279 lines
9.2 KiB
Python
279 lines
9.2 KiB
Python
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import asyncio
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import email
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import logging
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from smtplib import SMTP as SMTPClient
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from typing import Dict
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from aiosmtpd.proxy_protocol import ProxyData
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from python_socks.sync import Proxy
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import os
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import ssl
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from aiosmtpd.controller import Controller
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from aiosmtpd.smtp import Envelope, Session, SMTP
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from email.message import Message
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import dkim
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import spf
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from functools import lru_cache
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import dns.resolver
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PROXY = Proxy.from_url('socks5://5.78.86.156:2025')
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END_HOST = "localhost"
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END_PORT = 25
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PROXY_SMTP_HOST = "*"
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PROXY_SMTP_PORT = 2025
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END_SMTP_HOST = "*"
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END_SMTP_PORT = 3025
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GENERIC_SMTP_HOST = "*"
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GENERIC_SMTP_PORT = 25
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log = logging.getLogger("smtphandler")
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VALID_PROXY_ADDRS = {"5.78.86.156", "2a01:4ff:1f0:83de::1", "m-labs-intl.com", "mail.m-labs-intl.com"}
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VALID_END_ADDRS = {"localhost", "127.0.0.1"}
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VALID_RECEPIENTS = {"m-labs.hk", "m-labs.ph", "m-labs-intl.com", "193thz.com", "malloctech.fr"}
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@lru_cache(maxsize=256)
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def get_mx(domain):
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records = dns.resolver.resolve(domain, "MX")
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if not records:
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return None
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result = max(records, key=lambda r: r.preference)
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return str(result.exchange)
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class ProxiedSMTP(SMTPClient):
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def _get_socket(self, host, port, timeout):
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return PROXY.connect(dest_host=host, dest_port=port, timeout=timeout)
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class GenericMailServer:
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"""
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Accepts mail from everywhere, and passes it to the real SMTP server, after proper SPF and DKIM checks.
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"""
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async def handle_MAIL(self,
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server: SMTP,
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session: Session,
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envelope: Envelope,
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address: str,
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mail_options: list):
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ip = session.peer[0]
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result, description = spf.check2(ip, address, session.host_name)
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valid_spf = result == 'pass'
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envelope.spf = valid_spf
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log.info("SPF: %s, %s", result, description)
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if not valid_spf:
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return '550 SPF validation failed'
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envelope.mail_from = address
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envelope.mail_options.extend(mail_options)
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return '250 OK'
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async def handle_RCPT(self,
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server: SMTP,
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session: Session,
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envelope: Envelope,
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address: str,
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rcpt_options: list):
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if address.split("@")[1] not in VALID_RECEPIENTS:
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return '550 not relaying to that domain'
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log.debug("Handle RCPT for %s", address)
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envelope.rcpt_tos.append(address)
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return '250 OK'
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async def handle_DATA(self,
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server: SMTP,
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session: Session,
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envelope: Envelope):
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valid_dkim = dkim.verify(envelope.content)
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envelope.dkim = valid_dkim
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log.info("DKIM: %s", valid_dkim)
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message: Message = email.message_from_bytes(envelope.content)
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if not valid_dkim:
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return '550 DKIM validation failed'
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log.info('Message: %s', message)
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try:
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with SMTPClient(END_HOST, END_PORT) as client:
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client.sendmail(
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from_addr=envelope.mail_from,
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to_addrs=envelope.rcpt_tos,
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msg=envelope.original_content
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)
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except BaseException as e:
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print(e)
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return '500 Could not process your message'
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return '250 Message accepted for delivery'
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class EndMailServer:
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"""
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Accepts mail only from end server. Checks if mail is signed to be from proxy, and sends to proxy if needed.
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SPF and DKIM needs to be already included.
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"""
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async def handle_DATA(self,
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server: SMTP,
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session: Session,
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envelope: Envelope):
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ip = session.peer[0]
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if ip not in VALID_END_ADDRS:
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return "521 Server doesn't accept mail"
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message: Message = email.message_from_bytes(envelope.content)
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log.info('Message: %s', message)
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mx_rcpt: Dict[str, list[str]] = {}
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for rcpt in envelope.rcpt_tos:
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_, _, domain = rcpt.partition("@")
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mx = get_mx(domain)
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if mx is None:
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continue
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mx_rcpt.setdefault(mx, []).append(rcpt)
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try:
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for mx, rcpts in mx_rcpt.items():
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if envelope.mail_from in VALID_PROXY_ADDRS:
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with ProxiedSMTP(mx, 25) as client:
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client.sendmail(
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from_addr=envelope.mail_from,
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to_addrs=rcpts,
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msg=envelope.original_content
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)
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else:
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with SMTPClient(mx, 25) as client:
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client.sendmail(
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from_addr=envelope.mail_from,
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to_addrs=rcpts,
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msg=envelope.original_content
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)
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except BaseException as e:
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print(e)
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return '500 Could not process your message'
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return '250 Message accepted for delivery'
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class ProxyMailServer:
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"""
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Accepts mail only from proxy server, and passes it to the real SMTP server, after proper SPF and DKIM checks.
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"""
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async def handle_PROXY(self, server: SMTP, session: Session, envelope: Envelope, proxy_data: ProxyData):
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ip = session.peer[0]
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envelope.proxy_data = proxy_data
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return ip in VALID_PROXY_ADDRS
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async def handle_MAIL(self,
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server: SMTP,
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session: Session,
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envelope: Envelope,
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address: str,
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mail_options: list):
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ip = envelope.proxy_data.src_addr
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result, description = spf.check2(ip, address, session.host_name)
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valid_spf = result == 'pass'
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envelope.spf = valid_spf
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log.info("SPF: %s, %s", result, description)
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if not valid_spf:
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return '550 SPF validation failed'
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envelope.mail_from = address
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envelope.mail_options.extend(mail_options)
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return '250 OK'
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async def handle_RCPT(self,
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server: SMTP,
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session: Session,
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envelope: Envelope,
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address: str,
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rcpt_options: list):
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if address.split("@")[1] not in VALID_RECEPIENTS:
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return '550 not relaying to that domain'
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log.debug("Handle RCPT for %s", address)
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envelope.rcpt_tos.append(address)
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return '250 OK'
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async def handle_DATA(self,
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server: SMTP,
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session: Session,
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envelope: Envelope):
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valid_dkim = dkim.verify(envelope.content)
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envelope.dkim = valid_dkim
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log.info("DKIM: %s", valid_dkim)
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message: Message = email.message_from_bytes(envelope.content)
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if not valid_dkim:
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return '550 DKIM validation failed'
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log.info('Message: %s', message)
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try:
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with SMTPClient(END_HOST, END_PORT) as client:
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client.sendmail(
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from_addr=envelope.mail_from,
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to_addrs=envelope.rcpt_tos,
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msg=envelope.original_content
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)
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except BaseException as e:
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print(e)
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return '500 Could not process your message'
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return '250 Message accepted for delivery'
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if __name__ == '__main__':
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host = os.getenv('SMTP_HOST', '*')
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port = int(os.getenv('SMTP_PORT', '25'))
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accept_host = os.getenv('ACCEPT_HOST')
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ssl_keys = os.getenv('SSL_KEYS')
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loop = asyncio.get_event_loop()
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end_handler = EndMailServer()
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proxy_handler = ProxyMailServer()
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generic_handler = GenericMailServer()
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ssl_context = None
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if ssl_keys:
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ssl_context = ssl.create_default_context(ssl.Purpose.CLIENT_AUTH)
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ssl_context.load_cert_chain(ssl_keys + '.crt', ssl_keys + '.key')
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generic_controller = Controller(GenericMailServer, hostname=GENERIC_SMTP_HOST, port=GENERIC_SMTP_PORT)
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generic_controller.factory = lambda: SMTP(GenericMailServer, enable_SMTPUTF8=True, tls_context=ssl_context)
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generic_controller.start()
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log.info("Generic SMTP server started on %s:%s", GENERIC_SMTP_HOST, GENERIC_SMTP_PORT)
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end_controller = Controller(EndMailServer, hostname=END_SMTP_HOST, port=END_SMTP_PORT)
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end_controller.factory = lambda: SMTP(EndMailServer, enable_SMTPUTF8=True)
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end_controller.start()
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log.info("End SMTP server started on %s:%s", END_SMTP_HOST, END_SMTP_PORT)
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proxy_controller = Controller(ProxyMailServer, hostname=PROXY_SMTP_HOST, port=PROXY_SMTP_PORT)
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proxy_controller.factory = lambda: SMTP(ProxyMailServer, enable_SMTPUTF8=True, tls_context=ssl_context)
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proxy_controller.start()
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log.info("Proxy SMTP server started on %s:%s", PROXY_SMTP_HOST, PROXY_SMTP_PORT)
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try:
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loop.run_forever()
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except KeyboardInterrupt:
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print("Shutting down")
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finally:
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generic_controller.stop()
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end_controller.stop()
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proxy_controller.stop()
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loop.stop()
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loop.close()
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