initial version

.gitignore

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+.idea
+*.swp

Pipfile

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+[[source]]
+url = "https://pypi.org/simple"
+verify_ssl = true
+name = "pypi"
+
+[dev-packages]
+
+[packages]
+aiosmtpd = "*"
+
+[requires]
+python_version = "3.7"

Pipfile.lock

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+{
+    "_meta": {
+        "hash": {
+            "sha256": "a5227f0d0fa7f8bbf0a5557162679decfad227c16cc4fec15e138a30cc6703d7"
+        },
+        "pipfile-spec": 6,
+        "requires": {
+            "python_version": "3.7"
+        },
+        "sources": [
+            {
+                "name": "pypi",
+                "url": "https://pypi.org/simple",
+                "verify_ssl": true
+            }
+        ]
+    },
+    "default": {
+        "aiosmtpd": {
+            "hashes": [
+                "sha256:b7ea7ee663f3b8514d3224d55c4e8827148277b124ea862a0bbfca1bc899aef5"
+            ],
+            "index": "pypi",
+            "version": "==1.2"
+        },
+        "atpublic": {
+            "hashes": [
+                "sha256:7dca670499e9a9d3aae5a8914bc799475fe24be3bcd29c8129642dda665f7a44"
+            ],
+            "version": "==1.0"
+        }
+    },
+    "develop": {}
+}

mail4one/server.py

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+import asyncio
+import io
+import logging
+import mailbox
+import os
+import ssl
+import sys
+from argparse import ArgumentParser
+from functools import partial
+from pathlib import Path
+
+from aiosmtpd.controller import Controller
+from aiosmtpd.handlers import Mailbox
+from aiosmtpd.main import DATA_SIZE_DEFAULT
+from aiosmtpd.smtp import SMTP
+
+
+# from pop3 import a_main
+
+
+def create_tls_context(certfile, keyfile):
+    context = ssl.create_default_context(ssl.Purpose.CLIENT_AUTH)
+    context.load_cert_chain(certfile=certfile, keyfile=keyfile)
+    return context
+
+
+class STARTTLSController(Controller):
+    def __init__(self, *args, tls_context, smtp_args=None, **kwargs):
+        self.tls_context = tls_context
+        self.smtp_args = smtp_args or {}
+        self.has_privileges_dropped: asyncio.Future = None
+        if 'ssl_context' in kwargs:
+            raise Exception("ssl_context not allowed when using STARTTLS, set tls_context instead")
+        Controller.__init__(self, *args, **kwargs)
+
+    async def create_future(self):
+        self.has_privileges_dropped = asyncio.get_event_loop().create_future()
+
+    def factory(self):
+        if not self.has_privileges_dropped.done():
+            # Ideally  we should await here. But this is callback and not a coroutine
+            raise Exception("Client connected too fast before we could drop root privileges")
+        return SMTP(self.handler, require_starttls=True, tls_context=self.tls_context, **self.smtp_args)
+
+
+class MaildirCRLF(mailbox.Maildir):
+    _append_newline = True
+
+    def _dump_message(self, message, target, mangle_from_=False):
+        temp_buffer = io.BytesIO()
+        super()._dump_message(message, temp_buffer, mangle_from_=mangle_from_)
+        temp_buffer.seek(0)
+        data = temp_buffer.read()
+        data = data.replace(b'\n', b'\r\n')
+        target.write(data)
+
+
+class MailboxCRLF(Mailbox):
+    def __init__(self, mail_dir):
+        super().__init__(mail_dir)
+        self.mailbox = MaildirCRLF(mail_dir)
+
+
+def parse_args():
+    parser = ArgumentParser()
+    parser.add_argument('--certfile')
+    parser.add_argument('--keyfile')
+    parser.add_argument("mail_dir_path")
+
+    args = parser.parse_args()
+    args.mail_dir_path = Path(args.mail_dir_path)
+
+    # Hardcoded args
+    args.host = '0.0.0.0'
+    args.port = 25
+    args.size = DATA_SIZE_DEFAULT
+    args.classpath = MailboxCRLF
+    args.smtputf8 = True
+    args.debug = True
+    return args
+
+
+def setup_logging(args):
+    if args.debug:
+        logging.basicConfig(level=logging.DEBUG)
+    else:
+        logging.basicConfig(level=logging.INFO)
+
+
+def drop_privileges(future):
+    try:
+        import pwd
+    except ImportError:
+        logging.error("Cannot import pwd; run as root")
+        sys.exit(1)
+    nobody = pwd.getpwnam('nobody')
+    try:
+        os.setuid(nobody.pw_uid)
+        os.setgid(nobody.pw_gid)
+    except PermissionError:
+        logging.error("Cannot setuid nobody; run as root")
+        sys.exit(1)
+    logging.info("Dropped privileges")
+    future.set_result("Go!")
+    logging.debug("Signalled! Clients can come in")
+
+
+def main():
+    args = parse_args()
+    tls_context = create_tls_context(args.certfile, args.keyfile)
+    smtp_args = dict(data_size_limit=args.size, enable_SMTPUTF8=args.smtputf8)
+    setup_logging(args)
+    handler = args.classpath(args.mail_dir_path)
+    loop = asyncio.get_event_loop()
+    loop.set_debug(args.debug)
+    # loop.create_task(a_main(args.mail_dir_path, tls_context))
+    controller = STARTTLSController(
+        handler, tls_context=tls_context, smtp_args=smtp_args, hostname=args.host, port=args.port, loop=loop)
+
+    loop.create_task(controller.create_future())
+
+    controller.start()
+    loop.call_soon_threadsafe(partial(drop_privileges, controller.has_privileges_dropped))
+    input('Press enter to stop:')
+    controller.stop()
+    # loop.create_task(a_main(controller))
+    # loop.run_forever()
+
+
+if __name__ == '__main__':
+    main()