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 );
  14
  15 #
  16 ## The main parsing function.
  17 #
  18 ## It is used to determine which sub-parser has to be used to
  19 ## parse the given message in the right way and to return if
  20 ## any action should be performed.
  21 #
  22 sub Parser ($$) {
  23         my ($parser, @message) = @_;
  24
  25         # If no responsible message parser could be found, just return nothing.
  26         unless (exists($logfile_parsers{$parser})) {
  27                 return;
  28         }
  29
  30         # Call responsible message parser.
  31         my $action = $logfile_parsers{$parser}->(@message);
  32
  33         # If the parser successfully parsed the message, an action
  34         # has been returned.
  35         if ($action) {
  36                 # Return which action should be performed.
  37                 return "count $action";
  38         }
  39
  40         # If the parser was not able to parse the the given message
  41         # in the right way, return Nothing.
  42         return;
  43 }
  44
  45 #
  46 ## IsSupportedParser function.
  47 #
  48 ## This very tiny function checks if a given parser name is available and
  49 ## therefore a supported parser.
  50 #
  51 ## To perform these check, the function is going to lookup if a key in the
  52 ## hash of supported parsers is available
  53 #
  54 sub IsSupportedParser ($) {
  55         my $parser = $_[0];
  56
  57         # Check if a key for the given parser exists in the hash of logfile_parsers.
  58         if(exists($logfile_parsers{$parser})) {
  59                 # Found a valid parser, so return nothing.
  60                 return 1;
  61         }
  62
  63         # Return "False" if we got here, and therefore no parser
  64         # is available.
  65         return;
  66 }
  67
  68 #
  69 ## The Snort message parser.
  70 #
  71 ## This subfunction is responsible for parsing sort alerts and determine if
  72 ## an action should be performed.
  73 #
  74 ## XXX Currently the parser only supports IPv4. Add support for IPv6 at a
  75 ## later time.
  76 #
  77 sub message_parser_snort(@) {
  78         my @message = @_;
  79
  80         # The name of the parser module.
  81         my $name = "SNORT";
  82
  83         # Variable to store the grabbed IP-address.
  84         my $address;
  85
  86         # Default returned message in case no one could be grabbed
  87         # from the snort alert.
  88         my $message = "An active snort rule has matched and gained an alert.";
  89
  90         # A snort alert contains multiple lines, loop through all lines
  91         # to parse the complete alert.
  92         foreach my $line (@message) {
  93                 # Check Priority Level and skip the alert if it is to low.
  94                 #if ($line =~ /.*\[Priority: (\d+)\].*/) {
  95                 #       return unless($1 < $priority);
  96                 #}
  97
  98                 # Search for a line like xxx.xxx.xxx.xxx -> xxx.xxx.xxx.xxx
  99                 if ($line =~ /(\d+\.\d+\.\d+\.\d+)+ -\> (\d+\.\d+\.\d+\.\d+)+/) {
 100                         # Store the grabbed IP-address.
 101                         $address = $1;
 102                 }
 103
 104                 # Search for a line like xxx.xxx.xxx.xxx:xxx -> xxx.xxx.xxx.xxx:xxx
 105                 elsif ($line =~ /(\d+\.\d+\.\d+\.\d+):\d+ -\> (\d+\.\d+\.\d+\.\d+):\d+/) {
 106                         # Store the obtained IP-address.
 107                         $address = $1;
 108                 }
 109
 110                 # Obtain the reported reason.
 111                 if ($line =~ /.*msg:\"(.*)\".*/) {
 112                         # Store the extracted message.
 113                         $message = $1;
 114                 }
 115         }
 116
 117         # Check if at least the IP-address information are obtained from the
 118         # provided alert.
 119         if ($address) {
 120                 # Return the extracted values.
 121                 return "$address $name $message";
 122         }
 123
 124         # If we got here, the alert could not be parsed correctly, return nothing.
 125         return;
 126 }
 127
 128 1;