modules/Config.pm

   1 package Guardian::Config;
   2 use strict;
   3 use warnings;
   4
   5 use Exporter qw(import);
   6
   7 our @EXPORT_OK = qw(CheckConfig UseConfig);
   8
   9 # The default config file which is used, if no one has been specified.
  10 my $configfile = "/etc/guardian/guardian.conf";
  11
  12 # The maximum amount of chars, which a line in the configfile is allowed to contain.
  13 my $maxlength = "64";
  14
  15 # Hash with default settings. They may be overwritten by settings of the config file.
  16 my %defaults = (
  17         "LogLevel" => "info",
  18         "LogFacility" => "syslog",
  19         "BlockCount" => "3",
  20         "BlockTime" => "86400",
  21         "FirewallEngine" => "none",
  22 );
  23
  24 #
  25 ## UseConfig configuration function.
  26 #
  27 ## This function does the main work. It is responsible for calling the subfunction
  28 ## to read the given config file (or use the default one if none has been specified),
  29 ## and push the returned object to the validate subfunction. Finally the validated
  30 ## settings will be merged with the default ones (existing defaults will be overwritten).
  31 #
  32 sub UseConfig ($) {
  33         my $file = $_[0];
  34
  35         # If not file has been specified, use the default one.
  36         unless ($file) {
  37                 $file = $configfile;
  38         }
  39
  40         # Call subfunction to get the settings from config file.
  41         # Store the options and values in a temporary hash.
  42         my %temp = &ReadConfig($file);
  43
  44         # Validate config settings.
  45         my $error = &CheckConfig(\%temp);
  46
  47         # As long, as no error message is returned, the config is valid.
  48         unless ($error) {
  49                 # Merge hash with contains the default
  50                 # and temporary config hash. If both hashes contains
  51                 # the same keys, the keys+values of the first one (%defaults)
  52                 # will be overwritten.
  53                 my %config = (%defaults, %temp);
  54
  55                 # Return the final configuration hash.
  56                 return %config;
  57
  58         # If an error message is returned, exit and print the error message.
  59         } else {
  60                 die "Invalid configuration: $error";
  61         }
  62 }
  63
  64 #
  65 ## ReadConfig (configfile) function.
  66 #
  67 ## This function is used to read a given configuration file and store the
  68 ## values into a hash which will be returned.
  69 #
  70 sub ReadConfig ($) {
  71         my $file = $_[0];
  72
  73         # Hash to store the read-in configuration options and values.
  74         my %config = ();
  75
  76         # Check if the configfile exists and is read-able.
  77         unless (-r "$file") {
  78                         die "The given configfile ($file) does not exist, or is not read-able: $!";
  79         }
  80
  81         # Open the config file and read-in all configuration options and values.
  82         open(CONF, "$file") or die "Could not open $file: $!";
  83
  84         # Process line by line.
  85         while (my $line = <CONF>) {
  86                 # Skip comments.
  87                 next if ($line =~ /\#/);
  88
  89                 # Skip blank  lines.
  90                 next if ($line =~ /^\s*$/);
  91
  92                 # Remove any newlines.
  93                 chomp($line);
  94
  95                 # Check line lenght, skip it, if it is longer than, the
  96                 # allowed maximum.
  97                 my $length = length("$line");
  98                 next if ($length gt $maxlength);
  99
 100                 # Remove any whitespaces.
 101                 $line=~ s/ //g;
 102
 103                 # Splitt line into two parts.
 104                 my ($option, $value) = split (/=/, $line);
 105
 106                 # Add config option and value to the config hash.
 107                 $config{$option} = $value;
 108         }
 109
 110         # Close the config file.
 111         close(CONF);
 112
 113         # Return the configuration hash.
 114         return %config;
 115 }
 116
 117 #
 118 ## The CheckConfig function.
 119 #
 120 ## This function is responsible to validate configure options which has
 121 ## to be passed as a hash. It will return an error message which provides some
 122 ## deeper details, if any problems have been detected.
 123 #
 124 sub CheckConfig (\%) {
 125         # Dereference the given hash-ref and store
 126         # them into a new temporary hash.
 127         my %config = %{ $_[0] };
 128
 129         # If a BlockTime has been configured, check if the value is a natural number.
 130         if (exists($config{BlockTime})) {
 131                 # Get the configured value for "BlockTime".
 132                 my $value = $config{BlockTime};
 133
 134                 # Call subroutine for validation.
 135                 my $error = &check_number("$value");
 136
 137                 # If the check fails, immediately return an error message.
 138                 if ($error) {
 139                         return "Invalid BlockTime: $error";
 140                 }
 141         }
 142
 143         # If a BlockCount has been configured, check if the value is a natural number.
 144         if (exists($config{BlockCount})) {
 145                 # Get the configured value for "BlockCount".
 146                 my $value = $config{BlockCount};
 147
 148                 # Call subroutine for validation.
 149                 my $error = &check_number("$value");
 150
 151                 # If the check fails, immediately return an error message.
 152                 if ($error) {
 153                         return "Invalid BlockCount: $error";
 154                 }
 155         }
 156
 157         # Gather details about supported log levels.
 158         my %supported_loglevels = &Guardian::Logger::GetLogLevels();
 159
 160         # Check if the configured log level is valid.
 161         unless (exists ($supported_loglevels{$config{LogLevel}})) {
 162                 return "Invalid LogLevel: $config{LogLevel}";
 163         }
 164
 165         # The config looks good, so return nothing (no error message).
 166         return undef
 167 }
 168
 169 #
 170 ## The check_number subroutine.
 171 #
 172 ## This simple subroutine is used to check if a given string is numeric
 173 ## and contains a natural number which has to be greater than zero.
 174 #
 175 sub check_number ($) {
 176         my $input = $_[0];
 177
 178         # Check if the input is a natural number.
 179         unless ($input =~ /^\d+$/) {
 180                 return "$input is not a natural number";
 181         }
 182
 183         # Check if the number is greater than zero.
 184         unless ($input gt "0") {
 185                 return "$input has to be greater than zero";
 186         }
 187
 188         # Input is okay, return no error message (nothing).
 189         return undef;
 190 }
 191
 192 1;