check_mail_delivery

#!/usr/bin/perl
use strict;
use lib "/usr/lib64/nagios/plugins";
use utils qw(%ERRORS);


# die with an error if we're not on Linux
if ($^O ne 'linux') {
    print "This plugin only applicable on Linux.\n";
    exit $ERRORS{'UNKNOWN'};
}



###############################################################
# NAME: 	check_mail_delivery
# DESCRIPTION:	A Nagios/Icinga plugin that sends an email to a mail server
#		to check via Pop3 if it has been received afterwards.
#		Developed and tested for outlook.com, gmx, t-online and gmail
#		but should work with any other POP3 capable ESP, too.
#		(see bottom of file for hints)
#
# AUTHOR:	Martin Emberger, https://sporch.de/
#		inspired by https://forum.hetzner.de/thread/20761-von-hotmail-blockiert
#
# CO-AUTHORS:	Michael Seevogel, Postfix postmulti support and minor enhancements
#
# REQUIRES:	Mail::POP3Client, String::Random
# USAGE:	./check_mail_delivery profile_name
#		Adapt %CONFIG and %PROFILES here,
#		configure Nagios/Icinga accordingly.
#
# VERSION:	0.3.2
#
# CHANGELOG:    0.1	Useable version
#               0.2	Change license to CC BY-SA 4.0
#		0.3	Bugfix for Inbox overflow, deletion of emails via POP3
#		0.3.1	Added Postfix postmulti support
#		0.3.2	Additionaly set MAIL FROM: via sendmail command so that return-path will definitely match From: and not the local NRPE user as email sender address.
#		
# This script comes with ABSOLUTELY NO WARRANTY.
# This is free software, and you are welcome to redistribute it
# under certain conditions. See CC BY-SA 4.0 for details.
# https://creativecommons.org/licenses/by-sa/4.0/
#
###############################################################


###############################################################
# SETTINGS
###############################################################
#my %PROFILES = (
#	gmail	=> [ 'my-dummy-address@gmail.com', 'myPOP3Passw0rd', 'pop.gmail.com' ],
#	gmx	=> [ 'my-dummy-address@gmx.de', 'myPOP3Passw0rd', 'pop.gmx.net' ],
#	tonline	=> [ 'my-dummy-address@t-online.de', 'myPOP3Passw0rd', 'securepop.t-online.de' ],
#	hotmail	=> [ 'my-dummy-address@hotmail.com', 'myPOP3Passw0rd', 'pop-mail.outlook.com' ],
#	aol	=> [ 'my-dummy-address@aol.de', 'myPOP3Passw0rd', 'pop.aol.com' ],
#       yahoo   => [ 'my-dummy-address@yahoo.com', 'myPOP3Passw0rd', 'pop.mail.yahoo.com' ],
#
#);


my %CONFIG;
$CONFIG{'TESTMAIL_SUBJECT'} = 'Automatische Icinga Test Nachricht';	# unique ID will be appended later on
$CONFIG{'TESTMAIL_FROM'} = 'a-valid-sender@domain.de';
$CONFIG{'CHECK_WAITTIME'} = '30';	# recommended >=20 secs (consider Nagios' plugin execution time settings)
$CONFIG{'OTHER_DEBUG'} = 0;		# print debug information to STDOUT (Nagios/Icinga will see them, too)
$CONFIG{'OTHER_DELETE_TESTMAIL'} = 1;	# delete the test mail after it was detected (definitely recommended!)

#// END SETTINGS

###############################################################
# Let's go
###############################################################
my %WORK;

get_profile();
send_test_mail();
wait_before_check();
check_remote_server();
handle_return();
exit();


###
sub get_profile() {
	if ($#ARGV < 0) {
		die error ("Configuration", "no profile provided");
	}

	my $profile_param = $ARGV[0];
	debug("Provided profile '$profile_param'");
	
	my $postmulti_param = $ARGV[1];
	debug("Postfix instance '$postmulti_param'");

	if (!$PROFILES{$profile_param}) {
		die error ("Configuration", "unknown profile provided");
	}
	else {
		debug("Profile OK");
		$CONFIG{'TESTMAIL_TO'} = $PROFILES{$profile_param}[0];
		$CONFIG{'POP3_USER'} = $CONFIG{TESTMAIL_TO};
		$CONFIG{'POP3_PASS'} = $PROFILES{$profile_param}[1];
		$CONFIG{'POP3_SERVER'} = $PROFILES{$profile_param}[2];
		$CONFIG{'POSTMULTI_INSTANCE'} = $postmulti_param;
	}
}

sub send_test_mail() {
	debug("Sending mail to $CONFIG{TESTMAIL_TO}");

	use String::Random;
	$WORK{TMP_ID} = new String::Random->randpattern("CncCccCnnnc");
	my $tmp_subject = $CONFIG{TESTMAIL_SUBJECT} . " ($WORK{TMP_ID})";

	if ($CONFIG{'POSTMULTI_INSTANCE'})
	{
        debug("Using $CONFIG{'POSTMULTI_INSTANCE'} as Postfix Instance\n");
	open (MAIL, "|postmulti -i $CONFIG{'POSTMULTI_INSTANCE'} -x sendmail -t -f $CONFIG{TESTMAIL_FROM}") or die error('Sendmail', 'did not work');
	}
	else
	{
        debug("POSTMULTI_INSTANCE is NOT defined, gonna send an email from local/regular sendmail client\n");
	open (MAIL, "|/usr/sbin/sendmail -t -f $CONFIG{TESTMAIL_FROM}") or die error('Sendmail', 'did not work');
	}
	print MAIL "To: $CONFIG{TESTMAIL_TO}\n";
	print MAIL "From: $CONFIG{TESTMAIL_FROM}\n";
	print MAIL "Subject: $tmp_subject\n\n";
	print MAIL "Wenn Du meinst es geht nicht mehr, kommt von irgendwo ein Linux her! :-)";
	close (MAIL);

	debug("Send succeeded!");
}

sub wait_before_check() {
	debug("Waiting $CONFIG{CHECK_WAITTIME} seconds...");
	sleep ($CONFIG{CHECK_WAITTIME});
}

sub check_remote_server() {
	debug("Checking $CONFIG{POP3_SERVER} for our mail with ID $WORK{TMP_ID}");
	my $mail_was_found = 0;
	my $mail_id = -1;

	use Mail::POP3Client;
	use IO::Socket::SSL;
	my $conn = Mail::POP3Client->new(HOST => $CONFIG{POP3_SERVER}, USESSL => 1, USER => $CONFIG{POP3_USER}, PASSWORD => $CONFIG{POP3_PASS}) or die error("Connect",  "unable to connect");
	my $numMsg = $conn->Count;
	debug("Number of messages: " . $numMsg);

	if ($numMsg eq -1) {	# see documention of Mail::POP3Client
		die error ("Connect", "Invalid credentials");
	}

	for (my $msgNr = 1; $msgNr <= $numMsg; $msgNr++) {
		foreach ($conn->Head($msgNr)) {
			if (/^(Subject):/i) {
				debug("Message $msgNr: '$_'");
				if ($_ =~ m/\($WORK{TMP_ID}\)/) {
					debug("Yeah, we found our message!");
					$mail_was_found = 1;
					$mail_id = $msgNr;
				}

				if (($_ =~ m/$CONFIG{TESTMAIL_SUBJECT}/) && (!($_ =~ m/\($WORK{TMP_ID}\)/)) && ($CONFIG{OTHER_DELETE_TESTMAIL}))  {
					debug("Found an old test mail, deleting it");
					$conn->Delete($msgNr);
				}
			}
		}
	}

	debug("New message count: " . $conn->Count());

	if (($CONFIG{OTHER_DELETE_TESTMAIL}) && ($mail_was_found)) {
		$conn->Delete($mail_id);
		debug("Message deleted");
	}


	if ($mail_was_found) {
		$WORK{'RETURN_MSG'} = "Test Mail $WORK{TMP_ID} was found in $CONFIG{POP3_USER}'s Inbox";
		$WORK{'RETURN_CODE'} = 0;	# State OK for Nagios/Icinga
	} else {
		$WORK{'RETURN_MSG'} = "Did NOT found Test Mail $WORK{TMP_ID} in $CONFIG{POP3_USER}'s Inbox. Maybe you've been blocked or the timeout ($CONFIG{CHECK_WAITTIME}s) is too low.";
		$WORK{'RETURN_CODE'} = 2;	# State CRITICAL for Nagios/Icinga
		
	}

	$conn->Close();
}

sub handle_return() {
	print $WORK{RETURN_MSG}, "\n";		# STDOUT
	exit $WORK{RETURN_CODE};		# corresponding Nagios/Icinga code
#	exit ($ERRORS{$WORK{RETURN_CODE}});

}


sub debug() {
	my $msg = shift;
	if ($CONFIG{OTHER_DEBUG}) {
		print $msg . "\n";
	}
}

sub error() {
	my $source = shift;
	my $msg = shift;

	print "\n\n" . "ERROR: $source reports \"$msg\"!" . "\n\n";
	exit 2;
}





###############################################################
# Hints for setting up email accounts (had to learn by myself)
# GMAIL
# Option "Weniger sichere Apps zulassen:" has to be enabled
# via Kontoeinstellungen
#
# T-ONLINE
# Most stupid ESP ever. You have to set the
# "Email Passwort", as it's not the same as for web
###############################################################