require_tls=self._require_transport_security,
enable_tls=self._enable_tls,
)
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