#!/usr/bin/perl

# 
# Copyright (c) 2006 Jason L. Wright (jason@thought.net)
# 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.
#

#
# external mail validator for use with greyscanner.  Uses sendmail-isms
# (/etc/mail/local-host-names and /etc/mail/aliases) and the password
# file to validate local usernames and domains.
#

use Email::Valid;
use Sys::Hostname;
use Sys::Syslog qw(:DEFAULT setlogsock);

# by default, sendmail accepts mail for gethostname()
$LOCALHOST=hostname;

# sendmail style domain list (one per line, comments lines start with '#')
$DOMAINS_FILE='/etc/mail/local-host-names';

# sendmail aliases file
$ALIAS_FILE='/etc/mail/aliases';

sub build_domainlist {
	my $d;

	if (-f $DOMAINS_FILE) {
		open(F, $DOMAINS_FILE) || die "$DOMAINS_FILE";
		while (<F>) {
			chomp;
			next if (/$\#/);
			$d = $_;
			$d =~ tr/A-Z/a-z/;
			$domains{$d} = 1;
		}
		close(F);
	}
	$domains{$LOCALHOST} = 1;
}

sub build_userlist {
	my $name, $foo;

	# load in /etc/passwd
	while (($name, $foo) = getpwent()) {
		$name =~ tr/A-Z/a-z/;
		$users{$name} = 1;
	}
	endpwent();

	# aliases are kinda like users
	if (-f $ALIAS_FILE) {
		open(F, $ALIAS_FILE) || die "$ALIAS_FILE";
		while (<F>) {
			chomp;
			next if (/$\#/);
			($name, $foo) = split(':', $_, 2);
			next if ($name eq "");
			$name =~ tr/A-Z/a-z/;
			$users{$name} = 1;
		}
		close(F);
	}
}

build_domainlist();
build_userlist();

setlogsock('unix');
openlog("greyrcpt", 'pid', 'mail') || die "can't openlog";

while ($to = shift) {
	syslog('debug', "checking... $to");
	unless (($addr = Email::Valid->address(-address => "$to", -fudge => 1, -local_rules => 1))) {
		# No need to go further, the email address is borked.
		syslog('info', "$to: addr check fail: $Email::Valid::Details\n");
		exit(1);
	}

	# at this point we should have user@domain.com style address
	($user, $domain) = split('\@', $addr);
	$domain =~ tr/A-Z/a-z/;
	$user =~ tr/A-Z/a-z/;

	# verify the domain is one we care about
	unless ($domains{$domain}) {
		# not on this machine, sorry...
		syslog('info', "$to: to invalid domain\n");
		exit(1);
	}

	# now verify the user is one we care about
	unless ($users{$user}) {
		syslog('info', "$to: to invalid user\n");
		exit(1);
	}
	syslog('debug', "$to: pass\n");
}
exit(0);