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.\" $OpenBSD: spamd.8,v 1.22 2003/03/06 09:41:31 henning Exp $
.\"
.\" Copyright (c) 2002 Theo de Raadt. All rights reserved.
.\"
.\" Redistribution and use in source and binary forms, with or without
.\" modification, are permitted provided that the following conditions
.\" are met:
.\" 1. Redistributions of source code must retain the above copyright
.\" notice, this list of conditions and the following disclaimer.
.\" 2. Redistributions in binary form must reproduce the above copyright
.\" notice, this list of conditions and the following disclaimer in the
.\" documentation and/or other materials provided with the distribution.
.\"
.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
.\" IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
.\" OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
.\" IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
.\" INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
.\" NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
.\" DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
.\" THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
.\" (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
.\" THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
.\"
.Dd December 18, 2002
.Dt SPAMD 8
.Os
.Sh NAME
.Nm spamd
.Nd spam deferral daemon
.Sh SYNOPSIS
.Nm spamd
.Op Fl 45d
.Op Fl r Ar reply
.Op Fl c Ar maxcon
.Op Fl p Ar port
.Op Fl n Ar name
.Sh DESCRIPTION
.Nm
is a fake
.Xr sendmail 8 Ns -like
daemon which rejects false mail.
If the
.Xr pf 4
packet filter is configured to redirect port 25 (SMTP) to this daemon,
it will attempt to waste the time and resources of the spam sender.
.Pp
The options are as follows:
.Bl -tag -width Ds
.Pp
.It Fl 4
Return error code 450 to the spammer.
.It Fl 5
Return error code 550 to the spammer.
.It Fl d
Debug mode.
.Nm
does not
.Xr fork 2
into the background.
.It Fl r
The SMTP error to return to the spammer, i.e., 450, 451, 550.
This defaults to 450.
.It Fl c
The maximum number of concurrent connections to allow.
.It Fl p
Specify the port number that
.Nm
should operate on.
.It Fl n
The SMTP version banner that is reported upon initial connection.
.El
.Pp
.Nm
is designed to be very efficient so that it does not slow down the
receiving machine.
Spam is never accepted, but always rejected with either a 450 or 550
error message.
The normal way that spam has been dealt with in the past is to either
accept and drop, or outright block.
When configured to use 450 responses,
.Nm
takes neither of these actions: it rejects the mail back to the senders'
queue.
.Pp
.Nm
is best started from
.Xr rc 8
and is used in conjuction with
.Xr spamd-setup 8
which processes a list of spammers' addresses, and applies appropriate
.Xr pfctl 8
.Em rdr
rules.
.Pp
.Sh REDIRECTING SMTP CONNECTIONS
With
.Xr pf 4 ,
connections to port 25 (SMTP) can be redirected to another host or port,
based on the source address of the sender.
The
.Em rdr
rules used for this purpose are described in
.Xr pf.conf 5 .
The rules can be loaded into a
.Em table
to simplify handling.
.Bd -literal
table <spamd> persist
rdr proto tcp from { <spamd> } to any port smtp -> 127.0.0.1 port 8025
.Ed
.Pp
Any addresses in table
.Aq spamd
are then redirected to
.Nm
running on port 25.
Addresses can be loaded into the
.Em table ,
like:
.Bd -literal
# pfctl -q -t spamd -T replace -f /usr/local/share/spammers
.Ed
.Pp
.Xr spamd-setup 8
can also be used to load addresses into the
.Aq spamd
table.
.Xr spamd-setup 8
also has the added benefit of being able to remove addresses from
blacklists, and will connect to
.Nm
over a localhost socket, giving
.Nm
information about each source of blacklist addresses, as well as custom
rejection messages for each blacklist source
that can be used to let any real person whose mail
is deferred by spamd know why their address has been listed
from sending mail.
This is important as it allows legitimate mail
senders to pressure spam sources into behaving properly so that they
may be removed from the relevant blacklists.
.Pp
.Sh CONFIGURATION CONNECTIONS
.Nm
receives configuration information through a localhost connection.
Configuration information consists of blacklists, each with a name,
a message to reject mail with, and addresses in CIDR format.
When multiple lists are configured, each configuration line specifies
a blacklist, and must have the format:
.Bd -literal
tag;"rejection message";aaa.bbb.ccc.ddd/mm;aaa.bbb.ccc.ddd/mm
.Ed
The rejection message must be inside double quotes.
A \e" will produce a double quote in the output.
\en will produce a newline.
%A will expand to the connecting ip address in dotted quad format.
%% may be used to produce a single % in the output.
\e\e will produce a single \e.
.Nm
will reject mail by displaying all the messages from all blacklists in which
a connecting address is matched.
.Xr spamd-setup 8
is normally used to configure this information.
.Pp
.Sh SEE ALSO
.Xr pf.conf 5 ,
.Xr pfctl 8 ,
.Xr spamd-setup 8
.Sh HISTORY
The
.Nm
command
appeared in
.Tn OpenBSD 3.3.
|
