#! /usr/bin/perl -w

#modified to work with WRT54G linksys router by Thomas Epperson
# www.doors-software.com/forum
###############################################################
#
# Copyright (C) 2003 Philip Lawrence <www.amazingcs.com>
#
# This program is free software; you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation; either version 2 of the License, or
# (at your option) any later version.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
# GNU General Public License for more details.
#
# version 1.1 ddns_update.pl for systems with an ethernet router
# (WGR614 specifically, but it is easily changed to work with others)
#
# This allows a system to have an ethernet router, with port
# forwarding, and a server hidden behind the router firewall.
#
# this version uses curl to get the router status info, then uses that
# ip to update one or more domains on the server.
#
# The servers hidden behind the firewall can use dynamic or static
# ip addresses assigned by the router, as long as the router can
# route to them with port forwarding.
#
# The router status command, domain names, userids, and passwords
# are hidden in a secret file (which is checked at runtime).
#
# The secret file can contain user id's and passwords for different
# users, and for multiple domains
#
# A log file is appended to after completion of the update command
#
###############################################################

use Date::Format;

$verbose = 'false';
#$verbose = 'true';

$debug = 'false';
#$debug = 'true';

if ($debug eq 'true') {
	$verbose = 'true';
}

$ruid = '';
$rpwd = '';
$cuid = '';
$cpwd = '';
$rurl = '';
@domain = ();

my $indx = 0;
my @lines = ();
my $tmpstr;

$CFGDIR = '/etc/changeip';
$LOGFILE = '/var/log/cip.log';
$DNSSERVER = 'www.changeip.com:443';

sub nextline
{
	if ($indx > $#lines) {
		return '';
	}
	chomp($tmpstr = $lines[$indx++]);	
	while($tmpstr eq '') {
		if ($indx > $#lines) {
			return '';
		}
		chomp($tmpstr = $lines[$indx++]);
	}
	return $tmpstr;
}

sub get_secret_lines
{
	$tmpstr = nextline();
	($dstr) = ($tmpstr =~ /\s*([\w:\-.]*)\s*/);

	@domain = split(/:/,$dstr);

	$tmpstr = nextline();
	($cuid) = ($tmpstr =~ /\s*(\w*)\s*/);

	$tmpstr = nextline();
	($cpwd) = ($tmpstr =~ /\s*(\w*)\s*/);

	if ($#domain >= 0 && $cuid ne '' && $cpwd ne '') {
		if ($verbose eq 'true') {
			print "dstr - $dstr\n";
			print "cuid - $cuid\n";
			print "cpwd - $cpwd\n\n";
		}
		return 'true';
	}
	else {
		return 'false';
	}
}

sub get_router_ip
{
	my $line = '';
	my @lines;
	my $cnt = 0;

	my $off1 = 0;
	my $off2 = 0;

	@lines = `/usr/bin/curl -s -S --user $ruid:$rpwd $rurl | grep -A 1 "var wan_ip"`;

	if ($#lines < 1) {
		sleep(1);

		# try again before giving up
		@lines = `/usr/bin/curl -s -S --user $ruid:$rpwd $rurl | grep -A 1 "var wan_ip"`;

		if ($#lines < 1) {
			print "unable to get the router ip\n";
			print "lines returned:\n";
			print "@lines\n";
			exit 1;
		}
	}

	if ($verbose eq 'true') {
		print "router line: $lines[0]\n\n";
	}

	$_ = $lines[0];
	$off1 = index($lines[0], '"', 0);
	$off2 = index($lines[0], '"', $off1);
	($line) = substr($lines[0], $off1 + 1, $off2 - 1);

	if ($verbose eq 'true') {
		print "router_ip: $line\n\n";
	}

	return $line;
}

sub get_ns_ip
{
	my $str = '';
	my $dnsstr = `host $_[0]`;

	($str) = ($dnsstr =~ /(\S+)\n?$/);

	if ($verbose eq 'true') {
		print "domain: $_[0] ns_ip: $str\n\n";
	}

	return $str;
}

sub update_ns
{
	my $successstr = 'Successful Update!';
	my $ip = $_[0];
	my $dname = $_[1];

	if ($verbose eq 'true') {
		print "update_ns - router_ip: $ip dname: $dname\n\n";
	}
	
	my $getstring = "GET /update.asp?u=$cuid&p=$cpwd&cmd=update&hostname=$dname&ip=$ip";
	my $cmd = qq~echo "$getstring" | openssl s_client -quiet -connect $DNSSERVER 2>&1~;

	# run the update command

	if ($verbose eq 'true') {
		print "updating dns server with command:\n";
		print "$cmd\n\n";
	}
	
	if ($debug eq 'false') {
		my @output = `$cmd | grep "<ResultText>" | grep "$successstr"`;
	}

	if ($verbose eq 'true') {
		print "response from cmd:\n";
		print "$output[0]\n\n";
	}
	
	open(LOGFIL, ">>$LOGFILE");
	print LOGFIL time2str("%D %H:%M", time()) . "\n";

	if (index($output[0],$successstr) >= 0) {
		print LOGFIL "$successstr for domain name: $dname domain ip: $router_ip\n";
	}
	else {
		print LOGFIL "update failed for domain name: $dname domain ip: $router_ip\n";
	}

	close(LOGFIL);
}

sub update_user_domains
{
	$router_ip = get_router_ip();

	foreach my $tname (@domain)
	{
		$ns_ip = get_ns_ip($tname);

		# only modify the ddns ip address if it has changed
		if ($router_ip ne $ns_ip) {
			update_ns($router_ip,$tname);
		}
		else {
			if ($verbose eq 'true') {
				print "bypass update for domain $tname\n\n";
			}
			open(LOGFIL, ">>$LOGFILE");
			print LOGFIL time2str("%D %H:%M", time()) . "\n";
			print LOGFIL "bypass update for domain $tname\n";
			close(LOGFIL);
		}
	}
}

# this file MUST be owned by root with mode 600
my $sfile = "$CFGDIR/changeip.secret";

my $statstr = `stat -c "%U %a" $sfile`;
my $dstr = '';

($statstr ne 'root 600') or
	die "$sfile MUST be set to mode 600 and root";

# the format of the secrets file is:
#
# url to the router status. ie: (http://<router ip address>/s_status.htm)
# router user id
# router password
#
# colon separated list of domain names for user1.
#   ie: (domain1.com:www.domain1.com:domain2.com:ftp.domain2.com)
# changeip account user id
# changeip account password
#
# colon separated list of domain names for user2.
#   ie: (domain3.com:www.domain3.com:domain4.com:ftp.domain4.com)
# changeip account user id
# changeip account password
#

open(IN, "<$sfile") or die "unable to open $sfile";
@lines = <IN>;
close(IN);

# get the router status url, userid, and password

$tmpstr = nextline();
($rurl) = ($tmpstr =~ /\s*([\w:.\/]*)\s*/);

$tmpstr = nextline();
($ruid) = ($tmpstr =~ /\s*(\w*)\s*/);

$tmpstr = nextline();
($rpwd) = ($tmpstr =~ /\s*(\w*)\s*/);

if ($verbose eq 'true') {
	print "rurl - $rurl\n";
	print "ruid - $ruid\n";
	print "rpwd - $rpwd\n\n";
}

# get each users domains, userid, and password, and process the update

my $ret = get_secret_lines();

while ($ret eq 'true') {
	update_user_domains();
	$ret = get_secret_lines();
}