#!/usr/bin/env perl
# License: 3-Clause BSD. Author: Matthew Connelly.
# This is a (formerly Bash, now Perl) script for managing in-addr.arpa and ip6.arpa zones.
# If you have any questions or issues, open an issue at https://bitbucket.org/MaffC/script-collection/issues

use strict;
use warnings;

package DNS::Reverse::Manager;
use feature qw(switch say);
use vars '$VERSION'; $VERSION = '1.0.0';                             #Version number

use Data::Validate::IP qw(is_public_ipv4 is_public_ipv6);            #for validating v4/v6 addresses
use Getopt::Long qw(:config posix_default bundling pass_through);    #for intelligently handling cli arguments
use Net::DNS;                                                        #for doing forward and reverse lookups
use Net::IP;                                                         #for converting IPs to their reverse zones
use Data::Dumper; #debugging

#conf
my $def_rdns = 'hosted-by.mycompany.com';       #Recomend default is "hosted-by.your-website.tld".
my $def_dns = '8.8.8.8';                        #Recommended default is 8.8.8.8 or 4.2.2.1.
my $zone_dir = '/var/named/';                   #for cPanel, use /var/named/.
my $zone_ext = ".db";                           #Default for most environments is ".db".
my $net_type = "cpanel";                        #This was originally written to support cPanel-based DNS environments, and primarily impacts how rdns-manager "syncs".
my $nsd_type = "bind9";                         #I might in the future support more than just bind9.

#variables for arguments
my $verify = '';
my $force = '';
my $reset = '';
my $nosync = '';
my $fsync = '';
my $delptr = '';
my $newzone = '';
my $prefixlen = 64;

#other vars
my $made_modifications = '';

#functions
sub nicedie {
	print shift."\n";
	exit 1;
}
sub validate_domain {
	use Data::Validate::Domain qw(is_domain);
	my $domain = shift;
	return 1 if is_domain $domain;
	return 0;
}
sub validate_ip {
	my $ip = shift;
	return 1 if is_public_ipv4 $ip or is_public_ipv6 $ip;
	return 0;
}
sub get_arpa {
	my $ip = shift;
	if(is_public_ipv4 $ip) {
		$ip =~ m/^([0-9]+)\.([0-9]+)\.([0-9]+)\.([0-9]+)$/;
		return ($4, "$3.$2.$1.in-addr.arpa");
	}
	my $len = ($prefixlen/2);
	Net::IP->new($ip)->reverse_ip =~ /^(.*)\.(.{$len}ip6\.arpa)\.$/;
	return ($1,$2);
}
#TODO make these work for DNS roundrobins. I doubt anyone would be stupid enough to have more than one PTR of the same name
# and i'm not sure if it's even legal, but hey.
sub does_fqdn_match {
	my ($fqdn,$ip) = @_;
	my $r = Net::DNS::Resolver->new(recurse => 1,tcp_timepit => 5,udp_timeout => 5,nameservers => [$def_dns,]);
	my $p = $r->search($fqdn, 'A');
	$p = $r->search($fqdn, 'AAAA') unless is_public_ipv4 $ip;
	return 0 unless defined $p;
	my @res = $p->answer;
	#due to IPv6 shortening, we need to use Net::IP here
	return 1 unless scalar @res < 1 or Net::IP->new($res[0]->address)->ip ne Net::IP->new($ip)->ip;
	return 0;
}
sub confirm_rdns {
	my ($fqdn,$ip) = @_;
	my ($rec,$zone) = get_arpa $ip;
	my $rrec = $rec.".".$zone;
	my $r = Net::DNS::Resolver->new(recurse => 1,tcp_timeout => 5,udp_timeout => 5,nameservers => [$def_dns,]);
	my $p = $r->search($rrec, 'PTR');
	return 0 unless defined $p;
	my @res = $p->answer;
	return 1 unless scalar @res < 1 or $res[0]->ptrdname."." ne $fqdn;
	return 0;
}
sub does_zone_exist {
	my $ip = shift;
	my ($rec,$zone) = get_arpa $ip;
	return -2 if !-e "$zone_dir/$zone$zone_ext";
	return -1 if -z "$zone_dir/$zone$zone_ext";
	return 0 if !-w "$zone_dir/$zone$zone_ext";
	return 1;
}
sub get_zone_array {
	use Net::DNS::ZoneFile;
	#returns 1 on record exists, 0 on record doesn't exist, -1 on zone exists but isn't writeable, -2 on file exists but isn't a zone, -3 on file doesn't exist
	my $ip = shift;
	my ($rec,$zone) = get_arpa $ip;
	return unless does_zone_exist $ip;
	my $zf = new Net::DNS::ZoneFile("$zone_dir/$zone$zone_ext");
	my @z = $zf->read;
	return @z;
}
sub does_record_exist {
	my $ip = shift;
	my ($rec,$zone) = get_arpa $ip;
	my @z = get_zone_array $ip;
	return 0 unless @z;
	#I imagine this might be grossly inefficient on large zones (such as fully-populated IPv6 zones).
	foreach(@z) {
		return 1 if $_->name eq "$rec.$zone";
	}
	return 0;
}
sub generate_soa_serial {
	use POSIX qw(strftime);
	my $cur_serial = shift;
	my $yyyymmdd = strftime "%Y%m%d", localtime;
	return $cur_serial+1 if $cur_serial =~ /^$yyyymmdd[0-9]{2}$/;
	return $yyyymmdd."00";
}
sub write_zone {
	use File::Copy qw(copy);
	use Net::DNS::ZoneParse qw(writezone);
	my $zone = shift;
	my @z = @_;
	foreach(@z) {$_->serial(generate_soa_serial $_->serial) if $_->type eq "SOA";} #update SOA
	copy "$zone_dir$zone$zone_ext", "$zone_dir$zone$zone_ext.bak" or print "Warning: Couldn't create a backup of the zone $zone.\n";
	open ZONE, ">$zone_dir$zone$zone_ext" or nicedie "Failed to open zonefile for $zone for writing!";
	print ZONE writezone @z;
	close ZONE or nicedie "Seemingly failed to close $zone$zone_ext, cowardly quitting here.";
}
sub del_ptr {
	#I'm so sorry
	my $rec = shift;
	sub is_match {
		my ($rr,$rec) = @_;
		return 1 unless $rr->name eq $rec;
		return 0;
	}
	$made_modifications = 1;
	write_zone $rec,grep {&is_match(($_,$rec))} @_;
}
sub add_ptr {
	my ($ip,$fqdn) = @_;
	my ($rec,$zone) = get_arpa $ip;
	my @z = get_zone_array $ip;
	my $new_rr = Net::DNS::RR->new("$rec.$zone. 3600 IN PTR $fqdn");
	push @z,$new_rr;
	$made_modifications = 1;
	write_zone $zone,@z;
}
sub get_ptr {
	my $ip = shift;
	return unless does_record_exist $ip;
	my ($rec,$zone) = get_arpa $ip;
	my @z = get_zone_array $ip;
	#More inefficient to repeat the same operation twice even.
	foreach(@z) {
		return $_->ptrdname if $_->name eq "$rec.$zone";
	}
	return;
}
sub set_ptr {
	my ($ip,$fqdn) = @_;
	return add_ptr $ip,$fqdn unless does_record_exist $ip;
	my ($record,$zone) = get_arpa $ip;
	my @z = get_zone_array $ip;
	foreach(@z) {
		$_->ptrdname($fqdn) if $_->name eq "$record.$zone";
	}
	$made_modifications = 1;
	write_zone $zone,@z;
	return 1;
}
sub sync_cpanel {
	return 1;
}
sub do_sync {
	my $ip = shift;
	my ($rec,$zone) = get_arpa $ip;
	my $res = '';
	print "Syncing zone $zone... ";
	for($net_type) {
		$res = sync_cpanel $zone when /cpanel/;
		default { nicedie "Couldn't sync $zone: Don't have a known sync method for network type $net_type."; }
	}
	say (($res) ? "Synchronised" : "Failed");
}

#main
#do argument parsing. all unknown arguments get left in @ARGV so I can `shift`.
GetOptions
	'reset-hostname=s'	=>	\$def_rdns,
	'dns-server=s'		=>	\$def_dns,
	'v|verify-rdns'		=>	\$verify,
	'f|force'			=>	\$force,
	'r|reset'			=>	\$reset,
	'p|populate'		=>	\$newzone,
	'd|no-sync'			=>	\$nosync,
	's|force-sync'		=>	\$fsync,
	'R|remove-ptr'		=>	\$delptr;

#get IP and domain, validate.
my $ip = shift or nicedie "No IP given!";
$prefixlen = $1 if $ip =~ s/\/([0-9]+)//; #split off prefixlen (if given) into variable for later use
nicedie "Invalid IP address '$ip'!" unless validate_ip $ip;
my $domain = shift;
nicedie "Invalid FQDN '$domain'!" if defined $domain and !validate_domain $domain;
$domain =~ s/([a-zA-Z])$/$1./ if defined $domain; #Append final period if it doesn't exist

#Main program flow
#Argument intelligence. Omitting this probably won't impact program flow much but it's important that the user know they're stupid.
nicedie "You seem to have specified both --no-sync and --force-sync. Please make your mind up." if $nosync and $fsync;
nicedie "You seem to have specified some combination of --reset, --remove-ptr and --force. Please make your mind up." if ($reset and $delptr) or (($reset or $delptr) and $force);
nicedie "You seem to have specified arguments that don't make sense together. Please make your mind up." if ($newzone and ($delptr or $reset or $force)) or ($verify and !defined $domain) or (defined $domain and ($newzone or $delptr or $reset));

#Simple check that the zone exists.
for(does_zone_exist $ip) {
	my ($trec,$tz) = get_arpa $ip;
	nicedie "Authoritative zone for IP $ip doesn't exist! Please create zone $tz or ensure you specified the correct subnet mask if this is an IPv6 address!" when -2;
	nicedie "Zonefile $tz (supposedly authoritative for $ip) doesn't appear to be a valid BIND zone. Please check the zonefile and try again." when -1;
	nicedie "Authoritative zone for IP $ip exists but we can't write to it. Please check the permissions on the zonefile for $tz." when 0;
}

if(!defined $domain and $reset) {
	set_ptr $ip,$def_rdns or nicedie "Failed to set rDNS for $ip to '$def_rdns'!";
	print "rDNS set";
	print ((confirm_rdns $ip, $def_rdns) ? " and resolving" : " but not yet resolving (check manually with 'host $ip')") if $verify;
	print "\n";
} elsif(!defined $domain and $delptr) {
	del_ptr $ip or nicedie "Failed to delete PTR record for $ip!";
	say "PTR record for IP $ip deleted.";exit;
} elsif(!defined $domain and $newzone) {
	nicedie "Sorry, but the zone population functionality isn't yet written.";
} elsif(!defined $domain) {
	say "No rDNS record for IP $ip exists." and exit unless does_record_exist $ip;
	say "rDNS for IP $ip: ".get_ptr $ip;exit;
}
if(defined $domain) {
	nicedie "Forward DNS for $domain doesn't match $ip!" unless does_fqdn_match $ip or $force;
	set_ptr $ip,$domain or nicedie "Failed to set rDNS for $ip to '$domain'!";
	print "rDNS set";
	print ((confirm_rdns $ip, $def_rdns) ? " and resolving" : " but not yet resolving (check manually with 'host $ip')") if $verify;
	print ".\n";
}
do_sync $ip if (($made_modifications and !$nosync) or $fsync);