On Sat, 2021-10-16 at 18:44 +0200, Heiko Schlittermann via Exim-users
wrote:
> Adam D. Barratt via Exim-users <[email protected]> (Sa 16 Okt 2021
> 17:43:57 CEST):
> > > This hh.schlittermann.de runs the latest Exim, and probaby sends
> > > you
> > > an SNI your server for some reason doesn't accept?
> > 
> > FWIW, I've also seen two of these, at 23:53:41UTC yesterday and
> > 11:08:41UTC today. The server in question is running Debian's 4.92-
> > 8+deb10u6 exim4-daemon-heavy package and has "tls_sni" set in the
> > log
> > selector.
> > 
> > The log entries for the second failed connection are:
> > 
> > 2021-10-16 11:08:40 SMTP connection from [213.128.132.49] (TCP/IP
> > connection count = 1)
> > 2021-10-16 11:08:41 TLS error on connection from
> > hh.schlittermann.de [213.128.132.49] (gnutls_handshake): A
> > disallowed SNI server name has been received.
> > 2021-10-16 11:08:41 SMTP connection from hh.schlittermann.de
> > [213.128.132.49] closed by EOF
> > 2021-10-16 11:08:41 no MAIL in SMTP connection from
> > hh.schlittermann.de [213.128.132.49] D=0s C=EHLO,STARTTLS
> > 
> > The same server has received 21 successful connections from
> > hh.schlittermann.de in the past couple of days.
> 
> Interesting. Can you tell *what* SNI the server hh sent?

Unfortunately the above appears to be all that's logged.


> That's what the hh server uses as the transport:
> [...]

> So, it sends you *your* hostname as an SNI.

That's indeed what I see for successful connections.

I've hopefully enabled TLS debug logging for connections from hh, so
we'll see if that provides any useful information if it happens again.

Regards,

Adam


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