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  1"""SMTP email backend class."""
  2
  3import smtplib
  4import ssl
  5import threading
  6
  7from plain.runtime import settings
  8from plain.utils.functional import cached_property
  9
 10from ..backends.base import BaseEmailBackend
 11from ..message import sanitize_address
 12from ..utils import DNS_NAME
 13
 14
 15class EmailBackend(BaseEmailBackend):
 16    """
 17    A wrapper that manages the SMTP network connection.
 18    """
 19
 20    def __init__(
 21        self,
 22        host=None,
 23        port=None,
 24        username=None,
 25        password=None,
 26        use_tls=None,
 27        fail_silently=False,
 28        use_ssl=None,
 29        timeout=None,
 30        ssl_keyfile=None,
 31        ssl_certfile=None,
 32        **kwargs,
 33    ):
 34        super().__init__(fail_silently=fail_silently)
 35        self.host = host or settings.EMAIL_HOST
 36        self.port = port or settings.EMAIL_PORT
 37        self.username = settings.EMAIL_HOST_USER if username is None else username
 38        self.password = settings.EMAIL_HOST_PASSWORD if password is None else password
 39        self.use_tls = settings.EMAIL_USE_TLS if use_tls is None else use_tls
 40        self.use_ssl = settings.EMAIL_USE_SSL if use_ssl is None else use_ssl
 41        self.timeout = settings.EMAIL_TIMEOUT if timeout is None else timeout
 42        self.ssl_keyfile = (
 43            settings.EMAIL_SSL_KEYFILE if ssl_keyfile is None else ssl_keyfile
 44        )
 45        self.ssl_certfile = (
 46            settings.EMAIL_SSL_CERTFILE if ssl_certfile is None else ssl_certfile
 47        )
 48        if self.use_ssl and self.use_tls:
 49            raise ValueError(
 50                "EMAIL_USE_TLS/EMAIL_USE_SSL are mutually exclusive, so only set "
 51                "one of those settings to True."
 52            )
 53        self.connection = None
 54        self._lock = threading.RLock()
 55
 56    @property
 57    def connection_class(self):
 58        return smtplib.SMTP_SSL if self.use_ssl else smtplib.SMTP
 59
 60    @cached_property
 61    def ssl_context(self):
 62        if self.ssl_certfile or self.ssl_keyfile:
 63            ssl_context = ssl.SSLContext(protocol=ssl.PROTOCOL_TLS_CLIENT)
 64            ssl_context.load_cert_chain(self.ssl_certfile, self.ssl_keyfile)
 65            return ssl_context
 66        else:
 67            return ssl.create_default_context()
 68
 69    def open(self):
 70        """
 71        Ensure an open connection to the email server. Return whether or not a
 72        new connection was required (True or False) or None if an exception
 73        passed silently.
 74        """
 75        if self.connection:
 76            # Nothing to do if the connection is already open.
 77            return False
 78
 79        # If local_hostname is not specified, socket.getfqdn() gets used.
 80        # For performance, we use the cached FQDN for local_hostname.
 81        connection_params = {"local_hostname": DNS_NAME.get_fqdn()}
 82        if self.timeout is not None:
 83            connection_params["timeout"] = self.timeout
 84        if self.use_ssl:
 85            connection_params["context"] = self.ssl_context
 86        try:
 87            self.connection = self.connection_class(
 88                self.host, self.port, **connection_params
 89            )
 90
 91            # TLS/SSL are mutually exclusive, so only attempt TLS over
 92            # non-secure connections.
 93            if not self.use_ssl and self.use_tls:
 94                self.connection.starttls(context=self.ssl_context)
 95            if self.username and self.password:
 96                self.connection.login(self.username, self.password)
 97            return True
 98        except OSError:
 99            if not self.fail_silently:
100                raise
101
102    def close(self):
103        """Close the connection to the email server."""
104        if self.connection is None:
105            return
106        try:
107            try:
108                self.connection.quit()
109            except (ssl.SSLError, smtplib.SMTPServerDisconnected):
110                # This happens when calling quit() on a TLS connection
111                # sometimes, or when the connection was already disconnected
112                # by the server.
113                self.connection.close()
114            except smtplib.SMTPException:
115                if self.fail_silently:
116                    return
117                raise
118        finally:
119            self.connection = None
120
121    def send_messages(self, email_messages):
122        """
123        Send one or more EmailMessage objects and return the number of email
124        messages sent.
125        """
126        if not email_messages:
127            return 0
128        with self._lock:
129            new_conn_created = self.open()
130            if not self.connection or new_conn_created is None:
131                # We failed silently on open().
132                # Trying to send would be pointless.
133                return 0
134            num_sent = 0
135            try:
136                for message in email_messages:
137                    sent = self._send(message)
138                    if sent:
139                        num_sent += 1
140            finally:
141                if new_conn_created:
142                    self.close()
143        return num_sent
144
145    def _send(self, email_message):
146        """A helper method that does the actual sending."""
147        if not email_message.recipients():
148            return False
149        encoding = email_message.encoding or settings.DEFAULT_CHARSET
150        from_email = sanitize_address(email_message.from_email, encoding)
151        recipients = [
152            sanitize_address(addr, encoding) for addr in email_message.recipients()
153        ]
154        message = email_message.message()
155        try:
156            self.connection.sendmail(
157                from_email, recipients, message.as_bytes(linesep="\r\n")
158            )
159        except smtplib.SMTPException:
160            if not self.fail_silently:
161                raise
162            return False
163        return True