summary refs log tree commit diff
path: root/synapse/handlers/send_email.py
blob: e2844799e88675bb790382db7060a84b562ae717 (plain) (blame)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
# 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
from twisted.internet.ssl import optionsForClientTLS
from twisted.mail.smtp import ESMTPSender, ESMTPSenderFactory

from synapse.logging.context import make_deferred_yieldable
from synapse.types import ISynapseReactor

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: ISynapseReactor,
    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,
    force_tls: bool = False,
) -> 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 STARTTLS. If this is False and require_tls is True,
           the request will fail.
        force_tls: True to enable Implicit TLS.
    """
    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)

    if force_tls:
        reactor.connectSSL(
            smtphost,
            smtpport,
            factory,
            optionsForClientTLS(smtphost),
            timeout=30,
            bindAddress=None,
        )
    else:
        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._force_tls = hs.config.email.force_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,
            force_tls=self._force_tls,
        )