modules/Parser.pm

   1 package Guardian::Parser;
   2 use strict;
   3 use warnings;
   4
   5 use Exporter qw(import);
   6
   7 our @EXPORT_OK = qw(IsSupportedParser Parser);
   8
   9 # This hash contains all supported parsers and which function
  10 # has to be called to parse messages in the right way.
  11 my %logfile_parsers = (
  12         "snort" => \&message_parser_snort,
  13         "ssh" => \&message_parser_ssh,
  14 );
  15
  16 #
  17 ## The main parsing function.
  18 #
  19 ## It is used to determine which sub-parser has to be used to
  20 ## parse the given message in the right way and to return if
  21 ## any action should be performed.
  22 #
  23 sub Parser ($$) {
  24         my ($parser, @message) = @_;
  25
  26         # If no responsible message parser could be found, just return nothing.
  27         unless (exists($logfile_parsers{$parser})) {
  28                 return;
  29         }
  30
  31         # Call responsible message parser.
  32         my $action = $logfile_parsers{$parser}->(@message);
  33
  34         # Return which action should be performed.
  35         return "count $action";
  36 }
  37
  38 #
  39 ## IsSupportedParser function.
  40 #
  41 ## This very tiny function checks if a given parser name is available and
  42 ## therefore a supported parser.
  43 #
  44 ## To perform these check, the function is going to lookup if a key in the
  45 ## hash of supported parsers is available
  46 #
  47 sub IsSupportedParser ($) {
  48         my $parser = $_[0];
  49
  50         # Check if a key for the given parser exists in the hash of logfile_parsers.
  51         if(exists($logfile_parsers{$parser})) {
  52                 # Found a valid parser, so return nothing.
  53                 return 1;
  54         }
  55
  56         # Return "False" if we got here, and therefore no parser
  57         # is available.
  58         return;
  59 }
  60
  61 #
  62 ## The Snort message parser.
  63 #
  64 ## This subfunction is responsible for parsing sort alerts and determine if
  65 ## an action should be performed.
  66 #
  67 sub message_parser_snort($) {
  68         my @message = @_;
  69
  70         # XXX
  71         # Currently this parser just returns a simple message.
  72         return "$message[0] SNORT A simple Snort Message";
  73 }
  74
  75 #
  76 ## The SSH message parser.
  77 #
  78 ## This subfunction is used for parsing and detecting different attacks
  79 ## against the SSH service.
  80 #
  81 sub message_parser_ssh (@) {
  82         my @message = @_;
  83
  84         # The name of the parser module.
  85         my $name = "SSH";
  86
  87         # Variable to store the grabbed IP-address.
  88         my $address;
  89
  90         # Variable to store the parsed event.
  91         my $message;
  92
  93         # Loop through all lines, in case multiple one have
  94         # been passed.
  95         foreach my $line (@message) {
  96                 # Check for failed password attempts.
  97                 if ($line =~/.*sshd.*Failed password for (.*) from (.*) port.*/) {
  98                         # Store the grabbed IP-address.
  99                         $address = $2;
 100
 101                         # Set event message.
 102                         $message = "Possible SSH-Bruteforce Attack for user: $1.";
 103                 }
 104
 105                 # This should catch Bruteforce Attacks with enabled preauth
 106                 elsif ($line =~ /.*sshd.*Received disconnect from (.*):.*\[preauth\]/) {
 107                         # Store obtained IP-address.
 108                         $address = $1;
 109
 110                         # Set event message.
 111                         $message = "Possible SSH-Bruteforce Attack - failed preauth.";
 112                 }
 113         }
 114
 115         # Check if at least the IP-address information has been extracted.
 116         if (defined ($address)) {
 117                 # Return the extracted values and event message.
 118                 return "$address $name $message";
 119         }
 120
 121         # If we got here, the provided message is not affected by any filter and
 122         # therefore can be skipped. Return nothing (False) in this case.
 123         return;
 124 }
 125
 126 1;