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#!/usr/bin/perl -w
use strict;
use Getopt::Std;
use vars qw(%aliases $opt_a);
use subs qw(validate_recipient process_message read_aliases);
use Net::Server::Mail::ESMTP;
use IPC::Run qw( run );
use Sys::Syslog;
getopt('a:v');
my $smtp = new Net::Server::Mail::ESMTP;
$smtp->set_callback(RCPT => \&validate_recipient);
$smtp->set_callback(DATA => \&process_message);
openlog('[_smtpd]', '', 'mail');
read_aliases;
$smtp->process;
closelog();
#--
sub validate_recipient {
my($session, $recipient) = @_;
$recipient =~ s/^<//;
$recipient =~ s/\@.*$//;
return(0, 550, "Unknown user $recipient") unless exists $aliases{$recipient};
return(1);
}
sub process_message {
my($session, $data) = @_;
#warn "DATA: ". $$data;
my @recipients = $session->get_recipients();
return(0, 554, 'Error: no valid recipients')
unless(@recipients);
syslog('info',
'received '.length($$data).' bytes for '.join(',', @recipients)
);
foreach my $recipient ( @recipients ) {
$recipient =~ s/^<//;
$recipient =~ s/\@.*$//;
my $result = eval { run $aliases{$recipient}, $data };
if (!$result) {
syslog('info', "pipe command failed: $@");
return(0, 451, "pipe command failed: $@");
}
}
syslog('info', 'message piped');
return(1, 250, 'message piped');
}
#--
sub read_aliases {
open(ALIASES, $opt_a || '/etc/aliases' ) or die $!;
while(<ALIASES>) {
chomp;
s/^\s+//; s/\s+$//;
next if /^$/ or /^#/;
/^([\w\-\+\.]+):\s*("?)\|(.*)\2\s*$/ or next;
#$aliases{$1} = [ split(/\s+/, $3) ];
$aliases{$1} = [ qw(/bin/sh -c), $3 ];
}
}
=head1 NAME
_smtpd - UnderSMTPD, the underscore SMTP daemon
=head1 SYNOPSIS
#make some aliases
echo 'username: "|someprogram and args"' > /etc/aliases
#inetd setup
echo "smtp stream tcp nowait mail /usr/local/bin/_smtpd" >>/etc/inetd.conf
echo "_smtpd: my.mail.server.ip" >>/etc/hosts.allow
echo "_smtpd: ALL" >>/etc/hosts.deny
#or add an smtp file to /etc/xinetd.d/
service smtp
{
socket_type = stream
protocol = tcp
wait = no
user = mail
server = /usr/local/bin/_smtpd
}
=head1 DESCRIPTION
This is a minimal SMTP server which only forwards mail to pipe destinations
in /etc/aliases. It does nothing else. Its intended function is on an
internal mail server that forwards mail to other programs on a per address
basis.
UnderSMTPD reads /etc/aliases for usernames; if a match is identified
the message is piped to the given program. Any problems executing the program
will cause a temporary SMTP error to be returned to the connecting client.
Other kinds of aliases are not recognized and cause a permanent SMTP error
to be returned to the connecting client, as do usernames not found in
/etc/aliases
UnderSMTPD was originally written to be used with the Request Tracker ticketing
system.
UnderSMTPD uses Net::Server::Mail to do all the hard work.
=head1 OPTIONS
=over 4
=item -a filename: Alternate aliases file
=back
=head1 ALIASES FORMAT
username: |program and args
username: "|program and args"
Quotes are not necessary around the pipe symbol, program and arguments but are
stripped if present. Line continuations are not supported.
=head1 RT ALIASES EXAMPLE
support: |/opt/rt3/bin/rt-mailgate --queue support --action correspond --url http://rt.example.com/
billing: |/opt/rt3/bin/rt-mailgate --queue billing --action correspond --url http://rt.example.com/
=head1 BUGS
Yes.
=head1 AUTHOR
Ivan Kohler <ivan-undersmtpd@420.am>
=head1 SEE ALSO
L<Net::Server::Mail>
=cut
1;
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