Restructure SMTP check code
This commit is contained in:
Reinhard Müller
parent
59172783ce
commit
ef15fa994a
|
|
@ -1,8 +1,7 @@
|
|||
from logging import getLogger
|
||||
from smtplib import SMTP, SMTPNotSupportedError, SMTPServerDisconnected
|
||||
from socket import error as SocketError
|
||||
from socket import gethostname
|
||||
from typing import Optional, Tuple
|
||||
from smtplib import (
|
||||
SMTP, SMTPNotSupportedError, SMTPResponseException, SMTPServerDisconnected)
|
||||
from typing import List, Optional
|
||||
|
||||
from dns.exception import Timeout
|
||||
from dns.rdatatype import MX as rdtype_mx
|
||||
|
|
@ -20,21 +19,6 @@ from .exceptions import (
|
|||
LOGGER = getLogger(name=__name__)
|
||||
|
||||
|
||||
class _ProtocolError(Exception):
|
||||
"""
|
||||
Raised when there is an error during the SMTP conversation.
|
||||
Used only internally.
|
||||
"""
|
||||
|
||||
def __init__(self, command: str, code: int, message: bytes):
|
||||
self.command = command
|
||||
self.code = code
|
||||
self.message = message.decode(errors='ignore')
|
||||
|
||||
def __str__(self):
|
||||
return f'{self.code} {self.message} (in reply to {self.command})'
|
||||
|
||||
|
||||
def _get_mx_records(domain: str, timeout: int) -> list:
|
||||
'Return the DNS response for checking, optionally raise exceptions.'
|
||||
try:
|
||||
|
|
@ -73,99 +57,171 @@ def _get_cleaned_mx_records(domain: str, timeout: int) -> list:
|
|||
return result
|
||||
|
||||
|
||||
def _smtp_ehlo_tls(smtp: SMTP, helo_host: str):
|
||||
class _SMTPChecker(SMTP):
|
||||
"""
|
||||
Try and start the TLS session, fall back to unencrypted when
|
||||
unavailable.
|
||||
A specialized variant of `smtplib.SMTP` for checking the validity of
|
||||
email addresses.
|
||||
|
||||
All the commands used in the check process are modified to raise
|
||||
appropriate exceptions: `SMTPServerDisconnected` on connection
|
||||
issues and `SMTPResponseException` on negative SMTP server
|
||||
responses. Note that the methods of `smtplib.SMTP` already raise
|
||||
these exceptions on some conditions.
|
||||
|
||||
Also, a new method `check` is added to run the check for a given
|
||||
list of SMTP servers.
|
||||
"""
|
||||
code, message = smtp.ehlo(name=helo_host)
|
||||
if code >= 400:
|
||||
# EHLO bails out, no further SMTP commands are acceptable
|
||||
raise _ProtocolError('EHLO', code, message)
|
||||
try:
|
||||
smtp.starttls()
|
||||
code, message = smtp.ehlo(name=helo_host)
|
||||
except SMTPNotSupportedError:
|
||||
# The server does not support the STARTTLS extension
|
||||
pass
|
||||
except RuntimeError:
|
||||
# SSL/TLS support is not available to your Python interpreter
|
||||
pass
|
||||
def __init__(
|
||||
self, local_hostname: str, timeout: float, debug: bool,
|
||||
raise_communication_errors: bool,
|
||||
raise_temporary_errors: bool,
|
||||
sender: str, recip: str):
|
||||
"""
|
||||
Initialize the object with all the parameters which remain
|
||||
constant during the check of one email address on all the SMTP
|
||||
servers.
|
||||
"""
|
||||
super().__init__(local_hostname=local_hostname, timeout=timeout)
|
||||
self.set_debuglevel(debuglevel=2 if debug else False)
|
||||
self.__raise_communication_errors = raise_communication_errors
|
||||
self.__raise_temporary_errors = raise_temporary_errors
|
||||
self.__sender = sender
|
||||
self.__recip = recip
|
||||
self.__communication_errors = {}
|
||||
self.__temporary_errors = {}
|
||||
# Avoid error on close() after unsuccessful connect
|
||||
self.sock = None
|
||||
|
||||
def putcmd(self, cmd, args=""):
|
||||
"""
|
||||
Like `smtplib.SMTP.putcmd`, but remember the command for later
|
||||
use in error messages.
|
||||
"""
|
||||
if args:
|
||||
self.__command = f'{cmd} {args}'
|
||||
else:
|
||||
self.__command = cmd
|
||||
super().putcmd(cmd, args)
|
||||
|
||||
def _smtp_mail(smtp: SMTP, from_address: EmailAddress):
|
||||
'Send and evaluate the `MAIL FROM` command.'
|
||||
code, message = smtp.mail(sender=from_address.ace)
|
||||
if code >= 400:
|
||||
# MAIL FROM bails out, no further SMTP commands are acceptable
|
||||
raise _ProtocolError('MAIL FROM', code, message)
|
||||
|
||||
|
||||
def _smtp_converse(
|
||||
mx_record: str, smtp_timeout: int, debug: bool, helo_host: str,
|
||||
from_address: EmailAddress, email_address: EmailAddress
|
||||
) -> Tuple[int, str]:
|
||||
"""
|
||||
Do the `SMTP` conversation with one MX, and return code and message
|
||||
of the reply to the `RCPT TO:` command.
|
||||
|
||||
If the conversation fails before the `RCPT TO:` command can be
|
||||
issued, a `_ProtocolError` is raised.
|
||||
"""
|
||||
if debug:
|
||||
LOGGER.debug(msg=f'Trying {mx_record} ...')
|
||||
with SMTP(timeout=smtp_timeout) as smtp:
|
||||
smtp._host = mx_record # Workaround for bug in smtplib
|
||||
smtp.set_debuglevel(debuglevel=2 if debug else False)
|
||||
code, message = smtp.connect(host=mx_record)
|
||||
if code >= 400:
|
||||
raise _ProtocolError('connect', code, message)
|
||||
_smtp_ehlo_tls(smtp=smtp, helo_host=helo_host)
|
||||
_smtp_mail(smtp=smtp, from_address=from_address)
|
||||
return smtp.rcpt(recip=email_address.ace)
|
||||
|
||||
|
||||
def _check_mx_records(
|
||||
mx_records: list, smtp_timeout: int, helo_host: str,
|
||||
from_address: EmailAddress, email_address: EmailAddress,
|
||||
debug: bool, raise_communication_errors: bool,
|
||||
raise_temporary_errors: bool) -> Optional[bool]:
|
||||
'Check the mx records for a given email address.'
|
||||
communication_errors = {}
|
||||
temporary_errors = {}
|
||||
for mx_record in mx_records:
|
||||
def connect(self, host, *args, **kwargs):
|
||||
"""
|
||||
Like `smtplib.SMTP.connect`, but raise appropriate exceptions on
|
||||
connection failure or negative SMTP server response.
|
||||
"""
|
||||
self.__command = 'connect' # Used for error messages.
|
||||
self._host = host # Missing in standard smtplib!
|
||||
try:
|
||||
code, message = _smtp_converse(
|
||||
mx_record=mx_record, smtp_timeout=smtp_timeout, debug=debug,
|
||||
helo_host=helo_host, from_address=from_address,
|
||||
email_address=email_address)
|
||||
if code >= 500:
|
||||
# Address clearly invalid: exit early.
|
||||
raise AddressNotDeliverableError({mx_record: (
|
||||
'RCPT TO', code, message.decode(errors='ignore'))})
|
||||
elif code >= 400:
|
||||
# Temporary error on this MX: collect message and continue.
|
||||
temporary_errors[mx_record] = (
|
||||
'RCPT TO', code, message.decode(errors='ignore'))
|
||||
else:
|
||||
# Address clearly valid: exit early.
|
||||
code, message = super().connect(host, *args, **kwargs)
|
||||
except OSError as error:
|
||||
raise SMTPServerDisconnected(str(error))
|
||||
if code >= 400:
|
||||
raise SMTPResponseException(code, message)
|
||||
return code, message
|
||||
|
||||
def starttls(self, *args, **kwargs):
|
||||
"""
|
||||
Like `smtplib.SMTP.starttls`, but continue without TLS in case
|
||||
either end of the connection does not support it.
|
||||
"""
|
||||
try:
|
||||
super().starttls(*args, **kwargs)
|
||||
except SMTPNotSupportedError:
|
||||
# The server does not support the STARTTLS extension
|
||||
pass
|
||||
except RuntimeError:
|
||||
# SSL/TLS support is not available to your Python interpreter
|
||||
pass
|
||||
|
||||
def mail(self, *args, **kwargs):
|
||||
"""
|
||||
Like `smtplib.SMTP.mail`, but raise an appropriate exception on
|
||||
negative SMTP server response.
|
||||
"""
|
||||
code, message = super().mail(*args, **kwargs)
|
||||
if code >= 400:
|
||||
raise SMTPResponseException(code, message)
|
||||
return code, message
|
||||
|
||||
def rcpt(self, *args, **kwargs):
|
||||
"""
|
||||
Like `smtplib.SMTP.rcpt`, but handle negative SMTP server
|
||||
responses directly.
|
||||
"""
|
||||
code, message = super().rcpt(*args, **kwargs)
|
||||
if code >= 500:
|
||||
# Address clearly invalid: issue negative result
|
||||
raise AddressNotDeliverableError({self._host: (
|
||||
'RCPT TO', code, message.decode(errors='ignore'))})
|
||||
elif code >= 400:
|
||||
# Temporary error on this host: collect message
|
||||
self.__temporary_errors[self._host] = (
|
||||
'RCPT TO', code, message.decode(errors='ignore'))
|
||||
return code, message
|
||||
|
||||
def quit(self):
|
||||
"""
|
||||
Like `smtplib.SMTP.quit`, but make sure that everything is
|
||||
cleaned up properly even if the connection has been lost before.
|
||||
"""
|
||||
try:
|
||||
return super().quit()
|
||||
except SMTPServerDisconnected:
|
||||
self.ehlo_resp = self.helo_resp = None
|
||||
self.esmtp_features = {}
|
||||
self.does_esmtp = False
|
||||
self.close()
|
||||
|
||||
def _check_one(self, host: str) -> bool:
|
||||
"""
|
||||
Run the check for one SMTP server. On positive result, return
|
||||
`True`. On negative result, raise `AddressNotDeliverableError`.
|
||||
On ambiguous result (4xx response to `RCPT TO`) or any
|
||||
communication issue before even reaching `RCPT TO` in the
|
||||
protocol, collect error message for later use and return
|
||||
`False`.
|
||||
"""
|
||||
try:
|
||||
self.connect(host)
|
||||
self.starttls()
|
||||
self.ehlo_or_helo_if_needed()
|
||||
self.mail(self.__sender)
|
||||
code, message = self.rcpt(self.__recip)
|
||||
except SMTPServerDisconnected as e:
|
||||
self.__communication_errors[self._host] = (
|
||||
self.__command, 0, str(e))
|
||||
return False
|
||||
except SMTPResponseException as e:
|
||||
self.__communication_errors[self._host] = (
|
||||
self.__command, e.smtp_code,
|
||||
e.smtp_error.decode(errors='ignore'))
|
||||
return False
|
||||
finally:
|
||||
self.quit()
|
||||
return (code < 400)
|
||||
|
||||
def check(self, hosts: List[str]) -> Optional[bool]:
|
||||
"""
|
||||
Run the check for all given SMTP servers. On positive result,
|
||||
return `True`. On negative result, raise
|
||||
`AddressNotDeliverableError`. On ambiguous result (4xx
|
||||
response(s) to `RCPT TO`) or any communication issue(s) before
|
||||
even reaching `RCPT TO` in the protocol, either raise an
|
||||
exception or return `None` depending on the parameters.
|
||||
"""
|
||||
for host in hosts:
|
||||
if self.debuglevel > 0:
|
||||
LOGGER.debug(msg=f'Trying {host} ...')
|
||||
if self._check_one(host):
|
||||
return True
|
||||
except (SocketError, SMTPServerDisconnected) as error:
|
||||
# Connection problem: collect message and continue.
|
||||
communication_errors[mx_record] = ('connect', 0, error)
|
||||
except _ProtocolError as error:
|
||||
# SMTP communication error: collect message and continue.
|
||||
communication_errors[mx_record] = (
|
||||
error.command, error.code, error.message)
|
||||
# Raise exceptions on ambiguous results if desired. If in doubt, raise the
|
||||
# CommunicationError because that one might point to local configuration or
|
||||
# blacklisting issues.
|
||||
if communication_errors and raise_communication_errors:
|
||||
raise SMTPCommunicationError(communication_errors)
|
||||
if temporary_errors and raise_temporary_errors:
|
||||
raise SMTPTemporaryError(temporary_errors)
|
||||
# Can't verify whether or not email address exists.
|
||||
return None
|
||||
# Raise exceptions on ambiguous results if desired. If in doubt, raise
|
||||
# the CommunicationError because that one might point to local
|
||||
# configuration or blacklisting issues.
|
||||
if self.__communication_errors and self.__raise_communication_errors:
|
||||
raise SMTPCommunicationError(self.__communication_errors)
|
||||
if self.__temporary_errors and self.__raise_temporary_errors:
|
||||
raise SMTPTemporaryError(self.__temporary_errors)
|
||||
# Can't verify whether or not email address exists.
|
||||
return None
|
||||
|
||||
|
||||
def mx_check(
|
||||
|
|
@ -204,7 +260,6 @@ def mx_check(
|
|||
exceptions is raised depending on the exact issue, all derived from
|
||||
`MXError`.
|
||||
"""
|
||||
host = helo_host or gethostname()
|
||||
from_address = from_address or email_address
|
||||
if email_address.domain_literal_ip:
|
||||
mx_records = [email_address.domain_literal_ip]
|
||||
|
|
@ -213,8 +268,9 @@ def mx_check(
|
|||
domain=email_address.domain, timeout=dns_timeout)
|
||||
if skip_smtp:
|
||||
return True
|
||||
return _check_mx_records(
|
||||
mx_records=mx_records, smtp_timeout=smtp_timeout, helo_host=host,
|
||||
from_address=from_address, email_address=email_address, debug=debug,
|
||||
raise_communication_errors=raise_communication_errors,
|
||||
raise_temporary_errors=raise_temporary_errors)
|
||||
smtp_checker = _SMTPChecker(
|
||||
local_hostname=helo_host, timeout=smtp_timeout, debug=debug,
|
||||
raise_communication_errors=raise_communication_errors,
|
||||
raise_temporary_errors=raise_temporary_errors,
|
||||
sender=from_address.ace, recip=email_address.ace)
|
||||
return smtp_checker.check(mx_records)
|
||||
|
|
|
|||
Loading…
Reference in New Issue