#!/usr/bin/perl

# $Id: check_zone_rrsig_expiration,v 1.14 2015/10/12 16:54:20 wessels Exp $
#
# check_zone_rrsig_expiration
#
# nagios plugin to check expiration times of RRSIG records.  Reminds
# you if its time to re-sign your zone.

# Copyright (c) 2008, The Measurement Factory, Inc. All rights reserved.
# 
# Redistribution and use in source and binary forms, with or without
# modification, are permitted provided that the following conditions
# are met:
# 
# Redistributions of source code must retain the above copyright
# notice, this list of conditions and the following disclaimer.
# 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.
# Neither the name of The Measurement Factory nor the names of its
# contributors may be used to endorse or promote products derived
# from this software without specific prior written permission.
# 
# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
# "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
# COPYRIGHT OWNER OR CONTRIBUTORS 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.

# usage
#
# define command {
#   command_name    check-zone-rrsig
#   command_line    /usr/local/libexec/nagios-local/check_zone_rrsig -Z $HOSTADDRESS$
# }
# 
# define service {
#   name		dns-rrsig-service
#   check_command	check-zone-rrsig
#   ...
# }
# 
# define host {
#   use dns-zone
#   host_name zone.example.com
#   alias ZONE example.com
# }
# 
# define service {
#   use dns-rrsig-service
#   host_name zone.example.com
# }

use warnings;
use strict;

use Getopt::Std;
use Net::DNS::Resolver;
use Time::HiRes qw ( gettimeofday tv_interval);
use Time::Local;
use List::Util qw ( shuffle );

# options
#  -Z zone        Zone to test
#  -t seconds     DNS query timeout
#  -d             debug
#  -C days        Critical if expiring in this many days
#  -W days        Warning if expiring in this many days
#  -T type	  Query type (default SOA)
#  -4             use IPv4 only
#  -U size        EDNS0 UDP packet size (default 4096)
my %opts = (t=>30, C=>2, W=>3, T=>'SOA', U=>4096);
getopts('4Z:dt:W:C:T:U:', \%opts);
usage() unless $opts{Z};
usage() if $opts{h};
my $zone = $opts{Z};
$zone =~ s/^zone\.//;

my $data;
my $start;
my $stop;

my @refs = qw (
a.root-servers.net
b.root-servers.net
c.root-servers.net
d.root-servers.net
e.root-servers.net
f.root-servers.net
g.root-servers.net
h.root-servers.net
i.root-servers.net
j.root-servers.net
k.root-servers.net
l.root-servers.net
m.root-servers.net
);

$start = [gettimeofday()];
do_recursion();
do_queries();
$stop = [gettimeofday()];
do_analyze();

sub do_recursion {
	my $done = 0;
	my $res = Net::DNS::Resolver->new;
	do {
		print STDERR "\nRECURSE\n" if $opts{d};
		my $pkt;
		foreach my $ns (shuffle @refs) {
			print STDERR "sending query for $zone $opts{T} to $ns\n" if $opts{d};
			$res->nameserver($ns);
			$res->udp_timeout($opts{t});
			$res->recurse(0);
			$res->dnssec(1);
			$res->udppacketsize($opts{U});
			$res->force_v4(1) if $opts{'4'};
			$pkt = $res->send($zone, $opts{T});
			last if $pkt;
		}
		critical("No response to seed query") unless $pkt;
		critical($pkt->header->rcode . " from " . $pkt->answerfrom)
			unless ($pkt->header->rcode eq 'NOERROR');
		@refs = ();
		foreach my $rr ($pkt->authority) {
			next unless $rr->type eq 'NS';
			print STDERR $rr->string, "\n" if $opts{d};
			push (@refs, $rr->nsdname);
			next unless names_equal($rr->name, $zone);
			add_nslist_to_data($pkt);
			$done = 1;
		}
	} while (! $done);
}


sub do_queries {
	my $n;
	do {
		$n = 0;
		foreach my $ns (keys %$data) {
			next if $data->{$ns}->{done};
			print STDERR "\nQUERY $ns\n" if $opts{d};

			my $pkt = send_query($zone, $opts{T}, $ns);
			add_nslist_to_data($pkt);
			$data->{$ns}->{queries}->{$opts{T}} = $pkt;

			print STDERR "done with $ns\n" if $opts{d};
			$data->{$ns}->{done} = 1;
			$n++;
		}
	} while ($n);
}

sub do_analyze {
	my $nscount = 0;
	my $NOW = time;
	my %MAX_EXP_BY_TYPE;
	foreach my $ns (keys %$data) {
		print STDERR "\nANALYZE $ns\n" if $opts{d};
		my $pkt = $data->{$ns}->{queries}->{$opts{T}};
		critical("No response from $ns") unless $pkt;
		print STDERR $pkt->string if $opts{d};
		critical($pkt->header->rcode . " from $ns")
			unless ($pkt->header->rcode eq 'NOERROR');
		critical("$ns is lame") unless $pkt->header->ancount;
		foreach my $rr ($pkt->answer) {
			next unless $rr->type eq 'RRSIG';
			my $exp = sigrr_exp_epoch($rr);
			my $T = $rr->typecovered;
			if (!defined($MAX_EXP_BY_TYPE{$T}->{exp}) || $exp > $MAX_EXP_BY_TYPE{$T}->{exp}) {
				$MAX_EXP_BY_TYPE{$T}->{exp} = $exp;
				$MAX_EXP_BY_TYPE{$T}->{ns} = $ns;
			}
		}
		$nscount++;
	}
	warning("No nameservers found.  Is '$zone' a zone?") if ($nscount < 1);
	warning("No RRSIGs found") unless %MAX_EXP_BY_TYPE;
	my $min_exp = undef;
	my $min_ns = undef;
	my $min_type = undef;
	foreach my $T (keys %MAX_EXP_BY_TYPE) {
		printf STDERR ("%s RRSIG expires in %.1f days\n", $T, ($MAX_EXP_BY_TYPE{$T}->{exp}-$NOW)/86400) if $opts{d};
		if (!defined($min_exp) || $MAX_EXP_BY_TYPE{$T}->{exp} < $min_exp) {
			$min_exp = $MAX_EXP_BY_TYPE{$T}->{exp};
			$min_ns = $MAX_EXP_BY_TYPE{$T}->{ns};
			$min_type = $T;
		}
	}
	critical("$min_ns has expired RRSIGs") if ($min_exp < $NOW);
	if ($min_exp - $NOW < ($opts{C}*86400)) {
		my $ND = sprintf "%3.1f days", ($min_exp-$NOW)/86400;
		critical("$min_type RRSIG expires in $ND at $min_ns")
	}
	if ($min_exp - $NOW < ($opts{W}*86400)) {
		my $ND = sprintf "%3.1f days", ($min_exp-$NOW)/86400;
		warning("$min_type RRSIG expires in $ND at $min_ns")
	}
	success("No RRSIGs expiring in the next $opts{W} days");
}

sub sigrr_exp_epoch {
	my $rr = shift;
	die unless $rr->type eq 'RRSIG';
	my $exp = $rr->sigexpiration;
	die "bad exp time '$exp'"
		unless $exp =~ /^(\d\d\d\d)(\d\d)(\d\d)(\d\d)(\d\d)(\d\d)$/;
	my $exp_epoch = timegm($6,$5,$4,$3,$2-1,$1);
	return $exp_epoch;
}

sub add_nslist_to_data {
	my $pkt = shift;
	foreach my $ns (get_nslist($pkt)) {
		next if defined $data->{$ns}->{done};
		print STDERR "adding NS $ns\n" if $opts{d};
		$data->{$ns}->{done} |= 0;
	}
}

sub success {
	output('OK', shift);
	exit(0);
}

sub warning {
	output('WARNING', shift);
	exit(1);
}

sub critical {
	output('CRITICAL', shift);
	exit(2);
}

sub output {
	my $state = shift;
	my $msg = shift;
	$stop = [gettimeofday()] unless $stop;
	my $latency = tv_interval($start, $stop);
	printf "ZONE %s: %s; (%.2fs) |time=%.6fs;;;0.000000\n",
		$state,
		$msg,
		$latency,
		$latency;
}

sub usage {
	print STDERR "usage: $0 -Z zone -d -t timeout -W days -C days\n";
	print STDERR "\t-Z zone		zone to test\n";
	print STDERR "\t-T type		query type (default SOA)\n";
	print STDERR "\t-d 		debug\n";
	print STDERR "\t-t seconds	timeout on DNS queries\n";
	print STDERR "\t-W days		warning threshhold\n";
	print STDERR "\t-C days		critical threshold\n";
	print STDERR "\t-4		use IPv4 only\n";
	print STDERR "\t-U bytes	EDNS0 UDP buffer size (default 4096)\n";
	exit 3;
}

sub send_query {
	my $qname = shift;
	my $qtype = shift;
	my $server = shift;
	my $res = Net::DNS::Resolver->new;
	$res->nameserver($server) if $server;
	$res->udp_timeout($opts{t});
	$res->retry(2);
	$res->recurse(0);
	$res->dnssec(1);
	$res->udppacketsize($opts{U});
	$res->force_v4(1) if $opts{'4'};
	my $pkt = $res->send($qname, $qtype);
	unless ($pkt) {
		$res->usevc(1);
		$res->tcp_timeout($opts{t});
		$pkt = $res->send($qname, $qtype);
	}
	return $pkt;
}

sub get_nslist {
	my $pkt = shift;
	return () unless $pkt;
	return () unless $pkt->authority;
	my @nslist;
	foreach my $rr ($pkt->authority) {
		next unless ($rr->type eq 'NS');
		next unless names_equal($rr->name, $zone);
		push(@nslist, lc($rr->nsdname));
	}
	return @nslist;
}

sub names_equal {
	my $a = shift;
	my $b = shift;
	$a =~ s/\.$//;
	$b =~ s/\.$//;
	lc($a) eq lc($b);
}