#!/usr/bin/perl -w

# Spamassassin filter for POP3 mail accounts

# Copyright (C) 2003 Nigel Horne, Wharfedale Computers Ltd.
# njh@despammed.com
# 21/11/02:    Use DNS to check originating host exists to help stop s
+pam
# 22/11/02:    Use MX DNS records.
# 25/11/02:    Flush items put in sendmail's queue.
# 2/12/02:    Handle e-mail addresses without the realname
# 21/1/03:    Added spam blocker
# 22/1/03:    Don't forward spam message. Improved spam warning messag
+es
# 24/1/03:    Added virus checker.

use strict;
use Net::POP3;
use Net::DNS;
use Mail::SpamAssassin;

my $hostname = 'smsltd.demon.co.uk';
my $server = 'pop3.demon.co.uk';
my $user = 'smsltd';
my $password = 'xyzzy';

my $pop3 = Net::POP3->new($server, Timeout => 60) or
    die "Cannot connect to $server: $!";

my $nummessages = $pop3->login($user, $password);

if(!defined $nummessages) {
    die "Cannot login to $server: $!";
}

if($nummessages == 0) {
    print "Nothing to do\n";
    $pop3->quit();
    exit 0;
}

print "Retrieving $nummessages messages from $server\n";

my $messages = $pop3->list() or
    die "Cannot get list of messages from $server: $!";

my $resolver = Net::DNS::Resolver->new;

sub CATCH_PIPE { };
$SIG{'PIPE'} = "CATCH_PIPE";

MESSAGE: foreach my $msgid (keys %$messages) {
    print "Forwarding message $msgid ...";

    my $message = $pop3->get($msgid);

    defined $message or die "\nCan't retrieve message $msgid: $!";

    print "\n";

    my $from = "";

    my @messageArray = @$message;

    foreach (@messageArray) {
        if(/^From: (.+)/) {
            $from = $1;
            if(($from =~ /.*\<.+\@(.+)\>/) ||
               ($from =~ /.+\@(.+)/)) {
                unless(mx($resolver, $1)) {
                    print "Unknown host $1 in $from, message not forwa
+rded\n";
                    # You may wish to comment this out
                    $pop3->delete($msgid);
                    next MESSAGE;
                }
            } else {
                $from = 'unknown';
            }
            last;
        }
    }

    if(open(CLAM, "|clamscan --disable-summary -i --mbox -")) {
        print CLAM "From $from\n";

        foreach (@messageArray) {
            print CLAM $_;
        }

        if(close CLAM != 0) {
            if(($from ne "") && open(MAIL, "|/usr/lib/sendmail \"-f$fr
+om\" -t -odq")) {
                print MAIL "From MAILER-DAEMON\n";
                print MAIL "To: $from\n";
                print MAIL "Cc: postmaster\n";
                print MAIL "Subject: Virus intercepted\n\n";

                print MAIL "A message sent from you contained a virus.
+\n";
                print MAIL "It has not been forwarded to the $hostname
+ domain.\n";
                close MAIL;
            }
            print "Not forwarding message containing a virus\n";
            # You may wish to comment this out
            $pop3->delete($msgid);
            next MESSAGE;
        }
    }

    my $ma = Mail::SpamAssassin::NoMailAudit->new(data => \@messageArr
+ay);

    # This often gives this error:
    #    Use of uninitialized value in split at /usr/lib/perl5/5.8.0/F
+ile/Spec/Unix.pm line 216
    my $sa = Mail::SpamAssassin->new;
    my $status = $sa->check($ma);

    if($status->is_spam()) {
        $status->rewrite_mail();

        # Don't report if the from is forged as us, or if it's a bounc
+e
        # of a bounce
        my $isbounce = 0;
        foreach (@messageArray) {
            if(/^From: (.+)\@$hostname(.*)/) {
                $isbounce = 1;
                last;
            }
        }
        $sa->report_as_spam($ma) unless $isbounce;

        print "Not forwarding spam message\n";
        # You may wish to comment this out...
        $pop3->delete($msgid);

        $status->finish();

        next MESSAGE;
    }

    $status->finish();
    undef $status;
    undef $sa;
    undef $ma;

    # If we're here it probably isn't spam
    if($from eq "") {
        $from = 'unknown';
    } elsif(open(MAIL, "|/usr/lib/sendmail \"-f$from\" -t -odq")) {
        print MAIL "From njh\@despammed.com\n";
        print MAIL "To: $from\n";
        print MAIL "From: Nigel Horne <njh\@despammed.com>\n";
        print MAIL "Subject: Please update your address book\n\n";

        print MAIL "This is an automatic message that has been sent\n"
+;
        print MAIL "in response to a message sent to $hostname.\n\n";
        print MAIL "The domain $hostname is about to disappear.\n";
        print MAIL "Please update your address book to point to bandsm
+an.co.uk.\n";
        close MAIL;
    }

    if(open(MAIL, "|/usr/lib/sendmail \"-f$from\" -t")) {
        # Send TO field first
        foreach (@$message) {
            if(/^To: (.+)\@$hostname(.*)/i) {
                print MAIL "To: $1$2\n";
                print "To: $1$2\n";
                last;
            } elsif (/^To: (.+)/i) {
                print MAIL "To: $1\n";
                print "To: $1\n";
                last;
            } elsif (/^$/) {
                # End of headers. No To: found. Must be spam...
                print "Not forwarding spam message\n";
                $pop3->delete($msgid);

                close MAIL;

                next MESSAGE;
            }
        }
        my $inhead = 1;
        foreach (@$message) {
            if($inhead) {
                (/^From: (.+)/) && print "From: $1\n";
                (/^Subject: (.+)/) && print "Subject: $1\n";

                unless (/^To: .+\@$hostname.*/) {
                    print MAIL $_ || die "Sendmail has disappeared: $!
+\n";
                }
                $inhead = 0 if(/^$/);
            } else {
                print MAIL $_ || die "Sendmail has disappeared: $!\n";
            }
        }

        print MAIL "\nForwarded from the pop3 account at $server.";
        print MAIL "\nThis service will terminate soon. You *have* bee
+n warned.\n";

        if(close MAIL) {
            $pop3->delete($msgid);
        } else {
            warn "e-mail may have failed\n";
            # You may wish to comment this out...
            $pop3->delete($msgid);
        }
    }
}

print "Finished\n";

$pop3->quit();