CODEWITHSUNDEEP
aiosmtpd
gigglerg21
gigglerg21

Reputation: 41

Dropping connections by aiosmtpd when receiving email

I am using python3, aiosmtpd to capture emails from a dvr on a private lan and strip the attachments. I've written a handler for aiosmtp and some test python to send an email with attachment, plain, no encryption and it works. When the dvr sends email it yields connection lost.

I tried debugging using:

python3 -m aiosmtpd -d -n -l 192.168.66.1:11125

Adding "--no-requiretls" doesnt seem to change result.

  1. List item

This is result:

2021-06-07 21:29:30 - Available AUTH mechanisms: LOGIN(builtin) PLAIN(builtin)
Available AUTH mechanisms: LOGIN(builtin) PLAIN(builtin)
2021-06-07 21:29:30 - Peer: ('192.168.66.99', 47054)
Peer: ('192.168.66.99', 47054)
2021-06-07 21:29:30 - ('192.168.66.99', 47054) handling connection
('192.168.66.99', 47054) handling connection
2021-06-07 21:29:30 - ('192.168.66.99', 47054) >> b'EHLO 192.168.66.1'
('192.168.66.99', 47054) >> b'EHLO 192.168.66.1'
2021-06-07 21:29:31 - ('192.168.66.99', 47054) >> b'AUTH LOGIN'
('192.168.66.99', 47054) >> b'AUTH LOGIN'
2021-06-07 21:29:31 - ('192.168.66.99', 47054) connection lost
('192.168.66.99', 47054) connection lost
2021-06-07 21:29:31 - ('192.168.66.99', 47054) Connection lost during _handle_client()
('192.168.66.99', 47054) Connection lost during _handle_client()

smtp.py, part of aiosmtpd 1.4.2 installed by pip3:

def __init__(
            ...
            auth_require_tls=True,...)
        ...
        self._auth_require_tls = auth_require_tls


    async def smtp_AUTH(self, arg: str) -> None:
        ...
        elif self._auth_require_tls and not self._tls_protocol:
            return await self.push("538 5.7.11 Encryption required for requested authentication mechanism")

So the above default if AUTH received will fail because init, if not set by user code leaves _auth_require_tls as True. As the AUTH is plain in this case the protocol won't be tls.

A bit more debug and I found that the client is not responding to challenge.

INFO:mail.log:('192.168.66.99', 47054) << challenge: b'334 VXNlciBOYW1lAA=='

Not sure what to try now. Any suggestions?

Upvotes: 4

Views: 431

Answers (0)

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