From 0b1fe0462fe0e7837228129f6c1d89e64a5ab720 Mon Sep 17 00:00:00 2001
From: Stefan Schantl <stefan.schantl@ipfire.org>
Date: Thu, 18 Feb 2016 10:40:20 +0100
Subject: [PATCH] Introduce message parser for SSH related notifications.

This new messge parser is able to detect SSH related
brute-force login attempts and to report the source
IP-address (IPv4 and IPv6).

Signed-off-by: Stefan Schantl <stefan.schantl@ipfire.org>
---
 modules/Parser.pm | 52 +++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 52 insertions(+)

diff --git a/modules/Parser.pm b/modules/Parser.pm
index 9c3fc87..a73192d 100644
--- a/modules/Parser.pm
+++ b/modules/Parser.pm
@@ -10,6 +10,7 @@ our @EXPORT_OK = qw(IsSupportedParser Parser);
 # has to be called to parse messages in the right way.
 my %logfile_parsers = (
 	"snort" => \&message_parser_snort,
+	"ssh" => \&message_parser_ssh,
 );
 
 #
@@ -71,4 +72,55 @@ sub message_parser_snort($) {
 	return "$message[0] SNORT A simple Snort Message";
 }
 
+#
+## The SSH message parser.
+#
+## This subfunction is used for parsing and detecting different attacks
+## against the SSH service.
+#
+sub message_parser_ssh (@) {
+	my @message = @_;
+
+	# The name of the parser module.
+	my $name = "SSH";
+
+	# Variable to store the grabbed IP-address.
+	my $address;
+
+	# Variable to store the parsed event.
+	my $message;
+
+	# Loop through all lines, in case multiple one have
+	# been passed.
+	foreach my $line (@message) {
+		# Check for failed password attempts.
+		if ($line =~/.*sshd.*Failed password for (.*) from (.*) port.*/) {
+			# Store the grabbed IP-address.
+			$address = $2;
+
+			# Set event message.
+			$message = "Possible SSH-Bruteforce Attack for user: $1.";
+		}
+
+		# This should catch Bruteforce Attacks with enabled preauth
+		elsif ($line =~ /.*sshd.*Received disconnect from (.*):.*\[preauth\]/) {
+			# Store obtained IP-address.
+			$address = $1;
+
+			# Set event message.
+			$message = "Possible SSH-Bruteforce Attack - failed preauth.";
+		}
+	}
+
+	# Check if at least the IP-address information has been extracted.
+	if (defined ($address)) {
+		# Return the extracted values and event message.
+		return "$address $name $message";
+	}
+
+	# If we got here, the provided message is not affected by any filter and
+	# therefore can be skipped. Return nothing (False) in this case.
+	return;
+}
+
 1;
-- 
2.39.2